j /i&i)L . I.. l , S; / Chart of Primary, Secondary and Tertiary Colors Prosthetic Dentistry 
BY 
JAMES HARRISON PROTHERO, D.D.S. 
EMERITUS PROFESSOR OF PROSTHETIC DENTISTRY AND METALLURGY 
IN NORTHWESTERN UNIVERSITY DENTAL SCHOOL, CHICAGO 
THIRD EDITION 
Revised and Enlarged 1189 Pages 1382 Illustrations 
1923 
Medico-Dental Publishing Company 
CHICAGO 
C. Ash & Sons 
LONDON 
Made in U. S. A. Entered according to Act of Congress, in the year 1923, 
By J. H. BROTHERO, 
In the office of the Librarian of Congress, Washington, D. C. 
Entered at Stationers’ Hall, 
London, England. 
PRESS OF HEDSTROM BARRY CO.. CHICAGO As a Slight Token of Admiration and Appreciation for 
Kindly Help and Advice Rendered the Writer 
Through Years of Association, 
this Book is Dedicated 
to the Memory of 
(Srmir Barfiimau mark, M.®., Sr.®., HIL®. 
Whose Persistent and Untiring Efforts 
in the Fields of Science have Immeasurably Benefited 
NOT ONLY THE PROFESSION OF WHICH HE WAS A 
Most Distinguished Member, 
but Humanity as well PREFACE 
The revision of a former edition of this book has resulted 
in very nearly a fourfold enlargement. 
Prevailing dental educational methods, although covering 
only those subjects considered essential, leave little time to the 
beginner for collateral reading. In the hour to hour transition 
of his mind from one recitation to another the student some- 
times fails to realize the breadth and scope of some particular 
subject, or its relation as a part to the whole. This is espe- 
cially true in the prosthetic field. Innumerable devices and 
methods of technic have been evolved for the replacement of 
lost natural teeth. To burden the student’s mind with all of 
these would be impracticable. 
The writer has endeavored to introduce the essentials in 
four main subjects of prosthesis, viz., denture, crown, bridge 
and inlay construction, with sufficient elaboration to enable 
the beginner to acquire a practical as well as theoretical 
knowledge of them. Stress is laid upon the fact that, although 
involving many problems in physics and mechanics, the call- 
ing of a prosthetist is much more than that of a mechanic. 
The appliances which he constructs are placed in apposition 
to or rest upon living, sensitive tissue susceptible to patho- 
logic changes when substitutes are not well planned. Fre- 
quently, as a result of improper planning, many restorations, 
although well executed from a mechanical standpoint, result 
in infinitely more harm than benefit. 
A synopsis of color principles has been included because, 
without a knowledge of crude primary colors and their com- 
plements, it is impossible to discern fine distinctions between 
attenuated tints and their complements, as should be done in 
the harmonious selection of teeth. 
A section on metallurgy has been incorporated, since the 
prosthetist is constantly dealing with metals and alloys in one 
form or other; consequently a knowledge of their physical 
properties is essential. The outline of recent discoveries has 
been added, with the idea of exciting further interest in the 
wonderful phenomena of the elements and their relation to 
each other. 
A section on the history of prosthesis has been added, so 
that the student may form some conception of the sequent preface 
growth and progress in this field. Brief though it is, the 
subject-matter presented involved a considerable expenditure 
of time. It is hoped that it may aid in rounding out the 
beginner’s conception of the breadth and scope of the field he 
is entering. 
The writer desires to express his appreciation to various 
individuals, organizations and supply houses, as follows: 
To the National Dental Association, through its officers, 
for the use of cuts which appeared in Dr. Gfuerini’s History 
of Dentistry. 
To the S. S. White Dental Manufacturing Company for 
many cuts throughout the text, and particularly those relating 
to crown and bridge work, included in the chapter on history. 
To the Dentists’ Supply Company of New York for Dr. 
J. Leon Williams’ typal forms of teeth and Dr. Gfysi’s appli- 
ances. 
To H. D. Justi & Son, through Mr. Bowe; Ash & Sons, 
through Mr. Sykes; Lee S. Smith & Co., Samuel A. Crocker, 
Ransom & Randolph, Cleveland Dental Supply Company, 
J. W. Ivory, Lea & Febiger, Johnson & Lund, Goldsmith 
Bros., Detroit Dental Manufacturing Company and others for 
various cuts used through the text. 
To Dr. A. J. Bush of Columbus, Ohio, for his essay and 
charts on the classification of fixed bridgework. 
To Dr. L. J. Weinstein of New York for his recent work 
on alloys of gold, investments and fluxes. 
Finally, thanks are due to the untiring efforts of my 
assistant, Dr. Joseph Ridgway, for help in arranging text and 
illustrations and in proofreading. 
James Harrison Prothero. 
Chicago, January 25, 1916. 
This edition is a reprinting of the second edition, with forty 
new illustrations setting forth the principles of denture balance 
for partial cases. A more extensive revision does not seem to 
be necessary at this time. 
James Harrison Prothero. 
Chicago, August 3,1921. 
PREFACE TO THIRD EDITION TABLE OF CONTENTS 
PROSTHETIC DENTISTRY 
CHAPTER I 
General remarks—The three principal objects desirable to attain in denture con 
struction—Restoration of the function of mastication—Restoration of dis- 
turbed facial contour and fulfillment of general esthetic requirements—The 
construction of dentures that may be worn with comfort Pages 1 to 6 
BODILY FUNCTIONS CONCERNED IN DIGESTION 
CHAPTER II 
Metabolism—Impairment of bodily functions—The mouth—The lips—The vesti- 
bule—The oral cavity proper—Mucous membrane—Epithelium—The palatine 
vault—The bony structure of the hard palate—Palatine foramina—Thickness 
of the palatine process of the maxilla—-Mucous membrane of the palate—The 
rugae-—The tongue—The sense of taste—The salivary glands. . .Pages 7 to 15 
CHAPTER III 
EXAMINATION OF THE MOUTH 
Position of patient—Examination of mouth when natural teeth are present— 
Examination of edentulous mouths—Preparation of the mouth for dentures— 
Spongy borders—Reduction of spongy borders—Temporary dentures—Per- 
manent dentures Pages 16 to 22 
CHAPTER IY 
ARTIFICIAL DENTURES 
Physical and mechanical problems involved in their construction—Full dentures— 
Adhesion—Atmospheric pressure—Retention by means of atmospheric pres- 
sure—Conditions necessary for retention—Relieving pressure over hard areas 
in upper dentures—Vacuum chambers—Compensating for expansion of the 
cast—Position and outline form of the distal margin of an upper denture— 
Preparation of lower impressions—Soft alveolar borders Pages 23 to 32 
CHAPTER Y 
DEFINITION OF SOME COMMONLY USED TERMS 
Use of the terms “Cast” and “Model”—Impression trays—Tray nomenclature 
—Tray adaptation—Conforming the tray by bending—Conforming by cut- 
ting—Additions to the tray—Special trays—Cast—Swaged—Trays of ideal 
baseplate—Metallic extensions to stock trays Pages 33 to 40 
IMPRESSION TRAYS 
CHAPTER VI 
Requirements—Classification—Plaster of Paris—Manufacture—Physical proper- 
ties—Setting—Strength of hardened gypsum—Time required to crystallize— 
Size of crystals—Influence of mixing on quality—Expansion, measurement of 
—Contraction-—-Warpage—Means of obviating-—Compressibility of—Advan- 
tageous properties of—Impression compounds similar to plaster—Cement used 
as an impression material—Modeling compound—Beeswax—Beeswax and par- 
affin—Hard bite wax-—Gutta-percha Pages 41 to 62 
IMPRESSIONS AND IMPRESSION MATERIALS TABLE OF CONTENTS 
TECHNIC OF IMPRESSION TAKING 
CHAPTER VII 
Upper impressions indications for use of plaster—Preliminary steps—Position of 
patient-—Position of operator—Selecting and fitting trays-—Mixing the plas- 
ter—Introduction of filled tray—Securing peripheral adaptation—Muscle 
marking the periphery—Dislodging and removal of impression—Lower im- 
pressions—Selection of tray—Position of patient—Position of operator— 
Muscle marking—Partial cases, classifications of—Taking impressions of 
partial cases—Combination impressions of wax or modeling compound and 
plaster—Removal of impression—Assembling the fractured pieces—Breaking 
an impression along definite lines—Impressions of modeling compound—Full 
eases—Manner of softening the compound—Introducing the filled tray— 
Securing adaptation—Reheating for corrective measure—Summary of steps. 
Pages 63 to 89 
CHAPTER VIII 
PRODUCTION OF CASTS 
Treatment and filling of impression in the production of easts and models— 
Staining fluids—Separating mediums—Classification of separating mediums 
—Requirements—Alcoholic solution—V arnishes—Ethereal solutions—Collo - 
dion—Soap—Aqueous solutions—Oils—Forms for casts and models—For 
celluloid cases—For cast metal bases—Models for the production of dies— 
Models with cores—Materials used for casts—Magnesium oxychloride— 
Spence’s plaster compound—Coarse building plaster—French’s regular plaster 
—French’s impression plaster—Commercial plaster—Deleterious effect of 
accelerators on casts—Manipulation of various kinds of materials in cast 
production—Filling impressions—Removal of impressions from hardened 
casts—Full and partial cases—Artificial stone—-Description of—Advantages 
and Disadvantages—Discovery of Pages 90 to 117 
BASES FOR ARTIFICIAL DENTURES 
CHAPTER IX 
Requisite properties—Bases of gold—Platinum—Aluminum—Tin Alloy—Vulcan- 
ite—Celluloid—Thermal conductivity—Cause of oral inflammatory conditions 
under vulcanite bases—Deleterious effect of coloring matter in vegetable 
bases—Mechanical irritation—Unhygienic conditions Pages 118 to 125 
CHAPTER X 
Comparative results in adaptation of swaged and vulcanite bases—Sequent steps 
in swaged base denture construction—Sequent steps in vulcanite denture con- 
struction—Appliances and accessories used in die and counterdie construction 
—Molding flasks—Molding sand—Sieve—Talcum powder—Straight edge— 
Heating appliances—Melting ladle—Die metal—Zinc—Shrinkage of metals in 
passing from liquid to solid state—Treatment of plaster models to arrest 
expansion—Babbitt metal—Melotte’s metal and other fusible alloys—Compo- 
sition of fusible alloys—Counterdie metal—Whiting and alcohol solution— 
Brushes Pages 126 to 138 
SWAGED METAL BASE DENTURES 
CHAPTER XI 
TECHNIC OF DIE AND COUNTERDIE CONSTRUCTION 
Forming the sand matrix—Various methods of removing the model from the sand 
—Necessity for the use of cores-—Construction of sand matrix in the Hawe’s 
flask—Forming the die—Melting the die metal—Casting the die—Inspection 
and correction of the die—Construction of the counterdie—Melting the coun- TABLE OF CONTENTS 
IX 
terdie metal—Casting the counterdie—Construction of the counterdie by dip- 
ping—Separation of the die and counterdie—Partial counterdies, construction 
of—Matrix counterdies-—Parker shot swager—Counterdies for partial cases. 
Pages 139 to 165 
CHAPTER XII 
CONSTRUCTION OF SWAGED DENTURE BASES OF GOLD—(Upper Cases) 
Securing pattern for the gold plate—Carat and gauges of gold used for denture 
bases—Annealing the plate—Oiling the die and counterdie—Cleansing the 
plate—Pickling—Conforming the plate to die—Upper cases—Various steps 
of—Use of partial counterdies—Swaging in the eounterdie—Final trimming 
and finish—Securing anchorage for the teeth to baseplate—Various means 
employed—Forming peripheral shoulder for finish of the vulcanite—Locating 
position of wire line on baseplate—Attaching wire anchorage loops—Swaging 
full lower denture bases—Various steps described—Construction of partial 
baseplates of gold—Various ways of reinforcing the baseplate—How to esti- 
mate the proper thickness of a double baseplate—Soldering doubled bases— 
Application of frictional appliances in partial cases—Method of securing exact 
relationship—Attaching teeth to baseplate by soldering Pages 166 to 189 
CHAPTER XIII 
ALUMINUM BASE DENTURES 
Cast bases of aluminum—Cause of warpage in cast bases—Imperfect density of 
cast bases—Action of oral fluids on aluminum—Granular structure of alumi- 
num—Casting by the indirect method—Technic of forming the wax model— 
Investment of the wax model—Preparing the case for casting—Casting the 
fused metal—Finishing and swaging—Attaching teeth to base with vulcanite 
—Direct method of producing a cast base aluminum denture—Use of cen- 
trifugal casting machine—Technic—Mixing and applying the investment to 
the wax model base and east—Investing the case in flask—Drying out the case 
—Casting—Important properties of aluminum in reference to casting— 
Swaged bases of aluminum—Comparative durability of east and swaged 
bases of aluminum—Summary of causes of deterioration of swaged bases— 
Technic of swaging—Developing the vulcanite shoulders and anchorages— 
Forming the shoulder—Spurring the base—Anchorage by perforation—Use 
of a doubler—Some facts on the history of aluminum castings 
Pages 190 to 220 
CHAPTER XIY 
WEIGHTED LOWER DENTURES 
Dentures of weighted vulcanite—Vulcanite dentures weighted by means of a 
metallic core—Cast metal bases—Technic of a weighed cast base—Flashing 
the wax model base plate—Casting the base-—Modification of the foregoing 
method—History of the cheoplastie process. 
VULCANITE BASEPLATES (Double Vulcanization) 
Technic of construction-—Construction of temporary baseplates—Ideal baseplate 
—“ Special ’’—Temporary baseplates of metal Pages 221 to 232 
CHAPTER XY 
Atmospheric pressure and adhesion—Frictional retention of partial dentures— 
Specialized frictional appliances—Clasps-—Objection to the use of clasps— 
Advantages derived from the use of elasps—Requisites of a clasp—Adapta- 
tion—Resiliency—Inherent strength—Gauges of metal commonly employed—- 
Types of clasps most commonly used—Partial flat band clasp—Half round 
RETENTION OF PARTIAL DENTURES X 
TABLE OF CONTENTS 
wire clasp—Wire or loop clasp—The stop clasp—The doubli.stay—:Tb6 stay 
clasp—Indications and contraindications governing the application' of clasps— 
Denture balance—Fulcrum line—Object in using specialized frictional appli- 
ances Pages 233 to 249 
TECHNIC OF CLASP CONSTRUCTION 
CHAPTER XVI 
Axial contour forms of bicuspids and molars—Outline of steps of clasp construc- 
tion—Securing impression of tooth to be clasped—Rebuilding impression for 
reception of molten die metal—Casting the die-—Cutting the clasp metal to 
suitable dimensions—Securing peripheral adaptation of strip to die with pliers 
—Securing surface adaptation with hammer—Final adaptation of clasp to die 
—Soldering stops and anchorage lugs to clasp—Finishing the clasp—Various 
methods of clasp construction—Combination of pure gold with clasp metal— 
Cast clasps—The wire loop clasp—Continuous and open loop clasp—Securing 
relation between clasps, the teeth they embrace and the baseplate—Taking 
impression of clasps, teeth and baseplate—Soldering clasps to baseplate 
Pages 250 to 268 
CHAPTER XVII 
TJIE MASTICATORY MECHANISM 
The masticatory apparatus—The maxilla—The mandible—Functions—General 
description—Movements—Tempero-mandibular articulation — The condyles — 
The condyle path—Variations in pitch of paths—Muscles of mastication— 
The masseter—Temporal—External pterygoid—Internal pterygoid—Muscles 
which depress the mandible—Muscles which control the position of food— 
Summary of muscular action on the mandible—Mandibular ligaments—Cap- 
ular—External lateral—Internal lateral—Spheno-mandibular—Stylo-mandib- 
ular—The teeth—Occlusal surface markings—The central sulci of bicuspid 
and molar teeth—The bucco-lingual grooves—The masticatory or rectangular 
groove—Arrangement of the teeth in the dental arches—Occlusal view—Ante- 
rior curvature—Incisal view—Alignment of the posterior teeth—Buccal view 
of upper arch—The plane of occlusion—Curvature of occlusal plane—Rela- 
tionship of planes of occlusion to condyle paths—Governing factors in man- 
dibular movement—The incisor path—Condyle movement in protrusion— 
Function of incisor teeth in protrusive effort-—Lateral movements of the man- 
dible—Centers of mandibular rotation—Relation of lower to upper teeth on 
pivotal side—Side movements not controlled by rotating centers—-Relation of 
lower to upper teeth on protruded or balancing side—The compensating curve 
—The curve of Spee—Modification of the compensating curve 
Pages 269 to 303 
CHAPTER XVIII 
CONSTRUCTION OF FULL DENTURES 
Anatomic method—Masticatory movements of the carnivora, herbivora and om 
nivora—Main features of anatomic methods—Present methods of technic in 
anatomic denture construction—Snow appliances and methods—Face bow— 
Bite gauges—General constructive steps—Occlusion and contour models— 
Requirements of a baseplate—Requirements of the occlusion rim—Construc- 
tion of occlusion models—Approximate depth of occlusal rims—Bucco-lingual 
position of upper and lower wax rims in relation to border crests—Trial of 
occlusal models in the mouth—Testing adaptation of each baseplate to its 
ridge—Establishing height of lower occlusal rim—Restoring disturbed facial 
contour—Marking high and low lip lines-—Marking median line—Locating 
outer ends of condyles—Application of bite fork to upper occlusion model— 
Meaning of the term, “ Taking the bite "*—Difficulty encountered in taking 
the bite—Various methods of securing the bite—A practical method for secur- TABLE OF CONTENTS 
XI 
ing a correct bite—Inserting bite fork in upper occlusal model—Adjusting 
face bow to occlusion models—Adjusting face bow with occlusal models 
attached to the occluding frame—Attaching casts to the occluding frame— 
Registering condyle paths of patient—Christensen’s method—Technic of con- 
dyle registration—Limit of protrusive mandibular movement—Adjusting 
condyle paths of occluding frame—Developing compensating curves—Funda- 
mental principles—Practical steps—The Ulsaver method—Omitting develop- 
ment of compensating curve Pages 304 to 354 
CHAPTER XIX 
General considerations—Classification of temperaments—Harmony defined—Esthet- 
ics defined—Intuitive and acquired esthetics—Facial outlines—Natural tooth 
forms—Reproduction of natural tooth forms in porcelain—Observed outlines 
of natural teeth in the mouth—The color problem in tooth selection—A syn- 
opsis of color principles—Color—Primary colors (pigments)—Secondary col- 
ors—Tertiary colors—Intermediate colors—Complementary colors—Color func- 
tions of the visual organs—Colors found in natural teeth—Suggestions. 
Pages 355 to 381 
ESTHETICS OF TOOTH SELECTION 
CHAPTER XX 
ARRANGING AND OCCLUDING THE TEETH 
Upper arch—Arranging the six anterior teeth—Arranging the posterior teeth— 
Arranging the lower in occlusion with the upper teeth—Testing the occlusal 
surfaces for working efficiency—Securing contact of the lingual marginal 
ridges—Arranging the six lower anterior teeth—Developing balancing contact 
—Final test with carbon paper—Developing the contour of dentures in wax— 
Artistic principles involved—Developing the gum festoons—Trimming periph- 
eral outline of the dentures—Finishing touches in carving gums—Finishing 
lingual surfaces of wax model dentures—Development of the rugae—Trial of 
the dentures in the mouth—Final finish of the model dentures—Removing the 
casts from occluding frame Pages 382 to 406 
CHAPTER XXI 
REPRODUCTION OF THE WAX MODEL DENTURES IN PERMANENT 
MATERIALS 
Sectional molds—Flasks—Fitting east and wax model denture in flask—Flasking 
the wax model denture—Separating the flask—Preparatory steps—Opening 
the flask—Clearing the matrix of wax and baseplate material—Treatment of 
first section of mold containing east—Providing for escape of surplus rubber— 
Steps preparatory to packing the matrix—Heating the rubber before intro- 
ducing it in the matrix—Heating the matrix previous to packing the rubber— 
Preparing the rubber for packing—Basic rubber—Packing the matrix—Pack- 
ing the gum facing—Packing the basic rubber—Gauging the amount of rub- 
ber required—Flask closing—Estimating the force exerted by the screw— 
Test closing of the flask—Treatment of cast surfaces for vulcanization—Screw 
presses Pages 407 to 435 
CHAPTER XXII 
VULCANITE 
Rubber — Caoutchouc — Formulas for dental rubbers — Vulcanizable rubbers em- 
ployed for denture bases—Pink rubber employed for gum facing—Pink gran- 
ular gum facing—Chemical constituents of rubber—Chemistry of vulcaniza- 
tion—Porosity of vulcanite and how to obviate it—Closing flasks with spring 
pressure-—Dimensional changes occurring in rubber during vulcanization— 
Expansion—Contraction—Vulcanizers—Safety devices—The thermometer— TABLE OF CONTENTS 
Steam gauge—Table of steam pressure—Gas regulators—Time regulators— 
The safety valve—Vulcanization of eases in which automatic flask closing 
devices are used—Vulcanization of cases in whieh flasks are closed and bolted 
before vulcanization—Summary of facts of importance in regard to time of 
vulcanization—Removal of the flask from vulcanizer—Removal of denture 
from flask—Finishing the denture—Reproduction of the rugae—Use of cal- 
ipers—Final polishing of the denture—Finishing touches—Final fitting in the 
mouth—Finishing the palatine surfaces of a denture—Construction of a full 
upper or lower denture—Upper cases—Lower cases. 
THE GYSI SYSTEM OF ANATOMIC APPLIANCES 
Application in denture construction—Registering the forward condyle movement— 
Mounting casts on the articulator—Registering the incisor path—Registering 
the lateral condyle paths—Angular inclination of the lateral condyle paths— 
Subsequent steps in denture construction Pages 436 to 475 
CHAPTER XXIII 
CONSTRUCTION OF PARTIAL DENTURES 
Various types—Planning a partial denture—Baseplates for dentures—Partial den- 
tures of vulcanite—Technic of construction of partial upper dentures of vul- 
canite without clasps—Taking the protrusive bite—Selecting and grinding 
the teeth—Waxing the case—Flasking—Partial upper dentures of vulcanite 
with clasps—Partial lower denture of vulcanite—Mounting casts on occluding 
frame—Registering condyle paths-—Arranging teeth—Flasking case—Partial 
lower gold base dentures-—Forming the finishing shoulder for vulcanite— 
Adjusting the shoulder wire—Extent to whieh the wire is applied peripher- 
ally—Lingual bar dentures—Relation of lingual bar to oral tissues—Forms 
of lingual steps in lingual bar eases—Variation in form of 
connection between lingual bar and clasps—Soldering clasps and bar in correct 
relation to each other—Taking the wax bite—Taking the impression—Arti- 
ficial stone for casts in partial cases—The lingual bar combined with gold 
saddles—-Settling of dentures from use—Compensating for settling of gold 
base saddles—The Roach continuous loop clasp—Technic of construction— 
The open loop clasp—The Balkwill clasp—The Roach ball and tube attach- 
ment—Application of the Roach attachment — The Morgan attachment — 
Technic of application—The Condit attachment—The Gilmore attachment— 
Technic of application—Adjustment of clasps to bars—The palatal arch bar— 
The Kelly attachment—Technic of application—The Griswold attachment— 
Denture balance. 
FORMS OF PORCELAIN TEETH 
Plain teeth—Means of anchorage—Plain teeth for vulcanite work—Advantages— 
Objections—Diatoric teeth—Countersunk pin teeth—Ash’s tube teeth—Plain 
plate teeth—Various forms of plain teeth—Ash’s flat back repair facing— 
Ash’s helix tooth—Saddle back teeth-—Continuous gum teeth—Gum teeth for 
vulcanite work—Gum teeth for metal work—Proportionate parts of teeth— 
Ridge lap—Shut—Bite—The tooth shade guide—Application of the tooth 
shade guide in practice Pages 476 to 550 
CHAPTER XXIV 
CELLULOID DENTURES 
Discovery of celluloid—Composition — Manufacture — Advantages — Comparative 
strength of celluloid and vulcanite—Disadvantages—General methods of manip- 
ulation—Construction of the wax model denture—Flasking—Cutting the waste 
gates—Clearing the matrix—Selection of blank—Pressing the case—Eemoval 
from flask—Finishing—General remarks—Casts for celluloid eases 
Pages 551 to 560 TABLE OF CONTENTS 
CHAPTER XXY 
Fracture of vulcanite base—Reassembling a fractured baseplate—Securing cast— 
Method of joining the fractured pieces—Forming a bevel joint—Technical 
steps in repairing a median line fracture—Method of flasking case—Replacing 
a displaced tooth by vulcanization—Replacing by casting—Replacement by 
fusible metal in dovetail—Repairing with amalgam—Repair involving substi- 
tution of new tooth—Preliminary dovetailing of the denture base—Substi- 
tuting artificial for lost natural teeth in partial cases—Repairing gum section 
cases—Substitution of a baseplate—Construction of the matrix—Removal of 
teeth from old baseplate—Forming the wax baseplate—Modified methods of 
reconstruction—Mounting casts and old dentures on occluding frame—Form- 
ing the matrix—Forming the wax baseplate—Correcting imperfect adaptation 
by substitution of new base—Correcting adaptation by addition of new rub- 
ber to old base—Correcting adaptation with rubber paste—Correcting adapta- 
tion with Furlong’s plastic rubber—To correct occlusions when adaptation is 
satisfactory Pages 561 to 587 
REPAIRING VULCANITE DENTURES 
CONTINUOUS GUM DENTURES 
CHAPTER XXYI 
Advantages—Disadvantages—Technic—Forming the baseplate—Fitting baseplate 
to mouth—Reinforcing the baseplate—Forming the finishing shoulder for 
porcelain—Reswaging and cleansing the baseplate—Developing the occlusion 
and contour model-—Continuous gum teeth—Selection and arrangement of the 
teeth—Trial of the wax model denture in the mouth—Developing the contour 
matrix—Investment of the wax model denture—Fitting metal support be- 
tween teeth and baseplate—Supporting the teeth with wire—Continuous gum 
body and enamel—Preparation of the body—Application of body to teeth 
and baseplate-—Support for continuous gum cases while fusing—Porcelain 
furnaces—First baking of the case—Second baking—Preparation of case for 
third baking—Application of the gum enamel—Fusing the enamel—Special 
uses of porcelain—Interstitial blocks of porcelain—Gum sections—Construc- 
tion of gum section blocks for special cases Pages 588 to 624 
CHAPTER XXVIT 
CROWN WORK 
Preliminary considerations—Structures of the teeth and investing tissues—Physio- 
logical relations—Oral pathological conditions—Therapeutic methods of treat- 
ment of diseased conditions—Local anaesthetics—Treatment after setting a 
crown—Anatomic and esthetic forms of teeth—Flare of the axial surfaces of 
bicuspids and molars—Cutting molar and bicuspid bands by the conic system 
-—Stress—Hygienic requirements of crowns. 
PORCELAIN-FACED CROWNS FOR THE ANTERIOR TEETH. 
Technic of construction of a porcelain-faced crown—Upper central incisor—Devit- 
alization, treatment and filling of root canal—Removal of remaining portion 
of natural crown—Preparation of root—Removal of enamel—Smoothing root 
periphery with files—General form of prepared root—Testing—Flare of root 
surfaces-—Securing measurement of root periphery—Measuring and cutting 
band for root cap—Forming and soldering band—Sweating band—-Scribing 
band to gingival outline—Fitting scribed band to root—Trimming band to 
proper width—Construction of root cap—Soldering band to disc—Removing 
peripheral excess of disc—Construction of cap by indirect method—Taking 
impression of root—Constructing the root die—Imbedding die in swaging 
ring—Swaging root cap—Fitting cap to root—Enlarging root canal for recep- 
tion of dowel—Countersinking canal opening—Indenting eap in countersunk 
area—Perforating root eap for reception of dowel—Forcing dowel through 
cap into root canal—Maintaining correct relation between dowel and eap XIV 
TABLE OF CONTENTS 
while removing from root—Investing the cap and dowel for soldering—Tak- 
ing bite and impression—Use of face bow in crown work—Details of taking 
bite-—Securing an impression in plaster—Production of cast from impression 
—Attaching casts to occluding frame—Selection of facing—Grinding faeing 
to root cap—Beveling incisal edge of facing—Change of color in porcelain 
due to metal backing—Backing facing with gold—Perforating backing for 
pins—The Mason spacing calipers—The Young plate perforator—Adapting 
the backing to facing by burnishing—Swaging the backing—Fixing backing 
to facing—Fitting backed faeing to root cap—Investment of the assembled 
crown for soldering—Trimming investment preparatory to soldering—Re- 
moval of wax—Applying the flux—Developing the lingual contour of crown 
with solder—Finishing the crown—Setting the crown—Removal of excess 
cement—Setting a crown temporarily—Removal of a crown or bridge set with 
gutta-percha. 
DIFFERENT METHODS OF APPLYING PORCELAIN FACINGS AND RE- 
PLACEABLE TEETH IN SINGLE CROWNS AND DUMMIES 
FOR BRIDGES 
Interchangeable tooth facings—Steele’s facings—Application to anterior teeth— 
Application to posterior crowns—Technic for cast dummies—Construction of 
dummies with swaged cusps—Reflecting the backing over cervical margin of 
porcelain—Utilizing long pin plate teeth for removable facings-—The Evslin 
interchangeable tooth—Technic for anterior crowns—Technic for posterior 
crowns—Technic for anterior dummies in bridgework—Interchangeable teeth 
—The Goslee tooth—Technic of application in crown and bridge work—The 
Gardner replaceable tooth—Application in crown and bridge work—The Mer- 
ker replaceable tooth—Diatorie teeth used as replaceable teeth. 
FULL-CONTOURED PORCELAIN CROWNS 
Fixed dowel crowns—Technic of plain Logan crownwork—Adapting crown to root 
—Securing peripheral adaptation of crown base to root—Setting the crown— 
The banded Logan crown—Technic of application—Assembling the several 
parts — Investing—Soldering—Finishing—The Davis crown—Application of 
plain Davis crown—Reducing peripheral shoulder—General modification of 
crown by grinding—Setting the crown—The Davis crown in bridgework—The 
cast base Davis crown—Technic of a cast base crown—The banded Davis 
crown—Technic Pages 625 to 734 
CHAPTER XXVIII 
THE GOLD SHELL CROWN 
Advantages—Disadvantages—Where indicated — Modifications — Technic of con- 
struction—Preliminary preparation of tooth or root—Restoring badly decayed 
natural teeth for anchorage purposes—Amalgam restoration—Cast restora- 
tion—Cases of excessive restoration—Wedging—Preparation of tooth for 
band—Reduction of occlusal surface-—Reduction of axial wall—General form 
of prepared tooth or root—Testing correctness of root preparation—Securing 
peripheral measurement—Determining width of band—Cutting band—Cutting 
a cone band—Soldering—Pitting band to root—Contouring—Forcing band to 
position on root—Taking the bite—Mounting the bite on occluding frame— 
Developing cusps of crown in plaster—Typical forms of natural teeth—Upper 
right first molar—Lower right first molar—Lower right second molar—Upper 
left first bicuspid—Upper right second bicuspid—Lower left first bicuspid— 
Lower left second bicuspid—Reproducing the cusp surfaces in gold—Construc- 
ting the counterdie—Direct method—Indirect method—Developing a counter- 
die with Metalline compound—Swaging the cusps in an open counterdie— 
Removal of peripheral surplus of gold—Adapting occlusal cap to band—Devel- 
oping the marginal ridges of crown on axial band—Developing the cusp sur- 
faces in a swager—Assembling and soldering the band and occlusal cap— 
Finishing the crown—Setting—Casting the cusps—Cast crowns—The shoulder 
crown—Preparation of the natural tooth—Construction of the crown—Seam- TABLE OF CONTENTS 
XV 
less crowns-—-The matrix method—Swaging the crown—The die method—Swag- 
ing the crown—Finishing—Reproducing natural tooth forms in inlay wax 
Pages 735 to 782 
CHAPTER XXIX 
BRIDGEWORK 
Engineering principles—Application of stress to substructure of a bridge—The 
arch bridge—Girder or truss bridges—Pontoon bridges—Cantilever bridges. 
DENTAL BRIDGEWORK 
General classification of bridges—Distinction between fixed and removable bridges 
—Fixed bridges—-Fixed bridges so constructed as to be removable—Fixed 
saddle bridges—Individual saddles—Sanitary bridges—Extension bridges— 
Important factors to be considered in planning fixed bridges—Abutments and 
piers—Preparation of abutment and pier roots—Inlay abutments—Displace- 
ment of inlay abutments. 
APPLICATION OF FIXED BRIDGEWORK 
Technic—Requirements of dummies—Construction—Variation in the forms of 
dummies—Assembling the bridge—Investment—Soldering—Finishing — Set- 
ting. 
THE CARMICHAEL ATTACHMENT 
Construction—Finishing—Modified technic—Application to cuspid and bicuspid 
teeth. 
REMOVABLE ATTACHMENTS FOR FIXED BRIDGES 
The Corcoran attachment—Application—Construction—The Heddy attachment. 
REMOVABLE BRIDGES 
Attachments—Telescoping crown—The split dowel crown—Assembling the parts— 
Constructing the crown base—Constructing the saddle—Attaching the teeth— 
Finishing the bridge—Setting the root caps—-General remarks—The Goslee 
inlay clasp attachment-—The split dowel—Lingual half crown—Construction— 
Finishing the attachment—Modification of the telescoping molar crown. 
REPAIRING CROWNS AND BRIDGES 
Replacing porcelain facings—The Ash flat back repair facing—The Dimelow 
facing—The Steele repair outfit—The Bryant repair outfit—Long pin facings 
used in repairs—Starr’s method—Riveting facing to backing—Removing a 
banded dowel crown—Replacing facing on crown removed as described— 
Removing dowels from root canals—Little Giant post puller—The S. S. White 
crown repair outfit—Removal of a dowel from the deeper portion of a root 
canal—Removing a shell crown by slitting—Removing a shell crown by lever- 
age force—Repairing crowns, slit in the manner described—Repairing a frac- 
tured bridge Pages 783 to 848 
CHAPTER XXX 
Porcelain crown work—Indications for use—The banded, baked porcelain crown— 
Constructing root cap—Application of porcelain body—Modified forms of por- 
celain crowns—Porcelain jacket crown—Technic of construction—Taking 
impression of tooth—Constructing the die—Forming the platinum cap— 
Constructing the casts—Application of porcelain—Baking the crown—The 
“ Land Jacket Crown ”—Preparation of tooth—Construction of cap—Taking 
PORCELAIN CROWN AND BRIDGE WORK XVI 
TABLE OF CONTENTS 
bite and impression—Selection and grinding of facing—Application and fus- 
ing of porcelain—Porcelain bridgework—General considerations—Porcelain 
bridge construction—Preparation of roots or teeth—Construction of cap and 
shell crowns for abutments—Construction of saddle—Locating and fitting 
truss bars—Soldering—Application of body—Fusing the porcelain—Finishing 
and setting the bridge—Various types of metal structures. . .Pages 849 to 876 
CHAPTER XXXI 
Porcelain—Early application of porcelain in denture construction—Correction of 
warpage in the all-porcelain denture—Basic ingredients of porcelain—Kaolin 
—Preparation—Feldspar—Preparation—Silex—Preparation — Properties — 
Proportions-—Oxides of metal used in coloring porcelain—Gun enamel— 
Crown bridge and inlay porcelains—High and low fusing porcelain bodies— 
Comparative value. 
PORCELAIN AND METALLIC INLAYS 
PORCELAIN INLAY WORK 
Advantages—Objections—Friability—Constructive difficulties — Inlay retention— 
Warpage of the matrix—Annealing the foil—Warpage due to improper sup- 
port—Careless handling—Locations favorable for porcelain inlays—General 
rules for cavity preparation—Details—Gingival third cavities in the anterior 
teeth—Proximal cavities in the anterior teeth not involving angles—Buccal 
cavities—Proximal cavities in anterior teeth involving angles—Bicuspid and 
molar cavities involving an axial and an occlusal surface—Restoration of 
incisal edges and angles—Production of the matrix—Burnishing—Removal— 
Final annealing—Selection—Application and fusing of the porcelain—Selec- 
tion of shade—Mixing the porcelain—Application to the matrix—Furnaces 
and appliances used in fusing—First baking—Second baking—Deleterious 
effect of overfusing—The shadow problem—Removing the matrix—Etching 
the cavity surfaces of the inlay—Setting. 
GOLD INLAYS 
Cavity preparation for gold inlays—Outline form—Resistance form—Retention 
form—Pin anchorages—Convenience form—Removal of any remaining cari- 
ous dentine-—Finish of enamel walls—Toilet of cavity—Some special methods 
of cavity preparation. 
THE MATRIX METHOD OF INLAY PRODUCTION 
Direct method of producing a matrix—Variation in method—Indirect method of 
forming the matrix. 
CAST GOLD INLAYS 
General remarks—Physical properties of the materials employed in easting—Ex- 
pansive and contractile forces—Principal sources of error in inlay construc- 
tion—Waxes—Paraffin—Effect of combining wax and paraffin—Essential 
properties of a wax—Elastic properties of wax—Investment materials—Ex- 
pansion of investment ring and investment material—Essential properties of 
an investment material—Dimensional changes in gold due to temperature 
changes—Compensating for errors due to contraction of gold—Result of con- 
traction of gold on inlay adaptation—Technic of cast gold inlays—Forming 
the. wax model—Investment of the wax model—Drying out the investment and 
eliminating the wax—Variation in the method of preparing the invested case 
for casting—The casting of gold—Rough finishing the castings—Settling the 
inlay—Finishing Pages 877 to 935 TABLE OF CONTENTS 
XVII 
CHAPTER XXXII 
AN OUTLINE OF METALLURGY 
Facts, hypotheses, theories and speculations—Discovery of elements by means of 
the spectroscope—The mutability of matter—Brief outline of recent discover- 
ies—Elemental gases—Discovery of the X-ray—Discovery of radio-active 
substances—Decomposition of radium compounds—Character of the emana- 
tions from radio-active substances—The degradation of copper—Debasement 
of various substances into hydrogen-—Summary of statements presented— 
The elements arranged in the order of their discovery—Arranged in the order 
of their atomic weights—The Kinetic constitution of matter—The vibration 
of matter—The unequal distribution of elements—Elements and their atomic 
relation to each other—Prout’s hypothesis—The triads of Dobereiner—The 
octaves of Newlands—The periodic system of Mendeleeff—New elements— 
The elements considered in groups—The elements considered in series—Metals 
—Metalloids—Forms of matter—Occurrence of metals — Minerals — Native 
metals—Ores—Noble metals—Base metals—Physical properties of metals— 
Atomic weight—Specific gravity—Melting point—Malleability—Ductility— 
Tenacity—Annealing—Tensile strength — Elasticity — Flow — Conductivity— 
Heat and electricity—Exceptions—Specific heat—Expansion—Co-efficient of 
expansion of substances—Color—Welding—Welding copper to iron-—Alumin- 
othermy—Temperatures common and extraordinary—Soldering—Conditions 
essential to successful soldering—The structure of flame—The Bunsen flame— 
The blowpipe flame—Micro-structure of metals-—Alloys—Matthiessen’s theo- 
ries as to the nature of alloys—Affinity of metals for each other—Liquation- 
Object in alloying metals—Eutectic alloys—Amalgams—Specific gravity of 
alloys—Table of some of the physical properties of fifteen metals. 
Occurrence and distribution—Placer deposits—Placer mining—Vein gold—Extrac- 
tion of gold from ores—Chlorination process—Cyanide process—Physical 
properties—Preparation of pure gold—Treatment of scrap plate—Allowing 
gold—Eeduction of gold—Boser’s rule—Gold solders—Table of mixed carata- 
tion—Clasp gold—Platinum solder. 
SOME RECENT WORK CONCERNING GOLD ALLOYS 
By Dr. L. J. Weinstein 
Author’s preface—Introduction—Binary alloys—Necessity of a knowledge of 
binary alloys. 
Section I—Gold and Silver 
Effect of silver upon gold—Gold and copper—Gold and platinum—Gold and pal- 
ladium—Gold and the metals in group II—Iridium—Osmium—Rhodium— 
Gold and metals in group III—Gold and metals in group IV. 
Section II—A New Series of Alloys 
Gold for crown, bridge and plate work—Gold plate No. 2—Alloys for prosthetic 
casting—Gold for inlay casting. 
Section III—Clasp Metals 
Composition of clasp metalsi—Results of rolling and annealing on elasticity of 
clasp gold of various formulae. 
Section IV—Gold Solders 
Alloys of gold with metals in group III—Formulae for gold solders. 
Section V—Compounding of Gold Alloys 
Difficulty of alloying gold with platinum in small quantity—Necessity for pre- 
venting oxidation in gold and copper alloys. 
GOLD TABLE OF CONTENTS 
Section VI—Refractory Materials 
Investment compounds for soldering—Plaster of Paris—Powdered silex—Formula 
for investment compound (soldering)—Investment compounds for easting— 
Hot or cold mold, using illuminating gas and compressed air blowpipe—Hot 
or cold mold, using illuminating gas and nitrous oxide or oxygen blowpipe— 
Compounding of investment materials—Heating of investments. 
Section VII—Fluxes for Soldering and Casting 
Formula for soldering flux—Reducing flux—Formula for reducing flux—Oxidizing 
flux—Formula—Formula for soldering flux (substitute)—Table No. 4— 
Melting point of the new series of alloys and standard dental golds—Some of 
the applications of the new series of alloys in the Peeso system of removable 
bridgework—Construction of floors, bands and inner caps—Outer half bands 
and telescope caps—Inlay abutments—Construction of saddles—Construction 
of dummies. 
IRON 
Occurrence in nature—Reduction of iron ores—Production of wrought iron—Pro- 
duction of steel—The Bessemer process—The cementation process—Harden- 
ing and tempering of steel. 
PLATINUM 
Discovery—Distribution—Occurrence-—Physical properties—Fusing point—Uses— 
Alloys—Dental alloy—Platinum solder and clasp metal. 
IRIDIUM 
Physical properties and uses — Silver — Ores — Reduction — Amalgamation—Wet 
Method— Lead Method—Uses in dentistry—Alloys of silver—Uses in photog- 
raphy—Chemistry of photography. 
COPPER 
Ores—Reduction-uses—Alloys—Brass—Bronze. 
ALUMINUM 
Occurrence—Reduction—Physical properties—Soldering-uses—Alloys. 
ZINC 
Ores—Reduction-properties—Uses. 
CADMIUM 
Occurrence—Reduction-uses—Alloys. 
LEAD 
Occurrence—Reduction-properties—Uses—Alloys. 
TIN 
Occurrence—Reduction-properties—Uses—Haskell’s babbitt metal. 
MERCURY 
Occurrence—Distribution—Compounds—Alloys—Properties—Reduction. 
NICKEL 
Properties—Alloys—Uses. 
BISMUTH 
Properties—Alloys—Uses. 
ANTIMONY 
Properties—Alloys—Uses. 
TUNGSTEN 
Properties—Uses. TABLE OF CONTENTS 
XIX 
MEASUREMENT OF PLATE AND WIRE 
The unit of measurement of gauges—Lack of uniformity of the various gauge sys- 
tems—The Birmingham gauge—Discrepancies of the Birmingham gauge—Tne 
Brown and Sharp gauge—Forms of gauges—The jeweler’s gauge—The plate 
and wire gauge—The micrometer caliper—Various systems of wire and plate 
gauges and their equivalents in thousandths of an inch Pages 936 to 1076 
A BRIEF HISTORY OF PROSTHETIC DENTISTRY 
CHAPTER XXXIII 
The Ebert; papyrus—Antiquity of the papyrus—(luerini’s History of -Dentistry— 
The Fhomicians—Effect of Egyptian civilization on Fhcemcia—One of the 
most ancient specimens of prostnetie art—The Etruscans—Etruscan dental 
art—First references in history to prosthesis—-Dentistry among the ancient 
Hebrews—blow progress 01 uental prosthesis in the middle ages—First ref- 
erence to the use of models—First reference to full lower dentures—First rec- 
ord of application of mineral substances for dentures—Eetention of partial 
dentures without tne use ot ligatures or wires—Faucnard's writings—Trans- 
plantation of natural teeth—Crown work in Fauehard’s time—Mediaeval 
Dridgework—Full dentures—Construction of full dentures by Fauehard— 
Summary of Fauehard 7s work—Eeneffcial influence of Fauehard7s writings 
upon the profession—First work eonffned exclusively to dental prosthesis— 
First mention of plaster—First mention of gold bases—Implantation of teeth 
—Berdmore’s relerence to artilicial dentures—i'nncipal materials used as 
denture bases—First suggestion of porcelain work—Hu Chateau's efforts in 
porcelain work—The work of Dubois de Chemant—Introduction of single 
teeth and blocks of porcelain—Introduction of porcelain in the United btates 
—First manufacturer of porcelain teeth in America—Introduction of gold for 
denture bases—Hies for swaging metal bases—First use of cast denture bases 
—Special forms of teeth for use with cast bases—Dental vulcanite litigation— 
Collodion and celluloid as denture bases—Vulcanizing rubber between metal 
surfaces—Denture bases produced by electro-deposition of gold and silver. 
ARTICULATORS. 
Casts extended distally to form articulating surfaces—Evans articulator—Bonwill 
articulator—Plain line articulator—Starr articulator—Hayes articulator— 
First suggestion of the face bow—Study of condylar movements—Walker’s 
research work—Walker’s anatomical articulator—Facial clinometer—Gntman 
articulator—Snow face bow—Kerr articulator—Christensen’s work—Snow 
anatomical articulator—Schwarze articulator—Gysi’s work and anatomical 
appliances. 
Pivot teeth of De Chemant—The grooved flat back facing—Ash’s tube teeth—The 
Wood pivot tooth—The Smith crown—The Clark crown—The Lawrence-Foster 
crown—-The Dwindle crown—The Wood crowns—The Morrison crown—The 
Black crown—The Bean crown—The Mack crown—The Beers crown—The 
Gates crown—The Richmond crown—The Gates-Bonwill crown—The Biittner 
crown—The How crown—The Weston crown—The Logan crown—The Brown 
crown. 
CROWN WORK 
BRIDGEWORK 
The Bing bridge—Webb’s work—Litch’s work—Williams’ work—Starr’s work— 
Basis of our present system of bridgework—Porcelain bridges—Removable 
bridges. 
INLAYS 
First recorded attempts in filling teeth—First mention of inlays in dental liter- 
ature—Prehistoric inlay work—The beginning of modern inlay work—Brief 
summary of inlay work beginning with 1820—Land’s method of porcelain XX 
TABLE OF CONTENTS 
inlay work—Bing’s metallic facing—Rollins ’ method—Dunn’s method— 
Stokes’ method—Ames’ method—Various methods of inlay production in 
recent years—Alexander’s method—Slow progress of inlay work—Progress 
of gold inlay methods. 
Analysis of the casting process—Forming models in wax of the casting to be pro- 
duced—Method of forming a sprue or pouring gate—Enclosing the wax model 
in a single investment—Eliminating the wax pattern by heat—Fusing the 
metal in close proximity to the mold—Applying pressure to the fused metal 
to induce sharpness of detail in casting—Pioneers in the production of cast 
work—The Blandy process—Bean’s method of casting aluminum—Sauer’s 
method—Reese’s method—Hayford’s method—The Watt’s flask—Martin’s 
method of casting—The Carroll method—The Zeller casting appliances—The 
Fenner casting appliances—Harper’s cast crowns and bridges—The Alex- 
ander method—The Hollingsworth method—Flask designed by writer—Phil- 
brook’s method—Schottler’s clinic—The Lentz casting process—The Ollen- 
dorf casting process—Summary of progress in casting operations—Causes of 
failure in casting operations—Taggart’s method of casting—Recent appli- 
ances—The Solbrig casting pliers—The Biber casting appliance—Summary 
of foregoing facts Pages 1077 to 1176 
INCEPTION OF THE WAX MODEL METHOD CHAPTER I 
PROSTHETIC DENTISTRY 
GENERAL REMARKS 
The science of dentistry pertains to the recognition and 
treatment of diseases of the teeth and oral tissues, of the gen- 
eral neuritic conditions of the head and neck that may have 
their direct origin in, or be indirectly connected with, the fifth 
cranial nerve, and of the repair and replacement by operative 
or prosthetic procedures, of the partial or complete loss of 
the teeth through accident or by disease. 
Prosthetic dentistry is that branch of dental science which 
treats of the various methods of replacing the lost organs of 
the mouth in whole or in part, the artistic and mechanical 
processes involved in such restoration, together with a de- 
scription of the physical properties and peculiarities of the 
various materials employed. 
Specifically considered, prosthetic operations may be 
classed as follows: Construction of crowns, bridges and den- 
tures, obturators and appliances for correcting defects of the 
palate, appliances for correcting irregularities of the teeth 
and jaws, appliances for retaining in position fractured bones 
of the face when reduced, and the construction of metallic and 
porcelain inlays. 
In all prosthetic procedures the attainment of three objects 
is desirable: First, the restoration of the function of masti- 
cation; Second, the esthetic requirements should he given due 
consideration and wrought out correctly; Third, the substi- 
tute, of whatever character, should cause the wearer no dis- 
comfort. The late Dr. Pritchett concisely stated this by saying 
that in prosthetic procedures “we strive to give our patients 
dentures that are useful, will look well, and be comfortable.’’ 
RESTORATION OF THE FUNCTIONS OF MASTICATION UTILITY 
The first consideration is the most important. When 
from any cause the function of mastication is interfered with 
or impaired, the digestive organs are necessarily required to 
do an extra amount of work for which they are unfitted, and 2 
PROSTHETIC DENTISTRY 
which will eventually result in impaired digestion, systemic 
disturbances and general ill health of a more or less serious 
character. Without doubt, many lives are shortened by years 
because of the partial or total loss of this most important 
function, and in constructing substitutes for the natural teeth, 
they should be made to restore, as fully as possible, the func- 
tion of the natural organs. This point is of such importance 
as to bear repetition by restatement. Ability to masticate and 
digest food means good health and generally normal bodily 
functions, while inability to do so entails discomfort, ill health, 
disease and a curtailing of the span of life. 
The second consideration—esthetics—relates to the artis- 
tic phase of prosthesis, the ability to produce or create appro- 
priate and natural appearing devices and substitutes to take 
the place of the lost natural teeth, to reproduce by skilful 
technic not only a successful masticatory apparatus, but to 
restore lost facial contour as well. 
The principal part of the face to suffer change by the loss 
of the teeth, and the consequent absorption of the alveolar 
process, is the mouth, although at times a considerable portion 
of the lower half of the face is modified in outline. The lips 
lose their normal pose and assume an unnatural expression, 
more or less marked in proportion to the loss of the bony 
substructure. Premature wrinkles form upon and encompass 
the mouth and cheeks, and an appearance of age, not war- 
ranted by years, sets its seal upon the subject. 
It is the province of the prosthetist to correct, as far as 
possible, the ravages occasioned by disease, and time, as well, 
and restore to the patient his normal appearance. 
To do this the prosthetist should be a master of his art — 
one who can, at will, imitate nature in her ideal, as well as 
less typical forms and moods. From the nature of his voca- 
tion, he should be an anatomist, a sculptor, an artist and an 
artisan, thorough and proficient in each field mentioned, in 
order to fulfill, in the highest degree, the requirements im- 
posed upon him by his profession. 
Many eulogistic effusions on the beauty, attractiveness 
and importance of the mouth and teeth are to be found. 
They have emanated from the artists and poets of every 
race and clime. They emphasize the high regard and even 
veneration in which these features of the face have been held 
ESTHETICS PROSTHETIC DENTISTRY 
3 
by tlie human race in general from time immemorial. The 
following are some of the selections referred to. 
Lavater, one of the early writers on physiognomy, says, 
in reference to the mouth: “The mouth is the interpreter of 
the mind and of the heart. It combines, both in a state of 
rest and in the infinite variety of its motions, a world of char- 
acters. It is eloquent even in its silence.1 ’ * * * “I conjure 
our painters and every artist whose mission it is to represent 
man, I conjure them with all my might to study the most 
precious of all our organs in all its varieties; in all its pro- 
portions; in all its harmonies.” 
“What shall I say, painters and designers, that may 
induce you to study this sacred organ in all its beauteous 
expressions, in all its harmony and proportions?” “Take 
plaster impressions of characteristic mouths (lips) of the 
living and the dead; draw after, attentively examine them, 
learn, observe, continue day after day to study one only; 
and having perfectly studied that, you will have studied 
many. * * * Among ten or twenty draughtsmen to whom 
for three years I have preached, whom I have instructed, have 
drawn examples for, not one have I found who felt as he 
ought to feel, saw what was to be seen, or could represent 
that which was evident.” * * * “I expect everything 
from a collection of characteristic plaster impressions which 
might so easily be made, were such a collection once formed — 
but who can say whether such observations might not declare 
too much. The human machine may be incapable of suffering 
to be analyzed; man, perhaps, might not endure such a close 
inspection, and, therefore, having eyes, he sees not.” Lavater 
further lays down rules for the guidance of the artist, as 
follows: 
“Distinguish in each mouth, a the upper lip, singly; b the 
under lip, the same; c the line formed by the union of both 
when tranquilly closed, if they can be closed without con- 
straint ; d the middle of the upper lip in particular, and e of 
the under lip; / the bottom of the middle line at each end, 
and lastly g the extending of the middle line on both sides, 
for unless you distinguish you will not be able to delineate 
the mouth accurately.” 
Herder, the eminent German poet and critic, says of 
this prominent feature of the face: “It is from the mouth 
that the voice issues, interpreter of the heart and soul, expres- 
sion of feeling, of friendship, and of the purest enthusiasm. 
The upper lip translates the inclinations, the appetite, the 4 
PROSTHETIC DENTISTRY 
disquietude of Jove; pride and passion contract it; cunning 
attenuates it; goodness of lieart reflects it; debauchery ener- 
vates and debases it; love and tlie passions incarnate tlieni- 
selves tliere in an inexpressible charm. ’’ 
Concerning tlie teeth, Paolo Mantegazza, the noted Italian 
anthropologist, says: “It is a flaw in beauty to have bad 
teeth; it is like a spot on the sun. Since the hygiene of the 
teeth is at the same time the hygiene of beauty, good dentists 
merit a golden statue, or at least a place of honor among the 
principal benefactors of humanity.” * * * “The most 
beautiful teeth are not enough to make a man beautiful; but 
ugly teeth would spoil the beauty of the Venus of Milo 
herself. ’ ’ 
Again reverting to Lavater’s remarks on the teeth, he 
says: “Nothing is more certain, striking or.continually vis- 
ible than the characteristics of the teeth, and the manner in 
which they display themselves.” * * * “Whoever leaves 
bis teeth foul and does not attempt to clean them, certainly 
betrays much of the negligence of his character, which does 
him no honor. As are the teeth of man, that is to say, their 
form, position and cleanliness (so far as the latter depends 
upon himself), so is his taste.” 
The loss of the teeth and consequent absorption, to a 
greater or less extent, of the bony substructure supporting 
the lips and cheeks, results in marked disfigurement. The 
exterior of the dental arch, as well as the face, is convex. 
The lips form a movable curtain or pallium, to close the oral 
opening. They are supported by the dental arches and alveo- 
lar borders. The loss of the teeth allows the lips to sink in, 
and the profile, as well as contour of the face, suffers. 
It requires a keen artistic sense to determine the correct 
lines of contour to develop in order to restore harmony in 
each individual type or cast of countenance. Too much or 
too slight convexity of the substitute will mar the symmetry 
and pose of the patient’s face, through improper support 
of the lips. The color of tlie teeth in artificial cases must 
harmonize with the color of the eyes, hair and general tone 
of the patient’s complexion. The form, size and arrangement 
of the teeth and their general treatment by grinding to simu- 
late wear appropriate to the age of the patient, must also be 
determined. No two cases will be exactly the same. Each 
factor must be studied by itself, and all of the factors con- 
sidered as a whole in every case that presents. 
The prosthetist’s highest attainment in the esthetic field PROSTHETIC DENTISTRY 
5 
consists in imitating nature so closely that his work can not 
be detected by casual or even close observation, and so well 
done that his patient does not seriously feel the loss of the 
natural teeth, or will not be disturbed by the presence of the 
substitute. 
COMFORT 
The third desirable object sought in denture construction 
is a most important one. It is possible to construct substi- 
tutes that fulfill requirements from the standpoint of utility 
and esthetics as well, and yet cannot be worn by the patient 
with ease or comfort. Imperfect adaptation of denture to 
tissues, causing undue or uneven pressure at certain points; 
extension of baseplate on palatal muscles so far as to cause 
irritation, retching, or by the contraction of the muscles, dis- 
lodgment of the substitute; impingement of the periphery of 
the denture on the labial or buccal muscles or the frena; 
rough, unpolished surfaces, particularly in the palatine por- 
tion of the denture, are some of the sources of discomfort that 
impair, and at times seriously inhibit the usefulness of other- 
wise well-constructed dentures. 
The ability to recognize such annoying conditions as men- 
tioned, and be able to anticipate and overcome them during 
constructive processes, is a most important attainment, and 
should be developed by every prosthetist. 
In entering upon the study of dentistry, the student should 
understand and thoroughly appreciate the fact that the voca- 
tion of a dentist embraces a much broader field than is usually 
accorded it by the public or the uninformed in general. Den- 
tistry is a specialty of the healing art — medicine — and has 
been so recognized from ancient times. 
Herodotus (500 to 425 B. C.), m writing of the practice 
of medicine in Egypt, says: ‘‘The exercise of medicine is 
regulated and divided amongst the Egyptians in such a 
manner that special doctors are deputed to the curing of every 
kind of infirmity; and no doctor would ever lend himself to 
the treatment of different maladies. Thus Egypt is quite 
full of doctors; those for the eyes; those for the head; some 
for the teeth; others for the belly, or for occult maladies.” 
(Guerini.) 
In this day the dentist is a scientific specialist who is con- 
stantly called upon to treat living, sensitive, vital tissue; to 
recognize and treat obscure, as well as plainly apparent dis- 
orders and diseases having their origin in, and adjacent to, 6 
PROSTHETIC DENTISTRY 
the oral cavity. In addition to such treatment, it is the prov- 
ince of the prosthetist, through highly developed mechanical 
skill, to replace teeth and parts of teeth that have been lost 
through accident or by disease. 
The knowledge, skill and handcraft necessary to carry 
out the requirements mentioned come only with close, long- 
continued and patient application. The artistic and esthetic, 
as well as the mechanical faculties, should be encouraged and 
developed in the course of study laid down in the dental 
curriculum, for the student’s success depends upon the thor- 
ough, harmonious and balanced development of all of these 
faculties. He gets out of his course only what he puts into 
it. The half-hearted acquirement of a few smattering facts 
is not sufficient in these days of strenuous competition to fit 
one for the practice of dentistry in general, or any one of its 
special branches. 
Patience, persistence, energy and enthusiasm are essential 
to success in the acquirement of a dental education, as well 
as in other departments of science. Equipped with these 
qualities, no one can place a limit to the heights attainable by 
a student or practitioner in his chosen work. The field is 
broad. Many scientific problems are still unsolved. Investi- 
gators are few and in demand. Preventive measures are 
being devised and introduced for the benefit of the patient. 
The public is being gradually educated in the principles of 
personal care of, and attention to, the teeth. Dental inspec- 
tion in public schools is being realized, and the children are 
being taught that good teeth, good health and good minds go 
hand in hand, in the order named, for without good teeth the 
health suffers and the mind and mental processes are dis- 
turbed. CHAPTER II 
BODILY FUNCTIONS 
The human body is an organism, which exhibits the phe- 
nomena of life and in and through which the vital forces act. 
The history of a living entity, its daily routine of life from 
inception to final dissolution, is one of perpetual change. 
The general epochs in the life of an individual are con 
ception, birth, a varying period of growth, a vaguely deter- 
minate period of existence unmarked by radical change, and 
finally, gradual or sudden diminution and cessation of the 
vital functions, terminating in death, with ultimate resolution 
of the organism into primal chemical elements or compounds 
In the human body during life, constant changes are con- 
tinually going on. Every mental effort, every movement of 
the body or any portion of it, the normal or abnormal, volun- 
tary or involuntary, action of the functional organs them- 
selves, call for the expenditure of energy and result in loss 
of substance. These changes are known as metabolism. 
Every normal living organism contains within itself a 
varying amount of reserve force or stored up energy ready 
for use on demand. To maintain equilibrium and conse- 
quently a normal condition of health, the stock of energy when 
depleted, and the loss of substance as it occurs, must be 
replenished. 
In the human organism this repair of loss is accomplished 
by taking into the body substances known as food, capable 
of being masticated, digested, absorbed, circulated and assimi - 
lated. Food is composed, more or less, of extraneous matter 
That is, the intrinsic or nutritive elements contained therein, 
capable of being assimilated, or replacing waste tissue and 
developing heat, energy, etc., represent in bulk only a portion 
of the material taken into the body as food. 
Bulky, and in fact all varieties of food, when broken up 
and finely divided, are more readily acted upon by the saliva, 
the gastric juice and intestinal digestive fluids, and the nutri- 
METABOLISM 
7 8 
BODILY FUNCTIONS 
tive elements more quickly appropriated than when taken into 
the system unprepared by mastication. 
IMPAIRMENT OF BODILY FUNCTIONS 
The bodily functions are carried on by various organs, 
each of which performs its part in the maintenance of life. 
Some of the organs are of minor importance. Their functions 
may cease or the organs themselves may atrophy or be oblit- 
erated by disease or traumatism, and yet the general health 
of the individual may not be seriously impaired. 
The organs of the special senses are examples of this type, 
as the loss of hearing, the sense of smell, taste or eyesight 
are of common occurrence, and although the loss of any one 
of these senses may be keenly felt, yet existence may be pro- 
longed for many years, with a greater or less degree of 
comfort. 
Other organs are of vital importance. Should they from 
any cause be destroyed or cease to carry out their functions, 
the result usually involves serious and permanent impairment 
of health, or even the cessation of life itself. The respiratory, 
circulatory, masticatory and digestive organs are examples of 
the type under consideration. 
The Mouth 
The cavity of the mouth contains those tissues and organs 
which are of special interest to the oral surgeon and dentist. 
Through it all food substances and liquids are taken into the 
body. By the organs contained therein the food is triturated, 
insalivated, and prepared for deglutition. Prom it articulate 
sounds proceed. 
In the oral cavity many forms of bacteria find lodgment, 
and, on account of the heat and moisture present, it furnishes 
a favorable soil for their propagation and growth. The aver- 
age mouth usually contains from twenty to fifty varieties of 
micro-organisms, some harmless, while others are pathogenic 
in character. The latter, while not always, are frequently 
present, ready to exhibit destructive energy when favorable 
conditions develop. For this reason the mouth, under normal 
conditions, although a neutral focus of infection, is a constant 
menace to the health of the individual, unless given proper 
care and attention. 
ITS IMPORTANCE IN THE HUMAN ECONOMY BODILY FUNCTIONS 
9 
The mouth consists of two parts, viz., the vestibule and 
the oral cavity proper. 
One of the most prominent features of the face is the 
external orifice of the mouth. This is a transverse fissure 
bounded above and below by the upper and lower lips, respec- 
tively. At their extremities they unite to form the commis- 
sures. Internally they are covered with mucous tissue, and 
externally with integument. The orbicularis muscle, which 
largely develops mobility and closes the lips, is situated be- 
tween the internal and external surfaces. Composed as they 
are of two thick, fleshy folds, and containing within themselves 
no bony support, they settle inward and backward when loss 
of the teeth, and the resultant absorption of the alveolar proc- 
ess, occurs. It is the province of the prosthetist to restore 
such deformity of the face by means of suitably constructed 
and contoured substitutes as conditions require. 
THE LIPS 
The vestibule is that portion of the oral cavity which lies 
external to the teeth and alveolar arches, and internal to the 
cheeks and lips. It extends from the space just back of the 
third molar on one side, through which it communicates with 
the oral cavity proper, around the labial and buccal surfaces 
of the teeth and arches, to the corresponding space on the 
opposite side. Its upper and lower boundaries are terminated 
by the attachment or blending of the mucous membrane of 
the cheeks and lips with that covering the upper and lower 
alveolar arches. 
When the jaw and lips are closed, and the teeth are in nor- 
mal occlusion the mucous membrane of the cheeks and lips 
rests against the outer surfaces of the teeth and arches, and 
no appreciable space between these surfaces is noticeable. By 
inflation from within, or by parting the lips and distending 
the cheek walls, the cavity of the vestibule becomes apparent. 
The upper and lower peripheral circumferences of the ves- 
tibule are known as the superior and inferior cul de sacs. 
The salivary secretions from the parotid glands are dis- 
charged into the vestibule opposite the second upper molar 
through the ducts of Stenson. 
THE VESTIBULE 
THE ORAL CAVITY PROPER 
The oral cavity is hounded anteriorly and on each side by 
the lingual surfaces of all the teeth and the alveolar arches; 10 
BODILY FUNCTIONS 
above by the palatal vault, including both the hard and soft 
palate; below by the tongue and its mucous membrane re- 
flected against the lingual surfaces of the lower alveolar arch; 
posteriorly it merges into the pharyngeal space through the 
isthmus of the fauces. The tongue and palatal muscles acting 
conjointly form a temporary distal boundary, or wall, to the 
oral cavity as occasion requires, in the act of mastication, 
deglutition or phonation. 
The entire interior of the oral space is lined with mucous 
membrane, being ‘ ‘ composed of a layer of stratified squamous 
epithelium, supported upon a tunica propria, which is usually 
described as composed of two parts — the papillary layer and 
the reticular layer. The epithelium and the tunica propria 
make up the mucous membrane proper, which is supported 
upon a submucous layer composed of a coarse network of 
white and elastic fibres, containing the larger blood vessels” 
* # * 
MUCOUS MEMBRANE 
EPITHELIUM 
“The stratified squamous epithelium is provided with a 
horny, or cornous layer only in the portions covering the 
alveolar process and the hard palate, or in other words, where 
the submucosa is firmly attached to the periosteum. In these 
positions the horny layer consists of dead cells which have 
lost their nuclei, and whose cytoplasm lias been converted into 
keratin or horny material.” (Noyes’ Histology, p. 323.) 
The mucous membrane is continuous over cheeks and gum 
tissue and extends from the lips to, and merges with, that in 
the naso-pliaryngeal space. 
THE PALATINE VAULT 
The vault of the mouth is formed anteriorly by the hard, 
and posteriorly by the soft palate. The lingual surfaces of 
the alveolar arch form the lateral and anterior boundaries of 
the vault, while the free margin of the soft palate forms the 
posterior boundary. 
THE BONY STRUCTURE OF THE HARD PALATE 
The hard palate is formed by the junction of the palatine 
processes of the superior maxillae and the horizontal plates 
of the palate bones. These processes unite in the median line BODILY FUNCTIONS 
11 
to form a suture or linear ridge called the raphe. Sometimes 
this ridge is quite prominent and irregular, and renders the 
fitting of dentures a difficult task. 
PALATINE FORAMINA 
Just back of the central incisors in the median line is sit- 
uated the anterior palatine fossa, in which are seen the orifices 
of four small canals. Two of these, the foramina of Stenson, 
are located one on either side of the median suture, and trans- 
mit the anterior palatine vessels and nerves. Situated just 
inside the alveolar arch and about opposite the location of the 
third molars on either side, two, and sometimes three, open- 
Fig. 1.— The Maxilla, with Full Complement of Teeth Showing Anterior 
and Posterior Palatine Foraminae 
ings are seen. The larger, or anterior of these canals trans- 
mits the posterior palatine vessels and nerves, which pass 
forward in grooves parallel with the inner alveolar plates. 
These bony grooves are nearly always plainly marked at their 
beginning, but usually become indistinct and finally obliterated 
about opposite the bicuspid teeth. The vessels and nerves 
coming forward from these canals supply the mucous tissues 
of the hard palate. Some filaments of the nerves and branches 
from the arteries pass forward and anastomose with the ves- 
sels and nerves transmitted through the anterior palatine 
canal. 
When denuded of the soft tissues covering it, the bony 
surface of the palate presents a more or less irregular appear- 
ance. Frequently sharp, well-defined points of bone, and 
occasionally nodules of varying sizes, are present, sometimes 12 
BODILY FUNCTIONS 
along the margins of the grooves which transmit the palatine 
vessels, but more commonly at various places on the alveolar 
border. The sore spots and areas which so often develop on 
introducing a denture are often traceable to the presence of 
such irregular points and nodules, which, under pressure of 
the base plate, naturally become sources of irritation to the 
overlying soft tissues. It is advisable in such cases to relieve 
the pressure of the denture over these areas, as well as oppo- 
site the openings of the posterior and anterior palatine canals, 
especially when the mucous and submucous tissues are thin, 
hard and unyielding. Excessive continued pressure on the 
vessels and nerves, transmitted through these canals, will un- 
doubtedly lower the nutrition of the parts supplied, tempo- 
rarily at least, and cause unnecessary discomfort and pain to 
the wearer of the denture. 
THICKNESS OF THE PALATINE PROCESS OF THE MAXILLAE 
The palatine of the superior maxilke by their 
upper surfaces form the floor of the nasal fossa. The thick- 
ness of the bony partition between the oral and nasal cavities 
varies in different individuals. In some specimens of young 
adults the thickness of these plates scarcely exceeds 1-100 of 
an inch at a point about midway between the raphe and the 
outer wall of the nasal fossa. 
The extreme thinness of the palatine processes in this 
location converts them into sounding boards, so to speak, and 
gives a finer, clearer quality to both nasal and oral sounds 
than would be possible if the bony floor were thick. Base 
plates, whether of metal or vulcanite, frequently tend to 
impair tone quality, and therefore care should be taken in 
denture construction to avoid unnecessary bulk in the vault 
portion. 
Strength is given to the thin, bony vault on the nasal side 
in its central portion, by the junction of the nasal septum with 
the palatine processes at the median suture opposite and above 
the raphe. 
THE MUCOUS MEMBRANE OF THE PALATE 
The mucous membrane covering the hard palate and alveo- 
lar arches is provided with a horny or cornuous layer, as 
before stated. This layer is less sensitive than the ordinary 
mucous membrane, as well as firmer, denser and more fibrous. 
These characteristics render it less liable to injury during the BODILY FUNCTIONS 
13 
mastication of hard varieties of food, and less irritable to 
friction or stress than are membranes devoid of the eornuous 
layer. 
THE RUG2E 
Situated just back of the central incisors and slightly in 
front of the position of the anterior palatine canal, is a small 
pear-shaped eminence called the papilla of the palate. Ex- 
Fig. 2.— The Tongue, Showing Circumvallate Papilke (See p. 14) 
tending posteriorly from this, and following the raphe, is also 
a ridge of mucons tissue. 
A number of smaller irregular ridges pass out laterally, 
usually running obliquely, but not necessarily paralleling each 
other, sometimes extending back as far as the second bicuspid. 
These are called plicce palatines, or folds of the palate. The 
papilla, with its distal extension, together with the laterals 14 
BODILY FUNCTIONS 
which are arranged on either side, are known as the rugce, 
from ruga — a fold or wrinkle. Oftentimes when well defined, 
the central ridge and laterals present the appearance of a 
symmetrical tree trunk with spreading branches. 
The tongue is the organ of the special sense of taste; it 
is one of the principal organs of speech, and is an indispens- 
able factor in mastication and deglutition. When at rest it 
occupies the space between the internal walls of the body of 
the mandible, the lingual surface of the lower alveolar arch 
and practically all of the teeth (see cut, page 13). 
THE TONGUE 
THE SENSE OF TASTE 
The special sense of taste is located principally in the cir- 
cumvallate papillae which are situated on the dorsum of the 
tongue. They are in two rows, arranged in V form, the apex 
Fig. 3.— Direction of Fibres of Various Tongue Muscles 
being on the median line and pointing distally, the rows run- 
ning forward and outward. They are of large size and vary 
in number from eight to ten, or even more. In addition to 
these, there are numerous other papillae, called filiform pap- 
illae, distributed over the sides and dorsum of the tongue, BODILY FUNCTIONS 
15 
which give it a roughened, or furred, appearance. Still an- 
other variety, called fungiform, are found interspersed with 
the filiform papillae, but are less numerous than the latter. 
THE SALIVARY GLANDS 
The parotid, submaxillary and sublingual glands, to a 
limited extent, empty the salivary secretions in the mouth at 
Fig. 4.— The Salivary Glands 
all times, but more or less profusely during the mastication of 
food. The saliva is the first digestive fluid to act on the food, 
partially converting the starches into sugars, and in conjunc- 
tion with the mucous secretions, lubricates the bolus of food 
and prepares it for deglutition. CHAPTER III 
EXAMINATION OF THE MOUTH 
GENERAL REMARKS 
To render the most skillful service to a patient it is nec- 
essary for the dentist to know the exact conditions of the 
tissues and organs of the mouth in detail. Such knowledge 
can only be acquired by a close examination of the parts. In- 
telligent questioning of the patient will assist, to a certain 
extent, but the burden of the diagnosis rests upon the oper- 
ator. 
He must be a histologist and pathologist as well, to rec- 
ognize conditions of health and disease. No detail, that has a 
direct or even a remote bearing on the dental aspect of the 
case in hand, should escape his notice. The general method 
of procedure for an examination, as here outlined, may be fol- 
lowed with good results. 
POSITION OF PATIENT 
Seat the patient and adjust the chair, first, so that he may 
feel comfortable; second, so as to bring the mouth within 
convenient range for examination. Adjust a towel over the 
patient’s clothing, attaching it around the neck. A mouth 
mirror, probe, explorer, tongue depressor, pliers, cotton, water 
syringe, and a small electric mouth lamp, are the instruments 
most useful for examination, and should be placed conve- 
niently at hand, although not necessarily in sight. 
Everything being in readiness, the operator should cleanse 
his hands in the presence of the patient, or so the latter may 
know it is being done. This is necessary for two reasons — 
first, to prevent possible danger of carrying infection to the 
patient’s mouth, and second, to engender within the mind of 
the latter a feeling of confidence in the operator’s knowledge 
and ability to cope with disease. The free application of tepid 
water, or normal salt solution, with the syringe to the teeth 
and oral tissues is nearly always advisable before beginning 
an examination. 
The lips guard the entrance to the alimentary tract, and 
as they are first encountered, the examination should begin 
with them. Note whether they are of good color and normal 
16 EXAMINATION OP THE MOUTH 
17 
in appearance, or if lesions are present such as fissures, cold 
sores, etc. If so, avoid giving any unnecessary pain by dis- 
tension, or pressure on the parts. If in a healthy condition, 
the index finger should be passed around between the alve- 
olar process and cheeks, a general idea being thus gained of 
the distendability of the lips and cheek walls. The first glance 
in the mouth, in most cases, discloses to the examiner some- 
thing of the character of the patient and the class of oper- 
ations required. 
EXAMINATION OF MOUTH WHEN NATURAE TEETH ARE PRESENT 
Note specifically the general appearance of the mouth as 
to health and cleanliness. If any natural teeth are present, 
look for calculus, pyorrhea pockets, alveolar and gingival ab- 
scesses, dead pulps, peridental inflammation and gingivitis. 
Note any and all peculiarities of the mucous membrane, 
redness, discoloration and swelling usually being signs of 
some irritated or diseased condition. Stomatitis, leugoplakia, 
mucous patches, cancrum oris, etc., are liable to be present, 
and if so should be recognized immediately. If any condition 
found is infectious in character, the operator should take due 
precautions for his own safety during the examination, and 
thoroughly sterilize all instruments as soon as the patient is 
out of the chair. If teeth are carious, observe the extent to 
which the disease has progressed, the teeth affected, and the 
probable method of treatment. Note also the relation of the 
teeth in the same arch to each other, and to those in the oppo- 
site arch, as well. Observe the forms of the teeth themselves, 
whether constricted at the neck; elongated or normal; whether 
tissues have receded, leaving them standing more or less un- 
supported; whether they diverge or converge to an unusual 
degree; whether loss of proximate contact has occurred; the 
form of the spaces where the teeth and spaces alternate. By 
noticing the extent of abrasion on the occlusal surfaces of 
the teeth, some idea can be formed of the stress exerted in 
masticatory effort. 
If the patient is past middle age and no signs of occlusal 
abrasion appear, as it normally should at such an age, try to 
discover the cause, whether due to mal-occlusion or to a dis- 
eased condition of the peridental membrane of one or more 
of the natural teeth. Tenderness of the peridental mem- 
brane, and slight elongation of a single tooth, will often — 18 
EXAMINATION OF THE MOUTH 
sometimes for years — inhibit or seriously impair proper 
masticatory effort. 
EXAMINING EDENTULOUS MOUTHS 
In edentulous cases, note particularly the form of the alveo- 
lar processes, or as Dr. G. V. Black has appropriately termed 
them the residual ridges, the amount of absorption that has 
occurred, the extent and position of muscular attachments to 
the labial, buccal and lingual surfaces. In the upper jaw, 
determine the location and extent of the hard and soft areas, 
and the thickness of the mucous and sub-mucous tissues in 
the vault portion. Notice particularly the form of the raphe 
(the bony ridge formed by the union of the palatine processes 
of the upper maxillae) and compare the thickness of the 
mucous membrane which covers it with that covering the crest 
of the borders. Determine whether there are any sensitive 
or tender areas on which the prospective denture will rest. 
These areas usually will be found on either side of the vault 
just internal to, and a little in front of the tuberosities, and 
in the median line, just back of the central incisors, where 
the four canals are situated which transmit the posterior and 
anterior palatine vessels and nerves. 
When the mucous and submucous tissues are sparse and 
thin on these areas, the pressure of the denture is at times 
very disagreeable, sometimes producing pain. It can be ob- 
viated by properly relieving the impression. Examine par- 
ticularly the buccal aspect of the tuberosities as well as other 
locations, to determine whether undercuts are present. If so, 
what effect, if any, they will have on the removal of the im- 
pression. When the vault is deep, rising abruptly back of 
the incisor region, there will frequently be an undercut area 
in the anterior portion of the mouth, the distance from the 
labial to the palatine alveolar plates through the region of the 
incisive fossa being less than through the border portion near 
the crest. 
In examining the arch and tissues of the lower jaw, observe 
the amount of absorption and the position and extent of mus- 
cular attachment to the outer and inner sides of the alveolar 
arch, whether the tongue and cheek muscles, and the tissues 
above the submaxillary glands are liable to interfere in im- 
pression taking; how far distally and downward the lingual 
wings of a full denture case can extend without impeding 
tongue movements. Notice the relative size of the arches, EXAMINATION OF THE MOUTH 
19 
and tlie probable ease or difficulty of introducing tlie impres- 
sion tray through the oral opening. 
A pad of charts having diagrams of the upper and lower 
arches should he on the bracket, and any points of interest 
should be marked thereon as soon as found. While the chart 
can, or may not, be used after the examination is completed, 
the marking of the important points will fix them firmly in 
the mind. Every peculiarity of the teeth or tissues that may 
have a direct or even a remote bearing on prosthetic pro- 
cedures, should be recognized and kept in mind in order that 
the most efficient service may be rendered. 
PREPARATION OF THE MOUTH FOR DENTURES 
All operative procedures, as a rule, such as the placing 
of fillings and inlays, removal of calcareous deposits, and 
treatment of the soft tissues, should be completed before tak- 
ing impressions. Useless teeth and roots should be extracted, 
and in some cases the tissues should be allowed to heal before 
introducing a denture. Further surgical procedures are at 
times very necessary, such as freeing muscle fibers and tissues 
of the cheek wall that may at some previous time have been 
lacerated, and in healing, have been drawn over and become 
attached to the tissues on the process, in such manner as to 
interfere with the correct seating of the denture. The late 
Dr. Burchard’s suggestion is a good one, of taking an impres- 
sion of the mouth, including the cicatrized tissue, and from 
this securing a cast. This is then trimmed to represent the 
normal form of the ridge, that portion representing the cica- 
trized soft tissues being dissected away on the cast, and leav- 
ing the trimmed portion rather more prominent than the 
natural hard tissues. A denture of vulcanite is constructed, 
the margins rounded and polished smoothly, which when in 
position holds the severed tissues apart until healed, and thus 
the normal alveolar surfaces are regained. 
SPONGY BORDERS 
Often, when the teeth have been lost from phagedenic 
troubles, the bony process is practically all absorbed, or de- 
stroyed. The border in such cases, although presenting a 
fairly good form, is soft and flabby, consisting of thickened, 
sometimes fibrous, mucous membrane, devoid of bony sup- 
port. Such a ridge affords an unsatisfactory foundation for 20 
EXAMINATION OF THE MOUTH 
a denture, without some preliminary treatment of the mouth 
itself, or of the cast to be used in construction. 
REDUCING SPONGY BORDERS 
Three methods are in vogue for minimizing this very 
annoying condition: 
First. A method whereby the treatment of the cast used 
in denture construction will, in certain cases, correct the dif- 
ficulty mentioned. This will be described later in proper 
order. 
Second. A very satisfactory method suggested by Dr. C. 
P. Pruyn of absorbing excess tissues — construct a temporary 
baseplate for the case, or if the patient is wearing an old, even 
though ill-fitting, denture, it will serve the purpose. Line the 
interior with oxychloride or oxyphosphate of zinc, mixed to 
medium consistency. Place it labially and lingually of the 
border position, thus leaving sort of a groove for the crest of 
the ridge to enter. Under pressure the cement is compressed 
between the baseplate and the unyielding tissues, and is forced 
from both sides against the flabby ridge, reducing its bulk 
without materially distorting or changing its position or depth. 
Two or three weeks’ constant wear, of this cement corrected 
denture, will improve the density of the border very notice- 
ably. If further absorption is deemed advisable, the denture 
is thoroughly cleansed, an additional layer of cement is spread 
over that already adapted, and the ridge subjected to pressure 
as before. When the density of the border is satisfactory, a 
permanent denture is constructed. 
Third. The most severe method of treatment consists in 
surgically removing such portion of the spongy border as may 
be deemed necessary, and stitching the margins of the mem- 
brane together to accelerate the healing process. 
When, in preparing a mouth, extractions are performed, 
care should be taken to see that the sharp or prominent pieces 
of alveolar process that frequently project from the border, 
are removed. This can easily be done with a cutting forcep 
or bur while the trauma is fresh. The border, if left smooth 
and rounded, and free from sharp projections, will afford a 
better foundation for a denture, and the soft tissues will heal 
more rapidly than when this smoothing up process is neglected. 
When sharp, bony points are present as the result of 
previous operations, it is advisable, in most cases, to dissect 
away the gum and periosteum, remove the prominences, and EXAMINATION OF THE MOUTH 
21 
if the wound gaps open, stitch the gum tissues together. If, 
for any reason, it is not advisable to remove the points by 
cutting, then those areas in the impression impressed by the 
points should be scraped to obviate pressure and consequent 
irritation, when the denture is introduced. 
TEMPORARY DENTURES 
When, by recent extraction, the mouth has been cleared 
of all remaining teeth, the problem confronting the patient 
and prosthetist is — How soon shall dentures he fitted to the 
edentulous borders? Without question, in most cases, the 
patient will be best served by constructing dentures imme- 
diately, that is to say, within a few days after the loss of the 
teeth. It is a noticeable fact that patients who have never 
worn dentures become accustomed to the presence of substi- 
tutes with less effort, when introduced soon after the loss of 
the natural teeth than do patients for whom the introduction 
of dentures has been deferred for a varying period of from 
six months to a year. Just why this is so. is not clear. Per- 
haps the inconvenience felt from the introduction of the tem- 
porary dentures is so slight as to be nearly lost sight of, while 
the cataclysmic effect, both physical and mental, resulting 
from the loss of the natural teeth and the consequent inability 
to masticate food, is engrossing the attention of the patient. 
Another factor of importance is the marked aversion most 
persons have of presenting themselves, toothless, in public, or 
to their friends. Almost without exception they will submit 
to much inconvenience, and pain as well, rather than suffer 
the humiliation occasioned by the absence of the teeth. This 
is the psychological moment and should not be neglected by 
the operator. The ability to tolerate the presence of tempo- 
rary dentures in the mouth is positive assurance that the 
permanent substitutes will prove both useful and comfortable. 
Another point in favor of temporary substitutes is that the 
alveolar processes absorb more uniformly, as to density of 
tissue, and the ridges will maintain their form for a longer 
period with less change, than where the introduction of the 
dentures is deferred. 
PERMANENT DENTURES 
Usually the temporary should be replaced with perma- 
nent dentures in from six to twelve months. The inequalities 
of the borders will usually in this period have become smooth 22 
EXAMINATION OF THE MOUTH 
and rounded, the alveoli filled in, and the soreness will have 
disappeared from the soft tissues. Since as a result of the 
absorption that has occurred the adaptation of the denture 
to the tissues is imperfect, deferring the construction of the 
permanent sets beyond the time mentioned usually results in 
unnecessary and deleterious absorption of the alveolar pro- 
cess. Stress, therefore, should be laid upon this fact, and the 
patient advised accordingly. 
In the examination of any mouth with a view of carrying- 
out prosthetic procedures, certain things should be kept in 
mind by the operator. 
First, he should carefully consider what class of substi- 
tute will give the patient the best service, as indicated by the 
conditions in the mouth. 
Second, when the class of work indicated is not to be con- 
sidered on account of expense, what other method can be fol- 
lowed to the best advantage. 
Third, the operator and not the patient should determine 
what class of work is indicated, and how it should be done. 
This he can do if by his ability and sincerity he can inspire 
within the mind of his patient, confidence in his knowledge, 
judgment, and honesty of purpose, all of which are essential 
in order to bring together and hold a desirable clientele. CHAPTER IV 
ARTIFICIAL DENTURES 
Physical and Mechanical Problems Involved in Their 
Construction 
The production of artificial dentures, either full or par- 
tial, is accomplished by the carrying out of a series of tech- 
nical details that follow each other in sequence. 
The degree of success attained in denture construction is 
directly dependent on the skill with which the details are 
wrought out. The test of success lies first, in the patient’s 
ability to use the dentures successfully in masticatory effort; 
second, in the. greater or less complete fulfillment of esthetic 
requirements; and third in the ability of the wearer to use 
them without inconvenience, or to briefly summarize —useful- 
ness — good looks — comfort. 
THE THREE ESSENTIAL REQUIREMENTS 
FULL DENTURES 
Perhaps the most difficult problem confronting the pros- 
thetist is that of retention or securing stability of the finished 
dentures when introduced and subjected to use. In full cases, 
the natural teeth having been lost, no mechanical aids to re- 
tention can be resorted to, such as are used in partial sub- 
stitutes. In extreme instances spiral springs can be applied 
but they are objectionable, on account of the constant pres- 
sure exerted to force the mandible and maxilla apart, also 
on account of unhygienic conditions caused by their presence. 
Retention of full dentures is largely a question of physics 
and not of mechanics, although good mechanical judgment 
and skill must be exercised in developing the physical aids to 
retention. 
Full upper and lower dentures are retained in position on 
the alveolar borders by adhesion and atmospheric pressure. 
In lower cases gravity also assists. Partial dentures are 
usually retained with some form of clasps, or mechanical de- 
vices, which attach to some of the remaining natural teeth or 
roots. In favorable cases both means first mentioned, viz., 
adhesion and atmospheric pressure, are utilized. The same 
general conditions which are requisite for developing good 
23 24 
ARTIFICIAL DENTURES 
atmospheric pressure, are also essential for developing good 
adhesive qualities. 
ADHESION 
(a) Adhesion is defined as “the molecular attraction ex- 
erted between the surfaces of bodies in contact.” 
(b) This peculiar property is attributed to some reciprocal 
action between the contact surfaces. The particles 
must be brought within the limit or distance of mole- 
cular attraction. 
(c) “The attraction increases as the contact is prolonged 
and is greater in proportion as the contact is closer.” 
Adhesion takes place between dissimilar substances. It is 
more powerful between a solid and a liquid than between 
solids, or between the molecules of a liquid itself. 
If a thin layer of oil is interposed between two perfect 
planes of metal, they will adhere firmly, but when pulled 
asunder each plate is moistened by the oil, showing that in 
separating the plates, the cohesion of the liquid is overcome, 
but not the adhesion of the oil to the metal. (Ganot’s Physics.) 
That adhesion plays a part in the retention of dentures is 
beyond question, but the conditions surrounding a denture 
when in position and in use in the mouth, tend to reduce the 
effectiveness of adhesion, viz., the slight yet unavoidable move- 
ment which occurs when the denture is subjected to stress, 
due to the natural resiliency of the tissues. This movement 
is opposed to prolonged as well as close contact. (See para- 
graph c.) 
ATMOSPHERIC PRESSURE 
Tlie atmosphere is the aeriform fluid which envelops the 
earth and extends outward from its surface a distance of 
almost 50 miles. It is composed mostly of free oxygen (21) 
and nitrogen (79), with about 4 parts of carbonic acid to 
10,000. Ammonia, sulphuretted hydrogen and other gases are 
also present in varying quantities in different places, due to 
local causes. 
The air has weight. One hundred cubic inches of dry air, 
under ordinary atmospheric pressure of 30 inches, and at a 
temperature of 62 F., weigh 31 grains. Twelve cubic feet of 
air under the same conditions, weigh 1 pound. The air in a 
room 16x16x10 feet weighs 210 pounds. 
Since the air has weight, and the earth’s surface is at the ARTIFICIAL DENTURES 
25 
bottom of the aerial sea, the outer layers of the atmosphere 
are constantly pressing down upon the deeper layers with a 
very considerable force, the earth’s surface being the site of 
greatest pressure. 
This pressure is not noticeable under ordinary conditions, 
as the air presses equally in all directions, and upon all objects. 
If, however, it is excluded from between two surfaces, the 
pressure is immediately apparent. In case of perfect exclus- 
ion of the air, the pressure at sea level amounts to 14.7 pounds 
per square inch. When two perfectly ground plane plates of 
glass or metal are placed together, and the air between the 
contact surfaces is excluded, it will require a force equal to 
the area of the plates in square inches multiplied by 14.7, to 
separate them. If the plates are 4 inches square, the formula 
would be stated thus: 4X4X14.7=235.2. 
To summarize, it would require a pull of 235.2 pounds to 
overcome atmospheric pressure and separate the plates, with- 
out considering the adhesive force which is also present, and 
which would have to be overcome before separation could 
take place. 
RETENTION BY MEANS OF ATMOSPHERIC PRESSURE 
In applying the principle of atmospheric pressure to the 
retention of an artificial denture, it is necessary to develop 
certain conditions between the denture and the tissues on 
which it rests, similar to those present in the plane plates 
mentioned, viz., close or uniform adaptation of the contact sur- 
faces particularly peripheral contact. 
The denture is seated upon the mucous membrane of the 
mouth, which in turn is supported by and rests on a bony 
structure or foundation. The thickness of the mucous tissue 
varies in different mouths, and often varies greatly in dif- 
ferent areas of the same mouth. 
For example, as often happens, the central vault portion 
of the mouth is covered with a thin, unyielding, and the max- 
illary area with a thick and yielding, layer of mucous tissue. 
Unless precautionary measures are taken to prevent, a denture 
fitted to such a mouth will be readily dislodged under stress, 
the hard central area acting as a fulcrum on which the base 
plate will tip, the side on which stress is exerted being forced 
upward, the opposite side being carried downward corre- 
spondingly, just as the arms of a lever rotate about the ful- 
crum. This movement disturbs the equilibrium of the denture, 26 
ARTIFICIAL DENTURES 
breaks the contact surfaces, and the air, if at first excluded, 
rushes in between the denture and tissues. 
The same condition would prevail were the margins of 
the plane plates previously alluded to soft and yielding and 
the central area hard and unyielding. Pressure produced 
on the margins of the plates on one side, to force them to- 
gether, brings the hard central area into action as a fulcrum, 
separates the opposite sides and destroys atmospheric pres- 
sure. By proper precautionary measures the difficulty men- 
tioned in denture construction may, to a great extent, be 
obviated. 
NECESSARY CONDITIONS FOR RETENTION 
First, there must be uniform contact, or bearing, of the 
denture against the tissues on which it rests. 
Second, the peripheral margins of the denture at all 
points should be so formed that the tissues when at rest, or 
under muscular tension, will remain in close contact with these 
margins, thus preventing the ingress of air between the den- 
ture and tissues. 
With the first requirement realized, it is comparatively 
easy to develop the second one. In both cases the necessary 
conditions are developed, principally during the taking of 
the impression, the details of which will be given in the chap- 
ter on this subject. 
Briefly stated, the principle involved in carrying out the 
first requirement, viz., uniform bearing on hard and soft areas, 
consists in exerting pressure on the soft areas by means of 
suitable impression material, of proper plasticity, to com- 
press them so that the finished denture will bear firmly on 
the soft, and lightly and in some cases not at all on the hard 
areas. This condition can be still further carried out and 
accentuated by scraping the impression in certain areas, the 
details of which will shortly be given. 
The second requirement, viz., close peripheral adaptation, 
is accomplished first by careful manipulation of the impres- 
sion materials against the peripheral areas, and second, by 
having the patient exercise the muscles actively while the im- 
pression material is still soft and plastic, and thus mark their 
form, direction and limit of attachment to the alveolar process. 
The object sought in carrying out this step is to secure 
a peripheral outline to the denture that will not impinge on, 
or cause irritation of, the muscular or soft tissues, and yet ARTIFICIAL DENTURES 
27 
will have such close adaptation as to seal against the ingress 
of air — to afford “relief without leak,” as Dr. J. W. Greene 
expresses it. 
RELIEF FROM PRESSURE BY SCRAPING THE IMPRESSION 
When the impression is secured, those parts impressed 
by the exceedingly hard and unyielding areas of the mouth 
should be scraped slightly to insure relief from bearing of 
the finished denture on these areas. It is especially necessary 
to afford such relief in the central palatine portion of the 
mouth when the raphe is distinctly marked and prominent 
and is covered with only a thin layer of tissues. 
Fig. 5.— An Impression Showing Medium Amount of Relief 
In relieving this area the scraping should extend slightly 
beyond the margins of the hard outline in every direction. 
Usually the relief should not exceed 1/25 of an inch in depth 
in the deepest part, and should gradually taper out to a thin, 
invisible periphery, losing itself in the general contour of the 
vault impression. 
The idea in thus treating the impression is not to pro- 
duce a vacuum chamber in the denture, but to afford relief 
from pressure on the raphe and adjacent tissue, and thus pre- 
vent the hard areas from serving as a fulcrum to tip the 
denture when stress is applied. 
A little experience will enable one to readily determine 
the outline and extent of the hard areas by merely scanning 
the impression. It is a good plan, however, to make a digital 
examination of the mouth, either immediately before or after 28 
ARTIFICIAL DENTURES 
the impression is taken, to be absolutely certain of the extent 
of relief necessary to provide for. 
VACUUM CHAMBERS 
Vacuum chambers, often incorrectly called air chambers, 
are shallow, depressed areas with a definite outline, usually 
formed in the central palatine surfaces of dentures during 
the constructive steps, and which are supposed to assist in 
retention. As ordinarily constructed, they are not intended 
to, nor do they often afford, relief from pressure. The effi- 
ciency of a vacuum chamber is dependent upon its area, depth, 
Fig. 6.— An Impression Showing Slight Amount of Palatine Relief 
adaptation of its peripheral margins to the opposing tissues, 
and the ability of the patient to exhaust the air from the 
interior. 
Under the most favorable conditions, the usefulness of 
the vacuum chamber is questionable. The tissues are soon 
drawn into, and usually after a time permanently fill, the 
cavity, thereby defeating the object for which it was designed. 
When the chamber is very deep, the tissues, while they may 
not fill it entirely, are kept in an irritated condition, more or 
less annoying and frequently painful to the patient. On the 
other hand, when the chamber is shallow and the tissues are 
not drawn into it, it is not, as its name would indicate — a 
vacuum chamber — but merely a useless and unsightly de- 
pression which increases the thickness of the denture in a ARTIFICIAL DENTURES 
29 
region where bulk is objectionable on account of its tendency 
to modify tlie resonance of the voice. 
For more than fifteen years past the use of this very 
questionable method of retention lias been discontinued by 
the writer, both in clinical work and in private practice. Tlie 
results during this time furnish convincing proof of tlie 
greater advantages over vacuum chamber for retention pur- 
poses of well defined uniform bearing developed in taking the 
impression and by scraping the cast to secure peripheral adap- 
tation of the denture. 
COMPENSATING FOR EXPANSION OF THE CAST FULL UPPER 
DENTURES 
Since all plasters expand in setting, to a greater or less 
extent, some means of compensating for the enlargement of 
the cast should be adopted. 
Fig. 7.— Scraping the Periphery of a Cast 
The plan followed, and which has proven very satisfac- 
tory, is to scrape a slight groove, extending from one tuber- 
osity to the other, on the buccal and labial surfaces of the 
cast. This groove should be made with a discoid 20 or small 
Kingsley scraper, to avoid the formation of any angles, and 
be very shallow,— so slight as to scarcely be noticeable ex- 
cept on close inspection. It should occupy a position about 
midway between the crest of the border and the peripheral 
line of termination of the denture, and as before stated ex- 
tend from one tuberosity to the other on the labial and buccal 
surfaces. This groove on the cast produces a slight, rounded 
bead on the inner aspect of the labial and buccal surfaces of 
the denture, reducing the diameter of the latter by an amount 
equal to the elevation of the bead, thus insuring close peri- 
pheral adaptation, and overcoming any slight enlargement of 
the cast due to expansion. 30 
ARTIFICIAL DENTURES 
POSITION AND OUTLINE FORM OF THE DISTAL MARGIN OF 
UPPER DENTURES 
The distal terminal margin of an upper denture should 
follow the line of junction of the soft with the hard palate, 
or be laid on the soft immovable area, being careful to avoid 
encroaching on the soft movable tissues or palate muscles. 
The latter become an active cause of displacement when the 
denture overrides them to any appreciable extent. 
Usually the distal margin of the denture should assume 
a double compound curve, extending either way from the 
median line, to correspond in general with the distal margin 
of the hard palate. 
In those cases where the tissue between the hard central 
area and the tuberosities is soft, the terminal line on either 
side of the center may be carried forward somewhat, without 
Fig. 8.— Distal Form of Upper Baseplate 
impairing the adaptation. Such trimming will also relieve 
pressure to a certain extent on the posterior palatine vessels 
and nerves which find their exit from the canals situated just 
inside of the tuberosities. Pressure of the denture directly 
on the overlaying tissues and indirectly on the nerves in this 
region is a frequent cause of nausea. 
The distal terminal line when properly laid will form a 
pleasing symmetrical curve which will harmonize well with the 
buccal and labial outlines of the denture. See Fig. 8. . 
PREPARATION OF LOWER IMPRESSIONS 
In full lower cases it frequently happens that the alve- 
olar border is thin and the crest of the process is very hard. ARTIFICIAL DENTURFjS 
31 
In such cases the impression should be trimmed or scraped 
in the deepest part with a discoid instrument similar to the 
one used in the peripheral scraping of the upper cast. The 
scraping of the impression of the crest should not be carried 
Fig. 9.— Scraping the Deeper Portion of Lower Impression 
to Relieve Stress on Border Crest 
too close to the distal terminals, for when extended entirely 
back, a vent is formed, through which the air finds its way, 
affecting adversely the stability of the denture. 
The effect of scraping an impression as described, is to 
Fig. 10.— Linear Distance Usually Relieved on Lower Impression 
increase the height of the crest of the border on the cast so 
that a denture when moulded on the cast will not rest on the 
extreme crest, while the labial, buccal and lingual flanges will 
be brought in closer contact with their respective surfaces, 
the air forced out and atmospheric pressure utilized for re- 32 
ARTIFICIAL DENTURES 
tention purposes. In many cases, a considerable amount of 
adhesion that could not otherwise be realized, will be devel- 
oped in this manner. 
SOFT ALVEOLAR BORDERS 
When the alveolar border in either upper or lower cases 
is of average form, but devoid of bony support due to ex- 
cessive absorption of the process, it is frequently advanta- 
geous to pare the labial or buccal and lingual surfaces of 
the cast, slightly, being careful not to reduce the height of the 
crest, so that these surfaces of the border will be compressed 
when the denture is introduced. In many cases in practice 
the carrying out of this plan has added greatly to the sta- 
bility of dentures, the effect in most instances being to con- 
dense and render the tissues permanently harder without any 
ill effects. A method of correcting extreme cases of soft and 
yielding borders — spongy or flabby gums, as they are some- 
times called — is detailed cn pages 19-20. 
Partial dentures are usually retained in position by means 
of clasps, or some of the forms of frictional appliances in 
common use. In the case of a clasp, the pressure of the appli- 
ance, which is slightly smaller than the tooth it embraces, is 
due to the resiliency or springiness in the metal of which it is 
composed. When in position in the mouth, the clasp which is 
attached to the denture, grasps the tooth more or less firmly 
and prevents displacement. So also with the various special- 
ized appliances, except that usually they are made in two 
parts, one of which is permanently attached to a natural tooth, 
or crown set on a root, the other to the denture. They are so 
adjusted that when in position the friction between the two 
parts holds the substitute in place. The various appliances 
used for this purpose will be described later. CHAPTER V 
DEFINITIONS OF SOME COMMONLY USED 
TERMS 
Impression Trays 
An impression is a negative copy or counterpart of some 
object impressed. In prosthetic procedures, to which the fol- 
lowing definitions will refer, an impression is obtained by 
pressing a plastic material, such as plaster or modeling com- 
pound, against some portion of the oral tissues or teeth. 
A cast is a positive copy or likeness of the object im- 
pressed and is obtained by casting plaster, or some similar 
plastic material, into the impression or mold. Casts are used 
for giving the negative form of the mouth to plastic base 
dentures. 
A model is a positive or duplicate copy of the mouth or 
some portion of it, and is used for producing a similar posi- 
tive of itself, and consequently of the mouth, in metal. A 
model is produced in the same general manner as a cast, but 
differs from it in its use, and slightly in its form, being so 
shaped as to be readily withdrawn from the sand in which it 
is imbedded, in the sequent steps of die construction. 
A die is a metal duplicate of the mouth or some portion 
of it, also of the model from which it is derived. In construct- 
ing dentures with swaged metal bases, a die fulfills a sim- 
ilar purpose to that of a cast in the production of plastic 
base dentures, viz., giving the reverse form of the mouth to 
the metal base denture. A die is formed by pouring molten 
metal or alloy into a sand matrix derived from the model, 
or, in some cases, by pouring directly into the impression. 
A counterdie is a negative or reverse of the die, and is 
obtained by pouring a similar or a lower fusing metal or alloy 
directly against the face of the die. 
USE OF THE TERMS “CAST” AND “MODEL,” 
The term model has been and is still very generally used 
instead of cast to designate the product obtained by filling 
the impression with plaster or plaster compound. All such 
products so obtained are in reality casts. The term cast, is 
gradually coming into use to designate the product of the im- 
DEFINITIONS 
33 34 
DEFINITIONS OF SOME COMMONLY USED TERMS 
pression when it is used to give the reverse form of the mouth 
to a plastic base, and the term model, when it is used as a 
means- to reproduce a die which is a duplicate of itself. 
The following definitions of the two terms are given in 
the Standard Dictionary: 
“Cast.— An object founded or run in, or as in a mold, as 
of metal, plaster, wax, etc.” 
“A reverse copy of plaster of Paris, or similar material, 
of a mold, usually distinguished from a casting which is of 
iron or other metal or alloy. ’ ’ 
“Model.— An object usually in miniature, representing 
something to be made or already existing; a material pattern 
of natural size; more rarely a plan or drawing as a model 
of an invention; a model of a building; to draw a model.” 
“Specifically: In sculpture the plaster or clay original 
of a work to be executed in stone or metal. A person who 
does duty as a copy or pattern for sculptors and painters.” 
“A pattern is always, in modern use, that which is to be 
copied; a model may be either the thing to be copied or the 
copy that has been made from it, as the models in the Patent 
Office. A pattern is commonly superficial; a model is usually 
in relief. A pattern must be closely followed in its minutest 
particulars by a faithful copyist. A model may allow a great 
degree of freedom; a sculptor may idealize his living model; 
his workmen must exactly copy, in marble or metal, the model 
he has made in clay. ’ ’ 
Before the introduction of vulcanite, the plaster cast de- 
rived from an impression was used almost exclusively for the 
making of metal dies on which to swage gold, silver and 
platinum bases. For this purpose it is a true model, since it 
serves as a copy from which something like it (the die) is 
produced. 
On the introduction of vulcanite, which came into use 
rather gradually, the same general form of cast as was used 
in die construction, served as a shape over which to mold the 
vulcanite. The similarity in method of production and form 
of a cast accounts for the retention of the term model, even 
though it does not fulfill the purpose of a model. 
IMPRESSION TRAYS 
An impression tray is an appliance used for conveying 
impression material to, and holding it in position against, the 
tissues of the mouth or teeth while hardening. Tt is also of DEFINITIONS OF SOME COMMONLY USED TERMS 
35 
material assistance in removing the impression from the 
mouth, and in holding the parts of the impression, when frac- 
tured and removed, in correct relation to each other while 
securing the cast. 
A large assortment of trays, in varying sizes and forms, 
and constructed of metal, rubber, celluloid, porcelain and 
papier-mache, are procurable at the supply houses. The trays 
most commonly used are made of Britannia metal, brass, Ger- 
man silver or aluminum, all of which may be bent without 
much effort. This latter feature is an important one, since 
the stock tray will require more or less modification in each 
case, to meet some peculiar unbalanced or abnormal condi- 
tion of the alveolar ridge or oral tissue. 
The other classes of trays, being rigid, are incapable of 
much change, and are therefore limited in their application. 
In difficult cases, special trays are frequently constructed of 
block tin by casting, or from sheet metal by swaging, the de- 
tails of which will be given on pages 38, 39. 40. 
TRAY NOMENCLATURE 
The various surfaces of the oral cavity are definitely 
named, and those areas of the impression tray that come in 
close proximity to these oral surfaces are named accordingly. 
For instance, the outer surfaces (right and left) of the upper 
and lower alveolar arches, from the distal of the cuspids back- 
ward, are termed the buccal surfaces because of the close 
proximity of the buccal muscles to these surfaces. From cus- 
pid to cuspid, anteriorly, the outer surfaces of the arches are 
called the labial surfaces because the labial muscles are in 
close proximity. Those areas on the inner side of the border 
that are touched by, and are in close proximity to, the tongue 
are termed lingual surfaces. 
In order to describe clearly the adjustment of the tray 
and the taking of impressions, the tray nomenclature as given 
by Dr. G. H. Wilson in “Dental Prosthetics” will be made 
use of. 
“A tray has a body and a handle. The body consists of 
a floor and flanges. Upper trays have a vault portion. There 
are two types of floors, oval for edentulous jaws and flat for 
accommodating the remaining teeth. The flanges are called 
outer and inner. The outer flange has two portions, the an- 
terior, or labial, and the posterior, or buccal. The dividing 
line is the proximity of the distal surface of the cuspid tooth. DEFINITIONS OF SOME COMMONLY USED TERMS 
The inner flange is called the lingual flange. The surfaces of 
the tray are named for the surfaces they approximate, as 
maxillary, labial, buccal and lingual.” 
“The vault portion spans the space described by the 
curve of the lingual flange of the upper tray. The handle 
is an extension from the union of the floor and the anterior 
flange.” 
A tray when fitted should conform closely in general out- 
line and contour to the mouth. Since it receives or partially 
encloses the oral tissues, it should be slightly larger to ac- 
commodate the impression material, a uniform space of about 
one-eighth of an inch or less between the tray and tissues 
being sufficient for this purpose. 
Conforming the tray to meet the conditions mentioned, 
viz., close adaptation and uniform space for impression 
materia], is accomplished by bending, cutting, or making 
addition to the tray at points where deficient. Occasionally 
all three methods are resorted to in adjusting a tray to a 
given case. 
CONFORMING THE TRAY BY BENDING 
Trays are narrowed or widened by bending the flanges 
inward or outward, or by compressing or expanding the body 
of the tray across its buccal diameter. Compression of the 
body of upper trays increases and expanding reduces the 
height of the vault portion. 
In lower trays, decreasing the buccal diameter by bend- 
ing the body of the tray usually narrows the space between 
the labial and lingual flanges anteriorly. To correct this fault 
the lingual flange can be slit in the median line and the adja- 
cent portions bent and allowed to overlap so as to gain the 
necessary space. The flanges are bent inward or outward, 
as the position and form of the border indicates, always keep- 
ing in mind two points — the maintenance of the proper space 
for the reception of impression material, and freedom from 
muscle impingement by the flanges. 
Frequently it becomes necessary to reduce the height of 
the flanges of a tray, particularly in edentulous cases. While 
trays with deep or wide flanges may be used in such cases 
and fairly good impressions of the mouth secured, it will, in 
most cases, he found that the labial or buccal muscles, or both, 
CONFORMING BY CUTTING 37 
DEFINITIONS OF SOME COMMONLY USED TERMS 
have been distorted and forced out of normal position. In 
fact, the compression may be so severe as to obliterate the 
surface indications of their presence or position on the cast 
when secured. 
These muscles and the frenum frequently have their ori- 
gin near the crest or maxillary portion of the alveolar process, 
while the border itself may be deep or high, and if not con- 
sidered in outlining the peripheral margin of the base plate, 
may become active causes of displacement by lifting the den- 
ture off the crest of the border, thus breaking the adhesion. 
It is found that by selecting trays with narrow flanges 
which do not impede the muscular action, and having the pa- 
tient exercise these muscles at the proper time, while the 
impression material is still soft, that their position, under 
tension, can be determined and indicated on the impression 
Fig. 11.— Impression Showing Grooves Formed by Muscular Contraction 
and the peripheral outline of the denture properly laid on the 
cast. 
Therefore, in selecting trays for edentulous cases, the 
width of the flanges should be noted; when too wide, the 
excess should be cut away with the shears, and the margins 
smoothed with a file to prevent tissue injury, should the 
trimmed margin be forced through the impression material. 
In very flat upper arches it is at times necessary to cut away 
almost the entire labio-buccal flange, while in lower cases 
both outer and inner flanges are frequently to a great extent 
removed. The governing factor, in all cases of flange cutting, 
is the form of the bony tissue or border enclosed by the tray 
and the muscular attachments to the border with which the 
flanges may interfere. 
A common location calling for the use of the shears is in 
the median line of both upper and lower trays, in notching 
the labial flanges to relieve impingement at this point and on 
the lingual of the lower to obviate contact with the lingual 
frenum. 38 
DEFINITIONS OF SOME COMMONLY USED TERMS 
MAKING ADDITIONS TO THE TRAY 
Wlien the tray selected is of correct outline form and 
generally suitable for the case, but slightly deficient in some 
locations, additions may be made where required by build- 
ing up the deficient portion with wax or modeling compound, 
or by splicing a piece of metal to the tray. The most common 
location for building up a tray is on the vault portion, increas- 
ing its height and frequently extending it posteriorly. This 
applies almost exclusively to trays designed for plaster im- 
pressions, both full and partial. 
In most cases of plaster impressions, better results can 
be secured by taking a preliminary impression in beeswax or 
modeling compound, cutting off the excessive surplus and 
using this preliminary impression as a tray for holding the 
plaster. In partial cases the wax or compound is removed 
from around the impressions of the teeth, thus enlarging the 
openings to make room for a fair thickness of plaster to sur- 
round the teeth, so that when fractured the parts may be read- 
ily replaced. 
Where marked irregularity of the border is noticeable, 
or in some cases where a few of the natural teeth are present, 
it is sometimes advisable to construct a tray for the case. 
This may be done by casting it of block tin or some fusible 
metal, or by running a die and counterdie and swaging a tray 
of brass, German silver or aluminum, or by swaging a tray 
of Ash’s metal over plaster casts in a screw press with rub- 
ber pads. 
SPECIAL CAST TRAYS 
Secure as good an impression as possible with the trays 
at hand. From this impression a plaster cast is formed, and 
over the cast a sheet of wax is molded to represent the form 
of the desired tray, including a handle. The wax pattern is 
then removed from the cast and invested in some suitable 
investment compound, placing the handle portion upward. 
Heat is then applied and the wax burned out, after which the 
fusible metal is poured in through the gate left by melting 
out the wax handle. 
Dr. Walter M. Bartlett of St. Louis lias followed a sim- 
ilar method for many years, but has very materially improved 
the efficiency of the tray by beading it. He applies a narrow 
wax rim entirely around the inner periphery of the wax 
model, which bead is, of course, reproduced in the casting. 
This rim or bead serves to confine the impression ma- 39 
DEFINITIONS OF SOME COMMONLY USED TERMS 
terial within the compass of the tray, and minimizes the 
amount required. A tray constructed in this manner, when 
introduced in the mouth without any impression material 
present, will frequently exhibit a marked amount of adhesive- 
Fig. 12.— Wax Model for Special Impression Tray 
ness due to close peripheral adaptation. In constructing the 
tray, plaster may be used as the matrix and the latter may 
be of the three or four piece separable type, but the pieces 
Fig. 13.— Matrix of Plaster in Which Tray Is to Be Cast 
should be reasonably thin, and before casting should be warm 
and dry. The several pieces are held together with binding 
wire. 
SWAGED TRAYS 
A swaged tray may be made by securing a die and coun- 
terdie from the cast of the mouth. Brass, German silver or 
aluminum, usually 24 or 22 gauge, is cut to appropriate size, 40 
DEFINITIONS OF SOME COMMONLY USED TERMS 
and conformed by swaging. The surplus is trimmed away to 
give the tray its correct peripheral outline, and a handle 
attached in the usual location by soldering or riveting. 
A quickly formed and convenient tray for plaster impres- 
sion work can be made by adapting a sheet of special Ideal 
base plate to the cast, secured, as in the cases just mentioned. 
The surplus is trimmed off and correct peripheral outline 
given the base plate; a piece of 12-gauge German silver or 
steel wire is bent to the form of the border and extended for- 
ward to serve as a handle and laid on the base plate. With a 
hot spatula the scraps can be melted over the wire and at 
various points to strengthen the tray and give it necessary 
rigidity. Sometimes a second sheet of base plate is added to 
the first, the wire being between the two layers. 
SPECIAL TRAYS OF IDEAL BASE PLATE 
The distal vault portion of a tray is frequently too short 
to support the plaster against this area of the mouth. An 
extension may quickly be made by cutting a piece of sheet 
metal of suitable form so as to overlap the vault portion. 
Punch two or three holes to correspond, through the addition 
and the tray, with the plate punch, and attach together with 
binding wire. Usually, however, additions to the vault por- 
tion are made quite as well and more quickly with wax or 
compound. 
In taking impressions where modeling compound is the 
sole medium used, tray extension or contouring is not so essen- 
tial, since the compound which escapes distally can be con- 
formed and adapted to the tissues with the fingers, as well in 
this location as peripherally. 
The modeling compound tracing sticks are very convenient 
for making slight additions to trays, particularly along the 
rim portion. All additions, whether of wax, compound or 
metal, should be tested by trial in the mouth before introduc- 
ing the impression material. 
As a rule, trays that are too large and with labio-buccal 
flanges much too broad, are selected for edentulous cases. 
When it is understood that with close-fitting trays and a mini- 
mum quantity of impression material, more accurate impres- 
sions can be secured than when an excessive amount is used, 
much of the difficulty arising from lack of adaptation of den- 
tures will be eliminated. 
METALLIC EXTENSIONS OR ADDITIONS TO STOCK TRAYS CHAPTER VI 
IMPRESSIONS AND IMPRESSION MATERIALS 
GENERAL REMARKS 
An impression, in its dental sense, is an imprint, a reverse 
copy or counterpart of some portion of the oral cavity. It is 
secured by applying to the parts involved, some plastic me- 
dium that conforms readily to the surfaces impressed, and 
which, when adapted, will harden and retain its form. 
The surfaces embraced by an impression may vary from 
an area involving only a small portion of the mouth, or even 
of a tooth, to one containing the full complement of teeth, 
together with the alveolar border in which they are imbedded, 
and in edentulous cases (mouths devoid of teeth) to the bor- 
der and adjacent areas. 
The character and size of the substitute or replacement 
under construction determines the area to be included in an 
impression. It is a safe plan generally, and in partial cases 
especially, to extend the impression beyond the areas actually 
involved in an operation, since when the cast is secured, a 
better conception may be formed of the relationship and pro- 
portions of the contemplated substitute to the remaining nat- 
ural teeth than when the impression is restricted in size. 
Absolute accuracy of the impression in representing the 
parts impressed is positively essential, except in cases to be 
noted later, and no effort should be spared to secure such an 
end, since the cast, derived from an impression, becomes the 
basis and forms the ground work on which most technical 
procedures are carried out. If the foundation is faulty and 
imperfect, the structure built thereon will be proportionately 
inaccurate, and a probable failure. 
It does not follow, however, that all impressions for any 
purpose should be taken in the same manner and under the 
same conditions, nor do impressions always represent a true 
reverse copy of the parts impressed. For instance, it is found 
that in certain cases pressure sufficient to distort or com- 
press the soft and yielding tissues of the mouth is desirable, 
while in other cases, such compression is not only uncalled 
for, but detrimental to final results. In any procedure, the 
prosthetist must first plan his substitute, and then thought- 
fully and skillfully work out the details of the impression to 
41 42 
IMPRESSIONS AND IMPRESSION MATERIALS 
meet the requirements of the case in hand. Without doubt, 
most of the mishaps and misfits in prosthetic procedures are 
due, in part, to faulty manipulation in impression taking. The 
slighting of this operation in the carrying out of details in a 
perfunctory and careless manner, is a widespread evil, and 
cannot be too strongly condemned. 
It should be the ambition of the student, and of every prac- 
titioner as well, to perfect himself in the technical details, the 
art of impression taking, so that he may overcome any obsta- 
cle and meet every emergency that may arise. A thorough 
understanding of the conditions governing each case, together 
with painstaking effort in the handling of the material em- 
ployed, both in and out of the oral cavity, will accomplish the 
desired results. 
IMPRESSION MATERIALS 
Since accuracy in impression taking is an absolute ne- 
cessity, the choice of the medium used for this purpose re- 
quires careful consideration. The following statement of the 
requirements of an impression material represents the ideal, 
rather than the attainable, because no substance has yet been 
found which is absolutely free from imperfections. Several, 
however, approach closely to the ideal requirements, and with 
a knowledge of the desirable and detrimental qualities of each, 
fairly satisfactory and accurate results may be secured in 
most instances. 
REQUIREMENTS 
An impression material should possess, as nearly as pos- 
sible, the following qualities: 
First — It should be composed of some material that will 
not be unduly disagreeable to the patient. 
Second — It should become plastic at a temperature the 
oral tissues can tolerate. 
Third — It should copy accurately the fine lines and irreg- 
ular surfaces to which it is applied, and retain the form 
so copied, without becoming distorted in removal from the 
mouth. 
Fourth — It should harden in a reasonably short time — 
from one to three minutes. 
Fifth — It should neither expand, contract nor warp at 
ordinary temperatures to any appreciable degree. 
Several varieties of impression materials are in common 
use. These may be divided into two groups. First, those which 
CLASSIFICATION IMPRESSIONS AND IMPRESSION MATERIALS 
43 
are rendered plastic with a liquid and harden by crystalliza- 
tion. This class includes plaster, impression compounds, and 
the various dental cements, as oxy-chloride and oxy-phosphate 
of zinc, magnesia, and the silicates. 
The second class embraces those materials that are ren- 
dered plastic by heat and harden on cooling. The principal 
materials in this group are modeling compound, beeswax (both 
pure and combined with other substances), paraffin and gutta 
percha. The most commonly used, as well as practical, of 
these materials are modeling compound and gutta percha. 
Group I 
Impression Materials That Harden by Crystallization 
PLASTER OF PARIS 
Plaster of Paris is so called because in former times large 
quantities were produced at the gypsum quarries at Mont- 
martre, near Paris. 
Plaster is made from gypsum, a hydrated calcium sulphate, 
the chemical formula of which is CaS04 + 2H20. It occurs in 
a number of different forms, the transparent and crystalline 
variety being called selenite, from the Greek word selene, 
meaning the moon, due to its peculiar soft lustre. This variety 
sometimes occurs in large plates, and formerly was used 
instead of glass for window lights. In this form it some- 
what resembles mica, but is much softer, and the plates, 
although slightly flexible, are brittle and inelastic. When it 
occurs in needle-shaped crystals or in fibrous form, it is known 
as fibrous gypsum or satin spar. The ordinary massive, 
opaque crystals are called gypsum. This form presents many 
varying colors — red, brown, black and yellow — from the en- 
closed coloring matter, usually the oxides of iron. It also 
occurs amorphous, in compact, translucent and snowy white 
masses, and is then termed alabaster. This variety is very 
beautiful, and as it is easily carved, it is much used for small 
ornaments and statuary. 
Gypsum frequently contains more or less foreign matter, 
such as sand, clay, oxide of iron, or calcium or magnesium 
carbonate. These impurities are not usually present in ex- 
cessive quantities, and when not exceeding three per cent, do 
not seriously impair the commercial grades of plaster. Den- 
tal plaster, however, should be produced from the purest 44 
IMPRESSIONS AND IMPRESSION MATERIALS 
quality of gypsum obtainable, and special care should be used 
in its manufacture to insure uniform results. 
MANUFACTURE OF PLASTER 
Dental plaster is a half hydrated calcium sulphate, for- 
mula CaS04 + 1/2ILO. It is formed by heating gypsum, 
CaSo4 + 2H20, at a temperature ranging from 130 deg. to 
190 deg. C. If heated above 190 deg. C., the product is un- 
suitable for dental purposes, but a plaster is produced which 
has a wide range of usefulness in the manufacturing and 
building fields. 
Two general methods are employed in the conversion of 
gypsum into plaster. First, by pulverizing and then dehy- 
drating. Second, by dehydrating and then pulverizing the 
rock. The first method and the oldest is known as the kettle 
process, in which the gypsum is crushed, ground, then placed 
in large kettles and subjected to heat. This process drives 
off some of the water of crystallization, and if conducted at 
the right temperature and for the proper length of time, will 
produce a fairly uniform half hydrate. Glasenapp, however, 
says that on account of the difficulty of maintaining a perfectly 
uniform temperature, a small per cent of the mass may be 
reduced below a half hydrate or become a partially dehydrated 
half hydrate, which renders the product slower setting than 
the half hydrate. 
The second method is a more recent one, made possible 
by improved machinery. The gypsum is broken up into mod- 
erate sized pieces, and burned to drive off a portion of the 
water of crystallization, reducing it to a half hydrate. It is 
then led into a rotary drum and pulverized. In some cases, 
by means of a partial vacuum, the finest particles of the pul- 
verized product are drawn out into a suitable receptacle, and 
this constitutes the better grade of dental plaster. The qual- 
ity of the plaster, however, as before stated, is also dependent 
upon the purity of the gypsum used in its manufacture, the 
purer varieties producing the best grades. 
Regardless of the fact that plaster of Paris has been em- 
ployed for many years in dentistry, but little knowledge of 
its physical properties is current among those who use it, 
further than that it becomes plastic by mixture with water, 
that it sets or hardens quickly, and that it is more or less re- 
PHYSICAL PROPERTIES IMPRESSIONS AND IMPRESSION MATERIALS 
45 
sistant to stress. Why or how it sets, or how much pressure 
it will withstand without becoming distorted, are points of 
vital importance, practically unknown to, or at least disre- 
garded by, prosthetists. 
The entire bulk of plaster used by the dental profession 
represents but a very small per cent of the vast output of 
this material. The greater portion is used in the arts, build- 
ing trades, and in glass-making industries. A number of 
investigators, thoroughly competent, by training and with 
suitable apparatus, have made extended researches in the 
chemical and physical aspect of this material, and some of 
the results of their findings, together with some experimental 
work carried out by the writer, will here be presented. 
Professor M. Glasenapp, chief of the technical department 
of the University of Riga, Russia, an authority on building 
materials, has gone into this subject exhaustively. Although 
not relevant in all respects to the use of plaster in the pros- 
thetic field, the following extracts from his writings will shed 
much light on the chemical as well as the physical aspects of 
this material. The translation of Glasenapp’s work is by Dr. 
W. Michaels of Chicago. 
“If ordinary plaster of Paris, representing mainly the 
half hydrate CaS04 + 1/2H20 is mixed with water and exam- 
ined under a microscope, a lively process of crystallization 
can be observed to set in after five or six minutes. In the 
beginning, very thin needle-crystals form on the cover glass 
and shortly afterwards also in the liquid and on the particles 
of gypsum. After 15 or 20 minutes, single needle-crystals 
and groups of them can be seen in great numbers, and espe- 
cially the larger fragments of the half hydrate are covered 
with needle-crystals radiating from them, also the character- 
istic twin crystals appear abundantly. As fast as the crystals 
form, the original particles of the half hydrate disappear. 
After an hour they are completely used up and transformed 
into crystals, whereby the larger fragments of them become 
centers of accumulation of crystals, while the smaller have 
been converted into isolated star-shaped groups. After the 
same gypsum was heated for several hours to a temperature 
of 170 deg. C. (whereby the amount of water still remained 
6.2 per cent, corresponding with the half hydrate) crystal- 
lization began after 3 to 4 minutes, and was practically com- 
pleted after half an hour; only the largest particles required 
almost an hour to dissolve and re-crystallize. ” 
SETTING 46 
IMPRESSIONS AND IMPRESSION MATERIALS 
“The present state of our knowledge of the hardening of 
gypsum is that, after having been mixed with water, the half 
hydrate, plaster of Paris, and the first anhydrous modification 
of gypsum, which is supposed to be formed between 130 and 
200 deg. C., form over-saturated solutions, from which the 
di-liydrate precipitates in the shape of small crystals, a proc- 
ess which is finished only after all half hydrate or anhydrite 
is dissolved and transformed into crystals of di-hydrate. Ap- 
parently the half hydrate goes into solution more rapidly and 
crystallizes in a shorter time than the first modification of 
anhydrite; at least I conclude this from the fact that this first 
anhydrite, which is considered to be ‘easily soluble,’ dissolves 
the more slowly at a higher temperature than it was pro- 
duced.” * * * 
“To judge from even the most recent statements to be 
found in books on chemical technology, only a few chemists 
seem to be aware of the fact that a complete transformation 
of every particle of plaster is an essential point in its hard- 
ening. Owing to the greater solubility in water of burnt 
gypsum over crystallized gypsum, the hardening of plaster 
of Paris lias been attributed to a process of crystallization for 
some time; yet, this crystallizing has mostly been regarded as 
of secondary importance. The prevailing explanation was 
that the partly or completely dehydrated gypsum hydrated, 
combined with water, and hardened without changing its 
form or place; that is to say, without previous going into 
solution. The process, therefore, was considered to be sim- 
ilar to the hydration of calcined magnesia, and in many per- 
sons’ opinion seemed to resemble the hardening of Portland 
cement and of hydraulic limes. This erroneous conception 
likewise led to the belief that the strength of the casting de- 
pended upon the hardness of the native gypsum from which 
the plaster was burned. In fact, the difference in hardness 
between two kinds of raw gypsum is a matter of no conse- 
quence. 
THE STRENGTH OE HARDENED GYPSUM 
‘ ‘ The strength of the hardened gypsum depends solely upon 
the shape of the crystals, upon their size, and upon their 
more or less close contact. The more slowly the plaster hard- 
ens, the larger and stronger the crystals of di-liydrate grow, 
and the less water is mixed with the plaster, the denser and 
less porous the casting becomes. Molds which absorb water 
readily, therefore require a plaster containing as little an- 
hydrite as possible; furthermore, such molds call for a lib- IMPRESSIONS AND IMPRESSION MATERIALS 
47 
eral amount of water. Admixtures to the plaster, which re- 
tard the setting, so-called negative catalyzers, create large 
crystals and consequently are the cause of more resisting and 
stronger castings.” * * * 
“The microscopical examination of samples of powdered 
gypsum, burnt at temperatures higher than 200 deg. C., 
teaches nothing essentially ditferent from the behavior of the 
half hydrate or plaster of Paris toward water. Only the 
ability of this anhydrite to form over-saturated solutions is 
impaired; it is limited the more the higher the burning tem- 
perature has been, and the longer the material was heated. 
Transformation into crystals of di-hydrate takes place in the 
same manner, but more slowly. The following table gives the 
various temperatures to which the gypsum was exposed, as 
well as the time of heating in many instances, and the begin- 
ning and termination of the process of crystallization corre- 
sponding with them: 
TABLE OF “TIME OF CRYSTALLIZATION” OF PLASTER 
Beginning of 
Crystallization 
Temperature 
Burning Time 
Crystallization 
Completed After 
107 Centigrade 
6- 7 minutes 
y2 hour 
130 
<< 
6- 7 
y2 to 1 hour 
170 
< t 
3- 4 “ 
y2 hour 
200 
(< 
7 hours 
30-45 
y2 day 
200-250 
<< 
14 “ 
60 
7 days 
250-300 
u 
7 “ 
40 
3 “ 
400 
11 
i/2 hour 
1% hours 
17 “ 
450 
i i 
y2 <4 
10 days 
30 “ 
‘‘As the hardening of the castings of plaster is caused 
mainly by the transformation into the di-hydrate, and as this 
process of crystallization is the same also for ‘overburnt’ 
gypsum, the lack of hardening in the case of the latter must 
doubtlessly be ascribed, wherever it lias been observed, to the 
drying out of the uncovered castings; the process of crystal- 
lization, therefore, was interrupted and the casting could not 
obtain its full strength, which it otherwise would have done. 
This must happen, especially in cases in which the process 
of crystallization takes a number of days. With gypsum burnt 
at 200 deg. centigrade the transformation into crystallized 
di-hydrate is almost completed within 24 hours; only the 
larger particles take more time, and as, especially in the case 
of large castings, still a sufficient amount of water remains 
for crystallization after 24 or even 48 hours, this explains 48 
IMPRESSIONS AND IMPRESSION MATERIALS 
the fact that gypsum, burnt at 200 deg. centigrade and even 
above this temperature, unless heated for too long a time, or 
mixtures of this with standard plaster of Paris, show normal 
hardening and high strength. Rohland, who assumes that 
only a small portion of the gypsum, its active part, takes a 
share in the hardening, is therefore mistaken; the entire mass 
is active, if given time and opportunity to exhibit its activity, 
which is greatly diminished, indeed. ‘Complete hydration 
and transformation into di-hydrate without hardening,’ as 
Rohland describes it, is consequently out of the question. The 
term ‘overburnt or dead burnt’ gypsum is therefore mis- 
leading; the proper name for gypsum burnt at temperatures 
between 200 deg. and 300 deg. centigrade would be ‘slow 
setting. ’ 
“The process of hardening of such slow setting plaster 
shows two distinct phases. In the first place, the plastic 
dough assumes a dull surface and becomes stiff owing to the 
transformation of the anhydrite into the half hydrate. This 
point is reached after 1 or 2 minutes in the case of gypsum 
heated to 200 deg. centigrade and after 30 minutes or more 
with gypsum burnt at temperatures between 250 deg. and 300 
deg. centigrade. If further absorption of water is interrupted 
at this point by a rapid drying process, the stiff plaster is 
found to contain from 6 to 6.5 per cent of water of combina- 
tion, corresponding about with the half hydrate. During the 
second phase, which requires more time, the half hydrate 
previously formed goes into solution and crystallizes as di- 
hydrate. Setting and hardening are, therefore, two well pro- 
nounced processes in this case. Castings that have only time 
to set yield insufficient strength; they must be given time to 
harden. * * * * 
SIZE OF CRYSTALS OF ORDINARY PLASTER 
“The reason why castings made from ordinary quick set- 
ting plaster are low in strength and possess little resistance 
toward atmospheric influences, is evidently to be found in 
the minute size of the interlacing needle-crystals of di- 
hydrate, which, owing to the rapid process of crystallization, 
have not time to develop and grow larger. The following 
table illustrates this point by giving the dimensions of the 
crystals in millimeters and the corresponding temperatures 
at which the various kinds of quick-setting and slow-setting 
plasters have been burned: IMPRESSIONS AND IMPRESSION MATERIALS 
49 
Burning Temperature. 
Largest Dimensions of Crys- 
tals. 
Diameter. Length. 
107-130 centigrade 
0.0025 mm. 
0.04 mm. 
140 “ 
0.012 “ 
0.14 “ 
250-300 
0.075 “ 
0.50 “ 
400 
0.050 “ 
0.35 “ 
450 “ 
0.035 “ 
0.60 “ 
“The plaster burnt at 400 centigrade was heated only for 
half an hour; that burnt at 250-300 centigrade, however, for 
several hours. This explains the difference in the dimensions 
of the crystals. The first two of the plasters given in the pre- 
ceding table are quick-setting, the last three slow-setting. 
‘ ‘ The diameters of the needle-crystals of the plaster burnt 
at 107-130 centigrade are 30 times smaller than those origi- 
nating from the plaster burnt at 250-300 centigrade; their sec- 
tional areas, are, consequently, 900 times smaller. It is, there- 
fore, evident that, other things being equal, a casting made 
from slow-setting plaster must show greater strength. Hence, 
whenever time has not to be considered, and increased strength 
of the casting is desired, as, for instance, in the case of stat- 
ues for art galleries and so forth, experiments with slow- 
setting plaster seem to be very advisable. 
“In conclusion, the various calcined products obtainable 
from raw gypsum may be classified in accordance with the 
results derived from the foregoing research. The limits of 
temperatures stated must only be considered as approximate 
figures, of course, as the change from one kind to the other 
takes place very gradually, and because, as repeatedly stated, 
not only the height of temperature, but also its duration, deter- 
mine the properties of the calcined gypsum product. 
A. Native gypsum Di-hydrate containing two mole- 
cules of water. 
B. 107 centigrade Half hydrate containing y2 mole- 
cule of water. 
C. 107-170 centigrade... Consists mainly of half hydrate. 
D. 170-200 centigrade.. .More or less dehydrated half hy- 
drate. Combines with water 
readily until half hydrate is 
obtained. 
C. and D. represent the commer- 
cial plaster of 50 
IMPRESSIONS AND IMPRESSION MATERIALS 
E. 200-250 centigrade.. .Contains a very small amount of 
water. Sets more slowly than 
the former. 
F. 250-400 centigrade.. .Contains only a trace of water. 
Slow-setting. B., C., D., E. 
and F. form crystals of di-hy- 
drate, if mixed with water. 
Hardening due to crystalliza- 
tion. 
G. 400-750 centigrade... Completely dehydrated, anhy- 
drite, overburnt from a prac- 
tical point of view. 
H. 750-800 centigrade. . .Gradual transformation into the 
granular modification of anhy- 
drite; beginning of the forma- 
tion of hydraulic gypsum. 
G. and H. show in contact with 
water. No hardening, or only 
very imperfect hardening. 
T. 800 centigrade.. .Hydraulic gypsum containing 
minute grains of anhydrite. 
K. 900-1000 centigrade.. .Genuine hydraulic gypsum, 
grains fully developed. 
L. 1000-1400 centigrade...Hydraulic gypsum, showing 
grains increasing in size and 
hardness with rising tempera- 
ture. The percentage of *1 basic 
calcium sulphate” likewise in- 
creases in the same ratio. 
I., K. and L. harden slowly with 
water without crystallizing. 
G., H., I., K. and L. crystallize 
with alum solution. 
“A temperature of from 1300 deg. to 1400 deg. centi- 
grade, in my opinion, can be employed in the manufacture of 
hydraulic gypsum only in cases in which gypsum does not 
come in immediate contact with the fuel, as, for instance, in 
laboratory experiments, in which the burning is done with 
gas. 
“Where coal is used, the ashes of it, as well as the reduc- 
ing carbon, are bound to contaminate and spoil the calcined 
product. Moreover, temperatures as high as these are almost 
out of the question in practical operations.” IMPRESSIONS AND IMPRESSION MATERIALS 
51 
The foregoing extracts refer especially to the chemistry 
of setting, and the effects of varying temperatures and time 
in burning on the time of setting and hardness of plaster. 
The method of manipulation is not considered. This to the 
prosthetist is a matter of importance that cannot be over- 
looked. 
INFLUENCE OF MIXING ON QUALITY 
Plaster mixed at a medium to thick consistency will set 
more rapidly and be of better density when set than if an 
excess of water is present. Too thick a mix, however, should 
be avoided, particularly where accelerators are used, as under 
such circumstances the setting frequently begins before the 
mass is of uniform consistency, and further stirring breaks 
up the already forming crystals. This interference results in 
a mass of uncertain density, oftentimes with many spaces 
present. 
The other extreme, too much water, should be avoided, as 
it retards the setting, and the plaster, when set, is less resist- 
ant to stress. Various substances are added to accelerate 
the setting, particularly in impression work. Common table 
salt (NaCl) is frequently used, but should never be incor- 
porated in plaster used for casts for vulcanite work, since its 
affinity for moisture causes rapid softening and deterioration 
in the presence of steam or water. Sulphate of potassium 
(K2S04) is by far the best accelerator, because it not only 
hastens the setting, but has a controlling influence on expan- 
sion. This medium, however, should not be used in cast con- 
struction for the same reasons that apply to NaCl. Potas- 
sium alum has been highly recommended as an accelerator 
and hardening medium for plaster in dental laboratory pro- 
cedures, but tests made with this substance fail to verify the 
claims made for it. 
EXPANSION OF PLASTER 
The tendency of plaster to expand during and after set- 
ting and the deleterious effects of this movement in denture 
adaptation have long been recognized by some, but its impor- 
tance is not fully understood. 
When freshly mixed plaster begins to set, it contracts 
slightly, then remains stationary for a short time, then ex- 
pands, and after assuming a thoroughly dry condition it again 
contracts to a very slight degree. From 6 deg. to 10 deg. rise 
in temperature is noticeable during the setting process, due to 
the chemical action that occurs. 52 
IMPRESSIONS AND IMPRESSION MATERIALS 
In an ordinary mix of impression plaster that hardens in, 
say, 3 minutes, the first contractile period occurs between the 
time of mixing and that of the beginning of setting. Since 
the consistency of plaster, when freshly mixed, is soft and 
the mass yielding, no accurate records can be made of any 
change that may occur within the first minute after mixing. 
From the beginning of the second minute, usually, the mass 
being hard enough to resist the tension spring of the microm- 
eter, the contraction is perceptible and usually continues for 
about 2 minutes, or until the evolution of heat is noticeable. 
This would establish the contractile period in the last two of 
the three minutes that elapse between the time of mixing and 
that of setting. Any variation in the time required for setting 
would undoubtedly produce a corresponding change in the 
contractile period. 
The contractile stage is followed by a short period of 
inertia of usually about one-half minute, after which expan- 
sion sets in, slowly at first, then increases rapidly for two or 
three minutes, then decreases gradually, and finally ceases 
altogether. Usually the greatest expansion is over in ten min- 
utes, although the movement continues in a gradually decreas- 
ing ratio for twenty-four hours or more. 
The rate and amount of expansion is very greatly influ- 
enced by the manner in which the plaster is mixed with the 
water, and the method and length of time the mass is stirred. 
Long and rapid stirring increases the rapidity of setting, and 
the rate and amount of expansion as well, while on the other 
hand slight stirring for a short time induces only moderate 
movement. 
MEASUREMENT OF EXPANSION AND CONTRACTION OF 
PLASTER 
For the purpose of studying the behavior of plaster under 
different conditions, the writer constructed a micrometer 
which registers both the expansive and contractile movements 
of this and other materials as well. See Fig. 14. 
This instrument is graduated to read to the 1/10,000 of an 
inch and the 1/500 of a mm. In reality readings can be made 
to the 1/40,000 of an inch. The spring actuating the contact 
rod is very delicate and offers hut slight resistance to expan- 
sion, so that practically all of this movement can be noted. 
The following records, taken from many hundreds, show 
the results of stirring the several mixes varying lengths of 
time. French’s impression plaster was the material used, IMPRESSIONS AND IMPRESSION MATERIALS 
53 
the mixes being practically identical as to weight, amount of 
water, temperature of room and material. Nothing was added 
to accelerate setting or control expansion. The plaster was 
sifted into the water in the rubber bowl. The only appreci- 
able difference was in the length of time each mix was stirred. 
No. of Mix. 
Time Stirred. 
Minutes. 
Expansion 
After 
10 Minutes. 
Points. 
24 Hours. 
Points. 
1 
% 
2 
61 
2 
i 
32 
101.5 
3 
m 
61 
93.5 
4 
93 
118.5 
5 
i% 
118 
134 
6 
2 
137 
157.5 
7 
2i/4 
140 
160 
8 
2% 
142 
159 
9 
2% 
147 
165 
10 
3 
145 
162 
The point is 1/10,000 of an inch. 
The mixes were of a consistency suitable for impression 
work. 
Further experiments indicate that thinly mixed plaster 
exhibits less expansion than when more thickly mixed, but the 
density is proportionately less, as the mixes are made thinner. 
CONTROL OF EXPANSION 
Many experiments have been made with different sub- 
stances, singly, in combination, and in varying proportions, 
in an effort to control this expansive movement, but with the 
exception now to be mentioned, only negative results were 
observed. 
Potassium sulphate in definite proportions acts as an 
accelerator, and also decreases expansive movement. The 
slightest amount of stirring consistent with the production of 
a uniformly plastic mass is also important in keeping down 
the expansive movement. 
WARPAGE 
In prosthetic procedures the principal difficulty resulting 
from expansion is in the warpage of impressions and models 
when allowed to remain in the tray for any length of time 
after the plaster has set. 54 
IMPRESSIONS AND IMPRESSION MATERIALS 
Dr. Buckingham, in 18G0, first noticed the expansive move- 
ment in plaster, but he failed to realize the deleterious effect 
of it. Dr. W. Bowman McLeod, of Edinburgh, Scotland, in 
1880, first called attention to the warpage of plaster when con- 
fined in an impression tray. His experiment consisted in 
clamping metal bars to the edges of a rigid metal plate and 
filling the enclosed space with properly mixed plaster. 
Fig. 14.— Expansion Machine 
Fig. 15.— Warpage of Plaster on Slab with Fixed Sides (Dr. W. Bowman 
McLeod’s Experiment) 
After twenty-four hours the bars were removed, and the 
slab of plaster sawed diagonally through the center, when it 
was found that in the central portion it had arched up to a 
considerable extent, while the edges remained in contact with 
the plate. This was due to the fact that lateral expansion was IMPRESSIONS AND IMPRESSION MATERIALS 
55 
prevented by the fixed marginal bars, which, however, did not 
confine the material on its upper surface, and movement oc- 
curred in that direction. 
An impression tray with its fixed sides corresponds to the 
slab with clamped bars. The sides of the tray prevent lateral 
Fig. 16.— Warped Impression Due to Fixed Tray Flanges 
expansion, so that the movement is noticeable by the arching 
up or warping of the palatine portion of the impression, while 
the sides inclosed by the buccal and labial flanges of the tray 
remain in close contact with them. The result is that the pala- 
tine portion of the impression raises, while no corresponding 
movement occurs in the alveolar portion. Now if the plaster 
for the cast is introduced in the impression and allowed to 
remain for some time, a similar error due to a corresponding 
cause will result, and thus establish an additional increase in 
the height of the palatine arch of the cast. 
Fig. 17.— Warped Cast Due to Restricted Lateral Movement 
ERRORS DUE TO WARPAGE 
Two errors, due to warpage, have therefore occurred, 
either one of which might, and certainly both together will, 
result in the cast being an imperfect reproduction of the 
mouth it is intended to represent. A denture molded over 
such a cast will touch the palatine portion of the mouth before 
it is firmly seated on the alveolar borders, and under stress 56 
IMPRESSIONS AND IMPRESSION MATERIALS 
of mastication will readily tip. In some instances there will 
be no adhesion whatever. The method for reducing or par- 
tially controlling and overcoming expansion of plaster impres- 
sions and casts will be taken up when considering the technic 
of this work. 
COMPRESSIBILITY OF PLASTER OF PARIS 
An object composed of plaster of Paris appears like a solid 
substance and is resistant to ordinary stress without change 
of form. When we examine this material under a microscope, 
however, it is found, as before stated, to be composed of 
numerous crystals grouped irregularly in masses with many 
spaces between the masses and between the crystals them- 
selves. Within and below the modulus of resistance of these 
crystals, they retain their form and resist a very considerable 
amount of stress without crushing. 
Fig. 18.— Compression Machine 
In certain technical procedures, particularly in vulcanite 
work, plaster is usually subjected to heavy pressure. By ex- 
periment it lias been found that, in many cases, an amount of 
force far in excess of the modulus of resistance of this material 
is ordinarily used in laboratory procedures. While perhaps 
in some instances the physical change is not apparent to the 
eye, it can be readily discerned in others. In many instances 
where no visual change is noticeable, the adaptation of den- 
tures is seriously interfered with, which can be laid to no other 
cause than that of compressibility. Further discussion of this 
important problem will be continued under the subject of the 
flashing of vulcanite cases. 
Plaster has, however, a number of good qualities which 
commend it for impression work, and notwithstanding the 
ADVANTAGEOUS PROPERTIES OF PLASTER OF PARIS 57 
IMPRESSIONS AND IMPRESSION MATERIALS 
serious disadvantages which have already been cited, it is an 
indispensable material in prosthetic procedures. Its plasticity 
when freshly mixed, its tastelessness and freedom from odor, 
the facility with which the most irregular surfaces can be 
copied, its rapid setting property, and the fact that it can be 
introduced in the mouth at ordinary temperatures, commend 
it for general use. Being inelastic and brittle, it breaks with 
a clean fracture, and the broken pieces can easily be placed 
together again in exact relation to each other, so that by its 
use the impression of any surface, however irregular, may be 
secured with accuracy. 
Only the finest grades of dental plaster should be used for 
impression-taking, and it should be kept dry and in air-tight 
receptacles to retain its setting quality. When used with skill 
and in properly selected cases, it is an excellent medium for 
impression work, and indispensable for many other purposes. 
In mixing plaster, the best results are secured by placing 
the required amount of water in the bowl and sifting the 
plaster into it until a sufficient amount has been added to take 
up the water. No excess of water should be present, while an 
excess of plaster results in an insufficient amount of water to 
bring the half hydrate into solution. It should be subjected 
to the slightest amount of stirring — just enough to make 
the plastic mass homogeneous and of uniform consistency 
throughout. 
IMPRESSION COMPOUNDS 
These are manufacturers’ products intended for impres- 
sion work, and into which, on drying, metal dies can be run 
without resorting to the usual steps in such cases. The basis 
of all such compounds, however, is plaster of Paris, which acts 
as a cementing medium between the particles of refractory 
material, usually pulverized or granular calcium carbonate, 
silex, pumice-stone or coarsely ground asbestos. But little, if 
any, advantage is derived from their use. 
CEMENTS 
The various dental cements are at times employed in taking 
impressions of limited areas, as, for instance, of prepared 
teeth for inlay work, or in certain procedures in crown and 
bridge work. They are used to such a limited extent as not 
to be considered as general impression materials. 58 
IMPRESSIONS AND IMPRESSION MATERIALS 
Group II 
IMPRESSION MATERIALS RENDERED PLASTIC BY HEAT MODELING 
COMPOUND 
Modeling compound, as its name implies, is made up of 
several ingredients combined in such proportions as to pro- 
duce a material that is plastic and workable at low tempera- 
tures, which will copy accurately the surfaces against which 
it is pressed, and cool or harden quickly. Since the formulae 
of the manufacturers are not published, it is not possible to 
give exact data on this subject. The base of this material, in 
practically all cases, consists of one or more of the natural 
resinous gums used in varnish making, such as dammar, copal 
or kauri. These gums are more or less hard when dry and 
cold, but become sticky and plastic on heating. Stearin is 
added to reduce the stickiness, while pulverized soapstone is 
incorporated to give body to the mass. Carmine is usually 
used to tint the material, and sometimes a little aromatic 
flavoring substance is added to render it pleasant in taste 
and odor. 
FORMULA FOR MODELING COMPOUND 
A formula which will serve to illustrate the compounding 
of this material was given to the writer a number of years ago 
by Dr. E. Lloyd Williams of London: 
Kauri 1 part 
French chalk 1% parts 
Stearin iy> parts 
The stearin is first melted, the kauri added, and the two 
thoroughly incorporated, then the chalk is gradually sifted in 
and the mass kneaded until well mixed. The coloring and 
flavoring ingredients should be incorporated in the stearin and 
gum before adding the soapstone. 
Some varieties of compound show a decided tendency to 
contract, or warp, on cooling, which properties make them 
unreliable in impression work, while some, to render them 
efficiently plastic, require a degree of temperature unbearable 
to the oral tissues. While the tissues of the mouth can toler- 
ate temperatures ranging from 140 to 170 deg. F. without much 
discomfort, a compound should be selected that will copy fine 
lines and irregular surfaces at even lower temperatures than 
those mentioned, in order to be efficiently workable. 
As a rule, modeling compound is heated in water to soften 
for impression work, but should never be subjected to boiling 
temperature, as its quality is soon impaired and the material IMPRESSIONS AND IMPRESSION MATERIALS 
59 
is too sticky to handle conveniently when overheated. The 
bottom of the vessel used for heating should be covered with 
a piece of rubber dam, or clean paper, to prevent the compound 
adhering to it. Softening in water is preferable to dry heat, 
although some use the latter method. Modeling compound is 
inelastic and therefore when impressed against a surface it 
should be thoroughly hardened before removal from the mouth, 
since in the act of loosening the impression or in its with- 
drawal, pressure upon the prominent portions is liable to dis- 
tort it. This precaution also applies to most of the substances 
made plastic with heat. 
BEESWAX 
This material is elaborated by bees out of substances col- 
lected from flowers and from it the honeycomb is formed. 
The wax is prepared for use by melting the comb in water 
after removal of the honey. Impurities lighter than the wax 
are skimmed off, or if heavier are removed by trimming the 
under surface of the hardened cake. The natural color of bees- 
wax is yellow. It may be bleached by forming it into thin 
sheets and exposing it to bright sunlight, or by the use of 
dilute acids in the melting pan. It may be given almost any 
tint desired by the addition of suitable pigments. 
It was formerly much used as an impression material, but 
has been to a great extent supplanted by modeling compound. 
There are two serious objections to the use of beeswax as a 
material for general impression work: First, when disposed 
around the labial and buccal portions of the alveolar border 
unsupported by the tray, in a thin layer, it is very apt to be 
distorted in removal because of lack of inherent rigidity, even 
when chilled; second, there is a tendency for it to warp and 
contract in changing from a heated, plastic condition to a cold 
state. When manipulated with care it may be used to advan- 
tage in some cases, although it is difficult to say in what in- 
stances it would be preferable to modeling compound, since in 
recent years the quality of the latter has been so materially 
improved. 
Wax is furnished by the manufacturers in the form of 
sheets and cakes, both in a pure state and combined with other 
substances, such as paraffin or some of the resins, to render it 
harder or more adhesive, as desired. 
BEESWAX AND PARAFFIN 
The addition of paraffin to beeswax lowers its melting point 
and renders it harder when cold, but reduces the adhesiveness 60 
IMPRESSIONS AND IMPRESSION MATERIALS 
of the wax if used in excess. Tallow is frequently used as an 
adulterant of wax. The combination, however, is worthless 
for dental purposes. The sticky wax, so useful for many pur- 
poses in the laboratory, comes in the form of small sticks or 
cylinders, and is made by combining some of the resins with 
beeswax. It is adhesive and hard when cold, and is much used 
in the assembling of parts in crown and bridge work. 
HARD BITE WAX 
A material known as hard bite wax is procurable, which is 
very convenient in the making of wax contour models for use 
in warm weather. When formed of this wax, the rims with- 
stand the stress of trial in the mouth, as well as the effect of 
oral temperature, without becoming distorted. Wax of this 
class usually contains rosin. 
Beeswax is manipulated much the same as modeling com- 
pound, being softened in warm water. It should be broken 
up in small pieces, if in bulk, or in sheets of moderate thick- 
ness, so that the heat may penetrate readily at rather low 
temperatures, say 130 deg. to 140 deg. F. When thoroughly 
warmed, it is kneaded with the fingers into a uniform plastic 
mass and pressed with a towel to take up any moisture that 
may be present. 
None of the plastic, non-elastic impression materials, with 
one exception, are suitable for taking impressions in under- 
cut spaces, or in partial cases where the teeth have constricted 
services or the embrasures and interproximate spaces are de- 
void of gum tissue. Under certain conditions and by follow- 
ing methods to be outlined later, modeling compound may be 
used. 
The difficulty encountered in such cases is due to the draw- 
ing or distorting of the impression material in withdrawal 
from the teeth and spaces designated. 
Beeswax is frequently employed as a preliminary impres- 
sion material in partial as well as full cases, the impression 
thus obtained being relieved of excessive surplus and used as 
a matrix or improvised tray for holding the plaster for the 
final impression. By this means, the wax having been con- 
formed to the tissues, a minimum quantity of plaster is car- 
ried to every surface involved, with less discomfort to the 
patient, while the ratio of expansion in the plaster is corre- 
spondingly less. In partial cases, however, the wax should be 
trimmed well away from around the remaining teeth, so that 
the plaster enclosing them may be of sufficient thickness when IMPRESSIONS AND IMPRESSION MATERIALS 
61 
fractured in removal, to be readily placed together again in 
the wax matrix. 
GUTTA PERCHA 
This material is obtained from the juice of a tree, the Ison- 
andra or Dichopsis Gutta, found in the Malay Archipelago, on 
either side of the equator, for a distance of two or three 
degrees. 
The word “gutta” in the Malay language means “gum” 
and “percha” is the name of the tree, so the term means the 
“gum of the percha tree.” The juice is collected by a method 
similar to that followed in tapping the rubber tree (Siphonica 
Elastica) by making a long diagonal cut entirely through the 
bark and adjusting a trough under the incision, through which 
the escaping juice is carried into vessels to receive it. As 
more or less dirt and impurity is mixed with the juice, the 
crude material is unfit for use. It is refined by first tearing 
it into shreds in a special machine, washing and agitating in 
water, and afterward boiling, to bring it into a coherent mass, 
in which form it is known as commercial gutta percha. It is 
nearly similar in composition to rubber, being a hydrocarbon, 
but, unlike that substance, it deteriorates slowly if exposed 
to the air, the oxygen of the air uniting with it and causing 
the gum to become brittle and lose its elasticity and strength. 
It can be mixed with sulphur and vulcanized, but the product, 
while more durable than the crude material, is not so perma- 
nent or lasting as vulcanite, and consequently is not used in 
this form to any great extent. 
The fresh commercial product is sometimes used for taking 
impressions of the mouth. It becomes plastic enough for this 
purpose at a temperature of 130 deg. to 150 deg. F. and is pre- 
pared by softening in water. It will contract, however, unless 
dried and heated sufficiently to adhere to the sides of the tray. 
In general, it is manipulated the same as modeling compound, 
except that special care must be observed to cement it to the 
tray before introduction into the mouth and to chill it thor- 
oughly before removal. Being elastic, it will readily draw 
away from undercuts and teeth with constricted cervices, and 
immediately resume its proper form when pressure is relieved. 
CONSTITUENTS OF GUTTA PERCHA 
As it is difficult, or almost impossible, to secure the fresh, 
unadulterated product, its use as an impression material is 
very limited. The base plate gutta percha furnished by the 62 
IMPRESSIONS AND IMPRESSION MATERIALS 
supply houses is not composed of the pure gum, but contains 
chalk, magnesia or oxide of zinc, and frequently coloring 
matter. The addition of these substances prevents, to a certain 
extent, rapid deterioration, and also renders the product more 
rigid. While sometimes used for the base of trial plates, gutta 
percha is not sufficiently rigid to insure accuracy in such pro- 
cedures. The sheet base plate is frequently used for taking 
impression of faced roots in crown and bridge work where it 
is desirable to force the gingivae apically to obtain an outline 
of the root periphery. 
Gutta percha consists of a combination of hydrocarbons 
similar to caoutchouc. 
Payen’s analysis shows the following: 
Gutta 78 to 82 per cent 
Albane 16 to 14 per cent 
Fluavile 6 to 4 per cent 
Chemical composition: 
Carbon 86.36 
Hydrogen 12.15 
Oxygen 1.49 
Since the juice is collected from several varieties of trees 
and comes from different localities, it is a natural consequence 
that the physical as well as chemical proportions of constitu- 
ents must vary more or less, so the above may be considered 
as representing the general composition of this material and 
not an absolute unchangeable chemical formula. CHAPTER VII 
TECHNIC OF TAKING IMPRESSIONS 
GENERAL REMARKS 
In general, the taking of impressions in plaster for full 
and partial, upper and lower cases, is similar in many tech- 
nical details. A comparatively full description of the manipu- 
lative details carried out in taking an impression of an upper 
edentulous cast, will serve as a basis for all classes of plaster 
impressions. The difference in details will be presented as 
each class is described. 
The value of plaster as an impression material lies in the 
fact that it can be readily adapted to the most irregular sur- 
faces and carried into deep undercuts and embrasures, from 
which it can be removed by fracturing, and the broken parts 
readjusted with ease. 
An outline of those cases where plaster is most strongly 
indicated, is here in order: 
First — In all cases where any of the natural teeth are 
present. 
Second — In case undercuts exist, either on the opposite 
surfaces of the borders, or in spaces formed as the result of 
the loss of the natural teeth. 
Third — Where flabby ridges are present, such as have 
previously been described. 
Fourth — In edentulous cases where the mucous and sub- 
mucous tissues are thick and elastic, particularly in the pala- 
tine portion of the mouth. When such a condition prevails, 
the tissues, if compressed uniformly, as when modeling com- 
pound is used, assert their resiliency, on pressure being re- 
lieved, which breaks the peripheral adaptation of the impres- 
sion, and later, of the denture that may be constructed when 
such an impression is used as a basis. 
In practically all of the cases just cited, the use of bees- 
wax or modeling compound, as an impression material, is 
contra-indicated, but the use of either of these substances as 
a preliminary impression material, in which to hold the plaster 
for the final impression, is strongly indicated. 
INDICATIONS FOR THE USE OF PLASTER 
63 64 
TECHNIC OF TAKING IMPRESSIONS 
Upper Edentulous Cases 
PRELIMINARY STEPS IN IMPRESSION TAKING 
Taking it for granted that the mouth has been previously 
examined and is in condition to receive prosthetic substitutes, 
the patient is seated in the operating chair. 
POSITION AND COMFORT OF THE PATIENT 
As a general rule in all plaster impression work the patient 
should sit in an upright position. The chair may be slightly 
inclined backward, but not to any marked degree. The chair 
should be raised high enough to bring the patient’s mouth 
within convenient range for manipulation. Further adjust- 
ment of the chair should be made for the comfort of the patient, 
so far as may be consistent with the work in hand. 
A covering should be adjusted to protect the patient’s 
clothing from becoming soiled with particles of plaster, or 
the dripping or overflow of saliva from the mouth. When 
possible to do so, the saliva ejector should be used to over- 
come this difficulty. Before taking the impression, the mouth 
should be rinsed with tepid water, or, preferably, normal salt 
solution, to remove the viscid, stringy mucous. A glass of 
water should be placed on the bracket so that the patient may 
rinse the mouth after the removal of the impression. 
POSITION OF THE OPERATOR 
For upper impressions the operator should stand on the 
right side of the chair, and slightly back of the patient. He 
should stand erect and work with the upper arms perpen- 
dicular, and the forearm horizontal. In introducing an upper 
impression, his left arm should pass to the left of the patient’s 
face, so that the left hand may manipulate that angle of the 
mouth, and later, support the tray. 
In taking lower impressions, the operator will find it more 
convenient to stand slightly in front, to the right of, and facing 
the patient. In this position, both hands have more freedom 
of action, and the line of vision is less obstructed than when 
the operator stands back of the chair. 
SELECTING AND FITTING TRAY TO MOUTH 
By a glance in the mouth, the operator can determine the 
approximate form and size of tray to use, and select one 
accordingly. This is introduced in the mouth, and its general TECHNIC OF TAKING IMPRESSIONS 
65 
adaptability to the case ascertained. If approximately of the 
right form, but not exactly adapted to the case, the points need- 
ing modification are noted. By placing tbe tray in position 
and subjecting it to a side-to-side movement, the excess of 
buccal space can be estimated. By holding the distal margin 
of the tray against the palatine vault in approximately the 
correct mesio-distal position that it should occupy, and letting 
the anterior portion of the tray drop down below the border 
level, so that a view above the tray of the vault and tray cur- 
vature may be obtained, the adaptation of the vault portion of 
tray to tissue can be determined. 
Fig. 19.— Full Upper Impression Tray Suitable for Edentulous Cases 
The relative width of the labio-buccal flange to the alveo- 
lar border, and the several points of muscular attachment can 
be determined by holding the tray in position, rather loosely, 
of course, since the impression material is not present, and 
subjecting the lips and cheeks to outward and downward trac- 
tion. If too broad, the amount of excess width can be deter- 
mined by alternately pressing upward on the central portion 
of the tray and pulling downward on the lips and cheeks, the 
amount of movement in the tray indicating the excess present. 
Hold the tray in normal position with one hand and pass 
the index finger of the other hand backward along the central 66 
TECHNIC OF TAKING IMPRESSIONS 
vault portion, past the tray margin, onto the oral tissue, and 
determine whether this portion of the tray extends to the line 
of junction of hard with soft palate. If not, make an exten- 
sion, as described elsewhere. The usual space outline of an 
eighth of an inch, or less, between tray and tissue, should be 
closely adhered to, since a small amount of impression mate- 
rial, properly applied, will yield more accurate results and be 
less objectionable to the patient than an excessive bulk. 
MIXING THE PLASTER 
A clean rubber bowl is filled about one-fourth full of 
slightly warm water, into which should be sifted some impres- 
sion plaster (plaster which contains an accelerator). Or, if 
French’s regular dental plaster is used, dissolve about one- 
half gram of sulphate of potassium in the water before sifting 
in the plaster. This will hasten the setting and also have a 
slight control on expansion. 
Add enough plaster to take up the excessive moisture, and 
produce a plastic mass, which, when stirred slightly, will stand 
when piled upon itself, or in other words, will not drop from 
the inverted tray. Distribute the mixture in the tray selected, 
spreading it uniformly over the various surfaces and building 
it slightly higher on the vault portion than elsewhere, to in- 
sure a sufficient amount of material being present. The gen- 
eral contour of the plaster in the tray should be similar to the 
general contour of the mouth, but reversed, of course. 
INTRODUCING THE FILLED TRAY IN THE MOUTH 
Tlie tray handle is held in the right hand, thumb on top 
of handle, index and middle fingers underneath, to support the 
body on the right side. The right angle of the tray is inserted 
well back in the right angle of the mouth, while, the opposite 
side is rotated through the left angle of the mouth, the latter 
being distended with the index or middle finger of the left 
hand. 
After the greatest diameter of the tray has passed the oral 
opening, its adjustment, although requiring care, is easily 
accomplished. 
See that the tray is centered. The direction of the handle 
indicates this to a certain extent, although it cannot be de- 
pended on in those cases where the buccal alveolar process 
has been absorbed more on one side than on the other, or TECHNIC OF TAKING IMPRESSIONS 
67 
where the alveolar processes are not symmetrically related to 
the medium line of the cranium. 
Pass the tray back until the labial surface of the border 
is within about one-fourtli of an inch of the flange and press 
the tray upward until the border is fairly well imbedded in 
the plaster, not, however, to the full extent, as at this time 
muscular impingement is not yet relieved. The index and 
middle fingers of both hands are placed under the floor of the 
tray to carry the impression to place. This is the first, or 
pressure position of the hands. Apply the index and middle 
fingers of the left hand to the vault portion to support the tray, 
and quickly pass the index finger of the right hand along the 
buccal border of the right side of the tray, at the same time 
producing tension on the buccal muscles, drawing them out- 
ward to prevent them from becoming caught by and folded 
interiorly over the tray margin. Then reverse the position of 
the hands and carry out a similar procedure on the opposite 
side, being careful not to disturb the relation of the impression 
to the border during this step. Now return to first, or pres- 
sure position, and apply sufficient force to carry the impression 
firmly to place. 
SECURING PERIPHERAL ADAPTATION 
Return to the second, or tray supporting position, and with 
the free hand press against the lips and cheeks, directing the 
pressure from low down near the floor of the tray, inward and 
upward against the outer flange, so as to carry the plaster that 
has been forced outside the flange, upward against the labial 
and buccal surfaces of the border. 
MUSCLE MASKING OF THE PERIPHERY 
While still supporting the impression, instruct the patient 
to produce buccal and labial muscular tension on the periph- 
eral plaster margins, in order to indicate distinctly the position 
and form of muscle tendons and labial frenum. 
All of these steps should be carried out quickly, before the 
plaster has set to any appreciable extent, for if allowed to set 
too hard, the muscle markings will not show distinctly. Usu- 
ally all of the details as outlined can be carried out in from 
thirty to forty seconds. 
Steady, moderate and uniform pressure maintained on the 
floor of the tray with the index and middle fingers of both 
hands, until the plaster has become well hardened, is essential. 68 
TECHNIC OF TAKING IMPRESSIONS 
The hardness of the plaster is determined by breaking some 
of that remaining in the bowl. When it breaks with a clean 
fracture, and without crumbling, the impression is ready for 
removal. 
DISLODGING THE IMPRESSION 
If the impression is correct and well adapted, it should 
adhere to the tissues firmly, and require considerable effort 
to effect its removal. An impression that requires but slight 
effort to dislodge it can rarely be relied upon to serve as a 
basis for an accurately fitting denture. 
To break the adhesion, the index finger is passed back- 
ward inside the cheek opposite the buccinator muscles, and 
pressure made outward and upward on them. These regions 
on either side are the natural air valves to the vault portion, 
and with some slight traction on the handle, at the same time 
the buccal muscles are lifted as described, the adhesion of the 
impression will be broken without much difficulty. Should this 
method fail, instruct the patient to cough, and at the same 
time press upward on the tray handle. The sudden muscular 
contraction occurring in the soft palate lifts these muscles up 
from the distal margin of the impression, and at the same 
time forces the air in between the tissues and the plaster. 
REMOVAL OF THE IMPRESSION 
When loosened, the impression is dropped down, clear of 
the border, and rotated out of the mouth in much the same 
manner as it was introduced, but with reversal of movement, 
and without the necessity for distending the oral angle with 
the finger. 
In edentulous cases where decided undercuts are present, 
it is advisable to oil the tray before introducing the plaster, 
and when the impression is ready for removal, dislodge and 
remove the tray first. The impression can then be weakened 
by cutting, so as to be removed in pieces, thus preventing in- 
jury to the tissues that, in some cases, would most certainly 
follow its removal as a whole. 
INSPECTION OF THE IMPRESSION 
On removal, the impression should he carefully inspected 
to see that all essential surfaces have been copied, and that 
it is intact. Tf fractured at any point, the broken parts are TECHNIC of taking impressions 
69 
recovered, placed in their respective positions, and held there 
by melting a little wax along the external fracture line. 
The treatment of the impression and the production of the 
cast will be described in a subsequent chapter. 
Edentulous Lower Cases in Plaster 
The tray in these cases should be of such size that the crest 
of the alveolar process will occupy a central position between 
the outer and the inner flanges. The usual eighth of an inch 
space allowance for impression material should be present. 
The flanges should not impinge on the buccal, labial or lingual 
SELECTING THE TRAY 
Fig. 20.— Lower Tray Adapted to Border Showing Uniform 
Space for Impression Material 
muscles or franse. This requirement is essential in order that 
their subsequent movements may be unrestricted. 
When considerable absorption of the border has occurred, 
either uniform or unequal, a preliminary impression in wax 
or modeling compound should be taken, the excessive surplus 
trimmed away, and this modified impression used as a tray. 
Frequently, by extending the lingual wings of lower den- 
tures distally, when the shape of the mandible permits, and 
muscular attachments do not interfere, much greater stability 
of the substitute is assured. If such a plan is feasible, a tray 
with deep lingual wings should be selected, or if the tray at 
hand most suitable in other respects is deficient in this, addi- 
tions of suitable length to carry the impression material 
against the desired areas should be made with wax or com- 
pound, and tested in the mouth before attempting to take an 
impression. 
The tendency in selecting trays for lower cases is to choose 
one with too wide buccal and too narrow lingual flanges. The 70 
TECHNIC OF TAKING IMPRESSIONS 
plaster is mixed as described for upper cases. It should be 
distributed in the tray in a uniform layer about one-fourth of 
an inch thick, confining it within the tray flanges. 
POSITION OF PATIENT 
The position and elevation of the patient in the chair should 
be about the same as in taking impression of the upper arch. 
The operator should stand on the right side, somewhat in 
front of, and facing the patient. Some prefer to lower the 
chair a trifle below the point designated, and stand back of 
POSITION OF OPERATOR 
Fig. 21.— Lower Tray with Deep Lingual Flanges 
the patient during the manipulative procedures. The first 
described position is to be preferred in most cases, for, as 
before stated, the line of vision is less obstructed and the hands 
have more freedom of movement than when the operator 
stands behind the patient. 
INTRODUCING THE TRAY 
The operator holds the inverted tray between the thumb 
and index and middle fingers of the right hand, the thumb 
beneath and the index finger on the handle, the middle finger 
resting on the right side, just back of the first finger. The 
index finger of the left hand distends the right angle of the 
patient’s month. The left angle of the tray is inserted in the 
left angle of the mouth, while with a deft rotary movement the 
tray is brought into position over the border. TECHNIC OF TAKING IMPRESSIONS 
71 
When the operator assumes the position back of the chair, 
the right angle of the tray is inserted in the right angle of the 
mouth, while its left angle is rotated into position through the 
left angle of the mouth, which is being distended with the oper- 
ator’s left index finger. 
SEATING THE IMPRESSION 
The technic of carrying the impression to place is as fol- 
lows— the operator standing in front of the patient: The 
tray being centralized, the index fingers are placed on either 
side of the body, the thumbs under the mandible, and pressure 
applied to carry it partially to position. Now place the thumb 
of one hand under the mandible, the index finger across the 
tray body to steady it, and grasp the cheek well back with the 
thumb and index finger of the other hand and pull outward, 
to draw any folds of the cheek or buccal muscles outward that 
may have been caught under the tray margins. 
Reverse the hands and carry out the same procedure on the 
opposite side. Grasp the lip in a similar manner, drawing it 
out from under the tray margin. Instruct the patient to lift 
the tip of the tongue up and touch the high part of the vault. 
These movements clear-the tray margins of all abnormal mus- 
cle folds. With thumbs under the mandible and index fingers 
on the sides of the tray, the latter is forced down to place. 
Now steady the tray by placing the index and middle fingers 
of one hand across it from side to side, thumb under the man- 
dible, and with the other apply pressure on the outer side of 
the cheek and lip to force the surplus plaster along the flange 
margins into close contact with the border. 
Reverse the hands and carry out similar steps on the oppo- 
site side. With each free hand, in turn, pass the index finger 
around the periphery of the lingual flange margin to adapt 
the plaster in this location also, particularly under the tongue 
and along the disto-lingual surfaces. 
“muscle marking” the impression 
Steady the tray with both hands and instruct the patient 
to exert active muscular effort with cheeks, lower lip and 
tongue, to indicate clearly in the plaster the muscular attach- 
ments. As before stated, the time required to carry out all 
of these several steps ought not to exceed thirty or forty sec- 
onds, for the final muscle marking must be accomplished while 72 
TECHNIC OF TAKING IMPRESSIONS 
the plaster is still soft and capable of yielding to moderate 
pressure. 
REMOVAL OF THE IMPRESSION 
Lower impressions require a little longer time for hard- 
ening than do uppers, because of the excess of moisture pres- 
ent, the saliva usually accumulating in excessive quantity and 
retarding the crystallization somewhat. 
When well hardened, the impression is loosened by gently 
pulling the lips and cheeks away from the outer flange. Trac- 
tion up and down on the tray handle is made at the same time, 
and the air finds its way readily between impression and 
tissues. 
Should the lingual wings extend downward and outward, 
the anterior part of the impression should be raised above 
the border and the tray carried back a short distance. As the 
space between the lingual borders widens constantly from 
before backward, this brings the flanges into more open terri- 
tory. By tipping or lifting one side of the tray higher than 
the other and rotating the elevated side forward, the impres- 
sion can be disengaged and rotated out of the mouth, usually 
without fracture. Inspect it carefully before allowing the 
patient to rinse the mouth, and if fractured, recover the broken 
pieces, place in position, and lute with wax. 
PARTIAL IMPRESSIONS OF THE MOUTH IN PLASTER 
Partial cases are those in which some but not all of the 
natural teeth are missing. Substitutes designed for such cases 
contain a less number of teeth than are usually placed in full 
dentures. For obvious reasons, therefore, an impression of 
such a case, although usually involving as much area as an 
edentulous one, is termed a partial impression. 
While partial impressions may be secured in plaster alone, 
as a rule a preliminary impression in wax or modeling com- 
pound, corrected before introducing the plaster by freely en- 
larging the impressions made by the teeth, and cutting away 
the excessive surplus, will yield more accurate results than 
plaster alone. 
In practically all cases of partial impression work where 
plaster alone is used, the tray, having been previously oiled 
on the inside, is removed as soon as the plaster has set. 
The operator, being familiar with the undercuts present 
and spaces between the teeth, cuts the impression in suitable 
places to weaken it, so that with a little effort it may be frac- TECHNIC OF TAKING IMPRESSIONS 
73 
tured and removed in pieces. Sometimes the breaking of one 
or two pieces is sufficient to release the impression so that it 
will come away in very nearly a whole condition. Again, when 
teeth and spaces alternate, the teeth being long and having 
constricted cervices, the impression must be broken in a num- 
ber of pieces to effect its removal. In all cases an effort should 
be made to break away all areas that, if not disconnected, 
would either injure the tissue or be marred or destroyed in 
the removal of the impression. If the fractured pieces are 
not too small, and are of reasonable thickness, presenting 
clean-cut fractures, the impression may be practically restored, 
even though broken in many pieces. The accuracy of the 
impression depends on how perfectly the broken parts are re- 
assembled. 
The wide flange trays designed by Dr. Angle are intended 
for carrying the impression material, not only against the 
labial, buccal and lingual surfaces of the teeth, but for holding 
it in contact with these surfaces of the alveolar border as well. 
When a tray with narrow flanges is used in partial cases, the 
necessity for using wax or modeling compound as a prelimi- 
nary impression material for increasing the width of the flange 
is apparent. 
Partial cases may be grouped into six general classes, 
according to the teeth lost: 
Class I.— Posterior teeth on both sides missing; anterior 
teeth in place. 
Class II.— Posterior teeth on one side missing; opposite 
and anterior teeth present. 
Class III.— Anterior teeth missing; posterior teeth on both 
sides in place. 
Class IV.— Anterior, and posterior teeth on one side miss- 
ing; posterior teeth on opposite side in place. 
Class V.— Teeth and spaces alternating with more or less 
regularity. 
Class VI.— An occasional tooth missing. 
CLASSIFICATION OF COMMONLY OCCURRING PARTIAL CASES 
Impressions of Partial Cases 
Combination of Modeling Compound and Plaster — Class 1 
A tray of the flat-bottom type, with flanges of moderate 
width that will not impinge on the muscles, is best adapted to 
this case. Place sufficient softened compound for a regular 
SELECTING THE TRAY 74 
TECHNIC OF TAKING IMPRESSIONS 
impression in the tray, building it up thicker where the teeth 
are missing than anteriorly. The compound should be dis- 
posed in the tray to conform as nearly as possible to the sur- 
faces being copied, and be reasonably soft. 
TAKING THE PRELIMINARY IMPRESSION 
Introduce filled tray in the mouth, centralize and press up 
slightly. Steady with one hand and draw lip and cheek mus- 
cles outward to prevent them from folding inwardly, and press 
to place. 
Steady the tray and apply finger along buccal and labial 
surfaces, to secure sufficient height and peripheral adaptation. 
Instruct patient to exercise buccal and lip muscles freely to 
indicate their position. Chill with cold water applied with 
napkin, sponge or syringe, or with cold air, and remove. 
Fig. 22.— Tray for Partial Cases. Flat Bottom Type 
PREPARING THE PRELIMINARY IMPRESSION FOR THE PLASTER 
Trim off excessive surplus buccally, distally, and periph- 
erally. Enlarge freely, both labially and lingually, the impres- 
sions made by the teeth. Frequently the larger part of the 
anterior portion of the impression is removed to give greater 
bulk to the plaster which surrounds the teeth. 
TAKING THE FINAL IMPRESSION 
Mix the plaster to medium consistency, place in the tray 
to the depth of an eighth of an inch or so, quickly introduce TECHNIC OF TAKING IMPRESSIONS 
75 
in the mouth, partially carry to place, centralize and press it 
up against the teeth so they will occupy about the same relation 
to the tray flange as in the first impression. 
Steady the tray firmly, draw the lip over the labial flange, 
and the buccal muscles away from the impression margin. 
Fig. 23.— Preliminary Impression in Modeling Compound 
With slight vibratory movement and moderate pressure, carry 
the tray to place. 
With outside pressure against the lips and cheeks, adapt 
the plaster which extends above the compound margin to the 
border, holding the tray firmly while doing so. Instruct the 
patient to exercise the buccal and labial muscles freely and 
vigorously. 76 
TECHNIC OF TAKING IMPRESSIONS 
REMOVING THE IMPRESSION 
When set, traction on the tray handle will loosen the im- 
pression, although if the teeth are long, considerable force 
may be required to dislodge it, since in most cases the plaster 
impression must necessarily be fractured. On removal, place 
the impression within convenient reach on the bracket, and 
recover the fractured pieces before permitting the patient to 
rinse the mouth. As each piece is removed it is placed out- 
Fig. 24.— Preliminary Impression Enlarged to Receive 
Plaster for Final Impression 
side of the impression periphery, but as near to its proper 
position as possible, to simplify the adjustment of the several 
parts later. 
The fractured surfaces of both the impression and the 
pieces are cleared of small adhering particles with a moder- 
ately stiff camel’s hair brush. Care should be taken to clear 
the general surfaces of the modeling compound matrix of de- 
bris at the same time. The character of the fracture deter- 
mines the order of assembling, those pieces in the deepest 
portion of the tray or compound matrix being usually first 
placed in position. 
The pieces are luted together by applying a little wax to 
the fracture lines at various points, usually outside, in such 
ASSEMBLING THE FRACTURED PIECES TECHNIC OF TAKING IMPRESSIONS 
77 
manner as not to form an accretion to the impression proper 
and thus change its form. Wax does not adhere firmly to 
damp plaster unless the latter is well heated. To effect a 
good union of the pieces, a spatula is heated almost to redness 
and applied to the small piece of wax already placed on the 
fracture line. The spatula should be laid against the plaster 
so as to heat it quite hot. The wax in the meantime is melted 
and penetrates the substance, thus cementing the pieces to- 
gether much more firmly than when the union is superficial. 
Class 2 
BICUSPIDS AND MOLARS OF ONE SIDE MISSING 
A flat-bottomed tray, similar to No. 16, is selected, and wax 
or compound heated and adjusted for a preliminary impres- 
Fig. 25.— Angle Tray Adapted to Border and Natural Teeth 
sion, placing it thicker on the one side where the teeth are 
missing than elsewhere, to make up for loss of teeth and 
tissues. 
The general steps for securing the impression are similar 
to those in Class 1. When removed, the impression material 
is freely cut away around the impressions of the teeth, both 
labially and buccally, as well as lingually, to give ample space 
for the plaster which is to enclose them. 
Class 3 
ANTERIOR TEETH MISSING; BICUSPIDS AND MOLARS ON BOTH 
SIDES PRESENT 
The same general style of tray is selected as in the pre- 
ceding case. Wax or compound for preliminary impression 78 
TECHNIC or TAKING IMPRESSIONS 
is introduced in the form of rather a wide roll extending from 
labial flange, over vault portion, to distal margin of tray. 
The impression, when taken, will not extend out to the 
buccal surfaces of the teeth, nor will it usually be necessary 
to include them in the preliminary impression, since the tray 
flange is usually wide enough to support the plaster against 
the buccal surfaces of the teeth and the adjacent gingival mar- 
gin of the border as well. However, if it is necessary to secure 
an impression of the entire buccal surfaces of the border, the 
tray flange can be increased in width by spreading the prelimi- 
nary impression material over the entire tray. 
Class 4 
ANTERIOR AND POSTERIOR TEETH ON ONE SIDE MISSING ; THE 
OPPOSITE POSTERIOR TEETH IN PLACE 
The same general style of tray can be used as in the pre- 
ceding class. The compound should be thicker on the side 
where the teeth are missing. The preliminary impression is 
obtained, trimmed and enlarged at the proper points, and the 
final impression secured in plaster. 
Class 5 
TEETH AND SPACES ALTERNATING WITH MORE OR LESS 
REGULARITY 
Teeth and spaces alternating, in impression work, usually 
requires that the impression will be broken into several pieces 
in order to effect its removal. Such a case always requires 
special care to secure accurate results. 
The usual routine described for the preceding cases is 
applicable here, although with a deep-sided tray of the Angle 
type, oiled inside to prevent the plaster adhering, will often 
times prove more satisfactory than the combined impression. 
In fact, the Angle tray can be used for most any of the partial 
cases described, either with plaster alone, or combined with 
wax or modeling compound. The one serious objection to its 
use is due to the very wide flange, preventing ease of finger 
adaptation of the impression material. 
Class 6 
AN OCCASIONAL MISSING TOOTH 
These cases are handled in a similar manner to the pre- 
ceding class. A preliminary, compound or wax, impression is 
taken, enlarged and used as a receptacle for the plaster. TECHNIC OF TAKING IMPRESSIONS 
79 
Frequently, however, where teeth and spaces alternate 
throughout a considerable extent of the arch, a properly 
selected Angle tray, oiled to more readily part from the im- 
pression, and with plaster alone used as the impression mate- 
rial, will prove as satisfactory as the combined use of com- 
pound and plaster. The vault adaptation can, in most in- 
stances, be much improved with wax or compound additions 
On removal of the tray, the plaster which fills the spaces is 
notched and pried apart, to release the impression. 
TO BREAK AN IMPRESSION ALONG DEFINITE LINES 
Strips of sheet wax are attached edgewise to the floor of 
the tray, and so adjusted as to pass into the spaces where the 
teeth are missing. These strips, if properly adjusted, will 
serve to divide the plaster in a similar manner, but more effec- 
tively than can usually be done by notching with a knife. By 
inserting the knife blade into the wax and prying slightly, the 
impression can easily be broken. 
TAKING IMPRESSIONS OF ELONGATED AND LOOSE TEETH 
It is frequently necessary to secure an impression of one 
or more elongated or loose teeth, which if taken in the ordi- 
nary manner would very likely result in injury to the already 
weakened peridental membrane of the tooth, or at least cause 
the patient some discomfort. 
Fig. 26.— Sectional View of Plaster Cores, Natural Teeth, 
and Impression Tray 
The following method, if carried out as detailed, is con- 
venient, accurate, and practically painless: 
Mix a small amount of plaster of medium consistency, and 
apply to the lingual surfaces of the loose teeth and as much 
of the process as the final impression should cover in this area. 80 
TECHNIC OF TAKING IMPRESSIONS 
If other teeth are present, it may sometimes be best to extend 
the impression so as to include them for subsequent support. 
Now mix some plaster of medium consistency, and with the 
point of a spatula apply to the lingual surfaces of the teeth, 
making such additions as to give reasonable thickness to the 
body of the impression. The plaster should be forced into the 
embrasures and extend from where peripheral plate line will 
rest to the incisal edge. Should the embrasures be open, the 
plaster contained in them, which is forced labially to the point 
of shortest diameter of the space, should be removed with 
excavators, so that this half of the impression may be removed 
lingually without difficulty. 
When set, this portion is removed and trimmed smoothly, 
so as to flare from gingival to incisal or occlusal surfaces. It 
is then entirely coated with separating fluid and returned to 
its former position in the mouth. Another mix of plaster is 
applied to the labial or buccal surfaces, securing good adapta- 
tion to those surfaces, and against the lingual body of plaster 
presenting in the embrasures and at the incisal or occlusal 
surfaces. When the plaster is hard, insert the point of an 
instrument between the two halves, carefully pry them apart, 
and remove. Trim them so that when again returned to the 
teeth and set in position, they form a truncated cone, the base 
of which rests against the alveolar process, the smaller end 
coming even with or covering the incisal or occlusal surfaces, 
as the case demands. Usually the two pieces will be retained 
firmly in position without tying, but they can be ligated to- 
gether if necessary. In trimming, reduce the pieces labio or 
bucco-lingually as much as possible, yet without weakening 
them, so that there will be no excessive bulk to interfere with 
the next step. 
Now fit a tray over this matrix, or in reality the core-to-be, 
and see that it also conforms elsewhere to the tissue to be 
included in the impression. Either plaster or modeling com- 
pound can be used for the impression material, as the case 
requires. The impression is obtained in the ordinary manner, 
and removed. When the matrix or core has been properly 
flared, the impression will part from it without difficulty. The 
two halves of the matrix are now removed from the teeth they 
enclose, placed in their respective positions in the impression, 
and luted firmly with wax. 
This method is especially valuable in taking impressions 
of teeth in pyorrhea cases. It is also capable of application 
to a variety of difficult conditions that are frequently met with 
in practice. TECHNIC OF TAKING IMPRESSIONS 
81 
When manipulated properly, in well selected cases, mod- 
eling compound is a most reliable impression material. By 
reference to the “Indications for the Use of Plaster,” it will 
readily be seen when to avoid the use of modeling compound. 
IMPRESSIONS IN MODELING COMPOUND 
Fig. 27.— Palatine View of Kerr Tray Removable Handle 
In probably 70 per cent of edentulous cases presenting, com 
pound can be used to better advantage than plaster. 
FULL UPPER EDENTULOUS CASES IN MODELING COMPOUND 
The fitting of the impression tray differs in no respect from 
the fitting of a tray where plaster is used, except that the distal 
extension of the vault portion, so commonly required for plas- 
ter, is unnecessary when compound is used. Narrow flange, 
close-fitting trays of the Kerr-Gfreene type are especially indi- 
cated, although other forms of trays can often be used to 
advantage. The compound selected should become plastic at 
a low temperature, and harden quickly. 
The Perfection Compound made by the Kerrs of Detroit 
fulfills the requirements better, perhaps, than any other mate- 
rial on the market. It is furnished in the form of cakes for 
impressions, and also tracing sticks for making additions when 
necessary to the periphery, or any area of the impression. 
The amount of compound required for an impression, when 82 
TECHNIC OF TAKING IMPRESSIONS 
the tray is close fitting, is very slight, usually less than one- 
half a cake. 
SOFTENING THE COMPOUND 
The modeling compound is thoroughly warmed, preferably 
in hot water, removed, and the moisture taken up with a towel 
or napkin. With the fingers it is formed into a ball, working 
the wrinkles from above, underneath. This ball is then set 
Fig. 28.— Lingual View of Upper Tray 
ill the center of the vault portion of the tray, and with the 
fingers the compound is disposed against the flange so as to 
assume the general form of the impression. Or the compound 
may be worked out in a sheet of more or less uniform thick- 
ness, and disposed evenly in the interior of the tray. The 
former method is to be preferred, as a perfectly smooth 
impression surface is readily secured, while with the latter 
method, creases are apt to form while adjusting the material. 
The tray is heated around the flange and maxillary por- 
tion, over a small frame, to cause the compound to adhere to 
it slightly. The tray is inverted and the surface to be im- 
pressed is reheated over the flame, to render it soft and plas- 
tic. It should then be quickly dipped in warm water to prevent 
the compound sticking to the tissues while passing through 
the lips. TECHNIC OF TAKING IMPRESSIONS 
83 
INTRODUCING THE FILLED TRAY 
The tray is then introduced in the mouth by the same 
method of procedure as outlined under the head of “Full 
Cases in Plaster.” In fact, almost the same technic is fol- 
lowed with compound as with plaster, viz.: centering the tray; 
partial seating of the impression on the ridge; drawing out 
the lip and cheeks from the flange margin; carrying the im- 
pression to place under pressure; forcing the peripheral sur- 
plus in close adaptation to the tissues, particularly along the 
distal vault portion. The index and middle fingers of both 
hands can be applied to the compound which extends distally 
beyond the tray margin, to lift up and hold it in contact with 
the palatine tissues. These fingers can alternately support 
the tray, and develop adaptation of the compound to the tissues 
from one tuberosity to the other. 
When the adaptation is completed, moderate pressure is 
maintained on the central portion of the tray, and the impres- 
sion chilled with cold water, applied with syringe or small 
sponge or napkin. 
On removal, the impression is inspected closely to see that 
all essential areas have been copied. The excessive peripheral 
surplus is then trimmed away and the sharp angles caused 
by the cutting smoothed off. Should there be any slight defic- 
iency at any point, a little heated compound applied with the 
tracing stick and the impression returned to place and firmly 
seated will correct the error. 
PERIPHERAL READAPTATION 
The impression, as it now stands, even if the steps have 
been accurately carried out, is no better, and quite likely not 
as good, as an ordinary plaster impression. 
The efficiency of modeling compound lies in the fact that 
with proper technic the soft areas of the mouth may be com- 
pressed, and a corresponding relief from pressure on the hard 
area be secured. As a result, the denture, when constructed, 
will bear uniformly on the hard and soft areas alike, and in 
those cases of prominent, hard raphae, practically entire relief 
from pressure may be afforded. 
To secure the compressive effect of the compound, the 
impression, on removal, is thoroughly chilled, the surplus 
trimmed away, and the entire impressed areas heated quite 
hot over a small Bunsen or alcohol flame, to the depth of about 
one-sixteenth of an inch. In this condition it is again returned 84 
TECHNIC OF TAKING IMPRESSIONS 
to the mouth, properly seated, the muscles drawn outward, 
and steady pressure applied for two or three minutes. The 
amount of force necessary to apply varies from three to ten, 
or even fifteen pounds, according to conditions. Extremely 
soft, spongy, but not resilient, tissues are copied better with 
moderate, while harder areas require a greater amount of 
pressure. 
DISTRIBUTION OF THE PLASTIC COMPOUND UNDER MAINTAINED 
PRESSURE 
When the layer of softened compound is of uniform thick- 
ness and is sufficiently plastic, under continued pressure the 
material gradually flows from the hard to the soft areas, com- 
pressing the latter and relieving the pressure on the former, 
until a sort of equilibrium is established. If care is taken in 
carrying out the technical details, the finished denture will 
have a similarly uniform bearing on the tissues, which will 
add greatly to its stability. 
At the time of forcing the impression up against the tis- 
sues, the excess compound is naturally moved from the inter- 
ior of the tray, externally and over the flange margin. The 
tendency is for the compound to curl outward, away from the 
process. It therefore becomes necessary to readapt the per- 
iphery of the impression to the border, to seal against the in- 
gress of air. This step is accomplished as follows: 
PERIPHERAL READAPTATION 
On removal of the impression the second time, it is chilled 
and the peripheral margins, buccally, labially, and lingually, 
are reheated. It is again returned to the mouth and seated. 
With the index finger the softened margins are firmly pressed 
into close contact with the border, buccally and labially first, 
correcting the vault portion last. Sometimes, however, the 
adaptation of this margin is carried out as a separate, final 
step. Only the periphery is softened in this rim adjustment, 
since if the whole impression is reheated, the effect of the 
previous compressive steps would be lost and adaptation 
would be impaired. 
The impression can be tested as to adaptation by having 
the patient make muscular effort to displace it or by biting 
on something to see if it can be tipped. The removable handle 
trays of the Greene type are very convenient for testing the 
stability of the impression. They are also, on account of their 
small size and generally correct form, especially adapted to TECHNIC OF TAKING IMPRESSIONS 
85 
work in edentulous mouths with compound, either alone, or 
combined with plaster. 
Fig. 29.— An Upper Impression Showing “ Muscle Trimmed ” Margins 
If the impression is readily displaced by the patient’s 
efforts — can be thrown down in laughing, speaking, biting, or 
even coughing — the adaptation is not perfect, and an effort 
should be made to determine the weak point and correct it. 
A SUMMARY OF STEPS IX MODELING COMPOUND IMPRES- 
SION WORK 
To summarize, the steps for compound impression work 
are as follows: 
Examination of the mouth. 
Selection and adaptation of tray. 
Heating and adapting modeling compound to tray. 
Introduction into mouth, and centering tray. 
Partial seating of the impression. 
Steadying tray while lip and cheek muscles are pulled out- 
ward from tray margin. 
Carrying tray to place under medium pressure. 
General adaptation of peripheral surplus. 
Muscular exertion by patient to indicate location and extent 
of muscular attachment. 
All of these manipulative details should be quickly carried 
out, so that the last step mentioned may be accomplished while 
the compound is still capable of yielding under the stress of, 
and being indented by, the lip and cheek muscles. 
On removal the impression is chilled, the surplus moisture 
absorbed, the impressed areas heated to a depth of one to one 86 
TECHNIC OF TAKING IMPRESSIONS 
and one-lialf millimeters, and the tray returned to the mouth. 
It is correctly seated, and steady pressure applied for two or 
three minutes, or until fairly well hardened. 
Remove, chill, soften the peripheral margin to the depth 
of about two millimeters, and return to the mouth. 
Adapt labial and buccal periphery to the process, and the 
distal margin of the vault portion to tissues, using finger pres- 
sure, applied directly to the compound rim. 
Test stability; if satisfactory, remove, heat the periphery 
to a slight depth, and quickly return to the mouth for final 
muscular adaptation by the patient. 
Now remove the impression, again examine the vault por- 
tion of the mouth to determine the extent of the hard area, 
and with a scraper relieve that portion impressed by the raphe 
to the depth of one-fourth to one millimeter, depending on the 
condition of soft tissues. 
Return to the mouth for final trial. As before intimated, 
the best way to test an impression is for the patient to sub- 
ject it to every muscular action the denture will be subjected 
to, as well as its resistance to tipping stress. In no case will 
the cast derived from an impression be more accurate than 
the impression itself. It therefore follows that if an impres- 
sion is easily dislodged, the resultant denture will be even 
more readily dislodged than the impression. 
IMPRESSIONS OF LOWER EDENTULOUS CASES IN MODELING COMPOUND 
The general details of handling modeling compound, as 
just described for upper, applies in many respects to the lower 
cases as well. 
The fitting of the tray; heating and placing the compound; 
introduction into the mouth; centering; partial seating; draw- 
ing the tissue folds out from under the tray margin; forcing 
the impression to place; steadying tray while general adap- 
tation to the border is secured by pressure on lips and cheeks, 
are similar in detail to upper cases. 
The adaptation of the compound against the lingual sur- 
faces should be carefully wrought out. When the steps have 
been carried out as just mentioned, the tray should be held 
firmly in place and the compound adapted to the lingual border 
with the fingers, being especially careful to secure as perfect 
adaptation against the lower disto-lingual tissues as possible. 
The final test for the depth of impression is obtained by con- 
traction of the mylo-hyoid muscles. 
On first introducing the impression, the patient should TECHNIC OF TAKING IMPRESSIONS 
87 
elevate the tongue while the operator directs the compound 
into correct position with finger pressure. When adapted, the 
compound is chilled, the impression is removed, and the ex- 
cessive surplus is trimmed away. The impressed areas are 
then reheated and the impression again returned to the mouth. 
After drawing the muscles from under the tray margins, pres- 
sure is applied to force the compound from hard to soft areas, 
as previously outlined, peripheral adaptation with finger pres- 
sure is secured, and the impression is chilled and removed. 
A method for securing close peripheral adaptation of lower 
dentures to the process, with relief from pressure on the crest 
of the border, is suggested by Dr. J. W. Greene. A stream 
Fig. 30 
of hot water from a small-spouted vessel is allowed to run 
through the deepest part of the impression until the compound 
in this location is thoroughly softened, care being taken not 
to heat the edges. The entire impression is then quickly 
dipped in hot water so as to soften all of the impressed areas 
to a slight extent. The impression is then quickly returned to 
the mouth, and with a springy or “wave like” motion, it is 
lightly pressed down upon the border, chilled and removed. 
PARTIAL IMPRESSIONS IN MODELING COMPOUND 
There are few partial cases, indeed, where modeling com- 88 
TECHNIC OF TAKING IMPRESSIONS 
pound will meet the requirements as well as plaster. Almost 
without exception in the class of cases under consideration, 
undercut surfaces are present, which can only be copied by 
an unyielding material that will break on removal, or by tak- 
ing a sectional impression which can be separated along pre- 
determined lines. 
Modeling compound can be used to advantage in sectional 
work, the character and extent of the undercut surfaces deter- 
mining the form and number of the sections. The manner of 
procedure is as follows: 
Fig. 31.— Various Sizes of Narrow Lower Trays Suitable for 
Badly Absorbed Borders 
The form of the first section is decided upon. Compound 
is applied slightly in excess of what is needed to form this 
part. When cool, it is properly shaped and those surfaces of 
the first section which form contact areas with the second 
section, are varnished with shellac, and before it has become 
dry thin tin-foil is spread evenly over them and laid down 
smoothly. When this first section is chilled and the tin-foil 
slightly oiled, the next section can be adapted to it, and by TECHNIC OF TAKING IMPRESSIONS 
89 
quickly chilling the latter no change of form will occur in the 
first section. 
The two or more sections necessary to inclose teeth with 
constricted necks, fill undercut spaces, or open embrasures, 
should be so trimmed as to permit the impression proper, in 
which they are finally inclosed, to separate from them with- 
out distortion. On removal of the impression, the sections are 
separated and placed in their respective locations in the ma- 
trix formed by them in the impression. They may be held 
firmly in position by luting a little wax along the joints. 
Either compound or plaster may be used for the general 
impression material in these cases of “coring.” If the for- 
mer is used, the entire core should be covered with foil and 
oiled, and the manipulative procedures carried out rapidly, so 
that the inherent heat in the sectional material may not soften, 
and the pressure in placing it distort the impression. With 
plaster, as an impression material, the oiling of the cores is 
sufficient. CHAPTER VIII 
TREATMENT AND FILLING OF IMPRESSIONS 
PRODUCTION OF CASTS 
As previously stated, the degree of success attained in den- 
ture construction depends on the development of three essen- 
tial requisites, viz.: usefulness, good looks and comfort. 
The realization of two of these, usefulness and comfort, 
depends primarily upon the impression and the cast derived 
therefrom, since the latter gives the reverse form to the den- 
ture. The necessity, therefore, for accuracy in impression 
taking and cast construction is imperative, for, if the founda- 
tion is faulty, the superstructure will fail. A defective im- 
pression invariably yields an imperfect cast. It does not fol- 
low, however, that a satisfactory impression will always yield 
a perfect cast. The accuracy of the cast depends upon the 
care and precision exercised in its production. 
The technique of cast construction is similar, whether the 
impression is of plaster or of modeling compound. The 
details differ slightly. Each class will he taken up separately, 
and the important details noted. 
TREATMENT OF PLASTER IMPRESSIONS IN EDENTULOUS CASES 
Certain preparatory steps must be carefully carried out 
in the impression before the cast is produced: 
First — The impression should be examined closely to see 
that it is intact. If broken, the pieces should be placed in 
correct position, firmly luted with wax, and the impression 
itself secured in the tray. 
Second — The scraping of those parts impressed by the 
hard areas of the mouth, as detailed in a previous chapter, 
should be carefully executed, and the impression freed from 
debris with a clean sable brush. 
Third — A staining medium which will penetrate to the 
depth of 1 to 2 mm. should be applied to the exposed surfaces, 
so that in cutting the impression to weaken it, in removal from 
the cast, the stained portion will indicate the near approach 
to the line of demarkation between the two, and thus prevent 
injury from the knife. 
Fourth — A separating medium must be applied to the 
90 TREATMENT AND FILLING OF IMPRESSIONS 
91 
impression to prevent the plaster constituting the cast from 
becoming so firmly adherent to it that the two cannot be 
separated without defacing the cast. 
The reason why a second addition of plaster adheres to 
one previously hardened, unless steps are taken to prevent, 
is due to the fact that plaster crystallizes in setting and the 
crystals are grouped so as to leave many spaces between, as 
has been previously shown. The face of an impression pres- 
ents just such a formation. It has also been shown that in a 
fresh mix of plaster, the granules of the half hydrate are 
actually dissolved in the water, and that in and from this solu- 
tion the crystals of di-liydrate form. 
Where such a mixture is applied to a surface of plaster 
previously set, the solution, to a certain extent, is taken up 
by, and fills some of the interspaces in the hardened plaster, 
and there crystallizes. These crystals are in reality so many 
irregular points projecting from the freshly set plaster, ex- 
tending in various directions into the face of the previously 
set mass, thus anchoring the two bodies of plaster together. 
In separating the two, many of these projecting crystals 
are necessarily broken, and in breaking, the faces of both 
masses are more or less injured. Sometimes the two masses 
adhere so closely as to render separation impossible without 
destroying the cast and impression as well. The remedy lies 
in literally waterproofing the surface of plaster against which 
the fresh mix is to be cast, which prevents the plaster in solu- 
tion from entering the spaces referred to. 
The selection and proper application of suitable staining 
and separating mediums is therefore of the greatest impor- 
tance where the production of accurate casts is desired. 
STAINING FLUIDS 
A staining fluid should he capable of penetrating either 
moist or dry plaster to a depth of 1 or 2 mm. for reasons 
before stated. Since its purpose is to stain only, it should be 
absorbed by the plaster to which applied, without forming a 
film on the surface. 
A thin alcoholic solution of orange shellac is a most excel- 
lent medium for staining. If used thin, quite a dark tinge 
may be imparted to the impression by applying two or three 
coats without glazing the applied surfaces. Each application 
should be allowed to dry before the next is laid on. 
An aqueous solution of some of the aniline colors is fre- 
quently used, but, unless carefully handled, will stain the fin- 92 
TREATMENT AND FILLING OF IMPRESSIONS 
gers, and is difficult to remove. Coloring matter is sometimes 
added to the separating medium, the idea being to convert it 
into a staining medium as well. 
Most separating mediums, however, do not penetrate the 
plaster to any appreciable depth, and therefore the stain is 
confined very closely to the line of demarkation between the 
impression and the cast. The stain applied to an impression 
in this manner will not give sufficient warning when cutting 
the impression away, and in partial cases especially, the cast 
is very liable to be injured. The aqueous solutions to be 
described later may, by adding a suitable pigment, be effec- 
tive both as a separating and staining medium. 
SEPARATING MEDIUMS 
The preparations used for separating purposes are known 
under various names, as separating or parting mediums, 
fluids, varnishes, etc. They may be procured of the supply 
houses, or compounded in the laboratory with very little effort. 
REQUIREMENTS 
To accomplish the desired result, a separating medium to 
be used in cast production particularly, should possess certain 
requisite qualities: 
First — It should be impervious to moisture, after being 
applied to plaster and allowed to dry. 
Second — It should not modify the areas covered to any 
appreciable extent, and hence, should be effective when applied 
in an extremely thin film. 
Third — It should present a smooth, glazed surface when 
dry, so as to produce a correspondingly smooth surface to 
the cast. 
Fourth — It should have sufficient cohesiveness to stick to 
the applied surface, and not become adherent to the cast. 
Fifth — It should dry or harden quickly, and not combine 
chemically with the plaster, or be subject to deleterious change 
itself. 
CLASSIFICATION OF SEP ABATING MEDIUMS 
A simple classification of the separating mediums in com- 
mon use is here presented: 
Alcoholic solutions 
Ethereal solutions 
Aqueous solutions 
Oils TREATMENT AND FILLING OF IMPRESSIONS 
93 
Alcoholic Solutions 
Sandarac is a resinous exudate from the Tliyia Articulata 
of the pine family, which grows in northern Africa. The gum 
exudes from the tree in the form of small globules, called 
tears, ranging in color from pale yellow to brown. The light 
variety is considered the best, and selected tears of this color 
should be used in making the varnish for separating purposes. 
It combines in various proportions with alcohol, but if too 
small a percentage of the latter is used in its composition, or 
if the alcohol is allowed to evaporate, the varnish becomes 
too thick for use in accurate cast production. If from any 
cause it is too thick, the addition of a little alcohol will, after 
standing a time, reduce it to proper consistency. 
Sandarac and alcohol in the following proportions make a 
satisfactory varnish for separating purposes: 
Selected light sandarac 6 oz. 
Grain alcohol 24 oz. 
Digesting in a water bath of moderate temperature will 
aid in dissolving the gum. 
It is not advisable to add a pigment to this varnish in 
order that it may serve as a staining medium also. Sandarac 
varnish does not penetrate the surface of plaster to any appre- 
ciable depth, and the stain will not extend beyond the depth 
penetrated. 
The best plan is to stain the impression, as before sug- 
gested, with thin shellac, which readily penetrates, and after 
it is dry, apply the sandarac. If of proper fluid consistency, 
one coat of sandarac is sufficient. If rather thin, two coats 
should be applied, allowing the first to dry before making the 
second application, and the second should be dry before mak- 
ing the cast. 
SANDARAC VARNISH 
ETHEREAL SOLUTIONS 
Under this division two substances will be described which 
are dissolved in ether, viz.: collodion and soap. 
COLLODION 
Collodion may be procured at any drug store, or it can 
be compounded in the dental laboratory. It is made by dis- 
solving gun cotton in ether, using enough of the latter to make 
a thin, syrupy liquid. Since gun cotton is highly inflammable 94 
TREATMENT AND FILLING OF IMPRESSIONS 
and ether also, to a lesser extent, care must be exercised in 
making the solution to keep it away from a flame. The im- 
pression should be stained, as previously described, before 
using collodion as a separating medium. 
Ethereal soap is frequently used in the class of work under 
consideration. A fine quality can be procured from drug 
houses, and if used properly on a previously stained impres- 
sion, will serve as a good separating material. 
ETHEREAL SOAP 
Aqueous Solutions 
BORAX AND SHELLAC 
A saturated solution of borax in water will dissolve shellac, 
producing a fluid capable of staining the impression. This 
is really the only separating medium that combines both stain- 
ing and separating qualities so as to get the desired results. 
It can be compounded in the dental laboratory as follows: 
Water in large-moutli bottle 1 gal. 
Borax y2 lb. 
By applying heat (water bath) and stirring occasionally, 
the water becomes saturated. A little excess of borax remain- 
ing in the bottom of the vessel will do no harm, and insures 
full saturation of the water. 
To this solution add y2 lb. of ordinary brown shellac in 
flakes, and let stand a few days. It will be gradually dis- 
solved, and the liquid will assume a purplish tinge, due to the 
action of the borax on the shellac. The solution of the shellac 
may be hastened by the application of moderate heat, and also 
by stirring occasionally. A white scum arises to the surface 
of the fluid, which should be removed before bottling. By 
siphoning the liquid out of the bottle, neither the scum on top 
nor the excess of borax and shellac in the bottom will be dis- 
turbed. The best quality of medium is produced by allowing 
the solution to stand a week or more, stirring occasionally, 
before siphoning into bottles. It should be kept tightly corked 
when not in use, to prevent evaporation of the water. 
In using this as a separating medium, it should be applied 
freely and quickly with a fair-sized brush, bathing the entire 
impression surfaces with the liquid. The brush should be used 
to distribute it evenly at first, and before it begins to thicken, TREATMENT AND FILLING OF IMPRESSIONS 
95 
to take up the surplus. The first application is absorbed by 
the plaster without leaving a decided film, and in this manner 
the impression is stained. When dry, a second coat is applied 
and also allowed to dry before producing a cast. The final 
coat should, and if properly applied will, present a smooth, 
glazed, thin, uniform layer on all surfaces covered, and enable 
the impression to be readily removed from the cast. The first 
mention of this solution that the writer is aware of appeared 
in Gorgas, Ed. 1895. 
SOAP SOLUTION AQUEOUS 
Soap lather serves as a good separating medium when 
applied to a shellac stained impression. The soap should be 
worked well into the surfaces so as to fill the interspaces be- 
tween the crystals, after which practically all excess should 
be removed with clear water and a clean brush. In partial 
cases, special care must be taken to free the impression of 
the teeth from the lather, or the air contained therein will 
prevent the settling of the cast plaster into the matrices, or 
impressions of the teeth. 
WATER AS A SEPARATING MEDIUM 
By thoroughly saturating a plaster impression with water, 
no other separating medium need he applied. The impression 
must be filled while saturated, and separated from the cast as 
soon as the latter has set. Very good results can be secured 
in this manner, if the precautions mentioned are observed. 
If, however, the impression and cast are not separated very 
soon after the latter has set, a union of the two occurs which 
will inhibit separation without injuring one or both. 
Oils are not good separating mediums under any circum- 
stances, although commonly used for flask separation, and 
sometimes in impression work. The surface of the cast plas- 
ter contains many minute air bubbles not present when some 
of the other mediums mentioned are used. Lard, sperm and 
the paraffin oils are usually used for this purpose. When 
employed as a separating medium, the impression should be 
previously stained with shellac. 
OILS 
GENERAL REMARKS 
A thorough understanding of the physical nature of plas- 
ter and of the separating mediums in use is essential in secur- 96 
TREATMENT AND FILLING OF IMPRESSIONS 
ing accurate results. Carelessness in applying a medium to 
an impression usually results in an imperfect cast. 
Care and attention to details is just as necessary in the 
class of work being considered, as in any of the other essen- 
tial details of denture construction. 
A chain is only as strong as its weakest link, and therefore 
an imperfect cast, regardless of how accurately all other de- 
tails are carried out, will result in the finished denture prov- 
ing more or less disappointing to both patient and prosthetist. 
FORMS FOR CASTS AND MODELS 
All casts, whether full or partial, upper or lower, should 
have flat bases with sides either parallel or slightly converging 
from the base to the peripheral face outline. The flaring form 
is essential when the cast is to be used as a model. 
Fig. 32.— Testing Kerr Lower Metal Form to Impression 
Previous to Filling with Plaster 
The central palatine portion of upper and floor of lower 
casts should be about one-lialf an inch thick to give stability 
throughout the various steps to which they are subjected in 
denture and die construction. In general the peripheral out- 
line of casts should conform to those of the alveolar arches. 
In trimming, the peripheral surplus of plaster should be re- 
duced, so as to bring the sides close to the reflection of the 
labial and buccal tissues, so that later on, in waxing and flask- 
ing, there will be no excessive surplus to interfere with these 
steps. The crescent shape so frequently given lower cases is 
not recommended because of the liability of the cast to break 
in removal of the impression, and later on, when detaching 
the cast from the occluding frame. This form may be adopted 
when the Kerr metal forms are used in conjunction with 
plaster. TREATMENT AND FILLING OF IMPRESSIONS 
97 
CASTS FOR CELLULOID CASES 
In constructing casts for celluloid cases, they should be 
made sufficiently thick and of a coarse variety of plaster, 
or some harder material, to withstand heavy stress. Spence’s 
Plaster Compound makes a very resistant and satisfactory 
cast for celluloid cases, much better than any grade of plaster 
procurable. Casts for this class of work are made of the same 
general form as previously described. 
Magnesium oxy-cliloride is also an excellent material for 
casts for celluloid work, but is extremely difficult to remove 
from the denture. 
CASTS FOR PLASTIC METAL BASES 
Cast metal base plates are formed by casting aluminum, 
tin, tin alloys, or gold into matrices composed of some refrac- 
tory investment compound. The usual materials used are 
finely ground silex, asbestos, pumice stone, marble dust, soap- 
stone, etc., combined in varying proportions with sufficient 
plaster to fill the voids between the granules, and thus act as 
a cementing medium. The refractory material is incorporated 
to prevent cracking of the investment when heated, and be- 
cause less change in form will occur when and while heated, 
than with plaster alone. Casts for this class of work are of 
the same general form as those previously described. 
CASTS DESIGNED FOR MODELS IN THE PRODUCTION OF METAL DIES 
In shaping a cast for a model it should possess certain 
characteristics: 
First — Its sides should flare outward from face to base, 
at an angle ranging from 75 to 80 degrees from the horizontal, 
to facilitate its easy removal from the sand matrix. 
Second — It should be as thin as possible to be consistent 
with strength, since, according to brass and iron molders, thin 
patterns or models are less apt to distort the matrix in re- 
moval than thick and bulky ones. 
Third — The base should be flat, to afford a firm founda- 
tion for the model in packing the sand matrix. 
Fourth — The base should bear such relation to the vault 
portion that the inclination of the latter upward from the 
deeper or alveolar portions of the matrix shall be uniform 
and highest at the distal margin. If the central vault portion 
is higher than the distal margin of the matrix, a dome-shaped 
space in the die results, in which gases accumulate and find 98 
TREATMENT AND FILLING OF IMPRESSIONS 
vent through the partially solidified metal. This frequently 
causes so serious a defect as to render the die worthless. This 
danger is obviated by so forming the base of the model as to 
raise the anterior higher than the posterior portion. It may 
also be obviated by packing sand under the anterior portion of 
Fig. 33.— Plaster Model Showing Projections of Trimmed Teeth 
the model and elevating it in this manner, before placing the 
molding ring. The better plan is to develop the correct form 
of the model in plaster. 
CASTS DESIGNED FOR MODELS FOR PARTIAL DENTURES 
Models for partial cases are given the same general flaring- 
form as those for full cases. In addition, the teeth must be 
cut off squarely about one-sixteenth of an inch from the gin- 
Fig. 34.— Diagrammatic View of Trimmed Model 
gival line. This is necessary, first, because the general con- 
tour of the teeth will not permit of their withdrawal from the 
sand matrix without distorting the latter. Second, it permits 
the plate to be reflected against the tooth surfaces, thereby 
strengthening it. Tf reduced to the length suggested, the re- TEEATMENT AND FILLING OF IMPEESSIONS 
99 
moval of the model from the sand can in most cases be accom- 
plished readily. 
In lower partial cases when the anterior teeth are present, 
these teeth on the model should have only their incisal thirds 
removed. When the die is secured and the base is swaged, 
the latter should be allowed to extend up over the cinguke, to 
afford stability to the denture and protect the gums from 
stress, as well as to guard against the ingress of food between 
the teeth and substitute in this location. 
UNDEBCUT AEEAS 
Any depressions or decided undercuts on the labial or 
buccal surfaces of the model, not involving areas covered by 
the denture, can be eliminated by filling in with plaster or hard 
wax and giving such surfaces the proper flare for withdrawal 
from the matrix. 
The outer surfaces, as well as the bases of models, should 
be finished with fine sandpaper to render them smooth, and 
the entire model varnished with two or three coats of shellac 
evenly applied. 
COEES 
A core is an addition of investment compound, or some 
refractory material, which, when built against an undercut 
surface on a model and properly trimmed, is used for develop 
A, MODEL B, CORE 
Fig. 35 
ing the negative of that surface in the sand matrix, and fur- 
nishing a form against which the die may be cast. The con- 
structive steps are as follows: 
The varnished model is oiled over the area to be covered 
by the core. The investment compound is mixed to a thick 
consistency and applied to the undercut surface of the model, 
extending it from the base to near the crest of the border, and 
slightly beyond the undercut area at either end. It should be 
from 6 to 8 mm. thick. If too thin, it is liable to warp in dry- 100 
TREATMENT AND FILLING OF IMPRESSIONS 
ing, or break when in use. If too thick, it will interfere with 
the centering of the model in the molding ring. When set, it 
is trimmed so that its outer surface is parallel with the flaring 
side of the model it covers. The ends, as well as the sides, 
should converge slightly, from base to crest. The upper por- 
tion of the core, where it finishes against the border, should 
present a right angle to this surface, and thus give the core 
MODEL WITH CORE IN POSITION 
Fig. 36 
a flat seat in the sand matrix. When trimmed and sand- 
papered it is removed from the model and the moisture driven 
off at moderate temperature to prevent warping. The surface 
is rendered smooth by rubbing soapstone into it. When fin- 
ished as described, it is returned to the model and is ready 
for use. 
CONSTRUCTION OF CASTS GENERAL REMARKS 
The construction of the cast is ordinarily spoken of as 
“pouring the impression.” The term is incorrect and mis- 
leading as well, for the reason that plaster intended for casts 
and in the flashing of cases should never be so thin as to be 
readily “poured” from the howl. 
Plaster of such consistency, when set, is inherently weak, 
low in density, and less resistant to stress than is the case 
when the mix is thicker. This is due to the fact that when 
thin, an excess of water is present and occupying space that 
should contain calcium half hydrate. When crystallization 
sets in, the plaster in solution in the water is gradually taken 
up to complete the crystals partly formed, and to form the 
nuclei for other crystals. 
The half hydrate solution is thus constantly being depleted 
of its calcium sulphate in the building up of new crystals, with 
no corresponding diminution in the bulk of water. In other 
words, when set and the excess water has evaporated, the TREATMENT AND FILLING OF IMPRESSIONS 
101 
mass will contain fewer crystals and more spaces than will 
a mass of similar bulk mixed to proper consistency. 
A cast produced from a thin mix of plaster, as before 
stated, will be less resistant to stress than a denser one, and 
when subjected to heavy pressure, as in the closure of an over- 
packed flask, will yield, the crystals breaking under the load. 
DELETERIOUS PROPERTIES OF PLASTER 
Special care should be exercised in the mixing of plaster 
for any purpose to have it of proper consistency; also in 
avoiding excessive stirring, which induces needless expansion. 
It should be sufficiently plastic to conform to all irregular sur- 
faces by slight jarring, but not so thin as to pour readily. 
Disregard of the peculiar properties of this most sensitive 
material, viz.: its tendency to expand, its susceptibility to 
compression under load, and the deleterious action of heat 
and moisture upon it, results in manifold errors and mishaps 
that lead to impaired adaptation and frequent failures in den- 
ture construction. 
The recognition by many of these deleterious properties of 
plaster has resulted in greater care being exercised in manipu- 
lative procedures than was formerly displayed, as well as in 
the introduction of more stable and resistant materials for 
casts. Among these may be mentioned Spence’s Plaster Com- 
pound — a mixture of plaster, Portland cement, and other sub- 
stances for controlling expansion. This compound is much 
less compressible, while its expansive index is lower, than the 
best grades of plaster. 
MATERIALS USED FOR CASTS 
The materials commonly used for casts for both vulcanite 
and other cases are here presented in order, ranging from 
those having the greatest to those showing the least resistance 
to stress: 
a. Magnesium Oxy-cliloride. 
1. Spence’s Plaster Compound. 
2. Coarse Building Plaster. 
3. French’s Regular Plaster. 
4. French’s Impression Plaster. 
5. Ordinary Commercial Plaster. 
DELETERIOUS EFFECT OF ACCELERATORS ON CASTS 
Plaster casts containing accelerators such as common salt 
or potassium sulphate have a greater affinity for moisture and 102 
TREATMENT AND FILLING OF IMPRESSIONS 
soften more quickly in the vulcanizer in the presence of heat 
and moisture, than do those from which these substances have 
been omitted. Therefore, to avoid danger of distortion of 
casts in vulcanizing, Impression Plasters should not be used 
for casts, as they contain accelerators — usually potassium 
sulphate. The fourth class, therefore, for causes detailed, is 
unsuited for cast production. 
The fifth class mentioned is usually a plaster of uncertain 
quality, sometimes over or under burned, containing impur- 
ities which render it more or less granular, and of uncertain 
density when set. 
FINAL TREATMENT OF THE IMPRESSION 
The impression having been properly prepared by reliev- 
ing, staining and varnishing, as previously described, should 
be immersed and allowed to remain in water for a minute or 
two, while a camel’s hair brush is passed over its surface to 
dislodge the air bubbles present. It is then removed and freed 
from the excess water by throwing it out or passing a good 
sized pellet of absorbent cotton lightly over the surfaces. The 
idea is to moisten the surfaces of the impression immediately 
before filling, so that the cast material will flow freely over 
all areas, and that the face of the cast, when set, will be smooth 
and free from air spaces. 
MANIPULATION OF SPENCERS PLASTER COMPOUND 
This material is slow setting and therefore can be mixed 
very thick. The instructions are to use four ounces of the 
compound to one of water. The first step is to place three 
ounces of the compound in the bowl and add the full amount 
of water (one ounce) to it. Thoroughly mix until it becomes 
soft and uniformly plastic throughout, then add the other 
ounce, a little at a time, working each portion in well before 
making the next addition. The essential point in mixing this 
material, as in plaster, is to distribute the water evenly 
through the mass, so that each particle and granule may have 
an equal proportion to any other. 
FILLING THE IMPRESSION 
Since the mass is thick and plastic — much like putty — 
only a small quantity should be placed in the impression at 
a time, and by jarring and finger pressure, forced to place. 
The entire impression is filled in this manner, a little at a TREATMENT AND FILLING OF IMPRESSIONS 
103 
time, and the form of the cast developed with the spatula, 
squaring up the sides and making the base flat. The cast 
should be about one-half inch thick in the central portion to 
afford necessary strength. 
In lower casts the space between the lingual portions of 
the impression should be bridged across with the compound. 
This may be accomplished with the spatula, or by placing the 
impression on the bench after the deeper portions have been 
filled, and packing the lingual space with a compact mass of 
moist paper; a temporary support will thus be afforded the 
material while being bridged over and in setting. 
Another method often resorted to is to bridge over the 
lingual space with a sheet of wax before filling the impression. 
This should be fitted neatly and luted firmly to the lingual 
margins of the impression, so as not to interfere with the 
development of the areas on which the denture is to rest. 
MANIPULATION OF PLASTER IN CAST CONSTRUCTION 
Fill the bowl about one-tliird full of water, and into this 
sift French’s regular dental plaster until the free water is all 
taken up. By adding the plaster slowly, as it settles into the 
water, solution takes place quickly, and but little stirring will 
be required to render the mix homogeneous. It should be 
stirred slightly, but not to excess. The plastic mass should be 
stiff enough to require jarring to settle it to place. 
A portion is placed near the central part of the impres- 
sion and the tray grasped in the fingers and tapped on the 
edge of the bench to settle the plaster in the deepest portions. 
If the impression has been broken in a number of pieces and 
luted, it is sometimes best to use the fingers which grasp the 
tray as a cushion in jarring the plaster to place, to prevent 
the impression or the pieces from becoming detached — a mis- 
hap which sometimes occurs if the vibration is sharp and 
rapid. Additions of plaster are made and the vibration con- 
tinued until the entire impression is filled and the cast given 
its proper outline with the spatula. Care should be taken in 
forming the cast to avoid excessive bulk, either in thickness 
or peripheral outline, as the surplus peripherally impedes the 
removal of the impression and must eventually be cut away, 
while a thick base interferes with proper mounting of the cast 
on the frame, and later on in flasking, it must be reduced to 
FILLING THE IMPRESSION WITH PLASTER 104 
TREATMENT AND FILLING OF IMPRESSIONS 
centralize the case in the flask. Lower casts are produced in 
the same manner described in the use of the Spence compound. 
CASTS OF PARTIAL CASES SPENCERS COMPOUND 
In filling partial impressions with Spence’s compound, the 
material should be forced into each tooth matrix with a suit- 
able square end instrument, but care must be taken to avoid 
marring the impression in doing so. Each matrix is filled, 
and the compound as it is placed in the impression is jarred 
and pressed to place, to make a compact union with that 
already packed. The general form of the cast should be the 
same as for full cases. 
CASTS OF PARTIAL CASES PLASTER 
The plaster mix for partial should be of about the same 
consistency as for full impressions. If too thick, it will be 
Fig. 37.— Partial Impression Showing Application of 
Strengthening Pegs of Wood 
difficult, if not impossible, to fill the matrices of the teeth, 
while if too thin, the teeth on the cast will be frail and easily 
broken, because of the imperfect density of the plaster. 
In introducing the plaster into the impression, the first 
portion should be placed near, but not over, one of the tooth 
matrices, and by inclining the impression somewhat and jar- 
ring, the plaster will flow down one side of the matrix, spread 
out and settle over the bottom, and then rise up the opposite 
side until the opening is filled. Each matrix should receive 
individual attention in order that a perfect cast of each tooth 
may be obtained. If an attempt is made to fill several mat- 
rices at once, the plaster is liable to flow too freely into some 
of the openings, confining the air in the deeper portions, and 
thus result in an imperfectly filled impression. TREATMENT AND FILLING OF IMPRESSIONS 
105 
STRENGTHENING ISOLATED PLASTER TEETH ON CASTS 
Oftentimes when the natural teeth are long and isolated, 
the plaster teeth can be materially strengthened by inserting 
a small piece of orange wood in each matrix, while the plaster 
is yet plastic, and before the impression is entirely filled. The 
small round Japanese toothpicks of orange wood are well 
adapted to this purpose, being of suitable size and especially 
tough. The sharp point should be cut off, the stick cut to 
suitable length, usually an inch, and placed conveniently at 
hand before filling the impression. The advantage of wood 
over metal pins is that in cutting off the ends of the plaster 
teeth in flashing, the wood will cut as readily as the plaster, 
while metal pins must be cut very carefully, or the plaster 
teeth enclosing them will be fractured. 
Casts from Modeling Compound Impressions 
Preliminary Treatment for Cast Production 
EQUALIZING DENTURE BEARING BY SCRAPING HARD AREAS OF THE 
IMPRESSION 
Since the character of the material used, and the manner 
of manipulation followed in taking impressions in modeling 
compound, tend to relieve pressure of the denture on the hard, 
and increase its bearing on the soft, areas of the mouth, it is 
not necessary to scrape the areas impressed by the hard tis- 
sues to the same extent in modeling compound as in plaster 
impressions. Some slight relief, however, in most cases will 
prove beneficial, and with the variation just stated, the instruc- 
tions given in reference to the treatment by scraping of plas- 
ter impressions, apply to the class under consideration. 
TREATMENT OP THE SURFACE OF THE IMPRESSION 
Modeling compound impressions are waterproof, and 
therefore no separating or staining mediums are needed, as 
in plaster work. The impression, however, should be dipped 
in water, the air bubbles dislodged with a brush, and the ex- 
cess moisture removed with absorbent cotton. No free water 
should be allowed to remain in the deeper portions, for if 
present it will reduce the density of the plaster in the cast in 
that area, and weaken it, as previously explained. While the 
impression can be filled without moistening, a smoother sur- 
face to the cast will be produced if this precaution is taken. 106 
TREATMENT AND FILLING OF IMPRESSIONS 
Exception to this method of treatment must be made when 
magnesium oxy-cliloride is used. The impression should be 
given a thin film of sandarac varnish, the latter allowed to 
dry, and the surfaces not moistened previous to filling. 
FILLING THE IMPRESSION FULL CASES 
The mix of plaster should be made in the same manner, 
and of similar consistency to that used in plaster work. If 
any variation is made, the mass should be thicker, since the 
impression can be tapped sharply in settling the contents to 
place, without danger of dislodging it from the tray, and a 
comparatively thick mix can be readily adapted to full upper 
or lower impressions with ease. 
FILLING THE IMPRESSION IN PARTIAL CASES 
As previously stated, modeling compound is not a suitable 
material for partial cases unless the sectional method is em- 
ployed, but if used for impression purposes, the casts are pro- 
duced in the same manner as from partial impressions in 
plaster. Isolated plaster teeth should also be strengthened 
in the same manner as outlined. 
TIME REQUIRED FOR PLASTER CASTS TO SET BEFORE REMOVING 
THE IMPRESSION 
From fifteen to twenty minutes’ time should be given the 
plaster cast to harden before removing the impression. If 
this step is carried out too soon, the face of the cast is liable 
to be marred by handling, since it takes some time for the 
plaster to develop a reasonable degree of hardness. On the 
other hand, the separation should not be delayed too long, 
since at the beginning of crystallization expansion sets in rap- 
idly, and continues in a gradually decreasing ratio for twenty- 
four hours or more. 
As previously stated in the consideration of plaster, when 
an impression is allowed to remain in the tray and the cast 
in the impression for some time, both will be more or less 
warped. To obviate this difficulty as much as possible, the 
tray and impression should be removed as soon as the plaster 
constituting the cast has hardened sufficiently to permit. 
WARPING OF THE IMPRESSION AND CAST 
The first step in separating the impression and cast is the 
removal of all excess of the impression material extending 
REMOVAL OF THE TRAY TREATMENT AND FILLING OF IMPRESSIONS 
107 
over the outer surfaces of the labio-buccal flange of the tray. 
This is easily accomplished by paring it off with a suitable 
plaster knife. 
The cast and margins of the impression are then grasped 
with one hand, avoiding contact with the tray flange, when, 
by tapping the handle, and if necessary the flange, the tray 
and impression will readily separate. 
REMOVAL OF IMPRESSIONS FULL CASES 
With a sharp knife carefully pare away the impression 
opposite the alveolar crest until the staining medium indicates 
the near approach to the cast. The paring should extend from 
one tuberosity around the crest of the border to the opposite 
side. 
A few light taps on the buccal and labial portions of the 
impression, followed by inserting the point of the knife be- 
tween the latter and the cast at the peripheral line of junc- 
tion, will break away the outer portions of the impression. 
By tapping the vault portion and inserting the point of 
the knife at the line of demarkation distally, the remainder 
can be removed without difficulty. If, however, the rugae are 
prominent, and the vault is deep and narrow, it will be best 
to cut a V-shaped groove mesio-distally through the central 
vault portion and practically divide it. The groove should 
be carried deep enough to disclose the stained area. A slight 
prying movement on either half will cause fracture, when they 
will come away readily. 
REMOVAL OF THE IMPRESSION PARTIAL CASES 
The same steps as to removal of the surplus of the impres- 
sion from the tray, and the tray itself, as previously described 
in full, apply to partial cases as well. The removal of the 
impression from the cast, however, requires more care and 
necessitates the fracturing of the impression into smaller 
pieces, to obviate the breaking of the teeth from the cast. 
First — The impression opposite the occlusal and incisal 
portions of the teeth should be carefully pared away until the 
stained area opposite each tooth, and cusp as well, is plainly 
visible. If the cusps of the teeth are particularly sharp and 
well defined, to avoid breaking them, the paring may be car- 
ried along the mesial and distal slopes of the cusps until the 
stained areas present two nearly unbroken lines, indicating 
the position of the buccal and lingual marginal ridges. This 108 
TREATMENT AND PILLING OP IMPRESSIONS 
practically separates the labio-buccal portion from the body 
of the impression. 
CUTTING V-SHAPED GROOVES TO WEAKEN THE IMPRESSION 
Second — A V-sliaped groove is usually cut opposite each 
cuspid tooth and eminence perpendicularly, if not already cut 
in removing the impression from the mouth, extending from 
incisal to peripheral margin. The plaster which fills the voids 
occasioned by missing teeth should be carefully divided with 
the knife mesio-distally at the points of shortest diameter of 
the spaces. This permits the labial or buccal sections of plas- 
ter to be removed in an outward direction, and the lingual por- 
tions to be removed inwardly later on, without engaging with, 
or marring the adjacent teeth. 
If sheets of wax have been attached to the floor of the tray 
in fitting, so as to enter the spaces, these of themselves par- 
Fig. 38.— Partial Impression Partly Grooved for Removal 
dally divide the impression where placed, and facilitate the 
cutting with the knife. The sections should be tapped lightly 
to start them, or the point of the knife may be applied and 
slightly pressed into the peripheral line of junction of the cast 
and impression. By prying outward, the sections will come 
away readily, thus exposing the labial and buccal surfaces of 
the teeth. 
Third — A Y-shaped groove is cut around the lingual sur- 
face of the impression, near the occlusal third of the teeth, and 
divided perpendicularly opposite each tooth. These sections 
are then removed one at a time, which, when completed, ex- 
poses the occlusal and a portion of the lingual surfaces of the 
teeth. 
Still another groove is cut entirely around the lingual sur- 
face of the impression, the apex of which is directed toward 
the gingival area, and the plaster divided in sections as just TREATMENT AND FILLING OF IMPRESSIONS 
109 
described, which when removed will leave the teeth entirely 
exposed. 
Fourth — The central or vault portion still requires re- 
moval. If the vault is flat and no undercuts are present, a 
few light taps followed by a slight prying movement at the 
line of junction of the impression with the cast posteriorly, 
will dislodge it. When the vault is deep, the better plan will 
be to divide the remaining portion into two or three sections 
and remove them separately. If the point of the knife has 
been well under control, the removal of the impression, when 
carried out in detail as described, will result in a cast with 
unbroken teeth or cusps, and unmarred surfaces. 
REMOVAL OF MODELING COMPOUND IMPRESSIONS FROM CASTS 
Modeling compound impressions, both full and partial, can 
be removed from casts by the application of either dry or 
moist heat, preferably by softening in hot water. The tray, 
impression and cast are placed in a pan of water, and the 
latter heated sufficiently to render the compound plastic, but 
not excessively soft. The tray is first removed and the com- 
pound at the peripheral margins peeled away from the buccal 
and labial surfaces of the border, drawing it occlusally and 
incisally and away from the cast. But little difficulty will 
occur in removal in full cases, unless the compound has been 
overheated, in which case it will adhere to the cast. In remov- 
ing the impres-sion in partial cases, time should be given for 
the heat to penetrate through the compound and render it 
plastic throughout. If this precaution is not observed and an 
attempt is made to remove the compound from the voids or 
spaces, fracture of some of the teeth, in most instances, will 
occur. 
Should any of the compound adhere to the cast in various 
places, as it frequently does, it may be readily removed by 
heating some dry compound in the Bunsen flame until quite 
sticky, then dip the cast in warm water, first to slightly soften 
the undetaclied compound, and second, to prevent the heated 
mass from adhering to the cast. The dry, heated compound 
is firmly pressed against the adherent pieces and quickly with- 
drawn, reheating it in the flame each time, if necessary, to 
keep it adhesive, until all of the remaining portions are re- 
moved. 110 
TREATMENT AND FILLING OF IMPRESSIONS 
SPECIAL MATERIALS USED FOR CASTS IN VULCANITE WORK 
It is a well-established fact that when plaster is subjected 
to stress, or compressive force, the surface crystals, or those 
first taking the load, crush and break down, when the stress 
passes the modulus of resistance of the material. 
It has also been demonstrated that the force ordinarily 
exerted in closing an overpacked flask is far in excess of that 
which plaster can stand without the crystals crushing and the 
face of the cast becoming distorted. 
The effect of such distortion, be it small or great, on casts 
against which vulcanite or celluloid dentures are molded, is to 
impair, if not altogether destroy, the adaptation of the den- 
tures to the oral tissues. 
Two ways are possible for lessening if not entirely over- 
coming the danger of distortion of dentures, due to yielding 
of the plaster casts under the influence of excessive pressure, 
heat, and moisture, during vulcanization. 
The first of these does not require the use of any special 
materials other than those commonly employed in the dental 
laboratory. The method of technic differs in some respects 
from that usually followed in such procedures, the variations 
being noted under the closing of flasks, preparatory to vul- 
canizing. 
The second plan requires that the cast be constructed of 
a material harder and more resistant to stress, and to dele- 
terious influences in general, than is plaster. 
Several materials, capable of withstanding much greater 
crushing strain than plaster, may be made use of, the proper- 
ties of one of the most important of which will now be con- 
sidered, since its value when properly manipulated is unques- 
tioned. 
Artificial Stone 
OXYCHLORIDE OF MAGNESIUM 
Several years ago the idea occurred to the writer that be- 
cause of its density, smoothness of surface, and impervious- 
ness to water, the materials used in the manufacture of arti- 
ficial stone might be employed in cast construction, and the 
problem of denture warpage be solved, or the difficulties re- 
sulting therefrom greatly reduced. 
From data furnished by the late Prof. Vernon J. Hall 
many experiments were made with various materials, particu- 
larly with the oxide and chloride of magnesium. The first 
experiments, conducted with chemically pure products, were TREATMENT AND FILLING OF IMPRESSIONS 
unsuccessful. Attention was then given the commercial prod- 
ucts, since these were extensively used in various industrial 
lines. From the first, difficulties were encountered, due prin- 
cipally to fracture lines forming in the mass in hardening. In 
some cases very perceptible contraction was noticeable. 
Fracture was later found to be due to the presence of car- 
bon dioxide in the oxide of magnesia. Its presence may be 
accounted for in two ways. Magnesium oxide is produced 
usually by burning magnesium carbonate, just as calcium 
oxide or lime is produced by burning calcium carbonate. In 
both cases the carbon dioxide is driven off when the process 
is properly conducted. Unless the calcination is thorough all 
of the CO will not be eliminated. Again, the oxide of mag- 
nesia may be properly prepared, but if left exposed to the 
air, it will take up moisture and carbon dioxide, and gradually 
return to the carbonate. From whatever source it may come, 
its presence in the oxide of magnesia renders the latter worth- 
less for cast construction. The remedy consists in recalcining 
the mixed oxide and carbonate above a red heat, to expel the 
CO2, or if this is not practicable, discard it for a better grade 
of material. 
Contraction in the hardened mass, noticeable in the space 
seen between the impression and cast when the latter has 
hardened, is the result of using an under-saturated solution of 
the chloride, the liquid with which the powdered oxide is com- 
bined. By increasing the strength of the liquid to full satura- 
tion, adding crystal chloride until there is a slight excess in 
the bottom of the stock vessel, contraction can be overcome. 
The length of time required for setting — about twelve 
hours — is considered an objection by some, but the advan- 
tages gained in more perfect adaptation of the denture to the 
oral tissues and in increased density of the vulcanite far out- 
weigh the disadvantages mentioned. 
Advantages of Oxychloride of Magnesium 
The principal advantages of oxychloride of magnesium for 
casts in vulcanite work are these: hardness, density, smooth- 
ness of surface and an extremely low expansive index, less 
than one-fourth that of the best grades of plaster. It is suf- 
ficiently impervious to moisture and heat to maintain its form 
without crushing, even under heavy pressure. The writer has 
vulcanized two baseplates on the same cast, both of which 
showed satisfactory adaptation to the oral tissues. At the 112 
TREATMENT AND FILLING OF IMPRESSIONS 
end of the second vulcanization, the cast, although permeated 
with moisture, was quite hard and resistant to stress and on 
evaporation of the moisture appeared much harder than casts 
constructed from the best grades of plaster before vulcan- 
ization. 
liubber of any shade vulcanized in contact with oxychloride 
of magnesium is hard, dense, elastic, capable of taking a high 
polish, and on account of the density of the cast is practically 
free from nodules. 
Partial dentures vulcanized on casts of this material show 
all the characteristic lines and fine surface markings of the 
teeth and tissues against which it is molded as clearly as an 
accurate plaster impression can reproduce them, because the 
cast is not changed or defaced in the slightest degree by man- 
ipulative procedures. 
In tests made for expansion, the greatest movement regis- 
tered, from the buccal face of one tuberosity to the corre- 
sponding opposite surface, was 15/10,000 of an inch, against 
from 60/30,000 to 100/10,000 of an inch in casts made from the 
best grades of plaster. 
EXPANSION 
Comparative compression tests on blocks of plaster and 
of magnesium compound, set over night, showed the following 
result: size of blocks iy2xiy2xy2 inches; area of plunger, y± 
inch. In the plaster blocks, the plunger began sinking into 
the block at twenty pounds, and under continued pressure 
penetrated about i/s inch, the block breaking at 100 pounds. 
The magnesium blocks showed no perceptible compression 
up to 1,000 pounds, at which point they suddenly crushed. In 
one-inch cubes, the oxychloride of magnesium will stand a 
crushing strain of nearly 5,000 pounds, according to Major 
Gilmore, U. S. A. 
COMPRESSION 
MATERIALS USED FOR CAST CONSTRUCTION 
The following instruction in reference to procuring and 
handling the magnesium materials for casts covers the essen- 
tial points to he kept in mind. 
There are two varieties of magnesium oxide, known as the 
light and heavy oxide. The difference, which is one of specific 
MAGNESIUM OXIDE TREATMENT AND FILLING OF IMPRESSIONS 
113 
gravity and not of chemical constitution, is brought about by 
the manner in which the magnesite (MgCCte) is burned. In 
“Cements, Limes, and Plasters,” E. C. Eckel says: “If 
MgCO be strongly heated, the effect, as with lime carbonate, 
is to drive off the C02, leaving the MgO as a white solid. A 
curious and technologically important phenomenon connected 
with the temperature employed is to be noted. If the calcina- 
tion is carried on quickly at a red heat the magnesia resulting 
will have a specific gravity of 3.00 to 3.07, while if the calci- 
nation is long continued or carried on at a higher temperature 
the resulting MgO will be much denser, possessing a specific 
gravity of 3.61 to 3.80.” 
For the construction of casts, the heavy oxide commer- 
cially known as powdered magnesite, or calcined magnesia, 
should be employed. To prevent its return to MgC03, by 
absorbing C02 and moisture from the air, as indicated by its 
becoming granular and lumpy, it should be kept in airtight 
containers, just as plaster must be protected in damp climates. 
MAGNESIUM CHLORIDE 
Magnesium chloride is a crystalline, deliquescent sub- 
stance, having much the appearance of sea salt. It is obtained 
in several ways, a common source being by heating magne- 
sium ammonium chloride (MgCl2 NH4 Cl) to about 460° C. 
The ammonium chloride volatilizes, leaving anhydrous MgCl2. 
The ordinary commercial product, instead of the chem- 
ically pure chloride, is suitable for use in cast construction; 
some of the commercial products occasionally contain HS04 
as an impurity. When present, in the chloride solution, it will 
in time render the hardened mass of oxychloride somewhat 
soluble in water. The sulphuric acid can be eliminated by 
adding barium hydrate to the chloride solution. When the 
resulting precipitate, barium sulphate, ceases to form, it indi- 
cates that the acid has been neutralized. Prom 6 per cent to 
10 per cent by weight of the reagent compared with the chlo- 
ride is required. This method of neutralizing the acidity of 
the magnesium chloride solution is more strongly indicated 
when the oxychloride material is to be wrought into work of a 
permanent character and is not as essential for vulcanite casts, 
since the latter are destroyed after vulcanization, in removal 
from the dentures. After two years almost constant use of 
magnesium oxychloride, the writer has not found it necessary 
to purify any commercial chloride solution, but has frequently 114 
TREATMENT AND FILLING OF IMPRESSIONS 
been obliged to re-calcine the oxide to drive off the C02, as 
previously mentioned. 
PREPARING THE MAGNESIUM CHLORIDE SOLUTION 
In the average dental practice but a comparatively small 
amount of magnesium oxychloride will be used in the course 
of a month, so the preparation of a large quantity is not ad- 
visable. It is a better plan to make up one or two quarts of 
the liquid chloride, renewing the solution from time to time 
as needed. In this way the quality of the liquid can easily be 
kept up to standard. 
To make the solution, put 2 pints of water in a clean two- 
quart glass bottle, and add the crystal chloride until complete 
saturation of the water is effected. The visible test of full 
saturation of the water appears in the presence of undissolved 
crystals of chloride in the bottom of the vessel. 
A half-inch layer of crystals in the bottom of the vessel at 
all times will do no harm and will keep the solution fully satu- 
rated. If the crystals disappear, add more until the usual 
amount of excess is restored, and if they increase, due to evap- 
oration of the water, add more of the latter. After full satu- 
ration of the water has occurred, the liquid should not be 
shaken up nor the crystals disturbed in decanting off a por- 
tion for use. 
MANNER OF MIXING THE OXIDE WITH THE CHLORIDE 
SOLUTION 
Place a sufficient amount of the chloride solution to form 
a cast in the plaster bowl and sift in the oxide just as plaster 
is manipulated, stirring much more vigorously and for a 
longer time than when plaster is used. Additions of the oxide 
are made from time to time and the stirring continued until 
the mass is sufficiently thick to stand alone. This is an ex- 
tremely important requirement, for when too thin the oxy- 
chloride overflows the bounds of the impression and the cast 
can not be built up to proper form. 
The object in vigorous stirring is to eliminate all air that 
may be in the powdered magnesite and to coat every granule 
with a film of the liquid. The tendency of all beginners in 
using this material is to slight the stirring, and economize on 
the powder, with the result that although the mass hardens 
well and is smooth, there is an excess of the chloride present 
and the cast will more readily fracture under stress than when TREATMENT AND PILLING OF IMPRESSIONS 
115 
the material is thickly mixed. It is also inclined to soften 
more readily during vulcanization. 
TREATMENT OF IMPRESSIONS 
To get an absolutely smooth surface to a cast of this mate- 
rial it is necessary to have a smooth surface to the impres- 
sion. This can best be secured by treating either plaster or 
modeling compound impressions with a varnish having a san- 
darac base. Gilbert’s Imperial Varnish fulfills the require- 
ments well. 
In filling modeling compound impressions with plaster the 
surfaces are merely moistened with water to accelerate the 
flow of plaster over the impressed areas. With oxychloride, 
although moisture on the surface of the impression would 
insure ease of introduction, its presence would eventually de- 
teriorate the surface of the cast, rendering it softer and less 
resistant to stress than when the impression is dry. 
Modeling compound impressions are varnished because 
unless so treated the compound is at times extremely difficult 
to remove from the oxychloride cast. 
FILLING THE IMPRESSIONS 
The impression is filled with oxychloride mixture in much 
the same manner as with plaster, with this exception: Since 
the face of the impression is dry, for reasons previously 
stated, to prevent the formation of creases in the cast where 
two or more additions of the mixture may meet, it is best to 
apply each subsequent addition to an area already covered, 
and by vibration let the mass last added settle down and push 
the margins of that already adapted over the uncovered areas 
of the impression. 
In partial cases, impressions of teeth should be filled with 
a small tamper to avoid the confinement of air in the matrix. 
The mass of oxychloride should be built to the proper form 
of the cast, being careful to avoid any excess, since when set, 
it is very difficult to cut with a knife. By adjusting a bead 
of wax on the periphery of the impression to outline the ex- 
treme margins of the cast, and by building the material to 
this bead much annoyance will be averted later oil. 
GENERAL REMARKS 
By mixing from 50 to 80 per cent of clean sand with 50 
to 20 per cent of the oxide of magnesium a harder and much 116 
TREATMENT AND FILLING OF IMPRESSIONS 
more resistant mass will result tlian if the oxide and chloride 
alone are used. 
By filling the impression partially with oxychloride mix- 
ture and inserting a previously selected metal model form 
(Kerr’s) an extremely small amount of the material will be 
required and the peripheral outline, as well as the depth of 
the cast, will be kept within minimum limits, since the oxy- 
chloride need not cover the metal form on these surfaces. 
The material should not be disturbed by attempting to re- 
move the impression until thoroughly hardened. It usually 
requires about 12 hours to set. Should the mass have spread 
out over the sides of the impression much more than is desir- 
able it may be trimmed peripherally in four or five hours after 
mixing without endangering the cast. 
Thorp’s applied Chemistry has this to say in reference to 
the chemical reaction which occurs in combining the oxide and 
chloride of magnesium: 
“When highly claimed magnesia is treated with a strong 
solution of magnesium chloride it dries in a few hours to a 
hard mass of oxychloride, capable of receiving a high polish. 
A sample prepared in this manner and hardened by six 
months’ exposure to the air was found to consist of a mixture 
of Mg C O with a compound of Mg CL 5 Mg 0 17 IB 0. On 
heating to 180° C. it was converted into Mg CL 5 Mg 0 6 H2 0. 
By prolonged treatment with water the whole of the mag- 
nesium chloride was extracted and the compound 2 Mg 0 3 H2 
0 left. 
“This residual hydrate is a compact solid as hard as sand- 
stone and possessing a brilliant surface. 
“Magnesia cement is used very extensively as a hinder in 
connection with briquetting in the manufacture of artificial 
building stones, tiles, grindstones, and emery and polishing 
wheels. Its binding quality is very considerable and it is very 
plastic and cheap. 
“A good mixture for this use consists of: 
“25 parts magnesia (93 Mg 0). 
“25 parts magnesium chloride (45 per cent solution). 
“50 parts water. 
“About 5 pounds of this mixture will serve to cement 95 
parts of stone, emery, etc. The resulting blocks are very solid 
and harden thoroughly in a few hours. ’ ’ 
(Eckel. Cements, Limes, and Plasters.) TREATMENT AND FILLING OF IMPRESSIONS 
117 
HISTORY 
In 1853 M. Sorel, an eminent French chemist, discovered 
that zinc chloride when mixed with zinc oxide formed a cement. 
This is essentially the basis of our oxychloride of zinc cements 
today, hut it was not introduced to nor used by the dental pro- 
fession until many years after its discovery. 
Shortly after this discovery Sorel found that the chlorides 
and oxides of several other metals possessed similar prop- 
erties. 
The most important and valuable combination he discov- 
ered was that the oxide and chloride of magnesium united to 
form a substance as hard as stone. Further, that by combin- 
ing coarsely crushed rock, as marble, granite, limestone, etc., 
with a small percentage of the oxychloride of magnesium the 
resulting mass would stand an enormous strain before crush- 
ing. 
The value of this discovery was immediately recognized 
and made use of in the industrial field in the production of 
artificial stone known as Sorel’s stone. 
(Bibliography.) 
A practical treatise on Coignet-Beton and other artificial 
stone. Q. A. Gillmore, 1871. 
Cements, Limes, and Plasters. E. C. Eckel, 1909. CHAPTER IX 
BASES FOR ARTIFICIAL DENTURES 
In prosthetic procedures, that portion of a denture which 
rests upon the oral tissues, and to which the teeth are attached 
by various means, is called a base. 
Requisite Properties of a Denture Base 
The material selected for a base for an artificial denture 
should possess certain requisite properties: 
First — It should be rigid, in order to retain its form under 
stress. 
Second — It should be dense and non-porous. 
Third — It should be free from action by oral secretions 
or food products. 
Fourth — It should be odorless and tasteless. 
Fifth — It should be a reasonably good conductor of ther- 
mal changes. 
Sixth — It should be readily adapted to the die or cast of 
the mouth. 
Seventh — It should be capable of taking and retaining a 
high polish. 
Two general classes of materials are utilized as bases for 
artificial dentures. The first consists of metals, as gold and 
its alloys, platinum, aluminum, and various alloys of tin. The 
second class consists of plastic vegetable substances, as vul- 
canite, gutta percha, and celluloid. 
Gold Bases 
Pure gold, because of its softness and lack of rigidity, is 
not used as a base for artificial dentures, except in special 
cases, and then only when combined with gold of a lower carat. 
Twenty carat gold is most commonly employed in denture 
construction, although 18K gold is frequently used. The ob- 
jections to the latter are on account of its greater rigidity, 
which renders it more difficult to conform to the die, and its 
tendency to discolor in some mouths. 
Twenty carat gold plate more nearly fulfills the require- 
ments mentioned as a base than any of the other materials 
118 BASES FOR ARTIFICIAL DENTURES 
119 
employed for this purpose, except platinum. Its beautiful, 
rich yellow color, freedom from taste, odor or oxidation, or 
tendency to discolor, its rigidity in comparatively thin sheets, 
its high conductivity and the ease with which it can be pol- 
ished, place it in the front rank of materials used for dentures. 
The principal objections to its universal use are due, first, to 
the difficulty in securing close adaptation to the oral tissues, 
as a result of the sequent steps of construction, and, second, 
to the expense involved in the production of such substitutes. 
It could and should be used for bases in many cases where 
dentures of the less expensive class are now constructed, par- 
ticularly in partial cases. 
In addition to the advantages mentioned, gold combines 
the greatest strength with the least bulk, of any other base. 
Platinum Bases 
The oral tissues under a well adapted platinum base re- 
tain their normal tone, while but little change occurs in the 
bony processes. It has been noticed in porcelain crown and 
bridge work, the frame work of which is composed of plat- 
inum, that the tendency for food to accumulate or plaques to 
form on exposed or partially protected platinum surfaces, is 
decidedly negative as compared with alloyed or pure gold in 
similar situations. This is supposed to be due to some un- 
known, inherent quality in the platinum itself, not possessed 
by other metals, which tends to preserve hygienic conditions, 
even under adverse circumstances. Whether this view is cor- 
rect or not, the fact remains that when platinum base dentures 
are well adapted and free from mechanical causes of irrita- 
tion, the tissues remain remarkably healthy and normal under 
such substitutes. 
In addition to the peculiarly benign effect of platinum on 
the oral tissues, this metal possesses practically all of the 
good qualities ascribed to gold. In color it is bluish-white. It 
is practically infusible under the ordinary blowpipe flame. It 
may be used as a base plate in the same manner as gold is 
employed, the teeth being attached either by soldering, or with 
vulcanite. An alloy of platinum and iridium, which is harder 
and more resistant than platinum itself, would be preferable, 
however, since pure platinum is slightly softer and more 
easily bent than 20K gold of equal thickness. 
The usual method followed in making use of platinum in 
denture construction is in conjunction with porcelain. The 120 
BASES FOR ARTIFICIAL DENTURES 
teeth are first attached by soldering, the porcelain, which gives 
the denture its contour, being subsequently fused around them 
and over the base, blending with teeth and base to form a 
homogeneous mass. The advantages and disadvantages of 
continuous gum dentures will be discussed when dentures of 
this class are described. 
Aluminum Bases 
Aluminum is frequently used as a base for artificial den- 
tures in both cast and swaged form. It is the lightest of all 
of the metals, is a good conductor of thermal changes, and is 
non-irritating to the tissues. 
Since this metal can not be soldered successfully, it re- 
quires considerable care to develop the means for attaching 
the teeth to the base with vulcanite in swaged base dentures. 
When the base is produced by casting, this difficulty is easily 
overcome, the necessary anchorage for the vulcanite being 
formed in the wax model and reproduced in the casting 
process. 
Cast base aluminum dentures are inclined to disintegrate 
in some mouths, due largely to castings of this metal being 
of more or less imperfect density. When examined under a 
magnifying glass, many minute spaces are disclosed. When 
broken, and the fractured surfaces are examined, these spaces 
are present and can be seen in the body of the casting, as well 
as on the outer surfaces. The use of a pure aluminum, with 
proper technic in casting, will largely overcome this difficulty. 
For various reasons, however, a swaged base is usually 
more satisfactory and less inclined to irritate the tissues than 
a cast base. 
Tin Alloy Bases 
Alloys of tin and cadmium, tin and bismuth, and other 
similar combinations, are frequently used in the production 
of bases for lower substitutes, to give weight to the finished 
dentures, and by gravity assist in their retention. When prop- 
erly constructed, they are non-irritating to the tissues and 
serve well the purpose for which they are intended. Care 
should be taken, however, in the construction of dentures of 
this class to avoid excessive weight, on account of the tendency 
of such substitutes to tire the mandibular muscles and produce 
irritation of the soft tissues. BASES FOR ARTIFICIAL DENTURES 
121 
Vulcanite Bases 
Because of the slight expense involved and the compara- 
tively simple technical details attending its manipulation, vul- 
canite is very extensively used as a base for artificial dentures. 
When proper care is exercised, most efficient and serviceable 
substitutes for the natural teeth can be produced when this 
material is used as a base. 
First — Better adaptation can be secured with vulcanite 
than with any other basic material. 
Second — Ease of manipulation in the constructive steps. 
Third — Inexpensive, first, as to cost of material, and sec- 
ond, as to production; consequently dentures of this type are 
possible for persons of moderate means. 
ADVANTAGES 
DISADVANTAGES 
First — Vulcanite is a poor conductor of thermal changes. 
Second — In order to have the inherent strength to resist 
stress, vulcanite bases are necessarily more bulky than metal 
bases. 
Third — Vulcanite decreases the acoustic properties of the 
palatine vault to a greater extent than do metal bases. 
Fourth — Unless special care is exercised in finishing the 
palatine, as well as all surfaces of vulcanite dentures, inflam- 
matory conditions of the mucous tissues frequently ensue. 
Such conditions have been erroneously ascribed to other 
causes, some of which will be discussed later. 
Thermal Conductivity of Various Denture Base Materials 
Vegetable substances, as compared with the metals, are 
poor conductors of thermal changes. The following table by 
Prof. R. von Wardroff (slightly modified) on the conductivity 
of various substances, gives the conductivity of vulcanite, as 
well as of the metals used in denture construction. “The co- 
efficient of thermal conductivity of a substance indicates the 
amount of heat energy, measured in calories, conducted from 
one face to the opposite face of a centimeter cube of the sub- 
stance, when one of the faces is maintained one degree hotter 
than the other. The amount of heat energy conducted is pro- 122 
BASES FOR ARTIFICIAL DENTURES 
portional to the difference in temperature between the oppo- 
site faces.” 
“ A calorie is the amount of heat energy required to raise 
the temperature of a gram of water one degree Centigrade.” 
Silver at zero C 1.00000=1 
Copper at zero C 1.00000=1 
Gold at zero C 73200=% (Approx.) 
Aluminum at zero C 34300=1/3 
Platinum at zero C. 11500=1/9 
Paraffin at zero C 00061=1/166 
Vulcanite at zero C 00040=1/250 
Beeswax at zero C 00009=1/1111 
Silver being rated as 1, gold transmits only %, aluminum 
1/3, platinum 1/9 and vulcanite 1/250 calories in the same 
length of time. 
Cause of Oral Inflammatory Conditions Under 
Vulcanite Bases 
Several theories have been advanced as to the cause of 
inflammatory conditions frequently arising from the wearing 
of vulcanite dentures, the principal ones of which are as 
follows: 
(1) Lack of proper conduction of thermal changes to, and 
radiation of heat from, the oral tissues. 
(2) Deleterious effects of coloring matter in vegetable 
bases. 
(3) Mechanical irritation. 
(4) Unhygienic conditions. 
CONDUCTIVITY OF THERMAL CHANGES 
While there is a marked difference in the rate of conduc- 
tivity of the metals and the vegetable bases, there is no evi- 
dence to prove that the noticeable deficiency of vulcanite in 
this respect is directly responsible for the troubles sometimes 
ascribed to it. 
Possibly in rare cases, particularly when other active 
causes are present, the oral mucous membrane may be influ- 
enced by, and its general tonicity impaired through, the non- 
responsive medium of a vulcanite base. However, the fact 
that many hundreds of thousands of vulcanite dentures are 
being worn with comfort, under which no inflammatory con- 
ditions of the mucous membranes have developed, is evidence BASES FOR ARTIFICIAL DENTURES 
123 
in itself that the percentage of cases due solely to poor con- 
ductivity is extremely small. 
Many cases of so-called rubber sore mouths have come 
under the observation of the writer. Some of these were cor- 
rected by the substitution of metal base dentures of continu- 
ous gums, gold or aluminum, and others with gold-lined 
vulcanite dentures. The largest percentage of cases presented 
were satisfactorily relieved on the introduction of properly 
fitted and finished vulcanite cases. In no instance that can 
now be recalled was there a recurrence of the inflammatory 
conditions, which would undoubtedly have occurred had the 
primal cause been due to non-conductivity. 
DELETERIOUS EFFECT OF COLORING MATTER IN VEGETABLE BASES 
The red, pink, brown and maroon rubbers, as well as cel- 
luloid and zylonite, are usually given their tints by the addition 
of varying proportions of vermilion or the sulphuret of mer- 
cury, Hg.S. The idea has been advanced that during the proc- 
ess of vulcanization some of the sulphuret may fail to unite 
closely with, or it may be expelled from, the rubber, thus leav- 
ing the pigment comparatively free or only weakly combined 
with the base. After introduction and use of the denture, the 
vermilion becomes an irritant to the tissues and the inflam- 
matory conditions mentioned follow. Again, it has been 
thought possible that the comparatively free sulphuret by the 
action of the fluids of the mouth, which are sometimes slightly 
acid, may be converted into mercuric chloride or corrosive 
sublimate, a decided irritant, and the conditions mentioned be 
thus produced. These ideas, however, are unproven theories 
and can not account for the fact that inflammatory conditions 
sometimes develop under dentures of black vulcanite which 
contain no mercury or other irritating pigment of any charac- 
ter, and sometimes under metal base dentures as well. 
The more logical explanation of the conditions under con- 
sideration is that they are due to rough or defective surfaces 
of the denture, as well as to lack of hygienic attention to the 
mouth and denture on the part of the patient. 
MECHANICAL IRRITATION 
The negative form of the month is given to a vulcanite 
denture by molding the rubber while in a plastic state over a 
cast of plaster, or some similar material, and holding it in 
contact with the cast, under pressure, while hardening. 124 
BASES FOR ARTIFICIAL DENTURES 
As has been mentioned before, the manner of crystalliza- 
tion of plaster results in the formation of minute spaces be- 
tween the crystals. When examined under a magnifying glass, 
the surface of a plaster cast presents many minute irregular- 
ities. In addition to the spaces between the crystals, there 
are other and larger spherical spaces, due to the presence of 
air in the plastic mass itself, and also to air being caught be- 
tween the latter and the impression surface in filling. These 
spherical spaces are sometimes quite numerous, some visible, 
and others lying just under the surface of the cast, obscured 
by a thin film of plaster. 
Under the pressure exerted in closing the packed flask, the 
rubber is forced into the visible as well as some of the ob- 
scured irregularities and spherical spaces, and in vulcanizing, 
hardens in the irregular form thus assumed. 
When the case is vulcanized, removed from the flask, thor- 
oughly cleaned with a scrub brush, and examined, that por- 
tion moulded against the surfaces of the cast will be found 
irregular and nodular, as a result of the conditions mentioned. 
Unless thoroughly removed and the surfaces highly polished, 
these nodules and irregularities become mechanical sources 
of irritation, frequently sufficient to set up inflammatory con- 
ditions. 
Hyperaemic conditions and oftentimes traumatic injury 
frequently develop at local points, under a vulcanite denture. 
The cause may nearly always be traced to some defect in the 
denture at that point, either from roughness, undue pressure, 
or imperfect adaptation. Sometimes obscure spiculae are 
present in the palatine vault, and the pressure of the denture 
on the mucous tissues overlying these points causes discom- 
fort, and frequently marked inflammation develops. Sharp, 
uneven points in the process, resulting from recent extraction, 
are also sources of irritation. Such conditions develop under 
metal base, as well as vulcanite dentures. 
Lack of care of tlie denture on the part of the patient is a 
most common source of inflammatory conditions of the oral 
mucous membrane. Mucous plaques seem to form on, and 
particles of food to become attached more readily to, vulcanite 
than to metal base dentures. The reason for this is obvious. 
A metal base as a rule is usually smoothly finished, while vul- 
canite is seldom given the high polish it is capable of tak- 
ing on. 
UNHYGIENIC CONDITIONS BASES FOR ARTIFICIAL DENTURES 
125 
The rough surfaces on the palatine portion of a denture, 
previously referred to, furnish a favorable location for the 
formation of plaques in which micro-organisms flourish. Dr. 
Gr. V. Black called attention to this fact many years ago, and 
stated his belief that the by-products of the bacteria were 
largely responsible for many cases of rubber sore mouths. 
These plaques often form in protected locations on reasonably 
well-polislied vulcanite, and occasionally on metal, base den- 
tures, if the patient does not cleanse them thoroughly and 
regularly. 
Most of the disadvantages ascribed to vulcanite can be 
greatly reduced, or practically eliminated, if proper care is 
observed in the construction of dentures of this material, and 
they are given proper care by the patient. 
Celluloid is a mixture of gun cotton, camphor gum, oxide 
of zinc, and vermilion. As prepared for dental purposes if 
comes moulded in blanks of various sizes. A blank is placed 
in the flask matrix, subjected to heat, and the flask closed 
under heavy pressure. If imperfections are present in the 
cast, the negative of these will be reproduced in the denture. 
The avoidance of such imperfections is the first consideration; 
the second, equally as important, is their removal from the 
denture, if any are present. Otherwise, similar irritation of 
the oral mucous membrane is liable to occur, as in vulcanite 
cases. 
Celluloid is not as resistant to wear nor to the action of 
the oral fluids as vulcanite. Alcohol acts on it somewhat, and 
in some mouths it discolors badly. It is of a beautiful pink 
shade and occupies a place between porcelain and the best 
quality of pink vulcanite, in its resemblance to the natural 
gum tissues. When carefully manipulated and properly fin- 
ished, it is an excellent base for temporary dentures, and in 
some mouths will prove satisfactory for permanent substi- 
tutes. It is capable of taking an extremely high polish, which 
however, is soon lost if abrasive powders are used in cleans- 
ing it. 
When properly finished, the tissues retain their tonicity 
under celluloid fully as well as under metal base dentures. As 
a matter of fact, if reasonable skill is exercised in the technical 
details, good substitutes can be produced with any of the mate- 
rials here described; while on the other hand, poor technic 
with the best materials is productive of indifferent results, if 
not positive failure. 
Celluloid Bases CHAPTER X 
SWAGED METAL BASE DENTURES 
Sivaging is the process of adapting or conforming metal, 
usually in sheet form, to a carved, cast, or prepared harder 
object called a die, by means of blows or pressure. 
Swaged metal bases of gold, platinum or aluminum, such 
as are used in denture construction, are given the reverse or 
negative form of the mouth by swaging a plate of suitable 
thickness between a metallic die, and a counterdie of metal 
or some other material which fulfills the purpose of a metal 
counterdie, as rubber, soap, clay, etc. In case any of the latter 
named substances are employed, they must be confined within 
a suitable receptacle. 
In the production of a swaged, metallic base denture, there- 
fore, a die fulfills a similar purpose to that of a plaster cast 
in the production of a plastic base denture. 
Comparative Results in Adaptation of Swaged, 
and Vulcanite Bases 
As a general proposition it is more difficult to secure as 
close an adaptation of a swaged metal base to the oral tissues, 
as can be secured when vulcanite is employed. This statement 
is based on the fact that in the production of dentures with 
metal bases, a greater number of constructive steps must be 
carried out than are required in the production of vulcanite 
dentures. 
SEQUENT STEPS IN SWAGED BASE DENTURE CONSTRUCTION 
a. An impression of the mouth is secured. 
b. From the impression a cast of the mouth is obtained, 
which, by proper trimming, with additions if necessary, and 
final varnishing, is converted into a model. 
c. By imbedding the model in molding sand and with- 
drawing it, a sand matrix is formed. 
d. A die is produced by casting molten metal in the sand 
matrix. 
e. By imbedding all but the face of the die in sand, and 
casting a lower fusing metal over the exposed portion, a coun- 
terdie is obtained. 
126 SWAGED METAL BASE DENTURES 
127 
f. A baseplate is produced by swaging a sheet of metal 
of the required character and thickness between the counter 
die and die, until the plate metal closely conforms to all sur- 
faces of the latter. 
g. Wiring the periphery and lingual surface of the base 
and attaching anchorages for the vulcanite. 
h. Includes the general steps of occluding the teeth, wax- 
ing, flashing, packing, closing the flask, vulcanizing and finish- 
ing the case. 
In carrying out each one of the sequent steps mentioned, 
except (e), some loss of detail or departure from the true con- 
tour of the oral tissues to be covered by the denture, is liable 
to occur, which may impair the adaptation of the finished 
product. If more than one error occurs, the tendency is to 
increase, rather than diminish, any previous defect, while in 
the end any one, or the several errors combined, may seriously 
impair or entirely destroy the adaptation of the denture. 
SEQUENT STEPS IN VULCANITE DENTURE CONSTRUCTION 
In the sequent steps of vulcanite denture construction, it 
is necessary to carry out (a), the first part of (b), and (h), 
as detailed; (c), (d), (e), (f) and (g) are neither necessary 
nor applicable. Thus it is seen that of the eight general steps 
carried out in the production of swaged metal base dentures, 
but three are required to produce vulcanite substitutes. 
The intermediate steps, unnecessary in vulcanite work, but 
essential in the swaging process, require the greatest care in 
execution, to avoid errors. The principal mishaps liable to 
occur in these intermediate steps are as follows: 
(c) Distortion of the sand matrix in removal of the model. 
(d) (1) Distortion of the sand matrix in pouring the 
molten die metal. 
(2) Accumulation of steam or gas in the matrix, 
causing roughness and imperfections in the 
die. 
(3) Warpage of the die, due to contraction in cool- 
ing. 
(f) (1) Marring the high points on the face of the die 
in adapting the plate with the horn mallet, 
and subsequently in swaging. 
(2) Spreading or splitting of the die under hammer 
blows or pressure. 
(3) Failure to secure perfect adaptation of the base- 
plate to the face of the die. 128 
SWAGED METAL BASE DENTURES 
(g) Distortion of the plate in soldering, in attaching tiie 
rim wires and anchorages for the vulcanite. 
All of these steps, if carefully carried out, may be com- 
pleted without perceptible errors occurring, and the adapta- 
tion of the baseplate to the oral tissues may, on trial, be found 
satisfactory, yet under (h), in the final closing of the flask, 
when overpacked and subjected to undue pressure, the adapta- 
tion of the denture is frequently impaired or destroyed. 
The excess rubber in the overpacked matrix, in closure of 
the flask, forces the baseplate against the supporting plaster, 
and if excessive stress is applied, causes distortion not only 
of the foundation on which it rests, but bends the baseplate 
as well. The warped condition the denture thus assumes be- 
comes permanent after vulcanization. 
This brief summary of the commonly occurring errors 
which tend to impair the adaptation of swaged base dentures 
is not intended to disparage the utility of substitutes of this 
type, nor to discourage their more general production, but 
rather to emphasize the need of accuracy in technical proced- 
ures. When properly constructed, the usefulness, beauty and 
comfort of swaged metal base dentures—-their general excel- 
lence, in fact, is thoroughly established and unquestioned. 
Appliances and Accessories Used in Die and Counterdie 
Construction 
The necessary appliances used in the production of dies 
and counterdies are as follows: 
1. Molding flasks. 
2. Molding sand. 
3. Sieve. 
4. Talcum powder. 
5. Straight edge. 
6. Laboratory knife. 
7. Heating appliances. 
8. Melting ladles. 
9. Die metal. 
10. Counterdie metal. 
11. Whiting and alcohol. 
12. Sable brush. 
MOLDING FLASKS 
The ordinary molding flasks are hand-like, slightly taper- 
ing rings of cast iron, open at both ends. Peripherally, they SWAGED METAL BASE DENTURES 
129 
conform to the outline of the alveolar arches. They vary in 
size, the usual set consisting of a nest of four rings, ranging 
from 4 to 2y2 inches in diameter, and 21/4 inches in depth. The 
smallest flask, which corresponds in size and general outline 
form to the base of the average model, is used for confining 
the metal within the base outline of the die, and thus increas- 
ing its depth, to avoid spreading or splitting during swaging. 
Various forms of special flasks, such as the Bailey, Lewis, 
and Hawes flasks, are also in common use. The two former 
are designed to increase the depth of the die over that of the 
model, while the latter is intended to obviate the use of cores, 
when undercuts are present on the labial or buccal surfaces 
of the model. 
MOLDING SAND 
Sand of the finer variety, such as is used by brass or iron 
raolders may be used to advantage in the laboratory. It is 
Fig. 39.— Nest of Molding Rings 
rendered moist and workable by spraying occasionally with 
water, just enough being incorporated to render it cohesive. 
An excessive amount of moisture present would develop an 
excessive quantity of steam in casting, and result in imper- 
fections in the die. The sand should be sifted, thoroughly 
worked with the hands, and allowed to stand a short time be- 
fore use, to develop uniform density and cohesiveness, or 
temper, as it is called. 
The supply houses furnish prepared molding sand, such 
as “Chase’s,” a combination of fine sand with oil, and “Cal- 
car,” a combination of marble dust with glycerin or oil. With 
moderate use, these prepared sands give good service, last a 
considerable length of time, and are more convenient to use 
than the common sand. Used frequently, they soon deterior- 
ate and lose the cohesive property, because of the burning out 
of the oil or gvlcerin. The addition of a small quantity of the 130 
SWAGED METAL BASE DENTURES 
latter, and the thorough sifting and working of the mass will 
restore cohesiveness. 
THE SIEVE 
It is essential that sand of any variety should be kept free 
from lumps, foreign substances and particles of metal that 
may become detached from the die and counterdie in casting. 
For this purpose a No. 20 mesh sieve should be kept at hand, 
and before forming the matrix, the sand should be run through 
it once or twice. This treatment not only removes debris, but 
renders the sand more workable by disseminating the drier 
particles among the damper portions, and develops its cohes- 
ive property as well. 
The model, which should be flaring, smooth, varnished and 
perfectly dry, is dusted and thoroughly rubbed with soapstone 
to prevent the sand from adhering to it. The excess should 
be removed with a soft brush before imbedding the model in 
sand. 
TALCUM POWDER 
THE STRAIGHT EDGE 
A straight edge of metal or wood is used for striking off 
the excess sand that extends above the molding flask after 
packing. Since this surface of the sand becomes the base of 
the matrix and must support the weight of the molten metal 
in casting, it should set flat at all points upon the bench on 
which it rests, so that it will not yield or break under the 
weight of the molten die metal. 
A straight blade knife is used for removing a tapering 
section of sand, beginning at the ring margin and slightly in- 
creasing in depth to the periphery of the model. This trim- 
ming is necessary to free the model at its periphery and allow 
it to drop from the sand without fracturing the matrix mar- 
gins. 
THE LABORATORY KNIFE 
A burner capable of developing a considerable amount of 
beat is an essential factor in laboratory procedures. It is n 
time and money saver as well. Tlie very common method of 
placing the ladle over an ordinary Bunsen burner and apply- 
ing the blow-pipe flame directly on the die metal to more rap- 
idly fuse it, is to be discouraged, since this procedure induces 
HEATING APPLIANCES SWAGED METAL BASE DENTURES 
131 
oxidation and deterioration of the metal in a very short time. 
The application of the blow-pipe flame underneath the ladle 
is not objectionable, further than that it is usually unneces- 
sary, if sufficient heat is developed by the burner. 
MELTING LADLES 
Ladles used for melting the die metal should be of cast 
iron or stamped from heavy iron of not less than one-eighth 
inch in thickness. Ladles of this type are preferable to those 
made of thin sheet metal, first, because, being thicker, they 
absorb and retain more heat, thereby accelerating the fusing 
of the metal, and second, because of their greater rigidity. 
There should be a lip or spout on the side, through which the 
molten metal may be directed in a small stream while pouring 
Fig. 40.— Melting Ladles 
it into the matrix. Ladles used for melting zinc should be 
coated inside with whiting until the iron is thoroughly oxi- 
dized, to prevent the zinc from alloying with it. The alloy of 
zinc and iron, if it is allowed to form, is taken up by the molten 
zinc, which is thus rendered harder, while the ladle sides are 
gradually reduced in thickness by the constant alloying pro- 
cess, and are eventually perforated. 
Die Metal 
A metal used for die purposes should possess certain re- 
quisite properties. 
First — It should neither expand nor contract in assuming 
a solid state. 
Second — It should fuse at a moderately low temperature. 132 
SWAGED METAL BASE DENTURES 
Third — It should be sufficiently hard and resistant lo 
stress so that the high points and general surface markings 
of the die will not be defaced or battered down in swaging the 
plate. 
Fourth — It should be cohesive, so as to maintain its form 
without splitting or spreading under pressure or hammer 
blows. 
Metals Most Commonly Used for Dies 
Zinc, Babbitt’s metal, Melotte’s metal and a variety of 
alloys similar in composition to the latter, are used for die 
purposes. 
ZINC 
Zinc has long been used and is still very extensively em- 
ployed in the making of dies for dental purposes. It fuses 
at the highest temperature and is the hardest of any of the 
metals or alloys commonly used for dies for prosthetic pur- 
poses. Its fusing point is 419.4 deg. C. In cooling, it con- 
tracts perceptibly and oftentimes warps to a marked degree, 
depending on the form of the matrix in which it is cast. 
For years it has been known that plaster expands in set- 
ting and zinc contracts in cooling. From these facts, the 
axiom was deduced that the expansion of the plaster model 
compensates for the contraction of the zinc die. This cer- 
tainly would be a simple solution of the problem if the amount 
of contraction in the die equaled the expansion of the plaster 
model, and if the factor of warpage could be eliminated. Since 
there is no correlation of the movements, however, the absurd- 
ity of the axiom is apparent. 
Shrinkage of Metals in Passing from Liquid to Solid State 
The following table from Kent’s “Engineers’ Pocket 
Book” on the shrinkage of castings is as follows: 
Cast Iron 
.... 1/q inch per linear foot- 
-1 inch sectional 
area. 
Brass 
..3/16 
a << a 
a 
a a 
a 
it 
Steel 
it (i a 
u 
a a 
a 
it 
Malleable Iron .. 
it <C a 
a 
a a 
a 
a 
Zinc 
. .5/16 
a u a 
<t 
a a 
a 
it 
Tin 
. .1/12 
a a u 
a 
a a 
a 
a 
Aluminum 
..3/16 
u a a 
a 
a a 
a 
a 
Britannia 
. .1/32 
u a it 
a 
a a 
a 
a 
Larger or bulkier castings shrink slightly less proportion- 
ately, while smaller ones shrink more than the amounts indi- 
cated in the table. SWAGED METAL BASE DENTURES 
133 
A die of zinc derived from a sand matrix 21/, inches across 
from one buccal surface to the other shrinks about 1/16 of an 
inch, while a plaster model, in which the expansive movement 
is high, expands less than 1/64 of an inch. In cooling, the 
tendency of the metal is to rest on the dome, or that portion 
of the matrix which gives form to the palatal vault of the die, 
and for the borders to draw inward from the sides and upward 
from the base of the mold. The warpage thus resulting de- 
creases the height of the palatine vault and reduces the buc- 
cal diameter, in many cases, to such an extent as to require 
the construction of a more accurate die on which to finish the 
base. 
When zinc dies are used, it is the common practice to cast 
two, and frequently three, as a preliminary step in swaging 
a denture. It also frequently occurs that a baseplate, when 
adapted to one, will fit neither the other dies nor the plaster 
model from which they were derived. It is then a problem as 
to which die most nearly represents the true oral contour. 
This can only be determined by trial of the base in the mouth, 
after swaging on each die separately. 
To partially overcome the errors occurring in the use of 
zinc, as well as other dies, the following steps , are recom- 
mended : 
Treatment of Plaster Models to Arrest Expansion 
First — As soon as the plaster cast from which the model 
is to be formed has set sufficiently hard to permit, the impres- 
sion should be removed and the cast converted into model 
form by trimming and additions, as required. The moisture 
present should then be expelled by applying moderate heat. 
Overheating tends to both warp the model and disintegrate 
the plaster. The varnish should be applied last, since, if 
applied before heating, it prevents the ready evaporation of 
the moisture. Drying the model in this manner stops the 
chemical action, and hence expansion in the plaster, which 
otherwise would continue for twenty-four hours or more. 
Second — When the sand mold is secured, the molten die 
metal is cast into it at as low a temperature and in as thickly 
liquid a condition as may be, and yet be plastic enough to in- 
sure its becoming adapted to all portions of the matrix. In 
other words, thorough evaporation of moisture from the 
model, if driven off soon after the cast is constructed, lessens 
its expansion, and filling the matrix with the die metal, poured 134 
SWAGED METAL BASE DENTURES 
at as low a temperature as possible, reduces contraction and 
lessens warpage. If cast while overheated, the metal assumes 
a decidedly crystalline structure, is very brittle on hardening 
and contracts perceptibly. 
Zinc dies, after cooling, may be annealed and rendered 
much tougher and more cohesive if heated to a temperature 
of between 100 to 150 deg. C. If heated much above 150 deg. 
C. they again become very brittle. This process of annealing 
is resorted to in the production of sheet zinc, the cast ingot 
being heated as above indicated and passed through rolls until 
reduced to the required thickness. The malleability imparted 
to it by annealing is retained on cooling. 
Babbitt metal is an alloy of copper, tin and antimony in 
varying proportions. It was designed by the man whose name 
it bears — Isaac Babbitt — as an anti-friction metal for bear- 
ings. As commonly compounded it is too soft for die pur- 
poses, but when combined in the proportions suggested by Dr. 
L. P. Haskell, the alloy is non-shrinking, resistant to stress, 
nearly equal to zinc as to hardness, fuses at a lower tempera- 
ture, and is superior in other respects. Dr. Haskell’s formula 
is as follows: 
BABBITT METAL 
Copper 1 part 
Antimony 2 parts 
Tin 8 parts 
This Babbitt metal fuses at 260 deg. C., casts well, and 
copies accurately the surfaces against which it is poured, if 
of proper fluid consistency. The antimony present, which 
under ordinary conditions expands in cooling, eliminates to 
a great extent, if not altogether, any tendency of the alloy to 
contract in passing from the fused to the solid state. A die 
made of Babbitt metal therefore more nearly represents the 
form and proportion of the plaster model than does one made 
of zinc. Its comparatively low fusibility is also a decided, 
advantage. For these reasons, principally, the use of Babbitt 
metal for dies is gradually increasing. 
Haskell’s Babbitt metal, properly compounded, can be pro- 
cured of the supply houses. If it is deemed advisable to make 
it in the laboratory, the following directions by Hall will aid 
in producing a well-alloyed product: “Melt the copper and 
half of the tin, then add the antimony and the remainder of 
the tin. Stir vigorously and keep the surface of the alloy 
covered with powdered charcoal.” SWAGED METAL BASE DENTURES 
135 
When melted repeatedly, and especially at high tempera- 
tures, Babbitt metal deteriorates, owing to the formation and 
retention within the alloy of some of the oxides of the com- 
ponent metals. These oxides may be partially removed and 
the metal restored to working condition by heating to a high 
temperature, adding scrap beeswax, stirring thoroughly, and 
skimming off the dross as it accumulates on the surface. 
Covering the surface of the molten metal with tine charcoal 
and stirring well also removes some of the oxides present. 
Br. Haskell recommends the addition from time to time 
of a little tin for restoring the fluidity of the alloy, since by 
repeated fusing some of the latter metal is lost by oxidation 
and volatilization. 
As previously intimated, all die metals and alloys, if over- 
heated, deteriorate rapidly. Care should therefore be ob- 
served to remove the metal from the fire before the entire 
mass is in a molten condition. The heat absorbed by the 
already melted metal is usually sufficient to melt one-fourth, 
and frequently one-half, its bulk of the still unfused portion 
after removal from the fire. This plan obviates overheating, 
and consequent excessive oxidation. It also insures smoother 
castings, since the metal being poured at low temperature 
generates less gas or steam on coming in contact with the 
sand matrix, than when overheated. 
melotte's metal and other fusible alloys 
A class of metallic compounds known as fusible alloys or 
triple alloys is much used for die purposes in crown and 
bridge construction, and occasionally as dies for dentures. 
These alloys are not as hard as zinc or Babbitt metal, but on 
account of their low fusibility and the sharpness of castings 
produced, they are very serviceable and much used. 
The triple alloys contain three metals, usually tin, lead 
and bismuth, in varying proportions. Bismuth has the prop- 
erty of expanding, imparting hardness, and reducing the fus- 
ing point of the alloy considerably below the mean fusing- 
point of the three metals, which is 272 deg. C. When alloyed, 
the metals melt at about 100 deg. C. 
Another class of alloys similar in character to the triple 
alloys, but composed usually of four metals, is also in com- 
mon use. These, in addition to the metals mentioned, contain 
antimony or cadmium, both of which, like bismuth, have the 
property of reducing the fusing point of the alloy of which 136 
SWAGED METAL BASE DENTURES 
they are a part. They also expand in cooling, and when in- 
corporated, impart this property to alloys, resulting in the 
production of sharp castings. The low fusibility of this type 
of compounds permits of their being poured into fresh plaster 
impressions direct, without the necessity for drying out the 
latter. Such castings as a rule are very sharp, well defined, 
and of reasonable hardness. 
Name. 
Tin. 
Lead. 
Bismuth. Antimony. 
Melting 
Cadmium. Point. 
Melotte’s 
5 
3 
8 
100°C. 
Newton’s 
3 
5 
8 
95°C. 
D’Arcet’s 
./... 1 
1 
2 
93°C. 
Dalton’s 
3 
5 
io y2 
92°C. 
Onion’s 
2 
3 
5 
92°C. 
Rose’s 
3 
8 
8 
79 °C. 
Wood’s 
1 
2 
4 
1 
71°C. 
Clinche 
Richmond’s . . . . 
48 
20 
32.5 
19 
9 io y2 
48 
13 
65.5°C. 
Hodden’s 
3 
5 
8 2 
106.6°C. 
COMPOSITION OF FUSIBLE ALLOYS 
The fusible alloys, being hard and more or less crystalline, 
lack the cohesiveness of zinc or Babbitt’s metal. Dies for full 
dentures, composed of such alloys, should, therefore, be made 
sufficiently thick to prevent fracturing under hammer blows. 
When used under hydraulic or screw pressure, a die of mod- 
erate thickness will resist stress without change, if its base 
and that surface of the press on which it rests are flat. 
A counterdie should be composed of a softer metal than 
the die of which it is the complement. This is essential for 
three reasons: 
First — If the die and counterdie were of equal hardness, 
both must yield in swaging, the die becoming slightly smaller 
and the counterdie slightly larger, in order to make room for 
the interposed plate. Such change in the die and its conse- 
quent effect on the baseplate would impair, if not altogether 
destroy, the adaptation of the latter to the oral tissues. 
Second—The tendency of a die and counter die of equal 
hardness to shear, or at least reduce in thickness, the plate 
being swaged over opposite parallel surfaces, as on the buccal 
surfaces of prominent tuberosities, is very marked. This ten- 
dency is not apparent when the counterdie is composed of a 
softer metal than the die. 
Third — A somewhat yielding counterdie opposed to an 
unyielding die carries the plate into the inequalities of the 
COUNTERDIE METAL SWAGED METAL BASE DENTURES 
137 
die, with its irregularly disposed surfaces, better than if the 
two were of equal hardness. 
A counterdie is usually made by pouring molten metal 
over the face of a die. To prevent fusion of the face of the 
die, and consequent union of the two masses of metal while 
casting, the counterdie metal should, as a rule, melt at a lower 
temperature than that of the die; the die should be cold, and 
the counter die metal should be poured at as low a temperature 
as possible. 
When melted, the casting of the counterdie metal should 
be deferred until it begins to thicken around the sides of the 
ladle, when it may be cast against the face of the die in a 
semi-liquid condition. 
Lead is used for counterdies with zinc dies, the difference 
m the fusing points of the two metals being 92 deg. C. An 
alloy of 7 parts lead and 1 part tin is used for counterdies 
with Babbitt metal dies, the difference in the fusing points of 
the alloys being about 50 deg. C. 
Both die and counterdie can be made from the same alloy 
in the bismuth compounds, the only precautions necessary to 
observe to prevent union being to have the die cold, and to 
allow the metal for the counterdie to assume a pasty condition 
before casting. A square-end tamper pressed against the 
plastic mass immediately after casting will force it against 
the face of the die, and insure close adaptation of the former 
to the latter. 
Usually, however, the fusible alloys are used in conjunc- 
tion with some swaging device or press. In such cases, only 
the die or the counterdie is formed of the fusible alloy, the 
plate to be swaged being adapted between the metallic form 
on one side, and some yielding material on the opposite side, 
such as soft rubber, moldine, damp tissue paper, or modeling 
compound. Such methods, however, are only adapted to the 
swaging of the purer and thinner forms of gold plate, or of 
pure platinum. 
WHITING AND ALCOHOL SOLUTION 
A solution of whiting (precipitated chalk) and alcohol is 
essential for coating the surface of a die previous to casting 
the counterdie. A solution of whiting in water will fulfill the 
same purpose, but alcohol is much better, as this solution 
when applied, dries immediately, while the aqueous solution 
does not. A little gum arabic added to the solution will im- 
part adhesiveness to the film when applied dry, and prevent SWAGED METAL BASE DENTURES 
exposure of tlie metal surfaces by the rubbing off of the film, 
should anything come in contact with the die face. Carbon- 
izing the die is also recommended, but the process, although 
effective, is a filthy one and soils the hands unnecessarily. 
BRUSHES 
A medium-sized sable or soft bristle brush is very useful 
for removing soapstone or sand from the model, and for clean- 
ing up the outer surfaces of the matrix generally before re- 
moving the model. CHAPTER XI 
TECHNIC OF DIE AND COUNTER DIE 
CONSTRUCTION 
FORMING THE SAND MATRIX 
The table or laboratory bench should be covered with a 
large sheet of clean paper, to assist in recovering the sand 
after the die is cast. 
Fig. 41.—Molding Ring and Model 
Tlie model, having been prepared as previously described, 
is placed on the paper, face up, the largest molding flask of 
the nest of four placed over it, the large end down, and so 
adjusted that the model will occupy a central position within. 
139 140 
TECHNIC OF DIE AND COUNTER DIE CONSTRUCTION 
Sifted sand is now filled in the molding flask until even 
with the face of the model, and packed into the space between 
the latter and the flask periphery. The pressure on the sand 
should be light at first, so as not to move the model from its 
central position. As soon as the model is firmly fixed in place, 
the sand should be still further compressed, until firm and 
compact, special stress being exerted to force it outward 
against the flask walls. More sand is added, and with the 
fingers pressed compactly against the flask walls until the 
packed portion stands slightly above the crest of the model. 
The sand in the vault or central portion of the model, which 
is not yet compressed, should cover this area at this stage to 
a depth of about one-half an inch. 
Careful, uniform pressure with the fingers should be made 
on the sand over the central area of the model, sufficient to 
Fig. 42.—Sectional View of Cast and Molding Ring 
bring the granules in fairly close contact, without rendering 
the surface too dense or compact, or wedging the sand too 
tightly between the lingually inclined walls of the model. If 
too loosely packed, the sand will lack cohesion and be dis- 
turbed in pouring the molten metal into the If too 
densely compressed, the gases or steam generated by the hot 
metal coming in contact with the moisture or oil in the sand 
can not escape through the densely packed matrix as rapidly 
as formed. It then finds its way out between the matrix walls 
and the die, or forms vent holes through the die itself, in either 
case causing roughness and imperfections of the latter. 
When the sand is wedged too tightly in the vault portion 
of the model, it frequently fractures and parts from the matrix 
when the model is withdrawn. 
The remaining space in the flask is filled and compressed 
until the sand stands above the margin. The straight edge 
is now passed over the top of the flask and the surplus sand 
struck off. The flask is inverted and that surface from which TECHNIC OF DIE AND COUNTER DIE CONSTRUCTION 
141 
the excess sand was struck now becomes the base of the 
matrix. 
The upper surface of the packed flask shows the base of 
the model surrounded by the sand. (See cut, page 142.) A 
thin V-shaped section beginning at the flask periphery and 
extending to that of the model is sliced off with the knife, so 
as to expose the angle of the model base, and thus clear it 
from the matrix margins. By lifting and tipping the flask, 
the detached sand will fall off. The finer particles can be 
Fig. 43.— Removing Excess of Sand from Packed Ring 
removed with the brush, and by gently blowing them from the 
surface. 
REMOVAL OF THE MODEL FROM THE MATRIX 
When properly flared, dried, varnished and rubbed with 
talcum powder, the model can usually be removed from the 
matrix without difficulty. Unfavorable conditions, principally 
due to some peculiar form of the model itself, are sometimes 
present. In such cases, the exercise of extreme care is neces- 
sary to avoid distortion of the essential surfaces of the matrix 
in removing the model. The adhesion of the sand to the sur- 
faces of the model, as the result of compression in packing, 142 
TECHNIC OF DIE AND COUNTER DIE CONSTRUCTION 
must be overcome or broken, when, if no undercuts are pres- 
ent, the model will come away readily. 
The following is the usual order of removal of the model 
from the matrix, ranging from the simplest methods to those 
requiring careful attention: 
1. Gravity — Weight of model sufficient to dislodge it. 
2. Tapping base of model to break sand adhesion and 
rotating. 
Fig. 44.— Removing Thin Section of Sand to Release Model Margins 
3. Removal of model by rotation. 
4. Vibration — Tapping the side of the flask. 
5. Prying to break adhesion and rotating. 
6. Tapping and lifting outward. 
7. Removal of models with undercuts — cores. 
8. Removal of models with undercuts overcome with 
Hawes flask. TECHNIC OF DIE AND COUNTER DIE CONSTRUCTION 
143 
REMOVAL OF THE MODEL IN LIFTING THE FLASK 
When the form of the model is correct, the condition of 
the sand suitable, and the packing of the flask is of the proper 
density, the model will occasionally drop from the matrix in 
lifting the flask to invert it. This, however, occurs more often 
when the sand has been but loosely packed in the flask, or 
when the sides of the model are excessively flared. It may 
Fig. 45.—-Breaking Adhesion Between Sand and Model by Tapping Base of Latter 
occur, as before stated, under proper conditions. When the 
model drops out by its own weight, a close inspection of the 
matrix should be made to see that its several surfaces are 
smooth and the sand sufficiently compact to insure smooth 
surfaces to the die when cast. 
TAPPING THE MODEL BASE TO BREAK ADHESION 
A few light taps on the base of the’ model, near the center, 
with a small hammer or light instrument, will usually break 144 
TECHNIC OF DIE AND COUNTER DIE'CONSTRUCTION. 
the adhesion of the sand to the several surfaces. The tapping 
should not be sufficiently heavy to produce perceptible move- 
ment of the model in the matrix. Heavy or unequal tapping 
is liable to distort the sand and result in an imperfect matrix. 
By rotating the flask as will now be described, the model can 
usually be dislodged. 
REMOVAL OF THE MODEL BY ROTATION 
The flask is lifted from the bench, the base resting in the 
palm of the hand, the thumb against the flat side, when, with a 
quick pronating movement, the model may be rotated outward. 
If it is not dislodged in this manner, the flask should be set 
on a clear surface of the bench, so that the sand base may be 
firmly supported over its entire area and the adhesion broken 
as follows: 
Fig. 46.— Rotating Model Out of Position 
BREAKING ADHESION BY PRYING THE MODEL 
If tlie preceding steps fail to break the adhesion of the 
sand and free the model, it can be overcome by inserting the 
point of a knife against the back of the model, the blade rest- 
ing on the flask margin, which will serve as a fulcrum, and TECHNIC OF DIE AND COUNTER DIE CONSTRUCTION 
145 
with a slight prying movement lift the back of the model the 
least perceptible amount. Eotation of the flask should again 
be made, when the model will readily come away. 
REMOVAL OP THE MODEL BY VIBRATION 
A simple method of removal, frequently successful, con- 
sists in inverting the flask and tapping the sides lightly with 
a small instrument. The vibration thus produced will often 
be sufficient to dislodge the model. Vibration produced in this 
manner may also be applied in difficult cases after other means 
have been resorted to, for breaking the adhesion between sand 
and model. 
REMOVAL OF THE MODEL BY GRAVITY 
Occasionally, when the vault portion of the model is deep 
and the buccal, labial and lingual surfaces of the border at 
various points, particularly in the anterior portion, are nearly 
parallel with each other, it may not be possible to rotate the 
model out, as described, without distorting the matrix. In 
other words, the relationship of the several surfaces men- 
tioned, to each other, requires that the model be removed in a 
line of direction approximately parallel to these surfaces, in- 
stead of attempting to rotate it out. Eemoval in such cases 
may be accomplished in two ways: 
First — Tap the model base to break adhesion. Invert the 
flask, maintaining the model in position with finger pressure 
while doing so; place the inverted flask over the edge of the 
bench, holding it flat and moving forward until the model is 
well supported before releasing finger pressure, until finally 
the entire flask base rests on the bench; lift the flask, and if 
the model is still retained in the matrix, with a small instru- 
ment tap the outer side of the flask lightly. The vibration thus 
produced is usually sufficient to dislodge the model. 
Second — Should the preceding steps fail to free the model 
from the matrix, it may be removed by direct traction. The 
projection of the model margins above the sand is so slight 
that it can not be accurately and carefully lifted from the 
matrix by grasping its periphery, so other means for grasping 
it must be provided. A small hole may be drilled in the center 
of the base, into which a taper instrument can be driven to 
serve as a handle (see page 146), or two grooves may be cut 
on either side of the center, about one-fourth of an inch apart 
(see page 147). The sides of the intervening section of plas- 146 
TECHNIC OF DIE AND COUNTER DIE CONSTRUCTION 
ter should be parallel to each other, thus affording means 
for grasping the base of the model centrally with a pair of 
tweezers. 
While this method of removal is positive and can be 
applied to any model without undercuts, unless care is ob- 
served the matrix may be marred. To avoid error, the instru- 
Fig. 47.— Releasing Model by Tapping Side of Flask 
ment or tweezers must not be grasped too rigidly, while the 
line of traction must coincide with and be approximately par- 
allel to the several surfaces to be released. Holders follow a 
similar method in removing patterns from the sand. To break 
adhesion and free the pattern, they usually tap the instrument 
which serves as a handle, sideways in various directions, 
while traction is at the same time applied for the removal of 
the pattern. 
In prosthetic procedures, the instrument which serves as 
a handle in removing the model should not be tapped laterally, 
as the tendency would be to enlarge the matrix. 
With a properly flared model having no undercuts, and the TECHNIC OF DIE AND COUNTER DIE CONSTRUCTION 
147 
sand packed to proper density, the prying or lifting process 
for breaking the adhesion of the sand and dislodging the 
model, need seldom be resorted to. It should be borne in mind 
that the least possible manipulation of the model in effecting 
its removal will yield the most accurate matrix. 
NECESSITY FOR THE USE OF CORES 
Models having undercuts can not be removed from the 
sand without distorting the matrix, unless means are taken 
to overcome the difficulty. The usual method resorted to is by 
Fig. 48.— Lifting Model from Matrix 
means of cores, the construction of which has been previously 
described. 
A model having a core addition to its outer surface usually 
presents an unsymmetrical peripheral outline. In placing 
the molding flask over such a model, the former should be so 148 
TECHNIC OF DIE AND COUNTER DIE CONSTRUCTION 
adjusted that the model will occupy a central position, regard- 
less of the form or position of the core. 
Sand is packed around and over the model and core, care 
being taken to wedge the latter firmly against the model in 
the condensing process. Removal of the model and core from 
the matrix is effected by some of the methods described, 
usually by tapping and rotation. 
After removal, the core is separated from the model, dried, 
and returned to its position in the matrix, where its inner 
surface completes the matrix wall and reproduces the reverse 
form of the undercut surface of the model. 
Sufficient pressure should be made on the core in seating 
it in the matrix to wedge it slightly in the sand, so as to pre- 
Fig. 49.— The Hawe’s Flask 
vent displacement, since, if not firmly attached, the molten 
metal, when introduced, on account of its greater specific 
gravity, will raise the core out of its position. 
CONSTRUCTION OF TIIE MATRIX IN THE IIaWe’s FlASK 
An accurate sand matrix may be secured from a model 
having external undercut areas, without the use of cores, by 
means of the Hawe’s Molding Flask. 
This appliance is cylindrical in form, five inches in diam- 
eter and three inches deep. It is divided into an upper and 
a lower section, held in proper relation by means of guide 
pins. The lower half consists of three sections hinged to open 
outward. Each section has a flange at either end, directed 
radially inward. When pinned together, the end flange of 
each section approximates the flange of the adjoining section, 
thus dividing the interior space of the flask into three partial 
sectors. 
The model is placed between the three flanges of the lower 
section, its median line opposite one and its tuberosities oppo 
site the two other points, respectively. The crest of the bor- 
der should rise slightly above the level of the ring. TECHNIC OF DIE AND COUNTER DIE CONSTRUCTION 
149 
Sand is packed around the outer sides, into and above all 
undercut surfaces of the border, but not over the face of the 
model. Particular care should be taken to condense the sand 
firmly in each sector of the flask and against the model, so 
Fig. 50.— Lower Section of Hawe’s Flask Showing Model in Position 
Fig. 51.— First Section with Sand Packed Around Model 
that it will not be displaced in the subsequent steps of free- 
ing the model. 
Powdered charcoal is sifted over the packed sand and 
model face to prevent adhesion of the sand now to be added, 
the surplus blown off, the second section of the ring adjusted. 
In this the sand is packed and the surplus struck off in the 150 
TECHNIC OF DIE AND COUNTER DIE CONSTRUCTION 
usual manner. The upper half of the flask is now lifted off, 
inverted, and set aside so as not to disturb the sand surface 
which has copied the model face. 
Fig. 52.— Second. Section of Flask Set in Position 
Fig. 53.— Second Section Packed 
Tlie mode] is removed by drawing the pin from one of the 
disto-buccal flange joints and carefully opening the ring. As 
the sectors separate, the sand between the flange ends and the 
model breaks with a clean fracture, and, on account of the TECHNIC OF DIE AND COUNTER DIE CONSTRUCTION 
flask form, the matrix is thus divided into three sections. The 
model is drawn out through the open side of the ring. When 
Fig. 54.— Upper Section Removed, Lower Section Separated, for Release of Model 
the model is removed and the flask sections are brought to- 
gether again, the fractured surfaces of sand are again re- 
adapted to each other as before, and form the continuous 
outer wall of the matrix. 
Fig. 55.— Model Removed, Sectional Part of Flask Closed 
Special care should be taken to remove any sand that 
may have become lodged between the flask joints and flanges, 152 
TECHNIC OF DIE AND COUNTER DIE CONSTRUCTION 
for if allowed to remain, the sections can not be closed prop- 
erly. 
The pin removed in opening the flask is now slipped into 
its joint, and the inverted top half of the flask is lifted and 
carefully set in place on the sectional portion, the projecting 
pins guiding it to position. The entire flask is turned over, 
and if the steps have been properly carried out, the matrix 
will he found to be satisfactory. 
Should a margin of sand along any of the sectional lines 
be broken lightly, it will seldom be found necessary to attempt 
restoration of the matrix, as the metal which will fill the open- 
ing can easily be removed from the die when cast. 
Fig. 5G.— Upper Half of Flask Set and Case Invested for Reception of the Metal 
The utility of this special flask, both for accuracy of re- 
sults and the saving of time, is keenly appreciated by those 
who have used it. Unfortunately, its good points are unknown 
to many, and the core method, although less accurate and re- 
quiring longer time, is most frequently resorted to in cases 
of external undercut models. 
EXAMINATION OF THE MATRIX 
When, by whatever method, the sand matrix is formed, it 
should be closely examined to see that none of the essential 
surfaces have been disturbed; to see that the sand is suffi- 
ciently compact to insure smooth surfaces to the die when 
cast, and before pouring the molten metal, to see that no loose 
sand is present. TECHNIC OF DIE AND COUNTER DIE CONSTRUCTION 
153 
Forming the Die 
MELTING THE DIE METAL 
A satisfactory sand mold or matrix having been secured 
from the model, it is ready to receive the molten die metal. 
To conserve time, the ladle containing the latter is usually 
placed on the fire before making the matrix, since the pro- 
duction of the latter usually requires less time than is con- 
sumed in fusing the metal. The progress of fusion should be 
noted, however, and when about tliree-fourths melted, the ladle 
should be removed from the fire. The excess of heat absorbed 
by the metal up to this point is usually sufficient to effect the 
Fig. 57.— Completed Matrix in Sand 
fusion of the unmelted portion after removal from the fire. 
This plan also lowers the temperature of the mass to some- 
where near the proper degree for casting. 
A thin spatula of soft wood should be used for stirring 
the metal and removing the oxides and impurities. If the 
wood burns or chars, it indicates that the metal is too hot to 
cast. The lower the temperature at which the metal can be 
introduced into the matrix and yet be sufficiently fluid to con- 
form accurately to all irregularities, the less shrinkage of the 
die will occur. Also a less quantity of gas or steam will be gen- 
erated in the matrix, and as a result a smoother die will be 
produced. casting the die 
When the metal is melted, the oxides removed, and the 
proper degree of fluidity attained, the ladle is carried to one 154 
TECHNIC OF DIE AND COUNTER DIE CONSTRUCTION 
of the disto-buccal angles of the flask, and as close to the latter 
as possible without disturbing it by contact of the ladle lip. 
The object in bringing the ladle close to the matrix is to 
prevent displacement of the sand which occurs when, in pour 
ing, the metal falls from a considerable distance upon it. 
Through the ladle spout a small stream of metal is directed 
into the back of the mold and the entire matrix is filled in this 
Fig. 58.— Small Ring Adjusted and Banked to Receive Additional Die 
Metal. Pouring the Die 
manner, even with the sand margins. The ladle should be 
returned to the tire immediately in order to keep the re- 
mainder of the metal in a molten condition while adjusting the 
ring for increasing the depth of the die with additional metal. 
A flask ring, usually the smallest of the set, the periphery of 
which should be slightly greater than that of the matrix mar- 
gin, is placed, large end down, and pressed slightly into the 
sand. Some sand should be quickly packed around its outer 
base to prevent the escape of the metal now to be added to 
the die. TECHNIC OF DIE AND COUNTER DIE CONSTRUCTION 
155 
The ladle containing the remainder of the molten metal 
is brought close to the edge of the small ring just placed and 
a sufficient amount of metal added to that first cast to give 
the die a depth of about 2 inches in its central part. This step 
can and should be carried out so rapidly that union between 
the first and second casts of metal will be effected and a solid 
one-piece die result. 
When hardened, the die is removed by tipping the flask 
rings over and tapping to free the packed sand from the in- 
terior, while that on the outer surface of the die is scraped 
and brushed away. The die and flasks are usually cooled im- 
Fig. 59.— Sectional View of Small Ring Adjusted to Sand Matrix 
mediately in water and wiped dry, preparatory to casting the 
counterdie. The die, however, will be more tenacious and less 
inclined to crack under the hammer blows if allowed to cool 
slowly. 
INSPECTION AND CORRECTION OF THE DIE 
Any projecting imperfection on the die due to holes in the 
sand matrix should be removed with scrapers, chisels or burs, 
if necessary, and the surfaces, where such defects exist, made 
to correspond with those of the model. Any serious defects 
in the die, when cast, either as accretions, holes or pits are 
liable to result in imperfect adaptation of the base when 
swaged. Such a die should be discarded and a perfect one 
secured. TECHNIC OF DIE AND COUNTER DIE CONSTRUCTION 
Fig. 60.— Bailey Flask 
Fig. 61.— Die and Counterdie Produced in Bailey Flask TECHNIC OP DIE AND COUNTER DIE CONSTRUCTION 
Fig. 62.— Die and Counterdie Separated 
Fig. 63.— Lewis Flask TECHNIC OF DIE AND COUNTER DIE CONSTRUCTION 
Fig. 64.— Die and Counterdie Produced in Lewis Flask 
Fig. 65.— Die and Counterdie Separated TECHNIC OF DIE AND COUNTER DIE CONSTRUCTION 
159 
Construction of the Counterdie 
PREPARATORY STEPS 
The large flask in which the matrix for the die was formed 
is now inverted or placed small end down on the bench and 
partially filled with sand. In this the die is set and evenly 
centered to the ring. The depth of sand under the die base 
should be sufficient to raise the entire labial and buccal sur- 
faces of the die border slightly above the upper margin of 
the flask. 
The space between the flask walls and the die is now filled 
in with sand which should be firmly condensed and finished 
off evenly with the top margin of the flask, the inner margin 
of the sand terminating against the peripheral plate line on 
the die. This leaves only the essential surfaces of the die 
visible and standing above the general level of the sand and 
flask margin. 
The exposed surfaces of the die are now carefully brushed 
to remove any adhering sand. In case of decided undercuts, 
sand is tightly packed into them at this time so as to preclude 
the counterdie metal, when cast, from entering such areas 
and later preventing the ready separation of the die and 
counterdie. Subsequently, when swaging, this defect of the 
counterdie is overcome by placing strips of lead or tin against 
the plate opposite the deficient area, the strips being of suf- 
ficient thickness to make up for the lack of contour in the 
counterdie. 
The die is now coated with a solution of whiting and alco- 
hol, to which a little gum Arabic is added to render it adhes- 
ive after the alcohol evaporates. The film of whiting prac- 
tically obviates the tendency of the counterdie metal to unite 
with the die in casting. 
A flask ring, corresponding in size with the one in which 
the die is imbedded, is adjusted peripherally to the latter, 
large end down, to form the matrix in which to cast the 
counterdie. A smaller ring, however, may be used for form- 
ing the matrix walls for the counterdie, when the die is of 
medium or small size. Such a ring reduces the counterdie 
peripherally and adds to convenience in handling. When the 
small ring is used, it is set on the sand surrounding the die 
and its lower margin banked up with sand to prevent the 
escape of the molten metal while casting. 160 
TECHNIC OF DIE AND COUNTER DIE CONSTRUCTION 
MELTING THE COUNTERDIE METAL 
The fusing of the counterdie metal is accomplished in 
essentially the same manner as is employed for the die metal. 
It should be removed from the fire before the entire mass is 
melted and stirred to lower the temperature and collect the 
oxides and impurities present. These should be skimmed off 
and the stirring continued until the metal begins to assume 
a pasty condition. 
The object in allowing the metal to cool somewhat and 
thicken slightly before casting, is to avoid danger of fusion 
of the die and its consequent union with the counterdie, a mis- 
Fig. 66.— Sectional View of Rings and Imbedded Die 
Ready for Receiving Counterdie Metal 
hap which frequently occurs when the latter metal is cast 
while overheated. 
CASTING THE COUNTERDIE 
When the metal begins to congeal around the ladle, it is 
quickly emptied into the ring and over the face of the die. 
Should the metal be in such a thickly plastic state that it fails 
to assume a level position in the ring when cast, it should be 
pressed down, while yet soft, with a square-end tamper, to 
give a flat base to the counterdie. 
As a matter of fact, the counterdie metal can be cast while 
in a liquid condition if proper precautions are taken, viz.: 161 
TECHNIC OF DIE AND COUNTER DIE CONSTRUCTION 
tlie die must be cold, its exposed surfaces coated with whiting, 
the metal allowed to cool to about the point of congealing, or 
so that it will not char soft wood, and in casting, directing the 
stream of metal on the sand surrounding the die, and not on 
the die face. 
When poured in a liquid condition, the metal should be 
cast slowly. In this manner it rises gradually up over the 
surfaces of the die, and at the same time, from exposure to 
the air and through contact with the cold die, sand, and ring, 
the metal, if at or slightly above the point of fusion, is re- 
duced in temperature so that union of the two will not occur. 
CONSTRUCTION OF THE COUNTERDIE BY DIPPING 
A method sometimes followed for securing a counterdie 
consists in pouring the metal into a ring of suitable size and 
immersing the face of the chilled die in it the necessary depth 
to cover the surfaces involved by the base plate. The die is 
held with the fingers or a pair of tongs until the counterdie 
metal has hardened sufficiently to sustain its weight. 
THICKNESS OF THE COUNTERDIE 
In the swaging process the die and plate are driven more 
or less deeply into the counterdie, the latter yielding under 
the hammer blows. To prevent the defacement of the prom- 
inent points on the die, the counterdie should have a depth of 
at least one-half inch in its shallowest part, or that portion 
between the high points of the die face and the base of the 
counterdie, which rests on the anvil. A good die may be 
readily distorted when the counterdie is too shallow and much 
stress is applied in swaging. 
SEPARATION OF THE DIE AND COUNTERDIE 
When the counterdie metal has solidified, the rings are 
tipped over and disengaged, the sand brushed off, and the 
die and counterdie chilled in cold water. 
The two are loosened by placing on the swaging block and 
striking the die base sharply with the hammer, when they 
may readily be separated. If this procedure fails to break 
adhesion between the two. the die should be struck sideways 
in various directions. Should this effort prove futile, the 
source of adhesion will be the result of mechanical anchor- 
age, due to undercut surfaces on the die into which the coun- 162 
TECHNIC OF DIE AND COUNTER DIE CONSTRUCTION 
terdie metal has flowed in casting, or to fusion of the two 
masses of metal at some point. If due to undercuts on the 
die, properly directed hammer blows against its sides will 
enlarge the counterdie sufficiently to release the die. Adhe- 
sion from this source is the result of carelessness, and will not 
occur if the undercut surfaces of the die are corrected with 
sand before casting the counterdie. 
When adhesion is due to fusion and union of the two 
masses of metal, the die and counterdie are separated by 
hammering, prying, wedging or chiseling, as is found most 
convenient. Such means result in the defacement of both die 
and counterdie and usually necessitate the reconstruction of 
each. 
Special care should be exercised in such cases where fusion 
of the two occurs, to entirely remove and cast aside that por- 
tion of the die and counterdie that have become united, be- 
fore melting either one. 
If the alloy thus formed is allowed to remain adherent 
to the die metal, the hardness and fusibility of the latter, 
when used again, will be reduced, and if with the counterdie, 
it will render that alloy harder and higher fusing. 
PARTIAL COUNTERDIES 
A method of using several counterdies of gradually in- 
creasing area has been in vogue for many years. The object 
in using these progressive counterdies is to insure the close 
and uniform adaptation of the base plate to the central vault 
portion first, before the labial and buccal surfaces have been 
lapped over and conformed to the border. 
Such counterdies are very effective in those cases where 
the arch is narrow and the palatine vault is deep, as by their 
use the tearing of the plate is obviated. 
Usually in this method, three counterdies are required; 
the first covering the palatine vault and terminating some- 
what inside of the border crest; the second should cover the 
vault and extend somewhat outside of the border crest; the 
third consists of a counterdie of the regular form, made in 
the manner previously described. 
CONSTRUCTION OF PARTIAL COUNTERDIES 
To construct a partial counterdie, the die is set, base down, 
on the table, a large molding flask set evenly over it and sand 
packed around it and even with the top of the flask, leaving 163 
TECHNIC OF DIE AND COUNTER DIE CONSTRUCTION 
the central portion of the die exposed. With a suitable in- 
strument the sand is cleared away so as to make a slightly 
flaring matrix in the sand, the floor of which consists of that 
portion of the die to be covered by the partial counterdie. 
The exposed face of the die is coated with whiting and the 
partial counterdie cast in the matrix in the ordinary manner. 
Partial counterdies should be of sufficient depth or extend 
far enough above the die, when in position, to enable them 
to be grasped firmly with the fingers and thumb while swag- 
ing. The metal used for partial counterdies may be of lead, 
the regular counterdie metal of lead and tin, or composed 
of one of the triple alloys, such as Melotte’s metal. 
Matrix Counterdies 
Various substances, such as soap, clay, modeling com- 
pound, shot, etc., as previously mentioned, may be used in- 
stead of the ordinary cast counterdie, when the material is 
confined in a suitable receptacle, or matrix. 
The Parker shot swager is one type of appliance used for 
such purpose. This device, however, is intended more par- 
ticularly for securing the final adaptation of a base plate to 
the die or plaster model itself, if such step is deemed ad- 
visable. 
The device in which the other materials mentioned are 
used consists of a heavy cast iron base, in the center of which 
is a deep recess corresponding peripherally with the inner 
walls of the small casting ring used for increasing the depth 
of the die. The soap or other material is placed in the recess 
and covered with a sheet of soft, pliable leather, to prevent 
adhesion of the swaging material to the plate. 
When the adaptation of the plate has been fairly devel- 
oped with the horn mallet, it is placed on the die and the latter 
introduced into the recess. 
Since the periphery of the die coincides with and closely 
fits the opening in the ring, escape of the plastic material is 
prevented. Under hammer blows or screw power, the force 
thus delivered distributes the material and equalizes the pres- 
sure so as to drive the plate into all inequalities and against 
all surfaces of the die. 
This device obviates the making of counterdies in many 
instances, since it is applicable to the swaging of base plates 
of almost any form when the dies are properly constructed. 164 
TECHNIC OF DIE AND COUNTER DIE CONSTRUCTION 
The leather should be removed, the plastic material built 
high in the center, and the leather again returned to place, for 
each new case swaged. This step is necessary to insure pal- 
atine adaptation of the plate before the pressure is brought 
on the buccal surfaces. 
Fig. 67.— Top of Parker Shot Swager 
The method here outlined is especially useful in the swag- 
ing of aluminum base plates. On account of its stiffness and 
elasticity, 18K gold cannot be readily adapted by this means. 
The device, however, as a time saver, is a valuable adjunct 
to the laboratory equipment. 
Fig. 68.— Base of Parker Shot Swager 
Counterdies for Partial Cases 
In constructing counterdies for partial dentures, the die 
is imbedded in the sand, so as to leave exposed the area to be 
covered by the baseplate, the surfaces of the teeth removed by 
cutting and possibly a slight amount of the labial and buccal TECHNIC OF DIE AND COUNTER DIE CONSTRUCTION 
165 
surfaces of the die to guide and hold it in position in the 
counterdie while swaging. 
Nothing is gained by having the die deeply depressed in 
Fig. 69.—’Diagrammatic View of Model in Position, 
Surrounded with Shot 
the counterdie. In fact, such a condition is a disadvantage, 
rendering the removal of the plate more difficult, as from time 
to time it is taken out for inspection and trimming. CHAPTER XII 
CONSTRUCTION OF SWAGED DENTURE 
BASES OF GOLD 
Securing Pattern for the Gold Plate 
Suitable dies and counter dies having been constructed, 
the next step is to secure a pattern for cutting the gold plate. 
By the use of a pattern two important objects are attained, 
viz.: 
First. Unnecessary loss of gold will be obviated. The 
trimmings and tilings that accumulate in adapting a gold plate 
to a die are classed as 1 1scrap,” which must either be refined 
before using again, or be returned to the refiners at a loss of 
about 1-5 the original cost. When care is taken in keeping the 
scraps assorted and free from solder, filings and impurities, 
they can be remelted, rolled into plate, and used again without 
loss. 
Second. A piece of gold, cut to the required outline of 
the denture, is more easily adapted to the die than an exces 
sively large piece. The tendency of the plate to shift slightly 
in the preliminary steps of swaging necessitates a surplus of 
about 1-16 of an inch peripherally in the gold for full as well 
as partial cases. 
Tin foil, sheet lead or paper may be used as a pattern. 
A sheet of No. 60 tin or lead foil is conformed to the die with 
finger pressure or a large pellet of compact cotton, and the 
excessive surplus trimmed off. It is again returned to the die, 
readapted and finally swaged in the counterdie. One or two 
light blows with the hammer, or the weight of the die itself, 
will secure close adaptation. When removed, the excess is 
trimmed away, allowing for the 1-16 inch surplus previously 
mentioned. 
With the fingers the pattern is carefully bent and reduced 
to nearly a flat condition, care being taken not to strain or 
draw it more in one area than another. It is now laid on the 
flat palm of one hand and struck a sharp blow with the open 
palm of the other. This reduces the foil to flat sheet form 
slightly wrinkled in some places and possibly torn in others 
from the swaging, yet representing reasonably well the re- 
quired peripheral outline of the denture. 
166 CONSTRUCTION OF SWAGED DENTURE BASES OF GOLD 
167 
The foil itself may be used as a pattern or its outline may 
be traced on a sheet of thin cardboard, which, when cut, facil- 
itates the marking of the gold plate because of its greater 
thickness and stiffness. The tracing of the pattern on the gold 
is most easily accomplished with a round shank, sharp pointed 
instrument, held perpendicularly. If neither tin nor lead foil 
is at hand, ordinary tough writing paper, although not as sat- 
isfactory, will serve for the pattern. 
When trimmed to proper outline, the pattern is laid on the 
sheet of gold plate, so that when the latter is cut the grain or 
lamina developed in rolling runs crosswise or from buccal to 
buccal, this being the line of direction of greatest stress on the 
baseplate, in swaging as well as in masticatory effort. 
Carat or Gold Used for Denture Bases 
Twenty carat gold is the standard fineness of plate used 
for denture bases. The advantages of this grade of gold are: 
excellent color, but little tendency to discolor in the mouth, no 
metallic taste, comparatively easy to adapt to dies, good resil- 
iency when medium to thick gauges are used. 
The only disadvantage noticeable is the tendency of the 
lighter gauges to become distorted under heavy stress. Obvi- 
ated by using gauges of plate appropriate to the stress the 
denture will be subjected to in masticatory effort. 
Eighteen carat gold is frequently employed for both full 
and partial denture bases. The only decided advantage it has 
over twenty carat gold is in having greater resiliency than the 
latter in plates of equal thickness, and, therefore, lighter 
gauges can be employed to advantage in some cases than when 
higher carats of plate are used. 
The disadvantages of eighteen carat plate are: color not 
so good as the twenty carat, decided tendency to discolor in 
the mouth, and in some cases to exhibit a metallic taste. 
Pure, twenty-two and coin gold are deficient in resiliency 
and are not adapted for denture bases unless combined with 
gold of lower carat. In difficult cases, where the maxillary 
surfaces are very rough and irregular, and the rugae are well 
defined, a thin sheet of 22 carat or 24 carat gold is sometimes 
adapted to the die and a second piece of 18 or 20 carat swaged 
over and attached to the maxillary plate with solder. The use 
of the finer and softer grade of gold next the die permits all of 
the irregularities to be accurately copied, while the second 
plate, being harder and more resilient, furnishes the neces- 168 
CONSTRUCTION OF SWAGED DENTURE BASES OF GOLD 
sary rigidity. This method of forming a double base is fre- 
quently followed in partial cases, but is seldom required in 
full dentures. 
Gauges of Gold Used for Denture Bases 
For full upper dentures, 28, 27, and 26 gauges of gold are 
used as conditions require. Twenty-eiglit-gauge, 20-carat 
plate is sufficiently rigid for narrow arches where the stress 
of mastication is light to medium heavy. Twenty-seven-gauge, 
20-carat is indicated for arches of medium width, medium 
stress, and in narrow arches when stress is heavy. Twenty- 
six-gauge is indicated for wide arches when the denture will 
be subjected to heavy stress. 
Full lower dentures seldom require heavier than 28-gauge 
plate, since the vulcanite which furnishes attachment for the 
teeth usually covers the entire base, and this, together with 
the peripheral wiring, supplies the needed rigidity. Fre- 
quently 29-gauge will prove satisfactory. 
That one may form a just estimate of the relative thick- 
ness of the gauges mentioned, their value according to the 
Brown & Sharp micrometer scale is here given. This microm- 
eter scale is given entire in the section on metallurgy. 
26 gauge equals .01694 of an inch 
27 “ “ .01419 
Difference between 26 
and 27 gauge equals 
.00176 
28 “ “ .01264 “ “ 
“ “ 27 
“ 28 
.00166 
29 “ “ .01126 “ “ 
“ “ 28 
“ 29 
.00138 
30 “ “ .01002 “ “ 
“ “ 29 
“ 30 
.00123 
To gain rigidity within restricted areas, partial denture 
bases are frequently formed of two pieces of plate, swaged 
separately, then together, and finally soldered. Usually two 
pieces of 30-gauge or one of 30 and one of 29 gauge are com- 
bined in this manner. The two pieces of 30-gauge equal .0200, 
or approximately 24-gauge, which is .0201. The other com- 
bination equals .0212, or about 231/? gauge. Various other 
combinations of gauges can be utilized, as the conditions of 
individual cases demand, broad bases requiring thin, while 
narrow bases call for thicker gauges of plate. 
ANNEALING THE PLATE 
Gold plate, as usually furnished by the supply houses, is 
not in its softest possible condition, and therefore should be 
annealed before attempting to adapt it to the die, as well as 
at various times during the swaging process. 
Hammering, rolling, bending, burnishing and polishing 
tend to stiffen and render the gold, as well as other metals, CONSTRUCTION OF SWAGED DENTURE BASES OF GOLD 
169 
hard, more or less springy and elastic, and reduce their pli- 
ability. 
Molecular tension is also developed by working the plate, 
a property which tends to bring the molecules back to the 
original relation they sustained to each other before the plate 
was subjected to working stress. 
The hardness, tension and loss of pliability increase in 
proportion to the stress to which the molecules are subjected. 
Hardness and reduction of pliability render the securing of 
perfect adaptation of the base plate to the die difficult. Molec- 
ular tension tends to destroy adaptation by warping the plate, 
when swaged to correct form, particularly when subjected to 
high temperatures, as in soldering on the peripheral wires and 
the attachments for the vulcanite. 
Gold plate is annealed by laying it on a clean charcoal or 
asbestos soldering block and applying the soft brush flame of 
the blowpipe until the plate assumes a cherry red color, when 
it should be thrown quickly into clean, cold water or alcohol. 
Care should be taken not to overheat or fuse the gold at any 
point, or its toughness and cohesiveness will be impaired. 
OILING THE DIE AND COUNTERDIES 
Before beginning to adapt the plate, the surfaces of both 
die and counterdie should be coated with a thin film of thick, 
viscid oil, such as vaseline or heavy lubricating oil. This is 
done for two reasons: First, to prevent, as much as possible, 
the adhesion of the base metals to the gold under the heavy 
sliding friction induced by swaging the plate between the die 
and the counterdie. Second, the oil acts as a lubricant and 
permits the gold to slide over surfaces which, if not oiled, 
would result in tearing or shearing the plate. The oiling of 
the die and the counterdie is extremely important, and under 
no circumstances should it be neglected. Dies and counterdies 
composed of the triple alloys, such as are used in crown and 
bridge work, should receive the same treatment for similar 
reasons as stated. 
The old method of interposing a thin sheet of rubber dam 
between the plate and counterdie to prevent contamination by 
the base metal is not to be commended, as the rubber acts as 
a cushion and reduces the positive action of the metal matrix 
against the gold. 
CLEANSING THE PLATE PICKLING 
When gold plate becomes contaminated by any of the base 
metals such as are employed for die and counterdie purposes, 170 
construction of swaged denture bases of gold 
and is subjected to the blow-pipe or Bunsen flame in the an- 
nealing process, an alloy is formed at the points affected, 
which is brittle and low fusing in character. When this occurs, 
the strength and fusibility of the plate are reduced. Subse- 
quently, in soldering operations, the areas so contaminated 
are very liable to fuse and result in the formation of pits or 
holes, sometimes called “burning the plate.” This is an in- 
correct term, as the alloy is merely fused and its tendency to 
spheroid causes it to draw back to the more infusible portions 
of the plate not so affected. 
To remove the base metal that adheres to the plate as a 
result of hammering and friction between the die and counter- 
die, it should be boiled in dilute sulphuric acid from ten to 
fifty per cent strength. Even the action of the acid fails at 
times to remove all of the base metal, particularly the lead 
and tin, in reasonable time. Sulphuric acid, either full 
strength or diluted, does not act readily on these metals, as 
is apparent by the fact that it is often kept in lead containers 
for a long period without injury to the vessel. This, however, 
is partly due to the fact that after a time a film of lead sul- 
phate is gradually formed, which limits further action of the 
acid on the unaffected lead. 
A positive and final method of removing particles of base 
metal from the gold is by the application of pumice stone to 
the plate with a stiff brush wheel on the lathe. This should be 
resorted to after boiling in acid and rinsing in water. 
Conforming the Plate to the Die 
The gold plate having been cut according to pattern, is 
now evenly centered over the die, and with finger or thumb 
pressure forced down into the vault portions as closely as 
possible in this manner. The adaptation is carried further 
with a horn mallet, being careful not to mar the plate unnec- 
essarily with the pointed end. Two or three forms of mallet, 
with ends of different shapes and sizes, should be at hand to 
meet the varying conditions which present. The small end of 
the average new horn mallet is usually too sharp and too 
pointed to be serviceable and should be cut off and somewhat 
rounded with a rasp. 
From the very beginning, and until thoroughly close adap- 
tation is secured, wrinkles or folds in the plate are very liable 
to develop. Such mishaps usually occur when an attempt is 
STEPS OF ADAPTING THE GOLD, IN FULL UPPER CASES CONSTRUCTION OF SWAGED DENTURE BASES OF GOLD 
171 
made to closely conform a considerable area of plate to an 
irregular or constantly varying surface of the die, as for in- 
stance a deep palatine vault, the labial surfaces of a promi- 
nent or V-shaped arch, or prominent tuberosities. 
The physical conditions bearing upon the changing of a 
flat plate to the irregular form, assumed by a well-adapted 
base plate should be borne in mind. Certain areas must be 
raised, others depressed, and still others will require but little 
general modification. Molecular changes must be brought 
about uniformly. In some locations, the molecules will be 
stretched and pulled — occasionally to the point of destroy- 
ing their cohesion, which will result in thinning and tearing 
the plate. 
Fig. 70.— The Horn Mallet 
In other areas, the molecules must be compressed upon 
themselves, the first noticeable effect of which is in the forma- 
tion of wrinkles, with a slight tendency to thicken the plate. 
The folds and wrinkles must be obliterated as soon as they 
are formed and before they are jammed too closely together 
for correction. Flat and round-nosed pliers and the plate 
benders are used to advantage for this purpose. The judi- 
cious use of the horn mallet or a small riveting hammer will 
also correct the difficulty by striking the fold with a sliding 
blow peripherally, at the point on the adapted surface where 
it first appears. 
The vault portion having been fairly well adapted, either 
by the aid of the partial counterdie or with the horn mallet 
alone, the next step is to conform the plate to and over the 172 
CONSTRUCTION OF SWAGED DENTURE BASES OF GOLD 
crest of the maxillary borders. The die can conveniently be 
held in the hand, the thumb pressing the plate and keeping it 
closely in contact with the vault portion, while adapting the 
metal to the border crest. 
The large end of the horn mallet is applied here, using 
moderate blows to prevent thinning the plate unnecessarily — 
usually a few well-directed blows will accomplish the desired 
end. 
USE OF PARTIAL COUNTERDIES 
When partial counterdies have been constructed, the sec- 
ond or largest of the two partials is applied to advantage fol- 
lowing the use of the horn mallet, for setting the plate against 
the maxillary border. 
In difficult cases, where much irregularity of the border 
surface is present, a clamp may be used to advantage for 
holding the adapted vault portion of the plate firmly in con- 
tact with the die. A wad of compact, damp paper is placed 
against the vault portion of the plate to give bearing to the 
clamp screw, prevent the latter from marring the plate, and 
by its tendency to spread slightly under screw pressure, force 
and hold a considerable area of the adapted portion against 
the die. When partial counterdies have been constructed, the 
smallest of these can be used in lieu of the paper. 
The die, with the plate in position, can be clamped to the 
bench, when necessary, to give the prosthetist the free use of 
both hands, but usually it will be found best to clamp the die 
and plate together so that they may be held in the hand and 
turned in any convenient position for the application of the 
mallet blows. 
The plate is adapted to the labial and buccal surfaces of 
the die by striking a sliding blow from the border crest to 
the periphery. The adaptation should begin at the median 
line on the labial surface and be gradually developed distally, 
about equally on both sides. In other words, secure reason- 
ably close adaptation from the median line to the cuspid emi- 
nence on one side, then direct the effort to the opposite side in 
like manner, continuing the adaptation similarly on the buccal 
surfaces and finishing at the tuberosities. 
Another method in common practice is to slit the plate in 
the median line, on the labial surface, from the periphery to 
the crest of the border. The buccal surfaces are then adapted 
and the surplus plate worked forward, allowing it to lap at 
the median line. The excessive surplus of plate at the lap 
joint is removed with the shears and the joint soldered before CONSTRUCTION OF SWAGED DENTURE BASES OF GOLD 
173 
the final swaging. The method first described is usually to 
be preferred, although at times, when the general form of the 
arch is narrow and the labial and buccal surfaces are deep 
from the border crest peripherally, slitting and soldering the 
plate as outlined will be convenient and satisfactory, and will 
enable the prosthetist to economize on time. 
It is not expected that the adaptation of the base plate to 
the die with the horn mallet will be very close, but it should 
be reasonably well developed to prevent folds from forming 
in the final swaging in the counterdie. 
The peripheral excess of the base plate is trimmed away to 
the required outline of the finished denture, the plate pickled 
in dilute acid, polished on the lathe with a stiff brush wheel 
and pumice stone, to remove any adherent particles of base 
metal which the acid does not remove, washed clean, and thor- 
oughly annealed, before the final swaging. 
The base plate being clean and soft from annealing, and 
the counterdie freshly oiled, the final adaptation is quickly 
secured. The base plate is placed on the die and settled evenly 
into the counterdie, as far as the latter will receive it. Place 
the counterdie on the swaging block, and with a four to six 
pound hammer, strike the base of the die squarely, one rea- 
sonably sharp blow, separate, remove the plate, and note 
whether any folds or wrinkles have developed, and if so, re- 
move them. Return the plate and strike the die two or three 
heavy blows and again inspect, first for folds, and finally for 
adaptation. Repeat as often as may be necessary to secure 
perfect approximation of the plate to the die surfaces and 
especially around the periphery. 
Finally, when the adaptation is satisfactory, pickle, polish, 
anneal and return to the counterdie and strike a final blow to 
correct the warpage occasioned by the last annealing, and 
which almost invariably occurs. A single well-delivered, 
heavy blow following this final annealing corrects warpage and 
does not develop any further appreciable molecular tension. 
This latter step is very important, for if not carried out 
as described and the wiring of the base plate is undertaken 
while any molecular strain is present, warpage is most certain 
to occur. 
The periphery of the base plate should be trimmed with 
shears and files, as accurately as possible, to the required out- 
line of the finished denture before the final swaging, for if 
SWAGING IN THE COUNTERDIE 174 
CONSTRUCTION OF SWAGED DENTURE BASES OF GOLD 
after trial in the mouth the shears are used, distortion of the 
base plate is liable to follow from the strain. Should this 
occur, correction must be made by reswaging. 
Preliminary Steps in Securing Anchorage for Teeth 
to Baseplate 
In full gold base denture cases, the teeth are usually at- 
tached to the gold base by means of vulcanite. This method 
of attachment obviates the many angles and spaces which 
result from backing plate teeth and joining them to the base 
with solder. Again, when more or less absorption of the 
border has occurred, and for esthetic reasons restoration of 
such loss is necessary, it can be most easily accomplished in 
vulcanite. Therefore, for hygienic and esthetic reasons, this 
method is resorted to in practically all full denture cases. 
When rubber is molded and vulcanized against a smooth 
surface of gold plate, the two materials adhere quite firmly, 
but unless some positive mechanical anchorage is provided, 
the vulcanite will part from the baseplate sooner or later, 
under the constant vibratory stress of mastication. 
VARIOUS MEANS EMPLOYED FOR VULCANITE ANCHORAGE 
Several methods of anchorage can be utilized for increas- 
ing the bond of union between the gold and vulcanite, none of 
which alone will prove sufficient, but by combining usually 
three, a permanent and lasting attachment can be effected. 
First, in full cases, from three to five loops of wire or 
narrow corrugated strips of plate should be soldered to the 
maxillary surface of the gold base, at various points along 
the border, in such manner as subsequently not to interfere 
with the arrangement of the teeth. In closing the packed 
flask, the rubber is molded around and under these anchor 
loops, where it hardens during vulcanization. This is the best 
and most positive form of mechanical anchorage possible to 
develop. 
USE OF WIRE LOOPS 
Second, with a diamond point engraver, many opposing 
spurs should be raised over the entire area covered by the 
vulcanite. The spurs should extend to the extreme margins 
to prevent the thin edges of vulcanite from eventually warp- 
ing and curling away from the baseplate. 
SPUERING THE BORDER SURFACES CONSTRUCTION OF SWAGED DENTURE BASES OF GOLD 
175 
APPLICATION OF RUBBER CEMENT 
Third, by applying a thin film of ehloro-rubber to the sur- 
face of gold involved, just before closing the packed flask, it 
will act as a cementing medium and aid the mechanical reten- 
tion otherwise provided. 
In order that the line of junction of the vulcanite with the 
gold base may be symmetrical, and to further guard against 
the extreme margins of the vulcanite curling away from the 
FORMING THE PERIPHERAL SHOULDER 
Fig. 71.— Soldering the Shoulder Wires to an Upper Base 
base plate, a fine wire, usually 19 gauge, and 20 carat, is 
soldered to the labial and buccal surfaces and continued 
around the tuberosities along the lingual aspect of the bor- 
der. The surface included within this wire loop represents 
the area to be covered by the vulcanite. When soldered, the 
inner periphery of the wire is squared out with small stones 
and burs so as to present a square shoulder against which 
the vulcanite finishes. In attaching the wire, care should be 
taken to avoid filling with solder the angle formed by the 
junction of the baseplate with the inner periphery of the 
wire. The application of an anti-flux will prevent the solder 176 
CONSTRUCTION OF SWAGED DENTURE BASES OF GOLD 
from filling angles and covering surfaces from which it should 
be excluded. 
The outer side of the wire, or that surface presenting 
toward the periphery of the base and to the central vault por- 
tion, is filled in with solder and afterward ground to meet the 
baseplate, merging it into a symmetrical curve, thus obviating 
the formation of an angle into which food might find its way. 
LOCATING THE POSITION OF THE WIRE ON THE BASEPLATE 
The location of this wire which marks the boundaries of 
the vulcanite is determined by occluding and waxing the teeth 
to the base in the position they will occupy in the finished 
denture. On the lingual side the wax is contoured to repre- 
sent the normal curvature of the palatine vault, terminating 
it as soon as possible without forming an angle at its junction 
Fig. 72.— Sectional View of Base Showing Finished 
Shoulders with Vulcanite in Position 
with the base or alveolar border. On the other hand, it should 
not be extended too far toward the center of the vault, or the 
contour of the finished case will he unnecessarily bulky. 
The wire is attached to the labial and buccal surfaces of 
the baseplate about one-eighth of an inch from the peripheral 
margin. It is placed in from the margins to this extent so that 
after the denture is introduced, should peripheral trimming 
of the base become necessary, it may be accomplished without 
cutting into the vulcanite. 
The exact position of the wire is determined by scratching 
a line on the gold base with a sharp instrument, just within 
the peripheral margin of the contoured wax rim. The posi- 
tion of the anchor loops can also be determined at this time 
by thrusting a sharp pointed instrument through the wax 
rim to the baseplate and scratching it in the lingual embra- 
sures between the first and second molars, the first and second 
bicuspids, and as close in to the mesio-lingual angles of the 
central incisors as possible, so that this loop will not inter- CONSTRUCTION OF SWAGED DENTURE BASES OF GOLD 
177 
fere with the proper lingual contour of the vulcanite, back of 
the incisor teeth. 
The denture is now removed from the occluding frame 
on which it has previously been mounted, the teeth and wax 
rims are detached, and the baseplate thoroughly cleansed. A 
piece of wire about 9 inches long is required for forming the 
peripheral shoulder. One end of this is conformed and 
clamped to the wire line, beginning usually at one of the 
tuberosities, where it is fluxed and tacked with a small piece of 
solder. The baseplate is chilled, the wire is further con- 
formed along the line for a distance of one-half to one inch 
clamped and soldered. This is repeated until the 
wire is attached to the entire peripheral outline on the base- 
Fig. 73.— Finished Upper Base, Spurred/Wired, and 
with Loops Attached 
plate marked. The application of an anti-flux to the inner 
margin of the wire, before each section is soldered, will pre- 
vent the filling in of the angle with solder. 
ATTACHING THE WIRE LOOPS 
A convenient method of applying the wire anchorage 
loops is as follows: Make a right angle bend near the end 
of a piece of 19 or 20 gauge wire and touch the angle with 
flux; place a small piece of solder on the baseplate at a point 
indicated for a loop; apply the blowpipe and when the solder 
is fused touch the bent wire to the solder, remove the flame 
holding wire until solder congeals; clip off the long end of 
the wire near the baseplate, leaving two short spurs projecting 
for anchorage. By using a wire 6 or 8 inches long it will 
serve as a handle for holding the loop while soldering. In 
arranging the teeth, if the ends of the wire interfere they may 
be bent out of the way. The teeth are now returned to the 
baseplate and their position and occlusion verified by trial in 
the mouth. The steps of flasking, packing, vulcanizing and 
finishing differ in no essential particulars from tho'se em- 
ployed in vulcanite work, to which the reader is referred. 178 
CONSTRUCTION OF SWAGED DENTURE BASES OF GOLD 
Swaging Full Lower Baseplates of Gold 
CUTTING THE PATTERN AND PLATE 
The pattern for a full lower base is obtained in the same 
manner as for a full upper denture. Special care should 
be observed in flattening out the foil or tea lead not to dis- 
tort it by undue stretching of either the labial or lingual 
surfaces. When the labial surface is stretched more than 
the lingual, the pattern will be too narrow around the curve 
of the arch, or from buccal to buccal, while if the lingual sur- 
face is distorted the reverse conditions prevail. 
The lamina of the gold plate should run from buccal to 
buccal, as in full cases, to give strength in the median line to 
the finished denture. 
CONFORMING THE PLATE TO THE DIE 
It is somewhat more difficult, at the outset, to adapt the 
metal plate to a lower than to an upper die, because its nar- 
row, curved form, as well as the peculiar shape of the die, 
renders it a difficult task to prevent the plate from sliding. 
The base should be evenly centered over the oiled die, and 
with the fingers and thumb held as firmly as possible by 
its outer periphery. The lingual surfaces are bent downward 
and outward against the lingual surfaces of the die with light 
blows of the horn mallet. 
Fig. 74.— Plate Benders; Very Useful for Conforming a Baseplate Along 
the Border in Preliminary Swaging CONSTRUCTION OF SWAGED DENTURE BASES OF GOLD 
179 
No attempt need be made to secure close adaptation at 
the start; the lingual surfaces, however, should be conformed 
sufficiently to prevent the plate from sliding while bending 
the labio buccal flange downward in contact with the outer 
surfaces of the ridge. The plate benders are very convenient 
for starting the plate over the border. (See page 178.) 
Usually far too much time is devoted to the use of the 
horn mallet in conforming the plate to the die. 
The beating of the metal with the mallet develops undue 
molecular strain, thins the plate itself and reduces the high 
points on the die, all of which unfavorable features can be 
obviated, or at least greatly lessened, by the early use of the 
die and counterdie. 
Except in cases of marked irregularity of the alveolar 
ridge, the swaging may begin as soon as the plate is con- 
formed sufficiently to retain its position on the die. 
SWAGING IN THE COUNTERDIE 
A method applicable to all classes of cases for prelim- 
inary conformation of the plate to the die, with the minimum 
malleting, is as follows: 
Place the partially conformed plate in the counterdie 
and set the die in position upon it. Place the palm of the 
hand over the die, the fingers and thumb grasping the peri- 
phery of the counterdie. Lift the die and counterdie, the 
plate being interposed, and strike the anvil once only with 
the base of the counterdie. The resulting impact will drive 
the die partially into the counterdie, the plate being carried 
with it. Remove the die and plate and examine the latter 
for folds or wrinkles. Should any have developed, correct 
with pliers or mallet and repeat the step until all tendency 
of the plate to buckle is overcome. 
General adaptation of the plate to the die can be secured 
in this manner in a very short time. Final swaging is accom- 
plished and close adaptation is developed with a heavy ham- 
mer on the swaging block, the same as in upper cases, pre- 
viously described. 
When extreme irregularity of the maxillary ridge and 
border surfaces in general exists, it is sometimes advisable, 
in order to insure close adaptation of the baseplate to the 
tissues, to swage two thin plates of 30 or 31 gauge separately, 
then together, pickle, polish and unite with solder. After 
soldering, reswage to correct warpage. This method of 180 
CONSTRUCTION OF SWAGED DENTURE BASES OF GOLD 
doubling the plate in difficult cases of any class is productive 
of excellent results. 
SWAGING THE PLATE AGAINST UNDERCUT SURFACES 
In case undercut surfaces are present on the die, and 
these areas have been filled with sand in the production of 
the counterdie, as previously described, the latter will be 
deficient opposite such filled-in areas of the die. To conform 
the plate to the die and against these surfaces, strips of 
lead of approximately the thickness of the depth of under- 
cut are laid between the plate and deficient counterdie area, 
and the die and plate driven deeply into the counterdie. 
It is usually useless, however, to force the baseplate into 
deep undercuts, because it must necessarily be distorted in 
removal from the die. The better plan is to allow the plate 
to enter the undercut to a slight extent only, so that in re- 
moval, although requiring to be sprung in passing over the 
bulge of the die, its inherent elasticity will return it to origi- 
nal form. The deficiency of the base, in such cases, can usually 
be corrected with the vulcanite by means of which the teeth 
are attached. 
The same general steps of trimming to as nearly cor- 
rect peripheral outline as possible, before trial in the mouth, 
pickling, polishing and annealing to relieve molecular strain, 
followed by the final blow to correct warpage, apply to lower 
as well as all classes of swaged base dentures which must sub- 
sequently be subjected to soldering operations. 
Partial Baseplates of Gold 
The construction of gold base partial dentures requires 
the exercise of as much, and in many instances more care, than 
is involved in the production of full gold bases. 
The forms of dentures for partial cases vary widely, 
depending on the number of teeth to be replaced, the rela- 
tion to each other of the spaces to be filled, the stress liable 
to be exerted in masticatory effort and the means of retention 
to be employed. 
In a full-gold base denture the baseplate continues with- 
out a break, from the palatine vault, over the maxillary sur- 
faces, to the labial and buccal areas, against which its peri- 
pheral margins terminate. The constantly varying, continu- 
ous surfaces of such a baseplate, when adaptation has been 
secured and molecular strain relieved, together with the at- 
tachment of the teeth to the base by means of vulcanite, tend 
to impart rigidity to the entire denture base. CONSTRUCTION OF SWAGED DENTURE BASES OF GOLD 
181 
In partial cases, however, the presence of some of the 
natural teeth, against the lingual surfaces of which the peri- 
phery of the baseplate must terminate, necessitates cutting 
or notching the outer margin of the denture to receive them. 
This step materially weakens the base wherever such notch- 
ing occurs. 
Reinforcing Partial Baseplates of Gold 
To develop the required rigidity, so that under stress of 
mastication, or in handling, the denture may not become per- 
manently distorted, one of the several methods in vogue for 
reinforcing baseplates may be adopted. 
REINFORCING THE BASEPLATE BY DOUBLING 
First: Develop the base from two pieces of comparatively 
thin gold plate, swage each piece separately, then together, 
and finally unite them with solder. 
Advantages: Ease of adaptation, high degree of rigid- 
ity, uniform thickness of baseplate. 
Objections: None, aside from the extra work of solder- 
ing. 
REINFORCING THE BASEPLATE BY REFLECTION, OF 
MARGINS AND WITH SOLDER 
Second: Construct the base of a single sheet of gold plate, 
27 or 28 gauge, reflect the margins against the lingual sur- 
faces of the teeth involved and fill the resulting lingual angle 
with high-grade solder. 
Advantages: Rigidity combined with comparatively thin 
base. 
Objections: Possible tendency of the solder to discolor 
with use in the mouth. 
REINFORCING WITH WIRE AND SOLDER 
Third: Adapt plate or wire to the baseplate over the weak 
areas only, and attach with solder. 
Advantages: Rigidity over weak areas, where specially 
needed, with use of minimum amount of material. 
Objections: Unequal thickness of the baseplate because 
the reinforcement is not uniform. 182 
CONSTRUCTION OF SWAGED DENTURE BASES OF GOLD 
SECURING NEEDED RIGIDITY BY USE OF THICK PLATE 
Fourth: Use a single piece of thicker gauge than that men- 
tioned in the second method, No. 25 or 26 gauge being usually 
employed. 
Advantages: Rigidity. 
Objections: Difficult to adapt. 
DEVELOPING RIGIDITY BY USE OF SOLDER 
Fifth: Flow solder alone over the weak areas of the base- 
plate. 
Advantages: Rigidity. 
Objections: Tendency of the solder to discolor; unequal 
thickening of the baseplate, due to solder filling the inequali- 
ties and seeking its level. 
The first and second methods are most frequently fol- 
lowed and have proved most successful. In certain cases, 
however, some of the other methods mentioned may be used 
to advantage. 
The first-mentioned method of doubling the baseplate is 
specially applicable to those cases where the teeth and spaces 
alternate with considerable regularity, where the rugae are 
pronounced and well defined, and where the surface markings 
of the oral tissues in general are prominent. In such cases 
a baseplate consisting of a single piece, sufficiently rigid to 
withstand stress, cannot, because of its inherent rigidity, be 
driven into all of the irregularities of the die. 
By substituting two thin pieces for the single, thicker 
plate, and conforming and uniting them as mentioned, the 
necessary rigidity and required adaptation are readily se- 
cured. 
HOW TO ESTIMATE THE APPROXIMATE THICKNESS OF A DOUBLED 
BASEPLATE 
Experience lias shown that in partial dentures, where the 
baseplate is narrow, it should range in thickness from 27 to 
22 gauge, depending on its width, in order that it may have 
the necessary rigidity to withstand stress. 
The best method for determining the thickness of the com- 
ponent plates, where two are used, so that they may have 
approximately the same rigidity as the single, thicker plate, 
is by means of the table of gauges, shown on page 1075. CONSTRUCTION OF SWAGED DENTURE BASES OF GOLD 
183 
By reference to this table it will be seen that 24 gauge, 
for example, the probable required thickness of the base, is 
.0201 of an inch thick. Now by combining two thicknesses of 
plate of lighter gauge as follows, the doubled plate will be 
approximately equivalent to No. 24 gauge: 
27 g. = .0149 
34 g. = .0063 
.0212 
28 g. = .0126 
31 g. = .0089 
.0215 
29 g. = .0112 
30 g. = .0100 
.0212 
These three possible combinations range about midway 
between No. 24 and No. 23 gauge, any one of which can be 
used when deemed advisable. Other combinations, varying 
in thickness, are made in a similar manner, depending on the 
requirements of the case. 
Fig. 75.— Outline of a Tinfoil Pattern for Partial Case 184 
CONSTRUCTION OF SWAGED DENTURE BASES OF GOLD 
SWAGING PARTIAL GOLD BASES 
When the base is to be of a single thickness of plate, rein- 
forced by reflection of the margins and with solder as outlined 
in the second method, the construction steps are as follows: 
Oil the die and counterdie; secure tin or lead foil pat- 
terns and trim to the desired form; cut the base from plate 
gold, 27 or 28 gauge, and 20 carat, according to pattern; an- 
neal and adapt to the die, first with the fingers, then with horn 
mallet sufficiently to retain its position between the die and 
counter die in the initial stages of swaging; swage between 
die and counter die, using weight of die as previously sug- 
gested; with pliers correct any folds or wrinkles that form; 
return to counter die and strike one or two heavy, square 
blows with a hammer; correct wrinkles, trim off excess and 
again swage. 
Fig. 76.— Application of the Chaser or Burnisher 
To drive the gold into the linguo-gingival angles and em- 
brasures, and reflect it against the lingual surfaces of the 
teeth, a small instrument, shaped somewhat like a cold chisel, 
is used. Although in general form its end is chisel-shaped, 
its edge is rounded to prevent cutting the gold. 
This instrument is held firmly with the pen grasp, against 
the gold, opposite the depressions on the die into which it is 
to be carried. Under light, rapid mallet or light hammer 
blows, the chaser is gradually moved over the plate, along 
the linguo-gingival angles until finally the gold is forced into 
all of the depressions and inequalities of the die without the 
chaser perceptibly marring the plate or die. 
From time to time the plate is pickled, polished and an- 
nealed, and the surplus trimmed away with the shears, plate 
nippers and files. The plate nippers are very useful for cut- 
ting out or notching the plate where the teeth pass through, 
or for cutting any short-curved margin, where the use of the 
shears would distort the plate. (See page 186.) 
The reflected plate margin, which extends from the 
linguo-gingival angle, of tissues with teeth, occlusally or in- 
cisally, against the lingual surfaces of such teeth as are in- 
volved, should be about 1/16 of an inch wide. This margin CONSTRUCTION OF SWAGED DENTURE BASES OF GOLD 
185 
serves two purposes, first, being bent at a decided angle to 
the baseplate proper, it imparts marked rigidity to the peri- 
phery of the denture in decidedly weak areas; second, the 
increased frictional bearing afforded by reflecting the plate 
against the teeth, adds stability to the denture. By flowing 
solder into the lingual angle of the plate and reflected portion 
the rigidity can be still further increased. 
SWAGING DOUBLED UPPER BASES 
To develop tlie required degree of rigidity, together with 
the closest possible adaptation of the denture to the oral tis- 
sues, and, by the simplest means, the baseplate should be 
swaged from two pieces of plate and united by soldering as 
previously suggested. The steps are as follows: 
Cut two pieces of 20 carat gold plate, according to pat- 
tern, selecting from the gauge table two gauges of plate of 
suitable thickness, which when combined will afford the neces- 
sary strength. No. 29 and 31 gauge are commonly used. 
Adapt and swage the thinnest piece to the die. Trim it 
peripherally to the required outline of the baseplate, reflect- 
ing it against the lingual surfaces of the teeth as previously 
described. By using care in trimming to the exact outline 
at this time, the loss, both of material and time, will be 
avoided. When swaged, trimmed, annealed and finally re- 
swaged to the die to correct warpage it is laid aside. 
Now swage the second or thicker piece of plate. The 
adaptation of this piece of gold will not be quite so sharp as 
that of the first piece, first, because the plate is thicker, and 
second, because some loss of detail of the die must naturally 
occur during the swaging of the first plate. 
When much loss of detail occurs to the die, a new one 
should be run np, but not necessarily a new counter die, as 
one or two hammer blows will force the old counter die sur- 
faces into all the inequalities of the new die. 
The two plates are now swaged together, the first, or thin- 
nest, being placed next the die, since being sharpest, and show- 
ing the finest details, it should lie next the tissues. 
The peripheral surplus of the second base swaged is usu- 
ally allowed to extend beyond the margins of the first base, 
to afford a shoulder on which to lay the solder while uniting 
them. 
In some cases, however, it is advisable to reduce the sec- 
ond base periphery until it lies entirely within that of the 186 
CONSTRUCTION OF SWAGED DENTURE BASES OF GOLD 
first base. This method obviates the use of an excessive 
amount of gold, but is not always so convenient in soldering. 
Fig. 77.— Showing Two Methods of Applying the Doubler 
SOLDERING THE DOUBLED BASE 
After swaging, the bases are pickled, polished and washed 
in clean water. A film of clean borax paste is spread on their 
contact surfaces and three or four small steel soldering clamps 
are applied to hold them in contact. The clamped bases are 
now laid on the solder block, and small pieces of solder placed 
peripherally on the marginal shelf, and in close contact with 
the edge of the first plate. 
The brush flame of the blowpipe, properly applied, will 
fuse and draw the solder between the two plates until the 
space is perfectly filled and the two are united. Merely unit- 
ing the two bases at the peripheral margins will not be suffi- 
cient nor will the needed strength be developed; the solder 
must be drawn through from one margin to the other, and the 
baseplates united into one solid mass. A good plan to insure 
complete union between the two plates is to set the clamped 
piece on the block so that the shelf on which the solder is 
placed is higher than the opposite margin on which no solder 
is laid. Heating the piece uniformly, until the solder fuses, 
will result in its being drawn down until it shows continuously 
Fig. 78.— Various Forms of Wire Soldering Clamps CONSTRUCTION OF SWAGED DENTURE BASES OF GOLD 
187 
along the lower margin of the now united base. A break in 
the line of solder on either margin indicates that some of the 
area between the plates is not filled. 
The peripheral surplus is now removed with shears, plate 
nippers, files and stones, and the plate reswaged to correct 
Fig. 79.— Plate Nippers for Cutting Plate Around Teeth 
warpage due to soldering and from cutting. It is again pickled, 
polished, washed and is ready for trial in the mouth. 
DOUBLING PARTIAL LOWER BASES 
Frequently a lower partial denture of single thickness may 
be rendered sufficiently rigid by burnishing or swaging and 
soldering to it a piece of plate but little larger than the weak 
areas. 
Lower partial dentures, involving the replacement of the 
posterior teeth only, are frequently reinforced anteriorly by 
a second piece of plate overlaying the first, the ends of which 
pass backward and terminate about three-eighths of an inch 
back of the last natural teeth, or so as to extend well onto the 
saddle portion of the base and outward to or beyond the crest 
of the border. 
In dentures of this type the baseplate should extend well 
up over the cingula of all the anterior teeth present, to af- 
ford support to the denture in this region; prevent it set- 
tling down when subjected to stress, and thus avoid injury 
to the soft tissues underlying it. 188 
CONSTRUCTION OF SWAGED DENTURE BASES OF GOLD 
DEVELOPING RIGIDITY BY USE OF WIRE AND SOLDER 
When teeth are to be attached to the gold baseplate by 
means of a plastic base, the wire which is soldered on to form 
a shoulder against which to finish the vulcanite can fre- 
quently be placed in such position or extended onto weak 
areas so that when soldered the required rigidity is devel- 
oped without the necessity of doubling the entire baseplate, 
the wire and the solder used for the shoulder thus fulfilling 
two purposes. 
One of the most important considerations in the planning 
and construction of partial dentures is to determine the means 
of retention that will render the appliance most efficient. At 
the time of planning the denture retention means must be 
decided upon, as these, to a certain extent, determine the form 
of the baseplate. 
Application of Frictional Appliances 
When specialized frictional appliances, as the Roach or 
Gilmore attachments, are to be used, the crowns or inlays to 
which the stationary parts of the appliances are fixed are 
usually constructed before the impression is secured, from 
which in sequence the die will eventually be formed. In case 
crowns are used for the attachment of retention appliances, 
these are set in position on their respective roots, afterward 
reproduced in the die, wholly or in part, and the baseplate 
swaged to conform to them just as to the natural teeth. The 
application of the attachments under consideration will be 
given in another section. 
When any of the ordinary forms of clasps are to be em- 
ployed the order of procedure is as follows: 
The clasps and baseplate having been constructed, the 
clasps are placed in position on the teeth they are to embrace. 
The baseplate is introduced, the points of interference with 
the clasps noted and filed away until it can be firmly and 
evenly seated on the tissues, without displacing the clasps or 
itself becoming dislodged by them. 
An impression in plaster is now taken of the clasps, teeth 
and baseplate; when removed the clasps are returned to 
position in the impression, wedged apart, luted to place and 
a cast secured, by means of which the clasps and baseplate are 
held in correct relation; they are then attached to the base- 
plate by soldering in such manner as to interfere the least 
possible extent with the resiliency of the clasp. CONSTRUCTION OF SWAGED DENTURE BASES OF GOLD 
189 
Taking the Bite 
In partial cases, when a number of natural teeth are pres- 
ent and in normal occlusion, a mash bite, sufficiently bulky 
to receive and hold firmly the bite stem of the face bow in 
front of the anterior teeth and without interference with oc- 
clusion, will usually fulfil all requirements for occluding the 
teeth, after the casts have been secured and mounted on the 
occluding frame by means of the face bow. 
When any complications are present, or when a consid- 
erable number of teeth are being replaced, the best plan is to 
occlude the teeth, attach them to the baseplate with sticky 
wax and try the model denture in the mouth. This method 
proves the occlusion, the degree of esthetic success attained 
as to form, color and arrangement of the teeth, the position 
for the lingual shoulder wire against which the vulcanite will 
finish, when such means of attachment of teeth to base is 
employed, and enables the prosthetist to judge the value of 
his work at a time when corrections can readily be made, 
should occasion require. 
Attaching Teeth to Baseplate by Soldering 
When but little absorption of the process has occurred, 
in spaces occasioned by loss of the natural teeth, the best 
means of attaching the porcelain substitutes to the gold base 
is usually by backing a plate tooth with gold, in the usual 
manner, grinding it to position on the cast, attaching it to the 
base with sticky wax, investing the case in some good invest- 
ment material, and finally flowing solder over the entire back- 
ing and against the baseplate at its junction with the latter. 
Frequently, in order to render the repairing of the case 
simple, in case of accident, some of the replaceable types of 
crowns or facings in common use, as the Steele, Goslee, Davis, 
etc., can be used to advantage. 
When the bite is extremely close, so close, in fact, that 
porcelain cannot stand the stress of mastication without frac- 
turing, a wax tooth of the dimensions required may be formed 
and cast, or a cusp may be swaged, filled in solidly and 
attached to the base with solder. CHAPTER XIII 
ALUMINUM BASE DENTURES 
Aluminum is used to a considerable extent, in both cast 
and swaged form, as a base for dentures. The good qualities 
of this metal may be summed up as follows: It is malleable, 
tough, comparatively rigid, good color, shows but little ten- 
dency to discolor, odorless, tasteless, and a good conductor of 
thermal changes. 
Some of the objections and disadvantages of the metal, 
in general, in its application to denture construction are as 
follows: It is extremely difficult to solder, and when soldered 
the joints, under the influence of oral secretions, discolor 
badly; in some cases the solder itself is rapidly dissolved 
away, particularly when mercury is one of its constituents. 
Since soldering operations are difficult, the ordinary means 
for forming finishing shoulders, attaching loop anchorages, 
and, in partial cases, uniting one or more isolated teeth to 
the base, as carried out in gold base denture construction, 
are not practicable. Other means, therefore, must be resorted 
to for developing the attachment of the vulcanite to the den- 
ture base, and while these means are more or less efficient, 
they require more care and involve greater effort than when 
accomplished by soldering. 
Aluminum is susceptible to the action of dilute hydro- 
chloric acid, the alkalis, and salt solutions in general. Since 
food, and consequently the oral secretions at times, contain 
these substances more or less diluted, of course, aluminum 
bases frequently show a decided tendency to disintegration in 
the mouth. These facts are in accordance with observations 
made by Figuier in his Year Book for 1858. One of the early 
editions of Richardson quotes him as follows: ‘‘Caustic al- 
kalis, potash and soda, and even ammonia, dissolve alumi- 
num sensibly.” He also states that common salt and acetic 
acid (vinegar), especially when mixed, attack and dissolve 
aluminum. He adds that the mixture of salt and vinegar for 
seasoning a salad, made in a spoon of aluminum, feebly but 
inevitably attacks it. 
The same edition further says: ‘‘Calvert states that when 
aluminum is immersed in water for any considerable length 
190 ALUMINUM BASE DENTURES 
191 
of time, oxidation takes place slowly.” It is therefore plainly 
apparent why the surfaces of dentures of this type, both cast 
and swaged, become etched and roughened with use, and in 
time so reduced in thickness as to be useless. 
Pure aluminum is more resistant to the action of the sol- 
vents mentioned than the more or less impure commercial 
varieties, and, therefore, in both cast and swaged work, only 
the purest products obtainable should be employed. 
Aside from the general disadvantages just cited of the use 
of aluminum for denture bases, there are certain deleterious 
properties which arise in casting the material and which will 
need special mention. 
Cast Bases of Aluminum 
Tlie principal advantage of a cast aluminum base lies in 
the fact that the vulcanite anchorage can be more readily de- 
veloped on a cast than on a swaged base. Loops and spurs 
of wax, in addition to the usual peripheral rims, can be 
arranged on the model, and all reproduced at the time of cast- 
ing. Peripheral rims are of decided advantage, as when prop 
erly formed they will effectually prevent the thin margins of 
vulcanite from curling away from the base, a defect which 
is specially noticeable in both cast and swaged aluminum 
bases. 
Another decided advantage of a cast over a swaged base, 
from an esthetic point of view, is that in case absorption of 
the border has progressed irregularly, the greater portion of 
the required restoration can be accomplished in metal instead 
of vulcanite, as is necessary with swaged bases. The distribu- 
tion of the vulcanite can therefore be made symmetrical in 
cast bases, while in swaged bases it can seldom be accom- 
plished, the finished case often presenting a very unsightly 
and unbalanced appearance after the necessary contour has 
been developed. 
Cast aluminum base dentures, although promising much 
from an esthetic standpoint, usually fall very much short of 
perfection from the practical point of view. Two very serious 
drawbacks are manifest in dentures of this type; first, the 
tendency of castings to warp in the making, thus impairing, 
if not entirely inhibiting, successful adaptation and retention 
of the denture; second, imperfect density of the casting when 
produced. 192 
ALUMINUM BASE DENTURES 
Warpage of a cast base is due to two causes; first, the 
inherent tendency of most metals-to contract in passing from 
a fused to a solid state is very marked in aluminum; second, 
the heat necessary to volatilize the wax and prepare the mat- 
rix to receive the molten metal causes contraction and warp- 
age in the investment itself, so that when cast the fused metal 
is forced against a distorted form. In addition to this, warp- 
age in the metal, due to contraction, also occurs to further 
complicate the difficulty. Warpage is a most serious fault, 
and because of the resulting misfits it occasions' lias retarded 
the use of the cast base more than all other causes combined. 
The method for correcting warpage will be detailed later. 
WARPAGE OF CAST BASES 
IMPERFECT DENSITY OF CAST ALUMINUM BASES 
Imperfect density in a casting is due to contraction of the 
metal toward many centers as it assumes a crystalline, or 
rather granular, form in cooling, each granule or crystal be- 
coming a center toward which the cooling metal contracts. 
As a result of this contractile tendency, many spaces neces- 
sarily result throughout the substance of the casting. Very 
often they are invisible to the eye, and in a newly finished 
case, the metal appears dense and homogeneous, but with use 
in the mouth the porosity becomes apparent. A low power 
magnifying glass discloses many open spaces on the surface 
of any aluminum casting. If broken, the spaces will be found 
more or less generally disseminated throughout the fractured 
sections. 
ACTION OF ORAL FLUIDS ON ALUMINUM 
Fluids of the mouth find their way into these pits and 
open spaces, and in those mouths where solution of the metal 
does occur the action is much more rapid than when the metal 
is free from such imperfections. 
The oral fluids contain during and for some time after 
each meal attenuated particles of food; these find their way 
into the pits, are retained, and after a time decompose, often 
giving rise to very disagreeable odors. Bicarbonate of soda 
solution and sometimes, in extreme cases, dilute caustic soda 
are used for cleansing and removing odors from vulcanite and 
gold base dentures. These solutions should not be used for 
cleansing aluminum base dentures because of their solvent 
action on the metal. Dilute nitric or sulphuric acids, neither ALUMINUM BASE DENTURES 
193 
of which have any perceptible action on aluminum, may be 
used instead of the alkalis for removing odors. The acid 
should be neutralized with weak aqua ammonia and the den- 
ture washed thoroughly in water to remove all traces of the 
latter. 
GRANULAR STRUCTURE OP CAST ALUMINUM 
As before stated, in passing from a fused to solid con- 
dition aluminum assumes a granular form. The metal con- 
tracts toward the granular centers and thus produces the open 
spaces referred to. In addition to this change there is a molec- 
ular rearrangement distinctly noticeable by the slight crack- 
ling sound on removal of the casting from the flask, appar- 
ently regardless of the length of time it remains in the flask. 
This is no doubt due to the rplease of tension on the already 
contracted and warped base, by the removal of the investment 
cast and matrix, the presence of which, at the time of solidify- 
ing of the metal, partially restricted full contractile move- 
ment. 
For these and various other reasons not here detailed the 
casting of dense, well fitting baseplates of aluminum is prac- 
tically an impossible task. Summarized, the advantages and 
objectionable features of cast aluminum bases may be stated 
as follows: 
Advantages: Convenience in developing required vulcan- 
ite anchorage; great esthetic possibilities. 
Disadvantages: Warpage of the base during and after 
casting; imperfect density of the casting when produced; 
susceptibility of cast bases to solution by the oral fluids. 
There are many methods of technic in vogue, also many 
kinds of casting devices in use at the present time for the 
production of cast bases of aluminum. Lack of time and 
space as well will preclude more than an outline of the essen- 
tial steps common to most systems of casting. Two general 
methods will be described, known as the indirect and direct 
methods. Dr. Hart J. Goslee has recently described in detail 
an indirect system of casting he lias formulated, and which 
promises to correct some of the disadvantages of the cast 
base (Dental Review, August, 1914). The following is a brief 
outline of the indirect methods referred to. 
CASTING BASES BY THE INDIRECT METHOD 
The advantages of the indirect over the direct method of 
casting depend upon the preservation of the original cast 194 
ALUMINUM BARE DENTURES 
(model) of the mouth until after the base has been produced, 
and of the correction by swaging of this usually warped base 
on the original cast of the mouth. The technic of the system 
is as follows: 
TECHNIC OF FORMING THE WAX MODEL 
An accurate impression of the arcli is secured in the im- 
pression material most strongly indicated. 
This impression is filled with either a hard cast plaster, 
or, better still, a mixture of oxy-chloride of magnesia, because 
of its much greater hardness. 
The cast, of whatever material composed, should have a 
flat base, and be of good depth, to prevent fracture under the 
stress of subsequent swaging. 
To this cast of the mouth a sheet of pink wax slightly 
thicker than the base is to be, is conformed, and trimmed to 
correct outline of the baseplate. 
Small rolls of wax, about one-eighth of an inch in diam- 
eter, are adjusted peripherally, and burnished smoothly to the 
required form to afford finishing shoulders for the vulcanite. 
Anchorage loops for the vulcanite are attached at several 
points, in such manner as not to interfere with the correct 
arrangement of the teeth. 
Three rolls of wax, also an eighth of an inch in diameter 
or slightly larger, are attached, one to the most distal point 
of each tuberosity and the other to the extreme median, labial, 
surface of the baseplate. These are brought into a common 
point opposite the center of the palate and there united with 
a slightly larger roll standing at right angles, which serves 
as a sprue former. This arrangement of the wax rolls which 
form the smaller sprues is applicable to cases when invested 
in the open end ring flask. This type of flask is usually shal- 
low. In such case the three sprue formers should be placed 
nearly horizontal and as close to the baseplate as possible, to 
conserve perpendicular space and make room for ample deptli 
to the crucible in the top of the flask. 
When the deep box flask is used, the rolls of wax are at- 
tached to the baseplate in the same location as above de- 
scribed, but are all brought back of the distal margin of the 
cast and there united to a slightly larger sprue former, or 
they may be attached separately but close to each other to the 
crucible former. The flashed case in this instance will then 
present three separate openings leading from the base of the 
crucible to the matrix, while in the former instance there is ALUMINUM BASE DENTURES 
195 
only one exit, the divergence of the small sprues occurring in 
the investment. 
In both cases, regardless of whether the molten metal 
leaves the crucible by one or three exits, it enters the matrix 
at three widely divergent points. The three streams of metal 
which issue from the several entrances must spread out, fill 
the entire matrix, meet, and coalesce without forming seams. 
The pressure exerted on the molten metal must be sufficient to 
force the contained air within the matrix into the investment, 
or out through sprue vents, otherwise it will he caught and 
confined somewhere between the margins of the inflowing 
portions and result in holes. 
Still another method of attaching the wax sprue formers, 
applicable when the case is to be cast by centrifugal force, is 
as follows: A roll of wax three-sixteenths of an inch in diam- 
eter is attached to the extreme labial surface of the baseplate 
and extends up to the crucible to form the feed sprue. 
Two smaller vent sprue formers extend from the highest 
point of each tuberosity to the outer margin of the crucible, 
Fig. 80.— Wax Former for Making Sprue Rods 196 
ALUMINUM BASE DENTURES 
above the level of the contained metal when fused. In casting, 
the metal enters the matrix from the crucible at the lowest 
point, and on the principle that a liquid will seek its level it 
rises upward in the matrix, the air escaping through the vent 
sprues. Since the exits of these sprues are higher than the 
level of the metal in the crucible the latter will rise nearly to 
the top of the openings of the vent sprues, but cannot escape. 
INVESTMENT OF THE WAX MODEL 
The baseplate having been given its required form, and 
the anchorage lugs attached, it is ready for flashing. 
A fine grained, slightly porous investment material, which 
is hard when set, should be selected for flashing the wax model. 
A small amount of this is mixed moderately thin, and with a 
brush is spread carefully and evenly over the entire surface 
of the baseplate to eliminate all air bubbles. With a spatula 
more is now added, care being tahen to work: it under and 
around the sprue formers so as to entirely enclose them; the 
labial and buccal surfaces should also be fully covered with 
a layer sufficiently thich to withstand handling when the cast 
is removed. Altogether the investment should cover the base- 
plate from one-fourth to three-eighths of an inch thick. 
When hardened, the half invested wax baseplate is care- 
fully removed from the cast of the mouth on which it has been 
formed, another mix of investment made, and with a brush 
the entire interior of the baseplate is covered with it, care 
being taken here as before to eliminate all air bubbles. More 
investment is added to this, to take the place of the original 
cast, extending it labiallv, distallv, and buccally, to overlap 
and unite firmly with that on the reverse side. 
The wax model and most of the sprue formers are now 
encased in a comparatively rigid shell of hardened investment, 
which should be trimmed so as to enter the flask without en- 
croaching on the sides at any point. Completion of the invest- 
ment in a ring flask is carried out as follows : 
Sufficient investment material to surround the case and 
fill the ring is mixed somewhat thicker than that used in first 
covering the wax model. This is filled in the ring, the hard- 
ened core containing the wax model is soaked in water for 
a moment to exclude the air and insure perfect union between 
it and the freshly mixed mass and is then pressed well down 
to the bottom of the ring to give ample space for the crucible 197 
ALUMINUM BASE DENTURES 
in the upper end. A slight vibratory movement of the spatula 
in the plastic mass will cause it to settle around and over the 
core and permit the air to escape. 
The investment is smoothed up level with the top of the 
flask and around the wax sprue former which should occupy 
a central position in the upper surface and extend above the 
upper margin of the flask. 
When hardened, the investment is trimmed out to form 
a crucible for containing the metal while fusing and prepara- 
tory to casting. This should be deep and wide enough to hold 
considerably more metal than the matrix will contain. In 
some forms of flasks the wax sprue formers before the case is 
invested are united with a crucible former, which, by means 
of guides, is carried to correct position in the flask and the 
investment is molded around it, thus obviating the necessity 
of cutting the crucible. 
PREPARING THE CASE FOR CASTING THE METAL 
The flask should be placed above a low flame and gradu- 
ally heated to dissipate the wax. The heat may be increased 
from time to time to accelerate the volatilizing of the wax, 
but at no time should it exceed 370 degrees F., as that is the 
temperature at which plaster is readily and quickly disinte- 
grated. By heating the case for a long time at low tempera- 
ture the wax can be removed, the matrix cleared of residue, 
and the integrity of the investment maintained far better than 
with the rapid application of intense heat. 
As in inlay work, smoother castings will result if, after 
clearing the matrix, the invested case is allowed to cool some- 
what before introducing the molten metal. The temperature 
should not be allowed to drop too low or the metal, which even 
when well fused is slightly sluggish, will lose some of its heat 
by radiation and contact with cooler media, become chilled, 
and clog in the matrix, or in some cases in the sprues and 
result in an imperfect casting. 
CASTING THE FUSED METAL 
Aluminum may be cast by various means, compressed gas 
or air, by partial vacuum, by a combination of tbe two means 
just mentioned, by steam, centrifugal force, and by actual 
mechanical pressure. 
In any case and by whatever means the casting is accom- 
plished, the object in utilizing one or more of the forces men* 198 
ALUMINUM BASE DENTURES 
tioned is to rid the matrix of the contained air, either at the 
instant of casting, as in the case of the vacuum appliance, 
or force the molten metal into the matrix with sufficient pres- 
sure to drive the air into the porous investment or through 
vent sprues, and fill the entire space with fused metal under 
compression. 
Although more difficult to cast sharply than some of its 
alloys, pure aluminum should be used because of its greater 
resistance to chemical action. 
A thin, slightly tough film of oxide quickly forms on the 
surface of molten aluminum, which limits further oxidation. 
Because of the lightness of the metal and the slight tenacious- 
ness of the surrounding film of oxide the molten metal does 
not fall into or fill even a large sprue, as would be the case 
with any of the metals of greater specific gravity, but requires 
vibration or some applied force to drive it into the matrix. 
When first fused, aluminum, although plastic, is sluggish, 
and if cast in this condition will not copy fine lines sharply. 
The blowpipe flame should, therefore, be continued on the 
molten mass a sufficient time to bring it to a thinly liquid con- 
dition, yet without overfusing, before forcing it into the 
matrix. 
A new, clean ingot (not scraps nor previously used pieces) 
containing nearly twice as much metal as the case requires is 
placed in the crucible and the blowpipe flame applied. The 
flame should be large and the heat forced as rapidly as pos- 
sible, to melt the metal before any great degree of heat is 
transmitted to the matrix, and thereby cause unnecessary 
dimensional changes in its walls. 
When brought to a thoroughly liquid condition, the film of 
oxide is cleared away, the casting force, of whatever character 
employed, is applied and the metal is driven into the matrix. 
Since metals having much greater specific gravity than 
aluminum require pressure of 7 pounds or more to cast 
densely, it naturally follows that to produce sharp, well de- 
fined and dense castings of this much lighter metal more force 
should be applied in injecting it into the matrix. From 8 to 
12 pounds direct pressure, or 14.7 pounds, full vacuum pres- 
sure, which, however, even though the gauge records it is 
never realized, is none too much. Pressure should be main- 
tained until the metal congeals, the idea being to condense 
upon themselves the granules or crystals as long as the hard- 
ening mass will yield under the applied pressure. 
When cast, the case should be allowed to cool down gradu- ALUMINUM BASE DENTURES 
199 
ally; sudden chilling will induce more warpage and greater 
molecular change in the casting than will occur when the tem- 
perature is gradually lowered. 
FINISHING AND SWAGING 
On removal of the casting from the flask the waste gates 
are removed with a saw, the surfaces and margins smoothed 
Fig. 81.— Rough Casting. Loops too Large, Except in Case of 
Excessive Border Absorption 
up with files, stones, and fine emery cloth on the lathe man- 
drel. All nodules and irregular areas are removed from the 
palatine and border surfaces. The baseplate should, in fact, 
be practically finished, except the freshening of the margins 
of the vulcanite shoulder, which on account of danger of mar- 
ring should be deferred until after the final swaging. 
Fig. 82.— Partially Finished Casting, Not Spurred 
The baseplate is now set on the original cast of the mouth, 
placed in the swaging device, and subjected to screw or 
hydraulic pressure sufficiently heavy to adapt it to all parts 
of the cast face. The final finishing is now given the shoulder 
against which the vulcanite is to abut, with square edge stones. 200 
ALUMINUM BASE DENTURES 
Any other areas that may need attention are smoothed, and 
the baseplate is ready for the application of the wax rims. 
The constructive steps from this point on are the same as in 
vulcanite work. 
ATTACHING THE TEETH TO BASE WITH VULCANITE 
In addition to the anchorage loops usually provided in the 
waxing of the case before Tasking, a graver is used to raise 
heavy spurs in various directions around and under which the 
vulcanite will be molded. A film of chloro-rubber painted on 
the surfaces to be covered by the vulcanite acts as a cement- 
ing medium and increases the efficiency and permanency of 
the joint between the latter and the metal base. 
Direct Method of Producing a Cast Base of Aluminum 
The direct method of producing a cast base of aluminum 
is identical to that followed in indirect casting, up to the point 
of removal of the wax model from the cast, previous to invest- 
ing the case. In this method, the wax model baseplate re- 
mains with the cast, the two are invested together, the cast 
becomes a part of the matrix, and is destroyed in the produc- 
tion of the casting. To correct a misfit due to warpage by this 
method a new impression and another cast must be produced, 
on which the warped casting can be readapted by swaging or 
the entire case must be reconstructed, beginning with the im- 
pression. 
Since the average cast baseplate, made by the direct 
method, lacks that positive adhesion to the tissues so desir- 
able, and, in fact, essential to usefulness and comfort, and 
since a casting of this type can be readily corrected by swag- 
ing on an accurate cast of the mouth, it is obvious that the so- 
called indirect method is literally the most direct, because one 
impression and one cast of the mouth fulfills all requirements 
while the direct method usually requires two, since to secure 
the desired adaptation it must be reswaged. 
Until the dimensional changes in both investment mate- 
rials and aluminum due to thermal variations are overcome 
to a greater extent than is possible by present methods, the 
adaptation and general usefulness of cast aluminum bases can 
be greatly improved by swaging. 
Centrifugal Casting of Aluminum 
Another method of casting aluminum bases with centrif- 
ugal force by the Dr. W. W. Wood’s appliances will now he ALUMINUM BASE DENTURES 
201 
briefly described. These appliances consist of a special flask, 
an adjustable cover, a crucible former, a base for attaching 
the wax model to the sprue former, a liigh-geared centrifugal 
machine for forcing the molten metal into the matrix, double- 
burner stove for heating the invested case and for melting 
the aluminum, a small iron crucible for holding the metal 
while heating, and from which it is poured into the crucible 
of the flask, and, finally, two sheet-iron hoods for confining 
the heat around both flask and crucible in the preliminary 
steps. 
TECHNIC 
The crucible former has three openings in its apex, and 
in these, three rods of wax about one inch long are luted. 
Fig. 83.— Crucible Former and Wax Model Ready for Attachment 
The crucible former is adjusted to the cast-iron base. The 
wax rods bent to unite with the baseplate at each tuberosity 
and in the central vault portion. 
The cast should not extend beyond the round end of the 
base, otherwise, in forcing the crucible to place the wax 
sprues are liable to he disconnected. 
MIXING AND APPLYING THE INVESTMENT TO THE WAX MODEL 
BASE AND CAST 
A mix of some good quality of investment is applied to 
the wax base with a brush, painting it against all surfaces 
so as to eliminate the air. A mix of coarser investment can 202 
ALUMINUM BASE DENTURES 
Fig. 84.— Attaching Wax Model to Crucible Former on Iron Adjustment Base 
Fig. 85.— Wax Model Attached to Crucible Former, Ready for Investment ALUMINUM BASE DENTUBES 
203 
be made and extended not only over the wax, but carried up 
around the exposed sides of the crucible former in a layer 
sufficiently thick, when hardened, to rigidly unite the cast, 
wax base and crucible former. 
When hardened, the attached cast and crucible former are 
removed from the cast-iron base and investment applied to 
the opposite side in a similar manner as described. 
The flask is now filled about two-thirds full of coarse in 
vestment mixed moderately thin. 
INVESTING THE CASE IN THE FLASK 
Fig. 86.— Introducing the Partially Invested Wax Model in Flask 
Tlie invested wax model and crucible former are dipped 
in water and introduced in the partially-tilled flask, with a 
churning motion to eliminate air and cause the investment 
to settle closely around that already hardened. The crucible 
former should rest upon the margins of the flask. 
When set, the flask is inverted over the flame to slightly 
warm the wax sprues and crucible former when the latter, by 
tapping slightly, will readily come away. By oiling the cru 204 
ALUMINUM BASE DENTURES 
cible former before applying the investment it will part easily 
from the flask. 
DRYING OUT THE CASE 
The flask is placed on its side over a low flame until the 
wTax has melted and partially flowed out through the sprues. 
It is now inverted over the flame, the size of which is in- 
creased, the sheet-iron hood adjusted, and heat maintained 
until the investment is thoroughly dry. 
While the invested case is drying out, which requires 
usually about an hour, the aluminum should be placed in the 
Fig. 87.— Heating the Case and Aluminum 
iron crucible, set over the smaller burner and the hood ad- 
justed. 
Since aluminum requires a higher temperature to fuse 
than that developed bv the burner, the blow pipe flame should 
be applied, and the metal brought to n well-fused liquid con- 
dition. 
CASTING 
When the moisture has been driven from the investment, 
and the latter lias attained practically a low, red heat (900° 
F.), the flask is adjusted to the arm of the casting machine, 
the cover set in position and firmly clamped. ALUMINUM BASE DENTURES 
205 
Fig. 88.— Adjusting Heated Flask to Casting Machine 
Fig. 89.— Applying the Cover ALUMINUM BASE DENTURES 
Fig. 90.— Pouring the Molten Aluminum 
Fig. 91.— Casting ALUMINUM BASE DENTURES 
207 
The melted metal is now quickly poured into the crucible, 
through the small opening in the cover, and the machine set 
in motion as rapidly as possible. 
To thoroughly condense the metal the centrifugal force 
should be continued for at least three minutes or until the 
aluminum has solidified. 
Fig. 92.— Appearance of an Upper and Lower Base as They Come from Flask 
The methods here outlined vary somewhat from those 
previously described, principally in the manner and amount 
of heat applied. The results, however, in both density of 
castings and low shrinkage produced, justify the writer in 
Fig. 93.— Dr. Wood’s Method of Preparing the Vulcanite Attachment 
strongly recommending the centrifugal method and processes 
similar to those just described. 
Important Properties op Aluminum in Reference 
to Casting 
Schnabel gives the following data in reference to alumi- 
num. These facts are more appropriately placed here than 
in the section on metallurgy. 208 
ALUMINUM BASE DENTURES 
“The fracture of cast aluminum shows a coarse fiber and 
irregular grain, while it is sinewy or fine grained, and shows 
a high silky lustre after being hammered and rolled.” 
According to Deville, aluminum crystallizes in regular 
octahedra, if cooled slowly. According to Rose, the crystals 
do not belong to the regular system. 
The specific gravity of aluminum at 22° C. is 2.64 for cast, 
and 2.70 for drawn metal. Its specific heat is 0.202. 
It melts at red heat, 658.7 C. At a higher temperature it 
volatilizes, but the exact boiling point has not yet been deter- 
mined. 
As its specific heat is high, it needs much heat and some 
time to fuse; and as its latent heat is also great, it takes a 
long time to cool and solidify. 
According to Deville, when it is cast into small bars it is 
several hours before these can be held in the hand. 
There is a diminution of volume during solidifying, the 
shrinkage being 1.8 per cent of the original volume. 
Swaged Bases of Aluminum 
Because of the difficulty in the past, and even at the pres- 
ent time, attending the production of successful cast base 
aluminum dentures, yet recognizing the need of a metallic 
base less expensive than gold, many prosthetists have turned 
to the swaged aluminum base, hoping to find in that the much 
desired substitute. 
Swaged aluminum bases have been employed for years, 
with varying degrees of success, or what is more literally true, 
of disappointment, for in the larger percentage of cases they 
have not fulfilled the hopes of the prosthetist nor the prac- 
tical needs of the patient. 
The principal and valid objections to swaged bases of 
aluminum, as ordinarily constructed, are as follows: 
First, general deterioration of the metal in the mouth. 
The solvent action of the oral fluids and foodstuffs on alumi- 
num is manifested in several ways, first, by destroying the 
polish of the base, followed by deeper etching of the exposed 
surfaces; this in turn results in gradual thinning and even- 
tual weakening of the base plate, distortion under stress, for- 
mation of holes, and finally loss of adhesion. 
Second, difficulty in securing effective and permanent an- 
chorage between the metal and vulcanite, and of preventing 
the lingual margins of vulcanite from curling away from the ALUMINUM BASE DENTURES 
209 
baseplate, a fault which often occurs even though the gen- 
eral anchorage may be satisfactory. 
COMPARATIVE DURABILITY OF CAST AND SWAGED BASES OF 
ALUMINUM 
The statement is frequently made that the cast is more 
generally satisfactory and permanent than the swaged alumi- 
num base. This is undoubtedly true of the average swaged 
base as made today, but is not in accordance with fact with 
reference to bases of heavy gauge, constructed by the more 
improved methods of technic. 
Let us, for a moment, consider the difference in thickness, 
and bulk of metal in general, between the average cast, and 
the average swaged base. 
The wax which forms the model baseplate determines the 
thickness of the cast base, since the investment matrix is 
formed against and around it. Those familiar with the cast- 
ing of aluminum know that it cannot with certainty and at 
all times be cast into constricted spaces. Therefore, to be 
certain of producing a reasonably perfect casting, and, fur- 
ther, to insure its having the required inherent strength, the 
wax of which the model baseplate is formed must be of suffi- 
cient thickness to meet the above requirements in the forma- 
tion of the matrix. 
Usually the base of the wax model is formed by applying 
a sheet of pink baseplate wax over the face of the cast. This 
is further strengthened by the addition of the wax rolls which 
form the vulcanite finishing shoulders. In nearly every case 
a slight additional film of wax will be added to the palatine 
area, the prosthetist feeling that such an addition will make 
certain a perfect casting, while if too thick, the baseplate can 
be reduced without injury. 
Now the thickness of the average pink baseplate wax is 
16 gauge, or 0.050 of an inch thick. The completed wax model, 
and consequently the casting, on account of the addition of 
wax noted, usually measures 14 or 13 gauge, or 0.064 or 0.072 
thousandths. It is true, some of this thickness may be lost 
in the final finishing of the denture, but in the many prac- 
tical cases observed and gauged by the writer of work done 
by the best prosthetists, all exceeded 17 gauge or 0.045 of an 
inch in thickness, while a number ranged between 15 and 14 
gauge. 
Most of the swaged base dentures at the present time are 
constructed of 26 gauge, 0.016. It will be observed that 26 210 
ALUMINUM BASE DENTURES 
gauge is approximately only one-third the thickness of 17 
gauge, therefore the cast base, being three times thicker than 
the plate ordinarily used in swaged work, besides being thick- 
ened and thereby greatly strengthened by the peripheral rims, 
should outlast the swaged base a proportionate length of time 
under conditions most favorable to the swaged base, while 
under adverse conditions to be mentioned later the time effi- 
ciency of the latter becomes greatly reduced. 
The first well-written description within the writer’s 
knowledge of the swaged aluminum base appeared in the 
American System of Dentistry, 1888. In that article, 26 
gauge plate was recommended as being most suitable and 
practical and, unfortunately, many still adhere to the use of 
that and even lighter gauges. 
The anchorage for the vulcanite was obtained by raising 
opposing spurs on the labial, buccal and lingual border sur - 
faces. Practically, this method of anchorage proved insuf- 
ficient. Later someone suggested drilling a number of holes, 
one-sixteenth of an inch or larger, through the baseplate, at 
various points along the border surfaces, countersinking the 
border or palatine ends of the holes, filling the holes with wax 
in flashing to exclude the plaster so that the vulcanite would 
fill both holes and countersunk portions and become riveted, 
as it were, at several points, to the baseplate. Another 
method of anchorage consists in developing loops in the bor- 
der surface of the base itself by means of a special plier-like 
device. In a general way these methods solved the question 
of anchorage and obviated the frequent mishap of the body 
of vulcanite in which the teeth were mounted from being dis- 
lodged from the baseplate. 
In this system of technic as first outlined, no provision 
was made for a finishing shoulder for the vulcanite, conse- 
quently it was found that after being in use a short time the 
thin, sharp margins of vulcanite where they joined the base, 
particularly on the lingual side, would curl up, break off or 
draw away from the metal, leaving an unsightly joint, annoy- 
ing to the tongue, into which food would find its way. To 
overcome this very objectionable feature, a groove in the 
baseplate was cut at the line of termination of the vulcanite 
with the base, in order to thicken and strengthen the margin 
of the vulcanite. 
This method of forming the finishing shoulder on 26 gauge 
and even somewhat thicker bases is not successful, because 
if the groove is cut deeply enough to give the needed strength ALUMINUM BASE DENTURES 
211 
to the vulcanite margin, the baseplate is so weakened that 
fracture often occurs under stress in a short time. 
When 26 or even heavier gauges of aluminum are swaged 
in the ordinary manner, the plate being first adapted to the 
die with the horn mallet, the injudicious application of mallet 
force, particularly on high points and in deep depressions, as 
the central portion of a high vault, will result in thinning the 
base over such areas. These same high points and depressed 
areas are subject to special stress in swaging between the 
die and counter die. They are very liable to, and usually do, 
become contaminated with die and counter die metal. Unless 
the base metal is removed by thoroughly polishing before an 
nealing, an alloy is formed which apparently is more readily 
acted upon by the oral fluids than is the uncontaminated plate. 
The result of such action is seen in the formation of holes in 
the affected areas. The thinning of the plate from careless 
malleting undoubtedly aids in the early formation of these 
openings, probably through the disturbance of normal molec- 
ular cohesion, thus reducing the resistance of the aluminum 
to chemical action. 
SUMMARY CF THE CAUSES OF DETERIORATION OF SWAGED 
BASES OF ALUMINUM 
Briefly summed up, the real causes of the rapid deteriora- 
tion and general failure of the 26-gauge swaged aluminum 
base appear to be due to the following: 
First, contamination of the aluminum by the die and 
counter die metal, with possible formation of an alloy, easily 
disintegrated chemically. 
Second, excessive thinning by mechanical working, of a 
plate, which is conceded to be the lightest of the series of 
gauges used, suitable for denture bases of this type. 
Third, molecular disturbance of the metal in certain areas, 
which reduces its integrity as sheet metal and lowers its re- 
sistance to chemical action. 
Fourth, reduction of the inherent strength of the baseplate 
by the cutting of a lingual groove. 
Fifth, failure to develop thoroughly, the several means of 
anchorage possible, as previously outlined. 
It is the opinion of the writer, based on a number of years 
practical and clinical experience, that, compared hulk for 
bulk, the base swaged from sheet aluminum will outlast the 
cast base. 212 
ALUMINUM BASE DENTURES 
Construction of Swaged Aluminum Bases 
As has been previously intimated, only the heavier gauges 
of aluminum should be employed in the construction of swaged 
bases for dentures, in order that the baseplate, when weak- 
ened as it must be by grooving, to form the vulcanite shoul- 
der, may still have sufficient inherent strength to resist mas- 
ticatory stress. 
For a number of years past no lighter than 18, and fre- 
quently 16, gauge has been recommended and used in prac- 
tice by the writer, in most instances with very gratifying re- 
sults. Aluminum plate of these gauges and even heavier can. 
with proper technic, be conformed to a die with comparative 
ease. The plate should not be annealed before beginning nor 
at any time during or after the swaging operation. Any base 
metal from die or counterdie can be removed with polishing 
wheels and thus the formation of the low fusing alloy, due 
to annealing, either of which apparently renders the base 
more susceptible to oral fluids and food chemicals, can be 
avoided. 
TECHNIC OF SWAGING 
The actual constructive steps are as follows: 
A die and counter die are secured in the usual manner. 
Both are oiled with a film of heavy, viscid oil. Vaseline will 
answer if a thicker oil is not obtainable. The oil will, to a 
great extent, prevent contamination of the aluminum by the 
die and counter die and lubricate the surfaces, thus obviating 
the tearing of the base. 
Several large sheets of an ordinary newspaper are sat- 
urated with water and the excess expressed under heavy pres- 
sure, as one would squeeze the water out of a wadded up 
towel. The ball of condensed paper should be about three 
inches in diameter. This is placed directly over the opening 
of and on the counter die, and flattened slightly by pressure. 
On the paper a sheet of suitable size of 18 or 16 gauge alumi- 
num, as the case requires, is placed, the die set in position on 
the plate and held firmly with the fingers, and its base struck 
two or three heavy blows with the swaging hammer. The 
first effect of the swaging will be to drive the plate into the 
palatine vault of the die, to a greater or less extent, without 
bending it over the outer sides of the border, the sheet sliding 
over the inclined surfaces of the oiled die without tearing or 
becoming thinned to any appreciable degree. The plate is ALUMINUM BASE DENTURES 
213 
Fig. 94.— Roll of Damp Paper Adjusted to Counterdie 
Fig. 95.— Result of First Swaging on Paper Mass 214 
ALUMINUM BASE DENTURES 
now examined, and wrinkles corrected if any have formed. 
This preliminary swaging does not drive the plate or die 
into the counter die, but into the ball of paper which should 
now be reformed and the plate swaged again as before. Two 
or three swagings are usually sufficient to secure fair palatine 
and partial border adaptation. In case the palatine arch is 
deep and it is difficult to drive the plate into the deepest por- 
tion of it, the die may be set, base down, on the swaging block, 
a ball of paper large enough to fill the vault space is adjusted, 
and a piece of hardwood about an inch in diameter and long 
enough to serve as a handle, the end of which is rounded, is 
set against the paper, and with the hammer adaptation is 
quickly secured. The paper is now removed from the counter 
die and re-formed into a layer about one-fourtli inch thick. 
Fig. 96.— Result of First Swaging on Plate 
This is spread over the counterdie and into its depression, 
the plate set in position, and with the die it is driven partially 
to place, with two or three light blows of the hammer. Re- 
move, correct wrinkles, trim off excessive surplus, and repeat 
the swaging until adaptation is secured, always keeping a con- 
siderable layer of paper between the counterdie and plate. 
The time required for swaging a base of heavy plate by 
this method is usually less than ten minutes, after the die and 
counterdie have been secured and the paper ball prepared. 
The lingual surface of the base does not show an indentation 
or scratch, if reasonable care is observed. The baseplate 
is not perceptibly thinned at any point, and an adaptation to 
the die, equal to that secured in the usual way with thinner 
plate, can readily be developed. The paper acts as a cushion, 
and obviates tearing, stretching, and excessive thinning of 
the plate. With a thick die, heavy smashing blows can be 
delivered with a heavy hammer, and the plate quickly brought 215 
ALUMINUM BASE DENTURES 
into shape, the cushion-like action of the paper obviating to 
a great extent the marring of the die face. 
Care should be taken to keep the anterior margin of die 
back of the corresponding opening in the counter die while 
swaging in the paper ball, otherwise there is danger of shear- 
ing the plate anteriorly as the die is driven into the flattening 
mass of paper. 
Practically the same results can be secured with the Ash 
Rubber Cushion Swager, or with any good hydraulic press in 
which a yielding or plastic material can be interposed be- 
tween the plate and counterdie or which, by confining prop- 
erly, will answer for the counterdie. 
DEVELOPING THE VULCANITE SHOULDERS AND ANCHORAGES 
In all cases, whenever possible, the location of the finish- 
ing shoulder for the vulcanite should be determined after 
having occluded the teeth, waxed up the case and tried the 
denture in the mouth. This plan enables the prosthetist to 
develop the correct lingual contour of the denture in wax, so 
that enunciation may be normal, and lay the shoulder line at 
the margin of the wax as determined by this final test. The 
groove is cut and the shoulder developed in the aluminum 
base after the case is flashed and separated. Or this may be 
the order of procedure: 
The line may be located and the groove cut, after having 
occluded the teeth, before trial in the mouth. This plan will 
give approximately accurate results, but occasionally it will 
be found necessary to restrict or extend the area as first out- 
lined. In case extension is necessary this can be easily accom- 
plished, but when the area must be restricted, the shoulder 
having already been formed too far to the lingual, an un- 
sightly marring of the baseplate results which is difficult, if 
at all possible, to eliminate. Finally this method may be 
adopted. 
It is common practice, but decidedly a wrong method, to 
locate the position of and form the shoulder by guesswork 
before trial in the month or even arranging the teeth, because 
in nearly every instance some modification will be found nec- 
essary when the teeth have been occluded. 
TECHNIC OF FORMING THE SHOULDER 
The shoulder is formed by first cutting a groove with a 
small wheel bur in the engine, following the line scratched on 216 
ALUMINUM BASE DENTURES 
the plate which marks the line of junction of the wax with 
the baseplate. This groove usually extends from slightly in- 
side the center of the tuberosity on one side, lingually, around 
to the corresponding point on the opposite side. The outer 
or buccal margin of the groove is chiseled or ground away, 
cutting the plate freely and broadly, to give the necessary 
depth to the vulcanite margin which will later occupy the 
angle and adjacent area. The shoulder is not extended around 
the labial and buccal surfaces in these cases as it is in cast 
Fig. 97.— Baseplate Showing Anchorage Means Developed 
bases, or in gold base dentures, since, if properly anchored, 
the vulcanite will not curl or warp away from the base plate. 
The general anchorage for the vulcanite is developed by 
raising many heavy opposed spurs on the area to be covered 
by it. These spurs can be made heavier and longer, and are 
therefore much more effective than it is possible to develop 
on lighter gauges of plate. 
SPURRING THE BASE 
In addition to tlie spurs, five or more holes, one-sixteenth 
of an inch in diameter or slightly larger, are drilled through 
the base, one on each tuberosity, one opposite each cuspid 
eminence, on the labial surface, and one on the border crest 
opposite or between the central incisors. It is essential that 
holes be placed in these locations for obvious reasons; there 
is no objection to increasing the number, when by so doing 
the efficiency of the anchorage can be improved. The palatine 
ANCHORAGE BY PERFORATING THE BASE ALUMINUM BASE DENTURES 
217 
ends of the holes are countersunk, and later the entire hole 
should be filled with wax, to exclude the plaster in flasking, 
thus insuring the rubber becoming firmly anchored to the base 
at several divergent points. The loop forming plier may be 
used to raise anchorage loops instead of forming the holes as 
described. 
In these cases, as in all other classes of dentures where 
vulcanite and metal join, chloro-rubber or ordinary rubber 
Fig. 98.— Punch for Forming Anchorage 
Loops on Aluminum Bases 
Fig. 99.— Perforating Punch Used for Vul 
canite Anchorage Purposes 
cement should be painted on the metal parts just before clos- 
ing the packed matrix, to insure a permanent and watertight 
joint. 
Formation of the Vulcanite Shoulder by Means 
of a Doubler 
A method recently introduced for forming the lingual 
shoulder without grooving the baseplate is accomplished by 
swaging a partial base, covering the palatine portion of the 
base proper, its margins laid in correct position to form the 
lingual finishing shoulder. The doubler is attached to the 
base by three or more aluminum rivets, which are invisible if 
the holes on both sides of the plate are slightly countersunk 218 
ALUMINUM BASE DENTURES 
and the wire which serves as rivets fills the holes accurately. 
Since there is no actual union between the two pieces of plate 
other than being held in contact with the rivets, fluids of the 
mouth must sooner or later find their way between, and a dis- 
agreeable odor develop. With a successful solder for uniting 
the two plates the doubler would prove of great advantage 
in many cases, particularly in badly absorbed cases. In such 
instances the margin of the doubler in the absorbed area could 
be lifted away from the base and raised to a level with the 
plate at the corresponding point on the opposite side. This 
will permit the proper palatine contour to be developed with- 
out showing an unsymmetrical area of vulcanite at any point. 
Fig. 100.— Application of a Doubler Held by Riveting 
Some Facts on the History of Aluminum Casting 
The first efforts within the writer’s knowledge of attempts 
at casting aluminum were made by Dr. J. B. Bean, of Balti- 
more, who, in 1867, had granted to him Patent No. 68548, for 
a device for casting aluminum, a description of which may be 
found in the patent records of that year. 
The essential points of the apparatus consisted of a box- 
like flask, in which the matrix was formed in an investment 
of plaster and pumice stone. There were three openings com- 
municating with the interior of the flask, one for the intro- 
duction and another for the exit of hydrogen gas, which was 
forced into and filled the matrix at the instant of casting, 
thereby excluding the atmosphere and preventing oxidation 
of the metal. ALUMINUM BASE DENTUKES 
219 
The third opening had fitted to it a long, tapering, detach- 
able conduit of soapstone, which served also as a reservoir 
for sustaining a standing column of considerable height, of 
excess molten aluminum. The specific claim made for the 
conduit was that it afforded means for “supplying fluid metal 
to compensate for contraction of the metal in the mold, as 
well as to secure a denser casting by means of the detachable 
reservoir, D, heated previous to the pouring of the metal as 
described.” 
Dr. Bean’s demise occurred in 1870, and as no one at that 
time seemed to have succeeded in mastering the technic of 
liis process, but little progress was made in aluminum casting 
until the latter part of the eighties. 
In the June, 1888, Dental Register, Dr. C. C. Carroll, pre- 
sented a method of casting aluminum under pressure, together 
with a description of his apparatus for carrying out the steps 
as detailed. While interesting, time and space are too limited 
to present his method in full, and since it has no direct bear- 
ing on present day technic, for fuller details than those which 
follow the reader is referred to the article in the journal men- 
tioned or to Harris’ edition of 1892. 
The essential features of the Carroll apparatus consisted 
of a flash in which the matrix was formed of a mixture of 
three parts plaster and one of fine sand or marble dust. 
The crucible was detachable, and served as a receptacle 
for the metal while fusing. After adjusting the metal to 
the flask, the fused metal was cast directly into the matrix 
through a central sprue, which subdivided within the invest- 
ment into three, one leading to each tuberosity, the other to 
the distal vault portion. At the time of casting, the top of 
the crucible was closed with a tightly fitting plug. To this a 
rubber hand bulb was connected, which on compressing forced 
the molten metal into the matrix. 
In the hands of careful prosthetists, the Carroll apparatus 
was capable of producing a fairly dense casting, with proba- 
bly no more warpage than occurs in the castings of todav. 
The apparatus was easily thrown out of adjustment, while 
the melting of the metal was difficult to accomplish. These 
objections coupled with the frequent failures, due to various 
causes, led to its final abandonment. 
Between 1892 and 1895, the Fenner and the Zeller appli- 
ances were introduced. These were similar in this respect, 
that each consisted of a two-piece flask in which the wax model 
was invested, and to one of the halves of the flask was fixed a 
crucible in which the aluminum was fused. 220 
ALUMINUM BASE DENTURES 
In the Fenner appliance, the top of the crucible was turned 
true and a close fitting cap adjusted to it. A tube was set in 
the cap, through which was transmitted the compressed air, 
by means of which the metal was forced into the matrix. 
In the Zeller appliance a partial vacuum was created in 
the matrix and the metal was drawn in by suction. 
Later on Dr. R. C. Brophy demonstrated that by having 
reasonably large sprues, the aluminum when sufficiently fluid, 
could be made to fill the matrix by tapping the flask. An alloy 
of 90 per cent of aluminum and to which some other metals 
were added to increase the specific gravity, cast better by 
this method than the pure aluminum. CHAPTER XIV 
WEIGHTED LOWER DENTURES 
Weighted lower dentures are indicated in those cases in 
which the alveolar border is badly absorbed, and where a den- 
ture of ordinary weight is liable to be more or less disturbed 
by the action of the tongue and cheek muscles. Because of 
their greater specific gravity, dentures of this type retain 
their position better under masticatory stress and in speaking 
than do those composed of vulcanite alone. The weight for 
dentures of this class is provided for in three ways: 
First, by using weighted, instead of ordinary rubber for 
the base. 
Second, by inclosing a bar of metal within the body of a 
vulcanite case. 
Third, by casting a base of metal, to which the teeth are 
attached, usually with vulcanite. 
Dentures of Weighted Vulcanite 
Weighted rubber consists of ordinary dental rubber, hav- 
ing uniformly incorporated within it coarse filings of tin or 
some metal that does not readily oxidize. In the construction 
of weighted dentures, this rubber is substituted for the ordi- 
nary basic material, the incorporated metal furnishing the ad- 
ditional weight required. The technic of construction differs 
in no respect from that of an ordinary vulcanite case. 
Vulcanite Dentures Weighted by Means of a 
Metallic Core 
Additional weight may be given a vulcanite denture dur- 
ing the constructive steps as follows: Shape a bar of tin or 
one of its alloys, so that it will fit within the matrix walls of 
the flashed case without interfering with those walls, the bor- 
der crest of the cast, or the ridge laps of the enclosed porce- 
lain teeth. The outer wall or gum portion of the matrix is 
packed with pink rubber first; the lingual portion is lined 
with basic material, packing it carefully under the pins of the 
teeth; the bar of metal previously conformed, and tested, is 
laid in the partially filled matrix, the remainder of the rubber 
221 222 
WEIGHTED LOWER DENTURES 
is added, and the flask closed and vulcanized in the usual 
manner. 
This simple method of imparting varying degrees of 
weight to a denture, as the conditions of the case require, is 
oftentimes very effective. 
Cast Metal Bases 
When a denture of considerable weight is indicated, a base 
is cast in metal for supplying the required weight, and to this 
the teeth are attached by various means, the most convenient 
being vulcanite. Since the metal which forms the base is cast, 
the entire matrix into which it is cast must be composed of 
some refractory material that will not change form percepti- 
bly under the heat to which it will be subjected in preparing 
it to receive the molten metal. Plaster is unsuited for this 
purpose because of its tendency to crack under heat. A num- 
Fig. 101.— Sectional View of Lower Case, Flasked 
with Metal Core in Position 
ber of good investment compounds are procurable, those ordi- 
narily used for crown and bridge purposes being applicable 
to the casting of this type of denture bases. 
TECHNIC OF A WEIGHTED CAST BASE 
The details of construction of a cast lower base are as 
follows: 
From a suitable impression of the lower arch, develop a 
cast in investment material. 
Soften a sheet of pink baseplate wax, and apply to the 
face of the cast. 
Trim it to the approximate outline of the denture base. 
Adapt rolls of wax to the labio-buccal and lingual periph- 
eries of the base, burnishing them so as to form a continu- 
ous shoulder against which the vulcanite will rest. The outer 
surfaces of these strips, which in reality form the outer and 
inner walls of the denture base, should be squared up prac- 
tically parallel with each other, so that the metal base and the WEIGHTED LOWER DENTURES 
223 
vulcanite may form a continuous surface from the margins 
of the denture base to the gingivae of the teeth. These sur- 
faces may be, and usually are, more or less curved, but the 
line of junction of the vulcanite with the base should be free 
from angles. Or stated differently, both buccal and lingual 
surfaces of the metal base should meet the corresponding sur- 
faces of the vulcanite so as to form continuous surfaces with- 
out forming angles. 
Usually one thickness of baseplate wax over the general 
surface of the cast, increased by the rims around its margin, 
will prove sufficiently bulky, when reproduced in metal, to 
give the necessary weight to the denture for retention pur- 
poses. 
Excessive weight in lower base dentures should be avoided, 
as they tire the masticatory muscles, frequently to such an 
extent that the patient cannot wear a denture of this type 
with comfort, or continuously, but must lay it aside from time 
Fig. 102.—Sectional View of Lower Wax Model Base, 
Showing Flat Shoulder Surfaces 
to time, to give the muscles and oral tissues a rest. Irritable 
areas frequently develop under the denture base at various 
points, apparently without cause, but which are in reality 
directly traceable to the heavy, shifting load to which the 
mucous tissues overlying the hard, bony points are constantly 
subjected. Such cases are relieved by reducing the weight 
of the denture, and by scraping the base over the irritated 
areas. 
When the wax model is formed and anchorage loops for 
the vulcanite are properly placed, the case is invested in a 
Watt’s flask. Or an ordinary vulcanite flask will answer the 
same purpose, by making two half round openings in each 
side of the flask, opposite the tuberosities, through which the 
metal may be poured. 
The cast of the mouth on which the wax model has been 
formed is now trimmed peripherally, and reduced in depth, 
so that when set in the lower half of the flask, the peripheral 
FLASHING THE WAX MODEL BASEPLATE 224 
WEIGHTED LOWER DENTURES 
or border margin of wax is level with the line of separation 
between the two halves of the flask. The cast, when properly 
trimmed, is removed, a mix of investment is made and spread 
over the bottom and against the sides of the lower half flask. 
The cast is dipped in water, so that it will not absorb the 
moisture in the freshly mixed investment, and thus interfere 
with its proper setting, pressed into the investment, and the 
latter smoothed evenly from the inner margin of the flask 
to the periphery of the wax base. That portion of the flask 
in which the casting gates are formed should also be filled 
level at this time. When set, the exposed surfaces of the in- 
vestment are treated with soapstone, rubbing it in thoroughly, 
to prevent adhesion of the investment in the upper half of 
the flask, when added. Slight grooves, leading from the distal 
Fig. 103.— Watt’s Flask for Fusible Alloy Casting 
ends of the baseplate to the outer ends of the gate projec- 
tions, should be drawn on the upper surface of the investment 
of the half flashed case, to indicate the width and direction 
of the sprues to be cut, through which to pour the molten 
metal. These grooves on the lower produce ridges on the up- 
per investment, which coincide in location and direction with 
the opposite grooves. When half round grooves are scraped 
between these lines, the latter of which should diverge from 
within outward to give a funnel form to the feed sprue, and 
the two halves of the flask are placed together, a full, free, 
open gate is formed, leading from without inward to each 
distal end of the matrix. 
The second mix of investment is now made, and the top 
half of the flask entirely filled with it. Before adjusting the 
two halves of the flask together, some of the freshly mixed WEIGHTED LOWER DENTURES 
225 
investment, of which there should be a surplus, is applied to 
the exposed surface of the wax base, care being taken to work 
it into all of the irregular surfaces and angles. By piling 
the investment somewhat higher in the middle of the case 
than at the edges, adjusting the upper half of the flask, and 
closing under pressure, the excess is forced out around the 
margins and through the openings on the top and bottom of 
the flask, thus eliminating air spaces. 
When the investment has set, the flask is separated, the 
wax removed, the half gates cut on each side of the flask, all 
delicate margins are removed, the matrix freed from all de- 
bris, and its entire interior, together with the cast face, are 
brushed thoroughly with No. 1 graphite to aid in the produc- 
tion of smooth surfaces to the casting. The flask is closed 
and clamped, and the joint between the two halves luted with 
a paste of equal parts soapstone and plaster, which should 
be carefully forced into every crevice, to prevent the escape 
of the molten metal when poured. 
The flask is now set over a low flame to expel the moisture 
from the investment. The heat should not be so intense as 
to disintegrate the plaster binder of the investment. Tests 
for moisture should be made, from time to time, by holding 
a piece of polished cold steel or glass over the gate openings; 
when no steam condenses, the case is ready for casting. 
CASTING THE BASE 
For weighted dentures any of the several alloys prepared 
and sold for this purpose may be used, or an alloy which will 
serve equally as well can be compounded in the dental labora- 
tory. Kingsley’s alloy is composed of tin, 16 parts, and bis- 
muth, 1 part. Another which serves equally as well is tin, 16 
parts, cadmium, 1 part. Tin alone will not cast sharply, nor 
is it as hard as an alloy of this type should be for the purpose 
intended, therefore one or the other of the metals mentioned 
is added to correct the fault. 
The flask is now set upright, an ingot of alloy is fused in 
a small ladle and poured in one of the openings. If the case 
is sufficiently hot, perfectly free from moisture, and no cracks 
have developed in drying out, the metal will fill the matrix 
and rise in the opposite gate, thus indicating that the space 
is filled. Should crevices develop in the investment while pre- 
paring the case for casting, the flask should be entirely sur- 
rounded with molding sand, well packed around the sides, 
leaving only the sprues exposed, otherwise the metal will 226 
WEIGHTED LOWER DENTURES 
escape through some of the openings, and the matrix be im- 
perfectly filled. 
When the metal has crystallized, the flask is chilled in cold 
water, and the casting removed and cleansed. The excess 
metal is removed with saw and files, and those surfaces of the 
base not to be covered by the vulcanite are smoothly finished. 
With a graver retention is secured by raising heavy, oppos- 
ing spurs on the area to be covered by the vulcanite. These 
spurs are developed in addition to the loops which are formed 
in casting. 
When properly trimmed and polished, a roll of wax can 
Fig. 104.— Cast Base with Teeth Waxed in Position 
be mounted on the cast base and a wax contour model devel 
oped in the usual manner. 
Modification of the Foregoing Method 
Since tlie recent improvements in the technic of casting 
and in investments, and waxes, it is found that these weighted 
base dentures can be handled much the same as aluminum, 
that is, making a single investment and dissipating the wax 
by heat. 
The specific gravity of the alloy is sufficient to insure a 
dense and usually perfect casting without the application of 
pressure, as required in aluminum casting. 
In flashing a weighted base denture, preparatory to pack- 
ing and vulcanization, the line of separation of the flask 
should occur at the line of junction of the vulcanite with the 
metal, thus leaving the base in the lower half, while the mat- 
rix containing the teeth is in the upper half of the flask. 
The surface of the metal to be covered by the vulcanite 
should be painted with a film of chloro-rubber, or rubber 
cement, just before the final closure of the flask. weighted lower dentures 
227 
HISTORY 
In 1856, Dr. A. A. Blandy introduced a system of cast- 
ing denture bases, similar to the method just outlined, and 
which he designated the Cheoplastic Process, signifying “the 
making of plates by pouring a metal made plastic by heat” 
(Harris). 
The production of a denture in those days, by forming it 
in a matrix, of a plastic material which hardened, was an 
innovation. Vulcanite and celluloid were not yet introduced, 
and, therefore, this was the first plastic process of denture 
construction. 
The exact composition of Blandy’s alloy is not known, but 
the metals consisted of silver, bismuth and antimony. 
The introduction of vulcanite as well as celluloid follow- 
ing shortly after lessened the interest in cast metallic bases in 
general, but because of the advantages of the weighted base 
for lowers, more or less use has been made of it where 
indicated. 
Weston, Wood, Watt, B ose, Kingsley and others have for- 
mulated alloys for denture bases, which are mentioned else- 
where. 
Vulcanite Baseplates 
In cases where it is apparent that good adaptation of a 
denture to the oral tissues may be difficult to secure, because 
of peculiarities in form of the border or sonte unusual con- 
dition of the oral tissues, a preliminary baseplate of vulcan- 
ite can oftentimes be constructed to good advantage. This 
vulcanite form, molded over an accurate cast of the mouth, 
affords a reliable test as to adaptation and stability of the 
baseplate, before the bulk of technical details have been car- 
ried out and if successful becomes the permanent base. If 
unsuccessful, another one can be constructed, or a different 
plan of procedure adopted, early in the constructive stages, 
and without further loss of time. 
TECHNIC OF CONSTRUCTION 
Over an accurate cast of the month sheet wax is adapted 
in the usual manner, and trimmed to correct peripheral out- 
line. The wax baseplate should be slightly thicker than the 
permanent base is to be, so as to allow for loss of material 
in finishing. A roll of wax about one-eighth inch in diameter 
is laid, in a symmetrical curve, around the lingual surface of 228 
WEIGHTED LOWER DENTURES 
the border, beginning a little to the buccal of one tuberosity, 
passing lingually and terminating at a corresponding point 
on the opposite side. The margin of wax presenting toward 
the border crest should be finished squarely and without 
Fig. 106.— Vulcanite Base Ready to Receive Wax Occlusion Rims 
undercuts, for it is against this shoulder of the vulcanite that 
the rubber which encloses the teeth is molded. The shoulder 
should be carried well up toward the crest of the border, but 
must be broadened lingually to furnish an ample base for the 
Fig. 106.— Lingual View of a Finished Denture Com- 
posed of Three Colors of Vulcanite 
bicuspids and molars. If broader than necessary, it is easily 
reduced in the final finishing of the denture. 
It is not necessary to extend the strip around the labial 
and buccal periphery of the baseplate, as the pink vulcanite 229 
WEIGHTED LOWER DENTURES 
will present a better appearance than a rim of basic material 
in this location. That margin of the strip presenting toward 
the central vault portion of the baseplate should be burnished 
down smoothly so as to form a symmetrical curve with the 
general palatal arch. 
Having been given its proper form and being smoothly 
finished, the wax baseplate, on its cast, is flashed in the usual 
Fig. 107.— Plaster Casts Ready for Application of Baseplates 
manner, the flask packed, and vulcanized. The baseplate is 
now only roughly finished on the lingual, but thoroughly pol- 
ished on the palatine surface. In this condition it is ready to 
receive the wax rim, the formation and application of which 
will be described later. 
It is common practice to form the baseplate of dark or jet 
black rubber, and attach the teeth to it in the second vulcan- 
ization with maroon or some of the lighter shades of red 
Fig. 108.— Baseplates Applied to Casts 
rubber. When this plan is carefully executed most beautiful 
and artistic substitutes can be produced. Such a denture, 
finished, will present palatine and border surfaces entirely 
black, a similar lingual surface extending well out to the lin- 
gual surfaces of the teeth, a narrow, symmetrical band of 
maroon or red vulcanite between the black vault portion and 
the teeth, with full gum restoration of granular pink on the 
labio-buccal surface. 230 
WEIGHTED LOWER DENTURES 
Construction of Temporary Baseplates 
USING “ideal BASEPLATE, SPECIAL * ’ 
The following directions should be observed in the con- 
struction of temporary baseplates: 
Place cast on bench, face up. Center a sheet of rigid base- 
plate material (preferably Ideal, Special) over it. Apply the 
soft brush flame of the blowpipe, moving it quickly so as not 
to overheat any particular area and cause adhesion to the 
cast, but rather to soften the whole sheet uniformly. As soon 
as it begins to settle, remove the flame, and with the fingers 
apply light pressure to adapt it to all surfaces of the cast. 
Avoid undue pressure which thins and weakens the material 
unnecessarily. Apply the blowpipe to the labio-buccal por- 
Fig. 109.— Ideal Baseplate Removed from Cast 
tions to soften somewhat, remove the partially adapted base- 
plate, and with shears cut the base to approximately its 
correct peripheral outline. Return to the cast, correct the 
distortion that has occurred from the use of the shears, com- 
plete the adaptation, chill and use the vulcanite file for the 
final finish of the peripheral margins. The file should be 
Fig. 110.— Sectional View of Cast and Baseplate Uniformly Adapted WEIGHTED LOWER DENTURES 
231 
applied diagonally or somewhat along the line of direction of 
the margin rather than crosswise, to obviate fracturing the 
baseplate. A thin blade spatula, heated quite hot, may be 
used instead of the shears for cutting the baseplate to correct 
peripheral outline, passing it along the peripheral line while 
the baseplate is on the cast. 
The baseplate may be reinforced in several ways, one of 
the most common methods being to melt some of the surplus 
material against the areas it is desired to strengthen, and 
smooth the addition down with a very hot spatula. Another 
method is to bend a piece of 11 or 12 gauge brass, German 
silver, or iron wire to the form of the arch, but slightly 
smaller, attach it by warming and with melted wax to the 
baseplate just inside the border crest, so as neither to inter- 
fere with the proper arrangement of the teeth nor with the 
development of correct lingual contour in the final waxing of 
the denture. 
When trimmed to correct peripheral outline, strengthened 
in the weak areas, and final close adaptation has been secured, 
the baseplate is ready for the application and preliminary 
contouring of the wax rims. 
TEMPORARY BASEPLATES OF METAL 
Sheet tin or lead, 14 to 16 gauge, when properly adapted 
to the cast makes a most excellent base for wax contour 
models. The simplest method of developing a base of this 
class is as follows: A cast of the mouth having been secured 
and its base made flat, it is placed on the rubber cushion of 
the Ash Swaging Machine, a sheet of metal of suitable size 
is laid over its face, the other rubber cushion laid on the sheet 
and pressure applied to force the metal partially to place. 
The surplus is trimmed off with shears, the wrinkles cor- 
rected, and final swaging completed on returning to the press. 
If care is observed in these steps, no injury will occur to the 
cast, and it can be used subsequently for the completion of 
the case. In work of this class, the use of oxy-chloride of 
magnesia for casts is most strongly indicated, as, in fact, it 
is in all vulcanite denture construction. 
Another method, whereby a metal baseplate similar to the 
one just described can be formed without subjecting the per- 
manent or final casts to the pressure of swaging, is carried 
out as follows: 
A reasonably good impression of the arch, involving all 
of the areas to be covered by the finished denture, is secured 232 
WEIGHTED LOWER DENTURES 
in modeling compound, omitting the reheating steps pre- 
viously mentioned. From this impression a cast is secured 
and a tin base swaged as described. This base is trimmed 
to correct peripheral outline and tested by trial in the mouth. 
A thin layer of softened modeling compound not more than 
one-sixteenth of an inch thick is laid evenly over the interior 
of the baseplate, which now is to serve also as an improvised 
impression tray. An impression, worked out by reheating 
and the various corrective steps previously mentioned, is 
secured, and all excess carefully removed. This now con- 
stitutes an impression-baseplate, on which rims of wax can 
be built to form the wax contour model. When transferred 
from the mouth to the occluding frame by means of the face 
bow, instead of dropping the original casts on which the metal 
bases were formed into the wax contour model, freshly mixed 
plaster or the magnesio compound is filled in and built against 
the bows of the occluding frame. If oiled before forming the 
cast and no undercuts are present, the wax model denture will 
readily separate, when removed for final trial in the mouth. 
The advantage of this method consists almost solely in the 
increased stability of the wax model dentures during trial in 
the mouth, over temporary baseplates, of any type, adapted 
to casts in the ordinary manner. CHAPTER XV 
RETENTION OF PARTIAL DENTURES 
A partial denture, to be successful, must fulfill certain 
requirements: 
First: It should restore as fully as possible the function 
of mastication so far as the latter may have been impaired 
by the loss of the natural teeth. 
Second: It should restore the esthetic features of the 
dental arch by supplying substitutes which harmonize in form 
and color with the remaining natural organs. 
Third: It should be so adapted to the remaining teeth 
and tissues as to maintain its position with certainty and 
comfort when the masticatory apparatus is in an active, as 
well as a passive, state without causing immediate or gradual 
decay or injury to the natural teeth present. 
Of the several requirements mentioned, that of retention 
is usually the most difficult of accomplishment. Various 
means, both physical and mechanical, are employed to attain 
this end, the most important of which are atmospheric pres- 
sure, adhesion, friction and specialized frictional appliances. 
Atmospheric Pressure and Adhesion 
The principles of retention by means of atmospheric pres- 
sure, and adhesion also, have previously been explained. For 
various reasons these forces, although of value, are not as 
effective in the retention of partial as of full dentures. 
The degree of force exerted by the atmosphere and adhe- 
sion upon objects from between the contact surface of which 
the air has been exhausted and close adaptation secured, is 
directly proportional to the square of the area involved. 
Therefore the more limited the area of oral tissues covered 
by the baseplate, the less can these forces be relied upon for 
retention purposes. 
In partial cases the presence of natural teeth necessarily 
restricts the size of the base plate, since the periphery of the 
latter must fall within, or terminate against, the lingual sur- 
faces of the teeth involved. This reduction in size of the base- 
plate therefore reduces the effectiveness of adhesive force. 
Again, the line of junction of the denture with the natural 
233 234 
RETENTION OF PARTIAL DENTURES 
teeth is a peculiarly vulnerable point for the ingress of air, 
since the mucous tissues of the cheeks, lips and palate cannot 
be utilized for sealing up and protecting the margins against 
the return of air when once withdrawn from between baseplate 
and tissues, as is the case in full dentures, and this also is a 
further cause for reducing the force of adhesion. 
Frictional Retention of Partial Dentures 
The simplest form of frictional retention available for 
partial dentures consists in abutting the sides of the latter 
against the lingual surfaces of, and in the embrasures be- 
tween, teeth situated on opposite sides of the arch, or suf- 
ficiently far apart to present opposing surfaces, which, when 
the denture is in position, tend to resist displacement. The 
alignment of the teeth must be favorable for such retention, 
Fig. 111.— Cut Showing Inclination Toward Each Other of Teeth on Opposite 
Sides of the Arch 
viz., the distance between the cervices of the teeth opposite 
each other in the same arch must be greater than at the points 
of greatest lingual convexities, or points of their nearest 
approach. 
A denture moulded over the cast of a mouth with teeth 
bearing the relation to each other as stated, will spring as 
it passes over the points of nearest approach of the teeth 
involved, and resume its normal width without undue lateral 
pressure when firmly seated on the oral tissues. Such an 
appliance is called a spring plate or denture, and yet it does 
not exert lateral pressure against the teeth except on intro- 
duction and removal. 
When the lingual surfaces of the teeth diverge from gin- 
gival to occlusal this means of retention cannot usually be 
utilized, as the constantly diverging surfaces are mechani- 
cally opposed to such retention. Frequently, however, by RETENTION OF PARTIAL DENTURES 
235 
allowing the denture margins to extend into the embrasures, 
when the latter are well defined, frictional retention may be 
developed even in those cases where the general alignment of 
the teeth presents more or less parallel relation of surfaces. 
In such cases, and especially when the crowns of the teeth 
are too short for clasping, the writer has inserted inlays with 
projecting lugs in two suitably situated opposing teeth in 
such manner that the lugs will engage with, and offer fric- 
tional resistance to, the displacement of the denture. Some- 
times, too, How anchor screws inserted in the lingual sur- 
faces of the teeth will fulfill the requirements of the case. 
The nse of the inlays and wire lugs, as suggested, has proven 
very useful in many difficult cases, while no serious results 
have followed this method of practice. 
In case either the anchor wires or the lug inlays are used, 
the projections should be rounded so as to permit the denture 
Fig. 112.— Retention of Baseplate by Means of Wire Lugs 
to spring in and out of position without catching on the lug 
margins or straining the teeth to an undue extent. 
Specialized Frictional Appliances 
Various forms of specialized frictional appliances are in 
common use for retaining partial dentures in position in the 
mouth. These usually are attached to and become a part of 
the denture itself. In other cases the attachment consists of 
two parts, one of which is attached to the denture, the other 
to a natural tooth, to an inlay, to a crown set upon a natural 
tooth or root, or to a wire or bar permanently fixed to crown 
or inlay. 
Among the appliances in general use may be mentioned 
clasps of various forms, double bars or stays, and special 
attachment, such as the Roach, Gilmore, Morgan, etc. 236 
RETENTION OF PARTIAL DENTURES 
Clasps 
Clasps are partial band-like appliances adapted to the 
natural teeth for retaining in the mouth the partial denture 
of which they form a part. They are usually constructed 
of flat plate or half round wire of gold clasp metal, composed 
of pure gold, platinum, silver and copper. This alloy pos- 
sesses well defined elastic properties. The proportions of sil- 
ver and copper may be varied, however, or the silver omitted 
altogether, as its presence imparts but little resiliency. 
Considerable difference of opinion exists as to the ultimate 
value and utility of clasps, the argument of those opposed 
to their use being that the injury to the natural teeth far 
outweighs the good derived from their use. Those who favor 
the application of these appliances are equally as positive 
in their conviction of the benefits of such attachments. A 
statement of the objections and advantages of clasps will be 
in order. 
OBJECTIONS TO THE USE OF CLASPS 
The principal objections urged against the use of clasps 
are as follows: 
First — The accumulation, retention and fermentation of 
food in the space between clasp and tooth will invite, and in 
many cases does, induce caries. 
Second — Frictional action of the clasp against the enamel 
will abrade the latter, induce hypersensitiveness in the tooth 
structure, set up gingival, and in some cases, peridental irri- 
tation. As consequence the patient suffers more or less dis- 
comfort, and in time the crown or the entire tooth may be lost. 
The deleterious conditions here cited are frequently ob- 
served and therefore these objections have an apparently 
good foundation. They can, however, in almost every in- 
stance be traced to one or more of several causes, most of 
which may be averted, as for instance, injudicious applica- 
tion of clasps to teeth unsuited for the extra stress they must 
sustain; imperfect technic in the construction of the appli- 
ances ; or to lack of habitual care of the natural teeth and 
denture on the part of the patient. 
ADVANTAGES DERIVED FROM THE USE OF CLASPS 
First — Stability of the denture at all times, in speaking, 
laughing, and in masticatory effort is practically insured. RETENTION OF PARTIAL DENTURES 
237 
Second — By their use the baseplate which carries the 
replaced teeth need cover but a very small area of the oral 
tissues, since adhesion and atmospheric pressure as a means 
of retention are unimportant factors when clasps are used. 
When judiciously applied, properly constructed, and the 
mouth is given reasonable care and attention by the patient, 
clasps are of the greatest convenience and comfort, and will 
cause but little injury to the teeth or tissues. In the expe- 
rience of the writer, the advantages gained from the use of 
clasps, where indicated, are infinitely greater and far out- 
weigh any harm that may result from their presence. 
Should sensitiveness be induced, or caries eventually de- 
velop, the tooth can be devitalized and crowned when occasion 
requires, and be made to render still further service, by carry- 
ing a newly adapted clasp. It is seldom advisable to crown 
a tooth to be clasped in anticipation of subsequent caries, as 
such procedure may never be required. 
Requisites of a Clasp 
A clasp, as its name implies, is an appliance which grasps 
or clings to the tooth to which it is adapted. To be effective 
it should embrace more than one-half, usually about two- 
thirds, of the periphery of the tooth. A clasp should be so 
constructed that when in position firm, frictional contact is 
established between both its gingival and occlusal peripheries 
and the axial walls of the tooth to which it is adapted. In 
fact, the efficiency of a clasp depends on closeness of adapta- 
tion to the tooth, resiliency, and inherent strength. 
ADAPTATION 
Closeness of adaptation insures stability by lessening the 
tendency of the clasp to rotate, cant or slide when in position 
on the tooth, all of which movements tend to unbalance the 
denture when subjected to masticatory stress. The nearly 
parallel relationship of the axial walls of most teeth suitable 
for clasping renders the attainment of this requisite difficult, 
in clasps of the ordinary partial band type. Stability may 
be secured, when good adaptation has been developed, by the 
addition of a small but rigid lug extending from the occlusal 
margin of the clasp, up to and over the mesial or distal mar- 
ginal ridge of the tooth clasped. The lug should be located 
as centrally as possible between the two extremities of the 
clasp. Such an addition converts an ordinary partial band 
clasp into a stop clasp. 238 
RETENTION OF PARTIAL DENTURES 
Without doubt this form of clasp, or some modification 
of it, in which the stop principle is embodied, is the most 
satisfactory and serviceable of any of the common types of 
partial band clasps. By the addition of the stop, frictional 
wear of the enamel is practically overcome, undue pressure 
on the alveolar process covered by the denture and on the 
gingiva surrounding the tooth clasped is obviated, and a feel- 
ing of security and comfort to the wearer of the denture re- 
sults, not possible to be realized from the use of the ordinary 
type of clasp. The credit of having evolved, demonstrated 
and described the practical applicability of the stop clasp 
should be ascribed to Dr. Bonwill. 
Fig. 113.—Three Cases by Bonwill, Showing His Application of the Stop Clasp, and Wire 
Attachment of Clasp to Baseplate 
The degree of perfection of adaptation of the clasp to 
the tooth depends on the skill displayed by the prosthetist, 
the technical steps employed, and to a certain extent on the 
character and thickness of the metal used in its construction. 
RESILIENCY OF THE CLASP 
Resiliency in a clasp is that property which permits it to 
spring over the enlarged portion of the tooth it embraces in 
introducing and removing the denture, without becoming per- 
manently distorted when subjected to such stress. This RETENTION OF PARTIAL DENTURES 
239 
quality depends on the character of the metal of which the 
clasp is composed, as well as on the width and gauge of the 
clasp itself. The gold alloy known as clasp metal, previously 
mentioned, is used almost exclusively for clasp construction 
because of its hardness and well defined elastic property. The 
elasticity noticeable in a clasp when subjected to stress would 
be classified in physics under the term of elasticity of flexure, 
in which the molecules of the clasp metal on the inner per- 
iphery are elongated when subjected to stress, while those on 
the outer side are compressed. Permanent distortion occurs 
when the stress applied carries the metal beyond the modulus 
limit, in which condition it is said to be strained, as when 
stress is removed, the piece, of whatever shape, does not re- 
turn to its original form. 
A clasp may be well adapted to a tootli, possess sufficient 
resiliency to be carried to, and removed from, position in the 
mouth without becoming distorted under ordinary stress, and 
yet prove unsatisfactory with use. 
Undue stress exerted on clasps in polishing on the lathe, 
in introducing and removing the denture, careless handling 
in cleansing, letting the denture fall, as well as other acciden- 
tal causes, frequently distort and oftentimes destroy the 
effectiveness of these appliances. Many clasps otherwise 
suitable fail because of lack of inherent strength, and con- 
sequently the very object for which they are designed is de- 
feated. 
The remedy lies in correctly estimating the proper width 
and thickness of the clasp in proportion to its length, and 
developing the appliance accordingly. These two factors are 
determined by the length of tooth to be clasped. Short teeth 
require narrow, but rather thick, clasps, the thicker gauge 
compensating for the weakness resulting from restricted 
width. 
A thick, narrow clasp, however, is not as resilient as a 
thinner, wider appliance of equal length containing an equal 
amount of metal as the former. The truth of this proposition 
is plainly apparent by noting the difference in resiliency of 
steel springs of varying widths and gauges. A spring should 
be so proportioned as to carry the extreme load to which it 
may be subjected without the occurrence of permanent dis- 
tortion. In fact, it should possess a considerable range of 
elasticity between the extreme load limit to which it will be 
THE INHERENT STRENGTH OF CLASPS 240 
RETENTION OF PARTIAL DENTURES 
subjected and the modulus limit, or point where permanent 
distortion occurs. 
Inherent strength with bulk to carry extreme loads, while 
a high degree of resiliency is retained, is imparted to springs 
in the mechanical field by dividing the necessary bulk of metal 
into comparatively thin layers called leaves. In other words, 
the spring is made up of several members consisting of the 
principal spring reinforced by a series of leaves of gradually 
decreasing length, but of approximately the same thickness, 
rigidly fixed to the main spring, usually at the point where 
stress is applied. The leaves throughout the 
of their length are free to slide or move freely against each 
other as the load or stress varies, and thus the resilient power 
of each member of the spring is utilized in reducing shock 
and avoiding strain. 
This principle of reinforcement of clasps for dental pur- 
poses cannot well be applied for obvious reasons, although 
Fig 114.—-Clasp from Which Central Section Is 
Removed to Increase Resiliency 
at times it is necessary to vary the flexibility of a clasp at 
different points throughout its length. For instance, when 
a clasp must of necessity be narrow, thick and almost devoid 
of resiliency where it passes through the interproximate 
space, the buccal and lingual flanges may be increased in 
width and decreased in thickness to develop greater elasticity. 
In such cases extra thick plate is used for the clasp to give 
strength in its narrowest part, and the necessary reduction 
in thickness on the broad areas is made by filing, grinding 
and polishing. In a number of cases the writer has secured 
excellent results by cutting a section from the central portion 
of the broad areas of a clasp after adaptation has been devel- 
oped, without reducing the thickness of the appliance. 
Various modifications of the ordinary flat band clasp, 
specially of the broad type, are employed to decrease rigidity 
and increase resiliency. In addition to removing a central RETENTION OF PARTIAL DENTURES 
241 
section from the flange as detailed, it may be divided through- 
out a portion of its length, as suggested by Dr. G. H. Cushing, 
or the central area may be removed, and the gingival por- 
tion severed. 
While a clasp must possess inherent strength sufficient to 
withstand unusual stress, it should not be too unyielding. 
When deficient in elasticity because of its bulk, and at the 
same time possessing excessive inherent strength, the tooth 
which it embraces will be subjected to unnecessary strain in 
removal of the denture if the adaptation of the clasp to the 
tooth is reasonably close. 
Fig. 115.— A Case Constructed by Dr. G. H. Cushing in 1869 
Gauges of Clasp Metal Commonly Employed 
Many clasps fail under stress of usage, as before stated, 
because of lack of inherent strength. This is usually the re- 
sult of using too thin a gauge of clasp metal, or so reducing 
their width as to render them weak. 
As a rule, 26-gauge clasp metal is as thin as should be used. 
Fig. 116.— Various Methods of Increasing Resiliency in Clasps, Buccal View 
When 28-gauge is employed, unless very wide, it should be 
stiffened by flowing 18K solder on the outer periphery. While 
this method imparts rigidity, it reduces resiliency, and there- 
fore should seldom be adopted. 
Usually three gauges of clasp metal will answer for all 
ordinary cases that may present: 26 gauge for long, 24 gauge 
for medium and 22, or in extreme cases 20 gauge may be re- 
quired, for short teeth. Clasps of equal length may vary in 
width, thickness and resiliency, and yet contain essentially 242 
retention of partial dentures 
the same amount in bulk of material. For example, a clasp 
one-eighth inch wide, composed of 20-gauge plate, which 
equals .03196 of an inch thick, will contain essentially the 
same amount of metal as one of equal length and twice as 
wide of 26 gauge, which equals .01594 inch thick. Its resil- 
ient index, however, will be noticeably less than that of the 
26-gauge clasp. 
Types of Clasps Most Commonly Used 
Clasps vary in form according to the requirements of the 
case for which they are constructed. These requirements in- 
clude the class and forms of teeth to which they are adapted, 
the part they are to fulfill in the retention of the denture, and 
the load they are required to carry. 
The ordinary forms of clasps may be tabulated as fol- 
lows : 
1. Partial flat band clasp. 
2. Half-round wire clasp. 
3. Double wire or bow clasp. 
4. Stop, wire or band clasp. 
5. Double-stay clasp. 
(3. Stay clasp. 
The Partial Flat Band Clasp 
This form of clasp, as its name indicates, consists of a 
partial flat band, usually of clasp metal of suitable gauge and 
width, which embraces about two-thirds of the tooth periph- 
ery. The gingival and occlusal margins of the clasp should 
be practically parallel to insure as nearly equal resiliency 
throughout its entire length. This, however, does not imply 
that these margins should be straight, but curved somewhat 
similar to, but usually less pronounced than, the gingival gum 
curvature. 
Band clasps should be reasonably broad, the average width 
varying from two to five millimeters. The broader the clasp, 
the more stability will be afforded the denture. 
On the other hand, a clasp of this type should not be so 
broad as to encroach upon the gum tissue and thereby induce 
irritation; neither should it interfere with occlusion of the 
opposite teeth. The buccal and lingual flanges can usually 
be so formed as to avoid impingement on the soft tissues. 
When the tooth clasped proximates with two others, and the 
gum septum in the embrasures through which the appliance liETENTION OF PABTIAL DENTUBES 
243 
passes is normal, or nearly so, it is sometimes difficult to en- 
tirely avoid impingement on the tissues in such locations. 
While it is advisable in most instances to avoid the use 
of clasps where tissues fill the embrasures, it becomes neces- 
sary to apply them in other cases, especially where there are 
no other teeth of suitable form, or in proper location, to be 
utilized. 
When a clasp is applied in such cases, extreme care should 
be taken to conform it closely to the mesial or distal axial wall 
of the tooth clasped, to reduce it to the minimum width con- 
sistent with strength, and to smoothly round off all angles 
presenting toward the gingiva. The tissues, although subject 
to compression for a time, will usually adjust themselves to 
the clasp without permanent injury resulting. 
The Half-Round Wibe Clasp 
ADVANTAGES 
Various gauges of half-round clasp metal wire are fre- 
quently used in clasp construction. The advantages of half- 
round wire for this purpose are as follows: 
First — The clasp is of uniform thickness and resiliency 
throughout its entire length, except where attached to the 
plate, at which point it is rendered more rigid because of the 
solder. 
Second — It can be adapted to teeth with comparative 
ease. 
Third — Less tooth surface need be covered by the clasp, 
and consequently there is less liability for food to accumulate. 
Objections 
First — Wider space is required between proximating 
teeth for the accommodation of the clasp. 
Second — Limited stability afforded the denture because 
it does not grasp the axial walls of the tooth as firmly as a 
broader clasp. 
The Double Wire Clasp 
This type of clasp consists of a wire of 18 or 19 gauge 
clasp metal looped on itself and the ends soldered so as to 
form an elongated, more or less parallel sided, endless band. 
The distance between the gingival and occlusal wires varies 
from one to four m.m., depending on the length and form of 
the tooth clasped. To retain a firm grasp on the tooth, the 244 
RETENTION OF PARTIAL DENTURES 
gingival wire should lie to the gingival and the other wire to 
the occlusal of the greatest diameter of the tooth, thus tend- 
ing to resist displacement either gingivally or occlusally. 
The double-wire clasp may be converted into a stop clasp 
by the addition of a strip of heavy clasp metal of 19 or 20 
gauge, or square wire 18 gauge, bent so as to form an occlusal 
lug, and extending so as to connect the two wires and further 
furnish attachment of the clasp to the gold base or vulcanite, 
as the case requires. 
Another modification of this clasp, suggested by Dr. F. E. 
Roach, and by him designated the 4‘double-bow clasp,” con- 
sists in adapting the gingival wire closely to the proximate 
surface of the tooth, and leaving it unattached to the lug bar. 
More flexible adjustment is claimed for the clasp constructed 
in this manner, particularly in those cases where the substi- 
tute is designed to correct a space between two natural teeth, 
and where they lean slightly toward each other. (Dental Re- 
view, October, 1913.) 
While lacking the strength of some of the other forms of 
clasps described, when well planned and properly constructed 
the double-wire clasp clings to a tooth with wonderful tenac- 
ity, and will sustain a denture with firmness and comfort to 
the wearer. 
The principal advantages of the double-wire clasp may be 
summed up as follows: 
First — The large extent of linear contact existing be- 
tween the clasp peripherally and the tooth surfaces, with the 
minimum amount of surfaces actually covered. 
Second — Great resiliency and ready adaptability of the 
clasp to the tooth surfaces. 
Third — Comparatively simple to construct. 
The principal disadvantage lies in possible lack of inher- 
ent strength, particularly in those cases where the tooth is 
large, requiring a long clasp peripherally, and where the den- 
ture will be subjected to heavy stress or careless handling. 
The Stop Clasp 
The stop clasp lias been previously mentioned under ‘ ‘ Re- 
quisites of a Clasp.” Clinical experience with this type of 
clasp has been so satisfactory as to lead to its adoption in 
practically every case. 
Any of the forms of clasps described may be converted 
into a stop clasp by the addition of an occlusal lug. In case 
of the flat-band clasp the lug may be formed of the same piece RETENTION OF PARTIAL DENTURES 
245 
of plate as the clasp by allowing for the extra width in cutting 
the clasp metal, or it may be soldered on after the appliance 
is constructed. 
The lug should be so placed that, when the clasp is in 
position, it rests on, or hooks over, the mesial or distal mar- 
ginal ridge of the tooth clasped. If the ridge is excessively 
prominent, it may be reduced by grinding and polishing so 
that the lug may not interfere with the occlusion of the tooth 
Fig. 117.— Ordinary Band Clasp with Stop, Lingual View 
in the opposite arch, or the tip of the occluding cusp may be 
ground and polished until clearance space is gained. In case 
the tooth clasped is carious and suitable for the reception of 
an inlay, it may be restored in this manner and a depression 
made in the occlusal surface of the inlay, so as to permit the 
occlusal surface of the lug to rest flush with that of the re- 
stored part. It is essential that the lug should be slightly 
hook-shaped and the surface on which it rests correspondingly 
curved, to prevent the tendency of the clasp to slide away 
from the tooth when the denture is subjected to stress. 
The Double Stay 
A method much in vogue in Europe, but infrequently 
applied in this country, consists in attaching two rather thin 
pieces of clasp metal of 28 or 29 gauge to the baseplate. The 
strips should be in close apposition to each other, so as to 
pass through the interproximate space between two suitably 
located proximating teeth. The ends of the stays which ter- 
minate in the buccal embrasure are bent away from each other 
so as to lie in close apposition to the teeth they proximate. 
Retention by means of this “Doppel Klammern” (double 
clasp), as the Germans term it, is very effective in favorable 
cases. The retention does not depend on mesial and distal 
frictional contact, but on the action of the reflected ends of 
the two flanges tending to draw the two teeth inward toward 
the baseplate. The stops themselves should not exert spring 246 
RETENTION OF PARTIAL DENTURES 
pressure on the proximating surfaces of the teeth, or in time 
gradual and permanent separation of the latter will occur. 
The Stay 
This appliance is commonly called a stay clasp, but the 
term is incorrect since it embraces less than one-half of the 
Fig. 118.— The Double Stay, Showing Elemental Construction Details 
periphery of the tooth to which applied, and therefore does 
not perform the function nor fulfill the purpose of a clasp. 
Appliances of this type are seldom indicated, being usually 
applied in those cases where ordinary frictional retention of 
the denture is uncertain because of the parallel, or slightly 
diverging, relation of the lingual surfaces of the teeth on 
opposite sides of the arch, and when for any reason clasps 
are contra-indicated. Two well adapted, opposed stays, the 
Fig. 119.— The Stay Clasp 
ends of which pass well into the lingual embrasures, will fre- 
quently give the required stability. 
Indications and Contra-Indications Governing the 
Application of Clasps 
For tlie retention of partial dentures, clasps may gener- 
ally be used to advantage in all cases when the mouth is in a 
comparatively healthy condition and the teeth are so situated 
that when the clasp denture is introduced it will balance and 
not become displaced. 247 
RETENTION OF PARTIAL DENTURES 
Unless the teeth clasped are suitably located, displacement 
of the denture by gravity, muscular strain, or the two forces 
combined, will sooner or later occur, regardless of the pres- 
ence of the clasps. For example, in an upper case where all 
of the teeth, except the third molars, are missing and reten- 
tion of the denture depends solely on clasping these two teeth, 
gravity and the action of the lip and cheek muscles will over- 
come the resiliency of the clasps and result in partial, if not 
complete displacement. Or if the clasps are heavy enough 
to resist these displacing forces, the teeth themselves will be 
gradually and permanently tipped backward, thus permitting 
the denture to become unseated and the clasps will then be 
a detriment instead of an advantage. 
Fig. 120.— Diagrammatic View of Case Showing “ Denture Balance ” 
Tlie location for clasps best suited to insure stability is at 
a point midway between tlie anterior and posterior terminals 
of tlie denture on either side. The tendency to tip anteriorly 
is thus instantly counteracted by pressure of the distal end of 
the denture against the tissues, and vice versa. Such bal 
anting requirement really limits the number of teeth that may 
be clasped to advantage to the second bicuspid and first molar 
on either side, although at times the first bicuspid and second 
molar, if present and on opposite sides of the arch, may be 
utilized for such purpose. Although neither clasp would be 
situated midway between the mesial and distal terminal, yet 
a straight line drawn from one clasp to the other would dis- 248 
RETENTION OF PARTIAL DENTURES 
close a diagonal balance quite as effective as when the more 
centrally located teeth are clasped. 
There is oftentimes a temptation to utilize the diagonal 
balance by clasping the cuspid on one side — all of the poste- 
rior teeth on that side having been lost — and the second or 
third molars on the opposite side. Usually such attempts re- 
sult in failure because the conical form of the cuspid tooth 
precludes the application of a stable, partial-band clasp, ex- 
cept in those cases where tissue absorption has progressed 
to such an extent as to expose the constricted portion of the 
tooth, thus allowing the clasp to extend well up over the cin- 
gulum. 
When but little absorption of tissue has occurred, a modi- 
fied form of band clasp is sometimes constructed for cuspids, 
involving considerable effort in construction, but resulting in 
marked stability. A cavity is formed on the lingual surface 
Fig. 121.— Lingual, Distal and Labial View of Cuspid with Lingual Lug Clasp 
of the cuspid extending about two-thirds of the distance from 
distal to mesial, and from near the gingiva to the incisal third. 
In this cavity an inlay is placed, in which is formed a round- 
bottomed groove extending from its disto-lingual angle to 
near its mesial margin. This groove should be near the gin- 
gival margin of the inlay. The distance between the bottom 
of the groove and the labio-gingival surface of the tooth 
should be less than between that point and the diameter of 
the tooth immediately to the incisal of it. A clasp is now 
adapted to the gingival portion of the tooth as closely as pos- 
sible, and embracing more than one-half of the periphery. A 
piece of iridio-platinum or clasp metal wire is fitted in the 
groove and connected to the clasp by interposing a piece of 
plate or wire, and soldering. 
Usually some other form of specialized frictional appli- 
ance which involved no display of metal labially can be used 
to better advantage than the form of clasp just described. 249 
RETENTION OF PARTIAL DENTURES 
Sometimes the ingenuity of the prosthetist will be taxed to 
the utmost to devise adequate means of retention in partial 
cases. Frequently, although several teeth are present, they 
may not be suitable in form to carry clasps, or be in correct’ 
position to insure denture balance should clasps be adapted 
to them. In such cases specialized frictional appliances can 
usually be applied in some manner so as to develop the re- 
quired stability. 
Specialized Frictional Appliances 
Many forms of specialized frictional retention appliances 
have been devised in an effort to overcome the disadvantages 
and weak points of the various types of clasps commonly used. 
Specifically the main objects sought in devising and using 
these special appliances are, to avoid danger of caries, as well 
as other injuries to the natural teeth; to secure greater sta- 
bility to the denture than can be derived from the use of 
clasps; to produce esthetic restorations of the highest type; 
and finally, to develop a means of retention applicable in cases 
where clasps for any reason are contra-indicated. 
Most of these appliances consist of two parts, and require 
for their application the crowning of, or placing inlays in, one 
or more of the natural teeth. One of the parts is attached 
either directly or indirectly to the crown or inlay, the other 
to the denture. CHAPTER XVI 
TECHNIC OF CLASP CONSTRUCTION 
Axial Contour Forms of Bicuspids and Molars 
The form of the crown of a bicuspid or molar tooth usually 
represents sections of two more or less regular cones re- 
versed, the bases of which meet in a common plane passing 
through the greatest bucco-lingual diameter of the tooth, Cut 
I. The gingival cone is quite regular, since the buccal, lin- 
Cut I 
Fig. 122.— Proximal View of Bicuspid Showing the Occlusal and Gingival Cones 
gual, mesial and distal axial surfaces converge from tlie inter- 
secting mid-plane gingivally. The occlusal cone is less typical 
in form, the buccal and lingual axial surfaces converging 
more or less regularly from the mid-plane (A, B) occlusally, 
while the mesial and distal surfaces are to a greater or less 
extent parallel or divergent. 
An elemental factor of great importance, relative to the 
stability of clasps, should here be mentioned. 
In Cut II let a represent the buccal and b the lingual flange 
of a clasp in sectional area. It will readily be seen that a 
clasp, so adjusted to the occlusal cone, when possessing any 
appreciable grasping properties, will tend to lift or unseat 
the denture from the border. 
Again, a clasp without a stop, adjusted to the gingival 
cone as represented by c, d, Cut ITT, would offer no resistance 
to masticatory stress, and if capable of grasping the tooth, 
250 TECHNIC OF CLASP CONSTRUCTION 
251 
would constantly cause undue pressure of the denture against 
the border. As a result elongation of the tooth or absorption 
of the border must eventually occur. 
Third, let e, f, or g, h, Cuts IV and V, represent a clasp, 
one flange of which embraces the occlusal and the other the 
gingival cone of a tooth. In this case, while passive stability 
Cut II 
Fig. 123.— Clasp Adapted to Occlusal 
Cone of Tooth 
Cut III 
Fig. 124.— Clasp Adapted to Gin- 
gival Cone of Tooth 
may be developed, little or no resistance to movement, either 
gingivally or occlusally, will result. 
It is therefore apparent, that in order to develop maxi- 
mum stability under all conditions, a clasp should embrace 
a portion of each cone base, i, j, Cut VI, on both buccal and 
lingual surfaces of the tooth. While it is not always possible 
to secure this ideal relationship between clasp and tooth, the 
Cut IV 
Fig. 125.— Clasp Adapted to 
Bucco-Occlusal and Linguo- 
Gingival Cone of Tooth 
Cut V 
Fig. 126.— Clasp Adapted to 
Bucco-Gingival and Linguo- 
Occlusal Cone of Tooth 
Cut VI 
Fig. 127.— Clasp Adapted to 
Embrace Both Occlusal and 
Gingival Cones 
principle should be kept in mind, and an effort made to utilize 
it as fully as conditions permit. 
Outline of the Various Steps 
To encourage precise teclmic in the construction of clasps, 
and in the application of these appliances to denture reten- 
tion, the various steps which have proven satisfactory will 
now be given in sequence, with more or less detail. 252 
TECHNIC OF CLASP CONSTRUCTION 
Assuming that the plan of the denture has been deter- 
mined, and that suitable teeth for clasping are present and 
in proper position to insure denture balance, the outline of 
procedures is as follows. 
First — Securing an impression of each tooth to be 
clasped. 
Second — Rebuilding the impression for receiving and re- 
taining the die metal. 
Third — Melting the die metal and casting the die. 
Fourth — Cutting the clasp metal to suitable dimensions. 
Fifth — Consideration of the axial contour forms of bicus- 
pids and molars. 
Sixth — Preliminary concaving of the strip to aid in sur- 
face adaptation. 
Seventh — Securing peripheral adaptation of the strip to 
the die with pliers. 
Eighth — Securing surface adaptation with hammer. 
Ninth — Developing final surface and peripheral adapta- 
tion with pliers. 
Tenth — Soldering stops and anchorage lugs. 
Eleventh — Finishing with files and polishing. 
Twelfth — Securing the correct relation between the 
clasps, the teeth they embrace, and the baseplate. 
Thirteenth — Uniting the several factors of the denture. 
Securing an Impression of the Tooth to Be Clasped 
An impression of the tooth to be clasped, as well as those 
teeth which proximate it, if any are present, should be taken 
in plaster. The impression should include not only the tooth 
crowns but extend well onto the buccal and lingual alveolar 
borders as well. 
By using a small sectional or hinged tray, jointed mesio- 
distally along its occlusal floor, the plaster may be fractured 
and removed in two principal sections. This manner of re- 
moval obviates the breaking of the plaster which surrounds 
the crevices of, and fills the embrasures between, the teeth. 
An improvised cardboard tray, when properly shaped, will 
fulfill the same purpose as a divided metal tray. An ordinary 
metal tray may be used, but should first be oiled before intro- 
ducing the plaster, to permit its ready removal from the im- 
pression before the removal of the latter from the teeth. 
The impression may then be divided and removed, and re- 
turned to the tray, or the parts may be adjusted and the TECHNIC OF CLASP CONSTRUCTION 
253 
impression rebuilt, as subsequently described. In such case, 
the impression should be grooved along its occlusal surface, 
when by pressure outward on the buccal, and inward on the 
lingual parts, it can be easily fractured and removed. 
Fig. 128.— Hinged Tray, with Fractured Impression Closed 
To facilitate the ready fracture of the impression for re- 
moval, on introduction, it should be carried occlusally until 
the floor of the tray touches the cusps, thus reducing the 
Fig. 129.— Impression, Taken with Cardboard Tray 
depth of plaster in this area so that on pressure it will readily 
break. 
Modeling compound is not a suitable material for impres 
sions in clasp work for two reasons; first, because it usually 
distorts in removal, and second, because fusible metal will 
not cast sharply in such an impression. It may, however, be 
Fig. 130.— Sectional Tray Suitable for Impression of an Isolated Tooth 254 
TECHNIC OF CLASP CONSTRUCTION 
employed by the sectional method, when the models are to be 
run in cement or modelite. 
Rebuilding the Impression for Receiving and Retaining 
the Die Metal, When Cast 
An impression of one or more teeth intended for die con- 
struction in clasp work must be rebuilt, or prepared for the 
reception of the die metal. The steps are as follows: 
The impression having been removed from the mouth, the 
fractured surfaces are freed from debris, the broken parts 
replaced in proper relation to each other and luted with sticky 
wax sufficiently to hold them together. No wax should occupy 
any portion of the matrix, as its presence, on pouring the 
molten metal, would generate gas and result in an imperfect 
Fig. 131.— Impression of Tooth to Be Clasped, Taken with Hinged Tray 
casting. By exercising care in handling the assembled im- 
pression the use of wax can frequently be dispensed with. 
To strengthen the assembled impression and hold it firmly 
together a mix of plaster is made and spread on a piece of 
paper on the bench. Into this plastic mass, the impression, 
and tray, if the latter has been used for holding the fractured 
pieces together, should be sunk deeply, and the surplus built 
around the sides and into the ends of the impression to form 
walls for confining the metal in casting. It is frequently 
necessary to make additions to the buccal and lingual margins 
of the impression so as to bring them up to uniform height, 
and give good depth to the die. 
For convenience in clasp construction, the die should be 
from % to 1 inch in diameter across its base and about 1 inch 
in depth. These dimensions insure ease of handling, and TECHNIC OF CLASP CONSTRUCTION 
255 
afford sufficient weight to the die to render hammer blows 
effective when directed against the clasp. A die of these 
dimensions will require about iy2 to 2 ingots of Melotte’s 
metal. The use of too light and small a die is responsible for 
much of the difficulty encountered in clasp construction. 
Fig. 132.— A Rebuilt Impression. Tray and Impression 
Enclosed in Surrounding Plaster 
Since the matrix gives form to the die, with these dimen- 
sions in mind, its formation, by imbedding the impression in 
Fig. 133.— Top View of Rebuilt Impression, Showing Binding 
Wires Still in Position 
plaster as described and by proper trimming, is readily 
accomplished. The usual method of forming the matrix by 
the addition of mouldine is more tedious and less accurate 
than when plaster is employed. Unless firmly luted, the 256 
TECHNIC OF CLASP CONSTRUCTION 
broken parts are very liable to become distorted and wedged 
apart in applying the clay. 
When teeth proximate mesially and distally with the tooth 
to be clasped, the impression of the tooth adjacent to the 
interproximate space through which the clasp is to pass, 
should be filled in with plaster or mouldine, to exclude the 
molten metal in casting. The presence of a tooth in such 
location on the die seriously interferes with clasp construc- 
tion. The other proximating tooth should be developed in the 
casting, as it serves as a guide in finishing the terminal ends 
of the clasp. Any unnecessary irregularities such as high 
points or depressions, present within the matrix, should be 
corrected by trimming or additions as required. The general 
form of the die should be cone shaped, from its base occlusally. 
The impression having been converted into a matrix as 
described it should be closely inspected to see that all essen- 
tial parts are in place, that no loose particles of debris are 
Fig. 134.— Melting Ladle for Fusible Metal 
present, and that no openings exist at any point through 
which the molten metal can escape when cast. 
Drying the plaster matrix before casting the die is not 
essential, since the fused metal, when poured at a low tem- 
perature, generates but little steam, while that which does 
form finds ready exit outwardly through the matrix walls. 
On the other hand, overheated metal cast into a damp or even 
partially dried matrix will cause such rapid generation of 
steam that it cannot all escape before the metal solidifies. 
Casting under such conditions usually results in impaired 
density or deficient sharpness of the die. 
Casting the Die 
Two ingots of Melotte’s metal are placed in a small melt- 
ing ladle and held over the Bunsen flame until a little more 
than half of the mass is fused. The ladle is then removed 
and the half-melted metal stirred with a small instrument or 
flat wooden spatula, to disseminate the accumulated heat 
throughout the mass until all is fused. Stirring also prevents TECIINTC OF CLASP CONSTRUCTION 
257 
liquation of the component metals, which, on account of their 
different specific gravities, gradually occurs. The film of 
oxide which forms on the surface should be skimmed off be- 
fore pouring. 
By watching the surface of the fused metal at its margins, 
it will be seen that the spherical appearance noticeable in 
most metals when fused gradually disappears, and as the tem- 
perature is reduced the alloy will settle squarely against the 
ladle wall. This appearance denotes that the metal, although 
somewhat reduced in temperature, is in its most fluid con 
dition, and when cast will adapt itself to the most irregular 
surfaces. 
Usually in this class of work the casting is deferred until 
the metal begins to lose its fluidity, or is on the point of con- 
gealing, in which condition little or no steam will be gener- 
ated, and a dense, sharp casting may be obtained. 
As soon as the die has hardened it can be quickly chilled 
in cold water, although it will be less brittle if allowed to cool 
slowly. 
When freed from the impression and cooled, the die should 
be inspected for defects. These usually appear as excres- 
cences, due to openings or spaces in the impression, caused 
by loss of broken particles in assembling the impression and 
into which the metal is cast. These defects are filed or chis- 
eled away so as to restore the tooth to correct form. The 
embrasures, when filled in, should be burred or chiseled out 
and the die is ready for use. 
Cutting the Clasp Metal to Suitable Dimensions 
A strip of No. 60 tinfoil, adapted to the tooth with the 
fingers, and by burnishing if necessary, is cut to suitable 
length, and slightly wider than the required clasp, to serve as 
a pattern for cutting the strip of clasp metal. This pattern is 
laid on a piece of clasp plate of the required thickness, length- 
wise of the lamina developed in rolling the ingot into sheet 
form, and its outline marked with a sharp instrument. Fail- 
ure to parallel the clasp with the lamina of the plate usually 
results in fracture of the clasp during construction or under 
slight stress when in use. It also insures greater resiliency 
in the clasp. 
When a stop is to be formed from the same piece of plate 
it should he so indicated on the pattern and the strip cut 
wider at this point. 258 
TECHNIC OF CLASP CONSTRUCTION 
Before beginning to conform the strip of clasp metal to 
the die it should be carefully and uniformly annealed at a 
low, red heat. This reduces its stiffness but does not deprive 
it of all of its resiliency. The full degree of elasticity may be 
restored in the final polishing by subjecting the completed 
clasp, after the final soldering, to the action of a stiff brush 
wheel, on a high speed lathe, and by burnishing. 
PRELIMINARY CONCAVING OF THE STRIP OF CLASP METAL 
When the clasp strip has been cut as described, the first 
preliminary step in adaptation is to concave it from end to 
end with the hawkbill pliers, on that side to be applied to the 
Fig. 136.— Hawkbill Pliers as Applied in Concaving the Strip of Clasp Metal 
tooth. This concave depression embraces the cone bases or 
greatest diameter of the tooth, and permits the occlusal and 
gingival margins of the clasp to rest in contact with the more 
or less convex axial walls of the tooth as peripheral adapta- 
tion is carried on, step by step. 
The terminal end of the strip, which rests in the embras- 
ure and where adaptation is to begin, should be rounded on 
Fig. 136.— Applying the Curved End of Clasp Metal Strip to Tooth 
the gingival edge, curving it so as to parallel the gum mar- 
gin as it rises in the embrasure, where this end of the clasp 
will rest. 
Frequently the convexity of the strip produced by the technic of clasp construction 
259 
hawkbill pliers is greater than that of the axial walls of the 
tooth. The central portion of the clasp will then stand away 
from, while the occlusal and gingival margins will lie in con- 
Fig. 137.— Section of Tooth and Clasp, Showing 
Excess Curvature of Strip 
tact with the axial walls. This is an advantage rather than 
a detriment, as light hammer blows, in subsequent steps, will 
reduce the excess curvature and develop surface adaptation. 
Securing Peripheral Adaptation of the Strip to the Die 
With Pliers 
The peripheral adaptation of a clasp to a die should be 
developed by steps rather than by converting the strip at the 
outset into a partial band of general form by means of the 
clasp benders. The latter method, although most commonly 
followed, is less accurate at the start and in the end will re- 
sult in requiring greater care in securing adaptation than 
where the former method is employed. The following pro- 
cedure is practical, accurate and rapid, when once the technic 
is understood, and the required skill for carrying it out is de- 
veloped. 
The concaved strip, its angle rounded as described, is car- 
ried into the embrasure where it is eventually to rest, and laid 
closely against the axial surface of the tooth. By viewing it 
occlusally, the areas not in contact are readily noted. The 
strip is then removed, held firmly with the fingers near the 
end being adapted and with the hawkbill pliers applied to an 
area not in contact, a positive bend is made in a direction to 
secure the desired adaptation. It should again he returned 
to the die and the change wrought by bending noted. One 
or two additional bends and trials may he required to effect 
reasonably close adaptation of the strip against an area rep- 
resenting about one-sixtli of the tooth periphery. In the same 
manner the strip is grasped somewhat further in from the 
end already conformed, while other bends are similarly made 
until the areas of the clasp not touching the die are brought 
into reasonably close contact. 260 
TECHNIC OF CLASP CONSTRUCTION 
When a torsional bend in the clasp is required, as in turn- 
ing the angles of a bell-crowned tooth, it can be accomplished 
by substituting a pair of pliers for the fingers for holding the 
unadapted strip, the hawkbills being applied to the adapted 
portion, while round or flat beak or another pair of hawkbill 
pliers can be used on the unadapted portion, as the contour 
of the surfaces requires. 
To illustrate the steps as outlined, the adaptation of a 
clasp to an upper first bicuspid will be described. The two 
ends of the clasp will terminate mesially. 
The strip of concaved clasp metal is applied to the mesio- 
buccal angle of the axial surface of the tooth and the areas 
not in contact noted. These are corrected to the crest of the 
Fig. 138.— Clasp Adapted to the First One- 
Sixth of Tooth Periphery 
Fig. 139.— Clasp Adapted to the Buccal 
Surface of the Tooth 
buccal ridge, usually representing a linear distance of about 
three-sixteenths of an inch. Adaptation should then be se- 
cured between the buccal ridge and the disto-buccal angle in 
like manner. Then the turn is made around this angle and 
adaptation secured across the distal surface, to the disto- 
Fig. 140.—- Clasp Adapted to Buccal and 
Distal Surfaces of Tooth 
Fig. 141.— Peripheral Adaptation of 
Clasp Completed 
lingual angle. Prom this point the strip is bent against the 
lingual surface to the center of this side. The final step con- 
sists in turning the mesio-lingual end of the strip into place. 
Thus the process of peripheral adaptation of a clasp consists 
of five, or, in certain cases, seven distinct steps where the 
terminal ends of the clasp require special adaptation in the 
embrasures. 
Securing Surface Adaptation of the Clasp to Die 
With Hammer 
Peripheral adaptation refers to the bending of the strip 
into partial hand form, so that it embraces the periphery of TECHNIC OF CLASP CONSTRUCTION 
261 
the tooth closely throughout its entire length. Peripheral 
contact, however, does not imply that the entire inner: surface 
of the strip is in close adaptation to the die at all points or 
throughout its entire occluso-gingival width. 
Surface adaptation involves not only good peripheral con- 
tact, but close approximation, occluso-gingivally of the par- 
tial band to the axial walls of the tooth or die as well. Per- 
ipheral contact is comparatively easy to develop with suitable 
pliers, but of itself does not afford the required stability in 
the completed clasp. Surface adaptation is essential to sta- 
bility, but is much more difficult to secure, especially in the 
thicker gauges of clasp metal. The preliminary concaving 
Fig. 142.— Riveting Hammer 
of the strip with the hawkbill pliers aids greatly in securing 
surface adaptation. 
Since the concavity of the clasp is more or less uniform in 
curvature from end to end and the axial walls of the tooth 
constantly vary in curvature, it becomes necessary to decrease 
over some and increase over other areas the concavity of the 
clasp. This is most easily accomplished with the small rivet- 
ing hammer. 
The die, when of the dimensions previously mentioned, 
serves the same purpose as an anvil and affords ample resis- 
tance to hammer blows, so that heavy gauges of clasp metal 
are readily conformed to its surfaces under such stress, prop- 
erly applied. 262 
TECHNIC OF CLASP CONSTRUCTION 
To develop surface adaptation, the same order of pro 
cedure as was followed with the pliers is carried out with 
the hammer, the blows being first directed against the mesio 
buccal section of the clasp and continued around to the oppo- 
site terminal. The application of the hammer and the horn 
pene mallet causes the clasp to open, so that from time to 
Fig. 143.-— Melotte’s Horn Pene Hammer 
time it will be necessary to remove it from the die and reduce 
its diameter with pliers and by finger pressure, until it again 
grasps the metal pattern firmly. 
Final Adaptation op the Clasp to the Fie 
When general surface adaptation between clasp and die 
has been secured with the hammer, the final finishing touches TECHNIC OF CLASP CONSTRUCTION 
263 
are given with the pliers. The clasp should grasp the die 
tooth so firmly as to require considerable force to dislodge it. 
Usually a clasp, when transferred from the die to the natural 
tooth in the mouth, will fail to grasp it closely, even though it 
may fit the die perfectly. This is due to the fact that the die 
metal in cooling expands slightly, and therefore the die is in 
reality a trifle larger than the tooth. Correction is easily 
made in adjusting the clasp to the natural tooth in the mouth 
by bending the two flanges slightly toward one another. 
Soldering the Stops and Anchorage Lugs to the Clasp 
When the clasp is constructed without a stop, and it is 
deemed advisable to attach one, the steps are as follows: Cut 
a piece of 22 gauge clasp metal about 1-16 of an inch wide and 
of suitable length to form the hook over the marginal ridge, 
extend gingivally to the ridge and furnish attachment to the 
metal or vulcanite baseplate. The clasp is placed in position 
on the die and with a pair of pliers the strip of metal is con- 
formed as closely as may be to the clasp and die, the final 
adaptation being secured with the hammer. 
The clasp and stop are waxed together in proper relation 
to each other on the die, removed, invested and soldered. 
Final adjustment of the clasp to the die is now made, and the 
position of both the occlusal and gingival ends of the stop bar 
corrected if necessary. That portion of the bar which forms 
the anchorage lug should lie close to the crest of the border, 
somewhat to the lingual so as not to interfere with the placing 
of the artificial teeth. It is frequently necessary to reinforce 
this portion of the bar so as to render it rigid and unyielding, 
and thus obviate distortion of the relation between the clasp 
and denture when subjected to stress. Many clasps, other- 
wise well planned and serviceable, fail because the anchorage 
lugs are weak, lack rigidity and bend under stress. 
FINISHING THE CLASP 
The ends and outer margins of the clasp should be rounded 
and beveled with files and engine discs, and finally polished 
with felt wheels and polishing powders. When properly fin- 
ished, the tendency of the clasp margins to irritate the soft 
tissues of the cheeks and tongue is obviated, and the liability 
of food to accumulate around the appliance is reduced to the 
minimum. 264 
TECHNIC OF CLASP CONSTRUCTION 
Holding the finished clasp for a short time against a stiff 
brush wheel running at high speed will restore the elasticity 
in the metal, which lias become reduced as a result of solder- 
ing operations. Rubbing vigorously with a burnisher will 
also have a similar effect. 
Various Methods of Clasp Construction 
Other methods of clasp construction than those previously 
described are frequently employed to good advantage, some 
of which will here be briefly outlined. 
COMBINATION CLASP OF PURE GOLD WITH CLASP METAL 
Secure an impression of the tooth to be clasped. From 
this develop a model tooth in some good, hard investment 
compound. To this model adapt a piece of pure gold of the 
form of the clasp desired, of 32 or 34 gauge. The adaptation 
can be readily secured first with pliers and finally by burnish- 
ing to the model tooth. On this pure gold foundation apply 
a partial band of clasp metal, slightly narrower than the clasp 
is to be when finished, and usually of 26 gauge. The adapta- 
tion of the strip of clasp metal to the pure gold foundation 
clasp should be reasonably close, but not necessarily perfect. 
Between the pure gold and the clasp metal strengthener flow 
18 carat solder, contouring the outer surfaces of the clasp at 
the same time, as conditions require. The soldering of the 
two pieces is accomplished on the model tooth. This is nec- 
essary, because if removed from the tooth the pure gold foun- 
dation, which is practically devoid of resiliency, would in all 
probability be permanently distorted. Final adaptation, 
which usually consists in slightly reducing the diameter of the 
clasp, can be accomplished in adjusting to the natural tooth. 
The objections to a clasp of this type are, first, the gold 
which embraces the tooth, because of its softness, will in time 
be reduced by wear, and second, the resilient index of such a 
clasp is low in comparison to its bulk. Platinum, or prefer- 
ably iridio-platinum, being slightly harder, can be used to 
better advantage for the foundation than pure gold. 
Cast Clasps 
Clasps of any form desired, including stops and anchor- 
age lugs, can be readily east by the usual technic employed in 
inlay work. Clasps of this type, however, are lacking in resil- TECHNIC OF CLASP CONSTRUCTION 
265 
iency, and on account of the more or less granular or crystal- 
line character the clasp metal assumes when cast, are very 
liable to break under stress. 
The Wire Loop Clasp 
The construction of a round wire clasp is a comparatively 
simple operation. It is essential that a hard, resistant die be 
formed of Melotte’s metal, amalgam or some of the cements, 
to which the wire may be fitted with pliers and by light ham- 
mer blows. 
A plain wire loop clasp, which embraces a little more than 
one-half of the periphery of a tooth, may be readily and 
quickly conformed to the axial walls of the die as follows: 
As a preliminary requirement in such cases, the teeth 
proximating the one to be clasped should be eliminated in 
forming the die so that the latter may stand alone. The wire, 
bent in the form of an elongated loop, is conformed to the 
periphery of the die tooth with pliers. Through the two ends 
of the clasp a strip of 28-gauge German silver plate from 1-16 
to y8 inch wide, depending on the distance apart it is deemed 
advisable to place the occlusal and gingival loops, is threaded 
and doubled back on itself so as to form a loop. With the 
flat-nosed pliers the two ends of the strip are grasped and 
twisted tightly together. The resulting tension draws the 
wire loop clasp tightly around the die. A few light hammer 
blows applied peripherally to the wires will permanently set 
them to the form of the tooth. Stops and anchor lugs are 
attached by soldering as previously described. 
Continuous and Open-Loop Clasp 
A number of new forms of continuous and open wire loop 
clasps have been designed and presented to the profession by 
Dr. F. E. Roach. In many cases clasps of the type under con- 
sideration are most useful and efficient and have the advan- 
tage of extensive peripheral contact with the tooth, while the 
area covered by the clasp is extremely limited. 
A piece of 18-gauge clasp wire for open loop, and 19 or 
20 gauge for continuous loop, is bent in staple form. This 
bend or loop, forms an occlusal rest or stop, when a proximat- 
ing tooth is present. Its principal purpose, however, is to 
connect the buccal and lingual portions of the clasp, which, if 
not so joined, would lack inherent strength. From the occlu- 
sal bend both buccal and lingual wires drop into their respec- 266 
TECHNIC OF CLASP CONSTRUCTION 
tive embrasures to the gingival third of the tooth clasped 
when they are conformed to the buccal and lingual surfaces 
of the tooth, joining on the opposite proximate surface to 
form the anchorage lug. A continuous loop clasp of this type 
can be converted into an open loop clasp by soldering the two 
terminals together, which form the anchorage lug and sever- 
ing the labial or buccal loop. The two terminals may be 
doubled back upon themselves and soldered for greater 
strength or to increase the areal bearing of the clasp if nec- 
essary. The forms of these clasps and their range of appli- 
cation seem limited only by the ingenuity of the operator. 
In applying clasps of any type to a partial denture the 
fact should be borne in mind that clasps are not designed to 
take up the stress of mastication, but merely serve to keep 
the denture seated on its border in speaking and during mas- 
ticatory effort. Thus it will be seen that clasps of this type 
will, in very many cases, fulfill all the requirements efficiently. 
Securing the Relation Between Clasps, the Teeth They 
Embrace and the Baseplate 
When a partial clasp denture is finished and introduced 
in the mouth it should bear evenly and comfortably on the 
tissues and occasion the wearer no distress or inconvenience. 
Each clasp should embrace its respective tooth firmly and yet 
subject it to no leverage, wedging or torsional strain. These 
conditions can only be developed during the constructive 
stages, with skillful technic, by securing the correct relation- 
ship between the clasps, the teeth they embrace and the base- 
plate or denture. The following method is practical and accu- 
rate and should be carried out in the order detailed in most 
cases. The clasps, having been conformed, preferably to 
metal dies, are adjusted to the teeth in the mouth. This step 
proves the accuracy of their adaptation. Should they shift 
in any manner or fail to grasp the tooth firmly, correction 
must be made until satisfactory adaptation is secured before 
proceeding further. They are then removed and the base- 
plate is introduced when each clasp is returned to position on 
its respective tooth. Should either clasp fail to go to correct 
position, the baseplate or clasp, or both, should be filed away 
at the points of interference until each factor can assume its 
correct position without disturbing the other. 
Usually the baseplate should fit snugly against all of the 
teeth involved, including those clasped, the gingival margin TECHNIC OF CLASP CONSTRUCTION 
267 
of each clasp either resting on or clearing the periphery of 
the baseplate, and occupying a position to the occlusal of the 
latter. Variations from this rule are sometimes necessary, as 
in case a tooth crown is extremely short, to insure grasping 
properly it may be necessary to extend the gingival margin 
of the clasp slightly under the free margin of the gum. In 
such instances clearance for the clasp must be gained by filing 
the baseplate to accommodate the former. Such relationship 
between clasp and baseplate, although at times necessary, 
should be avoided when possible because of the liability of the 
clasp to set up gingival or peridental inflammation. 
Taking the Impression of the Clasps, Teeth and Baseplate 
The clasps being in position on the teeth and the base- 
plate firmly seated on the tissues an impression is taken in 
plaster. This need not be extensive, but should fully embrace 
the clasped teeth, both buccally and lingually, and the greater 
portion of the baseplate. 
On removal of the impression each clasp that is not re- 
tained in and removed with it is removed from its tooth, 
brushed free of particles and returned to position in its mat- 
rix. The hinged trays mentioned elsewhere can be used to 
good advantage in taking impressions in this class of work. 
The ends of the clasp are now sprung apart by means of a 
small peg of wood inserted between the buccal and lingual 
flanges to force them against the matrix walls in essentially 
the same relation they occupied in the impression when on the 
tooth. Neglecting to carry out this step usually results in 
permanently establishing an incorrect relationship between 
the clasp and baseplate. In securing a cast from the impres- 
sion, a clasp not properly forced against its matrix walls as 
outlined, instead of embracing the axial walls of the tooth, will 
be found partially imbedded within them. The extent to which 
it is imbedded in the lingual surface of the plaster tooth rep- 
resents the linear movement buccally that has resulted from 
the recoil of the clasp on removal from the tooth. When this 
error occurs, if not corrected, and the clasp is permanently 
attached to the baseplate in such relation, on introduction of 
the denture the tooth clasped will be forced buccally, often- 
times to such an extent as to render the presence of the den- 
ture unbearable. 
The clasps having been adjusted as described, the base- 
plate is set in place in the impression and luted firmly with 268 
TECHNIC OP CLASP CONSTRUCTION 
wax to hold it in place while securing the cast. When var- 
nished the impression is filled with investment compound, and 
the latter allowed time to set hard before removing the im- 
pression. 
Soldering the Clasps to the Baseplate 
The attachment of a clasp to baseplate is accomplished 
by flowing solder along the joint between the two. The extent 
of attachment should be limited, usually to 3-16 of an inch, or 
less. If joined to a much greater extent the clasp becomes a 
rigid, unyielding band and will not fulfill the purpose well 
for which designed. The attachment should be made in as 
nearly central a location between the two terminals of the 
clasp as possible, so as to utilize and not destroy the greatest 
grasping power of the clasp. 
When clasp and baseplate are not in contact, connection 
should be made by inserting a strip of clasp metal or a piece 
of plate in the space between the two and flowing solder over 
all, so as to make a firm and rigid attachment. 
Sometimes when the tooth clasped is long and the space 
between the clasp and plate is quite wide, a rigid wire ex- 
tended lengthwise between the two, the connection being com- 
pleted with solder, will afford a rigid, self-cleansing bond of 
union. 
The essential point to bear in mind in securing the correct 
relationship between clasps, teeth and baseplate is that the 
steps should be carried out as described by assembling the 
appliances in the mouth and securing the impression first 
hand from the tissues against which the denture is to rest. 
Assembling the several parts of the denture on a model, while 
sometimes satisfactory, more often leads to error, sometimes 
so marked as to require reconstruction, or at least reassem- 
bling of the several parts. CHAPTER XVII 
THE MASTICATORY MECHANISM 
At the present time, more than ever before, the fact is 
realized that the masticatory organs are of the most vital 
importance in the maintenance and preservation of health. 
Partial or complete failure of these organs to carry on their 
important functions in the daily routine of life will, sooner 
or later, result in the permanent impairment of other func- 
tions as well. 
When, through accident or by disease, a portion or all of 
the teeth are lost, it is imperative that they be replaced with 
artificial substitutes. Such substitutes should have the ap- 
pearance and perform the functions of the normally arranged 
natural teeth, and no effort should be considered too great 
in order to accomplish these ends. 
The normal arrangement of the teeth in one arch in their 
relation to each other and to the centers of rotation of the 
mandible, insures normal occlusion and correct cusp clearance 
in lateral movements with those in the opposite arch when 
the latter are also so arranged. 
A single tooth, however, when elongated, rotated, or out 
of alignment, may impair the efficiency of the entire masti- 
catory apparatus. It is therefore necessary to study care- 
fully the normal human denture in detail, in both passive and 
active states, to understand what is required in the replace- 
ment of the natural teeth with artificial .substitutes. 
The Masticatory Apparatus 
The normal adult human masticatory apparatus consists 
of four principal factors or groups of hard and soft tissues 
which, when acting conjointly, and in unison on food, reduce 
it to a condition suitable for introduction into the digestive 
tract. One of these factors is practically immovable or pas- 
sive in masticatory effort, except as the cranium itself, of 
which it forms a part, moves. The other three groups are 
active or movable. They may be classed as follows: 
First: The upper maxilla or immovable base. 
Second: The mandible or principal moving factor. 
269 270 
THE MASTICATORY MECHANISM 
Third: The group of muscles which control and guide the 
movements of the mandible. 
Fourth: The group of muscles which control the position 
of the food and keep it within the working limits of the teeth 
in masticatory effort. 
THE UPPER MAXILLA 
The two superior maxillary bones join at the median line 
in a firm, strong suture to form the maxilla. This united 
bone constitutes the anterior portion of the cranial base, be- 
ing directly and indirectly firmly united with all of the other 
cranial bones except the mandible. 
Since the maxilla moves only as the entire cranium is sub 
ject to movement, it may justly be regarded as the base or 
fixed factor of the masticatory apparatus. The upper teeth 
are imbedded in its alveolar process, and against these the 
food is forcibly carried in the process of reduction. 
The body of the bone in general is composed of rather thin, 
frail plates, but these are reinforced at various points where 
stress is heavy by what are termed buttresses. 
The alveolar process in which the teeth are imbedded is 
especially heavy and resistant to stress. This process in turn 
is reinforced by vertical ridges or columns running upward 
and merging into the malar processes opposite the first mo- 
lars, while anteriorly the cuspid eminences pass upward and 
merge into the nasal plates. The tuberosities are supported 
by the thickened perpendicular posterior walls of the maxilla 
itself. 
Each maxillary bone has within its body a cavity known 
as the maxillary sinus, or antrum. The floor of this sinus 
lies immediately over the roots of the second and third molar 
teeth, some of which at times penetrate the bony plate. It 
can thus be seen how easily oral infection may be transmitted 
to the tissue lining the antrum when these teeth contain dis- 
eased pulps. 
The several plates composing the upper maxilla enter into 
the formation of the floor and outer walls of the nasal fossa, 
the palatal vault, floor of the orbit and splieno maxillary 
fissure. 
THE MANDIBLE 
The mandible is the active working factor of the masti- 
catory apparatus. In its alveolar process the lower teeth are 
imbedded, and through its movements they are brought in THE MASTICATORY MECHANISM 
271 
forcible contact with the upper denture in the reduction of 
food. 
When all of the natural teeth are present in a healthy con- 
dition and normally arranged, they constitute a powerful mill, 
capable of cutting, tearing, crushing and grinding all varie- 
ties of food taken into the mouth as such, in a thoroughly 
efficient manner and with comparative ease. 
The mandible is of peculiar form and especially strong 
and rigid within itself, capable of a wide range of movement 
and of fulfilling various functions. 
AUXILIARY FUNCTIONS 
The mandible has various functions and is capable of 
many movements other than those concerned in masticatory 
effort. Indirectly, it assists in phonation by enlarging or 
reducing the size of the oral cavity, and by gauging the dis- 
tance between the upper and lower teeth, the tongue is en- 
abled to assume its proper position in modifying the vocal 
tones as they issue from the larynx. By its various move- 
ments, the mandible assists in giving expression to the face 
in speaking, laughing, and in the exhibition of the various 
emotions. In the lower animals, and occasionally in man, 
when brute instinct dominates his intellect, the masticatory 
apparatus becomes a weapon of offence and defence. 
GENERAL DESCRIPTION OF THE MANDIBLE 
A lever is a rigid arm, capable of turning about a point 
for transmitting force or motion or for applying power to 
overcome resistor,ce. 
A device of this type is composed of three factors, viz.: 
a point or area where power is applied, designated as P; a 
point or area where that force is made available for work 
or weight to he overcome, designated as W; and a point of 
rotation or bearing called the fulcrum and designated as F. 
Levers are divided into three classes, according to the 
position or arrangement of their factors, as follows: 
First Class, P F— W 
Second Class, P W F 
Third Class, W P F 
The mandible is a double lever of the third class; that is 
to say, being double, it has two bearing points which may 
move in unison, forward or slightly backward at the same or 272 
THE MASTICATORY MECHANISM 
different rates of speed, or one may travel in a definite path 
and the other merely act as a rotation center. 
The power is applied between the working area and the 
fulcrum or bearing points. The peculiar form of the bone 
permits of the application of great force, with but little ten- 
dency to tip or become unbalanced in masticatory effort. 
The mandible consists of a body, a thick, flat bone, curved 
on itself in the form of a U and of two perpendicular por- 
tions, called the ramii, which form the extremities. Each 
Fig. 144.— The Mandible 
ramus is surmounted by two eminences, the anterior called the 
coronoid process, to which the temporal muscle is attached, 
and the posterior, called the condyloid process, which forms 
the articular or sliding joint surface. The upper extremity 
or head of the condyloid process is called the condyle, and 
the constricted portion which connects it with the ramus is 
called the neck. 
The upper or articular surface of the condyle is convex 
from before backward, as well as from side to side. It is THE MASTICATOKY MECHANISM 
273 
elliptical in form, the long axis running from without inward 
and slightly backward and downward. 
In general proportions the mandible resembles an equi- 
lateral triangle. Bonwill’s researches led him to believe that 
the average distance from center to center of the condyles 
and from the center of each condyle to the mesi-incisal angles 
of the lower central incisors was approximately four inches, 
these measurements forming an equilateral triangle, and 
hence this has been termed the Bonwill triangle. 
On this basis of measurement he evolved his theory of 
“anatomical articulation” and constructed his “anatomical 
articulator.” 
MOVEMENTS OF THE MANDIBLE 
Because of its peculiar form and the manner of its attach- 
ment to the base of the cranium, the mandible is capable of, 
and subjected to, a great variety of movements. So free and 
varied are these that unless carefully considered they may 
appear to lack co-ordination. 
Although capable of wide range of action, there are but 
three definite movements of the mandible, however, that may 
be considered as important in masticatory effort. These 
should be carefully studied and thoroughly understood by the 
prosthetist in order that the product of his hand, when con- 
structed and subjected to masticatory action, may perform in 
an efficient manner the same functions that are carried out 
by the natural teeth. 
The three important movements mentioned may be out- 
lined as follows: First, a hinge-like movement employed in 
opening and closing the mouth for the introduction, and also 
to a limited extent for the crushing of certain varieties of 
brittle food. 
Second: A protrusive movement employed in the grasp- 
ing and incision of food and in rearranging or changing the 
position of food in the masticatory grooves in process of re- 
duction. 
Third: Right or left lateral movements employed in the 
reduction of fibrous, as well as all varieties of food. These 
movements are the most effective of any described, since by 
their action food can be finely triturated with about one-half 
the expenditure of muscular energy that is required with the 
hinge motion. 
To appreciate these movements in detail it will be neces- 
sary to consider the manner of attachment of the mandible to 274 
THE MASTICATORY MECHANISM 
the cranial base, and the form of articulation of the condyles 
with the temporal bones. 
THE TEMPERO-MANDIBULAR ARTICULATION 
The condyles articulate with the temporal bones, being 
received in elliptical concave depressions, called the glenoid 
fossae, and from which they travel forward; in some cases, to 
a limited extent slightly backward, and from side to side. 
These depressions are situated immediately in front of the 
auditory canals, from which they are separated by a thin, 
bony partition which limits the backward movement. In gen- 
eral contour these fossae resemble, in reverse, the form of the 
articular surfaces of the condyles, the adaptation of the two 
surfaces to each other, however, not necessarily being exact. 
Between each condyle and its dome-shaped socket is inter- 
posed an inter-articular fibro-cartilage, its upper surface con- 
vex, its lower surface concave. Synovial sacs partially enter 
between the cartilage and the condyle. The combined thick- 
ness of the three layers of tissue seldom exceeds 3/32 of an 
inch, and in many cases is less than 1/16 of an inch. 
By bearing in mind the average thickness of these tissues, 
the thickness of the bony plate separating the glenoid fossa 
from the auditory canal and the antero-posterior diameter 
of the condyle, which is usually about % of an inch, the loca- 
tion of the outer end of the condyle in the living subject can 
be determined with comparative accuracy. 
The synovial sac contents lubricate the articular surfaces, 
while the inter-articular fibro cartilage, being but loosely 
attached to and moving forward somewhat with the condyle 
in its movement, reduces friction and acts as a cushion as 
well, when the mandible is subjected to heavy stress. 
At the anterior margin of the glenoid fossa is usually an 
eminence formed by the middle root of the zygoma and called 
the eminentia articularis. 
Viewed from the side, the general contour of the roof of 
the glenoid fossa with that of the articular eminence at its 
anterior margin and with which it imperceptibly merges, is 
that of a compound curve. 
The condyles, in the various opening, closing, protrusive 
and lateral movements of the mandible, are guided by and 
must take the general direction of this concave-convex roof 
THE CONDYLE PATH THE MASTICATORY MECHANISM 
275 
throughout the extent traversed by them in each movement, 
and hence this surface is called the condyle path. 
The condyle path, as before stated, is usually curved, be- 
ing concave posteriorly and convex anteriorly. The central 
portion is approximately a straight line. This portion, the 
central one-half of the path, may be considered, and actually 
is, the working surface which guides the condyle in its move 
ments in carrying the lower against the upper teeth, in their 
protrusive and lateral excursions in masticatory effort. 
For practical purposes, in denture construction it is nec- 
essary to measure or record in some manner the angular in- 
clination of the central or straight portion of the path. When, 
hereafter, it becomes necessary to refer to the inclination, 
Fig. 145.—Variations in Condy'.e Paths, Left Side (Tomes & Dollamore) 
angle of inclination, or pitch, of the condyle path, these terms 
will refer to the central or working surface just described, 
unless otherwise specified. 
VARIATIONS IN THE PITCH OF CONDVLE PATHS 
The condyle paths vary in different individuals and fre- 
quently in the same person, in their length, curvature and 
angular inclination. 
Walker, Christensen, Gysi and many others who have in- 
vestigated on the living subject, vary slightly in their con- 
clusions. Gysi, whose work is perhaps the most thorough 
because of more accurate methods employed, estimates the 
average inclination of the condyle path at 35 degrees. 
Variations ranging from horizontal to a pitch of 72 de- 
grees, as recently recorded by the writer, have been noted. 
It is not uncommon to find a difference of 10 degrees in the 
pitch of the condyle paths of the same individual. 276 
THE MASTICATORY MECHANISM 
The contour and inclination of the condyle paths vary in 
the same individual from infancy to old age, just as the form 
of the mandible is itself modified by the lapse of time. 
Such changes of the condyle path may be ascribed to and 
are influenced by the partial or total lack or loss of the teeth. 
Loss of all of the teeth will result in time in a possible de- 
crease in pitch of the condyle path, the change in the path, 
however, occurring quite gradually. 
The loss of a portion of the teeth may produce a directly 
contrary result. In a specimen in possession of the writer 
the posterior teeth, except third molars on right, were lost a 
number of years prior to the death of the subject. That side 
Fig. 146.— A Skull with Abnormally Deep Glenoid Fossa on Left Side. Mandible Thrown to 
Left. Teeth in Working Relation. Balancing Relation Between Third Molars on 
Right. All Bicuspids and Molars on Right, Except Upper and 
Lower Third Having Been Lost 
of the month on which the loss occurred was useless for mas- 
tication, and consequently it became the moving arm of the 
mandible, or the balancing side of the masticatory apparatus. 
The bicuspids and molars on the opposite side were all pres- 
ent and in good condition and occlusion, while the condyle on 
this, the working side, merely rotated in its fossa. 
Protrusive and lateral movements of the mandible on the 
working side in the opposite direction accomplished nothing. 
So, nature, to maintain the masticatory function in as perfect 
a condition for as long a time as possible, increased the depth 
of the glenoid fossa on the working side by enlarging the 
eminentia articularis and by reducing the pitch of the condyle THE MASTICATORY MECHANISM 
277 
path on the opposite side, as the cusps and planes of the 
various teeth were worn away. 
It has been suggested that the registration of the condyle 
paths and the construction of dentures in accordance with 
such registration is unnecessary, since time and occlusal con- 
ditions of the teeth modify the pitch and form of the paths. 
This view is entirely unscientific as well as unwarranted 
by results in practice. In no instance within the experience 
of the writer has any marked improvement in the way of 
additional lateral movements been observed with the lapse of 
time, when such movements were not possible at first. It is 
not reasonable to suppose, except possibly in rare instances, 
Fig. 147.— A Second View of Preceding Skull, Mandible Thrown to Right. 
No Balancing Contact on Left. No Occlusion on Right 
that any material change does occur, since the artificial teeth 
in such cases are almost invariably arranged without refer- 
ence to future possible lateral mandibular movements. Con- 
sequently, unless the teeth are so assembled as to permit of 
anatomic movements other than simple occlusion at the time 
of constructing the denture, the habit of confining mastica- 
tory effort to the hinge movement alone, becomes perma- 
nently fixed long before any perceptible change occurs in the 
condyle paths. 
The Muscles of Mastication 
The muscles which move the mandible in masticatory 
effort, particularly those which close the jaw, are capable of 278 
THE MASTICATORY MECHANISM 
developing great power. In tests made a number of years 
ago by Dr. Black, with his gnatho-dynamometer, and since 
verified each year in class demonstrations, it was found that 
a force ranging from 150 to 300 lbs. could be developed by 
these muscles and delivered between the lower and upper 
molars. 
The two pairs of muscles, the masseters and temporals, 
furnish most of the power. The internal pterygoids assist 
in closing and also in protrusive movements. 
The masseter muscle is composed of a superficial and a 
deep portion. Each portion has a separate origin and inser- 
tion, and since these vary in position, the direction of the 
fibres of the two layers varies somewhat, and the action of each 
portion is slightly different. 
The superficial layer arises by a tendinous attachment 
from the malar process of the superior maxilla and from the 
anterior two-thirds of the lower border of the zygomatic arch. 
The fibres pass downward and backward and are inserted into 
the angle and lower half of the outer surface of the ramus. 
Its action is to draw the mandible upward and forward. 
The deep portion of the masseter arises from the inner 
surface of the zygomatic arch and from the lower border of 
the posterior third of the zygoma. It is inserted in the upper 
half of the outer surface of the ramus. Its fibres run perpen- 
dicularly downward and its action is to draw the mandible 
upward. 
THE MASSETER MUSCLE 
THE TEMPORAL MUSCLE 
The temporal muscle arises from the temporal ridge on 
the temporal bone, from the under surface of the temporal 
fascia, and from the temporal fossa. Tt is inserted in and 
around the coronoid process of the ramus, some of its fibres 
passing down the anterior margin of the latter as far as the 
third molar. In general outline it is fan-shaped, its origin 
representing a sweeping curve, its fibres converging to their 
point of insertion in the coronoid process. Its action is to 
close the jaw and to draw the condyle backward in its fossa 
when protruded, as in unilateral or bilateral position. 
The external pterygoid muscle has two origins and two 
insertions. The upper head arises from the pterygoid ridge 
THE EXTERNAL PTERYGOID MUSCLE 279 
THE MASTICATORY MECHANISM 
Fig. 148.— A Cut Showing the Direction of Fibres of Various Superficial Muscles Concerned 
in Facial Expression (Eckley’s Regional Anatomy) 280 
THE MASTICATORY MECHANISM 
of the outer and under surface of the greater ala of the sphe- 
noid bone. Its insertion is in the anterior margin of the in- 
terarticular fibro-cartilage, which covers the articular surface 
of the condyle. Its function is to draw the cartilage forward 
in the protrusive movements of the mandible, thus furnishing 
a concave cap for the condyle to rest in as it is carried for- 
ward onto the eminential articularis. 
Eckley attributes the cracking noise frequently noticed 
in the tempero-mandibular joint to partial or complete par- 
alysis of this portion of the pterygoid, which results in failure 
of the muscle to draw the cartilage forward in unison with the 
condyle and permits the latter, in its forward excursions, to 
override the anterior rim of the cartilage. 
The lower head of the external pterygoid muscle.has its 
origin in the outer surface of the external pterygoid plate of 
the sphenoid bone. It is inserted in the anterior surface of 
the neck of the condyle. 
The function of the muscle is extremely important. By its 
action principally, the mandible is given a lateral movement 
and with its mate on the opposite side protrusion is accom- 
plished. These muscles are not large as compared with the 
temporals and masseters, nor do they develop very great 
power, since that is unnecessary. 
The crushing of food is accomplished hv the masseter, 
temporal and internal pterygoid muscles in drawing the man- 
dible back to normal position, after having been carried lat- 
erally or forward by the external pterygoids. 
The combined action of the upper and lower portions of 
the external pterygoid muscle is to draw the condyle and its 
interarticular fibro-cartilage forward simultaneously. 
THE INTERNAL PTERYGOID MUSCLE 
The internal pterygoid has its origin on the inner surface 
of the external pterygoid plate, from the tuberosity of the 
palate bone. Tt passes downward and backward and is in- 
serted in the inner surface of the mandible from the mylohyoid 
ridge and the inferior dental canal downward to the angle of 
the ramus. Its action is to assist in closing the jaw and 
bringing it back to normal from lateral position, in the latter 
function assisting the posterior fibres of the temporal muscle 
on the opposite side. THE MASTICATORY MECHANISM 
Fig. 149.— The Temporal Muscle, Showing Direction of Its Various Fibres 
(Eckley’s Regional Anatomy) 282 
THE MASTICATORY MECHANISM 
The jaw is opened by the mylohyoid, genio-liyoid, genio- 
hyo-glossus, digastric muscles and gravity. In fact, most of 
the supra and infra hyoid muscles take part in the depression 
of the mandible. The hyoid bone acts as a movable fulcrum 
when the jaw is opened widely. The supra hyoid muscles 
contract and tend to lift the hyoid bone upward and draw the 
MUSCLES WHICH DEPRESS THE MANDIBLE 
Fig. 150.— Direction of Fibres of Internal and External Pterygoid Muscles 
(Eckley’s Regional Anatomy) 
mandible downward. This tendency is counterbalanced by the 
action of the infra hyoid muscles, which depress or at least 
make rigid the hyoid bone, so that the upper muscles may act 
effectively. 
Depression of the mandible, which is equivalent to open- 
ing the mouth, results in the drawing forward of the condyles 
in their paths, as well as in a greater or less rotary movement 
of their articular surfaces. THE MASTICATORY MECHANISM 
283 
Iii other words, the centers of rotation in the hinge action 
do not lie in the transverse centers of the condyles, but are 
situated about three-fourths of an inch below and slightly 
back of the distal margins of the rami. Even this location 
is variable in the same individual under different conditions, 
depending on the distance the mandible is depressed, and also 
whether it has been subjected to protrusive as well as open- 
ing movements. 
This is explained by Gysi as follows: 
“If a man were suspended in the air by ropes attached 
to each of his hands he could be pulled hither and thither by 
tugging at either rope. His body would describe certain mo- 
tions accordingly as force was applied to one rope or another. 
If an architect were to chart the motions described by the 
man’s body, he would find them to be sections of curves, with 
centers at the points where the opposing curves met, not at 
the points to which the ropes were attached to the wrists. 
When he found these points, he would probably call them 
‘centers of motion.’ 
“That illustration of the man suspended by ropes attached 
to each wrist is not much unlike the suspension of the jaw 
by ligaments attached to the heads and necks of the condyles. 
The articulation of the condyles with their fossae is very 
loose; a sort of hanging attachment. The jaw may be pulled 
in any direction by tension of the proper muscles, and when 
it moves it swings just as the man’s body did, not ivitli its 
center at the condyles, hut at the points where opposing pulls 
meet and balance each other/’ 
Bowditch and Luce, in 1899, and Walker in 1894, first 
called attention to the fact that the head of the condyle moved 
forward, and the angle of the ramus moved backward, in wide 
open movements. Others have since verified the accuracy of 
these first experiments. No special value attaches to the reg- 
istration of wide open jaw movements, since they have no 
bearing on occlusion. Any movement of the mandible, how- 
ever, which can be registered, increases the sum total of 
knowledge of the human dental mechanism and aids in solving 
this most intricate problem. 
Muscles Which Control the Position of Food 
This group includes the lips, cheeks, palatal and tongue 
muscles, which when co-ordinating, control the position of 
food and tend to keep it within the working limits of the 
teeth. 284 
THE MASTICATORY MECHANISM 
Specifically, the buccinators on the sides and the orbicu- 
laris oris in front, confine the food to a great extent and pre- 
vent it from being forced outward into the vestibule during 
masticatory effort. Within the oral cavity proper the tongue 
moves the bolus of food outwardly and as the mandible is 
depressed, moved laterally, elevated and the teetli brought 
together, the lingual marginal ridges shear off a portion, 
which is caught, confined, and reduced in the masticatory 
groove between the teeth as the mandible is returned to nor- 
mal from the unilateral position. 
SUMMARY OF MUSCULAR ACTION ON THE MANDIBLE 
Mylo-hyoid 
Genio-liyoid 
Genio-hyo glossus 
Infra-hyoid muscles 
Digastric 
Gravity 
Depression, or 
opening of mouth 
Elevation, or 
closure of mouth 
Temporals 
Masseters 
Internal pterygoids 
External pterygoids 
Internal pterygoids 
Masseters — superficial fibres 
Protrusion, 
bilateral 
Protrusion, 
unilateral 
External pterygoid )On protrud 
Internal pterygoid side 
Masseter — superficial fibres 
Retrusion, 
bilateral 
Temporals — posterior fibres 
Masseters — deep fibres 
Temporal — posterior fibres 
Masseters — deep fibres 
Internal pterygoid on 
opposite side. 
Retrusion, 
unilateral 
THE MANDIBULAR LIGAMENTS 
In addition to the muscles actuating the mandible, some 
of which in a state of rest tend to hold the condyles in their 
fossa?, there are three pairs of ligaments, which limit its 
range of movement and yet permit a variety of excursions THE MASTICATORY MECHANISM 
285 
to be carried out with freedom. These ligaments are as 
follows: 
The capsular ligament, divided into four parts — an an- 
terior, posterior, external and internal segment. 
The spheno-mandibular, or long internal lateral ligament. 
The stylo-mandibular ligament. 
Fig. 151.— The Capsular Ligament, External View (Deaver) 
THE CAPSULAR LIGAMENT 
The anterior and posterior portions of the capsular liga- 
ment are composed of thin layers of loose, flabby fibres. An- 
teriorly, these fibres are inserted into the anterior margin of 
the interarticular fibro-cartilage, from which they extend up- 
ward and downward. The upper fibres are attached to the 286 
THE MASTICATORY MECHANISM 
front of the eminentia articularis, the lower fibres to the an- 
terior margin of the condyle. 
The posterior fibres are attached to the margin of the 
glenoid fissure and from there extend to and are inserted in 
the posterior surface of the ramus below the neck of the 
condyle. 
Since the condyle movements to a great extent are for- 
ward, it can readily be seen that the anterior and posterior 
fibres of this ligament must be loose to give freedom of action 
to the mandible. 
THE EXTERNAL LATERAL LIGAMENT 
The external lateral ligament forms the outer portion of 
the capsular ligament, its fibres blending with the anterior 
and posterior portions of the latter. This ligament is the 
strongest part of the capsule. It has a broad attachment 
above to the zygoma and is inserted in the outer surface of 
the condyle neck. 
THE INTERNAL LATERAL LIGAMENT 
The short internal lateral ligament completes the capsule. 
Its fibres are attached above to the inner margin of the glen- 
oid fossa and to the spine of the sphenoid bone. It is inserted 
in the inner side of the condyle neck. 
The four portions of the capsular ligament, by the blend- 
ing of their fibres, encapsule the joint. Within this capsule 
is enclosed the interarticular fibro-cartilage, the capsular 
fibres being more or less closely attached to the cartilage 
around its periphery. 
THE SPHENO-MANDIBULAR LIGAMENT 
This ligament is also called the long internal lateral liga- 
ment to distinguish it from the short internal lateral liga- 
ment which forms a part of the capsule. 
It is attached to the spine of the sphenoid bone, from 
which it extends downward and is inserted in the mandibular 
spine and a portion of the area immediately surrounding the 
posterior dental foramen. 
THE STYLO-MANDIBULAR LIGAMENT 
The stylo-mandibular ligament is attached to the styloid 
process of the temporal bone, its fibres passing downward to THE MASTICATORY MECHANISM 
287 
find insertion in the posterior border and angle of the ramus, 
between the masseter externally and the internal pterygoid 
internally. 
These several ligaments being practically devoid of elas- 
ticity, resemble so many cables by which the mandible is sus- 
pended from the base of the cranium. They limit the action 
of the various muscles concerned in protrusion, lateral and 
Fig. 152.— Internal View of the Spheno-Mandibular and Stylo-Mandibular 
Ligaments (Deaver) 
wide-open movements. Without their restricting influence, 
the possibilities of useless mandibular movements can scarcely 
be conceived. 
Usually in dislocations of the mandible, the posterior 
fibres of the capsular ligament are broken by the excessive 
strain to which they are subjected, and as they seldom if ever 
again unite, recurrent dislocations in the same subject are 
frequent. 288 
THE MASTICATORY MECHANISM 
The Teeth 
The normal adult denture consists of thirty-two teeth, six- 
teen in the upper and a like number in the lower jaw, the 
formula of which is as follows: 
M. 
B. 
C. 
I. 
I. 
C. 
B. 
M. 
3 
2 
1 
2 
2 
1 
2 
3 
3 
2 
1 
2 
2 
1 
2 
3 
FRICTIONAL OR WORKING SURFACES OF THE TEETH 
Those surfaces of the bicuspids and molars in one arch 
presenting toward those in the opposite arch are known as 
occlusal surfaces, from occlude, which means to shut or close 
together. 
Those surfaces or edges of the incisors and cuspids in 
one arch presenting toward those in the opposite arch are 
called incisal surfaces or edges, from incise, which means to 
cut. 
Each cuspid tooth terminates in a point or cusp, with in- 
cisal edges, sloping away from it mesially and distally to the 
mesio and disto-incisal angles of the tooth. 
OCCLUSAL SURFACE MARKINGS 
The occlusal surfaces of the bicuspids and molars are 
made up of cusps, inclined planes, grooves, pits and ridges, 
displayed with more or less definite regularity. 
THE CENTRAL SULCUS OR MESIO-DISTAL GROOVE OF THE BICUSPID 
AND MOLAR TEETH 
Traversing tlie occlusal surface of each bicuspid and 
molar tooth, mesio-distally, is a general depression, or sulcus, 
formed by the planes, which slope lingually from the buccal, 
and buccally from the lingual, marginal ridges. 
These planes meet at varying angles near the center of 
the tooth, to form definite grooves. The grooves, which cross 
the mesial and distal marginal ridges, are accordingly named 
mesial and distal marginal grooves, and that which divides 
the central portion of the tooth is called the central groove. 
In normal occlusion these general depressions or sulci in 
the upper teeth receive the buccal cusps and marginal ridges 
of the lower teeth, while the central sulci of the lower teeth 
receive the lingual cusps and marginal ridges of the upper 
teeth. THE MASTICATORY MECHANISM 
289 
THE BUCCO-LINGUAL GROOVES 
In addition to the central grooves mentioned, the various 
cusps, and planes sloping away from them mesially and dis- 
tally, result in the formation of other grooves, which traverse 
the occlusal surfaces of the teeth from buccal to lingual. 
Fig. 153.— Diagram Showing the Relation of Lower to Upper 
Molars When Occluded 
Fig. 154.—- Section of Mandible and Maxilla, Showing Upper 
and Lower Teeth in Occlusion, Distal View 
These grooves run nearly at right angles to the mesio-distal 
grooves, the buccal being slightly in advance of the lingual 
end. 
Each pair of cusps, as, for instance, the mesio-buccal ana 
mesio-lingual cusps of the upper first molar, are situated 
approximately the same distance from the mandibular rota- 290 
THE MASTICATORY MECHANISM 
tion center of that side of the arch. The planes, sloping away 
from these cusps mesially and distally until they meet in the 
central groove, and finally merging with those from the adja- 
cent pairs of cusps, enter into the formation of grooves, which 
represent arcs of circles, also developed from the same rota- 
tion centers. This arc-like or geometrical bucco-lingual 
arrangement of cusps, ridges and grooves of the upper teeth 
permits the cusps and sloping planes of the occluding lower 
teeth, which bear a similar relation to the rotation center, to 
be moved freely back and forth, in the lateral swing of the 
mandible, without cusp interference. 
Fig. 155.— Anterior View of Upper and Lower Teeth in Occlusion 
THE MASTICATORY OR RECTANGULAR GROOVE 
When the mandible is rotated laterally, so as to bring the 
buccal cusps and marginal ridges of the lower teeth on the 
pivotal side outward from the central sulci of the upper teeth, 
and directly under the corresponding cusps and marginal 
ridges of the latter, a fairly close and unbroken line of con- 
tact between these wedge-like ridges is effected. 
At the same time the lingual cusps and marginal ridges 
of both lower and upper teeth on the same side are brought 
into similarly close contact. A rectangular space is thus 
formed, bounded above and below by the occlusal surfaces 
of the upper and lower teeth, and laterally by their buccal 
and lingual marginal ridges. This groove extends from the THE masticatory mechanism 
291 
first bicuspid to the third molar, inclusive, when present, and 
forms the receptacle in which food is held and crushed as 
the mandible is drawn back to normal position. The form 
and proportions of this masticatory groove are of the greatest 
importance. The efficiency of the masticatory apparatus is 
largely dependent on the width of this space hucco lingually; 
the wider it is, within normal limits, the greater the radial 
swing possible for the mandible and the more efficient its 
effort in the reduction of food. 
The definiteness of the angles of the marginal ridges which 
are formed by the junction of the buccal and lingual surfaces 
of the teeth with the various planes sloping to the central 
grooves is also important. These angles should not he too 
sharp, as the tongue and cheek muscles are liable to be caught 
between them and injured in masticatory effort. 
The closeness of apposition of the various occlusal planes 
and marginal ridges of the lower to those of the upper teeth, 
not only in occlusion, hut in radial movements of the mandible 
as well, increases efficiency in both natural and artificial den- 
tures. When loosely approximated, or possibly when only 
a few cusps or surfaces are in actual contact, the food is 
merely punctured, and the fibers are not torn asunder, as is 
the case when many planes and cusps find contact with those 
of the opposite teeth. 
Arrangement of the Teeth in the Dental Arches 
OCCLUSAL VIEW 
Viewed occlusally, the arrangement of the teeth in each 
dental arch presents the general appearance of a parabolic 
curve, or in some cases that of a half ellipse, the central in- 
cisors being at the outer extremity of the major half axis. 
The size and outline form of the curve vary in different indi- 
viduals, according to structural build. 
Since normally, the upper overlap the lower teeth to a 
greater or less extent, the curve of the upper arch is slightly 
larger than that of the lower arch. 
THE ANTERIOR CURVATURE, INCISAL VIEW 
The four incisors at their cutting edges usually present 
a symmetrically curved arrangement. The laterals may be 
slightly in or out of a true curved alignment, or, when a trifle 292 
THE MASTICATORY MECHANISM 
rotated, as is frequently the case, their mesio-linguo-incisal 
angles may overlap the disto-labial surfaces of the central 
incisors. The variations noted, when not too pronounced, are 
pleasing rather than otherwise, and give character and indi- 
viduality to the denture. 
The cutting edges of the cuspids usually are in symmet- 
rical labial alignment with the incisors. On account of the 
Fig. 156.— Upper and Lower Natural Dentures, Showing the Parabolic 
Forms of the Arches 
greater convexity of tlie labial face of the cuspids, as com- 
pared with the incisors, these surfaces stand out more or less 
prominently beyond the labial surfaces of the latter, especi- 
ally at their cervices. 
The cuspids are the corners of the dental arches, the labial 
curvature of the incisors merging here with the straighter 
alignment of the posterior teeth. The general form, size and THE MASTICATORY MECHANISM 
293 
position of the cuspids, therefore, give them greater promi- 
nence than any of the anterior teeth. 
ALIGNMENT OF THE POSTERIOR TEETH 
From the cuspids, to and including the first molars, the 
teeth are arranged in practically straight lines, which in pass- 
ing backward diverge. If projected, these lines would usually 
fall within and below the inner ends of the condyles. 
The second and third molars frequently curve inward 
somewhat to the lingual of these lines,*an arrangement which 
gives the general arch its parabolic or elliptical form. This 
inward curvature of the second and third molars is necessary 
to avoid contact of thin buccal surfaces with the coronoid 
processes of the mandible in its lateral and wide-open move- 
ments. 
When viewed anteriorly, less than one-fourth of the first 
bicuspids, taking their bucco-lingual diameters as a basis, are 
visible back of the cuspids. The second bicuspids exhibit 
about the same amount of surface as do the first bicuspids. 
This retiring position of the bicuspids adds very much to the 
esthetic appearance of the denture, particularly in the upper 
arch. 
Buccal View of the Upper Dental Arch 
THE PLANE OF OCCLUSION 
In normal occlusion the line of contact of the lower with 
the upper bicuspids and molars is called the plane of occlu- 
sion, for here their occlusal surfaces meet in normal closure 
as well as in lateral movements of the mandible. 
The general direction and position of the plane of occlu- 
sion is approximately parallel with, and about an inch below, 
a straight line extending from the base of the nose to the cen- 
ter of the condyle. 
CURVATURE OF THE OCCLUSAL PLANE 
In reality, however, the occlusal plane usually departs 
from a straight line, the second bicuspid, first, second and 
third molars curving upward toward the glenoid fossa, in 
most cases, in a fairly well-defined arc, the convexity pre- 
senting downward. 
The amount of curvature of the occlusal plane varies in 294 
THE MASTICATORY MECHANISM 
different individuals, and frequently there is a noticeable dif- 
ference in the planes on the two sides of the arch in the same 
subject. 
The curvature varies from a well-defined arc in most cases 
to a nearly or quite flat plane in a few instances. A few cases 
have come under the notice of the writer where the curvature 
of the occlusal planes was reversed. In other words, instead 
of the convexity presenting downward, the occlusal plane was 
concaved upward. Such cases are rare, however, and, within 
Fig. 157.— Buccal View of the Natural Dentures in Occlusion 
the writer’s observation, only occur when the occlusion is 
abnormal, the teeth in the lower protruding beyond those in 
the upper arch. 
Relationship of the Planes of Occlusion to the 
Condyle Paths 
The planes of occlusion and the condyle paths bear a defi- 
nite relationship to each other, as the following problems will 
demonstrate: 
First. On a photograph of a skull in which the teeth are 
normally occluded, strike an arc intersecting the tips of the 
buccal cusps of the bicuspids and molars. The center from 
which this arc is developed must be located by trial. This 
can easily be done when the curvature is pronounced, as the 
center will lie in the region of the frontal prominences. It THE MASTICATORY MECHANISM 
295 
will be more difficult to locate the center in those cases where 
the occlusal planes are nearly or quite flat, because its posi- 
tion will be higher up, beyond the range of the ordinary 
dividers. 
Second. Place one leg of the divider on the center from 
which the occlusal arc was developed; set the other leg on 
the margin of the middle half of the condyle path, and strike 
an arc in this location. It will be found that the arc last de- 
veloped will coincide with the condyle path along its working 
area, and, furthermore, that it will be parallel with the occlu- 
sal arc, since both are developed from the same center. These 
arcs may coincide, or, as is more commonly the case, be con- 
centric, the condyle arc lying above and within the one inter- 
secting the tips of the teeth. 
Governing Factors in Mandibular Movements 
The mandibular movements which are of the greatest im- 
portance to the prosthetist are those which bring the lower 
in contact with the upper teeth in some of their varied lateral 
and protrusive excursions. 
Any movement which, even to a slight degree, causes 
separation of the entire lower from the upper denture can 
have no bearing on occlusal conditions, and therefore need 
not here be considered. The excursions of the condyles in 
their paths in wide-open movements, however, are of impor- 
tance in certain technical procedures, which will later be men- 
tioned. 
There are three definite and comparatively fixed factors 
which guide the mandible in its protrusive movements. These 
are the incisor path and the two condyle paths. 
THE INCISOR PATH 
Protrusion of the mandible carries the incisal edges of the 
lower anterior teeth forward and downward against the lin- 
gual surfaces of the corresponding upper teeth. If projected 
sufficiently far forward their incisal edges will occlude with 
those of the upper teeth in an end-to-end relation. The dis- 
tance traversed by the incisal edges of the lower teeth from 
the position of rest, or normal occlusion, to that of edge-to- 
edge contact or incision is known as the incisor path. It is 
obvious that this path controls the movements of the mandible 
anteriorly, since,- with the exception of the last molars in 
occlusion, the remaining bicuspids and molars in one arch 296 
THE MASTICATORY MECHANISM 
are not usually in contact witli those in the opposite arch in 
protrusive effort. 
THE CONDYLE MOVEMENT IN PROTRUSION 
As the mandible is drawn forward in protrusion, the con- 
dyles, being held in close contact with their paths by the var- 
ious mandibular muscles and ligaments, must follow closely 
the direction of the condyle tracts, whatever may be their 
form or pitch. It naturally follows that these tracts deter- 
mine the movements of the mandible posteriorly. 
These three guiding factors in protrusive effort, the in- 
cisor path and the two condyle paths, are located one at each 
angle of the equilateral triangle, to which attention has pre- 
viously been directed. 
THE FUNCTION OF THE INCISOR TEETH IN PROTRUSIVE 
EFFORT 
Prehension, or tlie seizing hold of food by the teeth, is the 
first act in masticatory effort. 
Incision, or the cutting off of a portion of suitable size for 
reduction by the bicuspids and molars, is the second act. 
These functions are performed by depressing, protruding 
and raising the mandible while protruded, so as to bring the 
anterior teeth together in edge-to-edge contact, with final re- 
turn of the mandible to normal position and the teeth to nor- 
mal occlusion. The final act of retrusion, as outlined, shears 
off those portions of the morsel of food not completely sev- 
ered by direct incisive effort. Only the anterior teeth are 
concerned in the actual work accomplished. 
Since, then, the focus of useful effort is confined solely to 
the incisors and cuspids, there is no necessity for the bicus- 
pids and molars of the lower coming in contact with those 
in the upper arch in the incisive act, except at the extreme 
distal portion of the arches. Here the last lower molars, 
which normally occlude (the second molars, usually when the 
third molars are not fully erupted or are missing), move for- 
ward in sliding contact with those in the upper arch. Contact 
of the molars in this region does not increase the feld of 
effort or working area, since no food is being reduced here. 
Tt serves the purpose, however, of steadying or balancing the 
denture, and further of distributing or equalizing the force 
of closure, thus avoiding the undue stress that would be ex- 
erted on the central portion of each lateral half of the man- 297 
THE MASTICATORY MECHANISM 
dible if the incisor teeth and condyle, without such central 
bearing points, were required to sustain all of the force of 
masticatory incisive effort. 
LATERAL MOVEMENTS OF THE MANDIBLE 
In actual masticatory effort the lateral mandibular move- 
ments are the most important and effective of any of those 
mentioned. By such movements the food is crushed, torn 
asunder, finely triturated and insalivated as it cannot be in 
any other manner or by any other action. Food subjected to 
the hinge action is merely punctured, or at most slightly 
crushed. It cannot be torn and shredded as when caught be- 
tween sliding contact surfaces, any more than can wheat be 
reduced to flour by the lifting and dropping of the upper upon 
the lower millstone. Flour is produced by the grains of wheat 
being caught and broken up from contact with many sliding 
surfaces. So food, when caught and confined in the mastica- 
tory groove, is torn asunder by being brought in contact with 
the many sliding planes of the opposing teeth. 
To produce artificial dentures that will fulfill the func- 
tions of the natural masticatory organs it will be necessary 
to study the radial swing of the mandible and the relation 
of the teeth in the lower to those in the upper arch when sub- 
jected to such action. 
Analysis of the Lateral Mandibular Movements 
In the lateral movements one condyle is drawn forward, 
or protruded in its path, while the other remains compara 
tively stationary, serving, in a general way, as a pivotal or 
rotation center to guide the mandible in its radial movements. 
THE CENTERS OF MANDIBULAR ROTATION 
The centers of the condyles may be, and frequently are, 
the true centers of mandibular rotation. Oftentimes, how- 
ever, the rotation centers are situated inside or outside of the 
condyle centers at varying distances. Both actual rotation 
centers may be inside, or both outside, of the condyles, or one 
may be inside and the other outside, or, again, one may he 
located in the true condyle center and the other outside or 
inside of the opposite condyle. To determine their exact 298 
THE MASTICATORY MECHANISM 
location special appliances designed for such purposes must 
be used, the most accurate as well as convenient of which are 
those suggested by Dr. Gysi. 
When the rotation centers are located between the con- 
dyles the pivotal condyle has a slight backward movement 
as the other one is protruded. When the rotation centers are 
located outside the pivotal condyle moves slightly forward. 
Gysi’s appliances indicate that the true rotation centers 
may lie within two and tliree-fourtlis inches of each other, 
Fig. 158.— Diagram Showing Direction of Movement of Teeth from Various Rotation 
Centers, A, B, C — D, E, F 
and vary from that distance anywhere up to a trifle over five 
inches apart. 
The position of the teeth in the arches and of their var- 
ious occlusal surface markings in relation to the rotation cen- 
ters is of extreme importance. When the teeth are incor- 
rectly located co-ordinate movements between those in the 
lower against those in the upper ai*ch will be inhibited. 
RELATION OF THE LOWER TO THE UPPER TEETH ON 
THE PIVOTAL SIDE 
The working limit of the mandible in lateral masticatory 
effort is reached when the buccal and lingual cusps and mar- THE MASTICATORY MECHANISM 
299 
ginal ridges of the lower bicuspids and molars, on the pivotal 
side, are directly under and in contact with the correspond- 
ing cusps and marginal ridges of the upper teeth. 
The amount of side movement necessary to bring the teeth 
in this relation to form the masticatory space was designated 
the ‘‘differential limit” by the late Dr. T. W. Pritchett. Used 
in this sense, it means the limit of side movement of the teeth 
for doing effective work, and is a very appropriate term. 
“Differential” means a difference in rate or distances of 
movement of the parts of a mechanism in a given period. In 
true rotary movements of the mandible laterally the bicuspids 
travel a greater distance in the same period than do the molar 
teeth, since the former are situated farther from the rotation 
center. 
SIDE MOVEMENTS OF THE MANDIBLE NOT CONTROLLED BY 
THE ROTATING CENTERS 
In reality the rotation centers do not absolutely confine 
the mandible to an exact radial swing at all times or under 
all circumstances. Dr. Bennett of London has shown that 
there is frequently a side movement of the entire mandible 
independent of the ordinary rotation points. 
In some experiments carried out by the writer this side 
movement was found to be involuntary, or automatic, in some, 
and entirely volitional in other cases. In most instances it 
is so slight as to be of little importance in general masticatory 
effort, and need not be considered in denture construction as 
a separate or vital factor. 
A method of adapting artificial dentures to this side move- 
ment, when present and involuntary, will later on be de- 
scribed. 
RELATION OF THE LOWER TO THE UPPER TEETH ON THE 
PROTRUDED SIDE 
The lateral movement of the mandible carries the lower 
teeth on the protruded side lingually. During this movement 
the disto-buccal cusp of the lower second molar moves along 
the inclined planes leading from the central sulcus to the lin- 
gual marginal ridge of the upper second molar, and there 
finds contact with its mesio-lingual cusp. This is known as 
the balancing contact, and this, the protruded side of the man- 
dible, is known as the balancing side, in contradistinction to 
the opposite, or pivotal, side, which is the masticating or 
working side. 300 
THE MASTICATORY MECHANISM 
Balancing contact, as just stated, is usually developed be- 
tween the lower and upper second molars. Similar contact, 
however, may be developed between the lower and upper 
third molars, when fully erupted, although it frequently hap- 
pens that these teeth, even after a lapse of many years, fail 
to come into normal occlusion with each other. For this 
reason, therefore, balancing contact is most commonly devel- 
oped and remains most persistent between the lower and 
upper second molars. In radial movements of the mandible 
no contact exists, nor is any essential to the balancing of the 
masticatory apparatus, from the second molar forward to the 
opposite central, or even lateral, incisors. The actual work 
of mastication is being performed on the opposite of the 
mouth, and therefore the close interlocking of planes and 
cusps on the protruded side, exclusive of the balancing point, 
would tend to disturb, rather than aid, masticatory effort. 
THE COMPENSATING CURVE 
As previously stated, tlie tips of the buccal cusps of the 
bicuspids and molars, when viewed buccally, assume a curved 
arrangement, the convexity being downward. This curved 
arrangement of the teeth in the upper arch is called the com- 
pensating curve. The reason for it being so designated is as 
follows: 
When the occlusal plane is flat, and the condyle path is 
inclined downward and forward, separation occurs between 
the lower and upper bicuspids and molars in lateral move- 
ment, the lower teeth being carried downward to the lingual 
and away from the upper teeth on the protruded side. Bal- 
ancing contact, therefore, is not possible under such condi- 
tions, because of inco-ordinate movements the occlusal planes 
of the upper teeth being practically horizontal while the occlu- 
sal planes of the lower teeth are carried downward in an 
angular direction by the condylar movements. When ar- 
ranged on a proper curve, however, the disto-buccal cusp of 
the lower second molar occupies a higher position in the occlu- 
sal plane than the mesio-lingual cusp of the upper second 
molar, which occupies a position forward, downward and to 
the lingual in the occlusal plane. In lateral movements the 
disto-buccal cusps of the lower second molar move down- 
ward, forward and lingually, in contact with the plane lead- 
ing from the central groove to the mesio-lingual cusp of the 
upper second molar. THE MASTICATORY MECHANISM 
301 
This balancing area is present, and the disto-buccal cusp 
of the lower second molar, under normal conditions, is in con- 
tact with it at some point throughout the entire lateral excur- 
sion of the condyle, both out of and back to its fossa. 
The curved arrangement of the upper teeth, therefore, 
compensates for the dropping down of the condyle in its path 
in radial and forward movements, and makes possible the 
Fig. 159.— Diagram Showing Parallel Relation of Condyle Path and Compensating Curve 
contact just described. While tlie compensating curve rep- 
resents a fairly accurate arc where it intersects the tips of 
the buccal cusps of the bicuspids and molars, when projected 
forward, it passes above the incisal edges of the anterior teeth 
sometimes as high as the incisal third of the central incisors. 
This is due to the overlapping of the upper anterior over the 
lower teeth, there being a more or less definite correlation 
existing between the curvature of the teeth plane and the 
overbite. Variations as to the amount of overbite naturally 
occur, one of the most common being a deep overbite, with a 
comparatively shallow or flat compensating curve. In such 
cases some space must be present, when the teeth are in occlu- 302 
THE MASTICATORY MECHANISM 
sion, between the lingual surfaces of the upper and the incisal 
edges of the lower teeth, otherwise interference will occur 
with normal lateral and protrusive movements. 
THE CURVE OF SPEE 
The lower teeth, including the incisors and cuspids, usually 
present a very-well-defined arc-like arrangement when viewed 
buccally. This curved plane assumed by the lower teeth is 
sometimes called the “Curve of Spee,” because Graf von 
Spee, the German anatomist, first called attention to it, about 
1890. 
Spee says, in regard to the relation existing between the 
condyle paths and the teeth planes: “In the forward bite 
the teeth and condyles describe the same circular movement. 
The steeper the path of the condyle the more pronounced the 
tooth curve will be, because both will have the same radius.” 
This latter statement is incorrect, for, while the condyle 
path and the teeth plane may both be arcs of circles having 
a common center, their radii may vary, and the two curves 
will often represent concentric arcs. 
Spee’s writings refer especially to the curvature of the 
lower teeth plane and its relation to the condylar movements, 
and therefore the term, “Curve of Spee,” should not be 
applied to the upper teeth plane. 
MODIFICATION OF THE COMPENSATING CURVE 
Occasionally tlie occlusal surfaces of the upper molars 
present a series of parallel planes, instead of assuming a 
symmetrical curve, as described. The second molar is slightly 
higher than the first, and the third slightly higher than the 
second. The lower molars assume a similar relation, with the 
result that the occlusal plane when analyzed presents a step- 
like instead of a curved arrangement. 
It is claimed by some that this is the logical manner in 
which to arrange teeth in the construction of artificial den- 
tures. First, because balancing contact can be more easily 
secured; second, that there is less liability of the dentures 
becoming dislodged in masticatory effort. The argument is 
that the force of muscular effort is delivered upon the food 
more in the nature of an end thrust against right-angle sur- 
faces, rather than against inclined planes; third, that such an 
arrangement of the teeth is anatomical, natural and more 
common than the curved arrangement. THE MASTICATORY MECHANISM 
303 
It is the opinion of the writer, based upon the examination 
of many specimens, first, that the step-like arrangement is the 
exception, and not the rule, or at least occurs no more fre- 
quently than the curved arrangement; second, that balancing 
contact can as readily be secured by placing the second molars 
in a relation similar to that which they sustain in the natural 
denture, when the curvature is well defined, as previously out- 
lined ; third, that the varying planes on the occlusal surfaces 
of the intercuspating molars tend to prevent displacement 
of the dentures in masticatory effort; fourth, that better 
esthetic results can be secured by arranging the teeth by the 
curved rather than by the stepping method. However, either 
method is productive of satisfactory results if due attention 
is given to details, so it is largely a question of esthetics, in 
which neither comfort nor utility is concerned. CHAPTER XVIII 
CONSTRUCTION OF FULL DENTURES 
Anatomic Method 
GENERAL FEATURES 
In the construction of good dentures, as lias been previ- 
ously stated, the accomplishment of three objects is desirable, 
necessary, and, in most cases, possible, when careful atten- 
tion to detail is observed. These three objects — usefulness, 
good looks and comfort — when attained in prosthetic, as well 
as in all dental operations, represent that quality of service 
which our patients have a right to expect, and which the ten- 
ets of our profession impose upon us. 
It is therefore the duty of every practitioner to perfect 
himself in the highest degree, not only in theoretical knowl- 
edge, but in the acquirement of technical skill as well in all 
that pertains to his calling, whether it be the general or a spe- 
cialized field of dental practice. 
Anatomic occlusion of artificial teeth consists in following- 
nature’s plan of arrangement as observed in the normal 
human masticatory apparatus. 
Occasions arise, however, when this course is not pos- 
sible, but such cases are rare. When occurring the causes 
may be traced to some abnormality of the glenoid fossae, usu- 
ally the result of mandibular movements having since early 
youth been restricted because of malocclusion, or, in some 
cases, to the sequela of temporo-mandibular inflammation. 
Whatever the character of the abnormality an attempt 
should be made to discern the cause and discover such useful 
mandibular movements as are possible. With a thorough 
knowledge of existing conditions and the application of an- 
atomic methods far better service can be rendered a patient 
than when such abnormality is ignored. 
By way of introduction to anatomic methods a brief review 
of masticatory movements in general will be in order. 
Masticatory Movements of the Carnivora 
The most effective masticatory movements of the carniv- 
ora (flesh-eating animals) are hinge-like, no extensive lateral 
movements of the mandible being possible for two reasons: 
304 CONSTRUCTION OF FULL DENTURES 
305 
First, because of the form of the temporo-mandibular articu- 
lation, which does not permit of much unilateral action; and, 
second, because of the excessive length and relation to each 
other of the upper and lower canine teeth. In general, the 
posterior teeth of this class of mammalia have strongly 
marked cusps which intercuspate closely. Their function is 
to tear and cut food. 
Masticatory Movements of the Herbivora 
In the herbivora (animals that live on herbs and vegeta- 
tion), the effective mandibular movements are almost exclu- 
sively lateral, or from side to side. The occlusal surfaces of 
the teeth are not strongly cusped, but are ridged for grinding 
food. 
Masticatory Movements of the Omnivora 
In the omnivora or kerbi-carnivora (subsisting on both 
flesh and vegetation), the effective masticatory movements are 
hinge-like as well as from side to side, or lateral. The occlu- 
sal surfaces of the teeth consist of planes, ridges, grooves and 
cusps, usually so arranged that in unilateral movements the 
cusps of the lower may glide between those of the upper teeth 
in definite paths, without interference. 
Since man is omnivorous, the human masticatory appa- 
ratus, while modified somewhat from that of the lower animals 
because of different habits of life, corresponds in general to 
mammalia of this class. A more complete general description 
of the human masticatory apparatus will be found in the pre- 
ceding chapter. 
In the chewing of meats, the hinge action of the mandible 
is most effective at first until the meat fibres have been more 
or less torn and shredded by the cusps of the bicuspids and 
molars, after which the lateral movements are just as essen- 
tion in still further reducing the mass to a pulpy condition 
suitable for action by the digestive fluids. 
Cereals, fibrous vegetables and most all varieties of 
starchy foods require active lateral movement for proper re- 
duction. Dr. Gr. V. Black in ‘ ‘ Physical Characters of Human 
Teeth” (Cosmos, 1895), states: 
“In the mastication of cereal foods — those made from 
grain of almost all kinds — the lateral or grinding motions are 
largely employed. This is true also of all the brittle foods 
of whatever nature. Indeed, many of these are so difficult to 306 
CONSTRUCTION OF FULL DENTURES 
crush by direct pressure that it becomes impracticable. Many 
kinds of food will simply be packed together between the 
teeth, and a stress of two or three hundred pounds will be 
insufficient to crush it out as meats are crushed. Many of 
the crusts from ordinary baker’s bread, when subjected to 
stress between the molar teeth, will not be cut through with 
a stress of two hundred and fifty pounds; and they are not 
very hard crusts, either. They are readily broken up, how- 
ever, with a much lighter stress combined with a little lateral 
movement, especially as they become moistened with the secre- 
tions. It seems probable, however, that many persons uncon- 
sciously exert an enormous force upon such foods as are 
inclined to pack between the teeth. 1 am no longer surprised 
at the frequent breaking of frail teeth on bread crusts that 
are not very hard. It is but little wonder that porcelain fac- 
ings on crowns and bridges are so often broken.” 
In carrying out a line of experiments to determine the 
amount of direct stress required to crush various kinds of 
food, Dr. Black used an instrument called a pliago-dynamome- 
ter. The action of this instrument on the food tested was 
practically identical with that exerted by the natural teeth 
on food when the liinge-like action of the mandible is em- 
ployed. 
Some years later Dr. Joseph Head carried out a line of 
experiments to determine the amount of force required to 
reduce similar classes of food with lateral movements. He 
used for this purpose a human skull in which the natural 
teeth were present and occluded well. The following table 
of comparison shows that it requires only about one-half the 
effort to reduce food under lateral movements that is required 
under the hinge action of the mandible: 
Dr. Head’s 
Dr. Black’s 
Meats 
Experiments 
Experiments 
Corned Beef 
... 18 -22 lbs. 
30 -35 lbs. 
Tongue .• 
... 1 - 2 
i i 
3-5 
Tenderloin of Beef, very tender. 8 - 9 
C L 
35 -40 
Round of Beefsteak, tough... 
... 38 -42 
11 
60 -80 
Roast Beef 
...20 -35 
i i 
35 -50 “ 
Boiled Ham 
...10 -14 
< < 
40 -60 “ 
Pork Chop 
...25 -30 
11 
20 -25 
Roast Veal 
...16 -30 
i ( 
35 -40 
Average 
...17 -20 
11 
3214-41% “ CONSTRUCTION OF FULL DENTURES 
307 
Dr. Head’s 
Dr. Black’s 
Vegetables 
Experiments 
Experiments 
Raw Cabbage 
. .. 16 lbs. 
40 -60 lbs. 
Head Lettuce 
...16 
25 -30 
Radish, whole broke at... 
...20 -25 “ 
20 -25 
Radish, pieces pulverized at.. 
...10 -15 “ 
35 -40 
Average 
...12i/,-16 “ 
30 -383/4 “ 
(Dental Cosmos, 1906, P. 1191) 
Dentures constructed on a plain line, or similar articula- 
tor, or on an anatomical occluding frame, when all of the de- 
tails are not carefully attended to, limit the wearer to the 
hinge action of the mandible in the reduction of food. 
The advantage of the anatomic system of denture con- 
struction over the generally prevailing methods wherein 
masticatory effort is limited to the hinge action of the mandi- 
ble, have become an established fact. Dentures of the ana- 
tomic type balance when in action, while those constructed 
on plain line articulators become readily unseated when lat- 
eral movements are attempted. This fact alone is of sufficient 
importance to warrant the adoption of anatomic methods, 
because of greater efficiency, as well as comfort, derived by 
the patient from the use of dentures of this type. 
The normal human denture, and the various relations the 
lower sustain to the upper teeth in full and partial occlusion, 
is the ideal working model for the prosthetist, although at 
times departure from ideal conditions must be made. To carry 
out the many steps of denture construction by this method 
a knowledge of the mechanism of the masticatory apparatus 
is the first essential, while the use of suitable apparatus con- 
stitutes a second factor of equal importance. 
Main Features of Anatomic Methods 
Tlie essential practical features of anatomic denture con- 
struction, therefore, aside from a knowledge of mandibular 
movements, involve the use of special appliances and require 
that certain steps be carried out in logical sequence. The main 
factors of importance are as follows: 
First — An occluding frame capable of reproducing the 
most essential masticatory movements of the mandible. 
Second — A face bow, or caliper, for mounting the casts 
on the occluding frame in correct relation to the lateral centers 
of rotation. 
Third — Some means for registering the condyle path 308 
CONSTRUCTION OF FULL DENTURES 
pitch of the patient and of recording the same on the ocelud 
ing frame. 
Fourth — The selection of teeth of appropriate size, shade 
and anatomic forms to meet the requirements of each case. 
Fifth —Trial of the model dentures in the mouth under 
masticatory movements to verify their efficiency and esthetic 
appearance. 
Sixth — Testing and correction of occlusion of the finished 
dentures by means of carbon paper and engine stones, to com- 
pensate for variation of the natural lateral mandibular rota- 
tion centers from those of the occluding frame on which the 
teeth were arranged. 
Present Methods of Technic in Anatomic 
Denture Construction 
Two general methods of anatomic denture construction are 
in vogue in this country at the present time, each of which 
requires special appliances and the following of a rather 
closely defined system of technic. 
The two systems referred to are the Snow methods and 
appliances, a logical outcome of, with improvements on, the 
Bonwill and Christensen ideas, and the Gysi methods and ap- 
pliances, which are based on similar principles but differ in 
many important details. Both systems in the hands of com- 
petent prosthetists lead to the same desired results, viz., the 
production of high-type dentures, which for efficiency and 
comfort far surpass those produced by any other system in 
which lateral mandibular movements are not considered. 
Both methods involve the carrying out of many steps in com- 
mon, in some of which the same technic is employed, while 
in others considerable variation occurs. The essential details 
of these two systems will now be rendered sufficiently clear, 
it is hoped, to enable a prosthetist of average skill, who under- 
takes the work, to secure satisfactory results. 
The Snow Appliances and Methods 
The appliances used in the Snow method consist of an 
occluding frame, or as it is termed, an “articulator,” the 
condyle or lateral rotation centers of which are four inches 
apart, this being about the average distance from center to 
center of the human condyles. The lateral rotation centers of 
the frame are fixed at four inches and cannot be increased or 
diminished. The condyle paths of the frame are capable of CONSTRUCTION OF FULL DENTURES 
309 
adjustment and of being clamped at various angles, depending 
upon the pitch of the condyle paths of the patient, as regis- 
tered. The upper and lower bows of the occluding frame, to 
which, when the casts are attached, represent the maxilla and 
mandible, respectively, are adjustable for the accommodation 
of thick or thin casts. The back spring, by its tension, holds 
the mandibular portion of the frame in the back end of the 
condyle slots, or in that position representing the condyles 
at rest in the glenoid fossae. 
THE FACE BOW 
The face bow is a measuring device or caliper designed 
for registering the antero-posterior, as well as horizontal 
plane relationship of the alveolar ridges to the condyles when 
the latter are at rest in the glenoid fossae, as in normal closure. 
It is used in conjunction with the wax bite, or with occlusion 
models. This appliance is indispensable in order that the 
casts may be mounted in true relation to the rotation centers 
of the frame. By thus establishing the correct radial distance 
of the casts from the hinges, the teeth, when occluded on the 
frame and adjusted with clearance paths for the cusps of the 
lower to traverse laterally between those of the upper teeth, 
will follow the same lines of travel when the dentures are 
completed and fitted in the mouth. Increasing or decreas- 
ing the radial distance of the teeth on the frame from that 
which they will occupy in the mouth, will cause cusp interfer- 
ence in lateral movements. 
The face bow consists of a U-shaped frame, in the ex- 
tremities of which are two graduated sliding rods to enable 
the bow to be evenly balanced on the face. These are the 
condyle rods, the inner ends of which, in adjustment, are to 
be placed opposite the outer ends of the condyles and there 
clamped on points previously marked on the integument be- 
fore adjusting the bow. The bow in its central portion carries 
a universal clamp for receiving the bite rod after the latter 
has been firmly fixed in the occlusion model and for clamping 
it to the bow when proper adjustment of the condyle rods to 
the face has been secured. 
THE BITE GAUGES 
Two small flat plates of metal called bite gauges, having 
the edges turned down to engage with the lower wax rim, 
and with tapering pins projecting on the upper surfaces to 
engage with the upper wax rim, are used for taking the pro- 310 
CONSTRUCTION OF FULL DENTURES 
trusive bite — the means by which the condyle paths are regis- 
tered. The details for the application of these appliances 
will be given in the following described case of full upper and 
lower denture construction. 
General Constructive Steps 
The construction of full dentures anatomically involves 
the securing of suitable impressions; production of casts; 
development of wax contour models, first on the casts and 
afterward in the mouth, to develop lost facial contour and 
Fig. 160.— Upper Modeling Compound Impression, Showing 
Outline of Relieved Area 
establish the normal bite; the mounting of the casts on an 
anatomical occluding frame; registration of the condyle paths 
of the patient and the adjustment of the condyles of the frame 
to correspond; development of the compensating curve on 
the wax occlusion model; selection of teeth of suitable form 
and color to harmonize with anatomic and esthetic require- 
ments of the patient, and their arrangement in upper and 
lower arches so as to develop the greatest efficiency and pre- 
sent the best appearance; duplication in permanent materials 
of the wax model dentures, and finally, the fitting and adjust- 
ment of the dentures to the respective arches within the oral 
cavity. 311 
CONSTRUCTION OR FULL DENTURES 
More than one hundred individual steps must be carried 
out in sequence in the production of full dentures of any type. 
It is therefore imperative that the greatest care be constantly 
exercised to arrive at satisfactory results, since a single error 
in some particular step may minimize the efficiency, or result 
in the total failure of the substitutes. 
The technic of impression taking, cast construction and 
the formation of base plates of various kinds, has been pre- 
viously presented. Also a brief description of the oral cavity 
and the masticatory movements lias been given. These vari- 
ous subjects should be thoroughly considered by the student 
before undertaking the work now to be presented. 
Assuming that suitable casts have been derived from ac- 
curate impressions of the mouth, the next step in the construe- 
Fig. 161.— Side View of Impression Ready for Forming Cast 
tion of a full denture (upper and lower) is to form in wax, 
or some easily workable but comparatively rigid material, 
models of the dentures to be constructed. These model den- 
tures, before being duplicated in permanent materials, are 
tried in the mouth and tested as to occlusion, appearance and 
comfort. Should any modification be required, such changes 
as are necessary may be accomplished with less effort and loss 
of time while the dentures are in a plastic condition than 
subsequently. 
The model dentures are developed in two stages: first, 
base plates are fitted to the casts before the latter are mounted 
on the occluding frame, and on these, rims of wax are ad- 
justed to represent approximately in depth and contour the 
lost teeth and absorbed borders. These are ordinarily called 
trial base plates. 312 
CONSTRUCTION OF FULL DENTURES 
Dr. G. H. Wilson suggests the use of the terms occlusion 
and contour models, because by means of them occlusal rela- 
tions are determined, while subsequently by additions to, and 
trimming of the wax rims, the contour of the face is restored 
Fig. 162.— Upper Cast with Baseplate Applied and 
Trimmed to Correct Outline 
to normal outline. They also represent, in a crude way, mod- 
els of the dentures to be constructed. 
The second stage is described as follows: After certain 
sequent steps, to be described later, are carried out, sections 
Fig. 163.— Lower Cast with Baseplate Fitted to Border 
are cut out of the wax rims, and in the spaces so formed the 
selected teeth are adjusted, the lower to occlude with the up- 
per. The gums are then carved in the wax and the surplus 
material removed, which steps convert the wax occlusion and CONSTRUCTION OF FULL DENTURES 
313 
contour models into wax model dentures, by which term they 
will be designated in this description of denture construction. 
This term is appropriate because they are the models by means 
of which the matrices are produced in which the permanent 
dentures are molded. 
Occlusion and Contour Models 
In the construction of full dentures the upper and lower 
occlusion models represent two masses of crude material 
from which the prosthetist carves and shapes in outline and 
contour the forms of the permanent dentures, just as a sculp- 
tor molds in clay the model of a permanent statue. 
An occlusion model is usually developed in two steps and 
may be composed of different classes of materials. 
First, a base plate, either permanent or temporary, is 
formed over a die or cast, derived from an impression of the 
mouth. 
Second, to the base plate a rim of plastic material, usually 
wax, is firmly attached and by trial in the mouth is carved 
and molded to the required contour of the future denture. 
Fig. 164.— Distal View of Upper and Lower Occlusion Models 
Requirements of a Baseplate 
The base plate, of whatever class decided upon, should 
be rigid and unyielding, capable of withstanding oral tem- 314 
CONSTRUCTION OF FULL DENTURES 
perature without softening or bending under masticatory 
stress. It should be closely adapted to the oral tissues on 
which it rests and should not become dislodged by its own 
weight, or tip from the action of adjacent muscles. 
The prospect of success of a permanent denture is slight 
when the base plate of the occlusion model fails to show an 
equal amount of adhesion required in the finished denture. 
The most exact technic, therefore, should be carried out in 
forming the base for an occlusion model, for by this means 
the adaptation of the permanent denture can be determined 
at a time when corrections can be made with little loss of time. 
When a permanent base plate of swaged gold, platinum 
or aluminum fails to show good adaptation and adhesive prop- 
erties in preliminary trials it should be reswaged over a new 
die derived from a new impression, since in no case do sub- 
sequent steps tend to improve defective adaptation, but rather 
to increase it. The same holds true of vulcanite or cast 
metal bases and of base plates constructed of the more rigid 
temporary materials. Under no conditions should an elastic 
substance or a material that readily distorts by heat or 
pressure be employed in the construction of bases for oc- 
clusion models, because distortion of the pattern denture 
from any cause will result in similar errors in the permanent 
denture. 
Requirements of the Occlusion Rim 
The wax used in forming the occlusion rim must be of a 
hard variety, not softening at oral temperature or mashing 
down under masticatory stress either before or after the 
teeth are imbedded in it. The rim should not be built up in 
layers as is frequently the case, but the wax should be kneaded 
into a compact, solid mass before being attached to the base 
plate. A rim composed of a hard variety of pink wax will 
present a better appearance and enable the prosthetist to 
develop a more esthetic temporary, or model denture, than 
when yellow or brown waxes are employed. 
Construction of Occlusion Models 
The base plate, of whatever material determined upon, 
should be formed, introduced in the mouth and tested as to 
its fitness in peripheral outline, stability on and adhesiveness 
to the tissues. When found satisfactory in every respect the 
occlusal rim is formed and attached to it as follows: CONSTRUCTION OF FULL DENTURES 
315 
Tlie wax to be used in forming the rim is softened in water 
not exceeding 130 degrees Fahrenheit. When thoroughly 
plastic it is kneaded into a compact mass with palm and fin- 
gers, then transferred to a dry towel and the kneading process 
continued until all moisture is eliminated. 
The mass, while plastic, is then formed into a roll about 
one-lialf inch in diameter and four and one-half inches long. 
This roll is then bent around and placed upon the maxillary 
portion of the base plate, against which it is only slightly 
pressed. A heated spatula is passed along the line of junction 
of the roll with the base plate on the labial, buccal and lingual 
surfaces to melt the wax and cause it to adhere firmly to the 
base plate throughout the entire extent of the border. The 
angles are then filled in with melted wax until approximate 
contour on all surfaces is developed. Considerable heat is re- 
quired to properly attach the wax rim to the base plate. Wheu 
the latter is composed of temporary material it should res! 
upon the cast on which formed to prevent distortion while ap 
plying the rim and melting the wax. 
When the rim is firmly adherent and the wax has cooled 
somewhat, the labial, buccal and lingual surfaces are devel- 
oped approximately to the desired contour by additions and 
trimming as indicated. 
APPROXIMATE DEPTH OF OCCLUSION RIMS 
For ordinary cases, where an average amount of absorp- 
tion of the borders has occurred, the rim should be about 
three-eighths of an inch thick from maxillary to occlusal sur- 
faces and about the same breadth from buccal to lingual. 
The occlusal surface should be flat from before backward, 
as well as from side to side. This may be accomplished by 
paring off the excess occlusal wax with a knife, softening this 
area somewhat and pressing against any true flat surface as 
a slab or the top of the bench. During this step the base plate 
should rest upon its cast and the applied pressure should be 
uniform to prevent thinning the rim more on one side than 
the other. 
BUCCO-LINGUAL POSITION OF THE UPPER AND LOWER WAX RIMS 
IN RELATION TO THE BORDER CRESTS 
The rim should be set as nearly on the border as possible 
to reduce to the minimum the tipping leverage, which increases 
in direct proportion to the distance the teeth are placed labi- 
ally or buccally from the maxillary ridge. 316 
CONSTRUCTION OF FULL DENTURES 
There are two important factors, however, which largely 
control the labial and buccal position of the occlusal rim of 
an upper occlusion model. First, the width of the lower arch 
from buccal to buccal and its relation to the upper border; 
and second, the extent of loss of the upper alveolar ridge on 
labial and buccal surfaces by absorption. In full cases the 
teeth in the lower must occlude with those in the upper, re- 
gardless of the disparity in size of the two arches. When the 
lower arch is excessively large and the upper is under size 
in arranging the teeth on the upper base plate they must be 
placed out beyond the ridge, while the lowers must be set 
inward as much as possible without interfering with tongue 
Fig. 165.— Distal View of Upper and Lower Occlusion Models (Trial Plates) 
Showing the Relation of Wax Rims to Upper and Lower Border Crests 
movements. A general rule to follow is to so adjust the wax 
rims in full cases that the buccal and lingual surfaces of both 
rims will be parallel with, and about an equal distance from, 
a line drawn between the crests of the two borders. 
The second factor, which must frequently be considered 
in the development of the labial and buccal surfaces of an 
upper occlusion model, is the extent of contour necessary to 
develop on the rims to restore lost facial profile. The amount 
of such restoration varies in different cases, being greatest in 
those where the teeth were extracted early in life and dentures 
have been worn continuously for many years, the borders hav- 
ing constantly become reduced in size. In such cases the best 
judgment of the prosthetist must be exercised to determine 
just how far labially and buccallv the upper teeth may be 
carried beyond the fulcrum line, or crest of the border in re- CONSTRUCTION OF FULL DENTURES 
317 
storing lost facial contour, without endangering the stability 
of the substitute. Since anatomic methods have been devel- 
oped, however, it is found that in most cases the teeth in 
both arches can be lined up in accordance with esthetic re- 
quirements, the tendency to tip being practically overcome by 
the balancing contact. 
It is best, however, to establish the parabolic arch lines 
conservatively — that is, within rather than at the extreme 
outer position demanded by esthetics. Quite frequently in 
these most difficult cases the arch lines of the teeth may be 
Fig. 166.— Side View of Finished Occlusion Models 
kept within normal limits and yet the required facial restora 
tion may be accomplished by means of plumpers — reflections 
of the upper peripheral margin of the base plate. The neces- 
sity for this means of restoration cannot be determined be- 
forehand and therefore in the preliminary formation of the 
occlusion model it is not attempted. Trial in the mouth will 
determine the position and extent of such reflected margins 
and they can be developed accordingly. 
All surfaces of the wax rim should now be smoothed up so 
that when introduced in the mouth the patient may feel no 
special discomfort, and further, so that the occlusion model 
may present as good an appearance as possible. 
The foregoing outline, although referring more particu- 
larly to the construction of an upper occlusion model, applies 
in most essentials to the development of a lower model as 
well. Tn lower cases the slant of buccal and lingual surfaces 318 
CONSTRUCTION OF FULL DENTURES 
of the occlusion rim is usually to the lingual, from the border 
crest occlusally, in order that its periphery may coincide with 
that of the upper rim at the common occlusion plane. 
Trial of Occlusion Models in the Mouth 
The upper and lower occlusion models having been devel- 
oped to approximate form, they are introduced in the mouth. 
There are a number of important points to be considered 
and recorded by means of the occlusion models before they 
are finally removed from the mouth, the usual order of proce- 
dure being as follows: 
First, testing the adaptation of the base plates to their 
respective ridges. 
Second, determining the correct occlusal plane. 
Third, restoring disturbed facial profile and contour. 
Fourth, marking the high and low lip lines on the wax 
rims. 
Fifth, marking the median line of the face. 
Sixth, locating the ends of the condyles and marking same 
on the integument. 
Seventh, removing the upper contour model, inserting and 
removing the bite rod. 
Eighth, “taking the bite” and locking the contour models 
together. 
Ninth, applying, adjusting and clamping the face bow. 
Tenth, removal of the occlusal models from the mouth. 
Testing the Adaptation of Each Baseplate to Its Ridge 
Each occlusion model is independently fitted to its border 
and tested as to closeness of adaptation, freedom from muscu- 
lar impingement and whether or not it will retain its position 
on the border under muscular action. 
When the periphery of a base plate impinges on the 
fraenum or muscular attachments, even though it may rest 
firmly on the general surfaces of the ridge and vault under 
pressure, yet displacement may readily occur when pressure 
is discontinued and muscular tension is applied. Any points 
of interference not previously disclosed during trial of the 
base plate should be relieved before proceeding with the sub- 
sequent steps. CONSTRUCTION OF FULL DENTURES 
319 
Determining the Correct Occlusal Plane 
Various plans are suggested for determining the correct 
position of the occlusal plane between the two maxillary sur- 
faces. One of these is to draw a line on the face extending 
from the tragus of the ear to the ala of the nose and trim the 
planes of occlusion parallel with this line. While perhaps 
in the average case this rule might apply, variations are so 
frequent that it cannot be relied upon. Many cases have come 
under the writer’s notice where, if this plan had been adopted, 
the occlusal planes, while anteriorly correct, would have 
intersected one or the other borders in the region of the sec- 
ond molars, thus unequally dividing the space between the 
crests of the two processes in which the teeth are subsequently 
to he placed. 
The following plan is accurate and easy of application: 
First determine the correct length of the occlusal rim of the 
upper model anteriorly. In the largest percentage of cases 
the anterior teeth in normal arches extend about one-sixteenth 
of an inch below the upper lip when the lat-ter is relaxed, as 
can he seen when the lips are slightly parted. This amount 
of margin of the upper occlusion model should be seen under 
similar posing of the lips. Should the rim be too short an 
addition is made, and when too long the excess is pared off 
until the proper amount of wax is exposed. Whatever changes 
may be made to the rim anteriorly should be followed by cor- 
rections to the entire occlusal plane, keeping it flat and of uni- 
form thickness antero posteriorly from incisal region to the 
tuberosities, until subsequent changes are found necessary. 
The length of the upper rim having been determined and 
such changes as may be necessary effected the lower model 
is introduced and the patient instructed to close. Usually the 
rims strike in the molar region, while anteriorly there is more 
or less space between them. Instruct the patient to bring the 
lips together and notice the amount of muscular effort re- 
quired to effect their closure. 
Both occlusion models are now removed and pared off 
equally at their contact points, being careful to preserve the 
flat occlusal planes by shaving off long bevel slices of wax. 
The main point to keep in mind in this trimming process is 
to preserve an equal thickness of wax on each side of each 
rim from occlusal to maxillary surfaces, so that in occluding 
the teeth they may be placed in the space thus provided. 
Briefly stated, an effort should be made to establish the 320 
CONSTRUCTION OF FULL DENTURES 
occlusal plane midway between the crests of the upper and 
lower borders. The only exception to this method is in those 
cases where absorption of the borders has progressed un- 
equally, the teeth in one arch having long been lost and in 
the other having been extracted at a much later date. In 
such cases the occlusal plane must be located nearer the bor- 
der showing the least absorption. 
Establishing Height of the Lower Occlusion Rim 
The depth of the upper wax occlusion rim — that is, its 
thickness from the maxillary surface of the border to the 
occlusal plane — is to a very great extent determined by the 
length of the upper lip anteriorly, while posteriorly it com- 
monly fills about one-half the space between the crests of the 
two maxillary borders, the mandible being in normal position, 
which position usually places it parallel with the upper max- 
illary crest. 
With these two factors as a basis it is a comparatively 
simple task to develop the upper occlusion model. It is more 
difficult, however, to develop a correctly proportioned lower 
occlusion model, because of the absence of any fixed land- 
mark, by means of which the height of the lower rim can be 
established. 
Let us consider the relation of the mandible to the max- 
illa, first, with the natural teeth present and in occlusion, and 
second, after the jaws become edentulous. In the first instance 
the masticatory muscles bring the mandible upward until 
when the teeth are in occlusion it is in a state of rest. In this 
position the facial profile is normal, while the lips rest eas- 
ily against each other without apparent muscular tension, or 
conscious effort on the part of the individual. Since, however, 
it is possible for the patient to compress the lips and give 
them a strained appearance — a purely voluntary act of the 
orbicular muscles in which the mandibular take no part — it 
is well to instruct the patient to relax muscles of lip closure. 
Could a registration of the normal profile be made when 
the natural teeth are present and in occlusion, say by placing 
one leg of a caliper on the under side of the mandible and the 
other on the cranium on points that could afterward be located 
and the distance between the two be recorded, this measure- 
ment would enable the length of the face to be re-established 
after loss of the teeth. CONSTRUCTION OF FULL, DENTURES 
321 
This method is not practical, but the illustration shows 
what we hope to and should accomplish by means of occlusion 
and contour models of suitable height. 
Instead of the calipers the esthetic judgment of the pros- 
thetist is the court of last resort. His eye should be so trained 
as to detect defective profile or contour and restore his pa- 
tient’s face to normal appearance. 
Fig. 167.— Theoretical Measurement of Facial Profile 
In edentulous cases, there being no teeth present to ar- 
rest the progress of mandible toward the maxilla, restoration 
of the normal pose of the lips and the general profile and con- 
tour of the face must be depended upon in establishing the 
height of rim of the lower occlusion model. This can only be 
done by repeated trial and testing, building up or reducing the 
rim as facial contour and the pose of the lips indicate. 
The depth of the upper rim having been determined by 
the length of the upper lip, the height of the lower rim is 
established at such point that the lower lip may rest easily in 
contact with the upper without requiring muscular effort to 
effect closure. Pursing out of the lip indicates that the rim 
is too short, while muscular effort in closing the lips indicates 
that the rim is too high. 322 
CONSTRUCTION OF FULL DENTURES 
When the rims have been developed correctly labially 
the contour models should be tested posteriorly to determine 
whether there is uniform and equal contact between them and 
their respective borders. This test is made by having the 
patient maintain moderate mandibular pressure while the 
prosthetist endeavors to force the occlusion models apart, 
first on one side and then on the other. If on moderate 
pressure the two base plates separate while contact is main- 
tained labially, it indicates that the occlusion rims are too 
short where separation occurred, one or the other of the base 
plates having tipped or left its border. Such imperfect con- 
tact should be corrected by additions of wax to one or both 
rims until uniform bearing on both sides of the mouth is 
established. 
In making such additions care should be taken to preserve 
the flat plane areas of both occlusion models. 
Should the upper plane be flat and the rim of proper 
length the lower rim on the deficient side may be corrected by 
adding a sheet of soft wax to the occlusal plane where defi- 
cient, introducing in the mouth and having the patient exert 
gradual and uniform pressure upon it. The lower wax model 
is then removed and the surplus trimmed off to correct periph- 
eral outline. 
Restoring Lost Facial Contour 
One of the most important results of full denture construc- 
tion, when the steps are properly carried out, is the correction 
of disturbed facial contour. 
The teeth, the borders in which they are imbedded, with 
the overlying soft tissues in the natural masticatory appa- 
ratus, when viewed anteriorly present a generally convex 
appearance from side to side and a nearly perpendicular ar- 
rangement from above downward. The labial and buccal sur- 
faces of the teeth and alveolar arches support the lips and 
cheeks and in this manner aid in giving form and contour to 
the lower half of the face. 
When the teeth are lost and the alveolar borders absorb 
to a greater or less extent from without inward, as well as in 
height, the lips and cheeks lose their support and fall back- 
ward and inward. The symmetry of the face is thus disturbed 
to a marked degree and unless corrective measures are re- 
sorted to the patient becomes disfigured for life. By the in- 
troduction of suitably formed dentures disturbed facial profile 
and contour can in a great measure be overcome. CONSTRUCTION OF FULL DENTURES 
323 
The first stage in denture construction, where corrective 
measures can be developed and tested, is during the trial 
of the wax occlusion models in the mouth. Later on the final 
test occurs with the introduction of the wax model dentures. 
By molding and carving, varying the thickness of the labial 
and buccal rims of the wax occlusion models, introducing them 
in the mouth, having the patient close and bring the lips to- 
gether in a normal relation, or state of rest, the prosthetist 
can determine the measure of success attained. Repeated 
modifications and trials are sometimes necessary to secure 
satisfactory results, while in other cases but little difficulty is 
encountered. 
The occlusion rims, by their perpendicular height, estab- 
lish the profile and length of the face. Their labial and buccal 
surfaces lift out the sunken areas, particularly from the bicus- 
pids forward. 
In order to correct the wrinkles which extend from the 
alae of the nose outward, over the angles of the mouth, it is 
usually necessary to extend the periphery of the occlusion 
model upward in the region of the cuspids. Such extensions, 
however, should be neither too high nor too bulky, or they 
will interfere with the movements of buccal and orbicular 
muscles and displacement of the denture will result. 
In those cases where considerable restoration is required 
and the extension upward of the peripheral rim of the base 
plate is limited by muscular attachment the required contour 
can usually be developed by reflecting the peripheral margin 
of rim, as previously mentioned, outward and downward in 
the form of flanges, or so-called plumpers, shown on page 547. 
The width and slant of a flange of this type depends on the 
amount of restoration required and the tension of the muscles 
peripherally. In all cases they must be so disposed as not to 
interfere with freedom of muscular action or denture displace- 
ment will most certainly occur. 
The usual prominent features of an upper occlusion model 
when developed are as follows: 
The contour model is notched anteriorly, to allow free play 
for the labial frenum. 
There should be slightly depressed areas between cen- 
trals and cuspids above the laterals, thus reproducing the 
incisive fossae such as are noticeable in the maxilla. These 
depressions allow freedom of movement of the alae of the nose. 
Prominently contouring the labial rims above the lateral in- 324 
CONSTRUCTION OF FULL DENTURES 
cisors oftentimes restricts the size of the nasal orifice, inter- 
feres with respiration and is generally uncalled for. 
Prominent cuspid eminences do, partially, but not usually 
wholly, obliterate the wrinkles extending from the alae of the 
nose outward over the angles of the mouth. A slight sug- 
gestion of these wrinkles in persons of middle age, or past, 
produces a more esthetic result than when completely oblit- 
erated. 
Peripheral margins, from median line to tuberosities more 
or less notched, as indicated by the muscle-marking exercise 
carried out in impression taking. (See Fig. 85 ) 
Marking the High and Low Lip Lines 
The high and low lip lines are marked on the upper and 
lower occlusion models respectively, to serve as guides in 
determining the length of teeth to select for the case. 
The upper central incisors should extend from the incisal 
plane to the high lip line, or slightly above it, so that when 
the artificial gum material is applied over the cervical ends 
of the teeth, the highest curves of the gingival line coincide 
with the high lip line. The same arrangement can be fol- 
lowed in selecting and arranging the lower incisors and carv- 
ing the gums, although the gums of the lower teeth seldom 
show to the same extent as in upper cases. 
The object in selecting teeth of the length indicated by 
the high lip line is to avoid exposure of too much artificial 
gum, as would occur when shorter teeth are used, and also 
to obviate the monotony which is apparent when longer teeth 
and only the porcelain is visible. 
The patient is instructed to raise the upper and depress 
the lower lip as in broadly smiling, and while in this position 
the prosthetist marks on the occlusion models the lines of lip 
peripheries as they lie against the wax surfaces. 
Marking the Median Line of the Mouth 
The human face is seldom, if ever, symmetrical. Usually 
the nose is bent to one side; one eye may be slightly higher 
or nearer the median line than the other, or set at a different 
slant; the general line of the lips from side to side may not 
form a right angle with the perpendicular line of the face. 
In fact, the most symmetrical faces, when studied closely, will 
be found unsymmetrical. CONSTRUCTION OF FULL DENTURES 
325 
It is therefore a difficult matter at times in denture con- 
struction to determine just where the two central incisors 
should be placed because there is no fixed landmark to serve 
as a basis, or to indicate the position once occupied by the 
natural teeth. Usually the center of the philtrum of the lip 
will serve as a guide, but when the nose, chin and other fea- 
tures are out of alignment a general average must be struck 
to arrive at harmonious results. This may be done by placing 
a straight edge, or the edge of a card, flatwise against the face 
extending from the center of the chin to a point located mid- 
way between the inner ends of the eyebrows and making a 
slight mark on the occlusion models. The card is then re- 
moved and a point directly under the center of the philtrum 
is marked. When there is much variation in the two lines a 
third line midway between the two, yet favoring a location 
near the philtrum, will give a harmonious median line. 
When the correct position is determined a perpendicular 
line extending across both base plates should be distinctly 
marked in the wax. Care should be taken in subsequent 
steps not to obliterate it until the arrangement of the teeth is 
begun. 
Locating the Outer Ends of the Condyles 
Previous to taking the bite the outer ends of the con- 
dyles should be located and their exact position indicated by 
dotting the integument directly over their locations with a 
soft pencil. The outer ends of the condyles in most cases 
approach the outer margins of the glenoid fossae, sometimes 
coming quite to the margins so as to be detected with little 
difficulty. More frequently, however, they are slightly over- 
hung by the glenoid rims. When the integument is thick and 
the interarticular fibrocartilages and capsular ligaments are 
well developed it is sometimes difficult to locate them, either 
at rest or when in action. 
In the largest percentage of cases the condyle end will 
be found about one-half inch in front of, and on a horizontal 
plane with the upper margin of the external auditory meatus. 
The index finger should be placed perpendicularly against 
the side of the face, with that portion of the ball immediately 
below the finger nail resting on the immovable glenoid rim. 
The patient is then instructed to open and close slightly with 
the hinge motion. Wide open movements are confusing as the 
condyle not only rotates but moves forward in its path as 
well. By applying steady pressure with the finger against the 326 
CONSTRUCTION OF FULL DENTURES 
glenoid rim with slight opening and closing movements of the 
mandible a point of perceptible movement will be detected 
close up along the glenoid margin and in about the same rela- 
tion to the external auditory meatus as stated. While varia- 
Fig. 168.— Position of Finger in Locating Condyle End 
tions in position of the condyle ends occur in different indi- 
viduals, and frequently in the same person, they will not be 
very marked and usually are not difficult to detect. 
The greatest care should be exercised in determining the 
correct antero-posterior, as well as perpendicular position of 
the condyle ends when at rest in their fossae, as the measure- 
ment secured with the face bow becomes the basis of radial 
movement of the casts when mounted on the occluding frame. 
Application of the Bite Fork to Upper Occlusion Model 
The bite fork, with its crescent-shaped plate for insertion 
into the occlusion model, is heated and the plate inserted in 
the labial surface of the wax rim. The occlusion model is 
Fig. 169.— Upper Occlusion Model with Bite Fork in Position 
removed from the mouth during this step, since if carried out 
in the mouth the melted wax caused by the insertion of the 
heated fork is liable to burn the lips. 
The fork while heated is pressed into the rim until its 327 
CONSTRUCTION OF FULL DENTURES 
entire inner periphery engages with, and is firmly imbedded 
in the labial surface of the wax. The rod should be parallel 
with the occlusal plane and point as nearly forward, parallel 
with the median line of the occlusion model, as possible, so 
that the universal clamp of the face bow may grasp it firmly 
when tightened. 
After insertion it will be found most convenient to remove 
the bite fork from the occlusion model before taking the bite, 
as its weight tends to dislodge the upper occlusion model. 
When the latter step is carried out and the bite locks are in- 
serted the fork is returned to the groove previously made for 
it, the lip protected with a napkin and a hot spatula passed 
around the upper surface of the fork to lute it firmly to the 
occlusion model. 
Meaning of the Term, ‘‘Taking the Bite” 
Taking the bite refers to establishing the correct antero- 
posterior, as well as perpendicular, relation of the mandibular 
to the maxillary ridge. When the natural teeth are present 
and in normal occlusion, the condyles are at rest in the glenoid 
fossae. Since in edentulous cases the occlusion rims, when 
properly formed, take the place of the natural teeth- they 
establish the correct perpendicular distance of the mandible 
from the maxilla. The final step of taking the bite consists in 
having the patient close the mouth normally, that is, so that 
the condyles are at rest in the glenoid fossae while the occlusion 
rims are in contact, and registering the relation of the occlu- 
sion models to each other in this position. 
Difficulty Encountered in Taking the Bite 
More or less difficulty is encountered in taking the bite 
because of the tendency of patients to unconsciously protrude 
the mandible, either uni- or bi-laterally. It is also a notice- 
able fact that the more interested the patient is in this step, 
and the greater effort he displays in giving a correct bite, the 
greater is the liability of error resulting. It is therefore best 
not to inform the patient of the importance of the step about 
to be carried out, but merely instruct him at the proper time 
what to do. 
Various Methods of Securing the Bite 
Various methods are adopted for securing a normal bite, 
any one of which might prove successful in some cases and 328 
CONSTRUCTION OF FULL DENTURES 
result in failure in others. Some of these methods are as 
follows: 
First — The patient is instructed to swallow and at the 
same time close the mouth, the culmination of this muscular 
effort being supposed to — and in some cases does — bring the 
condyles back in their position of rest in the fossae. 
Second — A small pellet of wax is attached to the distal 
margin of the central vault portion of the baseplate. The 
patient is instructed to touch the pellet of wax with the tip 
of his tongue, and at the same time close the mouth until the 
occlusion rims are in contact. 
Third — A chin cup is applied to the mentum, to which 
straps are attached which pass around the head. When these 
straps are properly adjusted, tension is exerted on the mandi- 
Fig. 170.— The Garrison Bite Guide 
ble to force it backward. Repeated opening and closing of 
the mandible will frequently, but not in all cases, result in 
establishing the correct bite. An apparatus similar to the 
one just described is known as Garrison’s Bite Guide. 
Fourth — Pressure may be exerted upon the point of the 
chin, while the patient repeatedly opens and closes the mouth, 
attention in the meantime being given to the relation the 
occlusion rims sustain to each other when brought in contact. 
Fifth — It is a noticeable fact that when the masticatory 
muscles are wearied by rapid and they 
draw the mandible backward until the condoles are in normal 
resting position on the fossae. 
By combining the two methods last mentioned, a correct 
bite may, in practically all cases, be secured. 329 
CONSTRUCTION OF FULL DENTURES 
A Practical Method for Securing a Correct Bite 
The patient should be instructed to open and close the 
mouth rapidly many times, say for a period of one-half to one 
minute, the operator in the meantime paying but little atten- 
tion, further than to see that his instructions are followed. 
He will then say to the patient, “Relax your muscles and let 
me open and close your mouth. ’ ’ The point of the chin is then 
grasped lightly with the tips of the fingers and thumb so as 
not to displace the lower occlusion model, and the mandible 
is moved up and down, the lips being raised to note position 
in which the occlusion rims strike. Slight pressure may also 
be applied on the mandible to force it upward and backward. 
Undue pressure should be avoided, as it would result in com- 
pression of the tissues in the temporo-mandibular joint, and 
thus give a slightly backward or retruded bite. 
Under the slight pressure exerted, together with repeated 
opening and closing movements, the occlusion rims will finally 
Fig. 171.— Bite Locks. Left, Formed of 
Wire. Right, Dr. Snow's Design 
meet each time in the same relation to each other. The 
patient is then instructed to “keep the mouth closed.” The 
bite locks are then warmed and forced into the upper and 
lower occlusion models, about in the region of the bicuspid 
teeth. Care should be taken in placing them to avoid en- 
croaching on the groove previously made for the bite fork. 
A third bite lock is sometimes inserted in the labial region to 
prevent possible change of relation between the baseplates in 
removal from the mouth. 
In some cases where the wax occlusion models are large 
and the oral opening small, it is impossible to remove the 
two models when locked together. By cutting cross grooves 
in both occlusion rims opposite each other, one on either 
side and one anteriorly, placing small pellets of warm wax 
directly over them, and having the patient bite, the wax will 
be forced in the grooves and will serve as guides in placing 
the models in correct relation to each other on removal from 
the mouth. 330 
CONSTRUCTION OF FULL DENTURES 
The bite lock having been inserted or the grooves cut as 
described, the next step is to return the bite fork to position. 
Inserting the Bite Fork in the Upper Occlusion Model 
The bite fork is now warmed slightly, the lips opened and 
the fork inserted in the groove previously made by it, and 
from which it was removed previous to taking the bite. To 
secure it firmly in place, a heated spatula should be passed 
along the upper surface of the fork, the upper lip being held 
up and the lower protected with a napkin. When firmly fixed 
the face bow can be applied. 
Adjusting the Face Bow to the Occlusion Models 
As will be seen, the bite has been established, although 
the occlusion models have not yet been removed from the 
mouth. The face bow is now applied so that when the base- 
Fig. 172.— Adjusting the Condyle Rods 
plates are removed from the mouth, and the casts are in- 
serted each in its respective baseplate and attached to the 
occluding frame, their maxillary surfaces ivill bear the same 
relation to the frame hinges that the natural ridges sustain 
to the condyles when the latter are at rest in the glenoid fossce. 
The condyle rods of the bow are now drawn outward so as 
to allow them to pass on either side of the face without in- 
terference. The universal clamp in the center of the bow is 
carried over the projecting rod of the bite fork, and the back CONSTRUCTION OF FULL DENTURES 
331 
ends of tlie how are dropped down until the condyle rods are 
opposite the points previously marked in j)encil to indicate 
the condyle ends. The condyle rods are then pressed inward 
until their ends rest on the points marked. 
Care should he taken to see that the condyle rods show 
the same number of gradations between their inner ends 
which rest on the face and the inner sides of the bow. Should 
the bow be unequally balanced when clamped, the casts will, as 
a result, be mounted to one side instead of on the center of 
the occluding frame, and their radii of movement will be in- 
Fig. 173.— Patient Tightening the Bite Fork Clamp 
correct. When balanced, the clamps which lock the condyle 
rods are tightened, the rods readjusted to the natural con- 
dyle ends by springing the bow away slightly to allow the 
integument to assume its normal position, then returned to 
place and held in correct relation by the operator while the 
patient, or assistant, is instructed to tighten the central clamp, 
thus fixing the relation of the bite fork to the face bow. The 
operator should forcibly tighten the clamp to insure against 
any possible change from stress while removing the occlu- 
sion models. The condyle rods are now released and drawn 
outward, the patient instructed to open the mouth and the 
occlusion models and face bow are removed, using the bite 
fork as a handle. 332 
CONSTRUCTION OF FULL DENTURES 
Adjustment of the Face Bow, with Occlusion Models 
Attached, to the Occluding Frame 
On removal of contour models from the mouth, the condyle 
rods of the face bow are pressed inward their full extent, and 
tightly clamped. 
Fig. 174.— Occlusion Models, Attached to Face Bow, Removed from Mouth 
The sheet metal base is slipped on the lower bow of the 
occluding frame, to prevent the latter tipping backward. The 
occlusion models are carried between the upper and lower 
bows of frame, the ends of the face bow sprung apart, and 
Fig. 175.— Face Bow, with Occlusion Models Attached, Adjusted to Occluding Frame 
the condyle rods are attached to the projecting lugs of the 
frame hinges. 
The face bow should be made parallel with the bench on 
which the occluding frame rests. This may be done by plac- CONSTRUCTION OF FULL DENTURES 
333 
ing a cork, or small block of suitable thickness, under the cen- 
tral clamp as illustrated in Fig. 176. 
Attaching the Casts to the Occluding Frami 
The upper bow of the frame is thrown back, the upper 
cast is seated in its baseplate and luted with wax, if neces- 
sary, to hold it steadily in place. The bow is now dropped 
Fig. 176.— Upper Bow of Frame Thrown Back to Receive Upper Cast 
Fig. 177.— Upper Cast Seated in Its Baseplate 
down on the base of the cast, to which a mix of moderately 
thin plaster is applied. The bow should be fully enclosed in 
plaster and the latter given time to set before mounting the 
other cast. 
The face bow and frame are now inverted, the sheet 
metal base removed, the lower bow thrown back, the lower 334 
CONSTRUCTION OF FULL DENTURES 
Fig. 178.— Upper Cast Attached to Frame Bow 
Fig. 179.— Occluding Frame Inverted. Bow Thrown Back to Receive Lower Cast 
Fig. 180.— Lower Cast Seated in Its Baseplate CONSTRUCTION OF FULL DENTURES 
335 
Fig. 181.— Lower Cast Attached to Frame 
Fig. 1S2.— Casts Mounted Ready for Removal of Face Bow 
Fig. 183.— Case with Face Bow, Bite Fork and Bite Locks Removed, Buccal View 336 
CONSTRUCTION OF FULL DENTURES 
cast inserted and luted to its baseplate, and the mandibular 
bow dropped down upon the base of cast. 
By loosening the set screws of the mandibular bow, the 
latter may be raised or lowered in the frame sockets until it 
lies flat upon the base of the cast. When adjusted, the set 
screws of the bows should all be tightened so that the rela- 
tion of casts to frame hinges may not be disturbed by slipping 
of the bows in subsequent steps. The lower bow and cast are 
united with plaster, as in the preceding step, the plaster al- 
lowed to harden and the frame righted. 
The face bow is removed first, then the bite fork, and 
finally the bite locks, after which the surplus plaster is 
Fig. 184.— Labial View of Mounted Casts and Occlusion Models 
trimmed from the casts and occluding frame bows. This lat- 
ter step, although apparently unimportant, adds to the ap- 
pearance of the case, and where much surplus is present, 
enables the frame to be handled lpore conveniently. 
Registering the Condyle Paths of Patient 
There are two fundamental steps of vital importance in 
the construction of anatomic and scientific dentures that can- 
not be ignored without lessening the quality and efficiency of 
the substitute. 
The first is mounting the casts in correct horizontal plane 
relationship to, and radial distance from, the rotation cen- 
ters of the occluding frame. This step just described is ac- CONSTRUCTION OF FULL DENTURES 
337 
complislied by means of the face bow or some similar device. 
The second consists in registering the pitch of the con- 
dyle paths of the patient, and setting the condyle paths of 
the occluding frame at corresponding angles. This may be 
accomplished by two somewhat different methods, the very 
simple Christensen-Snow plan and appliances, and the more 
elaborate registration suggested by Gysi by means of his Con- 
dyle Register. The first method will be described here, the 
second subsequently in connection with the Gysi appliances 
on page 465. 
Christensen’s Method 
Dr. Carl Christensen of Copenhagen noticed that when 
correctly formed occlusion models were introduced in the 
mouth and the mandible was protruded, in all cases where 
Fig. 185.— Christensen's Theoretical Diagrrm of Space Between Distal 
Ends of Occlusion Rims 
the condyle paths inclined downward, the occlusion models 
separated in the molar region, while anteriorly they remained 
in contact. 
He further noticed that the amount of separation of the 
occlusal planes in the molar region increased in direct ratio 
to increased pitch of the condyle paths. 
He then conceived the idea that by rigidly fixing the occlu- 
sion models together while in the mouth, in the separated re- 
lation produced by mandibular protrusion, on returning them 
to the occluding frame and seating each cast in its respective 
baseplate, the condyle paths of the frame, which previously 338 
CONSTRUCTION OF FULL DENTURES 
were released, would assume the same angular inclination as 
those of the patient. The condyle paths of the frame thus 
automatically adjusted were then fixed in this position. 
While subject to errors from various causes, in the main 
points the idea is practical. Christensen’s efforts, therefore, 
have contributed much to solving the problem of anatomic 
occlusion. 
To hold the occlusion models in their separated relation, 
he introduced rolls of soft wax in the molar region, instructed 
the patient to protrude and close, after which the occlusion 
models were locked together with staples or bite locks. By 
exercising care in carrying out the steps, this method is accu- 
Fig. 186.— Christensen’s Method of Registering the Condyle 
Paths with Wax Rolls 
rate, but lack of precision on tlie part of the prosthetist will 
usually result in a distorted relation between the occlusion 
models in the various steps of removal from the mouth and 
readjustment on the occluding frame. 
Dr. Geo. B. Snow devised “bite gauges” to take the place 
of the rolls of wax, and by means of these simple appliances 
the liability of error occurring is greatly reduced. 
Technic of Condyle Registration 
The occlusion models are now removed from their casts 
on the frame, the two bite gauges heated slightly and pressed 
downward into the occlusal surface of the lower wax rim 
about five-eighths of an inch in front of the distal ends. The CONSTRUCTION OF FULL DENTURES 
339 
metal plate of the bite gauge should rest on the occlusal plane 
of wax. 
The object in placing the bite gauges forward of the dis- 
tal ends of the baseplate is to prevent the lower occlusion 
model from sliding forward when the patient closes. Placed 
in the position mentioned, the pressure on closure comes be- 
tween the two extremities of the model. Before introducing 
Fig. 187.— The Snow Bite Gauges 
in the mouth, the patient should be shown the occlusion mod- 
els, his attention called to the bite gauges, and a brief expla- 
nation be made of what is expected of him. 
The occlusion models are now introduced and the patient 
instructed to protrude the mandible, or “bite forward” until 
the occlusion rims touch anteriorly, while the pyramidal 
pointed pins of the bite gauges presenting upward enter the 
upper and keep the occlusion models apart at their distal ex- 
tremities, in direct proportion to the drop of the condyles in 
Fig. 188.— Lower Occlusion Model with Bite Gauges in Position 
their paths. The occlusion models are now locked together 
with three bite locks, one on either side and one anteriorly, and 
when firmly fixed are removed from the month. 
Limit op Protrusive Movement op Mandible 
The extreme forward limit of mandibular protrusion 
varies greatly in different individuals, the average distance 
being about one-fourth inch. When the protrusive movement 340 
CONSTRUCTION OF FULL DENTURES 
exceeds this amount, the condvle-bearing surfaces in some 
cases pass beyond the normal working slant of the condyle 
paths, onto the more nearly horizontal surfaces of the articu- 
Fig. 189.— Perspective View of Upper and Lower Occlusion Models. Plumpers on the Upper 
Model. These Additions Are Usually Situated More to the Distal 
Than as Shown in Cut 
lar eminences, and an incorrect registration will result, the 
pitch of the condyle paths of the frame being less than in the 
actual working area of the natural paths. 
Fig. 190.— Schematic Drawing of What Occurs in Taking the Protrusive Bite and Adjusting 
the Locked, Protruded, Occlusion Models to the Frame 
On the other hand, a protrusive movement of one-eighth 
inch or less, while capable of being registered, will not be 
sufficient to properly adjust the condyle slots of the occluding CONSTRUCTION OF FULL DENTURES 
341 
frame, on account of the short distance the hinge pin will 
travel in the slot in adjustment of the casts to their occlusion 
models. A slight amount of lost motion also contributes to 
further error, the hinge pins being a trifle less in diameter 
than the width of the slots. 
It may be stated definitely that the amount of protrusion 
should range between three-sixteenths and one-fourtli inch, in 
order that a correct record may be made on the occluding 
frame. 
Adjusting the Condyle Paths to the Occluding Frame 
The condyle slot clamps of the occluding frame are re- 
leased and the back spring unhooked, as a preliminary step in 
Fig. 191.— Upper and Lower Casts in Protruded Relation, Seated in Their Respective 
Baseplates 
the adjustment of the casts to the occlusion models in their 
protruded or unilateral relation. 
The lower occlusion model is now set upon its cast, the 
upper bow of the frame is moved backward until the upper 
cast enters its baseplate and is accurately seated. 
In seating the casts in their baseplates care should be 
taken to direct the pressure upon them in line with their cen- 
ters, to prevent tipping. Grasping the bows of the frame near 
the hinges will unseat the casts anteriorly and reduce the 
pitch of the condyle slots below that recorded by the pro- 342 
CONSTRUCTION OF FULL DENTURES 
trusive bite, while exerting pressure on the casts anteriorly 
will increase the pitch of the paths. 
The most accurate method of adjustment is to place the 
thumb in the center of the base of the lower cast, the middle 
finger in the center of the upper, and exert sufficient pressure 
to firmly seat and hold the casts in their baseplates while 
adjusting and clamping the condyle slots. The casts being 
seated and held firmly in their baseplates as described, the 
Fig. 192.— Manner of Applying Pressure to Avoid Tipping in Seating Casts in Protruded and 
Locked Occlusion Models 
projecting end of one condyle slot plate should be grasped 
with the thumb and index finger of the other hand, and sub- 
jected to gentle traction until a position of rest is found, where 
neither side of the condyle slot impinges on the hinge pin of 
the frame. When correctly adjusted, the condyle slot plate 
is clamped in that position, and similar steps carried out in 
adjusting the opposite condyle slot. 
The condyle paths of the frame being adjusted in the man- 
ner described, the bite locks and gauges are removed from 
the occlusion models and the hack spring again hooked on its 
pin, the tension of which returns the hinge pins of the frame 
to the distal ends of the condyle slots, the same position they 
occupied when the casts were first mounted. CONSTRUCTION OF FULL DENTURES 
343 
The occlusion models, therefore, sustain the same relation 
to each other as before. The only change effected by adjust- 
ing the occlusion models in their protruded relation to the 
unlocked frame is in the slant of the condyle paths which, if 
the steps have been accurately carried out, now coincide with 
the pitch of the condyle paths of the patient. 
Some patients cannot protrude the mandible directly for- 
ward to any extent, but usually are capable of moving it to 
either side in lateral effort. In such case the bite gauges 
are inserted as usual, and the patient is instructed to ‘ ‘ bite to 
one side.” The bite locks are then inserted, the occlusion 
models removed and returned to the occluding frame. The 
condyle slot of the frame on the protruded side is adjusted 
and locked, the clamps on both sides of the frame being re- 
leased while seating the casts in their baseplates. The bite 
locks are then removed, the occlusion models returned to the 
mouth, and the patient instructed to “bite sideways” in the 
opposite direction. The occlusion models are again locked to- 
gether, removed from the mouth, returned to the frame, and 
the other condyle slot adjusted and locked as before. 
Developing the Compensating Curves 
While it is not absolutely essential to the correct arrange- 
ment of teeth anatomically, it will be found much more con- 
venient for the beginner when the condyles move downward 
as well as forward, to change the occlusion rims from flat to 
curved planes, thus indicating the alignment of the teeth from 
before backward. When properly developed, these curved 
planes represent a plane section of a convex sphere in the up- 
per, and of a corresponding concave sphere in the lower occlu- 
sion model, which may be moved against each other in pro- 
trusive and lateral effort without loss of contact. Theoret- 
ically, the working area of the condyle paths also represents 
sections of a convex sphere which have a common center with 
the occlusal sphere sections. 
In taking the protrusive bite, the condyles traversed a 
distance along the condyle path sphere equal to the forward 
movement of the mandible. The incisal plane of the lower 
occlusion model traveled a like distance along the occlusal 
sphere incisally. 
Now since the condyle spheres are fixed factors, and the 
incisal rim need not be modified, these areas become the basis 
for developing the compensating curves in the occlusion rims. 344 
CONSTRUCTION OF FULL DENTURES 
or in correcting the flat planes of the upper and lower occlu- 
sion models so that they will remain in contact in lateral and 
protrusive effort. 
Fundamental Principles of Developing the Compen- 
sating Curve 
While the following example is not exactly applicable to 
developing the compensating curves, it will serve to illustrate 
the fundamental principle involved. 
In developing a cylindrical column from a square piece of 
Fig. 193.— Diagram Showing Variation in Relation of Occlusal Planes When Condyle Paths 
Are Inclined and Horizontal 
timber, when for any reason it cannot be turned in a lathe, 
the woodworker will first square the ends of the material, and 
on each end describe a circle of the same diameter as the col- 
umn to be developed. Around these circles he will circum- 
scribe polygons — usually octagons — the sides of which touch 
the circles tangentially and are parallel to each other. By 
drawing connecting lines from the angles of the polygon on 
one end, to the corresponding angles of the polygon on the 
opposite end, the surplus is marked off, which, when removed, 
reduces the square timber to polygonal form. Accurate me- 
chanical reduction of the remaining surplus may be accom- 
plished by again drawing polygons having twice the number 
of sides, on each end of the timber, their sides also tangential CONSTRUCTION OF FULL DENTURES 
345 
to the circles, connecting their angles and reducing the sur- 
plus in a similar manner. The remaining surplus is then re- 
duced by planing off the line angles and testing with templets 
of proper curvature as the work proceeds. 
Fig. 194.— Convex and Concave Sphere Occlusion Models. Diagrammatic 
In a similar manner the sculptor blocks out liis statue in 
the rough, and the lapidist grinds off the rough and super- 
fluous parts of gems, after which both apply the finishing 
touches. 
A simple yet comparatively accurate plan of blocking out 
the compensating curves in the rough is as follows: 
Fig. 195.— Diagram of Steps in Converting a Square Into a Cylindrical Figure 
The slight protrusive mandibular effort required to bring 
the teeth in working and balancing relation seldom exceeds 
one-eighth of an inch. This distance represents the forward 
movement of the protruded condyle in its path, which for all 
practical purposes can be considered as a straight line tan- 346 
CONSTRUCTION OP FULL DENTURES 
gential to the condyle path sphere. The slight deviation from 
a horizontal line of the lower occlusion model in the incisor 
region in its protruded position is scarcely perceptible, there 
being only one two hundred and fifty-sixth of an inch of sep- 
aration, one-eighth of an inch from the labial surface of the 
wax when the drop of the condyle in its path is one-eighth 
of an inch. 
The flat plane of occlusion in the incisor region may there- 
fore be considered as another line or plane, tangent to the 
compensating curve. 
Since the only object in developing the compensating curve, 
aside from esthetics, is to secure balancing contact, and since 
balancing contact is developed between the upper and lower 
second molars, it follows that if a tangent can be correctly 
located in the area to be occupied by the second molars, the 
plane thus developed will serve as a guide in setting the occlu- 
sal surfaces of these teeth. 
The average distance from the condyle centers to the 
mesio-incisal angles of the lower incisor teeth is four inches 
in a straight line. The second molars are situated practically 
half-way between these two points, but being below a straight 
line, drawn between the points mentioned, they are usually 
about two and one-fourth inches from the second molar 
position. 
The problem then may be stated as follows: Given two 
tangents of arcs developed from a common center from which 
to develop a third tangent between the two, having a similar 
angular inclination to each, or an angular mean between the 
two. This is an extremely simple problem to solve on a sheet 
of paper, and is accomplished as follows: 
Project the two given tangents until they intersect. From 
the point of intersection lay off a point on each tangent equi- 
distant from the point of intersection and connect the points 
so located with a straight line. If for any reason the two tan- 
gents cannot be extended to intersect, lines drawn parallel 
to them, which will intersect, may be developed, and the line 
of direction of the third tangent can easily be determined by 
these construction lines. 
Now the difficulty met with in developing the third tan- 
gent on occlusion models is that the condyle path tangent if 
projected may strike the occlusion tangent too far forward in 
case of slight, or not at all in case of steep, pitch of the former. 
Neither is there a flat surface on which to make the meas- 
urements required. Yet with these difficulties encountered, a 347 
CONSTRUCTION OF FULL DENTURES 
knowledge of a few fundamental facts will enable the pros- 
thetist to develop the third tangent in a very short time. 
The first fundamental fact to keep in mind is that under 
any and all conditions the occlusal plane, whether flat or 
curved, should be so located as to divide the space as equally 
as possible between the crests of the two borders, in order 
that there may be room for placing the teeth in each arch. 
The second relates to how this space may be approxi- 
mately divided evenly. Since the flat occlusal rims have pre- 
viously been formed in most cases so as to divide the space 
between the borders equally, it follows that if the flat plane 
is to be changed to a curved plane, the change must be effected 
Fig. 196.— Locating Point A 
by modifying both occlusion rims, paring off the upper and 
adding to the lower at the distal terminal, and reducing the 
lower and adding to the upper in the bicuspid region. 
The third point is that the condyle path and the occlusal 
plane represent short tangents of a common arc, or concentric 
arcs having a common center, and therefore since they are 
tangents of common or parallel arcs, the position of the third 
tangent may be determined by developing one or more lines 
parallel to them to find the angle of intersection. 
The direction of the third tangent, or, as it may be called, 
the second molar tangent, may be determined in several ways, 
the simplest being to project the occlusal plane backward be- 
yond the point of intersection with the condyle path plane, and 348 
CONSTRUCTION OF FULL DENTURES 
bisect the included angle, the bisection fine giving the direc- 
tion of the third tangent, but the line when developed may be 
too far forward or back of the required position. 
Again the line of direction of the second molar tangent 
may be determined by laying off equidistant points from the 
point of intersection on both condyle path and occlusal plane 
tangent, and connecting the two points, as stated previously. 
This method places the position of the second molar tangent 
above and at times too far forward or back of the required 
position. 
The objections mentioned, together with the fact that the 
point of intersection is often back of the distal ends of the 
occlusion models, and therefore in space, frequently render 
both of these methods impracticable. 
By the use of one or, in some cases, two parallel lines, these 
objections are overcome and the second molar tangent can 
be laid in its proper position without difficulty. The plan is as 
follows: 
Fig. 197.— Marking Line B-C Continuous with or Parallel to the Condyle Path 
Practical Steps 
Locate on tlie upper occlusion model at its distal termina- 
tion point A, Fig. 202, page 351, through which the compen- 
sating curve must and should pass. This point should be about 
one-sixteenth of an inch above the flat occlusal plane, since the CONSTRUCTION OF FULL DENTURES 
349 
latter, when changed to a curved plane, must be so developed 
as to divide the space between the upper and lower border 
crests equally, or as nearly so as is possible with a curved 
Fig. 198.— Calipering A-F on Condyle Line 
Fig. 199.— Laying Off Distance A-F on Sub-Occlusal Line 
plane. This is necessary, as before stated, in order that space 
may be preserved for reception of the lower teeth. When the 
compensating curve is developed so that its distal termination 350 
CONSTRUCTION OF FULL DENTURES 
coincides with the flat plane of occlusion, its curvature is de- 
veloped at the expense of the lower occlusion model entirely. 
Through point A draw line B, C, continuous or parallel 
witli the condyle path, extending it diagonally across the 
lower occlusion rim. With a pair of dividers scribe line 
D, E, on the buccal surface of lower occlusion model, and 
about one-fourth inch below the flat occlusal plane. This 
subocclusal line intersects the projected condyle path line 
at F. 
Place one leg of a divider on P, the other on A, with this 
as distance set off, F, G, on D, E. Draw line A, G, which rep- 
resents a short tangent of an arc developed from the same cen- 
Fig. 200.— Connecting A-G. This Line in the Position of Second Molar Represents a Tangent 
to the Compensating Curve 
ter as the compensating curve and condyle path. At a point 
one-fourth inch in front of the distal terminal of line A, G, 
project a symmetrical, curved line forward, terminating it just 
in front of the cuspid eminence. 
The distal one-fourth inch line of A, G, represents the 
second molar tangent, both in position and line of direction, 
and is not changed in this blocking out of the compensating 
curve. Later it may or may not be slightly modified in the 
final correction of the curved occlusal plane. 
With a condyle path pitch of 35 degs., the compensating 
curve will cut into the upper wax rim about one-sixteentli of 
an inch, as stated, and in the lower occlusion model about the 
same amount. When the condyle pitch is greater than the CONSTRUCTION OF FULL DENTURES 
351 
average, the curvature should be increased, and when less, 
decreased proportionately. 
With the exception of the second molar areas, the curved 
line is developed with the eye. With a little experience a 
Fig. 201.— Completed Diagram Showing All Lines Except the Curve from 
Second Molar Forward to Mesial of Cuspid 
Fig. 202.— Diagram of Lines and Points Used in Developing the Posterior End 
of Compensating Curve A-G 
just estimate of the correct curvature can be almost instantly 
determined. 
A thin, hot blade spatula is used to divide the wax along 
line marked, from distal to cuspid terminals. That separated 352 
CONSTRUCTION OF FULL DENTURES 
from each occlusion model by the blade is transferred to the 
opposite occlusal surface, and there attached with a hot 
spatula. 
Test the accuracy of the balancing area of the blocked-out 
compensating curve by subjecting the occluding frame to pro- 
trusive and lateral movements. 
By warming the occlusal surfaces of the rims, and rub- 
bing talcum powder on them to prevent adhesion when brought 
Fig. 203.— Compensating Curve Developed, Buccal View 
together, corrections can readily be made by subjecting them 
to slight pressure in lateral movements of the occluding frame. 
The Ulsaver Method 
Dr. E. S. Ulsaver suggests attaching a softened mass of 
wax on the distal end of the lower occlusion rim, throwing 
the frame forward on that side to a distance of an eighth of 
an inch or possibly a little more, and closing the frame in this 
protruded lateral position. 
Separate the occlusion models and trim off the excess wax, 
buccally and lingually. On closing the frame, it will be seen 
that the occlusion rims are prevented from striking by the wax 
addition, which presents the form of an inclined plane, the 
distal end being the thickest. CONSTRUCTION OF FULL DENTURES 
353 
The upper wax rim is now trimmed to accommodate itself 
to the form of the built up, distal end of the lower rim. This 
is done by paring away with a knife, a little at a time, until 
the two rims again occlude. 
With this incline as a basis, which is really the beginning 
of the compensating curve, it is a comparatively simple matter 
to develop symmetrical curves on both rims. The opposite 
side is developed in a similar manner. The addition of talcum 
powder to the rims prevents the softened wax from sticking 
in lateral and protrusive movements. 
Fig. 204.— Occlusion Models Showing Lateral Curvature, 
Labial View 
The only serious drawback to this otherwise excellent 
method of developing the compensating curve is that the curve 
is usually formed entirely at the expense of the upper rim. 
Omitting Development of Compensating Curve 
It is a fact that the teeth can be arranged to occlude, and 
balance as well, without previously developing the compen- 
sating curve on the occlusion models. To do so, however, 
departure from the flat occlusal plane must be made, either in 
the initial arrangement of the teeth or subsequently. This 
change involves the development of a similar curvature of 
the general occlusal surfaces of the teeth to that developed in 
the wax rims, as detailed. Comparison of the merits of the 
two methods is largely in favor of preliminary development of 354 
CONSTRUCTION OF FULL DENTURES 
the compensating curve in the occlusion models, both from the 
standpoint of accuracy of result, and saving of time as well. 
A method of developing balancing contact and which does 
not require the changing of the flat occlusion rim to curved 
planes has been suggested by Dr. G. H. Wilson. 
This consists in stepping the upper second molar slightly 
above the first and raising the lower second molar correspond- 
ingly. In lateral movements, the mesial margin of the lower 
second molar engages with the distal margin of the upper 
first molar and in this manner balancing contact is secured. 
Tn reality, this method of arrangement is a curve of steps. CHAPTER XIX 
THE ESTHETICS OF TOOTH SELECTION 
GENERAL CONSIDERATION 
One of the most difficult problems of esthetics in pros- 
thetic dentistry relates to the selection of teeth of such size, 
form and color as will harmonize with the features of edentu- 
lous patients. 
Could the human race be classified into a few, or even 
many groups, the face forms of the individual members of 
each group being alike, or so closely similar that when the 
peculiarities of one were known all of the other members of 
that group would immediately be recognized, the problem 
would be simple. As a matter of fact, the faces of no two 
individuals in all probability were ever exactly alike in con- 
tour, proportion, disposition of lines or color effects of the 
complexion; hence the difficulty of establishing an accurate 
classification. 
Numerous attempts have been made since Hippocrates’ 
time, 2,400 years ago, to classify the human race into groups 
according to dominant characteristics. Practically all of these 
classifications were based upon the form, color and activity of 
the individuals. 
In the older classifications, the cause of the differences 
noted in various individuals was attributed to the influence of 
four fluids, or humours, of the system, viz., the blood, phlegm, 
yellow and black bile. These several fluids, it was supposed, 
tempered or influenced both the form and habits of the indi- 
vidual, according to their relative predominance and potencies. 
The older classification of temperaments was given as 
follows: 
Sanguine (full blooded). 
Phlegmatic (excess of watery fluids supposed to be elab- 
orated in the brain). 
Choleric (excess of yellow bile from the liver). 
Melancholic or atrabilious (black bile supposed to come 
from the spleen). 
Within the last century, when physiological functions be- 
came better known, the fallacy of this ancient temperamental 
basis was disclosed, and various writers on this subject have 
355 356 
THE ESTHETICS OF TOOTH SELECTION 
at different times suggested modifications. Among those most 
prominently identified in this field may be mentioned Gregory, 
Jacque, Laycock, Hutchinson and Spurzlieim. A classifica- 
tion suggested by the latter is the best known of any at the 
present time, and is here presented with an abbreviated table 
in which the fundamental points of interest to the prosthetist 
are outlined: 
Sanguine (dominance of circulatory system). 
Nervous (preponderance of nervous element) 
Bilious (excess of bile in system). 
Lymphatic (superabundance of lymph). 
Classification of Temperaments 
Basal Tempera- 
Eyes 
Hair 
Teeth 
ments 
Color 
Shape 
Lymphatic 
Pale blue or 
gray 
Fine and silky, 
but without 
luster 
Pallid, opaque 
or muddy 
yellow 
Poorly shaped, 
broad and flat 
Sanguine 
Blue, brilliant 
and expressive 
Blond-red or 
chestnut, sel- 
dom dark or 
black 
Cream-yellow, 
darker at neck 
Well-propor- 
tioned, curved 
and rounded 
Nervous 
Light gray or 
blue, restless, 
often morbidly 
brilliant 
Fine, light and 
soft 
Pearl gray, or 
blue tinge 
Long, conical 
and rounded 
Bilious 
Black or brown, 
small and 
piercing 
Coarse, dark, 
often black 
and abundant 
Strong bronze 
yellow 
Conical, long 
and angular 
That the classification of temperaments just outlined, as 
a basis for the selection of teeth, is not without glaring de- 
fects, and very imperfect, cannot be denied; yet until quite 
recently, although much has been written, but little advance- 
ment has been made in this field. 
Dr. Hutchinson, as quoted by Dr. Ivy, says: ‘‘Are we 
not obliged to confess that we have but little to guide us in 
a classification excepting the conditions which go to make up 
what we mean by complexion? In complexion we include the 
color of the hair and eyes, the state of the skin as regards 
thickness, thinness or transparency, and the various degrees 
of freedom of distribution of blood in the capillaries of the 
face. It is easy to apply with tolerable accuracy such words 
as blond, fair, dark, brunette, sallow, pale, florid, clear, muddy, 
and the like, and these and many others are epithets appli- 
cable to the complexion. Temperament, however, although to 
a large extent indicated by complexion, is generally held to 
include something more. If it did not, I fear we should find 
it but a sorry basis upon which to build a knowledge of the 357 
THE ESTHETICS OE TOOTH SELECTION 
vital peculiarities of the individual. Yet again 1 ask what 
have we to which we can make appeal? We may examine a 
man’s features, note the size of his bones, the shape of his 
jaws, the brilliancy of his eyes, the coarseness or fineness of 
his hair, his stature, his muscularity, his abundance or other- 
wise of cellular tissue and fat; but in observing all these 
things we shall be reminded that some of them are simply 
Fig. 205.— Diagrammatic Cut Showing Correspondence in Form of Alveolar and Palatine 
Arches (American System of Dentistry) 
peculiarities of family or of race, and have little or nothing 
to do with health, while others are conditions which may 
vary much at different periods during the same life.” (Amer- 
ican System of Dentistry, p. 1031.) 
Because of the comparatively rare occurrence of true basal 
types of temperament as given, and the innumerable varia- 
tions from these types observed, the Spurzheim table is ex- 
tremely limited in its scope. That it has served a useful 
purpose in a general way cannot be denied; first, in suggest- 358 
THE ESTHETICS OF TOOTH SELECTION 
ing the possibility of form and color harmony of teeth with 
the individual, although lacking in adequate data for accom- 
plishing the desired results; and, second, by keeping before 
the eyes of the dental profession the need of a better and 
more scientific method for the selection of teeth. 
With the recognized imperfections of the temperamental 
table and the daily growing demands on the prosthetist in 
the esthetic field, some solution of this most intricate problem 
of tooth selection is not only desirable, but imperative. The 
basis of the solution lies apparently in a proper application of 
the laws of harmony of form and color, regardless of the age 
nationality, race or temporary physical condition of the indi- 
vidual. 
Harmony Defined 
Harmony is defined as: “ Completeness and perfection 
resulting from diversity in unity; agreement in relation; or- 
der; in art, a normal state of completeness and order in the 
relation of things to each other; an essential in form as an 
element of beauty; as the harmonies of nature; the harmony 
of a plan well thought out; the harmony of a ship’s lines.” 
(Standard Dictionary.) “Any arrangement or combination 
of related parts or elements that is consistent or esthetically 
pleasing; agreement of particulars according to some stand- 
ard of consistency or the esthetic judgment.” (Century Dic- 
tionary.) 
Esthetics Defined 
Esthetics is defined as “The philosophy of the beautiful.” 
(Standard Dictionary.) “Esthetics, the science which de- 
duces from nature and taste the rules and principles of art; 
the theory of the fine arts; the science of the beautiful, or that 
branch of philosophy which deals with its principles; the doc- 
trine of taste.” (Century Dictionary.) 
Intuitive and Acquired Esthetics 
We look upon certain recurring things in the material 
world as right and natural, because we are accustomed to them 
and because they are associated together. When one thing 
is mentioned, other things which usually occur with it are 
brought to mind. When mountains are spoken of, or seen in 
the distance, we immediately think of a range of them vary- 
ing in elevation, more or less covered with forests, the home THE ESTHETICS OF TOOTH SELECTION 
359 
of flowers and birds and beasts, and through which streams 
flow. 
When a particular color is seen, as, for instance, green, 
an artist will think of that color, its components, yellow and 
blue, and its complementary color, red. 
When an architect, or one familiar with architecture, sees 
a structure, say, of the Grecian Doric order, even at a dis- 
tance, he immediately recognizes it as such, and recalls to 
mind its massive, well-proportioned columns, its plain, sub- 
stantial capitals, its undecorated architrave, the decorated 
frieze, the cornice, the triangular ends of the structure — usu- 
ally sculptured — called the 'pediment, bounded above by the 
sloping cornice of the roof, and below by the horizontal cor- 
nice of the entablature. Structures of this type, as the Parthe- 
non at Athens before its partial destruction, are conceded to 
be the most pleasing and perfect from an esthetic standpoint, 
of any that the hand of man has ever produced. 
The production of such structures was rendered possible 
only by the gradual growth and development of the artistic 
sense and esthetic judgment, beginning with the dawn of civ- 
ilization — a growth in development of the sense of propor- 
tions, harmony and fitness of things. To combine in such a 
structure as the Parthenon some of the more radical elements 
of the Byzantine or other dissimilar styles of architecture, 
would detract from its dignity and grandeur, and shock the 
esthetic taste of all beholders. 
In these and innumerable other examples, the esthetic judg- 
ment is a law unto itself. It cannot be formulated by rule, 
but is dependent upon and has its origin in man’s innate sense 
of the fitness of things. This sense of harmony, although 
totally dormant in some and a natural gift in others, is capable 
of cultivation, and in no profession or calling is there more 
need for its enhancement than among the members of our 
profession. The prosthetist must be able, not only to keenly 
appreciate beautiful things and recognize them when har- 
moniously arranged, but he must be able to execute them as 
well. 
These examples, although apparently abstract, have a 
direct bearing on the subject under discussion — the selection 
of teeth of appropriate size, form and color for each edentu- 
lous patient who presents. Since, as is generally conceded, 
the temperamental table affords only the most meager assis- 
tance in this regard, some other means must be employed. 360 
THE ESTHETICS OF TOOTH SELECTION 
Basis for Tooth Selection 
Tlie basis of tooth selection, as previously stated, consists 
in judging what size, form and color of teeth will harmonize 
with the facial lineaments and color scheme of the individual. 
Just as in architecture, the openings of a building, the lines 
of its doors and windows must harmonize with the more mass- 
ive lines of structure, so must the teeth, in their size and out- 
line form, harmonize with the more massive lines of the face. 
Again, in the decoration of a building, the color schemes 
employed must harmonize. Violent contrasts are oppressive 
and should be avoided, while lack of contrasts, or absence of 
complementary colors, produces a sense of dull monotony. 
In the selection of teeth, the first two factors, size and form, 
are determined by the sense of proportion, the third by color 
judgment. 
The teeth occupy a comparatively central position in the 
face, and since observation clearly shows that there is a gen- 
eral similarity in form between face outline and tooth outline 
in the same individual, a study of facial outlines is essential 
as a basis in tooth selection. 
Facial Outlines 
In Dr. Wilson’s “Dental Prosthetics” is an illustration 
reproduced from a work published 100 years ago on the “Sci- 
ence of Beauty” by an English writer, Mme. Schimmelpen- 
nick, and which, by his permission, has been here introduced. 
The outlines of faces here shown are, of course, diagrammatic, 
and conform too rigidly to geometrical forms; yet they em- 
brace practically all of the types of faces one sees nowadays, 
with perhaps the exception of the ovoid, and even that is a 
combination of the square with the round. Other combina- 
tions are, of course, possible, as the tapering with the round, 
or square or rectangular. 
Naturally a tapering face indicates a tapering tooth. 
Since the outlines of such a face converge from forehead to 
chin and the taper of the tooth, when in position, is reversed, 
harmonious results will be secured if color and size are 
right. 
An oval face calls for an oval tooth — one with sides 
slightly convex and angles rounded. 
A square, or rectangular face, requires a tooth with nearly 
parallel sides, and with moderately well-defined angles, some- THE ESTHETICS OF TOOTH SELECTION 
361 
times sharply angular, as in cases where the incisal edges are 
reduced to stimulate wear. 
The width of a tooth should hear a similar relation to its 
length as the corresponding dimensions of the face bear to 
each other. 
The problem of harmony in form and shade of teeth, with 
the individual, is of vital interest to both patient and pros- 
Fig. 206.— Reproduction of Madame Schimmelpennick’s “ Facial Forms ” 
thetist. To the patient, because the denture is a part of him- 
self, to be worn in public and private life. To the prosthetist, 
if inharmonious, the denture, like Banquo’s Ghost, which 
would not down, rises up at most inopportune times to remind 
him of his deficient technic and lack of esthetic judgment. It 
is furthermore, figuratively speaking, a standing monument, 362 
THE ESTHETICS OF TOOTH SELECTION 
before the world at all times, of inartistic and misapplied den- 
tal effort. 
Since human faces vary in outline, form, contour and gen- 
eral proportion, and since there are no fixed measurements 
available, to indicate with precision the exact length and width 
of teeth to select for edentulous cases, the necessity for culti- 
vating the sense of proportion — esthetic judgment — becomes 
plainly apparent. 
Every practitioner and student should interest himself in 
the collateral studies of clay modeling, free hand drawing 
and coloring, to acquire a rudimentary knowledge, at least, 
Fig. 207.— The Three Typal Forms of Teeth (Dr. J. Leon Williams) 
to serve as a working basis in this most esthetic branch of 
dental science — prosthetic dentistry. 
Natural Tooth Forms 
Within recent years Dr. J. Leon Williams in his studies 
of natural forms has shown quite conclusively that although 
there are many variations in form and proportion in the teeth 
of different individuals of many races, there are but three 
distinct typal forms. 
While variation from these three types are of frequent 
occurrence, such variations show certain characteristics com- 
mon to the more distinctly marked types. Dr. Williams has 
classified these three most persistent typal forms, together 
with certain variations, as follows: 363 
THE ESTHETICS OF TOOTH SELECTION 
Class or Type I. 
Square Type. 
Mesial and distal sides straight and par- 
allel for one-lialf or more of the length 
of crown from incisal edge toward the 
cervix. 
Fig. 208.— Class I, Form 1, Severest Modification of the Square Type 
Fig. 209.— Class I, Form 4, Softest Modification of the Square Type 
Class or Type II.J 
Tapering Type.| 
Mesial and distal surfaces comparatively 
straight lines, but converging toward 
each other from incisal edge cervically. 
Fig. 210.— Class II, Form 1, Severest Modification of the Tapering Type 364 
THE ESTHETICS OF TOOTH SELECTION 
Fig. 211.— Class II, Form 4, Softest Modification of the Tapering Type 
Class or Type III. 
Ovoid Type. 
Mesial surface slightly convex, distal sur- 
face a compound curve, convex incisally, 
changing to concave as it passes toward 
the cervix. 
Fig. 212.— Class III, Form 1, Severe Modification of the Ovoid Type 
Fig. 213.— Class III, Form 4, Softest Modification of the Ovoid Type 
Reproduction of Natural Tooth Forms in Porcelain 
Using Dr. Williams’ data as a basis, tlie Dentists’ Supply 
Co. have reproduced in porcelain, from models carved by Dr. 
Williams himself, the three typal forms of teeth enumerated, 
in varying sizes, together with a sufficient number of modified 
types to meet average prosthetic requirements. 
Class I contains five, Class IT, four, and Class III, four 
modifications of form. Since each class and each modification THE ESTHETICS OF TOOTH SELECTION 
365 
is produced in several graded sizes, a large variety of sizes 
are thus available for use. 
Dr. Williams ’ efforts have been devoted to the production 
of typal forms and modifications of the anterior teeth, and 
in this field he has arrived at most commendable and esthetic 
results. 
Dr. Gysi, whose distinguished work in the field of anatomic 
occlusion is most widely and favorably known, has collabo- 
rated with Dr. Williams in the designing of full sets of typal 
Fig. 214.—Occlusion View of True Bite Teeth Pat- 
terns Carved by Dr. Gysi 
forms of teeth in porcelain. The patterns for the bicuspids 
and molars were furnished by Dr. Gysi. The upper and lower 
teeth of these classes are so proportioned in their mesio-distal 
diameters and their occlusal surfaces so formed that close- 
locking occlusion can be secured with comparative ease. 
Clearance paths for the cusps of the lower between those 
of the upper teeth can be developed with but little, and in some 
cases no change of form, thus leaving the occlusal surfaces, 
which are strongly ridged and grooved, undisturbed for the 
more effective reduction of food. 366 
THE ESTHETICS OF TOOTH SELECTION 
Observed Outlines oe Natural Teeth in the Mouth 
The fact should be borne in mind that in the living, hu- 
man subject the typal forms of teeth, as illustrated, do not 
show as distinctly as in extracted teeth, or in skull dentures, 
from around the teeth of which the gum tissues have been 
Fig. 215.— Sectional View of Molar Teeth, Showing 
Strongly Ridged Occlusal Surfaces 
removed, because these tissues, particularly in early life, often 
cover some of the characteristic or determining class lines. 
Later on, or when gingival absorption at any time occurs, the 
class to which the teeth belong becomes apparent. 
To know the typal forms of natural teeth is of vital im- 
portance, and time spent in analyzing these forms and varia- 
tions will be well expended. Such knowledge will enable the 
prosthetist to produce esthetic effects not otherwise possible. 
In the literature which the Dentists’ Supply Co. furnish, 
descriptive of these typal forms of teeth, are also illustrations 
Fig. 216.— Occlusal View of Molar Surface Markings 
showing not only mold forms of the teeth themselves, hut of 
types of faces for which each mold is appropriate. 
While a few of the illustrations referred to are here in- 
troduced, a perusal of the literature and a study of the entire 
series will prove most beneficial to the prosthetist in the selec- 
tion of teeth of suitable forms for individual cases. THE ESTHETICS OF TOOTH SELECTION 
367 
The accompanying lialf-tones of noted statues in the 
various galleries and museums of Europe and the United 
States illustrate quite plainly the types of faces to which 
Madame Seliimmelpennick called attention a century ago. 
“Admiral Farragut,” “Saphira” and “Vulcan” repre- 
sent the square type and would require the parallel-sided tooth 
of Class I. 
Fig. 217.—“Admiral Farragut ” 368 
THE ESTHETICS OF TOOTH SELECTION 
Fig. 218.—“ Saphira ” 
Fig. 219.—“ Vulcan ” THE ESTHETICS OF TOOTH SELECTION’ 
“Cicero,” the “Vestal Virgin” and the statue of “A 
Young Woman” represent the tapering face and would re- 
quire tapering teeth were dentures to he supplied them. Class 
II. 
Fig. 220.—“ Cicero ” 370 
THE ESTHETICS OF TOOTH SELECTION 
Fig. 221.—“A Vestal Virgin ” 
Fig. 222.—“ Statue of a Young Woman ” 371 
THE ESTHETICS OF TOOTH SELECTION 
“Juno,” “Aphrodite” and “David” represent the oval 
type and would require the ovoid tooth of Class ITT. 
Fig. 223V2.—“ David ” 
Fig. 223.—“ Juno ” 
Fig. 224.—“Aphrodite ” 372 
THE ESTHETICS OF TOOTH SELECTION 
“Nero” represents a circle, very nearly, and could be sup- 
plied with a short, wide tooth of Class III. 
The head of “A Roman Lady” shows a severely straight 
though harmonious facial line. 
Fig. 225.—“ Nero ” 
Fig- 226.—“A Roman Lady ” THE ESTHETICS OF TOOTH SELECTION 
373 
The Color Problem in Tooth Selection 
The problem of selection of artificial teeth that will har- 
monize with the general color scheme of the individual’s com- 
plexion is a vital factor in the production of dentures of 
esthetic value. 
That this subject is given too little consideration is appa- 
rent from observing the prosthetic restorations seen in the 
mouths of persons in all conditions of life. Many of these sub- 
stitutes are out of harmony in color. The reason for this can 
only be found in the prosthetist’s lack of knowledge of color 
principles. 
The most logical means of avoiding such inliarmony in 
this line as is daily apparent is by a study of the rules of 
harmony relating to colors, their complements and con- 
trasts. 
In Vanderpoel’s “Color Problems” we find the follow- 
ing: 
“The relation of color to light is much the same as that 
of music to sound. Color has its many hues, its long scales of 
tints and shades, its true and false chords. Mere sound gives 
us but little pleasure; when developed, however, into its high- 
est form, music, we are thrilled, as by the song of a bird, a 
favorite ballad, or a Beethoven symphony. So in light, our 
enjoyment culminates at the glories of color in a flower or a 
sunset, at the shadows that play over the hills, or at the varied 
hues of a salt marsh. Hence, we may aptly term color the 
music of light; and when we think of the wonderful ways in 
which it has been used and combined by painters and design- 
ers for hundreds of years, it must seem strange to us that its 
harmonies have not been as thoroughly studied and classified 
as those of sound.” 
It must not be inferred, however, from the above quota- 
tion that a classified system of color science, capable of being 
utilized by anyone who so desires, is not available. As a mat- 
ter of fact, many valuable scientific works have been written, 
some in the simplest language possible, in which the funda- 
mental principles of color harmony are fully explained. 
That these works have not been extensively recognized 
and more generally utilized in the past, particularly in spe- 
cialized lines, as in prosthetic esthetics, is largely due to pre- 
vailing educational methods. 
A brief outline of some of the principles of color harmony 
will now be given in the hope that it may not only be beneficial 374 
THE ESTHETICS OF TOOTH SELECTION 
in a practical way, but prove an incentive to further study in 
this most interesting field. 
A Synopsis of Color Principles 
DEFINITIONS 
“ Color is the immaterial result of the decomposition of light. 
A ray of light in passing through a triangular prism is 
decomposed into a series of colors the same as a rain- 
bow. 
“Paint or Pigment is the material basis which decomposes 
light so as to reflect only some of its constituent colors. 
“Shade refers to the chromatic composition of a color. Cobalt 
and cerulium offer us different shades of blue. 
“Tint is the condition of a shade of color which arises from 
its admixture with water or white. It becomes, thereby, 
more or less intense without any change in its chromatic 
composition. 
“Tone is the condition of a color in which it appears other 
than it is. A light blue under the effect of a bright or 
dull light will appear a light blue, yet, in the representa- 
tion of these different conditions, different shades must 
be used; different tints would fail to convey a just idea 
of the color. 
“Harmony is the effect of a proper arrangement of colors in 
a picture. 
“Contrast is the effect arising from different colors being 
adjacent to one another, as red beside blue or yellow, etc.” 
—(Bacon). 
Color 
The principal source of terrestrial light is the sun. Under 
ordinary conditions, light emanating from this source is white, 
or colorless. 
By a process called dispersion, sunlight, as well as that de- 
rived from artificial sources, can be resolved into a series of 
different colors, known as spectrum colors. 
Dispersion of light is accomplished by directing a ray of 
sun or artificial light through a shutter, into a darkened room, 
passing it through a horizontally fixed prism, or over a dif- 
fraction grating, and allowing it to fall upon a white screen. 
By fixing the prism in such position that the light enters 
it at a slant, the beam will be bent twice in its course, first on 
entering, and second, on leaving the crystal. As a result, in- THE ESTHETICS OE TOOTH SELECTION 
375 
stead of showing as a spot on the screen it shows as a perpen- 
dicular band, or line, presenting a series of juxtaposed colors. 
This indicates that certain colors, of which white light is 
composed, have different refractive indices, that is, the rays 
of one color will he bent at a different angle from those of 
another. 
The colors and their order from above downward, as they 
appear on the screen, are as follows: 
Purple. 
*Blue. 
Green. 
*Yellow. 
Orange. 
*Red. 
Purple. 
Formerly the top color was rated as two colors, violet 
and indigo, but in 1890 the discovery was made that indigo 
was composed solely of blue and black, and as black is not a 
component of sunlight, indigo is not a possible prismatic color. 
Each pair of juxtaposed colors blend almost imperceptibly 
into each other so as to present different shades and varying 
tints, just as they appear in the rainbow, yet the center of each 
color is clear, distinct and unmixed. 
A distinction must be made between white light, which is 
immaterial or intangible, including the colors resulting from 
its dispersion, and pigment colors, which are composed of 
material substances. 
Since we cannot distinguish the color of an object in the 
dark it naturally follows that either sun or artificial light must 
fall upon it to disclose its tint. 
The reason why one object appears one color and another 
object a different color in the same light and under similar 
conditions is due to some inherent quality of the substances 
themselves for absorbing certain spectral colors and reflecting 
others., 
For example, a red substance absorbs all the other colors 
of the spectrum but red, which is reflected. A green substance 
absorbs all the spectrum colors but blue and yellow, which, 
when mixed, produce green. 
PEIMAEY COLOES (PIGMENTS) 
A primary color is one which cannot be formed by combin- 
ing other colors. Bine, yellow and red are considered as pri- 
* Primary colors. 376 
THE ESTHETICS OF TOOTH SELECTION 
maries, in both prismatic and pigment colors. From these, 
by their admixture in proper proportions, practically all other 
colors except white and black can he produced, and a very 
close approximation to these is possible. 
SECONDARY COLORS 
A secondary color is made by combining two primary col- 
ors in equal parts. There are three secondary colors: Green, 
orange and purple, which are formed as follows: 
Green — from blue and yellow. 
Orange — from yellow and red. 
Purple — from blue and red. 
TERTIARY COLORS 
A tertiary color is made by mixing two secondary colors 
in equal parts. There are three tertiary colors: Citrine, 
russet and olive, which are formed as follows: 
Citrine — from orange and green. 
Russet — from orange and purple. 
Olive — from purple and green. 
The formation of a tertiary color, by mixing two sec- 
ondaries in equal parts, is equivalent to mixing two parts of 
one primary to one each of the other two primaries. For 
example, olive is formed from purple and green. Since pur- 
ple contains one part of blue and one of red, and green is com- 
posed of one part of blue and one of yellow, it naturally fol- 
lows that olive is composed of two parts of blue to one each 
of red and yellow. 
INTERMEDIATE COLORS 
When a primary and a secondary color are combined in 
equal parts they form what is known as an intermediate color. 
These are named and formed as follows: 
Sulphur (yellow-green), three parts yellow to one of 
blue. 
Saffron (yellow-orange), three parts yellow to one of red. 
Nasturtium (red-orange), three parts red to one of yellow. 
Garnet (red-purple), three parts red to one of blue. 
Campanula (blue-purple), three parts blue to one of red. 
Turquoise (blue-green), three parts blue to one of yellow. 
By varying the proportions of the constituent pigments, 
it is possible to produce an almost endless variety of colors. THE ESTHETICS OF TOOTH SELECTION 
377 
COMPLEMENTARY COLORS 
Certain colors are pleasing to the eye, or harmonize, when 
placed alongside each other, while others are displeasing, or 
inharmonious. Those which are most pleasing are termed 
complementary colors. Now, why is this so? 
As has been shown, the most satisfactory light to the visual 
organs is sunlight, subdued or diminished in its intensity to 
such degree as the optic nerve can tolerate with comfort. The 
same holds true of the more brilliant white varieties of artifi- 
cial light. 
Both natural and artificial light, as has been shown, when 
passed through a prism or over a diffraction grating are dis- 
persed into the primary and secondary spectral colors. 
It therefore follows that harmony in colors results from so 
mixing them or placing them in juxtaposition that all are rep- 
resented, as in white light, though not necessarily in balanced 
proportions. 
A complementary color is defined as one which supplies 
those colors that are lacking in another color. There are vari- 
ous ways of producing complementary effects, some compli- 
cated, and others quite simple. It is to the simplest of these 
that attention will now be directed. 
The complement of red is green, because green is com- 
posed of blue and yellow, and, therefore, it supplies these two 
colors, which are lacking in red. Likewise the rule works both 
ways, for red is the complement of green. 
The complement of blue is orange, and of orange, blue. 
The complement of yellow is purple, and of purple, yel- 
low. 
As a general rule more harmonious results are produced 
when the complementary color is less pronounced than the 
principal color. When too conspicuous it lessens the promi- 
nence of the main color. 
COLOR FUNCTIONS OF THE VISUAL ORGANS 
These statements in regard to colors and their comple- 
ments are not arbitrary rules, promulgated for convenience, 
but are based upon physiologic functions of the visual or- 
gans, and can be demonstrated by anyone to his own satis- 
faction. 
For example, when one gazes intently at a red object for 
two or three minutes, until the eyes become saturated with 378 
THE ESTHETICS OF TOOTH SELECTION 
that color, and then closes the eyes an image of the object will 
still be seen, not in red, however, but in green. 
If, instead of closing the eyes, one continues to gaze at 
the same or other red objects, a greater or less sense of 
monotony and visual fatigue is experienced, which is imme- 
diately relieved on looking at something green. The same 
holds true of the other colors and their complements. 
The tiring of the visual organs, when compelled to gaze 
continuously at incomplete spectral colors, together with the 
automatic formation of complementary colors within the eyes, 
clearly indicates that white light, which contains all of the 
prismatic colors, is normally and naturally demanded by the 
organs of vision. 
When the principal color viewed is not intense, but rep- 
resents a more or less dilute tint of a primary, secondary or 
intermediate color, the corresponding complement will be pro- 
portionately reduced. 
Whatever the color scheme may be, the strength or tone 
of the various colors should accord. “The note struck may 
be high or low, but should be maintained throughout the color 
scheme. A crude, strong color, though otherwise harmonious, 
will clash discordantly among delicate tints of a notably 
lighter tone.” (Sanford.) 
The question may arise in the reader’s mind, “Of what 
value is this discourse on the physics of light, and the harmony 
of colors, to the prosthetist!” Simply this: Without a rudi- 
mentary knowledge of the physics of light, and the natural 
laws of the harmony of crude colors and their complements, 
the selection of teeth of appropriate shade, or tint, becomes 
a difficult, and in some cases, an impossible task. 
The artist, or artisan, can lighten or strengthen the prin- 
cipals or complementaries of the color scheme he is creating, 
and arrive at a just balance of harmony between the two. 
The color scheme which presents to the prosthetist, which 
he works with, and he cannot change, is the patient’s face. 
Here the flesh tints of the complexion display themselves in 
the integument according to the general characteristics, habits 
of life and health of the individual. 
The prevailing tones are gray and yellow, tinged with red 
and brown. Now since gray consists of white and black, the 
degree of grayness determines the tone of the complexion, 
whether light or dark. The reds and browns always appear 
in more or less attenuated form, and usually are modified by THE ESTHETICS OF TOOTH SELECTION 
379 
admixture with other colors to suggest secondaries or inter- 
mediates. 
The hair, to a marked degree, contributes to the general 
color scheme of the individual. In color it may range from 
white to black, including intermediate shades of yellow, red 
and brown. As a rule, light hair and light complexions are 
associated, while dark or black hair usually implies a more 
strongly pigmented integument in which perceptible tints of 
reds and browns more or less diluted, yet plainly apparent, 
are noticeable. 
The lips range in color from a gray, which at times is 
scarcely distinguishable from the integument, through vary- 
ing shades of pink, red, brown to purple, depending largely on 
the vitality and age of the individual. They form the imme- 
diate setting, or frame work, for the teeth. 
In addition to the usually pronounced color of the lips 
in which the teeth are framed, the shadows of the lips and 
oral cavity must also be considered. These shadows tend to 
soften the lighter teeth and blend them with the more darkly 
shaded integument. 
Dr. G. W. Clapp, who, with the aid of a color expert, ex- 
amined many individuals, in an effort to determine the per- 
centage of various colors present in natural teeth, gives the 
data of one case as follows: 
Age 19 
Color Developed 
Miss D. A. 
Wt. 119 lbs. 
Black 
Orange 
Ht. 5.6 in. 
Red 
Yellow 
Blue 
Eyes 
17.5 
43.0 
16.0 
16.0 
1.5 
25.5 
yel. 
Hair 
Dead 
Black 
UPPERS 
Skin 
4.1 
3.0 
.88 
.88 
2.12 
1.1 
red 
U. R. Central 
| Cervical 
1.1 
1.4 
.20 
.20 
.90 
.3 
yel. 
| Incisal 
1.1 
1.35 
.34 
.34 
.76 
.25 yel. 
COLORS FOUND IN NATURAL TEETH 
According to Dr. Clapp’s analyses, many colors are to be 
found in the natural teeth. With gray as a foundation, the 
predominance of some one of the primary or secondary colors 
gives the tooth its color individuality. He says: “Natural 
teeth exhibit every color of the rainbow. The primary colors, 
red, blue and yellow, are found in every human tooth. At 
least one of the secondary colors, orange, green or violet, is 
found in every tooth, generally with an excess of some pri- 
mary color which gives to the tooth its recognized color as a 
blue, a yellow or a pink. Gray teeth occur when there is no 
excess of primary color.” 380 
THE ESTHETICS OE TOOTH SELECTION 
SUGGESTIONS 
In the selection of teeth for a given case no specific rules 
can be laid down, because of the wide variation in color 
schemes of different individuals. Persons with complexions 
showing pronounced reds or browns, and with dark hair, re- 
quire comparatively dark teeth, in which orange or pink tints 
predominate. 
Persons are frequently seen whose general color scheme 
is neutral, no pronounced primary or secondary colors appa- 
rent. Either a very dark or a light tooth for such a case 
would be inappropriate, by attracting too much attention to 
the mouth. Teeth of gray shade or neutral tint should be 
selected and of such depth of tint as will coincide with the 
complexion. 
Fair or light complected persons require correspondingly 
light teeth, tinged with yellow or blue, sometimes almost neu- 
tral as to primaries and secondaries. 
White teeth are inappropriate in all cases, although pa- 
tients frequently demand them. Natural teeth are never 
white, the nearest approach being a light shade of gray. The 
harmony and esthetic appearance of many otherwise good 
dentures is frequently spoiled by the use of teeth of too light 
shade. 
As has been shown, the color scheme of an individual may 
range from pronounced primaries or secondaries, through im- 
perceptibly attenuating gradations to neutral grays, in which 
none of the prismatic colors are discernible. 
This color scheme, painted by nature’s hand, is the pros- 
thetist’s canvas, in which he must place a central setting, the 
teeth. How, then, can he hope to attain esthetic results with- 
out a knowledge of the laws of harmony of colors? 
The physiologic color function of the eye, previously re- 
ferred to, which automatically creates the complementary of 
a pronounced color, is an aid, in the selection of teeth, to those 
deficient in a knowledge of the laws of harmony. 
In some individuals this intuition, if it might be so called, 
is an efficient, though unrecognized, guide in choosing teeth 
that will ‘‘look well,” while the results attained through this 
means are at times pleasing and harmonious. 
More often, however, when the physiologic function is im- 
perfectly developed or totally lacking, as in the color blind, 
most inharmonious selections result, a fact plainly apparent 
to anyone in whom this faculty is not deficient. THE ESTHETICS OE TOOTH SELECTION 
381 
The selection of teeth for edentulous cases is not a prob- 
lem of matching shades, but of harmonizing colors by grada- 
tions and complementaries, the general color scheme of the 
patient affording the basis for such selection. 
It is hoped that this discourse on color and form, brief 
and imperfect as it is, has disclosed its importance in the field 
of dental prosthetics, and that it will create in the mind of 
the reader an interest in and a desire for more extended knowl- 
edge in the esthetic field. CHAPTER XX 
ARRANGING AND OCCLUDING THE TEETH 
Upper Arch 
ARRANGING THE SIX ANTERIOR TEETH 
The full upper set of fourteen teeth should be first ar- 
ranged, beginning with the central incisors. A section of wax 
is removed from the upper occlusion rim of sufficient width, 
length and depth to receive a central incisor. Into the space 
so formed a central incisor is set, its mesio-labial angle in 
line with the median line previously marked on the wax rim. 
Fig. 227.— Diagrammatic Cut Showing Section of Wax Removed with Tooth in 
Correct Labial and Incisal Position 
The labial contour of the tooth should coincide with the gen- 
eral labial contour of the rim, the two undisturbed margins of 
wax on either side of the space serving as guides in securing 
correct alignment. Its incisal edge is brought even with the 
incisal rim of wax. When set, the tooth should occupy the 
space of and restore the disturbed contour occasioned by the 
removal of the section of wax. In nearly all cases the long 
axes of the centrals, when viewed labially, should diverge 
slightly from incisal to gingival, away from the median line, 
the horizontal alignment mesio-distally of the incisal edge 
serving as a guide, or at least strongly indicating the amount 
of such divergence. When in proper position, a hot spatula 
is passed in back of the tooth so as to melt the wax, not only 
around the pins, but against the entire lingual surface as well, 
and thus firmly fix it in place. 
In like manner a section of wax is removed and the lateral 
incisor is set in position, the central just placed on its mesial 
382 ARRANGING AND OCCLUDING THE TEETH 
383 
side, and the undisturbed wax in the cuspid area on the distal 
serving as guides for its correct labial alignment. The cuspid 
is then set and fixed in similar manner. 
Fig. 228.— View of Upper Left Central Incisor Adjusted in Occlusion Rim 
Fig. 229.— Upper Central Lateral and Cuspid Arranged 
It will usually be best to return to tbe median line and 
place the other three anterior teeth in the order mentioned, 
so that should rearrangement for esthetic reasons be neces- 384 
ARRANGING AND OCCLUDING THE TEETH 
sary, it can be more readily accomplished now than after any 
of the posterior teeth are placed. 
Arranging the Posterior Teeth 
The first and second bicuspids and first and second molars 
on one side are set in a similar manner in the order named, 
followed by the arrangement of the teeth on the opposite side. 
After removing the section of wax for each posterior 
tooth, the walls of the matrix so formed should be thoroughly 
softened with a hot spatula, the tooth pressed into buccal 
alignment, and the frame closed. This brings the occlusal rim 
of the lower occlusion model up in contact with the tooth, 
which, if longer than normal, establishes its correct incisal 
or occlusal length. 
If shorter than required, it must be brought down in close 
contact with the lower wax rim when closed. In fact, the tips 
of the cusps of all of the upper bicuspids and molars should 
be sunk one-half their depth in the lower occlusion rim. This 
may readily be done by softening the wax slightly where the 
cusps strike, as each tooth is placed. The reason for this is 
that when the tips of the upper bicuspids and molars are not 
imbedded as described, but are allowed to rest on the undis- 
Fig. 230.— Six Anteriors Arranged and Waxed in Position ARRANGING AND OCCLUDING THE TEETH 
385 
turbed lower wax rim, in arranging the corresponding lower 
teeth they must be raised the full depth of their cusps, and 
even higher, in order to bring them into occlusion with the 
upper teeth. This raises the occlusal plane of the denture in 
the bicuspid and molar region from one-sixteentli to one- 
eighth of an inch above the line established by trial of the 
wax occlusion models. 
By following the plan outlined, the cusps of the upper 
teeth pass slightly below, and those of the lower slightly 
Fig. 231.— Full Upper Denture Occluded 
above, the wax occlusal plane, thus maintaining the normal 
position of the plane as previously determined. 
ARRANGING THE LOWER TEETH IN OCCLUSION WITH 
UPPER TEETH 
The arrangement of the teeth in the lower arch should be- 
gin with the lower second bicuspid because better interlocking 
of the various planes and cusps can be secured with the 
occluding teeth than when the same order of arrangement is 
followed as in the upper arch, viz., centrals, laterals, cuspids, 
etc. 
A section of wax is removed from the lower occlusion rim 
directly opposite the distal one-half of the upper first and 
mesial one-half of the upper second bicuspids. A heated spa- 
tula is thrust deeply into the floor of the space, and the side 386 
ARRANGING AND OCCLUDING THE TEETH 
walls, particularly toward the lingual, are thoroughly soft- 
ened. 
The lower second bicuspid is set in this softened matrix, 
its occlusal surface considerably above normal position. The 
Fig. 232.— Lower Second Bicuspid Set in Softened Wax, but Slightly Above 
Position. By Closure of the Frame It Is Forced Downward 
and in Approximately Correct Occlusion 
Fig. 233.— Cut Showing Proper Contact Developed between the Marginal Ridges 
frame is then carefully and slowly closed, using reasonable 
force if necessary to bring the upper teeth in contact with the 
lower occlusion rim. The wax in which the upper teeth are 
imbedded should be thoroughly chilled, previous to and dur- ARRANGING AND OCCLUDING THE TEETH 
387 
ing this step, to prevent their displacement under the applied 
pressure. 
The closing of the frame brings the upper bicuspids in 
contact with the elongated lower second bicuspid, and forces 
it down to place. If carefully carried out and the wax is suf- 
ficiently plastic, the various planes of the teeth will become 
closely interlocked, as in normally occluded natural teeth. 
Care should be taken to see that in closing the frame the 
lower bicuspid is not forced outward gingivally. This will 
most certainly occur on account of the slope of the ridge lap 
Fig. 234.—Frame Thrown to Left to Test Contact of Buccal Marginal Ridges. In 
This Case There Is Imperfect Contact between Mesial Ridge of Lower 
Second, and Distal Ridge of Upper First Bicuspid 
acting as an inclined plane, thus directing the tooth outward 
as it settles into the wax, unless counter-pressure is applied 
gingivally to keep it in proper alignment. 
TESTING THE OCCLUSAL SURFACES FOR WORKING EFFICIENCY 
Before placing the next tooth the relation of the lower 
second to the upper first and second bicuspids should be tested 
as to its working efficiency. This is done by drawing the 
lower portion of the frame outward on the side being tested, 
so as to bring the buccal marginal ridge of the lower second 
bicuspid outward and directly under the corresponding ridges 
of the occluding teeth. 
Usually, although in full occlusion the tooth may have 
interlocked well with the opposite teeth, it will be found that 388 
ARRANGING AND OCCLUDING THE TEETH 
while the mesial or distal slope of the buccal marginal ridge 
finds contact with the opposite tooth, the other slope does not 
strike, a space of greater or less width being apparent (see 
Fig. 234, page 387). 
This defect may be remedied by holding the frame in lat- 
eral position, and moving the lower bicuspid bodily forward 
or backward, as required, until the planes are brought in close 
contact and the wax surrounding the tooth chilled, when the 
frame is allowed to spring back to position. 
A piece of carbon paper inserted between the occlusal sur- 
faces will, under pressure, disclose the points of interference 
in normal occlusion, which can be ground away with a small 
Fig. 235.-— Lower First Bicuspid in Occlusion. Brought in Occlusion by Moving 
It Forward 
engine-stone. The mesial and distal marginal ridges of the 
opposing teeth are usually the points needing correction. 
Another method quite as efficient in some cases, particu- 
larly where but little correction is required, is to soften the 
wax in which the three teeth are imbedded so that with slight 
pressure they may change their position. By carefully sub- 
jecting the frame to lateral movements, at the same time ex- 
erting slight pressure to keep the teeth in occlusion, the posi- 
tion of both upper and lower teeth may be modified so as to 
correct the defects mentioned, without much, if any, grinding. 
SECURING CONTACT OF THE LINGUAL MARGINAL RIDGES 
Now, while occlusal requirements may be perfectly devel- 
oped and contact of the mesial and distal slopes of the buccal ARRANGING AND OCCLUDING THE TEETH 
389 
marginal ridges may be secured, it is frequently the case that 
contact of the lingual marginal ridges between the lower and 
upper teeth is defective or entirely lacking. Since the effi- 
ciency of the masticatory apparatus depends upon close con- 
tact of both buccal and lingual marginal ridges quite as much 
as upon good occlusal contact, it is necessary to work out the 
required contact of the lingual marginal ridges also. 
Failure to develop contact lingually in the first steps of 
arrangement is usually the result of too long buccal cusps of 
the lower, or too short lingual cusps of the upper teeth. When, 
however, the teeth are well proportioned, lack of contact may 
Fig. 236.— The Left Lower Bicuspids and Molars Occluded 
be due to inclining or tipping the teeth in one or both arches 
too far lingually, that is to say, while their cervical position 
may be correct, their occlusal ends may incline too much to 
the lingual. Correction may he made in the former case by 
reducing the length of the cusps by grinding, and in the lat- 
ter by changing the inclination of the teeth in the wax. The 
time required for effecting such changes as noted is very 
slight, and when corrected as soon as discovered, and as each 
tooth is set, usually obviates more general or extensive modi- 
fications later on. 
A section of wax is now removed for the reception of the 
lower first molar, the matrix walls softened, the tooth set in 
a slightly elevated position, pressure exerted on its cervix, 
and occluding frame closed to force it into position as 390 
ARRANGING AND OCCLUDING THE TEETH 
previously described. In like manner similar tests are 
applied, and corrections made to improve occlusion and con- 
tact between the buccal and lingual marginal ridges. Similar 
steps are carried out in adjusting the second molar and first 
bicuspid in the order named, after which the bicuspids and 
molars on the opposite side are arranged in similar order 
and manner. 
ARRANGING THE SIX LOWER ANTERIOR TEETH 
The six anterior teeth can now be set in position. These 
are placed in the wax rim in the following order: cuspids, 
laterals and centrals. 
Fig. 237.— Buccal View of Full Denture Occluded. Gums Not Carved 
Should the teeth prove too narrow to fill the space when 
aligned in proper curvature, a wider set of sixes should be 
substituted, or if too wide, a narrow set can be used. When 
only slightly excessive in width, correction may be made by 
grinding the distal surfaces of the cuspids and the mesial 
surfaces of the first bicuspids at their points of contact. This 
procedure reduces the length of the arc described by the six 
anterior teeth, and increases the distance between the first 
bicuspids, so that teeth which at first glance appear too wide 
to be practicable, can be utilized with very little effort. 
As each tooth is set, the frame should be subjected to lat- 
eral movements to test the incisal relationship of the several 
teeth. Frequently by grinding the incisal edges of the lower ARRANGING AND OCCLUDING THE TEETH 
391 
teeth at the expense of the labio-incisal angle, clearance space 
may be developed without shortening the teeth or placing 
them to the lingual of their former position. 
Fig. 2371/^.— Diagram Showing the Relation of Lower to Upper Molars in the 
Initial Act of Mastication. Balancing Side on Right. Work- 
ing Side on Left 
Where much overbite of the upper over the lower teeth is 
deemed necessary, the arc described by the latter must be 
correspondingly reduced, in order to secure clearance space 
in lateral movements. In ordinary cases an overbite of one- 
sixteentli of an inch will prove sufficient for practical pur- 
poses, and produce satisfactory esthetic results as well. 
DEVELOPING BALANCING CONTACT 
In the arrangement of the teeth, so far nothing has been 
said of the balancing contact. This has purposely been left 
Fig. 238.— Distal View of a Full Denture, Showing Relation of Teeth on Working 
Side, Left, and Balancing Side, Right 
until the teeth have been occluded, since balancing adjust- 
ment must always be carefully developed in all cases as a 
final step. Test is now made as follows: 392 
ARRANGING AND OCCLUDING THE TEETH 
The frame is drawn to one side until the teeth on the work- 
ing side are carried to their differential limit, i. e., the buccal 
and lingual marginal ridges of the upper and lower teeth are 
in contact. While in this position the relation of the uppei 
and lower second molars on the opposite side should be ob- 
served. The disto-buccal cusp of the lower second molar 
should rest against the mesio-lingual cusp of the upper sec- 
ond molar, or in the case of disproportion in the mesio-distal 
diameters of the molar teeth, it sometimes finds contact with 
the disto-lingual cusp of the upper first molar. 
If on throwing the frame sidewise as described, the second 
molars do not meet, an instrument should be inserted under 
Fig. 239.— Left Buccal View of Case. Teeth in Working Relation 
the distal end of the lower second molar and the latter raised 
until contact is established. The frame should now be opened 
without disturbing the molar in its raised position, a heated 
spatula passed under it to melt the wax and form a new base 
on which to rest, and the wax allowed to cool. 
The lower are now brought into occlusion with the upper 
teeth by closing the occluding frame, if this can be done with- 
out disturbing the lower second molar in its corrected posi- 
tion, and the position of the upper molar changed to occlude 
with the lower. When on testing, the lower and upper teeth 
do not occlude, being held apart by the modified position of 
the second molars, the wax under the upper molar should be 
softened and the teeth brought together under pressure. The 
use of carbon paper will also disclose points of interference. ARRANGING AND OCCLUDING THE TEETH 
393 
It should be kept in mind that balancing contact is devel- 
oped between the upper and lower second molars in almost 
every instance, and when developed no other contact is re- 
quired on that side between that point and the opposite lateral 
incisor or cuspid tooth. The teeth on the balancing side are 
not in such relation to each other as to form a masticatory 
mill or to hold food, the actual work being accomplished on 
the opposite or working side, therefore any considerable con- 
tact is unnecessary. 
It will be found by reference to the diagram that the gen- 
eral contact between the teeth in the two arches, in the initial 
Fig. 240.— Right Buccal View of Case. Second Molars in Balancing Contact 
act of masticatory effort, i. e., tlie position where the teeth 
begin their return to normal occlusion, is as follows: 
The buccal and lingual marginal ridges of the lower and 
upper teeth on the working side from the cuspid to the second 
molars inclusive, are in contact. On the opposite side con- 
tact exists between the second molars. These points, if con- 
nected by imaginary lines, represent a triangle, the teeth 
along the working side occupying the base, the second molars 
on the opposite the apex of the figure. 
The fact that contact is thus ranged along the sides and 
at the angles of a three-sided figure no doubt gave rise to the 
term three-point contact. This term is misleading because, as 
a matter of fact, there are, or should be, many points of con- 394 
ARRANGING AND OCCLUDING THE TEETH 
Fig. 241.— Human Denture Showing Broken Contact of Lower with Upper 
Teeth from First Molars to Cuspids of Opposite Side 
Fig. 242.— Artificial Denture Showing Broken Contact from Mesial 
of Second Molars to Centrals of Opposite Side ARRANGING AND OCCLUDING THE TEETH 
395 
tact between the teeth on the working side of the mouth, but 
not necessarily more than one on the balancing side. 
This is Nature’s plan, as can be seen by examining the 
natural teeth in a normally arranged denture. Stress, there- 
fore, is laid upon this fact because many in attempting to 
occlude teeth anatomically, endeavor to secure close-locking 
contact between the upper and lower bicuspids and molars 
on the entire balancing, as well as working, side in lateral 
movements. 
FINAL TEST WITH CARBON PAPER 
When the arrangement of the teeth has been concluded 
and balancing contact has been secured, a final test of all sur- 
faces with carbon paper is made, and the high points thus 
disclosed removed with engine-stones. This test should be 
Fig. 243.— Diagram Showing How Contact on Working 
and Balancing Sides Occurs Along Base 
and at Apex of a Triangle 
repeated until smooth-gliding contact in lateral and protru- 
sive movements is developed. 
DEVELOPING THE CONTOUR OF THE DENTURES IN WAX 
Strips of wax are now placed on the labial and buccal sur- 
faces of the denture, one strip against and parallel with the 
periphery, and another overlaying the cervices of the teeth. 
The round end of the heavy burnishing spatula is heated and 
passed rapidly back and forth along the strips to soften and 
burnish them into close contact with, and cause them to ad- 
here to, the outer surfaces of the wax denture. The wax 
should overlay the cervices of the teeth about one-twentieth 396 
ARRANGING AND OCCLUDING THE TEETH 
of an inch in depth and cover the gingival thirds at this time, 
the idea being to apply a slight surplus everywhere, from 
which, by carving, the gum festoons and general contours are 
developed to proper curvature and thickness. 
It has been previously shown by the presentation of Dr. 
Williams’ work that there are three typal forms of human 
teeth, each type presenting certain modifications. 
Fig. 244.— Sectional Cut Showing Detail of Applying 
Wax Strip for Gum Contouring 
To one who has given this subject any consideration, it 
is a comparatively simple matter, according to the data, to 
select teeth of appropriate form for any individual case, since 
the manufacturers are supplying artificial teeth closely re- 
sembling the typal forms of the natural organs. 
Fig. 246.— Wax Carving and Burnishing Spatula 
Now, granting that teeth of correct form and size have 
been selected and occluded, it does not follow that esthetic 
results will inevitably follow their use. In fact, in the carv- 
ing and festooning of the gums one class may be easily made 
to resemble another, or any form may be so distorted as to 
Fig. 246.— Carving Tool Suitable for Use in Wax, Vulcanite or Porcelain 
be unrecognizable. Clearly, then, it is the prosthetist and not 
the manufacturer who finally determines the type of tooth 
the finished denture presents. 
As an artist, the prosthetist should recognize the type of 
tooth required. As a sculptor, he should be able to so mold ARRANGING AND OCCLUDING THE TEETH 
397 
the pliant materials around the rigid porcelain teeth as to 
frame them, as it were, to meet the esthetic requirements of 
the case. 
It requires quite as much judgment to fashion the artificial 
gums around teeth of appropriate form in order not to dis- 
tort their type, as to develop reasonably appropriate forms 
from types of teeth that do not strictly conform to the re- 
quirements of a given case. In either case the prosthetist 
must possess a well-developed esthetic sense to produce har- 
monious results. 
The advantage in using teeth of suitable typal forms is 
that, although the prosthetist’s esthetic judgment must be 
none the less well developed, the teeth themselves indicate 
the form of the gum festoons, and therefore serve as patterns 
in the carving of the case. When teeth are used which do not 
strictly conform in typal outline to the case, the prosthetist 
must be able to see a mental picture of the requirements of 
the case, and develop those forms by the disposition of his 
wax around the teeth. 
As an artisan, the prosthetist must reproduce in perma- 
nent materials the modeled wax -form of the denture and 
maintain in clearness and purity during the finishing stages 
the outlines of the typal forms of teeth he set out to develop. 
The dentures at this stage are in the rough, as it were, as 
slight surplus allowance of wax should be made for loss in 
final finishing. They should, however, represent in general 
detail, though roughly blocked, the typical outline forms of 
the finished dentures, just as the work of a sculptor, as, for 
example, the statue of Tolstoi, by Mucha, represents the char- 
acteristic features of the man. (See page 398.) 
The attainment of esthetic results along these lines, as 
well as in the arrangement of the teeth, is of the utmost im- 
portance. The denture which the prosthetist produces, and 
which is fitted in the patient’s mouth, is not like a garment 
which can be worn at pleasure or put off for something more 
attractive. It literally becomes a part of that patient’s body, 
to be worn for years, or until further tissue loss or accident 
requires renewal. It corrects impaired phonation, disturbed 
facial contour, and by its use, when properly constructed, the 
patient is enabled to masticate and assimilate food, thereby 
enabling normal bodily functions to be carried on. The health 
of the patient, his well-being, comfort and good looks depend 
upon the efficiency of the prosthetist’s efforts. 
He, therefore, who undertakes this specialty should have 398 
ARRANGING AND OCCLUDING THE TEETH 
the ambition, or be required, to develop more than average 
skill, since conditions of such vital importance depend upon 
the results of his efforts. 
DEVELOPING THE GUM FESTOONS 
When teeth of approximately the right form have been 
selected and arranged, and the wax has been applied and bur- 
nished against the labial and buccal surfaces of the denture 
Fig. 247.— Statue of Tolstoi (by Mucha), Showing Characteristic Lines 
without Fully Developed Details (See Page 397) 
slightly thicker than required, the gum festoons are developed 
as follows: 
With a sharp carving tool, or the pointed blade end of 
the burnishing spatula, the surplus wax is removed from the 
labial face of each tooth. The instrument, applied at right 
angles to the surfaces of the tooth, should be held with the 
pen grasp — thumb, index and middle fingers — the fourth 399 
ARRANGING AND OCCLUDING THE TEETH 
and little fingers resting at some convenient point on the case 
so as to control the movements of the blade. 
The gingiva of each tooth is then carefully outlined with 
the blade, the surplus wax removed, and the correctness of 
form noted. It is usually better to remove too little than too 
much wax in the first outlining, since more time is lost in mak- 
ing additions than is required in going over the case a second 
time after inspection. The wax should be allowed to fill the 
embrasures to as great an extent as is consistent with the 
development of correct typal forms, to avoid the formation 
of unnecessary food pockets. 
This fact, however, should be kept in mind: When teeth 
are selected for a given case which conform in length to the 
distance between the incisal rim of wax and the high lip line, 
and in typal form to the requirements of the case, they must 
Fig. 248.— Detail of Carving Tool as Applied in 
Developing Gingival Outlines 
not be distorted and their esthetic value impaired by the ex- 
cessive use of wax in gum festooning. 
The round end of the spatula, or a similar carving tool, 
is now used to develop the varying surfaces of the gum fes- 
toons above the embrasures and between the gingivae and per- 
iphery of the denture. 
It is not possible to describe accurately the outline of 
these uniform, yet plainly marked, undulating surfaces swell- 
ing out over the rounded labial and buccal curves of the teeth 
and sinking into the embrasures and areas as between the 
roots of the natural teeth, were they present. Many in the 
attempt to reproduce the gum festoons and surfaces extend 
grooves from the embrasures toward the periphery. While 
these are decidedly better from an esthetic standpoint than 
mechanically rounded, convex ridges, they lack that indescrib- 
able and delicate variation — the imperceptible fading of one 400 
ARRANGING AND OCCLUDING THE TEETH 
surface into another so often seen in normal, healthy gum 
tissue. 
One who is really interested in this work can find no better 
ideals than can be gained by taking impressions of the labial 
and buccal surfaces of the teeth and gums of normal mouths, 
securing casts of the same, and studying the forms and varia- 
tions there represented. 
TRIMMING THE PERIPHERAL OUTLINE OF THE DENTURES 
When the festooning of the gums has been completed, and 
frequently before, the excess peripheral wax should be re- 
moved so as to disclose the general outlines of the dentures. 
The attention should be directed to the form of the denture 
as a whole, as well as to specific details, and by early outlining 
them the proportion of the parts to the whole can be more 
easily determined. 
FINISHING TOUCHES IN CARVING 
Attention lias previously been called to certain prominent 
points in tlie development of the wax contour and occlusion 
models. These will bear brief repetition, since the final 
touches are given them at this time before trial in the mouth. 
The central notch providing for the unrestricted action 
of the frenum is cleared of excess wax, and the margins 
smoothly rounded. 
The incisive fossae or depressions should be developed 
above the lateral incisors. In most cases, in order to develop 
these depressions, it will be necessary to set the cervices of 
the laterals inward so that a straight edge applied to the 
cervices of the central and cuspid on either side will clear 
those of the laterals. This does not require that the incisal 
edge of the lateral shall be set within the anterior curve of the 
arch, but merely necessitates the slanting inward or backward 
of the long axis of the lateral. 
When set directly upright the incisive fossae, if developed, 
will form an abrupt, and usually an unsightly, depression, 
while the monotonous curvature of the labial surfaces and 
parallel arrangement of the central, lateral and cuspid, do 
not produce as fine esthetic effects as where the alignment is 
varied. The cuspid eminence is usually plainly developed, 
sometimes strongly marked, as conditions demand. It is usu- 
ally most prominent, though not always so, at the peripheral 
margin, slightly concave from above downward, and again 401 
ARRANGING AND OCCLUDING THE TEETH 
prominent as the gum festoon will permit at the cervix of 
the tooth. 
Usually back of the cuspid eminence the periphery of the 
denture drops down, frequently sufficient to form a decided 
notch, to permit the free play of the buccal muscles. The 
periphery of the baseplate in the region of the tuberosities 
should extend as high as tissue attachment will permit, to give 
stability to the denture in masticatory effort. 
It is best in all cases to so form the baseplate as to em- 
brace practically all of the tuberosities, not only on the buccal 
surfaces, but distally as well. When rounded or somewhat 
spherical, as the tuberosities frequently are, the baseplate, 
when enclosing them, is prevented from sliding forward in 
masticatory stress. 
FINISHING THE LINGUAL SURFACES OF THE WAX MODEL 
DENTURES 
The excess wax should be removed from the lingual sur- 
faces of the dentures and any depressions filled in to effect 
the desired contour. 
In many cases it is advisable to develop in wax the lingual 
forms of the incomplete porcelain teeth so as to represent 
the forms of natural teeth. By applying tinfoil to the pala- 
tine area and burnishing it carefully against the lingual wax 
contours of the various teeth, the work of final finishing in 
vulcanite is reduced to the minimum. 
Care should be taken to see that the baseplate is not ex- 
cessively thick at any point, and that the border portion is 
not bulky or over-developed. Special care should be bestowed 
on the correct development of the surfaces to the lingual of 
the incisors. If unnecessarily thick, the patient’s speech will 
be thickened to a marked degree, while if deficient a whistling 
tone is apt to be produced. This is because in phonation the 
tongue does not find normal contact with the denture, or, in 
those cases where, in the production of certain tones, the 
tongue does not touch the teeth or the baseplate, the space 
through which the air passes is of abnormal outline. 
Tests should be made as to the efficiency of the denture 
in phonation during trial in the mouth. Frequently the re- 
moval or addition of a little wax will correct what otherwise 
might prove a serious defect. Such changes are usually re- 
quired to be made back of the incisor, and occasionally along 
the lingual, surfaces of the bicuspids. 402 
ARRANGING AND OCCLUDING THE TEETH 
THE DEVELOPMENT OF THE RUGiE 
When the rugae are plainly marked in the palate they are 
easily reproduced in the denture by carefully adapting the 
softened baseplate to the case in such manner as to force it 
into the depression between the folds, and yet not thin it on 
the ridges. 
In preparing an impression for the production of a cast, 
the rugae should in most cases be slightly exaggerated by 
scraping the bottom of the grooves impressed by the high 
ridges with a discoid excavator. This not only allows the 
denture to become more firmly seated on the vault tissues, 
but clearly indicates the position and form of these folds so 
that they may he easily reproduced in the baseplate when 
desired. 
Just what the function of the ruga} may be is not known. 
In the lower animals they aid in prehension. In man their 
Fig. 249.— Section of Lower Denture, Showing Lin- 
gual Surface, A, Concaved to Increase 
Tongue Space. 
roughened surfaces may assist in separating triturated from 
imperfectly masticated food, and may result in a keener ap- 
preciation of taste as well. 
When rugae are developed in a denture special care must 
be taken to have the baseplate of the exact thickness required 
in the finished substitute, to cover the cast with thin tinfoil 
before vulcanizing, and the lingual surface of the wax model 
also before flashing, the tin lining remaining in the matrix 
side of the flask. This procedure forms an improvised metal 
matrix between which the rubber is vulcanized, and when care- 
fully carried out, the surfaces of the vulcanite in contact with 
the foil are practically finished when removed from the flask. 
The lower wax model denture is finished in much the same 
manner as the upper, the prominent points of the latter, how- 
ever, being developed to a lesser degree because the surface 
markings of the lower natural denture are not strongly ARRANGING AND OCCLUDING THE TEETH 
403 
marked. Special care should he observed to avoid unneces- 
sary bulk of wax on the lingual of lower cases, for unless re- 
moved in finishing the vulcanite, tongue movements are liable 
to be impeded. When finished in the manner described, the 
wax model dentures are ready for trial in the mouth. 
TRIAL OF THE DENTURES IN THE MOUTH 
The following points should be observed in the trial of 
the wax model dentures in the mouth: 
First, occlusion. The patient is instructed to open and 
close the mouth a number of times, and in doing so to avoid 
the application of excessive masticatory force, which tends 
to displace the teeth in the wax. 
Observe the following: 
Whether or not the teeth rest against each other, as in 
normal occlusion. 
See that they intercuspate properly. 
That the overhang of the buccal marginal ridges of the 
upper bicuspids and molars over the lower teeth is the same 
on both sides. 
Note whether the median lines of the upper and lower 
dentures coincide. 
Observe the pose of the lips when at rest and in smiling, 
and finally, the profile and fullness of the face, to see whether 
addition or reduction of wax in any area is required. 
Second, lateral movements. The patient is instructed to 
move the mandible from side to side to test the clearance 
paths of the teeth. 
Usually it is best at the beginning of this test to introduce 
carbon paper between the occlusal surfaces of the two den- 
tures, and by this means under lateral movements the high 
points are disclosed. These should be ground away with 
engine stones. Repeated trials, followed by grinding, first 
on one side and then on the other, should be made until the 
cusps of the lower denture glide smoothly between those of 
the upper teeth without interference. 
When there is much variation of the lateral mandibular 
rotation centers from those of the occluding frame, consider- 
able grinding will be required. When the rotation centers 
are approximately four inches apart, but few, if any, correc- 
tions will be necessary. 404 
ARRANGING AND OCCLUDING THE TEETH 
In carrying out the lateral movements the patient should 
be cautioned against exerting much force upon the teeth, 
since by these side movements they are much more readily 
displaced than under direct stress. 
The necessity for using hard wax that will not soften 
readily at oral temperature, for the rims in which to imbed 
the teeth, becomes apparent at this stage of construction. 
Third, balancing contact may be tested by placing carbon 
paper between the upper and lower second molars on the pro- 
truded side. If the porcelain is not discolored by the carbon, 
there is lack of proper contact. Correction is made by re- 
moving, the lower denture, raising the second molar distally, 
higher than the actual required position, melting wax in the 
space underneath to serve as a foundation, returning the den- 
ture to the mouth while the wax is still plastic, and having 
the patient throw the dentures into balancing relation and 
close. The elongated tooth will thus be forced down into cor- 
rect relation, the plastic wax underneath preventing the tooth 
from settling to its former shortened position. 
One other test still remains to be carried out. The change 
of position of the lower second molar, particularly when ele- 
vated as described, in order to develop balancing contact, 
usually requires that the central groove and sloping planes 
leading to it, of the upper second molar be deepened corre- 
spondingly to receive the buccal marginal ridge of the lower 
second molar when the teeth are in normal occlusion. This 
test and the correction is made with carbon paper and stones, 
or the wax under the upper second molar is softened, the 
lower baseplate removed, chilled and returned to place, and 
the patient instructed to close with sufficient effort to force 
the upper molar into the softened wax a sufficient depth to 
bring the remaining teeth into full occlusion. 
The latter method, although practicable at times, fre- 
quently results in loss of balancing contact, because the point 
of contact previously established by elevating the lower molar 
is moved upward in gaining normal occlusion. Correction 
by grinding, therefore, is preferable. 
When satisfied that the various important requirements 
of the dentures have been developed as outlined, tests of the 
patient’s ability to phonate correctly should be made, as pre- 
viously mentioned. 
It is difficult to correctly estimate the exact amount and 
general form of contour in a denture required for the cor- 
rect articulation of sounds in all cases, except by careful trial. ARRANGING AND OCCLUDING THE TEETH 
405 
In fact, in certain cases, as where the patient has never be- 
fore worn artificial dentures, the use of any appliance having 
a baseplate in excess of bulk of normal lost tissue will cause 
a thickening of speech for some time after its introduction. 
In all cases an effort should be made to develop as nearly 
as possible the normal surfaces seen in natural dentures by 
avoiding either excessive bulk or deficient contour. 
FINAL FINISHING OF THE WAX MODEL DENTURES 
After the various tests and corrections have been carried 
out as outlined until satisfactory results have been secured, 
the dentures are removed from the mouth and returned to 
the casts on the occluding frame. 
If during trial in the mouth the position of any of the 
teeth has been purposely changed, care should be taken to 
avoid closing the frame with any degree of force or the cor- 
rections made in the mouth are liable to be disturbed. 
Each denture is now carefully inspected to see that the 
gum festoons and general contour are as desired, or, if not, 
corrected. 
The surfaces of wax are carefully smoothed with a bur- 
nisher and all minute fissures or holes obliterated, since in 
subsequent flashing the plaster will enter them and show as 
rough points on the matrix walls. 
The surfaces of wax may be rendered very smooth by 
carefully rubbing them with a pellet of cotton moistened with 
chloroform. Since chloroform is a slow solvent of wax, care 
should be taken to avoid covering the teeth with the dissolved 
wax carried by the cotton. When this occurs the teeth will 
readily loosen in the matrix in the removal of the wax. 
The case is sometimes passed quickly through a Bunsen 
flame to smooth the surfaces, but this method should not be 
generally adopted, since the flame affects high points more 
readily than depressions and finely-carved surfaces and deli- 
cate festoons are quickly obliterated. 
Before removing the casts from the occluding frame care 
should be taken to see that each wax model denture is firmly 
attached to its cast. 
This is done by placing a little extra wax at various points 
around the periphery of the baseplate and with a hot spatula 
melting it along the junction of the baseplate with the cast. 406 
ARRANGING AND OCCLUDING THE TEETH 
REMOVING THE CASTS FROM THE OCCLUDING FRAME 
With a sharp knife, the plaster which was built around 
the bows and against the base of the cast in mounting, is 
pared away so as to expose and undermine the bows, after 
which the cast is easily detached. The adherent plaster is 
then removed so as to reduce the cast to its original form 
before attachment to the occluding frame. CHAPTER XXI 
REPRODUCTION OF THE WAX MODEL 
DENTURES IN PERMANENT 
MATERIALS 
The duplication of the wax model dentures in permanent 
materials may be roughly divided into five stages, as follows: 
Flasking the wax model denture. 
Packing the matrix with rubber. 
Closing the flask. 
Vulcanizing. 
Finishing. 
A wax model denture usually presents a very irregular 
outline and many varying surfaces. It is also composed of 
some of the permanent factors of the denture, viz., the teeth, 
and sometimes the baseplate. The wax portion of the model 
denture must be replaced with rubber applied in a plastic 
condition and afterward hardened. The problem is how to 
replace the wax with vulcanite without losing the 
between the teeth and cast of the mouth. 
Sectional Molds 
The reproduction of a pattern or model in metal or other 
materials capable of being rendered plastic is usually accom- 
plished by surrounding the object it is desired to reproduce 
with a sectional mold, so formed as to part from irregular 
surfaces without breaking, removing the model from the mold, 
replacing the various sections, and filling the space formed 
by the removal of the model, with the plastic material. 
To carry out such work accurately some means must be 
provided for holding the several parts of the sectional mold 
in exact relation to each other after removal of the pattern 
or model, and while filling the matrix. 
Iron and brass founders use what is termed a flask or 
molding box, consisting of two or more sections, in each of 
which a portion of the mold is formed. These various sec- 
tions of the molding box are held in position by means of 
accurately fitted guides, so that when separated and the model 
is removed, the several parts of the mold can be reassembled 
407 408 
FLASKING WAX MODEL DENTURES 
and held in the same relation they occupied when the pattern 
was enclosed within. 
When a pattern composed entirely of wax is used, and 
the object is to be reproduced in metal, as an inlay, crown, 
bridge or denture, the mold can be made in a single piece and 
the wax model dissipated by heat, thus clearing the matrix 
and obviating the necessity for forming the mold in sections. 
In prosthetic operations the reproduction of a wax model 
denture is usually accomplished by forming of plaster a two- 
piece sectional mold in a metal box termed a flash. Some- 
times in complicated cases, as in the construction of obtura- 
tors and artificial velae, a three or four section mold is re- 
quired, involving the use of flasks of special forms. 
Flasks 
Vulcanite flasks used for dental purposes are made of 
brass or cast iron. They usually consist of a lower section 
in which the base of the cast is invested, and an upper sec- 
tion in which the mold containing the teeth and representing 
Fig. 250.— A Flask of the Usual Type Used for 
Vulcanization of Dentures 
in reverse the gum and lingual areas of the denture is formed. 
The lower section may or may not have a removable bottom, 
while the top of the upper section is always removable, to 
facilitate the flashing of the case. 
These various parts of the flask are provided with pins, 
or lugs, which fit into holes or slots in the corresponding 
opposite parts, for accurately guiding and holding them in 
correct relation to one another while flashing, and during the 
final closing of the packed case. FLASHING WAX MODEL DENTURES 
409 
Two general styles of flasks are in common use: 
First — Flasks to which screw bolts are fitted, for closing 
and holding the packed case together during vulcanization. 
Second — Flasks which are closed and held together by 
means of a spring clamp or press. 
Fig. 251.— Cut Showing the Flask Separated 
An appliance called a flask press is frequently employed 
for closing packed cases, the bolts or clamps being used for 
holding the flask together. 
The usual methods followed in closing flasks and holding 
them together during vulcanization will yield satisfactory re- 
sults if reasonable care is observed in carrying out the sev- 
eral steps. If carelessly performed, errors are liable to occur 
during this operation which may result in destroying denture 
adaptation. Attention will be called to these sources of error, 
and means for obviating the same, under the heading, Closing 
the Packed Flask. 
Most of the flasks offered by the supply houses are too 
small to receive average and large sized casts. Since no ad- 
vantage is gained in the use of small flasks, the larger sizes 
should be used. 410 
FLASKING WAX MODEL DENTUEES 
FITTING THE CAST AND WAX MODEL DENTUEE IN THE FLASK 
In upper cases the cast with wax model denture attached 
is now set in the lower, or shallow, section of the flask. If 
too large peripherally to rest upon the bottom of the flask, 
the margins of the cast should be pared away at points of 
interference until it drops into position. Usually reducing 
the distal end of a cast, when trimming in this location is 
permissible, will be all that is required. 
The upper section of the flask is now set in position to 
test the depth of cast and denture as compared to the depth 
of the entire flask. Should the incisal ends or occlusal sur 
Fig. 252.— A Special Sized Flask for Vulcanizing Large Cases 
faces of the teeth project above the upper plane of the second 
section, they will interfere with the top plate going to place, 
and the teeth are liable to become displaced. This is obviated 
by reducing the base of the cast sufficiently to lower the teeth 
below the upper plane. 
FLASKING THE WAX MODEL DENTUEE 
The upper portion of the flask is now set aside and the 
cast and denture removed from the lower section. A mix of 
plaster of medium consistency and containing no accelerator 
is applied over the bottom and around the inside periphery 
of the first section of the flask. 
The cast should be set in water for a short time just pre- 
vious to investment to partially fill the pores, then set in 
position in the flask and pressed down into the soft plaster FLASK1NG WAX MODEL DENTURES 
411 
to the position previously determined. With a short, stiff 
blade spatula the plaster between the sides of the flask and 
the peripheral line of the wax model denture is smoothed 
down where high, and built in where deficient, so as to form 
a continuous surface from the denture margin to the upper 
plane of this first section. This surface of plaster forms the 
dividing line between the two halves of the invested case. 
Care should be taken to see that none of the gum portion 
of the denture is imbedded in the plaster investment of the 
first section, or the packing of the case becomes difficult. 
Under no circumstances should the line of separation of the 
two halves of the flask occur near the cervices of the teeth 
or the basic rubber will most certainly find its way through 
to, and mix with, the gum material. 
Fig. 253.— Diagram of Upper Wax Model Denture Invested in First or Lower 
Section of Flask 
The plaster is built against the distal margin of the base- 
plate, but not so as to overlay it at any point. When set, the 
surplus plaster is trimmed off and the surfaces surrounding 
the cast smoothed up with a piece of sandpaper. Particular 
attention should be given to removing all plaster from the 
flask margins and from the holes or grooves which receive 
the lugs of the second section. This is necessary in order that 
the metal edges of the two sections may come together with- 
out interference. When smoothed up and the loose debris 
is removed, the plaster surfaces are varnished with a good 
separating medium and allowed to dry. 
The second section of the flask is now set in position, into 
which plaster of medium consistency, too thick to pour, is 
introduced with a spatula, placing it on the incisal and occlu- 
sal surfaces of the teeth. By jarring the flask on the bench, 
the plaster is vibrated down between the labial and buccal 412 
FLASKING WAX MODEL DENTURES 
surfaces of the denture and flask and over the lingual areas 
as well. 
Special care should be taken in filling the upper half of 
the flask to avoid confining the air in the embrasures, or any- 
where throughout the plaster investment. When air spaces 
are present, pressure of the surplus rubber in the matrix is 
liable to force the teeth into these spaces in closing the flask, 
or result in uncontrolled loss of rubber from the matrix. 
Elongation of the teeth from this cause is of frequent occur- 
rence, particularly when the matrix contains much surplus 
rubber. 
To obviate this difficulty, a metal occlusion retainer sug- 
gested by Dr. Greene, is bent to lie in contact with the occlu- 
Fig. 254.— A Metal Occlusion Retainer Fitted to a Half Flasked 
Upper Denture 
sal surfaces of tlie teetli and extend over the labial and buc- 
cal surfaces as well. In the second stage of flashing when 
the plaster has assumed a level even with the occlusal sur- 
faces of the teeth, the occlusion retainer previously conformed 
to the arch is quickly tilled with plaster inverted and pressed 
down until in contact with the teeth at many points. The 
remaining space in the flask is now filled with plaster slightly 
above its upper margin. 
The top of the flask is now adjusted and pressure applied 
to force out the excess plaster while it is still plastic. Care 
should be taken to see that the projections of the top enter 
their respective guides of the flask. FLASKING WAX MODEL DENTURES 
413 
Since rubber is easily soiled from dirty fingers, and since 
the flask as well as the rubber must be handled more or less 
in packing the matrix, to obviate discoloration of the rubber, 
the outer surfaces of the flask should be cleaned with a scrub- 
brush and water. The holes and grooves which receive the 
bolts should also be cleared at this time, for if deferred until 
the case is packed, some of the debris is liable to become inter- 
mixed with the contents of the matrix. This scrubbing and 
cleaning of the flask can be carried on while the plaster is 
hardening. 
From fifteen to twenty minutes’ time should be given the 
plaster in the upper portion of the flask to set, or a longer 
time if necessary when slow-setting material is used. The 
plaster must be thoroughly hardened before separating the 
flask, to prevent displacement of the teeth. 
Separating the Flask 
The flask and contents should be warmed to render the 
wax soft, but not sufficiently heated to melt it. This is neces- 
sary so that the wax may part readily from the teeth with- 
out dislodging them from the matrix. Heating is best accom- 
plished in a warming oven, the temperature of which does 
not exceed 120 degrees Fahrenheit. This method requires but 
a short time, while the danger of melting the wax is entirely 
obviated. In case the warming oven is not available, the 
flask may be heated over a Bunsen stove. When so done, it 
should not be allowed to rest in one position for any length 
of time, particularly when the case is invested in a closed- 
bottom flask. With a pair of flask tongs it may be turned 
so that its various surfaces can all be heated without over- 
heating any part. 
The principal advantage of using dry heat in softening 
the wax is that the plaster of both cast and matrix as well 
is rendered harder and more resistant to stress than when 
saturated, as it is by the usual method of placing in hot water. 
Since plaster is low in conductivity, sufficient time should 
be allowed for the heat to penetrate the interior. When over- 
heated and the wax is melted, it soaks into the plaster mat- 
rix and cannot well be removed by the usual means. Its 
presence impairs the quality of the vulcanite, frequently pre- 
venting it from fully hardening, as well as modifying its color. 414 
FLASKING WAX MODEL DENTURES 
Opening the Flask 
The heated flask resting upon the bench is set edgewise 
and with a folded towel steadied with one hand. The point 
of a knife is inserted between the line of junction of the two 
sections just sufficiently to gain a hold. A slight rotary or 
prying motion is applied until the sections show a slight line 
of separation. The flask is then turned and the knife applied 
to the opposite side. The sides of the flask by the guides, 
especially when the latter fit closely, are the logical points to 
apply the wedging pressure. 
The force at the start should be very light and gradual, 
to permit the wax to yield without endangering any over- 
hang that may be present, either on the cast or matrix walls. 
Fig. 255.— First Section of Flask Containing Cast. After Separation 
When the two sections show a line of separation around their 
entire peripheries, with a folded towel in each hand the flask 
is picked up, and with a steady, rocking, manual force, the 
lower and upper halves are gradually parted. 
Insufficient warming of the wax within the matrix, or un- 
due force exerted in separating the flask, frequently results 
in fracturing the matrix, or the cast, or in dislodging some 
of the teeth. 
When separated, the cast will be found enclosed within 
the lower section of the flask, and the teeth covered by the 
wax in the upper section. 
When Ideal Baseplate, or any hard special material is 
used as a baseplate, it can best be removed by inserting the 
point of a knife at the back under the central vault portion, 
CLEARING THE MATRIX OF WAX AND BASEPLATE MATERIAL FLASKING WAX MODEL DENTURES 
415 
when by prying upward it may be readily fractured and the 
broken pieces removed. 
With a spoon-shaped instrument, such as a medium-sized 
Kingsley Scraper, the wax enclosing the teeth can be started 
at one tuberosity, and if of sufficient cohesiveness, can be 
gradually released from the teeth and matrix, en masse. 
When somewhat hardened, it should again be rendered 
plastic or removed in sections; otherwise the teeth will be 
displaced. When overheated, but not actually melted, a dash 
of cold water will restore its cohesiveness without entirely 
destroying its plasticity. When melted and partially ab- 
sorbed by the matrix, the entire elimination of the wax is not 
possible without the application of dry heat sufficient to lower 
the resistance of the plaster to stress; therefore such means 
should not be used. 
The bulk of wax having been removed, such smaller por- 
tions as are adherent to the pins of the teeth and in the em- 
brasures should be picked out with a delicate instrument, care 
being taken not to mar the matrix or dislodge the teeth. 
The flask is now set, tuberosities up, at an angle of about 
45 degrees, in the sink,, and a small stream of boiling water 
allowed to fall from a height of ten or twelve inches against 
the molar and bicuspid teeth on each side. A small teakettle 
is very convenient for this purpose, the spout producing a 
small stream which is easily directed where desired. A pan 
with handle and having a sharp lip will answer the same 
purpose. 
To rid the matrix quickly of wax, and prevent excessive 
absorption of water by the latter, the water must be boiling 
hot, must fall from a considerable height, must be directed 
where needed, the flask inclined so that the water will readily 
flow from the matrix and carry the melted wax with it, and 
the process carried out as quickly as possible and stopped 
as soon as all wax is removed. The plan adopted by some 
of placing the flask section in a pan of water and bringing 
to a boil, is an incorrect and careless procedure, resulting in 
full saturation of the plaster with water and frequently of a 
film of wax adhering to the flask, matrix surfaces and teeth. 
The matrix section is now emptied of the water in its 
deeper parts, a thorough examination made to see that the 
pins and embrasures are clear of debris and that the plaster 
has not found its way into interproximate spaces through 
crevices in the wax model denture while filling the second 
section. Should any be present, it is picked out with a deli- 416 
FLASKING WAX MODEL DENTURES 
cate instrument, and the defective parts carved to correct 
form. 
J ig. 256.—Top View of Prepared Matrix Ready for Packing 
Fig. 257.— Top View of First Section of Flask Containing Cast FLASKING WAX MODEL DENTURES 
417 
Any delicate overhanging margins of the matrix should 
be trimmed away to prevent fracture while closing the packed 
case. Its removal only slightly increases the bulk of excess 
peripheral vulcanite subsequently, while if allowed to remain, 
and fracture does not occur, the broken pieces are liable to 
become intermixed with the rubber. The correct order of pro- 
cedure is to remove the peripheral overhang of the matrix 
margin before washing out the wax, since the latter step will 
thus clear the matrix of the cuttings. 
Should any teeth become dislodged, they may be cemented 
in place by varnishing those surfaces which rest in the matrix 
with liquid silex, and returning them to place under pressure. 
Should the case have become overheated before opening 
the flask and the wax melted, the order of procedure just out- 
lined should be carried out. In addition and at this stage 
the use of chloroform applied with tweezers and cotton pellets 
will remove some of the superficial wax. 
Treatment of First Section of the Mold Contain- 
ing the Cast 
Since plaster when dry is much more resistant to stress 
than when moist, the application of water to the cast for the 
removal of adherent wax should be avoided if possible. When 
rigid baseplate material has been employed and the case is 
not overheated, the cast is free from wax on all areas except 
around the margins where the periphery of the baseplate has 
been luted to it. A slight amount of wax in this location can 
usually be removed by careful scraping, followed by wash- 
ing of the areas so covered with chloroform. 
PROVIDING FOR THE ESCAPE OF SURPLUS RUBBER 
Since no two bodies can occupy the same space at the 
same time, some means must be provided for the reception 
of the surplus rubber during the closing of the flask. When 
no provision is made for the purpose stated, and any excess 
of rubber is present in the matrix, then when the two sections 
of the flask are brought together under pressure, compression 
of some portion of the matrix will occur. The amount of 
space so formed will be in direct proportion to the excess of 
rubber retained within the flask. 
To overcome danger of distortion of the cast or matrix 
a shallow depression extending from the inner wall of the 
flask inward to within one-sixteenth of an inch of the cast 418 
FLASHING WAX MODEL DENTURES 
margin should be made around the entire periphery in the 
first section of the flask. This depression should not be con- 
nected at any point with the matrix, the idea being to leave 
a narrow line of contact at the peripheral margin of the den- 
ture between the surfaces of plaster in the two sections when 
the flask is closed. 
This line of contact retards the ready escape of the rub- 
ber during the closing of the flask, and subsequently during 
vulcanization. Furthermore, should much excess be present, 
this peripheral line of contact being so much more limited in 
area than the cast or matrix walls, will yield slightly and per- 
mit the surplus to escape into the groove, thus relieving undue 
pressure within the matrix. 
The cutting of waste gates leading from the periphery of 
the matrix to the outer groove is unnecessary, and, in fact, 
detrimental, as when present they permit the too ready escape 
of surplus rubber. 
The groove having been formed, the debris is brushed off 
and this section is set aside until the matrix is packed with 
rubber. 
Steps Preparatory to Packing the Matrix 
Dental rubber, while more or less plastic and adhesive, is 
not sufficiently so to be formed into a homogeneous mass as 
it is introduced into the matrix. In adding one piece of pink 
rubber to another, or in introducing the basic material, spaces 
are liable to result from the overlapping of one piece on an- 
other. Unless these spaces are eliminated while packing, an 
intermixture of the pink and basic rubber will often occur. 
Such mishaps always detract from the esthetic appearance 
of the finished denture. 
There are two methods in vogue for rendering the rubber 
more plastic preparatory to packing, viz., first heating the 
rubber before introduction, and second, heating the matrix, 
by which means the rubber, although cold, is immediately 
rendered plastic when carried to place. 
HEATING THE RUBBER BEFORE INTRODUCING IT IN THE MATRIX 
This is usually accomplished by placing the pink and basic 
rubber on a plate, as it is cut in pieces of suitable size for 
packing. The plate is placed over a pan of water and the 
latter heated over a burner. The greatest amount of heat 
possible to develop by this method will not exceed 212 degrees 
Fahrenheit, not sufficient to injure the rubber, yet ample to FLASKING WAX MODEL DENTURES 
419 
render it plastic and workable. The objection to this method 
lies in the fact that the rubber, although heated, is carried 
to a cold matrix where it immediately becomes chilled, and is 
almost as difficult to condense as though it had not been so 
treated. 
The second and much more practical method, when one 
becomes accustomed to it, consists in heating the matrix side 
of the flask to about 212 degrees Fahrenheit, or until steam 
begins to escape from the plaster. A matrix so heated will 
usually retain sufficient heat to permit the rubber to be con- 
densed, but should the packing of the case prove tedious, it 
may be reheated without injury to the rubber already packed. 
The advantages of this method are twofold, viz., first, dry- 
ing and hardening of the plaster matrix, rendering it more 
resistant to stress, thus reducing its liability to distortion in 
closing the flask; and second, the absorbed heat of the matrix 
not only softens the rubber as soon as placed, but keeps it 
plastic so that it may be united into a homogeneous mass en- 
tirely free from spaces, thus obviating the danger of inter- 
mixture of the basic and gum material. 
The disadvantages of this method consist in danger of 
overheating the flask, thus injuring the plaster, and the neces- 
sity for exercise of greater care in manipulation to avoid 
burning the fingers. In all other respects this method of ren- 
dering the rubber plastic is preferable to the former, and by 
observing reasonable care the objections mentioned can be 
obviated. 
To prepare the matrix for packing by the second method, 
the flask should be placed on a metal plate or sheet of gauze, 
over a Bunsen flame, and heat applied gradually so as not 
to disintegrate the plaster in the bottom of the flask. Since 
plaster is a poor conductor of thermal changes, the process 
should be continued a sufficient time to heat the entire matrix 
throughout. Care should be taken not to force the heating 
too strongly, or the rapid accumulation of steam next the 
bottom and walls of the flask may disturb the plaster contents. 
In the meantime, while the flask is heating, the rubber may be 
prepared for packing. 
HEATING THE MATRIX PREPARATORY TO PACKING THE RUBBER 
PREPARING THE RUBBER FOR PACKING THE MATRIX 
A good-sized sheet of clean paper is laid on the bench; 
the packing instruments, a pair of ball pointed pliers, a thin- 420 
FLASHING WAX MODEL DENTURES 
blade burnisher, a sharp-pointed instrument and the heavy 
wax burnishing spatula are laid conveniently at hand. 
The muslin, covering both sides of a sheet of granular 
gum facing or pink rubber, is stripped back so as to expose 
Fig. 258.— This Cut Shows the Essentials for Packing a Case. To the Left and Bottom Are 
the Instruments Required. To the Left, Strips and Triangular Pieces of Pink or 
Granular Gum Rubber. On the Right Side, Strips of Basic Rubber. 
Lower Right, a Single Piece of Basic Rubber for Over- 
laying the Vault Portion of Matrix 
from one-lialf to two-thirds of the sheet. Eight or ten strips 
three-sixteenths of an inch wide are cut from across the sheet 
and allowed to fall on the paper, but should not touch each 
Fig. 259.— Diagrammatic Cut Showing Method of Cutting 
Triangular Pieces of Pink Rubber 
other because of their tendency to adhere. From one or more 
of these strips are cut about twenty-eight triangular pieces 
for filling the embrasures between the teeth. These also 
should be kept separate. FLASKING WAX MODEL DENTURES 
421 
BASIC RUBBER 
Several strips of the red, maroon or black rubber, which 
is to constitute the base, are cut and laid to one side of the 
pink. As the packing proceeds, wider strips will be required, 
but they can be cut as needed and of a width suitable to the 
requirements of the case. The rubber being cut as described, 
and the matrix side of the flask heated, the case is now ready 
for packing. 
Since the outer matrix wall of a vulcanite case, being per- 
pendicular or nearly so, is most difficult to adapt the rubber 
to and hold in position until the flask is finally closed, this 
portion of the matrix is packed first because more accessible 
before the introduction of the basic material. 
The one essential point to keep in mind during the pack- 
ing of the rubber is to so place it as to avoid intermixture 
of the gum material and the basic portion. The gum facing 
must be applied piece by piece and formed into a solid homo- 
geneous mass free from spaces. It must lie in close contact 
with the matrix walls and show no tendency to draw away 
from them. It must entirely fill the embrasures between the 
teeth from the deepest portions represented by the interproxi- 
mate spaces in the bottom to the extreme upper periphery of 
the matrix. 
PACKING THE MATRIX 
PACKING TIIE GUM FACING 
With the sharp packing instrument, or a pair of ball 
pointed pliers, a triangular piece of granular gum or pink 
rubber is carried, pointed end down, into the embrasure be- 
tween two teeth, and with a suitable thin-bladed burnisher 
is forced into the deepest and narrowest portion. Another 
piece is carried to the adjoining embrasure and adapted in 
a similar manner. The adjacent angles of the two are pressed 
between the matrix walls and the labial cervix of the tooth, 
and if sufficiently long to meet, are united together by pres- 
sure. If too short, a third piece can be laid above the cervix 
of the tooth and the three united. 
The other embrasures are similarly filled, each triangular 
piece of rubber as it is added being closely conformed to the 
walls and its upper end united with the adjoining piece 
already placed. The embrasures, interproximate spaces and 
the space between the cervix of each tooth and the matrix 
wall for an eighth of an inch above the teeth should be filled 422 
FLASHING WAX MODEL DENTURES 
solidly with triangular pieces of gum, and all well condensed 
so as to eliminate all openings. 
A strip of pink or granular facing rubber is now applied 
against the lingual surfaces of the teeth, and pressed against 
that which already fills the embrasures. Its lower margin 
should not approach the pins of the teeth closer than one- 
sixteenth of an inch, nor should it ever enclose them, since 
teeth anchored in pink vulcanite are gradually dislodged 
under stress. 
The strips of rubber, when cut crosswise of the sheet, are 
not of sufficient length to pass around the matrix wall from 
Fig. 260.— Some of the Triangular Pieces of Pink Rubber Packed in the 
Embrasures 
one tuberosity to the other; therefore to complete the first 
layer, a second strip is abutted or allowed to slightly overlap 
the end of the first piece, after which it is adapted to the cor- 
responding unfinished part of the matrix above the tooth pins 
on the opposite side. In placing these and all other strips of 
the gum material, care should be taken to avoid stretching 
them, as the tendency of the mass of gum facing to leave the 
matrix w-all is very noticeable if the strips are stretched as 
applied. 
Another strip of facing is placed above that already 
packed, its lower slightly overlapping the upper margin of 
the first. When by pressure — usually with the round end of FLASHING WAX MODEL DENTURES 
423 
the burnishing spatula, slightly heated — it is adapted to the 
matrix wall and underlying rubber, other strips are added 
and pressed to place in like manner, one layer overlapping 
another, until the entire wall of the matrix is covered. When 
Fig. 261.— Diagrammatic Cut Showing How the Strips of Pink Rubber Should Overlap Each 
Other, Similar to the “ Breaking of Joints ” in a Brick Wall 
care has been exercised in carving the wax gums to correct 
contour, two layers of pink rubber will furnish ample thick- 
ness to obviate exposure of the basic material on the gum 
surfaces in the final finishing of the case. 
As a final step in the condensation of the gum portion, 
a folded towel should be placed against the outer surface of 
Fig. 262.— A Convenient Rubber Packing Instrument (Ivory) 
the flask to protect the thumbs from the heated metal, and 
finger pressure should be applied to the rubber built against 
the matrix wall, the force exerted being outward and slightly 
downward. 
Some prosthetists, before introducing the gum material, 
paint the matrix wall with a solution of pink chloro-rubber, 
which serves to cement the layers of gum material closely 
to the walls. When applied in a thin layer, and the chloro- 
form is allowed to evaporate before packing, it serves a use- 
ful purpose, but is more often harmful than beneficial, as at 
times it seems to retard the hardening of the pink rubber in 
vulcanizing. It is also liable to change the color of the outer 
surfaces of the gum facing to a slight extent. 424 
FLASHING WAX MODEL DENTURES 
The entire outer wall of the matrix having been packed 
and condensed as described, the next step is to introduce the 
basic rubber. 
A narrow strip is laid in the bottom of the matrix and 
pressed under the pins of the teeth, care being taken not to 
displace the gum facing which fills the deepest portions of 
the interproximate spaces. This strip of basic material, al- 
though placed under the pins, should lie to the lingual of the 
gum facing. 
A wider strip is now laid over the first one and pressed 
solidly against it, so as to eliminate any spaces that may be 
PACKING THE BASIC RUBBER 
Fig. 263.— The Gum Facing Packed. First Strip of Basic 
Rubber Packed Under the Pins 
present. The bottom of the matrix is filled in this manner 
so as to represent in hulk the amount of wax and baseplate 
material that formed the hulk of the wax contour model. 
In upper cases the palatine portion is covered with one, 
sometimes, though seldom, two, thicknesses of rubber cut so 
as to overlay this area and extend on and attach to that fill- 
ing the deeper part of the matrix. 
A pattern can quickly be cut from the muslin removed 
from the sheet rubber, and its size tested by placing in the 
matrix. When properly formed, it is laid on the sheet of 
rubber, a piece cut according to outline, the muslin removed, 
and the rubber placed in position and firmly condensed at FLASKING WAX MODEL DENTURES 
425 
its margins to that already packed around and to the lingual 
of the pins in the bottom of the matrix. A strip of basic 
material wide enough to line the gum portion of the matrix 
is cut and stretched to reduce its thickness. This is then laid 
Fig. 264.— The Pins Entirely Covered with Basic Rubber 
Fig. 265.— Vault Area Covered with a Single Layer of Basic Rubber 
against the gum facing and firmly pressed against it. This 
lining of basic material strengthens the gum portion, and fur- 
ther insures the entire palatine and border surfaces of the 
denture, being composed of the same colored vulcanite, a 
point of considerable esthetic importance. 426 
FLASKING WAX MODEL DENTURES 
A second layer of rubber, usually a strip about one-half 
inch wide and long enough to extend from anterior to pos- 
terior limits of the matrix, is laid in the central palatine area, 
to insure slight surplus in this region on closing the flask. 
Fig. 266.— Matrix Packed Ready for Closing the Flask 
When both basic rubber and gum facing have been introduced 
and thoroughly condensed, the case is ready for the final steps 
preparatory to closing the flask. 
When diatoric teeth are used it is necessary, in packing 
the matrix, to fill the central depressions of the bicuspids and 
Fig. 267.— Cut Showing Method of Packing 
Depressions in Diatoric Teeth 
molars with small pieces of basic rubber. This is an essential 
part of the packing process and is necessary in order that the 
anchorage spaces within the teeth for the rubber may be per- 
fectly filled in the final closing of the flask. FLASKING WAX MODEL DENTURES 
427 
The amount of basic material required is entirely depen- 
dent on the extent to which absorption of the residual ridge 
has progressed. When extensive, more rubber will be re- 
quired than when the ridge is prominent. 
A simple method of testing approximately the proper 
amount of rubber required to fill the matrix, is to collect all 
of the wax and baseplate material removed from the matrix, 
GAUGING THE AMOUNT OF RUBBER REQUIRED 
Fig. 268.— Water Gauge for Determining the 
Volume of Water Required to 
Fill the Matrix 
work it up into a solid, compact mass and test its bulk by 
displacement of water as follows : 
A glass is filled to overflowing with cold water. Into this 
the wax, held on the point of a small instrument, is immersed, 
which, of course, displaces an equal bulk of water. The wax 
is then removed, the required amount of gum facing — usually 
about one-half sheet — is placed in the glass, and sufficient 
basic material is added to again bring the water to the point 
of overflow of the glass. A slight addition should be made to 
compensate for the wax that adhered to the pins and was lost 
by washing the matrix with hot water. 
Dr. E. T. Starr suggested the use of a glass vessel hav- 
ing two adjustable pointers attached to a perpendicular post 
held by means of top and bottom bands. The top pointer 
was set at high-water mark, as established by the introduc- 428 
FLASKING WAX MODEL DENTURES 
tion of the wax. The lower pointer was set at low-water 
mark, determined by removal of the wax. Sufficient rubber, 
both facing and basic material, was added to raise the water 
to the upper pointer. The use of this appliance obviated the 
overflow of the water. 
Flask Closing 
Previous mention has been made of the crystalline char- 
acter of plaster, its tendency to crush under pressure when 
the modulus of resistance to stress of the crystals has been 
reached, and of its greater resistance to stress when in a dry 
condition than when saturated, or even slightly moistened 
with water. 
These facts are of vital importance in vulcanite denture 
construction, for when disregarded, distortion of the cast, of 
the matrix side of the flask, or of both, is very liable to occur. 
When so occurring, the result is frequently a partial or total 
loss of adaptation of the denture to the tissues. 
PRELIMINARY CONSIDERATIONS RELATIVE TO FLASK CLOSING 
ESTIMATING THE FORCE EXERTED BY THE SCREW 
Few prosthetists realize the enormous pressure capable 
of being exerted on both the cast face and the opposite matrix 
walls when the latter contain a considerable quantity of ex- 
cess rubber, the flask being completely closed at a rapid rate 
and under direct screw pressure. The rule for estimating 
the force exerted by a screw is stated as follows: 
distance between 
P : W :: contiguous threads = ttX twice the length of lever. 
Explanation 
P = power, indicates the amount of force exerted on the 
end of the lever or wrench handle. 
W = weight, indicates the load moved by the screw in ad- 
vancing through the nut, or the force applied 
against the excess rubber. 
Distance between contiguous threads of screw refers to 
pitch of screw. 
7r = pi, is the Greek letter used to indicate that number — 
3.1416 — which, when multiplied by the diameter 
of a circle = the circumference. 
The lever or wrench represents the radius of the circle 
described by the end of the handle in revolving the nut around FLASHING WAX MODEL DENTURES 
429 
the screw. To find the diameter of the circle, the radius must 
be doubled. 
In applying this rule to determine the force exerted by 
the flask screws, the principal factors concerned are as fol- 
lows : 
First. The power delivered on the end of the wrench 
handle by the hand. 
The record of over two hundred tests made by prosthet- 
ists under the writer’s observation, with a specially designed 
Fig. 269.— Diagram Showing Arc Described by Flask Wrench 
wrench capable of registering the pounds pressure applied, 
showed a range of from 15 to 80 pounds exerted on the end 
of the four-inch handle. The low average of the total was 
50 pounds. 
Second. The weight, or second factor, represents the 
force exerted by the surplus rubber against the cast in one 
side, and the matrix walls and teeth in the opposite side of 
the flask, as the screw pressure forces out the excess material. 
This, of course, is an unknown quantity, but is determined by 
the rules of proportion in the usual manner. 430 
FLASKING WAX MODEL DENTURES 
Third. The distance betiveen two continuous threads 
represents the approach of the two halves of the flask to each 
other in revolving the nnt once around by means of the 
wrench. The threads on the average flask bolts are 1-20 of 
an inch apart, or, as ordinarily spoken of, the pitch of the 
screw is 1-20. 
Fourth. The fourth term of the proportion is determined 
as follows: Multiply the length of the wrench by 2, which 
gives the diameter of the circle, in inches, traversed by its 
outer end. This multiplied by 3.1416 will give the circumfer- 
ence of the circle in inches. 
With three factors known, the fourth can easily be found. 
The following example will serve to illustrate the enormous 
force commonly delivered against the cast face in flask clos- 
ing: 
Number of pounds applied to the end of the 
wrench handle 4 inches long 50 
Force exerted against cast face by excess rubber 
under pressure X 
Distance between two contiguous threads 
1-20 of an inch 
Circumference of circle described by end of 
wrench 3.1416 X 2 X 4 = 25+. 
Formula, 50 : X :: 1-20 : 25 +. 
Multiplying the two extremes = 1250. 
Dividing 1250 by 1-20 to determine the other 
mean = 25000. 
Deducting 2-3 for friction, gives 8333 pounds ex- 
erted on cast face. 
Accompanying tests made by the writer in a specially 
designed compression dynamometer revealed the fact that a 
face plate with one inch superficial area could be forced from 
1-16 to y8 inch into hardened and comparatively dry plaster 
at 2,000 pounds pressure, and % to % inch in well hardened 
plaster, set four hours. It will thus be seen that distortion of 
both cast and matrix may readily occur under the pressure of 
over four tons as ordinarily applied. 
The only redemption from failure in denture construc- 
tion in every case is due to the fact that the rubber is plastic 
and does not resist the force of the screw, as would a hard, 
unyielding material. When the closing of the flask is forced 
too rapidly, however, with a large amount of excess rubber 
present, the effect is practically equivalent to that produced 
with a hard, unyielding material interposed. This is often 431 
FLASKING WAX MODEL DENTURES 
seen in fractured casts and distorted surfaces in the final 
opening of the flask. 
Five pounds of power on the end of the wrench handle 
represents the maximum force that should he applied in flash 
closing. Even this amount, limited as it is, yields a pressure 
of over 800 pounds on the cast face. 
TEST CLOSING OF THE FLASK 
To insure a sufficient quantity of rubber in the matrix 
and yet obviate distortion of the cast face and matrix walls, 
Fig. 270.— Dynamometer Flask Wrench for Registering the Force Applied in 
Closing Flasks 
as a result of undue force, the following method will be found 
satisfactory: 
The matrix should contain very little excess rubber. The 
proper amount may be determined with comparative accuracy 
by means of the water glass test previously described. 
The flask should be gradually raised in temperature to 
212 deg. F., dry heat, the two halves brought together by 
tightening the bolt nuts slowly, being careful not to exceed 
five pounds force on the wrench handle, and when closed the 
bolts are removed and the flask separated. 
To prevent adhesion of the rubber to the cast surfaces 
a square of muslin slightly larger than the area of the matrix 
should be interposed between the two halves of the flask. A 
piece of the cloth removed from the sheet rubber, when freed 
from the sizing or starch, will answer this purpose. On open- 432 
FLASHING WAX MODEL DENTURES 
ing the closed flask the muslin can readily be removed from 
the condensed rubber within the matrix without distorting the 
latter by moistening it with a pellet of wet cotton. 
Close examination should be made to see that the matrix 
contains sufficient rubber, usually determined by observing 
the peripheral surplus and by applying pressure interiorly. 
If deficient, additional rubber should be placed where re- 
quired and the flask closed without reheating. 
TREATMENT OF THE CAST SURFACES FOR VULCANIZATION 
Just before the final closing of the flask the surfaces of 
the plaster cast should be well saturated with liquid silex, a 
thick coating being applied and allowed to remain undisturbed 
for two or three minutes, when the surplus may be removed 
with a cloth or pellets of cotton. This film of silex penetrates 
the surface of the plaster to a slight extent, fills the minute 
openings between the crystals as well as the smaller air spaces 
and gives a smooth, hard finish to the cast. As a result the 
vulcanite will present a much smoother surface than when 
pressed and hardened against an untreated plaster surface. 
Casts formed from Spence’s plaster, which on account of 
its greater resistance to stress is preferable to plaster, should 
be covered with a layer of thin tin foil, usually No. 4. The 
foil is first applied to the cast surfaces with the fingers, the 
surplus removed with shears and final adaptation secured 
with a soft napkin or pellets of cotton and pressure. 
When adapted the foil is removed, the surface of the cast 
is coated with a film of LePage’s glue, the foil returned to 
place and by pressure and burnishing conformed closely to 
all surfaces of the cast. Sandarac or shellac varnish may also 
be employed. Whatever adhesive agent is used it should be 
applied in a thin coat and allowed to become somewhat sticky 
before returning the foil to the cast. 
To aid in the removal of the tin foil from the vulcanized 
case the former should be covered with a film of soap, either 
lather or liquid, the surplus being removed with pellets of 
cotton and the film allowed to dry before closing the flask. 
In case the tin foil cannot be readily stripped from the 
denture after vulcanization it can be removed by the applica- 
tion of mercury, rubbing it into the tinned surfaces with 
chamois leather. 
Casts formed from magnesium oxy-chloride require no 
coating or preliminary treatment, the surfaces being suffi- 433 
ELASKING WAX MODEL DENTURES 
ciently smooth to impart a dense and polished surface to the 
vulcanite. 
The steps having been carried out as described, the plas- 
ter contents of the flask are now in a comparatively dry and 
hardened condition, the matrix filled without distortion of its 
walls or the cast face. 
To prevent the rapid saturation of the now dry plaster 
investment in the flask during vulcanization, the latter should 
be placed above the water in the vulcanizer, and hardened 
in steam instead of under water, as is the usual method. 
Cases so manipulated often come from the vulcanizer with 
the plaster almost as hard and capable of resisting stress as 
when first introduced. 
SCREW PRESSES 
Screw presses are frequently employed for closing flasks. 
These appliances have screws of different pitches, ranging 
from 1-10 to 1-16, which with a short handle yield less force 
Fig. 271.— Double Handle Flask Closing Press. Screw 1/12 Pitch 
than a screw of less pitch, as 1-20. The handles of most flask 
presses, however, are double, permitting the use of both hands 
in closing, so that an equal, or greater, amount of force can 
be developed by means of the press with double handle than 
with the flask wrench. 
Spring devices, as the Donham or Wilson flask presses, 
are designed for maintaining the partially closed over-packed 434 
FLASKING WAX MODEL DENTURES 
Fig. 272.— Double Handle Flask Closing 
Press. Screw 1/16 Pitch 
Fig. 273.— The Donham Automatic Flask 
Closing Spring Press for Two Flasks 
Fig. 274.— Adjustable Automatic Flask Closing Spring Press for One, 
Two or Three Flasks FLASKING WAX MODEL DENTUBES 
435 
flask under continuous pressure until the elevation of tem- 
perature within the vulcanizer renders the rubber sufficiently 
plastic to escape into the space provided, without subjecting 
cast or matrix to excessive pressure or crushing strain. 
In the vulcanization of thick, bulky masses of rubber, 
spring closing devices are of decided advantage, for the rea- 
son that when excessive expansion of the mass occurs, the 
spring yields, allowing the flask to open slightly, thus reliev- 
ing the matrix walls and cast face from undue stress. Later 
on when contraction sets in, the resiliency of the spring will 
again force the flask together. CHAPTER XXII 
VULCANITE 
In prosthetic operations, vulcanization is the process by 
which rubber as prepared for dental purposes is changed 
from a plastic state to a hardened condition capable of re- 
taining its molded form and of resisting stress. 
Rubber so treated is termed vulcanite, and the apparatus 
by means of which the process is carried out is called a vul- 
canizer. 
In order to have a clear understanding of the process of 
vulcanization it will be necessary to learn something of the 
origin and physical properties of both crude and manufac- 
tured rubber, and of the chemical changes which occur dur- 
ing the hardening process. 
Rubber 
Rubber is a colloidal substance obtained by evaporating 
the juice derived from various species of tropical trees, 
shrubs, vines and creepers. The first importations of im- 
portance of this material into Europe, in the form of bags 
and bottles, occurred in the early part of the eighteenth cen- 
tury, but its real origin was apparently unknown. From the 
fact that it was found very useful in rubbing out lead-pencil 
marks it was called rubber. The name India was applied to 
it because the early shipments came from the West as well 
as the East Indies. 
Brantt states that “In 1735 La Condamine first discov- 
ered that the substance was the dried milky juice of a tree 
which the Indians on the coast of the Amazon River called 
Caout-Chouc and from which, from time immemorial, they 
had been making waterproof fabrics, shoes, vessels, etc.” 
Caoutchouc 
It is a long story — the history of investigation concern- 
ing the physical and chemical properties of caoutchouc. More 
than one hundred and seventy-five years have elapsed since 
La Condamine first discovered that it was of vegetable origin. 
Many eminent chemists have devoted a great deal of time to 
436 VULCANITE 
437 
investigating this natural product, and yet to-day there are 
some problems arising from the necessary mixture of caout- 
chouc with other substances for commercial purposes, but 
partially solved. 
Carl 0. Webber, Ph. D., Crumpsall, Eng., whose work is 
perhaps the most logical and up-to-date, in “The Chemistry 
of India Rubber” (1909), says in regard to the difficulties 
attending investigations of this material: 
“No class of bodies offers such formidable manipulative 
difficulties to the investigating chemist as the remarkable 
group of colloids comprised under the collective name of India 
rubber. These difficulties are physical rather than chemical 
— that is to say, they do not so much consist in the functional 
complexity of the molecules of India rubber as in the cir- 
cumstance that these molecules are, at any rate at present, 
known only with the colloidal state superimposed upon them. 
Matter in this state does not exhibit the abrupt changes of 
physical condition which, in crystalloids, take the form of 
melting points, boiling points and solution. The physical 
changes induced in colloids by heat, or by solvents, are per- 
fectly continuous changes as long as the underlying chemical 
molecule or configuration remains intact. As a consequence 
the characterization and identification of the colloids and 
their derivatives and their isolation and purification from 
mixtures of them, offers frequently almost insuperable diffi- 
culties.” 
Crude caoutchouc as it comes to market is of varying and 
uncertain composition. A lot produced in a given locality 
will oftentimes differ slightly in composition from another lot 
from the same species of trees in a nearby locality. 
The juice when it first issues from the tree is milklike in 
appearance and is termed latex. It consists of more than 50 
per cent water. On exposure to the air it loses most of the 
moisture, is reduced in bulk, turns brown and becomes more 
or less elastic. 
The rubber gatherer in the native forests dips a clay- 
covered paddle in the collected latex, gives it a few turns and 
subjects the adhering film to the heat and smoke of an open 
fire to evaporate the moisture rapidly, repeating the process 
many times until a good-sized oval mass, termed a “biscuit,” 
is formed. 
In this as well as various other crude methods of prepara- 
tion, sand, dirt and other foreign matter become incorporated, 
while covering an imperfectly evaporated layer with a fresh 
one causes the retention of excess moisture. 438 
VULCANITE 
Recent methods whereby the latex, when freshly collected, 
is subjected to the action of chemicals for the extraction of 
undesirable constituents, have resulted in the production of 
rubber of a superior quality. 
One formula for Para latex and another for the rubber 
after evaporation of the moisture are given below: 
Latex 
Water 55.15 
Caoutchouc 41.29 
Proteids 2.28 
Sugar 0.36 
Ash (Salts) 0.41 
Loss 0.51 
100.00 
Evaporated Juice 
Caoutchouc 94.6 
Resin 2.66 
Proteids 1.75 
Ash 0.14 
Moisture 0.85 
100.00 
Caoutchouc of commerce is prepared for manufacturing 
purposes by first shredding it and washing to remove the 
contained soluble constituents and foreign matter. It is then 
thoroughly dried and passed through heated rolls to render 
it again homogeneous. Caoutchouc prepared in this manner, 
although comparatively pure, is adaptable to but few pur- 
poses because of its tendency to stick to objects it comes in 
contact with, or when folded on itself. It also deteriorates, 
and in time loses its elasticity and becomes hard. 
The discovery of a method of rendering soft rubber less 
adhesive and more permanent was made by Charles Goodyear 
of Boston in 1839, and Thomas Hancock of England in 1842. 
Goodyear patented his process in 1843. While the methods 
of these men eliminated the stickiness and improved the qual- 
ity, the rubber was not hardened appreciably. Nelson Good- 
year discovered a process of hardening rubber in 1849, which 
process was, and is still, termed vulcanization. 
The hardening of all varieties of rubber is rendered pos- 
sible by the addition of sulphur. In the actual process of 
hardening, the rubber may be subjected to the action of heat 
and usually moisture, in a specially designed boiler termed 
a vulcanizer. “Thin articles may be vulcanized cold by dip- 
ping them in a cold mixture of 100 parts carbon disulphide 
and 2i/2 parts of bichloride of sulphur for from 1 y2 to 3 min- 
utes, according to the thickness of the articles.” (Braunt.) 
The first experiments with rubber in denture construction 
were made by Mr. Bevan of the Goodyear Rubber Company, 
in conjunction with Dr. Putnam of New York, and Dr. Mal- 
lett of New Haven in 1853. Their vulcanizer weighed 1,200 
pounds. (Harris, 1871.) VULCANITE 
439 
Formulas for Dental Rubbers 
The following formulae for various colored rubbers used 
for dental purposes are those furnished by Dr. Wildman: 
Dark 
Brown 
Red 
Dark Grayish Jet 
Pink White Black Black 
Ma- 
roon 
Caoutchouc 48 
48 
48 
48 
48 
48 
48 
Sulphur 24 
24 
24 
24 
24 
24 
24 
Vermilion 
36 
10 
30 
White Oxide of 
Zinc 
, . 
30 
96 
# # 
# # 
Ivory or Drop 
Black 
• • 
•. 
24 
48 
6 
— 
— 
— 
— 
— 
— 
— 
Per cent of Caout- 
chouc in mass..66 
44 
43 
22.6 
50 
40 
44 
Various shades of red and pink rubber are produced by 
modifying the percentage of vermilion; maroon, by increas- 
ing or decreasing the black pigment. 
VuLCANIZABLE RUBBER EMPLOYED FOR DENTURE BASES 
Red, maroon and black varieties of rubber of the best 
quality, in addition to sulphur, contain a comparatively small 
percentage of inert material usually represented by the col- 
oring pigments employed. Because of their greater strength 
and elasticity, the better grades of rubber should, as a rule, 
be employed for baseplate purposes. 
Cheap grades of basic rubber are heavily loaded with for- 
eign material to reduce the cost. When present in any con- 
siderable quantity they reduce the elasticity of the finished 
product and render it brittle as well. 
The cheaper grades of rubber, however, show less ten- 
dency to become porous in vulcanizing than do the better 
grades because of the comparatively low percentage of caout- 
chouc present, grayish white in the table of formulas, show- 
ing only 22 per cent of rubber. 
PINK RUBBER EMPLOYED FOR GUM FACING 
Since the basis of all vulcanized rubbers is a combination 
of sulphur and caoutchouc, and the color of this mixture is 
brown, it follows that in order to produce a pink the base 
must be lightened by the addition of a white pigment. White 
oxide of zinc, and sometimes kaolin are used for this purpose, 
to which vermilion is usually added for producing a pink 440 
VULCANITE 
tint. Varying shades of this color may be produced by modi- 
fying the proportions of the pigments. The best products, 
however, are but poor imitations of the natural gum tissues, 
being dense, opaque and flat. 
In full cases where the gum tissues are not visible the 
dissimilarity is not so striking as in partial cases where the 
natural gums are exposed to view. When possible to avoid 
it, pink vulcanite should not be applied when the line of junc- 
tion of the artificial gum with the natural tissues will be 
plainly apparent. 
To overcome the objection of the flat, lifeless appearance 
of pink vulcanite, various substitutes have been offered, one 
of the most satisfactory of which is that known as Granular 
Gum Facing. 
PINK GRANULAR GUM FACING 
This gum facing consists of many minute particles of var- 
ious colored rubbers, pink, white, red and possibly a little 
yellow, the pink largely predominating, so united as to form 
a homogeneous mass, yet not so blended that the particles 
lose their individual tints. 
As prepared for use it is lighter than the natural tissues 
but darkens slightly during vulcanization. Although opaque 
it does not appear as flat as the ordinary pink vulcanite, on 
account of the variegated colors of which it is composed. 
When this material is used for artificial gum facing, the 
carving and polishing having been properly accomplished, it 
presents the very best appearance of any of the pink varieties 
of vulcanite and should be used in preference to the latter. 
If on vulcanizing it presents a darker appearance than 
desired, it may be lightened or solarized by placing in a glass 
vessel, covering with alcohol and bleaching in the sun for one- 
half to three-fourths of an hour. Pink vulcanite can also be 
lightened in the same manner. The tint so imparted will in 
time disappear, but the favorable impression produced on the 
mind of the patient is well worth the time expended. 
The Chemical Constituents of Rubber 
Caoutchouc is classed as a colloidal hydrocarbon. When 
subjected to the action of the best-known solvents the greater 
portion, about ninety-five per cent, is brought into solution, 
while about five per cent remains insoluble. The chemical 
formula of the soluble portion is CioHi«, while that of the in- 
soluble constituent is CsoHesOio. The percentage of carbon VULCANITE 
441 
and hydrogen in the insoluble portion is the same as in the 
soluble portion, as is seen in the following: C30H08O10 = 
(CioHiejs-f 10 H2O. 
Webber, whose researches in this field are perhaps the 
most elaborate of any, refers to the insoluble constituent of 
rubber as follows: 
“In brief I suggest that this insoluble compound is a link 
between India rubber and the complex carbohydrates, the 
celluloses in particular, which I am inclined to consider the 
raw material from which the plant produces all the terpenes, 
including India rubber.” 
There is, on the other hand, no doubt that India rubber 
absorbs oxygen when exposed to the atmosphere, and this 
oxygen absorption finally always results in the conversion of 
the India rubber into a brittle resinous body, generally de- 
scribed as Spiller’s resin. Spiller has published an analysis 
of this body and gives the following figures: 
C —64 
H — 8.46 
0 — 27.54 
“It is interesting to note that these figures very exactly 
agree with the composition of a body of the formula CsoH-tsCho, 
the relation of which to our insoluble constituent, C30H06O10, 
is obviously significant. Equally interesting to observe is the 
fact immediately deducible from the above given percentage 
composition of Spider’s resin, that this oxidation of India 
rubber consists purely and simply in the addition of oxygen 
to the unsaturated India rubber molecule, and that conse- 
quently the carbon-hydrogen ratio of India rubber —10:16 — 
remains unaffected in this process.” * * * “From this 
we may infer that the oxygen percentage of India rubber in 
its free resin state of purity is due to two factors, one of 
which is the presence of the insoluble constituent, CsoHeeOio, 
the other to the formation of oxygen addition products of 
India rubber.” 
He further states that the insoluble constituent does not 
seem to be present in all varieties of rubber, and when present 
it occurs in very small quantities. 
Chemistry of Vulcanization 
Webber further sums up the observations and results of 
many experiments in the vulcanization of rubber as follows: 
“From these facts we are justified in drawing the follow- 
ing conclusions: 442 
VULCANITE 
“ First — The India-rubber hydrocarbon, polyprene CioHie 
combines with sulphur without evolution of hydrogen sul- 
phide. The vulcanization process of India rubber is, there- 
fore, an addition process. 
“Second — The insoluble constituent of India rubber, 
which forms only an insignificant proportion of the chemicai 
product, not exceeding five per cent of the total, combines 
with sulphur under vulcanizing conditions at a very slow rate, 
with the evolution of hydrogen sulphide and with the forma- 
tion of a substitution product. 
“The process of vulcanization consists in the formation 
of a continuous series of addition products — of polyprene 
and sulphur, with probably a polyprene sulphide C100H160S as 
the lower and C100H160S20 as the upper limit of series. Phys- 
ically this series is characterized by the decrease in distensi- 
bility, and increase in rigidity from the lower to the upper 
limit. Which term of the above series, i. e., which degree of 
vulcanization, is produced is in every case only a function of 
temperature, time, and proportion of sulphur present.” 
“There arises now, of course, at once the question as to 
the nature of the process by which sulphur enters into com- 
bination with the polyprene, whether the polyprene sulphide 
or sulphides formed are addition or substitution products. 
Certainly what we already know respecting the chemical na- 
ture of India rubber leads us to infer that the vulcanization 
process consists essentially in the formation of an addition 
product of sulphur and polyprene. This assumption, how- 
ever, requires further support in view of the fact that quite 
a number of writers, from Payen to most of the recent au- 
thors, declare that vulcanization is accompanied by the evolu- 
tion of sulphuretted hydrogen, thereby implying that the 
process is a substitution and not an addition process. Indeed, 
most of the recent authors on this subject state this in so 
many words. We shall therefore have to subject this point 
to a careful examination. 
“Assuming the compound of polyprene and sulphur, 
which indisputably forms in the vulcanization process, to be 
a substitution product, it follows with absolute necessity that 
for each 32 parts of sulphur combining with the polyprene we 
must obtain 34 parts of hydrogen sulphide. Now in the proc 
ess of vulcanization as practically carried out, we obtain on 
an average, say, 2.5 per cent of combined sulphur. Conse- 
quently, the vulcanization of one ton of India rubber, on the 
above assumption, would be bound to yield very nearly 60 VULCANITE 
443 
pounds of hydrogen sulphide, or approximately 18,000 litres. 
Considering that in a number of factories the amount of India 
rubber vulcanized daily largely exceeds one ton weight, we 
should expect to find the vulcanizing rooms of these factories 
reeking with this gas. As a matter of fact, however, there is 
scarcely ever a trace of this gas to be discovered in the rub- 
ber works atmosphere, and the very rare cases in which its 
presence becomes noticeable may always be considered as an 
indication of something ‘having gone wrong.’ ” 
Webber’s work may be briefly summed up as follows: 
That the hardening of rubber by vulcanization is brought 
about by a chemical union of CioHic or polyprene with sul- 
phur, resulting in the formation of a series of polyprene sul- 
phides, not by the breaking up of the CioHie molecules, but 
by the addition to them of sulphur; that the formation of 
hydrogen sulphide during the process of vulcanization is not 
an essential chemical reaction, necessary to the hardening of 
rubber; that when formed it is due to the presence of the 
insoluble constituent — CsoHesCho —in the rubber; that when 
the process of vulcanization is properly conducted, such slight 
amount of hydrogen sulphide as is formed does not seriously 
interfere with the quality of the hardened product; and, fin- 
ally, that when hydrogen sulphide is formed in excessive 
quantity it is an indication that something “has gone wrong,” 
and the quality of the vulcanite is impaired. 
While Webber’s observations seem generally logical, there 
are some peculiarities occurring in the vulcanization of cer- 
tain classes of cases that require further study. For example, 
thick cases in which there is a large bulk of rubber present, 
frequently come from the vulcanizer in a porous condition 
and with a strong odor of hydrogen sulphide, an indication 
of something having gone wrong. The same grade of rubber 
may be employed in thin or even medium thick cases, vulcan- 
ized under the same conditions of temperature, time, and 
moisture, or at the same time in the same apparatus, yet show 
no porosity, nor will the odor of hydrogen sulphide be per- 
ceptible. 
The cause of this is not clear. If Webber’s observations 
are correct that the development of hydrogen sulphide is due 
to the presence of the insoluble constituent in the rubber, and 
the same grade of rubber is used in both cases, why should 
not the case containing less bulk show at least a propor- 
tionate amount of porosity, accompanied by an appreciable 
amount of hydrogen sulphide1? 444 
VULCANITE 
Two hundred blocks of vulcanite, %x%x% inches, in all 
of which practically the same grade of rubber was used, when 
sawed through the center showed the following results: 
125 blocks, very porous. 
25 blocks, slightly porous. 
50 blocks, nop-porous. 
These cases were all vulcanized in the same apparatus, 
and under as nearly the same conditions of time and tem- 
perature as possible, yet seventy-five per cent were porous, 
while twenty-five per cent were solid. The most porous blocks 
were bulged out slightly, while some of the semi-porous and 
all of the solid blocks showed some contraction. The above 
tests were made for the purpose of illustrating the variation 
in porosity of the different blocks and were not tested for 
dimensional change. 
Wilson suggests that the expansion of the rubber in the 
matrix, which occurs before and possibly continues for a short 
time after the vulcanization point is reached, depletes the 
matrix of some of the solid material. This having escaped 
beyond the bounds of the matrix cannot return when con- 
traction later occurs, being prevented from doing so, first, by 
the natural sluggishness of the rubber, and, second, because 
as soon as vulcanization sets in the rubber next the outer sur- 
faces of the matrix forms a constantly hardening crust, which 
effectually prevents its return, and, third, the surplus itself 
being usually disposed in thin layers is quickly hardened by 
the vulcanizing process. 
Now, as vulcanizing proceeds, the interior of the bulky 
mass not yet hardened continually contracts, usually toward 
the hardened outer shell, resulting in the development of 
many internal spherical spaces, the formation of a partial 
vacuum, and on account of the heat attained, the hvdro-carbon 
be decomposed and unite with the sulphur to form sufficient 
H2S gas to fill the space. 
Whatever the cause, the fact remains that porous condi- 
tions frequently develop during vulcanization, oftentimes to 
such an extent as to require reconstruction of the denture. 
Porosity of Vulcanite an,d How to Overcome It 
Any means, therefore, that can be employed for reducing 
the excessive bulk of rubber without materially increasing the 
weight or disturbing the required contour of the case might 
be advantageously used for overcoming porosity. VULCANITE 
445 
Several methods, having this end in view, will here he 
mentioned: 
First — The baseplate itself may be formed in wax so as 
to represent one-lialf or more of the required bulk of the fin- 
ished denture. This may then be vulcanized, after which the 
teeth are occluded upon it, the deficient contour developed in 
wax and the case revulcanized. 
This method is specially applicable to lower cases where 
the alveolar border is almost completely absorbed and where 
the establishment of normal profile and bite requires that the 
teeth shall be set high above the border crest. It may also be 
used to advantage in badly absorbed ridges in upper cases. 
While this method does not reduce the bulk of rubber, the 
process of vulcanization is divided into two stages, which in 
practically every case will avert porosity. 
Second — When for any reason the double vulcanization 
method is not considered advisable, these and similar cases 
may be carried out as follows: 
The wax model denture is flashed in the usual manner. 
Pink gum facing is applied to the labial and buccal walls of 
the matrix. The lingual wall of the matrix is lined with basic 
material which should be carefully applied so as to leave no 
open spaces in the lining. This leaves the central portion or 
body of the matrix still unfilled. Into this space blocks of old 
vulcanite, cut in such manner as to fit into the opening with- 
out disturbing the packed rubber, are placed. The blocks 
should not extend so high as to interfere with the alveolar 
ridge of the cast when the two halves of the flask are closed. 
Additional basic rubber is now laid over the blocks, ex- 
tending from the inner to outer periphery of the matrix, thus 
entirely covering or sealing them in, so that none of the old 
rubber will be exposed to view when the case is finally fin- 
ished. Sufficient excess should be present to insure all spaces 
between the blocks and matrix walls being filled on closure 
of the flask. 
Third — Blocks of aluminum or tin may be employed in- 
stead of vulcanite, the technic of application being similar to 
that just described. When a considerable space is to be filled, 
aluminum is preferable to the tin on account of its lighter 
specific gravity. When either of these or similar metals are 
inclosed, the weight of the denture will be increased. 
Fourth — The interior of the matrix may be filled in with 
pink or white rubber, each of which is heavily loaded with 
inert foreign material, as the oxide of zinc or white kaolin. 446 
VULCANITE 
These rubbers, even in excessive bulk, seldom ever become 
porous in vulcanization. 
Closing Flasks With Spring Pressure 
To compensate, in part at least, for the excessive con- 
traction which occurs in bulky cases during vulcanization, the 
closing of the flask with spring pressure is advised. 
The matrix is packed in the usual manner, slightly in ex 
cess of the amount actually required to fill the space. The 
flask is set in a spring press of the Wilson or Donham type, 
and the screw turned to develop sufficient tension in the spring 
to force the flask together, as the rubber becomes semi-liquid 
with rise of temperature. 
Since closure of the flask is not accomplished immedi- 
ately but is extended over a considerable period of time, in 
Fig. 275.— Flask with Bolt Springs in Position 
many cases not until the hardening process begins, it is ar- 
gued that the expansion in the mass of rubber, due to heating, 
is over before all of the excess is removed from the matrix. 
Space is thus provided for some of the last excess by the con- 
traction of the mass of rubber which begins with the harden- 
ing process. 
Stated differently, some of the excess rubber is thus fed 
into the constantly contracting mass until the hardening proc- 
ess is well under way. The resulting vulcanite shows greater 
density with less contraction than when the flask is completely 
closed before introduction into the vulcanizer. 
All forms of spring-flask closing devices are designed, pri- 
marily, to partially compensate for excessive contraction in 
the mass of rubber by prolonging the closing process through- 
out the greater portion of the contractile period. Second- 
arily, the use of springs obviates excessive stress on the mat- 
rix walls and thus reduces the tendency toward distortion. VULCANITE 
447 
Dr. Geo. B. Snow suggests the use of small spiral springs 
interposed between the nuts and flask top. When applied, the 
flask need not be fully closed, but the springs must be com- 
pressed so that as the rubber becomes plastic with rise in tem- 
perature, the resiliency in the springs will effect complete 
closure. (See cut, page 446.) 
Dimensional Changes Occurring in Rubber During 
Vulcanization 
EXPANSION 
Two distinct changes occur in rubber during the vulcan- 
izing process, viz., first, expansion, followed by contraction. 
The expansive movement, which is very decided, begins 
with the first application of heat and continues until shortly 
after the hardening process sets in. The lowest point at 
which rubber begins to vulcanize or harden is approximately 
around 240 degs. F., while the highest point at which it may 
safely be conducted, without causing detrimental chemical 
change, is 320 degs. F. 
During the initial heating of a packed and closed flask, up 
to the lowest point of vulcanization, the matrix having been 
full and waste gates formed as described, the rubber flows 
outward into the spaces so provided as a result of expansion 
due to rise in temperature of the mass. 
In case no waste gates are present and the flask, fully 
packed, is closed before introducing into the vulcanizer, dis- 
tortion of the matrix will usually occur, the amount depend- 
ing, first, upon the excess of rubber present, and second, upon 
the tendency of the matrix walls to yield under stress or com- 
pressive force, and third, upon the temperature of the applied 
heat. 
That the expansive force of rubber is very positive and 
powerful as well is frequently seen in the distortion of matrix 
walls and cast surfaces, which distortion if wrought directly 
would require the application of heavy mechanical force. . 
The contractile movement sets in shortly after the rub- 
ber begins to harden and continues throughout the vulcanizing 
process in a moderately definite ratio, the amount depending 
upon the functions of time and temperature of applied heat. 
Since no appreciable amount of excess rubber, which from 
any cause has been expelled, can return to the matrix, it natu- 
CONTRACTION OP RUBBER VULCANITE 
rally follows that as contraction of the essential body of ma- 
terial occurs, there being no means of replenishing it as it 
becomes reduced in bulk, warpage of the baseplate is very 
liable to occur since the mass no longer completely fills the 
matrix space. 
At times contraction of the rubber is so marked that 
spaces develop between the vulcanite and the teeth, while that 
enclosing the pins contracts in such manner as to almost re- 
lease the latter. When such a condition arises the teeth will 
frequently be found loose, can readily be moved in their mat- 
Fig. 276.—■ This Cut Shows a Flask Forced and Held Apart One-eighth 
Inch by the Expansion of Rubber During Vulcanization. 
The Spring Exerted a Pressure of Over 600 Lbs. 
rices, and will be easily displaced under stress. When the 
denture is subjected to use, the spaces become filled with food, 
which, as it decomposes, gives rise to disagreeable odors. 
Gases in which marked contraction occurs usually require re- 
construction. 
VuLCANIZERS 
The apparatus in which the flasks containing the packed 
rubber are placed while hardening is called a vulcanizer. It 
consists of a boiler usually large enough to hold two or three 
flasks, and is commonly made of seamless hammered copper, 
the walls of which are about one-eighth of an inch thick. VULCANITE 
449 
Tlie top margin of the boiler is turned true and polished 
and to this a cap or cover is fitted for confining the steam. 
The cap is usually grooved to receive a packing of graphite, 
steam-proof fiber or metallic lead, to seal the boiler tightly 
and prevent the escape of steam during vulcanization. 
Various methods are employed for fastening the top to 
the boiler, the most convenient of which is by means of a 
cross-bar hinged to one side of the boiler. When the cover is 
adjusted, the bar rests upon it and is bolted to the opposite 
side with a single bolt. 
As before stated, the boiler is usually made of hammered 
or pressed copper, without brazed or soldered joints, so as 
to resist the expansive force of steam to which it is subjected 
during vulcanization. Cast boilers of copper, brass or iron, 
unless made specially heavy, are liable to prove defective and 
leak or burst with use. Explosions are by no means rare, and 
such accidents are always dangerous. Every precaution, 
therefore, should be taken to obviate them, first, in the selec- 
tion and use of the most trustworthy and well-constructed 
appliance it is possible to secure, and second, in bestowing the 
proper care upon it while in use. 
SAFETY DEVICES 
To the lid of the vulcanizer are usually attached various 
devices for registering temperature or indicating pressure 
within the appliance, those most commonly employed being 
the thermometer and the steam gauge. 
THE THERMOMETER 
An attached thermometer enclosed within a metal case 
indicates the temperature. The base of the thermometer case 
screws over a projection on the vulcanizer cover. 
The center of the projection is bored out to make a reser- 
voir for containing mercury. In this mercury bath the ther- 
mometer bulb rests and by this means the thermometer has 
a direct metallic connection with the interior of the vulcanizer 
through the mercury and the metal cover. The metal casing 
of the thermometer should be removed from the vulcanizer 
cap from time to time to see that the depression contains the 
required quantity of mercury, i. e., sufficient to surround the 
thermometer bulb. When the bulb does not rest in the mer- 
cury bath the temperature reading will be much lower than 
the temperature of the steam within the vulcanizer. The re- 450 
VULCANITE 
suit in such cases is that if the temperature is raised to the 
vulcanizing point as indicated by the thermometer, the con- 
tents of the flask will in all probability be ruined by overheat- 
ing. Deficient mercury in the depression oftentimes accounts 
for the safety valve of the vulcanizer blowing off before the 
thermometer registers the vulcanization point. 
THE STEAM GAUGE 
Since a definite ratio exists between steam pressure and 
temperature, a steam gauge of ordinary type and connected 
to the vulcanizer cover in the usual way may be used in con- 
junction with or independent of other registering devices. 
TABLE OF STEAM PRESSURE 
The following table, showing the relation of temperature 
to pressure of heated or unconfined, and superheated or con- 
fined steam, is furnished by the Buffalo Dental Manufactur- 
ing Co.: 
Degrees 
Fahrenheit 
Steam pressure 
per square inch 
212 0 
220 2 
230 6 
240 10 
250 . 15 
260 21 
270 27 
280 34 
290 43 
300 52 
310 63 
320 75 
330 89 
340 104 
350 120 
360 140 
370 160 
380 180 
390 205 
400 234 
410 264 
420 296 
430 335 VULCANITE 
451 
Degrees 
Fahrenheit 
Steam pressure 
per square inch 
440 375 
450 410 
460 455 
470 515 
480 565 
490 603 
500 663 
510 721 
520 798 
530 864 
540 937 
550 1015 
It will be noted that the elastic force of steam increases at 
a rapid rate and not in direct proportion to rise of tempera- 
trfre. For example: 
At 220° F. the pressure is 2 lbs. By steps of 50 degrees the 
increase is very marked. 
270° F. the pressure is 27 lbs., an increase of 25 lbs. 
320° F. the pressure is 75 lbs., an increase of 48 lbs. 
370° F. the pressure is 160 lbs., an increase of 85 lbs. 
420° F. the pressure is 296 lbs., an increase of 136 lbs. 
470° F. the pressure is 515 lbs., an increase of 219 lbs. 
520° F. the pressure is 798 lbs., an increase of 283 lbs. 
Without suitable means for controlling the temperature, 
or without almost constant watching of the vulcanizer, over- 
heating or burning of the rubber during the hardening process 
is very liable to occur. 
GAS REGULATORS 
To avoid the necessity of constant supervision of the vul- 
canizer when in use and still maintain a uniform and effective 
working temperature, an.appliance called a gas regulator can 
be used for controlling the amount of gas supplied to the 
burner. By proper adjustment of the regulator the gas sup- 
ply to the burner will he reduced when the temperature rises 
above the point of vulcanization determined upon and at 
which the pointer of the regulator was previously set. 
TIME REGULATORS 
To further reduce the responsibility of the prosthetist, a 
time regulator can he attached to the gas supply pipes, which 452 
VULCANITE 
will automatically cut off the fuel at whatever time the clock 
is set. By combining the gas regulator with the time regula- 
tor, the prosthetist introduces the flask, closes the vulcanizer, 
turns on and lights the gas and leaves the apparatus to itself, 
when, without further attention, the case is vulcanized and 
the gas automatically shut off. Before lighting the gas the 
lever arm of the clock which controls the gas valve should 
Fig. 277.— Automatic Gas Regulator 
Fig. 278.— Vulcanizer with Gas and Time 
Regulator Attachments 
be set on the threaded spindle of the hour hand at such point 
as to allow time for the temperature to rise to vulcanizing 
point and further to allow time for vulcanization to occur as 
well. 
Appliances of this type are not a luxury but a necessity 
in every well equipped dental laboratory. 
THE SAFETY VALVE 
Every vulcanizer should have attached to it a device called 
a safety valve, which, when the pressure within the boiler VULCANITE 
453 
exceeds somewhat the high vulcanizing pressure, will auto- 
matically open and release the steam. 
The simplest device of this type consists of a tube screwed 
into the top of the vulcanizer. The outer end of the tube is 
fitted with a screw cap having a hole in the center. The open- 
ing through the cap and tube leads directly into the vulcan- 
izer. By removing the cap, placing a disc of thin copper foil 
over the end of the tube and replacing the cap tightly, the 
Fig. 279.— Safety Valve and Blow-Off Attachment for Vulcanizer 
Fig. 280.— Detail of Safety Valve 
Fig. 281.— Detail of Blow-Off Valve 
vulcanizer chamber is thus sealed. The copper foil disc usu- 
ally breaks when the pressure exceeds 350° F., considerably 
above vulcanizing temperature, but well below the tensile lim- 
its of the boiler, thus avoiding danger of explosion. This 
safety valve is independent of thermometer, gas or time regu- 
lator or steam gauge and will work when other means fail, 
providing, however, that reasonable attention is given it to 
see that the tube, both internally as well as externally, of the 
disc does not become clogged. 454 
VULCANITE 
Vulcanization of Cases in Which Automatic Flask Closing 
Devices Are Used 
Practically all dental rubbers are so compounded that 
when heated to 320° F. and maintained at that temperature 
for one hour they will vulcanize. From twenty-five to forty 
minutes are usually required to raise the temperature within 
the apparatus to the vulcanizing point so that the actual time 
consumed in the process of hardening the rubber ranges from 
eighty-five to one hundred minutes. Bulky cases should be 
vulcanized at the same temperature, but for a somewhat 
longer period, since large masses of rubber naturally require 
more time to harden than do those of less bulk. 
It is the opinion of the writer, based upon many experi- 
ments in the vulcanization of all classes of cases, bulky and 
otherwise, that the use of automatic springs for closing the 
flask in the preliminary stages of vulcanization will result, 
first, in less dimensional change of the matrix; second, in a 
thicker external shell being formed, and third, in a denser 
quality of vulcanite when hardened. 
These observations coincide very closely with extensive 
experimental work carried on by Dr. G. Id. Wilson, and which 
is described in detail in his work, Dental Prosthetics. (1914, 
Lea & Febiger.) 
When automatic closing devices are used, space should 
be provided for the escape of surplus rubber. This should 
be in the form of a groove of ample size, close to and extend- 
ing entirely around the periphery of the matrix, but with no 
gateway connections leading from the matrix to the space. 
Vulcanization of Cases in Which the Flasks Are Closed 
and Bolted Before Placing Them in the 
Vulcanizer 
To avoid excessive dimensional change in the matrix dur- 
ing vulcanization, in those coses in which the flask is closed 
and bolted before placing in the vulcanizer, the following con- 
ditions must be observed: 
The case should be treated as described under the head- 
ing, “Test Closing of the Flask.” (See page 431.) 
In this, as in all methods of vulcanization, the case should 
be placed above water and the process conducted in an atmos- 
phere of steam. 
From thirty to forty minutes’ time should be allotted in 
raising the case to vulcanizing temperature, which, in this 
instance, is lower than by the method just described. VULCANITE 
455 
Vulcanization should be conducted at a temperature rang- 
ing from 290° F. to 300° F. and for a period varying from 
two to two and one-half hours. 
It is the belief of the writer that, although the rubber is, 
in all probability, in the most liquid condition at the highest 
temperature, it also exerts the greatest expansive force be- 
tween 300° F. and 320° F. 
If this assumption is true, it will thus be seen that by this 
method the matrix is relieved of considerable expansive force, 
which, if permitted to develop., would result in distortion. 
Summary of Facts of Importance in Regard to 
Vulcanization 
The important facts in regard to vulcanization may be 
summed up as follows: 
When automatic flask-closing devices are used, cases may 
be satisfactorily vulcanized at 320° F. for a period of one 
hour, or, when bulky, at the same temperature for a longer 
period. 
When flasks are closed and locked before introducing in 
the vulcanizer the process should be conducted at a tempera- 
ture not exceeding 300° F., preferably slightly lower, and for 
a sufficient length of time to induce the proper degree of hard- 
ness in the vulcanite. The time may range from two to three 
hours, depending on the bulk of material and the quality of 
the rubber employed. The actual time can only be determined 
by suitable tests for any particular rubber. Such tests, when 
once made and recorded, serve as a basis for subsequent oper- 
ations. 
Removal of the Flask from the Vulcanizer 
From ten to fifteen minutes should elapse, after vulcan- 
izing a case, before opening the blow-off valve for the release 
of the steam. It should then be opened but slightly so that 
the pressure may be gradually reduced. When opened widely, 
so that the steam pressure within the vulcanizer is lowered 
suddenly, before that within the flask, the contents of the lat- 
ter will frequently become distorted. 
Removal of the Denture from the Flask 
On removal of the flask from the vulcanizer, and before 
opening, it should be placed in cold water for another ten or 456 
VULCANITE 
fifteen minutes, or until the plaster and denture are thor- 
oughly chilled, otherwise warpage of the case will occur at 
this stage. 
When chilled, the bolts are removed and the flask care- 
fully pried apart. Sometimes it is advisable, when the plaster 
contents of the flask have not become softened to any extent 
in vulcanizing, to remove the top of the flask and with a knife, 
carefully remove the plaster from the outer surfaces of the 
denture, being careful while doing so not to mar the denture 
base or fracture the teeth. 
Fig. 282.— Vulcanite Lathe Burs 
The flask is then separated, the plaster beneath the den- 
ture undermined and the east and denture pried out. Re- 
moval of the surrounding plaster is a simple matter. The 
case should then be thoroughly scrubbed with a stiff brush 
to remove all remaining portions of plaster when it is ready 
for final finishing. 
POLISHING THE DENTURE 
With a coarse saw the surplus vulcanite is trimmed from 
the periphery of the baseplate. Further shaping of the mar- 
gins to correct peripheral outline can be done with the double 
end vulcanite file and vulcanite lathe bars. The final smootli- VULCANITE 
457 
ing of the margin and general surfaces can be quickly accom- 
plished with emery bands on the lathe arbor. 
Fig. 283.— Emery Band Lathe Mandrel 
When, in the final waxing of a denture, the correct gingi- 
val outline is given the gums, so that they represent the type 
of teeth required for that particular case, but little effort will 
be required in finishing the vulcanite. 
Fig. 284.— Dr. Wilson’s Set of Vulcanite Finishers 
The right and left bevel chisels are used to true up the 
gum festoons and develop clean, symmetrical, lingual margins 
of vulcanite against these surfaces of the teeth. The set of 
chisels and scrapers suggested by Dr. Gr. H. Wilson are excel- 458 
VULCANITE 
Fig. 285.— Right and Left Bevel and 
Square Chisels 
Fig. 286.— Large and Medium Scrapers of 
the Kingsley Type 
Fig. 287.— View of Upper and Lower Denture, Showing Lingual Surfaces of Teeth Devel- 
oped in Vulcanite. Constructed for Dr. John Rawlingson, a Noted English 
Surgeon, by Dr. Genese in 1864. Loaned by Mr. Sykes 
of C. Ash & Sons 
Fig. 288—Buccal View of the Rawlingson Case. This Shows Well-Proportioned 
Upper and Lower Teeth and Fine Occlusal Relations VULCANITE 
459 
lent for this purpose. This set contains a small pointed in- 
strument for removing vulcanite from constricted spaces in 
the embrasures and interproximate spaces. 
It is frequently advisable to develop in vulcanite, the lin- 
gual forms of the natural teeth, after the method introduced 
by Dr. Genese, in 1860, and later described by Dr. Fine, in 
1906. Three advantages are gained by this manner of con- 
tour development : First, the bulk of vulcanite is materially 
reduced without impairing the strength of the baseplate; sec- 
ond, the teeth are given approximately their true lingual 
forms and consequently feel natural and comfortable to the 
Fig. 289.— Sectional View of an Upper Denture. 
Lingual Surfaces of the Teeth Developed 
in Vulcanite (Fine) 
Fig. 290.— Sectional View of Upper 
Denture, Showing Form of In- 
strument Used in Carv- 
ing the Wax 
Fig. 291.— Lower and Upper Dentures in Section, with Lingual Surfaces of Teeth 
Developed in Vulcanite 
wearer; third, such a form of denture aids materially in cor- 
rect plionation. The only objections are the time required in 
the carving and the difficulty encountered in finishing the vul- 
canite in the linguo-gingival angles and embrasures. • 
By developing the lingual forms of the teeth in the final 
carving of the wax and lining the vault portion of the wax 
model denture with tinfoil before flashing the case, the finish- 
ing steps are comparatively simple. The tinfoil margins next 
the teeth should be turned away from the latter so as to be 
caught in the plaster investment in the upper half of the flask. 
When No. 30 foil or heavier is used it can readily be stripped 
from the vulcanite or the thinner gauges can be quickly re- 
moved by rubbing with mercury. 460 
VULCANITE 
Rubber vulcanized against tinfoil comes from the flask 
clean, polished and more dense than when vulcanized against 
plaster, and when care is used in waxing a case but little final 
polishing is required. 
REPRODUCTION OF THE RUG,® 
When reproduction of the rugae has been carried out, 
small scrapers of the Kingsley type are most useful for fresh- 
ening the depressions between these irregular ridges. If 
properly developed in wax, however, and the tinfoil is applied 
as described, care being taken to burnish it into the depres- 
sions, the polishing wheels will complete the finish without 
resorting to other means. 
USE OF THE-CALIPERS 
To avoid undue thinning and consequent weakening of the 
baseplate, the calipers should be applied at various times dur- 
ing the finishing process. The instrument shown in the illus 
tration is the type most commonly used. 
Fig. 292.— Registering Calipers 
The general finish is given the vulcanite with various grits 
of abrasive powders and water, in the form of a medium 
paste, and applied with brush, felt and muslin wheels of var- 
ious sizes, on the lathe. For rapid cutting, a rather coarse 
grit, pumice stone, followed by a finer to remove the slight 
scratches left by the former, is the usual method of reducing 
the irregular surfaces and slight angles left by the chisels, 
scrapers and emery bands. 
The scratches left by the pumice powder are removed with 
whiting and water. A still higher polish may be given the 
vulcanite by coating it with vaseline or heavy lubricating oil, 
dipping it in dry plaster, and applying lightly to a soft bristle 
FINAL POLISHING OF THE DENTURE VULCANITE 
461 
Fig. 293.,— Polishing Lathe. On Left Spindle Is a Two-Row, Converging Bristle Stiff 
Brush Wheel. On Right, a 314-inch Stitched Muslin Polishing Wheel 
Fig. 294.— Position of Denture Against Wheel in Polishing in 
the Embrasures 
wheel, running at high speed. The application of dry plaster 
is continued until all of the oil has been removed from the 
various surfaces. 
FINISHING TOUCHES 
The polished denture should be cleansed with soap and 
water, applied with a medium stiff brush and afterward in 
clear water. 462 
VULCANITE 
It may then be placed in a small glass vessel covered with 
alcohol and set in the sun to solarize or lighten the pink vul- 
canite when this step is considered necessary. About one 
hour will be required to complete the bleaching process, the 
position of the denture being changed from time to time so 
that all surfaces may be of uniform color. After solarizing, 
the denture should again be cleansed in water. 
FINAL FITTING IN THE MOUTH 
When the patient presents, the upper denture is intro- 
duced and tested as to adhesion. When seated, the finger 
should be passed a number of times from front to back, apply- 
ing considerable pressure on the lingual surface of the base- 
plate. This to a considerable extent forces the air from be- 
tween the contact surfaces, after which the patient is in- 
structed to apply the tongue to the baseplate and “draw the 
air” from beneath it. 
Should the peripheral margins impinge on the muscles or 
soft tissues to any marked degree the denture should be re- 
lieved at such points and the marred surfaces polished. 
The lower denture is introduced and seated on its border 
by drawing the lip and cheeks away from its lower margins 
and by applying downward pressure to partially expel the air. 
Tests of the excursions of cusps of lower against upper- 
teeth in lateral movements should be made, first without and 
later with interposed carbon paper. The high points are re- 
duced with engine stones until no interference can be detected. 
The final finish is given the vulcanite with whiting and water 
applied with clean felt, muslin and brush wheels, free from 
grit. All scratches should be removed and a highly polished 
surface developed, not only in the lingual and outer, but in 
the palatine areas as well. 
FINISHING THE PALATINE SURFACES OF A DENTURE 
To avoid subsequent irritation of mucous tissues against 
which the denture will rest, the palatine surfaces should be 
freed from all nodules, the roughened areas smoothed, and a 
uniform polish given them. 
Pumice stone applied with a stiff brush wheel, run at high 
speed, using but little pressure, followed with whiting and 
water, will accomplish desired results without in any way 
interfering with denture adaptation. 
Judgment must, of course, be used as to the amount of VULCANITE 
463 
pressure applied to avoid changing the form of the palatine 
or peripheral surfaces. 
Many avoid polishing the palatine and border areas of 
dentures, under the mistaken idea that such a step will im- 
pair adaptation. 
The experience of the writer of twenty years or more, 
together with that of many others, is offered as evidence that 
the polishing of all areas of a denture, and particularly those 
which bear the burden of masticatory effort, is not only pos- 
sible but imperative, and can be accomplished without per- 
ceptible interference to adaptation. 
The use of thin tinfoil on the surface of casts reduces to 
the minimum the amount of polishing required. The use of 
artificial stone for casts and the coating of cast surfaces with 
silex aid in the product of smooth vulcanite surfaces. 
A final, high polish can be given all surfaces by saturating 
the denture in thick oil and applying dry plaster freely while 
holding it against the soft bristle lathe wheel. The applica- 
tion of the plaster must be continued until all oil is removed. 
The regrinding of teeth in final trial in the mouth is of 
utmost importance. Such procedure corrects errors of occlu- 
sion occasioned by dissimilarity between mandibular and 
occluding frame movements, as well as slight errors arising 
from change in relation of teeth during flask closure and vul- 
canization. 
The prosthetist should keep in mind during the final trial 
and adjustment of dentures to the mouth the three principal 
objects he endeavored to accomplish when the case was under- 
taken, viz., to give his patient dentures that would be useful, 
look well, and feel comfortable. 
Construction of a Full Upper or Lower Denture 
With slight variations in technic, from that described for 
full cases, either upper or lower dentures may be constructed 
by the anatomic method, the natural teeth in the opposite arch 
being present. 
The principal departure is in the method of taking the 
bite and in registering the protrusive bite. To illustrate, the 
construction of a full upper denture will be outlined. 
The impression, cast, and wax occlusion model for the 
upper arch are formed as for an upper model in a full case. 
Developing uniform contact of the wax rim with occlud- 464 
VULCANITE 
ing teetli is essentially the same as between two occlusion 
models. The median and high lip lines are determined in the 
same manner, as is also facial contour. 
The condyle ends are located and points marked on the 
face. 
The bite fork is inserted in the occlusion rim and removed. 
An impression in compound is secured of the occlusal half 
or more, of all of the lower teeth, when it can be removed 
without distortion, and from this a lower occlusion cast is 
formed. 
A layer of softened wax one-eighth of an inch thick is 
now cut to the form of, and added to the occlusal surface of 
the upper occlusion rim which should be chilled. The occlu- 
sion model is introduced in the mouth, and, by trial, the nor- 
mal bite is determined, the patient biting into the softened, 
added layer when instructed, until the natural teeth come in 
contact with the chilled occlusion rim. 
The bite fork is returned to position and firmly luted in 
the occlusion model, after which the face bow is adjusted in 
position and the several clamps tightened. 
The occlusion model, attached wax bite and face bow are 
removed and the latter set in position on the occluding frame. 
The upper cast is seated in upper occlusion model and at- 
tached to the upper bow of occluding frame. The impression 
is removed from the lower cast and the latter seated in the 
wax bite, care being taken to see that the occlusal surfaces 
of the plaster teeth rest flat on the corresponding surfaces of 
wax bite. To be certain that this step may be carried out 
accurately, the inner and outer margins of the wax bite should 
be cut away so as to leave little more than the occlusal sur- 
face markings of the natural teeth. 
The lower cast is then attached to the lower bow of the 
occluding frame and the face bow and wax bite are removed. 
Since the bite locks cannot be applied in taking the protrusive 
bite, the latter step may be carried out as Christiansen first 
described it, viz., placing a roll of wax on either side between 
the bicuspids and molars, and having the patient close the 
mandible while in a protruded position. 
The occlusion model should be notched in the molar region 
so that on removal the protrusive wax bites will be correctly 
guided to place. The condyle paths of the frame are released, 
the back spring unhooked, the upper occlusion model set on its 
cast, the two wax bites placed in their respective locations and 
the final adjustment of the several factors accomplished by VULCANITE 
465 
exerting light but steady pressure, through the center of 
upper and lower casts, as in full cases. 
When proper relation is established, the condyle paths are 
clamped, the wax bites removed, the back spring hooked and 
the case is ready for arrangement of the teeth, which step is 
similar to the arrangement of teeth in full cases. 
FULL LOWER DENTURES 
In constructing a full lower denture, the upper natural 
teeth being present, the steps are similar in detail, except that 
the bite fork is attached to the lower occlusion model. In 
mounting the casts, the occluding frame should be inverted 
and the lower cast mounted first. 
The Gysi System of Anatomic Appliances 
The Gysi System of appliances for anatomic denture con- 
struction affords means of registering certain movements of 
the mandible, not possible by any other method. The appli- 
Fig. 295.— The Gysi Adaptable Articulator 
ances consist of an articulator having adjustable condyle 
paths, adjustable lateral rotation centers, an adjustable side 
movement, and the ordinary hinge movement common to all 
occluding frames; also a condyle path register, a lateral con- 
dyle path register, an incisor path register, and various other 
accessory appliances. 466 
VULCANITE 
In constructing dentures with these appliances, the steps, 
up to the application of the face bow, are practically the same 
as detailed in the preceding chapters. Although the order of 
procedure may be varied, the following will be convenient and 
practical: 
Register the condyle paths. 
Take the bite. 
Mount the casts on the articulator. 
Adjust the condyle paths of the articulator. (Protrusive.) 
Register the incisor path. 
Set the rotation centers of the articulator. 
Register the lateral condyle paths. 
Adjust the lateral condyle paths of the articulator. 
APPLICATION IN DENTURE CONSTRUCTION 
REGISTERING THE CONDYLE PATHS, EORWARD MOVEMENT 
The condyle path register records the downward and for- 
ward movement of the condyles, and also fulfills the purpose 
of a face bow in mounting casts on the occluding frame. It 
is applied as follows: 
The horseshoe plate is adjusted to the lower occlusion 
model, the pins of the plate being forced into the wax rim 
Fig. 296.— Horseshoe Plate Adapted to Lower Occlusion Model 
until the plate rests flat upon its occlusal surface. The an- 
terior portion of the plate should extend about tliree-eighths 
of an inch labially of the rim, so that later it may serve as a 
table for recording the incisor path. 
The occlusion models are now introduced in the mouth, 
the condyle path register adjusted to the anterior projections 
of the horseshoe plate, and the pencils on the horizontal arms VULCANITE 
467 
of the register brought in contact with face, against the pre- 
viously marked condyle ends. The adjustment is accom- 
plished by raising, lowering or rotating the pencil posts in 
their sockets and locking them firmly with the set screws; the 
pencils are moved inward by means of the rack and pinion 
adjustment on the ends of the register. 
A card, about two by three inches in size, is now inserted 
and held firmly between the pencil point and the face. Its 
Fig. 297.— Registering the Condyle Path 
lower edge should be parallel with the horizontal arm of the 
condyle register. 
The patient is instructed to bite sidewise, so as to project 
the condyle next the card. During this movement, the pencil 
point moves synchronously with the condyle and marks on the 
card the direction of its path. A card is now applied to the 
opposite side of the face, and a similar registration of the 
opposite path secured in like manner. 
A straight edge is laid on the card, parallel with the 
working part of the condyle path, and a line drawn along 
it to the lower margin of the card. The protractor is then 468 
VULCANITE 
applied to the card, by means of which the inclination of the 
condyle path in degrees is determined. The condyle paths of 
the frame are set according to the readings obtained from the 
two cards. 
Fig. 298.— Record of Right and Left Condyle Paths of Same Individual, 
Showing Difference of 10 Degrees in Pitch. (Gysi) 
Fig. 299.— Protractor Applied to Card to Determine 
Angular Pitch of Condyle Path 
Fig. 300.— Condyle Records with Essential Data Inscribed. 
Suggested by Dr. Gysi 
TAKING THE BITE 
The bite is now taken as outlined in Chapter XIX, the 
horseshoe plate being firmly affixed to the lower occlusion 
model, for by this means the occlusion models are attached to 
the condyle register for securing their correct relation to the 
condyles in normal or resting position in the glenoid fossae. 469 
VULCANITE 
When the normal bite is determined, the bite locks are 
introduced, the condyle register adjusted as before, and the 
occlusion models removed from the mouth. 
In this system, it is found more convenient to seat each 
cast in its baseplate and hold them in proper position by pass- 
ing rubber bands around both casts and occlusion models. 
MOUNTING THE CASTS ON THE ARTICULATOR 
The condyle register to which the occlusion models are 
attached is set upon its base, the goose-neck rod being raised 
or lowered as required to bring the pencil points opposite the 
condyle points of the articulator. (See page 470.) 
The iron stand, with condyle register and occlusion models 
attached, is now moved forward, clear of the articulator. 
Fig. 301.— Casts Attached to Occlusion Model with String Ready 
for Mounting on Articulator 
Plaster is applied around and over the lower bow, and the 
iron base pushed back until the pencil points of the register 
are opposite the condyle ends of the frame; further additions 
may he made to the plaster around the lower cast, to firmly 
attach it to the frame. 
The upper cast is attached to the upper bow by applying 
plaster in the usual manner. When set, the condyle register 
and bite locks are removed, the rubber bands cut, and the 
occlusion models removed from the casts. 
A pellet of cotton saturated in oil of cloves is ignited and 
the anterior end of the horseshoe plate held over it to blacken 
REGISTERING THE INCISOR PATH 470 
VULCANITE 
Fig. 302.— Casts and Condyle Register Adjusted to Articulator 
the surface. A thin film of wax is flowed over the smoked 
surface to prevent its being rubbed off. 
The incisor path register is now attached to the upper 
occlusion model so that the pin will project slightly below the 
occlusal surface. The register must not be set so low as to 
Fig. 303.— Explanatory Cut Showing the Various Adjustments of the Gysi Adaptable 
Articulator VULCANITE 
471 
obscure a view of the pin point in its excursions over the 
waxed surface of the horseshoe plate. 
The occlusion models are now introduced in the mouth and 
the patient instructed to move the mandible sidewise, at the 
same time holding the horseshoe plate in close contact with 
the upper occlusion rim. 
By this movement the pin of the register on the upper 
occlusion model marks an arc on either side of the median 
line of the horseshoe plate, the centers of which represent the 
centers of rotation of the mandible. The logic of this is appa- 
rent, for the condyles represent centers from which the arcs 
Fig. 304.— Registering the Incisor Path 
are developed. Usually, several movements will be required 
to mark distinct lines on the horseshoe plate. 
When the record is sufficiently sharp, the occlusion models 
are removed from the mouth, returned to the casts on the 
frame, and the latter subjected to lateral movements. The 
direction taken by the pin of the incisor register should be 
closely observed. If it follows the arc, the rotation center of 
the frame is correct, and the latter may be fixed accordingly. 
If not, the rotation center of the frame should be moved out- 
ward or inward as required, until the point accurately follows 
the arc it made while in the mouth. The rotation center on 
the opposite side of the frame is determined in like manner. 
The object in carrying out the steps as described is to 
insure correct lateral movements to the frame, so that when 472 
VULCANITE 
the teeth are arranged in the wax rims, the cusp clearance 
there developed will require but little change when the den- 
tures are introduced in the mouth. It is a step nearer true 
anatomic movements than can be secured from a frame, the 
rotation centers of which are fixed the average distance apart. 
REGISTERING THE LATERAL CONDYLE PATH 
The lateral paths must not be confused with the lateral 
rotary movements of the condyles. Naturally, when one con- 
dyle is the actual center of rotation, the other condyle in mov- 
ing forward describes an arc, the radius of which corresponds* 
to the distance between the two condyles. It is found, how- 
ever, that the radius of the arc described by a projected con- 
dyle is sometimes greater or less than the distance between 
the condyle centers. 
Again, in some persons, the mandible moves bodily, side- 
wise, in the lateral rotary movements, and in some cases there 
is a slight side movement, within certain limits, without any 
perceptible rotary movement. 
The lateral path register has attached to each extremity 
a glass plate ground on the under side, on which the perpen- 
dicular pencil of the condyle path register records the lateral 
movements of the mandible. 
By use of the lateral condyle path register, these side 
movements in individual cases may be recorded, and the artic- 
ulator set to reproduce them to a fairly accurate degree. The 
steps are carried out as follows: 
The condyle path register is attached to the lower occlu- 
sion model as in taking condyle registration, the perpendic- 
ular pencils being turned so that they come opposite the outer 
ends of the condyles. 
The operator stands back of the patient and applies the 
register, holding it at approximately the same inclination as 
the pitch of the condyle paths, previously registered. The 
ground glass plates should rest on the upturned pencil points, 
and the arms of the register be pressed in until the edges of 
the plates rest firmly against the sides of the face. The 
patient is instructed to move the mandible sidewise as before, 
which movement marks on the under side of the glass, the 
line or arc described by the moving condyle in its forward 
excursion. 
To translate the lines recorded on the glass plates into 
degrees, the following plan is adopted: VULCANITE 
473 
Fig. 305.— Registering the Lateral Condyle Paths 
Fig. 306.— Determining the Degree of Inward Inclination of the 
Lateral Condyle Paths 474 
VULCANITE 
On a sheet of white paper as wide as the register bow, a 
base line A B is drawn from side to side (see Fig. 306, page 
473). A perpendicular C D is erected on the base line, near 
one edge of the sheet. The lateral condyle path register is 
laid on the sheet, the points on the ground glass plate which 
indicate the beginning of forward movement of the condyle 
being placed at the junction of base with perpendicular line 
C, the base line. The points should also be directly over the 
perpendicular lines. With a straight edge placed beneath the 
ground glass, and resting on the paper, its edge is brought in 
line with the lateral path marked on the ground glass, and 
Fig. 307.— A Record of Sixteen Pairs of Condyle Paths. Average 
Angular Inclination, Inward, of Left Condyle Paths, 
Seventeen Degrees ; Right, Sixteen Degrees 
which can readily be seen through the transparent plate. If 
properly placed, its edge should coincide with the junction of 
the perpendicular with the base line. 
The register is removed and a line drawn along the 
straight edge on the paper C E. This line usually forms an 
angle with the perpendicular line, the apex of which is on the 
base line. By applying the protractor to the angle, the num- 
ber of degrees included may be read, and the lateral path 
recorded accordingly on the articulator. VULCANITE 
475 
THE ANGULAR INCLINATION OF THE LATERAL 
CONDYLE PATH 
Dr. Gysi states that the average angular inclination in- 
ward, of sixteen pairs of condyles recorded, shows 17 degrees 
for the left and 16 degrees for the right condyle. 
This lateral movement of the mandible is evidently the 
result of an unconscious or involuntary effort of the organism 
to increase the occlusal function of the molars on the working 
side, as well as to develop more effective balancing contact on 
the protruded side. That it is less important than the for- 
ward and downward condylar movement is self-evident, yet 
both should be reckoned with in denture construction. 
SUBSEQUENT STEPS OF DENTURE CONSTRUCTION 
When the registrations have been determined as outlined, 
and the articulator adjusted accordingly, the subsequent steps 
of denture construction are carried out in practically the same 
manner as detailed in the previous chapter. 
Because of the liability of errors occurring, in carrying 
out the various steps, the completed dentures should be tested 
with carbon paper, to correct any cusp interference that may 
exist and remove high points that, without such means of dis- 
closing them, are not discernible to either prosthetist or 
patient. CHAPTER XXIII 
CONSTRUCTION OF PARTIAL DENTURES 
Various Types 
A substitute which replaces one or more, but not all of the 
natural teeth in either arch, is commonly called a partial den- 
ture. This name is usually applied to a removable substitute 
having a base plate which rests upon and is principally sup- 
ported by the mucous tissues covering the bony substructure' 
of the dental arches, in contra-distinction of bridge work, 
which fulfills essentially the same purpose but is attached to, 
and mainly supported by some of the remaining natural teeth 
or roots. A piece of bridge work, however, in the broadest 
sense, is a partial denture, since it replaces a missing portion 
of the natural denture. The term bridge relates to the manner 
of replacement, the bridging over of spaces caused by loss of 
some of the natural teeth. 
PLANNING A PARTIAL DENTURE 
In planning a partial denture, aside from the general 
routine steps involved, several factors of importance must be 
determined, the dominant ones of which are as follows: 
First — The materials of which the substitute is to be 
constructed. 
Second — The general outline form of the base plate. 
Third — The means of retention to be employed. 
Fourth — The class of teeth to be used and the manner of 
their attachment. 
The base plate is the foundation of a denture which rests 
upon the oral tissues, and to which the substitute teeth are 
attached. Through it, under normal conditions, the force of 
masticatory effort is equalized and distributed to the mucous 
tissues overlying the bony sub-structure in such manner as to 
cause no injury to the tissues themselves and no inconveni- 
ence to the patient. 
Gold and vulcanite, either alone or in combination, are 
the materials most commonly employed for partial denture 
bases, preference in most cases being given the former be- 
BASEPLATES FOR PARTIAL DENTURES 
476 CONSTRUCTION OF PARTIAL DENTURES 
477 
cause of its better appearance, conductivity and greater 
strength with slight hulk as compared with vulcanite. How- 
ever, there are many cases where vulcanite alone can be used 
to good advantage, and other cases in which its use with gold 
is indispensable, particularly where much restoration of bor- 
der contour is required. 
PARTIAL DENTURES OF VULCANITE 
The outline form and size of a partial denture is governed 
to a great extent at least by the position of the teeth to be 
replaced. The manner of retention, however, has an impor- 
tant bearing on the linear dimensions of the base plate. When 
clasps or retaining appliances of similar character are used, 
the terminals of the base plate should be extended beyond 
these means of attachment when necessary, so as to develop 
denture balance, as explained under the heading, “ Indica- 
tions and Contra-Indications Governing the Application of 
Clasps.” (See page 246.) 
By drawing a line or laying a straight edge from one clasp 
or attachment to the other, the linear extension, both mesially 
and distally, necessary to secure correct denture balance, can 
readily be determined. 
In upper partial dentures, when retention depends upon 
atmospheric pressure and adhesion, the base plate should 
cover a considerable portion of the palatine vault, but seldom 
to such an extent as in a full denture. 
With the great variety of frictional appliances available 
and improved methods of their construction the retention of 
partial dentures is very much simplified, and the form of 
upper dentures can be materially reduced in size over those 
in which atmospheric pressure is employed. 
In width, the base plate of an upper partial denture need 
seldom exceed from one-fourth to five-sixteenths of an inch, 
where it passes along the lingual surface of the natural teeth, 
when retained in place by frictional appliances. 
The base plate need only be considered as a frame-work 
or splint for holding the teeth in position, the saddle, which 
rests upon the border and supports the tooth, coupled with 
but slight bearing of the base plate proper upon the tissues, 
usually affords ample resistance to masticatory stress. 
The thickness of a base plate of vulcanite is, of course, 
governed somewhat by its width, but not altogether, since a 
thin, wide base plate will, under use, fracture more quickly 
than a thicker but narrower one containing an equal or even 478 
CONSTRUCTION OF PARTIAL DENTURES 
less bulk of material. By actual measurement, a very nar- 
row base plate, if constructed of a good quality of vulcanite, 
need not exceed from one-sixteentli to one-twelfth of an inch 
in thickness except when absorption of tissues requires a 
greater amount for restoration of lost border contour. 
TECHNIC OF CONSTRUCTION OF PARTIAL UPPER VULCANITE DEN- 
TURES WITHOUT CLASPS 
In all cases an accurate plaster impression of the teeth 
and tissues involved should be secured in plaster. From this 
impression a cast should be developed in magnesium oxy- 
clilorid, or Spence’s plaster, because of the greater hardness 
of these materials. 
When loss of but few teeth has occurred, these not being 
contiguous, a mash bite of sufficient bulk to take an impres- 
sion of the lower teeth and project labially so that the bite 
fork of the face bow may be firmly imbedded in it, will usu- 
ally prove satisfactory for mounting the upper cast in correct 
position on the occluding frame, and for developing the lower 
cast as well. Or an impression of the lower arch can be 
secured, a cast developed from it and the special bite fork, 
designed for partial cases, can be used for securing the cor- 
rect relation between the mandible and maxilla, after which 
the two casts can be mounted on the frame in a similar man- 
ner to an edentulous case. 
TAKING THE PROTRUSIVE BITE 
Should it be deemed advisable to take a protrusive bite, 
it is accomplished as follows: Place two rolls of wax between 
the bicuspids and molars, one on either side; have the patient 
protrude and bite as in full cases where this step of condyle 
registration is carried out. The two bites are removed from 
the mouth and placed in position on the lower cast, the con- 
dyle slots of the frame loosened and the back spring unhooked. 
The upper cast is then moved backward and pressed down- 
ward until the teeth take their proper position in the bite. 
It is usually necessary to trim away the buccal and lingual 
margins of the wax bite before seating the casts, so that it 
may readily be seen when they are in exact position. Care 
should be taken not to distort the wax during the trimming 
process. The condyle slots are now set firmly as the wax bites 
indicate, the wax removed, and the back spring again con- 
nected, when the case is ready for the selection of the teeth. CONSTRUCTION OF PARTIAL DENTURES 
479 
SELECTING AND GRINDING THE TEETH 
Wlien only a few teeth are missing, it is seldom necessary 
to try the wax model denture in the mouth, therefore the use 
of a hard, unyielding base plate, such as is used in full cases, 
is uncalled for. A good quality of sheet base plate wax will 
answer the purpose. 
Teeth of suitable size and color are selected to fill the 
spaces. When possible to do so, plain teeth should be selected 
Fig. 308.— Reduction of Proximate Surfaces of 
Teeth Where Space Has Become 
Constricted 
and ground to accurately fit the border, thus obviating the 
application of artificial gum restoration. They should be of 
sufficient length not to require tipping inward at their cervical 
ends to meet the border and thereby be thrown out of 
alignment. 
When teeth adjoining a space have moved toward each 
other, for example, a central and opposite lateral incisor, thus 
reducing the space occupied by the lost central, it is often 
advisable to disc away their proximating surfaces. This in- 
Fig. 309.— Plate Teeth Backed, with Lingual 
Extension Added, for Close 
Bite Case 
creases tlie width of space and decreases the width of the 
immediately adjoining teeth so that the replacement will more 
nearly harmonize in form and proportion with the other in- 
cisor than would be the case were such change not made. (See 
a, b, Fig. 308.) 
By highly polishing the surfaces so reduced, no injury to 
the natural teeth is liable to result. 
There is, however, a limit to the application of plain teeth 
in partial cases. When gum restoration is required and the 480 
CONSTRUCTION OF PARTIAL DENTURES 
line of junction of the artificial with the natural gum tissue 
is visible, a gum section tooth, or if two or more contiguous 
teeth are missing, a gum section block which includes the 
teeth required should be selected and ground to neatly fill 
the space and restore the lost tissues with porcelain. When 
Fig. 310.— Stone with 120° Bevel Face for Reducing 
Marginal Ridges of Bicuspids and Molars 
such a block is not procurable, plain teeth may be selected and 
a porcelain gum attached by baking as described under the 
heading, “Special Uses of Porcelain.” (See page 619.) 
In some cases it may be possible to apply “Protesyn” in 
partial restorations, but since this material depends entirely 
upon undercut spaces for its retention, it will be difficult to 
develop the necessary anchorage in limited spaces. Pink or 
granular gum restorations are the least desirable of any of 
Fig. 311.— Fogg’s Interstitial 
Gum Facings 
the materials mentioned and when possible their use should 
be avoided in all partial cases. 
When two or more plain teeth, not requiring gum restora- 
tion, approximate, “Fogg’s Interstitial Gum Blocks” can be 
used to advantage in filling the embrasures, thus avoiding the 
display of vulcanite in these spaces. These also, together CONSTRUCTION OF PARTIAL DENTURES 
481 
with the method of application, are described under the head 
of “Special Uses of Porcelain,” oh page 620. 
WAXING THE CASE 
The teeth having been ground and waxed into position, the 
base plate is applied to the lingual surfaces of the teeth and 
given its desired outline form. The wax should be allowed 
to extend occlusally on the lingual surfaces of the natural 
teeth sufficiently to furnish a reasonably broad bearing for 
the base plate, for retention purposes. A single thickness of 
ordinary sheet wax will not afford enough bulk of material 
for the base plate and for loss of material as a result of fin- 
ishing the vulcanite. Two sheets will render the case too 
bulky, therefore the first sheet can be thickened somewhat by 
Fig. 312.— Type of Denture in Which Fogg’s 
Interstitial Gum Facings Are 
Indicated 
burnishing a slight addition of wax to it over all surfaces 
and more where deficient contour requires. The wax should 
extend well above the offset shoulder on the lingual surfaces 
of the porcelain teeth so as to insure ample material for de- 
veloping smooth surfaces in the final finishing. 
FLASHING THE CASE 
When plain teeth have been ground to the border, no 
gum restoration having been required, the teeth may be im- 
bedded in the first section of the flask with the cast of the 
mouth. Frequently, in spaces where gum sections have been 
fitted and absorption of the border is marked, so that con- 
siderable space exists between the border side of the block 
and the cast, gum sections may also be invested the same as 
plain teeth. Special care must be taken in packing the case to 
fill the space between the block and cast with rubber before 
closing the flask, otherwise the vulcanite is liable to be de- 
ficient from failure of surplus rubber being forced into the 482 
CONSTRUCTION OF PARTIAL DENTURES 
space. When, however, the space between cast and block is 
constricted, so that it will be difficult to introduce the rubber, 
the case should be invested so that the block will be caught 
and held by the plaster investment in the second half of the 
flask. This simplifies the packing of the case so that the vul- 
Fig. 313.— Sectional View of Flask, Showing How Teeth with and without Gum 
Restoration Should Be Invested 
canite will flow freely back of and surround the block as de- 
sired in the final closing of the flask. 
Sometimes both methods of investing the teeth are adopted 
in the same case. When the replaced teeth are on opposite 
sides of the cast, the latter can be set more deeply in the 
flask on that side occupied by the plain teeth without restora- 
tion than on the other side where gum restoration has been 
applied. This gives maximum strength with minimum bulk to 
the plaster which supports the plain teeth. 
Fig. 314.— Removal of Excess of Plaster 
Teeth in Flasking 
Projecting plaster teeth should be trimmed even with the 
lingual margin of wax, and the outer surfaces of the cast 
backed up with plaster and rounded down to the line of sep- 
aration of the flask in such manner as to obliterate all under- 
cuts and strengthen the cast. CONSTRUCTION OF PARTIAL DENTURES 
483 
The points involved in flasking any case are, first, to sup- 
port the cast under its base, so that it will not fracture under 
the stress of closing; second, to construct a matrix in which 
to mold the basic material which will not yield in forcing out 
the excess rubber, will not permit the teeth to become dis- 
lodged, and, third, to so shape the invested case in the first half 
of the flask that the second will readily separate from it with- 
out producing fracture of the investment. 
Partial Dentures of Vulcanite with Clasps 
GENERAL CONSIDERATIONS 
When a partial denture of vulcanite is to be retained in 
position with clasps, the order of procedure is as follows: 
Take impressions of the teeth to be embraced by the clasps, 
and from these develop metal dies. Construct the clasps as 
described under the heading, “Technic of Clasp Construc- 
tion, ’ * see page 500. Attach the anchorage lugs to the clasps 
in such position that they will neither interfere with correct 
alignment of the porcelain teeth nor require extra bulk of 
vulcanite to cover them. 
The clasps are now placed in position on the teeth in the 
mouth and a mash bite secured, using the face bow if the 
case calls for such procedure. Should the clasps come away 
with the bite, they are returned to proper position on the 
teeth. 
An impression in plaster is now taken which should in- 
clude all of the teeth involved in developing correct occlusion, 
and all of the border surfaces to be covered by the substi- 
tute. 
On removal from the mouth, the broken parts of the im- 
pression, if fractured, are replaced and firmly luted together, 
the clasps adjusted in correct position in their respective 
matrices and wedged apart so that each wing rests in con- 
tact with the matrix wall of the impression. Should any of the 
plaster which flowed under the anchorage lug, next the border, 
have become broken and lost in removal of the impression, a 
little wax should be flowed over the lug and the general con- 
tour of the impression be restored in this manner. When the 
loss of impression in this area is extensive and cannot be re- 
stored with comparative accuracy, a new impression should be 
secured. 
A cast is now developed in the usual manner, using pref- 
erably some of the harder materials for this purpose. When 484 
CONSTRUCTION OF PARTIAL DENTURES 
hardened, the impression is carefully removed to avoid dis- 
placing the clasps or fracturing the teeth. 
The wax bite is now trimmed freely on that side that re- 
ceives the working cast, so that both teeth and clasps may 
occupy the same position in the bite that the natural teeth 
and clasps sustained to it, when in the mouth. 
The steps from this point on are essentially the same as 
those concerned in the production of a partial vulcanite case 
without clasps. 
In case it is considered necessary to try the wax model 
dentures in the mouth, which is sometimes done for the pur- 
pose of testing occlusion, the base plate should be formed 
around the clasp lugs in such manner that the denture may be 
released without disturbing the clasps from their position on 
the teeth. Under no circumstances, in the class of dentures 
under consideration, should the clasps be disturbed from the 
time the impression is filled until the case is vulcanized. 
When, however, the base plate consists of metal, the clasps 
are usually permanently attached to it in the preliminary con- 
structive stages, as will be explained later. In such case they 
will come away from the cast with the base plate. 
In flasking the case, special care should be taken to cover 
the exposed ends of the clasps with the plaster investment in 
the first section of the flask, so as to hold them firmly in posi- 
tion after the wax is removed and during the packing and clos- 
ing of the case. 
It is also frequently advisable, before packing the matrix, 
to place between the anchorage lug and the cast a small wedge 
of vulcanite, of similar color to the basic rubber being used, 
to prevent displacement of the clasp by the rubber in the 
matrix in the closing of the flask. 
The wedge can be cut from an old base plate, should be 
clean, and all surfaces freshened so as to insure close union 
of the new rubber with it. When neatly applied, no difference 
in color will be noticeable, and practically all danger of clasp 
displacement will be obviated. 
Partial Lower Dentures of Vulcanite 
The construction of partial lower dentures of vulcanite, 
either with or without clasps, is much the same as for similar 
upper cases. Attention should be given one important detail 
which differs from upper partials, particularly in those cases 
where the anterior teeth are present, and the replacements 
occur along the posterior borders. 485 
CONSTRUCTION OF PARTIAL DENTURES 
While in upper partial cases the stress of mastication is 
resisted directly by the saddle under the replaced tooth or 
teeth, yet the comparatively flat or somewhat flaring sur- 
faces of the lingual border base plate, which rests upon the 
mucous tissues, receive some of the stress also and impart 
general stability to the denture. 
Fig. 315.— Labial View of Lower Partial Vulcanite 
Base Plate 
In lower cases but little if any support is afforded the den- 
ture by the lingual border surfaces of the base plate next the 
teeth, because of the generally perpendicular relation of these 
surfaces of the natural tissues. It is therefore necessary to 
extend the base plate well up on the cingulse of the anterior 
Fig. 316.— Occlusal View of Lower Partial Vulcanite Base Plate, 
Showing Finishing Shoulders for the Second 
Addition of Rubber 
teeth, otherwise if this is not done, irritation and absorption 
of the lingnal gingival tissues will occur in a very short time. 
The application of stop clasps to the first bicuspids, or even 
the second bicuspids, when the replaced teeth are situated to 
the distal of the clasps, will practically overcome the tendency 
of lower partials to tip anteriorly. The use of clasps without 486 
CONSTRUCTION OF PARTIAL DENTURES 
stops in the same location and under the same conditions usu- 
ally augments the undesirable conditions mentioned. 
Frequently, in difficult cases, it is advisable to construct 
the base of vulcanite to which, at the same time, clasp may 
be attached. This base plate is then fitted in the mouth the 
same as a gold base denture, a mash bite taken and the teeth 
selected, waxed, ground to meet requirements and vulcanized 
to the previously constructed base. 
By forming finishing shoulders on the base against which 
the second addition of vulcanite will finish and using a slightly 
different shade of rubber, very artistic results can be realized. 
The introduction of the lingual bar of metal for lower and 
the over-arch bar for upper cases combined with improved 
forms of frictional retention appliances, have proven so satis- 
factory that the technic of partial denture construction has 
been practically revolutionized within the last few years. 
MOUNTING THE CASTS ON THE OCCLUDING FRAME 
When a mash bite has been taken, in conjunction with the 
face bow, it is advisable in these, as in many other similar 
cases, to attach the face bow to the occluding frame and de- 
velop the occlusion cast before adjusting the ivorking cast or 
that one to which the artificial teeth are to be fitted, in the 
bite. The reason for so doing is that the bite which receives 
the working cast must be trimmed away freely so that the 
occlusal surfaces of the teeth may rest perfectly on the wax 
surfaces impressed by the natural teeth. This cannot be de- 
termined accurately unless practically all of the buccal, labial 
and lingual surfaces of the bite are cut away sufficiently to 
expose these occlusal areas to view, as has been previously 
stated. Now, if an attempt is made to force the working cast 
into the bite, or if the bite is trimmed before the occlusion cast 
is developed, distortion of the wax will most certainly occur, 
and later on, when the occlusion cast is developed, the rela- 
tion between the two will be incorrect. 
Summarized, the steps are as follows: 
Apply face bow, with mash bite attached, to the occluding 
frame. Fill the occlusion side of the bite with plaster, attach- 
ing it to the bow of the frame. Trim wax bite to receive the 
working cast, being careful not to injure the plaster teeth of 
the occlusion cast while doing so. Adjust working cast in 
trimmed wax bite and attach to occluding frame. When the 
plaster has set, warm the wax, open the frame and remove the 
wax from the occlusion cast. CONSTRUCTION OF PARTIAL DENTURES 
487 
REGISTERING THE CONDYLE PATHS IN PARTIAL CASES 
An ordinary protrusive mash bite, when properly trimmed 
so that the teeth of both casts may correctly enter their im- 
pressions, will serve to set the condyle paths of the occluding 
frame to coincide with those of the patient. 
ARRANGING THE TEETH 
Teeth of suitable form and color are selected and arranged 
as in full cases, the plaster teeth on the occlusion cast serv- 
ing as a guide in developing correct alignment and occlusion. 
Care must be taken, therefore, not to mutilate the occlusion 
model by attempting to force the porcelain teeth into imper- 
fectly softened wax by closing the frame as in full cases. 
Such procedure nearly always fractures the occluding plaster 
teeth and destroys the only means of testing the accuracy of 
occlusion in the constructive stages of the case. 
When the very slight connection between the wax saddles 
and anchorage spurs is considered it will readily be seen that 
trial of the wax model denture in the mouth is impracticable. 
Even when saddles of Ideal Base Plate are formed and firmly 
luted to the anchor spurs, to serve as a foundation on which 
to arrange the teeth, the benefit of a “try in” of the case is 
questionable, because of the general disturbance of relation 
of the several parts to each other, which commonly occurs 
during such procedure. 
The points of interference between porcelain teeth and 
those on the occluding cast should be noted and correction 
made by grinding as each tooth is set in position. When 
the protrusive bite is taken, as outlined, the relation of the 
lower and upper teeth to each other in lateral movements 
should be tested and corrections made accordingly. The neces- 
sity of developing perfect teeth on the occlusion cast and of 
avoiding their fracture during the arrangement of the sub- 
stitutes is, therefore, of extreme importance. 
The case is waxed to the required outline form and given 
the desired surface development of the finished denture, when 
it is ready for basking. 
FLASKING THE CASE 
Partial cases of the type here described are flashed the 
same as ordinary vulcanite dentures, except that the anterior 
lingual surface of the cast should be filled with plaster in the 
first investment of the case, so as to enclose the exposed por- 488 
CONSTRUCTION OF PARTIAL DENTURES 
tion of the lingual bar and hold it rigidly during subsequent 
procedures of flask separation, removal of wax, packing the 
rubber, final flask closing and vulcanizing. 
Since these steps, as well as finishing the case, are similar 
to those of ordinary cases, the details need not be repeated. 
LOWER PARTIAL GOLD BASE DENTURES 
In replacing lower posterior teeth it is frequently advis- 
able, and a common method of practice, to construct a gold 
base and attach the substitute teeth to it with vulcanite, or 
other means, as conditions require. 
One of the older methods, which in favorable cases has 
proven very satisfactory, is carried out as follows: 
A die and counterdie of the case are developed in the usual 
manner, on which a gold base, usually of 28 or 29 g, and 20 k. 
Fig. 317.— A Lower Gold Base with the Several Factors Assembled and 
Soldered But Not Finished with Stones and by Polishing 
is swaged. The lingual band of gold which connects the two 
saddles should extend well up on the cingula of the anterior 
teeth to prevent settling of the denture under stress as previ- 
ously mentioned. The principal base should be reinforced with 
a doubler, anteriorly, and extending back of the teeth clasped 
on either side, about one-lialf inch. This doubler may be of 
29 or 30 gauge gold. The base plate and doubler are pickled, 
polished and united with solder, trimmed to correct outline 
and reswaged. Clasps are developed on independent metal 
dies constructed for the purpose. These are fitted to the 489 
CONSTRUCTION OF PARTIAL DENTURES 
teeth in the mouth. The base plate is trimmed to take its 
proper position on the border without interfering with the 
clasps. An impression is then taken of the teeth clasped, 
preferably of one tooth at a time, with clasp in position, 
and including the contiguous part of the base plate. The 
base plate can thus be held in position while the plaster can 
be applied in a small hinged tray. When set, the impression 
is removed, the clasp and base plate adjusted in position, luted 
firmly with wax and a small cast developed, which holds the 
clasp and base plate in correct relation during soldering. 
When united, the base plate is returned to the mouth and 
an impression of the other tooth and clasp secured in like 
manner. This clasp and the base plate are united as just 
outlined. The metal structure is now pickled, polished and 
returned to the mouth for final bite and impression. 
FORMING THE FINISHING SHOULDER FOR VULCANITE WITH 
GOLD PLATE 
In these, as in practically all cases of gold base dentures, 
to which the teeth are attached with vulcanite, a shoulder 
should be formed against which to finish the latter. This 
may be done by cutting narrow, parallel-sided strips of gold 
plate of whatever curvature is required and applying and 
soldering the same along the line on the base plate where the 
vulcanite should terminate. These strips are applied and 
soldered neither at right angles to nor flatly against the base 
plate, but usually somewhat slanting so as to form a V-shaped 
groove, interiorly, while the outer surfaces form a continuous 
curve with gold base and vulcanite. This method is not only 
practical and economical, but artistic as well. It is particu- 
larly applicable to those cases where border absorption has 
progressed unequally and where, if correct contour be given 
the case, the vulcanite will be disposed in unsymmetrical out- 
line on the base. In such case a strip of suitable width and 
curvature can be cut, contoured, applied and soldered to the 
base in such manner as to develop normal contour to the den- 
ture, and symmetrical exposure of the vulcanite as well. 
FORMING THE SHOULDER WITH WIRE 
The most common method of developing the finishing 
shoulder for the vulcanite is by soldering a wire along the 
line on the base plate as indicated by the terminal margin of 
the previously contoured wax. That surface of the wire pre- 490 
CONSTRUCTION OF PARTIAL DENTURES 
senting toward the vulcanite area is squared out with stones 
and plug finishing burs, while the outer surfaces of wire and 
solder are given the approximate curvature of the finished 
case. 
The wire not only affords a finishing shoulder for the 
vulcanite, but when united to the gold base imparts rigidity to 
the latter to almost any degree desired, depending on the 
gauge used and the amount of solder applied. 
EXTENT TO WHICH THE WIRE IS APPLIED PERIPHERALLY 
A shoulder wire is applied along those areas on a base 
plate where loss of contour of the border becomes plainly 
noticeable. This applies not only to lines parallel with the 
border crest but to the end or perpendicular lines as well. 
Tn lower partial cases, of the type under consideration, the 
wire which forms the anterior terminal shoulder will usually 
be laid parallel with the disto-lingual line angle of the tooth 
clasped, or at such point that when the vulcanite is applied 
and the case finished, the general lingual contour of the case 
is continuous with that of the base plate along the lingual sur- 
faces of the natural teeth. 
The wire should extend from the anterior lingual shoul- 
der margin, distally, along the lingual border, curve over 
the crest of the latter to the buccal side and pass forward along 
the margin to near the anterior terminal of the base plate. 
It should not rise perpendicularly as on the lingual side be- 
cause the presentation of a line of gold in this area is un- 
sightly and unnecessary as well. By trimming the base plate 
a little scant at the anterior buccal terminal the artificial gum 
material can overrun the latter and thus obviate the display 
of any gold. The ability to recognize lost border surfaces and 
contours and lay the shoulder wires in correct position to 
restore them is an art that should be acquired by every pros- 
thetist and one which, when developed, stamps him a master 
of his calling. 
LINGUAL BAR DENTURES 
A very common and satisfactory method of replacing the 
lower posterior teeth is by means of saddles either of gold or 
of vulcanite, combined with the lingual bar to serve as a 
foundation for carrying the substitute teeth. Various meth- 
ods of retention are employed, the most common of which will 
now be mentioned. CONSTRUCTION OF PARTIAL DENTURES 
491 
RELATION OF LINGUAL BAR TO ORAL TISSUES 
In constructing lower lingual bar cases the assembling of 
the several parts in correct relation to each other and to 
the oral tissues must be carried out in a definite, systematic 
and orderly manner. The position of the bar in reference to 
the lingual border surfaces is particularly important. When 
in the finished denture, if allowed to touch the soft tissues, or 
to bear upon them with any degree of force, it will cause more 
or less discomfort, sometimes so much so as to require re- 
construction of the case. On the other hand, the bar cannot 
be placed too far from the border or too near the gingival 
margin of the gums, or tongue movements will be interfered 
with. 
It is impossible to state definitely the exact position of the 
bar as each case possesses peculiarities of its own. Usually 
when placed from one-fourth to three-eighths of an inch below 
the gingival margin, when the lingual margins will permit, 
Fig. 318.—- Relative Position of Lingual 
Bar to Tissues 
and about one twenty-fifth of an inch from the border tissues, 
neither tongue movements will be interfered with nor will the 
border tissues be impinged upon. 
FORMS OF LINGUAL BARS 
It is not possible to here describe all of the various forms 
of bars used, nor the many general methods of construction 
followed in these cases, but an outline of the principal steps 
will be given to serve as a foundation in this work. A case 
of replacement of the posterior teeth involving a lingual bar, 
stop clasps and vulcanite saddles will be described. 
Technical Steps in Lingual Bar Cases 
First, impressions of the teeth for clasp construction 
should be secured, and these appliances developed in accor- 
dance with steps previously described. 
The clasps are placed in position on the teeth and a plas- 492 
CONSTRUCTION OF PARTIAL DENTURES 
ter impression secured of the lingual areas of the border 
next which the bar will rest, and of sufficient border areas 
back of the teeth clasped to indicate the manner in which the 
terminal ends of the bar can be bent to best advantage for 
anchorage purposes. The clasped teeth must also be embraced 
by the impression. 
To prevent marring of the cast while adapting the lingual 
bar it should be formed from some of the harder materials, 
as Spence’s plaster or oxy-chloride of magnesia. 
The cast having been formed a measurement of the length 
of wire to be used in making the bar is secured, usually with 
a smaller wire which can be readily bent, or preferably with 
a piece of 12 gauge electric fuse wire. The latter wire is 
very pliable and can be formed to the exact shape of the per- 
manent bar, its ends flattened for retention purposes and 
any peculiar bends which the case calls for can be discovered 
before attempting to conform the very rigid wire of precious 
metal. This step will not be considered necessary by the 
experienced wire bender, but will prove most useful to the 
beginner. 
High-grade clasp metal wire, or iridio-platinum, from 12 
to 11 gauge thickness, is usually used for the bar in order that 
it may stand the various stresses to which subjected in the 
constructive stages and in subsequent use, without bend- 
ing. 
Two pieces of 16-gauge wire are sometimes bent sepa- 
rately to the form desired and afterward united with solder. 
This plan is followed by those who find difficulty in conform- 
ing the heavier gauge wire. Care should be taken to fill the 
Y-shaped spaces between the two wires with solder. When 
imperfectly filled, food lodges in them and the doubled wire 
feels uncomfortable to the tongue. 
To develop good anchorage in vulcanite saddles, it is nec- 
essary to extend the bar back of the clasped teeth from one- 
half to five-eighths of an inch. The bar should be bent 
outward and upward, to the crest of the border, each terminal 
end flattened broadly and a hole drilled through it, or a short 
cross-head soldered on to prevent the gradual loosening of 
the saddle under stress. 
The flattened ends of the bar should be warped to lie par- 
allel to, but not quite in contact, with the border surfaces. 
The ideal position for the terminal ends of the wire in the 
finished case is in the center of the saddles. CONSTRUCTION OF PARTIAL DENTURES 
493 
VARIATION IN FORM OF CONNECTION BETWEEN LINGUAL BAR 
AND CLASP 
A common and very practical method of constructing the 
skeleton frame work for a lingual bar case is as follows: 
The bar is conformed anteriorly to the cast, as previously 
described, but instead of being carried back of the teeth em- 
braced by the clasps and terminating in the vulcanite saddle 
it is bent upward and outward at the disto-lingual angle of 
each of the clasped teeth, in such position as not to render the 
lingual side of the case bulky nor interfere with arrangement 
of the substitute teeth. 
This manner of connection of clasp and bar affords no 
anchorage of metal framework to saddles. To supply such 
attachment, a piece of clasp wire of the same gauge as the bar, 
about one-half inch long, is flattened throughout about two- 
thirds of its length, bent to conform to the curvature of the 
border crest and distal surface of the tooth and clasp and 
soldered to the latter. The better plan is to fit the anchor 
spur in the angle between the turned-up end of the lingual 
bar and clasp and form the connection principally between the 
two wires, thus obviating too broad, an attachment to the 
clasp. Another method of anchoring the lingual bar to vul- 
canite saddles is as follows: 
The bar is adapted to correct lingual curvature, as de- 
scribed. The terminals, instead of being bent outward and 
over the crest of the border, pass backward, parallel with the 
lingual periphery of the saddle on either side, or it may lie 
somewhat above the peripheral margin of the saddle, so as 
to be entirely enclosed with the vulcanite. 
Two ribs of rigid metal are bent to the bucco-lingual con- 
tour of the borders and soldered to the lingual bar, one at the 
distal extremity of the latter, the other midway between that 
point and the clasped tooth. These ribs, as well as the bar, 
should be enclosed within the vulcanite. 
SOLDERING THE CLASPS AND BAB IN COBBECT BELATION TO 
EACH OTHEB 
The bar, when properly conformed, is blocked in position 
on the cast by interposing a small pellet of wax under each 
terminal end and one anteriorly. While the wax is soft the 
bar is pressed to the exact position desired and luted by melt- 
ing a portion of the wax to both bar and cast. The excess 
wax is then trimmed away, a small amount of investment 494 
CONSTRUCTION OF PARTIAL DENTURES 
mixed and flowed over tlie bar at these three points, leaving 
the greater portion of metal exposed. 
A strip of 20-gauge clasp metal, about one-eighth inch 
wide, is fitted between each clasp and the bar, the lower end 
of the strip resting between the bar and cast, the upper end 
extending above the gingival margin of the clasp so that the 
solder may develop a broad attachment between the two. No 
effort need be made to fit the strip accurately to the cast, 
since any slight space that may exist between the two will later 
on fill with vulcanite. 
Flux is now applied and the bar and clasp on each side 
are connected with solder, flowing it not only in the joints 
but over the strip as well, to stiffen it and form a rigid con- 
nection. This method, it will be seen, does not require the 
removal of the clasps from their position on the cast, and 
therefore the relation between them and the teeth they em- 
brace is the same as when in the mouth. When soldered the 
case is removed from the cast, pickled, polished and washed 
and is now ready for the final bite and impression. 
A slight variation from the above method is sometimes 
carried out whereby the attachment of clasps and bar may be 
made as described and stops developed on the clasps at the 
same time. This refers to cases in which stops were not de- 
veloped on the clasps or soldered to them during the con- 
structive stages or before the impression was taken. 
The strip which forms the connection between bar and 
clasps, either of clasp plate or half-round wire, is cut of suf- 
ficient length to reach from the bar across the clasp and to the 
point where the occlusal rest or stop should terminate. It is 
then annealed and with pliers shaped to meet the require- 
ments of both standard and stop, when it is attached with 
solder, as described. 
Sometimes the location of the stop will be out of normal 
alignment with position of the clasp and bar connection. In 
such case the stop can be formed separately and soldered at 
the time of connecting the bar and clasp. It will be found 
most convenient, and accurate as well, to form the stops on 
the clasps and unite them during the constructive stages, at 
which time more perfect adaptation can be secured while the 
clasps are on the metal dies. 
TAKING THE WAX BITE 
The bar, with clasps attached, is now introduced in the 
mouth and its relation and that of the clasps to the tissues CONSTRUCTION OF PARTIAL DENTURES 
495 
and teeth verified. If correct a wax mash bite is taken with 
the appliance in position, care being taken to include all nec- 
essary teeth, and the border areas as well. In this, as in 
practically all classes of extensive replacements, the face bow 
should be applied and the bite carefully removed without dis- 
tortion. 
TAKING THE IMPRESSION 
The final impression in all cases should be in plaster. In 
cases of the class under consideration a full impression of the 
border surfaces to be covered by the saddles, the teeth clasped 
and the anterior teeth to slightly below the gingival line is 
essential. Lingually the impression should extend deeply 
enough to embrace the bar opposite the teeth clasped, but not 
necessarily anterior to these locations. 
Special care must be observed in taking both bite and im- 
pression that undue stress is not brought upon the anchor 
spurs posteriorly, or the lingual bar anteriorly of the teeth 
clasped, otherwise the framework will be tipped and thrown 
in an abnormal relation to the teeth and oral tissues. By en- 
closing the terminal ends of each anchor spur in a small mass 
of soft modeling compound, then pressing the bar down until 
the clasps take their proper position on the teeth and the 
bar its correct relation to the border, the framework can be 
balanced and steadied while taking the impression. The com- 
pound serves the purpose of temporary saddles and when 
properly applied to the border becomes a part of the im- 
pression. 
The impression usually fractures and comes away in 
pieces. These should be cleared of debris, reassembled and 
luted firmly together, varnished and a cast of hard material 
constructed on which to vulcanize the case. 
ARTIFICIAL STONE 
Recently there lias been placed on the market an artificial 
stone product which can be mixed with water and which will 
harden in about four hours. It is dense and hard and will 
stand rough usage. It softens somewhat during vulcanization 
and is more readily removed from the vulcanite than is oxy- 
chlorid of magnesia. This product is specially useful in the 
construction of partial, and, in fact, all cases where the pres- 
ervation of relations of several parts in constructive stages 
is essential. The material referred to is “Weinstein’s Arti- 
ficial Stone,” prepared by C. A. Nielsen Co., New York. 496 
CONSTRUCTION OF PARTIAL DENTURES 
The Lingual Bar Combined with Gold Saddles 
In cases of this type, one of the common methods of con- 
struction is as follows: 
First — Impressions of the teeth to be clasped are secured 
and clasps constructed by methods previously outlined. 
Second — A full impression, in plaster, is secured of the 
lower arch, including all of the parts concerned in the forma- 
tion of saddles and lingual bar. In most cases the impression 
should be scraped along the border crests slightly, but the 
relief so afforded should not extend to anterior or posterior 
terminals. 
The derived cast is trimmed and converted into a model, 
so as to readily withdraw from the sand matrix, and a die 
and counterdie formed. 
Third — Saddles are swaged to the border surfaces and 
trimmed to approximately correct peripheral outline. 
Fourth — The lingual bar is adapted to the required con- 
tour of the case, using the die as a model on which to do the 
fitting. The Benson Plier is particularly well adapted to the 
work of bar bending, the wire being held in the concave de- 
pression back of the beak contact. 
In gold saddle cases, the terminals of the bar should lie 
parallel with and rest against the lingual margin of the sad- 
dles to which they are afterward soldered. By proper trim- 
ming, the upper margin of the bar may be formed into a finish- 
ing shoulder for the vulcanite attachment of the teeth. 
If any doubt exists as to the depth to which the lingual 
border of the saddles can extend without impingement on the 
tissues the safest plan will be to test the saddles in the mouth 
before uniting them to the bar. 
Fifth, after the saddles are trimmed to correct lingual 
width they are returned to the die, the lingual bar adjusted as 
described under the preceding heading, “Lingual Bar Den- 
tures, ’ ’ page 490. 
The terminal ends of the bar are now firmly waxed to the 
saddle margins, care being taken while adjusting it to avoid 
springing the bar. It is frequently a good plan, after the bar 
is perfectly adjusted to the two saddles, to unite one end 
only with its saddle, remove from the die, invest and solder 
the two together. The partially constructed frame is returned 
to the die and careful adjustment secured between it and the 
opposite saddle, after which they are invested and united as 
in the first instance. CONSTRUCTION OF PARTIAL DENTURES 
497 
Sixth, the skeleton denture is pickled, cleansed and in- 
troduced in the mouth for final peripheral trimming and gen- 
eral adjustment. 
Seventh, the clasps having been formed are adjusted to 
the teeth, the denture base introduced, trimmed where inter- 
ference with clasps occur and the relation between clasps, 
teeth and baseplate secured as ordinarily accomplished or by 
the compression method described, when such procedure is 
indicated. 
Eighth, when clasps and baseplate are united and the den- 
ture base cleansed, it is returned to the mouth for final im- 
pression and bite. By usual methods, casts are produced and 
mounted on the occluding frame. 
Ninth, the teeth are occluded, and when deemed advisable, 
cases of this type can be removed from the cast for final trial 
in the mouth. 
Tenth, after flasking and separating the case, if the sad- 
dles have not previously been spurred with a graver, this 
step should be carried out before final closing of the packed 
flask. In addition to this method of anchorage, small loops of 
wire should be soldered on the saddles and the latter coated 
with a film of thin chloro-rubber to act as a cementing me- 
dium between gold and vulcanite. 
Settling of Dentures from Use 
When a denture of any type is introduced in the mouth 
and worn for even a short time the mucous tissues on which 
it rests will, under pressure, yield slightly, and as a result 
the denture will settle, as it is commonly termed. The amount 
of such settling varies in different individual mouths and fre- 
quently in different areas of the same mouth, depending on 
the thickness and condition of mucous tissues. 
It is apparent, as a result of such settling, particularly in 
partial dentures, that two and possibly three conditions ad- 
versely affecting the usefulness of the denture may develop. 
First, the maximum service of the denture will be im- 
paired by the greater or less loss of occlusal contact which in- 
variably occurs. Second, when the substitute is fitted with 
retention appliances, and no provision is made for settling of 
the denture, undue stress may be brought upon the anchor 
teeth. Third, as a result of the preceding condition peri- 
dental inflammation of the roots of the teeth embraced by the 
clasps, or to which the denture may be anchored by other 498 
CONSTRUCTION OF PARTIAL DENTURES 
means, is liable to ensue. By the display of careful judg- 
ment as to the probable amount the tissues will yield under 
working conditions, and carrying out certain steps to com- 
pensate for such settling, the difficulties mentioned may be 
avoided. These steps will now be briefly detailed: 
In the construction of a partial vulcanite denture to which 
stop clasps are adjusted, a piece of cardboard should be placed 
between the stop and the occlusal area of the tooth on which 
it rests, at the time of placing the clasp on the tooth for final 
impression. The area of the cardboard need not exceed that 
of the occlusal area of the stop. Its thickness should be 
gauged by the extent it is estimated the denture will settle; 
it may range from the thickness of a sheet of medium weight 
writing paper to that of a heavy visiting card. The piece of 
card can be attached to the stop by flowing between the two a 
thin film of wax. After the impression is removed, and before 
constructing the cast, the cardboard should be removed from 
the stop. As a result of interposing the cardboard as de- 
scribed, the clasp occupies a position on the tooth slightly 
nearer the plane of occlusion than it did on the die, during its 
construction, or would occupy if placed on the natural tooth, 
without the interposition of the cardboard. 
The final result of such procedure is that when the com- 
pleted denture is placed in the mouth the stop may project 
slightly above the occlusal surface of the tooth it embraces. 
After a short period of use, oftentimes within twenty-four 
hours, the settling of the denture will bring the stop in con- 
tact with the tooth. 
In occluding the teeth, in partial cases, it is advisable to 
set the substitute teeth so that they strike strongly against the 
opposite occluding teeth to insure strong contact occlusally 
when introduced in the mouth. 
To further insure good contact between the replaced teeth 
and those in the opposite arch, after settling of the denture 
has occurred, the teeth on the substitute should not be ground 
to perfect occlusion on first introduction of the finished den- 
ture in the mouth. This should be done, however, after a 
lapse of twenty-four to forty-eight hours, provided the pa- 
tient has worn the denture in the meantime. 
COMPENSATING FOR SETTLING OF GOLD BASE SADDLES 
The preceding method is also applicable to the adjustment 
of clasps to a gold base denture, but the following plan, when 
it can be carried out with accuracy, is to be preferred: CONSTRUCTION OF PARTIAL DENTURES 
499 
Tlie clasps are placed in position on their respective teeth, 
without interposing the cardboard, as described, and the den- 
ture base introduced and seated on the border. 
A suitable tray is selected and softened modeling com- 
pound placed within, on each side, but not anteriorly, so as to 
embrace a portion of the central area of each saddle. Neither 
the anterior teeth nor clasps should be embraced by the com- 
pound. Pressure is brought upon the tray to force the im- 
pression material, not only on the border crests, but over the 
buccal and lingual areas of the saddles as well. There should 
be sufficient bulk to the compound so that the impressions of 
the two sides may be secured without depressing the tray 
below the level it should occupy in taking the final impression. 
When chilled the impression may usually be removed without 
disturbing the position of either baseplate or clasps. 
Both anterior and posterior terminals of each impression 
are removed, by cutting, leaving a ridge about one-fourth inch 
wide extending from buccal to lingual, across the tray. These 
transverse ridges of compound, one on either side of the tray, 
are actual cross-sections of the impressions and are designed 
to force the saddles firmly in contact with the tissues while the 
plaster impressions are secured of the base plate, the teeth 
and the unattached clasps. 
Each side of the tray is now filled with sufficient plaster, 
of suitable consistency, to secure impressions of the desired 
parts. When introduced and properly centered, pressure is 
applied and the tray forced borderward until the ridges of 
compound come in contact with the saddles. The pressure is 
now increased to a very considerable extent, the idea being 
to compress the mucous tissues to nearly the full extent of 
their yielding capacity, after which casts are developed and 
the clasps soldered. 
When the clasps are permanently attached to the base 
plate and the latter is returned to the mouth, it will be seen 
that the stops of the clasps usually stand slightly above the 
occlusal surfaces of the teeth embraced. 
By repeating the same steps for producing pressure on the 
base, in taking the final impression, the teeth, when ground 
and adjusted to the base plate as usual and later are perma- 
nently attached to the denture, will strike the occluding teeth 
strongly in occlusion. They should not, however, be ground 
to perfect occlusion at first sitting, but time be given for the 
tissues to yield before making final correction. 
Dr. Goslee suggests placing a small post of wood between 500 
CONSTRUCTION OF PARTIAL DENTURES 
the saddle and occlusal surfaces of the opposite teeth, the 
mouth being open sufficiently for the introduction of tray. 
By means of this post the patient can compress the tissues 
under the saddle during the hardening of the impression. A 
half tray, such as is used in partial cases, by having its floor 
slotted to accommodate the post, is used for carrying the im- 
pression material to place. 
To relieve strain on anchor teeth, elliptical springs unit- 
ing the clasps with base plate have been demonstrated by Dr. 
L. J. Weinstein of New York, who ascribes the suggestion to 
a Connecticut practitioner. 
Fig. 319.— An Elliptical Spring, Attached to Lingual Bar and Flat Band, Open 
Center, Stop Clasp 
With the several fundamental principles of partial den- 
ture construction outlined, of both vulcanite and gold bases in 
conjunction with stop clasps, the application of various other 
forms of retention appliances will be outlined. 
The Roach Continuous Loop Clasp 
TECHNIC OF CLASP CONSTRUCTION 
An impression of the tooth which the clasp is to embrace, 
and the proximating tooth also, is secured which should be 
filled with modelite, a very hard cement-like substance, which 
sets quickly and will withstand rough usage without marring 
readily; or a die may he formed of Melotte’s metal. A piece 
of 18, 19 or 20 gauge, sixteen per cent platinized clasp metal 
wire, about 2 inches long, is required for each clasp. The 501 
CONSTRUCTION OF PARTIAL DENTURES 
gauge depends on the length of the loop and bows and the 
stress to which it will be subjected. 
The wire is annealed and bent in the middle to form a 
close, parallel staple, after which it is opened slightly and 
pressed down between the two proximating teeth, the ends 
bent outward and around the buccal and lingual surfaces of 
Fig. 320.— Roach Open Continuous Loop Clasp. Clasp Applied to Lower Lingual Bar, Gold 
Saddle Case. Notice Finishing Shoulder for Vulcanite Formed by Soldered Wire 
to Saddle. Also Rib Extending from Lingual Bar, Over Border 
Crest, for Strengthening Purposes 
Fig. 321.— Occlusal View of Lower Partial 
the tooth to form the buccal and lingual spans so as to em- 
brace it closely. It must clear the gingival tissue at all points. 
The adaptation is completed by bending the buccal and 
lingual terminals so as to form a projecting lug for attach- 
ment to the baseplate, or by uniting with solder and turning 
the extreme outer ends slightly apart, they will serve for an 
anchorage in vulcanite. 502 
CONSTRUCTION OF PARTIAL DENTURES 
In most cases, when the embrasures between the proxi- 
mating teeth, in which the vertical loop of the bow will rest, 
are free from gingival tissue, the wire on both buccal and 
lingual sides should be carried well into these spaces and 
comparatively close to the gingiva before turning it to form 
the horizontal spans. By so doing the tendency of the dis- 
tal end of the denture to leave its border is overcome. 
Fig. 322.— Partial Upper and Lower Gold Base Dentures. The Upper Denture Is Fitted with 
Steel Facing and Flat Band Clasps. The Lower Denture with Roach 
Continuous Loop and Flat Band Clasp 
Fig. 323.— Lingual View of the Preceding Cases 
APPLICATION OF THE CONTINUOUS LOOP CLASP 
The application of clasps of this type to a lingual bar gold 
saddle case is as follows: 
The saddles and bar having been formed as previously 
described, the baseplate is introduced and the clasps adjusted 
to their respective teeth. The lugs of the clasps are bent so 
as to rest on the saddles. An impression is now taken, using 
the pressure method when advisable, when on removal and CONSTRUCTION OF PARTIAL DENTURES 
503 
reassembling of the parts a cast of investment is developed 
and the clasps soldered to the baseplate. 
THE ROACH OPEN LOOP CLASP 
The open loop clasp is constructed and applied in much 
the same manner as the continuous loop clasp. When clasps 
of this type are to be formed a heavier wire should be used, 
since, not being continuous, as is the preceding clasp, it is 
liable to be bent with use unless the wire is comparatively 
rigid. 
Fig. 324.— The Roach Open Loop Clasp 
The outer end may be returned back upon itself or be bent 
in any manner to take advantage of a depressed area on the 
tooth, thus adding to its stability. 
The open loop clasp may be formed, first, as a double bow 
clasp, the two terminals united with solder to form a rigid lug 
for attachment and the outer loop severed and bent as condi- 
tions indicate or they may merely be severed without bending. 
The advantages of this type of clasp are manifold. The 
long, linear contact of the wire, with varying surfaces of the 
tooth insuring great clasping property, together with but lit- 
tle superficial area of tooth surface covered, is the principal 
one. 
No provision need be made, as with stop clasps, for the 
settling of the denture, since, with slight effort, the vertical 
loop can be raised by bending the horizontal bows occlusally 
when occasion requires. 504 
CONSTRUCTION OF PARTIAL DENTURES 
Dentures fitted with loop clasps do not feel rigid and un- 
yielding, as is often the case when non-resilient clasps are 
used, yet they are retained and rest firmly in position. 
The loop clasp, by its form, obviates the necessity for a 
stop in most instances, excepting when no proximating tooth 
is present. 
THE BALKWILL CLASP 
A clasp similar in form to the open loop has been in use 
in England for many years. A loop clasp, together with one 
Fig. 325.— The Balkwill Open Loop Clasp and Modification 
of modified form, was described and illustrated by Balkwill 
in his book on Mechanical Dentistry, edition of 1880. 
The modified form of clasp referred to consisted in adapt- 
ing a strip of clasp metal to the buccal surfaces of two prox- 
imating teeth and connecting it with denture base on the lin- 
gual side with a wire loop. 
Still another form of retaining appliance is shown in the 
Dental Cosmos, Vol. 56, page 1194, by Dr. Heinricksen. 
This appliance consists of a loop of clasp metal bent to 
the curved contour of the gingival tissues, and having a ball 
terminal which rests in the embrasure against the tooth on CONSTRUCTION OF PARTIAL DENTURES 
505 
the opposite side from the replacement. The wire is bent so 
as not to impinge on the soft tissues nor does it touch the 
tooth except at its terminal end. 
To render the appliance effective there must be good 
contact, in normal position, between the natural and proxi- 
Fig. 326.— The Heinricksen Partial Loop Ball Pointed Clasp 
mating porcelain tooth on the denture, and the ball must be 
placed close to the gingiva. If in the case illustrated the con- 
tact of the ball was near the occlusal or incisal area and con- 
tact between the teeth was defective or close to the gingiva 
the action of the loop would be to unseat the denture at its 
distal terminal. 
The Roach Ball and Tube Attachment 
This appliance consists of a ball with projecting spur for 
anchorage purposes and a tube of heavy clasp metal which re- 
Fig. 327.— The Roach Ball and Open 
Tube Attachment 
ceives the ball. The tube is slotted throughout one side to 
accommodate the passage of the spur. 
Application op the Roach Attachment 
The usual method of applying the ball and open tube at- 
tachment is as follows: 
The crown, inlay, Carmichael attachment, or whatever 
means may be employed, for securing anchorage to the natural 506 
CONSTRUCTION OF PARTIAL DENTURES 
tooth or root is first constructed and temporarily set in place. 
For convenience of description, a crown will be considered as 
the means of attachment. 
The position of the ball, which should be close to the gin* 
givae, yet not touching it, is marked. To conserve space for 
adjusting the substitute teeth to the saddle, the ball should 
be set somewhat to the lingual of the border crest, yet not so 
far as to produce unnecessary bulk on the lingual side of the 
finished denture. 
Remove crown from the mouth and drill a hole at point 
marked for the reception of the ball stem. When applied to a 
shell crown, the stem should be cut short, so as not to interfere 
seriously with the inner periphery of the crown. The shoulder 
of the stem should rest flat against the surface of the crown. 
When soldered, the surplus, if any is present, is removed 
and the crown is returned to position on the root. A slot is 
made in the saddle, directly beneath the location of the ball 
to permit the free passage of the denture base to and from 
position without interference. The denture is now seated on 
its border. 
An impression in plaster is taken, by the pressure method, 
if indicated and when set, is removed, the crown usually com- 
ing away with it. If not, the crown is removed and placed 
in the impression. The latter is now prepared, and partially 
filled in with Modelite, into which one or two small wood 
screws are inserted so as to leave the heads freely exposed 
and projecting. The remainder of the impression is filled 
with plaster or investment compound, and when hardened the 
impression is removed. 
The case now consists of a cast representing a portion 
of the mouth carrying crowns with attached balls and saddles, 
all in correct relation to each other. The next step is to at- 
tach the tubes to the saddles in the correct relation to the balls. 
The tube may be attached to the saddle by various means, but 
the following method, suggested by Dr. Roach, is, for several 
reasons, the most practical: 
A piece of 15-gauge clasp metal wire, from one-half to 
three-fourths inch long, is bent at right angles, flattened 
slightly on one side, the tube laid and soldered on the flattened 
surface parallel with the vertical arm. This wire is called the 
contact bar, because it not only affords attachment of the tube 
to saddle, but the vertical portion at its upper extremity is 
bent to lie in contact with the anchor crown, at normal con- 
tact point. CONSTRUCTION OF PARTIAL DENTURES 
507 
The bar is now bent so as to bring the tube to a vertical 
position sufficiently high so that the ball rests in its lower end. 
The parts now sustain this relation to each other: the 
horizontal arm of the bar rests on and lies in contact with 
Fig. 328.— Diagrammatic Cut, Showing Relation of the 
Several Factors of Roach Appliance 
Fig. 329.— The Roach Attachment Combined with Stop Clasp 
saddle; the vertical arm, at its upper extremity, rests at point 
of contact with the anchor crown; the tube, vertically placed, 
contains the ball near its lower extremity. 
When this adjustment has been perfected, the horizontal 
arm is waxed firmly to the saddle. A mix of investment is 
applied around the tube, vertical arm, and anchor crown, a 
very small amount being sufficient to hold the part in correct 
relation. The horizontal arm is now soldered firmly to the 508 
CONSTRUCTION OF PARTIAL DENTURES 
saddle. A similar adjustment and attachment is now made 
between tube, contact bar and saddle on the opposite side. 
Fig. 330.— Roach Attachment, Showing One Form of Contact Bar 
These appliances, in favorable cases, when properly ad- 
justed, afford most efficient means for retention. In addition, 
should the denture settle, the tube follows without restriction 
by the ball. The necessity for fixing the tube high on the ver- 
tical arm in the constructive stage is apparent. 
Fig. 331.— Anterior Restoration with Roach Attachment Applied 
When the denture is subjected to masticatory stress the 
tube rotates on the ball, without subjecting the anchor tooth 
to side stresses or strains. The contact bar, resting as it does 
on the contact point of the tooth, prevents the raising of the CONSTRUCTION OF PARTIAL DENTURES 
509 
distal end of the denture, yet in no way resists compressive 
force. 
By the exercise of a little ingenuity, the ball and tube 
attachments may be applied to advantage in many ways for 
the retention of partial dentures in both arches. They may 
also be combined with clasps of various types, or with the Gil- 
more or other standard attachments in such manner as to re- 
duce to the minimum danger of injury to the remaining 
natural teeth. 
THE MORGAN ATTACHMENT 
This attachment consists of two parts, one of which tele- 
scopes within the other. The outer consists of a flattened, open 
loop or partial band, called the “keeper,” and is attached to 
Fig. 332.— The Morgan Anchor 
and Keeper 
the crown or inlay of the anchor tooth. The other part, which 
fits within the keeper, is termed the 11 anchor ’ ’ and is attached 
to the substitute or denture base. 
In applying these attachments to a denture it is necessary 
that they should be as nearly parallel as possible, so that the 
Fig. 333.— Crowns with Morgan Keeper Attached 
appliance may be introduced and removed without difficulty. 
An appliance called a “soldering jack” is used for para- 
lelling the keepers and for holding them in position against 
the crown while soldering. 510 
CONSTRUCTION OF PARTIAL DENTURES 
An impression, with crowns in position, is taken and re- 
moved, the crowns coming away with it. From this a cast of 
investment material is formed of usual size and proportions. 
TECHNIC OF APPLICATION 
Fig. 334.— Soldering Jack Used with Morgan 
Appliances 
This is set upon and clamped to the base of the soldering jack. 
A keeper is adjusted to the perpendicular arm of the jack. 
The latter is moved so as to bring the attachment against the 
Fig. 335.— Lower Posterior Restoration Supported with 
Two Morgan Appliances 
crown surface at the correct angle and in proper position, 
where it is united with solder to the crown. Without changing 
the perpendicular relation of the main post which governs the 
direction of the arm, the set screw of the latter is released, 
it is raised from the keeper already soldered; the other keeper CONSTRUCTION OP PARTIAL DENTURES 
511 
is adjusted to the arm, when it is rotated against the other 
crown and attached in a similar manner. 
The crowns may now be permanently set. The anchors 
are next placed in position in the keepers for the final impres- 
Fig. 336.-—- Upper Anterior Restoration Sustained by Two 
Morgan Attachments on Bicuspid Teeth 
sion. When allowance is to be made for settling of the den- 
ture a U-shaped piece of cardboard can be interposed between 
the flange of the anchor and the occlusal end of the keeper. 
The impression is now taken and removed, the anchors com- 
Fig. 337.— Posterior Restoration Supported at Each 
End with Morgan Attachment 
ing away with it or, if not dislodged, are removed from the 
keepers and returned to place in the impression. 
A piece of heavy German silver plate, bent to resemble 
the keeper but about one-half inch long, is passed over each 
anchor and the impression filled with plaster or hard cast 512 
CONSTRUCTION OF PARTIAL DENTURES 
material. The German silver posts which receive the flanges 
of the keeper prevent the disturbance of relation of the latter 
to the cast. Loops should be soldered on the extension of the 
anchor for attachment in vulcanite work. 
In case of a gold base denture, when the projection of the 
anchor does not touch the base, a piece of heavy plate may be 
adjusted between the two and all united with solder. The 
steps from now on are carried out as in an ordinary vulcanite 
case. 
THE CONDIT ATTACHMENT 
The Condit attachment consists of two pieces, the inner, 
a clasp metal tube, open at the side and ends, which is at- 
Fig. 338.— Lower Partial Denture with Condit 
Attachments Applied to Cuspids 
taehed to the anchor crown, the open side toward the space to 
be filled. The outer part is a telescoping tube, open at the 
side and one end. To the other, or occlusal, end is attached a 
floor, in the center of which is fixed a rigid post, the same 
diameter as that of the inside of the inner tube. It will be 
seen that this appliance possesses greater grasping property 
than any of the other standard types described, since the inner 
tube grasps the center post of the outer appliance, while the# 
outer tube grasps the outer surfaces of the inner tube. 
The application of these appliances is similar to that of 
the Morgan, just described, a paralleling device being neces- 
sary for the proper adjustment of the inner tubes to their 
respective crowns. CONSTRUCTION OF PARTIAL DENTURES 
513 
Fig. 339.— Single Saddle Supported by One Condit. 
Impractical 
Fig. 340.— Small Restorations Showing Variations in 
Application of Condit Attachment 
Fig. 341.— Lower Anterior Saddle Restoration 
Condit Attachments 
Fig. 312.— View of Above Case with Denture 
in Position 514 
CONSTRUCTION OF PARTIAL DENTURES 
Fig. 343.— Partial Upper Denture Supported by Two 
Condit Attachments 
When ample occluso-gingival space exists, these appli- 
ances, when properly balanced and adjusted, serve a most 
useful purpose. 
This appliance consists of a U-shaped clip or clasp of 
rigid yet resilient metal, the flanges of which receive a 14- 
gauge wire. No paralleling device is needed other than the eye 
in adjusting this attachment to a case, but at the same time 
THE GILMORE ATTACHMENT 
Fig. 344.— Enlarged View of Gilmore 
Attachment Designed for 
Metal or Vulcanite 
Work 
Fig. 345.— Enlarged View of Gilmore 
Attachment Designed for 
Vulcanite Work 
when two or more are used in a denture they should be placed 
with flanges as nearly parallel as possible with the line of 
direction of introduction to and removal from the mouth. 
APPLICATION OF THE GILMORE ATTACHMENT 
The application of the Gilmore attachment varies in dif- 
ferent cases according to the position of the anchor teeth and 
the spaces to be filled. CONSTRUCTION OF PARTIAL DENTURES 
515 
For example, in a lower partial denture in which the pos- 
terior teeth, hack of the cuspids or bicuspids, are to be re- 
placed, it is necessary to provide against the movement of 
the denture away from the anchor teeth. The necessity for 
Fig. 346.— Bars Bent Perpendicularly to Prevent Distal Movement, Applied 
and Soldered to Crowns, for Gilmore Attachment 
this is apparent, since the attachment itself cannot resist hori- 
zontal movement, under stress, of the denture along the ridge. 
When the space to be filled is bounded anteriorly and pos- 
Fig. 347.— Angle Bar Bent 
to Set Against Crown and 
Alveolar Border 
teriorly by natural teeth, these prevent such movement and 
the application of the appliance is simple. 
The technic of application of the Gilmore appliance in the 
Fig. 348.— Crown with Bar Ap- 
plied for Gilmore Attachment. 
The Vertical Arm Lies Too Close 
to Gingival Area of the Crown, 
Also Should Extend Nearly to 
Occlusal Surface 
Fig. 349.— Crown with Bar Ap- 
plied for Gilmore Attachment. 
The Bar Should Not Encroach 
Too Closely on Gingival Tissues 
Next to Crown 
first case mentioned, all of the teeth posterior to the first bicus- 
pids having been lost, is as follows: 
Crowns are constructed for the first bicuspids and placed 
in position, but not cemented to their respective roots. 516 
CONSTRUCTION OF PARTIAL DENTURES 
An impression is secured and removed, the crowns usu- 
ally coming away with it. From the impression, a cast, com- 
posed of investment material, is secured. To the distal sur- 
face of each crown a piece of 14-gauge wire of iridio-platinum 
or highly platinized clasp metal is adapted. 
The wire should be bent so as to lie in contact with the 
occlusal two-tliirds of the crown; at the gingival third it 
should leave the crown surface at a gradually increasing slant 
to form a clearance space for the protection of gingival tis- 
sue. The horizontal portion of the wire should conform to and 
rest lightly upon the border, its position being usually slightly 
to the lingual of the crest. At a distance not exceeding three- 
eighths of an inch from the crown the distal end should be 
turned up sharply at a right angle. The direction of this 
vertical portion of the wire should be parallel with the line of 
direction of introduction and removal of the denture. Its 
height may vary from one-sixteentli to three thirty-seconds of 
an inch. When the wire is properly conformed it is waxed 
in position against the distal crown wall, and a mix of in- 
vestment is made and applied over the bar along the ridge, 
being careful to enclose the distal, vertical end. This is neces- 
sary to obviate possible lateral rotation of the end against the 
crown wall in soldering. The wax is removed from the joint, 
flux applied and the bar is soldered to the crown. 
It is frequently advisable to extend the solder somewhat 
beyond the area of the bar connection with the crown to ren- 
der the latter rigid. A better plan is to adapt and solder a 
piece of plate to the distal wall of the crown during the con- 
structive stages. The addition should be attached with high- 
grade solder, so that the union may not later be disturbed in 
soldering the bar. 
When the bars are attached the rough surfaces of both 
crown and bar are removed and given the final finish. The 
crowns are again returned to position in the mouth and a bite 
and final impression secured. The teeth are occluded, the 
case carved, flashed and separated, and the matrix packed as 
usual. 
ADJUSTMENT OF CLASPS TO BARS 
A strip of cardboard, cut to fit between the flanges of the 
attachment, is pressed in place against the inner, curved sur- 
face of the attachment, and the latter set in position on the 
bar. This is to allow for subsequent settling of the denture. 
The clasp should occupy a position about midway between 
the crown and terminal end of the bar. It should be ranged CONSTRUCTION OR PARTIAL DENTURES 
517 
with flanges parallel or as nearly so as possible, with those of 
the opposite attachment; that is, both attachments should be 
placed so that the flanges stand perpendicular. Furthermore, 
Fig. 350.— Diagrammatic Cut Showing Rela- 
tion of the Several Parts of a 
Gilmore Attachment 
they should be forced as closely to the bar as the interposed 
cardboard will permit. 
The last step before closing the flask consists in obliter- 
ating the spaces between bars and borders so as to exclude 
the rubber in closing the flask. This is necessary so that the 
Fig. 351.— Case in Which It Is Unnecessary to Bend Terminal 
End of Bars Vertically from the Border. 
Gilmore Attachments 
bars and crowns may later be removed from the vulcanite 
without mutilation. A thin mix of plaster is applied in the 
space between the borders and bars, and along the outer sides 
of the flanges as well, so that the surfaces are free from under- 518 
CONSTRUCTION OF PARTIAL DENTURES 
cuts. The plaster should not enter the openings beneath 
anchor lugs, nor surround the latter. (See Fig. 350, page 517.) 
When the plaster has hardened, the flask is closed and the 
case vulcanized. On opening and cleansing the denture, the 
Fig. 352.— Palatal View of Gold Base Partial Den- 
ture Sustained by Two Gilmore Appliances 
surplus vulcanite is removed. A thin blade instrument is 
passed along on either side of the bar and flanges, to remove 
as much as possible of the plaster which Avas built in under 
the bar. With a little careful pressure and manipulation, the 
bars will part from the vulcanite without difficulty, after which 
the case is finished. The margins of the groo\7e which receives 
the bar should be smoothed and a round bur of approximately 
the diameter of the bar should be applied in the groove to 
deepen it slightly and also to deepen the opening into which 
the terminal end of the bar enters. This step is carried out 
to provide, for future settling of the denture. 
Fig. 353.— Lingual View of Preceding Cases CONSTRUCTION OF PARTIAL DENTURES 
519 
Oftentimes two or three widely separated roots or teeth 
can be utilized for supporting a denture. Roots should be 
filled and post inlays, which extend neatly to the peripheral 
Fig. 354.— Alveolar Bar Supported by Two Roots and Two Inlay 
Attachments. Three or More Gilmores May Be 
Attached as Required 
margins, constructed for anchorage purposes. Bar attach- 
ments may be combined with crowns set on roots of teeth or 
with inlays set within tooth crowns and all connected by a 
Fig. 355.— Extensive Restoration by Means of Alveolar 
Bar and Gilmore Attachments 
border bar. It is frequently advisable, when only two or 
three teeth remain, to remove the crowns and inlay the roots 
as described. By this procedure there will be no break in the 520 
CONSTRUCTION OF PARTIAL DENTURES 
Fig. 356.— Full Denture, Palatal View, Showing Groove 
For Alveolar Bar with Gilmore Appliance 
Near Extremities 
Fig. 357.—■ Alveolar Bar Supported by Two Cuspid Roots. 
A Gilmore Attachment Should Be Placed 
Back of Each Root and One in 
the Median Line 
Fig. 358.— Anterior Alveolar Bar, 
Attached to Two Cuspid Roots 
Fig. 359.— Sectional View 
of Root with Dowel and 
Inlay to Which Alveolar 
Bar Is to Attach 
Fig. 360.— Occlusal View 
of Inlay in Position on 
Root, with Alveolar Bar 
Attached CONSTRUCTION OF PARTIAL DENTURES 
521 
continuity of the artificial gum restoration, nor in the align- 
ment of the substitute teeth. 
This system, as well as the others previously described, 
are capable of a wide range of application. In fact, they seem 
limited only by the skill of the prosthetist. 
Fig. 361.— Two Other Variations in Application of 
Gilmore Appliances 
Fig. 362.— Gilmore Attachment 
Movement of Denture Distally 
Prevented by Locking Against 
Mesial of First Bicuspid 522 
CONSTRUCTION OF PARTIAL DENTURES 
THE PALATAL ARCH BAR 
The palatal arch bar fulfills a similar purpose in upper 
partial dentures as the lingual bar in lower cases. The idea 
of a bar is not to afford support by its bearing against the 
Fig. 363.— Gold Saddles, Palatal Arch Bar, Gilmore 
Appliances 
Fig. 364.— Lingual Bar, Gilmore Appliances 
tissues, but to unite widely divergent points of support by 
means of a light yet rigid structure, and convert them into 
what has been termed multiple anchorage. This may be ac- 
complished quite as efficiently in the upper as in lower arch. CONSTRUCTION OF PARTIAL DENTURES 
523 
The Kelly Attachment 
The Kelly attachment consists of two small thimbles, each 
closed at one end, which telescope one within the other, with 
reasonably tight contact. 
Retention of a denture, however, in which these appli- 
ances are utilized, is not dependent upon the closeness of 
Fig. 365.— Enlarged View of the 
Kelly Attachment 
adaptation of the thimble walls, but upon diverging or con- 
verging the appliances in setting them upon the anchor teeth. 
APPLICATION OF THE KELLY ATTACHMENT IN VULCAN- 
ITE WORK 
Caps are formed and fitted with dowels to prepared roots. 
To these caps the inner thimbles are adjusted and soldered 
so as to present from one-sixteenth to one-sixty-fourtli inch 
divergence from, or convergence to, each other. 
The outer are set in position on the inner thimbles and an 
impression secured. The cast produced from the impression 
carries the two outer thimbles as projections above the border 
surfaces. Frequently a shell crown is constructed to telescope 
loosely over the outer thimble, as its presence on the cast pre- 
vents placing an ordinary vulcanite tooth in this location. 
The vulcanite fills the space and forms the bond of union be- 
tween the thimble and crown. The thimbles remain with the 
cast in flask separation, but they become a component part of 
the denture. 
When finished, the margins around the opening of the 
thimbles are slightly beveled and smoothly polished. 
In introducing the denture, the yield of the peridental 
membranes of the roots involved, together with some slight 
spring in the denture itself, permits the inner thimbles to 
enter the outer, although not in perfect alignment. When 
seated, however, no strain upon the anchor roots is noticeable. 
These attachments, slightly modified, are frequently com- 
bined with others, as, for instance, the Gilmore. They can 524 
CONSTRUCTION OF PARTIAL DENTURES 
be applied in gold base dentures with even greater ease than 
in vulcanite work, the outer thimble being soldered to the base- 
Fig. 366.— Combination of Kelly with Gilmore Attachments. A, Kelly Thimble 
B, 14 Gauge Bar; C, Gilmore Attachment. Sketch from Case of Dr. A. F. James. 
plate. The thimbles vary in size from one-sixteenth to three- 
tliirty-seconds of an inch in diameter, or even larger. 
THE GRISWOLD ATTACHMENT 
This attachment consists of two triangular-shaped tele- 
scoping tubes, the outer one open along the angle, the other, 
or inner, beinsr slotted through the middle of one side. 
Fig. 367.— En- 
larged View of 
Griswold Attach- 
ment 
Fig. 368.— Sketch of Griswold Inner Tubes in Position 
The smaller is attached by its apex to a crown or inlay, 
while the other is soldered to the gold base or enclosed within 
the vulcanite. 
Denture Balance 
Before dosing the subject of partial denture construction 
attention is directed to the remarks on pages 246 to 249, inclu- 
sive, relating to denture balance. The principles there outlined 
have long been recognized and used by careful prosthetists, CONSTRUCTION OF PARTIAL DENTURES 
525 
Fig. 369.— Vulcanite Alveolar 
Arch Bar or Strip. Denture 
Supported by Four Gris- 
wold Attachments 
Fig. 370.— Upper Anterior Restoration Sad- 
dle Denture Supported by Griswold’s 
on First Bicuspids 
although until recently very little has appeared in dental litera- 
ture concerning the physics of this important phase of stabiliz- 
ing partial dentures. A number of diagrams and illustrations 
are presented on the following pages to show the general appli- 
cation of stabilizers or indirect retainers in securing denture 
balance in both upper and lower cases and will give both prac- 
titioner and student a working basis which can be expanded to 
cover a great variety of partial replacements. These are based 
upon illustrations in an article by Dr. W. E. Cummer in Oral 
Health in 1916. 
The illustrations show, first, the dental arch with missing 
teeth to be replaced; second, the means of direct retention em- 
ployed; and third, the appliance with indirect retainers com- 
plete and in position on cast of mouth. 
The direct retention here shown is by means of plain clasps, 
and clasps with stops, Roach attachments, Gilmore attach- 
ments, and inlays with grooves, sockets and studs; all bearing 
such relation to each other when assembled as to permit of the 
ready introduction and removal of the substitute. Indirect 
retention refers to the utilization of lever force by means of 
extensions, arms or rests, so arranged as to counteract the 
tendency of a saddle or partial denture, secured at one end only, 
from becoming unseated. In almost every instance the direct 
retainers represent the fulcrum or balancing point of a lever 
of the first class. 
Partial dentures of the removable type constructed as out- 
lined can be made sanitary, non-irritating, esthetic, efficient and 
comfortable, and in many cases will prove more serviceable 
than fixed type bridges. 526 
CONSTRUCTION OF PARTIAL DENTURES 
Fit-. 370.1 —A 
Fig. 370.1 — B 
Fig. 370.1 —C 
Fig. 370.1 —D 
Fig. 370.1 —E 
Fig. 370.1.— Bicuspids missing on right side; lateral, cuspid and bicuspids 
missing on left side 
A. — Cast. It is desirable in this, as in all partial restorations, to plan a substitute which will 
have inherent strength to stand the stress of mastication, avoid contact with the natural 
teeth present except where necessary for direct or indirect retention, and finally to so form 
the structure that it will not impede tongue movements nor interfere with correct 
enunciation. 
B. — To support the anterior of the structure firmly, inlays with grooves are formed and fitted 
in left central and right cuspid. Studs attached to the base rest in the grooves. Band 
clasps with stops attached are fitted to the molars for direct retention. In some cases the 
clasp stops can be omitted. 
C. — The skeleton framework of gold is here shown. The saddles may be constructed by casting 
or swaging. The over-arch bar can be formed of oval wire, platinized, and sufficiently 
heavy to give firm rigidity to the structure, or it can be formed of 20 K. plate and rein- 
forced with heavy clasp metal plate laid on and the two connected with solder. Care 
should be taken in the constructive steps to obviate pressure of the over-arch bar on hard 
areas of the palate. The indirect retainers or stabilizers which rest upon the second molars 
are formed in the same manner as the over-arch bar. 
D. — The completed case is here shown, the teeth attached to the base with vulcanite. The 
lingual aspect of the over-arch bar should present an oval surface to the tongue. In 
many cases some of the various forms of all porcelain crowns or English tube teeth can 
be fitted with sockets of gold, either swaged or cast, and attached to the base plate by 
soldering, thus obviating the use of vulcanite. 
E. — The completed case shown upon the cast and as it would appear in the mouth. CONSTRUCTION OF PARTIAL DENTURES 
527 
Fig. 370.2 —A 
Fig. 370.2 —B 
Fig. 370.2 —C 
Fig. 370.2 —D 
Fig. 370.2.— Right lateral missing 
A. — Cast. A difficult type of case to replace without extensive mutilation of the proximating 
teeth, as is frequently resorted to when a fixed bridge is applied. 
B. — Preparatory steps for direct retention and anterior support. Central and cuspid fitted 
with grooved inlays. Right second bicuspid carries a Roach ball attached to inlay, left 
molar a stud inlay. 
C. — Case complete consisting of a palatal ridge bar clearing the lingual surfaces of the teeth 
except at points of attachment, and an over-arch bar, the right extremity of which termi- 
nates in a flange with an opening to receive the stud of the molar inlay. Anteriorly, studs 
project mesially and distally and rest in the inlay grooves when the denture is seated. 
D. — Case completed and resting upon the cast. 528 
CONSTRUCTION OF PARTIAL DENTURES 
Fig. 370.3 —A 
Fig. 370.3 —B 
Fig. 370.3 —C 
Fig. 370.3 —D 
Pig. 370.3.— Molars on right and left sides missing 
A. — Cast. 
B. — Bicuspids fitted with inlays bearing Roach appliances. The Gilmore attachments or band 
clasps can be used to advantage in some cases. 
C. — Completed appliance. 
D. —- Appliance in position on cast. Note that in this case the indirect retainers or stabilizers 
extend forward from the balancing line about the same distance that the saddles carrying 
the teeth pass backward. 529 
CONSTRUCTION OF PARTIAL DENTURES 
Fig. 370.4 — B 
Fig. 370.4 — A 
Fig. 370.4 —C 
Fig. 370.4 —D 
Fig. 370.4 —E 
Fig. 370.4.— The eight anterior teeth missing 
A. —- Cast. When the second bicuspids are of suitable form for clasping, no special appliances 
or attachments to the natural teeth are required other than the adaptation of well fitting 
clasps. These may be with or without stops as the case demands. 
B. — Shows the completion of the case. Here stop clasps are employed as direct retainers, 
while stabilizers extend distally, their terminals being conformed to rest upon the occlusal 
surfaces of the second molars. 
C. — This diagram shows the appliance completed and as it would appear in the mouth. In 
case of settling of the tissues under continued masticatory stress on the denture, the 
stabilizers can be bent palatally to re-establish equilibrium. 
D. — A type of denture for the same case, somewhat more compact than shown in C, the 
stabilizers being terminated at and conformed to rest on the first molars. 
E. — The appliance as it would appear in position in the mouth. 530 
CONSTRUCTION OF PARTIAL DENTURES 
Fig. 370.5 — A 
Fig. 370.5 —- B 
Fig. 370.5 — C 
Fig. 370.5 —D 
Fig. 370.5.— Right cuspid and left second molar present. All other teeth missing 
A. — Cast. This is a typical case of diagonal balance and illustrates how practically a full 
denture can be successfully developed in skeleton form. 
B. Cuspid and molar crowned and fitted with Gilmore bare. 
C. — The cuspid being present divides the denture into two parts or saddles. These are united 
by an over-arch bar posteriorly and a rigid border bar placed to the lingual of the cuspid 
sufficiently far to give good clearance for food. 
D. Case completed and in position on cast. CONSTRUCTION OF PARTIAL DENTURES 
531 
Fig. 370.6 —A 
Fig. 370.6 — B 
Fig. 370.6 — C 
Fig. 370.6.—-The right lateral, cuspid, first bicuspid, first and second molars missing 
A. — Cast. The direct retainers consist of a Roach attachment on the crowned second bicuspid 
and a stud inlay in the left first molar. The stabilizers which here take up considerable 
direct masticatory stress consist of grooved inlays in the central incisor and third molar. 
B. — The completed appliance. A stop or occlusal rest is here shown to support the central 
portion of the denture by engaging with the mesial marginal ridge of the second bicuspid 
crown. An over-arch bar extends across the palate, its terminal engaging with the lingual 
projection of the first molar inlay. 
C. — The appliance in position in the mouth. 532 
CONSTRUCTION OF PARTIAL DENTURES 
Fig. 370.7 —A 
Fig. 370.7 — B 
Fig. 370.7 — C 
Fig. 370.7 — E 
Fig. 370.7 —D 
Fig. 370.7 —F 
Fig. 370.7 —G 
Fig. 370.7.— Second bicuspid and molars missing on left side 
A. —- Cast. 
B. — Preliminary direct retention. Left bicuspid fitted with inlay carrying Roach ball. Right 
second molar carrying inlay with recess for reception of terminal stud on over-arch bar. 
C. — Case completed showing indirect retainer extending forward to rest on lingual of cuspid. 
D. — Case completed and in position on cast. 
E. A modification of the preceding case in which the indirect retainer is shortened. In this 
case the teeth constituting the direct retainers are subjected to greater stress than when 
the stabilizing arm is longer. 
F. — Another modification of the preceding case in which the indirect retainer is located on 
same side of arch as saddle. Such an appliance will be subjected to less torsional stress 
than when direct retainer is on opposite side of arch. 
G. — Case completed and in position on cast. CONSTRUCTION OF PARTIAL DENTURES 
533 
Fig. 370.8 —A 
Fig. 370.8 —B 
Fig. 370.8 — C 
Fig. 370.8 —D 
Fig. 370.8.—-Lower case. Right central, second bicuspid and molars and left second 
bicuspid and molars missing 
A. — Cast. 
B. —- Left central and right lateral fitted with grooved inlays and bicuspids supplied with well 
adapted plain clasps. 
C. — Case completed. Right central incisor replacement supplied with metallic backing, carry- 
ing mesial and distal studs which rest in grooved inlays in proximating teeth. 
D. —- Appearance of completed case on cast. 534 
CONSTRUCTION OF PARTIAL DENTURES 
Fig. 370.9 — A 
Fig. 370.9 —B 
Fig. 370.9 —C 
Fig. 370.9 — D 
Fig. 370.9.— Lower unilateral replacement. Molars missing on right side 
A. — Cast. 
B. — Right second bicuspid fitted with stop clasp, left first molar with recessed inlay. 
C. — Completed case showing left end of lingual bar terminating in stud and indirect retainer 
attached to bar in cuspid region. 
D. —- Case completed and in position on cast. CONSTRUCTION OF PARTIAL DENTURES 
535 
Porcelain teeth as supplied by the manufacturers are 
divided into two classes, known as plain and gum teeth. Each 
of these classes can again be subdivided into two classes, vul- 
canite and plate teeth. 
Forms of Porcelain Teeth 
A plain tooth represents the crown, or a portion of the 
crown, of a natural tooth in porcelain. Since teeth of this 
type are designed to take the place of lost natural teeth, they 
represent, more or less perfectly, the anatomic forms of the 
natural organs in general outline. The linguo-gingival areas 
of most porcelain teeth are deficient, or lacking in contour, to 
afford means for attachment to the metal or vegetable mate- 
rial which forms the structure of the substitute. 
PLAIN TEETH 
MEANS OF ANCHORAGE 
Metallic pins are most commonly used for anchorage pur- 
poses, one end of each pin being enclosed and fixed in the 
porcelain by fusion of the latter around it, the other end 
projecting for attachment within the substitute material. A 
plain tooth is usually supplied with two pins, vulcanite teeth 
having headed pins while in plate teeth the pins are straight. 
Another means of anchorage consists in developing within 
the porcelain some mechanical form of attachment, as dove- 
tailed projections, or countersunk, depressed areas, with small 
openings extending through the proximate surfaces, as in dia- 
toric and similar forms of teeth. 
Plain Teeth for Vulcanite Work 
Teeth of this type are designed for use with plastic bases, 
of vulcanite and celluloid, headed pin, and diatoric teeth being 
Fig. 371.— Set of Twenty-eight Plain Teeth, Vulcanite (S. S. W.) 
the most common forms used. These are manufactured in 
great variety as to length, width and color, some in no wise 
resembling natural tooth forms, while others approach very 
closely to anatomic types. 536 
CONSTRUCTION OF PARTIAL DENTURES 
Both platinum and alloys of base metal, usually a nickel 
alloy, are used for pins of vulcanite teeth, the latter being em- 
ployed because of its cheapness. Unless protected by a film of 
non-oxidizable metal as an electro-deposition of gold, base 
metal pins are liable to disintegration with use in the mouth. 
Fig. 372.— Set of Twenty-eight Plain Teeth, Vulcanite (Justi) 
The oxidation of base metal pins during fusion of the 
porcelain frequently causes discoloration of the latter, some- 
times to such an extent as to render the product unfit for use. 
This occurs most frequently in anterior teeth, where the bulk 
of porcelain is limited. To overcome this difficulty, thin plati- 
num tubes, the inner ends flanged, are baked in the teeth, 
in the location of the pins, and the base metal pins are after- 
ward soldered within the tubes. 
There are two principal advantages in the use of plain 
teeth in vulcanite work as compared with gum teeth. 
ADVANTAGES OF PLAIN TEETH IN VULCANITE WORK 
Fig. 373.— Various Sizes of Plain Teeth, for Vulcanite or Celluloid, Constricted Cervices 
Fig. 374.— Plain Teeth, Vulcanite 
Transverse Corrugations, 
Constricted Cervices 
Fig. 375.— Plain Teeth, Bicuspids, 
for Vulcanite 
First, they are more easily arranged in anatomic align- 
ment, and, if necessary, can be readily modified to meet usual 
and unusual occlusal and esthetic requirements. CONSTRUCTION OF PARTIAL DENTURES 
537 
Second, they can be placed in restricted locations and 
spaces where gum teeth cannot be used. 
OBJECTIONS 
The principal objection to the use of plain teeth, wliere 
gum restoration is necessary, is on account of the gum mate- 
rial at present available. Pink vulcanite is opaque, and under 
most favorable conditions affords but little resemblance to 
living, healthy gum tissue. 
The silicate cements are being tested, as to durability, as a 
substitute for gum restorations. This material fulfills esthetic 
requirements quite as well as porcelain. 
Diatoric Teeth 
Diatoric or pinless teeth are so formed as to afford anchor- 
age for plastic materials around and within the porcelain. 
Teeth of this type, when bulk of material is not too restricted, 
Fig. 376.— Diatoric Teeth Arranged in Full Upper Denture with Sections of Some Teeth 
Removed to Show Vulcanite Anchorage 
and the mechanical retention forms are well proportioned, are 
capable of withstanding masticatory stress quite as well as 
pin teeth. In addition, they are much less expensive, a factor 
of some importance at times. 
Diatoric molar and bicuspid teeth, when slightly modified 
by grinding, are frequently used in conjunction with gold, in 
the construction of bridge work, the technic being similar to 
that employed in the application of full or partial porcelain 
crowns, for such purposes. 538 
CONSTRUCTION OF PARTIAL DENTURES 
COUNTERSUNK PIN TEETH 
A countersunk pin tooth consists of a fully contoured por- 
celain crown, in the base or cervical portion of which is a 
depression from which projects a headed pin for anchorage 
Fig. 377.— Countersunk Pin Teeth, Posteriors 
purposes. The advantage of this type of tooth in denture con- 
struction is due to the fact that the full lingual contour of each 
tooth, which the basic material need not envelop to any ex- 
tent, feels more comfortable, and enables the patient to speak 
more distinctly than when such contour is deficient. 
Fig. 378.— Countersunk Pin Teeth, Anteriors 
ash’s tube teeth 
A tube tooth consists of a fully contoured porcelain crown, 
having an opening extending entirely through it from cervical 
base to occlusal surface or just to the lingual of the incisal 
Fig. 379.— Tube Teeth, Bicuspids and 
Molars (Ash’s), Set on Gold Casting, 
in Which Iridio-Platinum Pins Are En- 
closed, Showing Application in 
Bridge Work 
edge. Teeth of this type are occasionally used in conjunction 
with vulcanite, a headed pin or wire, slightly smaller than the 
opening, and longer than the crown being fitted to each before 
packing the case. The head of the pin projects slightly be- 
yond the cervical end of crown. In closing the packed flask, 
the rubber is forced into the vacant space in the tube and CONSTRUCTION OF PARTIAL DENTURES 
539 
Fig. 380.— Various Forms of Ash’s Mineral Teeth 
A — Porcelain Tip with Pins for Anterior Restorations 
B — Flat Back Repair Facing 
C, D, E —- Very Short Bite Molars, Diatoric 
F, G — Dimelow Facings 
H, I, J — Tube Teeth 
around the pin head and thus firmly anchors the tooth in place. 
These teeth are capable of a wide range of application in 
crown and bridge restorations as well as in metal base den- 
ture construction, but unfortunately are not easily procured 
or extensively used in this country. 
Fig. 381.— Partial Denture, Gold Base, Tube 
Teeth (Ash’s) •> 
A plain plate tooth consists of a veneer or partial crown 
of porcelain. It is usually supplied with two straight, head- 
less pins which project from the flattened lingual surface. 
Teeth of this type are designed for use with metal, in crown, 
bridge and denture work. Because of the liability of fracture 
PLAIN PLATE TEETH 540 
CONSTRUCTION OF PARTIAL DENTURES 
occurring in these teeth during soldering operations, and the 
further difficulty of replacement, when fractured from any 
cause, facings of the replaceable type are gradually coming 
into general use for the purposes mentioned. 
VARIOUS FORMS OF PLAIN TEETH 
There are various forms of plain teeth designed for spe- 
cial purposes, among which may be mentioned the Dimelow 
Fig. 382.— Dimelow Facing with 
Backing Adjusted 
Fig. 383.— Backing with Staple Pins 
Adapted for Dimelow Facing 
facing, consisting of a flat back veneer, having two holes in 
the location usually occupied by the pins, and which slant 
slightly, from lingual to labial, incisally. These holes receive 
two pins, projecting at a corresponding angle from the substi- 
tute. Mechanical anchorage is thus afforded by the slant of 
the pins as well as by the cement which serves as a bond of 
Fig. 384.— Short and Long Bite Bicuspids and Molars, Dimelow Teeth 
union between the two factors. This tooth is used principally 
in repair work for crowns and bridges. 
ash’s flat back repair facing 
This tooth consists of a flat back veneer, having a trans- 
verse, oblong, dovetailed opening in its lingual surface, for the 
Fig. 385.— Flat Back Repair Facing Used Prin- 
cipally in Crown and Bridge Repairs 
reception of a metal projection on tlie substitute and for the 
cementing medium. It is used principally in repair work on 
crowns and bridges. 541 
construction of partial dentures 
ASH’s HELIX TOOTH 
This tooth consists of a flat back veneer, having a cylin- 
drical, threaded opening in its lingual surface, in the center 
Fig. 386.— Helix Tooth for Vulca- 
nite (Ash’s) 
of which is a threaded metal pin. A slight collar surrounds 
the opening, which may or may not be ground away as con- 
ditions of adjustment demand. 
SADDLE BACK TEETH 
Teeth of this type are intended for use in those cases 
where the alveolar ridge is prominent, and space is con- 
Fig. 387.— Short Bite Saddle Back Bicuspids 
stricted. They are intended principally for vulcanite work, 
although those supplied with plain or headless pins are often 
used in crown and bridge work. 
CONTINUOUS GUM TEETH 
The teeth used in continuous gum cases are of the plain 
type, but differ from those described in having cervical ex- 
tensions which resemble the outer surfaces of the roots. 
These extensions serve two purposes. First, they afford 
support to the tooth in its attachment to the platinum base, 
Fig. 388.— Continuous Gum Teeth 542 
CONSTRUCTION OF PARTIAL DENTURES 
during fusion of the added porcelain, and second, being com- 
posed of high fusing porcelain, they supply a portion of the 
required bulk or contour of the denture proper, thereby pro- 
portionately reducing contraction in the bulk of continuous 
gum body, due to fusion. 
GUM TEETH FOR VULCANITE WORK 
Gum teeth, as their name implies, have an extension root- 
ward, which in contour and color represents the natural gum 
tissue. They are made in single tooth sections and in blocks 
of twos and threes for full dentures. Special sections of two, 
three, and even four teeth are procurable, for use in partial 
denture construction. Sections of this type are indicated in 
Fig. 389.— Set of Twenty-eight Gum Section Teeth (S. S. W.) 
Fig. 390.— Occlusal View of Gum Section Teeth, Joints Ground 
Fig. 391.— The Usual Relation of Adjoining 
Blocks of Gum Section Teeth 
Before Grinding 
Fig. 392.— Two Gum Sections, 
Joints Ground CONSTRUCTION OF PARTIAL DENTURES 
543 
Fig. 393.— Various Forms of Anterior Blocks. Notice the Festoons and Undulating 
Surfaces of Gums 
cases where gum restoration is required, and the joint be 
tween natural and artificial gum is visible. 
Because of the difficulty in developing anatomic occlusal 
requirements in full dentures, gum section teeth are not used 
in such cases to any extent. 
Fig. 394.— Special Forms of Gum Blocks for Anterior Replacements 
GUM TEETH FOR METAL WORK 
Since there is a wide range of difference in contraction 
and expansion of metal and porcelain the nse of gum teeth in 
conjunction with gold or other metals is confined to single 
teeth or blocks. 
Gum teeth designed for metal work have flat backs, and 
straight or plain pins. Special care must be used in solder- 
ing operations to avoid fracture of the porcelain, which occurs 
from unequal distribution of heat, sudden changes of tem- 
perature and difference in expansion between teeth and metal. 544 
CONSTRUCTION OF PARTIAL DENTURES 
Proportionate Parts of Teeth 
In selecting a tooth for any given case attention should 
be given to the shape and angle of its cervical end or “ridge 
lap,” the “shut” and the “bite.” 
Fig. 395 
RIDGE LAP 
This term refers to the beveled surface of a tooth which 
slopes lingually from its cervical portion to the lingual side. 
The ridge lap varies in its length and angular inclination in 
different teeth, although the shut and bite in the same teeth 
may be alike. Likewise, either the shut, or bite, or both, may 
vary, while the ridge lap will be the same. 
When the alveolar ridge is prominent, but little absorp- 
tion having occurred, and the lip line is high, teeth with long 
Fig. 396 
ridge lap are indicated. When much absorption has occurred 
and but little, if any, of the ridge shows when the lip is raised, 
teeth with short ridge lap are indicated. 
The shut refers to the space between the upper and lower 
alveolar processes, or between the teeth of one arch and the 
alveolar process of the opposite arch. The shut of an arti- 
THE SHUT 
ficial tooth is indicated by the distance between its lingual 
shoulder and the angle formed by its ridge lap with its lingual 
surface. 
Fig. 397 CONSTRUCTION OF PARTIAL DENTURES 
545 
The bite, or overbite, in artificial teeth refers to the dis- 
tance between the incisal end of a tooth and its lingual 
shoulder. 
THE BITE 
Fig. 398 
In selecting teeth, special care must be given this point. 
When teeth with short bite are selected, and the case demands 
considerable overbite of the upper over the lower teeth, the 
lingual shoulders must be ground away to a greater or less 
extent, to secure the desired relation, which frequently weak- 
ens the porcelain. 
Another case in which long-bite teeth should be used is 
in lower anterior replacements. By the use of long-bite teeth 
much less vulcanite is required to develop proper lingual con- 
Fig. 402 
Long Ridge 
Lap 
Short Shut, Long 
Bite 
Fig. 399 
Short Ridge 
Lap 
Long Shut, Medium 
Bite 
Fig. 400 
Medium Ridge 
Lap 
Short Shut, Long 
Bite 
Fig. 401 
Extra Long 
Ridge Lap 
Short Shut. Medium 
Bite 
tour than when this portion of the crown is devoid of normal 
contour. 
This portion of the tooth may be, and usually is, described 
as having a long, medium or short bite. 
The Tooth Shade Guide 
Most manufacturers of porcelain teeth provide a shade 
guide on which, in some manner, are displayed the different 
shades or colors of teeth supplied by them. These guides 
usually are composed of from twenty-five to forty sample 546 
CONSTRUCTION OF PARTIAL DENTURES 
central incisors of average size, all differing in shade, tone 
or tint. By means of a guide of this type, teeth of suitable 
color may be selected with a reasonable degree of accuracy. 
Some prosthetists without a special knowledge of the laws 
of harmony are able to arrive at satisfactory results in the 
selection of teeth of appropriate shades for any. individual 
case. 
How they do it or why the results are satisfactory they do 
not attempt to explain further than it is by guesswork or 
intuition. 
Intuition, however, in color science is not the result of 
guesswork, but is due to a more or less conscious or uncon- 
scious development of color function in the visual organs, as 
lias been explained. 
APPLICATION OF THE TOOTH SHADE GUIDE IN PRACTICE 
The patient should be seated facing a direct light. The 
face, eyes and hair should be scanned as a whole, to deter- 
mine the general color scheme of the complexion and to esti- 
mate, as closely as possible, the complementaries of the tints 
there displayed. 
By careful observation, with a little experience, this ex- 
amination enables the prosthetist to select from the shade 
guide a tooth of the general tints required. The first selec- 
tion, even if possessing the fundamental tints indicated, may 
not meet requirements. The tooth may be too light, or too 
dark, or it may need the addition of some primary or sec- 
ondary color of greater or less intensity, to develop the 
necessary harmony. If not pleasing, other teeth are tested 
until one is found that, by its presence in the mouth, creates 
the impression of harmony and is satisfying to the esthetic 
sense. 
Strong colors displayed in the complexion call for strongly 
marked shades of teeth, within certain limits of course, while 
a person having a complexion made up of weak colors must 
be supplied with teeth of neutral tints, or highly attenuated 
colors of a generally neutral tone. 
Porcelain teeth are perceptibly darkened by the shadows 
of the lips and oral cavity, some more than others, depending 
on their translucency or power of transmitting light. 
In selecting teeth, therefore, it is advisable to test them 
not only in direct light but to change the position of the 
patient so that the teeth may be subjected to both lip and oral CONSTRUCTION OE PARTIAL DENTURES 
547 
shadows, and the effect noted. When tested by direct light 
only, too light a shade of tooth is liable to be selected, with 
the result that in the finished denture the teeth will appear 
too dark. 
When a suitable color of tooth has been selected a record 
should be made of its number, and from this teeth of a cor- 
responding color number are procured. 
Natural Dentures Reproduced in Porcelain Teeth 
and Wax 
The following series of cuts have been introduced to show 
some of the commonly occurring variations in arrangement 
of the natural teeth. These cases represent as nearly as pos- 
sible, by means of porcelain teeth arranged in wax, the con- 
ditions found in the mouths of living subjects. Most of these 
illustrations have appeared in the past in the Dental Cosmos 
and several of them appear in the American System of Den- 
tistry, 1888, in an article on celluloid and zylonite by Dr. 
W. W. Evans. 
I. Appearance of teeth of person past middle life, gum 
recession, strongly marked mechanical abrasion. 
Fig. 418.— I 
II. Teeth of a woman of thirty to thirty-five. There is 
rather long overbite, and the chamfering of the edges of the 
Fig 419.— II 548 
CONSTRUCTION OF PARTIAL DENTURES 
lower incisors is plainly seen. The right central overlaps 
the left. Two teeth are lost from these arches, the right 
upper first bicuspid and the left lower first molar. The upper 
denture is provided with plumpers to restore disturbed facial 
contour. 
Fig. 420.— Ill 
III. The denture of a man past fifty years of age. The 
teeth are inclined well forward, with end to end occlusion. 
The effect of wear is seen on the incisal edges of the lower 
incisors, and indicated by the squaring of those of the upper, 
lower incisors separated, as is often seen, gums receded. 
Fig. 421.— IV 
Fig. 422.—V 
IV. The denture of a girl of twelve or thirteen years of 
age. The cuspids are not yet fully erupted, and the incisors 
show a very marked example of the cusplets which adorn them 
when first erupted. 
V. The denture of a man between twenty-five and thirty 
years of age. Teeth are fully developed, large, with a long 
overbite. The upper cuspids are elongate and incline slightly 
inward. The lower incisors are considerably crowded and 
inclined. The upper right first bicuspid and lower left first 
molar have been lost. Two fillings are shown in the upper 
central incisors. 549 
CONSTRUCTION OF PARTIAL DENTURES 
VI. The denture of a young woman between eighteen 
and twenty years of age. All of the teeth are fully erupted. 
Fig. 423.— VI 
Fig. 424.— VII 
and the little cusps of the incisors are nearly effaced. Every 
tooth is in a healthy condition. 
Fig. 425.— VIII 
Fig. 426.—IX 
VII. The denture of a man between forty and fifty years 
of age. Occlusion almost end to end. Some recession of the 
gums. Plumpers to restore disturbed facial contour. 
VIII. Denture of a man between fifty and sixty years of 
age. The teeth show wear from use. 
Fig. 427.—X 
Fig. 428.— XI 550 
CONSTRUCTION OF PARTIAL DENTURES 
IX. Teeth of a man about fifty years old. Left upper first 
bicuspid lost. Teeth show mechanical abrasion. Plumpers. 
X. Overlapping lateral incisors. Gums are prominently 
ridged, indicating position of roots. 
Fig. 429.— XII 
Fig. 430.— XIII 
XI. Teeth arranged with close bite, considerable overlap, 
lateral rotated. 
XII. Central incisors rotated outward distally. Laterals 
rotated inward distally and slightly within the arch. 
XIII. Centrals inclined inward, laterals overlapping, cus- 
pids prominent. 
XIV. Centrals V-shaped. All incisors diverging strongly 
from incisal edges apicallv. 
Fig. 431.— XIV 
Fig. 432.— XV 
Fig. 433.— XVI 
XV. Incisors out of alignment. 
XVI. Plain teeth ground to border. Gum restoration 
from cuspids backward. CHAPTER NXIV 
CELLULOID DENTURES 
Of the plastic vegetable bases used in denture construc- 
tion, celluloid presents the most natural appearance, closely 
approaching porcelain in the translucent, live-tissue color of 
the gums and mucous membrane. 
It is not generally as durable as vulcanite, frequently dis- 
coloring and rapidly disintegrating in some mouths, while 
again it proves satisfactory in other cases. Its value as a 
denture base is largely dependent upon the manner of manip- 
ulation of the material during construction, as well as on the 
care bestowed upon it by its possessor. 
Discovery of Celluloid 
In 1855 an Englishman by the name of Parks- invented 
the material now known as celluloid, and which he named 
parksite or zylonite. In 1859 a man by the name of Mack- 
intosh, also in England, patented the material called collo- 
dion, from which he constructed denture bases. This sub- 
stance was improved upon by Dr. McClelland of Louisville, 
Ky., in 1860, who gave it the name of rose pearl. The denture 
base was made from sheet collodion, moistened in alcohol and 
ether sufficiently to render it plastic for securing adaptation 
to the cast. The teeth also were attached with additions of 
the same material, similarly softened. Dentures so constructed 
showed decided tendency to warp in drying out. 
The Newark Manufacturing Company, organized in this 
country in 1869, began, and for a number of years conducted, 
a series of experiments to determine the possibilities and lim- 
itations of this material. After the lapse of a number of 
years and the expenditure of large sums of money, during 
which time many almost insurmountable difficulties were met 
and overcome, a product of stable character was finally 
evolved, capable of application to innumerable purposes. 
Composition of Celluloid 
Celluloid is made from 'pyroxylin, or the woody fiber of 
plants. This material is treated with nitric and sulphuric 
551 552 
CELLULOID DENTURES 
acids, after which it is known as nitro-cellulose, or guncotton, 
a highly explosive substance. 
The proportions of this material with other substances, 
as used for dental purposes, are about as follows: Guncotton, 
100 parts; camphor, 40 parts; white oxide of zinc, 2 parts; 
vermilion, .06 part. 
Zylonite is made by first dissolving the guncotton in ether, 
or methyl alcohol, and then combining it with the other ingre- 
dients. Celluloid is made by effecting the union of the several 
ingredients by means of heat and pressure, without first dis- 
solving the guncotton. 
MANUFACTURE OF CELLULOID 
The following abbreviated description of the manufac- 
ture of celluloid appeared in the Dental Cosmos, January, 
1875, being a reprint from an article in the American Ar- 
tisan: 
“ After the pulp is ground in the beater engine, and the 
camphor and whatever coloring matter may be desired are 
thoroughly incorporated with it, the substance being kept, 
meanwhile, at the proper temperature, the superfluous water 
is removed by pressure and absorption, a peculiar porous 
material, made especially for the latter purpose, being em- 
ployed. 
“During the process of drying under pressure and ab- 
sorption, the material becomes nearly converted, so that it 
is no longer nitro-cellulose, but imperfect celluloid. In so 
far as conversion has taken place, its properties have under- 
gone a total change. All that remains to convert it into the 
various articles referred to is manipulation under heat and 
pressure, during which the chemical combination is com- 
pleted. 
“For some qualities of the material desired to be pro- 
duced, a small percentage of alcohol is added in the subse- 
quent manipulation. As evidence that there is a perfect chem- 
ical combination, and not a mere mechanical mixture of the 
materials, the fact may be stated that camphor in its uncom- 
bined state is an extremely volatile substance when exposed to 
the air; in its combination with nitro-cellulose it loses this 
property altogether. An enumeration of the properties of the 
material, which we shall give anon, will be further proof of 
the chemical combination. 
“When the material is properly converted, comparatively 
no shrinkage takes place. There is no escape of the cam- 553 
CELLULOID DENTURES 
phor, unless an excess has been employed, and in that case 
the excess of camphor will escape from the surface of the 
celluloid; but whatever uncombined camphor remains in the 
interior, it is so closely imprisoned by the solid surfaces that 
it cannot escape. By varying the proportion of the excess of 
camphor, different degrees of solidity and flexibility are ob- 
tained. . . . 
ADVANTAGES CLAIMED FOR CELLULOID 
“Without the admixture of coloring matter it has a pale 
amber color. If it is desired to make the material white, like 
ivory, oxide of zinc is used, and for other colors various 
mineral pigments are incorporated with it, or dyes soluble 
in alcohol, or any of the aniline dyes, may be caused to per- 
meate the material to give it any desired color. It is hard 
and elastic, having a hardness ranging from horn to that of 
ivory. It is as tough as whalebone. In elasticity it greatly 
exceeds ivory. . . . 
“Celluloid is also a very fair non-conductor of heat and 
electricity, not quite so much so as hard rubber, but approxi- 
mating the latter very closely in this particular. . . . 
“While it is so good a non-conductor, it is not perceptibly 
electric. . . . 
“But perhaps the most remarkable property of this other- 
wise very remarkable material is the fact that it becomes 
plastic at a temperature of from 250 to 300 deg. F., and this 
property enables it to be molded with facility into a great 
variety of forms for ornament and utility. Pure celluloid has 
a specific gravity of about 1.4. 
“A profitable and successful industry, based upon these 
properties of celluloid, is the manufacture of dental plates. 
The material can be made precisely the color of the palate 
and gums. 
COMPARATIVE STRENGTH OF CELLULOID AND VULCANITE 
“It is much stronger than rubber and has a perfectly 
clean surface. It may be more easily manipulated than rub- 
ber, as it does not require to be vulcanized. It possesses all 
the valuable qualities of rubber for dental purposes with none 
of its defects. It requires only about 1/60 as much vermilion 
to give the proper color to celluloid as is required to impart 
the usual color to rubber. The danger of salivation, which 
sometimes occurs in the use of rubber for dental purposes, is, 
therefore, obviated. The difficulties encountered in the appli- 554 
CELLULOID DENTURES 
cation of celluloid to dental plates have been very great, and 
many failures were at first experienced, but with untiring per- 
severance the inventors have pursued the subject until, during 
the last year or two, they claim to have produced an article 
possesing all the requirements desired, not a single failure 
having been experienced through any fault of the material 
made within a twelvemonth past.” 
The foregoing claims are somewhat exaggerated in sev- 
eral respects, but, taken as a whole, the description of this 
material is an admirable one. Just about the time celluloid 
came into use, much litigation was in progress between the 
Goodyear Rubber Company and members of the dental pro- 
fession, who refused to pay a royalty to the above-named 
company for the privilege of using vulcanizable rubber for 
dental purposes. At that time celluloid was welcomed and 
widely used, but owing to the fact that its properties were 
not fully understood, and that the methods of manipulation 
were not perfected, many failures have been recorded against 
it. These failures will now be mentioned and the causes ex- 
plained. 
DISADVANTAGES OF CELLULOID AS A DENTURE BASE 
First.— In some cases there seems to be a gradual solu- 
tion of the substance by the fluids of the mouth. Such action 
results in thinning and the consequent weakening of the base- 
plate. The material around the pins of the teeth is gradually 
worn or dissolved away, thus allowing the latter to become 
displaced under the stress of mastication. 
Second.—When used for some time, in many instances a 
very disagreeable odor develops, so objectionable that the den- 
ture cannot be worn with comfort. 
Third.— The baseplate often becomes badly discolored, 
assuming a dirty, brown appearance, and, in the case of smok- 
ers, a black film, extremely difficult to remove, forms on the 
surface. 
Fourth.— Liability of the cast to become distorted in mold- 
ing the celluloid blank over it. When this occurs, failure to 
secure adaptation to the oral tissues results. 
Most of these objectionable features mentioned are largely 
due to faulty technic, and can be obviated to a great extent 
by exercising care. When the blank is molded over the cast 
in the presence of oil, steam or glycerine, the volatile consti- 
tuents are not eliminated as they should be, but, on the con- 
trary, the celluloid seems to take up some of the liquids and CELLULOID DENTURES 
555 
becomes reduced in density and less resistant to the action of 
the fluids of the mouth. 
GENERAL METHODS OF MANIPULATION 
The best results are attained by pressing celluloid in a 
dry chamber, at high temperature, continuing the process as 
long as may be consistent with the work in hand. By this 
method the volatile constituents are driven off, the material 
rendered more dense and compact, while its elasticity will be 
increased and its color improved over the product resulting 
from the moist process. 
Steam, oil or glycerine softens the plaster cast and flask 
investment as well, rendering them more susceptible to com- 
pressive force and consequent distortion in closing the flask. 
When dry heat is employed, the flask contents become hard- 
ened by the evaporation of the moisture before the com- 
pression force is applied, and consequently there is less lia- 
bility of warpage or distortion occurring than by the moist 
method. 
The chief objection to the dry method is due to the dan- 
ger of burning the blank during the process of pressing. 
By cutting ample waste gates in the plaster investment sur- 
rounding the matrix, so that no surplus material comes in 
contact with the metal flask, this danger is largely overcome. 
An extra large sized flask for investment purposes is neces- 
sary in order to afford the needed space for deep and wide 
gates. 
The flask should be of the same general form as a vul- 
canite flask, but larger and heavier throughout. The guide- 
pins should be strong and long enough to hold the two halves 
of the flask in proper relation to each other when separated 
as they must be by the introduction of the impressed blank. 
The construction of the wax mode] denture for a cellu- 
loid case differs in no essential particulars from that for a 
vulcanite case. The wax contour model is constructed and 
fitted in the mouth to establish the bite and the direction of 
the condyle paths. On this the teeth are occluded and tried 
in the mouth for appearance, alignment, occlusion and bal- 
ancing contact, after which it is returned to the cast, the lat- 
ter detached from the occluding frame, and the case is ready 
for investment in the flask. 
CONSTRUCTION OF THE WAX MODEL DENTURE 556 
CELLULOID DENTURES 
FLASKING 
Upper cases should be invested in the shallow half of the 
flask; lower cases in the deeper portion, in order to conserve 
space. In upper cases the anterior part of the cast is ele- 
vated, more or less, to insure a parallel relation between the 
several surfaces of the cast and the guide-pins, or the line 
of direction in which the two halves of the flask must travel 
in closing. Should undercuts be present, the material may 
fail to find its way into them on account of the matrix mar- 
Fig. 434.— Celluloid Flask Designed by Dr. H. C. Miller of Portland, Ore. 
gins preventing; hence the necessity for elevating the cast, 
as suggested. 
Coarse plaster should be used for investment purposes, 
as it withstands high pressure, without perceptible yielding, 
much better than impression plaster. 
CUTTING THE WASTE GATES 
Deep and wide waste gates should extend entirely around 
the matrix, these being cut in the side of the flask contain- 
ing the cast, for if cut in the opposite, or matrix, side, the 
walls of the latter would be weakened and probably crushed 
under the pressure required to force out the excess mate- 
rial. The outer margin of the gate should be at least an 
eighth of an inch from the inner margin of the flask to pre- CELLULOID DENTURES 
557 
vent any possibility of the surplus celluloid coming in con- 
tact with the heated metal. It is a peculiar fact that combus- 
tion of celluloid almost invariably occurs when brought in 
contact with metal heated to 300° F. or above, while if enclosed 
entirely in plaster the temperature may be raised fifteen to 
twenty degrees higher before the material will burn. The 
inner margin of the gate should approach .very close to the 
matrix margin, so that the surplus material may flow out 
readily after it once passes the matrix periphery. The plas- 
ter between the two margins of the gate outline is cut out in 
Y-shaped form, sufficiently deep to afford ample space for any 
surplus present. 
CLEARING THE MATRIX OF WAX AND DEBRIS 
The gates having been formed, the wax is removed from 
the interior of the flask, the latter cleansed with boiling water, 
the sharp, angular margins of the matrix are trimmed off 
to prevent them fracturing and mixing with the celluloid in 
closing the flask. 
The face of the cast should be covered with a film of col- 
lodion to give smoothness to the surface of the denture pressed 
against it. # 
SELECTION OF THE BLANK 
Celluloid, as prepared for dental purposes, conies in the 
form of blanks, blocks having the general form of a denture 
baseplate, but considerably thicker than the finished denture 
will be, so as to supply the necessary surplus to fill the matrix 
under pressure. 
The blanks come in various sizes and are numbered as 
follows, beginning with the smallest: No. 2y>, 3, 3y2, 4, 4=y2, 
5, 5y2, 6, 6y2. These are sufficiently thick to insure a sur- 
plus of material for ordinary cases. When a large amount of 
absorption has occurred, it is sometimes necessary to use a 
thicker blank than those mentioned. For such purposes a 
series of extra-thick blanks are supplied and numbered as 
follows: 2y2a, 3a, 3y2a, 4a, 4y2a, etc., up to 6y2a. 
When using upper blanks of this variety it will invaria- 
bly be necessary to reduce the palatine portion to a reason- 
able thickness with a lathe burr, shown elsewhere. If not 
reduced, the matrix, and frequently the cast, is distorted in 
forcing out the excessive surplus, oftentimes to such an ex- 
tent as to destroy denture adaptation. 
Frequently it will be necessary to modify the form of a 558 
CELLULOID DENTURES 
blank before introducing and pressing, so that, in a general 
way, it will conform to the face of the cast. This is done 
by placing it in boiling water until thoroughly heated, and 
with pliers bending the outer rim to the required form, or if 
the vault portion, as in flat-arch cases, needs modifying, lay 
the blank on a flat surface, and with a round-end wood handle 
depress the central area until the outer rim settles down 
over and encloses the labial and buccal surfaces of the cast. 
It may be necessary to heat the blank three or four times in 
order to give it the proper form, but time devoted to this 
preliminary adaptation is well spent, as it reduces the lia- 
bility of the celluloid folding on itself, of the matrix failing 
to fill, and also of the latter becoming distorted from the appli- 
cation of unequal pressure. 
Usually during this preliminary adaptation the blank will 
become more or less soiled. This may be corrected by scrap- 
ing the soiled surfaces and also rubbing the blank with a clean 
piece of muslin moistened with spirits of camphor. The appli- 
cation of the latter will also prevent the tendency of the cel- 
luloid to flake or crack during the pressing process. The 
blank is now set upon the cast, and the upper half of the flask 
set in position to engage with the guide-pins of the opposite 
side, then carefully let down until the matrix margins are in 
contact with the blank. Care should be taken to see that the 
latter is not displaced during this step. 
PRESSING THE CASE 
A dry-chamber press should be used, for reasons pre- 
viously mentioned. The flask is set on the bedplate of the 
press, matrix side down, so that in case any of the teeth be- 
come loosened in the dry heat, gravity will retain them in 
position. The three screws which draw the bedplate up 
against the lid of the press should he tightened evenly, so 
that the gnide-pins may at all times travel in a perpendicu- 
lar direction and parallel with the screws. No pressure should 
be put upon the blank until the latter is thoroughly heated 
to a temperature of at least 300° F., at which point it should 
he maintained during the pressing process. At least twenty- 
five minutes should be allowed for raising the temperature in 
the interior of the press up to this point. 
When the proper temperature has been attained, the bolts 
are gradually tightened, and, as before suggested, care should 
he taken to keep the bedplate parallel at all times with the 
top of the press, so that the guide-pins will not be bent. The 559 
CELLULOID DENTURES 
case should be lifted out of the press from time to time for 
examination, to determine the progress of the closure, hut 
should be returned to the chamber as quickly as possible to 
prevent cooling. 
Too much pressure should be avoided. Celluloid, even 
when plastic, is rather sluggish and flows slowly. If forced 
too rapidly, or faster than the normal flow the material will 
warrant, distortion of the matrix and face of the cast will 
occur, and a misfit will result. 
When the flask is closed, the source of heat is cut off and 
the case allowed to cool for ten or fifteen minutes or longer, 
if time permits. This permits the molecules of the material, 
under the continued heat and pressure, to adjust themselves 
to each other, and lessens the danger of warpage which some- 
times occurs when pressure is relieved too suddenly. In every 
case the flask and contents, whether suddenly or quickly 
chilled, must be perfectly cold before the press bolts are loos- 
ened, otherwise distortion may result. 
REMOVAL OF THE CASE FROM THE FLASK 
In removing a case from the flask it will be found that 
the plaster is extremely hard and difficult to cut. The desire 
to pry the flask apart suddenly, or use a hammer to knock 
the investment out of the flask, is great, but if these methods 
are employed, some of the teeth will very likely be fractured. 
It is, therefore, best, even though more tedious, to saturate the 
case with water, pry off the top and bottom plates, and re- 
move the content of the flask by cutting close to the inner 
periphery of the flask. 
FINISHING 
No special directions are necessary for finishing celluloid 
cases, as this material is susceptible to the same methods of 
polishing as vulcanite. Should there be a decided odor of 
camphor present when the case is finished, it may be removed 
by immersing the denture in a 10 per cent solution of sul- 
phuric acid for a few minutes. If allowed to remain in the 
acid for a long time, or in a strong solution for a short time, 
solution of the celluloid will occur. 
GENERAL REMARKS 
As before stated, celluloid is not as durable a material 
as vulcanite, but it certainly deserves some consideration 
as a serviceable and inexpensive base for dentures, as well 560 
CELLULOID DENTURES 
as for its beauty and close resemblance to the natural gum 
tissues. 
Celluloid is peculiar, and its physical properties must be 
well understood in order to derive the best results from its 
use in denture construction. It forms an admirable base for 
temporary, and under favorable conditions for permanent den- 
tures also. Celluloid does not serve well as a base for partial 
dentures, for the reason that single or isolated teeth are more 
readily displaced from a base of this material than from one 
of vulcanite. 
CASTS FOR CELLULOID CASES 
Since the principal source of error in celluloid denture 
adaptation is due to compression and consequent distortion 
of the cast in pressing the material, and since the pressure 
applied cannot well be reduced under that usually employed, 
on account of the sluggishness of the material, even under 
high temperature and pressure, the remedy lies in the use 
of a harder substance than plaster for casts. Any of the three 
materials previously mentioned in connection with cast con- 
struction are applicable for this purpose, viz., oxy-chloride 
of magnesium, Spence’s plaster, and tin, although when the 
latter is used great care must be exercised to avoid overheat- 
ing and consequent combustion of the celluloid. CHAPTER XXV 
REPAIRING VULCANITE DENTURES 
The materials of which vulcanite dentures are composed 
are susceptible to wear and breakage under stress, and since 
dentures of this, as well as of all types, are subjected to more 
or less heavy masticatory effort, accidents of various kinds 
frequently occur to both the vulcanite base and the porcelain 
teeth. The accidents which are of most frequent occurrence, 
with methods for repairing such cases, will now be outlined. 
Fracture of the Vulcanite Base 
Fracture of the baseplate may be caused by the application 
of sudden or undue stress in handling while cleansing, or from 
a fall; or, in case unequal absorption of the alveolar process 
occurs after the denture is introduced, under heavy mastica- 
tory stress the baseplate may break from the resulting undue 
torsional strain, due to lack of support over the absorbed 
areas. 
Under such conditions a fissure usually makes its appear- 
ance at some point along the margin of the baseplate, and, 
unless corrected, extends more deeply into the vulcanite, 
finally resulting in fracture of the denture into two or more 
pieces. Occasionally complete fracture of the base plate will 
occur suddenly from undue strain, as from the sudden crush- 
ing of a hard morsel of food, as well as from some of the 
causes previously mentioned. 
Usually the plan of repair of a denture is easily deter- 
mined. Occasionally, however, the nature of the accident and 
the causes leading up to it clearly indicate that reconstruc- 
tion, instead of repair, will prove most serviceable. 
It should be noted that the preceding outline covers a com- 
mon class of accidents, due to two different causes — first, 
those resulting from sudden undue stress, as in careless hand- 
ling or from a fall; and, second, those resulting from tor- 
sional or bending strain in masticatory effort, 
In all cases where, up to the time of the accident, the adap- 
tation of the denture to the tissues has proven satisfactory, 
repairs are generally indicated. In those cases where the 
561 562 
REPAIRING VULCANITE DENTURES 
primary cause of the fracture is due to imperfect adaptation 
of denture to oral tissues, reconstruction of the case is, in 
most instances, indicated, since by the usual methods of repair 
the greatest efficiency can not be realized. 
Reassembling a Fractured Baseplate 
In repairing a fractured denture, the first consideration 
is to assemble and hold the several parts of the baseplate in 
correct relation to each other while preparing the joints and 
splicing the fractured pieces together with new material. This 
is best accomplished by constructing a cast, not in the usual 
way, by taking an impression of the mouth, but by reassem- 
bling the broken pieces of the denture and filling in the maxil- 
lary or border side with plaster to serve as a cast. 
Technic of Securing a Cast from the Baseplate 
The broken parts of the baseplate are pressed together 
until the fractured surfaces show perfect contact, and, while 
in this relation, sticky wax is applied to the lingual surfaces 
on either side of and across the fracture line, but, for obvious 
reasons, not on the border or palatine areas. The wax should 
be applied in sufficient bulk, so that when chilled it will hold 
the several broken pieces firmly and accurately while the cast 
is being formed. 
The border and palatine sides of the denture are now 
coated with a thin film of oil, and the material of which the 
cast is to be constructed is applied in the same manner as 
in an impression and allowed to harden. 
Sometimes the relation of the several parts of the den- 
ture can be best maintained, while securing the cast, by im- 
bedding them to a slight extent in modeling compound, care 
being taken to maintain the correct relationship of the frac- 
tured surfaces until the compound has hardened somewhat. 
This method is especially applicable for holding in correct 
relation the two halves of a full lower denture, fractured in 
the incisor region. When sticky wax alone is used in such 
cases, slight pressure on the outer sides of the denture while 
handling is liable to disturb the correct relation of the frac- 
tured surfaces before the cast is secured. This danger can 
be obviated, in most cases, by laying a small piece of wood, 
as a match or a rigid wire, between the distal ends of the EEPAIBING VULCANITE DENTUEES 
563 
baseplate and attaching each end firmly to the plate or teeth 
with wax before forming the cast. 
The method frequently followed of assembling the frac- 
tured parts of a baseplate on a cast derived directly from 
an impression of the mouth is objectionable, because it is 
inaccurate. The cast, being hard and unyielding, will not per- 
mit the baseplate to settle in position, as it does on the soft 
and yielding areas of the mouth, and when the repair is 
accomplished with the several parts thus sustaining an in- 
correct relation to each other, even though the distortion may 
Fig. 435.— A Fractured Baseplate Held Together with 
a Match, Waxed to Molars 
be slight, a misfit usually results, or the occlusion of the teeth 
is impaired. 
Repairs occasionally present, usually in partial dentures, 
however, where the broken pieces can be placed in the mouth 
and an impression secured which will give a more accurate 
relation of the parts to each other than is possible to obtain 
by adjusting the fractured surfaces together and applying 
wax, as outlined. 
Method oe Joining the Feactueed Pieces 
A long bevel joint, if properly formed, will present the 
best appearance and prove the strongest and most satisfac- 
tory manner of repairing a fractured vulcanite base of any 
of the methods in vogue. The practice of cutting a series of 
dovetailed spaces on either side of the fracture line for the 
reception of the new material, in most cases, tends to weaken 
the old vulcanite, and when the base is composed of other 564 
REPAIRING VULCANITE DENTURES 
than black, basic material, the repair, when completed, will 
present a very unsightly — or, at least, noticeable — appear- 
ance, because of the variation in the color of new and old 
vulcanite, as well as on account of the irregular outline mar- 
gins of the patch. 
A cabinetmaker who desires to produce the strongest pos- 
sible union between two pieces of wood — a joint that will 
resist both torsional strain and end pull — will make a long 
Fig. 436.— Lap or Bevel Joint of Two Pieces 
of Timber 
bevel joint instead of halving each piece and abutting each 
halved end against the corresponding shoulder of the oppo- 
site piece. Tests show that the bevel joint is the strongest of 
the two methods outlined, not only in wood, but in vulcanite 
as well. 
The dovetailed method of repairing a simple fracture is 
based upon the principle that some positive form of mechan- 
ical anchorage is essential, even though it be gained at the 
expense of weakening the old vulcanite, and in areas not 
previously involved in the break; it accords too much value 
to the dovetail, a joint calculated to resist end pull and not 
torsional strain, and not enough in the lap joint, which, with 
practically perfect union of surfaces between new and old 
vulcanite, will resist both torsional strain as well as end pull. 
The fact does not seem to be generally well understood that 
under proper conditions new rubber will unite firmly and 
permanently with old vulcanite. The necessary requisites for 
serviceable union between the old and new vulcanite are as 
follows: Fresh, clean surfaces to the old base, produced by 
filing, scraping or burring; the covering of these surfaces 
with a thin film of rubber cement before adding the new rub- 
ber, and the maintenance of pressure upon the newly added 
material during vulcanization; also freedom of the joint from 
wax, grease or dirt. 
The rubber cement should correspond in color with the 
vulcanite or the fresh rubber between the surfaces of which 
it is interposed, to avoid imparting a variegated appearance 
to the joint. 
The commercial rubber-tire cement, which is nearly in- 
visible when applied to, or used in connection with any color REPAIRING VULCANITE DENTURES 
565 
of vulcanite may be used, or a cement may be made by dis- 
solving red, pink or black rubber in any solvent, such as ben- 
zine, bisulphide of carbon or chloroform. When the latter 
is used the solution is called ‘ ‘ chloro-rubber. ’ ’ The three 
colors should be kept in stock, in the laboratory, in tightly 
Fig. 437.— Fractured Baseplate, Showing Beveled Areas 
on Either Side of the Break 
stoppered bottles, for use as occasion requires. Excessive 
application of cement to a joint, without removal of the sur- 
plus, will result in porosity of the newly added material. 
FORMING THE BEVEL JOINT 
Two shallow grooves, about one-sixth the thickness of the 
baseplate in depth, are cut, one on either side of the frac- 
Fig. 438.— Sectional View of 
Baseplate, Showing Outline of 
Bevel of Old Vulcanite. The 
Central Beveled Portion Is to Be 
Removed 
ture line, and approximately parallel with it on the lingual 
side of the baseplate. These grooves limit the area of the 
old base to be covered by the new vulcanite and determine 
the outline of the patch, as it might be called. When the 
fracture line is very irregular, the position of the limiting 566 
repairing vulcanite dentures 
marginal lines may be varied, if by so doing a more sym- 
metrical balancing of the new with the old vulcanite can be 
secured. 
The relative position of these lines to the fracture line 
may be modified by increasing or diminishing their distance 
from the latter uniformly; or, if the conditions of the case 
require, they may be laid in curved or diagonal directions. 
The result of varying the position of the marginal lines will 
be to vary the length and pitch of the bevel, but this will in 
no way interfere with the strength of the repair. The main 
object of varying the outline margins of the freshened area, 
as before stated, is to give a symmetrical form to the newly 
added vulcanite, and when good judgment is displayed in 
planning the repair, very presentable, and at times quite artis- 
tic, results are realized. In most instances the average repair 
is an unsightly, and often an unsatisfactory, operation, when 
in practically every instance where a repair is indicated, both 
satisfactory and esthetic results are possible when proper 
steps are taken. 
Summary of the Technical Steps Followed in Repairing 
a Median Line Fracture, Full Denture 
Assemble and unite the fractured pieces firmly, as pre- 
viously outlined; secure the cast; with a pencil, sketch on the 
Fig. 439.— Denture with Complete Fracture, 
Extending Entirely Through Palatine 
and Labial Gum Portions 
lingual surface of the baseplate, as symmetrically as possi- 
ble, the position of the marginal lines which limit the area 
to be covered by the new vulcanite; cut the grooves along 
these lines to the depth previously indicated; bevel off the REPAIRING VULCANITE DENTURES 
old vulcanite from the bottom of these grooves to the oppo- 
site or palatal surface of the baseplate, terminating the bevel 
in a feather-edge along the fracture line. This entirely re- 
moves the inner wall of each groove and converts the outer 
wall into a shoulder against which the new vulcanite finishes. 
When the break extends through the labial portion of the 
denture, the outer surface of the pink gum should be beveled 
in a similar manner to the alveolar border joint surface. In 
all cases of pink vulcanite gum repairs, where the fracture 
occurs anteriorly, or anywhere between the cuspids, the mar- 
ginal lines of the repair should be laid back of the cuspids, 
so as to render invisible, if possible, the line of junction of 
the old with the new vulcanite. This is imperative on account 
of the unsightly discoloration noticeable in joint areas on 
pink gum after vulcanization. 
In preparing the joint, the beveling is most easily accom- 
plished hv applying those areas of the baseplate to be reduced 
Fig. 440.— Labial View of Preceding Case 
against the emery band on the lathe mandrel. Constricted 
areas that cannot be reached by this means can be reduced 
with large fissure or round burs in the engine. 
After beveling, the fractured pieces are returned to the 
cast, a piece of sheet wax is applied to the freshened areas 
on the lingual surface of the denture, and with a hot spatula 
burnished, hut not melted, down to the required contour of 
the finished case. 
METHOD OF FLASHING A REPAIR CASE 
It is seldom possible to flask a full denture so that the 
matrix side of the flask can he withdrawn from that contain- 
ing the baseplate, to which the teeth have previously been 
permanently attached, without injuring the matrix, especially 
those portions of it which fill the embrasures. Therefore, in 
repairs involving the labial or buccal gum surfaces, as well 
as lingual portions of a denture, provision must be made for 568 
REPAIRING VULCANITE DENTURES 
placing the rubber on the gum surfaces in such manner as not 
to be disturbed in the final closing of the flask. 
This may be accomplished in two ways. First, by cover- 
ing the prepared and waxed portion of gum repair with the 
plaster in the first half of the flask, and by means of one or 
more suitably located connecting gates removing the wax from 
the gum surface, packing the matrix through these openings, 
and with an excess of rubber in the gates condense that form- 
ing the gum repair in the partially enclosed matrix in the 
final closing of the flask. 
Second, the following method, when carefully carried out, 
involves less time and is quite as effective as the first and 
can, in most cases, be followed. The details are as here out- 
lined : 
When the beveling of the several surfaces involved in the 
repair is completed and the parts are adjusted to the cast, 
the lingual surface is waxed as before described. Instead of 
waxing the gum areas they are coated with a thin film of rub- 
ber cement, well rubbed into the freshened surfaces with a 
pellet of cotton. 
A strip of pink, or granular, rubber, large enough to neatly 
cover the entire area of removed old gum, is applied, and 
with a large, hot burnishing spatula is pressed firmly against 
the freshened areas until perfect contact and firm adhesion 
is developed. Smaller pieces are added and burnished against 
that already placed until the required gum contour is devel- 
oped and a compact homogeneous mass results. 
When the pink gum restoration has been built up as de- 
scribed, the case is ready for flasking, and herein lies the 
Fig. 441.— Gum Facing Applied to Freshened Labial Areas 
advantage of packing the gum repair as outlined, since com- 
plications in flashing and subsequent packing are avoided. 
A mix of plaster is made and the case invested in the 
lower half of the flask just as though no gum surfaces were 
involved; that is to say, the entire labial and buccal portions, REPAIRING VULCANITE DENTURES 
569 
including the gum surfaces just packed, the teeth and the 
lingual surface of the baseplate not included in the repair 
area in this location, are covered or entirely enclosed within 
the plaster investment in the first half of the flask. The pink 
gum, packed as above described, is thus entirely enclosed 
within a matrix. No provision need be made for producing 
pressure on the pink rubber, for, if properly packed, the ex- 
pansion of the mass of pink rubber in vulcanizing is sufficient 
to hold it firmly in contact with the old vulcanite and cause it 
to unite perfectly with the latter. 
When the plaster in the lower half of the flask is smoothed 
up and varnished, the upper half of the flask is adjusted, 
filled, and when hardened, separated, the wax removed with 
hot water, the surfaces of freshened rubber covered with a 
film of rubber cement, well rubbed in, some basic rubber of 
appropriate shade is applied to the cut-out area, slightly in 
excess of the actual bulk required, so as to insure pressure 
in vulcanizing, the two halves of the flask are adjusted, and 
while cold the bolts are tightened with finger power only, the 
case is warmed with dry heat and finally closed in the usual 
manner. Vulcanization is carried out as for ordinary cases. 
Replacing a Displaced Tooth 
When a tootli has been forced from the denture base, its 
pins having pulled out of the vulcanite, or as sometimes 
occurs, when a small section of vulcanite enclosing the pins 
fractures and comes away with the tooth without injuring or 
in any way impairing the usefulness of the latter, replace- 
ment of the same tooth can in most cases be effected by very 
simple methods. The following means for replacing bicuspids 
and molars are both simple and serviceable. 
First, adjust and wax the tooth in its correct position in 
the vulcanite base, enlarging the old pin holes, if necessary, 
to let the tooth in place. The periphery of the vulcanite socket 
in which the tooth rested before displacement should be dis- 
turbed to the least possible extent at this time, as it guides 
the tooth to proper place. 
Second, oil the labial or buccal surfaces of the teeth and 
gums, including the displaced tooth and extending a short 
distance mesially and distally from it. 
Third, make a matrix of plaster by building it against 
these oiled surfaces. This is necessary in order that the dis- 
placed tooth can be returned to correct position after the sup- 570 
REPAIRING VULCANITE DENTURES 
porting vulcanite on the lingual side is removed preparatory 
to adding new vulcanite for the repair. 
Fourth, remove the matrix and the tooth, and with a vul- 
canite file or a large engine bur form a dovetail space in the 
baseplate, to the lingual of the tooth displaced, as wide as the 
latter and deep enough to entirely obliterate the old pin holes. 
Fifth, return and hold the tooth in correct position on the 
baseplate by means of the matrix, and apply wax in the dove- 
tailed space around the pins and against the porcelain, build- 
ing it out to the required contour of the finished denture. 
Sixth, remove the matrix, invest the case in the lower half 
of the flask, entirely enclosing the denture in plaster except a 
Fig. 442.— Denture Base Prepared for Replacement 
of One Tooth, Showing Formation 
o,f Dovetail Space 
small surface immediately surrounding and including tlie 
waxed repair area. The tooth itself should remain in posi- 
tion in the baseplate, and be covered sufficiently with plaster 
to obviate its being raised on forcing the rubber into the dove- 
tailed space and underneath the tooth in closing the flask. 
Smooth the upper surfaces of plaster, tapering the margin 
around the repair area so that the plaster in the upper sec- 
tion may separate readily, varnish, complete the investment 
in the upper half of the flask, and allow time for plaster to set. 
Seventh, separate flask; pick out as much wax as possible 
and use hot water for the removal of the last traces of it. 
Eighth, apply a thin film of rubber cement, being very 
careful to avoid excess, since as before stated a surplus will REPAIRING VULCANITE DENTURES 
571 
cause porosity in the newly added rubber in vulcanizing. Cut 
and apply some small pieces of basic rubber of appropriate 
shade, usually slightly darker than the denture base, as the 
latter will darken somewhat with each vulcanization. With a 
warm, round end rubber packing instrument the pieces should 
be fairly well condensed in the dovetailed space and around 
the pins, and a little surplus added to insure slight pressure 
on the mass when the flask is closed and during vulcanization. 
Ninth, close the flask, vulcanize and finish in the usual 
manner. When the pink gum margin has been fractured and 
requires restoration, the surfaces are freshened and small 
pieces of pink rubber are built up to the required contour, 
condensing them with a hot instrument. This should be done 
before flasking the case, the pink rubber being enclosed in the 
first half of the investment as previously outlined in repair- 
ing a fractured baseplate. Usually, however, as previously 
stated, on account of the unsightly discoloration at the line of 
junction of the new with the old pink vulcanite, visible areas 
needing repairs should be extended to such point that the dis- 
colored joints are invisible, and only new pink vulcanite will 
show. This often necessitates carrying the beveling back as 
far as the second bicuspid on each side. 
Replacing a Displaced Tooth by the Casting Method 
When the displaced tooth is situated between two proxi- 
mating teeth as in a full denture, and rests in a vulcanite 
socket or matrix having a complete periphery, attachment of 
a new tooth may be made by casting. The advantage of this 
method is that vulcanization is obviated, a process which, 
when resorted to as is usual in repair cases, while the plaster 
is “green,” soft and yielding, often results in warpage and 
consequent loss of adaptation of the denture to the oral tis- 
sues. 
The steps are as follows: 
The vulcanite which enclosed the pins is freely cut away 
and in addition a cavity, having a decided undercut, is formed 
in the sides and bottom of the vulcanite matrix in which the 
tooth rests. Care must be taken not to disturb the peripheral 
outline of the matrix, or if unavoidably disturbed, to re- 
store in wax the lost portion after the tooth is finally set in 
place. A positive connection of the wax so applied with the 
interior of the matrix is essential so that the metal, when cast, 572 
REPAIRING VULCANITE DENTURES 
Fill flow from the interior outwardly and take the place of 
the wax. 
Now at a point well within one of the lingual embrasures 
drill a hole connecting with the undercut cavity, as nearly 
parallel with the long axis of the tooth as possible. A broken 
engine bur converted into a drill of the full diameter of the 
shank produces a hole of convenient size. Later on the bur, 
by reversing, will assist in forming the sprue. 
The tooth is now returned to position in its matrix and 
waxed externally, if necessary, to hold it in place, thus leav- 
ing the undercut space free from wax or debris. 
A .093 wire (the diameter of an engine bur shank) is now 
passed into the sprue previously drilled in the baseplate, or 
Fig. 443.— Replacing a Tooth by the Casting Method 
the drill may be reversed and used for this purpose, a mix of 
investment or plaster is made, filled in the palatine or border 
side of the denture, to form a base to prevent the denture 
tipping, carried out against the buccal or labial surface, over 
the occlusal or incisal surfaces, and down on the lingual sur- 
face of the denture surrounding the sprue wire. 
While the plaster is yet soft, a small cup, similar to or 
made from a common thimble, having a hole drilled in the 
bottom, is slipped over the sprue wire and pressed down into 
the plaster sufficiently deep to support it when the wire is 
withdrawn, and to insure its stability under the pressure of 
casting. 
When the plaster has hardened, the sprue wire is with- 
drawn, thus forming a sprue connecting the thimble with the REPAIRING VULCANITE DENTURES 
573 
undercut space under the tooth. Fusible metal is melted and 
poured into the thimble, from which it is forced into the space 
by means of Melotte’s moldine, confined within a ring or cup 
somewhat larger than the diameter of the thimble. Forcing 
the metal in the undercut under pressure causes it to fill the 
Fig. 444.— Diagrammatic View of the Invested Case, Thimble 
in Position, and Moldine Carrier. Sprue 
Former Not Yet Removed 
entire space and enclose the heads of the pins perfectly, thus 
making a very serviceable repair. When finished, the only 
metal showing is that which fills the sprue, which, when 
dressed down and polished, is scarcely noticeable. 
Dr. A. C. Alexander of Kahoka, Mo., first called the writ- 
er’s attention to this method of repair two years ago, and 
since that time it has been applied satisfactorily in many 574 
REPAIRING VULCANITE DENTURES 
practical cases. In general, the principle is similar to the 
method suggested by Hr. J. B. Bean in 1869 for attaching gum 
sections to cast aluminum liases by forming an undercut in 
Pig. 445.— Cut of a Practical Case Invested Ready for 
Reception of Pusible Metal 
the baseplate and casting tin into the space so formed and 
around the pins of the section; described in Harris, Fd. 1870. 
Another Method of Repair by Means of Fusible Metal 
Cut a decided dovetail in tlie lingual surface of the den- 
ture, as for an ordinary vulcanite repair, but greater care 
must be exercised in developing positive mechanical anchor- 
age in the space in repairs of this type than where vulcanite 
is employed, since in the latter case the union is an adhesion 
of molecular material and not merely a mechanical anchor- 
age, while in the repair under consideration the union of the 
metal with the base is mechanical. 
Fill the palatine or border surface of the denture with 
plaster to form a base, extending it out over the outer sur- 
faces of the gums and teeth to serve as a matrix for holding 
the displaced tooth in position. 
The case should be set at such an angle in the investment 
that gravity will assist in filling the undercut space when the 
molten metal is poured. 
The case being properly invested as described, some Mel- 
lotte’s or other easily fusible metal is melted in a small ladle 
and poured into the dovetailed space. As it begins to congeal, REPAIRING VULCANITE DENTURES 
575 
a little surplus is added, and with a pad of blotting paper 
folded three or four times, pressure is made on the mushy or 
semi-liardened metal to force it into all parts of the space and 
around the pins of the tooth. When hardened, the excess is 
trimmed off and the surface polished to proper contour. 
Repairing by Means of Amalgam 
A very common method of attaching a displaced tooth is 
to form the dovetailed space as just described, adjust the 
tooth in position and form a matrix in such manner that it 
will not become displaced nor allow the tooth to be forced out 
of position under the pressure of packing the amalgam. A 
mix of amalgam of moderate consistency is made and quickly 
forced into the space prepared for it and around the tooth 
pins, using small-pointed pluggers to pack it into the deeper 
portions of the dovetail. 
Repairs made in this manner, although at times quite sat- 
isfactory, are usually temporary in character, the amalgam 
around the pins fracturing under masticatory stress and 
allowing the tooth to be dislodged. 
By forming a loop of fine, tinned iron wire, such as is 
used for root measurement, twisting it around the pins and 
weaving it back and forth between the two, three or four 
times, additional anchorage of the tooth to the denture will 
be gained over that afforded by the pin heads alone. This 
method is very applicable in amalgam or fusible metal re- 
pairs, where the tendency of the pin heads to pull out or the 
amalgam to readily fracture under stress is very marked. 
The loop should be well embedded in the amalgam. It can 
readily be seen that if a little tension is placed on the loop 
to take up the slack, and it is well surrounded with metal, that 
the tooth or pins will most likely fracture before displace- 
ment will occur. (See wire loop on tooth pins, page 572.) 
Still another method of increasing anchorage is by sold- 
ering to the pins a small loop of wire of suitable form to fit 
within the dovetailed space and be entirely enclosed within 
the metal. 
Repair Involving the Substitution of Another Tooth 
When in addition to being forced from the baseplate the 
tooth is fractured and rendered useless as well, another tooth 
must be selected for the repair. Since the chance is slight 576 
REPAIRING VULCANITE DENTURES 
of finding a substitute of the same size, mold and occlusal 
form as the fractured tooth, the steps just outlined, although 
in the main applicable, must be varied somewhat to insure 
correct alignment and satisfactory occlusal conditions in the 
completed repair. 
In the methods previously outlined, the position for and 
occlusion of the displaced tooth was found by returning it 
to the vulcanite socket in which it rested before displacement 
and of holding it there with wax, if necessary, while a satis- 
factory matrix was secured. This plan is not applicable in 
case a new tooth is used, because it will seldom fit in the old 
socket. In full denture cases, and in some partials as well, 
the denture is returned to the patient’s mouth and a wax or 
modeling compound mash bite is secured, involving the space 
to be filled, the proximating and occluding teeth. 
In case of complicated occlusion, the denture and bite 
should be transferred from the mouth to the occluding frame 
with the face bow, mounted, and the bite filled with plaster to 
develop the occluding teeth, after which the bite material is 
removed. 
In uncomplicated cases the bite may be filled in with 
plaster and an extension at the same time be made lingually 
so as to cover definite areas on the lingual surface of the den- 
ture, or it may even extend across the entire baseplate, the 
point of importance being to have a sufficient number of 
guides to bring the occluding plaster teeth into normal rela- 
tion with those of the denture when the bite material is re- 
moved. 
The old socket is now burred out in its interior, and the 
lingual side cut away to receive the new tooth. Care should 
be taken not to disturb the gum margin and further compli- 
cate the repair. In fitting the substitute tooth in place the 
porcelain itself can, in many cases, be ground to fit the socket 
on the gum side of the denture. Usually, however, a little 
careful trimming of the vulcanite socket, together with a little 
grinding of the tooth, will develop a satisfactory joint, that 
will not require the addition of new gum material. 
Preliminary Dovetailing of a Denture Base 
In partial dentures, where an isolated tooth is to be re- 
placed, it is frequently advisable to prepare the dovetail form 
on the baseplate for the reception of the new rubber before 
taking the bite. By so doing the danger of mutilating or REPAIRING VULCANITE DENTURES 
577 
breaking the proximating plaster teeth when the cast is run 
up will be obviated. 
A small wax bite is now taken, involving the space to be 
filled, the proximating teeth and the opposite occluding teeth. 
The denture and bite should be removed together, if possible, 
to obviate danger of distorting the latter. If for any reason 
the bite and denture are separated in removal, they should be 
carefully fitted together and held firmly by melting some of 
the bite wax at various points against the denture. 
The cast is now formed in the united denture and wax, 
and when hardened, the opposite side is run up. The occlu- 
sion cast should extend over onto the palatal surfaces of the 
denture so that it may be guided to place when the wax bite 
is removed. 
On removal of the wax a suitable tooth is selected, ground, 
tested for occlusion, waxed in place, and the case flasked, 
packed and vulcanized in the usual manner. 
Sometimes the neck or vulcanite connecting an isolated 
tooth with the denture base must, on account of the occluding 
teeth, be so reduced in thickness as to invite ready fracture 
Fig. 446.— A Plate Tooth 
Backed with Gold, to Which 
a Clasp Metal Extension Is 
Applied for Enclosure With- 
in the Vulcanite 
Fig. 447.— Side View of a Backed 
Plate Tooth in Position 
under stress, an accident which frequently occurs, in partial 
dentures carrying upper anterior teeth. To repair such a 
case, one of two methods must be adopted, either the opposing 
tooth must be shortened to make room for greater bulk of 
vulcanite, or a plate tooth must be selected, ground to posi- 
tion, backed with gold and a strip of heavy clasp metal 
abutted against the backing to which it is attached with solder. 
This strip should lie close against the maxillary surface, yet 
not quite in contact with it, and extend lingually so as to be 
enclosed in the vulcanite. Two or three holes should be 
punched in the extension, or its edges should be notched with 578 
REPAIRING VULCANITE DENTURES 
a file to afford anchorage in the vulcanite which encloses it. 
The clasp metal strip must be sufficiently broad and thick to 
withstand heavy masticatory stress without bending, or, if of 
light gauge, it may be stiffened by flowing solder over it. 
This plan of backing a tootli with metal and attaching 
to it a lingual extension in close bite cases is often resorted 
to in the initial construction of the denture when the bite is 
exceptionally close. 
Substituting Artificial for Lost Natural Teeth in 
Partial Cases 
It frequently occurs that when a partial denture has been 
worn for some time, one or more of the remaining natural 
teeth, through accident or as the result of disease, are lost. 
If the adaptation and general requirements of the den- 
ture are satisfactory, aside from the conditions noted, re- 
Fig. 448.— Denture Base with Dovetail Prepared for 
Addition of Two Bicuspids 
placement of the lost with artificial teeth may be readily ac- 
complished by the following method: 
With a file or engine burs form a dovetail in the base- 
plate to the lingual of the space to be filled. In case the bor- 
der in which the natural teeth were situated has absorbed, 
the baseplate should be cut back to a point where its maxillary 
surface rests upon the mucous tissues, thus permitting the 
new vulcanite to join the old baseplate and form a continuous 
bearing surface over the absorbed area. In such cases a long REPAIRING VULCANITE DENTURES 
579 
bevel splice will prove more serviceable than the dovetail 
method. 
The denture, having been cut out as described, is returned 
to the mouth and a mash bite is taken, being careful to press 
the wax or compound firmly against the labial or buccal 
absorbed areas, and to secure an accurate impression of the 
occluding teeth. 
On removal of the bite and denture they should be care- 
fully adjusted and luted together, and the subsequent steps 
carried out as described under the 4‘repair of partial den- 
tures.” 
Repairing Gum Section Cases 
When one of the sections of a gum section denture has 
been fractured beyond the possibility of further usefulness, 
a new block must be selected that will conform as perfectly 
as possible to the broken section in form, size, color, length of 
bite and curvature of the labial or buccal surface. 
Usually this is a difficult matter unless the prosthetist is 
fortunate in securing a block of the same manufacture, mold 
and shade. In repairs of this class the vulcanite in which 
the old pins are enclosed should be freely cut away, the den 
ture introduced in the mouth and a bite taken. The case is 
then mounted on the occluding frame and the block selected 
and ground to fit the ends of the proximating sections. The 
block, if thick, may need grinding or dressing down on the 
surface that approximates the baseplate, or the vulcanite it- 
self, if of sufficient thickness, can be reduced with burs to 
permit the block to settle into correct labial or buccal con- 
tour position. Special care should be taken in grinding the 
joints to hold the block in correct alignment when testing. 
Subsequent steps are carried out as outlined in the repair 
of a single tooth. 
Substitution op a Baseplate 
Although the adaptation of a denture may be satisfac- 
tory, and its occlusion correct, yet, because of frequent re- 
pairs which have deteriorated the quality of the vulcanite, or 
because of some peculiar fracture which renders impossible 
a satisfactory repair, a new baseplate may be substituted for 
the old vulcanite by the matrix method in much shorter time 
than is required to reconstruct the case in the usual way. 
The procedure is as follows: 580 
REPAIRING VULCANITE DENTURES 
The baseplate, if fractured, should be reassembled and 
the several parts held in proper relation by means previously 
described, “Repairing a Fractured Baseplate.” 
Oil the denture with a thin film of vaseline and develop 
a cast sufficiently deep to raise the peripheral margin of the 
denture about three-eighths of an inch above the base bottom 
and smooth its outer surfaces. 
Countersink the buccal walls of the cast at two points on 
each side so that the matrix, when formed and removed, may 
be returned to proper position again. Varnish the outer sur- 
faces with a separating medium. 
Oil the outer surfaces of the teeth and gum restoration; 
make a mix of and apply plaster to the buccal and anterior 
walls of the cast and denture surfaces, extending from the 
median line to the tuberosity on one side and from the base 
up over the incisal and occlusal surfaces of the teeth. This 
addition, which, when completed, forms one-half of the matrix, 
should be about three-eighths of an inch in thickness. 
When the plaster forming this portion has set, the mesial 
end is squared up, a countersunk depression made in the 
planed surface, the latter varnished, and a second application 
of plaster is applied in a similar manner extending back to 
the tuberosity on the opposite side. 
When hardened, the outer surfaces of plaster are smoothed 
up, and with a few light taps of the hammer on the sides and 
base of the matrix, it will come away in two pieces. 
CONSTRUCTION OF THE MATRIX 
REMOVAL OF THE TEETH FROM OLD BASEPLATE 
The teeth are now removed from the old vulcanite, one at 
a time, being careful to card them on wax in regular order so 
as to avoid confusion in their arrangement. 
Each tooth is now thoroughly cleaned, the old vulcanite, 
if remains, is removed from around the pins and the tooth 
returned to its position in the matrix. 
Should any tooth become disturbed or fall out of place in 
raising the matrix to an upright position, a little liquid silex 
touched to the labial or buccal surfaces will, on returning the 
tooth, under pressure, retain it firmly in place. 
FORMING THE WAX BASEPLATE 
A sheet of wax is now applied to the cast surfaces and 
trimmed peripherally so as not to interfere with the plaster REPAIRING VULCANITE DENTURES 
581 
matrix being carried to exact position against the cast sur- 
faces. 
Each half matrix is then returned to position against the 
sides of the cast and brought in contact anteriorly, being 
guided and held in place by the projections of the matrix fit- 
ting into the countersunk holes of the cast. Usually a string 
is wound several times around the matrix and cast and tied 
tightly to hold all firmly together, or a heavy rubber band ap- 
plied peripherally will be more convenient to apply and serve 
the purpose equally well. 
The teeth, each one in its individual matrix, and the two 
halves of the matrix in correct position against the cast, now 
bear the exact relation to the cast surfaces that they did be- 
fore removal of the vulcanite. 
Softened wax is pressed into the space between the teeth 
and cast, and the general contour of the case developed as it 
was before the removal of the old base. 
A heated spatula is now passed under the pins and along 
the ridge lap of each tooth, as well as into the interproximal 
spaces and embrasures, to firmly cement the teeth to the wax 
base, so that they will not be disturbed or come away with the 
matrix when the latter is removed. 
Care should be taken not to touch the matrix walls with 
the heated spatula, or in any manner melt the wax against 
these surfaces. Should this occur not only the adherent wax, 
but some of the teeth are liable to come away with the 
matrix. 
To obviate the union of the wax with the matrix, the lat- 
ter can be coated with a thin film of oil after the teeth are in 
place and just before assembling the parts of the matrix to 
the cast. Care should be taken not to apply any oil to the 
teeth. 
The string or band is now removed and the matrix is 
gradually and carefully worked free, so as not to disturb the 
position of the teeth in the wax. Each tooth should now be 
tested to see that it is still firmly adherent to the wax. A 
further test can be applied by returning the matrix to its 
former position. 
The wax model denture is now smoothly finished, flasked, 
packed, vulcanized and finished in the usual manner. 
In planning the reconstruction of the case, should it be 
deemed advisable to test the denture in the mouth, Ideal or 
some unyielding baseplate should be applied to the cast in- 
stead of the ordinary wax. 582 
REPAIRING VULCANITE DENTURES 
Modified Methods of Reconstruction 
A somewhat simpler, but less accurate, method of sub- 
stituting a new for an old baseplate frequently resorted to is 
as follows: 
Thoroughly clean the denture, oil the palatine surface and 
secure a cast. 
MOUNTING CAST AND OLD DENTURE ON THE OCCLUDING FRAME 
Mount the cast and denture on the occluding frame in as 
nearly the normal position as possible without the use of the 
Fig. 449.— Upper Denture Mounted on Occluding Frame. Teeth Embedded in Plaster Matrix 
face-bow. An occluding frame with an incisor guide pin is 
preferable, as such an appliance obviates springing of the 
bows in the subsequent steps. 
FORMING THE MATRIX 
Turn back the upper bow on which the case is mounted 
and apply a mix of plaster to the lower bow, building it up 
sufficiently high for the teeth of the denture to enter. (See 
Fig. 449.) 583 
REPAIRING VULCANITE DENTURES 
Drop the upper bow down and press the teeth into the 
plaster so that all exposed portions of porcelain are covered. 
It may be further extended against the labial and buccal gum 
surfaces, although this is not usually necessary. The set 
Fig. 450.— Preceding Case with Old Baseplate Removed and Teeth Returned to Their 
Respective Matrices 
screw at the back of the frame, or the incisor guide, should 
be firmly fixed so as to hold the upper and lower bows a fixed 
distance apart after removal of the old baseplate. 
FORMING THE WAX BASEPLATE 
When the plaster has set, carefully separate, remove the 
teeth from the old baseplate and return them to their respec- 
tive positions in the matrix. (See Fig. 450.) 
A baseplate with roll of wax is adapted to the cast, the 
wax warmed slightly, and the upper bow of the frame closed 
so as to force the wax against the teeth in the matrix. 
That portion of the matrix enveloping the outer surfaces 
of the teeth is cut away, so as to allow the teeth now attached 
to the baseplate to part from the matrix without interfer- 584 
REPAIRING VULCANITE DENTURES 
ence, after which the case is waxed and the subsequent steps 
are carried out as usual. (See Fig. 451.) 
The weak point of this method is in the liability of the 
frame springing in pressing the teeth into the wax and thus 
Fig. 451.— Same Case, Showing Teeth Waxed to Cast. Outer Portion of Matrix Cut Away to 
Release the Teeth 
shortening the bite. Such an error cannot well occur when 
the incisor guide pin is used. 
Correcting Imperfect Adaptation by Substitution of a 
New Base 
When the adaptation of a denture has become impaired, 
but the teeth which it carries occlude and interlock well with 
those in the opposite arch, adaptation may be restored by sev- 
eral methods, the first of which is as follows: 
Thoroughly clean the denture with a stiff brush wheel and 
pumice stone. Remove from the entire palatine and border 
surfaces a thin layer of the old vulcanite by means of a small 
lathe bur or a large surgical bur in the engine. 
Apply a thin layer of well-mixed, but rather thin, impres- 585 
REPAIRING VULCANITE DENTURES 
sion plaster over the entire interior of the vault and border 
surfaces. 
Introduce in the mouth and instruct patient to bite inter- 
mittently at first, then with steady, maintained pressure to 
compress the tissues, bring the denture into correct occlusion 
and force out all excess plaster. 
When hardened, trim off peripheral excess, relieve pres- 
sure over hard areas by scraping, coat impression with sepa- 
rating medium, secure a cast and mount it on the occluding 
frame in the usual manner. 
Either one of the methods previously described may be 
adopted for securing the correct relation between the teeth 
and cast, so that on removal of the old vulcanite the align- 
ment and occlusion of the teeth in the wax model may be cor- 
rectly established. 
When the matrix for the teeth is formed, the denture is 
first removed from the latter, then from the cast, the surfaces 
of which are then cleared from any remaining portions of the 
plaster impression. 
The steps from this point forward are the same as those 
already outlined under the head of ‘‘Substitution of a Base- 
plate,” page 579. 
Correcting Adaptation by Addition of New Rubber to 
Old Base 
When the impression has been secured in the manner de- 
scribed above and the cast secured, the case may be flasked 
immediately; when the investment plaster has set, the flask is 
separated, the plaster is removed from the impressed areas, 
and the exposed palatine and border surfaces of the denture 
thoroughly freed from all debris. 
All exposed areas of the baseplate not previously already 
freshened, and to which new vulcanite is to be added, should 
be renewed by scraping, these areas covered with a thin film 
of rubber cement; a sheet of new rubber is cut to correct size 
and carefully pressed against the old baseplate, being careful 
not to confine the air between the two surfaces. 
The two halves of the flask are now adjusted, the screws 
tightened slightly and the flask contents heated to about 200 
degrees F., dry heat, when gradual, but not excessive pres- 
sure is applied to force out the excess rubber. 
When closed the flask is separated, the muslin removed 
and the result of the work so far accomplished noted. Should 
there be an insufficient amount of rubber, more is added and 586 
REPAIRING VULCANITE DENTURES 
the flask finally closed and vulcanized and the case finished 
as usual. 
Previous to the application of the rubber cement, an am- 
ple waste gate should be cut close to and around the entire 
periphery of the denture, but not connected with the margin 
of the matrix at any point, to receive the excess rubber. 
Correcting Adaptation by Means of Rubber Paste 
Bur out and freshen the surfaces of the baseplate as above 
outlined and apply a film of Bridgeford’s rubber paste, a 
solution of rubber heavily loaded with powdered aluminum. 
Thickness of the film applied varies, depending on the amount 
of old vulcanite removed and the extent of absorption of the 
border that has occurred, but usually from one to one and a 
half millimeters will be sufficient. 
The denture with paste applied is immersed in cold water 
for an instant to chill it slightly and also to prevent it adher- 
ing to the oral tissues. 
On introduction into the mouth, the denture is pressed to 
place for a moment, removed, the excess around the margins 
brushed off, the case dipped in cold water and again returned 
to the mouth for further adaptation by closure on the part 
of the patient, as well as reapplied pressure on the palatine 
areas by the operator. 
These steps are repeated three or four times, or until sat- 
isfactory adaptation is secured, when the denture is removed, 
freed from excess and set aside for a short time to allow the 
volatile constituents time to evaporate, when the case is flasked 
in a single investment and vulcanized. 
To Renew the Adaptation of a Denture by Means of 
Furlong’s Plastic Rubber 
Prepare the palatine and border surfaces of the denture 
by freshening as outlined in the first method described. 
Apply to these surfaces a sheet of Furlong’s Plastic Im- 
pression Rubber, pressing it well against the old vulcanite, 
being careful not to confine any air between the surfaces. 
The plasticity of this rubber is increased and its impres- 
sion quality improved by immersing it in warm water for an 
Instant before introducing in the mouth. Apply pressure as 
when using Bridgeford’s paste. When satisfactory adhesion 
has been developed, the excess is removed and the denture is REPAIRING VULCANITE DENTURES 
587 
flasked in a single investment, vulcanized and finished in the 
usual manner. 
To Correct Occlusion When Denture Adaptation Is 
Satisfactory 
It sometimes occurs that a patient may persistently main- 
tain an incorrect bite in trial of the contour models and of the 
wax model denture in the mouth, and the error only be dis- 
covered when the cases are finished. 
The result is that the occlusion is incorrect, the teeth of 
one of the dentures occupying a position a little forward in 
upper and backward in lower cases, or to one side of the nor- 
mal alignment. 
The best plan, as a rule, is to reconstruct one or both den- 
tures, beginning with a new impression and carrying out the 
usual steps in such cases. 
When, however, the adaptation of the denture to be re- 
constructed is in every way satisfactory, equally good results 
may be attained, with minimum inconvenience to both patient 
and operator by adopting the following method: 
With a small engine bur cut the vulcanite from around the 
pins and remove the teeth. 
By means of a vulcanite file and the emery cloth band on 
the lathe, sufficient vulcanite is removed to permit the shift- 
ing of the teeth to proper position without interference. The 
entire outer gum surfaces should be removed so that in the 
completed case no joints or lines of junction will be visible, 
a layer of new material having replaced the old. 
The case now presents the same conditions as does the 
one in which the double vulcanization method is followed, the 
old base, denuded of teeth and surrounding vulcanite, serving 
as a foundation on which to construct the wax contour model. 
On this base the teeth are waxed and occluded and the subse- 
quent steps carried out in the usual manner. CHAPTER XXVI 
CONTINUOUS GUM DENTURES 
From an esthetic, as well as hygienic standpoint, contin- 
uous gum dentures fulfill most perfectly the requirements of 
substitutes for the lost natural teeth. They are most strongly 
indicated in full cases, although at times partial dentures of 
this type will prove very serviceable. 
ADVANTAGES 
Continuous gum dentures possess two important advan- 
tages over dentures of any other type. 
First, they are absolutely impervious to moisture, exempt 
from chemical action to which dentures are ordinarily sub- 
jected when in use, and afford but little opportunity for the 
lodgment and retention of food; consequently they are easily 
kept clean and free from decomposing food and from the odors 
of ptyalin and retained saliva. 
Second, the gum surfaces, being composed of glazed por- 
celain enamel tinged with pink, present an unbroken or con- 
tinuous gum surface free from joints, fissures, or cracks of 
any character, and which is united to the underlying vitrified 
porcelain, the teeth, and to the peripheral margins of the base- 
plate by fusion. 
When the denture is properly constructed and the gum 
enamel artistically applied, it is impossible in most cases to 
detect the fact that the substitute is artificial. 
DISADVANTAGES 
The principal objections nrged against dentures of this 
type are as follows: 
First, excessive weight, particularly in upper cases where 
much absorption of the border has occurred. 
Second, difficulty in construction, from warpage of the 
entire denture due to shrinkage of mass in fusing the silicious 
material around the teeth and to the base: to the formation 
of fissures in the underlying body and in the enamel in the 
final baking; to the tendency of the mass of porcelain to be- 
come porous at any stage of fusion after the first baking. 
Third, dentures of this type are liable to fracture if care- 589 
CONTINUOUS GUM DENTURES 
lessly handled, because of their excessive weight and the fria- 
bility of the materials of which composed. 
Fourth, the expense of time and material involved place 
them beyond the reach of persons of limited means. 
In regard to the first objection, when good adaptation of 
the denture is secured and the teeth are arranged anatomi- 
cally, the weight of the denture is seldom noticeable to the 
patient. 
The second objection can be overcome by patient attention 
to details on the part of the prosthetist. 
The third objection more especially concerns the patient, 
who, however, if properly instructed, can usually avoid acci- 
dents. 
The fourth disadvantage is an important one to both pa- 
tient and prosthetist. The patient must of course decide 
whether a denture of this type is within his means. The 
prosthetist, on the other hand, must exact such fee as will 
cover the cost of the materials and recompense him well for 
all possible time involved in constructing the case. Oversight 
in this particular is responsible for many failures in the class 
of work under consideration, the tendency being to rush the 
constructive details to their detriment, or turn the case over 
to someone who may prove incompetent. 
In no department of prosthetics is there an opportunity 
for the display of greater skill, or the realization of finer 
esthetic results, than in the planning and construction of 
dentures of this type. There is first, the development of a 
well trussed, yet light, platinum baseplate; second, the ar- 
rangement of the teeth anatomically, as well as esthetically; 
third, their attachment to the baseplate by soldering, and 
bracing when necessary, in such manner as to remain un- 
changed during the contraction of the porcelain in fusing; 
and finally, the application of the porcelain body, and subse- 
quently, the enamel so disposed as to represent nature’s best 
efforts in contour gum effects and vault irregularities. 
Formerly dentures of porcelain were constructed without 
metallic bases, but on account of the shrinkage which invari- 
ably occurred in baking, adaptation was seriously interfered 
with, or entirely destroyed. As a result corrections had to be 
made by the method mentioned elsewhere of securing a new 
cast of the mouth, pigmenting its surface, and by repeated 
trials of the denture to the cast, locating the high points, which 
were then ground away until close adaptation was secured. 
The grinding of the glazed surfaces exposed many minute 
spaces, and left the porcelain more or less rough and porous. 590 
CONTINUOUS GUM DENTURES 
A further objection to the all-porcelain denture was that 
unless formed thick and somewhat bulky, it was liable to frac- 
ture with usage in the mouth. 
About 1855 Dr. John Allen of New York, introduced the 
method of attaching the teeth to a platinum base and fusing 
the porcelain around them. By this means warpage of the 
denture during baking was to a large extent obviated. This 
is essentially the method in vogue today, the constructive de- 
tails of which are as follows: 
FORMING THE PLATINUM BASEPLATE 
From an impression of the mouth a model is secured. A 
die and counterdie are formed in the manner elsewhere de- 
Fig. 452.— Platinum Baseplate, Swaged and Trimmed to 
Approximately Correct Peripheral Outline 
scribed, and a pattern of the baseplate obtained. Usually pure 
platinum, No. 28 gauge, is used, since a thinner plate, unless 
heavily reinforced, will not furnish a sufficiently rigid founda- 
tion to prevent warpage of the porcelain during baking, or 
obviate fracture of the finished denture under stress. 
In the swaging of a platinum baseplate special care should 
be taken to avoid the formation of folds in any location, since 
if subsequently corrected by flowing solder into them, and re- 
ducing the excess by grinding, an unsightly area is left due to 
difference in color of solder and baseplate. 
FITTING THE BASEPLATE IN THE MOUTH 
When swaged and trimmed peripherally, the base should 
be introduced in the mouth and tested as to general adaptation CONTINUOUS GUM DENTURES 
591 
and stability. All margins which impinge on the muscles or 
frenum should be corrected, and the peripheral outline of the 
baseplate trimmed to as nearly the exact outline of the finished 
denture as possible. This is necessary in order to avoid the 
unsightly appearance caused by grinding away the metal rim, 
often into the porcelain, to relieve impingement when the fin- 
ished denture is introduced — a condition frequently seen in 
cases where proper care has not been exercised in peripheral 
trimming of the baseplate. 
REINFORCING THE BASEPLATE 
Since porcelain in thin layers is easily fractured, the metal 
framework of dentures and bridges which are to be overlaid 
with this material should have sufficient inherent strength, 
Fig. 453.— Distal Shoulder Wire Adapted to Plati- 
num Baseplate. This Wire Should Be 20 to 
22 Gauge, and Terminate About the 
Center of Each Tuberosity 
exclusive of the added porcelain, to withstand all stress to 
which they may be subjected. 
A platinum base may be strengthened in several ways, the 
most common methods of which will now be given: 
First, to strengthen an upper baseplate, a platinum wire 
of 22 to 24 gauge is adapted and soldered to the lingual side 
of the baseplate near its distal margin. It should be laid in a 
symmetrical curve, and advanced further forward in the vault 
portion than at either side. The object in placing the two ends 
near the margins at their terminal points on the tuberosities 
is to afford some space for a graceful curve to the porcelain 
in its extension distally from the second molars. 
Over this wire a second strip of platinum, usually 31 or 
32 gauge, is swaged to the plate. The anterior margin of this 592 
CONTINUOUS GUM DENTURES 
strip should overlap the wire anteriorly, and the posterior 
margin extend slightly beyond the distal margin of the base- 
plate, to afford a shoulder on which to lay the solder. When 
Fig. 454.— Doubler of 30 or 31 Gauge Conformed to 
Baseplate and Wire 
swaged, the anterior margin of the strip is trimmed to the an- 
terior surface of the wire and the two ends cut so as to termi- 
nate on the tuberosities and even with the underlying wire. 
Fig. 455.— Doubler Removed from Baseplate for Final 
Trimming 
In addition to the doubler just described, a second doubler 
is sometimes swaged and trimmed as illustrated, to overlay 
the border and extend into the palatine area. It should not CONTINUOUS GUM DENTURES 
593 
extend much beyond the crest of the border either labially or 
incisally; first, because it is not necessary for strength; sec- 
ond, the space it would occupy if extended can be best con- 
served for increasing bulk of porcelain; third, unnecessary 
metal adds to the weight of the denture. (See Fig. 457, page 
594.) 
Instead of the doubler just described, some prefer to adapt 
and solder a piece of 16 or 14 gauge iridio-platinum wire 
Fig. 456.— Doubler Trimmed and Soldered to Baseplate 
along the crest of the border in such position as not to inter- 
fere with correct tooth alignment. 
The doublers, of whatever form, should be firmly attached 
to the baseplate with high-grade platinum solder, and the base 
reswaged to correct any warpage that may have occurred. 
FORMING THE FINISHING SHOULDER FOR THE PORCELAIN 
It is necessary in order to avoid fracture, to form a right- 
angle shoulder around the entire periphery of the base, 
against which the porcelain may settle in fusing. The ante- 
rior margin of the doubler and underlying wire, when squared 
out with small stones and burs, constitute the distal shoulder, 
while that on the labial and buccal periphery is formed on 
these surfaces by soldering a wire of about 18 gauge to the 
baseplate. 
One end of the peripheral wire should abut the doubler 
and wire on one tuberosity, and be bent to lie in contact with 
the baseplate rim for a distance of about an inch anteriorly. 
It is then clamped in position and attached with solder 
throughout a portion of this distance, and the plate cooled. 
The adaptation of the wire and attachment with solder should 594 
CONTINUOUS GUM DENTURES 
proceed in sections, rather than to attempt to adapt and clamp 
it around the entire periphery at the start. 
The wire should be parallel with the periphery of the base- 
plate rim, but be placed about one-sixteenth of an inch from 
it, so that subsequent trimming, if necessary to relieve mus- 
cular impingement, may be accomplished without encroaching 
on the porcelain. 
Extensive contouring of the solder in the space on the 
peripheral side of the wire should not be attempted, as pits 
are liable to develop in bulky masses of platinum solder dur- 
ing the fusing of the porcelain. The angle, however, should 
Fig. 457.— Baseplate with Peripheral Wire Attached. 
Also a Strengthener Adapted to 
Border Areas 
be filled in to develop a uniform, but slightly tapering or con- 
cave surface. 
The angle between wire and baseplate presenting toward 
the crest of the border should not be filled to any extent with 
solder, since this surface of the wire must subsequently be 
squared out in forming the shoulder. 
Small square-edged carborundum stones are now applied 
to the wire to develop a square shoulder against which the 
porcelain may be fused. Plug-finishing burs are also useful 
for this purpose. The shoulder should present a definite angle 
around the entire periphery of the base, for if left round at 
any point a crease may form by the contraction of the porce- 
lain, or the latter may overlap the rounded surface of the wire 
forming a thin edge and be fractured in handling. 
The soldering is best accomplished by means of nitrous 
oxid and gas blow-pipe, or when pure gold is used as a solder CONTINUOUS GUM DENTURES 
595 
the ordinary gas blow-pipe may be employed. Platinum solder 
is preferable to pure gold, as it is not dissipated during the 
several bakings of the porcelain as is pure gold, the latter 
being absorbed by the platinum at high temperatures. Fre- 
Fig. 458.— The Turner Alcohol Blow-Pipe, Which Develops an 
Intense Flame Suitable for Fusing Platinum Solder 
quently joints united with pure gold as a solder pull apart 
during baking, or under slight stress when the finished piece 
is introduced in the mouth. 
The doubler and peripheral shoulder wire having been 
attached by soldering, the baseplate should be reswaged to 
correct the warpage that may have occurred during this 
operation. 
To prevent the baseplate from becoming lodged in the 
counterdie in swaging, due to the peripheral shoulder wire 
being driven into the sides of the latter, a few layers of damp 
newspaper can be interposed between the two. The die and 
counterdie should at all times be kept oiled to prevent con- 
tamination of the platinum by the base metals. In addition 
to this precautionary measure the baseplate should be boiled 
in dilute acid and thoroughly polished on the lathe with a 
stiff brush wheel and pumice stone, to prevent any possible 
danger from this source. 
RESWAGING AND CLEANSING THE BASEPLATE 
The baseplate is now in condition to receive the rim of 
wax, by means of which the occlusion and facial contour is 
DEVELOPING THE OCCLUSION AND CONTOUR MODEL 596 
CONTINUOUS GUM DENTURES 
established. The steps from now on are exactly similar to 
those described under the head of Full Denture Construction 
up to that of permanently attaching the teeth to the baseplate, 
with the exceptions resulting from the use of a special type of 
tooth for these cases. 
CONTINUOUS GUM TEETH 
Teeth intended for continuous gum work differ from vul- 
canite teeth in having gingival extensions resembling roots. 
These extensions are flattened somewhat on their lingual sur- 
faces to obviate excessive grinding in aligning the teeth on 
the baseplate. 
These root extensions serve two very useful purposes; 
first, being composed of high-fusing porcelain which is unaf- 
Fig. 469.— A Set of No. 28, Continuous Gum Teeth (Justi) 
Fig. 460.— A Set of No. 14, Continuous Gum Teeth, Molar, Central, and Bicuspid, Turned to 
Show Long, Single Pins. (S. S. W.) 
fected by contractile changes during vitrification of the con- 
tinuous gum body, the bulk of the latter required for the case 
is materially lessened, and shrinkage of the denture mass is 
proportionately reduced; second, in addition to the long pin 
attachment of the tooth to the baseplate, the extension serves 
to increase stability by resting upon the baseplate, thus ob- CONTINUOUS GUM DENTURES 
597 
viating the danger of displacement due to contraction of the 
body during baking. 
When but slight absorption of the ridge has occurred, it 
is frequently necessary to grind away a portion or all of the 
extension, thus bringing the body of the tooth directly in 
contact with the baseplate, much as the ridge lap of an ordi- 
nary vulcanite tooth is frequently set in contact with its base- 
plate, or sometimes upon the cast itself. 
In other cases when excessive absorption of the ridge has 
occurred and the correct labial, buccal and occlusal align- 
ment of the teeth have been secured, these extensions may 
fail to touch the baseplate at any point. It then becomes nec- 
essary to interpose blocks of high-fusing porcelain, as pieces 
Fig. 461.— Case Requiring Considerable 
Reduction of Lingual Side of Root 
Fig. 462.— Case Requiring Adjustment of 
Broken Pieces of Porcelain Between 
Teeth and Baseplate 
of broken teeth, between the baseplate and the extensions not 
in contact, or to truss them in proper position with platinum 
wire or plate. In addition to the difference in form noted, con- 
tinuous gum teeth are supplied with single platinum pins, 
larger and longer than those ordinarily used in other types of 
teeth. 
SELECTION AND ARRANGEMENT OP TEETH 
Teeth of suitable form, size and shade to meet the require- 
ments of the case having been selected, they are let within 
the wax rim by successively cutting out sections of the latter 
of sufficient depth to permit each tooth, with its extension, 
to assume proper alignment. No attention need be given the 
relation of the extension end of the tooth to the baseplate 
during arrangement, except when its length or lingual surface 
interferes with correct placing of the tooth, when it may be 
reduced by grinding, or entirely excised, as conditions require. 598 
CONTINUOUS GUM DENTURES 
The steps of arrangement and occlusion of full upper and 
lower cases of this type are carried out in other respects the 
same as for full dentures in general. When the teeth are 
occluded the denture should be waxed up labially and buccally 
to represent the natural gums, with such added contour as 
may be required for facial restoration. This step is seldom 
carried out, but more esthetic results can be produced by fol- 
lowing this plan than by developing the contour without defi- 
nite guidance. 
TRIAL OF THE WAX MODEL DENTURE IN THE MOUTH 
When properly contoured, the denture is tested in the 
mouth, first as to normal occlusion; second, as to clearance 
paths in lateral movements; third, balancing contact; and 
fourth, general esthetic results. When corrections have been 
made, if necessary, and the prosthetist is satisfied that all re- 
quired conditions have been fulfilled up to this stage of con- 
struction, the next step is to prepare a guide for testing the 
labial and buccal contour of the case at various stages of 
construction. 
DEVELOPING THE CONTOUR MATRIX 
The entire labial, buccal and palatine surfaces of the wax 
model denture are now coated with a thin film of oil, a mix 
of plaster made, and a cast of ordinary form developed by 
Fig. 463.— Four-Piece Matrix for Lower Denture. All Parts in Correct 
Apposition, the Denture Having Been Removed 
filling in the palatine and border surfaces of the baseplate. 
This cast should be about % inch thick in the vault region, 
or sufficiently deep to raise the peripheral margins of the 
baseplate about one-fourth inch above the base of the cast. 
The sides of the cast should be trimmed smooth, converging 
slightly from the base upward, to the outer peripheral line of 
the wax. At several points on the labial and buccal surfaces 
of the cast, shallow countersunk depressions are made to CONTINUOUS GUM DENTUBES 
599 
develop projections on the several sections of the labial and 
buccal matrix. This is necessary in order that any section of 
the matrix may be returned to position independently of the 
other pieces. The side of the base is varnished with shellac, 
which, when dry, is coated with a thin film of oil. 
Plaster is now applied to one of the buccal surfaces and 
built against the base of the cast, the wax and outer surfaces 
of the teeth. It should not extend over the buccal marginal 
ridges or incisal edges of the teeth. This first section includes 
the area from the tuberosity back of the second molar to the 
middle of the cuspid tooth. It should be about three-eighths 
Fig. 464.— Four-Piece Matrix for Lower Case, Used for Testing Contour of Case During Con- 
struction Stages, Partially Separated 
of an inch in thickness, its outer surface parallel with the buc- 
cal surface of the cast base and denture. When hardened the 
anterior end of this first section is squared up, varnished and 
oiled. 
Another mix of plaster is now applied to the incisal area, 
building against the squared end of the first section and ex- 
tending to the opposite cuspid tooth. When set, this section 
of plaster is trimmed, varnished, oiled, and the third piece cor- 
responding to the first on the opposite side is constructed. 
When the plaster has set the three sections are tapped 
slightly to loosen, then removed, and the wax model denture 
is detached from the cast. These are now set aside until after 
the application of the body in the second baking, when the 
baseplate is returned to the cast and the several labial and 
buccal areas are tested as to required fullness, or excess of 
applied body, by returning each section to position against 
the cast base. By sawing partly through any section at one or 
more points, cutting from without inward, it may be cleanly 
fractured into any number of required pieces, any one of 
which may be used for test purposes over its own particular 
area. 600 
CONTINUOUS GUM DENTURES 
It is possible by calipering a number of prominent areas 
of the waxed case, and recording the same, to arrive at com- 
paratively accurate results in the disposition of the gum body. 
The time required for measuring, recording, and later for 
reference, usually aggregates more than that required for 
forming a matrix, while the latter when suitably fractured will 
determine quickly the accuracy of many gingivo-peripheral 
surface contour lines. 
These various steps having been completed, the case is 
now ready for investment, preparatory to attaching the teeth 
to the baseplate. 
INVESTMENT OF THE WAX MODEL DENTURE 
In continuous gum cases the teeth must be rigidly attached 
to the baseplate by soldering and trussing to prevent their 
relation, as established in the wax rim and by trial in the 
mouth, from becoming distorted by the contraction of the 
porcelain while fusing the latter. The steps are carried out 
as follows: 
The wax representing the labial and buccal surfaces of 
the gums is removed from these areas and from between the 
embrasures and root extensions as well, so as to permit the 
investment to partially surround and hold the teeth when 
lingual support is removed. A mix is made of some standard 
investment material which possesses considerable hardness 
when set. A portion of the investment, about one-half inch 
Fig. 465.— Continuous Gum Teeth Arranged on 
Platinum Baseplate. Wax Removed from 
Embrasures to Allow Investment Ma- 
terial to Enter These Spaces 
thick and a little larger than the area of the baseplate, is 
placed on a sheet of paper on the bench. Another portion is 
filled in the palatine side of the platinum base and the latter 
pressed down upon that resting on the paper, until it ap- 
proaches within three-eighths of an inch of the bench. The 
investment is then worked into the embrasures and over the CONTINUOUS GUM DENTURES 
601 
occlusal and incisal surfaces of the teeth. To resist the more 
or less rough usage it will receive in applying the truss bars 
and soldering, the investment should be about three-eighths 
of an inch thick through the side walls. All overhanging por- 
tions should be removed from the occlusal and incisal surfaces, 
Fig. 466.— Teeth and Baseplate Invested. Wax Removed from Lingual 
Areas 
to permit of ready access in bending tlie pins and soldering 
them to the truss or baseplate. 
When hardened the rough excess of investment is trimmed 
away, the wax surrounding the lingual surfaces of the teeth 
in which the pins are imbedded is thoroughly warmed and 
removed — care being taken not to dislodge the teeth — the 
final trimming of all excess investment accomplished and the 
case thoroughly cleansed with a stream of hot water. 
FITTING AND APPLICATION OF THE METAL SUPPORT TO THE TEETH 
Occasionally cases present where the long pins of the con- 
tinuous gum teeth can be directly applied and soldered to 
the platinum baseplate in such manner as to give all necessary 
support to the teeth. More frequently, when much absorption 
of the border has occurred, it is necessary to extend some kind 
of metal support from the border crest to the angle of junction 
of the pins with the porcelain. The Allen method, although 
not the best, is most frequently resorted to, and is as follows: 602 
CONTINUOUS GUM DENTURES 
The platinum pins are straightened out at right angles 
to the long axes of the teeth. A strip of cardboard about four 
inches long is cut like the illustrated pattern, subject of 
course, to such modifications of form as the slant from the 
Fig. 467.— Invested Case Showing Pins Raised So Supporting Truss May 
Be Fitted 
border to the pins and to the varying width of the space be- 
tween the same at different points. (See cut on page 603.) 
This cardboard pattern is corrected by trial, and recon- 
structed if necessary, until when finally fitted it exactly repre- 
Fig. 468.— Sectional View of Tooth, Baseplate 
Metal Support and Investment 
sents the form of metal strip to cut for the proper support of 
the teeth. The pattern as shown usually represents the seg- 
ment of an ellipse. A metal duplicate of 30 or 31 gauge iridio- 
platinum plate is now made and bent to place. Marks are now 
made at various points on its lingual surface between the 603 
CONTINUOUS GUM DENTURES 
teeth, to indicate the position for punching the holes, the idea 
being to so place the holes that the pins when bent and sol- 
dered to the strip will not close them. The holes, usually about 
ten or twelve in number, should be located about midway be- 
tween the border crest and the pin margin of the strip and 
Fig. 469.— Paper Pattern of Metal Support for the Teeth 
should be about one-sixteenth of an inch in diameter. At 
various points along the margin which rests on the border, 
crescent-shaped notches are cut in the strip. Through these 
various openings the labial and buccal portions of porcelain 
become more or less firmly united and under stress of masti- 
Fig. 470.— Metal Support, Trimmed to Fit, Adapted and with Holes 
Perforated 
cation splitting of the denture is not so liable to occur as is the 
case when the openings are omitted. 
It will readily be seen that a support so formed mechani- 
cally divides the denture into two portions, and is therefore 
a source of weakness, which after construction of the case, can- 604 
CONTINUOUS GUM DENTURES 
not be overcome. More recent and better methods will be 
shown for trussing and holding the teeth in position. 
The holes having been punched and the notches cut as 
described, the strip is returned to position and the pins bent 
Fig. 471.— Pins Bent Closely to Metal Support. Case Ready for 
Soldering 
down in contact with it, and the baseplate also if the space is 
not too wide. 
The invested case is now placed on a Bunsen stove to 
thoroughly dry and become heated. Medium fusing platinum 
Fig. 472.— Section Showing Pin Adapted to Metal Support, 
and, in This Case, to the Baseplate as Well 
solder is cut in small pieces preparatory to the final union 
of the many parts. When thoroughly heated, the invested 
case is placed on a solder block in such position that gravity 
will retain the solder in position in certain areas to which 
it is now applied. The nitrous oxid and gas blow-pipe previ- CONTINUOUS GUM DENTURES 
605 
ously mentioned is now directed on the solder placed, and 
when fused the position of the case is changed. The process 
is repeated until all of the teeth are firmly united to the strip 
and the latter to the baseplate. The use of excessive amounts 
of solder should be avoided, as it only increases the weight 
of the denture without materially adding strength. 
Pure gold is often used as a solder in this class of work, 
and while commonly safe, there is danger of it being absorbed 
by the platinum and the joints becoming disconnected. 
In all soldering operations of the class under considera- 
tion, certain essentials should be kept in mind. These may 
be summarized as follows: 
Close, clean joints. 
Strong, yet not too bulky, investment. 
Plenty of preliminary, as well as blow-pipe, heat. 
Small pieces of platinum solder laid just where 
they are needed. 
Avoid the use of too concentrated or long-continued 
flame on any one tooth. 
Depend on gravity for retaining and carrying the 
solder in position when fused. 
Avoid the use of flux, since the metals do not oxi- 
dize and its presence, if allowed to come in contact 
with the porcelain at high temperatures, is certain 
to check the latter. 
SUPPORTING THE TEETH WITH WIRE 
When the distance between the border crest and the pin- 
porcelain junction of the teeth does not exceed one-fourth of 
an inch, a No. 18 gauge iridio-platinum wire can be bent as 
shown in the illustration (see Fig. 473, page 606), to afford a 
comparatively rigid support for the teeth, while the tendency 
to divide the porcelain into an outer and inner portion is ob- 
viated, or at least greatly reduced. The technic of application, 
fitting and trying is so simple that it need not be here detailed. 
When the amount of border absorption is excessive and the 
teeth must of necessity be raised a considerable distance from 
the baseplate, the following plan can be adopted. 
Two wires of 16-gauge iridio-platinum are bent to con- 
form to the arch. One is laid on the border crest, not neces- 
sarily in close contact, but touching, the baseplate at the distal 
extremities and at several intermediate points. The other 
wire is beut to lie in close contact with the pins and porcelain 606 
CONTINUOUS GUM DENTURES 
at tlieir junction. The extremities of this wire are carried 
from the pins of the second molar in a sloping direction, down 
alongside of, and in contact with, the wire on the border crest. 
Fig. 473.— Wire Truss, Corrugated to Support 
Teeth 
Five or six iridio-platinum posts are now cut and fitted 
so as to reach from the baseplate to the wire under the pins. 
They should also touch the wire on the border crest. The 
pins are now bent around the upper wire and the frame-work 
when soldered forms a rigid truss, capable of withstanding 
all ordinary strains. 
Fig. 474.— Extensive Truss Built to Support Teeth 
When Border Is Badly Absorbed 
In these cases of excessive absorption, the teeth are fre- 
quently so placed that their cervical extensions do not touch 
the baseplate, nor can the border wire of the truss at all times 
be bent in such manner as to afford them necessary support 
without reducing the efficiency of the truss. CONTINUOUS GUM DENTURES 
607 
By blocking in the space between the baseplate and the 
porcelain roots with broken pieces of old porcelain teeth, or 
even whole teeth, so placed as not to interfere with proper 
contouring of the gum body, the danger of distortion in fusing 
is obviated. The presence of the blocks of high-fusing porce- 
Fig. 476.— Case of Trussed and Blocked Teeth, 
Ready for Application of Body 
lain is not in the least objectionable, but rather an advantage, 
since the bulk of gum body required will be proportionally 
reduced. The soldering of the wires is carried out in a man- 
ner similar to that followed in attaching the teeth by means 
of the metal strip. (See Figs. 462 and 475.) 
When the teeth, by whatever method adopted, are attached 
to the baseplate, the investment is allowed to cool. It is then 
Fig. 476.— Case Soldered Ready for Application 
of Continuous Gum Body 
placed in water to soften and finally carefully removed so as 
not to disturb the position of the teeth. The latter, although 
firmly fixed to the truss bar or strip by the pins, can be rotated 
or bent under stress until rigidly fixed by fusion of the first 
application of body. 608 
CONTINUOUS GUM DENTURES 
In some cases it may be advisable after soldering to try 
the skeleton denture in the mouth to test the occlusal relations 
of the teeth. Frequently some slight change, as rotating a 
tooth or modifying its axial alignment at this time will obviate 
what might later on prove a glaring defect. 
The skeleton denture is now boiled in dilute HC1, thor- 
oughly washed and the palatine and outer surfaces of the 
platinum base roughened by passing a sharp-pointed blade 
over them in various directions to afford some slight hold for 
the porcelain. The case is now ready for the application of 
the continuous gum body. 
Continuous Gum Body and Enamel 
Under the description of porcelain on page 904 will be 
found the general formulae of continuous gum body, and gum 
enamel. These materials, supplied by the manufacturers for 
denture construction, come in powder form, usually in one- 
ounce packages. They are commonly referred to as body and 
enamel. The body is almost white in powder form; during 
fusion it assumes a yellowish tint much resembling dentin. 
The enamel is a delicate pink, which on fusing assumes 
varying shades ranging from almost imperceptible pink to a 
pinkish purple, depending on the thickness of the layer and the 
amount of heat applied. 
The body supplies the necessary bulk and contour to the 
case, and is usually applied and fused two times. The enamel 
supplies the color and is fused once, although at times two 
applications are necessary. 
PREPARATION OF THE BODY 
As a preliminary requirement in successful porcelain work 
the strictest care as to cleanliness must he observed. This 
includes clean hands, instruments, materials and a room free 
from dust. 
About one-half the contents of the box of body is placed 
upon a flat glass or porcelain slab four inches square, or even 
larger. With a drop tube sufficient distilled water is added 
to the powder to make a medium plastic mass. 
The specific gravity of titanium oxid is 4.2; of silex, 2.66; 
and of kaolin, 2.6. It is apparent that in a thinly-fluid mix 
of body the coloring matter will gravitate below the other 
ingredients if much time elapses before taking up the surplus 
moisture. While the quality of such mass when fused may not CONTINUOUS GUM DENTUKES 
609 
be impaired it will not be of exactly uniform color. To avoid 
separation of the constituents mentioned the pasty mass 
should be thoroughly spatulated and the excess moisture ab- 
sorbed by immediately pressing a clean linen towel or napkin 
over it. 
APPLICATION OF THE BODY TO THE TEETH AND BASEPLATE 
With a moderately broad spatula the body is applied to 
the lingual surfaces of the teeth, and vibrated to position by 
Fig. 477.— Manner of Holding Case to Prevent Porcelain Paste Flowing 
Through Interproximate Space When Applying It to Base 
drawing a knurled instrument against the side or back of the 
baseplate. 
The skeleton denture should be held by placing the thumb 
against the peripheral rim or within the maxillary portion of 
the baseplate and the index finger on the occlusal surfaces of 
the teeth. Now, by applying the middle finger against the 
buccal surfaces of the teeth and extensions and holding the 
baseplate edgewise the body will be prevented from dropping 
through the open spaces. The excess moisture which is forced 
out by the settling of the granules together is taken up with 610 
CONTINUOUS GUM DENTURES 
the napkin and another mass of body applied in like manner 
until the greater bulk of lingual contour required is developed. 
It will be found most convenient to apply the bulk of body 
to the lingual space in three sections; first, from the cuspid 
to the tuberosity on one side, vibrating and absorbing the 
moisture; second, from cuspid to cuspid incisally; third, 
from cuspid to tuberosity on the opposite side. Each addi- 
tion as it is applied and vibrated to place should be relieved 
of the surface moisture. In dentures requiring excessive 
restoration, it sometimes becomes necessary to further elim- 
Fig. 478.— Condensing the Body with Carving Tool 
inate tlie moisture by passing the case a few times rapidly 
through the Bunsen flame, to prevent the flowing of the 
adapted body while vibrating subsequent additions to place. 
Should further additions of body to areas which have been 
rendered comparatively dry be necessary, such areas should 
be moistened before making the addition, so that the two will 
intimately unite. When this precaution is neglected, the com- 
paratively dry body will absorb the moisture from the mass 
last added so rapidly that the latter cannot be vibrated into 
a dense, compact state. 
The lingual contour is developed roughly to approximately 
the required thickness of the finished case, as are the labial CONTINUOUS GUM DENTURES 
611 
and buccal surfaces also. Care should be taken to avoid excess 
of material in any area, for if present in excess, removal by 
grinding would be necessary, while any deficiency may be 
corrected in the second application of the body. 
Fig. 479.— Body Applied Ready for Division Before 
Baking 
The denture should be brushed free from all particles of 
the body that may be lodged upon the platinum baseplate or 
the teeth where not actually required, as during fusion they 
will become firmly attached to either platinum or teeth and 
must subsequently be removed with discs. 
Special care should be given to the exposed portion of the 
Fig. 480.—• The Case Ready for First Baking. Con- 
tinuous Gum Body Divided with Thin 
Blade Instrument 
teeth to see that proper gum curvature is outlined. Dr. L. P. 
Haskell recommends for this purpose an ordinary quill tooth- 
pick sharpened to a neat, smooth blade-like point. A delicate 
spatula will answer the same purpose. This step is followed 
by applying a delicately pointed camel’s-hair brush, moistened 612 
CONTINUOUS GUM DENTURES 
first, afterward drying and removing every particle of body 
not required from the gingival curvatures. 
Since porcelain contracts from one-sixtli to one-fifth its 
bulk in vitrifying when applied in the manner described, un- 
less preventive measures are used, the teeth are liable to be 
warped out of position from the contraction of the material 
between and around the root extensions. To obviate this diffi- 
culty, a thin spatula should be passed through the body to the 
baseplate on both external and vault surfaces. Each tooth 
previously fixed by its pin to the truss or stay wire thus be- 
comes a fixed center toward which the body composing that 
section will contract. 
The case should finally be inspected to see that all sur- 
faces are free from excess material before introducing in the 
furnace. 
SUPPORTING CONTINUOUS GUM CASES WHILE FUSING 
To obviate danger of warpage of the denture during bak- 
ing, it must be supported at widely divergent points. One of 
the most convenient methods consists in bending a 16-gauge 
platinum wire in the form of a V, bending the angled end and 
Fig. 481.— Case Ready for Second Bake. Sup- 
ported on Platinum Wire Tripod 
the two terminals upward so as to form three legs of sufficient 
height to raise the denture clear of the muffle slab. The two 
terminals support the case at the tuberosities, and the angular 
leg anteriorly. These three points of contact give uniform 
support to the case at all times and effectually prevent warp- 
age. 
This form of support is also of advantage because it does 
not absorb the radiated heat as does a support composed of 
fibre asbestos and investment material commonly employed. 
In case a support of the latter class is used, it should be re- 
duced to the smallest possible dimensions consistent with 
strength. CONTINUOUS gum dentures 
613 
Porcelain Furnaces 
Electric furnaces of various types are almost universally 
used at the present time for the fusing of porcelain in pros- 
thetic procedures. The Custer and the Hammond represent 
Fig. 482.— Denture in Position. Electric Furnace (Custer Type). Platinum Wire for 
Supporting Denture on Furnace Table 
two of the most serviceable forms, although there are others 
almost, if not quite, equally as dependable. 
The principle involved in the generation of heat depends 
upon the resistance offered by a fine platinum wire to the 
passage of a current of electricity. When a 110-v. current of 
low amperage is passed through a 28-gauge wire the resist- 614 
CONTINUOUS GUM DENTURES 
ance offered to the passage of the current is manifested by 
the wire becoming heated to high temperature of varying de- 
grees, depending on the length of wire and the time of current 
flow. 
When a conductor offers resistance to the passage of a 
current to such an extent that heat is manifested, the voltage 
of the current is reduced. By interposing outside resistance, 
as a rheostat in which the resistance can be gradually reduced 
Fig. 483.— Electric Furnace for Continuous Gum Cases. Floor Raises or Lowers by Counter- 
poised Weight 
or entirely cut out, the amount of heat generated within the 
furnace is easily controlled. This is an important advantage 
in the fusing of porcelain, for if heated too rapidly, bulky 
pieces contract unevenly, while the quality of the fused prod- 
uct is impaired. 
Time is a most important factor in the fusing of porcelain. 
Practically all of the high-fusing bodies, with the exception 
of tooth bodies, can be fused under 2,000 deg. F. if subjected 
to long continued heat. The quality of porcelain so fused is 
denser and its color better than when subjected to rapid fusion. CONTINUOUS GUM DENTURES 
615 
However, very satisfactory results may be secured by adopt- 
ing the plan of fusing at a temperature about midway between 
the lowest possible point of vitrification and that required for 
the shortest time for the particular body used. 
FIRST BAKING OF THE CONTINUOUS GUM CASE 
The case is now introduced into the furnace, teeth upward, 
and placed on its support. The latter, whether of wire, as 
suggested, or composed of investment materials, should rest 
on a fire-clay slab to afford protection to the slightly imbedded 
furnace wires. This is necessary to obviate short circuiting of 
the current, and also to prevent any small flakes of porcelain 
which might become detached from falling to the furnace floor 
and there fusing to the fire-clay lining, or over the nearly 
exposed wires. 
The muffle is closed, the rheostat arm set on the first but- 
ton and allowed to remain there a sufficient time to expel all 
moisture. This usually requires from 8 to 10 minutes. If 
this step is crowded too rapidly, the body will flake off as a 
result of the sndden generation of steam within the mass. 
Several methods are in vogue in the baking of porcelain, 
any one of which will give good results if carefully carried 
out. The following method, and one preferred by the writer, 
is to gradually increase the temperature in uniform steps as 
follows: 
When the moisture has been expelled, which can readily 
be seen by the chalky appearance of the case, the rheostat arm 
is moved from first to second button, where it is allowed to 
remain until the maximum heat of that section is developed. 
This usually requires from 15 to 20 minutes. The arm is now 
moved on, allowing five-minute interval between each change. 
In extra-bulky cases each interval may be safely extended one 
or two minutes longer. 
With a new or strange furnace, preliminary tests should 
always be made to determine the length of time required, and 
the particular button at which fusion will occur. The time 
of fusion will vary somewhat with the intensity of the current 
and various other conditions. If in a position where a strong 
draft of air strikes the furnace fusion is retarded. 
The body should not be glazed during the first baking, but 
carried to the point of fusing the most fusible ingredients, yet 
stopped before the granular surface is entirely lost. This 
stage is called “biscuit bake.” It presents a semi-granular, 616 
CONTINUOUS GUM DENTURES 
yet partially glazed appearance, while the porcelain is dense 
and darkened. 
When the fusing stage is reached the interior of the fur- 
nace and contents present a bright red appearance, so that it 
is sometimes difficult at first to distinguish the outlines of 
the case. By carefully viewing the buccal surfaces of the 
denture in line with the back of the furnace, the roughly gran- 
ular surface can be seen to gradually disappear. The fusion 
should be stopped at this stage by reversing the rheostat arm, 
opening the switch and allowing the case to cool. If removed 
and cooled suddenly, fracture of the porcelain is almost cer- 
tain to occur. 
SECOND BAKING 
The gum body should now be freshly spatulated, adding 
water and absorbing it as previously described. The case 
is first dipped in cold water, the surplus shaken out, fresh 
body applied to the fissures purposely formed before the first 
baking and all others that may have developed in any location 
from contraction in baking. The body should be actually com- 
pressed in these fissures, when possible, to reduce to the mini- 
mum the slightly greater contraction that must occur over 
these areas than will be noticeable where the freshly added 
material is thinner. 
The case should now be developed to full contour on all 
surfaces and the labial and buccal areas tested with the con- 
tour matrix previously formed. If deficient, more body should 
be added, and if too full the amount reduced as required. 
Palatine rugse should be developed somewhat stronger than 
the natural marking, as some detail will be lost in fusing. 
Again, all surplus body must be carefully brushed from 
the teeth and baseplate, the moisture expelled, and the case 
returned to the furnace for the second baking. This step 
is carried out as before, except that less time is required 
on first button — usually about 10 minutes, and the fusion 
stopped at the semi-granular stage. Since time of exposure 
to heat is an important factor in fusing porcelain, care must 
be taken not to over-fuse the case. 
In the second baking the body last applied is not alone 
affected. That first fused is also advanced from the biscuit 
to the glazed stage. It also contracts to a very slight extent, 
although the greatest contraction has previously occurred in 
the first fusing. CONTINUOUS GUM DENTURES 
617 
When the second application of body has been biscuited, 
fusion is stopped as in the first baking and the case allowed 
to cool, when it is ready for the third bake. 
PREPARATION OF THE CASE FOR THE THIRD BAKING 
The case should now be thoroughly inspected for fissures 
that may have formed during the last baking. These usually 
are found at the junction of the body with the lingual surfaces 
of the teeth, and around the periphery of the base, although 
they may occur in any location. When not extensive they may 
be filled with another mix of the gum body and the case enam- 
eled. The overlying enamel, although not requiring a tem- 
perature for fusion sufficiently high to fuse the body last 
added, will intermingle and unite with it to form a compact 
mass. 
APPLICATION OF THE GUM ENAMEL 
The gum enamel is now mixed with water, spatulated, and 
the surplus moisture absorbed as in the preparation of the 
body. It is applied to the case in a thin uniform layer about 
1-32 of an inch thick. Since slight variation in shade of the 
pink enamel is desirable in the finished case, this effect may 
be produced by varying the thickness of the layer of enamel 
as it is applied. Care should be taken to distribute it uni- 
formly over the rugae and avoid filling in the depressions be- 
tween the ridges, the tendency being for it to settle into de- 
pressed areas. By pressure and burnishing, the gum enamel 
while slightly moist can be distributed and condensed so that 
when fused it will display a very lifelike color. Since it is 
almost transparent if not applied in sufficient thickness, the 
enamel when fused will frequently present an anaemic and 
unsightly appearance. On the other hand, if applied too 
thickly, the color will be abnormally dark. 
Particular attention should be given the gum festoons to 
have them of proper curvature and distinctly developed. 
Every particle of surplus should be swept clear of exposed 
tooth surfaces, the baseplate, and from the lingual, labial and 
buccal embrasures, where its presence as a pigment would 
prove unsightly. 
Briefly summed up, the teeth should stand out clean and 
prominent, the gum festoons and other surface markings 
should be sharply, or at least plainly, defined, and the base- 
plate free from all adherent particles. 618 
CONTINUOUS GUM DENTURES 
The moisture is now gradually evaporated by passing the 
case through a current of heated air above a Bunsen flame, 
in preference to placing in the furnace to dry, so that if any 
of the gum enamel flakes off in drying it may be corrected 
before baking. 
FUSING THE ENAMEL 
The denture is now introduced into the furnace and heat 
applied as before. Gum enamel fuses at a considerably lower 
temperature than gum body, so when the furnace becomes 
well heated the case should be watched very closely to avoid 
overfusing and bleaching the color. 
The enamel should be perfectly glazed so that it may easily 
be kept clean, will look well, and not prove irritating to the 
mucous tissues as a result of roughened surfaces. 
Being able to distinguish the outlines of the denture when 
in the furnace and highly heated, and to determine the in- 
stant when the enamel is perfectly glazed, is one of the essen- 
Fig. 484.— Occlusal View of Finished Case. Slight Sug- 
gestion of Rugae 
tial points in porcelain technic, and comes only with experi- 
ence and careful observation. 
When fused, the current is shut off, the furnace opened, 
and the case examined to see that glazing has been accom- 
plished. If satisfactory, the furnace is closed and the denture 
allowed to remain within until perfectly cold. Sudden chill- 
ing or drafts of cold air striking the porcelain when heated 
will almost certainly check it, sometimes in a very unsightly 
manner. CONTINUOUS GUM DENTURES 
619 
FINISHING THE DENTURE 
The enamel surfaces, if properly fused, require no finish- 
ing. The peripheral margins, palatine vault of the platinum 
base, and the lingual surface of the doubler are first polished 
as in gold denture construction with felt wheels and pumice 
stone, following with the finer powders. 
The fact should be kept in mind that when porcelain bod- 
ies are brought to a state of fusion, continued heat, even 
though the temperature is not elevated, will gradually render 
Fig. 485.— Labial View of Finished Denture 
them glasslike, friable, porous, bleach the color, and render 
them weak and devoid of usefulness for prosthetic restora- 
tions. Much better and more certain results, therefore, can be 
attained by subjecting the case to only three bakings — two 
for the body and one for the enamel — than are possible when 
a greater number of bakings are required. 
Special Uses of Porcelain 
Oftentimes in the construction of dentures for partial 
cases some of the spaces to be supplied with teeth are in a 
conspicuous position. When but slight absorption of the 
ridge has occurred, plain teeth may be neatly fitted against 
the natural tissues in such manner as to escape detection. 
This may be done by first grinding the ridge lap of each tooth 
to conform to the irregularities of the ridge, and afterward 
paring away on the cast the area on which it rests. This step 
advances the teeth slightly beyond the palatine and border 
surfaces of the baseplate, so that with use they become 
slightly imbedded in the tissues and thus present about the 
same appearance as do natural teeth surrounded with their 
gingivae. 
INTSRSTITIAL BLOCKS OF PORCELAIN 
When two or more contiguous teeth are missing and they 
are replaced by plain teeth without gum restoration, it is fre- 620 
CONTINUOUS GUM DENTURES 
quently difficult to obviate the display of vulcanite in the em- 
brasures of the artificial teeth. 
Recently there has been placed on the market Fogg’s in- 
terstitial porcelain blocks, which, when properly applied, over- 
come the difficulty mentioned. These pieces of porcelain are 
Fig. 486.— Fogg’s Interstitial 
Gum Blocks 
wedge-sliape in form and slightly concaved on their mesial 
and distal areas to embrace the proximating surfaces of the 
teeth. Their exposed surfaces are overlaid with pink gum 
enamel. 
By selecting blocks of suitable length and grinding their 
proximating surfaces, as well as those of the teeth, these 
points may be so nicely adjusted that they have the appear- 
Fig. 487.— Fogg’s Interstitial Blocks 
Applied in Embrasures 
ance of natural gum tissue in the embrasures. They are 
ground and fitted in position before flashing the case, invested 
as though a part of the teeth, and become firmly attached by 
means of the flowing of the vulcanite in closing the packed 
flask. 
GUM SECTIONS 
Gum section teeth, either single or in blocks, can often be 
used to advantage in partial cases, particularly when border 
absorption is marked. 
By grinding the margins of the block to a thin edge where 
it joins the gum tissue, very natural restoration of the lost 
gum tissue can be accomplished. The block should be reduced 
at the expense of the lingual or border side, since if reduced 
from the labial or buccal margins the pink enameled surface CONTINUOUS GUM DENTURES 
621 
is destroyed and a light colored line of demarcation shows at 
the junction of the block with the soft tissues. 
Gum section teeth are used to a limited extent only, at the 
present time, in full cases because of the difficulty in develop- 
Fig. 488.— Gum Block of Three Teeth 
ing anatomic relations. Oftentimes when care is used in con- 
structive steps and the condyle path pitch is not excessively 
steep, most esthetic results may be secured with gum section 
teeth combined with vulcanite or gold and vulcanite bases. 
Fig. 489.— Set of Fourteen Gum Section Teeth Before Grinding. (Justi) 
Fig. 490.— Set of Twenty-Eight Gum Section Teeth. Joints Ground 
and Teeth Occluded. (S. S. W.) 622 
CONTINUOUS GUM DENTURES 
They are very useful in partial cases in the replacement of 
teeth in conspicuous positions. 
It is sometimes difficult to secure porcelain sections for 
special cases other than the usual three-tooth anterior and 
two-tooth posterior stock blocks. Stock blocks are frequently 
applicable when the number of teeth they include corresponds 
to, or is greater than, the number of teeth to be replaced in 
the space, the extra teeth being easily cut away, but unfortu- 
nately the loss of teeth does not occur with regularity. For 
example, two centrals and a lateral may be missing, or a 
cuspid and two bicuspids. In these and many other cases, 
stock blocks will not fulfill the requirements without the use 
of two blocks and the grinding of a joint. 
Construction of Gum Blocks for Special Cases 
Various methods have been suggested for baking single 
blocks to meet the requirements of unusual cases, but because 
of the friability of blocks so formed, few undertake their con- 
struction. Dr. Walter M. Bartlett of St. Louis lias produced 
some very artistic work in this line, and by a comparatively 
simple method of technic. His method is practically as fol- 
lows : 
An impression is secured from which a plaster cast is 
derived. Plain vulcanite or ordinary long pin facings are 
Fig. 491.— Two Plain Teeth Adapted to Platinum Foil- 
Covered Cast Ready for Application of Gum Body 
selected and ground, when necessary, to bring them in proper 
alignment in the usual manner. The teeth are now removed 
and a piece of platinum foil is burnished to the cast over the 
area to be covered by the block. The foil base should be so 
formed as to be easily released from the cast without distor- 
tion. When properly adapted and trimmed to suitable outline, 
it is retained on the cast until the model block is formed. CONTINUOUS GUM DENTURES 
623 
The teeth are now returned to the cast and wax flowed 
between them and the foil to hold them in position. The 
future block is now modeled in wax to the exact outline de- 
sired, and when hardened, the teeth, wax and foil are removed 
as one piece. Care should be taken to avoid covering the pins 
of the teeth with the wax, since in introducing the porcelain 
paste it will fill all spaces caused by the removal of the wax, 
and the pins would thus be obscured. 
The block is now invested, pins and border side down, in 
tenax. The investment should be as small as possible to be 
consistent with strength. When set, the wax is thoroughly 
removed with hot water, and continuous gum body, or the 
regular high fusing crown and bridge porcelain, is filled into 
the space between the foil and the teeth. The gum is now 
carved to the desired contour and the entire case carefully 
dried, when it is ready for fusing. 
In simple cases one application and baking of the body 
will be all that is required, the slight shrinkage which occurs 
being compensated for and covered over by the layer of 
enamel which follows. 
When fused, if much contraction of the body has occurred, 
a second application should be made and fused, followed by 
the application and fusing of the gum enamel. 
By scraping the cast slightly around the periphery of the 
gum block, so that the latter may fit the tissues closely, and 
Fig. 492.— Case Baked. Labial View. Block Constructed 
for Special Case. (Dr. G. W. Schwartz) 
by bringing the body and enamel to a gradual rather than an 
abrupt termination around the margins, the block when fitted 
in place in the mouth can be scarcely distinguished from the 
natural teeth and tissues. 
The platinum foil is now peeled off and the sharp margins 
of the periphery removed with fine discs, when the block is 
ready for use. 624 
CONTINUOUS GUM DENTURES 
Another method consists in swaging a thin plate of plat- 
inum in the form of a saddle, to cover the ridge and serve as 
a foundation for the hack of the gum portion. To this saddle, 
long pin facings are soldered and additional attachments 
Fig. 493.— Platinum Base with Long Pin Teeth Attached 
for Reception of Porcelain Body 
added for vulcanite anchorage, when advisable. The porce- 
lain is applied and baked as in the previous case. By this 
method the platinum is not removed, but becomes a part of 
the section. CHAPTER XXVII 
GROWN WORK 
Preliminary Considerations 
When through accident, or as the result of caries, the 
crown of a natural tooth has been impaired so that operative 
procedures will not fully restore it to usefulness, an artificial 
crown, when conditions are favorable, can be constructed to 
replace it. Oftentimes the perfectly formed natural crown 
of a healthy tooth is reduced in size, or entirely removed, and 
an artificial substitute placed over it or on the root, to serve 
as an abutment or pier for a bridge. 
Such a procedure, when necessary, is considered good 
practice and justifiable in well-selected cases, the benefits in 
improved masticatory function and esthetic appearance re- 
sulting from the replacement of missing teeth, more than 
compensating for the sacrifice of the natural tooth crown. 
The successful crowning of teeth requires a thorough 
knowledge of several correlated subjects, viz., histological 
and physiological structures of the teeth and tissues involved; 
oral pathological conditions; therapeutic methods of treat- 
ment of diseased conditions; anatomic and esthetic forms of 
the teeth; hygienic requirements of crowns; technical pro- 
cedures. ; i . ! i i! ,i 
Structures of the Tfeth and Investing Tissues 
The grosser structures of which a tooth is composed are 
as follows: 
Dentine, which constitutes the larger portion of both 
crown and root, and within which the pulp chamber is sit- 
uated. 
Enamel, which envelops the crown portion of dentine, and 
gives the crown its anatomic form. 
Cementum, which covers the root portion of dentine, and 
furnishes attachment to the fibres of the peridental membrane. 
The cementum at the cervix of a tooth comes to the enamel 
margin and, in some cases, slightly overlaps the latter. 
The Peridental Membrane, composed of fibrous tissue, is 
interposed between the root of a tooth and its bony socket or 
625 626 
CROWN WORK 
alveolus. The fibres of this membrane extend from the socket 
walls to the cementum covering the root, most of them running 
in an apical direction as well as tangentally. The tooth is re- 
tained in position principally by the network of fibres which 
pass in various directions through the gingival tissue. 
The attachment of the peridental fibres to the tooth termi- 
nates with the gingival termination of the cementum. They 
do not, however, terminate at the margin of the alveolus, but 
continue on incisally or occlusally into the gingivus, forming 
a sort of fibrous network or band which holds the gum tissues 
firmly in contact with the axial surfaces of the tooth. By 
passing through the interproximate spaces and across the em- 
brasures from tooth to tooth, they unite the lingual with the 
labial gingivi and buccal, and form what is termed the dental 
ligament. 
Now, since the cementum comes to, or slightly overlaps, 
the gingival margin of enamel, and since the peridental fibres 
are attached to the extreme gingival margin of the cementum, 
extending outward from this point and interlacing to form 
the dental ligament, in those cases where the peripheral ring 
of enamel is entirely removed for the reception of a crown 
band, more or less cutting and laceration of the peridental 
fibres in this region occurs from the use of the cleavers, files, 
discs and stones. These severed fibres may, or may never, 
again re-unite with the cementum, depending on the extent 
of injury done, the general tonicity of the parts and the 
character of the joint between the crown band and the root 
periphery. 
In line with this idea, Dr. F. B. Noyes in his Dental Histi- 
ology, page 189, says: “That the tissues (peridental mem- 
brane) may be re-attached to the surface of a root is both 
theoretically possible and clinically demonstrable, but for it 
to occur, biological laws must be observed and the conditions 
are very difficult to control, especially with the old methods 
involving the excessive use of strong antiseptics. It is well 
to remember that a dentist can never cure a suppurating 
pocket along the side of a tooth root, but if the conditions can 
be controlled the cells of the tissue may form a new layer of 
cementum, re-attaching the tissues, and so close the pocket. 
It is a biological problem, not a matter of drugs, except as 
they are a means of producing a cellular reaction. In view 
of its function, therefore, the cementum becomes not the least 
but the most important of the dental tissues, for no matter 
how perfect the crown may be, without firm attachment the 
tooth becomes useless and is soon lost.” CEOWN WORK 
627 
One of Ihe gravest dangers resulting from traumatic in- 
jury to the peridental fibres and their failure to again re- 
attach themselves to the root, is in the loss of tension of the 
dental ligament at or near the site of injury. In such cases 
the formation of a pocket is almost certain to occur, and into 
this food finds its way, is difficult to remove, decomposes, and 
pathological conditions arise, which in many cases from in- 
ducing infection eventually result in chronic suppurative peri- 
cementitis or other troubles. 
It will thus be seen that while a crown may restore the 
function of mastication, accomplish desired esthetic results, 
and, by wedging, maintain proximate contact which has been 
lost previous to its application, yet pathological conditions 
may be induced through improper technic and an imperfectly 
adapted band. 
Many prosthetists, either through carelessness or to avoid 
traumatic injury to the peridental membrane, fail to remove 
all of the peripheral enamel ring from the root when prepar- 
ing it for a band, with the result that the latter, when applied, 
presents a shoulder which not only invites the lodgment of 
food, but proves a constant mechanical irritant to the gingival 
tissues as well. The greatest care should, therefore, be ob- 
served to remove all of the enamel in cases where indicated, 
and yet avoid excessive injury to the peridental membrane 
and gingival tissues in general. 
Physiological Relations 
The pulp of a tooth occupies the central chamber, or what 
is termed the pulp chamber and root canal. It is largely com- 
posed of embryonal connective tissue in which very few con- 
nective tissue fibres are present. It contains nerve filaments 
and minute blood vessels which enter through the apical fora- 
men of the root. 
The primary function of the pulp is a dentine builder, the 
outer layer of columnar cells, called odontoblasts, receiving 
from the blood and depositing from without, inward, the cal- 
cific materials of which the dentine is composed. The den- 
tinal fibrils, occupying the dentinal tubuli, are the remnants 
of the odontoblastic cells which have become reduced in diam- 
eter and withdraw inward as calcific dentinal deposit pro- 
gresses. 
The secondary function of the pulp is that of a sensory 
organ, as it is very responsive to thermal changes, to chemical 
action on, and traumatic injury to the tooth. 628 
CROWN WORK 
In the preparation of a vital tooth for the reception of 
a crown, the friction caused by engine stones and discs is 
often exceedingly painful, even though the site of the opera- 
tion is far removed from the pulp. Since the dentinal fibrils 
are devoid of nerve filaments, external irritation when notice- 
able, is, without doubt, conveyed to the pulp by molecular 
vibration of the contents of the tubuli, and the heat caused 
by friction as well. 
Usually it is customary to devitalize a tooth before adapt- 
ing a shell crown, for two reasons: first, so as to reduce to 
the minimum the pain resulting from the use of stones and 
cleaners in the root preparation, and second, to avert possible 
pathological conditions subsequently arising from death of 
the pulp, either from the shock of denuding the crown of its 
enamel, or from thermal variations. 
When this practice is resorted to, the pulp removed, and 
the root apices perfectly filled, it is a most excellent pro- 
cedure. The danger of following this plan in every case lies 
in the fact that frequently teeth have multiple roots or mul- 
tiple canals — more than the normal number — and some of 
these are liable to be overlooked in the treatment and filling. 
Again the roots of teeth may be deformed, and the canals so 
tortuous and minute that by the most patient and conscien- 
tious effort it is impossible to clear and fill them. These con- 
ditions are frequently met with in peg-shaped lateral incisors, 
third molars, and occasionally in the lower anterior as well as 
other teeth. Should indications point to abnormalities, the 
X-ray will disclose their nature, and the prosthetist can then 
govern himself accordingly. When pathological conditions 
are not present and treatment is not called for, the safer plan 
in these abnormal cases is to crown the tooth without remov- 
ing the pulp, even though the tooth or root preparation may 
occasion some pain. 
Oral Pathological Conditions 
The prosthetist should be able to recognize any abnormal 
or pathological conditions present in the mouth, and be famil- 
iar with recognized and proven methods of treatment. 
The most frequently occurring abnormal conditions which 
present in practice are cases in which one or more of the teeth 
have lost their crowns, or the teeth themselves are missing. 
Such loss, if of long standing — usually the result of a sub- 
stitute crown not having been applied — almost always en- 
tails the loss of proximate contact of some, if not all, of the 629 
CROWN WORK 
remaining natural teeth. The spaces thus formed invite the 
lodgment and retention of food. As stated elsewhere, chronic 
suppurative pericementitis frequently has its origin in such 
mouths under these and similar conditions, and unless correc- 
tive measures are resorted to, the loss of all the teeth will 
sooner or later occur. 
When the axial surfaces of the teeth in general have not 
suffered from caries, and proximal contact has been lost 
through loss of the crowns of one or more teeth, the roots of 
which are in condition to carry substitute crowns, contact may 
frequently be restored between teeth considerably removed 
from the space to be supplied, by a slow wedging process. 
The substitute crowns should be constructed of sufficient 
dimensions to maintain the space gained in wedging. 
Hyperaemic or putrescent pulps should be removed, and 
the root canals of all pulpless teeth rendered aseptic and their 
apices filled, before attempting the preparation of roots for 
crowns. Pus sockets and alveolar abscesses connected with, 
or located near, the site of operation, must be eradicated. 
Inflammation of the gingival tissues and peridental mem- 
branes should be allayed, and when possible, restored to 
health, before extensive crowning operations are undertaken. 
In some cases complete restoration to normal conditions may 
not be effected, since the irritation occasioned by food wedg- 
ing on the tissues in unprotected locations — as in the embra- 
sures and interproximal spaces — may continue until afforded 
protection by suitably formed and well adapted crowns. 
Special care should be given to the removal of the excess 
cement, which in setting is forced out at the periphery of a 
crown. When this is not entirely removed inflammatory con- 
ditions frequently develop which may result not only in im- 
mediate discomfort to the patient, but later on in the forma- 
tion of a permanent gingival pocket. 
The prosthetist should endeavor by every possible means 
to temporarily and permanently correct all pathological con- 
ditions present, and to so form the substitutes, of whatever 
class, that they may in no way give rise to a recurrence of 
diseased conditions, or initiate others of a different character. 
Therapeutic Methods of Treatment of Diseased 
Conditions 
It is taken for granted that the student is pursuing the 
study of, and has access to, textbooks dealing with the ther- 
apy of the teeth and oral tisiies. Therefore it is unnecessary 630 
GROWN WORK 
to recount the various methods of treatment and the many 
general agents employed, except where they are of special in- 
terest to the prosthetist. 
LOCAL ANAESTHETICS 
Local anaesthetics in some cases are invaluable, as for 
instance in the removal of pulps, the excision of hypertro- 
phied gum tissue, the curetting of necrosed process, the scal- 
ing of roots in deep-seated alveolar pockets, and at times in 
the preparation of roots of teeth for the reception of crowns. 
Solutions of cocain, eucain, novo-cain and various similar 
agents, either alone or combined with other drugs, are used 
for this purpose. Such agents may be applied superficially 
or injected at or near the site of operation, in which case the 
peripheral nerve endings are influenced by the anaesthetic. 
Novo-cain and suprarenin dissolved in Ringer’s solution are 
frequently employed, especially in conductive anaesthesia. 
By this method the main nerve trunk back of the site of opera- 
tion is anaesthetized, the anaesthesia being more or less com- 
plete along the peripheral branches to the nerve endings, ex- 
cept where the tissues are also supplied with other nerve fila- 
ments coming from some other than the trunk anaesthetized. 
In such case an additional local injection at the site of opera- 
tion is sometimes resorted to, to complete the anaesthesia. 
In the use of anaesthetics of any character, and particu- 
larly when used by the injection method, extreme care should 
be exercised in the sterilization of the instruments, appliances 
and the agent itself, and in rendering aseptic the tissues to 
which the anaesthetic is applied, or through which the needle 
is inserted. 
Unless scrupulous care is observed in removing the pe- 
ripheral ring of enamel from the root of a tooth the adjacent 
tissues having been anaesthetized, serious traumatic injury 
to the dental ligament and gingival fibres of the peridental 
membrane is liable to occur, since the nerves are unresponsive 
and can give no warning of the extent of injury being in- 
flicted. When possible to do so, the use of anaesthetics in 
such operations should be avoided for the reason stated. 
Low per cent solutions of cocain or similar drugs, com- 
bined with pressure, usually produce effective anaesthesia in 
removal of pulps, when the solution and the unvulcanized rub- 
ber, by means of which pressure is usually applied, can be 
confined, as within a four-walled cavity, or one that may be 
so formed by means of a matrix. 631 
CROWN WORK 
TREATMENT AFTER SETTING A CROWN 
After setting a crown, the excess cement having been re- 
moved, the tissues should be massaged, syringed with warm 
normal salt solution, and where pain is experienced an appli- 
cation of tincture of iodine, or a saturated solution of iodine 
in beechwood creosote, should be applied under the free mar- 
gin of the gum around the root crowned. This method of 
treatment is frequently of value as an aid in relieving tender- 
ness in the peridental tissues. 
Hot water alone, when properly applied and continued a 
sufficient time, will very frequently reduce inflammation or 
abort an abscess in the incipient stage. The method is as fol- 
lows : 
A surgical tank used for irrigation purposes, holding a 
gallon or more, should be filled with water heated to about 
135 deg. F., or even higher if the patient can tolerate it with- 
out scalding the tissues. A nozzle with a very fine opening 
should be applied to the irrigating tube, the nozzle of the bulb 
water syringe or a glass dropper tube with curved point being 
suitable for this purpose, the curvature permitting the water 
to be directed against the gingiva in the embrasures and in- 
terproximate spaces of the teeth affected. 
The patient should sit with head inclined over the foun- 
tain cuspidor, and usually with a little instruction can, with- 
out assistance, irrigate the parts thoroughly. The application 
should he maintained for fifteen or twenty minutes continu- 
ously, the efficiency of the method depending upon the con- 
traction occasioned by heat of the arterioles and capillaries, 
thus reducing the flow of blood to the parts and enabling the 
tissues to recover their normal tone. 
The tank may require refilling once or twice in severe 
cases, and the stream of water should be directed not only 
around the gingivae of the tooth affected, but along the labial 
or buccal and lingual surfaces of the border of all of the teeth, 
so as to control the circulation of blood in the entire arch. 
The writer has in many instances effectively applied this 
method of treatment for the relief of conditions mentioned, 
and in various other forms of painful troubles as well. 
Anatomic and Esthetic Forms of Teeth 
The anatomic form of an artificial crown is governed by 
its position in the arch, and usually corresponds with the 
class of crown carried by the root which will support it. 632 
CROWN WORK 
Variations from this rule occur at times, examples of which 
are seen in the following instances : 
A lateral incisor has been lost and the space it occupied 
has been nearly, or quite, obliterated by the movement toward 
each other of the teeth on either side. In case the cuspid root 
requires crowning, a wide lateral incisor placed upon its roots 
would in all probability fill the space and be more in harmony 
with the proximating teeth than would a cuspid crown. 
Sometimes it becomes necessary to vary the form and pro- 
portions of an artificial crown for hygienic reasons, to raise 
or lower, omit or add, a cusp to meet occlusal requirements, 
or to secure contact with proximating teeth. 
In many instances a tooth has lost all or a portion of its 
crown long before the patient presents for a substitute. Fre- 
quently proximate contact of the remaining natural teeth has 
been disturbed by such loss. Before crowning the root, the 
lost space should, to as great an extent as possible, be re- 
gained by wedging, which in turn will frequently restore 
knuckling contact at other points where spaces have devel- 
oped from the movement toward each other of the teeth proxi- 
mating the missing crown. In many instances the wedging 
operation will not only regain the lost space, but may, with 
benefit to the other teeth, tighten up all lost contacts, when 
this can be done without disturbing the occlusion. The crown 
when constructed to fill the space may, therefore, be some- 
what greater in its mesio-distal diameter than was the origi- 
nal one it replaces. 
When the root of a tooth, capable of carrying a crown, is 
slightly out of alignment labio or bucco-lingually, should or- 
thodontic measures be deemed inadvisable for bringing it into 
position, an offset crown may be constructed, and by skill- 
ful root preparation and assembling of the several parts, the 
crown, although not of anatomic form, will present a good 
appearance and fulfill useful requirements. 
In the construction of crowns of any class, variations in 
form from true anatomic types are frequently necessary. The 
usual conditions calling for modified forms are excessively 
wide or narrow spaces, abnormal occlusal surfaces of the 
opposite teeth, movement of the remaining teeth from their 
normal position with loss of contact, and various other 
causes. 
A study of the axial surfaces of typical natural teeth 
should be made, and a reproduction of these surfaces carried 
out whenever possible in crown construction. The convexity CROWN WORK 
633 
of the buccal and lingual axial surfaces of the bicuspids and 
molars, aside from the esthetic value of such forms, serves a 
most useful purpose. The bulging mid-crown forms of these 
teeth, together with constricted cervices, afford efficient pro- 
tection to the free margin of the gums against the excursions 
of food that may be forced beyond the occlusal surfaces of 
the teeth in masticatory effort. 
As crowns are frequently constructed, their buccal and 
lingual axial surfaces are either parallel with each other, or 
converge from the gingivae occlusally, thus preventing in- 
clined planes for directing food towrard, instead of away from 
the gum margin. A crown so formed invites the lodgment 
of food, the formation of gingival pockets, and inflammatory 
conditions which will eventually result in loss of the tooth. 
An examination of many bicuspids and molars with a view 
of determining the average flare occlusally of their gingival 
cones was made as follows: 
A strip of No. 60 tin foil was cut about 1-3 of an inch wide, 
slightly curved to more readily adapt it to this portion of the 
FLAKE OF THE AXIAL SURFACES OF BICUSPIDS AND MOLARS 
Fig. 494.— Crown of Upper First Molar, with 
Tin-Foil Band Applied to Gingival Cone 
tooth. It was then bent around and burnished to the gingival 
cone of the tooth, the shorter, or concave, margin of the strip 
being applied gingivally. The ends were brought squarely 
together and cut at the angles of junction. The strip was 
then straightened out, one end laid parallel with the straight 634 
CROWN WORK 
edge of a cardboard, and a line drawn along, and parallel 
with, the opposite end, running toward and intersecting the 
margin of the cardboard. The angular divergence of the ends 
was read by means of a protractor. From fifty to one hun- 
Fig. 495.— Mesial View of Upper First Molar. 
Tin-Foil Strip Above 
Fig. 496.— Buccal Strip of Upper First Molar. 
Tin-Foil Strip Removed. Surplus Trimmed 
from Ends and Occlusal Margin 
dred teeth of each class were measured in this manner, the 
readings of which are as follows: 
Least 
Greatest 
Divergence 
Divergence 
Average 
Deg. 
Deg. 
Deg. 
Upper first bicuspids. .. 
... 21 
33 
27 
Upper second bicuspids. 
... 18 
32 
27.75 
Upper first molars 
. . . 19.4 
31 
25.5 
Upper second molars. .. 
. . . 16 
28 
24 
Lower first molars 
.. . 28 
40 
32 
Lower first bicuspids. .. 
.. . 24 
43 
30 
Lower second bicuspids. 
.. . 20 
35 
32 
Valuable assistance has been received in this work from 
Dr. J. F. Wallace of Canton, Missouri, who made many 
measurements of teeth by this method. His work, while vary- 
ing slightly from that of the writer, coincides closely, per- 
sonal equation accounting for the difference in findings. CROWN WORK 
635 
CUTTING MOLAR AND BICUSPID CROWN BANDS BY THE 
CONIC SYSTEM 
The practical application to crown work of the measure- 
ments seen in the table will now be shown. 
When a molar or bicuspid crown band is cut to approxi- 
mately the form of the tin foil pattern produced as above 
described, it represents, when the ends are united, a frustum 
of a cone instead of a cylinder, as would be the case when the 
ends of the band are parallel. The small end of the cone rep- 
resents the gingival margin of the band, while the large end, 
although excessive in peripheral outline, represents the occlu- 
sal margin. Reduction of the occlusal cone to correct form 
can easily and quickly be accomplished with the liawkbill or 
Benson pliers, using the latter without exerting excessive 
force, and when properly contoured the axial walls of the 
band will present a similar appearance to those of the natural 
tooth. The advantages of this method are that the band walls 
are not reduced in thickness at any point in contouring, while 
proximate contact can be secured without the usual narrow- 
ing of the band in its mid-crown, bucco-lingual diameter. 
The method of diverging the ends of a crown band from 
gingival to occlusal, has long been followed by careful pros- 
thetists for reasons above given. A few have even cut the 
band to represent the section of a cone instead of a cylinder, 
as is most frequently the case, but no definite rule has been 
evolved capable of application to the development of bicuspid 
and molar bands in general. 
By referring to the table of measurements previously 
shown, it will be seen that the average flare of a conic crown 
band of an upper first molar is 25.5 deg., while the average 
peripheral gingival measurement of this class of teeth is 
29.92 m. m. 
To cut a conic crown band by this system the only appli- 
ance required aside from the regular laboratory equipment 
is a pair of ordinary 6-incli dividers, a piece of cardboard and 
a straight edge. The method is as follows: 
Measure the prepared root with wire in the usual manner 
and cut the loop opposite the twist. 
Draw a straight perpendicular line on the cardboard par- 
allel with and near the edge, or the edge of the card can be 
used. 
Mark points on line A and B, 314 inches apart. 
Mark width of band B — C. 636 
CROWN WORK 
Lay a piece of gold plate from which the band is to be cut 
on the line, the upper corner at C. 
Set divider points at A — B, radius. 
Hold plate firmly on card and describe arc B I). 
Extend divider to reach from A to C. 
Describe arc C Gr. 
Fig. 497.— Plan of Card, Showing Construction Lines 
Used in the Development of a Cone Crown Band 
Lay root measurement slightly curved along arc 13 D and 
mark length of band B E. 
Lay ruler edge on points A and E and draw A F. 
B C E H represents the band which is cut with the shears. 
The band when bent around and the ends soldered, in the 
usual manner, represents the section of a cone instead of a 
cylinder, the smaller being the gingival end. 
In trimming the gingival end of the band to correspond to 
the gum festoon, the inner diameter of the band is increased 
as the gingival periphery is sheared away, and consequently CROWN WORK 
637 
is larger than tlie root. This may be corrected in two ways; 
first, by reducing the gingival periphery with the pliers, and 
second, by cutting the band slightly shorter than the wire 
measurement, when laying it out. 
By extending the line along the straight edge to the cen- 
ter, A, and reading the included angle it will usually be found 
to range from 22 deg. to 28 deg. This reading, however, is 
unnecessary for practical purposes. The variations noted in 
a number of readings are due to variations in peripheral root 
measurements, long measurements showing greater, and short 
measurements less, divergence of the band ends. 
In those cases where, for example, the space in which the 
crown is to be placed has become constricted by the leaning 
toward each other of the proximating teeth, the contact points 
of the remaining teeth in the arch being good, this method, 
for obvious reasons, is not applicable. 
In cases of normal or excessive width of spaces, it is the 
very best method to follow in the construction of two-piece 
or band and swaged cusp crowns. Its range of application 
can be extended to include band and cast cusp, and other 
varieties of crowns. 
The band of a crown cut to represent a cone, when cut 
gingivally to correspond with the festooning of the gums, is 
enlarged slightly since the smaller end of the cone is cut away, 
as before stated. To compensate for such enlargement, the 
band can be cut from y2 to 1 m. m. shorter than the root meas- 
urement. If, when festooned, the band is too small to be 
driven to place, it can be stretched slightly by placing on a 
round mandrel and tapping lightly with a riveting hammer. 
When too large, it can be reduced with contouring pliers. 
Any wide crown band, as for a molar or bicuspid, can be 
tightened gingivally, and its perfect peripheral adaptation 
insured, the root having been properly prepared, when, after 
fitting and axial contouring have been accomplished, its gin- 
gival margin is reduced as above outlined, after which it can 
be finally driven to place. A gingival shoulder on the natural 
tooth or root would preclude this plan of final adaptation. 
Badly decayed teeth, to which shell crowns are to be 
adapted, should in all cases have their axial surfaces restored 
by means of well anchored amalgam fillings or alloy castings, 
placed before the final preparation of the tooth or root is 
accomplished, so as to obliterate all gingival shoulders. 
When a tinfoil envelope is adapted to any of the twelve 
anterior teeth, the ends of the strip cut at their junction, and 638 
CROWN WORK 
the strip flattened, the two ends will be approximately par- 
allel, and when again united in band form would form the 
section of a cylinder. Anatomically, the anterior teeth rep- 
resent wedges or cylinders flattened at one end to form incisal 
edges. 
STRESS 
The amount of stress and the direction of its application 
are of the greatest importance in crown, bridge and denture 
construction. 
A crown, or a prosthetic appliance of any type, may be 
anatomical in form, yet when introduced into the mouth may 
become displaced, or rendered useless, through some abnor- 
mal condition present, as elongated cusps of teeth in the oppo- 
site arch. 
The sloping occlusal surfaces of the various cusps of a 
tooth, when brought into contact with occluding surfaces of 
opposite teeth, act as inclined planes, and tend to force the 
tooth of which they are a part forward or backward, or in or 
out of alignment, unless such tendency is counterbalanced by 
proximating teeth or by contact planes of occluding teeth 
sloping in a contrary direction. 
The greatest care, therefore, should be observed in the 
development of cusps to so form them that displacement from 
undue force on sloping planes cannot occur. Oftentimes the 
occlusal surfaces of the opposite teeth must be modified by 
grinding to meet new occlusal requirements arising from the 
introduction of prosthetic substitutes. The use of both single 
and double surface carbon paper will readily disclose points 
of interference between occluding planes and cusps, and cor- 
rections can be made accordingly. 
In constructing a crown with porcelain facing, care should 
be observed to so protect the incisal edge of the facing from 
direct stress, either by beveling and tipping it with gold as 
will hereafter be shown, or by avoiding contact with opposing 
teeth, under any and all conditions, otherwise the pins will be 
sheared off, or the porcelain itself fractured. 
A number of tests conducted by the writer, in which the 
facings of various manufacturers were employed in the con- 
struction of porcelain faced crowns with unprotected, as well 
as protected, tips, disclosed the following: That 60 pounds’ 
stress will fracture the strongest facings, or shear off the 
pins, while others will become dislodged at a pressure of 12 
pounds. Protected facings were not affected by stress and 639 
CROWN WORK 
remained intact until sufficient force was applied to bend the 
metal structure which constituted the metal tip, after which, 
with slight additional stress, they were dislodged. 
Gnatho-dynamometer tests show that the masticatory 
muscles can deliver a stress of from 20 to 90 pounds in the 
incisor, and a much greater amount in the bicuspid and molar 
region. The necessity for protecting facings from stress in 
some manner is therefore imperative. 
HYGIENIC REQUIREMENTS OF CROWNS 
In order that the health of the oral tissues may be main- 
tained, a crown should be so constructed as not to prove an 
irritant, either by directing food to and under the free margin 
of the gums and holding it there, or by presenting rough, un- 
finished surfaces to the tissues, and by this means setting up 
mechanical irritation. The first of these conditions arises 
from faulty contour, the second from too large or too wide a 
band. 
In a bandless crown, imperfect peripheral adaptation of 
the crown base to the root face will result in shoulders on 
either the root or the crown. Such shoulders may or may 
not prove mechanical irritants, but in any case they afford 
lodgment for food, which through decomposition will give rise 
to chemical irritation, with recession of the gingivae and fre- 
quently recurrent caries of the root. 
Correct occlusal forms should be developed in order that 
the usefulness of substitutes may be realized, that undue side 
stresses may be obviated, and that the crown may not be sub- 
jected to extra heavy direct stress. When possible to do so, 
firm knuckling contact with the proximating teeth should be 
established, and between neighboring teeth when such loss of 
contact is occasioned by movement of the teeth toward the 
space which the substitute occupies. 
These several requirements, although previously men- 
tioned, are again in order under this heading, since, if neg- 
lected, the hygiene of the mouth cannot be preserved. 
In introducing substitutes of any character into the mouth 
the dominant idea should be to so form them that with reason- 
able care on the part of the patient they may be kept clean; 
that they may not injure the remaining natural teeth or oral 
tissues; that the function of mastication may be restored; 
that the esthetic requirements may be fulfilled; and withal, 
that they may be worn with comfort. 640 
crown WORK 
Porcelain-Faced Crowns for the Anterior Teeth 
By the common methods in vogue, it is possible and prac- 
ticable to construct many classes and varieties of porcelain- 
faced crowns for the anterior teeth. It is not, however, ad- 
visable, in a work of this character, to attempt to describe all 
or even a comparatively limited number of such substitutes 
in extensive detail. 
One type of crown, in which a large number of the con- 
structive steps are based on familiar and accepted methods 
Fig. 498.— Impaired Central Incisor Crown to Be Replaced with a 
Porcelain Face Crown 
of practice, and applicable to many other similar types of 
crowns, will therefore be described in detail. Consequently, 
in mentioning variations from the type of crown about to be 
described, rehearsal of details as here presented need not be 
repeated. 
The crown selected for this description is a left, upper, 
central incisor, this being one of the most prominent teeth in 
the mouth, and one for which a substitute crown is frequently 
required. 
The same steps as here detailed are applicable to the 
crowning of all of the upper anterior teeth, and in most in- 
stances, to the corresponding teeth in the lower arch as well. 641 
CROWN WORK 
The student, therefore, is advised to become intimately 
familiar with every detail as here presented, with the assur- 
ance that when he has mastered the technic as outlined, he 
has laid a substantial foundation for further progress, and 
has mastered many details applicable to the construction of 
various other classes of crowns. 
Technic of Construction of a Porcelain-Faced Upper, 
Central Incisor Crown 
Devitalization, treatment and filling of root canal. 
Removal of remaining portion of natural crown. 
Preparation of root — removal of enamel. 
Measurement of root. 
Cutting and soldering of band. 
Scribing and fitting band to root. 
Reducing root face. 
Construction of root cap. 
Fitting cap to root, and perforating for reception of dowel. 
Adapting and soldering dowel to cap. 
Taking bite and impression. 
Selecting and grinding facing. 
Backing the facing. 
Assembling and waxing the facing and cap. 
Removal and investment of the assembled crown. 
Soldering. 
Finishing. 
Setting. 
These steps will now be taken up in order and the various 
details explained as clearly, yet briefly, as possible. 
GENERAL STEPS 
DEVITALIZATION, TREATMENT AND FILLING OF THE ROOT CANAL 
It is assumed that the prosthetist is familiar with the 
treatment of vital and non-vital teeth, their peridental mem- 
branes and adjacent tissues. Therefore, it is unnecessary to 
dwell extensively on this subject further than to emphasize 
the importance of adopting correct therapeutic measures and 
finally in sealing of the apical end of the root with a perma- 
nent filling before proceeding with the preparation of the root 
for the reception of the cap. 642 
CROWN WORK 
REMOVAL OF THE REMAINING PORTION OF THE NATURAL 
CROWN 
To avoid unnecessary injury to the dental ligament and 
soft tissues which surround the tooth cervix while adapting 
Fig. 500.— Grooving the Ename. 
of a Crown with Carborundum 
Stone for Application of Excis* 
ing Forceps 
Fig. 499.— Excising Forceps 
Fig. 601.— Preliminary Step in Removing Crown. Holes Drilled 
the band, the remaining portion of the natural crown should 
not be reduced beneath the gum margin until after the pe- 
ripheral ring of enamel has been removed, the wire ineasure- 643 
CROWN WORK 
ment secured, the band scribed and trimmed to correct gin- 
gival outline and is finally driven to place on the root. 
When a considerable portion of the natural crown re- 
Fig. 502.— Diagrammatic View of 
• Crown Perforated with 
Drill 
Fig. 503.— Diagrammatic View of 
Crown Partially Removed 
mains, the excising forceps can be used for its removal. 
Grooves should be cut through the enamel and well into the 
dentin in the gingival third area, on both labial and lingual 
surfaces, with a knife-edge carborundum stone. Tn these 
Fig. 504.— Application of Stone in Reduction of Gingival Section of Crown 
grooves the beaks or blades of the forceps are set, when, with 
the application of a little force, the crown can be fractured. 644 
CROWN WORK 
Another method, quite as convenient as that described, 
consists in drilling several holes through the crown at right 
angles to the long axis of the tooth and removing the inter- 
vening tooth structure between the holes with cross-cut fis- 
sure burs. The drill should be introduced in the cavity and 
the holes cut from within outward, when possible, or the 
enamel surface can be notched with a carborundum stone as 
described, and the drill entered in the groove. A bi-level 
drill made by flattening an inverted cone bur on two sides and 
beveling the point is most efficient for this purpose. 
After the bulk of the crown is thus removed, the remain- 
ing stump is reduced with engine stones to within about one- 
sixteenth of an inch of the gingiva, after which the enamel 
can be removed. 
REMOVAL OF THE ENAMEL 
The most effective instrument for removing the enamel is 
the Case cleaver, or some modification of it of which there 
Fig. 505.— Case Enamel Cleavers 
Fig. 506.— Ivory’s Contra-Angle Enamel 
Cleavers 
are several on the market, notably the Ivory and the Weaver. 
A selection of these instruments with both straight and con- 
tra-angle shanks should be on hand for this purpose. These 
Fig. 507.— Weaver Enamel Cleaver 
instruments have a side blade, terminating in a sharp, rather 
bulky point for strength, and are tempered very hard so as 
to readily break the enamel. CROWN WORK 
645 
The point of the instrument is applied to the enamel, 
under the gum margin, pressure exerted and the point drawn 
incisally. This step is repeated many times, the position of 
Fig. 508.— Enamel Cleavers of Various Forms 
the point being shifted each time, until as much of the periph- 
eral ring as it is possible to reach with the point has been 
so treated. The enamel will seldom come away as a result 
of application of the point in this manner, but the cohesion 
Fig. 509.— Root Showing Pe- 
ripheral Enamel Ring to 
Be Removed 
Fig. 510.—Position of Cleaver 
Point in Fracturing 
Enamel Surfaces 
Fig. 511.—Application of Side 
Blade of Cleaver in Re- 
moving Enamel 
of the rods will be disturbed by the many fracture lines de- 
veloped. 
The cleaver is now passed beneath the free margin of the 
gum, the side blade near the point being laid in contact with 
the enamel. The instrument should be held with the palm 
grasp, the thumb on the adjacent tooth to serve as a rest, 
and with a forward and outward movement incisally, the in- 
strument is rotated from beneath the free margin of the gum. 
With the application of moderate force applied to a great 
extent in a tangential direction, the enamel can readily be 
removed from the labial and lingual surfaces and from well 
into the four embrasures. 
When the interproximal spaces are constricted the enamel 
must be removed by other means, since the cleaver points are 
too bulky to enter these spaces to any great extent. 
A very small fissure bur can frequently be passed into the 
embrasure, and under proper control will fracture the remain- 646 
CROWN WORK 
ing enamel so that it can be removed with the root files. Care 
must be taken to avoid injuring the dental ligament, the peri- 
dental membrane and the proximating tooth with the bur, also 
Fig. 512.— Cut Showing Proximating Tooth Used as a Thumb Rest 
in Cleaving Enamel 
to avoid notching the root margin from the bur working be 
neath the enamel and into the dentin. 
SMOOTHING THE ROOT PERIPHERY WITH FILES 
A pair of right and left diagonally-cut, thin bladed files, 
such as designed by the writer, or others of similar type, will 
be found very useful for planing and smoothing the periph- 
ery of the root after the cleavers have removed the bulk of 
enamel. These files are designed to be used in a tangential 
direction, much the same as the cleavers, and are held with 
the palm grasp. They pass without difficulty in constricted 
embrasures. 
The entire periphery of the root, from its face end to as 
fai under the free margin of the gum as the crown band is 
to extend, must be made smooth and free from all irregu- 
larities. CROWN WORK 
647 
Fig. 513.— Enamel Files for Smooth- 
ing Root Periphery. 
(Prothero) 
Fig. 514.— Engine Root Trimmer 
for Peripheral Smoothing 
of Root 
Fig. 515.— Application of the Root Files in Peripheral Trimming of Root 648 
CROWN WORK 
GENERAL FORM OF THE PREPARED ROOT 
The peripheral form of a prepared root should be that 
of the frustum of a cone, the large end situated under the 
free margin of the gum at the terminal location of the crown 
band, the smaller end terminating at the face of the root. 
The flare of the sides of the cone should not be excessive, not 
Fig. 516.— Diagram of the Conic Form 
a Root Should Be Given for Re- 
ception of Band. Labial 
View 
Fig. 517.— Proximate View of Tooth, 
Showing General Reduction 
of Root for Band 
more than five degrees nor less than two degrees. A root 
prepared with too much flare affords but little retention for 
the band in fitting, while if not flared at all, as when the pe- 
riphery is not given a cone shape, the band when fitted will 
usually present a gingival shoulder under the free margin of 
the gum of more or less prominence, depending on the failure 
Fig. 518.—Diagrammatic View of 
File Applied to Root 
Periphery 
Fig. 519.— Diagrammatic View of 
Prepared Root 
of the prosthetist to produce a true flare or constriction on 
all surfaces, from gingival toward the incisal area. 
The exact fitting of the band of a crown to the root under 
the free margin of the gum is of vital importance, for regard- 
less of how carefully subsequent steps are carried out, an CROWN WORK 
649 
imperfect form of root preparation will invariably result in 
the production of a shoulder, either on the root itself or from 
too large a band. 
TESTING THE FLARE OF THE ROOT SURFACES 
Since a considerable portion of the root surfaces to which 
the band will be applied is obscured by the gum tissues, it 
is sometimes difficult to determine with the eye when proper 
form is developed. One test that may be applied is to place 
the point of a delicate instrument, as an explorer, on the side 
of the root, near the face end, and pass it carefully toward 
the apex, observing closely the direction it travels, or whether 
its line of movement changes as would be the case when it 
passes over a ridge and gradually or suddenly drops into a 
depression. 
By applying the instrument first on one, then on the oppo- 
site side of the root, comparing the line of movement each 
time with the same fixed surface, as the axial surface of a 
proximating tooth, it can soon be determined whether or not 
the proper flare to the root sides has been developed. 
A second test may be observed in the wire root measure- 
ment, which, when tightly twisted, if it can be readily sepa- 
rated from the root without stretching or untwisting, indi- 
cates that the gingival portion of the root is the largest. 
When it becomes necessary to cut or untwist the wire meas- 
urement to effect its removal this is positive proof that the 
sides of the root have not been reduced to a conical form, 
nor even brought to a parallel relation with each other. Fur- 
ther reduction of the root becomes necessary under such con- 
ditions. 
In general form, a root should be sufficiently cone-shaped 
so that as the band is forced apically it tightens. 
SECURING THE MEASUREMENT OF THE ROOT 
A piece of 36-gauge, annealed iron wire, about three inches 
long, is bent in the form of a loop, and fixed in a dentimeter 
or an ordinary broach holder. The loop is then passed over 
the projecting end of the root, the handle turned until the 
Fig. 520.— A Dentimeter for Holding and Applying the Wire Measurement to Root 650 
CROWN WORK 
wire engages loosely with the root surfaces. Careful adjust- 
ment of the loop is now made so that it occupies a place even 
with or slightly under the free margin of the gum. Under 
no condition should it be carried apically to the extreme limit 
of the cone base, as such a measurement would usually result 
Fig. 521.— Wire Loop Applied and Tightened 
Around Root 
in a loose-fitting band. The fundamental idea to keep in mind 
is the production of a band slightly smaller than the section 
of root cone where its apical end will terminate when finally 
fitted. As the metal is driven under the free margin of the 
Fig. 522.— View of Wire Measurement as Applied to Root in 
the Mouth 
gum, tlie conic form of the root will cause it not only to 
assume correct peripheral adaptation, but stretch it suf- 
ficiently to take its proper position. By adopting this method 
of fitting the hand, together with correct root preparation, 
gingival shoulders are avoided. CROWN WORK 
651 
MEASURING AND CUTTING THE BAND FOR THE ROOT CAP 
After removal of the wire measurement from the root, it 
is cut opposite the twist and the two halves are straightened 
out, care being taken not to untwist the wires, as such a mis- 
hap would increase the length. 
Fig. 523.— Wire Loop Measurement 
Removed from Root 
The straightened measurement is now laid on a piece of 
gold plate, usually 29 g. and 22 k. The lamina of the gold 
should run lengthwise of the band for greatest textile 
strength. One end of the measurement is placed exactly even 
with the edge of the plate, and with a thin, sharp blade, a 
Fig. 524.— Loop Measurement Severed, Straightened, and Laid 
on Gold Plate for Marking Length of Crown Band 
mark is made on the gold exactly even with the other end ot* 
the wire. This indicates the length of the band. 
The width of the band should be slightly greater than the 
apico-incisal curvature of the gingiva. Usually one-eighth of 
an inch in width is ample, but when the curvature is very 
marked a wider band will be required. 
The length and width of the band having been marked, the 
gold strip is cut with a pair of plate shears, being specially 
careful to cut it the exact length. 
Another method consists in making a lap joint to the band 
and after soldering reduce the excess thickness, the idea be- 
ing that such a joint is stronger as well as less liable to be- 
come unsoldered in subsequent steps. 
When a lap joint is to be formed the measurement is taken 
as described and the gold marked accordingly. An amount 
equal to the width of the lap is now added to the original band 652 
CROWN WORK 
length as determined by the wire measurement and the band 
cut that much longer. 
In forming the band, one end of the strip overlaps the 
other an amount equal to the excess length previously marked. 
FORMING AND SOLDERING THE BAND 
Tlie band is now bent in the form of a ring or ferrule and 
compressed so that the two ends of the strip pass each other 
slightly. When later adjusted, the ends will be held in con- 
tact by the resiliency of the metal. 
The band is now sprung apart and the ends abutted 
squarely against each other between which there should be 
absolute contact, otherwise it will be difficult to unite them 
perfectly with solder. Should either or both ends have been 
cut irregularly they must be corrected by filing. By observ- 
ing care in cutting the band the application of the file will be 
unnecessary. 
A piece of 36g., annealed, untinned, iron wire is bent 
around the band and twisted to form a loop, the twist opposite 
the joint. This twist serves as a plier grasp for holding the 
band while soldering, while the loop itself prevents the ends 
from springing apart. When tinned iron wire is used as a 
binder, the tin unites with the gold during soldering, to form 
a low fusing alloy, and frequently as a result the band may be 
partially melted. 
A little flux (pulverized borax and water, or soldering -flux 
paste) is applied on the inside of the band along the joint, 
being careful to place it only where needed, since the solder 
will spread unnecessarily on the band if the flux is applied 
carelessly or in excess. 
When the joint between the two ends of the band is close, 
as it should be, an almost inconceivably small amount of sol- 
der, properly placed and fused, will effect a perfect union. 
An excess of solder, which, when fused, extends any distance 
on either side of the joint stiffens the band and renders its 
perfect adaptation to the root difficult if not impossible. 
Usually a piece of solder one m. m. long and one-half 
m. m. wide, will prove ample for any ordinary band joint. 
The piece of solder is now laid on the inside of the band 
and across the joint, each end of the solder resting on a dif- 
ferent end of the band, the joint space being thus bridged 
over. As the solder fuses, being already in contact with the 
two ends of the band, gravity causes it to settle to place in 
the joint. CROWN WORK 
653 
The twisted ends of the loop are grasped with a pair of 
soldering pliers and the band is carried close to the Bunsen 
flame, but not into it, until the moisture has all been driven 
from the borax. This should be carefully done or the evapo- 
ration of the moisture from the paste, and later the driving 
out of the water of crystallization from the borax, during 
which the latter swells, will displace the solder before it fuses. 
Fig. 525.—- Soldering the Band 
Joint. Notice the Piece of Solder 
Crosses the Joint and Rests on 
Both Ends of the Band 
The band is now carried into the flame and held in the 
reducing flame until the solder is fused, when it must be in- 
stantly removed, as the gold itself is liable to fuse at the joint 
if only slightly overheated. 
The wire is now removed and the band contoured to the 
general form of the root. When the convexity of the alveolar 
border is very marked, the band can be cut out slightly on 
its mesial and distal sides, from the gingival border, to par- 
tially approximate the required curvature, after which the 
final fitting can best be done on the root. The joint of the 
band is usually placed to the lingual side of the root, some- 
times to the mesial or distal in certain bridge cases, but never 
to the labial. 
SWEATING THE BAND (AUTOGENOUS SOLDERING) 
The higher carats of gold can readily be autogenously 
soldered, or, as it is commonly expressed, sweated. This 
process consists in maintaining the parts to be united, as the 
ends of the band, in intimate contact and bringing the gold 
along the margins of the joint to such a state of fusion that 654 
CROWN WORK 
the molecules of the two pieces will intermingle. Though 
apparently a difficult process, with a keen vision and a steady 
hand, it can readily be accomplished. 
The essentials to success are a high grade gold that will 
not readily oxidize, close contact of the surfaces to be united, 
a limited application of clean flux along the joint, a strong 
but not large reducing flame, so that the heat may be concen- 
trated along the desired line of union, and finally the removal 
of the piece from the flame the instant fusion occurs. 
This method of joining pieces of gold without the inter- 
position of solder is applicable, not only to the forming of 
bands, but to the attachment of discs to bands in the produc- 
tion of root caps as well. 
SCRIBING THE BAND TO GINGIVAL OUTLINE 
In fitting a crown band of any class to the root or remain- 
ing portion of the crown of a natural tooth, its cervical end 
should be so shaped that as it is passed into position it wid 
touch the gingival gum margin at the same time. When 
trimmed in this manner, this will insure a uniform width of 
band under the free margin of the gum, when it is finally 
driven to place. 
The most convenient method for marking this trimming 
line on the band is by means of a pair of jeweler’s spring 
dividers. In mechanics, this process is known as scribing. 
The method is carried out as follows: 
The band is passed over the root until its mesial and dis- 
tal margins are in contact with or are carried slightly under 
Fig. 526.— Untrimmed Band Applied 
to Prepared Root 
Fig. 527.— Scribing Caliper Applied for Mark 
ing Gingival Curvature on Band 
the gingival tissues in the interproximate spaces. A space 
usually shows on the labial view of the root, between the gin- 
gival end of the band and the highest curve of the labial gin- 
giva. This space indicates the distance apart at which the CROWN WORK 
655 
points of the dividers must be set, one point being placed in 
contact with the gum margin, the other just resting on the 
gingival margin of the band. 
The dividers are now drawn along root and gold band from 
the center of the labial surface, first mesially then distally, 
the point on the plate marking a line as the other follows the 
gingival gum curvature. 
The dividers should not be rotated as in drawing an arc, 
but be held so that a line extending from one point to the 
other is at all times parallel with the long axis of the tooth. 
Fig. 528.— Jeweler’s Spring Calipers Used for Scribing Band. More 
Convenient Than the Preceding Instrument 
Since the dividers cannot conveniently be used within the 
oral cavity, for marking the lingual trimming line, an ex- 
plorer can be used for this purpose, keeping its point as far 
removed from the lingual, gingival curvature as the divider 
point which rested on the gold was removed from the labial 
gum margin while marking the labial surface of the band. 
When both labial and lingual trimming lines are thus 
marked, the band is removed, and with a pair of small, curved 
beak, crown shears, trimmed accordingly. The margins are 
now smoothed with a half round, fine cut file, so that they 
will not irritate the soft tissues in the subsequent steps of 
fitting to the root. 656 
CROWN WORK 
FITTING SCRIBED BAND TO THE ROOT 
The band, with its gingival end modified as described, is 
returned to the root and pressed cervically until about in con- 
tact with but not quite beneath the free gum margin. A close 
examination is now made to see whether the gingival margin 
of the band is parallel with that of the gum tissue. If not, the 
hand margin should be corrected by reducing with a file, the 
points which first touch the tissues, until the paralleling or 
approximation of the two margins is accomplished. There 
are cases where it is necessary to carry the gingival band 
margin farther beneath the gum at one point than another, as 
Fig. 529.— Band Scribed, Trimmed and Returned to Root. Notice 
Its Gingiva] Margin Coincides with Curve of the Gums 
where the free flap of the gum tissues varies in its width, or 
because of hypertrophy or some previous injury it is not of 
normal curvature or depth, or where a pocket may be present, 
and it is considered best to extend the band to line of attach- 
ment of the peridental fibers to the root. Such conditions 
should be noted and the band formed at this time to meet the 
requirements of the case. 
The band is now carefully and lightly driven beneath the 
free margin of the gum, usually to the depth of one to one and 
one-half millimeters when conditions are normal. The cer- 
vical margin of the hand should approach, but never encroach CROWN WORK 
657 
on the attachment of the peridental fibers to the root, nor 
should it ever pass beyond the base of the root cone developed 
by the cleavers and files. Should this occur, the result will 
be the formation of a shoulder under the free margin of the 
gum, which will prove a mechanical irritant to the soft tis- 
sues from the moment the crown is permanently set. Later, 
when food finds its way beneath the tissues and lodges on the 
shoulder, as decomposition sets in, chemical irritation aug- 
ments the mechanical, and loss of the root will eventually 
occur. The most painstaking and conscientious effort should 
be bestowed not only upon the preparation of the root, but 
in the fitting of the band as well, in order that the substitute 
crown may prove permanent and comfortable when set. 
TRIMMING BAND TO PROPER WIDTH 
The band being driven to place as described, its cervical 
margin in close contact with the sides of the cone base and 
the proper distance under the free margin of the gum, is still 
Fig. 530.— Cervical and In- 
cisal Ends of Band Reduced 
to Proper Outline. Band 
Driven to Place Under Free 
Gum Margin 
only partially formed. The opposite end of the band or that 
portion which projects beyond the free margin of the gum 
must be reduced to such length that when the root cap, of 
which it forms a part, and on which the porcelain facing rests, 
is completed, no gold will be visible on the labial surface. 
With a sharp pointed instrument a line is marked on the 
band close to and following the gingival curvature of the 
gums, around its entire periphery, labially, lingually and in 
the embrasures as well. 
The band is then removed from the root and with a pair 
of curved shears cut to the line marked on labial, mesial and 
distal surfaces, but not necessarily on the lingual surface, 
since a wide band in this area is desirable, affording greater 
resistance to outward stress than a narrow band. 658 
CROWN WORK 
Fig. 531.— Curved Blade Crown Shears Suitable for Trimming Band Margins 
Fig. 532.— Straight Blade Crown Shears for General Use 
Fig. 533.— Trimmed Band Fitted to Root. View Obscured by 
Gum Margin CROWN WORK 
659 
The band is returned to the root, driven to place and the 
projecting end of the root reduced to the gum margin on the 
mesial and distal, slightly beneath on the labial and near to 
but not beneath on the lingual surface in order, as before 
Fig. 534.— Stone Applied for 
Final Reduction of Root Face. 
Arrow Indicates Direction Stone 
Should Revolve to Avoid Injury 
to Free Gum Margin 
stated, that the band may be wider to better resist the stress 
of the opposing teeth. 
The general form of the face end of the root should be 
convex from labial to lingual and straight or slightly con- 
cave from side to side, depending on the depth of the labial 
curvature of the gingiva. The root may also be ground to 
present two planes, one sloping from the pulp chamber lab- 
ially, the other from the pulp chamber lingually. This form 
Fig. 535.— Ottolengui Root Facer 
as Applied in Reducing 
Excess of Root 
Fig. 536.— Various Sizes of Forms of Otto- 
lengui Root Facers 
of preparation, which is common, will usually require less 
grinding of the ridge lap of the facing than when the root 
face is decidedly convex. 660 
CROWN WORK 
The root may be faced with an engine stone about three- 
fourths of an inch in diameter and one-eighth inch face, or 
with the Ottolengui root facers, the various sizes of which 
afford the selection of one suitable to different sizes of roots. 
The Roach root facer can be used to advantage in reducing 
the projecting end of the root. This appliance has a central 
loose pin which keeps it within the root periphery. 
In facing the root with the stone it should revolve from 
the root toward the free margin of the gum to avoid lacera- 
tion of the soft tissues. 
The root should be faced even with but not shorter than 
the band, for when the disc which forms the end of the cap 
is attached it should rest directly upon the root end. Care 
Fig. 537.— The Roach Root Facer, with 
Movable Center Guide Pin 
should be taken, therefore, in facing the root, not to reduce it 
below the band margin or in driving the finished cap to place, 
the cervical end of the band will be forced too far apically. 
CONSTRUCTING THE ROOT CAP 
The root cap consists of the band formed as described, to 
which is attached a disc of metal, designed to rest upon the 
root face and which forms the foundation for the crown. The 
constructive steps are as follows: 
The band is removed from the root and a disc of 24 k. or 
22 k. 30 g. gold, slightly larger in diameter than the band, 
is adapted to its incisal end. General adaptation may be 
secured by placing the cervical end of the band on the ball of 
the thumb, adjusting the disc correctly against the other end 
and with the ball of the finger forcing it in contact with the CROWN WORK 
661 
band margins. While pressure is thus maintained, a thin 
blade burnisher is applied between the ball of the finger and 
the disc to conform it accurately at all points to the band edge. 
By scratching the side of the band and adjacent surface of 
Fig. 538.— First Step in Adapting Gold 
Plate to Completed Band in 
Forming Root Cap 
Fig. 539.— Plate Adapted to Band 
Periphery 
the disc at two or three points, the two parts may later be re- 
adjusted in exact relation as they must be when soldering. 
When closely adapted, which means positive contact of 
the disc with the band around its entire peripheral edge, the 
two are separated, a thin film of flux is applied to the disc 
surface on which the band will rest, a little to the band edge 
also, and the outer margin of the disc is caught in the beaks 
of a pair of self-locking soldering pliers. A very small piece 
Fig. 540.— Plate Burnisher for Adapting Backing to Facing (Prothero) 
of solder is cut and set endwise, one end resting on the disc, 
the other against the outside of the band, care being taken to 
see that the band and disc are in exact relation to each other, 
as previously marked. 
SOLDERING THE BAND TO THE DISC 
The disc with band and solder in place is quickly passed 
back and forth through the flame a few times to gradually 
expel the moisture and water of crystallization from the flux 
and thus obviate displacement of the band, after which it is 
held in the reducing flame until the solder fuses, when it is 
quickly withdrawn. When the adaptation between disc and 
band is perfect, the solder should flow around the entire joint 
periphery. Frequently, however, the solder will fail to flow 
along the joint immediately in front of the plier beaks because 662 
CROWN WORK 
the conduction of heat by the latter, away from the gold in 
that particular area, lowers the temperature below the fusing 
point of the solder. By grasping the opposite side of the disc 
Fig. 541.— Soldering the Band 
and Disc. Notice Two Small 
Pieces of Solder on Opposite 
Side from Plier Beaks. One 
Piece Is Usually Sufficient 
with the pliers and again introducing in the flame, complete 
union of band and disc can usually be effected without addi- 
tion of more solder. 
TRIMMING OFF THE PERIPHERAL EXCESS OF THE DISC 
The flat side of the shear blade is applied against the side 
of the band, and the excess margin of the disc removed. Fur- 
ther reduction should be made with the file, care being taken 
to avoid rounding the disc margin, but leave it square and 
Fig. 542.— Cap Completed. Excessive 
Surplus Margins Removed 
flush with the band. In some cases it is advisable to allow 
it to extend slightly beyond the outer surface of the band, 
particularly on the labial surface, when proper alignment of 
the facing requires that it be set to the labial of the band 
surface. 
In making a cap by the indirect method, the excising of 
the crown, removal of the enamel and smoothing up of the 
root cone is the same as by the direct method, in which the cap 
CONSTRUCTING CAP BY THE INDIRECT METHCD CROWN WORK 
663 
is constructed of two pieces, as described. The steps vary, 
however, from this point on. 
In the indirect method, the root must be faced to the final 
form desired, the labial portion being reduced beneath the 
free margin of the gums the full extent before the impression 
is secured. Counter-sinking the canal orifice should also be 
done so that this depression may be reproduced on the die. 
TAKING IMPRESSION OF ROOT 
A seamless copper band, slightly larger than the root, is 
contoured to its general peripheral outline, and the contoured 
end trimmed to approximate the curve of the gingiva. The 
band should be slightly longer than the proximating teeth for 
convenience in handling. 
The band is filled slightly in excess with softened model- 
ing compound, then introduced between the proximating teeth, 
Fig. 543.— Band Filled with Modeling 
Compound Preparatory to Taking 
Impression of Root Face 
and Periphery 
Fig. 544.— Impression of Root in 
Modeling Compound 
and evenly centered over the root. Pressure is now applied 
to force the compound against the root face and at the same 
time telescope the band over the root periphery so as to con- 
fine the compound and press it closely against the sides of 
the root. The thumb or finger should be placed over the outer 
or open end of the band to prevent the compound escaping 
in this direction. The Ivory impression cups, a number of 
varying sizes of which are supplied, which fit into a universal 
handle, are well adapted to this work. 
When properly carried out, the gum margin is pressed 
apically and an impression of the face end of the root and of 
the sides as well can be secured. Because of the limited com- 
pressibility of the gum tissues, an impression of the root 
sides, as far apically as the band will eventually extend, can 664 
CROWN WORK 
seldom be secured, but sufficient of the root surfaces can be 
embraced so that the die when developed can be filed away 
to represent a longer root. When this plan is followed care 
should be taken to preserve the original flare of the root cone. 
CONSTRUCTING THE ROOT DIE 
Any excess impression material that may have been forced 
out beyond the periphery of the impression band is removed. 
A section of rubber tubing which neatly fits the outside of the 
band is slipped over it and allowed to project about one- 
eighth inch beyond the impression, to confine the amalgam 
or cement and thus increase the depth of the die. 
Fig. 545.— Rubber Band Applied to Impression Periphery 
to Confine the Amalgam 
A mix of amalgam, such as is used for die purposes, is 
made and carefully worked into all inequalities of the im- 
pression, being careful while doing so not to mar any of the 
surfaces. Not only the impression, but the rubber ring is 
filled to give sufficient base to the die to resist the stress of 
swaging and that it may be well anchored in the swaging ring. 
IMBEDDING THE DIE IN THE SWAGING RING 
The die, when hardened, is removed from the impression 
by warming the latter, and set in a base of modeling com- 
pound in the swaging ring, placing it well above the margin 
Fig. 546.— Amalgam Die After Impres- 
sion Is Removed 
of the ring, so that the counterdie material may press the 
gold against the sides of the root. 
Should any change of form of the die be indicated, as in- 
creasing the length of the root apically, it can be made at this 
time. In practically all cases such change should be made, CROWN WORK 
665 
even to the extent of increasing the length of the root beyond 
what is required. The band of the cap when swaged will 
naturally be wider than necessary, but in fitting to the root it 
Fig. 547.— Die of Root End Adjusted 
in Swaging Ring 
Fig. 548.— Die Imbedded in Ring within Swager 
Fig. 549.—- A Two-Ring 
Swaging Device 
can readily be reduced to correct width, while if too narrow 
the form of the die must be changed as outlined and the cap 
reconstructed. 
SWAGING THE ROOT CAP 
The swaging ring is now placed in the base of the swager, 
a disc of pure gold, of 34 or 36 gauge, slightly larger than 
will be required to form the face and sides of the cap, is oiled 
on both sides and adapted by finger pressure and burnishing, 
to the die. The general outline of the cap can thus be defi- 
nitely determined and the surplus gold removed practically 
to the band margins. 
The swager is set in position, unvulcanized rubber or 
moldine being interposed between the plunger and the root 666 
CROWN WORK 
cap, and with two or three heavy blows of the swaging ham- 
mer the cap is swaged. 
The band margins are now trimmed to as nearly the cor- 
rect width as possible before trial in the mouth, and the cap 
reswaged to correct the distortion from trimming. Since a 
die formed in the manner described shows distinctly the en- 
Fig. 550.— Swaged Cap, in Position on 
Die. Surplus Not Yet 
Removed 
trance to the root canal, and this is indicated by a depression 
in the cap, the hole for the dowel may be punched before the 
last reswaging. 
The cap is boiled in acid to remove any adherent amalgam 
and cleanse the surfaces, then washed to remove the acid, 
when it is ready for fitting to the root. 
FITTING THE CAP TO THE ROOT 
The principal fitting to the root consists in trimming the 
band to proper width. The cap is placed on the root and 
light pressure applied. If any obstruction is met the loca- 
tion and cause are ascertained and correction made. The 
usual change necessary is to shorten the cervical end of the 
band so that it will not encroach on the tissues around the 
root cervix. When the cap can be firmly seated without im- 
pingement on the tissues, a thin flat burnisher is applied 
under the gum margin and the band burnished into close con- 
tact with the root periphery. While doing so the cap must be 
held in close contact with the root face. 
From now on, the steps are similar to those described for 
the two-piece crown, the next step being securing the relation 
between cap and dowel and attaching them as previously de- 
scribed. In flowing the solder which unites cap and dowel, 
the entire cap and band as well should be covered at the same 
time with a thin layer of solder to give it rigidity. CROWN WORK 
667 
ENLARGING ROOT CANAL FOR RECEPTION OF THE DOWEL 
If the root canal has not already been prepared to receive 
the dowel, it must be at this time, since the following steps 
relate to the fitting and adjustment of the dowel to the root 
and cap. 
The reaming out of a root canal is a comparatively simple 
step when the prosthetist himself has treated the root and 
filled the apex. When, however, the case presents, the root 
having previously been filled by another operator, an effort 
should be made to determine the probable length of the root 
and its position in the border. If any doubt exists as to its 
anatomic form, its position, or the thoroughness of the root 
filling, a skiagraph should be secured to determine as accu- 
rately as possible the existing conditions. 
Examination of the labial tissues overlying the root will 
frequently disclose a slight elevation of the mucous membrane 
and underlying alveolar plate, which will indicate the position 
of the root in the process. If no visible evidence is present, 
pressure with the ball of the finger, particularly in the apical 
region, will frequently locate the direction of the root. It is 
of the utmost importance that the general trend of the root be 
known before attempting to ream out and enlarge the canal. 
'When for any reason it is impossible to determine it, the 
greatest care should be observed in keeping the cutting in- 
strument within the canal and pointed in the right direction 
or serious injury is liable to occur., 
A rigid, inflexible drill, bur or root reamer, having a cut- 
tina point, is a dangerous instrument in the hands of an un- 
skilled or careless operator. Perforation of the side of the 
root is very liable to occur as a result of the instrument point 
leaving the canal and boring its way through the dentin and 
into the alveolus. The tissues injured as a result of such 
accident seldom ever recover their normal tone, the root hav- 
ing a feeling of chronic soreness, while frequently its extrac- 
tion in a short time becomes necessary. 
The safest method of removing a root filling and enlarg- 
ing the canal to the required diameter, or to such size that a 
reamer may with safety be used, is bv means of various sizes 
of round engine burs. The technic is as follows: 
"Determine, if possible, the general direction of the root, 
and keep this constantly in mind at all times until the initial 
reaming of the canal to proper depth has been accomplished. 
Place a No. y2 round bur in the handpiece and introduce 
the point in the entrance to the canal. 668 
CROWN WORK 
Line tlie handpiece up to conform to the general direction 
of the root, holding it loosely with the pen grasp. 
Start the engine and apply light pressure with the point 
of the bur, removing it frequently to bring out the gutta- 
percha cuttings and keep the canal clear. 
Do not attempt to guide the point; it will follow the canal 
if the handpiece is held loosely and in proper alignment, and 
the cuttings are removed frequently. 
Since a dowel should extend as far apically as the crown 
extends incisally, it will be necessary to ream out the canal to 
this depth when the length of root will permit. 
As soon as the bur begins to bind, and the feel or vibra- 
tion of the handpiece indicates that the bur is cutting dentin 
instead of root tilling, an examination should be made with a 
straight explorer to determine whether the bur is leaving the 
canal and if so, the cause. 
Should the tapering shank of the small bur jam against 
the sides of the canal before the latter has been opened to 
required depth, a No. 3 round bur can be substituted and the 
canal slightly enlarged from without inward for a short dis- 
tance, thus making room for the shank of the smaller bur with 
which the opening of the canal can be completed to the re- 
quired depth. 
The No. 3 bur is now used in the manner as described for 
No. y2 bur, holding the handpiece loosely and allowing the 
bur to make its own way in the now open canal as far as the 
latter has been opened by No. y2. 
The canal can now safely be enlarged to the required size 
for the reception of the dowel with either Nos. 4 or 5 round 
burs, depending on the diameter of the dowel to be used. Any 
of the ordinary forms of reamers can also with safety be 
used, since there is little danger, except when grossest care- 
lessness is displayed, of perforating the side of the root. 
Great care should he taken to avoid passing the small 
round bur through the apical end of the root, or of disturbing 
that portion of the filling which closes the terminal of the 
canal. Pressure on the bur must be extremely light at all 
times, but particularly so in the final steps of removing the 
root filling. 
COUNTERSINKING THE CANAL OPENING 
To give rigidity to the cap and a firmer attachment to it 
of the dowel when soldered, the entrance to the root canal CROWN WORK 
669 
should be slightly countersunk with a No. 10 round bur, and 
into this depression the cap disc is depressed. 
Fig. 551.—- Labial View of Root, 
Showing Canal Entrance 
Slightly Enlarged 
Fig. 552.—- Proximate V iew of 
Root, Showing Enlarged 
Canal Entrance 
INDENTING THE CAP IN COUNTERSUNK AREA 
The cap is now returned to position on the root and the 
small end of the large egg burnisher is applied to its central 
area with sufficient force to press it into the depressed area. 
Fig. 554.— Forcing the Cap Into 
the Root Canal Entrance 
Fig. 553.— Root Cap in Position, 
Notice That Labially the Band 
Is Beneath Gum Margin, While 
Lingually It Projects Slightly 
Beyond 
Usually, when the burnisher is somewhat pointed, the gold 
will be forced slightly beyond the countersunk area and into 
the entrance of the root canal itself, thus giving the exact 
location of the hole in the cap for the dowel. 
PERFORATING THE ROOT CAP FOR THE DOWEL 
A heavy instrument, with a sharp point, the diameter of 
which is slightly less than the dowel, is now forced against 
the cap directly over the opening in the root, and the gold 
punctured. A small engine drill may be used for the same 
purpose, or the cap can be removed and the hole punched 
with the plate punch. The opening, as before stated, should 
be smaller than the dowel, so that when the latter is forced 
through it the margins of the disc may fit tightly against and 
hold the dowel firmly in position. 670 
CROWN WORK 
FORCING THE DOWEL THROUGH THE CAP INTO THE ROOT 
The dowel, usually of 16 or 15 g. iridio-platinum, or clasp 
metal wire, is cut slightly longer than the actual depth of the 
reamed canal, so that it may project beyond the root cap and 
be surrounded by the solder which forms the lingual contour 
of the crown. Its apical end should be slightly reduced so 
as to readily enter the hole in the root cap. Better retention. 
Fig. 555.— Forcing the Dowel Into Canal Through Root Cap 
however, will be afforded the crown if the sides of the dowel 
are not tapered as is the common practice. 
With a pair of parallel jaw pliers, the dowel is grasped 
firmly, the reduced apical end outward. This end is entered 
in the opening in the root cap, the dowel brought in alignment 
with the root canal, and forced through the cap and into the 
root, the full depth of the reamed out portion. 
As the dowel is forced into the root through the con- 
stricted opening in the cap, the margins of the latter will be CROWN WORK 
671 
enlarged and carried into the entrance of the canal, and the 
bearing of the gold against the dowel be much increased. 
Fig. 556.— Diagram of Introduction of 
Dowel Through Cap, with Par- 
allel Jaw Pliers 
Fig. 557.— Root Cap with Attached 
Dowel in Position on Root 
MAINTAINING CORRECT RELATION BETWEEN DOWEL AND CAP WHILE 
REMOVING FROM ROOT 
The cap and dowel are now ready for attaching together 
with solder. To preserve the exact relationship which they 
now sustain to each other, on the root, during the soldering 
process, a piece of wax or modeling compound which will 
enter the space of the missing crown, is softened, pressed 
against the projecting dowel and root cap and chilled. A 
small 6-2-23 hoe, or instrument of similar shape, is carefully 
passed under the free margin of the gum, labially or lingually, 
hooked over the cervical margin of the band and the cap 
loosened. 
Should the cap and dowel cling to the root and fail to come 
away with the impression as it is removed, they can be re- 
leased and set in position without difficulty. 
Frequently, when the dowel fits tightly in the cap opening, 
and the cap and dowel release easily from the root, they can 
be removed from position, a little sticky wax applied to and 
melted on the cap and against the dowel, after which they are 
returned to the root to correct any disturbance of alignment 
of the dowel that may have occurred in removal. The wax 672 
CROWN WORK 
is now chilled and the two, now firmly held together in correct 
relation, are removed and invested for soldering. 
At times the dowel may be held so firmly by the cap that 
the two may be removed and soldered without investment. 
Fig. 558.— Soldering Cap and 
Dowel without Investment. Per- 
pendicular Position of Dowel. 
Notice Reflected Margin of Disc 
Around Dowel 
Fig. 559.— Soldering Cap and 
Dowel without Investment. Hori- 
zontal Position of Dowel 
Although requiring a little longer time than by the method 
just mentioned, it is much the safest plan to take the small 
impression and invest the two for soldering. 
A small mix of investment material or plaster alone, be- 
cause of its greater rapidity in setting, is prepared and ap- 
plied to the root side of the cap and around the dowel, build- 
ing it up the full length of the latter and squaring it off to 
form a base on which to rest while soldering. 
INVESTING THE CAP AND DOWEL FOR SOLDERING 
Fig. 660.— Cap and Dowel In- 
vested for Soldering. This Plan 
Is Preferable to the Two Pre- 
ceding Methods 
When set, the investment is reduced to small size to facil- 
itate soldering, the wax and moisture removed, a little flux 
applied over the surface of the cap and around the dowel 
where it is desired the solder should flow, a piece of solder is CROWN WORK 
673 
applied, one end resting on the cap, the other against the 
dowel, and with the blowpipe flame is fused. 
The investment is now removed, the cap pickled in acid to 
cleanse, and thoroughly washed in water to remove the acid, 
when it is ready to return to the mouth for final impression. 
Although there are many ways by which an accurate re- 
lation may be secured between the backed facing and cap in 
assembling the crown for final soldering, without taking an 
impression and bite and constructing casts the safest plan 
for the beginner at least is to carry out the steps as now out 
lined. 
TAKING THE BITE AND IMPRESSION 
USE OF THE FACE BOW IN CROWN WORK 
To secure esthetic results, it is essential that at least two 
teeth on either side of the space in which the crown is to be 
placed should be reproduced on the cast, in order that correct 
alignment and length of crown may be determined accurately, 
therefore the bite should include from five to six teeth. It 
Fig. 561.— Adjustment of Wax for Taking the Bite 674 
CROWN WORK 
is also essential that the crown be so constructed as not to 
interfere with the teeth in the opposite arch in lateral as well 
as incisive movements. The use of the face bow will enable 
the prosthetist to so construct the crown that subsequent 
changes by grinding will not be required. 
In crown work the bite should be secured before the im- 
pression is taken, for the reason that when the impression is 
taken in plaster, as in most cases it should be, the project- 
ing end of the dowel, being imbedded in the plaster, will bring 
the cap away from the root with the impression. In case the 
impression is taken first and the cap comes away with it, the 
cap must be removed and replaced on the root before taking 
the bite or the latter will be useless or at least unreliable. 
Some prosthetists take a combined bite and impression in 
modeling compound, which in simple cases, where there are 
Fig. 562.— Sectional View of Combined Impression 
and Bite. Root Cap and Dowel in Position 
no undercuts present, will answer for the separate bite in 
wax, and impression in plaster. 
DETAILS OF TAKING THE BITE 
The cap is set in position on the root, care being taken 
to see that it is firmly seated. 
A piece of wax is formed into a compact mass, about 
14x1x2 inches introduced between the teeth, and the patient 
instructed to close. The wax should extend sufficiently far 
labially of the teeth to receive and firmly hold the bite fork 
of the face bow, which is now applied and the face bow ad 
justed in the usual manner. 
While the wax is still soft the patient is instructed to 
press it against both upper and lower teeth with the tongue CROWN WORK 
675 
so as to secure as accurate an impression of their lingual sur- 
faces as possible. Stress should be laid on forcing the wax 
against the lower as well as the upper teeth, otherwise the 
tongue will raise it against the upper teeth only. 
Fig. 563.— Appearance in Mouth of Root Cap with Projecting 
Dowel. Extreme Labial Margin of Band Is 
Obscured by Gum Margin 
The wax is now chilled, the condyle rods of the face bow 
released, the patient instructed to open the mouth, and the 
bite attached to the face bow is removed and laid aside until 
the cast is secured. 
Fig. 564.— Modified Bite Fork with Adjustable Sleeve. Projection for 
Anchorage in Wax Shown on Concave Side of Fork 
A bite fork, modified by having the inner edge of each end 
reduced by grinding to increase its inner arc, will serve the 
purpose better than one of regular form. 676 
CROWN WORK 
Still another modification which will be found very use- 
ful for taking side bites, as for cuspids, bicuspids and the 
first molar, can be made as follows: Saw off one of the fork 
prongs next the stem; to the other, fit a sleeve which will 
slide freely along the fork, but which can be firmly fixed with 
a set screw at any point desired. The inner margin of the 
sleeve is supplied with a projection for extending into the 
space of a missing tooth. A firm hold is secured in the bite 
by having sufficient bulk of wax outside the arch to enclose 
the inner margin of the fork. The projection of the sleeve 
should be set so as to enter the space of the missing crown. 
When the root cap comes away with the bite, as is fre- 
quently the case, it must be removed and returned to the root 
before taking the impression. 
DETAILS OF SECURING AN IMPRESSION WITH PLASTER 
In crown work it is just as important to secure an accurate 
impression of that part of the mouth involved as in full den- 
ture construction. When much irregularity of surfaces exists, 
as in teeth with constricted cervices, or when the embrasure 
spaces are open as a result of tissue absorption, the impres- 
sion should always be in plaster. 
In order to preserve the essential parts of such an impres- 
sion, so that the teeth involved may he reproduced as per.- 
fectly as possible, it will be necessary to fracture it, carefully 
remove the pieces, and replace them in proper order for the 
production of the cast. 
Any one of three methods may be adopted, as follows: 
First, a tray of suitable size is selected and oiled to pre- 
vent the plaster from adhering to it. Plaster sufficient to 
secure an impression of the teeth involved is placed in the 
tray, introduced in the mouth and given sufficient time to 
thoroughly harden. The tray is then carefully removed so as 
not to disturb the impression. With the point of a knife an 
incisal groove is cut in the plaster to weaken it. The groove 
should extend well into the space of the missing crown. Pres- 
sure on the ends or the extreme border surface outward will 
fracture the labial portion, which will usually come away in- 
tact. With careful manipulation the lingual portion may be 
released and removed without further fracture. The tray and 
fractured surfaces of the impression are now cleared of all 
particles of debris, the pieces replaced in the tray, luted 
firmly with wax and the cast secured in the usual wav. 
Second method: A piece of cardboard is cut in the form CROWN WORK 
677 
of a square about iy2xiy2 inches, and the four corners 
rounded slightly. 
Two opposite sides, each a little less than one-half inch 
wide, are turned up at right angles to form an improvised 
impression tray, the bottom of which is a little more than one- 
Fig. 565.— Manner of Bending Cardboard 
for Impression Tray 
half inch wide. The sides and floor of the tray may be varied 
in width to conform to any special requirements, as a greater 
or less curvature of the arch or a deep or shallow alveolar 
border. 
The plaster is mixed to medium thick consistency, placed 
in the tray carried against the teeth so as to divide it about 
equally labially and lingually, and pressed borderward until 
the incisal edges of the teeth touch the tray floor. 
Since the sides of the tray are not rigid, they should be 
supported with the thumb and fingers while introducing the 
plaster and until it has begun to set. 
When the plaster has set, it is unnecessary to remove the 
tray from the impression, since the cardboard will be easily 
bent along the line where fracture will occur. Neither is it 
Fig. 566.— Hinge Tray Open 
Fig. 566a.— Hinge Tray Closed for Reception 
of Plaster. (See Page 678) 
necessary to groove the impression, for when the tray is car- 
ried borderward until its floor comes in contact with the teeth, 
the plaster is already practically divided into two sections 
and will readily break along the incisal line with the applica- 
tion of slight force. Furthermore, the cardboard serves the 
same purpose as a hinged tray, for by removing the particles 678 
CROWN WORK 
of debris from the fractured surfaces, the two halves of the 
impression can be brought together in exactly the right rela- 
tion to each other, and on luting with wax or wrapping a 
strand of fine binding wire around the outside, is ready for 
the production of the cast. 
Third method: A very serviceable and permanent tray 
may be constructed of an ordinary brass hinge, so bent as to 
present a floor and sides of about the same dimensions as 
those of the cardboard tray. The joint of the tray is in the 
center of the floor, while the hinge projects a little below and 
serves as a handle, or finger hold in introducing the tray. 
PRODUCTION OF CAST FROM THE IMPRESSION 
The impression having been secured, and the fractured 
pieces correctly adjusted, it is coated with separating medium 
and allowed to dry. 
Usually when an impression is fractured in removal, the 
cap will remain in position on the root. It may, however, 
come away, but its position in the impression will usually be 
disturbed. 
Before replacing it, the several parts of the impression 
are first placed together and firmly attached with sticky wax. 
The cap is then cleaned and a thin film of wax flowed over 
the dowel and inside the cap to obliterate any undercuts that 
may be present. The object of this is to subsequently permit 
the ready removal of the cap from the cast, without breaking 
the latter. Before the backed facing is finally attached to the 
cap, the latter is heated slightly to soften the wax, after which 
it is carefully removed from the cast, the wax cleared away 
and the cap returned to position, the outer periphery and 
dowel opening guiding it accurately to place on the cast. 
Then when the facing is attached with sticky wax, in the exact 
and final relation it should sustain to the cap, the assembled 
crown can be removed for investment without danger of dis- 
turbing the relation so established. 
The cap is now returned to its exact position in the im- 
pression where it is luted firmly with a little wax applied to 
the outside of the lingual band surface. 
Plaster is then mixed and the impression filled as for any 
partial case, special care being taken that no air is confined 
in the deeper parts of the impression. CROWN WORK 
679 
ATTACHING THE CASTS TO THE OCCLUDING FRAME 
When the face bow has been applied in taking the bite as 
described, the most convenient as well as accurate method 
of mounting the casts on the occluding frame is to mount the 
bite and produce the occlusion cast first. 
The face bow with bite fixed to the fork is attached to the 
frame and the latter inverted. The lower bow is thrown back- 
ward out of the way, the interior of the bite coated with a 
thin film of oil and filled with plaster, building it well above 
the bite margins. The bow of the frame is brought down in 
position and plaster applied around it to unite it with that in 
the bite. 
When the plaster has hardened, the face bow and bite 
fork are removed, and both labial and lingual portions of the 
bite in which the upper cast is to be fitted are pared down so 
as to permit the teeth to enter freely. The labial side of the 
bite should be cut away so as to expose the imprint made by 
the incisal edges of the natural teeth in the wax, so that in 
placing the cast in position it can readily be seen when the 
plaster teeth are in contact with the deepest portion of the 
bite. Sufficient wax, however, should be left to guide the cast 
into correct vertical position. 
rig. 567.— Full Casts Mounted on Occluding Frame. Cap in Position. 
Usually Only Partial Casts Are Developed 
The upper cast is now set in the bite, the upper bow of 
the frame dropped down upon its base, and plaster applied 
to attach the two firmly. When the plaster lias set the wax 
is thoroughly warmed to prevent breaking the teeth and if 680 
CROWN WORK 
then removed. The case is now ready for the selection and 
grinding of the facing. 
SELECTION OF THE FACING 
By means of the shade guide, the tints displayed in the 
natural teeth of the patient can be determined, the number of 
the shade required noted, and a facing of corresponding color 
and of suitable form selected. 
The form of the facing selected should correspond to the 
type of proximating natural teeth. In case such a tooth is not 
procurable, one of the correct shade but slightly larger than 
required can be selected and by grinding be modified to meet 
the requirements. The ground surfaces, when the proper con- 
tour is developed, can be finished with fine discs, and after- 
ward given a fine glaze with putty powder on a hard felt lathe 
wheel. 
The facing should be wide enough to fill the space and 
restore strong proximate contact with the adjoining teeth, 
unless for some special reason this is not advisable. 
Usually the facing selected should be slightly longer than 
required, since both incisal edge and ridge lap must be re- 
duced to required form by grinding. 
Since the pins afford the only anchorage of the porce- 
lain to the metal structure of the crown, a facing should be 
selected having the pins located as close to the incisal edge as 
possible, so as to bring the anchorage near the point of stress. 
To facilitate the soldering of the backed facing to the root 
cap, the ridge lap of the facing is beveled from its cervico- 
GRINDING THE FACING TO THE ROOT CAP 
Fig. 568.— Ridge Lap and Incisal Edge of Porcelain 
Facing Ground and Adjusted to Root Cap 
labial margin to the lingual surface. This leaves a V-shaped 
space of greater or less width between the base of porcelain 
and the root cap. CROWN WORK 
681 
In grinding the cervical end of a facing to the required 
form, care should be taken to develop a distinct line angle 
Fig. 569.— Cut Showing Direc- 
tion Stone Should Rotate in 
Grinding to Obviate Chipping 
Margins of Porcelain 
between the ridge lap surface and the labial surface to avoid 
a defective joint between the porcelain and backing. 
The stone should revolve from the labial surface lingually 
to prevent fracture of the margins. 
BEVELING THE INCISAL EDGE OF THE FACING 
The incisal edge of the facing should be ground to har- 
monious alignment with the proximating teeth, the facing, 
however, being shortened slightly to allow for the thickness 
of the gold tip to be added, and also for the backing, which 
must cover the ridge lap. 
The inciso-lingual line angle should be reduced to about 
30 degrees with the lingual surface taken as a base. This is 
somewhat less than is usually recommended, but when so 
formed will result in a metal tip of equal or greater strength 
with less labial exposure of gold than where the porcelain is 
beveled at an angle of 45 degrees. Special care should also 
be observed in developing the bevel to avoid fracturing the 
labial margins of porcelain wdth the stone. 
CHANGE OF COLOR IN PORCELAIN DUE TO METAL BACKING 
Different metals are used and various methods are in 
vogue in backing facings in crown and bridge work. The 
technic of applying the various metals is similar, but the color 
effect on the porcelain of the metal employed as a backing 
should be known in order to avoid undesirable change of tint 
in the facing of a finished crown. 
Pure gold imparts a slightly yellowish tint to very light 
porcelain, and increases or darkens the tint of yellow porce- 
lain, particularly when the facing is thin. 682 
CROWN WORK 
Allowance, therefore, should be made in the selection of a 
facing when pure gold is to be used as a backing by choosing 
one having the correct basic color, but slightly lighter than 
the shade desired, the variation depending on the thickness 
of the facing selected. 
When 22 k. gold is used, a similar effect is produced, but 
to a lesser degree, because of its less pronounced yellow color. 
Coin gold perceptibly darkens thin, translucent facings of 
any shade. 
Platinum imparts a bluish tint to light porcelain, in some 
cases darkening it perceptibly. 
A greenish yellow tint can be imparted to light yellow por- 
celain by using an 18 k. alloy known as “green gold,” com- 
posed of 18 parts of pure gold and 6 parts of pure silver. 
This gold is almost as soft and easily worked as pure gold. 
BACKING THE FACING WITH GOLD 
Pure gold is most generally used as a backing because of 
the ease with which it can be adapted to irregular surfaces. 
When conformed to a surface it shows but little tendency to 
warp or spring away as does gold of the lower carats. 
Two general methods are in vogue for applying the back- 
ings to teeth, first, by burnishing, and second, by swmging, 
both of which will be outlined. 
PERFORATING THE BACKING FOR THE PINS 
Spread a thin film of wax over the surface and near the 
corner of the piece of plate. Place the facing, pins resting on 
the wax, so that a slight margin of gold shows at the end and 
Fig. 570.— Method of Marking Correct Position of 
Holes, on Backing, for Tooth Pins 
along the side. Press the pins into the wax to indicate the 
location of the holes for the pins. Punch the holes as marked 
in the wax. Apply the facing and with a sharp instrument 
mark the outline of the tooth on the backing, allowing a little 
surplus all around, particularly at the cervical and incisal 
ends. The gold is then cut to the outline marked. CROWN WORK 
683 
Another method is to punch one hole near the edge of the 
plate for the outer pin. Apply the facing, entering the pin 
in the hole already punched, and rotate the tooth. Remove 
the facing and punch the other hole, its inner margin or that 
next the first hole being on the rotation line. 
Whatever method is employed, care should be taken to 
punch the holes the proper distance apart to avoid straining 
the porcelain as the gold is forced over the pins and against 
the facing. When the space between the pin holes is either 
too wide or narrow, such an accident is liable to occur. 
The holes should be of the exact diameter of the pins or 
slightly smaller, but never larger, to obviate the danger of 
fracture in final soldering, from the flux and solder being 
drawn into and through the holes next the pins, thereby com- 
ing directly in contact with the porcelain. 
Tlie Mason spacing calipers and auxiliaries, consisting of 
a pointed punch and an engine burnishing tool, was designed 
to and does effectually obviate the liability of both too large 
THE MASON SPACING CALIPER 
Fig. 571.— Application of Mason Spacing Caliper in Perforating the Backing 684 
CROWN WORK 
or incorrectly located holes. The directions for using the 
appliances are as follows: 
“The pins of the facing are placed in the holes on the 
side of the caliper which have guide slots to guide the pins 
into the holes; this accurately spaces the holes, which regis- 
ter with pins of the tooth, held in that position by the thumb 
nut; the backing is then marked or pierced by the hardened 
points, which gives the exact spacing for the pins; now place 
the backing thus marked on a piece of lead; then with the 
pointed punch the metal or gold is pierced, throwing up a lip, 
giving an aperture the same size as the pins; the backing 
thus pierced is placed on the tooth, the lips extending on the 
pins; finally, to burnish this lip of gold to the pin, the lathe 
tool is used; this has an aperture in the end which fits over 
the pin; with a high speed engine or lathe the gold is tightly 
burnished around and slightly raised against the sides of the 
pins . . . 
The writer’s experience with this appliance has proven it 
to be a most valuable addition to the laboratory equipment. 
Fig. 572.— The Mason Spacing Caliper and Accessories 
THE YOUNG PLATE PERFORATOR 
This is another convenient appliance by means of which 
the tooth serves as a gauge for setting the double end punch 
so that both holes are punched at the same time and at exact- 
ly the proper distance apart. 
Fig. 573.— The Young Plate Perforator CROWN WORK 
685 
ADAPTING THE BACKING TO THE FACING BY BURNISHING 
The backing, cut slightly larger than the surfaces it is to 
cover, and with holes punched, is applied to the facing and 
adapted as closely as possible to the porcelain with finger 
pressure. By means of the contra-angle burnisher or one of 
the Wilson type, general surface adaptation is secured, after 
which the borders are gradually worked into close contact 
with the margins of the facing. The gold should be removed 
and annealed occasionally to reduce the hardness developed 
by burnishing. Finally, when as close adaptation as possible 
has been secured by burnishing, the backing is removed, an- 
nealed, returned to place and the facing pressed, pins down, 
with backing interposed, into a broad cork that has previously 
been grooved to the general lingual contour of the facing. A 
piece of wood about the size of a lead pencil, concaved on the 
Fig. 574.— Adapting the Backing to Facing Against 
Cork with Light Hammer Blows 
end, is set on the facing and with both pressure and light 
hammer blows final and close adaptation of the gold to the 
porcelain is secured. 
Previous to this final adaptation, the surplus gold extend- 
ing over the margins of porcelain should be reduced with a 
file, applied so as to force the backing toward rather than 
away from the facing. As before mentioned, a slight surplus 
of the backing should be allowed to remain on both incisal 
and gingival margins, until the final finishing of the crown, so 
that the solder may be drawn outward to the full extent de- 
sired. Under no circumstances should the backing on these 
two ends be reflected over and onto the labial surface, as 
fracture of the porcelain will occur, due to contraction of the 
applied lingual solder. 
It is absolutely essential that the backing be brought into 
close and positive contact with the porcelain, not only at the 
margins, but on the lingual surfaces as well, to avoid the for- 
mation of a space between the two, into which organic matter 
will gradually find its way. When food accumulates in such 686 
CROWN WORK 
spaces it gives rise to disagreeable odors, and as it dccom 
poses and darkens wil1 modify the shade of the porcelain. 
SWAGING THE BACKING 
When the backing has been cut to proper size, the holes 
punched for the pins, and general adaptation secured with a 
burnisher, the facing is invested, labial face down, in model- 
ing compound, in the swaging ring. 
Fig. 576.—-Similar Method 
of Adapting Facing to 
Backing in Ajax Swager 
Fig. 575.— Adapting the Backing to Facing in S. S. W. Swager 
It should set well above the ring margins so as to freely 
expose the beveled incisal tip on one end and the ridge lap on 
the other. The compound should be trimmed so that the mar- 
gins of the facing are freely exposed to permit the gold being 
forced in close contact by the unvulcanized rubber. 
When the thinner gauges of gold or platinum are used, as 
34 or 36 g., two or three light blows on the plunger will set CROWN WORK 
687 
the backing in close contact with the facing. Heavier gauges 
of metal will require more force. When swaged, the backing 
is removed and trimmed to desired correct outline, and the 
backing returned to the facing and reswaged to correct any 
distortion that may have occurred. 
FIXING THE BACKING TO THE FACING 
When final adaptation has been developed between facing 
and backing, the latter should be firmly fixed to the porcelain 
so that the close and essential relation between the two may 
not be disturbed while assembling and soldering the crown. 
A common practice is to bend the pins over in contact with 
the backing. As a result, however, the porcelain is subjected 
to undue strain, and if not fractured immediately, as is fre- 
quently the case, is very liable to be in the subsequent solder- 
ing process. 
A much safer and quite as effectual method is to applj 
a sharp blade or chisel to the side of pin and turn a lighl 
shaving of the platinum down upon the backing. This puts no 
strain upon the porcelain and holds the gold firmly in place. 
The Reese Pin Shaver, a small, cylindrical, hollow mandrel, 
the opening in which is slightly larger than the diameter of a 
tooth pin, can also be used for shaving the pin and burnishing 
the shaving down in close contact with the backing. The in- 
strument is passed over the pin in a slightly diagonal direc- 
tion, and as it is forced along the pin toward the backing, the 
sharp inner margin of the tool cuts and carries a shaving of 
platinum down in contact with the gold. 
FITTING THE BACKED FACING TO THE BOOT CAP 
The facing now having its backing conformed and attached 
as described is ready for adjustment to the root cap. A small 
piece of soft wax is placed over the projecting dowel and on 
the lingual half of the cap, and the facing pressed against it 
so as to secure proper alignment with the proximating teeth. 
If in adjusting the facing the labial surface of the dowel 
interferes with its labial alignment, the dowel may be par- 
tially ground away. Sometimes it is necessary, when the fac- 
ing is thick or the labio-lingual diameter of the root is short, 
to remove the greater portion of the projecting dowel. When 
the root is countersunk and the cap has been burnished into 
it as previously described, the removal of the dowel projec- 688 
CROWN WORK 
tion will not appreciably weaken the attachment of the dowel 
to the finished crown. 
It is sometimes advisable to ream out the lingual side of 
the root canal, so that in adjusting the dowel it may be bent 
slightly to the lingual, and thus give more space for the 
facing. 
Special care should be observed to set the cervical mar- 
gin of the facing in line with the labial surface of the band. 
It may even project slightly if the alignment of the facing 
requires, but should never be set to the lingual or the labial 
band surface, or a projecting shoulder of gold, which cannot 
be obliterated, will result. 
The long axis of the facing must be set at a similar angle 
of divergence from the perpendicular line of the face or, in- 
ciso-apically, as the corresponding tooth on the opposite side 
of the arch, the line of direction, however, being reversed. 
In most cases the backing which covers the ridge lap of 
the facing can be slightly reduced in thickness by filing, and 
that portion of gold on the root cap against which the facing 
rests may also be thinned by grinding. The object of this 
is to bring the porcelain in as close contact as possible with 
Fig. 577.— Lingual Side of Root Canal 
Reamed to Receive Bent Dowel 
the root face, and thereby reduce the width of the labio-gin- 
gival margin of gold in the finished crown. By this step, in- 
stead of two thicknesses of gold being interposed between the 
face end of the root and facing there is the equivalent of only 
one. When the facing is adjusted in the exact desired rela- 
tion to the cap, the point of a heated instrument is passed into 
the wax supporting it and the two are firmly united. 
INVESTMENT OE THE ASSEMBLED CROWN FOR SOLDERING 
The crown is now carefully removed and its full lingual 
contour developed in wax. Special care should be taken to 
flow wax into the space between the backing and root cap 
around the labial surface to exclude the investment in which 
the crown is later on inclosed for soldering. CROWN WORK 
689 
The crown is now assembled, but all of the several parts 
are not yet permanently united. It must therefore be en- 
closed in some material capable of resisting heat without per- 
ceptible change, that will hold the cap and facing in correct 
relation to each other after removal of the wax and during 
the soldering process. 
Any of the standard investment materials prepared and 
sold for this purpose may be employed, or one can be com- 
pounded in the laboratory. One of the best “home made” 
investments for soldering purposes consists of a mixture of 
two-thirds coarse ground asbestos (short cut fibre), and one- 
third plaster. 
The two ingredients should be measured out in proper pro- 
portions and “dry mixed,” then placed in the bowl, a suffi- 
cient quantity of water added to make a rather stiff mass, and 
spatulated thoroughly. 
Fig. 578.— Backed Facing and Cap Assembled and 
Held with Wax, Ready for Investment 
An oiled slab should be prepared or a piece of paper 
placed on the bench. On this the investment is placed, build- 
ing it up to an inch or more in thickness. The crown cap is 
completely filled with investment before enclosing in the mass 
to subsequently exclude the solder. 
The crown is now pressed into the plastic mass, being 
careful to keep its labial face at least one-half inch above the 
base of the investment, so that the latter may not be fractured 
when subjected to heat, as is frequently the case when the 
bulk of investments is too limited. The investment is now 
built around the sides of the facing and even with, but not 
above, the incisal end. 
The crown should be settled into the plastic mass in a 
diagonal position rather than horizontally. This is to bring 
the linguo-gingival edge of the root cap and the incisal end of 690 
CROWN WORK 
the facing on a level, so that in flowing the solder gravity will 
assist in giving the lingual surface its proper contour. 
TRIMMING THE INVESTMENT PREPARATORY TO SOLDERING 
It is necessary, in order that the flame may be readily 
applied to all essential parts of the crown and the solder 
readily fused where needed, that the surplus investment be 
removed and the investment proper reduced to the smallest 
possible dimensions consistent with strength and the protec- 
tion of the porcelain. 
First, the sides of the investment are trimmed close to 
the mesial and distal surfaces of the facing, leaving a suffi- 
cient thickness, however, to protect the porcelain. 
Second, the ends are reduced close to but not so as to ex- 
pose the incisal edge of porcelain or the dowel at the oppo- 
site end. 
Third, an opening should be carefully made from one side 
to the other so as to expose the labial surface of band and 
Fig. 579.— Crown Invested for 
Soldering. Notice the Joint Is 
Entirely Exposed, While Porce- 
lain Is Protected 
margin of backing wliich projects beyond the ridge lap of 
the porcelain, but not the facing. 
The investment along the sides of the facing and extend- 
ing down to the labio-cervical opening is now beveled so as 
to freely expose the entire backing and joint area. The in- 
vestment next the incisal tip should be removed so that the 
solder may be freely drawn to the outermost limits of the 
backing and thus stiffen the gold which forms the incisal tip 
of the crown. 
By so forming the investment the entire joint between the 
backing and root cap is exposed to view, so that in flowing 
the solder it can readily be seen when perfect union and re 
quired contour has been effected. 
REMOVAL OF THE WAX 
The investment, trimmed as described, is cleared of de 
bris, the wax warmed and removed with a small instrument. CROWN WORK 
691 
That in the more constricted space can be entirely cleared 
away with a fine stream of boiling water. 
A thin film of thick borax paste, made by grinding crystal 
borax with water on a ground glass slab, is now applied to 
the backing and root cap on those surfaces to be covered by 
the solder. With a thin wooden spatula or toothpick it should 
be carried into the constricted V-shaped opening between the 
ridgelap and the root cap, and along the cervical joint. 
The flux should not be spread on the investment along the 
margins of the backing, where it can come in contact with the 
porcelain during the soldering, nor be applied so plentifully 
that it will overflow on these margins when heated. 
Should this occur, fracture of the porcelain is liable to 
result, due to difference in contractility of porcelain and 
borax, which, under heat, unite. When an oily soldering 
paste is used instead of one composed of borax and water, 
the same care should be observed in keeping it away from the 
porcelain. 
APPLYING THE FLUX 
DRYING OUT AND HEATING THE CASE FOR SOLDERING 
The investment is now set on a sheet of gauze, near the 
edge or slightly above the Bunsen flame, to gradually drive 
off the moisture and thoroughly heat it preparatory to sol- 
dering. 
When dry and thoroughly hot it is transferred to the sol- 
dering block, where the blowpipe flame is applied around the 
base and sides until the investment is red hot, when the solder 
can be applied and fused. 
DEVELOPING THE LINGUAL CONTOUR OF THE CROWN 
WITH SOLDER 
It is common practice to cut the solder into small pieces, 
apply a number of them at a time to the backing, and when 
fused to discontinue the flame until more is added, then re- 
apply the flame, continuing this process until the desired lin- 
gual contour is developed. 
While this method is effective so far as developing the 
required contour of the crown is concerned, it frequently re- 
sults in fracture of the facing, due to repeated change of tem- 
perature and consequent repeated expansion and contraction 
of the porcelain. 
By far the quickest, most convenient and safest method 692 
CROWN WORK 
of applying the solder is to cut it in thin strips about one- 
eightli inch wide and from three to six inches in length. All 
surfaces should be covered with a thin film of flux before use. 
One of these strips is clamped in the beaks of the soldering 
pliers, and when the investment is thoroughly heated and red, 
the point of the strip is directed into the deepest part of the 
V-shaped opening. 
The flame of the blowpipe is now applied to that area, 
when the solder will be instantly fused. As it settles into the 
Fig. 580.— Method of Applying the Solder 
in Strip Form 
joint more of the strip is fed into the molten mass, until the 
proper contour is developed. 
Special care should be observed in thickening the back- 
ing over the incisal tip and also allowing the solder to over- 
Fig. 581.— The Stiver Blowpipe 
flow the lingual surface of the root cap. When the lingual 
surface of the crown is developed to resemble the natural cin- CROWN WORK 
693 
gulum of the tooth, much better protection will be afforded 
the gum margin than where this surface presents an inclined 
plane inciso-gingivally. 
The blowpipe flame should never be directed against the 
platinum pins of a facing until the porcelain itself is thor- 
oughly heated and well expanded. The reason for this is 
obvious: porcelain is friable and easily broken; the platinum 
pins expand quickly when heated, and when highly heated 
exert great force, within certain limits; this limit of expan- 
sive force is greater than the porcelain can stand without 
fracturing unless itself first expanded. 
The three principal causes of fracture of porcelain facings 
have now been mentioned, viz., contact with and fusing of 
borax to the porcelain, expansion of the platinum pins, sud- 
den changes of temperature or the intermittent application 
of the flame. 
FINISHING THE CROWN 
After the soldering has been completed, the investment 
should be allowed to cool down gradually, or again fracture 
of the facing is liable to occur. The investment should be 
protected against strong, cold drafts of air by placing over 
it an inverted cup or plaster bowl until the temperature is 
reduced to such point that it may be comfortably handled with 
the fingers. 
The investment is then broken away, the crown examined 
to see that no accident has happened, and that the desired 
contour has been developed. Should contour be deficient at 
any point the crown must be reinvested and corrections made 
as needed. 
The crown is now pickled in acid to loosen any adherent 
investment and flux. A convenient method is to boil it in acid 
in a test tube, after which it should be thoroughly washed to 
remove the acid. 
Fig. 582.— Reducing the Surplus Margins of 
Gold with Stone 
Tlie surplus gold can be economically removed with a file, 
the filings being caught in the gold drawer or on a sheet of 
paper. The finer finish is accomplished with engine stones 
and discs, followed by the use of fine pumice stone first and 694 
CROWN WORK 
afterward rouge, applied with felt wheels on the lathe. Every 
file mark and all scratches produced by the coarser polishing 
powders must be removed and the metal parts polished as 
well as the finest piece of jewelry. The cervical margin of the 
band must be beveled and slightly rounded so that it may not 
prove an irritant to the gingival tissues or form a shoulder 
for the lodgment of food. 
Too much care cannot be bestowed on the finish of the 
cervical band margin, for on this, together with restoring 
close proximate contact with the adjoining teeth, will depend 
the future service and comfort of the substitute. 
One of the most essential requirements in the setting of a 
crown is to thoroughly dry the root and adjacent parts and 
keep them so until the operation is completed and the cement 
well set. 
Since the rubber dam cannot be applied, the lip should 
be raised with a cotton roll to prevent the oral fluids from in- 
terfering with the immediate and subsequent steps. 
The general moisture is removed from the mucous tissues 
and root face with pellets of cotton, from the canal with cot- 
ton on a brooch and small cotton or bibulous paper points. 
SETTING THE CROWN 
Fig. 583.— Labial View of Finished 
Crown 
Fig. 584.—Proximal View of Finished 
Crown. 
Filially, with blasts of air from the chip blower or the com- 
pressed air point the parts are thoroughly dried and made 
ready for the reception of the crown. The crown itself should 
be dry, clean and free from polishing powder, grease or wax. 
A previously tested crown cement should be mixed to thin- 
medium consistency and thoroughly spatulated. 
With a root canal plugger, a small portion of the cement 
is carried into the canal and worked against the sides and to 
the apex, continuing this until the entire opening is tilled. A CROWN WORK 
695 
thin layer should be worked over the face end of the root. 
The crown cap is now partially filled with the cement, a little 
smeared on the dowel and the crown is quickly pressed into 
position on the root. 
Heavy but intermittent pressure should be exerted at first 
and afterward steady pressure to force out the excess cement 
confined within the cap and root canal, and which, if not ex- 
pelled, would elongate the crown to a greater or less extent. 
Mallet blows are much less effective in seating a crown than 
heavy maintained pressure, because the cement being more 
or less plastic and sluggish and closely confined within the 
cap, is scarcely affected by heavy, sudden blows, while main- 
tained pressure causes it to flow as long as there is any open- 
ing through which it can escape. 
REMOVAL OF THE EXCESS CEMENT 
When the cement has set reasonably hard, which usually 
requires from fifteen to twenty-five minutes, the excess cement 
which can be removed without danger of disturbing the crown 
should be cleared away, first with pellets of cotton, followed 
by the use of the blunt explorer. • When time is limited it is 
advisable, as soon as the excessive surplus is removed, to 
dismiss the patient until the cement is thoroughly hardened, 
or after the lapse of two or three hours, when the removal of 
the remainder can be effected without danger of loosening the 
crown. 
When satisfied that every trace of the cement has been 
removed from beneath the gingival tissues, the parts should 
be syringed with warm normal salt solution, and the gums 
massaged to restore normal circulation and tone. 
Finally, before dismissing the patient a close examination 
should be made to see that the opposite teeth do not strike the 
crown in either occlusion or lateral movements. Should such 
be the case, correction must be made by grinding away the 
points of contact on either the crown or natural teeth or both, 
as good judgment dictates. 
SETTING A CROWN TEMPORARILY 
Sometimes it may be deemed advisable to set a crown tem- 
porarily in order to test its efficiency, or for other reasons. 
This may be done as follows: 
A piece of gutta percba baseplate material is cut and 
formed into a roll or cylinder which will approximately fill the 696 
CROWN WORK 
root canal. The canal, root, and adjoining tissues are thor- 
oughly dried, the canal moistened with oil of cajaput, or 
eucalyptus, the cylinder of gutta-percha is warmed and in- 
serted in the canal. The crown itself is gradually heated, 
particularly the dowel, and a blast of hot air from the syringe 
directed against the gutta-percha. The crown is then forced 
to place on the root, or when it cannot be perfectly seated is 
quickly removed and the cause determined. 
The cause may be due to too much material or to the gutta- 
percha not being sufficiently plastic. Removal of some of the 
material and the application of more heat, with quick action 
and heavy pressure, will usually result in success on second 
trial. 
REMOVAL OF A TEMPORARY CROWN OR A BRIDGE SET WITH 
GUTTA-PERCHA 
Since the easiest way of removing a crown set with gutta- 
percha is by the application of heat, and since the heat must 
be sufficient to soften the gutta-percha, the appliance now to 
be described will be found most efficient. 
Remove the bulb from a chip-blower. Pass a common 
twine string, large enough to fit closely, through the nozzle of 
the pipe, to form a wick. Pour a few drops of alcohol into the 
pipe and cork the large end. This forms an alcohol lamp, the 
wick projecting from the small end. Trim the wick short so 
that it projects but slightly from the nozzle. A flame varying 
from one-half inch in length to one no larger than a pin-head 
may be produced, depending on the projection of the wick. 
With this lamp a small flame is applied to the crown. The 
heat thus applied is transmitted through the dowel to the 
gutta-percha in the canal, which, when sufficiently softened, 
will release the crown. 
Different Methods of Applying Porcelain Facings and 
Replaceable Teeth in Single Crowns, and 
Dummies for Bridges 
Porcelain is utilized in various ways, other than that de- 
scribed, as a veneer or partial crown in single crown work, 
and bridge construction as well. 
Since a bridge is nothing more or less than an assemblage 
of full crowns, combined with partial crowns called dummies, 
some of the various methods of construction of the different 
factors of bridges will now be considered. CROWN WORK 
697 
INTERCHANGEABLE TOOTH FACINGS 
To obviate fracture in soldering and facilitate repairs of 
facings in crowns or bridges, various forms of interchange- 
able or replaceable porcelain facings are used instead of reg- 
ular long pin plate teeth. 
Replaceable teeth and facings of different forms are now 
procurable and in many cases are useful, not only in repair- 
cases, but are coming into general use in crown and bridge 
construction. 
The three most common forms of flat back teeth, or fac- 
ings of this type, are the Steele, the Evslin and the Dimelow. 
In addition to these, a number of types of partial crowns of 
the replaceable class, for both anterior and posterior teeth as 
well, are now available. 
Among these partial crowns may be mentioned the Gos- 
lee, Gardiner, Merker and posteriors of Steele and Evslin. 
steele's interchangeable tooth 
This consists of a facing of porcelain and a backing of 
metal. In the back of the facing, beginning at the ridge lap, 
a hole extends into the porcelain, toward but not to, the in- 
Fig. 585.— Sectional Views of Steele Facing 
and Backing 
cisal edge. This hole is slotted lingually to receive a pro- 
jection from the backing. The backing consists of a piece of 
flat metal plate, to which is affixed a tubular post which enters 
the hole in the facing, and forms the attachment between fac- 
ing and crown or bridge. 
APPLICATION OF THE STEELE FACING 
The application of a Steele facing to a central incisor 
crown, as just described, is as follows: 
The cap having been constructed and in position on the 
cast, a facing is selected and ground to fit the root cap. The 
backing is then adjusted and the surplus trimmed to the mar- 
gins of porcelain, leaving the incisal edge longer than the 
porcelain. 698 
CROWN WORK 
Should the tubular post of the backing extend beyond the 
porcelain at the ridge lap, it is ground flush with the latter. 
The facing and backing are now adjusted to the cap. 
Sticky wax is applied to the backing and melted against the 
root cap, being careful to keep it from flowing on the porce- 
Fig. 586.— Steele Facing Ground to 
Root Cap 
Fig. 587.-— Steele Facing with Backing 
Trimmed and in Position Ad- 
justed to Root Cap 
lain. The assembled crown is now removed from the cast and 
the facing slipped from the backing. 
A thin film of Anti-Flnx is applied to backing on that sur- 
face against which the porcelain rests. This is necessary to 
prevent the solder or borax flowing over the backing, as the 
slightest amount of either, if adherent to this surface, will 
prevent the facing passing to place. 
The metal parts of the crown are now invested and sol- 
dered as usual. 
To clean the metal structure and remove the borax after 
soldering, the crown should be heated and dropped in a pickle 
of 30 per cent HC1. If boiled, as is usually the case, the 
metal of which the tube is composed will be corroded or 
honey-combed. 
The facing is slipped in position on the backing, and the 
surplus gold reduced with stones and discs. The incisal edge 
of gold should be continuous with the labial contour of porce- 
lain for a short distance to afford protection to the latter 
against incisal stress. When the metal parts are polished, the 
facing is set in position with cement and the crown is ready 
for setting on the root. 
steele's interchangeable tooth — technic for 
POSTERIOR CROWNS 
Bicuspid and molar teeth of the Steele type can be em- 
ployed in crown construction, although they are more often CROWN WORK 
699 
used as dummies in bridge work. The method of procedure 
is as follows: 
The root is prepared, a root cap constructed and dowels 
extending into the root canals are fitted and attached to the 
cap by soldering. At the same time the cap should be stiff- 
ened by flowing solder over it. Casts should be constructed 
and mounted on the occluding frame. 
A porcelain tooth of suitable size is selected and ground 
to proper length, allowing for the interposed backing of gold 
over the ridge lap. 
The backing is then fitted to the porcelain in the usual 
manner. To its cervical end is attached an extension of 22 or 
24k. gold plate, to cover the ridge lap and extend slightly 
beyond the buccal margin of the tooth. 
The backed tooth is now set in position on the root cap 
and waxed in proper relation to the latter, after which the 
assembled crown is removed from the cast, the porcelain re- 
moved from position, Anti-Flux applied to the buccal surface 
of the backing, the metal structure invested and developed to 
proper contour with solder. By using inlay wax in assem- 
bling the crown, the cap and backing may be united and the 
lingual contour developed by the casting method. 
STEELE INTERCHANGEABLE TOOTH, TECHNIC FOR CAST 
DUMMIES 
A facing is selected and ground to the cast. The backing 
is then applied and trimmed to correct peripheral outline. 
Inlay wax is now applied to the lingual surface of the 
backing and the desired contour of the tooth is developed by 
carving. 
Fig. 588.— Bicuspid Dummy 
Consisting of Steele Facing, 
Backing, Occlusal Surface. 
Partial Lingual Contour De- 
veloped in Inlay Wax 
Fig. 589.— Backing and Wax 
with Steele Facing 
Removed 
Fig-. 590.— The Dummy, 
Minus Porcelain, Invested 
for Casting 
The facing is now removed, a sprue former attached to 
the wax in such manner that when invested the gold will enter 
the matrix at the highest point. 700 
CROWN WORK 
The case is invested and cast by usual methods of pro- 
cedure. 
CONSTRUCTION OF DUMMIES WITH SWAGED CUSPS 
When it is deemed advisable to construct the dummy with 
swaged occlusal surface the procedure is as follows: 
A tooth of suitable size is selected, ground and backed as 
previously described. A cusp is carved in plaster or some 
medium by means of which a counterdie may be secured and 
a cusp swaged. 
This is trimmed and fitted to the backing, the facing is 
adjusted and the assembled dummy tested as to its occlusal 
relations with the opposite teeth. When satisfactory, the fac- 
ing is removed, and the metal structure is invested and sol- 
dered. 
REFLECTING THE BACKING OVER THE CERVICAL MARGIN 
OF PORCELAIN 
In some cases it may be considered advisable to reflect the 
extension which is added to the principal backing of a Steele 
tooth or facing over the gingival margin of porcelain. The 
object in doing this is to form a socked or gingival cup for 
Fig. 591.— Bridge Showing Socket-Like Form, 
of Support for Steele Bicuspid 
Fig. 592.— Anterior Bridge Composed of 
Steele Facings. Central In- 
cisor Removed 
the better protection of the porcelain against stress. When 
this plan is followed the cervical margin of the porcelain 
should be beveled slightly at the expense of the labial or buc- 
cal surface. This permits the reflected gold being finished 
flush with the porcelain without eliminating the shoulder. 
Utilizing Long Pin Plate Teeth for Removable 
Facings 
One of the main considerations in the use of replaceable 
facings of any type, in addition to ease of repair when frac- 
tured with use, is to avoid danger of fracture of porcelain 
during soldering operations. 
A long pin facing, or ordinary plate tooth, is often util CROWN WORK 
701 
ized as a removable facing for the same reason that special- 
ized forms of interchangeable teeth are employed. 
One of the common methods of procedure is as follows: 
The facing is ground to correct form and backed with gold 
in the usual manner. The pins must be parallel with each 
Fig. 593.— Long Pin Tooth 
Ground, Backing Adapted 
and Waxed in Position on 
Root Cap. Facing Removed 
Fig. 594.— Proximal View of 
Removed Facing, Showing 
Pins Bent Gingivally 
Fig. 595.— Assembled Bicus- 
pid Dummy, Facing Removed, 
Carbon Points Inserted 
other but not necessarily at right angles to the inciso-gingival 
plane of the lingual surface of the facing. Usually the pins 
are bent slightly toward the ridge lap to give them a hook- 
like contact with the backing. 
Fig. 596.— Long Pm Facing 
Ground and Backed for Bi- 
cuspid Dummy 
Fig. 597.— Facing Backed, 
Lingual Contour Developed 
in Wax 
Fig. 598.— Facing Removed 
from Dummy, Carbon Points 
Inserted Through Backing in 
Wax 
The backed facing is waxed in correct relation to its root 
cap, or if for a dummy its lingual contour is developed in 
wax to the desired form. 
Fig. 599.— Dummy in Position for In- 
vesting within Casting Ring 
The facing is carefully removed and in the openings in 
the wax formed by withdrawal of the pins, small pieces of 
carbon are inserted, the ends of which should project from the 702 
CROWN WORK 
backing. This is necessary in order that they may be caught 
in and held by the investment. 
The assembled metal parts are now united by casting or 
soldering. The carbon points are broken off and that en- 
closed within the gold is drilled out to receive the pins. 
The facing is then fitted to the metal and when correctly 
adjusted, the pins are slightly roughened and the facing set 
with cement. 
The Evslin Interchangeable Tooth 
This tooth is made of porcelain in the form of facings for 
anterior replacements and with fully contoured bucco-occlusal 
surfaces for posterior replacements. 
A posterior tooth of this type, in its general contour, is 
deficient on the lingual surface. In this surface a dovetailed 
space exists for receiving a lug of clasp metal of correspond- 
ing shape, which forms a part of the metal structure of the 
crown or dummy, box or socket. 
In this, as in practically all other types of replaceable fac- 
ings, the porcelain serves as a veneer for obscuring the essen- 
tial metallic structural parts of a crown or bridge. 
. The dovetailed lug which is attached to the socket, and the 
opening in the porcelain are so related that, in adjusting the 
two parts together, the facing is not brought into close con- 
tact with the backing until the two are in nearly correct rela- 
Fig. 600.— Lingual View of Evslin 
Bicuspid and Molar 
tion to each other. Stated differently, the facing approaches 
its normal position or seat against the backing and base of 
the crown in an inclined direction and does not jam or become 
tightly wedged until practically seated. For this reason the 
incisal edge of an anterior facing may be beveled at an angle 
and the hacking adapted accordingly, which, when reinforced 
with solder, forms a tip or metal protection for the porcelain 
against stress. 
Backings of 24 k., 34-gauge gold with lugs attached may 
be procured or the prosthetist may attach the individual lug 
to any gauge and carat of gold he desires to use for the 
backing. CROWN WORK 
703 
EVSLIN FACINGS TECHNIC FOR ANTERIOR CROWNS 
Construct the root cap by either direct or indirect method, 
adapt and solder dowel. Place on natural root, take bite and 
impression and mount casts on occluding frame. Select fac- 
ing of suitable form and color and grind to position. Bevel 
incisal edge of porcelain at an angle of about 35 degs. to lin- 
gual surface. The facing should be slightly shorter than the 
required length of crown to allow for extension of backing 
over ridge lap and for the thickness of the metallic incisal tip. 
Anneal backing with lug attached and adjust to facing, 
passing the square end of the lug into the slot incisally. Bur- 
nish and swage backing directly against the tooth, annealing 
Fig. 601.— Tooth Ground, 
Incisal Edge Beveled 
Fig. 602.— Pin or Lug to Be 
Attached to Backing 
Fig. 603.— Lug Fitted in 
Recess in Facing 
and reswaging until perfect adaptation is secured. Trim 
backing flush with mesial and distal surfaces of facing, but 
allow it to project slightly beyond both cervical margin and 
incisal edge. 
Apply film of sticky wax over lingual surface of backing 
while the latter is still on the facing and chill it. This is to 
prevent distortion of the backing while removing the facing. 
Heat a piece of sticky wax and apply to the labial surface of 
the facing. This serves as a handle in separating it from the 
backing. The separation of the facing and backing at this 
time is necessary, to see that the two have not become wedged 
or jammed by the rough edges of the backing left by the file. 
A lien this test has been carried out, the sticky wax is 
removed from the facing, the latter is returned to the back- 
ing, the two are set in correct relation to the proximating 
teeth on the root cap and the backing firmly luted in position 
with sticky wax. 
The assembled crown is now removed from the model, the 
facing again removed from its position, and the backing and 
lug coated with Anti-Flux to prevent the solder from flowing 704 
CROWN WORK 
on those surfaces against which the porcelain comes in con- 
tact. 
When the dummy is constructed with an individual sad- 
dle, the backing should extend over the ridge lap of the facing 
Fig. 604.— Sectional View of 
Facing, Lug, and Backing 
Fig. 605.— Facing Removed 
from Metal Structure 
Fig. 606.—- Appearance of 
Finished Crown 
to the labial or buccal surface. The disc of gold which forms 
the saddle is adapted to the alveolar border and extended 
labially or buccally to meet the backing on these surfaces. 
When assembled, the lingual contour of the dummy is com- 
pleted with wax. Usually the surface of the plaster cast cov- 
ered by the saddle is scraped slightly before assembling and 
waxing the two parts together, to insure firm bearing of the 
completed dummy upon the ridge when the bridge is perma- 
nently set. 
EVSLIN TEETH TECHNIC FOR POSTERIOR CROWNS 
The root cap having been constructed, impression and bite 
taken, casts secured and mounted on the occluding frame, the 
construction steps are as follows: 
A posterior tooth of suitable form and color is selected 
and ground to suitable length. The mesial and distal surfaces 
Fig. 607.— Evslin Molar 
Fig. 608.— Backing or a Socket for 
Evslin Molar 
should be beveled by grinding from the ridge lap occlnsally. 
This is essential so that the sides of the gold socket may pass 
along these surfaces without producing unnecessary bulk in CROWN WORK 
705 
the interproximate space. Furthermore, the socket in which 
the porcelain rests can thus be made in boxlike form and will 
afford better retention for the tooth. 
A backing with lug attached is adjusted and burnished to 
the porcelain. The surplus is then cut away, the tooth im- 
bedded, occlusal and buccal surfaces down in moldine in the 
swaging ring and the backing swaged into close contact with 
the porcelain. 
Remove the tooth and backing from the swager, flow sticky 
wax over the backing and separate. Correct any overhang 
of the gold margins, return tooth to place and wax backing 
to root cap, building the lingual contour out as desired. 
The assembled crown is now removed from the model, the 
porcelain removed, Anti-Flux applied to the buccal surface 
of the backing, the case invested, as usual, for soldering. 
The wax is now removed from between the root cap and 
the socket which receives the base of the tooth, the case heated 
Fig. 609.— Buccal View of Posterior Bridge, 
Evslin Facings in Position 
Fig. 610.— Same Case as the Preceding, Fac- 
ings Removed 
and solder flowed in to complete tlie lingual contour of the 
crown. 
Pickle in acid wash and return the facing to position, be- 
ing careful not to use much force. If obstructions, as nodules 
or excess solder, are present, remove them with a file or en- 
gine burs. 
The surplus gold at the margins is removed with files, en- 
gine stones and discs. 
The direction of movement in filing, grinding and polish- 
ing should always be from the gold toward the porcelain. 
When the metal part of the crown is roughly contoured 
and moderately well smoothed up, the facing is cemented in 
place. 
The final polishing on the lathe should be deferred until 
the facing is cemented in position, or the square margins of 
the metal next the porcelain will be rounded and thus leave a 
visible groove between the two. 706 
CROWN WORK 
EVSLIN TEETH TECHNIC FOR ANTERIOR DUMMIES IN 
BRIDGE WORK 
The abutment crowns of the bridge having been con- 
structed, they are set in position on the roots in the mouth 
and a bite and an impression secured. The casts are then 
formed and mounted on the occluding frame. 
Evslin facings of suitable color and form to meet the re- 
quirements of the case are selected and ground, as when long 
Fig. 611.— These Cuts Show Protection Afforded Incisal 
Edge of Porcelain, also Form of Backing Some- 
times Employed for Anterior Facings 
pin, flat back facings are used, the ridge lap of the facing 
being ground to fit the irregularities of the border. 
The facing is then backed as for a crown except that 
usually the backing does not extend onto the ridge lap. 
The extent to which the backing covers the porcelain, how- 
ever, depends upon the type of dummy being constructed, as 
it is sometimes extended over the ridge lap to form a socket. 
Interchangeable Teeth 
Removable, replaceable and interchangeable teeth of vari- 
ous forms have been designed for use in crown and bridge 
work, the object of which is to obviate subjecting the porce- 
lain to soldering operations and thereby avoid danger of frac- 
ture from this cause. 
In the use of teeth of this type, the metal structure is built 
around and adapted to the porcelain, and after completion 
the teeth are cemented in position. 
A distinction should be made between removable flat back 
facings and certain types of removable or replaceable teeth. 
A replaceable facing usually has within the body of porcelain 
a slotted opening which receives a correspondingly shaped 
lug of metal projecting from the crown or bridge structure. 
A replaceable tooth usually has, in addition to this or some 
similar means of anchorage, a standardized base composed of 
planes, so disposed as to aid in resisting displacement under 
masticatory stress. CROWN WORK 
707 
A tooth formed with a standardized base of the character 
described can thus be readily replaced in case of fracture. 
lteplaceable teeth represent more nearly the anatomic 
types of natural teeth than facings of any class. Not only 
are the labial surfaces of the anterior teeth represented, but 
a portion of the lingual surfaces are reproduced, while in the 
posterior teeth, the buccal, occlusal and a portion of the lin- 
gual surfaces are developed in porcelain. 
Among the well-known teeth of this type, as well as new 
forms which have recently appeared, are the Goslee, the 
Steele and Evslin posteriors, the Gardiner and the Merker, 
A brief description of the Steele and the Evslin teeth has 
already been outlined. 
The Goslee Tooth 
This consists of a partially contoured porcelain crown, 
deficient in its lingual areas. Within the lingual side, and at 
Fig. 612.— Buccal and Lingual View of Goslee 
Interchangeable Posterior Teeth 
right angle to the long axis of the tooth, is developed a flat 
seat. In this seat is a cylindrical opening, extending incisally 
Fig. 613.— Proximal View of 
Goslee Incisor Facing 
Fig. 614.— A Goslee Incisor Fac- 
ing, Showing Basal Seat Opening 
for Dowel and Flaring Lingual 
Surfaces 
or occlusally into the body of the tooth, for the reception of 
a dowel which forms a part of the metal structure. The sides 708 
CROWN WORK 
flare outwardly, and occlusally or incisally, from the seat, 
in the bicuspids and molars, the flaring sides terminate within 
Fig. 615.— Proximal View of Goslee 
Interchangeable Tooth 
Fig. 616.— Cervical View of 
Goslee Tooth 
and form a depressed shoulder just beneath the mesial, distal 
and lingual surfaces of the crown. 
TECHNIC OF APPLICATION OF THE GOSLEE TOOTH IN 
CROWN WORK 
Prepare a root cap, preferably by the indirect method, 
using 36 gauge platinum or pure gold plate. By forming a 
depressed area in the central portion of the root, the walls of 
which are but slightly divergent, the root periphery may be 
decidedly beveled so that in the completed crown no periph- 
eral shoulder will be present. In forming the cap, it is swaged 
into the depressed area and thus forms a shoulder for guid- 
ing the cap to and holding it in correct position on the root. 
Through openings in the cap, dowels are introduced into 
the root canals. The relation between the dowels and cap is 
secured and their subsequent attachment by soldering is ac- 
complished by methods previously described. At the time of 
attaching the dowels, high grade solder or 22k. plate should 
be flowed over the root cap to stiffen it and fill the depressed 
central area. 
The cap, with dowels soldered in place, is now returned to 
the root and the peripheral margin of the band corrected by 
burnishing. 
An impression and bite or a bite-impression is secured, 
removing it from the mouth with the face bow. 
A film of wax is flowed over the dowels and inside the root 
cap to facilitate removal of the cap from the cast later on. 
The cap is placed in position in the impression and casts 
developed and attached to the occluding frame. 
A Goslee tooth of suitable size is selected and ground, if 
necessary, to meet requirements. CROWN WORK 
709 
It is then imbedded, occlusal end down, in modeling com- 
pound, in the swaging ring. The surfaces to which the gold is 
to be applied should be above the ring margins, so that the 
rubber in the swager may force the gold against all required 
areas. 
Fig. 617.— Goslee Tooth Invested in Swaging Ring, Prepara- 
tory to Adapting Socket. Tooth Set in a Diagonal 
Position for Swaging 
A disc of 36 g. pure gold, or platinum, somewhat larger 
than the areas to be covered, is applied to the crown base, and 
with finger pressure and burnisher adapted to the porcelain. 
When reasonably close adaptation has thus been secured 
and the excessive surplus removed, final adaptation is devel- 
oped by swaging. 
Fig. 618.— Goslee Tooth Set in Upright 
Position for Swaging Socket 
Fig. 619.— Backing or Socket Adapted 
to Goslee Tooth. Dowel in 
Position 
An opening in the gold socket is now made for the recep- 
tion of the short dowel, which may be of regular form and 
headed on one end, or a piece of 14 g. clasp metal wire, suf- 
ficiently long to project slightly beyond the socket, may be 
used. With dowel in position, the cap is reswaged. 710 
CROWN WORK 
Wax is applied to the dowel and against the gold, the two 
removed and united with high grade solder. The gold should 
also be stiffened by flowing a film of solder over its general 
surfaces, but not along the margins. 
Fig. 620.— Metal Socket, Swaged, with Dowel Attached, 
Goslee Tooth. Form of Root Cap Usually 
Employed for Molar Teeth 
The socket is now returned to the porcelain for final swag- 
ing, after which the tooth is removed from the moldine. 
The tooth in its socket is now adjusted to the root cap and 
waxed in position. 
Previously, however, the root cap is heated slightly to 
soften the wax around the dowel, removed, freed from wax, 
and returned to position on the cast. 
Fig. 621.— Crown with Socket, Ad- 
justed to Root Cap, Ready 
for Waxing Together 
The assembled crown is waxed to the desired contour, re- 
moved from the cast, the porcelain removed from its socket 
and the metal structure invested for completing the required 
contour, either by soldering or casting. 
The Goslee tooth is capable of a wide range of applica- 
tion in bridge work, when sufficient space is present in which, CROWN WORK 
711 
Fig. 622.— Two Views of Finished Crown 
Fig. 623.— A Bridge Composed of Goslee Teeth Combined 
with Gold Shell Crowns 
Fig. 624.— Goslee Bridge in Position on Cast 712 
CROWN WORK 
in addition to the porcelain replacements, a rigid metal struc- 
ture may be introduced. 
The individual saddle is often applied in connection with 
teeth of this type to very great hygienic advantage. 
The Gardiner Replaceable Tooth 
This tooth is supplied for both anterior and posterior re- 
placements. In form, it is somewhat novel, having a broader 
base than occlusal area. 
Instead of having an opening within the body of the crown 
for the reception of a lug, the base of porcelain presents a 
square or rectangular projection, which is received by and 
enclosed within a correspondingly shaped depression in the 
socket. 
To give the crown additional stability and resistance to 
stress, the base is composed of flat planes, placed at varying 
Fig. 626.— Cervical View, Showing Dis- 
positions of the Various 
Basal Planes 
Fig. 626.— Proximo-Cervical View of Gar- 
diner Tooth, Showing Anchor- 
age Lug of Porcelain 
angles. These planes are so disposed as to tend to seat the 
crown firmly in its socket under masticatory stress. 
Because of the extremely constricted bulk of porcelain 
entering into the construction of the tooth, it can be applied 
in many cases in limited spaces without requiring appreciable 
modification of form. 
The planes are so disposed as to give uniformity of thick- 
ness to the occlusal body of porcelain. The projecting lug is 
placed directly under the lingual cusps, thus giving support 
to an otherwise weak area of porcelain. 
TECHNIC OF APPLICATION OF THE GARDINER TOOTH 
The root cap is formed by any of the previously described 
methods, an impression secured, casts developed, and mounted 
on the occluding frame. CROWN WORK 
713 
A tooth of suitable form and color is selected and fitted 
to the root cap, due allowance being made in its length for 
the interposition of the socket. 
The tooth is then imbedded, occlusal end down, in mold- 
ine, in the swaging ring, and a 36 gauge pure gold or platinum 
socket developed by burnishing and swaging. 
When adapted, the margins of the socket are trimmed so 
as to form a collar around the entire peripheral margins of 
Fig. 627.— View of Gardiner Tooth 
with Swaged Socket 
the tooth, as should be the case in practically all types of re- 
placeable teeth. 
To prevent distortion in handling and soldering, a film 
of high grade solder should be flowed on the under, or cer- 
vical, areas of the socket, but not over the peripheral margins. 
When this plan is adopted, the margins should be rebur- 
nished to the porcelain before investment. 
The socket, with crown in position, is now adjusted to the 
root cap, the two united with wax, the assembled crown re- 
moved from cast, the porcelain removed from socket and the 
metal parts invested for soldering or casting. 
Teeth of suitable form and width are selected to fill the 
space between the abutment supports. Sockets are formed 
APPLICATION OF THE GARDINER TOOTH IN BRIDGE WORK 
Fig. 628.— Lingual View of 
Teeth Removed from 
Bridge 
Fig. 629.— Labial View of 
Metal Structure of 
Bridge 
Fig. 630.— Porcelain and 
Metal Structure 
Assembled 
in the manner described. These should be stiffened with a 
solder or plate that will not fuse in the final assembling and 
soldering of the bridge. 714 
CROWN WORK 
Before permanently attaching the porcelain teeth to their 
sockets with cement, the surfaces to be covered by the latter 
Fig. 631.— Four-Tooth Bridge, Porcelain 
Removed from Metal Sockets 
Fig. 632.— Porcelain and Metal Struc- 
ture Assembled 
Fig. 633.— Cut Showing Manner of Flanging the Metal 
Sockets to Increase Porcelain Anchorage 
should be etched with hydro-fluoric acid, or the glaze removed 
with discs. 
The Merker Replaceable Tooth 
This tooth, comparatively new, possesses two points of 
interest. The base is composed of two flat planes disposed at 
Fig. 634.— Proximal Views of Merker Anterior 
and Posterior Teeth, Seated on 
Metal Bases 
right angles to the long axis of the tooth. A small, rather 
deep opening in each plane extends occlusally for the recep CROWN WORK 
715 
tion of two iridio-platinum anchor dowels, which, during con- 
structive stages, are adjusted to the metal socket. 
Fig. 635.— Anterior Bridge Composed of 
Merker Replaceable Teeth, Two Central 
Incisors of Which Are Removed from 
Position 
Fig. 636.— Lingual View of the Anterior 
Bridge 
Fig. 637.— Posterior Bridge, First Molar 
Removed from Metal Structure 
The application of this crown in crown and bridge work 
is practically identical to the steps outlined for the Goslee 
crown. 
THE DIATORIC USED AS A REPLACEABLE TOOTH 
Diatoric posterior teeth are often used as replaceable 
teeth in bridge structures. When utilized for such purpose 
the basal periphery is usually reduced so as to permit the 
Fig. 638.— Posterior Bridge Fitted 
with Diatorics as Replaceable Teeth. 
A Long Pin, Cuspid Plate Tooth 
Applied as a Replaceable Filling 
formation of a collar around the socket. In addition to the 
anchorage afforded by the peripheral collar, during the swag- 
ing of the socket, the gold is carried into the central opening 
of the crown base. This forms a projection on the metal 716 
CROWN WORK 
structure and fulfills the purpose of a dowel. In some cases 
short, grooved dowels are adapted to the socket, as in the 
Goslee crown. 
Full Contoured Porcelain Crowns 
Crowns composed of porcelain and metal, although ad- 
mirably adapted to and indispensable in some cases, are fre- 
quently deficient in esthetic effects, the tinge of porcelain be- 
ing adversely affected by the presence of the metal. 
To overcome this very decided objection, full contoured 
porcelain crowns are very often used when conditions as to 
mesio-distal and occluso-gingival space will permit. 
Crowns of this type are supplied by the manufacturers, in 
great variety of forms and shades, and when well selected and 
skillfully applied to natural roots, are not distinguishable 
from natural teeth. 
Full contoured porcelain crowns may be divided into two 
general classes, viz., fixed dowel crowns and detached dowel 
crowns. The principal advantage of a detached dowel crown 
over one having a fixed dowel is that the porcelain base of 
the former can be readily adapted to the root face, the ab- 
sence of the dowel permitting unrestricted grinding on areas 
that interfere with close peripheral adaptation. 
FIXED DOWEL CROWNS 
The Logan, Twentieth Century and Johnson & Lund are 
types of the attached dowel crown, the dowel being enclosed 
Fig. 639.— Various Views of the Logan Crown and Dowel 
within the body of porcelain, and the latter fused around it. 
Since the technic of application of crowns of this type is sim- 
ilar, a description of one will answer for all, whether plain 
or combined with a root cap or cast base. CROWN WORK 
717 
TECHNIC OF ADAPTING A PLAIN LOGAN CROWN TO A 
NATURAL ROOT 
It will be assumed that the apex of the root to be crowned 
has been sealed with a permanent filling. 
The remaining portion of the natural crown is reduced by 
means of stones and Ottolengui root facers, slightly beneath 
the gum margin, being careful while doing so to avoid un- 
necessary injury of the soft tissues. 
The root canal is first enlarged with graded sizes of round 
burs as previously described, omitting the use of No. 10 and 
Fig. 640.— Sectional View of a 
Logan Crown 
Fig. 641.— Proximal View of a 
Logan Crown 
substituting therefor a fissure bur, the diameter of which is 
slightly larger than the mesio-distal thickness of the dowel, 
next the crown base. 
By means of the fissure bur the canal is enlarged labially 
and lingually sufficiently to receive the dowel at its greatest 
diameter, while the mesial and distal dentin walls of the root 
are not materially reduced and consequently weakened as is 
the case when a taper reamer is employed. 
From a stock of crowns one of suitable form and color is 
selected. In size it should be slightly longer than required, 
since both base and incisal edge must be modified by grind- 
ing, the first to secure necessary adaptation, the second for 
esthetic reasons. The width of the crown should be sufficient 
to afford strong knuckling contact with proximating teeth. 
The periphery of the crown base should slightly exceed that 
of the root face, since a subsequent step reduces the excess of 
porcelain until it coincides with the root periphery. If too 
small, a shoulder is formed which cannot be obliterated, the 
root projecting beyond the crown base. 
ADAPTING THE CROWN TO THE ROOT 
The crown is now applied to the root and the points re- 
quiring gross reduction are removed with suitable stones. 
Close adaptation is developed by interposing a disc of carbon 718 
CROWN WORK 
paper between the crown base and root face to mark the 
high points. These are ground away and the steps repeated 
until close peripheral adaptation between crown and root is 
secured. 
Care should be observed while making these tests to see 
that the crown is in correct alignment labio-lingually, which 
may be done, when necessary, by bending the dowel. 
When close adaptation of crown base to root face has been 
developed, the incisal edge or other areas of the crown are 
modified with stones and discs, to coincide with the type of 
Fig. 642.—- Logan Crown Ap- 
plied to Root Before Adapt- 
ing to Root Face Has Been 
Accomplished 
Fig. 643.— Carbon Paper In- 
terposed Between Crown Base 
and Root Face, to Disclose 
Points of Interference 
proximating teeth. When these show wear or ridged surface 
markings, similar surfaces and markings should be devel- 
oped on the crown. 
Sometimes the proximating natural teeth show unusual 
colors in or beneath the enamel, and which cannot be removed 
by any means employed. The setting of a porcelain crown 
or replacement of any type between teeth so marked, unless 
it is of closely corresponding color, is unsightly. 
Porcelain stains, both oil and water colors, are procurable, 
by means of which a tooth or crown can be made to match the 
most unusual shades found in natural teeth. The technic of 
application of such colors is simple. The tooth to be stained 
is thoroughly cleansed and washed in alcohol, a pigment of 
the desired shade is mixed with water or one of the essential 
oils as cloves or glycerin, and applied with a small brush by 
painting it over the surfaces or stippling, the degree of color 
being dependent upon the layer of pigment applied. 
When applied, the colors should be slowly dried, moderate 
heat accelerating the evaporation of the liquid. It is then 
introduced in the furnace and vitrified, the tooth resting on 
STAINING OF PORCELAIN TEETH CROWN WORK 
719 
a bed of pulverized silex, on the slab, and face upward. The 
colors glaze at a temperature varying from 1100 degs. F. to 
1500 degs. F. A little experience with these stains will enable 
the prosthetist to produce most beautiful esthetic results. 
In case a suitable shade of Logan or any of the types of 
crowns mentioned cannot be procured, they should be stained 
to coincide with the colors observed in the natural teeth. 
SECURING PERIPHERAL ADAPTATION OF CROWN BASE 
TO ROOT 
The final step in adaptation consists in removing the ex- 
cess or overhang of porcelain over the root, and lining the two 
peripheries up until they form continuous surfaces. The steps 
are as follows: 
A disc of white baseplate gutta percha, slightly larger 
than the crown base, is punctured in its center and passed 
over the dowel and against the porcelain. Moistening the 
Fig. 644.— Gutta Percha Inter- 
posed Between Crown Base and 
Root Face to Disclose Extent of 
Projecting Porcelain Over Root 
Margins 
surface of the disc next the crown base with oil of cajaput 
will cause the gutta percha to adhere firmly to the porcelain. 
The crown and disc are warmed and the crown forced to 
place on its root. Under pressure, the gutta percha being 
forced against the root, an impression of not only the face 
but of the periphery as well is secured. A blast of cold air 
directed on the disc will chill it so that removal can be 
effected without distortion. If the steps have been properly 
carried out a distinct impression of the root periphery wil] 
be seen in the gutta percha. 
A coarse, large size engine stone, running at a high speed, 
is lightly applied to the surplus gutta percha, and the lattei 
removed until the stone comes in contact with the projecting 
shoulder of porcelain. The grinding is continued until the 720 
CROWN WORK 
porcelain is reduced to the peripheral margin of the root as 
indicated in the gutta percha impression. During the grind- 
ing process the crown and disc should be immersed in cold 
water from time to time to obviate distortion of the gutta 
percha from frictional heat of the stone. 
During first grinding the prosthetist should not attempt 
to develop correct axial contour to the crown, but merely to 
Fig. 646.— Application of Stone to Remove 
Excess Peripheral Porcelain 
remove the projecting shoulder, after which the gutta percha 
may be removed and axial contour developed wTith suitable 
stones. The final polish on surfaces which have been ground 
and disced, is accomplished with putty powder, applied with 
a soft wood or hard felt wheel, running at high speed. 
The crown, having been ground to correct outline form, 
its base shaped to coincide with the root periphery, its sur- 
Fig. 646.— Appearance of a Properly 
Adapted Logan Crown 
faces polished, and, if necessary, stained, it is ready for 
mounting on the root. 
SETTING THE CROWN 
Cotton rolls should be placed under the lip or in such 
location as to guard against moisture during the setting of 
the crown. The root canal and root face should be thoroughly 
dried with cotton points and warm air. Cement of medium 
consistency is thoroughly mixed and worked into the root 721 
CROWN WORK 
canal and applied over the root face. The dowel and crown 
base is also covered with a thin film, and if a depression is 
present in the base of the crown it should also be filled. The 
crown is now set in position, considerable force being required 
to seat it and expel the excess cement. 
Pressure should be maintained upon the crown until the 
cement has set, which usually requires from eight to ten min- 
utes. Further time should be given the cement to thoroughly 
harden before removing the peripheral surplus. A small, 
angular blade instrument like a gold knife, used in finishing 
the margins of gold fillings, can be used in removing the sur- 
plus cement which should be cut or shaved rather than broken 
from along the joint. 
When loosened and the particles of cement are removed 
as well as can be with cotton and pliers, the gum tissues 
should be syringed with warm water and the crown tested as 
to its incisal or occlusal relation with opposite teeth. If sat- 
isfactory the patient is dismissed with instructions to avoid 
subjecting the crown to any stress for several hours, in order 
that the cement may not be disturbed until thoroughly crys- 
tallized. 
The Banded Logan Crown 
The technic of construction of a banded Logan crown is 
as follows: A root cap is constructed by methods previously 
outlined under the heading, “Construction of a Porcelain 
Faced Crown” (page 641). The enlargement of the root 
canal for the reception of the rectangular dowel of the Logan 
crown is essentially the same as detailed for a plain Logan 
crown. 
ADAPTING THE LOGAN CROWN TO THE ROOT CAP 
Before perforating the root cap for the reception of the 
dowel the root canal should be enlarged and the crown 
adapted to the root face by grinding. The lingual side of the 
crown base should be reduced to form a Y-shaped space, 
which later on is filled with solder. 
The general adaptation of the crown to root face having 
been developed, the root cap is set in position on the root 
and with a burnisher indented to indicate the location and 
extent of the opening for dowel. A series of small holes can 
be drilled through the cap while in position on the root, or it 
can be removed and the holes punched with plate punch. In 
either case the several holes are connected by passing a fine 
fissure bur through the intervening divisions. 722 
CROWN WORK 
The dowel is now forced through the more or less irregular 
slot, the excess gold being forced into the entrance of the root 
canal, the margins of gold thus fitting tightly against the 
dowel. 
Fig. 647.— Prepared Root with 
Cap. Notice Form of Opening 
in Cap Required for Dowel 
Fig. 648.— Crown Resting on 
Root Cap. Dotted Line Shows 
Lingua] Reduction of Porcelain 
Required 
A disc of gold, slightly larger than the crown base, is per- 
forated with a corresponding rectangular slot, placed on a 
large cork and the dowel forced through it until the crown 
base rests upon the disc. By repeated burnishing and anneal- 
ing the disc is closely adapted to the porcelain. 
The peripheral excess of the disc is removed, close to, but 
not exactly even with the crown periphery, a slight surplus 
Fig. 649.— Adapting Gold Disc to Crown 
Base, Against Cork 
Fig. 650.— Disc Adapted and Periph- 
eral Excess Removed 
being necessary to insure the solder being drawn out to full 
contour. 
The cap, disc and crown are now assembled on the root 
and their relation noted. Particular attention should be given 
the labial alignment of the crown and band. When the crown 
sets to the lingual of the labial band surface, it may be brought 
forward by bending the dowel to the lingual and extending 
the slot in the cap to the labial, it being necessary in some 
cases to ream the root canal also for the accommodation of 
the dowel. When the crown extends to the labial of the band CROWN WORK 
723 
surface and its labial alignment is approximately correct, the 
solder may be drawn through so as to fill the space between 
the disc and labial band surface, and the gold and porcelain 
Fig. 651.— Securing Relation Between Crown, Disc 
and Root Cap, with Wax 
dressed smoothly to form a continuous surface in the final 
finishing of the crown. 
Two thicknesses of gold plate, the disc and cap top, are 
interposed between the root face and crown base. Both of 
these may be reduced somewhat to bring the crown closer to 
the root, and lessen the display of gold on the labial surface 
of the finished crown. 
ASSEMBLING THE SEVERAL PARTS OF THE CROWN 
The cap, disc and crown having been fitted in correct rela- 
tion to each other on the natural root, they are assembled as 
follows: 
The crown and disc are removed, all of the parts dried, 
sticky wax is applied around the dowel and against the disc 
and softened with a hot spatula. The crown is then forced 
Fig. 652.— The Assembled Parts Removed, 
Ready for Investment 
against the cap, the interposed wax pressing the cap against 
the root, and the disc against the crown base. When the wax 
is chilled, the three parts, now firmly united, are removed from 724 
CROWN WORK 
the root (see Fig. 652), the surplux wax trimmed away and 
any openings between cap and disc filled in with wax, when 
the crown is ready for investment. 
INVESTING THE BANDED LOGAN FOR SOLDERING 
The investment of a banded Logan crown for soldering is 
essentially the same as the investment of a porcelain-faced 
crown. The joint surfaces between disc and root cap must 
be entirely exposed to prevent the confinement of air in con- 
Fig. 653.— Crown Invested for 
Soldering. Notice Small Wedge 
of Metal to Be Inserted Be- 
tween Root Cap and Disc to 
Prevent Displacement of the 
Latter in Soldering 
stricted spaces and, further, so that in soldering it may read- 
ily be seen when the joint is filled. 
When the investment has hardened, the surplus trimmed 
away, and the joint surfaces freely exposed, the wax is re- 
moved by pouring a fine stream of boiling water into the space. 
Care should be taken to remove every particle of wax, for if 
any is left and flux is applied, it will act as a carrier for the 
latter, and when heat is applied the wax will melt and pass 
beyond the gold surfaces onto the porcelain, thus inviting frac- 
ture of the crown. 
SOLDERING THE CROWN 
The joint areas to be soldered are covered with a thin film 
of thick borax paste, a thin piece of wood, as a delicate, wedge- 
shaped toothpick, being most useful in introducing it in con- 
stricted spaces. 
When fluxed, the invested case is set on a piece of gauze, 
over a Bunsen burner, and thoroughly heated, until the base of 
the investment is red, when it may be removed to the solder- 
ing block and the blow-pipe flame applied to bring it to suit- 
able temperature for soldering. 
The solder, in the form of a long strip, is applied in the CROWN WORK 
725 
deepest part of the joint area, and as it melts is fed into the 
fused mass until proper contour is attained. 
To obviate the tendency of the disc being drawn away from 
the crown base by the contraction of the solder in cooling, a 
wedge of plate metal should be inserted between the cap and 
disc, before placing the case on the Bunsen burner. 
FINISHING THE CROWN 
When cooled, the investment is broken away, the crown 
placed in a test tube and boiled in a pickle of 25 per cent H Cl, 
Fig. 654.— Appearance of the Finished 
Crown 
after which it is finished in the usual manner with stones and 
discs, the final polishing being accomplished with fine pow- 
ders on the lathe wheel. 
The Davis Crown 
The Davis is a fully-contoured porcelain crown, having a 
central cavity within its base for the reception of an anchor- 
age dowel. 
The dowel, which accompanies the crown, and of which 
there are varying sizes, consists of a pin having a shoulder 
Fig. 655.— Sectional View of Davis Crown Be- 
fore and After the Base Has Been Modified. 
Special Care Must Be Observed to Preserve the 
Shoulder Depression in Crown Base for Recep- 
tion of Dowel Collar 
near the crown end. From the shoulder, one portion tapers 
apically for insertion in the root, while the shorter is parallel 
sided for insertion in the crown base. The dowel is grooved 726 
CROWN WORK 
in several places throughout its length to afford better anchor- 
age within the cement. From 13 to 16 gauge iridio-platinum 
or clasp metal wire may be used as dowels if desired. 
There are three general methods of applying crowns of 
this type to the roots of natural teeth, the crowns so applied 
being designated as plain, cast base, and banded. 
APPLICATION OF THE PLAIN DAVIS CROWN 
A Davis crown without cap or metal base may be applied 
to the root of a tooth in several ways, the following of which, 
if carefully carried out, will yield good results. After the 
root has been properly treated and filled, the remaining por- 
tion of natural crown is reduced slightly beneath the gum 
margin. 
The root face should usually be given a distinct labio- 
lingual convexity sufficiently marked to guide the crown base 
to position without any tendency to rotate. 
Fig. 656.— Root Reamer in Canal 
Fig. 657.— Dowel in Canal 
The root canal is opened up first with small burs and after- 
ward enlarged with a reamer corresponding in taper with the 
Fig. 658.— Three Sizes of Root 
Reamers 
dowel. To avoid excessive enlargement of the root canal, the 
dowel should be inserted from time to time and tested as to 
closeness of adaptation to the canal walls. The shoulder CEOWN WORK 
727 
should rest squarely upon the root face, while the sides of the 
dowel fit closely within the canal. This latter requirement, 
however desirable, cannot always be realized, it being neces- 
sary at times to incline the dowel in some direction to bring 
the crown in alignment with proximating teeth. 
A crown should be selected slightly longer than required 
and with a base a little larger than the root face. 
The dowel is now removed from the canal and the crown 
base adapted to the root, first removing the grosser points of 
contact with moderately coarse stones. 
Close adaptation is developed by returning the dowel to 
the root canal, placing a disc of carbon paper over it and 
applying the crown to the root face, the interposed carbon 
indicating the points of interference. 
In all of these tests, care should be taken to hold the crown 
in correct alignment with the proximating teeth before apply- 
ing pressure against the carbon paper. 
The points indicated on the base of the crown by the car- 
bon are ground away and the tests repeated until close adap- 
tation, particularly peripherally, is obtained. 
In some cases it may be found necessary to bend the dowel 
slightly to bring the crown into correct alignment with the 
proximating teeth. In other cases an offset dowel may be re- 
Fig. 669.— Crowns Adjusted to Straight, 
Bent, and Offset Dowels 
Fig. 660.— Three Different Forms of 
Dowels 
Fig. 661.— Three Sizes of Offset Dowels 
quired, and again it may be necessary to ream the canal wall 
away, thus permitting the dowel to move bodily, in the direc- 
tion indicated. 728 
CROWN WORK 
Special care should be observed to see that the shoulder 
of the dowel rests in the depression in the crown base. When 
it fails to rest within the depression in the porcelain designed 
for it, the attachment of crown to dowel will be weakened be- 
cause of the shortening of the latter. 
REDUCING THE PERIPHERAL SHOULDER 
Apply a disc of white baseplate gutta pereha to the crown 
base, having first moistened the disc with oil of cajaput and 
warmed the porcelain slightly to develop adhesion. Perforate 
the disc in its central area to allow the dowel to pass through. 
Fig. 662.— Plain Davis, Adapted to Root Face, Excess 
Peripheral Shoulder Not Yet Removed 
Moisten the face end of root with water. Direct a blast of 
hot air on the gutta percha and force the crown to place. A 
few drops of cold water will chill the gutta percha, and on 
removal of the crown it will adhere to and come away with 
the latter. 
The excess porcelain is now ground away to the line of 
root periphery as indicated in the gutta percha impression. 
The steps are similar to those of correcting the base of a plain 
Logan crown. (See page 719.) 
GENERAL MODIFICATION OF THE CROWN BY GRINDING 
The incisal or occlusal relation of the crown is tested and 
any modification as to length or general contour corrected. 
All surfaces so modified should he polished with fine discs, 
followed with putty powder on the lathe wheel. 
SETTING THE CROWN 
The crown, dowel, root face and canal are thoroughly dried. 
A mix of cement of medium consistency is made and intro- CROWN WORK 
729 
duced in the canal and in the opening in crown, after which 
more is added to the crown base. The crown is now forced 
Fig. 663.—Sectional View of Crown, 
Offset Dowel, and Root 
to place and held firmly until the cement has hardened, when 
the surplus is carefully removed. 
THE DAVIS CROWN IN BRIDGE WORK 
The Davis crown can often be applied to advantage in 
bridge work. When so utilized, the base of the crown selected 
for the dummy must be reduced sufficiently to give space for 
Fig. 664.— Swaging Disc Against Crown Base and Dowel Collar 
Fi&. 6S5.— Crown Sockets Formed with Proximate 
Extensions or Ribs 730 
CROWN WORK 
Fig. 666.— Root Caps with Perpendicular Ribs, Designed to Unite with Corresponding Ribs of 
Dummy Socket. First View Removed, Second View in Position 
the metal structure. It is also advisable to groove the proxi- 
mating surfaces of crowns and swage base caps or sockets, 
the sides of which are conformed to and fit within the prox- 
imal grooves. These perpendicular ribs add greatly to the 
Fig. 667.— Interproximal Exten- 
sions, Incisally, of Gold in Small 
Bridge Structure Formed by 
Grooving Davis Crowns on Their 
Mesial and Distal Surfaces. Ob- 
ject, to Resist Tendency of 
Crowns to Tip Buccally or Lin- 
gually Under Stress 
Fig. 668.—The Completed Bridge 
Ready for Permanent 
Setting 
stability of the porcelain, tending, as they do, to resist tor- 
sional strain. The principal anchorage is secured by means of 
short dowels set within the sockets, to which they are attached 
during the constructive stages of the individual dummies. 
Fig. 669.— Justi Crown, Showing Crescent Opening for 
Dowel. Also Crown with Dowel in Position CROWN WORK 
731 
The Cast Base Davis Crown 
The prosthetist who can grind a perfect joint between 
crown base and root face will find only occasional need for 
interposing a cast base between crown and root. 
A cast base as ordinarily constructed neither obviates 
splitting of the root nor displacement of the crown under 
stress. 
The insertion of short dowels, or iridio-platinum, in lin- 
gual areas of the root face, to the mesial or distal of the root 
canal, or beveling the lingual periphery of the root so that the 
projecting lip of the cast base may engage with it, will largely 
reduce the tendency of a root to split under stress. 
These and other similar means of obviating root splitting, 
although simple and efficient, are often ignored in the class of 
work under consideration. 
Cast bases are most strongly indicated in those cases where 
considerable loss of root structure has occurred, and when 
the fitting of a peripheral band would be difficult, if not im- 
possible. 
CONSTRUCTION OF A CAST BASE DAVIS CROWN 
After the apex of the root is filled the remaining portion 
of the natural crown is removed. Tn case the crown has been 
Fig. 670.— Root Prepared with Inside Shoulder Depression, 
Showing Labial V-Shaped Notch 
lost through extensive caries, all leathery decay should be re- 
moved and the root margins rendered smooth and firm. 
A crown is now selected and ground to meet requirements. 
When the root has not suffered loss of structure from 
caries, space for the cast base is gained at the expense of 
grinding both root and lingual areas of the crown base. 732 
CROWN WORK 
When space to be occupied by the cast base is limited it 
is advisable, in order to impart rigidity to the wax pattern, 
to extend a V-shaped groove from the canal to the labial sur- 
face of the root. Notching of the crown base will also prove 
beneficial, but the notch should terminate within the labial 
periphery. 
Such notches form strengthening ribs in the wax pattern 
and prevent distortion while handling and investing. 
The crown having been ground to requirements, the root 
face prepared, the canal reamed and dowel fitted, the next 
step is to form the wax pattern. 
The crown base is coated with a thin film of oil, the dowel 
inserted in the crown, a piece of softened inlay wax passed 
over the dowel and against the crown base. The crown is now 
Fig. 671.— Davis Crown in Position on 
Root Wax Model for Cast 
Base Interposed 
Fig. 672.— Crown and United Wax 
Base and Dowel Removed 
from Root 
forced firmly against the root face, being careful to keep it 
in proper alignment with the proximating teeth. 
When chilled, the surplus wax is trimmed away, even with 
root and crown peripheries. This step must be carefully car- 
ried out or the peripheral margins of the pattern will be dis- 
turbed. 
The crown is now removed, which usually is easily accom- 
plished if the base was previously oiled. 
The wax pattern is removed by grasping the projecting 
end of the dowel lightly with the pliers, being careful not to 
rotate or oscillate it. 
If satisfactory, the oil is removed with a camel’s-hair 
brush and soapy water, or its surfaces can be cleansed with 
a spray of acetone, which will dissolve the oil without affect- 
ing the wax. CROWN WORK 
733 
A sprue former is now attached in the thickest portion of 
the lingual area, usually at right angles to the dowel, and it 
is ready for investment in the casting ring. 
Fig. 673.— Wax Model Mounted for 
Investing 
The Banded Davis Crown 
The following method of applying a Davis crown to a 
banded or capped root is comparatively simple and satis- 
factory: 
After treatment and filling of the canal, the remaining por 
tion of natural crown is removed, the peripheral ring of 
enamel cleaved away, and the root faced, practically at right 
angles to its long axis. To this the cap is fitted in the usual 
manner and perforated in line with the root canal, previously 
reamed, for the reception of the dowel. 
The crown is now selected and ground away on its lingual 
side to form a V-shaped opening with the cap. 
In the base of the crown a shallow, yet distinct, V-groove 
should be cut, extending from the lingual surface to the central 
area. The gold, when forced into this groove, forms a rib 
which guides the crown into proper position on the base. 
The crown, base upward, is now imbedded in moldine, in 
the swaging ring. A short dowel is inserted in the crown and 
a disc of 36 gauge pure gold, perforated in the center, is passed 
over the dowel and against the base of the crown. 
The disc is now adapted to the crown base with burnishers 
and the adaptation completed by swaging. Care should be 
taken to force the gold into the V-shaped groove in the crown 
base. 
The peripheral surplus is now removed and the disc, if 
distorted, is reswaged. 
The short dowel is formed by excising the apical four- 
fifths of a dowel of regular size. It is used so that a place 
may be made in the disc for the regular dowel, which is now 
substituted. CROWN WORK 
The several parts are assembled in the following order: 
The cap is set in position on the root, the dowel inserted in 
crown base, and the disc passed over the dowel until it rests 
against the porcelain. A pellet of softened wax is placed on 
Fig. 674.— Davis Crown, 
Modified, in Position on Root, 
Disc and Cap Interposed 
Fig. 675.—Crown, Disc, In- 
terposed Wax, Dowel and 
Root Cap, Removed from 
Root 
Fig. 676.— Finished Banded 
Davis as It Appears 
on Root 
the root cap, the dowel inserted in the wax and the crown and 
disc forced to position on the root. 
If the parts are free from moisture and the wax sufficiently 
plastic and adhesive, the assembled crown can be removed 
without difficulty. 
To obviate disturbance of relation, a hot spatula should 
be applied to the wax at several points between disc and cap. 
All .spaces should be filled in with additional wax where 
needed, and the structure contoured to desired form. 
The crown is now removed and the assembled metal parts 
united either by casting or soldering. CHAPTER XXVIII 
THE GOLD SHELL GROWN 
(MORRISON CROWN) 
The two-piece, gold shell crown, as ordinarily constructed, 
consists of an axial band and a swaged occlusal surface, both 
developed from plate gold, so contoured and united as to rep- 
resent the anatomic form of the lost natural crown it is de- 
signed to replace. 
ADVANTAGES 
A crown of this type is strong, economical and efficient. 
The constructive details, although requiring care in their exe- 
cution, are comparatively simple. Because of the ease with 
which sheet gold can be wrought in this method of crown con- 
struction, most beautiful esthetic forms can be produced by 
“the man who knows” anatomic tooth forms, and technic as 
well. 
DISADVANTAGES 
The color of gold as compared with porcelain for tooth 
replacement, is objectionable, therefore gold crowns should 
not be placed in conspicuous locations. 
WHERE INDICATED 
Gold shell crowns are most commonly indicated in the 
restoration of badly decayed molars in either arch, occasion- 
ally in second bicuspids, and sometimes, but rarely, in first 
bicuspids, when filling operations are likely to prove unsatis- 
factory. In bridge work, when occluso-gingival space is too 
limited for the combined use of metal and porcelain, a shell 
crown of the type under consideration, or some modification 
of it for an abutment is practically indispensable. 
MODIFICATIONS OF THE METAL SHELL CROWN 
There are many modifications in constructive details of 
the metallic shell crown, consisting principally of the manner 
of obtaining axial contour of the band and of forming and 
attaching the cusp surfaces to the axial section. 
A sufficient knowledge for practical purposes of these vari- 
ous types of crowns can be gained from a full description of 
735 736 
THE GOLD SHELL CEOWN 
the two-piece Morrison crown, as now constructed, together 
with a brief description of the cast crown. 
Technical Details of Gold Shell Ceown 
CoNSTEUCTION 
PBELIMINAEY PEEPAEATION OF THE TOOTH OE BOOT 
The preliminary work of most importance in this as in 
all classes of crown construction is the proper treatment and 
successful filling of the root canals. This should, in prac- 
tically all cases, be completed before attempting the peripheral 
reduction of the tooth or root. 
EESTOBING A BADLY DECAYED NATUEAL TOOTH FOE 
ANCHOEAGE PUEPOSES 
When most of the natural crown has been lost from any 
cause, it is imperative that a considerable portion of it be 
restored by operative procedures, to afford firm anchorage for 
the substitute crown. This may be accomplished in two ways: 
first, with amalgam, and second, by means of a suitably shaped 
casting, usually of Weston’s metal or silver. 
THE AMALGAM METHOD OF EESTOBATION 
When the roots have been properly filled, the canals are 
reamed out to receive one or more anchorage posts, depending 
on the requirements for such means of anchorage. The wire 
posts should extend deeply in the canals to avoid danger of 
loosening when the crown is set and later subjected to stress. 
The How anchor screw post is most useful for such purpose. 
Also a special form of screw made by the Blue Island 
Specialty Co. By this method both root canal and post are 
threaded, and when, in setting the post, a little cement is 
applied around it, firm anchorage of the post within the canal 
of the root is insured. When a taper screw is employed care 
should be taken to avoid splitting the root in its introduction. 
After posts are set, a soldered copper band constructed 
to fit the root is adapted to its periphery and trimmed suffi- 
ciently short to clear the occlusal surfaces of the opposite 
teeth. Into this matrix amalgam is packed and the patient 
dismissed for twenty-four hours or longer, so that the amal- 
gam may harden, and will not be disturbed in removal of the 
matrix or in subsequent root preparation. 
On removal of the matrix, usually accomplished by cut- 
ting with a sharp chisel, the amalgam stump is treated as if it THE GOLD SHELL CROWN 
737 
were tooth structure, and reduced with stones, discs and files 
in conjunction with the peripheral ring of enamel. 
RESTORATION BY MEANS OF A CASTING 
To restore a defective crown with a casting, the root canals 
should be enlarged as previously mentioned. When two posts 
are to supply the anchorage, the canals which receive them 
should be reamed parallel with each other, so that the posts 
may come away with the wax model without distorting their 
relation. If this is not possible, one good-sized post, deeply 
Fig. 678.— Molar Tooth with 
Anchor Screws Set in 
Root Canals 
Fig. 679.— Tooth Restored 
with Amalgam 
Fig. 677.— Various Sizes of 
Anchor Screws 
Fig. 680.— Molar Root Band- 
ed, Anchor Screws Set in 
Root Canals, Matrix 
in Position 
Fig. 681.— Molar Restored 
with Amalgam. Band Still 
in Position. For Crown Res- 
toration the Band Should 
Not Be Contoured Nor the 
Occlusal Surfaces Developed 
seated, in conjunction with such additional anchorage as may 
be developed by squaring out the pulp chamber will usually 
fulfill requirements. 
The posts are set in position in the canals, after which 
inlay wax is applied and built to required form. The wax 
model is then removed — the post, or posts, coming away with 
it — invested, cast, and set in position with cement. 
The object in making such restoration is to increase the 
hold of the crown to the natural root, as well as afford a 
solid foundation for the crown when subjected to masticatory 
stress. Without such means the attachment of the substitute 
to the natural crown, when the latter is badly decayed, is liable 
to prove unstable. 738 
THE GOLD SHELL CROWN 
CASES IN WHICH EXCESSIVE ROOT RESTORATION IS 
REQUIRED 
Cases frequently present in which the axial walls of a 
tooth may be partially or wholly decayed or broken away be- 
neath the gum margin. In such case peripheral root prepara- 
tion cannot be undertaken without forcing back the soft tissues 
and freely exposing the root face and margins. 
When the pulp chamber is open and of such form as to 
afford anchorage, baseplate gutta percha can be packed into 
it and over the face end of the root, of sufficient thickness 
when compressed, to “overflow” and force the soft tissues 
beyond the root periphery. The packing should be left in 
position for twenty-four or forty-eight hours. If, on removal, 
the root face is not sufficiently exposed, the packing should 
be renewed so as to still further force the tissues outward 
beyond the root periphery. 
Should the pulp chamber anchorage prove insufficient to 
hold the gutta percha in position, a small, flat-headed screw, 
about one-fourtli to three-eightlis of an inch long, or longer if 
necessary, may be screwed into the root canal, and the pack- 
ing material built around the projecting head. In case the 
root canals have not yet been treated and filled, extreme care 
should be exercised not to force any putrescent matter through 
the apex. It is also usually best to puncture the gutta percha 
with a small instrument to permit any gas that might accumu- 
late in the pulp chamber to escape during the compression 
process. 
When sufficient clearance space has been gained in the 
manner described a matrix should be applied and adapted to 
the root periphery. The entire band is then filled with cement, 
which is allowed to set, when an opening may be drilled 
through the center, into the pulp chamber, through which the 
canals may be treated and filled. 
The matrix must remain in position during the entire treat- 
ment of the root to prevent return of soft tissues. After 
treatment is completed the cement is removed from the matrix, 
anchor screws or posts inserted in the canals, and amalgam 
substituted, as previously outlined. 
WEDGING 
When the teeth adjoining the space the crown is to occupy 
have moved toward each other, thus reducing it, they should 
be forced apart by wedging, so that interproximal space next 
the crown, both mesially and distallv, may be restored. THE GOLD SHELL CROWN 
739 
A wedge, shaped from palm wood (the handle of a palm 
leaf fan) should be inserted tightly between the inclined teeth, 
its base resting on the stump of root to be crowned. The 
fibers of wood should run bucco-lingually. When inserted dry 
the wood fibers will swell and gradually force the teeth apart, 
usually without much inconvenience. While the process is 
slow, requiring a week or more of time and insertion of pro- 
gressively larger wedges as space is gained, it is an essential 
step and should in all cases, when possible, be accomplished 
by this or other effective means. 
PREPARATION OF THE TOOTH OR ROOT FOR THE BAND 
The same general principles of root preparation previously 
outlined in the porcelain-faced anterior crown, of converting 
the remaining portion of natural tooth into a slightly tapering 
cone, the base beneath free margin of gum at point of termi- 
nation of crown band, apex pointing occlusally or incisally, 
apply with equal force in preparing posterior teeth for the 
reception of shell crowns. 
REDUCTION OF THE OCCLUSAL SURFACE OF THE CROWN 
The preparation of a root or tooth for the reception of a 
shell crown does not involve the shortening of the natural 
crown when present to the same extent as is required for an- 
terior porcelain-faced restorations. In fact, the natural crown 
is left as long as possible to furnish anchorage and obviate 
displacement of the substitute crown under lateral stress. 
Sufficient reduction, however, must be made to afford space 
for a thick, well-reinforced occlusal cap to the shell. About 
one-sixteenth of an inch space, seen from the buccal, when the 
teeth are in occlusion will usually be ample. Should this not 
prove sufficient, the face of the root may be readily reduced 
later on when fitting the band. The occlusal surface is cut 
away to the required extent with a five-eighths to three-fourths 
inch, coarse carborundum stone. Care should be taken not 
to mar the proximating teeth. 
REDUCTION OF THE AXIAL WALLS OF THE TOOTH 
A thin edge carborundum stone is used to reduce the mesial 
and distal surfaces. The wheel is allowed to touch the tooth 
lightly, yet must be held firmly and under perfect control of 
the operator to avoid injury to the lips, cheeks, tongue and 740 
THE GOLD SHELL CROWN 
gums. The first cut is begun slightly inside of or at the dento- 
enamel junction, and the stone so held that its edge will come 
through to the proximate surface of enamel at the gingival 
line. A second cut is usually required on both mesial and 
Fig. 682.— Thin-Edge Carborundum Stone in Position for Removing Distal 
Contour of Lower First Molar 
distal surfaces, to complete the rough blocking off of these 
surfaces. 
The buccal and lingual surfaces are reduced with rather 
small square-faced stones so applied as to avoid injury to the 
Fig. 683.— Diagrammatic View of Position of Stone. 
Cutting at Expense of Molar Tooth 
cheeks and tongue. The removal of enamel with these stones 
cannot usually be carried below the gingival line. 
With small knife-edge stones and discs the peripheral ring 
of enamel just under the gum margin can be partially, and in 
some areas entirely, removed. It is frequently a difficult task 
to remove the enamel from those locations where the surfaces THE GOLD SHELL CROWN 
741 
turn from buccal and lingual into the mesial and distal em- 
brasures. Small rubber and carborundum wheels carried in 
the port polisher, applied so that their outer surfaces or ends 
can reach the constricted areas will be found very useful in 
reducing the root to symmetrical form. 
The enamel cleavers of ordinary form are of but little ser- 
vice in removing enamel from molar teeth, since it is not pos- 
Fig. 684.— Application of Small Stone 
in Right Angle Hand Piece to Disto- 
Lingual Angle of Crown 
sible to apply the necessary force effectively back of the bi- 
cuspids. 
Dr. W. E. Harper has designed a contra-angle handle 
which holds a variety of short shank, regular and other forms 
of cleavers and files. These can be used to advantage in the 
Fig. 685.— Left Cut Shows Application 
of Stone in Removal of Buccal Enamel. 
Dotted Line, the Usual Amount of Tooth 
Structure Removed. Right Cut, Outline 
of Prepared Tooth 
removal of enamel in difficult locations, where the ordinary 
forms of cleavers are inapplicable. 
By carefully introducing carborundum paper discs and 
warping them around the angles, much of the final prepara- 
tion can he accomplished without serious injury to the soft 
parts. 
The root files can be used to advantage, particularly in 
the embrasures. When the instrument is held in the right 
hand, the thumb of the left is placed against the buccal border 742 
THE GOLD SHELL CROWN 
surface, the index finger to the lingual. The thumb is used 
as a fulcrum with the result that greater and more direct force 
can be applied against the enamel in the interproximate spaces 
than is possible with any other position. 
GENERAL FORM OF THE PREPARED ROOT OR TOOTH 
The flare of axial surfaces should be plainly noticeable, 
but not too marked; that is, the convergence of peripheral 
Fig. 686.— General Form of Reversed Cone After Removal of Enamel 
surfaces from the base of the cone under free margin of the 
gum outward or occlusally should range from two to five 
degrees. 
Certain facts must be kept continually in mind during root 
preparation, viz., the gingival cone of the natural tooth must 
Fig. 687.— Cut Showing Relation of Prepared 
Tooth to Occluding Teeth 
in all cases be reversed; the base of the new cone must be 
extended apically as far or even slightly beyond the point 
where the cervical end of the band, when permanently set, 
will rest; the formation of shoulders or grooves, or any irreg THE GOLD SHELL CROWN 
743 
ular surfaces that will interfere with the correct fitting of the 
band, must be avoided. 
TESTING THE CORRECTNESS OF ROOT PREPARATION 
The two tests previously mentioned under root prepara- 
tion for a porcelain-faced crown are applicable for proving 
the correctness of root preparation for shell, as well as other 
classes of crowns. The first of these — passing a delicate in- 
strument apically — is dependent quite as much on tactile 
sense as on the eye, for revealing irregular surfaces, grooves, 
shoulders or any remaining portions of enamel, and for deter- 
mining whether the sides have the proper flare. 
The final test is in the root measurement itself, which, if 
easily removed, indicates that the remaining portion of the 
tooth between the position of measurement and its occlusal 
end converges or becomes smaller. 
TAKING THE PERIPHERAL MEASUREMENT OF ROOT FOR BAND 
The wire loop is formed, placed in a holder, applied to the 
root and tightened. The loop should seldom ever be pressed 
under the free margin of the gum, unless the root is exces- 
Fig. 688.— Securing the Wire Measurement. The Wire Loop Should Not 
Be Carried to the Extreme Gingival Position of Cone 
sively cone-shaped, the idea being to form the band slightly 
smaller than actually required and drive it to place in fitting, 
thus insuring a close and accurate adaptation to the root per- 
iphery. On removal of the measurement, the loop is cut oppo- 744 
THE GOLD SHELL CROWN 
site the twist, and laid aside until the measurement for the 
band width is obtained. 
As a matter of economy, the band should be cut of approxi- 
mately correct width. The width may be determined by meas- 
uring the distance between the deepest curve of the gingiva 
of the root to be crowned, to the tips of the cusps of the oppos- 
ing teeth. Should the dip of the gingival gum curvature 
approach the root apex more closely on one side than the other, 
the greater width must be used for the band measurement. 
For example, when marked tissue absorption extends apically, 
exposing more or less of the surface of the lingual root of an 
DETERMINING WIDTH OF BAND 
Fig. 689.— Tapering Cardboard, Used to Determine Width of Band 
upper first molar, tlie band should be wide enough to cover 
the entire exposed area. There are better methods, however, 
of adapting crowns to teeth around which gingival absorption 
has occurred to a considerable extent than by the application 
of a band. In such cases the shoulder crown in which no over- 
lapping of gold on the root occurs, is far more hygienic and 
serviceable than any type of banded crown. 
A piece of ordinary cardboard, cut on a taper with the 
narrow end squared, serves as a convenient gauge. If too 
wide, the sides of the card are reduced, while if too narrow 
the end is cut away until the width coincides with the distance 
designated. A pair of dividers may also be used for securing 
the measurement. The length and width of band having been THE GOLD SHELL CROWN 
745 
determined, the next step is to lay it out, and cut it from the 
piece of gold plate. 
CUTTING THE BAND ACCORDING TO MEASUREMENT 
As has been previously pointed out, the outer envelop of 
the average posterior natural tooth represents two cones, an 
occlusal and a gingival, reversed, and with their bases meet- 
ing in a common plane in the mid-crown region. 
Fig. 690.— Scribing the Cervical End of Axial Cone Band. The Outer Arc Represents the 
Occlusal End of the Band. The Distance Between the Two Arcs Is Deter- 
mined by the Cardboard Measurement 
To reproduce such an envelop in gold, one of two plans is 
followed: first, form the band as a cylinder and by swelling 
and stretching, gain contact with proximating teeth, increase 
the mesio-distal diameter of the hand at the occlusal surface, 
and the bucco-lingual diameter in its mid-crown area to rep- 
resent the axial contour of the natural tooth. Second, form 
the band as a section of a cone, representing the flare of the 746 
THE GOLD SHELL CROWN 
average, natural gingival cone, and reduce the occlusal end 
by compression, contouring to the required dimensions. Of 
the two methods, the latter is much the simpler and better in 
every way. 
By referring to anatomic forms of teeth on page 634 it will 
be seen that the average flare of the gingival cone of molars 
is 25 degrees. Unless the space which the crown will occupy 
is constricted, a cone having this flare should be used. 
CUTTING A CONE BAND 
To cut a band by this method, the dividers are placed at 
the edge of the card or piece of gold plate, the points set at 
Fig. 691.— Marking the Length of Band 
with Wire Root Measurement 
3y4 inches apart and an arc is struck, somewhat longer than 
the root measurement. The radius is then increased the width 
of the band, as determined by the cardboard measurement, 
and from the same center a second arc is struck, representing 
the occlusal end of the band. 
When curvature of the gingival gum margin, around the THE GOLD SHELL CROWN 
747 
root being crowned, is very marked, as is frequently the case, 
the cervical end of the cone band must be reduced by scribing 
and trimming, to conform to such curvature. This naturally 
reduces the height of the cone, entirely at the expense of its 
Fig. 692.— Rule Placed on Measurement Length of Band and 
on Center from which Arcs Were Developed 
smaller end, and enlarges its cervical diameter or peripheral 
length proportionately. 
On returning the band to the root it will usually be found 
entirely too large. And while reduction of its cervical diam- 
eter may be effected with contouring pliers, anatomic outlines 
of the axial surfaces will be disturbed. 
When it is evident that much reduction of the cervical end 
of the cone must be made, the band should be marked and cut 748 
THE GOLD SHELL CROWN 
from one to three thirty-seconds of an inch shorter than the 
root measurement. 
The measurement is laid off on the gold plate and the band 
cut as follows: 
The wire measurement is curved to correspond with the 
gingival arc on which it is now laid, one end of the wire being 
brought even with the outer margin of the gold plate. The 
other end of the band is marked even with the wire measure- 
Fig. 693.—• Line Drawn with Rule to Indicate Divergence of Inner End 
of Band. The Outer End of the Band at the Edge of Plate 
Is Correct. Upper Left Corner Shows Form of Band 
ment, or in case of decided gingival curvature, proportion- 
ately shorter, in accordance with the slight or pronounced 
curvature of the gingival tissues. 
Lay a rule against this point and the center from which 
the arc was developed and mark the end of the band. When 
the gold plate is placed parallel with the outer edge of the card 
the opposite or outer end of the band will have the proper 
flare. The gold is cut and bent in the form of a cone, the two 
ends abutting squarely against each other. THE GOLD SHELL CROWN 
749 
The band ends should be held in contact with binding wire, 
for, although they may be soldered without the use of the 
binder, they will usually spring apart, at one or the other edge 
of the band, and the union be imperfect. 
WIRING THE BAND 
Fig. 694.— Diagrammatic View of Band 
Before Bending 
Fig. 695.— Band Ends, Butted and Held 
with Crossed Binding Wire 
Since the wire will not keep its position on the cone as 
ordinarily applied it should be crossed and carried around the 
band occluso-gingivally and twisted tightly, the surplus being 
placed on the opposite side of the cone, from the joint. 
SOLDERING THE BAND 
Borax is applied to the joint, a small piece of solder laid 
across, and the band ends united in the usual manner. 
FITTING THE BAND TO THE ROOT 
The band is conformed to the general outline of the root 
and pressed down until in contact with the gingiva. The 
scribing tool is applied and the gingival line marked on the 
buccal surface. Usually, because of difficulty in applying the 
scribing instrument to the lingual surface, an explorer can be 
substituted and the lingual curvature approximately marked 
in this manner. It is advisable to mark too close rather than 
too far from the gingiva and cut accordingly to avoid short- 
ening of the band width. After trimming off the gross surplus 
a second application of band to root will disclose the points 
needing further reduction. 
Naturally, as previously stated, when much curvature is 
present the band, when trimmed, will become enlarged. This 
may be compensated for in two ways: first, by cutting the 
band slightly shorter than the measurement at the start, and 
second, by reducing the gingival periphery with suitable con- 
touring pliers of the Peso or Benson type. 
CONTOURING THE BAND 
In forcing the band to place its bucco-lingual diameter will 
be somewhat increased beyond true anatomic dimension. This 750 
THE GOLD SHELL CKOWN 
distortion, however, can be readily corrected by applying the 
round beak of the Benson plier inside the band about the 
middle, occluso-gingivally, and with careful pressure on the 
outer side with the flatbeak the occlusal cone can be reduced 
to proper form. No appreciable pressure should be exerted 
Fig. 696.— Reducing the Occlusal End of Band with Benson Pliers 
on the handles to force the beaks together, as this, by thinning 
the gold, would increase the diameter and contour of the band 
in the mid-crown area. 
The Benson pliers are designed primarily for effective 
contouring of bands in any location where convex surfaces 
are required, the heavy handles and short beaks being speci- 
ally adapted for developing great force. One beak is flat, the 
other round, the latter acting on gold plate as a ball pene 
hammer does against metal on an anvil. 
The accompanying cut shows an extensively contoured 
crown, formed with these pliers by Dr. Benson, the axial band 
Fig. 697.— Second Molar Inclined For- 
ward from Loss of First Molar. Crown 
Contoured to Form Proximal Contact 
with Second Bicuspid (Benson) 
Fig. 698.— Bicuspid Bands Con- 
toured. Strip at Bottom Shows 
Doubler Attached to Main Band. 
Notice Flaring Ends of Latter 
(Benson) THE GOLD SHELL CROWN 
751 
being expanded in order to develop contact with a tooth some 
distance removed. In this case, a piece of gold was sweated 
against the straight band to give additional material for ex- 
panding and thus obviate weakening of the crown walls. 
The thickening of the band walls is essential where exten- 
sive contouring is carried out. It is not essential when the 
band is developed to represent the section of a cone except in 
unusual cases. 
FORCING THE BAND TO PLACE ON ROOT 
When properly contoured, it should be forced to position 
under the free margin of the gum, usually about one-twentieth 
of an inch, in some cases a little more, when the peridental 
attachment will permit. 
By placing a flattened piece of wood on the occlusal sur- 
face of the band, the patient can assist in setting it by biting 
on the wood. Test of the length of band is made by closure 
of the teeth, and any points of interference are reduced by 
trimming. The occlusal end of the band should be squared 
with the flat side of a file so that the cusp when developed and 
similarly treated will form a close joint with the band. 
Fig. 699.— Contouring and Band-Expanding Pliers Designed by Writer 
TESTING THE BITE 
The band, having been fitted to the root, a wax bite should 
be taken with the band on its root, together with the proxi- 
mating teeth. The mass of wax should be large enough to 
receive and firmly hold the bite fork of the face bow. It 
should also be of the hard variety, so that when chilled it will 
retain its shape, and not become distorted in subsequent han- 
dling. 752 
THE GOLD SHELL CROWN 
The bite fork is inserted in the wax, to the outside, in such 
manner as not to interfere with occlusion, the wax introduced 
in the mouth and the patient instructed to close. The face 
Fig. 700.— Band in Position on Root 
Fig. 701.-— Occlusal View of the Contoured Band in Position 
bow is adjusted to the bite fork, and over the condyles, the 
several clamps tightened, and the bite, attached to the bow, 
removed from the mouth. THE GOLD SHELL CROWN 
753 
An impression of the band on its root is obtained, together 
with two or three of the adjoining teeth on either side. From 
this a cast is developed, which, when removed and trimmed, 
Fig. 702.— Taking the Bite with Molar Band in Position 
Fig. 703.— Bite Mounted on Occluding Frame, Lower Cast Developed 
is fitted to the wax bite and attached to the upper bow of the 
frame. The sides of the wax bite should be trimmed as previ- 
ously described to permit the occlusal surfaces of the teeth to 
become seated against the wax. 754 
THE GOLD SHELL CROWN 
MOUNTING THE BITE ON THE OCCLUDING FRAME 
The face bow is adjusted to the occluding frame, the wax 
bite oiled, and that side which is to form the occlusion cast 
is filled with plaster, and at the same time attached to the bow 
of the frame. When hardened, the cast carrying the band is 
Fig. 704.— Both Casts Mounted, Axial Band Contoured and Occluded 
Against Upper Teeth 
fitted in its bite and attached to the opposite bow. After re- 
moval of the bite, the occlusal surfaces of the occluding teeth 
opposite the band are coated with separating medium. 
DEVELOPING THE CUSPS OF THE CROWN IN PLASTER 
When the occlusal surface of a crown is to be swaged, it 
is necessary to develop a pattern of the form desired, in plas- 
ter or some medium, by means of which a suitable counterdie 
can be constructed. One of the most common methods of 
carrying out this step is as follows: 
A mix of plaster is made and applied in the occlusal end 
of the baud, slightly in excess of the amount required for the 
cusps. While soft, the two casts are occluded, the surplus 
plaster being forced buccally and lingually. On separating 
the casts it will be seen that the central groove of the occlusal 
surface to be carved has been fairly well developed by the 
buccal marginal ridges of the lower occluding teeth. The 
groove, however, should be deepened slightly, and some small, 
unnecessary ridges on the occlusal surface reduced, to bring THE GOLD SHELL CROWN 
755 
out the general anatomic form of the tooth. The peripheral 
surplus is trimmed even, and continuous with the axial walls 
of the band at this time, but later on must be rounded in to 
form the marginal ridges. 
The frame should be subjected to lateral movements and 
the points of interference noted and trimmed accordingly. 
This step might be termed development of clearance paths. 
The trimming of the peripheral margins of the plaster to rep- 
resent the marginal ridges of the crown should be carefully 
carried out, since these boundaries of the occlusal surface give 
character and individuality to the substitute. 
Finally, the developmental lines and finer surface mark- 
ings are carved in the occlusal surface. To do this well, the 
prosthetist should have a knowledge of typical forms of the 
teeth. 
TYPICAL FORMS OF NATURAL TEETH 
A number of sketches of natural teeth have been carefully 
drawn, showing various surfaces, among them the occlusal 
surfaces of seven types of teeth that the crown and bridge 
worker should be thoroughly familiar with, able to draw in 
Fig. 705.— Diagrammatic Drawing of Upper Teeth, Showing 
Principal Lines 
pencil, carve in wax or plaster, or model in clay. These are 
not presented in reverse, it being taken for granted that famil- 
iarity with one type of tooth will enable the prosthetist to 
carve it for either right or left side. (See Figs. 706 to 740, 
inclusive.) 756 
THE GOLD SHELL CROWN 
UPPER RIGHT FIRST MOLAR 
Fig. 706.— Buccal Fig. 707.— Lingual 
Fig. 708.— Mesial Fig. 709.— Distal 
Fig. 710.— Occlusal 
LOWER RIGHT FIRST MOLAR 
Fig. 711.— Buccal 
Fig. 712.— Lingual 
Fig. 713.— Mesial 
Fig. 714.— Distal 
Fig. 715.— Occlusal THE GOLD SHELL CROWN 
757 
LOWER RIGHT SECOND MOLAR 
Fig. 716.— Buccal 
Fig. 717.— Lingual 
Fig. 718.— Mesial 
Fig. 719.— Distal 
Fig. 720.— Occlusal 
UPPER LEFT FIRST BICUSPID 
Fig. 721.— Buccal 
Fig. 722.— Lingual 
Fig. 723.— Mesial 
Fig. 724.— Distal 
Fig. 725.— Occlusal 758 
THE GOLD SHELL CROWN 
UPPER RIGHT SECOND BICUSPID 
Fig. 726.— Buccal 
Fig. 727.— Lingual 
Fig. 728.— Mesial 
Fig. 729.— Distal 
Fig. 730.— Occlusal 
LOWER LEFT FIRST BICUSPID 
Fig. 731.— Buccal 
Fig. 732.— Lingual 
Fig. 733.— Mesial 
Fig. 734.— Distal 
Fig. 736.— Occlusal THE GOLD SHELL CROWN 
759 
LOWER LEFT SECOND BICUSPID 
Fig. 736.— Buccal 
Fig. 737.— Lingual 
Fig. 738.— Mesial 
Fig. 739.— Distal 
Fig. 740.— Occlusal 
REPRODUCING THE CUSP SURFACES IN GOLD 
Two general methods are in vogue for forming the occlu- 
sal surfaces of a crown. First, by swaging the cusps, and 
second, by casting them. When swaged, a counterdie is con- 
structed and in this the cusps are formed. When cast, the 
cusps are carved in wax, in the gold band, the two invested, 
and the cusps cast directly to the axial band. 
CONSTRUCTING THE COUNTERDIE DIRECT METHOD 
A common procedure in forming the counterdie is as fol- 
lows : The cusps having been developed in plaster, the crown 
Fig. 741.— Crown Band Imbedded in 
Moldine. Carved Cusps Exposed Ready 
for Placing the Swaging Ring and Cast- 
ing the Counterdie 
band with cusps attached is removed from the cast and im- 
bedded, cervical end down, in moldine to the line of junction 760 
THE GOLD SHELL CROWN 
of the gold with the plaster, thus leaving only the cusps ex- 
posed. A small rubber ring, or the metal ring of a swaging 
device, is centered over the cusps, on the moldine, and fusible 
metal poured in the ring and over the cusp surfaces in suffi- 
cient quantity to form a resistant counterdie. When chilled, 
the moldine and crown are removed and the counterdie, if sat- 
isfactory, is oiled, the gold annealed, and swaged into the cusp 
depressions. 
Very often the cusp surfaces of the counterdie matrix will 
be defective, as a result of pouring the heated metal over the 
imperfectly dried plaster carving. This may be largely over- 
come by eliminating all moisture from the plaster before im- 
bedding the crown in moldine. Two or three very small holes 
may be drilled through the plaster cusps and after the crown 
is imbedded in the ring a small wire is introduced through the 
holes and passed entirely through the moldine base, to form 
free vents for the downward escape of steam. The disturb- 
ance of the molten metal while hardening is thus, in most 
cases, averted. 
A very excellent method of constructing a counterdie with- 
out casting directly to the carved surfaces, and which will 
yield a dense casting, is as follows: 
It is well known that dense castings of fusible metal, free 
from porosity or surface imperfections, can be successfully 
cast against moldine, because the latter contains no moisture. 
Neither does the glycerine, with which moldine is mixed, to 
render it plastic, volatilize under the fused metal. Therefore, 
by reproducing the reverse of the desired counterdie surfaces 
in moldine a dense counterdie will result from casting fusible 
metal against such surfaces. 
The cusps are carved in the same manner as previously 
described. By this method hard wax or modeling compound 
will serve quite as well as plaster as a medium in which to 
carve the cusps. 
When carved, remove the crown from the cast, make a mix 
of plaster and spread on a piece of paper, forming a flat mass 
about three-eighths inch thick and one and one-half inches in 
diameter. With the point of a knife or a brush fill in the in- 
equalities of the carved surfaces and quickly press the crown, 
occlusal end down, in the soft plaster. The cusps should be 
fully imbedded to the band margin. Remove the surplus plas- 
ter from around the crown. When the plaster has set, remove 
CONSTRUCTING THE COUNTERDIE INDIRECT METHOD THE GOLD SHELL CROWN 
761 
crown and carving. Trim the margins of the matrix to elimi- 
nate undercuts. The plaster with cusp depression now repre- 
sents the essential surfaces of a counterdie. This must be re- 
produced in metal which can be accomplished as follows: 
Dust the cusp surfaces and plaster slab with talcum powder 
and brush off the surplus. Press a small mass of moldine in 
the cusp depressions and a larger mass over the upper surface 
of the plaster slab. The two masses of moldine should firmly 
unite, which will occur if surfaces are fresh and sufficient pres- 
sure is applied. The upper surface of the moldine should be 
flat, to afford a firm base on which to rest when, later on, it 
is inverted. 
The plaster and moldine are carefully separated to avoid 
distorting the latter. On the surface of moldine, which was 
pressed against the plaster, will be seen a raised occlusal sur- 
face of exactly the same size and form as the plaster pattern 
The moldine is set on the bench, a casting ring centered over 
the cusps and filled with fusible metal. 
When the metal has hardened and the ring and moldine 
are separated, the counterdie surfaces will be found dense, 
and with finest details reproduced. Since the steps are carried 
out quickly while the plaster is damp, the surface of the mold- 
ine may absorb a little moisture from the latter. This can be 
removed before casting, by dusting freely with talcum powder 
and removing the surplus with a soft brush. 
Metalline Compound is a moderately hard substance, heav- 
ily loaded with graphite, somewhat resembling modeling com- 
pound in that it becomes plastic with heat and hardens quickly. 
Fusible metal can be cast directly against it without distorting 
its surfaces, since a higher temperature is required to soften 
it than modeling compound. 
It can be carved readily, and if, in carving, too much is 
removed, more can be added with a hot spatula and the sur- 
face corrected. By its use a most excellent counterdie can be 
quickly formed as follows: With the casts mounted on the 
occluding frame and the band in position on its cast, a pellet 
of Metalline Compound, slightly larger than that required for 
the cusps, is softened, placed in the occlusal end of the band 
and the casts occluded. When hard, the cusps are carved as 
usual. With a small burnisher the cusp surfaces are rendered 
perfectly smooth. 
DEVELOPING A COUNTERDIE WITH METALLINE COMPOUND 762 
THE GOLD SHELL CROWN 
The Metalline carving is carefully lifted out of the band, 
to prevent distortion, and that portion which entered the 
band is pared away with a sharp knife, even with the impres- 
sion of its occlusal end. This converts the Metalline carving 
into an occlusal form of exactly the right depth for the cusps. 
It now resembles in form one of the Hollingsworth metal cusp 
patterns. 
The upper or occlusal surfaces are now coated with a thin 
film of glycerin, and all surplus removed with absorbent 
cotton. 
A small pellet of soft moldine no larger than a pin-head 
is thinly spread on a flat surface of polished steel. On this 
the metalline carving is set and pressed lightly against the 
moldine, to cause the base of the carving to adhere to the steel. 
The object in cementing the carving to the steel is to prevent 
its displacement by the metal in casting. If the cusp carving 
is not adherent to the steel, the fusible metal, because of its 
greater specific gravity, will settle under and cause it to rise 
to the surface. Another method of obviating displacement of 
the carving is to press it against the steel with a small wire 
while pouring the metal. The steel should be moderately cool, 
so as to chill the fusible metal quickly before the cusp forms 
are softened. 
A ring is centered over the cusp and the fusible metal cast 
into it. When the steps are properly carried out, a sharp, 
well defined counterdie is obtained. 
SWAGING THE CUSPS IN AN OPEN COUNTERDIE 
A piece of soft wood about four inches long and one-half 
inch square is shaped, on one end, to the general outline of the 
cusp depression and driven into it and the counterdie is oiled. 
Fig. 742.— Disc of Gold with Softwood in Posi- 
tion Ready for Swaging in Counterdie 
A disc of 31 or 32 gauge, 22 carat gold plate is annealed, 
evenly centered over tlie cusp depression, the conformed end 
of the stick set squarely on it and given a sharp blow with the 
hammer. THE GOLD SHELL CROWN 
763 
Any folds that have begun to form around the margins 
are corrected with pliers, and the swaging process continued 
until general adaptation is secured. The finer lines and sharp 
ridges of the cusps are developed with a blunt-pointed hickory 
Fig. 743.— Developing the Finer Occlusal Sur- 
face Markings with Hardwood Point 
stick, or a rather small but round edge chaser, using light, 
rapid hammer blows. Finally, by applying the piece of soft 
wood with heavy hammer, the gold is driven against all sur- 
faces of the matrix. The gold is pickled in acid, polished with 
pumice to remove all traces of base metal, when it is ready 
for the final step of fitting. 
REMOVING PERIPHERAL SURPLUS OF GOLD 
With a pair of shears the marginal surplus of gold is re- 
moved and the surfaces of the occlusal cap to be united with 
the band are flattened with a file. 
ADAPTING THE OCCLUSAL CAP TO THE BAND 
By placing a pellet of soft wax in the band to steady the 
cusps and returning the latter to position, from time to time, 
on the band, both length and occlusal relations may be deter- 
mined and corrected as required. 
The cusp margins should rest flat upon the occlusal end 
of the axial band, while the peripheries of both should coin- 
cide. 
When trimmed to correct length, so that in lateral move- 
ments the cusp planes do not interfere with the opposite 
occluding teeth, the crown can be removed from its cast and 
the two permanently united by soldering. 
DEVELOPING THE MARGINAL RIDGES OP THE CROWN ON 
THE AXIAL BAND 
A most excellent method of developing the cusp elevations 
on a crown, and which largely reduces the difficulties of carv- 
ing the occlusal surface, is as follows: 764 
THE GOLD SHELL CROWN 
The axial band is formed as wide or even slightly wider 
than the occluso-cervical height of the finished crown. 
The steps of fitting of band to root and contouring of the 
axial surfaces are carried out as previously described. Since 
the length of band will not permit the teeth to occlude, a bite 
cannot be taken until the occlusal band margins are corrected. 
Instead of trimming this end of the band to represent a 
horizontal plane, as is usually done and as has been previ- 
ously described, it is notched to represent the various cusp 
elevations and sloping planes of the marginal ridges. 
The mesial and distal occlusal margins must also be 
notched to receive the opposite occluding cusps which rest 
in the central groove. 
This can easily and quickly be carried out in the mouth, 
the general alignment of the cusps of proximating teeth and 
the cusps of the occluding teeth serving as guides while trim- 
ming the band margin. 
The patient should subject the mandible to lateral move- 
ments to test the correctness of clearance paths. 
When trimmed so that the occlusal band margins inter- 
cuspate properly, not only in occlusion, but in lateral mandib- 
ular movements as well, the bite may be taken as usual, casts 
developed and the crown finished by any of the ordinary meth- 
ods desired. 
If the cusps are to be cast, inlay wax may be applied and 
carved in the mouth, the band and carving removed and in- 
Fig. 744.— The Axial Crown Band Notched to Occlude with Opposite Teeth THE GOLD SHELL CROWN 
765 
vested directly, without taking an impression or bite or devel- 
oping casts. 
Carving the cusps is a very simple operation, since the 
cusp elevations and depth of grooves are already established 
while the central groove is clearly indicated by the cusps of 
the occluding teeth in the wax bite. 
DEVELOPING THE CUSP SURFACES IN A SWAGER 
Crown swagers are very commonly used in dental labora- 
tory procedures, and for many purposes are most useful and 
convenient. A swager, however, is not as effective in the 
development of cusp surfaces from thick gold plate as is the 
method previously outlined. Therefore, when the swager 
alone is employed, the cusps must be developed from light 
gauges of gold plate, or when a heavy gauge is used, which 
in all cases is more desirable, the two methods may be com- 
bined. The following plan is productive of good results: 
Before placing the counterdie in the swager its surfaces 
are oiled. A disc of 30 or 31 gauge, 22 carat gold plate is 
annealed and centered over the depression, into which it is 
Fig. 745.— Counterdie in Position in Swager Base 
swaged by means of the soft and hard wood punches, as pre- 
viously described on page 762. 
Remove the excessive peripheral surplus, pickle and an- 
neal the partially developed cap, return it to the counterdie, 
place the latter in the swager, and with a heavy rawhide mal- 
let drive the gold into the matrix. Usually it will be necessary 
to develop the finer surface markings of the cusps with the 
blunt hardwood point, or fine-pointed steel chaser. Final 766 
THE GOLD SHELL CROWN 
adaptation and removal of warpage are accomplished in the 
swager. 
Fitting the occlusal cap to the axial band is accomplished 
as previously outlined. It should be pickled in acid, cleansed 
and polished to remove all traces of base metal. 
ASSEMBLING AND SOLDERING THE BAND AND OCCLUSAL CAP 
Remove the band from the cast, pickle in acid and cleanse 
in water. Apply borax to the inner cusp surfaces and the 
occlusal end of the band. 
Adjust the occlusal cap and band in proper relation to 
each other as indicated by the coincidence of their peripheries, 
and bind together with untinned binding wire, bringing the 
ends over the cervical end of the crown, to form a loop for 
Fig. 746.— The Kerr Soldering Tweezers Holding Occlusal Cap and Crown Band in Position 
holding while soldering. The wires may be crossed, if neces- 
sary, to hold the occlusal cap in proper relation. 
The occlusal cap and band may be held in proper relation 
to each other without wiring by means of the Kerr soldering 
tweezers. One beak of this appliance is bent at right angles 
to the handle. Opposite this point and attached to the other 
beak is a loose, three-prong table. The crown is held by set- 
ting the cervical end of the band on the adjustable table, while 
the right angle point rests in the central area of the occlusal 
cap. 
Small pieces of fluxed solder are placed within the crown, 
the latter carried to and held within the Bunsen flame, occlu- 
sal end down, where it is carefully and uniformly heated until 
the solder fuses. Sufficient solder should be applied to form 
a thick, rigid, occlusal cap, three or four times thicker than 
the swaged cusps. Care should be taken to see that not only 
the joint areas are perfectly united, but that the solder has 
been drawn up slightly along the inner margins of the band THE GOLD SHELL CROWN 
767 
as well. The solder, when so disposed, strengthens the occlu- 
sal surface and obviates the danger of it wearing through 
under masticatory stress. 
FINISHING THE CROWN 
The finishing of the crown is accomplished with engine 
stones and discs, and the final polish developed with felt and 
brush wheels on the lathe. 
A piece of wood about four inches long and tliree-eighths 
inch in diameter, reduced at one end so as to fit loosely within 
the crown, will serve as a handle for holding it while polish- 
ing. The handle is applied by placing a pellet of heated mod- 
eling compound on the reduced end, pressing it into the crown 
Fig. 747.— Crown Holder 
Fig. 748.— Crown Holder Applied 
and chilling. When the crown is polished, by warming it 
slightly to soften the compound, the handle may be removed. 
A convenient appliance designed for holding crowns con- 
sists of a group of divergent steel springs, set in a handle. 
When compressed inwardly, and introduced in the crown, the 
springs press outward and hold it firmly while polishing (see 
Figures 747 and 748). 
SETTING THE CROWN 
When finished and the polishing powder is removed, the 
crown is washed in alcohol and laid aside while the tooth is 
cleansed and dried and the cement mixed. 
Cotton rolls may be used to guard against the encroach- 
ment of saliva during the earlier stages of setting the crown 
and until the cement begins to set. 
The cotton may be held in various ways, one of the most 
convenient being to apply a clamp to a proximating tooth, 
and place cotton rolls under its lingual buccal bows. 768 
THE GOLD SHELL CROWN 
A convenient type of cotton roll holder, specially designed 
for such purpose, the Ivory, is illustrated in Figure 749. 
One objection to the use of any clamp in this operation is 
that when applied before the setting of the crown, the occlu- 
Fig. 749.— The Ivory Cotton Roll Holder 
sion cannot be tested, the clamp bows interfering with closure 
of the opposing teeth. 
After forcing the crown to place, a clamp may be applied 
to advantage. 
The usual order of procedure is to apply cement within 
the crown somewhat in excess of the amount required, and 
quickly carry it to place. 
It should be forced in position with finger pressure, after 
which the patient is instructed to bite the crown to place. 
Usually a piece of soft wood is inserted between the occlusal 
Fig. 750.— The Cotton Roll Holder Applied to Teeth 
surface of the crown and the opposing teeth to act as a cush- 
ion on which to bite. 
This procedure will force out the excess cement if the lat- 
ter is of suitable consistency to flow. If too stiff to flow under 
steady pressure, mallet blows will be even less effective, al- 
though the latter method is frequently adopted, usually to the 
injury of the peridental membrane. THE GOLD SHELL CROWN 
769 
When seated and the cement has set, the surplus should 
be removed, the gums syringed with warm, normal salt solu- 
tion, and massaged to relieve the general discomfort resulting 
from the operation. 
CASTING THE CUSPS 
The occlusal surface of a crown may be cast directly to 
the axial band. This method, in some cases, obviates the con- 
struction of a counterdie, as well as the necessity for form- 
ing casts of the mouth. Technical procedures of this method 
of developing a crown vary considerably, but the general prin- 
ciples are similar. The following is a simple and common 
method of procedure: 
Form, fit and contour the axial band to the tooth as de- 
scribed. Apply a block of softened inlay wax to the occlusal 
end of the tooth, within the band. Instruct the patient to 
close in simple occlusion. Trim off peripheral surplus of wax 
and instruct the patient to bite sideways and in various direc- 
tions. This step develops clearance paths for the cusps of 
opposite teeth. With small carving instruments, the fine lines 
and surface markings are developed in the wax, and the occlu- 
sal surface given its desired form and contour. 
Remove the band and carving from the tooth. Usually 
the bulk of wax within the band is greater than necessary to 
reproduce in gold. It may be removed by chilling the wax 
and scraping from the interior of the crown with a discoid 
instrument. The wax may be reduced to a layer of uniform 
thickness, over the entire occlusal area, by holding the crown 
against a strong light while scraping away the excess. The 
transmission of light through the wax clearly indicates the 
thick and thip areas. This method was suggested by Dr. J. 
W. Birkland a number of years ago. Another method of re- 
moving the wax is as follows: 
A small metal tube with a receptacle for holding the 
melted wax is heated and passed against the interior of the 
crown. As the wax melts it is withdrawn by suction, a small 
rubber hose, attached to the metal tube, being held in the 
mouth. This is a design of Dr. F. E. Roach and is called a 
wax sucker. 
A sprue former is attached to the cusp surfaces at some 
convenient point, the crown invested in a casting ring, so that 
the wax occupies as nearly a central position as possible in 
the ring. Casting is accomplished in the usual manner. 770 
THE GOLD SHELL CROWN 
Sometimes the cast cusps fail to unite perfectly with the 
axial band at all points, and in some instances not at all. 
When this occurs, the casting may be soldered to the band. 
To obviate the failure of union mentioned, the occlusal 
end of the band may be notched with the shears, and the den- 
tated edges bent slightly before applying the wax and carving 
the cusps. This method develops positive mechanical anchor- 
age between the band and casting. 
Cast Crowns 
Various other methods are in vogue for casting crowns, 
either whole or in part, which have proved more or less sat- 
isfactory. 
One of these methods consists in preparing the root de- 
cidedly cone shaped or so that the band, when adapted closely 
to it, will withdraw. 
The band is now formed to fit the root closely, so that when 
driven on it will cling to the axial walls firmly. It may have 
a disc soldered to the occlusal end, thus converting it into a 
deep cap, or the occlusal end may be left open. 
Inlay wax is applied to the axial walls and occlusal sur- 
face of the cap and the crown developed to the desired con- 
tour by carving. 
Since it is difficult to adapt the wax to the cap in the 
mouth, an impression-bite should be taken with the band or 
root cap in position. From this casts are developed and 
mounted on the occluding frame. The band is then carefully 
removed from its cast, being careful not to disturb its cervical 
matrix. Inlay wax is now applied to and melted against its 
outer surface and over its occlusal end. It is now returned to 
position on the cast, the occlusal area softened and the occlud- 
ing teeth pressed into it, after which the cusps are carved to 
desired form. The axial outlines of the crown are developed 
by removing surplus or making additions of wax as required. 
The waxed crown can be returned to the mouth if neces- 
sary for testing its occlusal adaptation, length, general con- 
tour, etc. 
When satisfactory, it is invested and cast in the usual 
manner. 
Oftentimes in casting a crown of this type, the contrac- 
tion of investment within the band walls is sufficient to per- 
mit the gold to enter, thus interfering with the fit of closely 
adapted bands. THE GOLD SHELL CROWN 
771 
Dr. Weinstein suggests the insertion of a closed end cop- 
per thimble, slightly smaller than the interior of the crown. 
The crown is first filled with investment, and the thimble in- 
serted, closed end first, so as not to touch the crown walls. 
Fig. 751.— Thimble Inserted 
in Crown to Prevent Exces- 
sive Contraction of Inclosed 
Investment 
The interior of the thimble is also filled with investment, after 
which the crown may be invested in the usual manner. 
The contraction of investment between interior crown 
walls and thimble is so slight that no gold will enter in casting. 
The Shoulder Crown 
The Shoulder Crown is designed to obviate the overlay- 
ing of a band against the peripheral surfaces of a tooth. The 
axial surfaces adjacent to the joint junction between the tooth 
and a crown of this type being continuous, is similar to that of 
an inlay with adjacent tooth surfaces. The advantages of 
such a crown, therefore, when well adapted, are obvious. 
The axial surfaces of the tooth are prepared so as to con- 
verge more or less uniformly cervico-occlusally. Instead of 
terminating cervically, in a cone, the base of which is more or 
less indefinite, the axial surfaces should terminate in a dis- 
tinct cervical shoulder. This shoulder should be formed at 
right angles to the long axis of the tooth, should be about 
one thirty-second of an inch wide, more or less, and should 
follow the curve of the gingival gum tissues. 
When possible it should be located under the free gum 
margin, but if inconvenient to so locate it, the hygienic value 
of the crown will not be impaired, since, as before stated, the 
surface of the crown with that of the tooth is continuous. 
PREPARATION OP THE NATURAL TOOTH 772 
THE GOLD SHELL CROWN 
CONSTRUCTION OF THE CROWN 
The usual method of construction consists in taking an 
impression of the prepared tooth in an open end band, filled 
with softened modeling compound. This is filled with amal- 
gam, forming the base sufficiently wide and deep to resist 
stress of swaging. 
When separated from the impression the die is imbedded 
in moldine, in the swaging ring, and a cap fitted to it. A light 
gauge, 22 carat gold, seamless thimble, slightly longer than 
the cervico-occlusal length of the prepared tooth, is adapted 
to the metal die, first with the horn pene mallet and afterward 
by swaging. The cervical end of the cap should be reflected 
against the shoulder and its outer margin trimmed to coincide 
with the root periphery. The cap may be formed of a band, 
and its occlusal end closed with a disc. 
Heavy platinum or gold foil is sometimes used, being con- 
formed to the die, first by burnishing and afterward by swag- 
ing. The folds or wrinkles, which naturally result from this 
method of adapting the foil, in no way seriously interfere 
with the adaptation of the crown. 
When the cap is developed it is returned to the root for 
an impression-bite, from which casts are developed. 
Inlay wax is now applied to the outer surfaces of the cap 
and the crown carved to meet occlusal and esthetic require- 
ments, after which it is cast in the usual manner. 
Seamless Gold Crowns 
A seamless crown is formed from a single disc of gold 
plate, and is therefore devoid of soldered joints. 
With mandrels of gradually decreasing size, the disc is 
forced through a series of holes in a device much like a draw 
plate, and is thus converted into a thimble. From this thimble 
the crown is developed by swaging. 
Thimbles are comparatively simple to construct, but most 
prosthetists use the manufactured thimbles which the supply 
houses carry in stock in various sizes and gauges of gold. 
Although there are many variations in detail, there are 
only two general methods of constructing seamless gold 
crowns. 
First, by swaging the thimble within a matrix, and sec- 
ond, by swaging it over a die. By either method a model or 
pattern of the desired form of crown must first be formed, 
in order to construct the matrix or die. The construction of THE GOLD SHELL CROWN 
773 
the pattern is practically the same in either case except that 
in the die method the pattern must be slightly smaller than 
the proposed crown is to be, since the gold is adapted over or 
outside of the die, and is therefore larger than the latter, or 
the pattern from which the die is developed. 
THE MATRIX METHOD 
First, the tooth is prepared as for an ordinary shell crown. 
To this is fitted a seamless or soldered copper band of the 
same gauge as the gold thimble to be used. The band should 
be scribed and fitted under the gingival margin of the gums 
exactly the same as a gold band is fitted. 
Its axial walls should be contoured to the desired form, 
its occlusal end notched to represent the cusp elevations. 
The occlusal surface is filled in with softened metalline 
compound and when carved to correct form, the band and 
carving are removed from the tooth. 
Fill the inside of the band with moldine, flush with its gin- 
gival margin, and within this insert a small wood or metal 
peg, allowing it to project about one-fourth inch, to serve as 
an anchorage for the pattern in casting the counterdie. 
Form some moldine into a cake about two inches in diam- 
eter and one-half inch thick, giving its upper central surface 
a slightly convex form. 
Set the crown on this convex surface, cervical end down, 
the projecting peg entering the moldine base. With the point 
Fig. 752.— Left Cut Shows Pattern Crown Set on Moldine Slab with Cardboard Set in Position 
to Divide the Metal as It Is Poured. Right Cut Shows Swaging Ring Ready 
to Apply Over Crown, on Moldine Base 
of a knife adapt the moldine neatly to the cervical margin of 
the band, being careful not to imbed the latter in the clay. 
The upper surface of moldine on which the cervical end of 
the crown rests gives form to the cervical margin of the coun- 774 
THE GOLD SHELL CROWN 
terdie, and since the gingival curvature as well as length of 
crown depends upon this margin of the counterdie, care 
should be taken to carry out this step accurately. 
A special ring, of which there are two general forms, is 
used in which to cast the counterdie matrix. Both forms of 
rings have tapered openings extending through them so that 
counterdies, when cast, will part readily from them. In one 
ring there are two slots formed in the inner wall and opposite 
each other for holding a U-shaped piece of cardboard, for par- 
tially dividing the metal in casting. In the other, there are 
two metal ribs extending centrally toward the pattern, which 
fulfill the same purpose as the cardboard. A plain, heavy- 
walled ring with a taper opening will, however, answer the 
purpose equally as well. 
The U-shaped cardboard is now cut and fitted in the ring 
slots, the central portion of the card being removed, and the 
opening made sufficiently large to avoid encroachment of the 
card margins on the pattern crown. 
The ring should be so centered over the pattern that the 
card edges are opposite its greatest diameter, so that when 
Fig. 753.—Swaging Ring Resting on 
Moldine Base Ready for the 
Counterdie Metal 
Fig. 754.— Counterdie or Metal Matrix Cast 
and Split Apart 
cast and the counterdie is split, both halves will be readily 
released from the pattern. 
Fusible metal is now cast into the ring, around and over 
the model crown. When hardened, the casting is removed, 
the blade of a knife is inserted in the slot made by the card- 
board, and with a sharp hammer blow the die is split in two 
pieces. 
The pattern is now removed and the counterdie, if sat- 
isfactory, is trimmed, oiled, and returned to the casting ring. THE GOLD SHELL CROWN 
775 
SWAGING THE CROWN 
A gold thimble is selected, slightly longer than the depth 
of matrix and which fits closely into it. The interior of the 
thimble is filled with baseplate gutta percha, a square end, 
steel mandrel, which will pass into the thimble and fit it 
closely, is pressed against the gutta percha and given two or 
three blows with the hammer. 
The thimble is now removed and examined, to note the 
result of the first swaging. The principal accident liable to 
Fig. 755.— Preliminary Stage of Swag- 
ing the Thimble in Matrix 
occur during swaging is tearing of the gold. By thoroughly 
cleaning the crown, polishing, annealing and continuing the 
swaging process slowly, the gold can be forced out against the 
matrix walls and partially into correct occlusal form. 
Development of the fine occlusal lines usually requires the 
application of a hardwood point or a small, somewhat round- 
pointed steel mandrel. At no time during the swaging proc- 
ess can the gold be forced too rapidly, or splitting of the walls 
will most likely result. When developed to correct form, the 
cervical surplus of the crown is removed even with the cer- 
vical margin of the matrix. 776 
the gold shell crown 
Usually a little correction of this end of the crown with 
the contouring pliers is required. 
The inner cusp surfaces should be thickened by flowing 
solder inside the crown. 
Sometimes, to avoid danger of the gingival end of a seam- 
less crown stretching, when set and subjected to stress, a film 
of high grade solder is flowed around its entire outer periph- 
ery. When polished, such addition will not be noticeable. 
The steps of finishing and setting the crown are similar 
to those of any gold shell crown. 
Swaging a Seamless Crown by the Die Method 
When the crown is to be swaged over a die, the pattern 
must, as before stated, be smaller than the required crown by 
an amount equal to the thickness of the walls of the gold thim- 
ble, otherwise when completed the finished crown will be cor- 
respondingly larger than the pattern. 
A convenient and accurate method of forming the pattern 
is as follows: 
A copper band of the same gauge as the gold to be used 
is fitted to the root, as previously described. The axial walls 
should be contoured and the occlusal end notched or occluded 
with the opposite teeth. The cusps are carved in plaster and 
when the crown is removed the inner walls of the band are 
coated with a thin film of oil. The remaining interior space 
is filled with plaster, which should unite with the cusp carv- 
ing. The plaster last added should also extend about one- 
eighth inch beyond the cervical end of the crown to form a 
pedestal for the pattern. 
The band is now carefully divided with a fine fissure bur 
usually applied on the lingual side, being careful not to mar 
the plaster while doing so. The ends are then bent outward 
and the band carefully removed, leaving a pattern of the tooth 
in plaster. 
The plaster cusps overhang the axial surfaces an amount 
equal to the thickness of the band walls. 
This overhang should be carved away so that the surfaces 
are continuous. No reduction of the occlusal surfaces is nec- 
essary, as the slight amount in extra length of the crown 
(about 1-100 of an inch) can be removed from the cervical 
end in final fitting. The pedestal or cervical extension should 
be trimmed so as to show a slight shoulder, to outline the 
termination of the cervical end of the crown. THE GOLD SHELL CROWN 
777 
The pattern, now wholly composed of plaster, is coated 
with separating medium. 
A small mix of plaster is made and spread on a sheet of 
paper. It should be about three-eighths inch thick and one 
and one-fourth inches square, flattened on its upper surface. 
Fig. 756.— Occlusal Surface of Pattern 
Crown Imbedded in Plaster 
Into this the varnished pattern is pressed, so as to imbed the 
occlusal area and some of the axio-occlusal periphery, usually 
about one-eighth inch of the occlusal end of the pattern. When 
hardened, the plaster is trimmed smoothly, small depressions 
made in the four angles to serve as guides for the subsequent 
pieces to be constructed, and its surface varnished. 
Another mix of plaster is now made and applied to one- 
half the crown and pedestal. This should embrace approxi- 
Fig. 757.— First Section of Side Matrix of 
Plaster Applied 
mately one-half the pattern, the line of greatest diameter in- 
dicating the amount of surface to cover. Its ends and sides 
should be squared up, and the surfaces extending from the 
pattern outward, trimmed perpendicularly. Guide depres- 
sions should also be made in these surfaces. 778 
THE GOLD SHELL CKOWN 
When hardened, the fresh areas of plaster are varnished 
and another mix made and applied against the opposite side 
of the pattern, building it up in conjunction with the other 
two pieces to form a rectangular block, in the top of which 
the base of the pedestal is seen. 
Fig. 768.— Plaster Matrix Complete, But Not 
Separated 
Fig. 759.— Upper Half of Matrix Removed 
Fig. 760.— Matrix Separated and Pattern Crown Removed 
When hardened and squared up, a few light hammer blows 
will loosen the several pieces and the pattern can be removed. 
On placing the three pieces together, a matrix will be 
formed, representing in reverse the form of the pattern. 
The external opening is now beveled slightly, the block 
bound together with rubber bands or binding wire, the ring THE GOLD SHELL CROWN 
779 
of a swaging device is set on top of the block and evenly cen- 
tered over the opening. 
Fusible alloy is now melted and cast into the matrix and 
ring. 
Fig. 761.— Matrix Assembled, Showing 
Cervical Opening 
Fig. 762.— Swaging Ring Placed Ready 
for Casting the Die 
Fig. 763.— Die in Position in Swager 
When cold, and the plaster is removed, a die of the tooth 
with a cervical extension will be seen, attached to and stand- 
ing above the metal within the swaging ring. 
The rough margins of the die are smoothed up, the latter 780 
THE GOLD SHELL CROWN 
oiled, and a thimble selected that will telescope over the die 
tooth and extend to its cervical line or slightly below. 
SWAGING THE CROWN 
The thimble and upper surface of the die are now covered 
with tissue paper, to prevent the swaging material of what- 
ever kind from finding its way between thimble and die. 
The ring is placed in the swager, the outer barrel set over 
it and with one heavy hammer blow the adaptation of gold to 
die is begun. An examination of the thimble is now made. 
Fig. 764.— Thimble in Position on Die 
Invariably, after the first swaging, one or more folds of gold 
have begun to form around the cervical constriction. These 
can be obliterated without removing the thimble from the die 
by means of light blows with the horn pene mallet or the small 
riveting hammer. 
When corrected, the gold is again subjected to another 
single, heavy hammer blow in the swager, and wrinkles or 
folds removed as before. 
This process is repeated until the gold is constricted gin- 
givally so that folds cannot develop. 
The occlusal surface, in the meantime, has become only 
partially conformed. With the riveting hammer and a small THE GOLD SHELL CROWN 
781 
steel mandrel, the occlusal surface lines are developed, after 
which the crown is once more returned to the swager for final 
adaptation. 
Since in practically every case the crown pattern, and 
consequently the die, are bell-shaped, the gold cannot be re- 
moved from the die during the swaging process. 
It is finally removed by placing the die with crown 
attached, in water and bringing it to boiling point, at which 
temperature the fusible metal melts. This method prevents 
Fig. 765.— Crown Swaged, But Not 
Removed from Die 
contamination of the gold by the base metal, which usually 
occurs when the die metal is melted in the open flame. 
By this method of construction the crown walls are thick- 
ened, while in the matrix method the walls are to a greater 
or less extent reduced in thickness. 
FINISHING THE CROWN 
The gingival surplus is trimmed to the line of junction 
of crown with pedestal, the crown boiled in acid and polished. 
The occlusal or incisal ends should be stiffened interiorly, and 
the cervical end covered exteriorly with a thin film of high- 
grade solder. 
GENERAL REMARKS 
In all cases of pattern construction, a copper band should 
be carefully scribed and fitted to the natural tooth. This may 
be wide or narrow, depending on how the pattern is to be 
formed. On or within this band, the wax, plaster or other 
material is built and carved as required. 
It will be seen that since the pattern is at no time sub- 
jected to heat, it may be formed of wax or any material suffi- 
ciently resistant to carve well and retain its form in handling. 
One who can carve well can produce very satisfactory 
forms of crowns by this method. One who cannot carve 782 
THE GOLD SHELL CROWN 
should not attempt this method of construction, for he will 
most certainly be disappointed with esthetic results. 
Certain mechanical aids, however, can be resorted to, 
which will relieve one of most of the carving, but not of nice 
adjustment of the several parts of the whole. 
REPRODUCING NATURAL TOOTH FORMS IN INLAY WAX 
One of these mechanical aids that may be applied in vari- 
ous ways consists in pressing the crown of a natural tooth, or 
a typically formed artificial tooth, into moldine, the surface 
of which should be dusted with talcum powder. On removal, 
a distinct matrix is seen, into which melted inlay wax is 
poured. Since this wax cools quickly, and when cool is quite 
hard, the reproduction may be carved to any desired form. 
At any rate, it furnishes a very good basis on which to build 
the form desired. 
This method is often adopted in forming dummies in wax 
that are to be reproduced by casting. 
In the hands of the writer the swaging of crowns over a 
die has proven very satisfactory. CHAPTER XXIX 
BRIDGEWORK 
Engineering Principles 
In scientific fields it is a recognized fact that the use of 
exact terms encourages the development of exact methods. It 
is, therefore of advantage to the student to become familiar 
with the terms commonly used in dental bridgework, and their 
concise meaning as understood and applied in engineering, 
from which field these terms have been selected and adapted 
to dental purposes. 
A bridge is a structure which spans a space, and which is 
designed for sustaining or supporting not only its own weight, 
but additional loads or stresses that may be brought upon it. 
A bridge consists of a substructure and a superstructure 
The substructure of a bridge is the supporting foundations 
while the superstructure is that part which rests upon the 
foundation supports, spans the space and carries the load. 
The term abutment is defined as “the terminal mass of a 
bridge, usually of masonry, which receives the thrust of an 
arch or the end weight of a truss; in distinction from a pier 
which carries intermediate points . . .” (Century Dic- 
tionary.) 
APPLICATION OF STRESS TO THE SUBSTRUCTURE OF A 
BRIDGE # 
There are five principal types of bridges recognized in 
engineering, differentiated by the manner in which the weight 
of the superstructure and load is sustained by the foundation 
supports. 
First, the arch bridge of masonry, in which the abutments 
must not only support vertical stress, but end thrust as well. 
In a bridge of this type the arch is not a complete factor in 
itself, but is dependent upon constant end compression be- 
tween opposing abutments for maintainance of form and 
capacity for sustaining load. This end compression, which 
tends to force the abutments apart, is usually provided for by 
broadening the end terminals of the abutments with flaring 
walls, and filling the inclosed space between these abutting 
783 784 
BRIDGEWORK 
walls and the principal foundation with earth or rock. The 
end abutment therefore derives its name from the fact that it 
abuts the bank. 
Fig. 766.— A Stone Arch Bridge 
The weight of the structure and applied load exerts down- 
ward vertical stress and an outward push against the abut- 
ments. 
GIRDER OF TRUSS BRIDGES 
Second. The girder, or truss bridge, is one in which the 
structure which bridges the space between the two abutments, 
or when consisting of more than one span, between an abut- 
ment and a pier, is a complete factor in itself, rigid, and capa- 
ble of sustaining its own weight and of the applied load as 
well. The span may be solid, consisting of simple, solid gir- 
ders of wood or iron, or it may consist of several members so 
united as to act as a solid beam. As an example, the Howe 
Truss is composed of an upper and lower chord united by 
Fig. 767.— A Howe Truss Bridge 
vertical and diagonal web members. This truss is so framed 
that the upper chord is always in compression, the lower al- 
ways in tension, the vertical members under tensile strain, 
and the diagonal under compressive stress. The weight of the 
truss and load exert a downward vertical stress upon the abut- 
ments and piers. BRIDGEWORK 
785 
Third. A suspension bridge consists of a platform, hung 
on cables which span the space and are supported by abut- 
SUSPENSION BRIDGES 
Fig. 768.— A Suspension Bridge 
ment towers. The weight of the structure and the load it 
carries exert a vertical stress and an inward pull upon the 
abutments. 
PONTOON BRIDGES 
Fourth. A pontoon bridge consists of a platform super- 
structure, supported by shallow vessels, or boats which float 
upon, and are anchored in a stream of water. Bridges of this 
type have no solid or fixed abutments or piers, except the ter- 
minal banks, each boat carrying its proportion of weight of 
the immediate superstructure, and yielding under the immedi- 
ate load imposed, according to its capacity for displacement 
of water. 
The term ‘‘politic” has been suggested as a substitute for 
‘‘dummy” in describing a bridge tooth replacement. The 
term seems scarcely appropriate, since practically all fixed 
bridges are of the rigid truss type. 
THE CANTILEVER BRIDGE 
Fifth. A cantilever bridge is a structure consisting of 
two or more rigid trusses which span a space, each of which is 
supported in or near its center by a foundation pier. That 
portion of the truss extending from the foundation pier to the 
abutment bank is called the shore arm, while its opposite end, 
which overhangs the stream, is called the river arm. 
In a structure of this type, consisting of two trusses which 
bridge a river, the length or weight of the shore arm is in- 
creased over that of the river arm. To counteract the effect 
of load applied at the terminal end of the river arm, the shore 
arm is tied down to the bank abutment. This is necessary, 
since the terminal end of the river arm is unsupported and 
its stability under load depends upon the rigidity of the entire 
truss structure. 786 
BRIDGEWORK 
For the purpose of equalizing stress as well as for con- 
venience in construction, particularly when the space to be 
bridged is wide, an independent truss is interposed between 
and supported by the terminal river arms. 
Fig. 769.— A Cantilever Bridge 
The stress upon the central foundation of the truss of a 
cantilever bridge is downward, while that upon the bank abut- 
ment, when the weight of the river arm, together with its load, 
exceeds the weight of the shore arm, is upward. 
Dental Bridgework 
Bridgework, in its dental meaning, refers to the replace- 
ment of some of the lost natural teeth by means of substitutes 
or dummies, which are attached to and held in position by 
some of the remaining natural teeth or roots. The teeth or 
roots so utilized, according to the nomenclature previously 
outlined, are termed abutments and piers. 
GENERAL CLASSIFICATION OF BRIDGES 
Bridges naturally fall into two classes, fixed and remov- 
able. Both types mentioned are capable of division into sub- 
classes, generally similar in form, yet varying in detail, ac- 
cording to the means of retention or attachment employed, 
the forms of the individual factors or dummies of which they 
are composed, and the class and arrangement of the materials 
entering into their construction. 
Distinction Between Fixed and Removable Bridges 
FIXED BRIDGES 
A fixed bridge is so designated because, when permanently 
set, it cannot be removed by the patient. As ordinarily con- 
structed, a fixed bridge cannot be removed by the operator BRIDGEWORK 
787 
without more or less mutilation of some of its parts. Occa- 
sionally, when a bridge has previously been partially loosened 
through disturbance of the cementing medium, as from stress 
of mastication or other causes, it may be removed without 
mutilation. 
FIXED BRIDGES SO CONSTRUCTED AS TO BE REMOVABLE 
It is possible, and practicable as well, to construct a bridge 
of the fixed or stationary type, which can readily be removed 
and replaced by the operator, but not by the patient. This is 
a decided convenience, for in case of repair, or if the roots 
forming the substructure require treatment, removal may be 
made without mutilation of the substitute, or injury to the 
supporting roots, and the bridge later returned to and set in 
position. 
A bridge in which the “Corcoran” block and screw is 
applied is a representative of this type. (See page 835.) 
Various other attachments have been suggested and success- 
fully used. One of the most practical of these consists of a 
projection extending from a crown or inlay, which is received 
in a correspondingly shaped socket in the substitute. An 
opening extends through both bridge and projection and in 
this a dowel or screw is fitted. 
By reference to “Application of stress to the substructure 
of a bridge” (see page 783) it will be seen that fixed bridges 
come under the second classification, viz., rigid truss, vertical 
stress, no end thrust on abutments. 
FIXED SADDLE BRIDGES 
Fixed bridges are sometimes constructed with saddles to 
rest upon and cover the border to a greater or less extent. 
By some it is thought that two advantages are gained by the 
use of a saddle in a fixed bridge. 
First. It is claimed that the saddle affords some resist- 
ance to stress, and thereby relieves the sub-structure or abut- 
ments and piers, of some of the extra load they must neces- 
sarily sustain, in performing their own work and that of the 
substitute crowns as well. 
Second. That by the use of a saddle, better general con- 
tour can be given the individual members of the bridge, and 
the formation of constricted spaces between the structure and 
the border, in which food will accumulate, can to a great ex- 
tent be obviated. 788 
BRIDGEWORK 
It is the opinion of the writer, based on observation and 
experience, that the first of these so-called advantages is ex- 
tremely doubtful. A saddle which bears so firmly upon the 
mucous, and indirectly upon the bony tissues when in a state 
of rest as to yield support under the slight movement of the 
abutment roots in their peridental membranes, will sooner or 
later result in absorption of the bony tissues. The constant 
pressure exerted may or may not result in absorption of the 
mucous tissues. In any event, the slight resistance to stress 
afforded by these tissues, even though they may not be per- 
ceptibly absorbed, is not worth considering. 
The second advantage, that of better contour afforded the 
substitute teeth, however, is unquestionable in those cases 
where a saddle is applicable. Wide saddles are always objec- 
tionable and should never be applied. Even with a narrow 
saddle, it is sometimes impossible for the patient to maintain 
correct hygienic conditions around the structure because of 
the difficulty in removing food particles which find their way 
beneath it. Discrimination, therefore, should be observed in 
the application of saddles of any type in fixed bridge work. 
INDIVIDUAL SADDLES 
More than thirty years ago, Dr. H. H. Keith of St. Louis 
advocated the use of individual saddles; that is, an individual 
saddle for each dummy, not greater, usually less in area, than 
the normal cross-section at the border, of the natural tooth 
replaced. Within recent years this method has been revived, 
and is being used by many with very satisfactory results. 
The advantages of an individual saddle are threefold, viz.: 
first, more esthetic form may be given the dummy; second, 
the structure feels more comfortable to the tongue, the dummy 
being given the approximate lingual contour of the natural 
tooth, and, third, there is less tendency for food to accumulate 
in bulk, or become as tightly wedged as when the dummies 
approach close to or rest against the labial or buccal border 
surfaces only. 
As before stated, a saddle, either continuous or of the in- 
dividual type, cannot afford any appreciable resistance to 
masticatory stress, in fixed bridge work, and should not be 
applied in those cases where the abutment teeth are inherently 
weak and unable of themselves to withstand the stress. In 
such case a bridge is contra-indicated. BRIDGEWORK 
789 
SANITARY BRIDGES 
A type of fixed bridge, commonly known as a sanitary 
bridge, is frequently constructed, in lower restorations of 
bicuspids and molars particularly, when absorption of the 
ridge has progressed to a considerable extent, and when the 
deficient portion of the substitute is not visible when the 
mouth is opened as in speaking or laughing. 
A bridge of this type consists of an occlusal platform, 
attached to abutment crowns or inlays. The buccal and lin- 
gual margins of the dummies are rounded in and terminate in 
a more or less convex surface presenting toward the border. 
Not more than one-tliird, usually less, of the buccal and lin- 
gual surfaces are developed to anatomic form, the idea being 
to preserve as much space as possible between ridge and dum- 
mies, so that food may be readily removed. In most cases 
these bridges are constructed entirely of metal. Certain types 
of replaceable porcelain teeth may, however, be utilized in 
such structures when conditions are favorable. 
EXTENSION BRIDGES 
An extension bridge is purely and simply a cantilever 
bridge. The cantilever principle is often misapplied in bridge 
work, one abutment root having to carry one, or even two, 
proximating teeth without any additional anchorage, further 
than that afforded by contact of the terminal dummy with a 
proximating tooth. This principle is wrong under any cir- 
cumstance, even in the attachment of a single dummy to a 
single root. 
When two proximating roots are available as abutments 
for anchorage, and one dummy extended from the two 
attached crowns, if it is possible to so unite them that the 
structure will not impinge upon the soft tissues, and it can be 
kept clean, this principle may at times be employed to ad- 
vantage. 
Again, in bridges of considerable length, where teeth or 
roots and spaces alternate, an extension dummy can be ap- 
plied to fill the terminal space at one or the other end of the 
structure, thus reducing the number of supporting crowns 
without curtailing necessary support. 
Practically the only advantage of an extension bridge 
under any conditions is in obviating the crowning or inlaying 
of a sound and useful tooth. The problem the prosthetist 
must determine is whether a rigid, well-supported, sanitary 
structure can be introduced without a terminal support at 
each extremity. 790 
BRIDGEWORK 
IMPORTANT FACTORS TO BE CONSIDERED IN PLANNING 
FIXED BRIDGES 
The engineer, in planning and constructing a bridge, can 
select the material and build the foundations for the structure 
in whatever location is best calculated for its support. 
The prosthetist cannot build the foundation for the bridge 
he constructs. He must select from among the teeth and roots 
present those which, in his judgment, are most favorably 
located and best calculated to perform, not only their own 
work, but sustain the extra stress thrown upon them by the 
added masticatory area of the teeth supplied. 
ABUTMENTS AND PIERS 
No engineer will plan or construct a bridge truss with lat- 
eral curvature without adequate support. In case a curve in 
the road is required he will either construct short, straight 
Fig. 770.— Ground Plan of a Curved Truss Supported by Only Two Abutments. 
Incorrect Because When Load Is Applied to Outermost Curve 
the Tendency Would Be to Rotate 
Fig. 771.— The Same Truss Supported by an Abutment in the Center 
trusses with piers at each end, and dispose them in curved 
alignment, or plan somewhat longer trusses of greater breadth 
on which the required curve of roadbed may be laid out. In 
any case, change of direction requires that the outermost 
curve shall have a firm foundation to support it or the struc- BRIDGEWORK 
791 
ture will fail. Again, in engineering the foundations of a 
bridge rest upon bedrock or its equivalent, and the abutments 
are not susceptible to any marked lateral stress or vibration. 
Neither does the substructure suffer materially under direct 
stress, being capable of successfully sustaining not only the 
weight of the constant superimposed structure, but many 
times more than that of the heaviest intermittent load will be 
applied. 
A bridge designed and built in a manner, or of such ma- 
terials, that the dividing line between safety and disaster is 
indefinite, would subject the designer to severest criticism, if 
not criminal prosecution. 
In the construction of dental bridges, the prosthetist is 
confronted with more serious problems than arise in the engi- 
neering field. The foundations of a dental bridge are not firm 
and unyielding. They are subject to depression under direcl 
and a much greater degree of movement under lateral stress 
The power of resistance to stress, without injury, of the 
peridental membranes of teeth, varies in different individuals. 
The dividing line between the amount of stress ordinarily 
delivered upon the abutment roots under a bridge, and that 
which will cause permanent injury to the peridental mem- 
brane is very indefinite, so close, in fact, that frequently in- 
jury beyond repair occurs before the patient is aware of it. 
The amount of stress actually delivered upon a bridge to 
the supporting roots is directly dependent upon two factors; 
first, the habitual masticatory effort of the individual, and 
second, the occlusal area of the bridge involved. 
This stress cannot be determined, or at least only approxi- 
mately, nor can the power of resistance of the peridental mem- 
brane to withstand stress, without injury, be estimated. The 
necessity, therefore, of selecting sound, healthy roots or teeth, 
in sufficient number, and properly located for supporting a 
bridge, is obvious. 
Since the vital factors which determine the possibility of 
placing a successful bridge depend upon the position and 
condition of health of the abutments and piers, the utmost 
care should be observed in their selection. 
Long span bridges, extending, for example, from cuspid 
or first bicuspid to third molar, inclusive, without an inter- 
mediate pier, are, as a rule, unsatisfactory. In such case the 
abutment teeth or roots are required to perform not only their 
own functions, but sustain the stress delivered upon the in- 
tervening teeth as well, for which, physiologically, they are 
not capable. 792 
BRIDGE WORK 
A favorable foundation for such a span would be, cuspid 
and third molar for abutments, and second bicuspid or first 
molar for a pier. 
In case no intervening pier is present, the prosthetist can- 
not build one as can the engineer. A saddle will not fulfill 
the requirement, therefore, some form of removable denture 
of the saddle type should be considered, in which the border 
will receive the burden of stress, the terminal teeth serving 
principally to retain the appliance in position. 
A simple anterior bridge in which the two lateral incisors 
are to be replaced, the two central incisors serving as abut- 
Fig. 772.— A Simple Anterior, 
Cantilever Bridge 
ments, will frequently prove successful. A structure of this 
type is classed as a cantilever bridge. 
A simple anterior bridge, involving the replacement of the 
four incisors, the two cuspids serving as abutments, is not 
usually successful, when the anterior curvature is consider- 
able, even though the incisive stress is moderate. In such case 
Fig. 773.— A Simple Anterior Truss Bridge, Cantilever Type. 
Incorrect Because of Lack of Central Support 
the line of force against the abutment roots is outward instead 
of apically as it should be. 
The cantilever principle, however, can frequently be em- 
ployed to advantage by extending the bridge distallv at each 
end, to include the first bicuspids. When extended, the cuspid 
and bicuspid crowns should be so united as not to impinge 
on the soft tissues. This may be done by joining them at their 
contact surfaces, leaving the interproximal space free and 
open. 
Again a frequent combination consists of cuspids and 
second bicuspids utilized as supporting roots, the four an- 
terior and the two first bicuspid teeth being replaced. This BRIDGE WORK 
793 
is a complex bridge of stable form based on the cantilever 
principle and when conditions are favorable will prove suc- 
cessful. 
Fig. 774.— Same Bridge as on Pre- 
ceding Page Extended to Include 
First Bicuspids, Thus Forming a 
Complex Structure 
Fig. 775.— Complex Bridge, of the 
Cantilever Type, of the Cuspid and 
Second Bicuspid Series 
A complex bridge, extending from the first bicuspid on 
one side to the corresponding opposite tooth, with a sound 
and healthy central incisor present to serve as a pier, might 
possibly prove successful if the stress of occlusion is light. 
Under these conditions, however, a fixed bridge is usually 
contra-indicated. 
Frequently the space resulting from the loss of one tooth 
or of two teeth that proximated, can be successfully filled by 
a fixed bridge of the cantilever type, that is, having only one 
fixed abutment. To support the extension, a lug is attached 
to and carried beyond the terminal end of the dummy, on a 
line with or slightly below its occlusal surface. This lug 
rests in a depression, in an inlay carried by the proximating 
tooth. Such an attachment converts the extension bridge into 
one of the regular type, since the tooth carrying the inlay, 
although not attached, serves as an abutment. 
A very common type of simple posterior replacement con- 
sists in utilizing the cuspid and first molar as abutments, the 
two bicuspids being supplied. Again, the first bicuspid and 
second molar may serve as abutments, carrying the second 
bicuspid and first molar dummies. (See Figure 777.) 
Fig. 776.—-Buccal and Lingual View of Simple 
Posterior Bridge. In This Case the Space Occupied 
by the Second Bicuspid Has Widened and a Molar 
Dummy Is Substituted 
Fig. 777.—-A Simple, Posterior 
Bridge, First Bicuspid and Second 
Molar Series, in Which Saddle Back 
Teeth are Utilized for the Substitutes 
Sometimes the cuspid and second molar are used as abut- 
ments, the two bicuspids and first molar dummies being swung 
between. In this case the cuspid and second molar must sus- 794 
BRIDGE WORK 
tain not only their own load, but each perform the work of 
one and one-half additional teeth. In many instances a bridge 
of this type will prove unsuccessful. 
Fig. 778.—A Simple Posterior Bridge 
of the Cuspid and Second Molar 
Series. Diatoric Teeth Utilized for 
Substitutes 
Fig. 779.— A Simple Posterior Bridge of the 
First Bicuspid and Second Molar Series 
A type of structure called an interrupted bridge is some- 
times constructed to avoid involving sound proximating teeth. 
The bridge is converted into a rigid structure by joining the 
Fig. 780.— A Complex Cantilever Bridge Formed by Uniting 
a Central and Cuspid Series with a Cuspid 
and Second Molar Series 
several factors with heavy iridio-platinum wire, bent to lie.in 
contact with the tissues, yet so as to avoid contact with the 
teeth not involved. This type of bridge was suggested by Dr. BRIDGEWORK 
795 
J. Leon Williams about 1886 and illustrated in the Dental 
Cosmos of that year. 
Occasionally a full denture bridge is constructed in which 
practically all of the missing teeth and the natural teeth pres- 
ent are united to form a rigid structure. 
Usually bridges of this type are unsatisfactory. First, 
because of constructive difficulties encountered; second, be- 
cause of danger of fracture under masticatory stress, and, 
Fig. 781.— A Complex Full Denture Bridge of the Cuspid 
and Second Molar Series 
third, the liability of the abutment and pier roots giving way 
under the excessive strain to which subjected. 
Some form of removable denture will, in most cases, prove 
very much more satisfactory than a structure of this type. 
PREPARATION OF ABUTMENT ROOTS AND PIERS 
The abutment and pier attachments of a bridge which rest 
upon the supporting roots usually consist of crowns. Since 
these differ in no essential detail from individual crowns, the 
preparation of roots and teeth for their reception differs but 
little from the outlines previously given under “Crown Con- 
struction.” There is, however, one important consideration 
in bridge work that does not apply to individual crowns which 
must be carefully observed. 
When the supporting crowns of a bridge which rest upon 
the roots consist of either shell or dowel crowns, the axial 
surfaces of the teeth involved must be parallel to each other, 
as nearly as possible. This is necessary in order that the 
abutment and pier pieces may be withdrawn from and re- 
turned to position on their respective roots without hindrance 
In some cases excessive reduction of the axial surfaces 
of divergent or convergent natural crowns is required to 796 
BlllDGE WOKK 
bring them in parallel relation. Frequently, also, the canal, 
of a root out of general alignment, must he reamed from its 
face end, apically, to the mesial or distal, to release and re- 
ceive the dowel of the super-imposed crown. 
When such procedures are necessary, extreme caution 
must be observed to avoid, first, the formation of cervical 
shoulders on supporting teeth or projecting margins on the 
substitute crowns, and second, to avoid weakening a root to 
too great an extent by excessive lateral reaming of its canal. 
Various methods have been suggested for overcoming the 
difficulties of the class just mentioned, one of the simplest and 
most practical of which can be illustrated in a case shown by 
Dr. C. L. Anderson of Tomali, Wis. (See page 816.) 
This case consisted of an upper bridge extending from 
cuspid to first molar, inclusive. The divergence of the roots 
of the two abutments, apico-incisally and occlusally, was so 
marked that excessive reaming of the cuspid root canal and 
reduction of the distal surface of the molar would be required 
to permit the introduction of the bridge. The case was con- 
structed as follows: 
The molar tooth was prepared and a shell crown con- 
structed for it by the usual method. A close-fitting cap, extra 
heavy, was constructed for the cuspid root, in the center of 
which and in alignment with the root canal was an opening. 
A lingual half-band disc was conformed to the root cap and 
on this base a cuspid dowel crown was constructed, being 
adapted to but independent of the root cap. The bicuspid 
dummies were united to the molar crown and root cap. 
The bridge was set by cementing the molar crown and cap 
on their respective roots, and immediately forcing the inde- 
pendent cuspid crown in position, its dowel passing into the 
root canal through the central opening in the root cap. 
Another method consists in removing the crown of the in- 
clined tooth, and constructing a cap for or adapting an inlay 
to the root. The appliance in either case should be supplied 
with dowels of suitable size and length for anchorage pur- 
poses. 
On the cap or inlay is fitted and soldered a vertically in- 
clined block, of the Corcoran or Heddy type. It should be 
placed parallel with the line of axial surfaces of the other 
involved teeth or roots. To this block is fitted a removable 
jacket, around and over which a crown, of the anatomic form 
required, is constructed. By means of an occlusal screw pass- 
ing through the crown and into the block, or a set-screw pass- BRIDGEWORK 
797 
ing through the axial wall of the crown and against the block, 
the removable crown may be firmly locked in position. 
Various types of paralleling devices are procurable, with 
which the alignments of the several canals and tooth surfaces 
involved may be tested. An instrument made by the J. W. 
Ivory Company is very convenient for general paralleling 
purposes, although possibly not sufficiently exact for compli- 
cated cases of removable bridgework in which the structure 
is attached to several widely separated roots or teeth. 
INLAY ABUTMENTS 
« 
Inlays are frequently used as abutment and pier supports 
in bridgework. There is a tendency to utilize this form of 
attachment in extensive cases, oftentimes with disastrous re- 
sults. The most frequent accidents which occur are dislodge- 
ment of the inlay or splitting of the tooth under side stresses. 
DISPLACEMENT OF INLAYS 
The fact should be kept in mind that the stresses and 
strains to which an inlay bridge abutment is subjected vary 
radically from the stress to which the same inlay in the same 
tooth will be subjected when not so involved. 
First, torsional stress is very marked as when the inlay 
occupies a comparatively central position in the mesial or 
distal axial surface of a tooth while buccal and lingual mar- 
ginal ridges of the dummies occupy a position to the outside 
and inside of the perpendicular line or anchorage of the inlay. 
In masticatory effort, the resulting torsional strain invites 
not only dislodgment of the inlay, but fracture of the tooth 
itself, particularly in case of weakening of the tooth from 
caries. 
Second, when two inlays carry one or more dummies, and 
the roots of the teeth diverge or converge relatively to each 
other, the yielding of either tooth in its socket or the synchro- 
nous movement of the two under direct stress exerts a lever- 
age either in the gingival or occlusal areas on the inlays, 
which, unless very firmly anchored, will result in their dis- 
placement. 
These observed facts have proven conclusively that the 
use of inlays as abutments must be confined to favorable cases, 
and that in practically every instance some form of pin an- 
chorage should be employed. 
Various forms of modified inlays or onlays are made use 
of for abutment purposes, among which may be mentioned 798 
BRIDGEWORK 
the Carmichael Attachment, applicable more particularly to 
the cuspids, and a modified form of attachment for bicuspids 
as well as cuspids suggested by Dr. E. Kennedy. 
In this latter attachment the tooth is prepared and the 
inlay attached to its mesial or distal half instead of the lingual 
half of the tooth as in the Carmichael Attachment. 
Application of Fixed Bridgework 
Success in the field of fixed bridgework, to a very large 
extent, is dependent upon the correct application and con- 
struction of full and partial crowns to the roots, or remain- 
ing portions of crowns of natural teeth which, by reason of 
their position, have been selected to serve as abutment and 
pier supports for the completed truss or superstructure. 
The same general requirements governing the successful 
application of crowns to individual roots or teeth apply with 
equal force to those employed as supports for a bridge. 
In addition to this, certain hygienic requirements must be 
observed in bridge construction, in the application of dum- 
mies or substitutes for the lost natural teeth, to so form and 
assemble them that not only the tissues upon which they rest, 
or approximate, but those around the adjacent crowns may 
be maintained in a condition of health. 
The union of a dummy with a crown in such manner as to 
form a constricted space or pocket, difficult of access to cleans- 
ing appliances, is one of the common causes of failure in fixed 
bridgework. 
Therefore, gingival interproximate spaces, and particu- 
larly the embrasures between crowns and dummies, should 
be left as free and open as is consistent with esthetics, and 
the required strength of the structure. 
A dummy fitted with an individual saddle which rests with 
firmness upon the border is, in many cases, preferable to a 
dummy applied to the labial or buccal surface of the border 
in such manner as to form a deep, constricted, V-shaped space 
between the two. A ligature passed under the saddle will re- 
move debris from both structure and border, while neither 
ligature nor toothbrush will prove efficient in the V-shaped 
space. 
Since the function of an individual saddle is not to afford 
support to a fixed bridge, but to develop reasonable lingual 
contour to the dummy to which attached, its bearing on the 
tissues should be restricted to the smallest possible area con- 
sistent with desired contour. BRIDGEWORK 
799 
By means of the preceding “Classification of Fixed 
Bridges” it can be shown that it is possible to construct more 
than fifty-four thousand different varieties of fixed bridges. 
To attempt to explain in detail the technical methods em- 
ployed in the construction of each would be a well-nigh im- 
possible task, and entirely uncalled for in a treatise of this 
character. Fundamental principles for all, however, are es- 
sentially the same, therefore, when the student has mastered 
these principles, which are comparatively few, he should be 
capable of undertaking the construction of ordinary, as well 
as complicated, cases. 
TECHNIC OF BRIDGE CONSTRUCTION 
By way of illustrating some of the preceding principles 
outlined, the technical procedures involved in the construction 
of a simple, fixed bridge, extending from right lower cuspid 
to second molar, inclusive, the second bicuspid present tc 
serve as a pier, will now be described. 
In examining the mouth and noting the relation of the 
teeth to each other in this particular case, it is deemed advis- 
able to place on the abutment and pier teeth the following 
crowns: 
Cuspid root, porcelain face, banded crown. 
Second bicuspid and second molar roots, shell crowns, be- 
cause of restricted space occluso-gingivally. 
Fig. 800.— Teeth Prepared for Reception of Five-Tooth 
Bridge 
It is further assumed that the teeth have been devitalized 
and their roots filled, if such procedure is considered advis- 
able. 
The enamel is removed from the axial surfaces of the 
three roots, as previously described for crowns of the types 
indicated. 800 
BRIDGEWORK 
In addition to reversing the cone form of the roots, their 
mesial and distal, axial surfaces must not diverge, but rather 
converge, from gingival to occlusal surfaces. The necessity 
for establishing this relation is obvious, since divergence of 
these surfaces will prevent the removal of the several crowns 
with the impression, or the return of the finished bridge to 
place. 
The line of direction of the canal of the cuspid root must 
also be considered. When not in parallel alignment with the 
axial surfaces of the bicuspid and molar, a like difficulty will 
be encountered as that mentioned. Since, however, reaming 
the canal to any extent will weaken the root, in order to estab- 
lish parallel relationship, it is a better plan to bring such 
axial surfaces of the bicuspid and molar as diverge from the 
general direction of the root canal into alignment with it 
rather than ream the canal to the extent of weakening it. 
In practically all other respects, the preparation of the 
three roots is essentially the same as has been previously out- 
lined for crowns of similar types as those used in the present 
case. 
When root preparation has been completed, the crowns 
are constructed individually, keeping in mind their correct 
alignment buccally and the reservation of proportionate 
spaces for the first bicuspid and first molar dummies. 
The crowns are roughly finished, set on their respective 
roots, a wax bite taken, the face bow applied, the bite mounted 
on the occluding frame and the occlusion cast developed. 
If, in taking the bite, the crowns are disturbed, they are 
returned to position on their respective roots and a plaster 
impression secured. Usually, in such case as is being de- 
scribed, the impression can be removed without fracture, the 
crowns coming away with it. When fractured, however, the 
broken pieces are assembled, the crowns set in their respec- 
tive matrices, and all luted firmly with wax. 
The object in taking a bite and an impression as well, in- 
stead of an impression-bite combined, in modeling compound, 
as is frequently done, is to secure an accurate relation of the 
crowns to each other. While it is possible, in some cases, to 
remove the crowns from their respective roots without chang- 
ing their relation to each other with a combined bite and im- 
pression in modeling compound, disturbance of relation is 
liable to occur, and therefore plaster should always be used 
in preference to a material which is liable to distort under 
stress. BRIDGEWORK 
801 
From the impression, a cast is formed which, when hard- 
ened, is fitted in the bite and attached to the occluding frame. 
By flowing a film of wax in the interior of the shell crowns 
and in the cap and around the dowel of the cuspid crown, 
before filling the impression, the bridge, when assembled and 
waxed together, can readily be removed from its cast without 
mutilating the latter. The wax within the crowns should be 
thoroughly removed before investment of the bridge. 
REQUIREMENTS OF THE DUMMIES 
For esthetic reasons, the first bicuspid dummy should be 
of porcelain, or at least be porcelain-faced. When consider- 
able absorption of the alveolar border has occurred and the 
cervical half of the dummy will not be exposed to view in 
laughing or speaking, a space may be left between this end of 
the dummy and the ridge for hygienic reasons. 
The application of a short dummy in such location leaves 
the gingival tissues next the crowns which proximate the 
space, more or less exposed and accessible to the toothbrush 
and other cleansing devices. 
In case it is deemed advisable to extend the dummy to the 
alveolar border, or saddle the latter, as is frequently done, 
it should be uniformly reduced on its proximal surfaces, so 
as to leave the interproximate spaces in the gingival half 
areas free and accessible for cleansing purposes. 
Too often the union between crowns and dummies extends 
from the occlusal points of contact to the gingivae, thus pre- 
cluding the possibility of proper cleansing of the tissues and 
appliance. 
CONSTRUCTION OF THE BICUSPID DUMMY 
A dummy may be constructed by any of the several meth- 
ods outlined, using facings or teeth of the removable type, or 
a long pin, plate tooth may be employed. 
By this latter method a facing of suitable form and color 
is selected to fit within the space between the cuspid and sec- 
ond bicuspid crowns. 
Reduce the mesial and distal surfaces so as to taper some- 
what from occlusal to gingival. 
Bevel the buccal marginal ridge, or that portion of the 
facing which corresponds to the incisal edge of an anterior 802 
BRIDGEWORR 
tooth, to allow for an extension of backing to the buccal mar- 
gin for protection from stress. 
The cervical end of the dummy may be finished in three 
ways: 
First, it may simply be rounded and swing clear of the 
border, so as to leave a self-cleansing space between the bor- 
der and the structure. 
Fig. 801.— Porcelain Faced Dummy Formed 
with Cervical Clearance Space 
Second, it may be adapted by grinding to lie in close con- 
tact with the border at its cervico-buccal margin, with more 
or less of a V-shaped space, opening lingually. 
Fig. 802.— Porcelain Faced Dummy Which Rests 
on Buccal Surface of the Border 
Third, a saddle may be adapted to the cervical end, which, 
when closely fitted to the border, permits the lingual contour 
of the dummy to be developed, and obviates the formation of 
the objectionable space referred to. 
Fig. 803.—- Porcelain Faced Dummy with Saddle 
Which Rests Upon the Border 
The type of dummy suitable for each individual case can 
be determined by setting the facing or crown in correct buc- 
cal alignment with the proximating crowns and noting the 
relation of its cervical end to the border. BRIDGEWORK 
803 
In this case, a dummy, to which a saddle is applied, will 
be considered the most appropriate. 
The facing should he ground at its cervical end to tit the 
inequalities of the border, and its buccal marginal ridge bev- 
eled as previously described. 
A backing is now applied to its lingual surface, extend- 
ing from the ridge lap to, or slightly beyond, the bucco- 
occlusal margin. When the ridge lap of the porcelain does 
not tit closely to the border except at its cervico-buccal mar- 
gin, the backing should extend buccally, so as to cover it, 
usually slightly beyond the cervico-buccal margin. 
A piece of thin, pure gold or platinum is burnished to the 
border, immediately on the area on which the dummy will rest, 
and is trimmed to the approximate outline of the dummy base. 
The facing to which the backing is attached is set in cor- 
rect alignment with the proximating teeth on the saddle, and 
the two are attached with wax. 
Sufficient bulk of wax is now added, in which the occlusal 
surface of the dummy can be carved. 
When carved to desired form, a counterdie can be con- 
structed by the indirect method by casting over moldine as 
described. 
Develop the cusp by swaging in the usual manner. Trim 
peripherally, soften the wax and adapt to the dummy, return 
the latter to the cast and by trimming and adjustment de- 
velop correct occlusal relation. 
Remove the dummy from the cast and wax to the desired 
axial form. 
The facing is now removed from the assembled dummy, 
carbon points are inserted in the holes left by the withdrawal 
of the pins and the dummy, minus the facing, is invested in a 
casting ring, and the operation completed by the casting 
process. 
By using a heavier gauge of metal for the saddle, to pre- 
vent warpage or contraction in fusing the metal, the lingual 
contour of the case can be developed by soldering. 
When this plan is followed the mesial and distal margins 
of the saddle should project slightly beyond the wax so as 
to be caught in the investment. 
After the metal structure is completed, the carbon points 
are drilled out and the facing fitted ready for cementation in 
position, after the bridge is completed. The pins of the facing 804 
BRIDGEWORK 
should, in all cases, be roughened before cementation to afford 
maximum anchorage in the cement. 
The dummy is now rough dressed to the desired form, re- 
turned to place between cuspid and second bicuspid crown 
and waxed in position. 
VARIATIONS IN THE FORMS OF DUMMIES 
Various other forms of dummies can be applied with equal 
facility to the case under consideration. For example, a 
Steele, or an Evslin facing, or a partial crown of either type, 
may be used. Again, a Goslee or a Gardiner partial crown 
is equally applicable, either with or without a saddle, pro- 
viding sufficient space exists to permit the introduction of a 
rigid metal structure beneath. 
CONSTRUCTING THE MOLAR DUMMY 
To illustrate still another type of dummy frequently used, 
the technic of an all metal replacement for the first molar will 
be described. 
A mass of casting wax is warmed and pressed into the 
space between second bicuspid and second molar, and the 
occlusion developed in the usual manner. 
The gingival half of the block of wax is excised, the occlu- 
sal portion being carved to correct peripheral outline. 
Since the object in applying a dummy of this type is to 
gain space for cleansing purposes, the buccal and lingual sur- 
faces of the dummy should be rounded inward, so as to form 
Fig. 804.— All Metal Molar Dummy. A Type of Dummy 
Frequently Used in “ Sanitary Bridges ” 
a convex, or even V-shape, to the surface which looks toward 
the border. By avoiding the formation of a flat or a slightly 
convex surface to this portion of the dummy, practically all 
parts are rendered accessible to the toothbrush and cleansing 
appliances. 
When carved to correct outline form, the wax is removed, 
invested and cast in the usual manner. 
Another method whereby practically the same form of 
dummy may be produced is by carving the cusp in some suit- 
able medium, developing a counterdie and swaging the occlu- BRIDGEWORK 
805 
sal surface and occlusal third periphery from gold plate in 
the counterdie. 
This is trimmed to proper depth, the border margins con- 
toured inward slightly with pliers, the interior of the partial 
crown filled in with plate scrap, building it high in the form of 
a mesio-distal ridge, and filling in the voids with solder to the 
required contour. 
After developing the dummy, by whatever method em- 
ployed, it is rough finished, and fitted in position between the 
second bicuspid and second molar crowns. 
ASSEMBLING THE BRIDGE 
Before the final waxing of the several parts of the bridge, 
the dummies are laid aside, the three crowns warmed suffi- 
ciently to soften the film of interior wax, and removed from 
the cast. By observing care in removal, their cervical mat- 
rices on the cast will not be appreciably disturbed. The wax 
is cleared from the interior of the crowns, after which they 
should be boiled in acid, washed thoroughly, and returned 
to position on the cast. A little sticky wax, applied at two 
or three points along the gingival margins, will hold them 
firmly in position while assembling the bridge. 
The dummies are now adjusted and luted firmly with hard, 
sticky wax, applying it in sufficient quantity to firmly unite 
them to the crowns. 
Before final removal from the cast, the occlusions should 
be tested, the general alignment of the crowns and dummies 
noted and the assembled bridge, as a whole, inspected, to 
see that every part is in exact relation. 
In grinding and adjusting porcelain facings in a bridge, 
special care should be taken that a very slight space exists 
between them, or between the porcelain and proximating metal 
crowns. The metal backings of the facings, however, should, 
whenever possible, rest in close contact with each other and 
with adjacent metal crowns. 
This is necessary, in order that shortening of the bridge 
may not occur as a result of contraction of both investment 
and solder, as the latter cools. 
On removal of the bridge from the cast the joints between 
the several dummies should be flushed with wax to prevent 
the ingress of the investment material, the result of which is 
to exclude the solder, and thus weaken the union between the 
several parts of the structure. 806 
BRIDGEWORK 
Finally the cuspid facing is removed from the crown and 
laid aside until after the several parts are soldered, when it 
is returned to position and permanently set with cement. 
INVESTING THE BRIDGE 
A mix of medium consistency of some thoroughly tested 
investment material should be made. This is placed on a slab 
or piece of paper on the bench, building it up to one inch or 
slightly more in thickness, approximately the same width, and 
somewhat longer than the bridge. 
With the point of a small instrument some of the invest- 
ment is carefully applied to the interior of the cap of the cus- 
pid crown, in the pin holes left by removal of the facing, and 
in the two shell crowns as well. 
The bridge is now laid, buccal side down, on the invest- 
ment, into which it is gradually settled, to within about one- 
half inch of the bottom of the mass. If pressed too deeply, the 
investment, when trimmed, will be weak and is very liable to 
fracture during soldering. 
When hardened, the surplus investment is trimmed away, 
being specially careful to clear away all obstructions from 
around the teeth and dummies which might interfere with 
the direct application of the flame to the solder in the various 
joints. 
The wax is removed, first by picking out the bulky portion, 
and afterward applying boiling water for the removal of that 
in the deepest parts. 
A thin film of thick borax paste is applied to all parts on 
which it is desired that the solder should flow, and the invest- 
ment placed on a gauze over the Bunsen flame. 
When heated to a dull red heat along the base of the in- 
vestment, the case is transferred to the soldering block, the 
blow-pipe flame applied and strip solder fused and fed into 
the lingual surfaces and embrasures until the required con- 
tour is attained. 
The finishing of a bridge of this type is similar to that of 
a single crown. In bridgework, however, particular care 
should be taken to finish the metal smoothly in the inter- 
proximal spaces. Rough surfaces in any location invite the 
lodgment of food. Therefore, all file marks should be re- 
moved with fine discs, and the finer scratches left by these 
removed by coarse, followed by fine polishing powders, with 
felt and brush wheels, on the lathe. 
FINISHING BRIDGEWORK 
807 
SETTING THE BRIDGE 
The bridge when finished is adjusted in position on the 
natural roots to test its correctness of form, and probable 
fulfillment of function, after which it is washed, dried, and 
laid aside while the mouth is prepared for its reception. 
The mouth should be syringed with warm normal salt 
solution, cotton rolls applied to dam against the encroach- 
ment of moisture, and the teeth and roots thoroughly dried. 
From a thoroughly mixed mass of medium thin cement, 
the shell crowns are partially filled and some applied around 
the dowel and on the root cap. The root canal is also filled, 
using for this purpose a small plugger point, or the regular 
root canal plugger. 
The bridge is now quickly set in position and forced to 
place with heavy, steady pressure, and the patient instructed 
to close the teeth with force. If occlusion is correct, the 
Fig. 805.— Bridge in Position on Cast, Showing Consid- 
erable Interproximal Space to the Mesial and 
Distal of First Bicuspid Dummy 
mouth is opened and the parts, guarded from moisture until 
the cement has had time to become fairly hard. 
Removing the excess cement requires care and close at- 
tention not only from beneath the gingival, but from the 
various surfaces of the structure against which it may have 
become lodged. If not removed at this time it may remain 
adherent for a long time, particularly in protected locations, 
as in the interproximal spaces, where, although it may not 
prove a direct irritant, it will invite the accumulation of food. 
Finally the bridge is tested with carbon paper to disclose 
any points of interference in lateral mandibular movements. 
If any are present they are reduced with stones and the rough- 
ened surfaces again polished. 808 
BRIDGEWORK 
The Carmichael Attachment 
An attachment often applied to good advantage in fixed 
bridgework is that known as the “Staple Half Crown,” 
“Carmichael Attachment,” and under various other names. 
This attachment is in reality a shallow inlay, covering a 
considerable area of tooth surface from which the enamel and 
a superficial layer of denture has been removed. 
Anchorage of the attachment to the tooth is secured by 
means of interior, peripheral ribs in the metal structure, 
formed during constructing, which fit within corresponding 
grooves in the prepared tooth surface or shallow cavity. 
The particular advantages of this attachment, when prop- 
erly constructed and applied, are as follows: 
First, it can be applied to the lingual surface of a vital 
tooth without endangering the pulp. 
Second, a secure attachment to the tooth can be devel- 
oped without involving much of the labial or buccal surface. 
Third, the joint between the attachment and cavo-surface 
angles is the same as in ordinary inlay work, or gold foil fill- 
ings, thus obviating the formation of a shoulder, which, in 
many cases, particularly in constricted locations, invites the 
lodgment of food and, subsequently, caries. 
Attachments of this type are most applicable to cuspid 
teeth, although they may at times be applied to central in- 
cisors. When slightly modified they may be applied to very 
great advantage to the bicuspids. 
The name Staple Half Crown was given this attachment 
because formerly an iridio-platinum wire staple was applied 
in the groove in the tooth, a gold or platinum matrix adapted 
to the tooth and staple and the two attached. The staple thus 
formed the interior rib alluded to. 
CONSTRUCTION 
To illustrate the constructive steps, the application of a 
Carmichael attachment to a cuspid tooth will he described: 
With suitable stones and discs the plate of enamel is re- 
moved from the entire lingual and proximal surfaces of the 
tooth, except at the cervical periphery, and the incisal edge 
beveled at the expense of the lingual surface. 
Usually, for subsequent protection of the tooth, removal 
of enamel on proximal surfaces is carried slightly to the labial 
of the contact points. BRIDGE WORK 
809 
A gingival shoulder is formed by means of square-end burs. 
This should be carried either under the free gum margin, or 
terminated a short distance to the incisal of it, to avoid the 
formation of a joint at the margin. 
With a fissure bur, grooves are cut on the proximal sur- 
faces, next the labial plate of enamel, from gingival seat to 
incisal edge, converging slightly, incisally. 
Fig. 806.— Proximal View of 
Cuspid Prepared for a Car- 
michael Attachment 
Fig. 807.— Lingual View of 
Same 
Fig. 808.— Incisal View of 
Same 
These grooves are united by another transverse groove 
located as close to the incisal edge as possible in order to de- 
velop anchorage for the resistance of labio-lingual, torsional 
strain. 
All surfaces, margins and grooves should be so correlated 
that, when formed, removal of the wax model may be ac- 
complished without distortion. 
This requires that all overhanging or rough margins and 
surfaces be smoothed and all undercuts obliterated before 
forming the model. 
A modeling compound impression enclosed within a band 
or half thimble cup is secured, of surfaces and margins of the 
tooth involved. 
From this an amalgam, or a modelite, die is developed, 
which, when hardened, is smoothed, and on this the pattern is 
developed in inlay wax. 
The wax should be forced into all grooves and against all 
cavity surfaces, particular care being taken to adapt it closely 
to the margins and against the beveled incisal edge. It is 
then carved to restore the tooth to its original form. 
Usually it is best to test the wax model on the natural 
tooth to see that it fulfills requirement, when, if found satis- 
factory, it is invested and cast, preferably in a good grade of 
platinized gold. 810 
BHIDGEWORK 
FINISHING 
When cast, it is washed, heated and dropped in acid, the 
nodular surfaces corrected, after which it is fitted to the tooth 
and the margins disced to coincide with the tooth surfaces. 
Fig. 809.— Carmichael Completed, Ready 
for Attachment to Bridge 
When the other abutment and pier structures are com- 
pleted, all are placed in position, an impression and bite se- 
cured and the Carmichael attachment is treated in the same 
manner as a full crown. 
MODIFIED TECHNIC 
Another method of construction consists in applying a 
piece of 34 or 36 gauge gold or platinum to the die, and by 
burnishing, form a matrix which fits accurately within grooves 
and against the reduced surfaces of the tooth. 
When perfectly adapted and trimmed to correct periph- 
eral outline, sticky wax is flowed over the lingual side of the 
matrix to prevent distortion, after which the latter is re- 
moved, invested, the wax burned off and high-grade solder 
flowed on the gold to develop required lingual contour. 
Still another method consists in applying inlay wax to 
the burnished matrix, developing the wax to correct form, 
investing and casting against the matrix. By this method 
the surfaces which rest against the tooth are free from nodu- 
lar imperfections, resulting from casting the entire appliance. BRIDGEWORK 
811 
MODIFIED CARMICHAEL APPLIED TO CUSPIDS AND BICUSPIDS 
An application of the Carmichael attachment applied to 
cuspids and bicuspids, suggested by Dr. E. Kennedy, is as 
follows: 
The enamel and a layer of dentin is removed from a por- 
tion of the lingual, proximal, and labial or buccal surfaces 
of the tooth, extending from incisal, or occlusal, to gingival 
areas. In bicuspids, an occlusal step, having a decided dove- 
MODIFIED 
CARM ICHAEL 
ATTACHMENT 
Fig. 810.— Modified Carmichael in, 
and Removed from, Position 
Fig. 811.— Preparation for Modified Car- 
michael in Bicuspid 
tail shape, is formed, while the gingival area terminates in a 
right-angle shoulder. 
The axial surfaces of the tooth should present a slightly 
conical form to permit the removal of the wax pattern. 
Grooves are now cut in the lingual and labial, or buccal, 
axial surfaces in the dentin, for anchorage purposes. The 
process of forming the wax pattern, casting, fitting and fin- 
ishing is the same as described in the construction of a Car- 
michael attachment. 
This attachment can be applied to vital teeth and, when 
properly constructed, affords an anchorage for small bridges 
equal to that of the average crown. 
The Corcoran Attachment 
The Corcoran attachment is applied to abutment crowns 
in those cases where it is desirable that a bridge of the fixed 
type be removed from time to time for cleansing, or for treat- 
ment of the supporting teeth and adjacent tissues. 
This attachment consists of a gold block, threaded in- 
ternally, and which receives a threaded bushing. The bush- 812 
BRIDGEWORK 
ing also is threaded to receive a headed screw, by means of 
which the crown is anchored. 
In case of wear, both bushing and screw may be replaced 
with new ones, the parts being interchangeable. 
-CONSTRUCTION 
The root is prepared as previously described, with dis- 
tinctly conical periphery, and having an interior shoulder. 
Fig. 812.— Impression Cup as 
Applied in Taking Model- 
ing Compound Impression of 
Root Face and Periphery of 
Molar Tooth 
Fig. 813.— Impression 
Removed 
Fig. 814.— Impression Re- 
moved from Amalgam 
Die 
Fig. 815.— Root Cap 
Constructed 
Fig. 816.— Corcoran At- 
tachment, Showing Com- 
pleted Crown, Block At- 
tached to Root Cap, with 
Bushing and Screw in 
Dosition, But Not Screwed 
to Place 
Fig. 817.— Crown in Po- 
sition on Root BRIDGEWORK 
813 
An open band impression is secured in modeling com- 
pound, from which an amalgam die is formed. 
Over this die a root cap is swaged, through which dowels 
are passed and attached with high-grade solder. 
The central shoulder depression should be filled at the 
same time, and the cap stiffened by flowing solder over its 
entire area. 
A Corcoran block is now set in position on the cap and 
attached to the latter with a lower fusing solder than that 
previously applied. 
The sides of the block should be parallel with the long 
axis of the tooth, or the line of direction of introduction and 
removal of the bridge. 
Fig. 818.— A Bridge Anchored by the Corcoran Attachments Removed 
From Its Multiple Anchorage, Which, In This Case, Con- 
sists of Five Roots, Three of Which 
Carry Blocks 
A solid metal crown can be formed on the root cap and 
around the Cofcoran block by applying and carving inlay 
wax to the desired form and casting. 
A countersunk opening, directly in line with that in the 
block, made through the occlusal surface of the crown, re- 
ceives the headed screw which anchors the crown to the root 
cap. 814 
BRIDGEWORK 
By setting the block somewhat to the lingual, a porcelain- 
faced crown can be constructed in the usual manner. 
To obviate the tediousness of final fitting of the crown 
to the block, which in all cases must be done in cast work, a 
Fig. 819.— Bridge Set in Position and Held by Three Screws. The Two 
Distal Roots Carry Kelly Attachments and One on Left 
a Bar for Gilmore Attachment, Enclosed 
within Partial Denture 
boxing, composed of platinum or high fusing gold, is first 
formed and fitted to the block on the root cap. 
Over this the crown is built in any manner that the con- 
ditions of the case demand, after which it is removed from 
the cap, the box covering the block coming away with the pat- 
tern crown, and the solder flowed, or gold cast against it. 
The crowns and bridge showing application of the Cor- 
coran appliances were kindly loaned for illustration by Dr. 
H. F. Methven. 
Still another modification is sometimes carried out. A disc 
of gold or platinum, to serve as a crown base, is perforated, 
fitted around the block and swaged to accurately conform to 
the root cap. To this the boxing, which encloses the block, is 
soldered, and on this metal base the crown is built. BRIDGEWORK 
815 
Fig. 820.— Side View of Bridge on Cast, with Partial 
Denture Above 
Fig. 821.— Bridge and Denture in Position on Cast 816 
bridgework 
On page 796 reference is made to a bridge constructed by 
Dr. Anderson, in which the substitute, although composed of 
two pieces, is of the fixed type when set. 
Fig. 822.— Bridge Constructed by Dr. C. L 
Anderson. For Description, 
See Page 796 
Mueller of Zurich, Switzerland, suggests a similar method 
of anchoring a removable bridge in position. 
He constructs a root cap fitted with a tube, near the apical 
end of which a slight rib is attached to one side. The dowel 
of the crown is split, and sprung apart slightly at its apical 
end. A groove is formed in the dowel at a point which, when 
the latter is in position in the tube, will fit over the rib in the 
tube. The split dowel as it passes the rib is sprung together, 
and as the crown is seated the notch of the dowel receives 
the rib, and in this manner the crown is latched in position. 
The structure is composed of a perforated root cap, 
through which the independent doweled crown passes. 
A telescoping crown or heavy stop clasp is fitted to the 
other supporting root and the two connected by a saddle, to 
which the teeth are attached. 
The Heddy Attachment 
The Heddy attachment consists of a metallic block simi- 
lar in form to the Corcoran attachment, differing, however, in 
being solid. BRIDGEWORK 
817 
The general steps of root cap construction, as well as that 
of the crown, are similar to those just outlined. Anchorage 
of the crown to the block attached to the root cap is secured 
Fig. 823.— Root Cap with 
Heddy Block At- 
tached 
Fig. 824.— Root Cap in Po- 
sition. Crown Completed, 
But Not Seated 
Fig. 825.— Heddy Molar 
Crown Completed and 
in Position 
by cutting a V-shaped groove transversely across the block, 
about midway between cap and occlusal end. 
Fig. 826.— Heddy Anterior Crown 
in Position 
An opening is made through one of the axial surfaces of 
the crown. This is threaded to receive a set-screw having a 
beveled point. 
The crown is locked in position by setting the screw firmly 
into the Y-shaped groove of the central block. 
Removable Bridges 
A removable bridge, in the ordinary acceptation of the 
term, refers to a substitute for lost natural teeth, which is held 
in position and supported by some of the remaining natural 
teeth or roots, and which can be removed from position and re- 
placed by the patient at will. 
For hygienic as well as esthetic reasons, bridges of this 
type are usually supplied with saddles. These may or may 818 
BRIDGEWORK 
not relieve the abutment and pier roots of a certain amount of 
masticatory stress. As previously stated, in structures which 
conform to bridge engineering principles, whether fixed or 
removable, the abutment and pier roots must resist practi- 
cally all masticatory stress, regardless of the presence of 
saddles. 
When the structure is so planned that the saddle will re- 
ceive the burden of stress, the abutment and pier roots being 
utilized principally for retention purposes, it should be classed 
as a partial denture. 
REMOVABLE BRIDGE ATTACHMENTS 
The Roach, Gilmore, Morgan and similar appliances are 
frequently used in cases of so-called removable bridge work, 
when, in reality, the structures should be classed as partial 
dentures, since resistance to masticatory stress devolves upon 
saddles, and not on the appliances themselves. 
Various forms of attachments and many peculiar and 
ingenious devices have been designed for the retention and 
support of removable bridges. Many of these, because of the 
exacting care required in their construction, or of certain 
weaknesses which developed with use, have been discontinued. 
The forms of attachments which have proven most satis- 
factory and capable of resisting masticatory stress consist of 
rigid telescoping devices, as cap crowns and crowns fitted with 
heavy dowels which are received within, and accurately fitted 
to, tubes enclosed within the roots of natural teeth. 
Dr. F. A. Peeso of New York, who is a recognized author- 
ity in the field of removable bridge work, applies this princi- 
ple, or some slight modification of it, in practically all cases 
where removable work is indicated. Although most satisfac- 
tory, these forms of attachment require the use of compara- 
tively rigid gold, and very exact technic in their production, 
otherwise unsatisfactory results attend their application. 
When a removable bridge structure is supported by two 
or more roots, or teeth, these must be so prepared that the 
attached crowns or retention devices may sustain a parallel 
relation to each other. 
This is necessary, as before stated, in order that the bridge 
may be readily removed and replaced by the patient without 
special care or annoyance. 
In addition, a bridge sustained by abutment and pier sup- 
ports not in parallel alignment must sooner or later, in many BRIDGE WORK 
819 
cases at least, cause irritation of the enveloping structures of 
the supporting roots. 
Fig. 827.— Paralleling Device for Use in Crown and Bridge Work (Ivory) 
Various devices have been suggested for determining 
whether, in root preparation, the axial surfaces and root 
canals are being shaped to meet the requirements. 
Fig. 828.— Paralleling Device Applied to Test Axial Surfaces of Second Bicuspid and 
Second Molar 
A simple appliance is here shown, with which the general 
alignment or parallelism of the surfaces and canals involved 
may he tested. 
Fig. 829.—- Paralleling Device Testing Alignment of Cuspid Root with Distal Surface of 
Second Bicuspid 
When two or more removable crowns with dowels are em- 
ployed—the dowels fitting accurately within tubes in the root 
canals—the necessity for establishing accurate parallel align- 
ment of the removable with the stationary parts to which they 
are adapted is obvious. 820 
BRIDGEWORK 
THE TELESCOPING CROWN 
This form of crown is applicable to bicuspid and molar 
teeth, when such teeth are properly aligned, or when they can, 
by suitable preparation, be brought in correct alignment with 
the other teeth involved. 
Briefly, the general steps of constructing a crown by this 
method are as follows: 
The tooth is prepared as for a shell crown, its axial sur- 
faces being slightly but uniformly tapered, and its occlusal 
end reduced to a flat plane sufficiently to provide ample space 
between its face end and the occluding teeth for not only the 
inner cap, but for a thick, heavy, occlusal end to the outer or 
telescoping crown. 
The root cap, as before stated, should be tapered uni- 
formly from gingival to occlusal plane, so as to present the 
form of a more or less true frustum of a very slightly taper- 
ing cone. 
Its cervical end is accurately scribed to the gingival mar- 
gin and in fitting is driven beneath the latter to the full extent 
permissible by the peridental attachment, terminating it, how- 
ever, on the still flaring, conical, axial surfaces of the tooth. 
The occlusal margin is trimmed even with the flat tooth 
plane. To this a disc is soldered, and its margins trimmed 
even with the axial surfaces of the band, which step completes 
the assembling of the root cap. 
The cap is now mounted on a wooden mandrel, with mod- 
eling compound, and its outer surface wrought into a perfectly 
true cone by means of a fine cut, flat file, after which it is 
smoothly polished. 
On removing the cap from the mandrel, it is cleaned and 
its inner surfaces are covered with a thin film of whiting and 
water, in which a little gum arabie is dissolved, to cause the 
whiting to adhere closely to the metal. 
The cap is now imbedded in moldine, occlusal end down, a 
swaging ring centered over it, and a die cast directly into the 
cap and ring. By tapping the cap lightly on its sides with a 
mallet the die is released. 
Over this root cap an outer or telescoping cap having the 
same taper as the latter is closely fitted. It should, in fact, 
be driven onto the root cap, while the latter is on the die, thus 
insuring close adaptation between the two. 
Its gingival end is trimmed so as to terminate close to, 
but not pass beneath, the gum margin. Its occlusal end should BRIDGEWORK 
821 
be covered with a disc similar to that which completed the root 
cap. 
When in position and its inner surfaces are in friction- 
tight contact with the axial surfaces of root cap, its occlusal 
end should not rest upon the latter, a space of about one- 
sixty-fourth of an inch between the two being reserved for 
the bridge to settle as the contact surfaces become worn. This 
insures close gripping contact between the root cone and tlie 
inner walls of the telescoping crown under continued use. 
The root cap is returned to position in the mouth, a bite 
and impression taken and casts developed and mounted on 
the occluding frame. 
The occlusal end and axial surfaces of the outer cap are 
covered with inlay wax, melting it on to insure close union. 
The wax on the occlusal end is now softened and the oc- 
cluding teeth pressed into it and subjected to lateral move- 
ments as well, after which these surfaces are carved to re- 
quired form. 
Fig. 830.— Bicuspid Root Cap, with 
Telescoping Crown 
The axial surfaces are developed by addition or reduction 
of wax as indicated and the crown given its anatomic form. 
The outer cap, or crown proper, is now removed from the 
root cap, and after smoothing the wax, is invested and cast 
the same as any ordinary cast crown. 
THE SPLIT DOWEL CROWN 
The split dowel crown, combined with a tubed root cap, 
is frequently employed in conjunction with the telescoping 
crown in removable bridge work. 822 
BRIDGEWORK 
Crowns of this type are more particularly applicable to 
cuspids and large-sized, single-root teeth. They may, how- 
ever, be applied to roots of any class, under favorable condi- 
tions. The general constructive steps are as follows: 
The root is prepared as for an ordinary cap crown, ex- 
cept that the lingual side is not reduced to the margin of the 
gum. In fact, it should project one-sixteenth of an inch be- 
yond the margin, so that the half band of the crown base may 
not encroach upon the latter. 
A band, usually of coin gold, or plate equally as hard and 
high fusing, is formed and fitted beneath the gum margin. 
The incisal end of the band is trimmed even with the face end 
of the root, to which a disc of gold of similar character is 
attached, either with high fusing solder or by sweating. 
The cap is perforated for the reception of a tube which 
serves the double purpose of anchoring the cap to the root, 
and for the reception of the crown dowel as well. 
The size of the dowel having been decided upon, a hard- 
ened steel mandrel of corresponding diameter is selected, and 
around this a piece of coin gold plate is formed into a tube 
and soldered with high grade solder. 
A reamer of the exact size as the dowel is now passed into 
the tube and its inner walls reamed true, and to exact size. 
One end of the tube is closed with a small disc of gold 
plate, the peripheral surplus trimmed even with the outer sur- 
faces of the tube, and its corners chamfered or rounded 
slightly. 
The dowel is formed from half-round clasp metal wire, 
as follows: 
A piece of half-round wire, slightly larger than the dowel 
and about one and one-half inches long, is bent in the form 
of a loop, the two ends bent to lie in close contact from their 
terminals inward, for about one-fourth inch, the remainder 
of the loop being open. 
Fig. 831.— Method of Soldering Half- 
Round Wire for Dowel 
A little coin gold is now applied in tlie V-shaped space, 
next the contact area, and the two ends united by fusion. It is 
necessary to use coin, or equally high fusing gold, to effect 
this union, to avoid the split portion of the dowel from being 
united in subsequent soldering operations. 
The loop portion of the half-round wire is now carefully 823 
BRIDGEWORK 
battered down with a small rawhide mallet, in a half-round, 
grooved anvil, until the flattened surfaces of the wire are in 
contact. 
The doubled wire, with ends united, now presents the 
appearance of a round wire, about three-fourths of an inch 
long. This is passed through gradually decreasing holes in 
the draw plate, until it is brought to very nearly the required 
diameter to enter the tube. 
The final reduction to exact size is accomplished by plac- 
ing the wire in a pin vise, resting it in a grooved block, and 
with a fine cut, flat file carefully reducing it under rotary 
action. 
It should be tested from time to time in the tube, and when 
it just begins to enter the latter, the file marks are removed 
with fine flour of emery cloth or crocus. The soldered end of 
the dowel may be placed in a true running lathe chuck, and 
the final finish given by applying the fine polishing cloth 
against it by means of a flat stick, or by laying it on the flat, 
fine file and running the lathe at high speed. 
The dowel should fit the tube with friction-tight contact, 
yet not so tightly as to preclude its ready introduction and 
removal. When properly reduced the folded end of the dowel 
is cut off, thus leaving the two halves of the dowel held by the 
soldered portion. 
ASSEMBLING THE PARTS 
An opening is made in the root cap for the reception of 
the tube, as before stated. This opening, although in some 
cases it may be located directly in line with the canal, is usu- 
ally made a little to the lingual, and the canal reamed accord- 
ingly, so that the dowel may not interfere with proper adjust- 
ment of the facing. 
In this case, as in that of all cap and dowel crowns, the 
entrance to the root canal can be reamed out slightly and the 
margins of the cap around the tube opening depressed into the 
countersunk area. This adds strength to the attachment be- 
tween cap and tube, and further permits the tube opening to 
be countersunk for the more ready introduction of the dowel. 
The cap is set in position on the root, the tube passed 
through it, into the root canal, which previously has been en- 
larged to receive it, and an impression taken to secure the re- 
lation between the two. 
When secured and a small investment model formed, the 
two are united in the same manner as an ordinary cap and 
dowel. The tube should be filled with investment previous to 824 
BRIDGEWORK 
soldering to prevent its becoming filled with solder during this 
operation. 
CONSTRUCTING THE CROWN BASE 
Usually a lingual, half-band cap is adapted to the root 
cap to serve as a crown base and to which the split dowel is 
attached. Such a cap affords resistance to outward displace- 
ment, and obviates the presence of a second band beneath the 
gum margin. 
For convenience in construction a full band is adapted to 
the periphery of the root cap, to which a disc, or floor, is con- 
formed and the two united with high grade solder on the lin- 
gual, but not on the labial half of the cap. 
After uniting the band and floor of the telescoping cap 
and completing its adaptation to the root cap, the floor is per- 
forated for the reception of split dowel of the crown. This 
should be in perfect alignment with the opening in the tube 
of the root cap. 
The telescoping cap, or crown base, is adjusted to the root 
cap, the dowel having been cut to suitable length, its free or 
divided end is inserted in the tube to full depth, a small im- 
pression taken to secure correct relation between the two, and 
in which they are placed previous to running up the cast in 
investment. 
Since subsequent soldering operations must follow, the 
union between cap and dowel should be made with high grade 
solder, or the special plate recommended for this purpose in 
the section on metallurgy. 
The labial half of the band is removed and the terminals 
of the lingual half neatly finished against floor. This may be 
easily accomplished if, when soldering, care was observed to 
prevent the labial joint area from filling with solder. Wein- 
stein suggests notching the incisal edge of the band before 
soldering, the break in the continuity of surfaces thus pre- 
venting the solder being drawn to the labial. 
When the several steps have been carried out accurately, 
the floor of the crown base will rest firmly on the root cap, its 
Fig. 832.— A Band, Notched to Prevent Solder 
Flowing to Labial Half of Cap 
lingual half band in close contact with that of the cap over 
which it telescopes, while the dowel tits with almost friction- 
tight contact within the tube. BRIDGE WORK 
825 
On this base a crown of any desired type is built to meet 
the requirements of the case, which, when completed, would 
be called a half hand, split dowel crown. 
Fig. 833.— Half Band, Split Dowel Crown, Par- 
tially Removed from Position on Root Cap 
CONSTRUCTING THE SADDLE 
The saddle may be swaged by methods outlined under 
partial denture construction or a wax model of the desired 
form may be developed and cast. When the latter plan is 
followed, ample though not very large sprues should be pro- 
vided for the ingress of gold into the matrix, two or three 
being sufficient for the purpose. 
When constructed, the saddle is adjusted to the border, 
the two complete crowns being in position on their respective 
roots, and an impression taken by the pressure method as de- 
scribed on page 499. 
The crowns should come away with the impression, or, 
if not, they are set in their respective matrices and a cast of 
some reliable investment material formed. 
The saddle and crowns are now firmly united, and if not 
previously provided for, attachments should be made for vul- 
canite anchorage. These attachments, however, are omitted 
when the structure is to be composed entirely of metal and 
porcelain. 
The now assembled and united metal framework is re- 
turned to the mouth for final bite and impression. The metal 
structure is correctly placed in its matrix in the impression, 
the root caps removed and set in their respective crowns and 
a cast of one of the hard materials formed. 826 
BRIDGEWORK 
ATTACHING THE TEETH 
Plain or gum section teeth may be ground to position and 
attached to the saddle in the usual manner, or some of the 
replaceable type of teeth are frequently used. When this plan 
is followed, gold sockets are adapted to the bases of the sev- 
eral teeth, the teeth with sockets attached, waxed in position, 
the porcelain removed, the case invested and the union of 
sockets to saddle accomplished by flowing plate or high grade 
solder between to complete the contour of the case. 
FINISHING THE CASE 
The steps of finishing are similar to those followed in 
regular bridge or partial denture work, the idea being to 
remove all surplus material, remove sharp margins that may, 
by their presence, produce irritation, and finish the case as 
smoothly and perfectly as the most finished piece of jewelry 
ever produced. 
SETTING THE ROOT CAPS 
In cases of the type under consideration, setting the root 
caps is practically the last operation. This is purposely de- 
layed until this time, so that, should any warpage occur in the 
Fig. 834.— Bridge Composed of Half 
Band, Split Dowel Bicuspid, Crown, 
A Telescoping Molar Crown and Two 
Dummies Completed. Root Caps in 
Position 
final assembling and soldering of the structure, the exact rela- 
tion between root caps and their telescoping crowns may be 
preserved. BRIDGEWORK 
827 
The caps are set as follows: 
The interior of the telescoping crowns is coated with a 
thin film of oil, the root caps cleansed and dried and set in 
position in their respective crowns, cement applied in their 
interior and to the roots, and the entire structure carried to 
position and forced to place, first with direct pressure and 
immediately tested with the occluding teeth to see that it is 
correctly seated. 
GENERAL REMARKS 
The details of this most excellent system of removable 
bridge work have been presented in book form by Dr. F. A. 
Peeso, a man most eminently qualified by years of successful 
experience to present it in a clear, logical and practical man- 
ner. He is, in fact, responsible for the development of the 
finer and more accurate details, a neglect of which would re- 
sult in indifferent success, or total failure. 
Coin gold, because of its hardness and comparatively high 
fusibility, is recommended for root caps, tubes and telescop- 
ing caps as well, and highly platinized gold for split dowels. 
In initial operations, when possible, the joints are sweated 
to obviate danger of fusion in subsequent operations. When 
union cannot be thus effected the highest fusing solder pos- 
sible to use on the plate with safety is employed, for reasons 
before stated. 
The Inlay Clasp Attachment 
A combined inlay clasp attachment, suggested by Dr. H. 
J. Goslee, can at times be used to advantage in removable 
bridge work when stress of mastication is not excessively 
heavy. This can best be illustrated by describing the applica- 
tion of such an attachment to a crown, in this case a lower 
first molar. 
The tooth is prepared slightly cone shape, to which a deep 
root cap or thimble is fitted, similar to that used in the tele- 
scoping crown. Inlay wax is now applied to the occlusal and 
axial surfaces and carved to meet anatomic and occlusal re- 
quirements. 
From the axio-occlusal third of the crown, the wax is re- 
moved from the axial surfaces to form a shoulder depression 
for the reception of the clasp. A dovetail depression, similar 
to an occlusal step cavity, is cut in the occlusal surface of wax. 
The axial walls of both inlay step and outer surfaces of re- 828 
BRIDGEWORK 
duced portion of the crown are rendered parallel or slightly 
convergent to permit the withdrawal of the wax pattern for 
the clasp attachment later on. 
The crown, minus the portions removed, is cast, and fin- 
ished. Wax is filled in the removed areas and carved to com- 
plete the anatomic form of the crown, after which it is care- 
fully separated, invested and cast. When made sufficiently 
rigid and wide, and the walls of the crown which it embraces 
are formed practically parallel, this attachment grasps the 
crown very firmly. 
An attachment of this type may be combined with another 
of similar style, or combined with the telescope, or the half 
band dowel crown, in the construction of small bridges. 
A tube attached to the inlay seat of the crown, extending 
toward or into the pulp chamber, for the reception of a split 
dowel anchored in the inlay, will add greatly to the stability 
of the appliance. 
The Split Dowel, Lingual Half Crown 
This attachment is really a removable Carmichael attach- 
ment, combined with a split dowel, applied to a partial, arti- 
ficial crown. The writer is unable to state who first suggested 
Fig. 836.— Lingual View of 
Crown. Cervical View of 
Lingual Half Crown 
Fig. 836.— Buccal View of 
Crown. Cervical View of 
Half Crown, Showing Split 
Dowel. Slightly Modified 
it as a removable bridge anchorage. When accurately con- 
structed, in well-selected cases, it is a very rigid and service- 
able attachment. It is particularly applicable to bicuspids 
and molars. BRIDGEWORK 
829 
CONSTRUCTION OF THE HALF CROWN 
The crown, or remaining portion, is reduced to the gin- 
giva, the peripheral ring of enamel removed and the root end 
prepared decidedly cone shape, and for which a root cap is 
swaged, by methods previously outlined. By preparing the 
pulp chamber walls with a slight flare outwardly, an inside 
shoulder may be developed on the root cap, which will hold 
the latter in position, regardless of the pronounced flare of 
the root periphery. 
One or more dowels are passed through the cap and into 
the root canals and attached as in any similar case. 
Usually a porcelain facing is ground, backed and applied 
to the root cap in proper alignment with the proximating 
teeth. The backing should be extended so as to protect the 
buccal marginal ridge of porcelain from stress. 
Inlay wax is melted against the backing and on the root 
cap in excess of what will be required to form the lingual 
shoulder, and when hardened is carved somewhat in the form 
of a half cylinder, or very slightly tapering cone, or rectangu- 
lar block, the axis of which lies parallel with the long axis of 
the tooth. 
The backing itself should be thickened with wax, especially 
the beveled portion extending over the marginal ridge. Usu- 
ally the outer half of the buccal cusps are developed in this 
wax. 
The sides of the cylinder terminate within the mesial and 
distal surfaces of the crown, the angle between the backing 
and half cylinder being grooved to form a sort of dovetail, by 
means of which the lingual attachment is locked in position. 
The occlusal end of the cylinder is reduced sufficiently to 
allow space for a thick occlusal cap to the attachment. 
The gingival end of the cylinder is squared and a flat cervi- 
cal shoulder is thus formed on which the lingual half of the 
crown may rest. 
The cylinder, as before stated, should converge somewhat 
from gingival toward occlusal areas, to permit the pattern for 
the lingual half crown to be removed. 
A closed end tube, of suitable size to receive the split 
dowel, and somewhat longer than required, is heated and 
pressed into the occlusal end of the wax cylinder, until its 
closed end rests on the crown base. Care should be taken to 
adjust it parallel with the line of direction, of introduction 
and removal of the half crown. 830 
BRIDGEWORK 
The facing is now removed and carbon points inserted in 
the pin holes, the case invested and cast, after which it is fin- 
ished with plug finishing burs, stones, discs, etc. 
The carbon points are drilled out, the facing fitted in po- 
sition, its pins roughened, when it can be temporarily set in 
position with gutta percha while finishing the crown. This 
is essential, for if the metal parts are polished without the 
facing being in position, the point area between porcelain and 
backing will be impaired. 
Later on in soldering the assembled bridge, the facing is 
removed when, after completion of the metal structure, it is 
permanently set with cement. 
CONSTRUCTION OF THE LINGUAL HALF OF THE CROWN 
A split dowel, slightly longer than required, is adjusted to 
the tube within the cylinder, the surfaces of gold against which 
the lingual half crown rests are coated with a thin film of oil 
and inlay wax applied in sufficient bulk to complete the re- 
quired contour. By means of a metal matrix slightly longer 
than the crown, an excess of softened inlay wax can be ap- 
plied and forced into every angle, groove and irregularity. 
On removal of the matrix the excess can be carved off and 
the crown developed to required anatomic form. 
The carved model of the half crown is carefully removed, 
care being taken to bring the dowel away with it without dis- 
torting the relation between the two. Should it become loos- 
ened, the wax immediately around it must be melted and the 
model returned to the metal parts for final adjustment, when 
it may be removed, invested and cast. 
FINISHING THE ATTACHMENT 
The natural contraction, together with the more or less 
nodular surfaces present, demands the exercise of the greatest 
care in finishing, to avoid cutting away unnecessary gold, be- 
fore the actual points of interference are discovered. 
When an amalgam die has been formed on which to con- 
struct the root cap, the crown can be returned to it, and by 
tapping the lingual half crown in the direction of the long axis 
of the tooth and removing, burnished spots will disclose the 
points of interference. 
These attachments are used in conjunction with and with- 
out saddles, if conditions demand their application in such 
manner. BRIDGEWORK 
831 
MODIFICATION OF THE TELESCOPING MOLAR CROWN 
A modification of the telescoping, shell molar crown, com- 
bined with split dowel crown, is sometimes employed in ex- 
tensive bridges of the compound or complex types. It is not 
adaptable to simple bridges for the reason that the abutment 
being in nearly straight alignment, torsional strain will unseat 
the appliance. 
Fig. 837.— Occlusal View of Cast with Root Caps in Posi- 
tion. Cervical View of Bridge 
Instead of a deep root cap with a telescoping cap of prac- 
tically the same depth adapted to it, the molar root is reduced 
to within a short distance of the gingiva and fitted with a 
doweled cap having practically parallel sides. 
On the top of the cap a Gilmore attachment is soldered, 
the flanges presenting occlusally. 832 
BRIDGEWORK 
A crown is constructed the base of which rests upon the 
root cap and telescopes over it slightly. 
In the central portion of the crown base is a recess which 
receives the flanges of the Gilmore attachment, while extend- 
Fig. 838.— Buccal View of Cast and Bridge 
ing across the recess and fixed within the body of the crown 
is a 14-gauge bar. 
This bar is so adjusted that, when the crown is seated on 
the root cap, the flanges of the Gilmore attachment grasp it 
and thus aid in retention of the appliance. 
The appliance here illustrated is the work of J. B. Rideout 
of Minneapolis, who kindly loaned it to the writer. 
Still other combinations of the various attachments men- 
tioned are possible, depending upon the ingenuity of the 
prosthetist and his skill in carrying out the ideas conceived. 
Repairing Crowns and Bridges 
The most common accidents which occur to crowns and 
bridges, when permanently set and subjected to use, are frac- 
ture of the porcelain teeth or facings and fracture of some 
portion of the metal structures. 
When a crown or bridge can be removed from the sup- 
porting roots or teeth, without injury to itself or to them, re- 
pair can be most easily accomplished out of the mouth. 
Since, as is most frequently the case, removal of a crown 
or bridge is accompanied by more or less mutilation of the 
metal parts, or subjecting the foundation supports to undue 
strain, the general method of procedure is to repair such 
cases, if possible, without removal. BRIDGEWORK 
833 
The replacement of dislodged facings can frequently be 
accomplished quite as well in the mouth as by removal of the 
substitute, with some of the available repair outfits. Some of 
the common methods of repair will now be outlined. 
REPLACING PORCELAIN FACINGS THE ASH FLAT BACK REPAIR 
FACING 
One of the simplest methods of replacing a flat back por- 
celain facing where the pins of the fractured facing remain 
with and project from the old backing is accomplished by 
grinding and fitting to the metal parts an Ash flat back repair 
tooth, shown under ‘‘Various Forms of Teeth.” 
When the pins are short and practically headless, they 
may be threaded and a small washer attached to each to in- 
crease their hold in the cement which fills the dovetail space 
within the porcelain. 
In case the tooth pins have broken or are weak, with suit- 
able drill and tap, threaded holes may be made in the labial 
or buccal face of the old backing to coincide with the opening 
in the porcelain and a screw wire of iridio-platinum or plat- 
inized gold inserted for anchorage purposes. The pins should 
be as long as the depth of dovetail space in the porcelain will 
receive, or they may be cut somewhat long, and after being 
inserted in the backing, bent inwardly toward each other to 
form a sort of staple anchorage. 
When the pins are adjusted, cement is applied to both 
backing and facing, and the latter forced and held in place 
until the cement has hardened, after which the surplus is re- 
moved. 
A facing of this type is applied in repair work as follows: 
The porcelain, if any remains of the old facing, and the 
pins, are removed from the backing. 
A facing is selected and ground to meet requirements. A 
very small quantity of wax is melted on the old backing in 
that area which corresponds to the position of the pinholes in 
the facing. 
While the wax is soft, the facing is moistened and pressed 
firmly against it. On removal, the position for the pinholes 
will be indicated by the raised points of wax which entered 
the holes. These points are carefully marked on the backing 
with a sharp-pointed instrument. A bi-beveled drill is se- 
lected, corresponding in size with the openings in the porce- 
THE DIMELOW FACING 834 
BRIDGEWORK 
lain, and with this the holes are drilled in a linguo-gingival 
direction to correspond with the angular inclination of the 
holes in the facing. See Figs. 382-383. 
Two small pins made of threaded clasp metal wire, which 
will fit the holes closely, are cut of suitable length, extending 
to the full depth in the holes of both backing and facing. 
Cement is applied in the holes of both backing and facing 
and over the contact surfaces, the pins set in position in the 
backing, and the facing adjusted and forced to place. 
THE STEELE REPAIR OUTFIT 
This set of appliances, consisting of drills, taps, headed 
screws, and a screwdriver, is intended to be used in conjunc- 
Fig. 839.— Case to Be Repaired, Showing Old 
Pins in Position on Backing 
tion with the Steele facing in repair work. The method of 
application is simple. 
Fig. 840.— Old Pins Removed 
The old pins and any of the old facing present are re- 
moved and a Steele facing of suitable form and color selected BRIDGEWORK 
835 
and ground to meet requirements. It will usually be found 
more convenient, and a better repair can be made by select- 
ing a facing slightly wider and longer than the space it is to 
fill, and adapting it by grinding rather than to select one that 
will drop in position without fitting. A little wax is applied 
in the central area of the backing extending from the crown 
base to near the incisal edge. 
Fig. 841.— Grinding the Steele Facing to 
Meet Requirements 
This should be melted against the backing, and while soft 
the selected facing, having been ground, is pressed firmly 
against it, being careful to see that it is in correct alignment. 
Fig. 842.— Melting the Wax on the Backing 
Fig. 843.— Pressing the Backing Against the 
Hot Wax 
On removal of the facing a ridge will be seen on the wax 
where it entered the slotted groove of the porcelain. 
With a sharp-pointed instrument two points are marked 
on the backing, one near the crown base, the other near the 836 
BRIDGE WORK 
incisal termination of the wax ridge. These points indicate 
the position for the pins. The incisal point should be marked 
slightly within the ridge. 
Fig. 844.— Facing Removed, Showing the Ridge 
of Wax Where It Entered the Groove 
of the Facing 
Holes are now drilled for the reception of the headed 
screws at the points indicated. 
Since the holes must be very small and the drills corre- 
spondingly so, special care must be exercised to avoid break- 
ing the drill in the backing, an accident which is very liable 
to occur. 
Fig. 845.— Wax Ridge Perforated to Indi- 
cate Position for the Screws 
Fig. 846.— Drilling the Holes in Backing 
The holes are now threaded with the tap for the reception 
of the screws, and the latter set in position. 
The facing is applied, passing it over the screws from an 
incisal direction. If, in its passage to place, interference 
occurs, locate the cause, which is probably due to setting the BRIDGEWORK 
837 
screws too deeply in the backing, thus bringing their heads 
too close to the interior wall of the slot of the facing. 
Fig. 847.— Tapping the Holes with the 
Screw Tap 
Fig. 848.— Setting the Screws 
If too long, they may prevent the facing resting against 
the backing. The screw heads should be so set as to permit 
the backing sliding readily to place yet close enough to avoid 
any labial movement of the facing from the backing when 
once seated. 
Fig. 849.— The Facing Set in Position on Backing 
Cement is now applied around the pins, over the backing, 
in the groove of the facing, and the latter is forced in position. 
This set of appliances consists of threaded taps, a taper 
reamer, a split end, screwdriver, and taper nuts, which, in the 
replacement of a flat back, porcelain facing, are used as 
follows: 
THE BRYANT REPAIR OUTFIT 838 
BRIDGEWORK 
The old pins are removed, a layer of wax is applied to 
the backing, into which the pins of the selected facing are 
pressed, to indicate the position for drilling the holes. 
The holes are drilled entirely through the backing with 
a bi-beveled drill a little larger than the diameter of the plati- 
num pins. 
The facing, which should be slightly larger than actually 
required, to permit of reduction for exact fitting, is ground 
to place. 
The lingual ends of the holes in the backing are enlarged 
with the taper reamer by means of the right angle hand piece. 
They should be large enough to receive the taper nuts so that 
the small ends of the latter may approach close to, but not 
project through, the labial surface of the backing. Should the 
small ends pass through the labial of the backing, they must 
be reduced by grinding, or the facing cannot be drawn tightly 
against the backing. 
Fig. 850.— The Bryant Repair Outfit, Showing Taps, Reamer, Screwdriver, Nuts, Etc. 
Threads are cut on the pins, first using No. 1 tap, which 
cuts a partial thread, and followed by No. 2 tap, which cuts 
the thread to full depth. 
The pins should be oiled and the taps applied carefully 
to prevent the pins being twisted off during the cutting of the 
threads. 
Cement is now applied to the backing, and the facing ad- 
justed in position. 
A nut is dropped into the small sleeve of the screwdriver, 
small end outward, applied to one of the pins and tightened, 
after which the other is applied in like manner. 
This step should be carried out quickly, before the cement 
has perceptibly hardened, otherwise the nuts cannot be forced 
into close contact with the backing and the facing will soon 
become loosened. BRIDGEWORK 
839 
The facing should be held by positive mechanical anchor- 
age, developed by jamming the nut tightly against the walls 
of the opening in the backing, on the lingual side, while the 
porcelain should rest firmly against the hacking labially. 
The cement is used only as a sealing agent, to close the 
space between porcelain and metal. 
When hardened, the surplus cement is cleared away, the 
projecting ends of the nuts on the lingual surface reduced 
with stones, and the rough surfaces polished with fine discs. 
Long Pin Facings Used in Repairs 
METHOD OF REPLACEMENT SUGGESTED BY DR. R. W. STARR 
When the backing of a crown, or a bridge dummy is ex- 
ceptionally thick, so that the pins of the facing will not readily 
engage with the Bryant nuts, as ordinarily applied, the mode 
of attachment may he varied as follows: 
Place a piece of platinum foil between and around the 
pins of the selected facing, and bend them down in close con- 
tact with the foil, so that they lie parallel and touch each 
other. 
Invest the porcelain and unite the pins with solder. Flat- 
ten them somewhat by filing, and square up the sides of the 
rectangular projection which they now form. 
Remove the old pins from the backing, apply wax and 
press the partially" prepared facing into it to secure an im- 
pression of the ridge formed by the united pins. 
A groove is cut in the backing, of the same dimensions 
as outlined in the wax, of sufficient depth to receive the folded 
pins and let the facing rest firmly against the backing. 
The facing is now ground to correct position, which previ- 
ously could not be done, because the facing was prevented 
from coming in contact with the hacking on account of the 
pins. 
Drill a hole through the hacking, locating it in the center 
of the groove which receives the pins. 
Apply a thin film of oil to the backing, in the bottom of 
the groove, and to the sides of the opening through the back- 
ing. 
Melt a little sticky wax to the pins, opposite the opening 
in the hacking, and set the facing in position. 
A piece of iridio-platinum or clasp metal wire, about 16 g., 
previously threaded, and slightly longer than required, to 
pass through the hacking, is heated, and passed through the 840 
BRIDGEWORK 
opening, from the lingual, until it enters the wax and rests 
against the pins. 
The heated screw wire melts the wax, which, when cold, 
unites it with metal ridge of the pins, and the two may be re- 
moved in a labial direction in correct relation to each other, 
after which they may be invested and soldered. 
Fig. 851.—- Left, Pins Bent and Screw At- 
tached. Right, Backing Slatted and Drilled 
for Reception of Facing 
Fig. 852.— Left, Facing in Position. Surplus 
Screw and Nut Reduced and Polished. Right, 
Labial Appearance of Facing 
The lingual end of the hole in the backing is enlarged with 
a taper reamer, to receive a taper nut, formed to fit the screw. 
Attachment of the facing to backing and reduction of sur- 
plus screw and nut are accomplished in a similar manner as 
described under the Bryant System. 
RIVETING THE FACING TO BACKING 
When the pins of the new facing are long enough to ex- 
tend through the old backing and permit of spreading, the 
facing may be attached by riveting. 
Mark position on backing, and drill holes which corre- 
spond closely with the diameter of the pins, countersinking 
their lingual ends slightly. 
Grind facing to meet requirements, and if the pins are 
excessively long, cut them so that they will extend but slightly 
beyond the lingual surface of the backing. 
The ends of the pins should be squared and their centers 
depressed with a delicate, bi-beveled drill, to prevent the point 
of the riveting punch from slipping when applied. A sleeve 
Fig. 853.— Sleeve Drill Separated, and in Position, 
for Countersinking Ends of Pins 
drill, designed for this purpose, can be used to good advan- 
tage, and is, in fact, indispensable. 
The Shriver riveting punch, one beak of which is supplied 
with a cup for holding a rubber pad, or modeling compound, 
for producing pressure on the porcelain, the other fitted with 841 
BRIDGEWORK 
a round end and a pointed end punch for compressing and 
spreading the pins is used as follows: 
Cement is spread over the backing and the facing pressed 
to place. The padded beak of the punch is applied to the 
Fig. 854.— Riveting Punch, Showing 
Cup Beak and Two Riveting 
Points (Shriver) 
Fig. 855.— Riveting Punch as Applied 
in Heading a Pin 
facing, the round punch applied to the pin, being careful to 
center it so that the pin may not be bent to one side, and pres- 
sure made to compress the pin upon itself. This step shortens 
the pin and increases its diameter and causes it to fill the 
Fig. 856.— Backings of Cuspid Crown and 
Central Dummy Drilled for Recep- 
tion of Long Pin Facings 
Fig. 857.— Pins of Facing Threaded for 
Reception of Nuts 
hole in the backing, just as a rivet is compressed endwise, to 
fill the hole before the head is formed. 
The pointed pnnch is applied to spread the end and form 
the head of the rivet, after which the round end is again ap- 842 
BRIDGEWORK 
plied to smooth any roughness raised by the point, while 
any surplus that remains is removed with discs. 
When modeling compound instead of rubber is used as a 
pad, it should be softened, placed in the cup, the punch ad- 
justed in position and slight pressure applied to secure an 
impression of the labial surface of the tooth, when it is re- 
moved and chilled, after which the steps are carried out as 
described. 
An ordinary plate punch, modified as suggested by Dr. 
George Evans, may be used instead of the Shriver Punch if 
desired. To the beak in which the hole is located, a lead block 
Fig. 858.— Ordinary Plate Punch 
Converted Into a Riveting Punch by 
Application of Lead Block to Right 
and Heavy Pin to Left Beak 
is applied for producing pressure against the facing, while a 
larger pin replaces the ordinary pin in the other beak. The 
method of application is similar to that described. 
With either method, in addition to gripping the handles 
while compressing the pin, pressure should be made lingually 
to keep the facing firmly seated against the backing. 
A slight side to side movement of the handles will aid in 
compressing and heading the pin as well. 
REMOVING A BANDED DOWEL CROWN 
When, for any reason, it becomes necessary to remove a 
banded, dowel crown which is to be reset, care should be taken 
to avoid mutilating the root cap. 
The most convenient method is to release the crown from 
the dowel which constitutes the main anchorage. This may be 
done by drilling through the lingual surface of the crown, in 
an apical direction, to the root face, alongside the dowel. BRIDGEWORK 
843 
With a fissure bur, the first opening is enlarged, cutting 
around the dowel in such manner that the latter will project 
beyond the root face, thus facilitating its removal later on. 
Figs. 1049 and 1050. 
Fig. 859.—-Lingual 
View of Central, 
Showing Opening 
Through Which Dow- 
el Has Been Released 
Fig.860.—Same Tooth, 
Proximal View. Dot- 
ted Line Shows Di- 
rection of Opening 
Fig. 861.— Proximal 
View of Incisor. Re- 
lease of Dowel from 
Labial Side 
Fig. 862.— Cervical 
View of Crown. Prox- 
imal View of Root, 
Showing Projecting 
Dowel 
When the facing is fractured, release of the crown can be 
most readily accomplished by entering the crown base from 
the labial surface and cutting around the dowel as described. 
Fig. 1051. 
A single crown, when thus freed from its dowel, can be 
removed without difficulty, but when attached to a bridge the 
other abutment crowns must also be released before removal 
can be effected. 
REPLACING A FACING ON A CROWN REMOVED AS DESCRIBED 
The best and quickest method of replacing a facing on a 
crown is by removal of the bulk of old backing, grinding and 
backing a new facing, adjusting and waxing it in position, 
investing and soldering in the usual manner. 
Usually, after the backing is removed, the root cap should 
be returned to position, a new dowel fitted, and impression to 
secure correct relation of the two taken, or the two waxed to- 
gether, removed, invested and soldered, after which the fac- 
ing is adjusted. 
When the facing of the removed crown is present, the lat- 
ter having been removed by releasing the dowel from the lin- 
gual side, a dowel is fitted, its incisal end being allowed to 
project beyond the opening, after which it is waxed in correct 
relation, the crown removed, invested, and the two united 
with solder. 
Before investing the crown, the opening around the dowel, 
in the crown base, should be covered with a small disc of 844 
BRIDGEWORK 
platinum foil, to complete the floor of the root cap, and form 
a metallic surface against which the solder may flow. 
REMOVING DOWELS FROM ROOT CANALS 
Various devices have been suggested for removing dowels 
from root canals. When applicable, appliances of this type 
relieve the tooth from both excessive cutting and strain. 
LITTLE GIANT POST PULLER 
The Little Giant Post Puller, designed by Dr. F. H. Skin- 
ner, consists of a clamp, having thin yet strong beaks, for 
Fig. 863.— Shoulder Pin of Post Puller 
grasping the dowel, together with a shoulder post for resting 
upon the root face. 
By turning the screw, the shoulder post is brought in 
contact with the root face, while the clamp and dowel are 
moved incisally. 
Fig. 864.— Little Giant Post Puller 
To apply the device, the entrance to the root canal must 
be enlarged sufficiently to permit the clamp beaks to enter and 
grasp the sides of the dowel firmly. 
THE S. S. WHITE CROWN REPAIR OUTFIT 
The devices in this outfit, intended for removal of dowels 
from root canals, consist of trephines for gaining space 
around the dowel within the root, and at the same time reduc- 
ing the dowel to a definite size to correspond with the opening 
in a threading die. 
After space is gained, threads are cut on the projecting, 
formed end of the dowel, to which the inner barrel of a de- 
vice, much like a jack screw, is applied. By turning the milled BRIDGEWORK 
845 
nut of the outer barrel until it rests against the face end of 
the root, the inner screw, which is attached to the dowel, is 
moved incisally, bringing the dowel with it. 
Fig 865.— Crown Post Puller. (S. S. White) 
When a dowel is fractured within the canal, some distance 
from the face of the root, the appliances described are un- 
suited for its removal, and some other means must be em- 
ployed. 
A method which will result in but little sacrifice of tooth 
structure consists in squaring the end of the dowel, applying 
a delicate bi-beveled drill to its center and drilling inward a 
short distance, removing the drill, and with a square end bur 
reducing the periphery of the dowel by end cutting. 
These steps are repeated until, by careful cutting, the 
entire dowel is removed. Careful manipulation is required 
to prevent the drill cutting from center to periphery of the 
dowel. 
When the dowel is very small, a fine fissure bur can be 
passed around it, dividing the cutting as much as possible be- 
tween tooth structure and metal to avoid weakening the root 
and excessively enlarging the canal, or in some cases the 
dowel itself may be gradually cut away with small fissure 
burs. 
This is a most unsatisfactory method of removing a dowel, 
yet at times it is the only means of clearing the canal. 
REMOVAL OE A DOWEL EROM THE DEEPER PORTIONS OE A CANAL 
REMOVING A SHELL CROWN BY SLITTING 
The quickest method of removing a shell crown is by slit- 
ting one of its axial walls, introducing an instrument in the 846 
BRIDGEWORK 
opening and prying the crown walls away from the tooth, 
thus breaking the adhesion of the cement. 
A fine fissure bur may be used for cutting the slot from 
gingival to occlusal areas. This method results in loss of sub- 
stance of the crown wall, and where the crown is to be re- 
placed the space must be filled in with a strip of gold of cor- 
responding width of the slot, or the crown when joined will be 
too small. 
By means of a crown slitter, the walls may be divided 
without loss of gold, and when properly contoured and sol- 
dered the crown will fit as before. 
This appliance is a plier-like device, one beak carrying 
a sharp, cutting blade, the other being somewhat broadened 
Fig. 866.— Crown Slitter for Removing Shell Crown: 
and curved, for resting upon the occlusal surface of the crown. 
By introducing the point of the blade against the cervical 
margin of the crown, the other beak on the occlusal surface, 
and closing the handles, the wall is readily slit. 
REMOVING A SHELL CROWN BY LEVERAGE FORCE 
A shell crown can, in most cases, be removed with very 
little mutilation by the following method: 
Drill a hole at a convenient point, just beneath the occlu- 
sal surface of the crown, extending it through nearly to the 
opposite side. BRIDGEWORK 
847 
In this hole, which should be about the size of an engine 
bur wire, a long-handled instrument is inserted to serve as a 
lever. 
Brace the tooth with the finger, on the opposite side from 
the opening, and exert pressure on the handle in an occlusal 
direction. This forces the inner point of the instrument 
against the end of the tooth, or body of enclosed cement, 
breaks adhesion and releases the crown. 
REPAIRING CROWNS THAT HAVE BEEN SLIT IN THE MANNER 
DESCRIBED 
When, in removal, a crown has been mutilated by slitting 
or by cutting with a bur, the first step in its repair is to re- 
move all cement by boiling in acid. Such portions as fail to 
come away readily by this means should be removed by scrap- 
ing and the crown again treated with the acid as before. 
This is necessary, because, if not all removed, the oxide of 
zinc in the cement will, under heat of the blowpipe, be re- 
solved into metallic zinc, which will unite with the gold, form- 
ing a low alloy, and cause the latter to fuse, or burn, as it is 
usually expressed. 
After cleansing as described, the band ends, or axial walls, 
are contoured to correct form, wax flowed in any existing 
space between the ends, trimming it to exact internal contour, 
the interior of the crown filled with investment, the wax re- 
moved, flux applied and solder flowed into and over the joint. 
The same method may be employed in closing the drill 
hole near the occlusal surface, or when waxed, invested and 
the wax removed, a piece of platinum foil may be pressed in 
the opening in the crown to the investment, and solder applied 
to fill the depression and restore axial contour. 
REPAIRING A FRACTURED BRIDGE 
When the metal part of a bridge is fractured at some point 
between the abutments, it may be repaired in two ways: 
First, remove the parts, saw otf the intervening dum- 
mies, replace the abutment crowns in position, secure a bite 
and impression, construct and mount casts on the occluding 
frame, readjust and wax the dummies in position, remove and 
invest the assembled bridge, and solder. 
Second, when fractured in only one place, remove the 
broken parts, cleanse thoroughly, press some softened model- 
ing compound on the border between the abutment crowns, 848 
BRIDGEWORK 
return the two parts to position, pressing the dummies into 
the modeling compound interposed between their cervical ends 
and the border; instruct the patient to close, thus biting the 
bridge into correct occlusal relation. 
Fig. 867.— Sanitary Bridge. To Secure Re- 
lation of Parts, When Structure Is Frac- 
tured at A, Interpose Modeling Compound 
Between A and B 
Pressure should be made on the buccal surface of the 
bridge to prevent outward displacement while the patient is 
forcing it to place. 
When compound is chilled, secure an impression of the 
bridge in its reassembled relation, remove, invest, and solder. CHAPTER XXX 
PORCELAIN CROWN AND BRIDGE WORK 
Porcelain Crown Work 
In addition to the many varieties of crowns it is possible 
to construct by means of facings, partial and full crowns of 
porcelain as shown, still another type of crown can be con- 
structed and applied in certain cases to advantage. This is 
ordinarily known as the baked porcelain crown, because it is 
subjected to the process of fusion or baking by the prosthe- 
tist in his laboratory. 
Crowns of this type may be subdivided into three general 
classes, viz.: 
First—A crown supported by and built upon a perma- 
nent substructure of metal, usually composed of a cap and 
dowel of platinum, to which a facing is attached, the lingual 
portion of porcelain being applied and fused to the cap and 
affixed facing by the prosthetist. 
Second—A crown supported by, and built upon, a per- 
manent platinum cap or base, the entire crown portion being 
built up and contoured in porcelain body and afterward 
fused. 
Third—A crown built upon and around a cap of platinum 
foil, which when the crown is fused is removed. 
The two former crowns are usually designated as banded, 
baked porcelain crowns, the latter as a porcelain jacket crown. 
The introduction within recent years of many new and 
excellent forms of replaceable facings and partial crowns of 
porcelain, together with improved methods of technic, have 
to a great extent rendered unnecessary the baking of crowns 
and bridges, except in special cases. 
As a preliminary consideration the fact should be kept 
in mind that porcelain is strong only in bulk; therefore, in 
constricted spaces it is liable to fracture under stress. 
Again, the porcelain used in inlay, crown, bridge and con- 
tinuous gum and denture construction is less dense and more 
friable than that of which porcelain teeth is composed; there- 
fore the former material will not stand the stress, bulk for 
849 850 
PORCELAIN CROWN AND BRIDGE WORK 
bulk, that tooth body will resist, without danger of fracture. 
Occasionally, however, cases present where a specially 
baked substitute will fulfill esthetic requirements more satis- 
factorily than will one constructed by any other method. 
INDICATIONS FOR USE 
Baked porcelain crowns can be successfully applied in 
any location where sufficient space is present for a reasonable 
bulk of porcelain and where the metal structure can be well 
adapted to the supporting roots. 
Crowns of this type are, however, specially indicated when 
departure from the ordinary anatomic form of the tooth is re- 
quired, provided such departure will not tend to weaken the 
crown when constructed. 
The porcelain jacket crown is admirably adapted to peg- 
shaped lateral incisors and frequently to other classes of teeth 
as well. The placing of a crown of this type on a vital tooth 
in no way endangers the pulp, providing, of course, proper 
tooth preparation can be successfully accomplished without 
serious inconvenience to the patient. 
THE BANDED BAKED PORCELAIN CROWN 
This crown consists of a rigid root cap of platinum or 
iridio-platinum, a dowel of iridio-platinum, a tooth facing ap- 
plied to the dowel by soldering, while its lingual contour is 
developed by application and fusing of porcelain to facing and 
root cap. 
CONSTRUCTING THE ROOT CAP 
Methods vary as to root-cap construction for crowns of 
this type. The following technic is adopted by many because 
the metal band on the labial or buccal surface may be entirely 
obscured by the facing and applied porcelain. 
Prepare the root as for an ordinary cap crown described 
on page 600. 
Construct a band of 29 or 30 gauge iridio-platinum. 
Platinum may be used, but it is liable to stretch under stress. 
Cut the strip about 1-20 of an inch longer than the actual 
root measurement, to allow for a lap joint. 
Bend one end at right angle to the band, turning over the 
amount of surplus allowed. The other end is then brought 
under the bent portion and butted tightly against both the PORCELAIN CROWN AND BRIDGE WORK 
851 
turned portion and band end proper. Solder with high-fus- 
ing platinum solder. 
Place on a round mandrel and tap lightly to flatten and 
form a continuous, curved inner surface to band, being care- 
ful not to stretch or elongate the metal. 
Reduce the excessive thickness of the joint, from the out- 
side, by filing or with engine stones. 
Fit the band to root, scribing and trimming the cervical 
end until perfectly and uniformly adapted to the gingiva, 
when it is driven to correct position under the gum. 
Trim the incisal end of the band to coincide with gingival 
curvature, allowing it, however, to project slightly beyond 
the gum margin, lingually. 
Fig. 868.— Details of Porcelain Crown. A Shows Labial Bevel of 
Cap ; B C D, Lap Joint; E, Ridge Lap of Facing 
Concaved; F G, Parts Assembled 
Drive the band to position on the root, and face the latter 
to the incisal end of the band. 
Remove the band and further reduce the outer or labial 
third of the root face to a point about where the cervical mar- 
gin of the band will rest. 
Thin the band by grinding, along the labial area corre- 
sponding to the reduced root, being careful, however, to leave 
its extreme cervical margin full thickness. 
Return it to the root and with a square end plugger in the 
automatic mallet, reflect the thinned labial portion over 
against the root face. 
Adapt a disc of 30-gauge iridio-platinum plate to the in- 
cisal end of the band, being careful to develop a perfect joint 
between the two. 
Perforate the cap for reception of the dowel, locating the 
opening far enough to the lingual to avoid interference of the 
facing from the projecting dowel. When the opening does 
not coincide with the root canal, ream the latter to correspond. 
No. 16 or 15 gauge iridio-platinum, round wire, is usually 
employed for dowels in central and cuspid teeth, while 17- 
gauge is used in upper laterals, lower incisors, and when two 
dowels are applied, in bicuspid teeth. 852 
PORCELAIN CROWN AND BRIDGE WORK 
The opening in the root cap should be slightly smaller 
than the diameter of dowel, the entrance to canal countersunk 
slightly, the dowel forced through cap as previously described, 
relation between the two secured with wax, after which they 
are removed from root, invested and soldered with medium 
or high-fusing platinum solder. 
Pickle and cleanse the cap and by grinding reduce the 
labial portion of the cap along the angle, between band and 
disc, so as to produce a decided bevel in this area. This is 
necessary in order that the facing, when reduced to a thin 
edge by grinding, may cover the labial surface of the cap. 
Return cap to root, take impression and bite, remove, de- 
velop casts and mount on occluding frame. 
Select a facing slightly lighter in color than the natural 
teeth, yet containing the proper basic colors, because, when 
thickened by the addition of lingual porcelain, its depth of 
color will be increased. 
Grind the ridge lap of the facing somewhat concave, so 
that it may clear the cap at all points, except along the ex- 
treme labial margin, which should be brought to a thin, deli- 
cate edge, to rest closely in contact with the cervical margin 
of the band. 
Flatten the pins so that the flattened surfaces lie parallel 
with the dowel in order that they may present a broad sur- 
face bearing when adapted to the latter. 
Fig. 869.— Pin Bending and Cutting Pliers 
The pin bending and cutting pliers here shown is a most 
useful instrument for this and many other purposes in crown 
work. PORCELAIN CROWN AND BRIDGE WORK 
853 
Set the facing in correct alignment and wax in position. 
Test its length under lateral movements of the frame and 
if interference occurs grind away the points of obstruction. 
When ground to meet requirements, the facing is again 
returned to the cap, the flattened pins adapted closely to the 
dowel, wax applied, the assembled parts removed, invested, 
and soldered with medium or low-fusing platinum solder. 
Care should be taken, in removing the assembled cap and 
facing, to avoid marring the cast, since, during constructive 
stages, the crown must be returned to it, from time to time, 
for testing contour development. 
Fig. 870.— Cap, Dowel and 
Facing Assembled, Ready for 
Application of the Porcelain 
Since the porcelain cannot be perfectly protected from the 
blow-pipe flame, the investment should be raised to a full red 
heat before soldering the pins to dowel, otherwise fracture of 
the porcelain is very liable to occur. 
When soldered, the crown should be boiled in acid and 
thoroughly washed, after which the dowel is grasped in a piu 
vise to serve as a handle when it is ready for the applicatior 
of the body. 
APPLICATION OP THE PORCELAIN BODY 
A small quantity of well mixed crown and bridge porce- 
lain body, of medium thick consistency, is taken up on the 
point of the spatula and placed on the end of cap close to the 
ridge lap of facing. 
Draw a serrated instrument across the pin vise, when the 
vibration thus produced will cause the granules to settle 
closely together, and as the water is expelled from the mass 
it is absorbed by a clean linen napkin or with bibulous paper. 
Special care should be taken to fill the space between ridge 854 
PORCELAIN CROWN AND BRIDGE WORK 
lap of facing and cap during the first application of body, for 
if not packed densely at this time it may be impossible to in- 
troduce it after the first baking. 
The crown may be developed to practically the required 
contour during the first application of the body. When fused, 
additions are made where needed to correct loss of contour 
occasioned by shrinkage of the mass in first baking. 
An effort should be made to complete the crown in two 
fusings. When a third or fourth baking is required the qual- 
ity of the porcelain rapidly deteriorates. 
Dr. F. T. Van Woert has found that by compressing 
plastic, comparatively dry porcelain to a certain degree by 
means of a screw press, shrinkage of the mass during the first 
bake is reduced to one-tenth instead of one-fifth, as usually 
occurs. 
By means of a metal matrix slightly larger than the crown 
is to be, in which the root cap is placed, the porcelain is ap- 
plied to it, under pressure, and condensed. 
The actual dimensions of the crown having been previ- 
ously determined, a double end caliper, the beaks on one end 
of which register one-tentli more than the others, is applied 
to the crown from time to time, while carving the compact 
mass to form. 
The crown, when carved, ready for the first bake, is one- 
tenth larger than actually required, but in the first fusing is 
reduced to actual dimensions. 
It is possible by means of these ingenious devices to com- 
plete a crown in one baking, while another advantage of great 
importance is that there is less distortion and greater den- 
sity of the mass when fused. 
The details of fusing porcelain will be given under Porce- 
lain Bridgework. 
Finishing the crown consists in polishing such portions of 
the cervical margins of the platinum cap as may be exposed 
after fusion of the porcelain is completed. 
In setting crowns of this type, special care should be 
taken to avoid the use of the mallet, as a sudden blow is liable 
to fracture the porcelain. 
Various modifications of the baked porcelain crown are 
constructed, some of which are as follows: 
A lingual half band crown, the dowel and facing being 
attached to a half band diaphragm, instead of the regular 
form of root cap. 
Modified Forms of Porcelain Crowns PORCELAIN CROWN AND BRIDGE WORK 
855 
A bandless crown built upon a disc of platinum; usually the 
root is faced so as to present a decided labial and a lingual 
plane. The dowel and disc are united, while the facing is 
ground to rest upon the cervical margin of the disc and is 
soldered to the dowel. 
Bicuspid and molar crowns are frequently constructed 
by capping the roots as described and fitting dowels in the 
Fig. 871.—-Essential Parts of an Upper First Bicuspid 
Crown Assembled, Ready for Application of Body 
root canals, to the outer or projecting ends of which the fac- 
ings are attached. In such cases it is advisable to solder some 
auxiliary projections on the root caps in the form of loops or 
pins to afford additional anchorage for the porcelain. 
Frequently entire crowns, without facings, are thus built 
up on root caps so constructed. 
Fig. 872.— Preparation of a Mo- 
lar Tooth for a Full Baked Por- 
celain Crown. The Foil Cap Is 
Constructed and the Porcelain 
Applied and Baked in a Similar 
Manner to the Steps Just De- 
scribed 
Fig. 878.— The Finished 
Crown in Position 
Fig. 874.— Proximal Flanges 
of Iridio-Platinum Added for 
Strengthening Crown and 
Aiding in Holding Contour 
of Porcelain During Baking. 
Suggested by Dr. C. A. 
White 856 
PORCELAIN CROWN AND BRIDGE WORK 
Flanges of iridio-platinum are applied to the root cap, 
extending incisally or occlusally, to give additional strength 
to the porcelain and assist in developing contour. 
The Porcelain Jacket Crown 
The porcelain jacket crown, as before stated, is specially 
indicated in the restoration of peg-shaped lateral incisors. 
The reason for this lies in the fact that an anomaly of 
this type usually has a small, sometimes distorted, root, in 
which the placing of a suitable dowel is questionable. Often- 
times it is impossible to successfully remove the pulp and fill 
the root canal in a satisfactory manner. The crown, also 
being undersized, requires but little preparation for the re- 
ception of a shell crown of porcelain. 
Fig. 875.—- A Case Showing Peg-Shape Lat- 
eral Incisor Before Preparation 
This form of crown can be successfully applied to various 
other classes of teeth, both vital and non-vital, and when prop- 
erly constructed and permanently set, fulfills esthetic require- 
ments in the highest degree. 
Fig. 876.—-Labial View of Prepared Tooth, 
Showing Gingival Shoulder 
TECHNIC OF CONSTRUCTION 
Prepare the tooth so that it presents a perceptible cone 
form, thinning it on labial and lingual surfaces so as to give 
space for a uniform layer of porcelain. PORCELAIN CROWN AND BRIDGE WORK 
857 
The mesial and distal surfaces need not be reduced to the 
same extent as the labial and lingual surfaces, yet they must 
also converge slightly from gingival to incisal areas. 
The sides of the cone should terminate in a distinct cer- 
vical shoulder, located just beneath the free gum margin. 
TAKING IMPRESSION OF TOOTH 
Construct a reasonably close fitting copper band suffi- 
ciently long to handle easily, and adapt to the periphery of 
the tooth. It should not encroach on the peripheral shoulder 
at any point nor upon the gum margin, but should pass be- 
tween the latter and the undisturbed peripheral enamel ring. 
Fig. 877.— Proximal View of Tooth. Impression 
Taken and Removed 
Fill tlie band with softened modeling compound and apply 
to the prepared tooth, at the same time closing the incisal end 
of the band with the finger to prevent escape of impression 
material. 
Apply sufficient force to secure an impression, not only 
of the axial surfaces of the tooth, and flattened cervical shoul- 
der, but of the root periphery as well. 
Chill the compound, remove the impression and trim off 
gingival surplus. 
CONSTRUCTING THE DIE 
Apply a section of rubber tubing to the band periphery 
and pack the impression with amalgam, building it up suffi- 
Fig. 878.— Impression Filled 
with Modelite 
ciently to afford a firm base for attachment to the cast, or 
plaster base. 858 
PORCELAIN CROWN AND BRIDGE WORK 
Modelite may be used to advantage instead of amalgam; 
in which case, before hardening, a small wood screw should 
be inserted in the base for anchorage purposes. 
Fig. 879.— Modelite Die of 
the Tooth 
Fig. 880.— Die of the Tooth Set in Base. 
Triangular Pattern of Foil 
Secure an impression in plaster and a bite in wax, of the 
prepared tooth and of the two proximating teeth also and set 
aside for later use. 
Imbed the die base in modeling compound in a swaging 
ring and trim so as to freely expose the cervical shoulder. 
FORMING THE PLATINUM CAP 
Cut a triangular piece of 1-1000 platinum foil of sufficient 
dimensions to encircle the cervical periphery, and extend 
somewhat beyond the incisal end of the die tooth. 
Anneal the foil and cut off the excess points from the 
cervical ends of the triangle, as indicated in cut F. 
Apply the foil to the die to form a cone, the base of which 
should extend beyond the cervical shoulder. 
Fig. 881.— Foil Partially Adapted to 
the Die 
Slit the foil near the apex, so that the sides of the triangle 
may be wrapped around the die. 
Before closing the two sides together, the apex of the 
triangle should be turned over the incisal edge of the die so 
as to lie beneath them and thus close the incisal end of the 
cone cap. 
With a pair of foil carriers the two sides are grasped and 
brought together against the lingual surface of the die and 
there folded together to form a lap or stove-pipe joint. PORCELAIN CROWN AND BRIDGE WORK 
859 
At the time of making the folded joint, care should be 
taken to see that the cone base is embracing the root peripheiy. 
Burnish the now closed cap to the die, carrying the bur- 
nisher along the axial surfaces and downward in a cervical 
direction. 
Fig. 882.— Sections Showing Partial and 
Complete Form of Joint 
Trim off excessive surplus, both incisally and cervically, 
and with a large pellet of absorbent cotton or punk, enclose 
the entire cap and apply pressure with the fingers from all 
sides against the axial surfaces, and in a cervical direction 
as well. 
Care should be taken to avoid undue force at all times 
or the foil will be torn. 
Fig. 883.— Platinum Cap Adapted to Die and 
Trimmed to Correct Outline Form 
When the foil cap is perfectly adapted and its cervical 
margin trimmed close, but not quite, to the peripheral cervical 
shoulder, it should be carefully removed and laid aside until 
the body is applied. 
Since the porcelain must be applied and the crown carved 
so that its incisal edge will come in correct alignment with the 
proximating teeth, it should be formed on a cast in which 
these proximating teeth are present. 
CONSTRUCTING THE CASTS 
The die is now removed from the swaging ring or base 
in which it was imbedded, the gingival portion of the impres- 
sion trimmed somewhat freely to admit the die, the latter 
placed in its matrix and a cast developed in the usual manner. 
The bite is applied to the cast, the latter mounted on the 
occluding frame and the occlusion cast developed. 
Trim the plaster from around the cervical end of the die 
tooth, so as to freely expose the shoulder and permit the foil 
cap to be set in proper position without interference. 860 
PORCELAIN CROWN AND BRIDGE WORK 
Make a small cylinder of oiled writing paper and apply 
around the platinum cone, holding it in position with a loosely 
tied ligature. This is to assist in condensing the porcelain. 
APPLICATION OF THE PORCELAIN 
High-fusing tooth body (2560 degs.), of suitable shade to 
match the tooth, is now mixed ready for application. 
Usually two shades, sometimes three, are selected and 
mixed, the darkest being applied to the gingival third, the 
medium to the middle, and the lightest to the incisal third of 
the cylinder. 
The body should be mixed to medium consistency, and 
as each portion is applied it should be vibrated to place. 
When of medium consistency the sharp lines of demarka- 
tion of the two or three colors will disappear during vibra- 
tion and when fused will show gradual blending of the colors. 
As the incisal portion is added, the paper cylinder is flat- 
tened mesio-distally to give correct alignment to the incisal 
portion. 
Absorb the moisture that comes to the surface with bibu- 
lous or blotting paper, and when compact and reasonably dry 
remove the ligature and oiled paper. 
Fig. 884.— The Outer Dotted 
Line Shows Approximately How 
Much Larger the Crown Should 
Be Formed in the Body to Com- 
plete It in One Baking 
The body is now carved to the required form and such 
additions made as are necessary. 
Particular attention should be given the cervical end, to 
see that the body comes flush with, but does not overlap, the 
peripheral root portion of the matrix. 
Smooth up all surfaces with a fine sable brush, carefully 
remove and set on a soapstone base, carved to the general 
form of the die, but slightly smaller. 
The interior point of the support should be sufficiently 
long to afford a rest for the crown without its weight being 
thrown on the cervical end. PORCELAIN CROWN AND BRIDGE WORK 
861 
Dry out the moisture in the body very carefully, to pre- 
vent flaking, and when ready introduce the crown in the fur- 
nace, heat slowly, and bring to a semi-glazed condition. 
Since in these cases tooth body is used, a longer time will 
be required to vitrify the material than is required for con- 
tinuous gum body. 
BAKING THE CROWN 
Fig. 885.— The Finished Crown 
When fused, the crown is returned to position on the cast, 
its relations to the other teeth noted, correction made by addi- 
tion of body to such areas as need further contouring, and 
the case is returned to the furnace, usually for the final bak- 
ing, this time bringing the porcelain to a glaze. 
If by trial on the cast it is found correct, the crown is 
moistened, the matrix carefully peeled out of the interior, 
rough margins are smoothed and the crown is ready for 
setting. 
The “Land” Jacket Crown 
Dr. C. H. Land of Detroit was probably the first to in- 
troduce a system of practical technic for the jacket crown. 
The following outline presents the essential steps of the 
Land system: 
PREPARATION OF THE TOOTH 
Remove all of the enamel and prepare the tooth cone- 
shaped, without cervical shoulder, hut in other respects much 
the same as required for the preceding crown. 
Fig. 886.— Case Showing a Peg-Shape Lateral 
Incisor Before Preparation 862 
PORCELAIN CROWN AND BRIDGE WORK 
CONSTRUCTION OF THE CAP 
Construct and adapt a wide band of 30-gauge platinum 
to the tooth, scribing and fitting it carefully under the free 
gum margin as for any banded crown. 
Fig. 887.— Labial View of Pre- 
pared Tooth 
Fig. 888.— Proximal View of Pre- 
pared Tooth 
The band should extend from the cervix to a short dis- 
tance beyond the incisal end of the prepared tooth. 
Bevel cuts are now made in both mesial and distal sur- 
faces of the band, in line with the labial and lingual planes 
of the tooth, extending from incisal edge to near the cervical 
margin. 
Bend both labial and lingual sections outward to give 
space for adapting and burnishing the mesial and distal sec- 
tions of platinum against these surfaces of the tooth. 
Fig. 889.— Platinum Band 
Adapted to Tooth. The Dot- 
ted Lines Show Where Bevel 
Cuts Are to Be Made 
Fig. 890.— Labial and Lin- 
gual Sections Bent Outward. 
Proximal Sections Adapted 
to the Tooth 
When close adaptation of these sections is secured, the 
edges of the triangular margins may be reduced with discs to 
permit the other sections of platinum being brought in close 
contact with the tooth along the joints. 
Bend and adapt the lingual section of platinum against 
this surface of the tooth, removing the excess so that it over- 
laps the mesial and distal margins of platinum to a slight 
extent only. PORCELAIN CROWN AND BRIDGE WORK 
863 
Burnish the joints closely and solder with high-fusing 
platinum solder. 
Adapt and trim the labial section to the sides, and solder 
in like manner. 
Fig. 891.— Lingual Section Adapted 
to the Sides 
Fig. 892.— The Cap Completed 
After soldering, the four angles of the cone cap may be 
rounded off with discs, to reduce the platinum to uniform 
thickness. 
TAKING BITE AND IMPRESSION 
Take an impression and bite of the proximating teeth with 
cap in position. 
Flow a film of wax inside the cap, develop casts, and 
mount on the occluding frame. 
Warm the cap, remove, clear its interior of wax and re- 
turn to the cast. 
SELECTION AND GRINDING OF FACING 
Select a facing of desired shade and form and grind to 
proper alignment. 
This step usually requires the concaving of the facing on 
its lingual side, to a very considerable extent, and the reduc- 
tion of its ridge lap to a thin margin. 
Fig. 893.— Method of Grooving the 
Porcelain Facing 
Frequently, the porcelain must be grooved from cervical 
near the incisal areas carrying the groove between the pins. 
In some cases the pins themselves are ground away in order 864 
PORCELAIN CROWN AND BRIDGE WORK 
to bring the facing into correct labial alignment. When this 
is necessary, however, it is best to form a shoulder in the 
porcelain to rest upon the incisal end of the cap. 
Fig. 894.— Facing Prepared 
for Adjustment to Cap 
Figs. 895 and 896.—- Proximal and Lingual View of 
Facing Adapted to Cap 
When ground to correct labial alignment, the pins, if 
present, are bent in close contact with the cap, the facing and 
cap waxed in correct relation, when they are removed from 
the cast, invested, soldered, pickled in acid and washed. 
APPLICATION AND FUSING OF PORCELAIN 
High-fusing porcelain is now applied around the margins 
of the facing, next the cap and with vigorous vibration worked 
into the entire space between the two. 
Additions are now made where needed to develop required 
contour, all surfaces smoothed and with a fine sable brush 
all particles are removed from the labial surface of the fac- 
ing and exposed cervical portion of the root cap. 
Frequently during the application of the body some of it 
may become lodged in the interior of the cap, and, if so, 
should be removed before fusing. 
Fig. 897.— The Finished Crown 
Set the crown on a soapstone base having a projection 
for entering the cap of sufficient height to support the crown 
in an upright position. PORCELAIN CROWN AND BRIDGE WORK 
865 
Remove the moisture by gradually applied heat, introduce 
the crown in the furnace and raise the temperature gradually 
to fusing point, stopping the fusion while the porcelain is in 
a semi-glazed condition. 
Cool slowly and, when in condition to handle, additions 
of body are made to fill any fissures that may be present, and 
develop contour where required. 
Since, in a crown of this type, the bulk of porcelain is 
comparatively slight, and contraction proportionately so, two 
bakings are usually sufficient to develop required contour, 
therefore the porcelain should be fully glazed during the sec- 
ond fusing. 
Fig. 898.— The Crown in Position 
Porcelain Bridgework 
As previously stated, there is less necessity at the pres- 
ent time than formerly for the construction of porcelain 
bridges by the baking process. 
This is due to the introduction of various types of re- 
placeable, full and partial crowns, which, when properly com- 
bined with metal, fulfill esthetic requirements, in many cases, 
quite as well as do baked porcelain bridges. 
Bridges composed of metal, and to which replaceable teeth 
are adapted, have a decided advantage over those of the for- 
mer type, in that they are easily repaired in case of fracture 
of the porcelain parts. 
However, cases present when a baked porcelain bridge 
will fulfill esthetic requirements where one of another type 
would prove inadequate. 
GENERAL CONSIDERATIONS 
Most of the failures recorded against porcelain, when 
used in bridgework, are due to its injudicious application 866 
PORCELAIN CROWN AND BRIDGE WORK 
Certain conditions are often found in the mouth which pre- 
clude the introduction of a bridge of this character. 
Porcelain is strong only in bulk. In thin, attenuated 
plates it is friable and breaks readily under stress. The truss 
or platinum framework must be depended upon primarily to 
furnish the necessary strength to resist stress. A truss may 
be constructed that fulfills this requirement and the case still 
be unsuitable for porcelain if the remaining spaces not occu- 
pied by the metal structure are so limited that the porcelain 
will be spread over the framework in thin layers, especially 
on occlusal surfaces. The constantly repeated force of mas- 
tication, directed against the cusps of porcelain, will fracture 
and break them away from the truss, even though the latter 
may be rigid enough to retain its form. 
In addition, therefore, to having sufficient space for a 
rigid truss, there must be sufficient additional space remaining 
to apply the porcelain in ample bulk to resist stress. It is 
impossible to state just how wide this space should be. A 
great deal depends upon the habits of the patient, the amount 
of force exerted by the muscles of mastication, the length of 
span and the number and position of abutments and piers. 
It may be stated that, as a general rule, there must be a 
minimum space of at least 5 mm. between the alveolar border 
and the occlusal surfaces of the opposite teeth in short spans, 
while longer spans will naturally require more space, since 
the truss itself must be more bulky. 
The length of span is a matter of great importance and 
should be closely studied. In long spans, where such curva- 
ture in the bridge will be required and where only two abut- 
ments afford support, a porcelain bridge would most certainly 
prove a failure. If, however, there is an intervening pier, 
with sufficient space to insure bulk of porcelain, the case 
would be suitable for an appliance of this character. 
The points to be carefully observed and studied are: 
First—The number, position and condition of the roots 
or teeth that are to serve as supports for the bridge. 
Second—The length of span to be covered by the truss. 
Third—The amount of space between the alveolar border 
and the occlusal surfaces of the opposite teeth. 
Fourth—The habits of the patient as to the care of the 
teeth. 
Fifth—The amount of force exerted by the muscles of mas- 
tication. PORCELAIN CROWN AND BRIDGE WORK 
867 
Sixth—Study carefully, whether a substitute of any other 
character might be equally as serviceable if not more effi- 
cient than porcelain. 
The various steps involved in the construction of a porce- 
lain bridge may be arranged in the following order: 
First—Preparation of the abutment or pier roots or teeth. 
Second—Construction of caps or shell crowns for same. 
Third—Taking bite and impression, and mounting casts 
on occluding frame. 
Fourth—Locating position of, and constructing and sol- 
dering saddle to caps and crowns. 
Fifth—Locating position of, and fitting truss bars in posi- 
tion. 
Sixth—Investing and soldering same to caps and crowns. 
Seventh—Attaching facings to metal framework. 
Eighth—Application of body. 
N inth—B aking. 
Tenth—Finishing. 
Eleventh—Setting the bridge. 
PORCELAIN BRIDGE CONSTRUCTION 
PREPARATION OF ROOTS OR TEETH 
The preparation of the roots or teeth for the reception 
of caps and crowns which are to serve as abutments and piers 
for bridges differs in no essential particular from the instruc- 
tion previously given under the heads of porcelain crowns and 
shell crowns, therefore it is unnecessary to enter into the de- 
tails of this procedure here. 
CONSTRUCTION OF CAPS AND SHELL CROWNS 
When the abutment and pier crowns are to be of porce- 
lain, the construction of the caps is similar to, or identical 
with, the methods outlined under the head of porcelain crowns. 
When platinum shell crowns are constructed for the bicus- 
pids or molars, as is frequently advisable, the details differ 
in a few essential particulars, from the methods followed in 
ordinary shell crown construction. 
The cusps of crowns, when platinum is used, are more 
difficult to swage in this material than from 22 k. gold of equal 
thickness. Therefore, in order to have the needed bulk of 
platinum in the occlusal surface of a crown, to withstand attri- 868 
PORCELAIN CROWN AND BRIDGE WORK 
tion, two thicknesses of platinum are swaged, separately at 
first, and then together and solidly attached by soldering. 
This is necessary since the interior of such crowns can- 
not be reinforced with solder, as is done in ordinary crown 
work, as the latter would be more or less dissipated by the 
heat necessary to fuse the porcelain. 
Special care should be taken to contour the occlusal mar- 
gin of the band and the corresponding margin of the cusps 
until they coincide perfectly, then true both contact margins, 
first with a flat file, following this by dressing on an oil stone 
until perfect contact is secured, thus obviating the use of 
much solder in attaching the two pieces together. 
The method of constructing a crown of this class in the 
ordinary manner, and afterward swaging a second piece to the 
interior to stiffen up the occlusal surface, allowing the mar- 
gins of the second piece to overlap the joint between the band 
and cusp, is frequently resorted to with satisfactory results. 
To give additional strength to the crown, at the point 
where the saddle and truss bars join it, a second piece of 
Fig. 899.— On Left, Dressing Down Occlusal Cap and Axial Band 
on Oil Stone. On Right, Occlusal Cap, Composed of 
Two Thicknesses of Platinum Plate 
platinum plate is often adapted and soldered to this surface, 
on the outer side of the crown. 
The caps and crowns having been constructed and fitted 
in their respective places, an accurate bite and an impression 
are secured, the casts constructed, and mounted on an occlud- 
ing frame. 
CONSTRUCTION OF SADDLE 
The saddle, although not universally, is frequently used 
to give the porcelain proper contour on both labial or buccal 
and lingual surfaces. 
Formerly broad saddles were recommended and much 
used, as previously mentioned, but for reasons already stated 
their use has been discontinued. 
Saddles, therefore, when indicated, should be as narrow 
as possible, yet sufficiently wide to fulfill the requirements of 
proper contouring of the case. 869 
PORCELAIN CROWN AND BRIDGE WORK 
The position as well as outline for the saddle can be best 
determined by waxing the facings in position and trimming 
the wax to correct form, then trimming the saddle to the line 
thus indicated. Another method frequently followed is to 
make the saddle broader than necessary, and after the first 
application and baking of the body, cut away the surplus mar- 
gins. This gives good results, but entails considerable waste 
of material. 
The saddle should lap well over caps and against crowns, 
to insure secure attachment of the several parts. It is cut 
to proper length and width as indicated by the outline on the 
cast, and either burnished and conformed to it, or swaged on 
a Melotte’s metal die. Where the surfaces on which the sad- 
dle is to rest are very irregular, the latter method is an ex- 
cellent and accurate one. 
When swaged or conformed perfectly to the cast or die, 
it is attached to the caps and crowns by soldering and the 
several connected parts are fitted in the mouth for final ad- 
justment of the saddle to the natural tissues. A large round 
end burnisher, or one of the contra-angled form designed by 
the author, can be used for this purpose. The saddle should 
be pressed uniformly against the soft tissues until a slight 
blanching of the gum is noticeable. This should disappear 
in three or four minutes and the tissues regain their normal 
appearance. Too great pressure will produce hypertrophy of 
the tissues and finally atrophy and absorption, while under a 
properly adjusted saddle they will usually remain in a healthy 
condition and in contact with it for a varying period. 
At this time the partially constructed framework is in 
position in the mouth, and the soft tissues in a more or less 
compressed condition. If removed and placed on the original 
cast, the saddle would be distorted, since the cast, unlike the 
gum tissue, is unyielding. Therefore it becomes necessary to 
take a new bite and impression, and mount the cast as before. 
LOCATING AND FITTING TRUSS BARS 
In short spans a single bar of 16 or 15 gauge round iridio- 
platinnm wire is usually sufficient to fnrnish the needed rigid- 
ity and support to the bridge. Longer spans frequently re- 
quire two bans of 16-gauge, or a single bar of 14-gauge. 
The position for the truss bar is found by grinding the 
facings accurately to place and waxing them in position. Var- 
nish the outer surface of the cast with separating medium and 
build a matrix of plaster against the labial or buccal surfaces 870 
PORCELAIN CROWN AND BRIDGE WORK 
of the teeth and cast. When set, remove from the cast, and, 
if the facings have remained with the framework, remove 
and place them in their respective positions in the plaster 
matrix. 
The wax is all removed and the plaster matrix carrying 
the teeth returned to the cast. The truss bar is then bent and 
conformed to the lingual surfaces of the facings, usually occu- 
pying a position between the pins and the ridge lap. By plac- 
ing in this position, more space is afforded for the porcelain 
and the liability of its breaking away under stress will be 
much less than when the bar is placed between the pins and 
the occlusal or incisal margins of the facings. 
Broad surface contact should be secured between the bar 
and dowels and the several parts held in absolute contact 
while soldering, so as to insure the greatest possible amount 
of strength. 
The attachment of the bar to a shell crown is usually made 
by splitting the abutting end and adapting the split portions 
to the reinforced section of the crown before mentioned; or 
a hole may be drilled through the axial wall of the crown and 
the bar bent so as to pass up the inner side of the wall and 
across the occlusal surfaces, a groove being cut in the tooth, 
if necessary, for the accommodation of the bar. This affords 
a firm anchorage to the crown and one that will not pull away, 
as frequently occurs when the contact of the bar with the 
crown is limited and superficial. 
Round or oval are preferable to square bars, since the 
sharp angles on the latter seem to induce fracture in the 
porcelain, under stress. 
Tf square wire is used the sharp angles should be rounded 
off to obviate this difficulty. 
When the bar is accurately adapted, the ends are waxed 
to the dowels and crown attachments. 
In the series of drawings shown in Fig. 900 from a former 
edition of this text, the construction of a two-bar truss of 
square wire is illustrated. Tn 31 d the bar next to the saddle 
is first fitted and attached to cap, dowel and shell crown. The 
second bar nearest the occlusal surface is next fitted, bending 
it so as to lie in close contact with the lingual surfaces of the 
facings as shown in 32 e. Tt can be bent to pass over the pins 
if necessarv, but when possible should pass under them, for 
reasons before stated. Tt can be bent irreemlarlv to follow the 
line of the runs, should they be uneven. The ends of the bars 
connected with the dowel can be notched as indicated in 34 
and the reduced portion bent around it, as shown in 35. PORCELAIN CROWN AND BRIDGE WORK 
871 
Thirty-three shows imperfect contact of post and bar; 37, 
a condition in which there is not space enough between the 
labial side of the dowel and the lingual surface of the facing 
to receive the truss bar, and, to overcome the difficulty, both 
dowel and bar are notched. In some cases both bars lie on the 
same side of the dowel, one upon the other, as indicated in 
31 c, and again there are cases where, if arranged in this 
manner, the outer one would be thrown too far occlusally. 
Fig. 900.— Cuts Showing Various Steps in the Fitting of Saddles, Truss Bars, and Teeth 
of a Porcelain Bridge. In This Case the Molar Is a Shell 
Platinum Crown 
One is then placed on the lingual side of the dowel and the 
other one on the opposite side, as in 38. 
In 36 the method of splitting the bar and bending the 
split ends so as to partly encircle the shell crown is illustrated. 
When bicuspids and molar roots carry full porcelain crowns 
the bars are attached to their caps and posts in the manner 
described. 
The bars, when fitted, are connected by braces, which are 
cut and accurately fitted in position. Both ends can be 
notched as shown in 31 f. 872 
PORCELAIN CROWN AND BRIDGE WORK 
Cut II 
Cut III 
Fig. 901.— Bridge Before and After Application and Fusing 
of the Porcelain Body 
Cut II shows a single bar truss, with short posts soldered 
on the molar cap and at intervals along the truss bar, to afford 
firmer attachment to the lingual body of porcelain. 
Fig. 902.— Framework of an Upper, Four- 
Tooth Bridge, Showing Heavy Truss Bar 
Attached to Dowels of Cuspid and First 
Molar Crown. Fitted with Narrow Saddle 
Cut III shows the piece after the porcelain has been ap 
plied and baked. 
SOLDERING 
The several parts having been accurately fitted they are 
waxed together, the facings removed, the cap, crown, saddle 
and truss removed from the cast and invested so that the in- 
vesting material extends over the bars and holds them firmly 
in position after the wax is removed. When soldered, the 
frame is returned to the model and the facings returned to 
place, waxed in position, the piece removed, again invested, 
the pins, after having been flattened, bent in actual and close 
contact with the bar and soldered. 
The essential points to be observed in constructing the 
framework for a porcelain bridge are: 
First, be accurate in every detail. Second, develop close 
joints. Third, flow solder into and between all junctions so as 
to perfectly unite the several parts together. 
APPLICATION OF THE BODY 
Before applying the porcelain body, the framework should 
be pickled, cleansed and roughened on those surfaces against PORCELAIN CROWN AND BRIDGE WORK 
873 
which the porcelain is to be fused to afford some additional 
attachment of the porcelain to the metal framework. 
As mentioned in connection with crown work, a pin vise 
can be used to good advantage in handling the piece while 
applying the body. 
The body is built on the lingual surfaces of the facings 
and against the saddle a little at a time, the piece vibrated 
to settle the granules of powder close together, the moisture 
is taken up as it appears on the surface, and a rough contour 
given the piece for the first baking. 
All particles of body should be removed from the labial 
or buccal surfaces of the facings, for if carried through the 
furnace they become attached and can only be removed by 
discing or grinding, which destroys the fine glaze on the por- 
celain. 
FUSING THE PORCELAIN 
The directions, beginning on page 615, with reference to 
the fusing of continuous-gum body apply with equal force in 
the fusing of porcelain in bridge work. Usually, the piece, 
being smaller, can be fused in somewhat shorter time than a 
Fig. 903.— Small Electric Furnace Suitable for Porce- 
lain, Crown, Bridge, and Inlay Work 
(Hammond) 
full denture, and since less time is required, greater care must 
be observed in the latter stages of baking, to prevent over 
fusion. 
When possible to do so, the bridge should be completed in 
two bakings to avoid friability of the material, which char- 
acteristic, as well as a tendency to become porous, develops 
rapidly after the second fusion. 874 
PORCELAIN CROWN AND BRIDGE WORK 
FINISHING AND SETTING THE BRIDGE 
Finishing and setting a porcelain bridge differ in no es- 
sential particulars from the steps involved in the finishing 
and setting of porcelain crowns, the details of which have been 
given. As previously mentioned, however, the use of the 
Fig. 904.— Small Gasoline Furnace Suitable for Porcelain Crown, 
Bridge, and Inlay Work (Turner) 
mallet, either hand or automatic, should be avoided in the set- 
ting of baked crowns of porcelain, combined with metal, be- 
cause of the very great danger of fracture. 
VARIOUS TYPES OF METAL STRUCTURES 
The principal thought to keep in mind in planning a por- 
celain bridge is to form a rigid metal structure, capable of 
sustaining all stress to which the bridge may be subjected, 
without depending upon the applied porcelain. 
Therefore, the forms of trusses may be varied according 
to conditions, as space occluso-gingivally, length of span, posi- 
tion of abutments, width of alveolar border, etc. 
Frequently, in the replacement of a single tooth, a truss 
of the cantilever type may be united with a single crown, the 
opposite end from the crown terminating in a projection for 
resting in a grooved inlay in the proximating tooth. 
In other cases, instead of a saddle being adapted to the 
border, a half-round wire is fitted close to, or in contact with, PORCELAIN CROWN AND BRIDGE WORK 
875 
the border crest, against which the buccal and lingual sur 
faces of applied porcelain may terminate. 
Fig. 906.— Framework of an 
Extension Bridge, with Sup- 
porting Lug to Rest in 
Grooved Inlay in Cuspid 
Tooth 
Fig. 906.— Framework of a Lower Four-Tooth 
Bridge. Heavy Truss Bar for Supporting 
Teeth. Half-Round Wire to Rest on Border 
Crest, and Against Which Both Buccal and 
Lingual Surfaces of Porcelain Will Terminate 
Fig. 907.— Framework of an Upper, Four- 
Tooth Bridge Fitted with Saddle, to Which a 
Lingual Flange Is Applied for Support of 
Porcelain 
Again a flange of platinum is adapted and attached to 
the lingual border of the saddle or wire to add strength to the 
framework and afford a matrix for supporting the porcelain 
under stress. 876 
PORCELAIN CROWN AND BRIDGE WORK 
The Peeso and Benson pliers, because of their short beaks 
and heavy handles, are particularly useful for contouring of 
Fig. 908.— The Peeso Contouring Pliers 
Fig. 909.— The Benson Contouring Pliers 
plate and bending of wires in this, as in many other classes of 
crown and bridge work. CHAPTER XXXI 
INLAYS 
Porcelain and Metallic 
PORCELAIN 
Porcelain, or “chinaware,” was imported into Europe 
principally by the Portuguese, who gave it the name of porce- 
lain, from its resemblance to the nacre or lining of the sea- 
shell Porcellana (Cyprea). The shells of this species derive 
their name from their supposed resemblance to the back of a 
hog (Porcus). It was at first supposed that porcelain con- 
sisted of pulverized egg shells, fish scales and fish glue. 
The first authentic record we can find of porcelain being 
used for dental purposes appears in the “Art of Dentistry,” 
published by Faucliard in 1728. In this he says: “I have 
thought that advantage might be derived from a regular and 
unalterable coloration from enamel artificially composed. I 
have also thought that I might from this not only perfectly 
imitate the enamel of the teeth, but the gum in cases where it 
is necessary to replace the teeth in whole or in parts of sets. 
I have consulted the most able enamelers, and by conversa- 
tions which I have had with them I have rendered practicable 
that which I believe no one else has ever thought of; the teeth 
or dentures made of enamel will endure a very considerable 
time, since the enamel is a substance scarcely susceptible of 
change or alteration.” 
EARLY APPLICATION OF PORCELAIN IN DENTURE CONSTRUCTION 
The development of porcelain in its application to den- 
tistry is a most interesting story, an outline of which will be 
found in the chapter on the “History of Prosthetic Den- 
tistry. ’ ’ 
The efforts of the pioneers in the porcelain field until 
Fonzi’s time, 1808, were directed principally to the produc- 
tion of full and partial dentures in a single piece, yet but 
little progress was made in this class of work until about 
1850, when Dr. John Allen introduced the continuous gum 
denture. His work consisted in improving the character of 
the porcelain then in use, reducing its fusing point and oon- 
877 878 
INLAYS 
tractile tendency, improving the color of the gum enamel, 
and of baking the denture on a platinum base to which the 
teeth were previously attached by soldering. The use of the 
platinum base obviated the warpage, which invariably oc- 
curred when the porcelain was fused on a silex and plaster 
form. 
correction of warpage in the all-porcelain denture 
Previous to Allen’s improvement, it was necessary, after 
the denture was baked, to secure an accurate cast of the mouth 
in plaster, paint the areas to be covered by the denture with 
red lead or similar pigment, and apply the denture to the 
cast; the areas of contact between denture base and cast were 
colored on the base with the pigment, and on removal were 
ground with small stones. This process of trial and grinding 
was repeated until finally the entire denture surfaces which 
rested upon the oral tissues showed color, when pressed upon 
the cast. The same general technic was followed in securing 
adaptation to the oral tissues, of the old-time dentures carved 
from the elephant or hippopotamus ivory. 
Dentures constructed by this method, while occasionally 
showing good adaptation and stability, usually required the 
aid of springs for their retention under masticatory stress. 
Basic Ingredients of Porcelain 
The basic ingredients in most of the porcelain bodies of 
today consist of kaolin, silex and feldspar in proportions 
varying according to the purpose for which the material is 
intended. The porcelain used for tooth bodies is the highest 
fusing of any used for dental purposes, the point of vitrifica- 
tion ranging from 2,440 to 2,600° F. 
kaolin (A12H2 (Si04)2H20) 
The word kaolin is a corruption of the Chinese word 
Kauling, which means a high ridge, and is the name of a hill 
near Jachau Fu, China, from which a great deal of this ma- 
terial is derived. A fine variety of clay is also found in 
Germany. Both of these varieties of clay are practically free 
from iron oxide and other deleterious impurities and are used 
almost exclusively in the compounding of dental porcelains. 
Kaolin is a fine pure variety of clay, or aluminum sili- 
cate. It is formed by the disintegration and decomposition INLAYS 
879 
of granitic and feldspathic rocks through weathering, or con- 
tinued freezing and thawing. These rocks being granular, 
take up moisture, and this when expanded by freezing splits 
off the outer surfaces of the rock. The rain in time dissolves 
out some of the constituents and washes away the small par- 
ticles, which, as they are carried down the stream, grind upon 
each other and become still more finely divided until all sem- 
blance of their original form is lost. These particles, mixed 
with sand, float or are washed down stream and settle in beds. 
Some of these clay beds are at the present time high above 
the water line, having been deposited ages ago and placed in 
their present location by volcanic upheavals. 
PREPARING THE CLAY FOR USE 
The clay is prepared for use by mixing with water in a 
tank, agitating and allowing the sand and heavier particles to 
settle, after which the water is drawn off into another tank, 
while the finer particles of clay are still held by it in solution. 
These finer particles are allowed to settle in the second 
tank, and when the water becomes clear it is carefully drawn 
off and the clay allowed to dry. The slab of dry clay is then 
turned over and the coarser particles which settled to the bot- 
tom as the first precipitate are scraped off, when it is ready 
for use. 
feldspar (K A1 Si308) 
Feldspar is a double silicate of aluminum and potassium 
known as Ortlioclase. It occurs crystallized in rhombic 
prisms. There are many varieties of this mineral, but only 
those that are free from soda or lime are used in compound- 
ing porcelain. It is yellowish pink in color in its natural state, 
but transparent and colorless when fused. 
A variety of this mineral suitable for tooth bodies is 
found in many parts of the United States. The principal de- 
posits suitable for the compounding of porcelain are found 
near Wilmington, Del. 
PREPARING THE FELDSPAR FOR USE 
Feldspar is prepared for use by beating to redness, drop- 
ping in water while hot, to break it up into small pieces, 
ground to powder in a special pulverizing machine or with a 
large mortar and pestle, and under water, to facilitate the 
grinding. The powder is then run through a No. 10 bolting 
sieve, placed in closed vessels to keep dry and free from im- 880 
INLAYS 
purities until needed for use. Pulverizing too finely detracts 
from the translucency of the porcelain when fused. 
SILICA (Si02) 
This mineral is a silicic oxide, ordinarily known as quartz. 
It is one of the constituents of granite rocks; it also occurs 
free in large masses in many parts of the United States, as 
well as in many parts of the world. 
PREPARING THE SILICA FOR USE 
Silica is prepared for use by grinding to a fine powder 
in a powerful mill constructed especially for this class of work. 
It is extremely hard and fuses only at very high tempera- 
tures, about 2,500° F. 
These three materials, kaolin, silex and feldspar, as before 
stated, are combined in varying proportions to form tooth 
bodies, and the more fusible continuous gum and inlay bodies. 
Properties of the Basic Constituents of Porcelain 
Kaolin imparts plasticity to the tooth body, enabling it 
to be molded into the desired form before baking. It also 
contracts somewhat in fusing, and as a result draws together 
the more infusible constituents, thereby impairing density to 
the mass. 
Silex, on account of its infusible property, tends to keep 
the form into which it is molded, whether inlay, tooth, crown, 
bridge or denture, from melting down in the heat of the fur- 
nace. 
Feldspar imparts translucency and also acts as a flux, 
closely uniting the kaolin and silex. By varying the propor- 
tion of this material in compounding the body, a number of 
porcelains differing in texture and fusibility can be produced. 
APPROXIMATE PROPORTIONS OF INGREDIENTS IN PORCELAIN 
The manufacturers do not publish the formulas of their 
tooth, or other porcelain bodies of the lower fusing types de- 
signed to be used in continuous gum and other classes of 
work. Since it is not necessary for the prosthetist to com- 
pound his own porcelain materials, as the pioneers in this 
field were required to do, still it is essential that he know INLAYS 
881 
the elementary constituents and their physical properties in 
order that the best results may be derived from their use. 
The names of Wildman, Hunter and Allen are inseparably 
connected with the history of continuous gum work and 
carved block teeth in this country, and to them the profession 
owes much for improvements in porcelain bodies and tech- 
nical methods. The period of greatest activity of these early 
porcelain workers extended from 1835 to 1860. Since the 
latter date the carving and baking of single and block teeth 
in the dental laboratory, as was the prevailing custom in their 
time, has been discontinued because of the continually ad- 
vancing improvements in these lines of the manufactured 
products. Continuous gum dentures, however, cannot be 
made in a factory. The prosthetist, therefore, should be 
capable of selecting the best material and of manipulating 
it in the best possible manner to secure artistic and perma- 
nent results in the construction of dentures of this type. 
The following formulas will show, in a general manner, 
the proportions of the basic ingredients used in compound- 
ing some of the many porcelains: 
Dr. Wildman’s formula for tooth body: 
No. 1. Kaolin 1 oz. 
Silex 3 ozs. 
Feldspar 18 ozs. 
Titanium oxide 65 grs. 
Titanium oxide imparts a yellowish tint to porcelain. The 
oxides of some of the other metals are used for producing 
various tints, as required; they are mixed in and thoroughly 
incorporated with the porcelain in process of manufacture, 
the latter often, after the addition of the metallic oxide, being 
fused, crushed and pulverized, to more thoroughly dissemi- 
nate the tint. 
OXIDES OF THE METALS USED IX TINTING POECELAIN 
Gold in a state of minute subdivision Rose red 
Oxide of gold Bright rose red 
Purple of Cassius (double oxide of tin and gold) Purplish red 
Sponge platinum and filings Grayish blue 
Oxide of cobalt Bright blue 
Oxide of manganese Purple 
Oxide of uranium Greenish yellow 
Oxide of silver Lemon yellow 
Oxide of zinc Lemon yellow 
Oxide of titanium Bright yellow 882 
INLAYS 
The formula for continuous gum body is similar to that 
of the Wildman tooth body, previously given, except that more 
kaolin and feldspar are added to reduce the fusing point; this 
is necessary in order that the teeth, which have previously 
been attached to the platinum base, will not be fused and lose 
their shape or color while vitrifying the continuous gum body. 
THE CONSTITUENTS OF GUM ENAMEL 
The continuous gum body, when applied around the 
teeth and over the metallic base, gives form and contour to 
the denture; in color it does not resemble the natural gums, 
being white, or, when oxide of titanium is present, slightly 
yellow; the denture must be tinted to give it a natural ap- 
pearance. A material called gum enamel, purplish pink or 
red in color, is distributed in a thin, more or less uniform 
layer, over those surfaces representing the mucous tissues 
and fused to the continuous gum body, thus giving the re- 
quired color and the proper glaze, to the surfaces of the 
denture as well. 
Gum enamel is made by combining certain compounds in 
definite proportions with feldspar. These compounds are 
known as frits and fluxes, the formulae of which are similar to 
the following: 
No. 2. Flux. 
Carbonate of potassium 1 oz. 
Fused borax (powdered) 1 oz. 
Quartz 4 oz. 
These materials are fused together, then crushed and 
ground to a fine powder, to prepare them for combining with 
the following: 
No. 3. Gum frit. 
Purple of Cassius 16 grs. 
Feldspar 700 grs. 
Flux (as per Formula No. 2)... .175 grs. 
This gum frit is fused, crushed and ground to a fine 
powder, preparatory to the final compounding of the pink 
gum enamel. 
No. 4. Gum enamel. 
Gum frit (as per Formula No. 3). . 1 oz. 
Feldspar 3 oz. 
This also is fused, crushed and ground, when it is ready 
for use. Fortunately, both continuous gum body and gum 
enamel of excellent quality are procurable at the supply 
houses, which, by mixing into a paste with water, is ready INLAYS 
883 
for immediate use. From the preceding formulas a vague 
idea can be formed as to the amount of study and effort it 
has taken to develop suitable materials for use in dento- 
eeramic art. 
CROWN, BRIDGE AND INLAY PORCELAINS 
The porcelain most commonly used in crown, bridge and 
inlay work closely resembles in composition and physical 
properties that prepared for continuous gum work, except 
that it is ground a little finer and fuses at a slightly lower 
temperature. Crown, bridge and inlay porcelain is also pre- 
pared in a variety of colors, in order to match the varying 
shades of teeth in and next to which it may be placed. 
HIGH AND LOW FUSING PORCELAIN BODIES 
The fusibility of porcelain separates this material into two 
general classes, the fusing point of pure gold being the divid- 
ing line. Those fusing at or above this point are called high 
fusing, and those fusing under this point are denominated low 
fusing porcelain. 
The following table, from Dr. W. A. Price’s temperature 
scale, gives the approximate temperatures required to vitrify 
the principal bodies and enamels, also the fusing point of gold 
and copper as registered by the same scale: 
Consolidated tooth body 2630-F. 
S. S. White’s tooth body 2515-F. 
Dental protective tooth body 2440-F. 
Justi’s tooth body 2440-F. 
Sibley’s tooth body 2410-F. 
White’s porcelain (crown and bridge)... .2300-F. 
Close’s body 2300-F. 
Ash’s tooth body 2260-F. 
Whiteley’s porcelain 2210-F. 
Brewster’s body 2210-F. 
Consolidated high fusing 2200-F. 
Brewster’s enamel 2080-F. 
Moffitt’s porcelain 2050-F. 
Copper 1980-F. 
Gold 1950-F. 
Ash’s high fusing 1900-F. 
Downie’s 1550-F. 
Jenkins’ 1550-F. 
Ash’s 1550-F. 
Brewster’s low J500-F. 884 
INLAYS 
COMPARATIVE VALUE OF HIGH AND LOW FUSING PORCELAINS 
Experience has shown that high-fusing porcelain is a 
stronger and more permanent material for use in the mouth 
than is the low-fusing porcelain. For this reason, therefore, 
it has almost entirely displaced the latter, especially in crown 
and bridge construction, and in inlay work where the filling 
will be subjected to any considerable stress. 
The principal advantage of low-fusing porcelain for in- 
lay work is in the ease with which it may be fused, and in 
certain cases because of its more opaque texture, better color 
results in the matching of the natural teeth are possible than 
with high-fusing bodies. In the hands of the inexperienced 
it is doubtful whether the low fusing will yield as good re- 
sults as will the high-fusing bodies. 
Porcelain Inlay Work 
The system of inlay work most generally in vogue at the 
present time consists in preparing the tooth cavity, conform- 
ing a matrix of platinum or pure gold to it, or a reproduc- 
tion of it, fusing the inlay material into the matrix thus 
formed, removing the matrix from the fused filling and set- 
ting the latter in the cavity with cement. Like all classes 
of filling materials, porcelain has its advantages and disad- 
vantages. 
ADVANTAGES 
With care, skill and experience, porcelain inlays may, in 
many cases, be so accurately constructed, and the shades of 
the natural teeth in which they are placed so perfectly matched, 
that it will be impossible to detect these restorations from the 
natural tooth structure, except by the closest scrutiny. The 
esthetic properties of this material, therefore, place porcelain 
above that of any other filling material for the artistic restor- 
ation of natural teeth. Its insolubility places it above the 
synthetic cements. 
Second, porcelain is a poor thermal conductor, and for 
this reason, inlays may be placed in cavities of teeth, the pulps 
of which are sensitive to sudden temperature changes, where 
metallic fillings could not be tolerated. 
patients are relieved from long and tedious sittings 
in the chair, when for any reason they are physically unfit for 
lengthy operations. INLAYS 
885 
Fourth, the strain upon the operator is much less than in 
ordinary filling operations. 
OBJECTIONS 
The principal disadvantages resulting from inherent de- 
fects in the material itself, or from the use in the mouth, may 
be stated as follows: Friability, constructive difficulties, 
shadow problem and retention. 
FRIABILITY 
In thin, attenuated plates, porcelain is friable and very 
easily broken. It is strong only in bulk, and, therefore, the 
utmost care should be exercised in the preparation of cavi- 
ties to so shape them that the inlay, when set, may be sub- 
jected to but little, if any, stress. Cavities involving an in- 
cisal edge or the proximo-occlusal surfaces of a bicuspid or 
molar should be so formed that the inlay will have strong, 
well-defined margins and ample bulk to withstand masticatory 
action without fracturing. When conditions preclude the for- 
mation of cavities in this manner, porcelain is contraindicated. 
DIFFICULTIES MET WITH IN CONSTRUCTION 
Among the most important difficulties which arise during 
the construction and in the application and use of porcelain 
inlays, the following deserve careful consideration: 
First, inlay retention, or developing retention form in the 
cavity, so that the inlay, when formed and set, may not be- 
come displaced under stress. 
Second, securing correct adaptation of the matrix to cavity 
walls. 
Third, avoiding warpage of the matrix during the fusing 
of the porcelain. 
Fourth, the selection, application and fusing of the sev- 
eral tints of porcelain in proper succession, so that the fin- 
ished inlay will coincide in color with the natural tooth in 
which it is to be placed. These constructive problems will 
now be briefly considered. 
INLAY RETENTION 
The walls of cavities intended for the reception of in- 
lays of any class must show slight divergence from within 
outward in order that the matrix, or wax model, may be 886 
INLAYS 
released without distortion. This applies to both gold and 
porcelain inlays. 
A cavity should be so shaped that when the inlay is 
constructed and set, the forces to which the latter is sub- 
jected will tend to drive it into the cavity rather than out of 
position. Where an inlay is solely dependent upon cement for 
retention purposes, particularly when subjected to any ap- 
preciable stress, its permanence and value as a filling are 
questionable. 
The usual means of retention capable of being developed 
in the formation of the cavity are: parallel or slightly di- 
vergent, opposing walls, flat seats, and grooves so formed as 
to permit not only the ready removal of the matrix without 
distortion, but to allow the inlay, when completed, to go to 
place without interference. 
As a means of retention for porcelain inlays, Dr. F. H. 
Skinner suggests the following: 
Drill one or more small retention pits in gingival wall or 
incisal step of the cavity, in line with the direction of removal 
of the matrix. 
When the matrix has been conformed to the cavity, that 
over the retention pits is punctured and the margins turned 
into the opening. 
Each pit is now lined with a small cylinder of foil made 
by cutting a strip slightly wider than depth of pit and a little 
more than three times longer than its diameter. 
This strip is formed into a cylinder, slit at three or four 
points around the periphery, so that the sections of foil be- 
tween may be reflected outward. 
The cylinder is passed through the opening in the foil, to 
the bottom of the pit, the slit sections of the opposite ends 
turned down on the foil covering the gingival wall, or incisal 
step of the cavity, and there closely adapted to the matrix. 
The cylinder which lines the pit should be pressed out- 
ward against its walls so as to form a clear opening into which 
the porcelain may later find its way. 
Sticky wax is now softened and pressed into the cavity, 
against all matrix walls, and when hardened the foil can be 
removed without distortion. 
The matrix is invested in high-fusing investment material 
and when set the wax is removed and the porcelain applied 
for first bake. 
If, in applying the wax, care is taken to fill the small INLAYS 
887 
cylinders in the retention pits also, to exclude the investment, 
the porcelain will flow into and fill them. 
When the inlay is fused, and the foil is removed, the small 
projections of porcelain which are seen will fit into the reten- 
tion pits of the cavity and prevent displacement. 
WARPAGE OF THE MATRIX 
Platinum foil 1/1000 of an inch thick is most commonly 
used for matrix construction in porcelain work. Thicker 
foil, say 1/500 of an inch, while naturally more rigid, when 
stripped from the completed inlay, results in too much space 
between the latter and the cavity walls; again, it is more dif- 
ficult to adapt to small or complex cavities than the lighter 
gauges. On the other hand, 1/2000 foil, occasionally used, is 
too easily distorted, both in handling and through contraction 
of the porcelain in fusing, to be depended upon as a reliable 
matrix material. 
NECESSITY FOR ANNEALING THE FOIL 
Unless thoroughly annealed before beginning, kept soft 
by occasional reheatings throughout the steps of adaptation, 
and given a thorough final annealing, followed by final pres- 
sure swedging with spunk, camphor gum or sticky wax, be- 
fore applying the porcelain, any of the platinum foils ordi- 
narily used in matrix construction are very liable to spring 
away from the cavity walls, either before or during the fusing 
process, and thus present from the very start an imperfect 
matrix in which to fuse the porcelain. 
WARPAGE RESULTING FROM IMPROPER SUPPORT OF THE MATRIX 
Warpage of the matrix may also result from its improper 
support in the furnace while baking the porcelain. Before 
final adaptation of the foil to the cavity is secured, excessive 
overlapping peripheral margins and long, angular points must 
be removed; otherwise one or more of such points may prevent 
the matrix proper, with the added weight of the porcelain, 
from resting uniformly upon the muffle slab. Under ordinary 
temperatures no mishap would occur, but with the platinum 
highly heated and somewhat soft, contraction occurring in the 
porcelain contained within it, together with more or less ad- 
hesion, developed and active, between the latter and the metal, 
warpage is most certain to occur. A muffle tray or slab for 888 
INLAYS 
supporting and carrying the matrix, having a slight depres- 
sion in its upper surface, can be used to advantage in the 
fusing of inlays of complicated form. In the depression of 
the slab, some granular silex is placed, building it higher in the 
center, if necessary, to meet and support the matrix. On this 
granular bed the matrix is carefully placed, moving it just 
sufficiently to develop support at several divergent points, 
particularly in the center. 
WARPAGE DUE TO CARELESS HANDLING 
In addition to these causes of warpage mentioned a matrix 
may be distorted through careless handling in removal from 
the cavity, or in any of the manipulative procedures up to the 
time the porcelain is fused within it. The necessity for exer- 
cising constant, ever-watchful care in the production and 
manipulation of the matrix and in applying and fusing the 
materials is one of the principal reasons why porcelain is not 
used more extensively than it is at the present time. 
FAVORABLE LOCATIONS FOR PORCELAIN INLAYS 
Porcelain inlays are indicated in all cavities exposed to 
view, when proper retention can be secured, and the fillings, 
when constructed, will have sufficient bulk to withstand stress. 
The classification of cavities, ranging from those in which 
porcelain is most strongly indicated, to those in which it is 
least required, may be stated as follows: 
First—Gingival third cavities in the anterior teeth. 
Second—Proximal cavities in the anterior teeth, not in- 
volving the angles. 
Third—Proximal cavities in the anterior teeth, involving 
the angles. 
Fourth—Cavities in bicuspids and molars, involving a 
visible axial and occlusal surface. 
Fifth—Occlusal cavities in the posterior teeth. 
Cavity walls should be formed at right angles to the sur- 
faces in which they are located. 
Opposing axial walls should he formed as nearly parallel 
as possible, yet be sufficiently divergent to permit the matrix 
to be withdrawn without distortion. 
Gingival and pulpal walls should be flat, and at right 
angles to the long axes of the teeth. 
GENERAL RULES IN REGARD TO CAVITY PREPARATION INLAYS 
889 
Cavo-surface angles should be planed true, but not per- 
ceptibly beveled as for gold foil or amalgam fillings. This is 
to avoid the formation of a frail margin to the porcelain. 
Cavities occurring in occlusal surfaces should, when prac- 
ticable, have the cavo-surface angle of their walls laid be- 
yond points of contact or occlusion with the opposite teeth. 
This will greatly reduce the liability of margins to frac- 
ture under stress. 
When an inlay is properly set, under pressure maintained 
while the cement is crystallizing, the minutest space between 
the cavo-surface angles and the periphery of the inlay is filled 
with condensed cement. This supports both enamel margins 
and those of the inlay, and since condensed cement maintains 
its integrity much better and solution occurs more slowly than 
when introduced as an ordinary filling, it is reasonable to sup- 
pose, and observation has shown, that cavity margins, though 
only slightly beveled, will stand for a considerable length of 
time. 
Details of Cavity Preparation 
GINGIVAL THIRD CAVITIES IN THE ANTERIOR TEETH 
In cavities of this class, as well as in all others, the prin- 
ciples of extension for prevention should be carried out as 
fully as possible. 
Undermined enamel should be broken down and the cav- 
ity outlines made symmetrical. 
The walls should be as nearly parallel as conditions will 
permit to insure retention of the filling. 
Fig. 910.— Square End, Parallel Side, 
Burs, Useful in Cavity 
Preparation 
Fig. 911.— Various Forms of Small Arkan- 
sas Stones, Sometimes Used in 
Smoothing Margins 
In surfaces where much curvature exists a parallel con- 
dition of the walls may be secured, partially at least, by squar- 
ing out the dentine slightly below the deuto-enamel junction. 
The angle formed by the junction of the axial with other 
walls should not be squared out too definitely. 
The cavo-surface angles should be sharp and well defined 890 
INLAYS 
and but slightly beveled, if at all, in order that the peripheral 
margins of the inlay will not be frail. 
PROXIMAL CAVITIES IN THE ANTERIOR TEETH NOT INVOLVING THE 
ANGLES 
In cavities of this class it is necessary to separate the 
teeth before beginning operations. These cavities must be 
Fig. 912 
formed without undercuts. They should be so shaped that 
the matrix when burnished in position can be removed without 
distortion. The location of the cavity will determine the di- 
rection in which the matrix can be most readily removed, 
whether labially or lingually. If the cavity of decay has pro- 
gressed more to the labial than to the lingual, the cavity prep- 
aration should be made to allow the removal of the matrix 
labially. If decay has progressed to a greater extent lin- 
gually, the preparation of the cavity should be made accord- 
ingly to meet this condition. (See Fig. 912.) 
The gingival and incisal walls should be made as nearly INLAYS 
891 
parallel to each other as practicable. When the cavity is 
formed for the introduction of the matrix from the lingual 
side, the labial margin should be carried far enough labially 
to insure the porcelain being well exposed to view. This will 
partially obviate the shadow problem that arises in this loca- 
tion. The cavo-surface angles should be prepared as outlined 
in cavities of the previous class. 
Fig. 913 
The preparation of cavities of this class is similar in 
most respects to those of the first class mentioned, and the 
rules there laid down apply with equal force to the class under 
consideration. 
BUCCAL CAVITIES 
PROXIMAL CAVITIES IN THE ANTERIOR TEETH INVOLVING THE 
ANGLES 
The preparation of cavities of this class requires much 
thought and skill, since the completed fillings are exposed to a 
greater or less amount of stress in mastication. 892 
INLAYS 
The gingival wall or seat should be made flat arid at right 
angles to the long axis of the tooth. 
The introduction of inlays in cavities of this class must 
naturally be in a labial, lingual or incisal direction, therefore 
the labial and lingual cavity walls must be formed at least 
parallel with the long axis of the tooth. 
In the upper anterior teeth, when the cavity does not 
Fig. 914 
extend far on the labial surface, preparation can be made as 
follows: 
Square the gingival wall. Cut away the labial and lingual 
walls to permit of the ready removal of the matrix. Cut a 
step on the lingual surface of the tooth, extending from the 
incisal edge to the gingival wall. 
This is done by removing a section of the lingual plate 
of enamel, as shown in Fig 913. 
Cut a groove at the junction of the linguo-axio-mesial or 
distal walls, as the case may be, extending from the gingival INLAYS 
893 
wall to the incisal edge, and bevel the several cavo-surface 
angles slightly. 
It is usually best to cut away the labial plate of enamel 
at the incisal edge to the same extent that the lingual has been 
carried back, to avoid a long irregular line of junction oc- 
curring on the incisal edge. 
Fig. 914 illustrates a cavity prepared as directed and the 
inlay baked around a post which extends into the root canal, 
Fig. 915 
thus furnishing additional anchorage. Note that there is a 
labial shoulder to prevent outward displacement. 
CAVITIES IN BICUSPIDS AND MOLARS INVOLVING AN AXIAL AND AN 
OCCLUSAL SURFACE 
The same general principles followed in the preparation 
of cavities for the reception of gold or amalgam fillings apply 
in inlay work with a few exceptions, which will be noted. (See 
Fig. 915.) 
First—The cavity must be formed without undercuts. 
Second—The axial, buccal and lingual walls should slightly 894 
INLAYS 
diverge, from gingival to occlusal, to allow the ready removal 
of the matrix in an occlusal direction. 
Third—When the line of junction of the cavity wall and 
the periphery of the inlay comes within a contact area of a 
tooth in the opposite arch, fracture of one or both margins is 
liable to occur. Therefore cavity walls should be laid beyond 
such points of contact to prevent stress on the periphery of 
the inlay. 
Fig. 916 
Fig. 916 represents a method of restoring the angle of an 
incisor tooth. The cut shows a lingual view of the cavity, with 
the inlay rotated to the left. The labial shoulder, flat seat and 
slight groove in both seat and shoulder furnish needed resist- 
ance to displacement. The preparation for lower incisors 
should be reversed. 
RESTORATION OF INCISAL EDGES 
Fig. 917 illustrates a method of restoring a notched in- 
cisal edge. A lingnal view of the cavity is presented. The 
shoulder prevents outward displacement. In lower incisors INLAYS 
895 
the shoulder should be prepared in the labial plate to prevent 
lingual displacement by the upper teeth. 
The preparation of the cavities as outlined is similar in 
most respects to the methods recommended and taught by Dr. 
A. E. Peck, who deserves much credit for the interest he has 
Fig. 917 
displayed along this line. Those who are familiar with his 
system will note the points of difference as they occur. 
The conformation of the platinum foil to the cavity is a 
step requiring skill, patience and experience. Two methods 
are followed at the present time, both of which are reliable if 
proper care is exercised. The first consists in burnishing the 
foil directly into the cavity with pellets of cotton or spunk 
PRODUCTION OF THE MATRIX 896 
INLAYS 
carried in the pliers and by the use of suitable burnishers of 
ordinary and special shapes. 
The other method consists in forming the matrix against 
an impression of the cavity or a model derived from an im- 
pression, with a suitable swaging device. 
BURNISHING THE MATRIX 
The rubber dam should be applied in all cases and the 
cavity dusted with soapstone to prevent tearing the foil. 
A piece of platinum foil, thoroughly annealed, should be 
cut of sufficient size to extend beyond the cavity margins when 
pressed into place. This is centered over the cavity and held 
in position with the fingers, while a small piece of spunk car- 
ried in a pair of ball-pointed pliers is pressed against the cen- 
ter of the foil to force it against the floor of the cavity. 
Special care should be taken to obviate the wrinkling of 
the foil against the cavity walls, to prevent its tearing while 
being forced to place, or its perforation by the pliers or burn- 
ishers. Wherever a wrinkle or fold appears it represents 
three thicknesses of foil at that point, and while the bulk of 
material may be thinned down somewhat in burnishing, it 
cannot be reduced to any great extent. The result is that 
when the inlay is completed a very perceptible space exists 
where the fold occurred, which must be filled with cement. 
This is objectionable on account of the color of the cement and 
because of its ready dissolution under such conditions. 
The foil, having been carefully forced to the floor of the 
cavity, is held there by a burnisher resting on a pellet of 
spunk. Another pellet is taken up with the pliers and forced 
into the cavity, carefully adapting the foil to the entire floor 
first, before making any attempt to adapt it to the walls. 
A ligature or strip of thin tape passed through the inter- 
proximate spaces and against the matrix will oftentimes assist 
in holding it in place while securing adaptation of the foil to 
the various surfaces. 
The adaptation to the walls is secured by pressing a small 
pellet into the cavity near the floor and drawing it outward, 
producing pressure toward the wall at the same time. The 
entire floor of the cavity should be covered with spunk, held 
with some suitable instrument during the operation. 
Some prefer to use various shapes of rubber points for 
this purpose, and very good results are secured in this way, 
but as the spunk and cotton are always conveniently at hand 
and pellets of any size can be formed quickly, these materials 
are perhaps more commonly used than the rubber points. INLAYS 
897 
Fig. 918.—Ball-Pointed Pliers 
for Applying Cotton or Spunk 
to the Matrix 
Fig. 919.—Carving Tool with 
Corrugated Shank, Which, 
by Drawing Across the 
Tweezers, Vibrates and Con- 
denses the Porcelain Body 
Fig. 920.— Small Spatula for 
Mixing and Applying the 
Porcelain to the Matrix 898 
INLAYS 
Burnishers of various forms, as the Thompson or Reeves 
selections, may be used to advantage in securing adaptation 
of the foil to the cavity walls and angles. 
When fairly close general adaptation has been secured 
the entire matrix is filled with spunk and pressure applied 
with an instrument which will force the foil against the floor 
and walls of the cavity at the same time. 
The adaptation of the foil to the outer surfaces of the 
tooth can be accomplished with spunk in the manner outlined, 
drawing the pellet from the cavo-surface angle outward in all 
directions until the foil lies flat upon the tooth surface. 
The adaptation of the foil to the cavo-surface angle yet 
remains to be done. This is one of the most important steps 
in the whole operation. Securing perfect adaptation at this 
point, with sharp angle definition, without folds in the foil, in- 
sures practically perfect margins to the inlay. 
The entire interior of the matrix should now be filled 
with spunk and a piece larger than the cavity applied over all. 
Pressure with a suitably shaped instrument slightly larger 
than the cavity or with the finger, when this is possible, is 
made against the spunk to force the matrix into all parts of 
the cavity, against the cavity margins and the tooth surfaces 
at the same time. 
REMOVAL OF THE MATRIX 
The spunk should then be removed and the matrix lifted 
out, the surplus, if excessive, trimmed away and the foil thor- 
oughly annealed and returned to the cavity for adaptation. 
NECESSITY FOR FINAL ANNEALING 
When metal plate is swaged, hammered or burnished the 
relation of the molecules to each other is changed. This is 
especially true of platinum foil used in matrix construction. 
By repeatedly annealing and returning the matrix to the cav- 
ity for final adaptation the foil can be made to lie “dead flat” 
without change under high temperature. 
Selection, Application and Fusing of the Porcelain 
As porcelain powders are now supplied by the manufac- 
turers they appear to be white, or but slightly tinted with 
yellow or brown. No definite idea can be formed from looking 
at the powder, or when made into a paste with water, as to 
SELECTION OF SHADE INLAYS 
899 
what its tint will be when fused, as its true color is only de- 
veloped by vitrifying. 
To select a suitable porcelain for an inlay, to match the 
shade of a natural tooth, small sticks of fused porcelain, each 
made of a particular single shade, are supplied by the manu- 
facturers. These sticks are made from, and numbered to cor- 
respond with, the numbers of the powders supplied. In de- 
termining the shade of porcelain to use in a given case, one 
of these fused pieces is placed alongside of the tooth for 
which the inlay is to be constructed and the similarity or dif- 
ference in shade noted. This process is repeated until a satis- 
factory shade has been found to match the tooth, or some 
portion of it, against which the inlay is to rest. 
It is frequently necessary to select two, sometimes three, 
shades of porcelain for a proximo-incisal inlay when the tooth 
presents marked variation in shade from gingival to incisal 
areas. In applying these vari-sliaded porcelains to the matrix 
they are not blended on the slab but are applied in the matrix 
in the particular location where indicated. By drawing a 
rough instrument across the pliers with which the matrix is 
held the vibration so caused will blend the several colors at 
their margins sufficiently to obviate a sharp line of demarka- 
tion of tints. Usually after fusing the primary colors selected 
a neutral shade of porcelain is applied and fused to complete 
the contour and still further soften and blend the more pro- 
nounced underlying tints. 
MIXING THE PORCELAIN 
The proper colors having been selected, corresponding 
powders are placed separately on a clean glass slab and with 
a drop tube, sufficient distilled water is added to form each 
into a mass of medium plasticity. The powder and water 
should be well spatulated to thoroughly incorporate the sev- 
eral ingredients in each shade. To prevent the heavier from 
settling and forcing the lighter particles to the top of the 
mass, when well mixed, a linen napkin, or piece of bibulous 
paper, should be pressed against the paste to take up the ex- 
cess moisture. 
APPLICATION OF THE PORCELAIN TO THE MATRIX 
The matrix is grasped with a pair of K tweezers (Fig. 921) 
at some point on the surplus margin in such manner as not to 
distort it, yet with sufficient hold to sustain not only the 
matrix but the porcelain to be added as well. A small amount 900 
INLAYS 
of the paste, usually of a yellowish tinge, to serve as a founda- 
tion body, is transferred from the slab to the matrix, applied 
to the latter without pressure and the serrated surface of the 
carving tool drawn over the tweezer beaks to vibrate the 
porcelain in position. More is added in like manner until the 
matrix is from one-lialf to two-thirds full, leaving the labial 
portion deficient in order to add the proper colors later. The 
Fig. 921.— K Tweezers for Holding the Matrix. The Headed Rivet Locks the 
Beaks Together 
partially filled matrix is now carefully passed above a Bunsen 
flame, or placed near the entrance of the furnace, to gradually 
expel the moisture, after which it is placed on a muffle tray, 
introduced and fused. 
When removed, the various tints are applied in their re- 
spective locations, this time filling the matrix to its margins 
and vibrating as before so as to blend the several colors. Any 
excess paste which overflows is carefully brushed off with a 
dampened sable brush, thus avoiding thin overhanging mar- 
gins in the finished inlay. 
Should the colors be too pronounced when fused, a thin 
layer of gray or neutral tint may be overlaid and fused, as 
before suggested, to tone them down. 
Usually in simple cavities two applications of the body 
and two fusings will be sufficient to produce a satisfactory 
inlay. In complicated cases, however, three, or possibly four, 
fusings may be required. It must be kept in mind, however, 
that each additional fusing not only produces contraction in 
the porcelain last added, but in the entire mass, thus increasing 
the danger of warpage and a misfit. The fewer times required 
for fusing and finishing a piece of porcelain of any class, the 
better the quality of the material and the less contraction and 
warpage will occur. 
When slightly overfused, or when the vitrifying process 
is continued too long, both the texture of the porcelain and its 
color are impaired. Long continued low temperature, just suf- 
ficient to vitrify porcelain, will produce better results as to 
texture and color than when the process is carried on rapidly 
and at a higher temperature. INLAYS 
901 
FURNACES FOR FUSING PORCELAIN 
Various types of furnaces are used for fusing or “bak- 
ing” porcelain, as this process is usually termed. The most 
common method of developing the required temperature is 
Fig. 923.—Two Forms of Muffle 
Trays for Supporting 
the Matrix 
Fig. 922.— Muffle Tray Tongs, for Introduction and 
Removal of the Tray During the Steps 
of Fusion of the Porcelain 
by passing an electric current through a fine platinum wire 
imbedded to a slight depth within the fire clay muffle walls. 
The resistance of the wire to the passage of the current de- 902 
INLAYS 
velops an intense heat within the wire when fine, which in 
turn is transmitted to the fire-clay lining of the furnace. 
The amount of heat capable of being developed within a 
muffle is dependent upon the length and sectional area of the 
wire, the depth it is imbedded in the fire-clay lining and the 
intensity of the current which flows through it. Furnaces of 
this type are called “electric furnaces,” and as a rule are 
capable of developing a considerably higher temperature than 
that required to fuse the common porcelain bodies. In most 
cases a rheostat is employed to control the flow of the cur- 
rent and keep the temperature within working range. In some 
cases furnaces are fitted with pyrometers for indicating the 
point of fusion of the porcelain. 
To Dr. L. E. Custer belongs the credit of having first con- 
structed a practical electric furnace suitable for fusing porce- 
lain (1894). At the present time a number of excellent electric 
furnaces are procurable. Gas, gasoline, oil and coke furnaces 
are also manufactured which, from a practical standpoint, are 
applicable to porcelain work. The electric furnace is prefer- 
able in dental operations because of its compactness, ease of 
manipulation and freedom from gases which always accom- 
pany the use of the fuels mentioned. 
The temperature usually required to fuse the various in- 
lay, crown and bridge, porcelain bodies is given under the 
heading of “High and Low Fusing Porcelain Bodies.” 
The moisture having been expelled from the porcelain, 
the matrix is placed upon the muffle slab and introduced in 
the furnace. Care should be taken to see that the body of the 
matrix rests upon the fire-clay slab, or that a sufficient number 
of marginal points touch to afford ample support and prevent 
warpage. When the form of the matrix is complicated some 
granular silex should be placed upon the slab and the matrix 
settled carefully down upon it. 
When a furnace having no pyrometer is used, a pellet of 
pure gold is usually placed alongside of the matrix to serve 
as a guide in determining the point of vitrification. A little 
device made of soapstone or fire-clay, having a small under- 
cut groove with slightly enlarged extremities, is cut in the 
concave face of the block. In the upper extremity of the 
groove a pellet of gold is placed and when fusion of the latter 
occurs it disappears by falling to the lower extremity, much 
as the sand in an hour glass flows from upper to lower com- 
FUSING THE PORCELAIN INLAYS 
903 
partment. When the temperature is reduced and the gold 
solidifies, by inverting the block the gold is again at the upper 
extremity of the groove and in position for another test. 
The matrix and test block being in position, the current 
is turned on by moving the rheostat arm from its initial po- 
sition of rest to the first contact, where it should be allowed 
to remain for five minutes, when it can be moved to the second 
contact. The arm should remain on each contact about the 
same length of time before moving to the next in order to re- 
duce to the minimum the strain on both platinum wire and 
fire-clay lining, and also so that the porcelain may not be 
subjected to sudden increase of temperature. In most fur- 
naces the rheostats are supplied with five or six contacts. 
When the arm is moved at five-minute intervals the porcelain 
will usually be near the point of fusion by the time the arm is 
transferred to the last contact. The gold must be closely 
watched and the instant it fuses the time should be noted. 
By previously determined tests, the difference in time be- 
tween the melting of the gold and the biscniting, as well as 
glazing of the porcelain, is known, and this time should be 
allowed according to the degree of fusion required. This 
period varies usually from forty seconds to six or seven 
minutes, depending on the intensity of the current, the class 
of porcelain used and the type of furnace employed. 
The first bake should be carried to the “biscuit” stage, 
i. e., where vitrification has occurred but the granular surface 
has not disappeared. 
The rheostat arm is now returned to the second contact 
to conserve time, and heat as well, by not allowing the furnace 
to become cold, the muffle opened and the slab partially with- 
drawn, allowed to cool somewhat and, finally, the matrix is 
picked up with the K tweezers and the result of the first bake 
noted. If free from porosity, of good color and not overfused 
the second application of body is made as at first. When an 
effort is made to complete the inlay in two bakes the second 
application of porcelain should be very carefully executed, 
developing very slightly fuller contour than required to com- 
pensate for final contraction that always occurs on fusing. 
When two or more colors are required to match the tooth 
shade they are applied at this time and blended as before 
described. 
SECOND BAKING 
The contour of the second application of body having been 
completed, surplus removed from the margins and the mois- 904 
INLAYS 
ture expelled, the matrix is again returned to the furnace. 
The temperature is gradually raised as before until the sur- 
face of the inlay is glazed and perfectly free from granules, 
the idea being to give it such a surface as will not require the 
application of discs or polishing powders. Porcelain inlays 
baked under ordinary conditions are liable to be slightly 
porous under the glazed surface, and these porous spaces are 
frequently disclosed on grinding. Since reglazing does not 
always remove the pits, and if more is added to correct the 
defects the additional fusion will induce further dimensional 
changes in the inlay itself, it is best to avoid grinding and 
polishing if possible to do so. 
DELETERIOUS EFFECT OF OVERFUSING THE PORCELAIN 
Special care should be taken to not overfuse the porcelain. 
Some of the defects arising from this mishap are bleaching 
of the porcelain, friability, undue contraction and warpage 
and the development of porosity—sometimes to such an extent 
as to render the inlay useless. 
THE SHADOW PROBLEM 
Comparatively little difficulty is encountered in selecting 
porcelain of suitable translucency and color, which when fused 
to proper form and introduced in the cavity without cementa- 
tion will harmonize with tooth structure. 
The discouraging feature connected with porcelain inlay 
work, however, is in the variation in shade observed between 
the natural teeth and inlay when the latter is finished and 
set with cement. All varieties of cement used in the setting 
of inlays are opaque. Light will not readily pass through 
even thin, attenuated layers of this material. Therefore, un- 
less the light which falls upon a tooth filled with a cemented 
inlay is directly parallel with the exposed cavity walls a 
shadow will be cast upon either tooth or the inlay, depending 
upon which is nearest the source of light. 
For example, in a distal cavity in a central incisor involv- 
ing the angle, when the light falls upon the tooth first—the 
direction of the rays slanting toward the inlay—a shadow 
will be observed in the latter next to the line of junction, 
owing to the cutting off of the light by the film of interposed 
cement. When the light comes from the opposite direction, 
striking the inlay first, the shadow will appear in the tooth, 
but to a less extent because of a. more or less general diffusion 905 
INLAYS 
of light in the greater bulk of tooth structure. In the upper 
teeth the overhang of the upper lip will often cast a shadow 
in the gingival portion of an inlay, though the light may be 
comparatively direct and well diffused. 
To overcome, or at least reduce somewhat, the shadow 
caused by indirect rays of light on an inlay, the labial walls of 
cavities in the anterior teeth should be carried well to the 
labial. The result of such cavity formation is to increase the 
bulk of porcelain in the inlay and permit diffused light to 
enter through the porcelain, thus reducing the depth of 
shadow cast in inlays of limited labial exposure. The neces- 
sity for this line of procedure is evident when the form and 
position of an inlay, in proximal cavities, is considered. On 
one side the inlay is limited by an opaque layer of cement, and 
on the other by the proximating tooth, both of which tend to 
restrict the uniform diffusion of light through the porcelain 
except under the most favorable circumstances. 
Again, the color of the cement used in setting an inlay 
may modify the shade of both the restoration and the tooth 
next to, and for a short distance away from, the cavity walls, 
lightening or darkening both according to the inherent tinge 
of the cement. The remedy for the latter defect is overcome 
to a great extent by using a cement which in color coincides 
as nearly as possible with the shade of the natural tooth. 
It lias been suggested that an opaque, low-fusing porce- 
lain of the Jenkins type, in which color effects are not so 
much dependent upon translucency as is the case in the higher 
fusing porcelains, may be applied to overcome the shadow 
effects noted. An inlay constructed of an opaque porcelain 
having the essential, component colors of the tooth brought 
to the labial surface is but slightly affected by light striking 
it at various angles. The tooth in which it is placed, however, 
is subjected to shadow variations to the same extent as when 
high fusing porcelains are employed. 
REMOVING THE MATRIX 
When the fusing of the inlay is completed the platinum 
foil matrix must be removed. This may be accomplished by 
carefully grasping the surplus margin with the beaks of the 
K tweezers and with a rotary movement roll the foil away 
from the margins of the porcelain, using special care to avoid 
fracturing the latter. By wetting the inlay and matrix the 
danger of fracture is greatly reduced. Usually the matrix 
can be peeled off by grasping the surplus margin between 906 
INLAYS 
the thumb nail and the ball of the mdex finger, the latter 
acting as a resilient cushion on which to rotate the inlay. In 
case the matrix tears, the adherent portion being devoid of 
free margins, it must be chiseled, scraped or ground away, as 
when allowed to remain it will interfere with the correct seat- 
ing of the inlay. 
ETCHING THE CAVITY SURFACES OF THE INLAY 
To break up the glaze and afford better retention of the 
cement to the porcelain the cavity surfaces of the inlay should 
be etched with hydrofluoric acid. The labial, and, in fact, all 
the exposed surfaces of the inlay, must be protected from the 
action of the acid covering them with wax, the acid having 
no effect on the latter material. The wax should be formed 
into a roll, the end heated and the inlay pressed against it, 
being careful to see that all surfaces on which the glaze is to 
be preserved are perfectly covered. 
With a pencil of wax, or a toothpick, the acid is applied 
to the cavity surfaces, the application renewed once or twice 
until the glaze is removed. The acid is then washed off with 
water and neutralized with a solution of bicarbonate of soda, 
again washed and dried, when it is ready to set. 
SETTING THE INLAY WITH CEMENT 
The rubber dam should be applied to the tooth involved, 
and the proximating teeth as well, and the cavity thoroughly 
cleansed and dehydrated. 
Cement of suitable shade mixed to medium consistency is 
quickly applied to both inlay surfaces and cavity walls, the 
inlay introduced and forced to place under gradual, heavy, 
maintained pressure. In proximal cavities, this pressure may 
be applied by forcing between the inlay and the proximating 
tooth a previously-prepared wedge of orange wood. Care 
should be taken to see that in forcing the wedge in place the 
inlav is not displaced or unseated at any point. 
The force capable of being exerted by a thinlv-tapered 
wedge is enormous, therefore caution must be exercised to 
avoid undue force in its application. The mallet should never 
be used in setting a porcelain inlay, as the instantaneous blow 
will scarcely produce flow in cement of medium consistency, 
while the impact is liable to fracture the porcelain. 
A piece of pine stick a little larger than a lead pencil, 
with one end trimmed to suitable size and slightly concaved to INLAYS 
907 
fit snugly against the inlay, affords a most convenient means 
of producing and maintaining pressure upon the restoration 
until the excess cement has been expelled and crystallization 
has set in. Pressure on the inlay should usually be main- 
tained from five to eight minutes, depending on the rapid set- 
ting qualities of the cement used. 
In setting inlays in proximal cavities, a strip of rubber 
dam about six inches long and one-fourth inch wide can be 
passed between the inlay and the proximating tooth, the two 
ends of the strip placed together and the rubber stretched al- 
most to its limit, in a direction at right angles to the long axis 
of the tooth. The resilient rubber forces the inlay into the 
cavity and condenses the cement in the joint line as well. 
When hardened, the excess cement is removed from the 
joint and adjacent surfaces, the rubber dam removed, the 
parts syringed with warm water, and the occlusion verified to 
see that in setting it has not been modified by the cementing 
medium. If so, it should be corrected by grinding and polish- 
ing until clearance space is gained, to avoid fracture from 
stress of opposing teeth. 
Gold Inlays 
The production of gold inlays may be accomplished in 
various ways. With one or two exceptions, all of the many 
methods in vogue may be grouped into two general classes, 
viz., the matrix method and the casting process. A descrip- 
tion of both methods will follow cavity preparation. 
Cavity Preparation for Gold Inlays 
The general principles followed in cavity formation for 
gold foil or amalgam fillings apply with equal force to those 
designed for the reception of inlays of any class. Briefly 
stated, these principles, as laid down in Black’s Operative 
Dentistry, are as follows: 
First—Obtain the required outline form. 
Second—Obtain the required resistance form. 
Third—Obtain the required retention form. 
Fourth—Obtain the required convenience form. 
Fifth—Remove any remaining carious dentin. 
Sixth—Finish the enamel wall. 
Seventh—Make the toilet of the cavity. 908 
INLAYS 
OUTLINE FORM 
To secure the correct outline form involves the breaking 
down of unsound overhanging enamel walls, the removal of 
practically all undercuts, the opening up of fissures when re- 
quired, extension for prevention of all margins to immune 
areas, and further extension of margins, if necessary, for 
convenience of introduction and removal, without distortion, 
of the wax model, or the foil matrix. 
RESISTANCE FORM 
Resistance form refers to the development of flat gingival 
and pulpal walls so as to withstand the stress of mastication, 
thus obviating the tendency of the inlay to slide from or rotate 
out of position under direct stress. 
RETENTION FORM 
In the preparation of a cavity for an inlay, the walls that 
lie parallel with the line of direction of introduction of the 
inlay should be formed at an angle of divergence of at least 
one degree from perpendicular to the base, to obviate distor- 
tion of the wax model in removing from the cavity. A greater 
amount of divergence may be permissible in some cases, but 
firmer and better retention follows with slight than with ex- 
cessive divergence of the walls. 
While cement is employed for the retention of all classes 
of inlays, this means alone will prove ineffectual against side 
stresses and strains, particularly when the inlays are to be 
utilized as abutments in bridgework. 
Since, for obvious reasons, neither undercuts nor parallel 
walls are permissible in the finished cavity, and since cement 
is unreliable under heavy stress, some more positive means 
of retention must be developed in practically all cases; this 
may he accomplished in several ways, depending on the form 
and location of the cavity. 
In cavities involving an axial and an occlusal surface, 
flat pulpal and gingival seats afford resistance to direct stress, 
while a dovetail on the occlusal surface will prevent the tip- 
ping stress. 
When more than one axial surface is involved, and it is 
deemed advisable to connect the cavities and thus construct 
the inlay iu one piece, the proper flare of the walls, to avoid 
undercuts, should he constantly kept in view, so as to obviate 
distortion of the wax model in removal from the cavitv. INLAYS 
909 
Frequently when two or more axial surfaces are involved, 
and the preparation of the cavity so as to permit the release 
of the matrix would require excessive sacrifice of good tooth 
structure, an interlocking inlay constructed in two pieces can 
be used to advantage. In such case one inlay having a dove- 
tailed space to receive the interlocking spur of the adjacent 
piece or complement, is first cast and set, after which the wax 
model of the other is formed and cast in like manner. By 
this sectional method of construction, maximum resistance to 
displacement of the inlay is gained, with the sacrifice of the 
minimum amount of tooth structure. 
Oftentimes a slightly divergent groove can be formed in 
the pulpal wall of the cavity in such manner as to release the 
wax, the resulting shoulder of which on the inlay will effectu- 
ally prevent it from tipping. 
In obtaining retention form in cavities in the anterior 
teeth, an incisal step with a notch in the lingual plate of en- 
amel will effectually counteract the tendency to displacement 
from tipping stress. 
Frequently, by stripping both labial and lingual plates 
of enamel away so as to expose the dentine, the latter may be 
Fig. 924 
Fig. 925 
Fig. 926 
Fig. 927 
Fig. 928 
Various Forms of Cavities in Which Dentin Shoulders and Lingual Grooves Are Developed for 
Retention Purposes (St. John) 
Fig. 929 
used as a shoulder or hook, as it were, over which the inlay 
may he formed, and which will effectually counteract the 
tendency to tip. This form of cavity preparation was recom- 910 
INLAYS 
mended many years ago by Dr. I. C. St. John of St. Paul, for 
the reception of gold foil fillings. In certain cases it has 
proven very serviceable for inlays. 
PIN ANCHORAGE FOR INLAYS 
The application of pins for the retention of inlays, and 
in obviating displacement under heavy stresses, has proven 
of great value, particularly when the inlays are utilized as 
abutments for bridges. 
The form and location of the cavity and the condition of 
the tooth, whether vital or pulpless, govern the size and length 
of the pin. 
The usual manner of developing a pin anchorage consists 
in drilling a hole in the gingival or pulpal wall of the cavity 
entirely within the dentine, in such location as not to inter- 
fere with the pulp. The direction of the hole should corre- 
spond with the line of removal, or at least not interfere with 
the release of the wax model from the cavity. The diameter 
of the hole should be but slightly larger than the pin to be 
employed. Before introducing the wax, the pin, cut slightly 
longer than the depth of the hole, is inserted and as the wax 
is pressed to place it surrounds the projecting end of the pin. 
When the wax model is removed, the pin is removed with it 
and caught in the investment and the gold cast around it. 
CONVENIENCE FORM 
Convenience form relates to such modifications in pre- 
pared cavities as will admit of the most perfect as well as con- 
venient placing of the filling. In gold foil operations this re- 
fers to cutting away a wall or some area that interferes with 
proper instrumentation or the development of slight under- 
cuts in certain locations to aid in holding the filling material 
until the general retention form can be made effective. 
These points do not directly apply to inlay work, but in- 
directly the shaping of the cavity so as to permit the ready 
removal of the wax model and the introduction of the inlay 
come under this head. When the general form of a cavity has 
been developed, it is frequently found that some slight under- 
cut within the dentine will seriously interfere with removal of 
the wax model. The removal of the undercut by reshaping 
the cavity may result in weakening an otherwise firm cavity 
wall when by carefully filling the depression with cement, the 
difficulty may be overcome. As a general rule, however, the INLAYS 
911 
best plan is to eliminate all undercuts in the development of 
the outline form, and not depend upon cement for such pur- 
pose. 
It is just as important, in cavity preparation for inlays 
as for other classes of fillings, that all decayed dentine be 
removed to obviate recurrent caries. 
Some prefer to leave a layer of leathery, decayed dentine 
in the pulpal or axial walls of deep cavities, under the mis- 
taken idea that the transmission of thermal changes will be 
impeded and the vitality of the pulp be conserved. 
This is, in nearly every instance, an incorrect procedure, 
for in cavities which encroach so closely on the pulp as to 
need a protection of this character, the varying thermal 
changes transmitted by a large gold inlay will very soon set 
up hyperemic conditions, and the pulp will die. 
REMOVAL OF ANY REMAINING CARIOUS DENTINE 
FINISH OF THE ENAMEL WALLS 
In gold inlay as well as in gold foil operations, the cavo- 
surface angles should be beveled for the protection of the 
exposed enamel rods. This is carried out as in general opdla- 
tive procedures by carefully planing the outer cavity margins 
with sharp chisels and gingival margin trimmers. 
The method of using stones on the margins and in smooth- 
ing up the walls of cavities is bad practice and to be deplored. 
The method cannot be made effective in, nor is it universally 
applicable to, all classes of cavities, and where applicable the 
tendency is to weaken frail walls and obliterate definite re- 
tention surfaces. The only possible advantage resulting from 
this method is in reducing to a slight degree the discomfort 
to the patient, in those cases where the tooth structure is sen- 
sitive to the application of the bur. 
The removal of all chips and debris, not only from the 
cavity but from the mouth as well, is important and can best 
be accomplished by use of the water syringe and wiping the 
cavity thoroughly with pellets of cotton before forming the 
wax model. 
In forming the wax model, as will be seen later, a lubri- 
cant is used to facilitate the ready application and adaptation 
of the wax to all cavity surfaces. This lubricant, whatever its 
class, should be thoroughly removed, the cavity dried and 
TOILET OF THE CAVITY 912 
INLAYS 
packed with a good quality of gutta percha until the time 
of setting of the inlay. 
SOME SPECIAL METHODS OF CAVITY PREPARATIONS 
Proximal cavities in the anterior teeth, in which gold in- 
lays are to be placed, require special attention. In case a 
tooth proximates the one in which the cavity occurs and the 
angle is involved, the cavity must be formed so as to release 
the wax model usually lingually or incisally. 
Provision must be made to prevent the inlay when set, 
from becoming dislodged under tipping stress. Several meth- 
ods are resorted to for accomplishing this object. These usu- 
ally consist of a dovetail or some form of step in the lingual 
surface of the tooth involved, some of which will be illustrated. 
Fig. 930.— Two Views of Tooth Prepared with an Incisal Hook of 
Dentin (St. John) 
The first of these, the St. John method of cavity prepara- 
tion, previously alluded to, consists of stripping off the plates 
of enamel so as to expose sufficient solid dentine to form a 
hook for incisal anchorage. A gingival seat takes up the in- 
cisal stress. See Fig. 930. 
A method of forming a dovetailed space in the lingual 
surface of the tooth as near the incisal edge as possible, to 
provide for tipping as well as outward displacement. Figs. 
931 and 932. 
A method of forming a step along the linguo-incisal edge, 
involving principally the lingual plate of enamel. The bottom 
of the step may be grooved slightly, and near its farthest 
extremity from the cavity a small hole is drilled in the dentine 
to receive an iridio-platinmn post. The line of junction of 
the inlay with the labial plate of enamel, occurring on the in- INLAYS 
913 
cisal edge, invites displacement of the inlay as well as frac- 
ture of the labial plate of enamel under stress. 
A method of step preparation, similar to the above, but 
with the labial plate reduced slightly so that the inlay will 
Fig. 931.— Proximal View of 
Distal Cavity in Cuspid 
Tooth, Showing Lingual Step 
Fig. 932.— Lingual View, 
Showing Dovetail of Step 
Fig. 933.— Lingual 
View of Both, Show- 
ing Incisal Step Cav- 
ity with Pin in Step 
Fig. 934.— Disto-Lin- 
gual View of Preced- 
ing Tooth 
Fig. 935.—L a b i a 1 
View of Cavity 
Outline 
Fig. 936.— Labial 
View of Tooth with 
Inlay in Position 
Fig. 937.— Lingual 
View of Incisal Step 
Cavity, Showing 
Groove Retention 
Fig. 938.—-Labial 
View of Tooth with 
Inlay in Position 
Fig. 939.—Labial, Distal and Incisal View 
of Cavity in Cuspid Prepared with Dove- 
tailed Anchorage Combined with Pin 
form a tip of gold over the two plates of enamel. This form 
of cavity preparation is preferable to the preceding. Figs. 
933 to 936, inclusive. 
A method of forming a step similar to the above, but in- 
stead of the pin anchorage, a drop of the step gingivally, in 
the lingual plate of enamel and the dentine as well, furnishes 
the resistance to tipping stress. Figs. 937-938. 914 
INLAYS 
A method of anchoring a large contour filling in a pulp- 
less tooth by means of a pin extending into the root canal. 
Fig. 939. 
A method of forming in the labial or buccal surface of 
the wax model, a cavity with undercuts, in which, after the 
inlay is set, a synthetic cement filling is placed to avoid the 
display of gold. 
Fig. 940.— Proximal 
View of Tooth with 
Mesio - Inciso - Distal 
Cavity Prepared 
Fig. 941.— Lingual 
View of the Pre- 
ceding 
Fig. 942.— Lingua! 
View of Tooth with 
Filling in Position 
Fig. 943.— Labial 
View of Tooth with 
Filling in Position 
A method of preparation for a mesio-inciso-distal cavity 
in an anterior tooth, formed with a grooved step, cut princi- 
pally at the expense of the lingual plate of enamel. The in- 
cisal edge of the tooth is reduced so that it may be tipped with 
gold for its protection. Figs. 940 to 945, inclusive. 
In casting fillings of this type, a piece of iridio-platinum 
wire should be bent so that it will not interfere with the mar- 
gins of the inlay. This is inserted in, and as close to the 
cervical terminals of the wax model as possible to prevent 
change of relation due to contraction. 
Fig. 944.— Three Views of the Wax Model for a Mesio-Inciso-Distal Inlay INLAYS 
915 
A straight pieqe with square ends will serve this purpose 
equally as well, if inserted between the axial surfaces of the 
mesial and distal sections. 
A mesio-occlusal, grooved cavity in an upper molar. The 
pulpal wall is grooved to provide against tipping stress. This 
Fig. 945.— Three Views of the Completed Inlay 
form of activity preparation is frequently employed when the 
inlay is to serve as a bridge abutment. 
A loose pin anchorage for an inlay to be used as an abut- 
ment for a bridge. A square iridio-platinum bar, from 12 to 
Fig. 946.— Sectional View of 
a Molar, Showing Grooved 
Step for Guarding Against 
Tipping Stress 
Fig. 947.— Simple Mesio-Oc- 
clusal, Dovetail Step Cavity 
in Molar 
14 gauge, is uniformly tapered on the four sides, extending 
back about three-fourth s of an inch from one end, and reduced 
sufficiently to enter the enlarged root canal the required depth 
for anchorage purposes. Around the tapered portion and in- 916 
INLAYS 
volving the area which will rest within the inlay, is wrapped 
a band of 1-1000 platinum foil which should lap on itself about 
one-half turn of the wire. The taper pin is withdrawn and 
the square tube of foil is tacked with a little pure gold solder 
to prevent it from opening. It is returned to the pin and re- 
adapted to correct any change that may have occurred in 
soldering. 
The wax model is carved to proper contour, and the pin 
without the sleeve is warmed, passed through the wax and to 
position in the root canal and withdrawn. It is now heated to 
burn off the adherent wax and oiled to prevent the sleeve be- 
Fig, 948.— Mesio-Occluso-Distal Cavity 
and Wax Model for Same 
coming fast. The sleeve is again returned to position, pin 
warmed and the two are passed through the opening in the in- 
lay and into the canal to proper position. A small heated in- 
strument is passed around the sides of the tube so as to cause 
the wax to adhere to it, but not to the pin. The latter is now 
withdrawn, while the tube remains in the wax. The tube 
should be long enough to project beyond the upper and lower 
surfaces of the wax, so as to become inclosed in the invest- 
ment. On removal of the wax model, the tube is first filled 
with investment, after which the model is invested in the usual 
manner. When cast, the projecting ends of the tube are re- 
duced to the level of the inlay surfaces, the opening cleared INLAYS 
917 
for the reception of the pin, the inlay finished and set and 
while the cement is still soft the pin is forced to place. Care 
should be taken to avoid the excessive use of cement which 
might be forced into the canal from which it would be difficult 
to expel it. 
This attachment is intended to be used in conjunction with 
bridge work, and as the setting of the bridge is of itself a 
particular operation, the following plan oould be adopted: 
Fill the root canal, or the outer portion of it, with tem- 
porary stopping, being careful not to encroach on the base 
of the cavity. Set the bridge in the usual manner, and when 
the cement has hardened, with a small, rough, heated instru- 
ment remove the temporary stopping, and free the canal from 
all debris, after which the pin may be set independently and 
the projecting end reduced with stones to the level of the in- 
lay. This method was suggested and has been successfully 
used by Dr. A. L. Le Gro of Detroit, Mich., who has demon- 
strated it at various times within the past few years. 
A method of utilizing short pins for anchorage purposes, 
placed in various locations in cavities prepared in vital teeth, 
has been extensively applied by Dr. M. L. Ward of Ann 
Arbor, Mich. In this system he makes use of one or more 
pins or a two-point staple, the bent portion of which is en- 
closed in the inlay. 
The main points to keep in mind in applying this system 
of anchorage to inlays are to arrange the pins parallel with 
the line of direction in which the wax model is withdrawn 
from the cavity, and in drilling the holes to avoid encroaching 
on the pulp. 
A method of shoulder anchorage, applicable to axio-occlu- 
sal cavities in vital bicuspid and molar teeth. In this system 
a groove is cut at the extremity of the step farthest from the 
axial wall involved and of sufficient depth to prevent radial 
movement of the inlay outward. Usually from one to one and 
one-half millimeters in width and depth will be ample dimen- 
sions for the groove. Fig. 946. 
A simple method of dovetailed anchorage, applicable to 
axio-occlusal cavities in vital teeth. This cavity preparation 
differs but little from that followed in gold foil operations 
except that all axial walls must flare slightly from gingival 
and pulpal surfaces, from one to two degrees. Fig. 947. 918 
inlays 
The Matrix Method of Inlay Production 
The preparation of cavities intended for the reception of 
inlays formed in a matrix is essentially the same as for in- 
lays of any class, viz., the development of flat seats, and 
slightly flaring walls, to permit release of the matrix without 
distortion. The subject of cavity preparation will be found 
on page 907. 
The matrix of gold or platinum may be formed in two 
ways, by the direct, or by the indirect method. 
DIRECT METHOD OF PRODUCING A MATRIX 
The direct method consists in adapting a piece of 24- 
carat gold, or platinum foil, to and against the cavity sur- 
faces of the natural tooth. The steps are as follows: 
Cut a piece of foil somewhat larger than the cavity and 
from 1-1000 to 1-500 of an inch thick; the thicker foils, while 
being more difficult to adapt, are less liable to distort in sub- 
sequent steps. 
Anneal the piece, center it over the cavity, and with spunk 
or pellets of cotton, in the ball-pointed pliers, press it against 
the cavity floor and gradually adapt it to the cavity walls and 
margins. 
Since the steps are practically the same as in forming a 
platinum matrix for a porcelain inlay further details may be 
found on page 896. 
When general adaptation of the foil to the cavity surfaces 
has been secured, the peripheral excess is trimmed away, a 
narrow margin, however, being left to outline the cavity mar- 
gins and prevent the gold, in fusing, from being drawn out- 
side to the cavity surfaces of the matrix. 
Finally, the matrix should be annealed and readapted to 
the cavity with spunk or cotton, applied under heavy pressure, 
to correct warpage. 
In simple cases the matrix is carefully removed, laid on 
the solder block, some small squares of plate or pellets of pure 
gold, previously spheroided and fluxed, placed in the interior, 
and high-grade solder fused into the matrix and around them. 
During the fusing of the solder the pure gold pellets or 
pieces are not fused, consequently there will be less contrac- 
tion and less danger of warpage of the matrix than when 
solder alone is used. 
Sufficient gold is added and fused to develop desired con- 919 
INLAYS 
tour, the inlay pickled in acid, washed and returned to the 
cavity for final reduction with stones and discs. 
It is then cemented in position and the final polish applied 
as with a gold foil filling. 
VARIATION IN METHOD 
In compound cavities, it is frequently advisable to force 
slightly softened wax in the matrix while in the cavity, being 
particularly careful to adapt it to the margins. 
The matrix is then removed and its cavity surfaces im- 
bedded in some good investment material. When hardened, 
the wax is removed, the matrix fluxed, case heated, and solder 
applied as above described. 
Forming the Matrix By the Indirect Method 
An impression of the tooth is secured in modeling com- 
pound. One of the cup pattern trays, suggested by Dr. Roach, 
may be used or one can be improvised from thin aluminum 
plate by the method described by Dr. Van Woert. (Items of 
Interest, 1913.) 
The impression is dusted with talcum powder and the 
surplus carefully brushed from the deeper portions. This is 
to serve as a separating medium. 
Modelite or a good quality of cement is mixed to medium 
thick consistency, applied and forced into every portion of the 
impression, building it up in sufficient bulk to withstand the 
stress of matrix adaptation, without fracturing. 
When the cement has hardened, the modeling compound is 
removed, and the cement tooth partially imbedded in model- 
ing compound for support, or it may be set in a ring of the 
swaging device. 
In either case, the cement reproduction of the tooth should 
be so placed that its axial walls will be supported to resist side 
stress. Most of the force of matrix adaptation should be ap- 
plied vertically, downward. 
The matrix may be adapted, either by burnishing or 
swaging, or by both methods combined. 
When possible to do so it is advisable to test the adapta- 
tion of matrix to tooth cavity before contouring with gold. 
When the matrix method is carried out accuratelv, com- 
paratively perfect adaptation of an inlay to tooth and cavity 
surfaces can be secured. 920 
INLAYS 
Cast Gold Inlays 
GENERAL REMARKS 
To be reasonably successful in the casting of inlays and 
of prosthetic restorations in general, it is necessary to know 
something of the physical properties of the materials em- 
ployed. 
Casting operations involve the use of waxes, investments, 
and the metal of which the restorations are to be made, usu- 
ally gold. These materials, within certain limits, are subject 
to the same law as are nearly all solid substances, viz., that 
heat expands and cold contracts, the amount of dimensional 
change being generally dependent on temperature variations. 
In the various steps, from the formation of the wax model 
to its reproduction in metal by casting, the materials under 
consideration are subjected to widely varying temperature 
changes. These changes, as the work is carried forward, tend 
to produce errors, by increasing or decreasing the size of the 
model, the form of the investment, and, finally, reduction in 
size, or in warpage of the metal casting itself, which changes 
are oftentimes sufficient to render it worthless. 
While no absolute line of procedure, for avoiding error in 
the casting process has been determined, certain facts of im- 
portance are known, which, if observed, will minimize the 
tendency to error. 
PHYSICAL PROPERTIES OF THE MATERIALS EMPLOYED IN CASTING 
With few exceptions, the physical law, as previously 
stated, that heat expands and cold contracts, applies to solids, 
liquids, and gases alike. The standard of measurement of the 
linear, superficial, or cubical change, occasioned by raising 
the temperature of a given substance, is based on the increase 
noted in elevating the temperature of that substance from 
0 to 1° C. The amount of such increase is termed the co-effi- 
cient of expansion. 
Between 0 and 100° C., the co-efficient of expansion in a 
metal, an alloy, or any substance of standard character, is 
comparatively constant for that or any like class of substances. 
When metals are alloyed, or when the composition of sub- 
stances is modified, their co-efficients of expansion change, 
sometimes to a remarkable degree. The following four alloys INLAYS 
921 
of nickel and iron, although instances of the extreme type, 
serve to illustrate this fact. 
Nickel. 
Iron. 
Mean co-efficient of expansion 
between 0 and 100 deg. C. 
No. 1 
28 
72 
.000015 
No. 2 
36 
64 
.0000015 (Known as “invar”) 
No. 3 
45 
55 
.0000088 
No. 4 
60 
40 
.000012 
Varying the proportion of nickel and iron only 8 per cent 
reduces the co-efficient of expansion of the invar to one-tentli 
that of the first alloy. Combining the same two metals in the 
proportions as shown in the fourth alloy, results in increas- 
ing the expansive index to within .000003 that of the first. 
When metal is expanded by beat, a certain amount of 
energy is developed which becomes apparent on restricting 
its free movement. According to Joule’s data, when a pound 
of iron is raised in temperature from 0 to 100° C., it expands 
one-two-hundred-and-eightieth of its bulk. The energy or 
force of this expansion is sufficient to raise seven tons one foot 
in height. 
A bar of iron 10 inches long ydll expand 1/200 of an inch 
with a raise in temperature of 45° C. The force of this ex- 
pansion is equivalent to 50 tons. 
A bar of malleable iron, of one inch sectional area, is 
stretched 1/10000 of its length by a weight of one ton. Rais- 
ing its temperature about 9° C. will elongate it to the same 
extent. 
When bodies have been heated to a high temperature, the 
force produced by their contraction in cooling is equivalent 
to the force which is needed to compress them to the same 
extent by mechanical means. (Ganot’s Physics.) 
The relation of these examples of expansive and con- 
tractile forces to inlay work, particularly to investments, will 
be brought out later. 
EXPANSIVE AND CONTRACTILE FORCES 
The three principal classes of materials used in inlay con- 
struction, as previously stated, are waxes, refractory invest- 
ments and gold of varying carats. In manipulative proced- 
ures these materials are subjected to dimensional changes 
which vary according to the composition of the substance 
used, and the technical methods employed. The many varie- 
ties of wax exhibit a wide range of difference in their hard- 
PRINCIPAL SOURCES OP ERROR IN INLAY CONSTRUCTION 922 
INLAYS 
ness, adhesiveness, cohesiveness, expansive tendency, liability 
to warp, and general susceptibility to thermal changes. 
Investment materials vary greatly in composition, density 
and porosity. Some maintain their integrity at high tempera- 
tures without crumbling, crushing, or flaking, while others are 
more or less disintegrated. 
Gold of varying carats and compositions shows different 
expansive indices, and more or less variation in fluidity, as a 
general rule, when fused. The higher the carat of gold used, 
the sharper will be the casting, while less contraction will 
occur in cooling. There are, however, exceptions to this in 
some of the more recent alloys of gold. 
Two or more men using identically the same materials, fol- 
lowing the same technic, and working under as nearly the 
same conditions as possible, will not produce identical results. 
Duplicate pieces produced by the same individual, even when 
extreme care is taken to follow the same methods, vary more 
or less. 
This fact, together with variations in the physical prop- 
erties of materials employed, renders impossible the produc- 
tion of perfect inlays. A near approach to good adaptation 
and general requirements, however, may be secured by using 
carefully selected materials, and by exercising care in tech- 
nical details. 
WAXES 
The basis of most of the inlay waxes is beeswax. In its 
natural condition beeswax is not suitable for inlay models. It 
is too soft and bends too easily to retain its form in handling. 
Beeswax consists of three principal substances, first, Myricyl 
palmitate, C3oH6i CiaH3iOs; second, Cerotic acid, C27Hr)402, and 
Cerolein, a waxy organic compound. 
Beeswax melts at 63° C. (145° F.), Sp. Gr. .960. When 
melted on a plaster slab it is gradually absorbed, and if pure 
leaves no residue. On applying increased heat it is volatil- 
ized. It is quite adhesive when pressed firmly against an 
object. This is a detrimental quality, as it tends to stick to 
cavity walls. Beeswax lacks cohesiveness and consequently 
its molecules do not cling together firmly. For this reason it 
is brittle, and in carving, thin margins tear away easily. 
Paraffin is a natural, wax-like substance, usually com- 
posed of two or more members of the paraffin series of hydro- 
PARAEFIN INLAYS 
923 
carbons. Its formula varies somewhat, depending on its 
derivation, but corresponds generally with the following: 
CasHssCsgHeoCaoHca. It melts between 113° to 149° F , depend- 
ing on the source from which procured, and on cooling forms 
a white, rather hard, compact crystalline mass. It is quite 
cohesive, but not very adhesive in a cold state. 
EFFECT OF COMBINING WAX AND PARAFFIN 
By combining beeswax with paraffin, frequently having 
a very considerable excess of the latter, the product is less 
adhesive, more cohesive, and somewhat harder than when 
uncombined. Some of the resins are frequently added to the 
foregoing combination, to give increased hardness. Such 
products sometimes fail to volatilize, leave a residue in the 
matrix, and are usually detrimental. 
Briefly stated, the necessary qualities of an inlay wax are 
as follows: 
First, it must have a low coefficient of expansion. 
Second, it should be strongly cohesive, but not perceptibly 
adhesive. 
Third, when cold, it should break before bending. 
Fourth, it should be hard enough at body temperature to 
carve well. 
Fifth, it should become plastic at a reasonably low point 
above body temperature. 
Sixth, it should be dark in color and translucent, so that 
in carving, tooth surfaces may be seen through thin layers of 
it. 
In practice, a wax should be selected, as previously stated, 
which, on testing, leaves no residue. If a residue remains, it 
should be discarded, as its use would result in rough and im- 
perfect surfaces to the inlay. The next most important qual- 
ity in a wax is a low range of expansion. It must be borne in 
mind that the wax is forced into the cavity in its most ex- 
panded condition. The higher the temperature required to 
render it plastic, the greater its expansion, and, consequently, 
the more contraction will occur in cooling to room tempera- 
ture. While in this contracted state, the investment of the 
model is usually accomplished. It is therefore smaller than 
when first adapted to the cavity walls. Wliile, in the subse- 
quent steps of casting, the investment and ring expand under 
ESSENTIAL REQUISITES OF A WAX 924 
INLAYS 
heat, and possibly the matrix itself may become slightly en- 
larged, such changes are beyond control. They may correct, 
partially or wholly, the error of contraction in the wax, or 
they may lead to still greater error, through unequal expan- 
sion, since the crucible portion of the investment is much hot- 
ter than the bottom, at the moment of casting. 
ELASTIC PROPERTIES OF WAX 
When a roll of wax is rendered plastic by heat, bent in 
the form of a ring, and chilled, the ends being unattached, it 
will remain in that form so long as the temperature is not 
raised. In bending, the molecules on the outer periphery of 
the ring are elongated, while those along the inner periphery 
are compressed. 
In most materials, and in wax as well, the tendency of 
molecules, when stretched or distorted, is to return to normal 
Fig. 949.— Diagrammatic Draw- 
ing, Showing Molecular Arrange- 
ment of Wax When Melted and 
Run in Bar Form. Diagram of 
Tooth with Bar Bent Into a 
Mesio-Occluso-Distal Cavity. No- 
tice the Elongation of Theoret- 
ical Molecules on the Outer 
Periphery and the Compressed 
Condition of Those in the Inner 
Periphery 
form and relation to each other, when the stress which dis- 
torted them, or the force which holds them in abnormal form 
and position, is removed. Chilling the wax hardens it, and 
renders inert the tendency of the molecules to return to nor- 
mal form. By subsequently raising the temperature of the 
wax, the force which locks the molecules in their strained rela- 
tion is partially overcome, and, to a limited extent, they re- 
turn to their original form, causing the ends of the wax ring 
to separate. The temperature at which the inherent tendency 
of the molecules of wax to recover their form becomes per- INLAYS 
925 
ceptible varies according to the composition of the material. 
It is evident that some waxes, hard enough to carve at body 
temperature, change form on removal from the mouth, while 
others apparently do not exhibit such tendency. Time, and 
fluctuating temperature, without doubt, encourage warpage, 
therefore, to avoid excessive dimensional change and warpage, 
the wax model should be invested as soon as possible. 
INVESTMENT MATERIALS 
The refractory basis of most investment materials, used 
for casting purposes, is pulverized silex, of varying degrees 
of fineness, and in some cases graphite. Plaster of paris 
serves as a binder, or cementing medium, and fills the voids 
between the granules of silex. Various other substances are 
added to control the time of setting, prevent contraction, and 
impart smoothness and density to the mass when mixed. 
EXPANSION OF INVESTMENT RING AND INVESTMENT MATERIAL 
The coefficient of expansion of brass of which most casting 
rings are made is .000018, between 0 and 100° C., that of 
quartz between 0 and 1000° C., 00000055. (Ganot’s Physics.) 
The expansion of the brass is therefore thirty-three times 
greater at only one-tenth the temperature, than that of quartz. 
The coefficient of expansion of graphite is .0000078 (Ganot’s 
Physics), or about 14 times greater than that of quartz, but 
perceptibly less than brass. Its effect, when combined with 
quartz in an investment, is to increase the coefficient of ex- 
pansion. Some of the best investments procurable contain a 
considerable percentage of graphite incorporated for this pur- 
pose. The coefficient of expansion of the materials mentioned 
is variable, according to composition, variety, etc. 
Since the investment ring expands on heating, the invest- 
ment itself should also expand and follow the walls as closely 
as possible, first, to counteract the internal force brought upon 
the matrix walls in casting the gold under pressure, thus pre- 
venting the investment from cracking or bulging outward in 
thin places, and second, to prevent the investment dropping 
from the ring in handling; third, to enlarge the mold slightly, 
thus compensating to a slight extent for contraction of the 
gold. Expansion of the investment, therefore, is a necessary 
quality. 
Some investment materials show a tendency to contract 
toward several common centers when overheated. When this 926 
INLAYS 
occurs, cracking of the investment follows and the general 
surfaces of the matrix are warped. 
Some investment materials are subject to varying dimen- 
sional changes on the application of heat, depending on the 
quantity of water used in mixing. Thin mixes, as a rule, show 
a greater tendency to contract and warp than thick mixes of 
the same material. Taggart’s investment is an exception to 
this rule, as it has a high coefficient of expansion when mixed 
thin enough to be poured. 
ESSENTIAL PROPERTIES OF AN INVESTMENT MATERIAL 
The essential properties of an inlay investment material, 
briefly stated, are as follows: 
First, it should not contract in setting, even when mixed 
thin. 
Second, it should be dense and free from perceptible por- 
osity when set. 
Third, it should be hard, resistant to stress, and show no 
tendency to crack when heated to casting temperature. 
Fourth, it should possess a high expansive index, and a 
low coefficient of conductivity under heat. 
Fifth, it should not be fused, by the molten gold, in cast- 
ing the latter. 
Since there is no cohesion whatever between the granules 
of refractory materials themselves, a binder must be incor- 
porated, which in practically all cases is plaster of Paris. As 
has previously been shown, this material is a crystallized, 
di-hydrate of calcium sulphate, which decomposes to a greater 
or less extent at 190° C. The crystals do not immediately 
crumble on being heated, but are greatly weakened, so that 
the application of slight force is sufficient to disintegrate 
them. That the matrix walls of overheated cases do not flake 
away more readily than would at first appear from the disin- 
tegration of plaster is due to the mechanical interlocking of 
the granules of the various materials of which the investment 
is composed, and which lie in more or less close contact. 
Decomposition of the binder from overheating is largely re- 
sponsible for the roughening and bulging outward of the 
matrix walls under the pressure of casting. 
As an example, casts and investments composed of plaster 
alone, although at first expanded with slight rise in tempera- 
ture, when heated to high temperatures, contract, crack and 
distort very quickly. Plaster, therefore, should not be used to INLAYS 
927 
excess in inlay investments or the quality of the latter will be 
impaired in proportion to the excess of this material present. 
By using but little more than an amount sufficient to fill the 
voids between the granules of refractory materials, contrac- 
tion is, to a great extent, obviated and the tendency to crack 
and warp is greatly reduced. Roughly estimated, the propor- 
tion of plaster to refractory materials ranges from 25 to 40 
per cent. 
Further valuable discussion of this subject will be found 
under the heading, “Refractory Materials,” by Dr. Wein- 
stein, page 1016. 
DIMENSIONAL CHANGES IN GOLD, DUE TO TEMPERATURE CHANGES 
When gold changes from a fused to solid state and normal 
temperature, its cubical contraction, according to Dr. W. A. 
Price’s findings, is about 6.75 per cent of volume. 
Linear, being one-third that of cubical contraction, is, 
therefore, about 2.25 per cent. In an inlay one-fourth inch 
wide, or long, the linear contraction of that surface would 
show a deficiency of about .005 of an inch. 
While heavy pressure, applied during and after injection 
of the molten gold into the mold, might, by the compressive 
force exerted, reduce to a slight extent the percentage of 
contraction noted, such method is impracticable, because of 
the comparative non-resistance of the investment materials 
to heavy pressure. 
Contraction of the gold, therefore, is a constant source of 
error in the production of castings of exact dimensions. 
COMPENSATING FOR ERRORS DUE TO CONTRACTION OF GOLD 
Various means have been suggested for minimizing the 
errors arising from the contraction of gold in cooling, a few 
of which will now be mentioned. 
First, the use of an investment which will expand on heat- 
ing, thus enlarging the matrix to a slight extent. This method, 
however, is subject to error, for unless the investment is uni- 
formly heated it will not be equally expanded, and as a result 
the mold walls will be distorted. 
Second, heating the wax model somewhat above body tem- 
perature by investing in warm, instead of cold, investment, 
thus expanding it slightly before the investing medium hard- 
ens. Error may or may not occur when this method is fol- 928 
INLAYS 
lowed; if the wax is under molecular strain, yet rigid at room 
or body temperature, investing it in a warm medium may re- 
lease the tension and result in warpage of the model before 
the investment hardens. When not subjected to molecular 
tension, expansion without distortion will occur, thus favor- 
ably increasing the dimensions of the matrix. 
Third, the use of sufficient gold to insure a considerably 
larger residual button in the crucible after injection into mold 
than the bulk of gold in the casting. Naturally, the casting, 
being smaller, and the matrix walls in a less heated state than 
the crucible, the contents of the mold will solidify first. 
When the sprue is of sufficient size and its length not exces- 
sive, as contraction of the gold within the matrix sets in, the 
pressure on the more highly heated residual gold in the cruci- 
ble forces it in and feeds the contracting mass within the mold 
until it solidifies. 
The necessity for the unequal balancing of the gold as 
suggested is apparent for the following reasons: 
To produce sharp castings it is necessary that the gold be 
in a superheated condition, considerably above its actual fus- 
ing point. The contraction of superheated gold may be di- 
vided into two stages, first, that which occurs in passing from 
its highest heated and most expanded condition to the freez- 
ing state, and second, from the point of congealing to normal 
temperature. 
Now, if gold, in a superheated condition, be cast into 
either a hot or cold matrix, and no provision is made for re- 
plenishing the contracting, fluid mass, the casting will be de- 
fective, and in case of inlays the margins will be rounded. 
The result of contraction of gold in inlay construction is 
that, in a simple cavity, the inlay will fail to fill the cavity per- 
fectly, a more or less open space showing around the margins, 
while the axial surface usually sinks slightly below that of the 
tooth. 
Since, as has been previously shown, the contractile force 
exerted by a casting, in cooling, is equivalent to the mechan- 
ical force required to compress gold, of similar bulk, an equal 
amount by mechanical means, it therefore follows that in 
mesio-occluso-distal inlays the investment interposed between 
the mesial and distal flanges of the inlay will be compressed 
and distorted to a greater or less extent. 
As a result of such contraction, the inlay frequently fails 
RESULT OF CONTRACTION OF GOLD IN INLAY ADAPTATION INLAYS 
929 
to go to place. To seat it, the tooth may be reduced, the inner 
walls of the matrix enlarged or the occlusal portion of the in- 
lay stretched sufficiently to permit its being driven to place. 
Dr. Price suggests two means for overcoming the diffi- 
culty; first to cast the inlay against a reproduction of the 
tooth, developed in a special artificial stone, or to cast the in- 
lay around a threaded iridio-platinum bar, extended through 
and beyond the occlusal body of the inlay, sufficiently to gain 
a firm hold in the investment. 
Still another method, suggested by a member of the pro- 
fession in Wisconsin, whose name the writer cannot recall, 
consists in drilling a hole through the occlusal portion of the 
inlay, inserting a fine saw and cutting buccally and lingually 
almost, but not quite, to the walls to weaken the gold, introduc- 
ing the inlay and driving it to place. As a result the gold is 
stretched and the inlay lengthened. Care should be taken to 
see that the gingival ends are not bent outward, or, if so, to 
readjust them, after which wax is filled in the hole and saw 
cut, the inlay invested and the opening filled with solder. 
Since ordinary investments, used in casting, are unable 
to resist the force of contraction of the gold, practically the 
only means left is to select a material that expands perceptibly 
during the heating and casting process. 
Technic of Cast Gold Inlay Construction 
Inlay waxes are prepared in stick form and are also sup- 
plied in the form of cones and various irregular shapes suit- 
FORMING THE WAX MODEL 
Fig. 950.— Various Forms of Inlay, Wax Blocks 
able for introduction into different classes of cavities, with- 
out bending. 
These blocks and sticks are formed by melting the wax 
and casting into molds. They are, therefore, free from mole- 
cular tension. 930 
INLAYS 
Select a wax form of approximately the shape, but larger 
than is required to fill the cavity. 
If the cavity is irregular as one of the mesio-occluso-dis- 
tal class, a form should be carved, of the desired shape, from 
a large block, or two forms may be joined by melting their 
contact surfaces, and the required form carved from the 
united pieces. 
Soften by placing in hot water, the temperature of which 
should range from 115° to 139° F., according to the variety 
of wax used. 
Price’s wax becomes workable at 115° F., Peck’s at 120° 
F., Cleveland Dental at 127° F., S. S. White at 128° F., Con- 
solidated at 130° F., Goslee’s at 135° F. and Taggart’s and 
Klewe’s at 139° F. 
The wax should be entirely immersed in the water, re- 
maining there a sufficient time to become uniformly heated 
throughout. Dry the cavity and apply a thin film of oil to 
prevent wax adhesion. Introduce wax in the cavity, and with 
ball of the thumb or finger apply steady, positive pressure in 
such direction as will force the wax into and against cavity 
walls and margins. 
Avoid changing direction of pressure, or rolling the ball 
of the finger over the wax. When change of direction of 
pressure, from any cause, occurs, the wax is liable to become 
unseated, or moved away from the cavity walls. Then, when 
contraction of the wax occurs, as is invariably the case, errors 
in adaptation are still further increased. 
Continue pressure until wax has cooled to body tempera- 
ture. Heat a spatula and soften the occlusal surfaces. In- 
struct patient to subject the wax to the action of opposing 
teeth, not only in full occlusion, but to lateral movements as 
well. 
Remove peripheral surplus of wax and carve to desired 
form. The carving tool should be applied so as to cut parallel 
with the line of junction of wax with cavity margin or be 
drawn diagonally across the junction from wax to tooth. 
When drawn from tooth to wax, the latter is liable to be torn 
or drawn away from the cavity margin and thus result in a 
defective margin of the wax model. 
A smooth finish may be given axial surfaces by means of 
silk strips, moistened with oil of cajeput. Flat surfaces may 
be smoothed with pellets of cotton, slightly moistened with 
the oil. 
Remove the wax model carefully with small instrument, 
and attach sprue former. INLAYS 
931 
In all cases the attachment of the sprue to the wax should 
be at the highest point of the matrix, when the ring is set in 
proper position for casting. 
When any portion of the mold is higher than the point 
of entrance of the gold into the latter, air frequently becomes 
Fig. 951.—- Wax Model of Inlay At- 
tached to Sprue Former, Ready 
for Investment 
Fig. 952.— Wax Model of Small Sad- 
dle, Ready for Investment. Three 
Wax Sprue Formers Lead from 
Metal Sprue Former to Extremities 
and Center of Model 
confined or the gold becomes chilled and fails to perfectly fill 
such high areas. 
A small strip of gold plate may be heated sufficiently to 
melt its way into the wax, and when cold this will serve as a 
plier grasp in removing the model. It may be allowed to 
remain in the wax when, invested, and when the inlay is cast, 
the projecting end will facilitate handling the inlay while 
fitting. After serving its purpose it may be removed by cut- 
ting and the surfaces polished smoothly. Suggested by Dr. 
T. L. Pepperling. 
The sprue former is now heated and applied at the point 
of proximate contact. It must be imbedded sufficiently to ob- 
tain a firm hold upon the model so that displacement will not 
occur during investment. 
The wax around the sprue former should be smoothed 
properly and a slight amount added, if necessary, to insure 
strong proximate contact. 
INVESTMENT OF THE WAX MODEL 
The sprue former with wax model attached, is now set in 
the opening of the crucible former and the wax washed with 
a soapy water solution and afterward clear water, applied 
with fine brush, to remove the oil. 
. A mix of investment of medium consistency is now made 
and with a fine brush the surfaces of the wax are carefully 
coated with a film of it. The investment ring is now set in 932 
INLAYS 
position, the rounded margin down, and the space around the 
model entirely filled with investment. 
Care should be taken, both in coating the wax and in fill- 
ing the ring with investment, to avoid the formation of air 
spaces. 
When the investment has hardened, the surplus project- 
ing from the open end of the ring is squared off, the crucible 
former removed, the sprue former heated sufficiently to melt 
the wax at its inclosed end, after which it is carefully removed. 
Remove from the crucible and the sprue any particles of 
investment that may be present, so that when ready to cast 
the mold may be clear. 
DRYING OUT THE INVESTMENT AND ELIMINATING THE WAX 
Place the investment ring about three inches above a low 
Bunsen flame for five minutes, that it may become gradually 
heated. 
Lower the ring and raise the flame until the latter touches 
the investment, and continue the heating process for five or 
ten minutes longer. 
Increase the flame until it passes up, surrounding the 
sides of the ring. Continue the heat at this higher tempera- 
ture until the investment is freed from all moisture and the 
gas has been driven off. At no time should the heat be applied 
so rapidly as to boil the wax and force it through the sprue. 
Test by holding a piece of cool glass close to upper end 
of ring. 
When all gas and moisture has been expelled, the ring is 
set aside and allowed to cool before casting. 
VARIATION IN THE METHOD OF PREPARING THE MOLD FOR CASTING 
When investment has hardened, the ring is placed about 
six inches above a medium-sized Bunsen flame and allowed 
to remain in the current of heated air until all moisture is 
expelled. 
This may require thirty minutes or more, and during the 
process the temperature will be raised somewhat above 212° 
F. It should not at any time be raised much above that point. 
Now, since wax melts at about 150° F., it will be absorbed 
by the investment as the moisture is expelled from the latter. 
A film of wax, however, will remain on the matrix walls. 
The ring may be set aside to cool, before casting the gold, INLAYS 
933 
or the button of gold may be placed in the crucible, fused and 
cast immediately, if desired. 
The film of wax in no way interferes with the production 
of a sharp casting. In fact, when the gold is sufficiently super- 
heated and injected into the mold, under proper conditions, 
a sharper and cleaner casting can be produced by this than by 
the former method. 
The instant the gold is forced into the matrix its tempera- 
ture is considerably above 2000° F. All gas and air in the 
matrix is forced outward through the walls into the invest- 
ment, the film of wax is instantly carbonized and prevents the 
oxygen in the air, forced out, from coming in contact with the 
gold, the result being a clean, bright casting. 
The greatest advantage, however, is that the binder in 
the investment has not been disintegrated by previous heat- 
ing, and as a result the matrix walls are firm and compara- 
tively unyielding. The roughness, therefore, so frequently 
seen on cast gold surfaces, when the investment is previously 
highly heated, is not noticeable in a casting produced by the 
method just described. 
Credit for this method of treatment of the invested case 
belongs to Dr. Chas. B. Meade of Bockford, 111., who first dem- 
onstrated it at a clinic of the Chicago Dental Society. 
THE CASTING OF GOLD 
Under the most favorable circumstances a certain amount 
of time unavoidably elapses between the discontinuance of the 
heat applied in fusing the gold and its injection into the mold. 
The instant the flame is discontinued the temperature of 
the gold begins, and continues to drop, resulting in change 
from a fluid to a pasty and finally a solid state. 
When gold is brought to a fused condition only, and the 
flame is discontinued, these changes occur very quickly, so 
rapidly, in fact, that in introducing it in the mold, even under 
heavy pressure, the latter will seldom be filled perfectly, be- 
cause of the changes mentioned. 
Therefore, to insure sharp castings, gold must be super- 
heated considerably above its actual fusing point in order 
that it may not only enter the mold, but be sufficiently fluid, 
after injection, to conform to all irregular surfaces of the 
matrix under the compressive force applied. 
The most important contribution of Dr. Taggart to the 
casting process was the discovery that in order to cast sharply, 
gold must be superheated considerably above its fusing point. 934 
INLAYS 
This he accomplished readily by means of a slight modifica- 
tion of the Knapp nitrous oxide and gas blowpipe. 
When all moisture has been eliminated, the ring is placed 
in the casting device, a button of gold considerably larger 
than required is placed in the crucible, brought to a super- 
heated condition and as quickly as possible forced into the 
matrix under pressure. 
With the Taggart appliances the gold may be quickly 
brought to a superheated condition by means of the nitrous 
Fig. 953.— The Taggart Compressed Gas 
Casting Machine 
oxide and gas blowpipe and the casting quickly accomplished 
by forcing the sealing cap down tightly upon the ring margins. 
With the R. & R. vacuum machine, the chamber should 
be emptied of air before fusing the gold, when, after this has 
been accomplished, by opening the valve, the gold is drawn 
into the matrix by suction. 
Further details of gold, reducing fluxes, investments, etc., 
of practical value will be found in the section on metallurgy, 
under the general topic, “Alloys of Gold,” etc., by Dr. Wein- 
stein. 
ROUGH FINISHING THE CASTING 
On removal of the casting from the investment, it should 
be washed, boiled in acid, and again washed, to remove the 
acid. 
The button is now removed from the casting, the rough 
points removed with discs, being careful while doing so not INLAYS 
935 
to mar the margins, and in proximo-occlusal inlays to pre- 
serve a strong contact point. 
Should nodules be present in any of the inlay surfaces 
which proximate cavity walls, they should be smoothed down 
Fig. 954.— The Ransom & Randolph Vacuum Casting Machine 
with chisels, discs or stones or reduced in any manner most 
convenient. When present, they prevent proper seating of 
the inlay. 
SETTING THE INLAY 
When, by test, the inlay can be perfectly seated, it is re- 
moved, the cavity rendered thoroughly dry, cement mixed and 
applied in the usual manner, and the filling set under con- 
tinued, heavy pressure. 
FINISHING 
When the cement has thoroughly hardened, the margins 
of the inlay are now given their final finish with discs, strips, 
and polishing powders. 
Previous to the final setting, however, the contact and 
adjacent areas of the filling are polished, thereby reducing 
danger of loss of proximate contact, which frequently occurs 
in final finishing, unless separation of the teeth is previously 
made. CHAPTER XXXII 
AN OUTLINE OF METALLURGY 
The science of metallurgy deals with the extraction of 
metals from their ores, with their physical properties when 
free and uncombined, and with the changed conditions 
brought about by alloying the individual metals, or by the 
presence of some other substances, either in the form of im- 
purities or that may have been added for some definite pur- 
pose. 
Metallography deals more particularly with the structural 
form of metals and their alloys, the study in this compar- 
atively new field in physics being carried on chiefly with the 
microscope. It is closely related to the chemistry of metals, 
and yet it covers a field not occupied, and yields information 
not obtainable, by ordinary chemical analysis. 
In the practice of prosthetic dentistry, about fifteen of 
the metals are used to a greater or less extent, either in their 
pure state, or in the form of alloys. To handle these various 
metals intelligently and economically, so as to secure the best 
results, the prosthetic dentist should have an intimate knowl- 
edge of general and metallurgical chemistry, as well as of the 
collateral sciences. In the description of the metals now about 
to be considered an effort will be made to point out those 
essential physical and chemical properties and peculiarities 
which, if overlooked or misunderstood by the prosthetist, may 
result in mishaps of a more or less serious character. 
All of the material substances of the universe with which 
we are acquainted consist of elements alone or in combination 
with each other. 
An element is a substance which cannot be split up or 
decomposed into dissimilar substances by any means now 
known, and differs from a compound, which may be split up 
or separated into dissimilar substances. 
At this time there are about eighty elements known, fifty- 
two of which are metals. It is possible that some of these sub- 
stances which are now considered elements may prove to be 
compounds. 
936 an outline of metallurgy 
937 
Facts, Hypotheses, Theories and Speculations 
ELEMENTS 
An element is a substance which cannot be decomposed 
into simpler substances by any method now known. Stated 
differently, “an element is a distinct species of matter which 
lias not been shown to be composite.” 
As before stated, at the present time, so far as is known, 
there are about eighty elements in the universe. The physical 
properties of most of these are well understood, but a few, 
because of their scarceness and the difficulties attending their 
examination, have but sparse accumulated data. It is not only 
possible, but quite probable that other elements now unknown 
may be discovered, and that some of those now classed as 
elements may prove to be compounds. 
DISCOVERY OF ELEMENTS BY MEANS OF THE SPECTROSCOPE 
The spectroscope has aided materially in the detection 
of some of the elements, and by means of it their presence in 
the universe was recognized before they themselves were iso- 
lated. As an illustration, in 1868 a bright line was noticed 
in the spectrum of the sun’s atmosphere which differed from 
that of any element then known. Lockyer and Frankland. be- 
lieving it to be a new element in the sun, called it helium, from 
the Greek, meaning the sun. Twenty-seven years later Sir 
William Ramsay discovered in the spectrum of cleveite, a line 
corresponding with that of helium, which was still unknown 
except by its spectrum. On further examination this new 
element proved to be a gas, a constant component of the 
earth’s atmosphere, and, as will be shown later, an end 
product of radio active substances under certain conditions. 
Because of its spectroscopic position it received the name of 
helium. For many years the spectrum of the Aurora Borealis 
was a subject of puzzling investigation. This light shows in 
it a peculiar, greenish yellow line, unlike that of any other 
element known. The discovery of krypton solved the prob- 
lem, its spectrum showing the identical line found in that of 
the “Northern Lights.” 
THE MUTABILITY OF MATTER 
There is a growing belief among physicists that some, 
possibly all substances now known ns elements, may be trans- 
mutable or capable of being changed from one to the other. 
The change, however, appears to be one of degradation. 938 
AN OUTLINE OF METALLURGY 
No laws have been discovered by which this mutability of 
matter can be brought about at will or among the elements 
indiscriminately. Certain facts, however, have been observed 
and verified time and again, beyond the question of doubt, 
that under definite conditions degradation of elements occurs. 
The character of the element before such change occurs can 
be recognized, the intense energy exhibited while decomposi- 
tion is going on can be noted and even measured to a certain 
degree, and the character of the substance into which the 
original element is finally resolved can be determined. 
BRIEF OUTLINE OF RECENT DISCOVERIES 
To make these facts more plainly apparent, a statement 
of some of the discoveries in physical and chemical fields in 
the last twenty years, together with their bearing on the sub- 
ject under discussion, will be in order. 
ELEMENTAL GASES 
In 1894 Lord Rayleigh discovered in the atmosphere a 
new and hitherto unsuspected gaseous element. Because it 
would not combine chemically with any other substance except 
at intensely high temperatures, and in other ways seemed 
generally inert, it was named “argon,” which means “lazy.” 
It closely resembles nitrogen in its physical properties, is 
slightly heavier and extremely difficult to separate from the 
latter gas with which it is associated in the atmosphere. 
In 1895, Sir Wm. Ramsay discovered four other elemental 
gases in the air, viz., helium, neon, krypton, and xenon, all of 
which have similarly inert properties to argon. These five 
gases have all been “won out of the hidden places in the air,” 
and as will be seen later, the presence of most of them in this 
medium can be accounted for. 
DISCOVERY OF THE X-RAYS 
In the same year Prof. William Konrad Roentgen dis- 
covered the peculiar penetrating power of the rays from an 
induced electric current when passed through a vacuum. 
These rays are now known as Roentgen, or X-rays, and their 
power of penetrating opaque substances and affecting light 
proof photographic plates is well understood and made use of 
in innumerable ways, particularly in the medical and dental 
fields, for diagnostic purposes. AN OUTLINE OF METALLURGY 
939 
DISCOVERY OF RADIO-ACTIVE SUBSTANCES 
In 1896, Becquerel discovered that all compounds of 
uranium emitted a radiation capable of penetrating opaque 
objects similar to but not with the same energy or rapidity 
displayed by the X-ray. Uranium compounds are derived 
from pitchblende, a complex mineral containing many other 
elements. The residue left after extracting practically all of 
the uranium is the source from which radium is derived. 
The Curies noticed that this residue possessed considerable 
radio-activity. In an effort to locate the true source of the 
emanations, they found that after separating the residue into 
its constituent parts, so far as could be done at that time, that 
most of the radio-activity was concentrated in the chloride of 
barium. On subjecting the barium chloride to further reduc- 
tion, the barium was finally eliminated and a substance which 
proved to be radium chloride was secured. "Radium, the ele- 
ment, has not yet been isolated. Its salts KaCL and BaBr., 
are commonly prepared and employed for experimental and 
other purposes. The spectrum of radium and its chemical 
relations to other elements indicate that it should be classed 
among the metals of the alkaline earths. 
There are about twenty-five substances which possess, in 
varying degrees, distinct radio-active properties. The salts 
of radium mentioned exhibit this property more strongly 
than any of the others. 
DECOMPOSITION OF RADIUM COMPOUNDS 
The peculiar feature of the radium compounds is that 
they decompose, rapidly at first, then more slowly, until finally 
practically nothing remains of the original salt. The intense 
energy displayed in their decomposition is half spent in the 
first four days after the preparation of the salt, but in that 
time there has been emitted, proportionately, three million 
times more heat than will result from any other chemical 
action known. 
There are three principal types of rays emitted by radio- 
active substances, designated as alpha, beta, and gamma rays. 
The alpha rays are electro-positive particles or electrons of 
atomic size which fly through space at the amazing velocity of 
twenty thousand miles per second. A little radium brought 
near a screen of zinc sulphide produces brilliant, scintillating 
stars of light. Each star is the result of impact of an alpha 940 
AN OUTLINE OF METALLURGY 
particle or atom against the screen. The beta rays act most 
readily on photographic plates. The gamma rays possess 
the greatest penetrating power, readily passing through a 
lead plate seven centimeters thick. The principal difference 
aside from the effect of the several rays seems to be one of 
velocity, the alpha rays having the greatest and the gamma 
rays the least speed. 
CHARACTER OF THE EMANATION FROM RADIO-ACTIVE SUBSTANCES 
Born lias proven that the emanation from radio-active 
substances is a gas, which, under dry atmospheric conditions, 
eventually breaks down or decays into helium. 
Later Ramsay, in an effort to utilize or conserve some 
of the enormous energy which is manifested during and is 
apparently the result of its debasement, placed the radium 
compound in water. Instead of decaying into helium as it 
does in dry atmosphere, it is finally resolved into neon, the 
second of the elemental gases mentioned. 
When copper sulphate is dissolved in the water in which 
the radio-active substance is placed, neither helium nor neon 
is found, but argon is the final product. 
Prof. Duncan sums up these facts as follows: “It ap- 
pears then, that this gas, this radium emanation, which, it 
must be said, has a good claim to the name of element, decays 
or becomes transmuted, not into one other element, hut into 
three, according to its surrounding circumstances.” 
THE DEGRADATION OF COPPER 
Ramsay’s researches further led him to believe that the 
action of the radium emanations on the copper sulphate broke 
down or changed some of the copper into lithium. He bases 
his deduction on the following: At the beginning of his ex- 
periments lithium was not present in the water, in the copper, 
in the emanations, in the air, nor in the glass apparatus with 
which the experiments were conducted, but the final results 
showed loss of copper and the presence of lithium. Every- 
thing else could be accounted for but the loss and additions 
noted, and those only on the basis of the degradation of cop- 
per into lithium through the influence of radio-activity. 
DEBASEMENT OF VARIOUS SUBSTANCES INTO HYDROGEN 
Still another fact of extreme interest was observed, viz.: 
that water in the presence of radium emanations breaks np AN OUTLINE OF METALLURGY 
941 
into oxygen and hydrogen, not in the usual proportions of two 
volumes of hydrogen to one of oxygen, but the resulting un- 
combined gases show from 10 to 20 per cent too much 
hydrogen. 
Prof. J. J. Thompson has shown that in the energetic elec- 
trical field generated in a Crookes tube, various substances 
give off particles charged with positive electricity, that these 
particles are independent of or differ in character from the 
gas from which they originate, that they are of two kinds, one 
to all appearances identical with the hydrogen atom, the 
others resembling in every respect the alpha particles which 
emanate from radio-active substances. All of the substances 
with which he experimented were decomposed, in part, into 
the element of hydrogen. 
These experiments of Thompson’s, conducted in a differ- 
ent field with unlike apparatus without employing any of the 
so-called radio-active substances, serve to confirm most forci- 
bly the work of Ramsay and others, and establish the fact that 
hydrogen results from the debasement of other elements when 
conditions are favorable. 
SUMMARY OF THE STATEMENTS PRESENTED 
From present knowledge it appears evident that uranium 
is transmuted into radium; that radium may be transmuted 
into helium, neon, or argon, depending on surrounding condi- 
tions ; that copper, under the influence of the alpha rays, may 
be debased into lithium; that the energizing influence of the 
alpha as well as the X-rays, acting on inert substances, causes 
them to break down into hydrogen, and finally, that the radium 
emanations are themselves the product and evidence of ele- 
mental change and decay. 
The atomic weight of copper is 63.6 and that of lithium 
is 7.03. In every case the substance resulting from the de- 
gradation of an element stands lower in the atomic scale than 
that from which it'was derived, copper and lithium being 
examples of what is seen in all of the other elements in which 
such changes have been noted. 
• In reference to “The decay of an element,” Prof. Alexan- 
der Smith, Director of General and Physical Chemistry, Uni- 
versity of Chicago, says : ‘ ‘ The phenomena of radio-active 
substances lead undeniably to the startling conclusion that 
some, if not all, of the element are capable of spontaneous 
decomposition.” 942 
AN OUTLINE OF METALLURGY 
The following table from “Scientific Ideas of Today,” by 
Charles R. Gibson, shows the progress of chemical discovery 
of the elements in the last 464 years. 
The Elements in Order of Their Discovery 
A. D. Elements Discovered by 
1450 Antimony Valentine (German alchemist) 
1450 Bismuth Valentine (German alchemist) 
1520 Zinc Paracelsus (Swiss chemist) 
1694 Arsenic Schroder (German) 
1733 Cobalt Brandt (German) 
1738 Phosphorus Brandt (German) 
1751 Nickel Cronstadt (Russian) 
1766 Hydrogen Cavendish (English) 
1772 Nitrogen Rutherford (English) 
1774 Manganese Gahn (Swedish) 
1774 Oxygen Priestley (English) 
1780 Uranium Klaproth (German) 
1781 Tungsten d’Elihujar (Spanish) 
1782 Molyodenum Hjelm (Swedish) 
1782 Tellurium Reichenstein (German) 
1785 Titanium Klaproth (German) 
1798 Chromium Vauquelin (French) 
1801 Tantalum Hatchett (English) 
1801 Cerium Berzelius and Hisinger 
(Swedish) 
1801 Vanadium Del Rio (Spanish) 
1803 Osmium Tennant (English) 
1803 Palladium Wollaston (English) 
1804 Iridium Tennant (English) 
1804 Rhodium Wollaston (English) 
1807 Potassium Davy (English) 
1807 Sodium Davy (English) 
1808 Barium Davy (English) and Berzelius 
(Swedish) 
1808 Strontium Davy (English) 
1808 Boron .. Davy (English) and Gay-Lusac 
(French) 
1808 Magnesium ..Davy (English) 
1808 Calcium Davy (English) and Berzelius 
(Swedish) 
1810 • Chlorine Davy (English) 
1810 Fluorine Ampere (French) AN OUTLINE OF METALLURGY 
943 
A. D. Elements I liscovered by 
1811 Iodine Courtois (French) 
1817 Selenium Berzelius (Swedish) 
1817 Lithium Arfvedson (Swedish) 
1817 Cadmium Herman and Stromyer (German) 
1823 Silicon Berzelius (Swedish) 
1824 Zirconium Berzelius (Swedish) 
1826 Bromine Balard (French) 
1827 Berylium Wohler (German) 
1828 Aluminum Wohler (German) 
1828 Thorium Berzelius (Swedish) 
1828 Yttrium Wohler (German) 
1841 Lanthanum Mosander (Swedish) 
1843 Terbium Mosander (Swedish) 
1843 Erbium Mosander (Swedish) 
1844 Ruthenium Claus (German) 
1846 Columbium Rose (English) 
I860 Caesium Bunsen and Kirchloff (German) 
1862 Thallium Crookes (English) 
1863 Indium Reich and Richter (German) 
1868 Helium (in the Sun) .Lockler (English) 
1868 Rubidium Bunsen (German) 
1875 Gallium Boisbaudran (French) 
1878 Ytterbium Marignac (French) 
1879 Thulium Cleve (Swedish) 
1879 Scandium Nilson (Swedish) 
1879 Samarium Boisbaudran (French) 
1885 Praseodymium Welsbach (German) 
1885 Neodymium WTelsbach (German) 
1886 Gadolinium Marignac (French) 
1886 Germanium Winkler (German) 
1894 Argon Rayleigh and Ramsay (English) 
1895 Helium (On Earth).. Ramsay (English) 
1897 Krypton Ramsay and Travers (English) 
1898 Xenon Ramsay (English) 
1898 Neon Ramsay and Travers (English) 
1898 Radium Curie (French) 
The Elements in the Order of Their Atomic Weights 
1. Hydrogen 1.008 
2. Helium 4.00 
3. Lithium 7.03 
4. Glucinum 9.1 
5. Boron 11.0 
6. Carbon 12.0 944 
AN OUTLINE OF METALLURGY 
7. Nitrogen 14.04 
8. Oxygen 16.0 
9. Fluorine 19.0 
10. Neon 20.0 
11. Sodium 23.05 
12. Magnesium 24.36 
13. Aluminum 27.1 
14. Silicon 28.4 
15. Phosphorus 31.0 
16. Sulphur 32.06 
17. Chlorine 35.45 
18. Potassium 39.15 
19. Argon 39.90 
20. Calcium 40.1 
21. Scandium 44.1 
22. Titanium 48.1 
23. Vanadium 51.2 
24. Chromium 52.1 
25. Manganese 55.0 
26. Iron 55;9 
27. Nickel 58.7 
28. Cobalt 59.0 
29. Copper 63.6 
30. Zinc 65.4 
31. Gallium 70.0 
32. Germanium 72.5 
33. Arsenic 75.0 
34. Selenium 79.2 
35. Bromine 79.96 
36. Krypton 81.8 
37. Rubidium 85.4 
38. Strontium 87.6 
39. Yttrium 89.0 
40. Zirconium 90.6 
41. Columbium 94.0 
42. Molybdenum .... 96.0 
43. Ruthenium 101.7 
44. Rhodium 103.0 
45. Palladium 106.5 
46. Silver 107.93 
47. Cadmium 112.4 
48. Indium 114.0 
49. Tin 119.0 
50. Antimony 120.2 
51. Iodine 126.85 
52. Tellurium 127.6 
53. Xenon 128.0 
54. CaBsium 132.9 
55. Barium 137.4 
56. Lanthanum 138.9 
57. Praseodymium .. 140.5 
58. Cerium 140.25 
59. Neodymium 143.6 
60. ' Samarium 150.0 
61. Gadolinium .... 156.0 
62. Terbium 160.0 
63. Erbium 166.0 
64. Thulium 171.0 
65. Yitterbium 173.0 
66. Tantalum 183.0 
67. Tungsten 184.0 
68. Osmium 191.0 
69. Iridium 193.0 
70. Platinum 194.8 
71. Gold 197.2 
72. Mercury 200.0 
73. Thallium 204.1 
74. Lead 206.9 
75. Bismuth 208.5 
76. Radium 225.0 
77. Thorium 232.5 
78. Uranium 238.0 
The Kinetic Constitution of Matter 
Matter is composed of or at least presents itself to our 
senses in three distinct forms, viz., solids, liquids and gases. 
The molecular theory of matter, as believed in and taught 
by the physicists of today, may be briefly stated as follows: 
Matter consists of units called molecules; these in turn AN OUTLINE OF METALLURGY 
945 
are composed of still smaller units of elements called atoms; 
atoms are made up of still smaller units consisting of ele- 
mentary charges of negative electricity, called electrons, each 
of which probably has a nucleus or center of positive elec- 
tricity. 
THE VIBRATION OF MATTER 
It is believed that the electrons move about or vibrate 
within the atom; that the atoms vibrate within the molecule, 
to a lesser degree; and that the molecules move about within 
the mass of matter, freely when the matter is gaseous, re- 
stricted in movement when solid or liquid, but still posses- 
ing movement. 
The infinitesimal particles of gold in a colloidal state, al- 
though much larger than the estimated size of electrons, when 
viewed through that wonderfully simple but simply wonder- 
ful instrument, the ultra-microscope of Zsigmondy, enable 
one to form some slight conception of the vibration of matter. 
Here is his own description of what may be seen: 
“ * * * The small gold particles no longer float, they 
move—and that with astonishing rapidity. A swarm of danc- 
ing gnats in a sunbeam will give one an idea of the motion of 
the gold particles in the hydrosol of gold. They hop, dance, 
jump, dash together and fly away from each other, so that it is 
difficult in the whirl to get one’s bearings. 
“This motion gives an indication of the continuous mix- 
ing up of the fluid, and it lasts for hours, weeks, months, and, 
if the fluid is stable, even years. 
“Sluggish and slow in comparison is the analogous 
Brownian movement of the larger gold particles in the fluid, 
which are the transition forms of ordinary gold that settles. 
“The smallest particles which can be seen in the hydrosol 
of gold show a combined motion, consisting of a motion by 
which the particle moves from 100 to 1,000 times its own 
diameter in one-sixth to one-eiglith of a second, and a motion 
of oscillation of a considerably shorter period, because of 
which the possibility of the presence of a motion of oscillation 
of a higher frequency and smaller amplitude could not be de- 
termined, but is probable.” (Colloids and the Ultra-Micro- 
scope, Zsigmondy). 
The following comparison will give an idea of the size of 
the smaller gold particles: 
The limit of visibility of an ordinary high power micro- 
scope is about one-fourth micron, or one-four-thousandth of a 946 
AN OUTLINE OF METALLURGY 
millimeter, a micron being one-one-tliousandth of a milli- 
meter, or about one-twenty-five-tliousandth of an inch. 
Under favorable conditions, particles of one one-millionth 
millimeters in diameter can readily be seen with the ultra- 
microscope. Some of the smaller particles of gold are barely 
visible with this instrument, and it is believed that still smaller 
particles exist. 
When planed surfaces of gold and lead are brought in 
contact and held together firmly for several weeks, on ex- 
amination it will be found that particles of gold have made 
their way into the lead, likewise particles of lead can be found 
within the gold, thus showing that molecules of solid sub- 
stances vibrate or move about not only in the mass of like 
material, but wander away into unlike substances. 
Prof. A. Wilmer Duff, of the Worcester Polytechnic In- 
stitute, after citing this and similar instances of diffusion, 
states: “There are many other reasons for believing that 
the particles of matter are in all cases in motion. This 
hypothesis is called the hypothesis of the kinetic constitution 
of matter.” 
In reference to electrons, Sir William Ramsay has ex- 
pressed himself as follows: “Electrons are atoms of the 
chemical element electricity; they possess mass; they form 
compounds with other elements; they are known in the free 
state, that is, as molecules.” (Trans. Chemical Society, Great 
Britain, 1908.) 
THE UNEQUAL DISTRIBUTION OF ELEMENTS 
‘ ‘ More than 99 per cent of terrestrial material is made up 
of eighteen or twenty elements, of which the quantities of the 
firsf eleven, as estimated by F. W. Clarke, are given in the 
following table: 
Oxygen 49.98 
Silicon 25.30 
Aluminum ... * 7.26 
Iron 5.08 
Calcium 3.51 
Magnesium 2.50 
Sodium 2.28 
Potassium 2.23 
Hydrogen 0.94 
Titanium 0.30 
Carbon 0.21 
99.59 
“The evidence of the spectroscope shows that the sun and 
stars contain many of the very same elements as does the 
earth. ’ ’—Alexander Smith. 
“Recent researches have thrown a flood of light upon 
these questions (the unequal distribution of elements). It is AN OUTLINE OP METALLURGY 
947 
now believed that the elements are not the changeless sys- 
tems that they were once thought to be, but rather systems 
in slow but incessant mutation. 
“According to Prof. J. J. Thompson, all of the elements 
represent successive condensations of one primary stuff, 
whose atoms, called electrons or corpuscles, weigh less than 
the 1/1,000 part of an atom of the lightest known terrestrial 
element, namely hydrogen. This primary stuff is negative 
electricity, which is therefore a true chemical element.’’— 
Geoffrey Martin, in Triumphs and Wonders of Modern 
Chemistry. 
Elements and Their Atomic Relation to Each Other 
The elements when studied collectively, although differ 
ing in many respects from each other, as, for instance, ir 
their atomic weight, specific gravity, valence and physical 
appearance, have many peculiar properties in common. 
Observation has shown that certain definite relations exist 
between the elements, particularly when arranged in series 
or groups. The gradual and almost uniform increase in the 
atomic scale, beginning with hydrogen, the lowest, and pro- 
gressing up to uranium, the highest, in the atomic series, has 
long attracted attention and given rise to the idea that such 
orderly progression is not the result of chance, but of some 
so far undiscovered law. v ' 
Hydrogen, discovered by Cavendish in 1776, is the light- 
est known terrestrial element. Until recently its atom has 
been rated as 1 of the atomic scale, but for reasons subse- 
quently to be stated, it is now accorded the value of 1.008. 
When the atomic weights of the other elements are computed 
on the basis of 1 for hydrogen, it is found that several are 
whole numbers and many more approximate whole numbers. 
PROUT’s HYPOTHESIS 
Just one hundred years ago William Prout, an English 
physician, observing that the atomic weights of many of the 
elements were either exactly or approximately whole num- 
bers, advanced the idea that all of the other elements were 
composed of hydrogen atoms in various stages of condensa- 
tion, and that therefore their atomic weights must be even 
multiples of that of hydrogen. The fact that some of the 948 
AN OUTLINE OF METALLURGY 
atomic weights as then determined terminated in decimals, 
he regarded as the result of errors in calculation. 
Chemists lined up in support of, or in an effort to dis- 
prove, Prout’s theory, and for a time great diversity of 
opinion prevailed, due largely to the fact that the atomic 
weights of some of the various elements had not been deter- 
mined accurately. 
The brilliant work of Stas, a Belgian chemist, in the 
period between 1855 and 1865, in accurately computing the 
atomic weights of many of the elements, cleared up much 
of the existing confusion. As a result of his efforts, the even 
multiple theory of Prout was proven incorrect. Later it was 
shown that the atomic weight of oxygen was not 16, as Prout’s 
hypothesis called for, but 15.879, which, however, was within 
y8 of 1 per cent of a whole number. 
Further, it was found that by allotting to oxygen the 
atomic weight of 16, and computing the atomic weights of all 
of the other elements on this basis, a much larger percentage 
of them was resolved into whole numbers than when calcu- 
lated on the basis of 1 for hydrogen. By this system of com- 
putation, which is the accepted one at present, the atomic 
weight of hydrogen is 1.008, as before stated. Considering 
the atomic weight of oxygen as 16, the atomic weights of 
fifty-five elements are found to be either whole, or within 
1/10 of 1 per cent of whole numbers. 
Now since it is clearly shown that the atomic weights of 
more than five-eighths of all known elements are approxi- 
mately whole numbers, much interest in chemical and physical 
fields has been aroused, and efforts have been made to deter- 
mine, if possible, the laws governing the atomic, as well as 
other interesting relations discernible in the elements. This 
interest, which is greater at present than ever before, first 
found tangible expression in the hypothesis of Prout, although 
L.he theory of the unity of matter is one of very ancient origin. 
THE TRIADS OF DOBEREINER 
In 1827 Dobereiner called attention to the fact that among 
the elements then known, there occurred here and there groups 
of three having remarkably similar chemical properties. 
These groups have since been termed the “Triads of Pobe- 
reiner.” AX OUTLINE OF METALLURGY 
949 
The following will serve to illustrate some of the various 
triads observed. 
Atomic Weight 
Calcium 40.1 
Strontium ... 87.7 
Barium 137.4 
Atomic Weight 
Sulphur 32.1 
Selenium .... 79.2 
Tellurium .. .127.5 
Atomic Weight 
Chlorine .... 35.4 
Bromine .... 80.0 
Iodine 126.8 
The first group is composed of alkaline earth metals. 
They are white in color, about as soft as lead, and decom- 
pose water at ordinary temperatures, resulting in the forma- 
tion of hydroxides with the liberation of hydrogen. In most 
compounds these metals are divalent. 
The second group, consisting of Sulphur, which is very 
abundant, and Selenium and Tellurium, which are compara- 
tively rare, forms a series of similar compounds. 
The third group are sometimes called the halogens (pro- 
ducers of sea salt), because they are found in sea water. The 
first is a greenish-yellow gas, the second is a red liquid and 
the third is a purplish-black solid. They are monovalent in 
their compounds with hydrogen, and when combined with the 
latter, form acid gases soluble in water. 
The most remarkable characteristic noted, however, was 
in the ratio existing between their atomic weights. Dobe- 
reiner noticed that when the atomic weights of the first and 
third element of any triad were added and the sum divided by 
two, the resulting mean coincided very closely with the atomic 
weight of the intermediate element of the triad, as is shown 
below: 
Calcium .. . .Atomic Weight. . 40.1 
Barium ... .Atomic Weight. . 137.4 
2/177.5 
88.7 mean 
Strontium ..Atomic Weight.. 87.7 
Sulphur ... .Atomic Weight.. 32.1 
Tellurium ..Atomic Weight.. 127.5 
2/159.6 
79.8 mean 
Selenium . . .Atomic Weight. . 79.2 950 
AN OUTLINE OF METALLURGY 
Chlorine .. .Atomic Weight.. 35.4 
Iodine Atomic Weight.. 126.8 
2/162.2 
81.1 mean 
Bromine .. .Atomic Weight. . 80.0 
While in no case is the resulting mean exactly equal to 
the atomic weight of the second member of the triad, it is so 
close in each instance as to suggest the possibility of an un- 
discovered law which, if known, might clear up the discrep- 
ancies. The work of Dobereiner and others since his time 
has resulted in the discovery of many other interesting and 
peculiar correlated properties of the elements. 
THE OCTAVES OF NEWLANDS 
In 1863 Newlands called attention to the fact that when 
the elements were arranged in the order of their atomic 
weights, beginning with the lowest, hydrogen 1, running 
through the entire list of the elements then known and ending 
with uranium 240, at regular intervals, every eighth element, 
in most instances, bore a striking resemblance in certain 
properties to the preceding eighth below, or the succeeding 
eighth element above. This method of classification is known 
as the Octaves of Newlands. While the discovery of New- 
lands was remarkable, he failed to realize its great impor- 
tance, or work out the full details of it, being unable to clas- 
sify all of the elements satisfactorily. 
In 1869 two chemists, Dimitri Mendeleeff, a Russian, and 
Lothar Meyer, a German, working independently, presented 
almost simultaneously what is known as the Periodic System 
of the Elements. Priority in this manner of classifying the 
elements has been accorded Mendeleeff, although Meyer’s 
work, which was almost identical, was performed without 
knowledge of Mendeleeff’s efforts. The periodic system, as 
presented by Mendeleeff and Meyer, was based on the Octaves 
of Newlands, but differed from the work of the latter by in- 
cluding all of the then known elements. Previous to his death 
in 1907, Mendeleeff revised the periodic table,, modifying it 
to include all of the more recently discovered elements (1903). 
THE PERIODIC SYSTEM OF MENDELEEFF AN OUTLINE OF METALLURGY 
951 
Series 
Zero Group 
Group I 
Group II 
Group III 
Group IV 
Group V 
Group VI 
Group VII 
Group VIII 
0 
X 
1 
V 
Hydrogen 
H=1.008 
2 
Helium 
He=4.0 
Lithium 
Li=7.03 
Beryllium 
Be=9.1 
Boron 
B=11.0 
Carbon 
C=12.0 
Nitrogen 
N=14.04 
Oxygen 
0=16.00 
Fluorine 
F=19.0 
3 
Neon 
Ne=19.9 
Sodium 
Na=23.05 
Magnesium 
Mg=24.1 
Aluminum 
Al=27.0 
Silicon 
Si=28.4 
Phosphorus 
P=31.0 
Sulphur 
S=32.06 
Chlorine 
Cl=35.45 
4 
Argon 
Ar=38 
Potassium 
K=39.1 
Calcium 
Ca=40.1 
Scandium 
Sc=44.1 
Titanium 
Ti=48.1 
Vanadium 
V=51.4 
Chromium 
Cr=52.1 
Manganese 
Ma=55.0 
Iron Cobalt Nickel 
Fe=55.9 Co=59 Ni=59 (Cu) 
5 
Copper 
Cu=63.6 
Zinc 
Zn=65.4 
Gallium 
Ga=70.0 
Germanium 
Ge=72.3 
Arsenic 
As=75.0 
Selenium 
Se=79 
Bromine 
Br=79.95 
6 
Krypton 
Kr=81.8 
Rubidium 
Rb=85.4 
Strontium 
Sr=87.6 
Yttrium 
Y=89.0 
Zirconium 
Zr=90.6 
Niobium 
Nb=94.0 
Molybdenum 
Mo=96.0 
— 
Ruthenium Rhodium Palladium 
Ru=101.7 Rh= 103.0 Pd=106.5(Ag) 
7 
Silver 
Ag=107.9 
Cadmium 
Cd= 122.4 
Indium 
In=114.0 
Tin 
Sn=119.0 
Antimony 
Sb=120.0 
Tellurium 
Te=127 
Iodine 
1=127 
8 
Xenon 
Xe= 128 
Caesium 
Cs=132.9 
Barium 
Ba=137.4 
Lanthanum 
La=139 
Cerium 
Ce=140 
— 
— 
Osmium Iridium Platinum 
Os=191 Ir=193 Pt = 194.9 (Au) 
9 
— 
— 
— 
— 
— 
— 
10 
— 
— 
— 
Ytterbium 
Yb=173 
— 
Tantalum 
Ta=183 
Tungsten 
W=184 
— 
11 
Gold 
Au=197.2 
Mercury 
Hg=200.00 
Thallium 
Tl = 204.1 
Lead 
Pb=206.9 
Bismuth 
Bi=208 
— 
— 
12 
— 
— 
Radium 
Rd = 224 
— 
Thorium 
Th = 232 
— 
Uranium 
U = 239 
13 
R*0 
RH 
RO 
RH* . 
R2O3 
RHa 
RO* 
RH4 
R2O6 
RHa 
RO* 
RH* 
R2O7 
RH 
RO« 
TABLE OF THE PERIODIC LAW. (Mendeleeff, 1904.) 952 
AN OUTLINE OF METALLURGY 
A chart of the periodic system of the elements consists 
of 13 horizontal columns called series, numbered from zero to 
12, inclusive, subdivided into 9 perpendicular columns called 
groups, numbered from zero to 8, inclusive. The elements 
are arranged in the series from left to right in the order of 
their atomic weights, and in the perpendicular group columns 
according to their chemical properties. 
It will be noticed that certain spaces are unoccupied by 
elements because of breaks in the regular progression of the 
atomic weights, and which, if closed up, would throw the re- 
maining elements out of their natural groups. From this the 
inference is drawn that elements may yet be discovered to fill 
these vacant spaces. 
When Mendeleeff first devised the table there was a space 
in series 4, group III, another in series 5, group III, and still 
another in series 5, group IV. Two years later, in 1871, he 
declared his belief that elements would be found to occupy 
these spaces.- He described their properties and atomic 
weights, and named them eka-aluminum, eka-boron and eka- 
silicon. In 1878 Boisbaudrau, a French chemist, discovered 
gallium, eka-boron; in 1879 Nilson, a Swedish chemist, dis- 
covered scandium, eka-aluminum, and in 1886 Winkler, a Ger- 
man chemist, discovered germanium, eka-silicon, all of which 
corresponded to Mendeleeff’s predictions as to properties, and 
fit exactly in the vacant spaces. 
NEW ELEMENTS 
In Mendeleeff’s latest table lie includes two new elements, 
neither of which, so far as is known, have a place among the 
terrestrial elements. These two head the list and are desig- 
nated as x and y, both supposed to be gases and lighter than 
hydrogen. 
Coronium, found in the spectrum of the sun’s highest at- 
mosphere, beyond the tips of the sun’s flames and highest 
protuberances, is believed to coincide with y, whose atomic 
weight is estimated by Mendeleeff at 0.4, or possibly less. 
X is called Newtonium, after the famed English physicist. 
This gas element, according to Mendeleeff’s calculations, has 
an atomic weight of probably 0.000001. Arrhenius states that 
“its atoms ought, therefore, to be about 500 times lighter than 
electrons.” Now since electrons are 1,000 times smaller than 
the hydrogen atom, it naturally follows that it would require 
500,000 Newtonium atoms to equal one of hydrogen. 
Mendeleeff further believed that the element x, or New- AN OUTLINE OE METALLURGY 
953 
to ilium, is the substance from which the luminiferous ether, 
which pervades all space, is formed. 
THE ELEMENTS CONSIDERED IN GROUPS 
Tlie zero group of elements is composed of the gases of 
the helium family. These are all monoatomic and generally 
inert, forming no compounds with other elements. On ac- 
count of their scarcity, obscure nature and lack of combining 
power, their presence among the terrestrial elements was for 
a long. time unknown. It is only within recent years that 
they have been isolated. The original periodic table, there- 
fore, contained no zero group, because all but one of the ele- 
ments now embraced in it had at that time not yet been dis- 
covered. Helium was known by its spectrum only as a sun 
element. Because of their atomic weights, they naturally 
precede Group 1, but their presence in nowise invalidates the 
periodicity of the other elements. In fact, their discovery and 
position only confirms the previous findings. 
Take, for instance, the first triad of Series 4, argon, at. 
wt. 38, calcium, at. wt. 40.1 = 78.1 divided by 2 = 39.5. The 
atomic weight of potassium, the middle factor of the triad, 
is 39.1. Observe, again, the first triad of Series 8, xenon, 
at. wt. 128, barium, at. wt. 137.4 = 265.4 divided by 2 = 132.7. 
The atomic weight of caesium, the middle factor, is 132.9. 
When the elements in any group are considered closely 
it will be seen that while their atomic weights increase rap- 
idly from above downward, and they differ in other respects, 
yet there is in most cases a marked resemblance as to chem- 
ical properties. 
Prof. Duncan calls attention to the fact that each group 
may be arranged in two sub-groups, the elements embraced 
in each of which are very closely related. Group 2 is taken 
as an example. 
The elements in the order of their atomic weights are: 
Beryllium, magnesium, calcium, zinc, strontium, cadmium, 
barium, mercury and radium. By the sub-group arrange- 
ment the elements having the greatest number of common 
properties are brought together as follows: 
Sub-group A. 
Calcium. 
Strontium. 
Barium. 
Radium. 
Sub-group B. 
Beryllium. 
Magnesium. 
Zinc. 
Cadmium. 
Mercury. 954 
AN OUTLINE OF METALLURGY 
THE ELEMENTS CONSIDERED IN SERIES 
As before stated, the elements arranged in horizontal 
rows are termed series. 
Hydrogen is unlike any other element, because it is an 
essential component of all acids, and it, therefore, forms a 
series by itself. 
While there is a general similarity between the elements 
in one series to those in another, there is a marked and pro- 
gressive variation between the elements in the same series. 
First, the atomic weights rise from left to right, or from 1 
to 7, in comparatively regular gradations. Second, in each 
horizontal row the first element of the series is a well-marked 
metal or base-forming element, while the succeeding ones 
gradually merge from metallic into the non-metallic class, or 
acid-forming elements, with the exception of manganese, the 
seventh element of the fourth series. 
Third, in every series the valence toward oxygen ascends 
from 1 to 7, while the valence toward hydrogen or chlorine 
ascends from 1 to 4, and then uniformly descends to 1. 
The elements in Group 8 belong to the metallic class, 
have similar properties to each other, but do not fit in the 
scheme of the octaves, as their presence in the beginning of 
the succeeding series would disarrange the grouping of the 
remaining elements, according to their chemical group simi- 
larities. They are, therefore, placed in Group 7, outside of 
the octave system, although their valences are continuous 
with those of the regular table. 
From the many correlated facts observed, the periodic 
laiv has been formulated as follows: The properties of ele- 
ments are periodic functions of their atomic weights. 
Many other interesting relations have been disclosed, the 
details of which can be found in various works on advanced 
chemistry, particularly Hr. Gordin’s Inorganic Chemistry, 
in which will be found a clear and concise statement of the 
periodic correlations of the elements and of the imperfections 
of the system as well. These few crudely-stated facts have 
been introduced with the idea of creating a desire for further 
knowledge in this most interesting field. 
The following works have been consulted and largely 
utilized in the presentation of the foregoing facts: 
Gordin’s Inorganic Chemistry. 
Smith’s General Chemistry for Colleges. 
Levy and Willis, Radium. 
Arrhenius’ Theories of Chemistry. AN OUTLINE OF METALLURGY 
955 
Gibson’s Scientific Ideas of To-day. 
Martin’s Triumphs and Wonders of Modern Chemistry. 
Kennedy Duncan’s Some Chemical Problems of To-day 
and the New Knowledge. 
Duff’s Physics. 
Ganot’s Physics. 
Metals 
Of the fifty-two metals, about fifteen are used in the arts 
and sciences in their true metallic condition, as well as in com- 
bination with each other and with the non-metallic elements. 
A metal is an opaque elementary substance which, with 
the single exception of mercury, is solid at ordinary tempera- 
ture; is a good conductor of heat and electricity; has a metal- 
lic luster; has the property of replacing hydrogen in acids 
forming salts, and is electropositive as compared with the 
non-metallic elements. 
METALLOIDS 
Certain of the non-metallic elements, iodine, arsenic, phos- 
phorus, silicon, sulphur and carbon, possess to a greater or 
less degree the properties attributed to metals, especially the 
power of reflecting light, and which is known as metallic 
lustre. 
They are all more or less opaque, while carbon is a conduc- 
tor of both heat and electricity, which properties, with the ex- 
ception just noted, are confined exclusively to the metals. 
This group of elements, therefore, while not metals, are called 
metalloids, from the resemblance in some respect to the metals. 
FORMS OF MATTER 
Matter, as previously stated, presents itself to our senses 
in three distinct forms, as solids, liquids, or gases. These 
forms, in most instances and under proper conditions, are 
susceptible of change. 
For example, a metal liquefies when subjected to heat. 
Water vaporizes under heat and solidifies at low temper- 
atures. 
Hydrogen at extremely low temperature and under high 
pressure liquefies and can be solidified on further reduction of 
temperature and increase of pressure. 
OCCURRENCE OF METALS IN NATURE MINERALS 
Most of the metals are found in combination with some of 
the non-metallic elements, as oxides, sulphides, or carbonates, 
etc. 956 
AN OUTLINE OF METALLURGY 
Usually the combinations are of such nature as to entirely 
mask their metallic character and render them unrecognizable 
as metals, and, when so occurring, are called minerals. 
NATIVE METALS 
Gold, silver, copper, platinum, mercury, bismuth, anti- 
mony and iron frequently occur in nature in their true metallic 
condition, and are known as native metals. Those just men- 
tioned are about the only ones so occurring. 
ORES 
When a mineral is found which contains a particular metal 
in sufficient quantity to pay for its extraction on a commercial 
basis, it is called an ore of that metal. 
NOBLE METALS 
Metals included under this head are those whose com- 
pounds with oxygen are decomposable by heat alone at a tem- 
perature not exceeding redness. The following comprise the 
list of noble metals. 
Gold, silver, platinum, palladium, rhodium, ruthenium, os- 
mium, iridium, mercury. 
BASE METALS 
Under this classification are included the metals whose 
compounds with oxygen are not decomposable by heat alone, 
but retain oxygen at high temperatures. 
PHYSICAL PROPERTIES OF METALS 
Since there are properties common to all metals, these 
properties will be briefly explained before taking up the study 
of the individual metals. 
Some of these properties, common to all, but which, of 
course, vary, according to the individual metal, are atomic 
weight, specific gravity, melting point, malleability, ductility, 
tenacity, conductivity of heat, and electricity, specific heat, 
color, etc. 
ATOMIC WEIGHT 
The atomic weight of an element is the weight of one of 
its atoms compared with the weight of an atom of hydrogen. 
Hydrogen is the lightest of all known substances, and is 
taken as the unit or 1 of the atomic scale. Atomic weight, AN OUTLINE OF METALLURGY 
957 
therefore, may be considered as the proportion by weight in 
which elements unite chemically. 
SPECIFIC GRAVITY 
The specific gravity of any substance, whether solid, liquid 
or gas, is the measure of its density. The standard or unit of 
measurement of solids and liquids is water, and that of gases 
is hydrogen. 
The specific gravity of a solid or a liquid of a given bulk 
is its relative weight to a like bulk of water under like condi- 
tions of temperature and pressure. 
In order to find the specific gravity of any solid, it is first 
weighed in air, then in water, and its weight in water deducted 
from its weight in air. The weight in air is then divided 
by the difference thus obtained, and the result represents 
the specific gravity of the substance. A convenient formula 
for determining the specific gravity of solids and liquids is 
as follows: 
Let W=weight of substance in air. 
Let W!=weight of substance in water. 
Let sp. gr.=specific gravity. 
W 
ien yy yyi = SP- &r- 
The specific gravity of most metals can be somewhat in- 
creased by hammering, rolling, wire drawing or cold pressure. 
The specific gravity of aluminum, it being the lightest 
metal of commercial importance, is 2.5, while osmium, which 
is the heaviest, is 22.47. 
Comparing two cubes of equal size of aluminum and os- 
mium, the first would weigh 2.5 and the latter 22.47 times more 
than an equal bulk of water. 
MELTING POINT 
When an element or substance is changed from a solid to 
a liquid state as the result of thermal increase, the point at 
which such change occurs is called its “melting’’ or “fusing” 
point. 
*When a liquid is reduced to a solid state by lowering its 
temperature, the point where such change occurs is called 
its “freezing” point. 
The melting point and the freezing point of a metal usually 958 
AN OUTLINE OF METALLUEGY 
approach each other very closely, but are never quite the 
same. They are so close at times as to be incapable of regis- 
tration by the thermometer. 
Some substances expand on being melted, while others 
contract. When a substance expands on being melted, and 
it is subjected to increase of pressure above normal during 
the fusion process, the effect is to raise its melting point. On 
the other hand, a substance which contracts on melting, when 
subjected to increase of pressure, has its fusing point de- 
creased. By reversing the pressures, opposite results are ob- 
tained. 
The range of fusibility or the melting points of the various 
metals differs greatly. Mercury melts at—38.9 deg. C., and, 
consequently, is liquid at ordinary temperatures. Bismuth, 
tin, lead, zinc and antimony melt below a red heat; aluminum 
requires a red heat; gold, silver and copper a bright red heat; 
iron and nickel, an intense white heat, while platinum and 
palladium are still more refractory, fusing only in the electric 
arc or the oxyhydrogen flame. 
Some metals, when heated beyond their melting points, 
readily vaporize, zinc, antimony and mercury being the most 
common examples of this class. As a matter of fact, all of 
the metals can be volatilized if subjected to a sufficiently high 
temperature. 
Most of the metals pass from the solid to the liquid state 
under the influence of heat and under increased temperature 
volatilize. Osmium, however, is an exception to this rule, as 
:t passes from tl*e solid to the volatile condition without as- 
suming the liquid state. 
The following table, by Pouillet, will give an idea of tem- 
perature as displayed by color: 
°C. °F. 
Incipient red corresponds to 525 977 
Dull red corresponds to 700 1292 
Incipient cherry red corresponds to 800 1472 
Cherry red corresponds to 900 1652 
Clear cherry red corresponds to 1000 1832 
Deep orange corresponds to 1100 2012 
Clear orange corresponds to 1200 2192 
White corresponds to 1300 2372 
Bright white corresponds to 1400 2552 
Dazzling white corresponds to 1500 2732 AN OUTLINE OF METALLURGY 
959 
Most metals expand when heated, and contract on cooling. 
Within certain limits the expansion is proportional to the 
degree of heat to which they are subjected. There are, how- 
ever, certain exceptions to this rule. Antimony expands at 
the moment of becoming solid, and bismuth occupies more 
space in the solid than in the liquid state. This property ren- 
ders these metals particularly useful in alloys of type and 
fusible metals, where sharp, well-defined castings are desir- 
able. 
MALLEABILITY 
Malleability is that property of metals by which they may 
be beaten out or otherwise extended into thin sheets without 
a break in the continuity of their surfaces. This property 
varies in different metals, some possessing it to a marked 
degree, while in others it is almost entirely absent. 
Gold is the most malleable of all the metals. It can be beaten 
out into extremely thin attenuated sheets, 1/300000 of an inch 
thick. In other words, it would require 300,000 sheets laid one 
upon the other to measure an inch in thickness. Gold, there- 
fore, is taken as the standard or unit of measurement of the 
degree of malleability of metals, and is rated “first rank.” 
This property is seriously impaired by the presence of 
impurities, and also by heat, although the latter tends to in- 
crease the malleability in zinc. This metal, when cast, is 
crystalline and brittle, but when heated to about 150°C., it is 
capable of being rolled into thin sheets, and these retain their 
malleability to a considerable degree when cold. 
Metals of a crystalline structure are almost totally devoid 
of this property, while those of a soft and tenacious character 
are the most malleable. 
DUCTILITY 
Ductility is that property possessed by metals by means 
of which they may be drawn out into wire or rods, by lateral 
compression, without breaking. 
Gold possesses this in the highest degree, since it can be 
drawn out into the most delicate wire; a piece one mile in 
length having been drawn from less than one gram weight. 
The softness and tenacity of a metal control the degree 
of ductility. 
Ductility is affected by heat, which increases this property 
in some metals and decreases it in others. 
Lead is the least ductile because of the slight tenacity by 
which the molecules are held together. Bismuth and anti 960 
AN OUTLINE OF METALLURGY 
mony are examples of metals in which this property is almost 
wholly absent because of their crystalline structure. 
Steel is extremely ductile, and is now being drawn into 
wire 1/1000 of an inch in diameter for commercial purposes. 
Ductility is modified by mechanical working, the latter 
affecting metals to such an extent at times as to render them 
unworkable until this property is again restored by annealing. 
ANNEALING 
This process consists in heating metals and cooling, slowly 
in some cases, and rapidly in others. 
Annealing changes metals from the hardened condition 
produced by hammering, rolling, wire-drawing, burnishing 
and polishing, to a soft, pliable condition. 
It is supposed that the molecules in a metal, changed by 
the processes mentioned, are under a greater or less degree 
of tension which, while not of sufficient force to do so, tends 
to return them to their former relation. Under the influence 
of heat, and, as before stated, in the case of some metals, fol- 
lowed by sudden chilling, as when plunged into cold water 
while hot, the tension referred to is destroyed and the mole- 
cules are brought to a normal relation to each other under 
the changed conditions. 
The degree of hardness developed in metals by mechan- 
ical working is dependent upon the character and amount of 
force applied within and up to certain limits. In other words, 
a moderate amount of manipulation will produce a moderate 
degree of hardness, while an excessive amount of working will 
produce the extreme degree of hardness capable of being pro- 
duced in a particular metal. 
If a metal be worked to its extreme limit of hardness, and 
is then annealed, a greater or less amount of warpage is 
noticeable. This is apparent in swaging metal plates. The 
base, when swaged, may lie in absolute contact with the die, 
yet, when annealed, the adaptation will be found to have 
changed. A slight amount of swaging will again restore the 
cdaptation, and, if annealed again, very little, if any, change 
r"' be noticeable. 
his fact renders it imperative that matrices of platinum 
or Told foil, when adapted to cavities for inlay work, should 
be annealed thoroughly, and a final adaptation secured before 
ntroducing the porcelain for baking. By observing this sug- 
gestion, misfits traceable to this cause are obviated. AN OUTLINE OE METALLURGY 
961 
Intentional or accidental alloying of the metals also modi- 
fies their degrees of ductility, sometimes increasing, and again 
diminishing, this property. The slightest trace of lead, zinc, 
bismuth or antimony in gold impairs its ductility to a marked 
degree, hence the necessity in dental laboratory procedures of 
keeping gold perfectly free from these baser metals. 
TENACITY 
Tenacity is that property of metals which enables them to 
resist stress or dead weight when applied to rods or wires in 
the direction of their length. 
This property, as well as those of malleability and duc- 
tility, is greatly affected and readily influenced by the pres- 
ence of other metals or impurities, and by heat, which in some 
cases increase and in others decrease these various properties. 
The tenacity of iron, for instance, is greatly increased by 
the addition of a small per cent of carbon, while the presence 
of silicon diminishes it. 
In addition to the ordinary or comparative tests of te- 
nacity of a metal, several other kinds should be considered, 
and these are classified according to the externally acting- 
force. 
Ordinary tenacity, as before stated, relates to resistance 
to traction or direct pull; relative tenacity, resistance to frac- 
ture; reactive tenacity, resistance to crushing; shearing te- 
nacity, resistance to lateral displacement; torsional tenacity, 
resistance to twisting. 
When metal bars are subjected to a certain amount of 
tension, permanent elongation occurs. If the tension is not 
sufficient to produce this result, the bar will return to its orig- 
inal length. This line of division is called the elastic limit. 
In machine construction, when wires or rods are used, it 
is essential that such parts be composed of metals of suitable 
kind, and be of sufficient size, to withstand stress without 
passing beyond the elastic limit. 
TENSILE STRENGTH 
The tenacity of tensile strength of metals and alloys is 
tested by placing a bar of the metal of one inch sectional area 
in a suitable testing machine and applying stress sufficient to 
fracture it. The following table will convey an idea of the 962 
AN OUTLINE OF METALLURGY 
wide range of difference in tenacity of various metals and 
alloys. (From Carnegie’s handbook.) 
Average, 
Pounds. 
Brass 18,000 
Brass, wire 49,000 
Bronze or gunmetal 36,000 
Copper, cast 19,000 
Copper, bolts 36,000 
Copper, wire 16,500 
Iron, cast 16,500 
Iron, wrought 53,000 
Iron, wire 70,000 to 100,000 
Lead, sheet 3,300 
Steel 50,000 to 80,000 
Tin, cast 4,600 
Zinc 7,000 to 8,000 
This property refers to the amount of force which can be 
resisted by metals under stress without permanent deforma- 
tion or “set” being produced. 
The “modulus of elasticity” is the force that would be re- 
quired to double the length of a bar if its elasticity remained 
perfect. The “modulus” is an index of the stretching capac- 
ity of a metal. 
ELASTICITY 
FLOW 
Metals which in a solid state can be shaped into any re- 
quired form by pressure are said to possess the property of 
flowing. 
Stampings, lead pipe, rods, coins, medals, etc., are ex- 
amples of what can be accomplished through this property. 
The flowing property depends upon a combination of other 
qualities, such as malleability, ductility and toughness, to- 
gether with a sufficient amount of tenacity to permit the mole- 
cules of metals to roll over each other without adhesion being 
destroyed. 
CONDUCTIVITY OF HEAT 
Conductivity of heat refers to the property of different 
substances for transmitting heat. The degree of rapidity of 
heat transmission varies greatly in different substances, 
metals being the best conductors. This property also varies AN OUTLINE OF METALLURGY 
963 
in the different metals, silver being the best, and it is, there- 
fore, taken as the standard of measurement, and is rated 100. 
Conductivity of electricity refers to the capacity of metals 
for receiving and transmitting a current of electricity. Silver 
in this case also is the best conductor, and is taken as the 
standard of comparison, being rated 100. As a general thing, 
the best conductors of boat are also the best conductors of 
electricity. There are, however, exceptions to this. 
Those metals ranking low in the scale of conductivity of 
electricity offer resistance to the passage of a current. This 
resistance is very apparent in platinum, iron and nickel, and 
as resistance to the passage of a current is marked by a rise 
in temperature, these metals, as well as the alloy known as 
German silver, are used for rheostat and electric furnace con- 
struction. 
The electric furnace, commonly used in porcelain work, 
consists of a metal case lined with fireclay, so shaped as to 
give a muffle form to the interior, in which the piece to be 
baked is placed. In the inner walls of the fireclay is imbedded 
fine platinum wire, and as the current passes through this, it 
becomes heated, and the temperature in the interior of the 
furnace is gradually raised to the point of fusion of the por- 
celain, usually about 1200° C. 
The following table gives the comparative conductivity of 
heat and electricity of fourteen metals, and, as before stated, 
silver heads the list in both tables: 
CONDUCTIVITY OF ELECTRICITY 
Heat. 
Silver 100 
Copper 85 
Cold 53.2 
Aluminum 31.3 
Zinc '.. 28.1 
Cadmium 20.1 
Tin 15.5 
Mercury 13.5 
Iron 11.9 
Nickel 
Lead 8.5 
Platinum 8.4 
Antimony 4.0 
Bismuth 1.8 
Electricity. 
Silver 100 
Copper 97.8 
Cold 76.7 
Aluminum 65.5 
Zinc 29.6 
Cadmium 24.4 
Iron 14.6 
Platinum 14.5 
Tin 14.4 
Nickel 12.9 
Lead 8.4 
Antimony 3.6 
Mercury 1.8 
Bismuth 1.4 
Nickel 
The conductivity of a substance, as a rule, diminishes with 
a rise in temperature. 964 
AN OUTLINE OF METALLURGY 
EXCEPTION TO THE GENERAL RULE OF CONDUCTIVITY OF 
ELECTRICITY 
One important exception to this might be mentioned here. 
The oxides of some of the metals, especially when combined, 
exhibit the opposite quality, viz., being non-conductors when 
cold and conductors when heated. This principle is made use 
of in the construction of pyrometers or instruments for meas- 
uring heat units and applied to poru lain furnaces. 
Two methods are employed. In one case a thermopile, 
an apparatus consisting of two or more plates of dissimilar 
metals, which upon being heated generate a mild current of 
electricity, is built in the back of the furnace. As the fur- 
nace gradually rises in temperature, the current in the ther- 
mopile increases, which is indicated by a mila-voltmeter modi- 
fied to correctly register the fusing point of the various por- 
celains. 
In the other case, a Nernst glower, a small rod composed 
of the oxides of zirconium and yttrium, which when cold is a 
non-conductor, but which when heated readily transmits a 
current, is placed in the muffle and connected with an inde- 
pendent dry cell current. 
As the furnace temperature rises the dry cell current finds 
its way through the glower and is registered by an apparatus 
similar to the one before described. 
Profs. Dewar and Jenkins, in determining the conduc- 
tivity of metals and alloys at very low temperatures, found 
that the resistances of pure metals decrease in such ratio as 
to convey the idea that, if absolute zero could be obtained, 
all resistance would vanish. The resistance of alloys, how- 
ever, does not diminish in the same ratio. For example, at— 
200° C. the alloys—platinoid, German silver, platinum silver 
and phosphor bronze—show nearly the same resistance as at 
0° C. 
An illustration of the wide range of conductivity of the 
metals can be presented by making a chain composed of al- 
ternative links of platinum and silver wire of the same size 
and passing a current of electricity through it. The platinum 
links will become heated, while the silver links will remain 
normal except at their junction with the platinum, where the 
heat from the latter is transmitted by contact. 
SPECIFIC HEAT 
It has been found that different metals are capable of 
absorbing different amounts of heat when subjected to the 
same degree of temperature. AN OUTLINE OF METALLURGY 
965 
The amount of heat necessary to raise one kilogram of 
water through one degree of temperature, from 4° to 5° C., 
is taken as the unit or standard of specific heat, and this is 
called the thermal unit. 
The quantity of heat necessary to raise a kilogram of mer- 
cury through one degree C. is only 0.033 of the heat unit, and 
this fraction expresses the specific heat of mercury relatively 
to water. It, therefore, follows that the same quantity of heat 
required to raise one kilogram of water through one degree 
of temperature would produce an equal increase in temper- 
ature in about 30 kilograms of mercury. 
The greater the specific heat of a substance, the greater 
the heat necessary to raise the temperature through any given 
degree, and conversely, the less the specific heat, the smaller 
quantity of heat required. 
TABLE OF SPECIFIC HEAT 
Mercury 0.03332 
Gold 0.03244 
Iron 0.1138 
Nickel 0.1086 
Cobalt 0.1070 
Zinc 0.0956 
Copper 0.0952 
Palladium 0.0593 
Silver 0.0570 
Cadmium 0.0567 
Tin 0.0562 
Antimony 0.0508 
Lead 0.0314 
Palladium 0.0308 
Platinum 0.0311 
EXPANSION 
It is a well-known law of physics that substances expand 
when heated. 
This movement is particularly marked in metals, since 
they are good conductors of heat. 
The co-efficient of expansion of any substance is the 
amount which the unit of length (surface of volume) expands 
in passing from 0° to 1° C. 
The co-efficient of expansion is constant in metals crystal- 
lizing in the regular system. In the others, the expansion 
varies according to crystallization, this movement occurring 
in the direction of the various axes. Such metals are usually 
tested by compressing their powders. 
In the industrial field a thorough knowledge of the ex- 
pansion of different material is essential so that provision 
THE CO-EFFICIENT OF EXPANSION OF SUBSTANCES 966 
AN OUTLINE OF METALLURGY 
may be made for compensating for it in the construction of 
buildings, bridges, and large pieces of machinery. 
In assembling bridges in the dental laboratory it is es- 
sential that an investing material be used whose co-efficient 
of expansion is about equal to that of gold. 
If one is employed whose co-efficient of expansion is much 
greater, the assembled pieces will be moved apart as the in- 
vestment expands under heat, and while in that changed re- 
lation become fixed by the solder, the result being that the 
bridge is lengthened. 
The following table gives the linear expansion occurring 
in metals when raised from a temperature of 0° to 100° C. 
The fraction represents the ratio of linear expansion per 
length of rod: 
Cadmium 003067 or 1/326 
Lead 002932 “ 1/342 
Zinc 002915 “ 1/343 
Aluminum 002307 “ 1/432 
Tin 002232 “ 1/448 
Silver 001930 “ 1/518 
Copper 001672 “ 1/598 
Bismuth 001620 “ 1/617 
Gold 001451 “ 1/689 
Nickel 001270 “ 1/787 
Iron 001070 “ 1/934 
Antimony 001050 “ 1/952 
Platinum 000900 “ 1/1123 
COLOR 
Most metals are gray or white in color, these colors merg- 
ing into bluish tinges in some cases. Gold is a rich yellow 
color in masses, but transmits a greenish tinge in thin atten- 
uated sheets. Copper is of a decidedly red color. The color 
of most metals is changed by alloying with other metals. 
Gold alloyed with silver is changed to a greenish tinge, 
and when alloyed with copper a decidedly red color is im- 
parted to it. By combining silver and copper in proper pro- 
portions, gold may be reduced in fineness without material 
change in color. 
WELDING 
This process consists in uniting two pieces of metal to- 
gether by pressure so as to form one compact piece. The 
requisites of a metal necessary to successful welding are that 967 
AN OUTLINE OP METALLURGY 
it must be clean, soft, and that it should possess considerable 
malleability and toughness. 
In .the case of iron, some of these properties are devel- 
oped only at a high temperature, in which condition it is in 
a pasty state. The surfaces to be united are cleaned and cov- 
ered with borax to remove any oxide that may be present 
and prevent further oxidation, or sand can be used also, which 
by combining with the iron forms a fusible silicate, and which, 
under the blows of the hammer, is forced out from the contact 
surfaces. 
When subjected to hammering or pressure, the molecules 
of metal are capable of interpenetrating or diffusing into and 
among each other so as to form a continuous piece. 
Steel must be welded at a considerably lower temperature 
than iron because of its lower fusing point. The carbon also 
is liable to burn out when overheated, and its quality thus be- 
come impaired. Because of the difference in the melting 
points, and for the reason just stated, it is difficult to weld 
iron and steel together. 
Gold is an example of a metal which can be welded cold. 
In the form of foil, pure gold is rolled into pellets or folded 
into small pieces and packed into tooth cavities by mallet 
force or hand pressure. Under favorable conditions it can 
be worked into a mass seemingly as solid as though it had 
been cast. 
In electric welding, the pieces to be united are placed in 
a suitable device for holding them in proper contact and re- 
lation to each other, and a powerful current of low tension 
is passed from one piece to the other. The high resistance at 
the junction, caused by imperfect contact, develops an intense 
heat at this point, and when heated sufficiently the surfaces 
are jammed together and union occurs. 
The metals which weld most readily are gold, silver, tin, 
lead, iron and nickel. 
As a matter of fact, a number of the metals, when pow- 
dered and subjected to intense pressure, can be welded cold. 
The following table, by Professor Spring, shows the 
amount of compression required to unite those listed into a 
solid mass: 
Tons per 
sq. inch. 
Lead 13 
Tin 19 
Zinc 38 968 
AN OUTLINE OE METALLURGY 
Antimony 38 
Aluminum '38 
Bismuth 38 
Copper 33 
Lead flows at 33 
Tin flows at 47 
WELDING COPPEli TO IRON 
A remarkable yet simple method of welding copper to 
iron is being employed for many purposes in the industrial 
fields. The copper and iron objects it is desired to unite are 
bound in contact, placed in a crucible, and finely ground retort 
carbon, moistened slightly with sugar water to make it ad- 
hesive, is packed closely around them. The crucible is then 
heated in a furnace for half an hour at a temperature about 
midway between the melting point of copper and iron, when 
perfect fusion of the two metals will occur, the welded joint 
being tougher than either of the two metals. 
A peculiar fact concerning this process is that the sur- 
faces of the metals to be united need not be prepared, cleansed 
or fluxed in any manner, the graphite and sugar taking the 
place of the ordinary fluxes, clearing away any oxide that 
may be present, and preventing the atmospheric oxygen from 
getting to the joint. The molecular cohesion is as strong and 
perfect between copper and iron as between the molecules of 
the individual metals; such a weld is not to be compared to 
the ordinary brazed joint, which is merely an imperfect super- 
ficial surface union. 
The process is utilized in welding steel teeth to cast iron 
wheels, in joining pieces of wrought iron where ordinary 
welding operations are not practicable, in the construction 
of large gun projectiles, in ship construction, in the electrical 
and many other fields where an absolute union between pieces 
of similar as well as dissimilar metals is desirable. Professor 
Simpson, of London, is given credit for this remarkable 
method of welding copper to dissimilar metals. 
ALUMINOTHERMY 
From 1760, when Moreau, a French chemist, named the 
white substances he obtained by calcining alum, “alumina,” 
because he believed it to be the oxide of a metal, until Wohler 
isolated it in 1827, repeated but futile efforts were made by 
many to discover some means of reduction of aluminum from 
its ores. AN OUTLINE OF METALLURGY 
969 
The strong affinity of aluminum for certain non-metallic 
elements, particularly oxygen, is very marked. It is only 
through the action of a powerful electric current together 
with suitable fluxes that the oxide of aluminum is decomposed. 
When freed from oxygen, however, aluminum under ordinary 
conditions is not readily oxidized, hut under favorable con- 
ditions the two elements most energetically unite, with the 
evolution of intense heat. 
This places aluminum among the most powerful of the 
reducing agents, since many metallic oxides which cannot be 
broken up with carbon are readily reduced by it. Professor 
Goldschmidt, of Essen, Germany, in 1904, discovered this fact 
and applied it to industrial purposes. So effective has it 
proven that “ alumino-thermics, ” as the process is called, 
occupies a unique and previously unfilled place in high tem- 
perature chemical, metallurgical, and industrial fields. 
The process is comparatively simple and easy of applica- 
tion. Finely granular, metallic aluminum together with the 
oxide of iron and some substance to act as a flux, as fluor spar, 
are placed in a suitable receptacle. Some magnesium filings 
mixed with barium or sodium peroxide — a mixture highly 
combustible—are thrown on top to “kindle the fire,” or start 
chemical action. 
Almost instantly there is a flash, the development of a 
temperature of more than 3000 C., and in the bottom of the 
crucible lies a little button of iron with a film of slag, the oxide 
of aluminum, covering its surface. 
A mixture of granular aluminum and oxide of iron is sold 
for industrial purposes under the name of “thermit.” This 
mixture when placed in a very simple hopper-like apparatus 
from which it is fed to the point desired, constitutes a most 
powerful, portable blacksmith shop. It is used for uniting 
the ends of street car rails, welding them together to form a 
“continuous rail.” Large castings of iron or steel when 
broken can be perfectly welded by this means, and, as before 
intimated, the oxides of many of the metals can be easily and 
quickly reduced without the annoying combinations of metal 
with carbon that so frequently follow ordinary fuel reduction 
processes. 
TEMPERATURES, COMMON AND EXTRAORDINARY 
Although most of the metals can be welded cold, under 
heavy pressure, it is found more convenient as well as eco- 
nomical to render the surface to be united plastic by heat, so 970 
AN OUTLINE OE METALLURGY 
that the molecules may more readily interpenetrate and mo- 
lecular union be established. 
The degree of heat necessary to apply in successful weld- 
ing operations coincides closely with the fusing {mints of the 
metals to be united, and in soldering operations with the fus- 
ing point of the solder employed. 
The following list indicates some of the temperatures or- 
dinarily employed in soldering and welding operations, as 
well as some developed for special purposes. Comparative 
heat of the sun and hottest stars as indicated by the spectro- 
scope is also given. 
180 to 200 C soft soldering operations. 
1000 to 1200 C hard soldering, as silver and the various 
alloys of gold. 
1800 C is about the highest temperature attainable in a 
fuel furnace on account of the fire clay lining fusing at this 
point. 
2000 C represents about the temperature of the oxy-hydro- 
gen flame. 
3000 to 3300 C. Thermit. 
3400 C oxy-acetylene blow-pipe. 
3500 to 4000 C. electric arc. 
5000 C. cordite, confined and exploded exerts a pressure 
of 50 tons per square inch. 
6000 C. estimated temperature of the sun. 
30000 C. estimated temperature of some of the hottest 
stars (Lockyer). 
The last of these records can, of course, he only approx- 
imate, since time, space, refraction of light, and other possible 
sources of error, detract from the accuracy of the spectro- 
scopic scale, by means of which temperature readings of ce- 
lestial spheres are determined. 
Even Lockyer’s temperature estimates, astonishing though 
they seem, pale into insignificance when compared with those 
of Arrhenius, who suggests a possible temperature of 7,000,000 
C. in some of the larger stellar bodies, which, of course, con- 
sist of elements in a highly rarefied gaseous state, and in an 
intensely heated and active condition. 
SOLDERING 
Soldering consists in uniting the surfaces of metals to- 
gether by heat without pressure. This is usually accomplished 
by the interposition of another metal or alloy, called a solder, AN OUTLINE OF METALLURGY 
971 
that fuses at a lower temperature than the metals to be united. 
Soft soldering is accomplished by using a solder that fuses 
below a red heat, and hard soldering by means of one that 
fuses above a red heat. 
Autogenous soldering is a process of uniting metals by 
direct fusion of their contact surfaces, and is used principally 
in plumbing operations. In crown and bridge work this 
method is sometimes employed for uniting the two ends of a 
gold band together without the interposition of solder, and 
is commonly termed sweating. 
In all three methods of soldering it is essential that a flux 
be used. This prevents oxidation of the solder and surfaces 
to be united, and also dissolves any oxide that may be present. 
In hard soldering and sweating operations, borax or a solu- 
tion of boracic acid is used most frequently. For soft solder, 
chloride of zinc, to which a little sal ammoniac is sometimes 
added, is most frequently used. 
Rosin is also used for this purpose, and in plumbing op- 
erations where lead joints are to be united, stearin, or tallow, 
is often employed. 
CONDITION ESSENTIAL TO SUCCESSFUL SOLDERING 
The conditions necessary to successful soldering are as 
follows: 
1. Close contact of the surfaces to be united. 
2. Exposure of clean, bright surfaces over which the 
solder is to flow. 
3. Use and proper distribution of a suitable flux. 
4. A solder which will fuse at a slightly lower tempera- 
ture than the metals on which it is to be used, and which 
will flow freely. It should also conform, as closely as possible, 
in color and fineness to the metals to be united. This is a 
necessary consideration in gold dental substitutes. 
5. There should be a gradual and uniform application 
and distribution of heat, and in dental operations involving 
the use of porcelain facings, the flame should be directed 
around the base and sides of the investment to drive off the 
moisture, heat the porcelain and allow it to expand before 
the platinum pins are heated, otherwise fracture of the por- 
celain is likely to occur. 
6. The reducing flame should be used to prevent oxida- 
tion of the solder and the surfaces to be united. 972 
AN OUTLINE OF METALLURGY 
THE STRUCTURE OF FLAME 
To solder successfully, it is necessary to understand the 
structure of flame. A common candle flame will serve as an 
illustration. A flame of this character consists of four parts: 
(1) a dark central zone or supply of unburned gas surround- 
ing the wick; (2) the luminous zone or area of incomplete 
Fig. 955.— Cut of Candle Flame 
I Semi-Luminous Flame 
II Luminous Flame 
III Unburned Gas Zone 
IV Carbon Monoxid Flame 
combustion immediately outside the inner zone; (3) the outer 
or non-luminous zone, or area of complete combustion; (4) a 
deep blue flame at the base which extends only a slight dis- 
tance upward, consisting of carbon monoxide gas. The cen- 
tral zone of unburned gas is generated by the heat of the 
flame acting on and decomposing the fat, and is highly 
charged with carbon. Tn the luminous flame the particles of 
carbon in the inner zone float outward and become heated and 
incandescent, imperfect combustion occurring, since the sup- 
ply of oxygen is insufficient to form C02. 
Tn the outer zone the supply of oxygen from the surround- 
ing air is sufficient to produce complete combustion. 
The small, deep blue part at the base of the flame con- 
sists of carbon monoxide gas. AN OUTLINE OF METALLURGY 
973 
THE BUNSEN FLAME 
In the Bunsen flame the gas is admitted into the base of 
the burner, and passes up through a tube to the point of ig- 
nition. Near the bottom of the tube are openings for admit- 
ting air. As the gas passes upward, the air is drawn in also, 
and mixes with the gas; and when ignited the flame burns 
without luminosity, but with intense heat, because the admitted 
air furnishes the necessary amount of oxygen for complete 
combustion. 
THE BLOWPIPE FLAME 
The blowpipe usually consists of two tubes—a large outer 
one for conducting the gas, and a small inner one for admit- 
ting the air—and so shaped as to be convenient to handle. 
(See page 974.) 
When in operation the air is forced in the center of the 
flame through the inner tube by compression, and the requisite 
amount of oxygen for complete combustion thus supplied. 
The blowpipe flame consists of three zones, an inner one 
of mixed unburned gas and air; a middle zone of bluish tinge, 
Fig. 956.— Bunsen Flame 974 
AN OUTLINE OF METALLURGY 
and an outer zone, slightly yellowish in color. Just beyond 
the tip of the inner blue flame is a point termed the reduc- 
ing flame. If this flame be directed upon the oxidized surface 
of a metal, for example, a copper coin, the surface is immedi- 
ately brightened, and the oxide removed. This is due to the 
presence of particles of carbon in excess in this part of the 
flame uniting with the oxygen in combination with the copper, 
and under the influence of heat C02 is formed, and passes off 
as a gas, leaving the metal clean and untarnished. 
When the flame is removed, however, the oxygen from the 
air immediately re-combines with the copper again, unless 
some means, such as a flux, like borax, is used to prevent it. 
Near the extremity of the outer cone is a point known 
as the oxidizing flame, so-called because, when applied to 
Fig. 957.— Blowpipe Flame 
metallic surfaces, regardless of liow bright and clean, they 
immediately become oxidized by the action of the external air. 
In all soldering operations, therefore, care should he taken 
to cover the solder and the surfaces over which it is to flow 
with flux, and apply the reducing flame. 
When solder is applied in considerable bulk, as in back- 
ing crowns and dummies, in bridge work, the flame of the 
blowpipe should be continued some little time upon the fused 
solder, to permit the flux in the deeper parts to find its way 
to the surface. If this precaution is not observed, the re- 
tention of the flux in the solder causes pits to form through- 
out the mass, and in grinding down and finishing the piece 
these are frequently exposed. When this condition occurs, 
the case requires resoldering, or the exposed pits must be 
filled by plugging with material of essentially the same char- 
acter as that of which the piece is constructed. AN OUTLINE OF METALLURGY 
975 
MICRO STRUCTURE OF METALS 
The study of the structure of metals under the microscope 
is a field apart from that of general metallurgy, and may 
more properly be included in the science of metallography. 
It is impossible to obtain sections of metals transparent 
enough for examination in the ordinary manner under the 
microscope, therefore they must be studied by reflected light. 
The surfaces of specimens to be examined are first ground, 
and then highly polished. 
This is accomplished by the use of stones and emery paper 
of gradually increasing fineness, and afterwards finishing 
with fine polishing powder. 
The polished surface is then etched with very dilute nitric 
acid. A mixture of equal parts sulphuric acid and bichromate 
of potassium, with ten times its bulk of water, is frequently 
used for this purpose. 
The etching process brings out the structure of the metal 
or alloy being examined, so that under the microscope it is 
readily determined whether the structure is crystalline, gran- 
ular, or amorphous. 
In the examination of some steels by this method it has 
been observed that they are not homogeneous throughout, but 
composed of imperfectly crystallized grains called ferrite, 
crystals of iron and carbon called cementite, and a combina- 
tion of ferrite and cementite, called pearlite. This method 
of examining metals and alloys has proven of great practical 
value in the industrial world, for by it the means of producing 
the best qualities of crude and finished material have been 
determined, and data established by means of which stock 
material already manufactured may be selected for a given 
purpose. 
Alloys 
Most of the metals can be united with one another in 
various proportions by the aid of heat. The product of such 
a combination is termed an alloy. 
Alloys cannot be regarded as chemical combinations, al- 
though it is probable in some instances that chemical com- 
binations may occur. 
MATTHIESSEN 's THEORIES AS TO THE NATURE OP ALLOYS 
Matthiessen expressed the belief that an alloy of two 
metals may be: 
First, a solution of one metal in another. 976 
AN OUTLINE OF METALLURGY 
Second, a chemical combination. 
Third, a mechanical mixture. 
Fourth, a solution or mixture of two, or all of those men- 
tioned, or a perfectly homogeneous diffusion of one body in 
another. 
AFFINITY OF METALS FOR EACH OTHER 
The affinity of metals for each other is variable, and con- 
sequently they will not alloy uniformly. A good example of 
this is seen by melting lead and zinc together. When melted 
and agitated they may be diffused through each other, but if 
allowed to cool slowly, they separate, the zinc, being lighter, 
rising to the top, while the lead will settle to the bottom of the 
crucible. 
LIQUATION 
This tendency of metals to separate on cooling is known 
as liquation. In some cases it can be overcome, and in others 
partially so, by breaking up the ingot and remelting it. 
OBJECT IN ALLOYING METALS 
The prime object in alloying metals is to fit them for some 
special application for which in their pure state they are un- 
fitted. 
Some of the results of alloying may he tabulated as fol- 
lows : 
1. To increase strength, elasticity and tenacity. 
2. To harden. 
3. To reduce the melting point. 
4. To modify the color or structure. 
5. To facilitate the production of sound and workable 
castings. 
6. To resist corrosion or oxidation. 
Examples: Gold is alloyed with copper and silver to 
harden it; its fusing point reduced and its color modified ac- 
cording to the proportions of the metals used. 
Silver is rendered harder and its color modified by the 
addition of copper. 
Copper is hardened by the addition of zinc, its toughness 
reduced, and its reddish color changed to yellow, as is appa- 
rent in the many-colored brasses produced. Its strength, 
tenacity, and elasticity are enhanced by the addition of nickel. 
By the addition of tin to copper an alloy known as bell AN OUTLINE OF METALLURGY 
977 
metal is produced, in which is developed a quality of sonor- 
ousness not present in either of the uncombined metals. 
As a general rule, the alloying of one metal with another 
reduces the melting point of the most difficultly fusible, and 
sometimes reduces the fusing point of the alloy below that 
of the least fusible. 
In making alloys, if the fusing points of the metals being 
combined are widely separated, it is best to melt the most 
refractory first, and then add the lower fusing constituents. 
This will prevent to a great extent, at least, the tendency of 
the latter to volatilize. The union of the low with the high 
fusing metal should be effected at as low a temperature as 
possible. 
EUTECTICS 
When two or more metals are fused, and combined by 
heat, on cooling down, or freezing, certain portions of the 
molten alloy frequently exhibit a tendency to crystallize be- 
fore the entire mass solidifies. Such behavior indicates that 
the union by fusion of the component metals has resulted in 
not one, but a series of alloys, differing in fusibility and usu- 
ally in physical properties. 
The most liquid portion of the alloy, or that which solidi- 
fies last, is called a eutectic alloy, from eu well, and teko fuse, 
meaning well fused. (Gr.) 
The formation of eutectics may be partially obviated by 
stirring the molten alloy until it begins to congeal. 
When metals are alloyed in certain proportions for some 
definite purpose, as in the compounding of solders and dental 
amalgam alloys, the formation of eutectics is a disadvantage 
because the component metals will not be uniformly diffused 
throughout the mass. 
AMALGAMS 
An amalgam is an alloy of two or more metals, one of 
which is mercury. 
A dental amalgam alloy usually consists of tin and sil- 
ver, to which is sometimes added a small percentage of other 
metals, such as platinum, gold, zinc, copper, etc., for the sup- 
posed improvement of color, edge strength, hardness and 
resistance to stress. 
As a matter of fact, any amalgam alloy will in time dis- 
color in the mouth, while as to resistance to stress, edge 
strength, etc., it has been demonstrated that an alloy of silver 
and tin in the proportion of 72.5 to 27.5, when properly tern- 978 
AN OUTLINE OF METALLURGY 
pered and amalgamated, fulfills the requirements as well as 
most of the alloys containing additional metals. 
Dental amalgam alloys are finely comminuted, being either 
in the form of filings or of shavings, in order to facilitate 
their amalgamation with mercury. 
Copper amalgam consists of pure copper and mercury 
usually brought into combination with the galvanic current. 
It softens when heated and hardens again on cooling. It is 
used very often in the filling of temporary teeth. On account 
of its tendency to discolor, oftentimes becoming black, it is 
not extensively used for permanent operations. 
The specific gravity of an alloy, as a rule, differs from 
the mean of the specific gravities of its constituents. In case 
of contraction occurring, the density of the mass has in- 
creased, and when expansion occurs, the reverse condition 
prevails. It is thought probable that, when the density of an 
alloy is greater than the mean of the specific gravities of the 
metals involved, chemical combination has occurred. 
The following table, by Thenard, illustrates the varia- 
tions of density in a number of alloys: 
SPECIFIC GRAVITY OF ALLOYS 
Alloys of greater specific 
gravity than the mean 
of their constituents. 
Gold and zinc. 
Gold and tin. 
Gold and bismuth. 
Gold and antimony. 
Gold and cobalt. 
Silver and zinc. 
Silver and lead. 
Silver and tin. 
Silver and bismuth. 
Silver and antimony. 
Copper and zinc. 
Copper and tin. 
Copper and palladium. 
Copper and bismuth. 
Copper and antimony. 
Lead and bismuth. 
Lead and antimony. 
Platinum and molybdenum. 
Alloys of lower specific grav- 
ity than the mean of their 
constituents. 
Palladium and bismuth. 
Gold and silver. 
Gold and iron. 
Gold and lead. 
Gold and copper. 
Gold and iridium. 
Gold and nickel. 
Silver and copper. 
Copper and lead. 
Iron and bismuth. 
Iron and antimony. 
Iron and lead. 
Tin and lead. 
Tin and palladium. 
Tin and antimony. 
Nickel and arsenic. 
Zinc and antimony. AN OUTLINE OF METALLURGY 
979 
Symbol 
Atomic 
weight 
Specific 
gravity 
Melting 
point 
Mallea- 
bility 
Ductility 
Tenacity 
Conduc- 
tivity 
heat 
Conduc- 
tivity 
electricity 
Specific 
heat 
Gold 
Au. 
197.2 
19.4 
1063°C 
1"rank 
1" rank 
7"rank 
53.3 
76.7 
0.0324 
Iron 
Fe. 
55.84 
7.84 
1530 
9 “ 
4 “ 
3 “ 
11.9 
14.8 
0.1138 
Platinum 
Pt. 
195.2 
21.4 
1755 
6 “ 
3 “ 
5 “ 
8.4 
14.5 
0.0311 
Iridium 
Ir. 
193.1 
22.4 
2350 
Red Heat 
Brittle 
Brittle 
Silver 
Ag. 
107.88 
10.5 
960.5 
2"rank 
2"rank 
6"rank 
100 . 
100 
0.057 
Copper 
Cu. 
63.57 
8.9 
1083 
3 “ 
5 “ 
4 “ 
85 
97.8 
0.0952 
Aluminum 
Al. 
27.1 
2.6 
658.7 
2 “ 
7 “ 
8 “ 
31.3 
65.5 
0.0956 
Zinc 
Zn. 
65.37 
.7 
419.4 
8 “ 
6 “ 
9 “ 
28.1 
29.6 
Cadmium 
Cd. 
112.4 
8.54 
320.9 
5 “ 
11 “ 
10 “ 
20.1 
24.4 
0.0567 
Lead 
Pb. 
207.10 
11.4 
327.4 
7 “ 
8 “ 
12 “ 
8.5 
8.4 
0.0314 
Tin 
Sn. 
119.0 
7.3 
231.9 
4 “ 
7 “ 
11 “ 
15.5 
14.4 
0.0562 
Mercury 
Hg. 
200.6 
13.6 
38.9 
13 5 
1 8 
0 0333 
Nickel 
Nil 
58.68 
9 
1452 
11" rank 
5" rank 
2"rank 
12 9 
0 1108 
Bismuth 
Bi. 
208.0 
9.75 
271 
Brittle 
Brittle 
Brittle 
1.8 
1.4 
0.0308 
Antimony 
Sb. 
120.2 
6.7 
630 
« 
U 
4 
3.6 
0.0508 
Melting points according to U. S. Bureau of Standards. (Revision of 1915.) 
TABLE OF THE PHYSICAL PROPERTIES OF SOME OF THE METALS 980 
AN OUTLINE OF METALLURGY 
Gold 
Gold has been known and used from the remotest an- 
tiquity, and its value as a medium of exchange recognized by 
civilized and uncivilized peoples in all ages. 
Alchemy was defined as the art of transmuting the base 
metals into gold and silver, and the ancient alchemists ex- 
perimented with this end in view. Their labors, however, 
while not accomplishing the discovery of this much desired 
process, did result in the discovery of many curious scientific 
truths on which the foundation of modern chemistry stands, 
and thus gold has played a very important part in the ad- 
vancement of science and civilization. 
There is, perhaps, no other metal whose intrinsic value 
has remained so permanent as has that of gold. Its compara- 
tive scarceness, its beautiful, rich, yellow color, the ease with 
which it can be worked into different forms, together with 
the fact that it does not readily tarnish or oxidize under ordi- 
nary conditions, may account for the high regard in which 
gold is held. As before stated, it has been used from time 
immemorial as a medium of exchange, and in most countries 
to-day is the basis or standard of the monetary systems. 
OCCURRENCE AND DISTRIBUTION 
Although comparatively scarce, gold is found quite widely 
distributed over the earth. It occurs native or in metallic 
condition, and also combined with silver, lead, tellurium, or 
with sulphides. It is obtained from two very different 
sources; first, from placer or alluvial deposits of rivers and 
streams, both ancient and modern, and, second, from veins 
in rocks. 
PLACER DEPOSITS 
The placer deposits are the result of the weathering and 
disintegration of the rocks carrying the vein gold, and as 
these fall to pieces they are washed down stream with the 
sand, gravel and soil and settle in the beds of rivers. In time 
the channels of the streams change, and the beds of gravel 
or placer, bearing the gold, are left high and dry sometimes 
miles from any water. The vast placer deposits on the west- 
ern slopes of the Sierra Nevada mountains are supposed to be 
the beds of ancient rivers long since obliterated. 
Placer gold is usually in the form of small pellets, flakes, 
or rounded grains, the larger pieces, those weighing 1/2 ounce 
or more, being called nuggets. The largest mass of gold ever AN OUTLINE OF METALLURGY 
981 
found in one piece was taken from the placer deposits of Vic- 
toria, Australia, and weighed 183 pounds, its value being over 
$40,000. Another one, the “Blanch Barkley” nugget, also 
found in Australia, weighed 146 pounds. A nugget was found 
in Prussia in 1842 which weighed 96 pounds, and in Califor- 
nia a number of pieces have been found which weighed 20 
pounds or more. These, however, are rare instances of gold 
occurring in large masses, the usual form being, as before 
stated, in small flakes and grains, and frequently as fine dust, 
the particles being so small as to be indistinguishable without 
the aid of a lens. 
Fig. 958.— Panning Placer Gold 
Gold is obtained from placer deposits in several ways, the 
most simple of which is by means of the “pan.” This con- 
sists of a shallow vessel, usually of sheet iron, about 14 or 16 
inches in diameter and two or three inches deep, in which the 
PLACER MINING 982 
AN OUTLINE OF METALLURGY 
soil bearing the gold is placed. This is then held in water 
and the pan given a rotary and side-to-side motion, which 
washes out the soil and sand and leaves the gold in the bot- 
tom of the pan. 
Fig. 959.— Washing Placer Gold in a Cradle 
The Cradle is a similar device, constructed on a somewliat 
larger scale, for washing larger quantities of soil. 
The Sluice is a convenient means of washing still larger 
quantities of soil where running water is convenient. It con- 
sists of a long flat-bottomed trough set on a slight incline so 
that the water may readily run through it from end to end. 
Fig. 960.— Washing Placer Gold in a Sluice 
Across the bottom, strips are placed parallel with the 
water current, and others are placed at right angles to these, 
thus forming a series of small compartments which contain 
mercury. Since mercury has a strong affinity for gold, the 
smallest particles are saved in this manner. The soil is AN OUTLINE OF METALLURGY 
983 
thrown into the upper end of the sluice and the current washes 
it down over the ridges, the lighter particles being thus car- 
ried off, leaving the gold amalgam in the bottom. 
At regular intervals the mercury charged with the gold is 
removed, placed in retorts and subjected to heat. This dis- 
tills off the mercury and leaves the gold. The mercury is re- 
covered by conducting its vapor into suitable condensers, 
when it is again ready for use. 
These sluices vary from a few feet to several hundred in 
length, those used in hydraulic mining often being a mile long. 
In the small sluices the soil is thrown in with shovels, 
while in hydraulic mining it is loosened by a large forcible 
stream of water directed against the bank or hill of gravel by 
means of a hose with nozzle. The water used for tearing 
down the soil is directed into the sluices and is utilized for 
washing the gravel. 
When gold is found in veins in rocks, the rock or mineral 
with which it is associated is first mined, then crushed to re- 
duce it all practically to a powder. This is accomplished by 
first crushing the rock into small pieces, and then stamping 
the broken pieces by special machinery called a stamp mill. 
VEIN GOLD 
EXTRACTION OF GOLD FROM ORES 
More or less variation exists in the construction and opera- 
tion of stamp mills, depending principally on the character 
of the ore to he reduced. Stamp mills are usually built on a 
side hill or inclination having a fall of at least 30 feet in the 
length of the mill. For economical reasons they should be 
situated convenient to both fuel and water. 
The inclination of the ground enables the various pieces 
of machinery to be placed so that gravity carries the crushed 
ore from one to the other without difficulty. In the highest 
part of the mill is placed the platform, which receives the ore, 
and from which it is shoveled into the crusher. This breaks 
the mineral into pieces 3 inches or less in diameter, in which 
condition it is carried down to the stamp mill. 
The stamp mill consists of large, flat-bottomed iron mor- 
tars, into which are fitted heavy iron pestles, each weighing 
from 500 to 1,000 pounds. These are lifted by cam devices, 
keyed on a revolving horizontal shaft, and fall by their own 
weight. Stamps are usually ranged in line, in groups of five 
stamps each, operating in a common mortar box. A stream 984 
AN OUTLINE OF METALLURGY 
of water carries the pulverized material against amalgamated 
copper plates, placed in the sides of the mortar, the mercury 
on which retains the gold, while the earthy constituents are 
washed away. 
At intervals, before the mercury has become saturated 
with the gold, the plates are removed and scraped, and the 
amalgam thus collected subjected to powerful pressure in 
leather bags. This squeezes out the excess of mercury 
through the pores of the leather. The thick amalgam remain- 
ing is then placed in retorts, subjected to heat, and the mer- 
cury distilled off. 
The gold remains in the retort in a spongy state, and is 
usually quite free from other metals, with the exception of 
silver. It is then melted with suitable fluxes, cast into bars 
and shipped as bullion. 
CHLORINATION PROCESS 
Gold ores can be reduced and the gold freed by means of 
chlorine gas. The process is as follows: 
The ore is first crushed, then roasted to expel sulphur, 
arsenic, antimony or other volatile substances that may be 
present. The roasted ore, slightly dampened, is then placed 
in wooden vats having false bottoms. 
When the vats are charged, close-fitting covers are placed 
over them and chlorine gas is introduced under the false bot- 
tom. This in time rises through the false bottom and into the 
moistened ore, converting the gold into a soluble chloride, 
which is afterward removed by washing. From this solution 
the gold can be precipitated by the sulphate of iron. 
CYANIDE PROCESS 
This process is much in favor in many parts of the world 
because of its cheapness and from the fact that low-grade ores 
which cannot be worked economically by other processes can 
be reduced profitably by this method. 
The advantage of the cyanide over the chlorination process 
lies in the fact that in the method under consideration it is 
unnecessary to roast the ore. 
The process is as follows: The ore is first crushed, and 
in this condition is placed in vats with false bottoms similar 
to those used in the chlorination process, but deeper. Water 
containing a small percentage of cyanide of potassium is then 
added to the contents and allowed to slowly percolate through 
the mass. This process is known as lixiviation. The gold AN OUTLINE OF METALLURGY 
985 
is dissolved by the cyanide and carried out in solution, when 
it is afterward precipitated by zinc shavings. 
PHYSICAL PROPERTIES 
The fusing point of pure gold is 1063 deg. C., its specific 
gravity 19.4, malleability and ductility first rank, tenacity 
seventh rank, conductivity of heat 53.3, electricity 76.7, and 
specific heat .0324. 
In the dental laboratory gold scraps and filings accumu- 
late, and these can be refined, the base metals eliminated and 
the pure gold reduced to the desired carat by alloying with 
pure metals in proper proportions. 
Filings should be spread on a paper and a horseshoe mag- 
net passed back and forth through them to remove any par- 
ticles of iron that may be present. They should then be 
treated with acids, to remove such of the baser metals as are 
not actually alloyed with the gold. 
The gold is now placed in a flat-bottomed flask that may 
be subjected to heat without breaking and covered with aqua 
regia. This is composed of two parts of concentrated hydro- 
chloric to one part of nitric acid. Heat is then applied and 
additions made to the acid from time to time until the gold is 
all in solution. 
The solution is then weakened with water and filtered. If 
any silver is present, it will be retained on the filter paper. 
The solution should be further diluted until only very slightly 
acid. A clear solution of ferrous sulphate is now slowly added 
and time allowed the gold in solution to precipitate. This 
usually requires several hours. The clear liquid is then 
drawn off and the brown precipitate of metallic gold is heated 
several times with dilute hydrochloric acid to remove iron. 
The precipitate is then thoroughly washed to remove every 
trace of acid, dried out, the filter paper carrying the gold 
folded and placed on charcoal block or in furnace, borax and 
saltpeter added and the metal fused. 
PREPARATION OF PURE GOLD 
TREATMENT OF SCRAP PLATE 
When the clippings from plate of the same carat are al- 
lowed to accumulate and kept separate, these may be simply 
remelted, cast into the ingot mold and rolled out into plate 
of the required thickness without the necessity of refining. 986 
AN OUTLINE OF METALLURGY 
Alloying Gold 
For most dental purposes, with the exception of foil for 
filling and plate for backing porcelain facings, gold is reduced 
in fineness. That in most common use for crowns and bridges 
is 22 C. and 21.6 C. (coin gold); 20 and 18 C. gold is used for 
dentures. 
The term carat, used in this connection, indicates the num- 
ber of parts of pure gold there is in an alloy. Pure gold is 
called 24 carat, and may be regarded as 24-24th pure; 22 carat 
is 22-24tli pure, or 22 parts pure gold and 2-24 alloy; 20 carat 
is 20-24ths pure and 4-24 alloy, etc. 
The dentist can make his own gold plate and solder of 
any desired carat, if ordinary skill is exercised. 
Gold plate of a known carat can be increased or decreased 
in fineness by the addition of pure gold, or of gold plate of a 
higher or lower carat. This process, whether raising or low- 
ering, is called reduction. 
REDUCTION OF GOLD 
boser's rule 
A general rule that answers for both methods is that 
known as Boser’s rule. “The difference between the carat of 
gold used to reduce with and the required carat, is to the dif- 
ference between the required carat and the carat of gold to 
be reduced, as the weight of the gold to be reduced is to the 
weight of reduction metal required. The weight of the entire 
mass, when alloyed, may be found by adding the weight of 
gold reduced to the weight of reduction metal required.” 
U. S. gold coin is 90 per cent pure gold and 10 per cent 
alloy (silver and copper), or 21.6 carat fine. This is fre- 
quently employed in crown and bridge work. It is a little 
darker in color than 22 carat gold because of the percentage 
of copper contained, and is more difficult to work, since it is 
harder and stiffer; 22 carat gold is, perhaps, most generally 
used in crown and bridge work, and 20 carat and 18 carat in 
denture construction. 
Pure gold is frequently used for backing teeth because of 
its softness and ease of adaptation to the porcelain. 
An alloy of 75 parts pure gold and 25 parts pure silver 
(18 carat) is sometimes used for backing teeth when it is 
necessary to impart a greenish tinge to the porcelain. This 
alloy is known as green gold. AN OUTLINE OE METALLURGY 
987 
GOLD SOLDEES 
Most solders contain a trace of zinc or cadmium to reduce 
the fusing point of the gold so that solder of a given carat 
may be fused upon plate of the same carat without danger of 
melting the latter. 
Dr. Dorrance gives the following alloy as a practical one 
for making good colored gold solders: 
Pure silver 1 part 
Pure zinc 2 parts 
Pure copper 3 parts 
These are melted together to form an alloy, the copper 
and silver being melted first, after which the zinc is added 
quickly in small pieces and the mass stirred to insure thor- 
ough mixing of the metals, then poured into water to granu- 
late it. 
If 20 carat solder is desired, it can be made by taking 4 
parts of this alloy and 20 parts pure gold; 18 carat gold 
solder may be made by taking 6 parts of the alloy and 18 parts 
pure gold, etc. 
The proportion of the zinc in most solders is 1 to 24 parts 
of the entire alloyed mass. 
Dr. W. H. Trueman recommends the following solders as 
being of good color, easy flowing, and as tough as gold plate. 
An excess of zinc is added to compensate for some slight loss 
from volatilization: 
22 Carat Solder 
Pure gold 22 
Copper 1 
Zinc li/4 
18 Carat Solder. 
Gold 18 
Copper 2 
Silver 3 
Zinc li/2 
TABLE OF MIXED CARATATION 
The following table gives the proportions of the various 
metals used in jewelers’ gold plate: 
Carats. 
Copper. 
Parts - 
Silver. 
Gold. 
23 
y2 
y2 
23 
22 
1 
i 
22 
20 
2 
2 
20 
18 
3 
3 
18 
16 
5 
3 
16 
15 
6 
3 
15 
14 
7 
3 
14 
12 
8% 
3y2 
12 
10 
10 
4 
10 
8 
ioy2 
sy2 
8 988 
AN OUTLINE OF METALLURGY 
Gold plate may be made by using all copper, or all silver, 
as the alloying agent, but its color is materially changed in 
either case, becoming darker when alloyed with the former, 
and lighter or of a green tinge when alloyed with the latter. 
As before stated, pure gold may be reduced in fineness 
without material change of color by the use of silver and cop- 
per in proper proportions. 
CLASP GOLD 
Platinum is added to gold to impart elasticity to it, and 
when gold is so alloyed it is called clasp metal. The follow- 
ing formula is one recommended by Harris: 
20 carat clasp gold: 
Pure gold 20 dwt. 
Copper 2 dwt. 
Silver 1 dwt. 
Platinum 1 dwt. 
Clasp gold is usually made of 26, 24 and 22 gauge, the 
thickness of plate required for a given case depending on the 
length of teeth to be clasped, long teeth requiring thin, and 
short teeth thick, plate. (See Clasp Metals, page 1009.) 
PLATINUM SOLDER 
Formerly platinum base plates, dentures and the metal 
parts of porcelain crowns and bridges were soldered with 
pure gold, but this method was not satisfactory, because the 
gold diffused itself into the platinum and formed a brittle, 
crystalline alloy, incapable of resisting much stress. For this 
reason the use of pure gold as a solder for platinum has been 
abandoned and an alloy of gold and platinum substituted by 
which the difficulty mentioned is obviated: 
No. 1. 
Pure gold 75 parts 
Pure platinum 25 parts 
No. 2. 
Pure gold 80 parts 
Pure platinum 20 parts 
No. 3. 
Pure gold 85 parts 
Pure platinum 15 parts 989 
AN OUTLINE OF METALLURGY 
Some Recent Work Concerning Gold Alloys 
The following section, from page 989 to 1039, is the result 
of a series of recent researches in gold alloys and kindred 
subjects, by Dr. L. J. Weinstein of New York, the copyright 
of which he holds. 
This section was written specially for and will appear in 
Dr. F. A. Peeso’s work on “Removable Crown and Bridge 
Work,” now in press. 
The author of this valuable contribution has kindly granted 
the writer the privilege of its presentation in this book. 
Author’s Preface 
‘‘In the preparation of this contribution, it has been the 
aim of the author to present a brief and practical rather than 
an academic discussion of the subject. 
“In addition to a consideration of the gold alloys, it was 
found advisable to include a section on the closely allied and 
important subjects of refractory materials and fluxes used in 
connection with gold, during soldering or casting operations. 
“The series of investigations, upon which this contribu- 
tion is based, was started during the year 1908, when the 
author experienced considerable difficulty in attempting the 
execution of removable bridge work along the lines laid down 
by Dr. Peeso. 
“In attempting to use the coin gold and modifications of 
same in the form of solders, he was seriously handicapped by 
the comparatively low melting point of the coin gold and the 
inadequacy of the other gold alloys usually obtainable, which, 
to the man of exceptional skill, is not so apparent as to one 
of average, or even less than average, skill. 
“In view of the well-known fact that platinum is a metal 
that could be alloyed with gold to increase the melting point 
of the latter, a number of experiments were made to produce 
a formula for a gold alloy sufficiently high in melting point 
so that it could be used as a substitute for coin gold and 
thereby eliminate the process of “sweating,” which, in the 
hands of the author and many other novices, was a more or 
less hazardous procedure, and instead, soldering the resultant 
high fusing gold with other gold of a melting point equal to 
that of 24 or 22k., and thus obtaining a strong union that 
would withstand the subsequent, and often numerous, solder- 
ing operations required for the completion of the case. 990 
AN OUTLINE OF METALLURGY 
“The alloys finally developed were found so satisfactory 
that it is not too much to say that even in the hands of the 
most skilled operator these alloys will prove of considerable 
value, if for no other reason than the very great difference in 
the melting point between the highest and lowest fusing alloys 
in the series and the consequent increased facility and safety 
during the necessary subsequent soldering operations. 
“In the author’s efforts to obtain information from which 
to formulate alloys he was greatly handicapped, inasmuch 
as there were no dental publications bearing to any extent on 
the subject. After a thorough study of the then recently re- 
vised books on dental matallurgy, a number of experiments 
were made, the results of which did not appear to correspond 
with the data in the text books. A number of works on 
general metallurgy were consulted and found to differ ma- 
terially with the dental text books in a great many instances, 
particularly on data concerning the properties of the binary 
alloys of gold and silver, gold and platinum, etc. In order to 
establish a definite foundation upon which to base further re- 
searches, the author proceeded to make a series of binary 
alloys and from the resultant data was enabled to proceed 
with the development of more complex alloys. 
“The resultant formulae given herein have been in prac- 
tical use for a period ranging from two to five years, and 
while the author does not claim that his is by any means the 
last word on the subject, he trusts that the results of his re- 
search will prove of some immediate benefit to both advanced 
students and practitioners. .” 
Introduction 
The elements following gold have been divided into four 
groups. This division is an arbitrary one, and made solely 
for the purpose of facilitating future references. (See table 
1, page 991.) 
Binary Alloys 
It is a well-known fact that pure gold has but a limited use 
in the construction of various dental appliances and that it 
is necessary to alloy it with various other metals in order to 
increase its durability, hardness, tenacity and to vary the 
melting point above or below that of pure gold, as may be re- 
quired. The metals in common use for this purpose have been AN OUTLINE OF METALLURGY 
991 
copper, silver and platinum, the latter to a limited extent; 
also zinc, cadmium, etc., for solders, which, of course, require 
a considerably lower melting point than the gold upon which 
they are to be used. 
NECESSITY OF A KNOWLEDGE OF BINARY ALLOYS 
A thorough knowledge of the properties of the simple 
binary alloys is of paramount importance, because these prop- 
erties almost invariably give an indication of what may be 
expected from more complex alloys. 
It is generally accepted by metallurgists that binary alloys 
of gold and silver, copper, platinum or palladium form solid 
TABLE No. 1. 
THE MELTING POINTS* AND DENSITIES OF METALS. 
Name of Metal 
Symbol 
M.P.°F 
M.P.°C 
Density 
GOLD 
Au 
1945 
1063 
19.3 
Silver 
Ag 
1761 
960 
10.5 
GROUP 
Copper 
Cu 
1981 
1083 
8.9 
I 
Platinum 
Pt 
3190 
1755 
21.5 
Palladium 
Pd 
2820 
1550 
11.4 
Iridium 
Ir 
4170 
2300 
22.5 
Osmium 
Os 
4900 
2700 
22.5 
Rhodium 
Rh 
3525 
1940 
12.1 
Zinc 
Zn 
787 
420 
7.1 
GROUP 
Cadmium 
Cd 
610 
321 
8.6 
III 
Tin 
Sn 
450 
232 
7.3 
Aluminum 
A1 
1218 
658 
2.7 
Nickel 
Ni 
2646 
1452 
8.9 
Cobalt 
Co 
2714 
1490 
8.7 
Manganese 
Mn 
2237 
1225 
7.4 
Chromium 
Cr 
2750 
1510 
6.9 
Tantalum 
Ta 
5160 
2850 
14.5 
Tungsten 
W 
5430 
3000 
18.7 
Molybdenum 
Mo 
4500 
2500 
8.6 
Vanadium 
V 
3150 
1730 
6 1 
Titanium 
Ti 
3450 
1900 
4.5 
*From Circular No. 35, U. S. Bureau of Standards. 
solutions. That is, solutions of one metal in another, if in 
proportions within certain limits. Such binary alloys as will 
be discussed, form solid homogeneous solutions except when 
otherwise noted. 
It is therefore unnecessary to enter into an academic dis- 
cussion of the possible molecular affinity existing among vari- 
ous elements or of eutectics formed between the metals in the 
binary alloys that will be considered, because such compounds 
or mixtures do not occur in such alloys as may be considered 
fit for use in the mouth. For example, alloys of gold and 
copper in the proportion of 82 per cent gold to 18 per cent 
copper (by weight) form a eutectic, which is the lowest fus- 992 
AN OUTLINE OF METALLURGY 
ing of the gold copper series, and when more than 18 per cent 
copper is present the copper is not in uniform solution and 
segregates. As the alloys containing over 15 per cent copper 
are extremely brittle and lack uniformity, no binary alloys 
containing more than 10 to 12 per cent copper will be consid- 
ered. In other words, alloys of gold and copper, where cop- 
per does not exceed 12 or 13 per cent, do not form any com- 
pounds with special characteristics. 
To simplify the references to ternary, quaternary or more 
complex combinations of metals, alloys of only two metals will 
be termed, as is customary, “binary,” but the alloys com- 
posed of three or more metals will be termed “complex” 
alloys. 
Section I 
Gold and Silver 
Silver is commonly utilized as an alloying element with 
gold. It is used, to a considerable extent, as part of the alloy 
in dental golds, and, as will be shown later, principally as a 
cheapening agent. 
EFFECT OF SILVER UPON GOLD 
There seems to prevail generally an erroneous concep- 
tion regarding the properties of silver-gold alloys. It has 
been stated* that silver is used to harden and to lower the 
melting point of gold. This deduction is distinctly contrary 
to the results obtained by the author. After making a num- 
ber of binary alloys, it was proven that even the maximum 
percentage that may be used in dental work, say 25 per cent 
of silver to 75 per cent gold, does not confer any perceptible 
hardness upon the gold, neither does it lower the melting 
point to such an extent that the difference could be measured 
with a pyrometer. 
Practically the only effect silver (even if present to the 
extent of 25 per cent) has upon gold is to discolor the gold, 
making it greenish, and lower the specific gravity, thus in- 
creasing the volume. Tt will thus be seen that silver confers 
no special benefit upon gold, except cheapening it and acting 
as a color modifying agent. On the other hand, it may prove 
detrimental, as a considerable proportion of silver may inter- 
fere with the action of other alloying elements when attempt- 
* Essig’s Metallurgy (Koenig’s revision), p. 163. 
* Hodgen’s Metallurgy (Milberry’s revision), p. 278. AN OUTLINE OP METALLURGY 
993 
ing to produce a complex gold alloy, and also on account of the 
strong affinity that oxygen and other gases possess for silver. 
It will thus be readily seen that small percentages may some- 
times be used to advantage as a color modifying agent, but 
a large percentage of silver is distinctly contraindicated. 
Silver, in such proportions as may be needed for dental 
golds, alloys uniformly and without difficulty and may be de- 
pended upon to remain in uniform distribution. 
The author has found that gold alloys, with a high per- 
centage of silver, when remelted and cast, show in the casting 
a considerable variation of the silver content which indicates 
that a partial separation takes place. This has not been in- 
Melting Points Of Alloys 
Of Gold And Silver. 
5% Ag. M.P 1945° F. 1063°C. 
10% - 
15% ” ” 1943° F. 1062° C. 
30% ” " 1942°F. 1061° C. 
vestigated further for the reason that castings of gold with 
a high percentage of silver have no practical application. 
As stated before, small percentages of silver have practically 
no effect upon the gold and this fact has been taken advan- 
tage of for a considerable period of time by at least one manu- 
facturer who alloys pure gold with from one to two per cent 
of silver and sells it as 24k. This alloy appears so similar to 
pure gold that the ordinary eye is deceived and the unprinci- 
pled manufacturer is the gainer. 
Fig. 961 illustrates the melting point curve of gold-silver 
alloys. 
Practically the same determination appears in very recent 
works on metallurgy.* 
Fig. 961 
* Fenchel’s Metallurgy. 
32 994 
AN OUTLINE OF METALLUBGY 
Silver-platinum alloys have been used to a considerable 
extent for crown posts, dowels, backings, etc. As a rule, 
alloys of this character (20 to 30 per cent) are extremely un- 
satisfactory, both during their manipulation and in ultimate 
service, and their use should be avoided. They are somewhat 
improved with higher percentages of platinum, but the alloys 
are extremely non-uniform and still quite soluble in acids and 
apt to discolor and corrode. The cost with more platinum 
is considerably higher, and even then the alloys are not equal 
to a fair grade of alloyed gold, either in usefulness or 
economy. 
GOLD AND COPPEE 
Copper is one of the most commonly used and most use- 
ful alloying elements. It confers hardness and elasticity upon 
gold, but is detrimental when used in large proportions on 
account of its great tendency to lower the melting point of the 
alloy and the strong oxidation and brittleness of the alloys 
when the copper is in high proportion. It is, however, a most 
useful, and, in fact, an indispensable alloying element if em- 
ployed judiciously. Alloys of gold and copper, such as U. S. 
coin gold (Au. 90 Cu. 10), have been used with most satis- 
factory results, both from the standpoint of durability and 
resistance, against action of the oral fluids, and an alloy of 
this character is ideal for crown work, except for the disad- 
vantage of its low melting point, which is caused by the cop- 
per content, and its range of usefulness is therefore limited 
even in the hands of the skilled operator. This inadequacy, 
as will be shown later, can be corrected by substituting plat- 
inum, etc., for some of the copper, thus raising the melting 
point and reducing oxidation without changing the valuable 
properties the coin gold possesses, namely, strength and dur- 
ability. 
Fig. 962 illustrates the melting point curve of gold-copper 
alloys. 
As will be seen from the chart, the melting point of pure 
gold drops rapidly upon the addition of copper; 5 per cent 
copper lowers the melting point about 100 degs. F., 10 per 
cent copper lowers the melting point of gold about 200 degs. 
F., 15 per cent copper lowers the melting point about 250 degs. 
F., and 18 per cent causes a drop in melting point of about 
300 degs. F. As will be seen from the illustration, the lowest 
melting point between gold and copper is when 18 per cent 
cu. is present. The addition of more than 18 per cent eu. 995 
AN OUTLINE OF METALLURGY 
causes a rise in melting point until the melting point of cop- 
per, 1980 degs. F., is reached. 
As mentioned previously, it is advisable to limit the total 
copper content to 10 or 12 per cent. Consequently, if the 
melting point of an alloy of gold and copper of requisite 
strength and hardness is too low, it is necessary to use 
platinum or palladium to bring it to the point desired. 
The valuable properties of copper as a hardening agent 
have apparently been underestimated by writers, but taken 
Melting Points Of Alloys 
Of Gold And Copper. 
5% Cu. M.P 1840°F, 1004°C. 
10% '• ” 1735°F, 946° C. 
15% » •• 1690°F, 9 21°C. 
18% •• •• 1661°F, 905°C. 
Fig. 962 
advantage of by manufacturers, as will be noted in the com 
position of commercial clasp metals. 
Platinum is being used to some extent as an alloying ele- 
ment with gold principally for clasp metal, etc. It has been 
stated that platinum confers great elasticity and hardness 
upon gold, which appears correct, only to a limited extent. 
The author’s experiments have indicated that platinum has 
comparatively little effect as a hardening agent upon gold. It 
does, however, raise the melting point considerably, as will 
be shown later. 
GOLD AND PLATINUM 996 
AN OUTLINE OF METALLURGY 
Platinum is much inferior to copper as a hardening agent. 
This is readily proven upon an examination of a binary alloy 
of gold and copper containing 10 per cent copper and a binary 
alloy of gold and platinum containing 25 per cent platinum 
(so called platinum solder). A comparison of two pieces of 
equal dimensions will show that the gold-copper alloy, with 10 
per cent copper, is quite as hard and elastic as the gold alloy 
Melting Points Of alloys 
Of Gold And Platinum. 
5% Pt. M.P 2015°F. 1102°C. 
10% " •• 2085°F, 1141° C. 
15% ” •• 2165°F, 1165°C. 
20% •• »• 2260°F, 1228°C 
Fig. 963 
with 25 per cent platinum, and more uniform. It is there- 
fore evident that platinum is not the most suitable hardening 
agent and its range of usefulness as an alloying element is 
therefore limited. 
Platinum, however, is an excellent adjunct to copper, as 
it tends to raise the melting point, which is lowered sensibly 
by any considerable percentage of copper. 
Fig. 963 illustrates the melting point curve of gold-plati- 
num alloys. AN OUTLINE OF METALLURGY 
997 
Large percentages of platinum cannot be alloyed uni- 
formly with gold, and in order to insure a uniform alloy it is 
not advisable to use more than 5-10 per cent in a binary alloy 
and 10-15 per cent in a complex alloy. In the latter the other 
alloying elements help to hold the platinum in uniform dis- 
tribution. If it is desired to raise the melting point of an 
au.-cu. alloy higher than 5-10 per cent platinum makes pos- 
sible, it is advisable to use palladium, which combines per- 
fectly in both the binary and complex alloys that will be con- 
sidered. 
Palladium is as yet a comparatively rare metal. It has 
been used to some extent in the industries and arts, but prac- 
tically to no extent in dental golds. Palladium is a metal 
very similar to platinum except for its specific gravity, 11.4, 
which is considerably lower than platinum and its melting 
point, which is also considerably lower than that of 'platinum. 
GOLD AND PALLADIUM 
TABLE 2 
MELTING POINTS OF BINARY ALLOYS 
GOLD, 1945° F, 1063° C 
SILVER, 1761° F, 960° C 
GOLD, 1945° F, 1063° C 
PLATINUM, 3190° F, 1755° C 
Gold 95%—Silver 5% 
1945° F 
1063° C 
Gold 90%—Silver 10% 
1945° F 
1063° C 
Gold 85%—Silver 15% 
1943° F 
1062° C 
Gold 70%—Silver 30% 
1942° F 
1061° C 
Gold 95%—Platinum 5% 
2015° F 
1102° C 
Gold 90%—Platinum 10% 
2085° F 
1141° C 
Gold 85%—Platinum 15% 
2165° F 
1165° C 
Gold 80%—Platinum 20% 
2260° F 
1228° C 
GOLD, 1945° F, 1083° C 
GOLD, 1945° F, 1063° C 
COPPER, 1980° F, 1083° C 
PALLADIUM, 2820° F, 1550° C 
Gold 95%—Copper 5% 
Gold 95%—Palladium 5% 
1840° F 
2060° F 
1004° C 
1127° C 
Gold 90%—Copper 10% 
Gold 90%—Palladium 10% 
1735° F 
2145° F 
946° C 
1174° C 
Gold 85%—Copper 15% 
Gold 85%—Palladium 15% 
1690° F 
2250° F 
921° C 
1232° C 
Gold 82%—Copper 18% 
Gold 80%—Palladium 20% 
1661° F 
2340° F 
905° C 
1282° C 998 
AN OUTLINE OF METALLURGY 
It has been stated that palladium makes gold brittle. 
This is contrary to the author’s findings. More than twenty- 
five different alloys were made containing from 1 to 30 per 
cent palladium. All of them appeared perfectly uniform and 
remarkably malleable, ductile and tenacious. 
Palladium also forms excellent uniform alloys with cop- 
per, silver, etc., and it is a very valuable adjunct to platinum 
Melting Points Of Allots 
Of Gold And Palladium. 
5% Pd. M.P 2060°F, 1127°C 
10% •• •• 2145°F, 1174°C 
15% •• •• 2250°F, 1232°C 
20% ” •• 2340°F. 1282°C 
Fig. 964 
in complex gold alloys. Its use, however, is limited on ac- 
count of the fact that it exerts a strong decolorizing action 
upon gold, 3-5 per cent turning gold sensibly lighter and 15 
to 20 per cent almost white (platinum color). 
Fig. 964 illustrates the melting point curve of gold-pal- 
ladium alloys. 
Another remarkable and most valuable property that pal- 
ladium possesses is the fact that, although the melting point, 999 
AN OUTLINE OF METALLURGY 
2820 degs. F. (1550 degs. C), is considerably lower than that 
of platinum, a given percentage of palladium (by weight) 
will increase the melting point of gold more than an equal 
amount of platinum, and in view of the fact that platinum in 
considerable percentages does not alloy uniformly with gold, 
it is well to use palladium, as it alloys uniformly with gold in 
all proportions. Therefore, in alloys where color is no object, 
palladium may be incorporated to very great advantage. 
Gold and Metals 1st Group II 
IRIDIUM 
Iridio platinum is usually employed in place of pure plat- 
inum on account of its greater hardness and durability. 
When experimenting with the series of binary alloys previ- 
ously discussed, it naturally occurred to the author that gold 
alloyed with iridio platinum instead of pure platinum would 
prove superior to gold alloyed with pure platinum. A number 
of alloys were attempted and the results obtained were found 
invariably inferior to alloys of gold and pure platinum. The 
unsatisfactory results should have been anticipated because 
it is well known that iridium will not alloy with gold uni- 
formly, but segregates on account of its extremely high melt- 
ing point and high specific gravity. It is quite certain that in 
attempting to make the alloy, the following occurred: When 
the iridio-platinum was brought into the gold, the heat used 
was sufficient to melt the platinum and set free the particles 
of iridium which did not go into solution with the gold plat- 
inum mixture, but suspended and then segregated in the same 
way as if free iridium were added to gold without the pres- 
ence of the platinum. 
The experimental alloys were made of pure gold and 15 
per cent iridio-platinum and compared with alloys made of 
pure gold and 15 per cent platinum. On rolling both to equal 
gauge, polishing and etching, the gold-platinum alloy was 
found quite uniform, whereas some sections of the gold iridio- 
platinum alloy (?) were harder and higher fusing, while 
other sections were softer and lower fusing than the gold- 
platinum alloy. In addition, all the gold-platinum-iridium 
mixtures appeared streaky and non-uniform, even to the 
naked eye, while the gold-platinum alloys appeared almost 
perfect, even under the microscope. 
Numerous other experiments were made along these lines, 
and in spite of the fact that some have advocated the use of 1000 
AN OUTLINE OF METALLURGY 
iridio-platinum instead of pure platinum in alloys, it is the 
author’s conclusion that pure platinum is far superior to 
iridio-platinum as an alloying element with gold. 
OSMIUM 
No attempts have yet been made to form alloys with 
osmium, as it is even higher fusing than iridium and therefore 
poor results may be anticipated. The author expects, how- 
ever, to experiment with osmium shortly to determine if there 
is any possible benefit to be derived from it, because alloys of 
Os. per cent are claimed to be superior to alloys of Ir. per 
cent.* 
RHODIUM 
Rhodium is a metal of the platinum group that will prove 
of considerable benefit if sufficient of it can be obtained at a 
moderate cost. It is quite similar to palladium. It also has a 
low specific gravity, 12.1, and is considerably higher fusing 
than platinum (according to U. S. Bureau of Standards). 
The author has not experimented with it in the pure state, 
but procured a quantity of it in the form of platinum con- 
taining 10 per cent rhodium. This platinum-rhodium alloy 
was used for a considerable time instead of pure platinum. 
The alloys were quite satisfactory, but the advantages over 
pure platinum as an alloying agent are so slight and the cost 
so high that it appeared advisable to discontinue its use at 
the time. 
GOLD AND METALS IN GROUP III 
A discussion of gold and metals in Group ITT will be found 
in the section on Gold Solders, page 1012. 
GOLD AND METALS IN GROUP IV 
Some time after the introduction of recent casting proc- 
esses, it became apparent that in order to utilize such proc- 
esses to advantage, alloys other than ordinarily obtainable 
would have to be made in order to insure satisfactory results. 
The ordinary plate golds obtainable when cast in small bulk 
were too soft and frail, and the sections had to be cast larger 
and heavier than normal and were therefore objectionable. 
A number of experiments were made in attempting to cast 
the various clasp metals and the results obtained were very 
unsatisfactory. At this time began to appear literature re- 
* F. Zimmerman. Alloy of Platinum and Osmium, U. S. Patent No. 1055119. AN OUTLINE OF METALLURGY 
1001 
garding industrial alloys, both ferrous and non-ferrous, with 
the so-called rare, or little known, metals, sueli as nickel, 
cobalt manganese, tungsten, vanadium, etc., enumerated in the 
table of elements under group 4. 
Some remarkable results were obtained in various indus- 
trial steels, brasses and bronzes and it was not unreasonable 
to expect that some of these rare metals could be utilized to 
advantage in the formation of gold alloys for casting pur- 
poses. 
In view of the fact that there was no precedent to follow 
and no literature on the relation of these metals to gold ob- 
tainable, it can readily be understood that the author’s at- 
tempts to alloy these rare metals with gold were more or less 
empirical and the results obtained were no better than should 
have been anticipated. Meeting with such poor success, the 
author proceeded with the series of researches into both the 
binary and complex alloys of gold with the elements in groups 
one, two and three, and the resultant formulae developed are 
given in the following pages. 
Since then a number of experiments have been made by 
other investigators in attempting to utilize some of the rare 
metals, such as nickel, tungsten, molybdenum, titanium, etc., 
as substitutes for iridio-platinum. The results so far have 
not proven successful. 
This non-success will not appear strange to those familiar 
with both the chemical and physical characteristics of the ele- 
ments mentioned. Unless some radical method of handling 
these metals is evolved iridio-platinum will continue to retain 
the position it occupies. (See “elastic” gold under clasp 
metals.) 
The author has not by any means given up hope of the 
possible utilization of some of the “rare” elements in connec- 
tion with alloys for casting. He is now engaged in a series 
of experiments which have already shown promising results 
and he hopes to have data of importance available for pub- 
lication in the near future. 
Section IT 
A New Series of Alloys 
From the preceding data on the properties of the binary 
alloys of gold with the metals in group one, certain conclu- 
sions may be drawn and data obtained and it then becomes 
a comparatively simple matter to form complex alloys for 
our requirements. Before proceeding to formulate a com- 1002 
AN OUTLINE OF METALLURGY 
plex alloy, it will be well to consider again the hardness con- 
ferred upon gold by the metals in group one. 
As will be seen from Fig. 965, pure silver has practically 
no effect on gold as far as increasing the hardness. Palladium 
has some hardening properties and it is well to bear that in 
mind when formulating an alloy. Platinum has considerably 
Comparative Hardness Or Binary Alloys 
Of Gold With 10% Ag., Pa., Pt., and Cu. 
Fig. 965 
more hardening power than palladium and is a factor, but cop- 
per is the most valuable agent of them all and in proceeding 
to formulate the complex alloys we must consider the copper 
as the principal hardening agent and the others as adjuncts. 
GOLD FOR CROWN, BRIDGE AND PLATE WORK 
Bearing in mind the hardening power and the effect on 
melting point produced by the alloying elements, let us con- 
sider such a formula as the following: 
Formula of Gold Plate No. 1 
Per Cent 
Gold 88.0 
Platinum 7.5 
Palladium 2.5 
Silver 2.0 
Total 100.0 
Melting point, 2075 degs. F., 1135 degs. C. 
This alloy is equivalent in hardness to ordinary 22k. gold, 
containing 91.6 per cent gold, 3.5 to 4 per cent copper and 4.5 
to 5 per cent silver—100 per cent. Now, as the copper is the 
active hardening agent in the 22k. gold, and as we know from 
the preceding data that platinum and palladium exert some- 
what less than half of the hardening influence of copper, it 
will he seen that the total of 10 parts platinum and palladium AN OUTLINE OF METALLURGY 
1003 
is about equal in hardening power to the 3.5 to 4 parts of 
copper usually present in 22k. gold, and thus we get an alloy 
equivalent in hardness to the ordinary 22k. plate. 
The silver content, 2 parts, is no factor whatever, except 
as a color modifying agent, because it is an object to adhere 
to a certain standard of color throughout the whole series of 
alloys. As there is no copper present in this alloy, it is abso- 
lutely non-oxidizable, but the great advantage that an alloy of 
this character possesses over ordinary 22k. plate is the fact 
that its melting point is much above that of ordinary 22k. gold, 
approximately 225 degs. F. to 250 degs. F. higher, and instead 
of sweating a band and floor it may be very easily soldered 
with pure gold or 22k. plate and resoldered with the same or 
lower grade plate gold innumerable times without any dan- 
ger of burning or blistering. 
Any, or all, of the alloys in the series following plate No. 
2 may be safely used as solders on plate No. 1, thus permit- 
ting many soldering operations without danger of burning the 
gold, as may occur in sweating, or the danger of the solder 
(if poor quality) burning into and alloying with the gold, as 
often occurs when using the so-called “easy flowing” solders. 
It is evident, therefore, that this alloy offers a great many 
advantages over the ordinary 22k. plate gold. 
GOLD PLATE NO. 2 
As has been impressed by Dr. Peeso, it is absolutely es- 
sential to use for removable bridge work a hard, durable 
gold such as U. S. coin gold. It may be well at this time to 
state that U. S. coin gold contains 90 per cent pure gold and 
10 per cent copper, whereas the so-called coin gold obtainable 
from most supply bouses contains, as a rule, some silver, 
which softens it and makes it work more easily, and it there- 
fore does not possess the strength and durability required. 
The following formula replaces coin gold most satisfac- 
torily : 
Formula of Gold Plate No. 2 
Per Cent 
Gold 84.5 
Platinum 8.5 
Palladium 2.0 
Silver 0.5 
Copper 4.5 
Total 100.0 
Melting point, 1975 degs. F., 1080 degs. C. 1004 
AN OUTLINE OF METALLURGY 
In this formula, in order to obtain the equivalent hardness 
of coin gold, it is necessary to use copper. We can again 
readily see just how the hardening properties of the alloying 
elements are utilized. We have 4.5 per cent copper and the 
platinum and palladium replace the rest of the copper, thus 
giving us an alloy equal to U. S. coin gold. This oxidizes, 
of course, to a slight extent, but the oxidation is not objec- 
tionable, and this alloy can be used to replace coin gold prac- 
tically for every purpose and may be soldered with other al- 
loys in the series which have the same color. When soldered 
with casting gold, B or C, the attachment of the floor to a 
band cannot open up during the final soldering unless de- 
liberately abused, because the soldered junctions are actually 
higher in melting point than ordinary gold plate. 
The fusing point of this alloy is approximately 225 degs. 
F. higher than coin gold, and it possesses all the advantages 
over coin that the No. 1 formula has over 22k. gold. 
These alloys, Nos. 1 and 2, can be utilized to great ad- 
vantage in the construction of swaged plates, both full and 
partial, especially where it is desired to make the plates of 
two or three thin layers, on account of the high melting point 
of the alloys which permits of thorough soldering of the 
laminae without danger of burning. When used in conjunc- 
tion with the other alloys in the series, these golds enable 
the operator to produce dentures far superior to those made 
from the golds ordinarily employed on account of increased 
strength, minimized bulk and perfect color harmony through- 
out the whole structure. 
It should be borne in mind that high fusing golds, such as 
these, cannot be “sweated” advantageously. This is a char- 
acteristic of all gold alloys high in platinum metals, on ac- 
count of the total absence of or minimum oxidation. The 
“sweating” of an alloy such as coin gold is facilitated by the 
fact that the high oxidation of the copper content helps to 
prevent the flow of areas not fluxed. 
ALLOYS FOR PROSTHETIC CASTING 
As lias been previously stated, in order to cast sections 
of bridge work, saddles, partial plates, etc., it is essential to 
have alloys that are rigid in the cast form to obviate the 
necessity for increased bulk. Again, the value of the harden- 
ing properties of the alloying elements becomes apparent, as 
in the following: AN OUTLINE OF METALLURGY 
1005 
Formula of Casting Gold “B” 
Per Cent 
Gold :. 80.0 
Platinum 9.5 
Palladium 2.5 
Silver 1.0 
Copper 7.0 
Total 100.0 
Melting point, 1900 degs. F., 1035 degs. C. 
We have here 7 per cent copper and a total of 12 per cent 
of the platinum metals which makes an alloy considerably 
harder than coin gold. When cast, this alloy is about mid- 
way in hardness between rolled coin gold and clasp metal. 
The melting point of this alloy is about 50 degs. F. below pure 
gold. It is intended for use with the nitrous oxide blow-pipe 
and should be melted with same, if a considerable quantity of 
gold is to be cast. Sufficient quantities for small castings can 
be melted with the ordinary blow-pipe. The copper content 
being comparatively low permits of the use of the nitrous- 
oxide blow-pipe without any material change or deterioration 
of the alloy, if a suitable reducing flux is used in connection 
with it. 
This alloy corresponds in color with plates Nos. 1 and 2 
and may be used to cast cusps or cusps and contours directly 
to bands of either plate No. 1 or plate No. 2. It makes a 
particularly suitable gold for cast occlusal surfaces on ac- 
count of its hardness and durability. 
The next formula is a modification of and brings out 
an interesting point in connection with the effect of copper 
and the platinum metals on the decrease and increase of melt- 
ing points. 
Formula of Casting Gold “C” 
Per Cent 
Gold 80.5 
Platinum 6.5 
Palladium 2.0 
Silver 2.0 
Copper 9.0 
Total 100.0 
Melting point, 1800 degs. F., 980 degs. C. 
We note in this formula an increase of two parts of cop- 
per and a decrease of a total of 3.5 parts platinum and pal- 1006 
AN OUTLINE OF METALLURGY 
ladium, the consequence being that the melting point is 
dropped by the increase of copper and by the decrease of the 
platinum metals. The melting point is dropped about 100 
degs. F. and brought down to approximately that of 22k. gold. 
This lowering of the melting point permits this alloy to be 
melted readily for large or small castings with an efficient 
illuminating gas and air blow-pipe. It is identical in strength, 
hardness, color, etc., with casting gold “B” except the fusing 
point and resistance to the nitrous-oxide blow-pipe flame. If 
the latter is used, precaution must be taken to use a reducing 
flux and not superheat the metal. This applies to coin gold, 
too, if same is cast. Excessive heat, if applied with the ni- 
trous-oxide blow-pipe, and lack of a suitable reducing flux will 
permit the oxidation of considerable copper and the dissem- 
ination of oxide throughout the casting. 
GOLD FOR INLAY CASTING 
Since the introduction of the casting process, pure gold 
has been generally advocated for cast fillings, etc., on account 
of its supposed minimum shrinkage, softness and malleabil- 
ity and consequent ease with which the margins could be bur- 
nished to eliminate the cement line of an inlay. 
A good many operators have failed to cast pure gold sat- 
isfactorily and claim that they can cast inlays with scrap gold 
and produce better and sharper margins. To those who have 
not experienced this difficulty it may appear very strange, but, 
nevertheless, it is a fact that alloyed gold, when properly 
alloyed, and under fair casting conditions, invariably casts 
with sharp, true margins, whereas pure gold has very often 
failed to accomplish the purpose, both at the hands of the 
author and many others. 
It may be well to consider that the casting of scrap gold 
of indefinite composition is rather a hazardous and usually 
unsatisfactory procedure, and a great many operators recog- 
nizing that fact are using 22k. gold, coin gold, etc., with bet- 
ter results than they have been able to obtain with pure gold. 
It is a well-known fact that pure platinum, pure palla- 
dium and pure silver absorb hydrogen, oxygen and other 
gases while in the molten state and retain some of the gases 
upon solidification. Tt is not generally known, but neverthe- 
less true, that pure gold absorbs nitrogen, hydrogen and oxy- 
gen, and retains a considerable percentage of one or more of 
the absorbed gases upon solidification.* This tendency on the 
* T. K. Rose (in Metallurgy of Gold), quoting Roberts-Austen. AN OUTLINE OF METALLUKGY 
1007 
part of the metals mentioned to absorb gases is minimized 
and sometimes entirely eliminated by alloying and a small 
percentage of copper, palladium or platinum will materially 
alter the behavior of pure gold upon solidification. Castings 
made with a slightly alloyed pure gold will be found to pos- 
sess sharp margins and practically equal to pure gold in 
color, ductility and facility of burnishing, but comparatively 
free from cavities or blow-holes, such as are often found in 
the unalloyed gold castings. 
A number of cases under observation have shown that fill- 
ings of slightly alloyed gold do not, after a period of wear, 
present the same pitted surface so characteristic of cast pure 
gold fillings under the same conditions. 
The rounding of the margins in cast pure gold fillings is 
usually accompanied by a separation of the residue button 
from the casting, which takes place just prior to the comple- 
tion of solidification. This occurs particularly when a com- 
paratively large sprue is used and more especially when a 
large residue button is used at the same time. An explanation 
of this occurrence may reasonably be attributed to the follow- 
ing: If the sprue is quite large and the gold residue button 
large, the residue remains fluid for a considerable period of 
time after the casting pressure has been applied and there 
appears to be a tendency for the large button to draw to it the 
gold of the casting through the medium of the large gate (the 
sprue). A large button of gold very often draws only part 
of the sprue to it, thus separating the connection between the 
residue button and the casting and arresting the exercise of 
the casting pressure which would otherwise be transmitted 
from the button to the sprue and then to the casting proper. 
For those who wish to use pure gold for casting it is suggested 
that the quantity of gold used in the casting operation should 
not exceed more than three pennyweights above the amount 
actually required for the casting proper, and also that the 
sprue be no larger than 16 gauge B. and S. This will serve to 
lessen the area of connection between the casting and residue 
button so that this area (the sprue) may solidify more rapidly 
and in conjunction with the smaller button, which naturally 
freezes more rapidly, tend to prevent the separation previ- 
ously discussed. 
Another point that is well to consider is the fact that alloy- 
ing of gold reduces the surface tension and cohesion of the 
molecules while in a molten state and increases the fluidity, 
thus facilitating the flow of the metal, requiring less pressure 1008 
AN OUTLINE OE METALLURGY 
to force the gold into the mold, and consequently lessening 
the danger of distorting the mold. (See investment com- 
pounds for casting.) 
Formula of Casting Gold “A” 
Per Cent 
Gold 97.0 
Platinum 1.5 
Palladium 0.3 
Silver 0.3 
Copper 0.9 
Total 100.0 
Melting point, 1945 degs. F., 1063 degs. C. 
This alloy makes an efficient substitute for pure gold, as 
the comparatively small amount of alloy does not harden the 
gold sufficiently to prevent burnishing, nor does it affect the 
color perceptibly. Copper is the most suitable agent for in- 
creasing the fluidity and the small percentage used does not 
materially harden the gold. The drop in melting point is 
compensated for by the platinum, and the small percentage of 
silver counteracts the coloring effect of the copper on the 
gold, the consequent alloy possessing practically the same 
melting point as pure gold and producing, almost invariably, 
sound castings without the special precautions which must be 
taken when pure gold is used. 
This alloy will be found suitable for use in teeth close to 
others, with fillings or inlays made of pure gold, in order to 
maintain color harmony. 
As all the alloys in the series, excepting the casting gold 
A and the elastic alloy described later, are practically of a 
uniform color and somewhat lighter (grayish red) and less 
conspicuous than pure gold or coin gold, it has been found 
advisable to also formulate an alloy for casting inlays to 
harmonize in color with the rest of the series. 
Formula for Casting Gold “D” 
Per Cent 
Gold 95.0 
Palladium 3.3 
Silver 0.4 
Copper 1.3 
Total 100.0 
Melting point, 1945 degs. F., 1063 degs. C. AN OUTLINE OF METALLURGY 
1009 
In this alloy, the palladium decolorizes the pure gold and 
raises the melting point. The copper brings it back to the 
pure gold standard and by the addition of the small percent- 
age of silver to counteract the reddening effect of the copper 
a color effect is obtained in perfect harmony with the rest of 
the series. 
This gold is quite soft and malleable and may be burnished 
with practically the same facility as pure gold. This question 
of burnishing margins of inlays is rather a more or less in- 
definite procedure. Tt is the author’s opinion that very little 
effective burnishing (spinning) can be done on inlay margins 
and that only after the margins are stoned down to an ex- 
tremely thin edge. Experience has shown that it is advisable 
to use hard and durable alloys for inlays, especially those in- 
tended to aid in supporting bridge work and then only when 
supplemented with posts or dowels. 
This alloy D can be combined with B or C to obtain harder 
alloys, with no difficulty and no change in color, thus enabling 
the operator to obtain practically any degree of hardness for 
special requirements in inlay casting. 
Section III 
Clasp Metals 
The alloys known as clasp metal, or platinized gold, as 
ordinarily obtainable, have been used, with poor results, for 
casting sections of bridge work, etc., and are being used to a 
large extent and with but mediocre results as a substitute for 
iridio-platinum for crown posts, dowels, etc. The ordinary 
clasp metal is also used to a considerable extent for posts or 
dowels in the construction of cast base crowns, with usually 
poor results on account of its brittleness, especially after it 
has been cast again. There appear to be about four distinct 
types of clasp metal obtainable at the supply houses. 
The following formulae are nearly exact and types one and 
two readily indicate the particular role that copper plays as 
a hardening agent. 
Type one represents a class of clasp metals of which there 
are several on the market. They contain a trace of platinum, 
so that they may legally be called platinized gold, and a very 
high percentage of copper. The copper content confers a high 
degree of hardness and elasticity upon the alloy, but during 
subsequent heating (soldering and annealing) and working, 1010 
AN OUTLINE OF METALLURGY 
the alloy softens considerably and loses a good deal of the 
original elasticity and sometimes becomes very brittle, espe- 
cially when overheated.* As the melting point is quite low, 
soldering with even a comparatively low fusing solder is apt 
to endanger the integrity of the alloy more often than not. 
COMPOSITION OF CLASP METALS 
CONSTITUENT 
Type 
Type 
Type 
Type 
“Elastic’ 
METALS. 
1* 
2* 
3* 
Gold 
GOLD 
63 
65 
63 
65 
64 
SILVER 
14 
15 
17 
6 
1.5 
COPPER 
21 
13 
7 
7 
7.0 
PLATINUM 
2 
7 
13 
18 
11 
PALLADIUM 
4 
16.5 
COMPARATIVE 
1600°F 
1725°F 
1860°F 
1960°F 
2100°F 
MELTING POINT 
870°C 
940°C 
1015°C 
1070°C 
1150°C 
♦From analysis. 
**Is known commercially as “ high-fusing ” clasp metal. 
Type two represents a class of clasp metals which contain 
a larger percentage of platinum and less copper. This alloy, 
while not quite as elastic before annealing, retains its elas- 
ticity after annealing or soldering, better than type one, and 
makes a quite satisfactory material for clasps for vulcanite 
work, etc., if not excessively heated and otherwise abused. 
Neither of the two alloys is suitable for work requiring 
repeated soldering operations. Posts or dowels made of these 
alloys and cast against usually show a partial fusion, and 
although this fusion is not always evident, the posts if cast 
against break away (at the junction) ultimately. These al- 
loys are absolutely unfit for the making of split pins. 
Type three offers a much better material. It contains still 
less copper and more platinum, but has not sufficient strength 
and elasticity. For want of a better material it has been used 
for the construction of split pins for a number of years. In 
addition, the fusing point, although higher than that of types 
one and two, is too low, and when attempting to solder the 
* Gold-silver-copper alloys containing over 15 per cent copper are quite brittle, 
very non-uniform, and variable in behavior upon annealing. AN OUTLINE OF METALLUKGY 
1011 
solid portion of a split pin with coin gold, the metal is apt to 
fuse partly, becoming granular and brittle, and the finished 
pin is apt to give out in use. The type three clasp metal has 
been cast against with fair results, but the danger of burning 
it is imminent. 
In the three types of clasp metals, under discussion, are 
demonstrated the value of copper and its superiority over 
platinum as a hardening agent and the value of platinum in 
raising the melting point lowered by the copper. 
A number of experiments were made to improve the type 
three clasp metal and it can readily be seen from formula of 
type four how comparatively simple it was to do so, having- 
established the properties of the binary alloys as a founda- 
tion. By raising the platinum to 18 points, the melting point 
and the elasticity were increased somewhat. Even at this 
stage the advance in melting point appeared insufficient, and, 
as it was deemed advisable to avoid more platinum on account 
of the danger of its not alloying uniformly, palladium, which 
alloys readily, was added and the melting point increased to 
a total of app. 100 degs. F. above type three. No more pal- 
ladium was used on account of its decolorizing action. With 
the comparatively small content (4 per cent), the color of the 
alloy is still quite goldlike. 
This alloy has been used with uniformly good results. 
It may be soldered safely with coin gold (for split pins) and 
may be cast against safely if a comparatively heavy gauge 
of wire (above 16 g. B. & S.) is used. 
In view of the fact that for split pins, dowels for cast base 
crowns, etc., color is no object, it was deemed advisable to 
raise the melting point even above that of type four and the 
elastic gold was formulated, using a considerable percentage 
of palladium. The palladium, of course, decolorized the alloy 
completely, but raised the melting point very considerably, 
and, in conjunction with the copper and the considerable per- 
centage of platinum, produced an elasticity even beyond that 
of type four and a melting point very considerably higher. 
This alloy can be soldered with perfect safety with pure 
gold or anything below that in melting point. It may be cast 
against with perfect safety (except very thin wire) and re- 
tains its strength and elasticity after any reasonable num- 
ber of soldering, operations that it may necessarily be sub- 
jected to. It may be soldered very readily and with better 
union than iridio platinum. It is much more rigid than ordi- 
nary iridio platinum and possesses elasticity that is prac- 1012 
AN OUTLINE OF METALLURGY 
tically absent in all of the iridio platinum alloys, and it may 
therefore replace the latter and ordinary clasp metal for a 
great many purposes. 
In the making of split posts of the elastic gold it is advis- 
able to solder the area that is intended should remain solid 
with coin gold, as it offers a strong color contrast to the com- 
paratively white elastic gold. 
The line of demarkation between the solid and the split 
portions of the post will be then readily distinguished. As 
the coin gold is of sufficiently high melting point it will not 
reflow during later soldering operations. 
The comparative hardness and the elasticity of the four 
types of clasp metals and the “elastic” gold are approxi- 
mately as illustrated in the following: 
COMPARATIVE ELASTICITY AFTER 
ROLLING AND ANNEALING ONCE 
Type 
Type 
Type 
Type 
“Elastic” 
One 
Two 
Three 
Fo^r 
Gold 
10 
9 
8 
9 + 
10+ 
COMPARATIVE LOSS OF ELASTICITY AFTER 
SOLDERING AND ANNEALING THREE TIMES 
Type 
Type 
Type 
Type 
“ Elastic” 
One 
Two 
Three 
Four 
Gold 
2-3 
1-2 
1 + 
1 
.5-1 
Types one and two become very brittle if overheated dur- 
ing soldering. Type three is subject to same to a lesser de- 
gree, and type four only rarely. The “Elastic” gold appears 
practically immune to temperatures below the melting point 
of pure gold. 
Clasp metal should always be annealed before use, as 
manufacturers often neglect to do so after the rolling or draw- 
ing operations. 
Section IV 
Gold Solders 
In order to obtain the desirable uniformity of color in a 
denture without subsequent gold “washing,” it was neces- 
sary to formulate solders to correspond in color with the other AN OUTLINE OF METALLURGY 
1013 
alloys. Incidentally, it is well to consider the imposition that 
has been practiced upon the profession by some of the un- 
scrupulous manufacturers of gold solders. 
For many years a great many in the profession have been 
under the impression that gold solders stamped 18k. were 
actually 18k. (75 per cent gold) in fineness. This was not so, 
and a number of the manufacturers were producing, and are 
still producing, solders marked 18k., etc., anywhere from two 
to six karats below the mark. In addition, the solders men- 
tioned are not only deficient in gold content, but contain many 
deleterious alloying elements, such as high percentages of 
cadmium, iron, etc., in order to complete the required total 
content of metals in the solders. 
On the other hand, the reputable manufacturers have con- 
sistently stated that their solders were approximately two 
karats below the mark and intended for use on that karat of 
plate. The reputable manufacturers have recently started to 
stamp the actual fineness on their solders and the others have 
followed suit; hut some manufacturers still persist in the 
practice of misrepresentation by not actually furnishing the 
gold content indicated by the fineness stamp on the product. 
ALLOYS OF GOLD WITH METALS IX GROUP 3 
Besides zinc, the other three metals in Group 3, namely, 
cadmium, tin and aluminum, are being used to a very large 
extent as alloying elements in making gold solders. Cadmium 
if used in large percentages, debases the alloy very consid- 
erably and renders it practically unfit for use in the mouth. 
Tin is also used to a considerable extent, as it lowers the 
melting point of gold very considerably, hut it renders the 
gold quite brittle and aids materially in the tendency of the 
solder to burn into the work, which property is characteristic 
of all the so-called easy flowing solders. The term “easy 
flowing” is undoubtedly a misnomer. Rather, these solders 
melt “easy,” but do not flow easy. They ball up and stick 
and if the heat is forced to induce flow, they burn into the 
work with consequences too well known to require further 
discussion. 
The value of aluminum as a constituent of gold solders 
is yet to be proven. It is a constituent of most of the patent 
commercial alloys used by jewelers in compounding their 
solders. 
Solders made according to the following formulae will be 
found satisfactory in color, strength and fusing point, al- 
though higher in fusing point than the so-called easy flowing 1014 
AN OUTLINE OF METALLURGY 
solders for which there seems to be a “popular” demand. 
They will be found to flow readily if the work on which they 
are to be used is brought up to the proper temperature. 
FORMULAE FOR GOLD SOLDERS 
SOLDER No. 84 
1 
r Gold 
.. .84.0%] 
M. 
P. 
1650° 
F, 900° 
C.J 
Copper 
Silver 
. . . 7.5% | 
. . . 5.5% | 
Karat 
fine. 
1 
[ Zinc 
... 3.0% j 
SOLDER 
No. 76 
1 
[Gold 
...76.0%] 
1 
M. 
P. 
1550° 
F, 840° 
O.J 
Copper 
1 Silver 
...11.5% | 
.. . 8.5% 1 
18 
Karat 
fine. 
[ Zinc 
... 4.0% J 
1 
SOLDER 
No. 68 
1 
[Gold 
.. .68.0%] 
M. 
P. 
1450° 
F, 785° 
C.J 
Copper 
| Silver 
.. .14.5% | 
.. .12.5% | 
L161/2 
Karat 
fine. 
1 
[ Zinc 
... 5.0% J 
The first and second, 84 and 76, will be found sufficiently 
low in melting point for all ordinary operations, and where 
Dr. Peeso recommends the use of his No. 21 and No. 19 solder. 
The number 68 solder, although higher in actual gold content 
than the best so-called 18k. solder obtainable, is still too low 
a grade to be used in general work, especially in fixed bridge 
work, but may be used in connection with removable bridge 
work or plate work, because in that work or repair work there 
is required at times a lower fusing solder. 
Section V 
Compounding of Gold Alloys 
Although, the new series of alloys, made with practically 
no deviation from the formuhe which are given herein, may 
be purchased from the supply houses, the author considers it 
well to give a number of directions to those who may desire 
to compound the various alloys. 
It is not practical to make a small quantity, especially if 
for plate gold or solder, which is to be poured into an ingot 
mold and rolled. The higher the melting point of the alloy, 
the more necessary it is to have a comparatively large quan- 
titv and it is well not to attempt less than five ounces for plate 
gold and three ounces for solder. The elastic alloy should he 
made in even larger quantity, as it freezes very rapidly. 
Tt is practically impossible to alloy platinum or palladium 
with gold in the small blast furnace which the practitioner is AN OUTLINE OF METALLURGY 
1015 
likely to have in his laboratory. For all alloys with platinum 
metals (made on the small scale previously mentioned) it is 
well to alloy the gold and the platinum metals (rolled very 
thin) first on a charcoal block, using the nitrous oxide and 
illuminating gas blow-pipe, or preferably the oxygen and 
illuminating gas blow-pipe. A number of the alloyed nuggets 
can then be placed in a crucible on top of the required silver 
and copper content, covered with a suitable reducing flux and 
melted, poured into an ingot mold and rolled or drawn. 
When copper is to be used, it is essential that same be 
chemically pure and especial precaution must be exercised to 
prevent oxidation as far as possible, which latter can be 
accomplished by the use of a strong reducing flux. (See 
under fluxes.) 
A slight excess of copper should always be added to allow 
for some loss which invariably occurs. 
If the alloy that it is intended to make is to be used for 
casting purposes, the procedure is the same as previously de- 
scribed, excepting that the metal, when properly molten, can 
be poured into a pail of water and thus granulated. This 
procedure saves the labor of rolling the ingot and the granu- 
lated form of gold is as convenient to use for casting as any 
other. 
In all cases, just before pouring the contents, the crucible 
should be well shaken to insure a thorough admixture of the 
metals. 
Some writers advocate the preparation of alloys for cast- 
ing in the following manner: Melt the gold, feed the platinum 
(very thin) into the molten gold and then add copper, etc. It 
is impossible to make a uniform alloy in this manner, espec- 
ially if copper is used, because a considerable amount of the 
copper is oxidized on account of direct contact with the blow- 
pipe flame and in the author’s hands the directions previously 
given have been found to work out admirably. 
Tn compounding solders where zinc and copper are the 
constituents it has been advocated that brass which contains 
copper and zinc be used in order to prevent the loss of zinc 
through oxidation and volatilization. This is a very danger- 
ous practice and the results are very unsatisfactory, because 
it is impossible to obtain a commercial brass that does not 
contain a considerable percentage of lead, tin, and traces of 
antimony, etc., which are all very harmful substances and 
invariably tend to make the solders brittle. It is therefore 
necessary to first make an alloy of chemically pure zinc and 
chemically pure copper in a proportion of, say, one part zinc 1016 
AN OUTLINE OF METALLURGY 
and two parts copper. This alloy, when properly melted, is 
granulated by pouring into water and then, if carefully gath- 
ered, dried and weighed, the loss of zinc can be determined. 
The necessary additional copper to make the required alloy 
is then calculated and added when compounding the solder. 
It is well, of course, to make a considerable quantity of 
the copper zinc alloy, as the cost is slight and the prepared 
alloy is then available when wanted. It has been stated that 
zinc volatilates very readily from solders. This is quite con- 
trary to the author’s findings. The small percentage of zinc 
as given in the formulas herein is quite stable after remelting 
several times. The authors who claim this strong volatiliza- 
tion of zinc may have been dealing with a solder of unknown 
constitution in which they suspected zinc, but which probably 
contained a high percentage of cadmium, which volatilates 
quite readily. 
Section VI 
Refractory Materials 
INVESTMENT COMPOUNDS FOR SOLDERING 
The normal contraction of gold from the molten to solid 
state is approximately 2 per cent. The contraction of gold 
solder is practically the same, although some of the constitu- 
ents have a higher contraction than gold, but when combined 
in an alloy the movement is practically the same. 
While possibly there may be a slight difference between 
the contraction of solder and gold, a considerable contraction 
occurs nevertheless and is the cause of a great deal of trouble. 
A number of soldering investment compounds on the mar- 
ket are claimed by the manufacturers to possess neither ex- 
pansion nor contraction and therefore perfect. Granting, for 
the sake of the argument, that such is the case, we still have 
the contraction of solder to contend with and how are we to 
produce a soldered bridge or denture that will fit and go into 
place accurately when a number of the units in the work have 
been drawn together by the contraction of the solder? 
Unfortunately, we have not merely the contraction of the 
solder to contend with, but we have a much more prolific cause 
of disaster. For example, we have a number of completed 
sections, such as castings, to join together where but a very 
small quantity of solder is to be used, and yet after soldering 
we find that the finished piece is contracted and distorted and AN OUTLINE OF METALLUliGY 
1017 
will not go into position. The fact of the matter is, that prac- 
tically all the commercial compounds shrink npon heating 
when brought up to the proper temperature for soldering. 
In some commercial investment compounds, the shrinkage 
is extremely high, fully six or seven per cent* so it is evident 
that the principal cause of the trouble lies not so much in the 
actual contraction of the solder as it does in the great contrac- 
tion of the average investment, even before the case is quite 
hot enough to apply the solder. 
Fig. 968 
Fig. 968 shows an ordinary simple bridge assembled and 
ready for investment. The porcelain facings are spaced as 
Fig. 969 
per instructions from time immemorial. Fig. 969 shows the 
case invested and the distinct spacing of the backings. 
Fig. 970 
The case is then heated, and if an examination of the in- 
vestment is made with a magnifying glass, just before plac- 
ing it on the soldering block, it will he noticed that the units 
have been drawn together, as in Fig. 970, and when the case 
* See papers of J. G. Lane in Dental Cosmos and Dental Digest, 1910-14. Also 
M. A. Ward in Dental Cosmos. These contributions are very interesting and the 
most valuable that have appeared pertaining to the subject. 1018 
AN OUTLINE OF METALLURGY 
is soldered and cooled, the facings are very apt to be checked 
on account of having been brought together into very strong 
contact. 
When attempting to place back on the cast, difficulty is 
encountered, but as the plaster yields, the bridge is forced 
Fig. 971 
down and then becomes evident the loss of the contact points, 
as illustrated in Fig. 971. 
This discrepancy will not be considered by some opera- 
tors as a serious factor. In fact, those who solder directly 
on the cast destroy the evidence for the time being. If it is a 
fixed bridge, it is forced home some way or other and let go 
at that, but, on the other hand, if a removable bridge, even as 
small in dimension as the one illustrated, it is practically 
impossible to place it in position and the matter is a most 
serious one, as a good many operators have found. 
Some writers advocate completing the dummies and then 
placing them in perfect contact to prevent the shrinkage of 
the solder used to unite the sections. This is practically im- 
possible, because the metallic units are infinitely stronger than 
Fig. 972 
the investment and expanding under heat will invariably split 
the investment (see Fig. 972), and thus often cause a serious 
distortion in the soldered piece. 
There seems to have been, as a search of the literature 
has shown, absolutely no consideration given to the movement 
of the refractory mass that holds the parts in situ during the 
preliminary heating and final soldering operations. AN OUTLINE OF METALLURGY 
1019 
The author’s aim in experimenting lias been not merely 
to produce an investment compound that would not shrink, 
but one that would actually expand, move in unison with the 
solid invested metal, and spread the units sufficiently so that 
when a reasonable amount of solder is flowed to connect the 
units, the contraction of the total piece would he neutralized 
hy the expansion of the investment. 
Before attempting to formulate an investment compound 
possessing such properties, it is necessary to consider the 
chemical and physical properties of refractory materials 
which may be employed in the compounding of investment 
materials. 
In one of the well-known books on crown and bridge 
work,* the following appears: 
“ Many substances may be used in combination with plaster of paris, 
which is necessarily the basis because imparting the property of crystalliza- 
tion, and which must be incorporated to the extent of at least 50%. 
“ The remaining proportion may be then composed of such materials as 
will, by virtue of their characteristics and physical properties, meet such 
requirements. The following are serviceable: 
Powdered Silex, 
Fine Asbestos, 
Beach Sand, 
Marble Dust, 
Pulverized Pipe Clay, 
Powdered Fire Brick, 
Magnesium Oxide, 
Pumice Stone. 
“A combination of any, of these ingredients in varying proportions with 
the proper quantity of plaster will usually possess the necessary qualities, 
etc., etc.” 
Before even considering a compound of expanding prop- 
erties, it is well to thoroughly understand the properties of 
plaster of paris and the other materials enumerated in the 
list of suitable refractories in order to see if it is possible to 
even produce an investment compound that will at least not 
shrink under heat. 
Plaster of paris, Oa S04 (calcium sulphate), is made by 
burning: gypsum rock. In the process of burning, most of the 
water is driven off. The phenomena of recombining with 
water and crystallizing is well known and need not be dis- 
cussed here. It is universallv employed as the binder for all 
investment compounds used both for soldering and casting. 
It shrinks very strongly upon heating, but for want of a bet- 
ter material must be employed. 
The wore plaster used in an investment compound, the 
harder the resultant mass will be and the more shrinkage will 
take place. As will be shown subsequently, any such propor- 
tion as the 50 per cent mentioned hy the author quoted is ahso- 
PLASTER OF PARIS 
* Goslee's Principles and Practice of Crown and Bridge Work, pp. 36-37. 1020 
AN OUTLINE OF METALLURGY 
lately out of question, because it has been found, so far, im- 
possible to compensate for this contraction of the binder by 
the addition of any other material, even if possessing the 
property of expansion. 
POWDERED SILEX 
Silex is the commercial term applied to silicon dioxide 
(Si 02), which is the main constituent of rocks, stones, clays 
and many other minerals. A great deal of it is also found 
in a free state and in the form of quartz, rock crystal, flint, 
opal, chalcedony, etc. The so-called silex is often practically 
pure Si 02. However, different varieties of silicon dioxide 
exist, and although all of a similar chemical composition they 
possess varying physical properties. 
Silica obtained from quartz or rock crystal consists of 
sharp crystalline particles and possesses a high specific grav- 
ity, 2.6 to 2.8. It expands considerably upon heating, hut 
loses this property gradually upon reheating frequently or 
fusing completely.* The melting point of pure silica is ap- 
proximately 3,200 degs. F. 
Another variety of silica that exists quite as frequently as 
the crystalline is an amorphous form which possesses a lower 
specific gravity, 2.2 to 2.4. It has very little expansion upon 
heating and some varieties of the same tvpe do not expand 
at all.** 
Still a third variety exists in a tabular form and is ex- 
tremely light and porous. It is known as diatomaceous earth 
or kieselguhr. Its specific gravity is 1.6 to 1.8. It is mined 
in very great quantities and used very extensively as a heat 
insulating agent, but contracts very strongly and therefore is 
totally unfit for use as part of a dental refractory compound. 
As stated before, these various forms of silica can be ob- 
tained in almost a pure state and are alike chemically, but 
the term “powdered silex” means nothing unless a particu- 
lar type is specified, and the individual who is not conversant 
with the matter is as likely as not to purchase and use a 
grade of least expansion. The crystalline variety, of high 
* Utensils made of fused silica are replacing platinum ware to a great extent 
in chemical work. As the coefficient expansion is very small (.00000054 per ° C), 
it is possible to subject crucibles, casseroles, etc., to rapid changes of tempera- 
ture without danger of breakage. Apparatus suitable for dental purposes is man- 
ufactured by the Thermal Syndicate, Ltd., of New York. 
** Both surface and volume expansion of silica must be considered in selecting 
the grades of silica to be used. AN OUTLINE OF METALLURGY 
1021 
specific gravity, expands considerably under heat, and in this 
fact lies the solution of the ivhole problem. 
A mixture of 50 per cent plaster of paris and 50 per cent 
silica, even if the latter is of the variety possessing the high- 
est expanding properties, contracts very considerably when 
brought up to the temperature required for soldering or cast- 
ing operations. 
In order to be brief, the author will state that all the other 
items in the list of suitable materials have a positive shrink- 
age, with the exception of beach sand. The objection to the 
latter is the fact that it is often quite impure and the iron and 
alkalies that form the major portion of the impurities usually 
act as a flux and thus lower the melting point. 
It is well to state that magnesium oxide and marble dust, 
which latter is, of course, calcium carbonate, are subject to a 
particularly strong contraction under heat. 
Fig. 973 illustrates the comparative shrinkage of one of the 
best commercial compounds obtainable. A considerable space 
Fig. 973 
Fig. 974 
will be noted between the mass of investment and the rim of 
the metallic ring in which it was placed after mixing, permit- 
ted to set and heated to soldering temperature. 
Fig. 974 (in cross-section) shows even more clearly the 
contraction, after heating, when a straight edge is placed 
across the top of the flask. 
To summarize the whole proposition, the author will state 
that in order to produce an investment compound which merely 
does not shrink, hut actually expands sufficiently to follow the 
movement of a red hot ring, it is necessary to use a grade 
of silica as pure as possible and of the highest expansion, 1022 
AN OUTLINE OF METALLURGY 
which means, of course, a grade silica from the quartz group 
and a grade of plaster of paris of the least contraction* As 
previously mentioned, any such proportion as 50 per cent 
plaster cannot be used, because the expansion of the best sil- 
ica, great as it is, is not sufficient to compensate for even the 
shrinkage of the plaster, hence a lower percentage of plaster 
and a higher percentage of silica must be used. 
Formula for Investment Compound (Soldering) 
Per Cent 
Plaster of paris (Excelsior Brand No. 3). .Parts 33 
Silica (fine) (F. F. F.) Parts 45 
Silica (coarser) (M. C.) Parts 22 
Total 100 
A compound made according to this formula will be found 
to expand upon heating to soldering temperature sufficiently 
to fill a red hot ring, as in Figs. 975 and 976. 
Fig. 976 
Fig. 976 
This property of expansion is sufficient to counteract the 
contraction of a normal hulk of solder. Furthermore, this 
expansion is sufficient to follow the movement of invested 
metallic sections that have been previously completed. This 
compound sets promptly and is sufficiently strong to hold the 
invested parts in situ firmly. It will withstand the action of 
boiling water (when washing out the wax) without disintegra- 
tion. 
* It is, no doubt, well known that fine plaster contracts more than coarse plas- 
ter when subjected to heat. Most of the coarse building plasters are rather non- 
uniform and do not possess the binding power of the finer plasters. The grade 
selected is quite uniform and not too coarse to prevent efficient binding of the 
mass. AN OUTLINE OF METALLURGY 
1023 
Dr. Peeso has long ago demonstrated the great impor- 
tance of not soldering work directly on the cast. The work 
should be so assembled that the waxed up structure could be 
lifted off the cast, which is made of plaster of paris or a more 
durable material, such as “Artificial Stone” (made from the 
author’s formula) and then transferred to the investment 
compound. After soldering, the work could be placed hack 
on the cast, which is intact, and required corrections could be 
made by grinding or trimming where necessary before the 
structure is even tried in the mouth. 
Of course, the author has made numerous and exhaustive 
experiments to determine the properties and behavior of vari- 
ous refractory materials and it is important that the grades 
of silica and plaster specified be used. 
As the reader can deduct from the preceding, the terim 
silica and plaster of paris mean very little, because while the 
different grades of silica are practically alike chemically, they 
differ very materially physically. To the author’s knowledge 
it is possible to purchase at least three or four hundred dif- 
ferent brands of plaster and over a thousand distinct grades 
of silica with varying percentages of impurities and varying 
sizes of particles.* There is no intention to claim that this 
is the last word on the subject. No doubt, other experi- 
menters will succeed in producing as good or even a better 
compound with other grades of material. 
INVESTMENT COMPOUNDS FOR CASTING 
The elements of error caused by the physical behavior of 
the metallic alloys and the refractory materials utilized in 
the casting process are quite analogous to the conditions that 
exist in the soldering process. Gold, no matter how alloyed, 
as far as present knowledge of the subject indicates, does con- 
tract in the transition from the fluid or plastic state to the 
solid or frozen state, and an inlay investment compound that 
possesses the property of expansion will at least in a measure 
compensate for the contraction of gold. 
It is not the author’s aim here to exhaustively discuss 
casting problems in general. He simply wishes to suggest a 
* The materials used in the formulae given were obtained from W. B. Daniels. 
252 Front street, New York City, who is a dealer in minerals and chemicals. He 
will supply the ingredients for both the soldering and casting compounds in quan- 
tities suitable for the requirements of the practitioner. Of course, it must be 
remembered that such comparatively cheap materials are, as a rule, sold by the 
ton or carload. Hence, Mr. Daniels’ willingness to furnish these materials in small 
quantities at a moderate price deserves commendation. 1024 
AN OUTLINE OF METALLURGY 
formula for wliat he considers a better investment compound 
than is purchasable and to point out some of the physical 
phenomena of existing conditions. Before discussing the for- 
mula, it is well to first consider some of the conditions that 
have to be dealt with. We have not only the contraction of 
gold to contend with, but we also have the contraction of the 
wax, and that is a most serious factor indeed. The contrac- 
tion of wax is usually productive of a greater degree of error 
than the actual contraction of gold. 
This subject has been covered most thoroughly by Dr. C. 
S. Van Horn of Bloomsburg, Pa., in his articles in the Dental 
Cosmos,* and his conclusions are yet to be controverted. 
The conditions which he successfully corrects are the fol- 
lowing: After the removal of a wax pattern from the mouth 
at body temperature, it contracts considerably upon reaching 
room temperature and still more when invested with cold 
water. His method consists of investing the pattern at ap- 
proximately 110 degs. F., which increase in temperature not 
merely compensates for the contraction of the wax, but also 
expands the wax to almost completely counteract the shrink- 
age of the gold. 
In addition, he uses an expanding investment (made from 
the author’s formula) and the total expansion of the wax, 
coupled with the expansion of the investment, enables Dr. Van 
Horn to produce the most accurate fitting inlays the author 
has ever seen. 
A study of Dr. Van Horn’s technique will amply repay 
anyone who is desirous of obtaining better results. 
Dr. James G. Lane of Philadelphia was among the first 
to point out the value of silica as an ingredient of inlay in- 
vestment compounds, on account of its expansion and conse- 
quent ability to counteract the contraction of plaster of paris 
(the binder). The formula that he used (plaster 25 per cent 
and silica 75 per cent) expands considerably. Dr. Lane was 
also among the first to point out the fact that a hot mold was 
stronger than one that was heated and allowed to cool. 
In the utilization of the casting process, there are a great 
many important factors to be considered, among them the fus- 
ing point of the investment compound which constitutes the 
mold; the relation of this degree of fusibility to the tempera- 
ture of the mold, at the time the molten metal enters it; the 
temperature of the molten metal at the time it enters the mold 
and the pressure used to force the molten metal into the mold. 
* 1911, pp. 664, 472, 1109; 1912, pp. 890, 973; 1914, p. 940. AN OUTLINE OE METALLURGY 
1025 
The fusing point of an investment compound, made of 
plaster of paris and pure silica, is under 3000 degs. F. Some 
of the commercial investment compounds, which are made 
with impure silica containing a considerable percentage of 
iron and feldspar, which latter contains alkalines, such as 
sodium and potassium, are often considerably lower fusing, 
consequently when superheated gold is cast into such a com- 
paratively fusible investment a partial union is bound to take 
place, with the consequence that the gold partly unites with 
the investment and the resultant casting is quite rough and 
inaccurate. 
The strong possibility of such a condition as described 
leads the author to state his opinion on that apparently never 
ending controversy regarding the casting of gold in a hot or 
cold flask. This point has been argued time and time again, 
some operators claiming that they obtain better results by 
casting into a hot flask and others maintaining the reverse. 
In order to discuss the subject intelligently, we must also bear 
in mind the degree of heat that is utilized for melting the 
metal to prepare for its entrance into the mold. 
Let us first consider the following: 
HOT OR COLD MOLD USING ILLUMINATING GAS AND COMPRESSED 
AIR BLOW-PIPE 
We will discuss this phase first, because the great majority 
of castings are accomplished by using the ordinary gas and 
air blow-pipe. The maximum temperature that it is possible 
to produce with artificial gas and compressed air is approxi- 
mately 2450 degs. F. The temperature of the investment in 
the casting ring when red hot is about 1300 degs. F. If this 
“red hot” flask is placed on the casting apparatus and a quan- 
tity of gold, say, 5 dwts., placed in the crucible, it will take 
about two and a half minutes’ exposure to an efficient blow- 
pipe flame to bring the gold to the proper state of fluidity to 
enter the mold. In the meantime, the “red hot” mold (on the 
casting apparatus) has cooled considerably and the actual 
temperature of the cavity in the mold at the time the gold 
enters it can be safely calculated not to exceed 900 degs. F. 
Therefore, casting into a “red hot” flask with an ordinary 
gas and air blow-pipe is done with the mold not red hot, but 
at a temperature approximately 900 degs. F. 
In casting into a so-called “cold” flask, using the same 
blow-pipe and quantity of metal, it will be found that it takes 
longer, say four minutes, to bring the metal into a state of 1026 
AN OUTLINE OF METALLURGY 
fluidity, and although the flask is at room temperature when 
the process of melting the gold is started, the subjection of the 
mold to the flame of the efficient blow-pipe for a period of 
approximately four minutes raises the temperature of the 
mold to an extent of nearly 700 degs. F. Therefore, when it 
is attempted to make a casting with the ordinary gas and air 
blow-pipe in a so-called “cold” flask, the temperature of the 
mold at the time the gold enters it is approximately 700 degs. 
F. 
Upon considering both conditions and comparing the tem- 
peratures of the molds, namely, 900 degs. and 700 degs., it 
will be readily seen that there is comparatively little differ- 
ence between the two at the actual time that the casting is 
done, and consequently both the “hot mold” and cold mold” 
advocates are right, strange as that may appear, providing, of 
course, that the ordinary gas and air blow-pipe is employed. 
The author’s experiments along this line have shown con- 
clusively that it is hardly possible to superheat the gold with 
an ordinary gas and air blow-pipe or bring the gold to such a 
temperature that it will unite with the investment at any stage 
of the procedure, and it is the author’s firm opinion that in 
the hands of the careless or inexperienced operator, the ordi- 
nary gas and air blow-pipe is a positive insurance against 
superheating the gold, and therefore insures a casting satis- 
factory, at least as far as errors consequent to the superheat- 
ing of gold are concerned. 
HOT OR COLD MOLD USING ILLUMINATING GAS AND NITROUS 
OXIDE OR OXYGEN BLOW-PIPE 
Here we have a totally different and quite often a dan- 
gerous condition to contend with. While the ordinary gas 
and air blow-pipe is capable of producing temperatures only 
somewhat beyond 2400 degs. F., it is possible to obtain, with- 
out difficulty, 3400 to 3500 degs. F. from nitrous oxide and 
illuminating gas and over 4000 degs. F. from pure oxygen 
and illuminating gas. It may be well at this time to call 
attention to the fact that the often used term “Oxyhydrogen” 
is incorrect when used in connection with illuminating gas 
because of the fact that in order to produce an oxyhydrogen 
flame it is necessary to have both oxygen gas and hydrogen 
gas, whereas ordinary illuminating gas contains less than 
half of its volume of hydrogen and the balance is principally 
methane (carbon, etc.). AN OUTLINE OF METALLUBGY 
1027 
It is rather difficult to avoid superheating gold when apply- 
ing such extreme temperatures and extreme caution must be 
exercised by the operator. 
As a rule, the cold flask is indicated when using extreme 
temperatures for melting the gold, because the gold melts very 
rapidly (15 to 20 seconds), and comparatively little heat is 
transmitted to the mold. The mold is then comparatively 
cool, and even if somewhat superheated gold is cast it is'not 
so apt to unite with the investment as when both the gold and 
the mold are superheated. 
The author has very often made failures of castings on 
account of superheating the gold and he wishes to impress 
strongly the fact that extreme caution must he exercised in 
this connection. 
The nitrous oxide or oxygen end gas blow-pipe offers ad- 
vantages over the ordinary gas and air blow-pipe as a means 
of producing heat rapidly, but the maximum temperature 
attainable with the ordinary gas and air blow-pipe acts as a 
sort of an insurance against superheating and, in fact, if 
efficiently used, produces satisfactory casting results in all 
ordinary operations. 
One of the most prolific causes, in fact, probably the great- 
est cause that is productive of faulty castings, is the excessive 
pressure used in forcing metal into the mold. The principal 
reason for this is due to the fact that in the majority of cast- 
ing apparatus, there is no provision for obtaining a definitely 
measured and indicated amount of force. It takes just so 
much and no more pressure to force gold into a given mold 
and hold it there until solidification begins. Excessive pres- 
sure will not, under ordinary conditions, prevent the normal 
contraction of gold, because the mold into which the gold is 
cast yields and hence will distort in the same proportion as 
excessive pressure is applied. It may be true that a pressure 
of 2,000 pounds per square inch may totally prevent contrac- 
tion, hut where is the mold that will stand that pressuref 
It is unfortunate that more operators do not realize the 
true value of an efficient casting apparatus, such as the Tag- 
gart, and the false economy resulting from the use of an in- 
trinsically faulty or makeshift device. 
By using a grade of silica of maximum expansion and a 
grade of plaster of minimum contraction, it is possible to pro- 
duce an investment compound as follows: 1028 
AN OUTLINE OF METALLURGY 
Formula for Investment (Casting) 
Plaster (Excelsior Brand No. 3) Parts 29 
Silica (Fine) (F. F. W.) Parts 71 
Total 100 
The plaster is the same as is used in the soldering invest- 
ment. The silica is similar to the fine grade utilized in the 
soldering investment formula, but it is purified and combines 
with water readily without releasing dirt, scum, etc.,* and 
consequent bubbles. An investment made from this formula 
will be found to expand slightly more than Dr. Lane’s for- 
mula, although the plaster of paris content is higher and, for 
the same reason, somewhat stronger and more resistant to 
excessive pressure. 
It is a well-known fact that very few commercial invest- 
ment compounds are uniform in composition. In other words, 
although manufacturers claim that their formulae are adhered 
to, there appear variations in batches purchased at different 
times. This is due to the fact that insufficient attention is 
paid to testing the different batches of raw material and also 
to the faulty compounding due to the large quantities mixed 
at a time. One commercial preparation has been found, on 
the contrary, quite uniform, for the simple reason that the 
manufacturer pays especial attention to the testing of the raw 
materials and compounds the mixture in comparatively small 
quantities (200 to 300 lbs. to the mix). 
In mixing the plaster of paris and silica, it is not neces- 
sary to do any sifting, because the specified materials may 
be obtained evenly and definitely graded. All that is required 
is a thorough mixture without excessive trituration. 
A very efficient small mixing apparatus may be obtained 
from J. H. Day Co., Cincinnati, Ohio. It is known as the 
“Hunter” (experimental size) and will handle from seven 
to eight pounds of material. The ingredients are weighed 
out, placed in the container and the apparatus revolved slowly 
for 25 to 30 minutes. This produces a uniform and intimate 
mixture without crushing or grinding the plaster. This point 
is very important, and if smaller quantities are mixed in a 
mortar, it is important to use very light pressure in order not 
COMPOUNDING OF INVESTMENT MATERIALS 
* Bubbles and froth produced upon attempting to combine investment com- 
pound and water are often caused by dirt or such impurities as mica, etc., con- 
tained in the silica. AN OUTLINE OF METALLURGY 
1029 
to crush the plaster particles. The mixed material, of course, 
should be properly stored and protected against moisture. 
The soldering investment should be mixed quite thick. 
The thicker, the better, up to a certain limit, of course. If 
mixed too dry, the plaster of paris content does not obtain 
sufficient moisture to crystallize properly and act efficiently. 
A good consistency is 41 to 42 grammes powder to each 15 
c.c. water, or 26 dwts. (Troy) to one-half fluid oz. water. 
The inlay investment should be mixed in a proportion of 
32 grammes powder to 15 c.c. water, or 20 dwts. (1 Troy oz.) 
powder to y2 fluid oz. water. This quantity is sufficient to 
fill an ordinary inlay flask. 
These proportions produce a mixture that allows ample 
time for manipulation, provided considerable time is not spent 
in adding a little more water, a little more powder, etc. The 
setting time of the plaster naturally controls the setting time 
of the whole mixture, and as the action of retarding agents 
added to control the set of plaster is sometimes indefinite and 
often harmful, it is advisable not to attempt to interfere ivitli 
the normal setting time of the plaster. 
The compound, if mixed without any unnecessary delay, 
sets sufficiently slow for all ordinary operations. It is the 
author’s practice to have on hand a number of cork-stoppered 
bottles containing the dry compound (weighed) and a num- 
ber of rubber-stoppered vials containing water (measured). 
The accurately measured powder and water are thrown sim- 
ultaneously into the mixing bowl and having no bubbles or 
froth (as with graphite compounds*) to contend with, the 
mix can be made ready for use in from 30 to 40 seconds, thus 
allowing ample time for coating the pattern and imbedding in 
flask. This method is superior to using the automatic weigh- 
ing apparatus furnished bv some of the compound manufac- 
turers, as they are often either inaccurate or not sufficiently 
“flexible.” 
Tt is not advisable to attempt to invest more than one 
pattern at a time. When a larger mix is to be made for a 
INVESTMENTS, DIRECTIONS FOR USE 
* Most of the compounds that contain flake graphite are very difficult to mix 
on account of the air content in the flakes and their tendency to “ float.” Such a 
compound requires a considerable period of time to mix, and therefore a retarded 
plaster is usually employed. Nodules, or “ ghosts,” on castings occur frequently 
because the material is not “ dormant ” until “ set.” A manufacturer of such a 
compound claims that it is the plaster and not the graphite that causes the bubbles. 
This statement appears quite contrary to the facts. Kerr’s “ Graphite ” Invest- 
ment is made with previously treated graphite and it is the best commercial 
preparation that the author knows of. 1030 
AN OUTLINE OF METALLURGY 
larger flask, three to five per cent more powder than a given 
quantity of water demands is not only permissible, but ad- 
visable. 
Another advantage in using measured and stored water 
lies in the fact that it is, when used, at room temperature and 
not at hydrant temperature, and the room temperature water 
does not induce a further contraction of the wax pattern dur- 
ing the process of investing. 
HEATING OF INVESTMENTS 
The soldering investment may be heated quite promptly 
upon setting. Boiling water does not affect it materially and 
the wax may be washed out thoroughly, the case fluxed and 
immediately placed on the heat, moderate at first and then 
brought up quite rapidly to a good red heat prior to the actual 
soldering operation. 
It is the inefficient and insufficient heating of the invested 
work that is partly to blame for the “popular” demand for 
“ easy flowing” solders. Properly heated investments facili- 
tate the flow of normal or even high fusing solder. 
A small quantity of potassium sulphate or sodium chlo- 
ride may be used to hasten the setting of the investment, but 
that is rarely, if ever, necessary, because it sets quite 
promptly if mixed to the proper consistency. 
The inlay investment should be permitted to set for at least 
thirty minutes to insure a fair crystallization (so-called “in- 
itial set”) of the plaster. The flask should then be placed 
over a low heat and kept there until the moisture disappears 
and the wax begins to diffuse and carbonize. The heat is in- 
creased somewhat during the latter part of this operation and 
still further increased until the mold is brought up to either 
a dull red heat (for cold mold) or a bright red heat (for hot 
mold). 
The initial stages of heating must be a temperature that 
will not permit the wax to run out of the mold, as it is im- 
portant that the wax be absorbed in the mold. Forced heat- 
ing and a generation of steam during the initial stages of the 
drying process will force the wax out of the mold and pro- 
duce a rough interior which in turn will show its effects upon 
the casting, the resultant casting being rough, incorrect, and 
usually unfit for use. Tt is, of course, essential to confine and 
concentrate the (higher) heat in order to bring the mold to 
the proper temperature within a reasonable period of time. 
Prolonged heating of the investment is even more dan- AN OUTLINE OF METALLURGY 
1031 
gerous than underheating, as plaster of paris, which is the 
binder, shrinks in proportion to the time that it is exposed to 
heat. The total heating operation for an ordinary mold (in- 
lay, etc.) should not exceed fifty minutes, or an hour at most. 
It may be divided into three periods, say twenty-five to thirty 
minutes for low drying heat, then increased somewhat for ten 
to fifteen minutes, and finally subjected to the highest heat for 
not more than from ten to fifteen minutes. 
It is permissible not to heat a case until two or three hours 
after the investment has been mixed, but if it is permitted 
to stand for a day or two and loses all moisture, if then heated 
and cast, the resultant casting is apt to be very poor. It is 
hard to determine the actual principle involved, and it is not 
important to do so, but the fact does exist. In addition, under 
such conditions, the investment is very apt to crack or split 
upon heating. The author usually heats and casts into 
“green” molds, but has found that a dry mold, if moistened 
prior to heating, appears to behave almost as well as a 
“green” mold. If the mold is only a few hours old it is moist- 
ened slightly, but if it is more than a day old it is placed in 
water until saturated to the extent of a “green” mold. 
Both the soldering and casting investment compounds are 
practically immune to “checking” or “cracking” even under 
the most severe heating conditions.* 
Section YII 
Fluxes 
FLUXES FOR SOLDERING AND CASTING 
For sweating, soldering or melting metals in the construc- 
tion of bands, crowns, bridges or castings, the selection and 
use of the proper flux or fluxes is a matter of the utmost im- 
portance, especially if the metals or alloys used are oxidizable 
or volatile when subjected to heat. 
Ordinary borax, or calcined borax, has been the principal 
flux used for this purpose. It has been almost universally 
used by jewelers and the dentist has followed suit. There is, 
* This fault is inherent in most investment compounds; the causes are numer- 
ous and principally due to the producers ignoring the physical laws governing the 
selection and compounding of materials for the purpose. One of the principal 
errors in this connection is the attempt to form a “ concrete-like ” mass without 
realizing that there is a very great difference in the behavior of dental investment 
compounds and concrete used in building operations. 1032 
AN OUTLINE OF METALLURGY 
however, a considerable difference between the class of work 
that the jeweler and the dentist perform. 
In dental soldering, we use higher grade solders and a 
considerably higher heat, during the various operations. As 
ordinary borax melts at a comparatively low temperature, it 
does not act as efficiently during the higher temperature stages 
as the requirements demand. The tendency of borax when 
considerable heat is applied is to liquefy strongly and run 
down to the deep portions, leaving the other portions, that 
it is desired to solder, insufficiently protected. Dr. Peeso 
recognized this long ago by using a combination of borax and 
boric acid, which combination melts at a higher temperature 
than borax alone, does not liquefy so readily, stays on the 
surface and protects the work longer and is more efficient in 
every way. 
An efficient flux that has served very satisfactorily in the 
author’s hands for a considerable period of time is the fol- 
lowing: 
Formula for Soldering Flux 
C. P. Borax Glass (fused) Parts 55 
C. P. Boric Acid (not fused) Parts 35 
C. P. Silica Parts 10 
Total 100 
The ingredients are placed in a clean clay or sand crucible 
and brought to a fair red beat. They combine quite readily 
and when quite fluid the mixture is poured into cold water. 
As this glass is quite soluble, it must be removed from the 
water as soon as possible, dried and pulverized to pass an 
80-mesh sieve. It may be pulverized without difficulty, as the 
particles are very frail and brittle. 
This flux may be used either in the powdered form or 
compounded with (<vaselineto form a paste, or dissolved in 
boiling water and the saturated solution used. In the liquid 
form, it will he found suitable for all general operations where 
the work can be heated so as to drive off the moisture and 
thus leave a coating of the flux, as in bands, crowns, etc. 
When the work is in an investment, the grease flux will be 
found most useful, as it may be applied just after the case is 
washed out and still warm. The carrier (vaseline) flows down 
into the deep portions and crevices, carrying the particles of 
flux along. The powdered dry flux can be used on invested 
work under the blow-pipe when more flux is required. Strips AN OUTLINE OF METALLURGY 
1033 
of solder can, of course, be coated with either the liquid or 
the grease flux and heated prior to use. 
This soldering flux in a powdered form will also be used 
as the base for both the reducing and oxidizing fluxes to be 
discussed. 
It is important that the forms of borax and boric acid 
specified be adhered to because of the variable amount of 
water that these materials contain when purchased. 
The formula of borax glass is NaoBXb, whereas ordinary 
borax, either powdered or crystals, contains a considerable 
proportion of water which is evident from the formula Na2B4 
07 + 10H2O. Therefore the borax glass is preferable to the 
ordinary borax containing water because it occupies much less 
space and is, therefore, more convenient to handle in small 
crucibles. However, if ordinary borax is used the water con- 
tent must be calculated and provided for in weighing out the 
ingredients. The boric acid used does contain water, as will 
be seen from the formula H:!B03, because it is more stable 
than the fused boric acid Bl.O.> and more readily obtainable. 
The silica should be pure and in the form of a fine powder so 
that it may combine readily.* 
In connection with the casting process, it is necessary to 
treat buttons of gold, both during casting and before recast- 
ing, with a flux that will take care of the acquired impurities, 
Very often there have appeared statements to the effect that 
a mixture of potassium nitrate and borax be used to cleanse 
buttons before recasting. This statement has been, in a good 
many cases to the author’s knowledge, misunderstood. Potas- 
sium nitrate is an excellent oxidizing agent and does remove 
base metals, but its use in treatment of casting buttons is con- 
tra-indicated, because generally when casting gold alloys con- 
taining copper, etc., it is desired to retain the base metal, the 
copper, in a reduced metallic form and not in an oxidized 
form. Consequently, if a flux is to be used it must be of a 
distinctly reducing nature. 
Reducing fluxes are used extensively in assaying and 
smelting operations and their properties are well known. In 
the case of casting, it is rather difficult to utilize all the benefit 
that may be derived from a reducing flux on account of the 
REDUCING FLUX 
* The grade (F. F. W.) used in inlay casting investment is quite suitable. 1034 
AN OUTLINE OE METALLURGY 
difficulty of applying same to the molten metal which is ex- 
posed to the blow-pipe flame which drives off the flux almost 
as fast as it is applied. Therefore, to obtain any considerable 
benefit from a reducing flux, it is necessary to not merely 
apply same while the gold is fluid under the blow-pipe, but 
also to sprinkle an additional amount in the manner described 
in the following: After placing flask on casting apparatus, 
place button or nuggets of gold into crucible, melt without flux 
until the mass of gold assumes a spheroidal form and com- 
pletely covers the sprue hole. Then apply some flux by sprin- 
kling, continue melting until the gold is in a proper state of 
fluidity for casting, then remove flame, add some more flux 
and instantly apply the casting pressure. 
Formula for Reducing Flux 
Soldering Flux (Base) Parts 40 
Borax Glass Parts 30 
Argol... Parts 25 
Animal Charcoal Parts 5 
Total 100 
Argol is the commercial term for crude potassium bitar- 
trate, KHC4H406 (cream of tartar), and has a higher reduc- 
ing power than pure cream of tartar. Tf the latter is used it 
should be increased to about 25 parts and the soldering flux 
and borax glass content reduced in proportion. 
A flux of this character will practically prevent the bring- 
ing into the casting of oxidized material and can be used to 
advantage in remelting and cleansing buttons of gold for re- 
casting. 
The author’s procedure for this operation is as follows: 
After a casting is made, the residue button is placed into 
hydrofluoric acid for 15 or 20 minutes, removed and melted 
with the blow-pipe in a charcoal block, using the reducing flux, 
which, in addition to reducing the oxidized copper in the but- 
ton, combines with the silica, traces of which may still adhere 
to the button. After the button is melted and the flux used 
has segregated into a globule, the blow-pipe is removed and 
a small quantity of ammonium chloride is sprinkled on the 
button. As soon as the button has solidified, and while still 
red, it is plunged in dilute hydrochloric or sulphuric acid. 
Most of the glass formed by the flux will splinter off. If any 1035 
AN OUTLINE OF METALLURGY 
considerable quantity adheres, it may be removed by boiling 
in the same acid. 
Potassium nitrate is a most excellent oxidizing agent and 
removes base metals, the only objection being the strong 
fumes which are given off during the melting process. Al- 
though the operator should rarely attempt to do refining, it 
is well to have a suitable oxidizing flux that will not give off 
the objectionable fumes characteristic of potassium nitrate. 
OXIDIZING FLUX 
Formula for Oxidizing Flux 
Soldering Flux (base) Parts 55 
Potassium Chlorate Parts 20 
Sodium Perborate Parts 25 
Total 100 
This flux will be found useful for revivifying buttons of 
gold which are contaminated. It is sufficiently powerful to 
volatilize such impurities as tin, cadmium, bismuth, etc. It 
will combine with adherent investment compound and not 
attack copper very strongly, so that a button of gold that has 
been used several times and is quite sluggish and dirty can 
be usually brought into good shape without difficulty. 
A button treated with this flux should be cleansed in acid, 
as previously described, and then remelted with the reducing 
flux prior to use for casting. 
In cases of refining, where a stronger action is required, 
the potassium chlorate and sodium perborate can be increased 
to obtain the same efficiency that a high percentage of potas- 
sium nitrate would give without the objectionable fumes char- 
acteristic of the latter. 
It is expected that prepared flux made according to the 
formulas given will be very shortly available from the supply 
houses. Until such time, a modification of the soldering flux 
formula, which also acts as a base for the reducing* and oxi- 
dizing fluxes, is given herewith for the benefit of those who 
have not the facilities for fusing and pulverizing the material. 
These ingredients make a flux which appears to work much 
* There are a number of better reducing agents than those suggested by the 
author used industrially. They are not mentioned because of either difficulty of 
application under casting conditions, or on account of not being obtainable in 
small quantities. A study of the methods used in deoxidizing copper, brass and 
bronze is suggested to those particularly interested. 1036 
AN OUTLINE OF METALLURGY 
more satisfactorily than ordinary borax or any of the secret 
preparations purchasable. 
Formula for Soldering Flux (Substitute) 
C. P. Borax Glass Parts 50 
C. P. Boric Acid Parts 43 
C. P. Sodium Silicate (dry powd.) Parts 7 
Total 100 
This is mixed thoroughly in a mortar and must be fine 
enough to pass an 80-mesh sieve. 
The author trusts that his remarks upon the importance 
of producing castings with all the metal in a reduced form and 
not in a partially oxidized form will be given some considera- 
tion by the reader, as this problem, on an immeasurably larger 
scale, has been and is one of the most important ones in the 
application of industrial alloys, and is being coped with suc- 
cessfully. 
TABLE 4 
MELTING POINTS OF THE NEW SERIES OF ALLOYS 
AND STANDARD DENTAL GOLDS 
ojr> 
Alloy 
°C 
2100 
* “ Elastic ” Gold 
1150 
2075 
*Plate No. 1 
1135 
1975 
*Plate No. 2 
1080 
1960 
Type 4 Clasp 
1070 
1945 
Pure Gold 
1063 
1945 
*Casting Gold “A” 
1063 
1945 
* Casting Gold “D” 
1063 
1945 
“Green” Gold [App. Au. 80%—Ag. 20%] 
1061 
1900 
* Casting Gold “B” 
1035 
1900 
Light 22K Plate 
1035 
1860 
Medium 22K Plate 
1015 
1860 
Type 3 Clasp 
1015 
1825 
Dark 22K Plate 
995 
1800 
*Casting Gold “C” 
980 
1760 
Light 20K Plate 
960 
1735 
Coin Gold (21.6K) 
946 
1725 
Type 2 Clasp 
940 
1650 
*Gold Solder No. 84 
900 
1625 
Gold Solder for 22K 
885 
1600 
Type 1 Clasp 
870 
1550 
*Gold Solder No. 76 
840 
1525 
Gold Solder for 20K 
820 
1450 
*Gold Solder No. 68 
785 
1425 
Gold Solder for 18K 
770 
The ten alloys marked * constitute the new series. They 
are all uniform in color with the exception of ‘‘Elastic” Gold, 
which is similar to platinum in color, and Casting Gold “A,” 
which is similar to pure gold in color. AN OUTLINE OF METALLURGY 
1037 
Some of the Applications of the New Series of Alloys 
in the Peeso System of Removable 
Bridgework 
As will be seen from the preceding table, the series of 
alloys offers a wide range of variation in melting point over 
the ordinary alloys, thus facilitating the performance of suc- 
cessive soldering operations. 
CONSTRUCTION OF BANDS, FLOORS AND INNER CAPS 
As has been previously stated, coin gold is the most suit- 
able alloy for the construction of bands, floors, etc. It is 
therefore necessary to use its equivalent in the new series of 
alloys. The band should, therefore, be made of the No. 2 
plates (M. P. 1975 degs. F., 1080 degs. C.), and united* by 
soldering with the next lowest fusing alloy, namely, Casting 
Gold “B” (M. P. 1900 degs. F., 1035 degs. C.). 
The band is also prepared of No. 2 plate and attached 
with Casting Gold “B” (the pliers grasping the band at pre- 
viously joined portion). 
The method will make, for all intents and purposes, a 
seamless cap. The melting point of the soldered junctions 
will be still considerably above that of coin gold. The tube 
may be then attached with the No. 84 solder. 
Outer caps for telescope crowns are made in exactly the 
same manner. As the hardness and tenacity of the No. 2 
plate is the same as that of coin gold, the same gauges of plate 
are to be used as with coin gold. The casting gold, if used as 
solder, should be of practically the same thickness as ordinary 
gold solder, app. 27 or 28 gauge B. & S., or preferably thinner 
(30 to 32 g.). 
OUTER HALF BANDS AND TELESCOPE CROWNS 
After completing the inner cap, the outer half band and 
floor are made of suitable gauge No. 2 plate and the split pin 
is attached and the half band united to the floor with the No. 
84 solder. 
For telescope crowns, the outer band is made of the No. 
2 plate and the joint soldered with Casting Gold “B.” The 
wings are made of No. 2 plate and soldered to the band with 
Casting Gold “C.” The cusp is swaged of No. 1 plate (higher 
fusing than pure gold), filled with Casting Gold “C” in the 
same manner as a pure gold cusp is filled with coin gold and 
* See Dr. Peeso’s method of band preparation for sweating. 1038 
AN OUTLINE OF METALLURGY 
attached to the previously completed outer band and wings 
with No. 84 solder. 
If the cusp is to be cast, Casting Gold “B” or “C” should 
be selected according to the blow-pipe used and attached to 
the contoured band with No. 84 solder. 
As all of the alloys of the series used in this operation 
are of the same color and the No. 84 solder is actually 20k. 
fine, there will be no line of demarkation evident in the fin- 
ished work. 
INLAY ABUTMENTS 
The shell for the inner inlay may be cast with Casting 
Gold “D” and adapted to the cavity by burnishing. The 
tube is then soldered and completed with No. 84 solder. The 
outer inlay matrix can then be made, using the comparatively 
soft but high fusing plate gold No. 1 and Casting Gold “C,” 
instead of pure gold and coin gold. 
CONSTRUCTION OF SADDLES 
The saddles, if swaged of platinum, may be reinforced 
with Casting Gold “B” or “C,” instead of coin gold, or the 
saddles may be swaged of No. 1 plate (softer than No. 2) and 
reinforced with Casting Gold “C.” If the saddles are to he 
cast, Casting Gold “B” or “C” should be selected according 
to the blow-pipe used. 
In constructing the dummies (if all porcelain), the bases 
and dowels may be cast with either “B” or “C” and attached 
to the saddles with the 84 or 76 solder. 
They may also be made by burnishing 34 g. pure gold 
backings to the prepared porcelain crowns, fitting and sol- 
dering dowels made of “Elastic” gold or type four clasp 
metal to the backings (or boxes) and attaching the completed 
backings to the saddles with 84 and 76 solder. 
CONSTRUCTION OF DUMMIES 
The author cannot close without calling attention to the 
fact that a broad conception of the scientific principles in- 
volved in the chemical and physical behavior of the various 
materials utilized in connection with the construction of pros- 
thetic restorations is a most potent factor toward the attain- 
ment of the ideal. 
He has been aided materially in arriving at the conclu- 
REMARKS 1039 
AN OUTLINE OF METALLURGY 
sions presented herein by the kindness of Mr. H. C. Ney, 
president of the J. M. Ney Co., who unstintingly placed at 
the author’s command all the facilities of their metallurgical 
research laboratory in Hartford. (“Dental Metallurgy,” 
Weinstein.) 
Iron 
PHYSICAL PROPERTIES 
Atomic weight, 55.84. Specific gravity, 7.84. Melting 
point, 1530° C. Malleability, 9th rank. Ductility, 4th rank. 
Tenacity, 3d rank. Conductivity of heat, 11.9. Conductivity 
of electricity, 14.8. Specific heat, 0.1138. 
Iron, like gold has been known and used since the earliest 
times. It is almost universally distributed over the earth in 
some form or other. The oxide of iron in the form of red 
and yellow ochre is the principal coloring pigment in clay, 
sand and rocks. The ores of iron are also found in almost 
every country on the face of the globe. These are in the form 
of oxides, carbonates and sulphides, and their name and 
chemical composition, according to Bloxam, are given in the 
table below: 
Common Name. 
Chemical Name. 
Composition. 
Magnetic iron ore. 
Protosesquioxide of iron. 
Fe3 04. 
Red haematite. 
Sesquioxide of iron. 
Fe2 03. 
Specular iron. 
Sesquioxide of iron. 
Fe2 03. 
Brown haematite. 
Hydrated sesquioxide of 
iron. 
2 Fe2 03 3H2 0. 
Spathic iron ore. 
Carbonate of iron. 
Fe 0 Co2. 
Clay iron stone. 
Carbonate of iron with 
clay. 
[Carbonate of iron with 
Black band. i 
clay and bituminous 
matter. 
Iron pyrites. 
Bisulphide of iron. 
Fe S2. 
Iron very rarely occurs native, owing to its strong affinity 
for oxygen and other non-metallic elements. It is found 
native in meteorites and in minute particles in basaltic rocks, 
but not in quantity sufficient to be of recognized value. 
Magnetic iron ore is the protosesquioxide of iron, and is 
commonly called lodestone when strongly magnetic, and pos- 
sesses the property of attracting small particles of iron sim- 
ilar to a horseshoe magnet. It furnishes a most excellent 
quality of iron, examples of which are the Wootz steel and 
the Swedish iron. 
Bed haematite, so called from its dark, blood-red color, 
is a sesqui oxide of iron. It is a remarkably abundant or*s 1040 
AN OUTLINE OF METALLURGY 
being found all over the world, and contains about 70 per 
cent iron, 30 per cent oxygen. 
The sesquioxide sometimes occurs as a steel-gray mineral, 
and it is then called specular iron ore. 
Brown haematite is also a very common ore of iron, and 
is the hydrated sesquioxide of iron, containing about 15 per 
cent water. It is sedimentary in character and is often mixed 
with wood, clay and sand. The lake ores of Europe and this 
country are of this variety. 
Spathic iron ore is the carbonate of iron and occurs crys- 
tallized in veins and beds, and also in globular masses. When 
first mined it is yellow, but soon turns brown on exposure to 
air. Most of the iron used by the Krupp iron works of Essen 
is derived from this ore. 
Clay ironstone is the carbonate of iron with clay, and con- 
tains about 34 per cent of iron. It often occurs with or 
accompanies coal formations, of which it is the characteristic 
ore. 
Black hand. When clay ironstone contains more than 10 
per cent coaly matter it resembles shale, slate or cannel coal, 
and is a valuable ore for the reason that the coal it contains 
is sufficient to burn or roast it. 
Iron pyrites is the bisulphide of iron and is of a bright 
yellow, crystalline structure, with a distinct metallic luster. 
It is largely used in the manufacture of sulphuric acid, but is 
not, to any extent, of value as an ore of iron. 
REDUCTION OF IRON ORES 
Most iron ores containing carbon dioxide or sulphur are 
roasted to drive off these elements or combinations and to 
reduce the ore to an oxide. The ore is then mixed with cer- 
tain proportions of calcium carbonate (limestone), which acts 
as a flux, and with coal, charcoal or coke, and thrown into a 
blast furnace. Under the influence of heat and the blasts of 
air which are directed into the bottom of the furnace the fuel 
is converted into C02. As this ascends in the furnace it 
passes over the red-hot fuel in the higher portions and is con- 
verted into CO. 
The carbon monoxide thus formed reduces the ore to the 
metallic state by combining with the oxygen with which the 
iron is united and becomes C02 gas, which is thrown out of 
the furnace, leaving the iron free and uncombined. This sinks 
through the slag (the calcium carbonate which has united with 
the earthly impurities of the ore) to the bottom of the fur- 
nace, where it is retained in a fluid condition until sufficient 1041 
AN OUTLINE OF METALLURGY 
quantity lias accumulated, when the furnace is tapped. The 
slag from time to time is removed through openings placed 
higher in the furnace than that from which the iron is drawn. 
The metal is drawn off from the furnace and conducted 
into a ditch or trough formed in the sand, and from this into 
lateral openings in the form of half cylinders, called pigs. In 
this condition it is crude cast iron, and can be used in this 
form for many purposes or be refined by subsequent opera- 
tions and reduced to the purer condition of steel or wrought 
iron. 
For general purposes iron is used in three distinct forms, 
as cast iron, steel and wrought iron, all consisting of iron with 
more or less carbon. 
Cast iron contains the largest percentage of carbon, the 
quantity varying from iy2 to 7 per cent. Steel contains from 
1 to 1 y2 per cent of carbon, and wrought iron contains the 
smallest percentage of the three varieties, having less than 
14 of 1 per cent. 
PRODUCTION OP WROUGHT IRON 
Wrought iron is produced from cast iron by extracting 
most of the carbon present. This is accomplished by remelt- 
ing pig iron and directing a blast of air upon the heated sur- 
face of the molten metal to remove some carbon and other 
impurities that may be present, after which it is cast into 
molds, and is now known as plate metal. 
The second step is designed to more fully free the metal 
from its carbon, and this is done by the process called 'pud- 
dling. The ingots of plate metal are introduced into a rever- 
beratory furnace, and again melted. At a certain stage oxide 
of iron is added to the molten metal and the mass mixed, or 
puddled, as it is called, with long iron bars, until the oxide of 
iron is diffused through the molten metal. 
Under continued heat the oxygen in the last mass added 
unites with the carbon in the plate metal and forms C02, 
which escapes as a gas. After a time the mass assumes a 
pasty condition, when it is divided into balls of about 90 
pounds each, removed from the furnace and subjected to in- 
tense pressure by rolls and converted into bars or blooms. 
Two or three of these blooms are again heated and welded 
together, and the rolling process repeated once, twice and 
sometimes three times, depending on the quality of the iron 
desired. In this changed condition it is tough and fibrous and 
elastic, its malleability, ductility and tenacity have increased, 1042 
AN OUTLINE OF METALLURGY 
and it is now capable of being welded, a property which cast 
iron does not possess. 
PRODUCTION OF STEEL 
Steel is made in two ways, first by direct process from 
cast iron, which is known as the Bessemer process, and from 
wrought iron by the cementation process. 
THE BESSEMER PROCESS 
The Bessemer process consists in melting cast iron in large 
crucibles called converters, capable of holding several tons, 
and when in a molten condition, directing a blast of cold air 
upon its surface. The oxygen in the air unites with the car- 
bon in the molten metal and frees the iron from carbon in 
this manner to a greater or less extent, depending on the 
length of time the process is continued. The best results are 
attained by purifying the iron to as great a degree as pos- 
sible, and afterward adding a given quantity of cast iron 
containing a known percentage of carbon. 
THE CEMENTATION PROCESS 
The Cementation process consists in placing bars of 
wrought iron in fire brick muffles, together with alternate lay- 
ers of charcoal, and sealing the charge in so as to exclude the 
air. Heat is then applied to the exterior of the muffle and 
maintained for 7 or 8 days. 
Upon examination it will be found that the fibrous struc- 
ture of the iron has become granular and that its hardness, 
elasticity and sonorousness have increased. 
It is more brittle and less malleable and ductile than be- 
fore. Its surface is covered with blisters, and in this condi- 
tion is known as blister steel. By arranging it in bundles, 
subjecting it to heat and the blows of a trip hammer, it is 
rendered dense and compact. 
This reduces it to a condition known as shear steel. This 
process is sometimes repeated, and it is then known as double 
shear steel. When blister steel is remelted and cast into in- 
gots it is known as cast steel. 
Steel possesses the property of being rendered so hard 
that no tools of ordinary form or composition will affect its 
surface. This is accomplished by heating it a full (cherry) 
HARDENING AND TEMPERING STEEL AN OUTLINE OF METALLURGY 
1043 
red, and suddenly chilling it by plunging in water or some 
medium that will rapidly conduct away the heat. This is 
called full hardening. For many purposes steel in this con- 
dition is too hard for use, and its hardness must be reduced 
or tempered to meet the required purposes. 
When instruments are shaped to proper form they are 
first full hardened. The surfaces are then polished so that 
the colors which appear on subsequent heating, and which 
indicate the varying degree of hardness, may be accurately 
observed. 
The polished steel is now passed back and forth through 
a Bunsen flame or heated in any other manner, if more con- 
venient, until the proper color appears, when the instrument 
should be suddenly cooled to prevent further reduction of its 
hardness. Sometimes an alloy of tin and lead, which melts at 
a known temperature, is used for drawing the temper to the 
required point. 
Bessemer steel usually contains such a small percentage 
of carbon that it is not possible to render it full hard, and, 
consequently, it cannot be tempered. 
All dental instruments, especially edge tools, should be 
made from the finest tool steel. 
The following table indicates the various colors as they 
appear on steel when drawing the temper, the yellows appear- 
ing first. It also indicates the alloy that may be used for 
securing any given temper: 
TEMPERING STEEL 
ALLOYS FOR TEMPERING 
Temperature 
Color. 
Temper. 
Lead. Tin. 
Melting 
215°—232°C 
Very faint yellow to 
Lancets, razors, surgical instruments, 
enamel 
points. 
pale straw color 
chisels 
7.85 4 
215°—232°C 
243 °C 
Full yellow 
Excavator s, very small cold chisels 
10 4 
243°C 
254°C 
Brown 
Pluggers, scissors, pen knives 
14 4 
254°C 
265°C 
Brown with purple 
spots 
Axes, plain irons, saws, cold chisels—large 
Table knives, large shears 
19 4 
265°C 
276°C 
Purple 
30 4 
276°C 
287°C 
Bright blue 
Swords, watch springs 
48 4 
287°C 
293°C 
Full blue 
Fine saws, augers 
50 4 
293°C 
315°C 
Dark blue 
Hand and pit saws 
315°C 
Platinum 
Platinum was discovered in 1735 in the province of Choeo, 
Colombia, South America, in the sands of the river Pinto. 
The credit of this discovery belongs to Antonio de Ulloa, a 
Spanish naval officer and explorer. Six years later an En- 
glishman, a Mr. Wood, who was traveling in Jamaica, secured 
some specimens of this metal and presented them to Watson, 
a noted chemist at that time, who recognized in them the pres- 
ence of an unknown metal. Some years later Schaffer, who 1044 
AN OUTLINE OF METALLURGY- 
was examining the new metal, declared it to be “white gold.” 
In Spain it was called “platina del Pinto,” which, translated, 
means “little silver of the Pinto,” and from which the pres- 
ent name, platinum, was derived. 
In 1803 Wollaston discovered two other metals associated 
with platinum, viz., palladium and rhodium. 
About the same time Tennant discovered iridium and 
osmium. 
In 1828 Berzelius analyzed polyxene, the Siberian plat- 
inum mineral, and found it contained platinum, iron, pallad- 
ium, iridium, rhodium, osmium and copper. With the excep- 
tion of iron and copper, these metals largely constitute what 
is known as the platinum group. 
DISTRIBUTION 
Platinum is found in many parts of the world, South 
America, Australia, Canada, United States and Mexico — all 
yielding moderate amounts. 
Recently some discoveries of vein platinum in Wyoming 
have been made which promise to he very productive. 
The largest bulk of the world’s supply comes from Rus- 
sia, whose platinum placers and mines have become world 
renowned. 
The total production in that country from 1824 to the 
present time amounts in round numbers to 250,000 pounds. 
Platinum was used as money in Russia from 1828 to 1845. 
During this period the volume of coinage amounted to 4,250,- 
000 roubles, or about $3,000,000. 
The production of platinum during the period of its coin- 
age was greatly stimulated, which, however, almost entirely 
ceased when it was demonetized. 
The great demand for platinum in recent years for elec- 
trical, chemical and general scientific purposes has been so 
marked that the metal is being as eagerly sought for as is gold 
in all of the principal productive fields of the world. On 
account of the great demand and limited supply, it ranks in 
value very much above gold. 
OCCURRENCE 
Platinum usually occurs in nature in placer deposits, sim- 
ilar to gold, frequently accompanying the latter in the alluvial 
deposits of rivers. 
The mother lode, from which the placer deposits are de- 
rived, consists usually of serpentine or magnesium iron sili- 
cate, which is closely related to chrysolite. 1045 
AN OUTLINE OF METALLURGY 
Placer platinum usually occurs in rounded grains, flakes 
or pellets. Occasionally nuggets of medium size are found, 
and in two or three instances large ones weighing from 15 to 
21 pounds have been discovered. The largest one mentioned 
is preserved in the Demidoff museum. 
PHYSICAL PROPERTIES 
Pure platinum is a very soft metal, tin white in color. It 
is not readily acted on by acids, with the exception of nitro- 
muriatic, in which it is readily dissolved. It does not oxidize 
even at very high temperatures, and for this reason fills a 
place in the arts and sciences for which the oxidizable metals 
are unsuited. 
MALLEABILITY 
Platinum is very malleable, and can be beaten out into 
extremely thin foil, in which form it is used for many pur- 
poses. It ranks sixth in this quality among the other metals. 
DUCTILITY 
This metal can be drawn into extremely fine wire. Dr. 
Arendt states that a cylinder of platinum 5 inches long and 1 
inch in diameter can be drawn into a wire sufficiently long to 
encircle the globe. The fine wire used in microscopic eye- 
pieces is made by coating platinum wire with silver and draw- 
ing this composite wire to the finest possible state, then dis- 
solving off the silver with nitric acid. 
In point of tenacity platinum occupies third rank. This 
property is so marked in platinum as to render it especially 
valuable for dowels in crowns and for the truss work in porce- 
lain bridges. The addition of from 10 to 15 per cent of 
iridium greatly increases its tenacity, as well as its hardness, 
elasticity, infusibility, and resistance to chemical action. 
TENACITY 
SPECIFIC GRAVITY 
The specific gravity of platinum is 21.4, two others hav- 
ing greater density — osmium 22.47 and iridium 22.40. These 
three are the heaviest of the metals. 
CONDUCTIVITY OF HEAT 
Platinum is low in lieat conductivity. Compared with 
silver at 100, it ranks 8.4. Its co-efficient of expansion is low, 1046 
AN OUTLINE OF METALLURGY 
being only .0009. For this reason it is especially valuable for 
the pins of porcelain teeth, since the expansion of both the 
metal and porcelain is nearly the same, and, consequently, 
there is less liability of fracturing the porcelain in baking. 
Compared with silver, which ranks 100 in conductivity of 
electricity, platinum ranks 14.5, or, in other words, this metal 
offers about seven times more resistance to the passage of a 
current than does silver. 
CONDUCTIVITY OF ELECTRICITY 
Platinum fuses at 1755 deg. C., the oxyliydrogen blowpipe 
or the electric arc being required to effect it. 
Dr. L. E. Custer of Dayton, Ohio, has devised a simple 
yet effective method of fusing platinum scrap, the outline of 
which is here given: 
The first method consists in fastening the positive end of 
a wire capable of carrying a 110-volt current into a carbon 
block. An ordinary battery plate will answer the purpose. 
To the negative pole is attached an electric light carbon of 
ordinary size. A resistance coil, lamp or electric furnace 
should be included in the circuit capable of furnishing from 
8 to 12 ohms resistance to prevent the fuses from blowing out. 
It is necessary to make the positive and negative connec- 
tions as described, as when so arranged the fusing can be 
accomplished more rapidly and with less noise than when re- 
versed. 
With 12 ohms resistance from 6 to 8 pwts. can be fused at 
once, while with 8 ohms an ounce can be melted at one time. 
By keeping the edge of a bulk heated and adding a fresh 
supply, the mass can be elongated indefinitely. As much as 10 
ounces have been melted in this manner in the form of a rod, 
and the rod afterward drawn into a fine wire. 
Platinum fused in this manner is harder than new plat- 
inum, the cause assigned being due to a small per cent of car- 
bon uniting with the platinum. 
To obviate this hardness a second method was devised, 
which is as follows: 
A piece of heavy platinum wire is attached to the positive 
terminal, and this is laid on a block of lime so shaped as to 
serve as a receptacle for the scrap. The other terminal con- 
sists of a brass rod five-eighths of an inch in diameter and 8 
inches long, covered most of its length with wood to insulate 
FUSING POINT AN OUTLINE OF METALLURGY 
1047 
it. In the exposed end a slit is made, in which a nugget of 
platinum of at least one-half oz. weight is fastened. Too 
small a piece would fuse in the arc. The scraps are laid on 
the platinum wire forming the positive terminal, which is 
placed in the depression in the lime block. The arc is estab- 
lished by interposing a stick of carbon between the negative 
pencil and the scrap, and, when established, quickly removing 
it. This step is necessary to prevent the scrap fusing to the 
nugget on the negative end. 
The eyes should be protected by wearing glasses of the 
darkest variety, as the arc light is intensely brilliant. This 
Fig. 977 
method of fusing platinum is recommended as practical for 
dental laboratory procedures. 
In a fused condition platinum absorbs oxygen, and when 
cooling “spits” as the gas is given off, none of it being re- 
tained or occluded when cold. 
When a jet of hydrogen is directed on spongy platinum, 
the latter begins to glow, and the gas ignites. 
Platinum black is formed by adding platinum chloride 
solution to a boiling mixture of 3 parts of glycerine and 2 
parts of caustic soda. The platinum is thrown down as a 
black powder. In this form it absorbs about 800 times its 
volume of oxygen from the air. 
USES 
Platinum is used for many purposes in dentistry, espec- 
ially in combination with porcelain. It is used for base plates 1048 
AN OUTLINE OF METALLURGY 
and the metal parts and trusses in continuous gum dentures 
and in porcelain crown and bridge work, as a matrix material 
in inlay work, for pins in porcelain teeth and for electric fur- 
nace construction. It is also used in combination with gold in 
the form of foil, for filling teeth, being harder and more neu- 
tral in color than pure gold. It requires more care in condensa- 
tion than pure gold, however, to develop its welding property 
in the highest degree. 
In the chemical, electrical and scientific fields, it has a wide 
range of usefulness, being utilized in many instances for pur- 
poses for which no other metal is adapted. 
ALLOYS 
Its principal alloys for dental purposes are its combina- 
tions with iridium, for hardening and increasing its tenacity, 
and gold in the composition of solders for platinum, and for 
clasp metal. 
It is also combined with silver, the resulting alloy being 
harder than either of component metals and less oxidizable 
than silver. This alloy is known as dental alloy, and is used 
to a considerable extent in Europe as a base for artificial 
dentures. 
DENTAL ALLOY 
Silver 70 or 80 
Platinum 30 or 20 
Gold solder can be used in conjunction with this alloy. 
PLATINUM SOLDER AND CLASP METAL 
These formulas are given in connection with the alloys of 
gold. 
Iridium 
Iridium is one of the metals of the platinum group, and 
resembles the latter in some respects, but is much harder. 
When combined with platinum, the resulting alloy has greater 
tenacity and hardness than platinum, and, therefore, for this 
quality alone it is valuable for dental uses. 
The specific gravity of iridium is 22.40, atomic weight 
192.65, and fusing point 2350 deg. C. 
On account of its hardness, it is used alone and in com- 
bination with osmium for watch and compass bearing, the 
knife edges of delicate balances, and for the nibs of gold pens. 
It ranks in value somewhat higher than platinum. AN OUTLINE OF METALLURGY 
1049 
Silver 
Silver is found in many parts of the world, but the West- 
ern Continent has the richest and most extensive deposits 
known. 
It is impossible to briefly enumerate the many practical 
uses found for this metal. 
It is brilliant white in color, very soft, malleable and duc- 
tile, and moderately tenacious. Its specific gravity is 10.53, 
specific heat .056, and it fuses at 960.5 deg. C. It is the best 
known conductor of heat and electricity, and is taken as the 
standard of measurement of all of the metals in these proper- 
ties, being rated at 100. 
ORES OF SILVER 
Silver sometimes occurs native, but is more often asso- 
ciated with other metals and with non-metallic substances. 
One of the principal ores of silver is the sulphide Ag. S,.called 
argentite. This is grayish black in color, and is readily fus- 
ible. It contains about 87 of silver. Pyrargyrite Ag3 Sb S3. 
Silver copper glance (Ag Cu) 2S. Stephanite Ag5 Sb S4, with 
lead as argentiferous galena and in several other combina- 
tions. 
The reduction of silver is accomplished by three principal 
methods. 
First. Amalgamation. 
Second. By the wet method. 
Third. By the lead method. 
REDUCTION 
AMALGAMATION 
In the first process, the silver, after being reduced to a 
chloride, is amalgamated with mercury, from which it is re- 
covered by distilling the latter off. There are three different 
methods of recovery of silver by amalgamation, each of which 
is more or less complicated, and in this treatise it is not ad- 
visable to enter into the details of them. 
There are several wet processes, all of which depend upon 
the solubility of the sulphide and chloride of silver in water, 
or some other solvent, from which the silver is thrown down 
by a precipitant, usually copper. 
WET METHOD 1050 
AN OUTLINE OF METALLURGY 
THE LEAD METHOD 
By this method the silver is concentrated in a quantity of 
lead, from which it is recovered by cupellation. 
Cupellation consists in heating an alloy of silver and lead 
in a porous cupel, or shallow crucible, made from prepared 
bone ash. Under the influence of heat, the lead is oxidized 
and absorbed by the porous cupel, while the silver remains 
in the crucible. 
USES IN DENTISTRY 
Silver occupies a prominent place in the dental office and 
laboratory. It is the principal metal used in the compounding 
of dental amalgam alloys. It is used as an alloying agent with 
copper and gold in the various gold plates and solders used in 
the laboratory. 
Were it not for the fact that sulphur has such a strong 
affinity for silver, as to readily discolor it, the latter would 
have a much greater range of usefulness. For the reason 
mentioned, although it possesses most of the necessary re- 
quirements, silver is not suitable as a base for artificial den- 
tures, nor for crowns and bridges. Before the introduction 
of vulcanite, however, it was used extensively as a base plate 
because of its cheapness as compared with gold or continuous 
gum dentures. 
It is not possible to attach teeth to silver base plates with 
vulcanite, because the sulphur in the rubber acts on the silver, 
forming silver sulphide. It disintegrates the rubber to such 
an extent that all attachment of vulcanite to base plate is 
destroyed or never effected. 
Silver is not readily acted upon by oxygen, but when fused 
it mechanically absorbs about 22 times its volume of this gas. 
The “spitting” so noticeable when fused silver solidifies, is 
due to the forcing out or escape of the oxygen, nearly all of 
which Is expelled. 
This peculiar affinity between oxygen and silver in a fused 
state renders the production of sharp castings of this metal 
a difficult matter. 
ALLOYS OF SILVER 
U. S. coin silver is composed of 90 parts silver and 10 
copper. The latter is added to harden the silver, which, un- 
alloyed, is almost as soft as pnre gold. 
In Great Britain and Europe the profession is using an 
alloy composed of silver and platinum for dental purposes. AN OUTLINE OF METALLURGY 
1051 
It does not discolor quite so readily as silver alone, but is 
not by any means free from the action of sulphur. It is more 
rigid than coin silver, and in some mouths can be worn for a 
long time without discoloring. 
In compounding this alloy, the rule commonly followed 
of melting the highest fusing ingredient first is reversed. The 
platinum is rolled into a very thin ribbon, the silver melted, 
and the platinum gradually fed into it. The two metals will 
unite at a temperature far below the fusing point of platinum. 
Silver solders are composed of silver and copper, with 
some other ingredient, usually zinc, to reduce the fusing point. 
The following are standard formulas for some of the solder 
used in the dental laboratory and by jewelers: 
Low fusing, 
Silver 6 
Copper 3 
Zinc 2 
High fusing. 
Silver 6 
Copper 2 
Zinc 1 
A method followed by jewelers is to take a silver coin, 
add one-half its weight of spring brass wire, and fuse under 
a flux. Solder prepared in this manner usually flows readily. 
Purple of Cassius, a pigment used to impart a pink color 
to porcelain enamel, is formulated as follows: 
Silver 432 grs. 
Gold 48 grs. 
Tin 36 grs. 
The gold, silver and tin are melted together in the order 
named, and granulated hv pouring into cold water, repeating 
the process several times to insure thorough mixture of the 
metals. 
The granulated alloy is then treated with nitric acid to 
remove the silver, the residue is a brown powder of unknown 
composition, hut containing gold and tin, which is called 
Purple of Cassius, and which, as before stated, will produce 
varving shades of pink in porcelain, according to the amount 
used. Tt may also he prepared by addins: a solution of stan- 
nous end stannic chlorides to auric chloride. 
The Chemistry of Photography 
Some of the salts of silver, as the bromide and the iodide, 
are exceedingly sensitive to the influence of light, and when 
exposed to it are readily reduced to black metallic silver on 
being subjected to the action of various reducing agents. 1052 
AN OUTLINE OF METALLURGY 
Photographic plates or films are coated with a layer of 
gelatin emulsion, containing one or both of the salts men- 
tioned. The emulsion is applied to one side of the plates only, 
in the dark, or with ruby light, allowed to dry, after which 
they are wrapped in light-proof paper, packed and sealed in 
boxes or packages, in which condition they must be kept until 
ready for use. 
When a plate so prepared is placed in the plate-holder of 
the camera and light is transmitted to it through the lens, 
the various areas of the plate are affected in different degrees 
by the light which falls upon them, according to the depth or 
intensity of the shadows and lights of the view reflected and 
the time of exposure. Where no light falls, the silver salt 
is unaffected. Medium shadows produce moderate decompo- 
sition, while bright light affects the silver salt most intensely. 
When an exposed plate is examined under ruby light, no 
visible alteration in the film can be seen until brought to view 
by developing. 
To develop the latent image and make it visible, the plate 
is immersed in a liquid developer. The silver salt upon which 
the strongest light was directed is first and most readily de- 
composed by the developer, being resolved into metallic silver. 
The portions not so strongly affected by the light are acted 
upon more slowly, and on developing show correspondingly 
lighter shadows. When the image shows up distinctly and 
clearly, the development must be stopped immediately; other- 
wise the plate will become fogged from the action of the de- 
veloper on the less affected portions of the silver, which will 
in time be reduced. 
The development is arrested and the plate cleared up by 
immersing it in a solution of hyposulphite of soda, which dis- 
solves out the unreduced silver bromide, but does not act 
readily on the metallic silver. The heavy shades and shad- 
ows are formed by the reduced or metallic silver, which is 
held in suspension in the film of gelatin and thus accounts 
for the varying degrees of intensity of the negative. 
The hypo, as it is called, must be removed by thorough 
washing before the negative is exposed to the light, other- 
wise the silver salt which is dissolved by it, but not yet re- 
moved, will thicken the shadows and the transparency of the 
plate be affected. 
Many kinds of developers are in use, each having some 
peculiar quality which renders it specially adapted for some 
particular purpose. The following expresses in a general AN OUTLINE OF METALLURGY 
1053 
way the chemical action which occurs in the use of any of 
the standard developers: 
3AgCl + 3FeS04 = 3Ag + FeCl3 + Fe2 (S04)3. 
The negative is a reverse of the object photographed, the 
light shades being dark and the dark tints light. To obtain 
a positive or true likeness, a similar process is carried out, 
the silver salts again being the sensitized factor in the paper 
on which the picture is to be printed. In printing, the dark 
areas of the negative produce light tints on the paper, and 
the light, dark, according to the facility with which the light 
passes through negative and decomposes the silver in the sen- 
sitized paper. 
Ag.I., the iodide, Ag.Br., the bromide, and Ag.Cl., the chlo- 
ride, are used in photography. 
Copper 
Copper was one of the first metals known to the ancients, 
probably because it is found so widely distributed over the 
earth. From it weapons, ornaments, and useful implements 
of all kinds were made. The ancients employed a method of 
tempering edge tools made from this metal, which is now con- 
sidered a lost art. 
Copper is distinguished from all other metals by its red 
color. It is very soft, malleable, ductile and tenacious. It 
fuses at 1083° C., or a little below pure gold. Copper is an 
excellent conductor of electricity, ranking 97.8, silver being 
100. Its specific gravity is 8.9, specific heat, .093 and atomic 
weight, 63.57. 
Copper is not readily oxidized in dry air at ordinary tem- 
perature, but is easily affected under the influence of heat. 
In moist air a green carbonate is quickly formed, and when 
acted upon by acid fumes, it oxidizes rapidly. 
ores 
Copper frequently occurs native in large masses, particu- 
larly in the Lake Superior region. The most common ores 
of copper are tabulated below: 
Cu 02— cuprite, or red oxide. 
Cu 0 — Melaconite, or black oxide. 
Cu Fe So Chalcopyrite — copper pyrites. 
Cu CO:! Cu Ho Oo— Green malachite. 
(2 Cu CO, Cu Ho 02)—Blue malachite. 
Cu2 S — Chalcocite — Copper glance. 1054 
AN OUTLINE OF METALLURGY 
REDUCTION 
The ores of copper are reduced by two principal methods, 
known as the dry and the wet method. In the dry method the 
ore is subjected to treatment in the reverberatory furnace, 
which drives off impurities and leaves it free as a sulphide. 
It is then strongly heated with sand, which reduces it to an 
oxide. The oxide is then mixed with some form of carbon 
and subjected to a very high temperature. The oxygen, in 
combination with the copper, unites with the carbon to form 
C02 which escapes, leaving the metal free. 
When the wet method is employed, the ore is mixed with 
rock salt and calcined, which converts the copper into a sol- 
uble cupric chloride. The calcined ore is then lixiviated with 
water, and from the resulting solution the copper is thrown 
down in a metallic state by the addition of scrap iron. 
USES 
Copper is used for many purposes, and in great quanti- 
ties, unalloyed, especially in the electrical field. On land, and 
under the sea, hundreds of thousands of miles of copper wire 
are laid, and by means of the telephone and telegraph, com- 
munication with most parts of the civilized world is possible 
in a few minutes or hours ’ time at most. 
In every dynamo and motor, copper wire is used, and in 
numberless instances a single machine contains many miles 
of wire. 
It is used in the manufacturing and chemical industries, 
and occupies a field no other metal can fill. 
ALLOYS 
Copper forms the basis of two prominent classes of alloys 
— brasses and bronzes — and occupies a minor but important 
place in the composition of many other useful and valuable 
alloys, particularly in the compounding of gold plate and 
solder. 
BRASS 
Under this head may be included most of the alloys of 
copper and zinc. Brasses, with a wide range of strength and 
color, can be produced by alloying copper and zinc together 
in varying proportions. 
Name and Color. 
Copper. 
Zinc. 
Pinchbeck (reddish yellow).... 
88.8 
11.2 
Sheet brass (yellow) 
84 
16 AN OUTLINE OF METALLUKGY 
1055 
Name and Color. 
Copper. 
Zinc. 
Similor (yellow) 
80 
20 
Brass wire (bright yellow) 
70 
30 
White brass (very light) 
34 
66 
Common brass (full yellow) 
64 
36 
Machine brasses, bearing metal, pump valves, steam whis- 
tles, cog wheels, etc., usually contain some tin, in addition to 
copper and zinc. 
Bronzes are metallic alloys, composed principally of cop- 
per and tin. They cast with great clearness of outline, and 
are, therefore, extensively used in making statues, medals, 
busts, and were also formerly much used in making cannon 
and field ordnance. 
BBONZES 
Phos- 
Copper. 
Tin. 
phorous. 
Zinc. 
U. S. ordnance bronze... 
90 
10 
Phosphor bronze 
90.34 
8.90 
.76 
Statuary bronze 
84.42 
4.30 
11.28 
Speculum metal 
66.66 
33.34 
Bell metal 
72-85 
28-15 
Aluminum bronze consists of: Copper, 90; and alumi- 
num, 10 parts. This alloy very much resembles gold in color, 
is not readily tarnished, has pronounced elastic property, can 
be turned and engraved, and fuses at about 860° C. 
Aluminum 
Although aluminum is the most abundant metal in the 
earth’s crust, it never occurs native. It forms the basis of 
the feldspar rocks, which when disintegrated by the action of 
the elements, lose their potassium and sodium. The residue 
is silicate of aluminum, or common clay, which is found almost 
everywhere. Clay containing impurities and coloring matter 
as iron oxides is known as sienna, umber, ochre, Fuller’s 
earth, etc., according to composition. 
It also enters into the composition of slate rocks, mica, 
pumice stone, and is found in many other forms too numer- 
ous to mention. 
It occurs in crystalline form as an oxide, and among the 
many interesting and curious results of this combination, may 
be mentioned the ruby, garnet, sapphire, emerald, topaz and 
amethyst. Corundum and emery, substances in crystalline 1056 
AN OUTLINE OF METALLURGY 
form and extreme hardness, used for grinding and polishing 
purposes, are also included in this class of oxides. 
REDUCTION 
Most of the aluminum at the present time is produced at 
the gigantic electrical works at Niagara Falls, N. Y., and is 
obtained by the electrolytic process. 
The principle of reduction depends upon the power the 
fused double fluoride of aluminum and potassium or sodium 
has of reducing the ores of aluminum. The apparatus con- 
sists of a large iron box, lined with carbon, in which there is 
a receptacle for the ore about 4y2 feet long by 2y2 feet wide 
and 6 inches in depth. 
The carbon lining acts as the cathode. There are usually 
40 anodes, consisting of carbon cylinders 3x10 inches, sup- 
ported above the pot in which the ore is placed, their lower 
ends resting in the bath of fused fluorides. The heat is de- 
veloped by the resistance of the fluoride to the passage of 
the current from the anode to the cathode. The ore to be 
reduced is placed in the bath of fluoride, and renewed from 
time to time as that in the pot becomes reduced. 
The resistance, and consequently the heat, increases as 
the ore is reduced, which, by means of an incandescent lamp 
attached to the furnace, becomes apparent to the furnace 
attendant by the brightening of the lamp, when he immedi- 
ately replenishes the charge. 
The ore introduced in the furnace is an oxide, and the re- 
action under heat is due to the oxygen in combination with the 
metal uniting with the carbon of the anodes forming C02, 
which escapes, leaving the metal free. The process is con- 
tinuous, being carried on day and night. The metal is drawn 
off every twenty-four hours, 100 pounds per furnace being 
the usual amount reduced in that length of time. As there 
are more than 100 of these furnaces in operation in a plant, 
the yield per day is about 10,000 pounds. A current of 20 
volts and 1700 amperes is required to effect the reduction. 
PHYSICAL PROPERTIES 
Aluminum is a white metal, with a slightly bluish tint, 
resembling zinc in color. It is soft and workable, capable of 
taking a high polish, and does not discolor appreciably on 
exposure to air, moisture or sulphur. It is not readily acted 
upon by nitric or sulphuric, but can readily be dissolved in 
hydrochloric acid or solutions of caustic potash or soda. 1057 
AN OUTLINE OF METALLURGY 
Aluminum is very malleable, ductile and quite tenacious, 
ranking eighth in respect to the latter property. It is a mod- 
erately good conductor of heat and electricity, ranking about 
half way between silver and platinum. 
Its specific gravity is 2.6, the lightest of all of the metals 
except magnesium. Its atomic weight is 27.1, specific heat 
.0956, its melting point 658.7° C. 
Aluminum is soft, and in working it, files soon clog. It is 
best to use single rather than cross-cut files, and when clogged 
they may be cleaned by dipping in a solution of caustic soda 
and washing in hot water. In annealing, aluminum should 
not be heated above 200° C. The proper heat is attained when 
a soft wood stick will leave a brown streak when drawn across 
the heated surface. 
SOLDERING 
It is very difficult to solder successfully, although this 
operation can be accomplished under proper conditions. The 
difficulty is supposed to be due to a film of oxygen adhering 
to the surface, which by means of the known fluxes can only 
with difficulty be removed. 
Many formulas for fluxes and solders have been proposed, 
some of which are successful when applied with skill. The 
following solder and flux is recommended as being success- 
fully used in the manufacture of aluminum jewelry: 
Zinc 80 or 85 or 90 
A1 20 or 15 or 10 
The soldering iron is dipped in a mixture of copaiba bal- 
sam, 3 parts; Venetian turpentine, 1 part; lemon juice, a 
few drops. 
Another method recommended by Page and Anderson con- 
sists in spreading powdered silver chloride along the joint to 
be united, and applying common solder with a blowpipe. 
USES 
Aluminum can be applied in many ways in dentistry. It 
makes an excellent base for dentures, 16 or 18 gauge plate 
being recommended, and the teeth attached with vulcanite. 
Although not as lasting as some other bases, on account of 
the action upon it of the fluids of the mouth, its lightness, 
cleanliness and good conductivity commend its use. 
Baseplates are frequently cast over models of investment 
material, which to a limited extent are satisfactory, but as 
the density of such casting is frequently imperfect, the action 1058 
AN OUTLINE OE METALLURGY 
of the fluids of the mouth is more rapid than upon swaged 
base-plates. 
On account of its extreme lightness, aluminum is employed 
to a considerable extent in the manufacture of physical appa- 
ratus of all varieties. It is especially valuable for light bal- 
ance weights, instrument handles, etc. In powder form it is 
used as a paint, which is not readily acted upon by the air or 
moisture. 
As mentioned elsewhere, aluminum with copper makes an 
excellent bronze, which is used for many purposes. It also 
unites with zinc to form alloys used as solders for the metal 
itself. 
Silver and aluminum unite readily, and produce alloys of 
commercial importance. 
The silicate of aluminum, or kaolin, the double silicate, 
feldspar and the oxide of silicon, form the basis of porcelain 
teeth, and the porcelain bodies used in continuous gum, crown, 
bridge and inlay work. 
It is not generally known that aluminum can be used as 
a whetting agent, like the ordinary oil stone. A keen, smooth 
edge, not possible to secure with fine oil or water stones, can 
be developed on fine edge instruments, and especially razors, 
by using a true plane slab of aluminum and oil. 
Combined with magnesium, a very important alloy known 
as magnalium is formed. It is used in the making of fine 
instruments, such as mathematical instruments, balances, etc. 
ALLOYS 
Zinc 
The ancients were familiar with the ores of zinc, since 
they were able to compound brass, but the separation of the 
metal itself from its ores is of comparatively recent date. 
The carbonate, sulphide, silicate and oxide are the prin- 
cipal ores of this metal, the formulas of which are as follows: 
Zn CO?.— calamine or carbonate. 
Zn S — zinc blend or sulphide. 
Zn 0 Si 02— willemite or silicate. 
Zn 0 — red zinc ore or oxide. 
ORES 
REDUCTION 
Those ores, other than the oxide, are reduced by roast- 
ing to an oxide. Tn this form the ore is mixed with coke or AN OUTLINE OF METALLURGY 
1059 
charcoal, and heated in a retort. The carbon unites with the 
oxygen of the ore to form C02 and the zinc volatilizes and is 
condensed in receivers. 
Usually some slight amount of oxide passes over with the 
zinc, which can be removed by remelting. 
PROPERTIES 
Zinc is bluish white in color. It tarnishes readily in moist 
air or when heated, an oxide being formed on the surface. 
When exposed to the vapor of, or fluids containing, carbonic 
acid, a film of zinc carbonate is formed. It is soluble in most 
of the acids, and is more readily acted upon by alkaline solu- 
tions. 
Its fusing point is 419.4° C. Specific gravity, 7; atomic 
weight, 65.37, and specific heat, .0956. It ranks low in malle- 
ability, ductility, and tenacity, on account of its crystalline 
character, which renders it brittle at ordinary temperatures. 
When heated to a temperature between 100° and 150° C. it 
can be rolled and drawn into wire, becoming both malleable 
and ductile, and retaining these properties in a degree when 
cold. 
Considerable contraction occurs in passing from the fused 
to the solid state. 
USES 
For many years zinc was about the only metal in use 
for constructing dies for swaging baseplates, but Babbitt’s 
metal has largely taken its place. The advantages claimed 
for it were its hardness and ability to stand the stress of 
swaging without the face of the die becoming mutilated, and 
that its contraction in cooling compensated for the expansion 
in the plaster model. It does not seem possible, however, that 
uniform contraction without warpage can readily occur, and 
therefore, it is best to compensate for the expansion of the 
plaster model by scraping properly and use a die metal that 
will not perceptibly contract, such as Babbitt’s metal. 
When zinc is used for dies, lead can be used for counter- 
dies, as there is enough variation in their respective melting 
points to obviate the melting of the zinc by the lead when the 
latter is poured upon the die. 
A coating of whiting and alcohol painted over the exposed 
surface of the die will further tend to prevent the fusion of 
the zinc and union of the two metals in counterdie construc- 
tion. 1060 
AN OUTLINE OF METALLUKGY 
The oxide of zinc enters into the composition of oxy- 
phospliate and oxychloride dental cements. In fact, the pow- 
der of these cements is nothing more than the refined oxide 
of zinc, either pure, or containing some pigment to slightly 
color it. 
The liquid constituent of the oxyphosphate consists of 
glacial phosphoric acid in distilled water, reduced to a syrup- 
like consistency by evaporation. 
The oxychloride liquid is made by adding one-half ounce 
of crystalline chloride of zinc to two drams of distilled water, 
allowing it to stand for two or three days, then drawing off 
the clear liquid. Both liquids should be kept in tightly stop- 
pered bottles to prevent deterioration. 
Zinc has a wide range of application in the chemical, 
scientific and industrial fields. In recent years there has been 
an increasing demand for it as a precipitant of gold in the 
cyaniding process of recovery. Its use in the electrical field 
for cheap and efficient battery work is fully as great as ever, 
while in foundry work there seems to be a greater demand 
for zinc than ever in the compounding of brasses, some of the 
formulas for which are given in connection with copper. Zinc 
is used for coating iron to prevent oxidation (galvanized 
iron), in the development of hydrogen gas, and for very many 
other useful purposes. 
Cadmium 
Cadmium is usually found associated with zinc as a sul- 
phide, and is recovered in the refining of zinc. As it is more 
volatile than the latter, the vapor first given off is directed 
into a separate chamber and condensed, the product being 
cadmium with some zinc and oxides. 
Redistillation further refines it. 
Cadmium resembles tin in color, and is capable of taking 
a high polish. It is subject to slow oxidation on exposure to 
air. It is malleable, ductile and slightly tenacious. It fuses 
at 320.9° C., has a specific gravity of 8.54, and specific heat of 
.0567. Its principal ore is greenockite. 
ALLOYS 
Cadmium enters into the composition of a number of 
alloys, among which might be specifically mentioned one fre- AN OUTLINE OF METALLURGY 
1061 
quently used in cast base lower dentures, instead of Watt 
metal, the formula of which is as follows: 
Tin, 16. 
Cadmium, 1. 
Cadmium also is one of the component metals of “Wood’s 
Alloy.” 
Lead 
Lead might be called an abundant metal, yet the constant 
and increasing demand for it for old as well as new purposes 
is so great that its value is constantly being enhanced. 
It occurs in nature in several forms, the principal ones of 
which are here mentioned: 
(Pb S)— Galena or sulphide. 
(Pb CO:i)—White lead or carbonate. (Cerussite.) 
(Pb Cr 04)— Crocoesite or chromate. 
(M 04 Pb)—Wulfenite. 
(Pb So4)— Sulphate. 
Lead ore carrying silver is designated as argentiferous 
galena. 
REDUCTION 
The ores are first roasted to reduce them to oxides and 
sulphates. Upon raising the temperature of the furnace these 
two compounds react on themselves, as indicated, lead and 
S02 resulting: 
2Pb 0 + Pb S = SO., + 3 Pb and 
Pb S04+ Pb S = 2S02+ 2 Pb. 
PROPERTIES 
Lead is a bluish gray metal, so soft that it can be readily 
cut or scratched, quickly tarnishes in the air, forming a sub- 
oxide, hut is not readily acted on by water, hence its extensive 
use in plumbing operations. 
Its fusing point is 327.4° C. Specific gravity, 11.4. Atomic 
weight, 207.10, and specific heat, .0314. It is quite malleable 
and ductile, but is deficient in tenacity. 
USES 
The principal use of this metal in the laboratory is for 
counterdies, being used unalloyed with zinc, and in the propor- 
tion of 1 of tin to 7 of lead with Babbitt’s metal dies. 1062 
AN OUTLINE OF METALLURGY 
ALLOYS 
Common tinners’ solder consists of lead and tin in vary- 
ing proportions, those having the most tin being considered 
the best. 
Grade 
Tin 
Lead 
Fine 
2 
1 
Common 
1 
1 
Coarse 
1 
2 
Another series of valuable alloys in which lead plays an 
important part is given in the section on bismuth. 
The alloys given in the section on tempering steel also 
form an important series in which lead is the principal metal 
employed. 
Tin 
Tin occurs usually as a native oxide, Sn 02, in crystals of 
quadratic form, usually colored by manganic or ferric oxide. 
REDUCTION 
The ore is first washed and stamped, then roasted to drive 
off any arsenic or sulphur that may be present, at a tempera- 
ture that will not fuse the ore. It is then mixed with fine an- 
thracite coal and smelted for five or six hours, when, after 
thorough stirring the melted metal is drawn off. The reaction 
during the process is as follows: 
Sn 0,+ 2 C = Sn + 2CO. 
PROPERTIES 
Tin is a white, soft, lustrous metal, quite malleable, some- 
what ductile, but with very little tenacity. It fuses at 231.9° 
0., and is not perceptibly volatilized at ordinary tempera- 
tures. It does not oxidize readily, and for this reason is 
largely used as a coating or protection for iron plates. In this 
form it is known as the sheet tin of commerce. 
When a bar of tin is cut, it appears to be devoid of crys- 
talline structure, but if the surface is etched with dilute acids, 
its crystalline character becomes apparent. When a bar of 
tin is bent, it emits a peculiar creaking sound, known as the 
tin cry, and which is undoubtedly due to the sliding or rear- 
rangement of the crystalline facets. 
The specific gravity of tin is 7.3, and its specific heat 
0.0562. 1063 
AN OUTLINE OF METALLURGY 
USES 
Tin is used in the dental office and laboratory in the form 
of foil for filling teeth and for covering plaster models in 
vulcanite work, to give a finished surface to rubber. After 
being vulcanized, the foil is removed. It is questionable 
whether this is a good plan to follow, since the model is en- 
larged by the addition of the foil, which must impair the close 
adaptation of the denture to the tissues. 
Tin is also one of the principal ingredients in the compo- 
sition of dental amalgam alloys, from 22 to 35 per cent being 
used with 77 to 65 per cent of silver. 
haskell’s babbitt metal 
It is also used in the composition of fusible alloys and 
counterdie metal, and forms in conjunction with copper and 
antimony a hard and practically non-contractile die material, 
known as Babbitt’s metal. 
The formula for Haskell’s Babbitt metal is Cu 1, anti- 
mony 2, tin 8 parts. 
The counterdie metal used in conjunction with Babbitt’s 
metal is: Lead 7, tin 1 part. The tin is added to reduce the 
melting point of the lead. Babbitt’s metal melts at 260° C., 
while the fusing point of lead is 327.4° C. If lead is poured 
upon a Babbitt metal die, the heat is sufficient to fuse the lat- 
ter, and union of the two will very likely occur. 
This undesirable result is obviated by the addition of tin 
to lead in the proportions before mentioned, which gives an 
alloy with a fusing point of about 225° C. 
Mercury 
Mercury sometimes occurs in nature free, though it is com- 
monly found as the red sulphide Hg. S., called cinnabar. It 
is frequently found forming an amalgam with silver, and also 
in the form of a protochloride or native calomel. 
DISTRIBUTION 
Mercury is found in Spain, Corsica, Mexico, California, 
Pern and China. 
At the present time California produces a greater hulk 
than any other country in the world. The ore is very rich 
in mercury, yielding as high as 70 per cent, while the ore from 1064 
AN OUTLINE OF METALLURGY 
the Spanish mines, the next largest producers, yields only 38 
per cent. 
Mercury forms two oxides, mercurous oxide, Hg20, and 
mercuric oxide, Hg O. It also forms two chlorides of promi- 
nence, IlgCL— corrosive sublimate — a powerful disinfectant, 
and Hg2 CL, called calomel. 
Vermilion — or mercuric sulphide, Hg. S.— a brilliant red 
color, is used extensively as a pigment in paints and for the 
coloring agent in the manufacture of red and pink rubber and 
celluloid. 
As is well known, mercury is extensively employed for 
thermometers, barometers, etc., and for many other useful 
purposes in the arts and sciences. 
COMBINATIONS 
Mercury unites with many of the metals to form amal- 
gams. It is used very extensively with dental alloys for the 
filling of teeth. 
ALLOYS OP MERCURY 
Mercury is silver white in color, tarnishes slightly in air, 
but is not acted upon by water. It is tasteless and odorless. 
It is liquid at ordinary temperature, boils at 357.3° C., and 
can be solidified by subjecting it to a temperature of —38.9° C. 
It contracts noticeably in passing from the liquid to the solid 
state, and assumes a crystalline form. When solid it can be 
flattened out under hammer blows, thus proving that it is 
malleable. In this condition it can also be welded, and can be 
cut into shavings with a knife. 
The specific gravity of mercury is 13.6, specific heat .0333, 
and its atomic weight 200.6. 
PROPERTIES 
Mercury is obtained from the native sulphide in two ways. 
The first method consists in crushing the cinnabar ore and 
mixing with lime. The mixture is then placed in cast-iron 
retorts, which are connected with earthenware receivers par- 
tially filled with water. Upon the application of heat the sul- 
phur combines with the calcium and forms calcium sulphide, 
while the mercury is distilled over and condensed in the re- 
ceivers. 
4HgS + 4CaO = 3CaO + CaS04 + 4Hg. The second 
method of recovery consists in exposing the ore directly to the 
REDUCTION AN OUTLINE OF METALLURGY 
1065 
oxidizing flame, and conducting the mercurial vapor with 
suitable apparatus into condensers. 
Nickel 
Nickel is a silvery white metal, with a brilliant luster, 
which does not tarnish readily in air. It is as tenacious as 
iron, is ductile, hard, and somewhat malleable. It is slightly 
magnetic, resembling iron somewhat in this respect. Its spe- 
cific gravity is 9, increased by hammering to 9.93. Specific 
heat .1108. Atomic weight 58.68, and fuses at about 1452° C. 
Nickel is used extensively with copper to form german silver 
— an alloy which, on account of its color, hardness, tenacity, 
and many other good qualities, is used in large quantities for 
innumerable purposes. 
A common formula for german silver is: Copper 55, zinc 
25, nickel 16 parts each. 
The hardness and strength of steel is increased by the 
addition of a small per cent of nickel. This alloy is known 
as armor plate, and is used in the construction of warships. 
USES 
This metal is made use of to a great extent for plating 
purposes, since it does not readily tarnish, is not easily oxi- 
dized, and can be quickly and firmly deposited upon iron, steel, 
brass, german silver, and copper, by electro-deposition. 
Bismuth 
Bismuth is a crystalline metal of a grav-white color, with 
a decidedly reddish tinge. On account of its highly crystal- 
line character it can be easily pulverized. It is almost totally 
lacking in the qualities of malleability, ductility, and tenacity. 
Tts specific gravity is 9.75, and specific heat 0.0308. Fuses at 
271° C. Atomic weight 208. 
Bismuth is the most diamagnetic element known, a sphere 
of it when suspended close to, is repelled by a magnet. 
Bismuth is very useful in the composition of fusible alloys, 
reducing the fusing points of the more difficultly fusible in- 
gredients, and imparting clearness and sharpness of outline 
to castings made from such alloys. 
In conjunction with tin and lead, it forms a number of 
alloys which are in constant use in the dental laboratory. The 
following is a partial list of such alloys: 1066 
AN OUTLINE OF METALLURGY 
FUSIBLE ALLOYS 
Cad- 
Melting 
Name 
Bismuth 
Tin 
Lead 
mium 
Mercury Antimony 
Point 
Hodgen’s metal 
8 
3 
5 
2 
105° C. 
Mellotte’s “ 
8 
5 
3 
100° C. 
Essig’s 
3 
5 
3 
96° C. 
Dareet’s “ 
4 
1 
3 
96° C. 
Rose’s 
2 
1 
1 
95° C. 
Newton’s “ 
8 
3 
5 
94° C. 
Onion’s “ 
5 
2 
3 
92° C. 
Wood’s “ 
4 
1 
2 
1 
65° C. 
Lipowitz’s “ 
15 
4 
8 
3 
63° C. 
Darcet’s “ 
2 
1 
1 
10 
45° C. 
In compounding alloys of this character they should be 
melted under charcoal to prevent oxidation, and stirred with 
a stick of soft wood just before pouring, to prevent the lead 
from separating. 
When cadmium or mercury are incorporated, the other 
metals should be melted first, and these added just before 
pouring, to prevent volatilization. 
Antimony 
Antimony usually occurs as a sulphide, and with other 
metals, as silver, iron and copper. Tt is reduced by heating 
the sulphide with scrap iron, iron sulphide being formed and 
the antimony set free. 
PROPERTIES 
It is extremely low in malleability, ductility and tenacity, 
being crystalline in structure and very brittle. The atomic 
weight of antimony is 120.2, fusing point 630° C., specific 
gravity 6.7, specific heat .0508. 
Its principal uses in dentistry are as a component of 
Haskell’s Babbitt metal and for certain low-fusing alloys. It 
is also used extensively in the manufacture of type for print- 
ing, as alloys containing antimony expand in cooling, thus 
insuring sharp castings. 
Primarily common Babbitt metal is an anti-friction alloy, 
and that intended for such purpose contains a larger per- 
centage of copper and antimony, while it is softer and more 
easily defaced than that prepared after the formula of Dr. 
Haskell. (See page 1063.) 
Britannia metal is an alloy used for making spoons, tea- 
pots, trays, etc., and is composed of several metals and in 
different proportions. AN OUTLINE OF METALLURGY 
1067 
The following is one of the formulas much used: Copper 
1.85, tin 81.90, antimony 16.25. Zinc, lead and bismuth are 
also used in some of the formulas of this alloy. 
Tungsten 
Tungsten occurs combined with ferrous oxide in the min- 
eral called wolfram, or wolframite, FeW04, also with calcium 
in the mineral called sclieelite, CaW04. These are called the 
tungstates of iron and calcium, respectively. 
Its principal use until recently was as a mordant in dye- 
ing and a fireproofing material for cotton goods. It has also 
been used as a hardening component for steel, usually in the 
proportion of from 5 per cent to 9 per cent. 
PHYSICAL PROPERTIES 
The fusing point of tungsten is 3000 C. Atomic weight, 
184. Specific gravity, 19.2. Acids have but slight effect upon 
the metal at ordinary temperatures. It is very difficult to con- 
vert the powder, in which form it is usually sold commer- 
cially, into a solid, on account of its extremely high fusing 
point. By heavy compression into definite form, and the 
application of an electric current of high amperage, coupled 
with careful swaging, the rod or bar of compressed powder 
is gradually rendered compact and the granules sufficiently 
coherent to enable it to be drawn out into wires of various 
sizes, even as fine as the 1/1000 of an inch. 
At high temperatures it is readily oxidized, unless pro- 
tected from the air. This deleterious property, however, does 
not inhibit its use for electric lanrp filaments, since it is placed 
within a vacuum globe or one filled with nitrogen. In either 
case the oxygen is excluded, and consequently oxidation does 
not occur. 
USES 
Dr. Weston A. Price, of the Scientific Research Commis- 
sion of the N. T). A., presented a paper on metals and alloys 
at the meeting in Rochester, N. Y., in July, 1915, in which 
some of the valuable points of this metal were disclosed. In 
that he showed that the high fusing point of tungsten, its low 
range of expansion, its great rigidity and hardness, rendered 
it extremely valuable in prosthetic operations. 
A bar of this material, threaded, coated with palladium 1068 
AN OUTLINE OF METALLURGY 
or gold to prevent oxidation, and invested in a matrix for a 
complex inlay, the wire extending mesio-distally through the 
casting, practically inhibits the contraction of the gold on 
itself, which, without such control, always occurs in cooling. 
Its rigidity, coupled with great tensile strength, renders it 
specially valuable for dowels in crowns and inlays. 
The principal disadvantages are its oxidation at soldering 
and casting temperatures and the difficulty in fusing any of 
the metals to it in the open air because of such oxidation. 
The solution offered was to coat the wire with an alloy of 
Pd-Au or PdAg., after which gold may be cast or soldered to 
it readily. 
To illustrate its hardness, mention was made of the fact 
that a phonographic needle of tungsten will outwear two 
hundred of the standard hard-steel points in common use. 
The possibilities of this metal for use in cutting instruments 
were suggested, when the methods of working it are better 
developed. 
The Measurement of Plate and Wire 
In all scientific and mechanical fields, the accurate deter- 
mination of weights, dimensions and strength of materials, 
when such measurements are called for, is a recognized neces- 
sity; the same holds true in prosthetic procedures, for with- 
out a reasonably accurate knowledge of the strength of the 
various materials entering into the structure of replacements, 
the prosthetist’s efforts will often prove inefficient. 
Gold, platinum, and various other metals, are reduced 
from ingot form to plate by means of a device called a rolling 
mill. This may be done in the dental laboratory with proper 
equipment. 
More often, however, the prosthetist obtains the precious 
metals in plate form, direct from the supply houses. 
In either case, it is essential that the laboratory be 
equipped with suitable measuring devices for testing the dif- 
ferent gauges of material used. 
The measurement of the thickness of gold and platinum 
plate and the gauging of the diameter of wire in an intelligent 
manner —that is, so that a just estimate may be formed of 
the relative thickness and strength of the materials being used 
— aids materially in the planning and construction of success- 
ful prosthetic substitutes of all classes. AN OUTLINE OF METALLURGY 
1069 
With this end in view, the prosthetist should become 
familiar with, and can to advantage apply in practice, the 
methods and instruments used by scientists and artisans in 
other lines of work. 
Various measuring devices are in use for determining the 
thickness of plate and the diameter of wire, as well as for 
Fig. 978.— A Common Type of Rolling Mill 
sundry other measurement readings. These instruments are 
known under the common name of gauges, calipers, etc., the 
forms of which vary, depending upon the purposes for which 
they are designed. 
THE UNIT OF MEASUREMENT OF GAUGES 
The unit of measurement of gauges used in England and 
the United States is generally the fractional part of an inch 
and of the millimeter. 1070 
AN OUTLINE OF METALLURGY 
LACK OF UNIFORMITY OF THE VARIOUS GAUGE SYSTEMS 
With exceptions to be noted, most of the various gauge 
systems do not show a uniformly decreasing ratio from thick 
to thin measurements, but the steps between the various gauge 
numbers appear to have been arbitrarily established, with- 
out following any fixed standard. 
This is true of the Birmingham, also known as the English 
Standard, and again as Stub’s Soft Iron Wire Gauge, so 
called to distinguish it from Stub’s Steel Wire Gauge. The 
discrepancies noted are plainly apparent in this gauge, as will 
be seen by examining the first few largest numbers. 
THE BIRMINGHAM GAUGE 
No. 0000 = .454 of an inch. 
No. 
0 = 
.340 
No. 000 =.425 
No. 
1 = 
.300 
Difference .029 
Difference 
.040 
No. 000 ==.425 
No. 
1 = 
.300 
No. 00 = .380 
No. 2 = 
.284 
Difference .045 
Difference 
.016 
No. 00 = .380 
No. 
2 = 
.284 
No. 0 = .340 
No. 
3 = 
.259 
Difference .040 
Difference 
.025 
DISCREPANCIES OF THE BIRMINGHAM GAUGE 
To summarize, the difference between the first seven num- 
bers of the Birmingham gauge is as follows: .029—.045— 
.040—.040—.016—.025. 
The Birmingham gauge was for years used extensively, 
but not exclusively, in this country, in machine-shop practice 
and various other fields. Some wire and plate manufacturers 
used one gauge, some another. More or less confusion and 
misunderstanding naturally resulted, since no one gauge sys- 
tem was accepted as standard and each varied slightly from 
the others. 
THE BROWN AND SHARP GAUGE 
To correct the discrepancies noted, the Brown & Sharp 
Manufacturing Company of Providence, R. I., designed a 
gauge having approximately the same range of measurement 1071 
AN OUTLINE OF METALLURGY 
as the Birmingham, but the various gauge numbers, from the 
largest downward, decrease in a definite ratio. 
This gauge has proven so satisfactory that it has been 
generally adopted in this country, and is now known as the 
American Standard Gauge. It should not, however, be con- 
founded with the United States Standard Gauge, which was 
designed for, and approved by, Congress in 1893, and is used 
in determining duties and taxes levied by the United States 
Government on sheet and plate iron and steel. 
The principle on which the Brown & Sharp gauge is con- 
structed is as follows: Two straight bars of steel are fitted 
together at one of their ends, and permanently fixed in such 
manner as to form a divergent space between the two, about 
one-lialf inch across at the outer end of the gauge. The gauge 
numbers are marked on the inner edges of the arms, next the 
divergent space. The general form of this gauge is similar 
to the jeweler gauge. (See page 1072.) 
No. 0000, or .46 of an inch, is the largest dimension of the 
gauge, and from this all of the other gauge dimensions are, 
either directly or indirectly, derived. 
The next lowest dimension — No. 000 — is obtained by 
multiplying its predecessor, .46, by 0.890522, which is equiva- 
lent to deducting 10.9478 per cent. Each succeeding lower 
number is obtained in a similar manner, by multiplying the 
last determined gauge length, or thickness, established, by the 
decimal above given. 
It will thus be seen that any gauge number under 0000 is 
approximately 10 per cent less than the preceding higher, or 
greater than the succeeding lower number. The steps between 
the various gauges represent gradual and uniform decrements 
as the gauge numbers, although rising numerically, become 
thinner. The last gauge of the scale is No. 40, or .003144 of 
an inch thick, although still thinner numbers can be correctly 
formulated by the plan given. 
Forms of Gauges 
THE jeweler’s GAUGE 
The jeweler’s gauge is based upon the same general prin- 
ciple as the original Brown & Sharp gauge, viz., two rigidly 
fixed, diverging arms. These are graduated on the inner mar- 
gins so as to read in multiples of one-thousandths of an inch. 1072 
AN OUTLINE OF METALLURGY 
Although the form of gauge just described is suitable and 
very convenient for measuring wire and small rods, it is not 
well adapted for gauging plate, because the edge of the latter 
is very frequently marred in shearing, so that a marginal 
reading, in such cases, will seldom be accurate. Some form 
Fig. 979.— A Jeweler’s Gauge Reading to 
the 1-1000 of an Inch 
of appliance capable of passing beyond the margin of the 
plate, and calipering undisturbed surfaces, is, therefore, nec- 
essary for securing accurate measurements. 
One of tlie most common forms of plate and wire gauge 
in use consists of a steel disc about two and one-half inches 
in diameter and one-eiglith of an inch thick. In the periphery 
of this disc are accurately cut and numbered slots, which 
THE PLATE AND WIRE GAUGE 1073 
AN OUTLINE OF METALLURGY 
represent the thickness of the various gauge numbers of the 
system used. To measure a piece of plate or wire, the various 
slots of the gauge are applied to the piece until a neat fit is 
obtained, or, in case the piece being measured is not of exact 
gauge thickness, the two proximating gauges are found, one 
of which is larger and the other smaller than the wire or plate 
being calipered. This form of gauge, as before stated, is 
satisfactory for measuring standard thickness of plate and 
wire, but is not adapted to accurate and universal readings, 
when the materials are not standardized. 
Fig. 980.— An Ordinary Form of Gauge for Plate and Wire 
THE MICROMETER CALIPER 
An instrument of this type consists of a U-shaped steel 
frame, the arms of which are parallel. One arm is threaded 
and contains the adjustable screw, by means of which read- 
ings are made. The other arm holds an adjustable stop, 
which is never moved except for adjustment purposes, when 
the instrument is worn or sprung. The face of the stop and 
the end of the screw, presented toward it, form exactly 
parallel planes. The object to be gauged is placed, one side 
against the face of the stop, while the screw in the other arm 
is brought in contact with the opposite side. The reading is 
made in the screw spindle and on the hub, or nut, through 
which it passes. In the following description, the micrometer 
graduated to read to the 1/1000 of an inch, will be used as 
an example of this general type. Some of the more recent 1074 
AN OUTLINE OF METALLURGY 
forms have a vernier attachment, by means of which read- 
ings can be made as fine as the 1/10000 of an inch. 
The screw spindle has a hollow head in the form of a deep 
sleeve, which telescopes over the cylindrical extension of the 
nut of the frame. As the screw is turned toward or away 
from the stop in the opposite arm, the sleeve rotates and 
travels with it. The inner end of the sleeve is beveled and 
graduated into 25 equal parts, and numbered 0, 5, 10, 15, 20, 
while 25 is reached on the complete revolution to 0. When the 
screw is closed and in close contact with the stop, the 0 of 
the sleeve stands opposite the 0 on the nut. The screw pitch 
is 40 — that is, there are 40 threads to the inch on the spindle. 
By multiplying the divisions on the sleeve by the number of 
threads to the inch on the spindle, it will be seen that 1,000 
divisions must pass the longitudinal line on the hub in mov- 
ing the screw outward one inch. Each division, therefore, 
registers the 1/1000 of an inch movement of the screw toward 
or away from the stop in the opposite arm. To facilitate 
rapid readings of pieces of considerable thickness, the hub is 
also graduated. The space between the gradations on the 
hub, or nut, is equal to the distance between contiguous 
threads. As the screw is turned once around, in opening, an 
unexposed gradation appears on the hub under the edge of 
the sleeve, showing that the screw has been moved 25/1000 
of an inch. Every fourth gradation on the hub is accordingly 
numbered, the beginning or closed position of screw being 0, 
the fourth division 1, or 100/1000; the second 2, or 200/1000, 
etc. 
In using this gauge three sources of error must be kept 
in mind, viz., imperfect paralleling of the piece being meas- 
Fig. 981.— A Micrometer Gauge Reading to the 1-1000 of an Inch AN OUTLINE OF METALLURGY 
1075 
ured, with the face of the screw; excessive pressure will 
spring the frame and give imperfect results; slight variation 
in the pitch of the screw, due to wear. 
No dust or dirt should adhere to the screw, stop or piece 
being gauged. A spring ratchet is frequently applied to the 
extreme outer end of the screw to insure against excessive 
force being applied in making measurements. 
Various Systems of Wire and Plate Gauges and Their 
Equivalents in Thousandths of an Inch 
For convenience in finding any required gauge, the wire 
and plate gauge numbers are given on the right and left sides 
of the table. 
No. of 
Wire 
Gauge. 
Brown & 
Sharp 
American 
Standard 
Difference 
between 
Consecu- 
tive 
Numbers 
in 
Decimals. 
Birming- 
ham or 
Stub’s 
Wire. 
Wash- 
burn & 
Moen Co. 
Wire. 
Imperial 
Wire 
Gauge. 
Stub’s 
Steel 
Wire. 
U.S.Stand- 
ard for 
Plate. 
Piano 
W. & M. 
Wire 
Gauge. 
No. of 
Wire 
Gauge. 
000000 
.464 
.46875 
.0095 
000000 
00000 
.432 
.4375 
.010 
00000 
0000 
.46 
.454 
.3938 
.400 
.40625 
011 
0000 
000 
.40964 
.05036 
.425 
.3625 
.372 
.375 
.012 
000 
00 
.3648 
.04484 
.38 
.3310 
.348 
.34375 
.0133 
00 
0 
.32486 
.03994 
.34 
.3065 
.324 
.3125 
.0144 
0 
1 
.2893 
.03556 
.3 
.2830 
.300 
.227 
.28125 
.0156 
1 
2 
.25763 
.03167 
.284 
.2625 
.276 
.219 
.265625 
.0166 
2 
3 
.22942 
.02821 
.259 
.2437 
.252 
.212 
.25 
.0178 
3 
4 
.20431 
.02511 
.238 
.2253 
.232 
.207 
.234375 
.0188 
4 
5 
.18194 
.02237 
.22 
.2070 
.212 
.204 
.21875 
.0202 
5 
6 
.16202 
.01992 
.203 
.1920 
.192 
.201 
.203125 
.0215 
6 
7 
.14428 
.01774 
.18 
.1770 
.176 
.199 
.1875 
.023 
7 
8 
.12849 
.01579 
.165 
.1620 
.160 
. 197 
.171875 
.0243 
8 
9 
.11443 
.01406 
.148 
.1483 
.144 
.194 
.15625 
.0256 
9 
10 
.10189 
.01254 
.134 
.1350 
.128 
.191 
.140625 
.027 
10 
11 
.090742 
.01105 
.12 
. 1205 
. 116 
.188 
.125 
.0284 
11 
12 
.080808 
.00993 
.109 
.1055 
.104 
.185 
.109375 
.0295 
12 
13 
.071961 
.00885 
.095 
.0915 
.092 
.182 
.09375 
.0311 
13 
14 
.064084 
.00788 
.083 
.0800 
.080 
180 
.078125 
.0325 
14 
15 
.05768 
.00702 
.072 
.0720 
.072 
. 178 
.0703125 
.0343 
15 
16 
.05082 
.00625 
.065 
.0625 
.064 
.175 
.0625 
.0359 
16 
17 
.045257 
.00556 
.058 
.0540 
.056 
. 172 
.05625 
.0378 
17 
18 
.040303 
.00495 
.049 
.0475 
.048 
.165 
.05 
.0395 
18 
19 
.03589 
.00441 
.042 
.0410 
.040 
. 164 
.04375 
.0414 
19 
20 
.031961 
.00393 
.035 
.0348 
.036 
.161 
.0375 
.043 
20 
21 
.028462 
.00350 
.032 
.03175 
.032 
.157 
.034375 
.0461 
21 
22 
.025347 
.00311 
.028 
.0286 
.028 
.155 
.03125 
.0481 
22 
23 
.022571 
.00278 
.025 
.0258 
.024 
.153 
.028125 
.0506 
23 
24 
.0201 
.00247 
.022 
.0230 
.022 
.151 
.025 
.0547 
24 
25 
.0179 
.00220 
.02 
.0204 
.020 
. 148 
.021875 
.0585 
25 
26 
.01594 
.00196 
.018 
.0181 
.018 
.146 
.01875 
.0626 
26 
27 
.014195 
.00174 
.016 
.0173 
.0164 
.143 
.0171875 
.0663 
27 
28 
.012641 
.00155 
.014 
.0162 
.0149 
.139 
.015625 
.0719 
28 
29 
.011257 
.00138 
.013 
.0150 
.0136 
134 
.0140625 
.076 
29 
30 
.010025 
.00123 
.012 
.0140 
.0124 
.127 
.0125 
.080 
30 
31 
.008928 
.00110 
.01 
.0132 
.0116 
.120 
.0109375 
31 
32 
.00795 
.00098 
.009 
.0128 
.0108 
.115 
.01015625 
32 
33 
.00708 
.00087 
.008 
.0118 
.0100 
.112 
.009375 
33 
34 
.006304 
.00078 
.007 
.0104 
.0092 
. 110 
.00959375 
34 
35 
.005614 
.00069 
.005 
.0095 
.0084 
.108 
.0078125 
35 
36 
.005 
.00061 
.004 
.0090 
.0076 
.106 
.00703125 
36 
37 
.004453 
.00055 
.0068 
. 103 
.006640625 
37 
38 
003965 
.00049 
.0060 
.101 
.00625 
38 
39 
003531 
.00043 
.0052 
.099 
39 
40 
.003144 
.00039 
.0048 
.097 
40 1076 
AN OUTLINE OF METALLURGY 
Tables of Some of the Various Gauge Systems in Use 
The table of gauges which is here appended will enable any 
one to determine accurately, by means of a micrometer gauge, 
the relative thickness of plate and wire, regardless of what 
system of gauging has been used by the manufacturer in its 
production. 
Attention is specially called to the table of piano-wire 
gauges, as it is at variance with the other systems tabulated. 
The diameters, or thicknesses, of the gauges in this system 
increase as the numbers rise numerically. Since piano wire 
is used extensively in orthodontic operations, those engaged 
in this specialty will find the table of assistance in judging 
the relative thickness of the various sizes of wire employed. 
Practically all supply houses use the American Standard, 
also called the Brown & Sharp gauge, for gauging the precious 
metals. For this reason, therefore, distinction should be 
made between the American Standard gauge, which is almost 
universally employed for the purpose mentioned, and the 
United States Standard gauge, the principal use of which, as 
before stated, is in the measurement of iron and steel plate, 
and is seldom used in prosthetic operations. CHAPTER XXXIII 
A BRIEF HISTORY OF PROSTHETIC 
DENTISTRY 
An exact and detailed history of the treatment of dental 
lesions, spanning the period from very ancient to modern 
times, however interesting and instructive it might prove, 
has not been and never can be written, because of lack of 
accurate and consecutive data. 
Many of the records of earlier times on this subject are 
incomplete, or sadly lacking in detail; some have been lost; 
and still others now in existence are only copies of manu- 
scripts having a much earlier origin. 
Some of the original old records now remaining, rest in 
government archives of Old World countries, or in the libra 
ries of their universities. 
To the uninitiated student of dental lore, many of these 
historic treasures, written in a foreign, dead, or almost unde- 
cipherable and forgotten language, have been until recently 
as completely out of his reach as though they never existed. 
The efforts of a number of men, fitted by training and 
experience, and conveniently located near to these manu- 
script depositories as well, have been directed to clearing 
up and collating such ancient and mediaeval historical data 
of medicine and dentistry as are available. Notable among 
these the names of Prof. George Ebers, a celebrated German 
Egyptologist, and Dr. Vincenzo Guerini, of Naples, Italy, 
stand out most prominently. 
THE EBERS PAPYRUS 
In 1873 Professor Ebers obtained from “an inhabitant 
of Luxor, Upper Egypt,’’ a manuscript written in hieratic 
characters on papyrus paper, which upon deciphering proved 
to be the most complete, as well as probably the most ancient 
of the early records relating to the treatment of disease, both 
general and dental. 
Two translations of this manuscript have been made, one 
by Professor Ebers in 1875, and the other by Dr. Heinrich 
Joachim in 1890. Quoting from Guerini, the scope and an- 
tiquity of this manuscript is made apparent: 
“Lepsius, and with him the greater part of Egyptolo- 
gists are of the opinion that the Ebers papyrus is not an 
1077 1078 
A BRIEF HISTORY OF PROSTHETIC DENTISTRY 
original work at all, but simply a copy of medical writings 
of still earlier date, belonging to different epochs, and which 
were collected and reunited to form a kind of manual on 
medicine. 
ANTIQUITY OF THE PAPYRUS 
“From some indications existing in the papyrus itself, 
Ebers lias been able to argue, with quasi certainty, that the 
papyrus was written toward the year 1550 B. C. But some 
parts of it have their origin in a far more remote epoch; 
they go back, that is, to thirty-seven centuries or more be- 
fore the Christian era. In fact, at page ciii of the Ebers 
papyrus one reads: 
“ ‘Beginning of the book about the treatment of the 
uxeda in all the members of a person, such as was found in 
a writing under the feet of the god Anubis, in the city of 
Letopolis; it was brought to His Majesty Usapliais, King 
of Upper and Lower Egypt.’ Now, as Joachim remarks, 
the Usapliais herein named was the fifth king of the first 
Egyptian dynasty, and he reigned toward 3,700 years before 
the Christian era. Hence, it may be argued that some, at 
least, of the writings from which the Ebers papyrus was 
taken were composed in the very remote epoch to which we 
have just alluded, or perhaps still farther, for it is impossi- 
ble to know whether the book, deposited by unknown hands 
at the foot of the statue of the god Anubis, had been written 
but a short time previous or at a much earlier epoch.”— 
Guerini. 
This suggests a possible age of 5,600 years for some of 
the prescriptions offered for the relief of pain. The uxeda 
mentioned literally means a 'painful swelling, and might 
apply to inflammatory conditions, accompanied by swelling, 
in any part of the body, alveolar abscess included. In fact, 
specific mention is made in several places, of remedies for 
the cure of “growth of the uxeda in the teeth (alveolar ab- 
scess'?) and also “bennut blisters in the teeth,” the latter 
supposed to mean small fistulous openings to abscesses of 
dental origin. 
No reference of any sort in regard to prosthetic oper- 
ations is found in the papyrus. It does not follow, however, 
that prosthesis was not attempted in very ancient times. 
In fact, positive evidence exists to prove that replacement 
of one or more teeth was a recognized, although perhaps 
not common method of practice, almost or quite 3,000 years 
ago. Mention of this will be made later. A BRIEF HISTORY OF PROSTHETIC DENTISTRY 
1079 
GUERINI’s HISTORY OF DENTISTRY 
Within recent years, the most thorough, exhaustive, and 
painstaking inquiry in ancient and mediaeval history of den- 
tistry ever undertaken by one individual, has been carried 
out by Dr. Vincenzo Guerini, of Naples, Italy. It repre- 
sents an effort on the part of this distinguished gentleman, 
quoting his words, to “contribute to the diffusion of exact 
historical knowledge as to the origin and gradual develop- 
ment of dentistry. ’9 
The results of his labours, which represent a vast amount 
of research work and much financial outlay as well, he has 
generously presented to the profession in America, through 
the National Dental Association, as a token of his apprecia- 
tion of American progress in dental science and develop- 
ment. 
That the results of Dr. Guerini’s efforts are appreciated, 
not only by the profession of America, but of the world, goes 
without saying. His work is frequently quoted by writers 
on historical dental subjects, and with a feeling of security 
as to fact, hitherto noticeably lacking in much of the pre- 
viously available data, because of its questionable authentic- 
ity. Much of the contents of the present chapter is based 
either directly or indirectly upon Guerini’s work. 
The facts as presented in Guerini’s History lead to the 
belief that the origin of dentistry was coeval with that of 
medicine; that in all probability, in very ancient times, den- 
tistry as a specialty was not recognized as such, and therefore 
the treatment of dental lesions came properly within the 
domain of the medical practitioner. 
Although the statement has repeatedly been made that 
teeth filled with gold and various substances, and prosthetic 
pieces of different forms, have been found in the sarcophagi 
of mummies, in the pyramids and necropoli of Egypt, the 
fact lias not been substantiated. Schmidt, Ebers, Virchow 
and Mummery, all of whom devoted considerable effort to 
this phase of research, failed to find authentic specimens 
of the classes of work mentioned. Neither has Guerini, in 
his examination of ancient specimens or in historical re- 
search, found anything to indicate that the very early Egyp- 
tians knew “how to insert gold fillings, and still less to apply 
pivot teeth.” He further states, however, that, although the 
direct proof may be lacking, he believed the Egyptians knew 
how to apply artificial teeth. 1080 
A BRIEF HISTORY OF PROSTHETIC DENTISTRY 
He bases his deduction on the following: “And even 
though it may not be possible to demonstrate this by direct 
proof, one is equally prone to admit it when one considers 
on the one hand, the remarkable ability of the ancient Egyp- 
tians in all plastic arts, and, on the other hand, the great 
importance they attributed to beautifying the human body; 
so much so, that even in so ancient a document as the Ebers 
papyrus, one finds formulae for medicaments against bald- 
ness, for lotions for the hair, and other kinds of cosmetics. 
Is it not likely, therefore, that so refined and ingenious a 
people should not have found the means of remedying the 
deformity resulting from the loss of one or more front teeth?” 
The ancient Phoenicians, a race of Semitic origin, were 
a thrifty nation of maritime traders. Their country, the 
northern Palestine Mediterranean coast land, afterwards 
known as Canaan, consisted of a strip about 15 miles wide 
and 150 long. It lay between the Lebanon Mountains and 
the sea, on the borders of which were situated the populous 
cities of Tyre, near the center, and Si don to the north. All 
of the principal ports of the world were known to, and vis- 
ited by her merchantmen, whose bartering excursions and 
voyages of discovery brought them in contact with the trad- 
ers, artisans, and scholars of many lands. 
THE PHOENICIANS 
Beginning about 1700 B. C. Egypt assumed a protecto- 
rate over Phoenicia, which was maintained for about three 
hundred years. This political bond, coupled with mutual com- 
mercial exchange, brought the people of the two countries 
into close business and social relations with each other. 
Since the beneficent influence of Egypt’s advanced civili- 
zation was felt and recognized in the known remote cor- 
ners of the earth in those times, it naturally followed that 
Phoenicia, by reason of the connection noted, must have bene- 
fited thereby, and appropriated to herself some of the ad- 
vanced ideas of the older country in culture, fine arts and 
medical science. 
EFFECT OF EGYPTIAN CIVILIZATION ON PHOENICIA 
ONE OE THE MOST ANCIENT SPECIMENS OF PROSTHETIC ART 
Now, although she has left no papyrus scrolls, no pyra- 
mids, no obelisks to commemorate important historical events, 
Phoenicia has left what Egypt has not, viz., a well preserved A BKIEF HISTORY OF PROSTHETIC DENTISTRY 
1081 
specimen of ancient prosthesis. How old this piece may be 
no one can tell, but that it is very ancient there can be no 
doubt. The outline of Guerini’s history of it is about as 
follows: 
In 1362, Dr. Gaillardot, connected with Renan’s Syrian 
Exploring Expedition, found in the most ancient part of 
the necropolis of Sidon, a part of the upper jaiv of a woman, 
in which the six anterior teeth were united together with 
gold wire. A central and proximating lateral incisor appear 
Fig. 982.— Phoenician Appliance Found 
at Sidon, as Represented in a Cut of 
Renan’s Mission de Phenice (Guerini) 
Fig. 983.—- The Same Figure Reversed, 
as It Ought to Be if the Piece Found 
at Sidon Belonged to a Lower Jaw 
(Guerini) 
to have belonged to another person, and from the manner 
of their attachment were substituted for lost teeth. This 
piece is now in the Louvre in Paris. In addition to this 
prosthetic piece there were also found in the same grave 
two copper coins, an iron ring, a vase of most graceful out- 
line, a scarab, and twelve very small statues of Egyptian 
deities, probably a necklace, judging by the holes bored in 
them. 
Concluding his remarks on “Dental Art Among the Egyp- 
tians,” Guerini says: 
“The remains discovered in many of the Phoenician tombs 
would of themselves alone be sufficient to demonstrate lumi- 
nously, the enormous influence exercised by the Egyptian 
civilization on the life and customs of that people. Now, if 
there were dentists in Sidon capable of applying false teeth, 
it may reasonably be admitted that the dentists of the great 
Egyptian metropoli, Thebes and Memphis, were able to do 
as much and more, the level of civilization being without doubt 
higher there than in Tyre or in Sidon, or in other non- 
Egyptian cities.” 
THE ETRUSCANS 
The Etruscans were a people who inhabited Upper Cen- 
tral Ttalv from about 800 B. C. to 283 B. C., when they were 
conquered by the Romans. One author has said of them: 
“Ancient writers concur in representing the Etruscans as 
the most cultivated and refined people of ancient Italy, and 1082 
A BRIEF HISTORY OF PROSTHETIC DENTISTRY 
as especially skillful in ornamental and useful arts, in which 
the ideas and patterns used singularly resemble those of 
Egypt.”—“They made great progress in architecture, sculp- 
ture, and painting, and especially in bronze work and gold 
jewelry.”—“They excelled in agriculture, navigation, engi- 
neering and in useful public works.” (Universal Encyclo- 
pedia.) 
Guerini says: “They were a laborious and courageous 
race, not only active in agriculture, in art and commerce, 
but also brave warriors and hardy navigators. In their long 
sea voyages the Etruscans frequently visited Egypt and 
Phoenicia, trading especially in the more flourishing cities, 
which were at that time Memphis, in Egypt, and Tyre and 
Sidon in Phoenicia. On the other hand, the Phoenicians, who 
were also active merchants and navigators, not only visited 
Etruria and other regions of Italy very frequently, but also 
established numerous colonies in many islands of the Medi- 
terranean, and especially in those nearer Italy. 
“This continual intercourse between Etruscans on one 
side, and Egyptians and Phoenicians on the other, accounts 
for the great influence exercised by the Egyptians and Phoeni- 
cian civilization upon the later developed Etruscan culture 
— an influence manifesting itself very distinctly in the works 
of art of the latter, which often have an altogether Oriental 
character, and not seldom represent scenes drawn from the 
domestic life of the Egyptians and Phoenicians. 
ETRUSCAN DENTAL ART 
“As to wliat concerns dental art, everything leads up to 
the belief that it was practiced by the Egyptians and Phoeni- 
cians earlier than by the Etruscans, whose civilization, as 
already hinted, is certainly less ancient. Nevertheless, in 
comparing the dental appliances found in the Etruscan tombs 
with the sole and authentic dental appliance of Phoenician 
workmanship known at the present day, we cannot but be 
struck with the greater superiority of the Etruscan appli- 
ances. It is therefore probable that the Etruscans, although 
they had learned the dental art from the Egyptians and 
Phoenicians, had subsequently carried it to a much higher 
degree of perfection than it had arrived at in Egypt or in 
Phoenicia. ’ ’ 
A number of specimens of ancient prosthetic appliances 
of Etruscan workmanship have been found within recent 
years, the genuineness of which are unquestioned. Most of A BRIEF HISTORY OF PROSTHETIC DENTISTRY 
1083 
these specimens are preserved in various Italian museums. 
Some of them are illustrated in Dr. Guerini’s admirable work, 
a few of which are here reproduced. 
In an excavated tomb at Valsiarosa, near the ancient 
Falerii, was found an appliance consisting of four gold rings 
Fig. 984.— Etruscan Appliance Found at Valsiarosa, Destined to 
Support an Artificial Bicuspid, Now Disappeared (Guerini) 
soldered together and fitted to the cuspid, first bicuspid, and 
first molar. The ring over the site of the second bicuspid, 
the missing tooth, had a rivet extending through it from buc- 
cal to lingual, evidently intended for holding the substituted 
tooth, which, however, was lost. 
Fig. 986.— Etruscan Appliance for Supporting Three 
Artificial Teeth, Two of Which Were Made from One 
Ox Tooth (Civic Museum of Corneto) (Guerini) 
Fig. 986.— The Same Appliance Reversed 
Guerini suggests that the substitute tooth may have been 
made of some destructible material, and had disintegrated, 
or that it might have been slotted at its base to pass on 1084 
A BRIEF HISTORY OF PROSTHETIC DENTISTRY 
either side of the rivet, and not having been rigidly fixed 
within the ring, was dislodged and lost during the excavation. 
This appliance is now in the museum of Pope Julius, in Rome. 
Two appliances similar in character to the one just de- 
scribed will serve to illustrate the general type of the an- 
cient prosthetic pieces found in other Etruscan tombs, and 
which are supposed to be about 3000 years old. Both of 
these specimens repose in the civic museum of Corneto, the 
ancient city of Tarquinii. 
The first of these specimens to be described consists of 
bands of pure gold, soldered together and fitted to the cus- 
pid and lateral on the right, and to the cuspid, first bicuspid, 
and first molar on the left side. A band of gold con- 
taining a rivet extending through it from buccal to lingual, 
occupies the site of the missing natural second bicuspid, 
and served for the attachment of its substitute, the latter, 
however, having become disintegrated or in some manner, 
lost. A single, elongated band of gold, occupying the space 
of the three missing anterior teeth, extends from the right 
lateral to the left cuspid. Fitted within this band and filling 
the entire space, was a wide ox tooth, grooved longitudinally 
in its center to represent two central incisors. The space 
once occupied by these three teeth, having closed slightly, 
no effort was made to reproduce the lateral incisor. This 
block was firmly fixed in position by means of two rivets. 
(Figs. 985 and 986.) 
Whether the dentist in this case recognized the prophy- 
lactic advantage of keeping the gingival ends of the bands 
far removed from the gum line as possible, or was merely 
Fig. 987.— Etruscan Appliance 
for Supporting Two Inserted Hu- 
man Teeth, One of Which Is Now 
Wanting (Civic Museum of Cor- 
neto) (Guerini) 
actuated through motives of convenience in fitting and at- 
taching the appliance, cannot, of course, be determined, but 
the fact is apparent that the hands occupied a position well 
toward the incisal and occlusal third areas of the anchor 
teeth. 
The second specimen consisted of two strips of rolled 1085 
A BRIEF HISTORY OF PROSTHETIC DENTISTRY 
gold, adapted, one labially and tlie other lingually to the 
remaining anterior teeth, and soldered at their extremities 
to form an elongated hand. Four small sections of gold, 
spaced and soldered within this elongated band, divided 
it into five square spaces. Three of these spaces were oc- 
cupied by supporting natural teeth. The other two spaces 
served as sockets to carry the substitutes, which in this 
case were natural teeth, one of which was missing. The 
same method of anchorage as previously described — the 
rivet — was used for attaching the substitute teeth to the 
gold structure. (Fig. 987.) 
Fig. 988.— Etruscan Appliance 
Intended to Avoid the Bad Ef- 
fects of Convergence, or, Per- 
haps, to Support a Purely Or- 
namental Artificial Substitute 
(Museum of Conte Bruschi at 
Corneto) (Guerini) 
These methods of wiring and banding together, with gold, 
loose natural teeth, and of applying the same means for the 
retention of substitutes for missing teeth, in the manner de- 
scribed, represent quite fully the first efforts of the early 
dentists in bridge construction. 
Fig. 989 
Fig. 990 
Examples of Dental Prosthesis as Practiced by the Hindus at the Present Time (Guerini) 
The addition of a saddle to rest upon the border, and 
thus furnish greater support and security to the substitute 
than was afforded by ligating or banding to the proximat- 
ing, and adjacent teeth, was evidently not conceived until 
a much later period. 1086 
A BRIEF HISTORY OF PROSTHETIC DENTISTRY 
ANCIENT CROWN WORK 
The first and only specimen of ancient gold crown work 
so far known was found within recent years, at Satricum, 
near Rome, and is now in the museum of Pope Julius. This 
crown consists of two pieces of gold, stamped to represent 
Fig. 991.—- Roman Appliance 
Found at Satricum. Crown of 
Lower Incisor Made of Gold 
Fig. 992.— The Same Seen from 
Below (Guerini) 
the labial and lingual surfaces of a lower central incisor, 
and united along the mesio-inciso-distal surfaces with solder, 
just as the Hollingsworth two-piece anterior crown is joined 
together. It was held in place by an elongated band wdiich 
embraced the proximating and adjacent tooth on either side 
of the crown. The attachment of the band was close to the 
gingival margin of the crown. (Figs. 991 and 992.) 
FIRST REFERENCES IN HISTORY TO PROSTHESIS 
Although these ancient specimens of dental prosthesis 
have been found, and somewhere near the probable time of 
their construction determined by deductive reasoning, no writ- 
ten records of such or similar work appears until about the 
beginning of the Christian Era. 
In Edersheim’s “Life and Times of Jesus, the Messiah,” 
according to Dr. W. C. Miller, in Dental Cosmos, December, 
1905, the following statement is found: “Speaking of things 
purchasable in Jerusalem in the time of Herod the Great, 40 
to 4 B. C., ‘And then the lady visitor might get anything in 
Jerusalem, from a false tooth to an Arabian veil, or a Per- 
sian shawl, or an Indian dress.’ ” 
Martial, a Latin poet, who lived in Borne during the 
first century A. D., in a number of his epigrams mentions 
artificial teeth. Guerini says: “There is therefore, not the 
least doubt that in the days of Martial, artificial teeth were 
in use; and that these, as may be seen from the epigram 
just quoted, were made of ivory and bone; we do not know 
whether they were formed of other substances. The ques- 
tion, however, arises: In those days did they manufacture 
movable artificial sets, or was the dental art then limited 1087 
A BRIEF HISTORY OF PROSTHETIC DENTISTRY 
to fixing the artificial teeth immovably to the neighboring 
firm teeth, by means of silk threads, gold wire and the like? 
The answer to this question may be found in another epi- 
gram of Martial, where the latter ridicules a wanton old 
woman, telling her, among other things still worse, that 
she at night lays down her teeth just as she does the silken 
robes. 
“It is, therefore, beyond all doubt that, at that period, 
the manner of constructing movable artificial sets was 
known; and most probably not only partial pieces were made, 
but even full sets. In fact, from the verse quoted above 
we have justly the impression that the poet means a whole 
set rather than a few teeth. From the words of Martial, 
it may also be concluded that these dentures could be put on 
and off with the greatest ease; or, as we may say, by a 
maneuver as simple as that of removing any articles of wear- 
ing apparel; they must, therefore, have been extremely well 
constructed.’ ’ 
DENTISTRY AMONG THE ANCIENT HEBREWS 
In Dr. Koch’s “History of Dental Surgery” is found the 
following from the pen of Dr. H. L. Ambler: “ The ancient 
Hebrews did not have any large amount of mechanical in- 
genuity, and dentistry with them was in a state of semi- 
cultivation, but they replaced natural teeth with false ones 
more than two thousand years ago. A law of the Talmud 
allowed the women ‘to go out on the Sabbath with their 
false golden or silver teeth.’ Some rabbis allowed their 
people ‘to wear the false silver teeth, since these appeared 
natural, but the use of golden false teeth on the Sabbath 
was prohibited.’ Many teeth were made of wood, and later 
on from the ivory of the elephant’s tusk.” 
SLOW PROGRESS OF DENTAL PROSTHESIS IN THE MIDDLE AGES 
Passing down through the centuries but little progress 
seems to have been made in denture construction until within 
the last one hundred and fifty years. It is true that various 
monographs on medical and dental subjects previous to the 
date last mentioned, contain frequent references to teeth 
carved from bone, or ivory, or hippopotamus tusks, but it is 
more than likely that most of these were partials, held in 
place with ligatures of silk or gold wire, in the manner already 
described. 1088 
A BRIEF HISTORY OF PROSTHETIC DENTISTRY 
The construction of satisfactory full upper and lower den- 
tures must have been a considerable undertaking in the olden 
time, considering the manner in which impressions of the 
mouth were secured and casts were derived from them, and 
finally the development of adaptation of the block of bone or 
ivory to the cast by carving and scraping. 
FIRST REFERENCE TO THE USE OF MODELS 
Brief as it is, the outline of technic of full denture con- 
struction as given by Matthias Gottfried Purmann, of Bres- 
lau, 1648 to 1721, is the most complete description found up 
to his time. He was the first to refer to the use of models 
in dental prosthesis, but he does not state how they were 
obtained. Here is his outline as given by Guerini: 
“The front teeth, or pronouncing teeth, ought, when 
they are wanting, to be substituted by artificial ones, in 
order to avoid the defects of pronunciation, as well as to 
obviate deformity of the mouth, and this is carried out in 
the following manner: One lias other teeth made of bone, 
or of ivory, according to the number, the size, and the pro- 
portions of those wanting; for which purpose one may 
previously have a model executed in wax, reproducing the 
particular conditions of the teeth and jaws, in order after- 
ward to make and exactly adjust the whole on the pattern 
of it; then when the base of these teeth is well fitted on 
the jaw and small holes have been made in the artificial 
teeth and also in the natural ones next to them, one applies 
the artificial teeth in the existing void and fixes them as 
neatly as possible with a silver wire by the help of pincers.” 
Because he advised the perforation of the natural teeth 
for the passage of the silver wire, a method which would 
prove exceedingly painful, and invite pathological complica- 
tions as well, Guerini concludes that Purmann simply de- 
scribed, “and not even accurately, a prosthetic method al- 
ready in use among specialists of that period. * 
On examination of the passage cited above, which, however, 
is not so clear as might be desired — it would appear that 
the models of which the author speaks were most probably 
quite different from those in use now. It is almost certain 
that the specialists of those days first made a sketch of the 
prosthetic part to be constructed, using for the purpose a 
piece of wax, which they modeled partly with the hand and 
partly carved; and after having tried on this model until it A BRIEF HISTORY OF PROSTHETIC DENTISTRY 
1089 
fitted perfectly in the mouth, and was in every way satisfac- 
tory, they probably passed it on to a craftsman to make an 
exact reproduction of it in bone or ivory.” 
The first reference to a full lower denture is found in 
the writings of Anton Nuck, an eminent Dutch surgeon and 
anatomist, 1650 to 1692. lie says, “In the case of all of the 
teeth of the lower jaw being wanting, the entire dental arch 
ought to be framed in with a single piece of ivory or tusk 
of hippopotamus.” Prom this we infer that full upper den- 
tures, being more difficult to retain, were not frequently con- 
structed, else they also would have been mentioned in this 
connection. 
Nuck further recommends that artificial teeth be made 
of hippopotamus tusk, specially favoring the whitest, which 
he estimated would preserve its color for seventy years, in 
preference to ivory, which turned yellow from the action of 
food, drink, and the saliva. 
FIRST REFERENCE TO FULL LOWER DENTURES 
FIRST RECORD OF APPLICATION OF MINERAL SUBSTANCES 
FOR DENTURES 
Pierre Dionis, a surgeon and anatomist of Paris, in 1690, 
states that artificial teeth are generally made of ivory, but 
may be made of ox bone, which will retain its color better 
than ivory. He also states that Guillemeau constructed arti- 
ficial dentures from a composition made by fusing together 
white wax, gum elemi, ground mastic, and powder of white 
coral and of pearls. 
On this Guerini remarks: “This fact is, as everyone can 
see, most important, for it constitutes the first step toward 
the manufacture and use of mineral teeth. Ilionis tells us 
that the teeth made of Guillemeau’s composition never be- 
came yellow, and that it was also very good for stopping de- 
cayed teeth. It would seem, therefore, that it could be used 
as cement is now used.” 
RETENTION OF PARTIAL DENTURES WITHOUT THE USE OF LIGA- 
TURES OR WIRES 
While it is possible, and in fact quite probable, that par- 
tial dentures had been constructed and used, which were not 
dependent on the use of the ligatures for their retention, yet 
no clear statement of this fact has so far appeared. The 1090 
A BRIEF HISTORY OF PROSTHETIC DENTISTRY 
first attempts to construct easily removable pieces, in all 
probability, consisted in longitudinally grooving the ends of 
the partial denture so as to partially embrace the proximate 
ing teeth, just as the natives of the Orient now do in their 
prosthetic restorations. It will therefore be interesting to 
mention the first record of such practice. 
Lorenze Heister, a celebrated surgeon, in 1611 first rec- 
ommends the use of movable prosthetic appliances of ivory 
or hippopotamus tusk without special means for fixing them, 
and further, that they should be removed at night and not 
be returned to the mouth again until well cleansed. 
Johann Adolph Goritz, in 1725, recommended that the 
natural teeth be preserved by every possible means. He 
discouraged the use of prosthetic appliances where only a 
few natural teeth were lost, but suggested that in the worst 
cases, to avoid defective ‘ ‘ pronunciation, or for some other 
reason (presumably unsightliness) the space might be filled 
by an imitation in soft wood. 
Heinrich Bass of Bremen, 1690 to 1754, professor of anat- 
omy and surgery in Halle, recommended the application of 
“whole dental sets, even in the upper jaw, so long as there 
be two natural teeth existing to fix the prosthetic piece to.” 
From this we again infer that the construction of full upper 
cases was not frequently attempted, on account of the diffi- 
culty in securing adequate adaptation and guarding against 
the force of gravity and masticatory stress. 
fauchard’s writings 
Pierre Fauckard, born in Brittany, 1690, died in Paris 
in 1761, has been called the ‘4 founder of modern scientific 
dentistry.” He published a work in 1728, entitled “Le Chi- 
rurgien Dentiste, ” consisting of two volumes, which was by 
far the best exposition on dentistry that up to that time had 
ever been written. 
In olden times, down to a period within the memory of 
some of the members of the profession still living, there was 
a tendency on the part of many practitioners to jealously 
guard with secrecy their methods of practice, especially pros- 
thetic operations, and thus prevent competitors from profit- 
ing thereby. 
Fauchard’s writings cover a wide range of dental sub- 
jects and in prosthetic operations he is particularly explicit. 
He recognized the existence of the petty jealousies alluded 
to, but was able to rise above them, as his descriptive details A BRIEF HISTORY OF PROSTHETIC DENTISTRY 
1091 
plainly show. In reference to this he says: “I have per- 
fected and also invented several artificial pieces, both for 
substituting a part of the teeth and for remedying their en- 
tire loss, and these pieces substitute them so well that they 
serve perfectly for the same uses as the natural teeth. To 
the prejudice of my own interests I now give the most exact 
descriptions possible of them.” 
While Fauchard did perfect some of the prevailing forms 
of artificial substitutes and invent others, the greatest bene- 
fit he rendered the profession and posterity consisted in hav- 
ing collected and included in his work “the whole doctrine 
of dental art, theoretical as well as practical, thus setting 
in full light the importance of the specialty, and giving it a 
solid scientific basis.” (Guerini.) 
Interesting as all of Fauchard’s writings are, only a 
few of the principal methods he describes can be here in- 
troduced. 
He mentions tliat in transplanting a tootli, whether re- 
cently extracted or not, its root should be grooved hori- 
zontally, so that when ligated firmly in position, the alveolar 
process would eventually be built in the depressions so 
formed, and as he expressed it, “the tooth will remain mor- 
tised and may be preserved for a considerable length of 
time.” 
He describes several methods in detail for replacing the 
loss of two, three, or more contiguous teeth. One of these 
consisted in carving from ivory, hippopotamus tusk, or bone, 
each tooth, individually, to be replaced and fixing them to- 
gether in a single piece by drilling holes and ligating with 
wire. This was then bound to the natural teeth with gold 
or silver wire, or silk or linen thread. Another method, in- 
stead of ligating the substituted teeth together, consisted of 
applying a strip of gold fitted into a horizontal groove 
formed in the lingual surfaces of the carvings, and to which 
each tooth was attached by means of two rivets. Again, the 
teeth to be replaced were sometimes carved from a single 
block of the materials commonly used and attached in the 
manner previously mentioned. 
TRANSPLANTATION OF NATURAL TEETH 
CROWN WORK IN FAUCHARD’s TIME 
Crowns were attached to roots of teeth by means of a 
metal pivot extending into the root, which in case of enlarged 1092 
A BRIEF HISTORY OF PROSTHETIC DENTISTRY 
canal had previously been filled with lead. A hole drilled 
in the lead received the root end of the pivot, while the crown 
was attached to the projecting end of the pivot with a cement 
Fig. 993.— Fauchard’s Illustration of a Crown 
of Ivory or Hippopotamus Tusk 
with Metal Dowel 
composed of gum lac, Venice turpentine, and powdered white 
coral. The crown of a natural tooth was frequently employed 
in such cases. 
MEDIAEVAL BRIDGEWORK 
The first mention of fixed bridgework, although not so 
designated, is made by Fauchard, wherein he describes how 
a prosthetic piece may be held in position, in case the crowns 
of the teeth had been lost but the roots were present. Two 
Fig. 994.— Bridge Carved from Ivory, Retained by 
Two Screws Fitted in Roots of Lateral 
Incisors (Fauchard) 
holes were made in the substitute, corresponding to and in 
alignment with the canals of two roots, through which pyra- 
midal screws were introduced and screwed firmly into the 
roots. 
FULL DENTURES 
Full lower dentures were recommended, with the sugges- 
tion that the piece should be so formed as to fit the irreg- 
ularities of the arch perfectly, when, with the aid of the A BRIEF HISTORY OF PROSTHETIC DENTISTRY 
1093 
tongue interiorly and the cheek and lower lip exteriorly, the 
substitute would be held steadily in place and the patient 
would be able to masticate with it after becoming accustomed 
to its presence. 
CONSTRUCTION OF FULL DENTURES BY FAUCHARD 
Although full upper dentures were constructed long be- 
fore Fauchard’s time, it is evident that they were seldom 
Fig. 995.— An Upper Denture Supported by Springs Fixed 
to a Gold Appliance Which Embraces the Natural 
Teeth of the Lower Jaw (Fauchard) 
(Guerini) 
satisfactory. One case is mentioned which illustrates the 
helplessness and inability of some who were considered other- 
wise well qualified in the construction of full upper cases. 
Fauchard says: “In 1737 a lady of high rank, of about the 
age of sixty, who had not lost any of her lower teeth, but 1094 
A BRIEF HISTORY OF PROSTHETIC DENTISTRY 
was deprived entirely of the upper ones, applied to M. 
Caperon, dentist to the King, who was most able in his pro- 
fession, in the hope that he might be able to furnish her 
mouth with an upper set. But he said that, ‘no tooth what- 
ever being left in existence, every possible point of attach- 
ment was wanting, and it would therefore be as difficult to 
do this thing as it would be to build in the air.’ ” M. Caperon 
referred her to Fauchard, who after some deliberation “suc- 
ceeded in devising a means of applying an upper set of teeth 
which, in fact, entirely satisfied the wishes and wants of his 
client.” (Guerini.) 
The appliance in this case did not include the full com- 
plement of teeth, some of the posterior space being occupied 
by the springs, by means of which, in conjunction with a 
double bow frame of gold fitted around the lower teeth, the 
denture was retained in position. 
Mention is also made of three successful cases of full 
upper dentures which were retained without the aid of 
springs. Several points of interest are seen in Fauchard’s 
own description of these cases, which is as follows: 
“One can adapt an entire set of teeth to the upper jaw 
of much greater simplicity than those described, and which 
Fig. 996.— Full Lower Set in Hippopotamus Ivory with Human Front 
Teeth, Seventeenth Century (Guerini’s Collection) 
is maintained in its place by the sole support of the cheeks 
and the lower teeth. It must he very light indeed and serves 
almost solely to improve the appearance and the pronunci- 
ation ; hut when the individual gets used to it, he can also 
masticate with it. A set of teeth of this kind ought to ad- 
here well to the gums and to he constructed in such a man- 
ner that the cheeks may afford it sufficient pressure and A BRIEF HISTORY OF PROSTHETIC DENTISTRY 
1095 
support, together with the aid of the lower teeth. These 
latter sometimes bring it back into its place without anyone 
perceiving the movement except the wearer himself. Not 
long since I had occasion to renovate a set of teeth of this 
kind made by me more than twenty-four years ago and 
worn by the owner to the greatest advantage. I have since 
made two others which have proved most useful to the per- 
Fig. 997.— Upper Denture in Ivory, at the End of the Eighteenth Cen- 
tury, for a Case in Which the Last Molars and the Front 
Teeth Were Present (Guerini’s Collection) 
sons wearing them. It is true that there are few mouths 
adapted for wearing these sets, so much so that, excepting 
the three referred to, I have never made any others. To be 
able to construct similar sets successfully, the dentist must 
be possessed of skill and ingenuity. Apart from this, they 
are the most suitable for poor persons who cannot spend 
much, as they cost less to make.” 
SUMMARY OF FAUCHARD’s WORK 
Fauchard made use of both flat steel and coiled gold wire 
springs for the retention of both full and partial dentures. 
Summed up briefly, the main facts of prosthesis which 
Fauchard elaborated upon are as follows: 
The transplantation and replantation of natural teeth. 
The application of both carved and natural crowns to the 
roots of teeth by means of metal pivots, or by binding them 
to proximating natural teeth with ligatures of gold or silver 
wire, or silk or linen thread. 
The application of a crude form of bridgework consisting 
of a carved replacement rigidly fixed to two natural roots by 1096 
A BRIEF HISTORY OF PROSTHETIC DENTISTRY 
means of two tapering screws passing through the substitute 
into the root canals. 
The carving of partial and full dentures from ivory, hip- 
popotamus tusk, or bone, together with a description of means 
Fig. 998.—Complete Dentures (Fauchard). F3 Represents an Enam- 
eled Denture with Artificial Gums, F4 and F5 Steel 
Springs (Guerini) 
of attachment with ligatures, springs and metal cribs, and 
adhesion. 
The enameling of artificial teeth to represent the varia- 
tions in color of the natural teeth, and the staining or enam- 
eling of the gum portion to represent the color of the mucous 
tissues. 1097 
A BRIEF HISTORY OF PROSTHETIC DENTISTRY 
The construction of obturators for correcting defects of 
the palate. 
Finally, the suggestion, but not the development and use, 
of porcelain for teeth and dentures, as noted in the chapter 
on porcelain. 
Fig. 999.— A Spring Denture for a Case in Which the Lower Front 
Teeth Still Exist. Figs. 1 to 6 Illustrate Various Parts 
of the Apparatus (Fauchard) (Guerini) 
BENEFICIAL INFLUENCE OF FAUCHARD’s WRITINGS UPON 
THE PROFESSION 
Undoubtedly, tlie example of Fauchard in giving freely 
and unstintingly to the profession, the benefits of his knowl- 
edge, experience and improvements, exerted a widespread and 1098 
A BBIEF HISTOBY OF PBOSTHETIC DENTISTKY 
beneficial influence on his contemporaries and the men who 
followed. This is evident from the sparseness of detail in 
previous writings and the marked tendency of subsequent 
writers to more fully elaborate their ideas. 
That the work of Fauchard was up to date and in some 
respects in advance of the times is apparent from the fact 
that although other works appeared at about that time and 
at intervals afterward, none of importance was presented un- 
til eighteen years after the publication just reviewed. 
FIBST WORK CONFINED EXCLUSIVELY TO DENTAL PBOSTHESIS 
In 1746 Mouton published the first work of record con- 
fined to dental prosthesis. Most of the methods detailed by 
Fauchard were included in this later publication, and some 
new ideas were introduced, among which may be mentioned 
the application of gold crowns to badly decayed front and 
back teeth, the front crowns being enameled to correspond in 
color with the natural teeth. 
For the first time mention is also made of the use of spring 
clasps for the retention of partial dentures. 
FIBST MENTION OF PLASTEK 
In 1756 Philip Pfaff, dentist to Frederick the Great, in 
a work confined to dental subjects, first describes the use of 
plaster models. Guerini remarks: “It is therefore to two 
Germans — Pfaff and Purmann, the latter who, as we have 
already seen, used wax models — that one of the greatest pro- 
gressive movements in dental prosthesis is indebted; that is. 
the method of taking casts and making models, of which 
method one finds no trace whatever in the authors of antiquity, 
and which, it would appear, was not known even to Fauchard 
himself. The wax casts of an entire jaw were taken by Pfaff 
in two pieces, one of the right half of the jaw, the other of 
the left, which were then reunited, and one thus avoided spoil- 
ing the cast in removing it from the mouth.” 
FIB ST MENTION OF GOLD BASES 
In 1757 Bourdet described the use of gold bases for rest- 
ing upon the alveolar process, to which the replaced teeth 
were attached by means of small pins and the whole base 
overlaid with flesh colored enamel, similar to the continuous 
gum pieces of to day. He also described another denture in A BRIEF HISTORY OF PROSTHETIC DENTISTRY 
1099 
which lie carved the three back teeth on either side from the 
same block of hippopotamus tusk, which formed the base, 
while the ten anteriors were human teeth fixed to the carved 
base by means of rivets. 
IMPLANTATION OF TEETH 
The first mention of implantation of teeth is made by 
Bourdet, which is related by Guerini as follows: “This cel- 
ebrated author inveighs bitterly against charlatans and quack 
dentists, and throws light on all their impostures. It appears, 
however, that in the midst of this despicable class, so justly 
condemned by him, there existed a courageous though unscien- 
tific operator, to whom posterity would have attributed due 
honor had his name been handed down, for he was the first, 
in all probability, to try the implanting of teeth in artificial 
alveoli. This is, at least, what we deduce from a passage in 
one of Bourdet’s works, in which we read that a charlatan 
sought to impose on the public the belief that he could make 
a hole in the jaw bone and plant therein an expressly pre- 
pared artificial tooth, which in a brief space of time would be- 
come firm and as useful as a natural one. Bourdet adds that 
an attentive investigation led to the recognition of said tooth 
being simply that of a sheep. It would appear, therefore, that 
the operation had been in reality performed, it matters but 
little whether with the tooth of a sheep or with one of another 
kind.” 
Adam Anton Brunner, a German, in 1766, described a 
method of applying pivot teeth by screwing the pivot into the 
base of the crown, then enlarging the root canal just enough 
to tightly embrace the root portion of the pivot. Light ham- 
mer blows directed against the crown forced the pivot into 
the root canal and held it firmly without the aid of cement. 
BERDMORE’s REFERENCE TO ARTIFICIAL DENTURES 
Tliomas Berdmore, dentist to George III of England in 
1768, makes this statement in regard to artificial teeth: “Al- 
though artificial teeth are evidently ornamental, although they 
give a juvenile air to the countenance, improve the tone of the 
voice, render pronunciation more agreeable and distinct, help 
mastication, and preserve the opposite teeth from growing 
prominent, yet many are prejudiced against them on account 
of some inconveniences which are often found to attend the 
use of them. For they are said to become very soon yellow 1100 
A BRIEF HISTORY OF PROSTHETIC DENTISTRY 
and dirty, to give a stinking breath, not to fit easy on the 
gums, seldom to stand firm, and to loosen after some time 
the neighboring teeth to which they are fastened, or the hard 
ligature, which is commonly used, is often seen to cut very 
deep into the sound teeth.” He lavs these difficulties to the 
fault of the “artist,” the negligence of the patient, or the want 
of proper instructions. He recommended the frequent use 
of the brush with suitable powders, and to avoid the use of 
red wines and staining liquors, and the use of silk twist in- 
stead of wire ligatures. 
“A whole set of artificial teeth may be made for one or 
both jaws, so well fitted to admit of the necessary motions, 
and so conveniently retained in the proper situation by the 
help of springs of a new and peculiar construction that they 
will answer every purpose of natural teeth, and can be taken 
Fig. 1000.— Carved Ivory Dentures Fitted 
with “ Grasshopper Springs ” 
out, cleaned and replaced by the patient himself, with the 
greatest ease. I say springs of a peculiar construction, be- 
cause they are totally different in shape and action from 
those which have been used by my predecessors, because they 
follow all the various motions of the jaw very freely, and be- 
cause the pressure which they give is always equal and gen- 
tle, whether the mouth be shut or not.” He further states 
that dentures made from soft bone or ivory discolor readily, 
but may be made of more durable materials which will retain 
their polish and whiteness for a long time. Further, that the 
gum portion may be stained so perfectly that “ nobody in 
common conversation can distinguish the artificial from the 
natural gums.” 
Jourdain, in 1784, described a full upper and lower den- 
ture sustained in position by means of four springs, the idea 
of which, he states, was conceived, but probably not developed, A BRIEF HISTORY OF PROSTHETIC DENTISTRY 
1101 
by Massez in 1772. Because this means of retention was com- 
plicated and difficult to adapt, it did not come into general use. 
PRINCIPAL MATERIALS USED AS DENTURE BASES 
Tlie principal materials so far mentioned and used as sub- 
stitutes for natural teeth were bone, ivory, hippopotamus tusk, 
wood, gold, silver, white wax, mother of pearl, human teeth 
and those of animals, all more or less perishable except the 
metals mentioned. 
The effort of Guillemeau, mentioned by Dionis, in 1690, 
was the first of record to compound a substance which would 
more nearly fulfill the requirements of durability, appearance 
and ease of application, for prosthetic substitutes, than did 
the organic materials in common use. 
FIRST SUGGESTION OF PORCELAIN WORK 
Fauchard, in 1728, suggested the use of porcelain for teeth 
and dentures, but did not follow up and develop what has 
since proven to be one of the most important as well as 
esthetic phases of prosthetic science. It seems that he made 
use of enamels for staining both teeth and gums to resemble 
those of nature. Bourdet, in 1756, stated that he “had used 
the pink enamel of Fauchard.” This enamel must have been 
in the nature of a paint or varnish, and so applied, since, if of 
porcelain, the heat necessary to fuse the latter would have 
destroyed both teeth and base of bone or ivory. 
DUCHATEAU’s EFFORTS IN PORCELAIN WORK 
In 1774, Duchateau, a French chemist, near Paris, who 
was wearing a denture made from hippopotamus tusk, and 
which had acquired a disagreeable odor, conceived the idea 
that a porcelain denture would be free from the objection men- 
tioned. He presented his idea to Guerhard, a porcelain manu- 
facturer in Paris, and together they proceeded to experiment. 
The first denture, on account of the contraction of the porce- 
lain in baking, was too small. A number of others were con- 
structed, none of which for various reasons proved satis- 
factory. 
THE WORK OF DUBOIS DE CHEMANT 
Discouraged by the many failures encountered, Duclia- 
teau applied to Dubois de Cliemant, a well-known dentist of 
Paris, for advice and assistance. By modifying tbe porce- 1102 
A BRIEF HISTORY OF PROSTHETIC DENTISTRY 
lain of Duchateau with pipe clay and coloring earth, its fus- 
ing point was reduced, the color improved, and contraction 
was lessened. Finally, after a number of efforts, a denture 
was produced that Duchateau was able to use. Although he 
endeavored to construct dentures for others, Duchateau’s ef- 
forts resulted only in failure, his general knowledge of pros- 
thesis being insufficient to accomplish the required results. 
He received a vote of thanks and an honorable mention 
from the Royal Academy of Surgeons of Paris in 1776, be- 
fore whom his process was laid. The failures mentioned dis- 
couraged Duchateau from further efforts in this field, nor 
does it appear that he again renewed them. 
De Chemant, to whom the success of Duchateau’s efforts 
was largely due, continued his experiments, and, after a 
number of years, succeeded in compounding a porcelain, the 
contraction of which could be determined to a fairly accurate 
degree, of modifying the shade to a considerable extent as 
desired, and of improving the springs and other means of 
attachment. 
Desirabode, writing in 1848, says in reference to the in- 
troduction of porcelain: “Faucliard seems to be the inventor 
of porcelain teeth, then Duchateau improves the manufacture; 
De Chemant, by accident, gets hold of the secret, which he 
further improves and gives as his own in 1788 when he pub- 
lished the first edition of his work. De Chemant carried the 
art to England, where he obtained the exclusive right to work 
the invention for twelve years.” 
In the work alluded to, De Chemant shows by means of 
engravings the various types of prosthetic substitutes he 
could produce in porcelain. Among these were included a 
crown, a bridge, full dentures and an obturator. 
With few exceptions, Fauchard being a notable example 
to the contrary, the writer on dentistry in those days pub- 
lished a book, not so much to enlighten his professional breth- 
ren, as to impress the public with his superior attainments. 
De Chemant was one of the latter class. His work was largely 
made up of eulogistic effusions of himself and the new process 
of which he claimed to be the sole inventor, thus denying to 
Duchateau any credit whatever, in either the conception or 
development of the porcelain idea. 
Furthermore, he studiously avoided giving to the profes- 
sion so much as a hint of the composition or manner of work- 
ing the paste for the making of “indestructible teeth,” which, 
as appears, still lacked many desirable qualities. Indirectly A BRIEF HISTORY OF PROSTHETIC DENTISTRY 
1103 
his selfish, commercial attitude resulted in benefit to the pro- 
fession by instigating others to enter the field in an effort to 
find something as good or better than that which he had dis- 
covered. 
Dubois Foucou, dentist to the King, was one of the jury 
appointed by the French Academy of Surgeons to examine 
into the merits of De Chemant’s discovery. He was at first 
opposed to the idea, but later on began experimenting and 
succeeded in improving both the quality and color of the por- 
celain over that used by De Chemant. While this was indeed 
laudable, the greatest benefit resulting from Foucou’s re- 
searches consisted in publishing to the profession all of the 
formulas and methods he had discovered. His dentures were 
produced in three shades, bluish white, grayish white and yel- 
lowish white, in varying gradations. 
INTRODUCTION OF SINGLE TEETH AND BLOCKS OF PORCELAIN 
Fonzi, an Italian, practicing in Paris, in 1808, introduced 
for the first time single teetli and blocks of teeth, having baked 
within and projecting from them small pins or hooks of 
platinum, by means of which they could be attached to bases of 
various kinds. This was a decided and valuable improvement 
in itself, for it encouraged the production of bases of more 
permanent character, such as gold, silver, and platinum, and 
the consequent development of technic in metallurgical lines. 
The porcelain of which these teeth were composed was some- 
what translucent and much more nearly resembled the natu- 
ral teeth than did that of either De Chemant or Foucou. Still 
further credit should be given Fonzi from the fact that these 
teeth were, to a limited extent, manufactured and rendered 
available to other members of the profession, and, further, 
were capable of comparative ease of application. 
Thus when the facts are known Fonzi stands out as a 
prominent character in the advancement of prosthetic sci- 
ence, for it is apparent that from his time on progress in the 
porcelain field shows gradual but marked improvement. 
The production of dentures carved from bone, ivory and 
similar substances continued for many years after Fonzi’s 
time, largely because of imperfect technical methods, and the 
difficulties encountered of fusing porcelain in the cumbersome 
furnaces in use in those days, some of this material requiring 
a temperature of 3,000 degrees F. to vitrify. 1104 
A BRIEF HISTORY OF PROSTHETIC DENTISTRY 
FIRST INTRODUCTION OF PORCELAIN IN THE UNITED STATES 
In 1817, Plantou of Paris came to Philadelphia, bringing 
with him a stock of porcelain teeth made in France. These 
have been described as being inferior in both quality and 
color, somewhat resembling a split bean, having a half-round 
groove in the back, in the sides of which were inserted small 
Fig. 1001.— Grooved Porcelain Facings Used Both for Crown and Denture Work 
About 1820 
strips of platinum for bending over and soldering to a gold 
wire post attached to the denture base. 
The arrival of Plantou proved an incentive to members of 
the profession in this country to enter the porcelain field in 
an endeavor to improve the quality and forms of the teeth 
then available. 
THE FIRST MANUFACTURE OF PORCELAIN TEETH IN AMERICA 
In 1822, Chas. W. Peale began tlie manufacture of porce- 
lain teeth, in the backs of which platinum pins were inserted 
and baked for attachment purposes. 
In 1825 S. W. Stockton began the manufacture of porce- 
lain teeth with sucli success that in a few years his business 
had grown to quite extensive proportions. In reality he was 
the first in this country to engage extensively in the produc- 
tion of porcelain teeth for the profession. 
It was customary, about this time and for many years 
later, with a number of men in the profession to manufacture 
teeth, both single and in blocks or sections, to meet the re- 
quirements of individual cases in practice. 
These teeth and blocks were attached to bases of various 
kinds, being mounted on ivory or hippopotamus tusk by means 
of screws or rivets, passing through holes drilled through both A BRIEF HISTORY OF PROSTHETIC DENTISTRY 
1105 
base and porcelain, while to metal bases they were attached 
in the same manner and by soldering1 a backing to pins baked 
in the porcelain. 
Ambler states that “among those who made teeth for 
their own use were Doctors Mcllhenny (1826), Ambler and 
Spooner (1828), Flagg (1830), S. Spooner (1831), Harwood 
and Tucker (1833), Alcock and Allen (1835), and Wildman, 
who began his experiments in 1837. The latter made pains- 
taking investigations and achieved notable results. ‘His work 
was so important and far-reaching that he has been accorded 
Fig. 1002.— Labial and Lingual Views of Denture Con- 
structed by Dr. Mcllhenny in 1835. Tooth 
Blocks Were Carved by Hand 
the honor of having been first to place the manufacture of 
teeth on a scientific basis.’ ” 
In 1844, Samuel S. White of Philadelphia began th° manu- 
facture of teeth, in a small way at first, but his products were 
of such excellent quality that the business soon grew to large 
proportions. Upon the foundation which he laid was estab- 
lished the S. S. White Dental Manufacturing Company, which 
to-day is one of the most extensive, if not the largest, concern 
of its kind in the world. 
For many years the quality of porcelain teeth, both for- 
eign and domestic, has been reasonably satisfactory in color 
and texture, but few, if any, have fulfilled anatomic require- 
ments. The bicuspids and molars are usually too small and 1106 
A BRIEF HISTORY OF FROSTHETIC DENTISTRY 
are relatively disproportioned to each other as well. Labial 
and buccal surfaces, while falling short of perfection in 
form, presented a much better appearance than did the in- 
cisal edges of the anterior or the occlusal surfaces of bicuspids 
and molars, particularly the latter, the planes and surface 
markings of which oftentimes in no way resembled in form 
the surfaces they were supposed to represent. 
Within recent years, since mandibular movements are bet- 
ter understood, the demands of the profession for better forms 
Fig. 1003.— Type of Coke Fur- 
nace Commonly Used in the 
Early Days for Fusing Block 
Teeth and Contiguous Gum Den- 
tures 
of artificial teeth have been and are being met by the manu- 
facturers with commendable and in many instances extremely 
gratifying results. 
INTRODUCTION OF GOLD FOR DENTURE BASES 
As previously stated, Bourdet, in 1757, mentions the use 
of gold fo** denture bases. It was not introduced into the 
United States until 1780, when Dr. James Gardette of Phila- 
delphia described and used it for this purpose. 
Silver and platinum were also employed for baseplates, 
but the use of all of these metals was limited, because of the 
difficulty met with in securing adaptation to the oral tissues. 
DIES FOR SWAGING METAL BASES 
Dies were frequently made of brass, the model being sent 
to. a brass foundry for casting, no laboratory being equipped 
with furnaces suitable for fusing this alloy. A BRIEF HISTORY OF PROSTHETIC DENTISTRY 
1107 
Later on zinc was employed for dies because of its com- 
paratively low fusibility and hardness. Still later, about 1860, 
Babbitt’s metal was made use of for the same purpose, it 
being almost as hard as zinc, fused lower and contracted less 
Fig. 1004.— English Tube Teeth Mounted on 
Swaged Gold Base. Constructed About 
1844 (Loaned by C. E. Sykes, of 
C. Ash & Sons) 
than the latter metal. Dr. L. P. Haskell is largely responsi 
ble for the introduction of and improvement in Babbitt metal, 
which, without doubt, is the best alloy available for die pur- 
poses. 
As late as 1840, De Loude of London, in writing of his 
methods of technic, says: ‘ ‘ The impression is poured 1 
Fig. 1005.— Full Upper and Lower Dentures, Gold Bases, with Springs from Fox and 
Harris (Ed. 1855) 
plaster and the model sent to a brass founder to have a simi- 
lar one made of brass; after which a she-mold of lead is made 
on the one of brass, then plates of gold, silver or platina are 
swaged.” (Ambler.) 1108 
A BRIEF HISTORY OF PROSTHETIC DENTISTRY 
Tin bases made by casting the molten metal into a matrix 
containing the teeth, and directly to them, was introduced by 
Dr. Edward Hudson of Philadelphia in 1820. Further work 
along similar lines was carried on by Dr. W. A. Boyce of 
Newburgh, N. Y., in 1836, and by Dr. George E. Hawes of 
New York in 1850, but with more or less indifferent success. 
Dr. A. A. Biandy of Baltimore, in 1856, greatly improved 
the then existing methods of technic, and introduced an alloy 
for denture bases which cast more sharply than tin. The 
process was termed “ Cheoplasty, ” and dentures so con- 
FIRST USE OF CAST BASES 
Fig. 1007 
Fig. 1008.— Gold Base Denture, Single Gum 
Section Teeth, Backed and Soldered, with Periph- 
eral Rim. Constructed by Dr. W. N. Morrison 
About 1869 
structed were called cheoplastic dentures. Harris’ Edition, 
1873, stares that “the name chosen by him (Blandy), signify- 
ing the making of plates by pouring a metal, made plastic by 
heat, is equally applicable to all alloys of tin now used. 
Biandy’s alloy of cheoplastic metal was silver, with some 
bismuth and a trace of antimony.” Tin, combined with bis- 
muth or cadmium, was introduced shortly afterward, and 
these alloys are used, more or less, for lower weighted den- 
tures at the present time. 
Hard vulcanite, although discovered in 1851, had not come 
into general use as a denture base, and the teeth used in metal 1109 
A BRIEF HISTORY OF PROSTHETIC DENTISTRY 
base denture construction were not suited, because of their 
form and type of pins, for firm attachment in the cast bases, 
therefore teeth of modified forms were designed and used for 
this purpose. 
SPECIAL FORMS OF TEETH FOR USE WITH CAST BASES 
In 1856, W. G. Oliver and Thomas Harrison introduced 
teeth with grooves and holes for anchorage purposes, to be 
Fig. 1009 
Fig. 1010 
Fig-. 1011.— Various Forms of Teeth Designed for Cheoplastic Work by and Marshall 
About 1855 
used in the casting process. These teeth some 
what on the order of the present diatoric teeth. 
In 1852 John A. Cummings of Boston filed a s "'at, and 
in 1855 applied for a patent for the method and use of rubber 
in denture construction in practically the same manner as :t 
is used to-day. This patent was granted in 1864, and the *e- 
upon began a long and drastic siege of litigation, on the part 
of Cummings and others, to enforce upon the members of the 
profession who were using vulcanite the payment of office 
rights or royalty for the privilege of using rubber for this 
purpose. 
The final summing up and outcome of this now famous 
legal battle can be found in the Dental Cosmos, April, 1873. 
DENTAL VULCANITE LITIGATION 1110 
A BRIEF HISTORY OF PROSTHETIC DENTISTRY 
the entire issue of that month being devoted to the court 
transactions in the final case. 
The following paragraphs briefly explain the principal 
points of history of the vulcanite litigation: 
‘‘Letters patent were granted to John A. Cummings on 
June 7, 1864, for an ‘improvement in artificial gums and pal- 
ates,’ and on account of a defect were reissued January 10, 
1865, to the Dental Vulcanite Company, and later on account 
of a defect were again reissued March 21, 1865, to said com- 
pany. 
“The Goodyear Company, by assignment, became the 
legal owners and issued to dentists, for various sums, 
‘ licenses and agreements ’ to use its process only in their own 
business, the license not to be assigned, sold, transferred or 
otherwise disposed of, and the licensee not to encourage in- 
fringements, and if he found any one infringing he was to re- 
port it to the company and they were to bring suit against the 
infringer. These licenses were generally given for one year, 
and were signed by the licensee, the agent and Josiah Bacon 
treasurer, who, on account of his arbitrary methods and mean- 
ness in dealing with the dental profession, was shot and killed 
in San Francisco. 
“rnhe contest as to the validity of the patent between the 
Good) ar Company and the whole dental profession of the 
United States was long and bitter. Finally S. S. White took 
up the cause for the profession and spent much time and 
money and in the end won the case and wiped out the abomina- 
tion.” (Dr. H. T. Ambler, in History of Dental Surgery.) 
COLLODION AND CELLULOID AS DENTURE BASES. 
The refusal of many to use rubber, on account of pending 
claims of the patentee, led to the introduction of collodion as 
a denture base in 1859, by John Mackintosh of England. 
Dr. J. A. McClelland of Louisville, Ky., in 1860, improved 
the collodion base and introduced it under the name of “Rose 
Pearl,” but this, as well as Mackintosh’s product, proved un- 
satisfactory on account of contraction, warpage and lack of 
permanent quality. 
Celluloid, having collodion as a base, was invented by 
Isaiah S. and John W7. Hyatt of Albany, N. Y., in 1870, and 
for many years was used extensively, and is to a limited ex- 
tent to-day employed in denture construction. 
Although any of the existing forms of vulcanite teeth can 
be used in conjunction with celluloid as a base, a special 
form of tooth having a constricted cervix and of more natural A BRIEF HISTORY OF PROSTHETIC DENTISTRY 
1111 
form generally was designed for this purpose. The counter- 
sunk pin tooth followed closely on the introduction of im- 
proved teeth for celluloid work. 
Some of the most notable attempts to reproduce natural 
tooth forms were made by Dr. E. T. Starr in 1869. A few of 
the molds he produced are scarcely equaled by the best efforts 
of present-day tooth designers. 
Ash & Sons of London have long been noted for the pro- 
duction of teeth which, in both form and color, closely resem- 
ble the natural organs of mastication. Their tube teeth, which 
were introduced about 1840, are capable of varied applica- 
tion, both for dentures and single crowns. These teeth can 
be reshaped by grinding and the glaze restored by polishing so 
perfectly that the modification cannot be detected. Because 
of the materials employed and the mode of manufacturing, the 
finished product is very dense and free from porosity. 
Most of the manufacturers of teeth have, within recent 
years, improved the quality of materials in their products, and 
practically all of the present-day teeth can be modified and 
repolished as described. 
VULCANIZING RUBBER BETWEEN METAL SURFACES 
The process of vulcanizing rubber between two polished 
metal surfaces was introduced by Dr. Stuck in 1868 His 
method consisted in forming a cast of the mouth in n, de- 
veloping the base plate in wax or securing the required thick- 
ness and form of the model denture base with several layers 
of tinfoil, investing the case in the flask, and on opening re- 
moving all but the outermost layer of tinfoil from the matrix 
side. This resulted in the formation of a metal matrix in 
which the rubber was packed and vulcanized. The product 
was much denser than when vulcanized in a plaster matrix, 
and in addition required no polishing except where the sur- 
plus margins were trimmed away. A similar method is some- 
times resorted to at present, except that instead of the tin 
cast of the mouth a plaster cast as ordinarily constructed is 
used, to which a thin sheet of tinfoil is carefully adapted, 
cemented to the cast with a thin film of sandarac varnish or 
Le Page’s glue, which thus affords a metallic surface against 
which the vulcanite is molded. 
DENTURE BASES PRODUCED BY ELECTRO-DEPOSITION OF 
GOLD AND SILVER 
Denture bases formed by electro-deposition of gold, and 
also of gold combined with silver, have at various times been 1112 
A BRIEF HISTORY OF PROSTHETIC DENTISTRY 
tried, but with indifferent success. Metal deposited by this 
process lacks the cohesiveness of either cast or rolled plate, 
and although beautiful results and good adaptation may be 
secured, unless the base is formed very heavy, so thick, in 
fact, as to be objectionable, it will fracture readily under 
stress. 
ARTICULATORS 
The progress of improvement in articulators, or, more 
correctly, occluding frames, is extremely interesting. The 
development of this appliance, which is practically indispensa- 
ble in the correct occlusion of teeth, has been retarded because 
of lack of accurate knowledge of mandibular movements, or, 
more exactly, those movements of the mandible concerned in 
the frictional contact of the lower against the upper teeth. 
Without a fundamental and exact knowledge of these move- 
ments, it is impossible to construct an appliance which will 
reproduce them. 
Even with present established data, there is no appliance 
yet devised that will reproduce all of the varied essential 
movements discerned in every individual with exactness, but 
some approach very closely the desired requirements. Only 
a brief outline of those appliances most familiarly known can 
be given here. 
A method of building a distal extension to each cast, the 
first having notches or depressions into which the plaster of 
Fig. 1012.— Casts Extended Distally to Form Articulating Surfaces 
the opposite side was filled, to serve as guides, constituted the 
first articulator. 
J. B. Gariot is credited with having invented the first den- 
tal articulator in 1805. An extended search through dental A BRIEF HISTORY OF PROSTHETIC DENTISTRY 
1113 
literature by the writer has failed to disclose more than a 
mere mention of the fact as stated. 
In 1840, Dr. Daniel T. Evans of Philadelphia patented an 
articulator in which an effort was made to reproduce the lat- 
eral movements of the mandible. 
Fig. 1013.— The Evans Anatomical .1, . .«ttor 
Tlie distance between the condyle slots of the frame was 
less than the average, while the center of rotation in lateral 
movements was located in the center of the frame. 
In 1858, Dr. W. G. Bonwill introduced his “Anatomical 
Articulator,” and presented his theory of the equilateral tri- 
angular relation of the mandibular condyles and the lower 
central incisors. He claimed that by such an arrangement it 
was clearly Nature’s plan to thus provide a. more perfect bal- 
ance for the masticatory apparatus-iq, lateral movements; that 
these movements were most effective in the reduction of food, 
and that dentures should be so constructed that the mandibu- 
lar muscles could perform their functions in the same manner 
as when the natural teeth were present. 
His theories, although in the main correct, aroused con- 
siderable antagonism, because, in many cases, the results he 
claimed could be derived from the of his articulator were 
not realized. 
This was largely due to ignoring the variation in pitch 
of condyle paths of different individuals, and in an inaccurate 
method of mounting casts on the articulator. 1114 
A BRIEF HISTORY OF PROSTHETIC DENTISTRY 
Dr. Bonwill was a natural born prosthetist and in the 
anatomic field overcame, by intuition, the obstacles resulting 
from his imperfect appliance. In his enthusiasm he failed 
Fig. 1014.— The Bonwill Articulator 
to recognize the limitations of the articulator, or to realize 
that it was his intuitive skill and not the appliance that was 
responsible for m h of his success. 
His persistent effort in this field for more than forty years 
finally aroused the interest. of various investigators, with 
Fisr. 1015 PI- ' I 'tip o- Common Hinge Articulator Used for Many Years 
the result that to-day the problem of anatomic occlusion has 
almost reached solution. The anatomic method of denture 
construction is a reality, established on a practical working A BRIEF HISTORY OF PROSTHETIC DENTISTRY 
1115 
basis, and its great importance and value are gradually be- 
coming recognized by the profession in general. 
In 1868, Dr. E. T. Starr devised an articulator, having a 
lateral movement, with horizontal condyle paths. 
Fig. 1016.— The Starr Articulator 
In 1889, Dr. Richmond S. Hayes introduced an articula- 
tor having a lateral movement and with inclined condyle 
paths. From the Patent Office drawings of this appliance it 
appears that the condyle paths inclined too steeply and were 
not capable of adjustment. 
Fig. 1017.— The Hayes Articulator 
Asa matter of fact, a practical method of registering the 
human condyle paths had not yet been discovered, nor had the 
importance of such registration been recognized, so that ad- 
justable condyle paths were not even considered. Dr. Hayes 1116 
A BRIEF HISTORY OF PROSTHETIC DENTISTRY 
also devised a crude sort of face bow for establishing the cor- 
rect distance of casts from the frame hinges. 
FIRST SUGGESTION OF THE FACE BOW 
Previous to this time, Dr. T. L. Gilmer, in a paper pre- 
sented before the Illinois State Dental Society, in 1882, sug- 
gested measurement of the distance from condyles to the 
middle of the upper jaw so that casts might be mounted a cor- 
responding distance from the articulator hinges, thus avoid- 
ing disturbance of occlusion in fracture cases. This in reality 
was equivalent to the use of a face bow. 
STUDY OF CONDYLAR MOVEMENTS 
In 1889, Drs. Bowditch and Luce of Harvard, Conn., con- 
ducted a series of experiments to determine definitely the 
condylar movements of the mandible. The results of these 
experiments were published in the Boston Medical and Sur- 
gical g Jamal of that year, but not being reprinted in any of 
the dental journals, were not brought prominently to the at- 
tention of the pr^>|£Ssion. 
walker’s RESEARCH WORK 
In 1895, Dr. W. E. Walker, without knowing of the work 
of Bowditch and Luce, carried out a similar line of investiga- 
tion, and arrived at practically the same results. Just what 
he strove to and did, accomplish can best be stated by quot- 
ing from one of his published the following year: 
“Up to that time II ~t, been able to find mention of 
the facts which 1 had observed 'hat, in the movements of mas- 
tication, the mandibular ~'"dyle moves ‘not only forward, 
but downward also, causing the ramus to drop in the anterior 
and.lateral excursions'of the mandible,’ and that the condyle 
on the side toward which the jaw is advancing, in the lateral 
excursions, does not merely ‘rotate on its axis,’ otherwise ‘re- 
maining stationary,’ as we are taught, but that it also moves 
both upward and backward, very slightly, it is true, in many 
subjects, and not at all in some, but quite considerably in 
others. 
I lie discovery of this fact led to another hitherto unrecog- 
nized fact, viz., that the lateral rotation centers of the man- 
dible may or may not be located in the condyle centers. A BRIEF HISTORY OF PROSTHETIC DENTISTRY 
1117 
walker's anatomical articulator 
Walker designed an anatomical articulator, having both 
adjustable condyle paths and variable rotation centers which 
could be set in accordance with records obtained in each in- 
dividual case. 
These records were secured by means of another appli- 
ance he devised and called a “facial clinometer.” In the 
light of our present knowledge, a prosthetist familiar with the 
present-day appliances, if given the Walker articulator and 
Fig. 1018.— Walker o +omical Articulator 
clinometer and a Snow face bow, could construct anatomic 
dentures equal to those constructed by any other system. 
Practically the only essential point which Walker over- 
looked was the importance of and necessity for setting the 
casts on the occluding frame so that their alveolar planes 
sustained a similar relation to the frame hinges that the 
natural alveolar planes did to the condyles. Although he does 
not explain how he mounted the casts on the frame, A is more 
than likely that he followed BonwilPs method of calipering — 
setting them so that the calipers registered four inches from 
each rotation center, to the position to be occupied by the 1118 
A BRIEF HISTORY OF PROSTHETIC DENTISTRY 
mesio-incisal angles of the lower central incisors, when oc- 
cluded- This method, although decidedly better than the 
usual plan of guessing the proper position of the casts, pro- 
vided for neither perpendicular nor horizontal plane relation- 
ship and, therefore, led to errors. 
Fig. 1019.— Walker’s Facial Clinometer 
Walker’s efforts were more far-reaching and valuable than 
he himself or the profession realized at the time, but on the 
foundation which Bonwill laid, and he strengthened and added 
to, the present system of anatomic occlusion of artificial den- 
tures rests. Three valuable papers by Walker on mandibular 
movements and methods of registering them appeared in the 
Dental Cosmos, in 1896-7. A BRIEF HISTORY OF PROSTHETIC DENTISTRY 
1119 
In 1894 Dr. C. E. Bixby designed an attachment for mount- 
ing casts on a plain line articulator. 
This device regulated the correct antero-posterior posi- 
tion, but provided no means for establishing the horizontal 
Fig. 1020.— The Bixby Attachment 
plane relationship. It, however, was a forerunner of the face 
bow. 
GRITMAN *S ARTICULATOR 
In 1899, Dr. A. D. Gritman introduced an improved form 
of articulator, having the same general proportions as the 
Bonwill, but more rigid, and with condyle slots set at an angle 
Fig. 1021.— The Gritman Articulator 
of about 15 degrees slant. In tliis, as in all articulators hav- 
ing fixed condyle paths, the pitch of the path of the frame was 
often increased or decreased in mounting the casts on the 
frame, depending on the thickness of the cast and the care 
used in mounting them. 1120 
A BRIEF HISTORY OF PROSTHETIC DENTISTRY 
snow’s face bow 
In the same year, Dr. George B. Snow of the University 
of Buffalo introduced the face bow, a caliper-like device used 
Fig 1022.— The Snow Face Bow and Gritman Articulator 
in mounting casts on the occluding frame. This device is one 
of the most valuable acquisitions in the anatomic field. By 
means of this appliance, correct antero-posterior, as well as 
Fig. 1023.— The Kerr Anatomical Articulator 
perpendicular and horizontal plane, relationship of casts to 
frame hinges can he established. As a result, when teeth are 
arranged on occlusion models, clearance paths for the cusps A BRIEF HISTORY OF PROSTHETIC DENTISTRY 
1121 
of the lower bicuspids and molars between those of the upper 
teeth can be developed, so that in lateral excursions there is 
no marked interference. 
In 1902 the Kerr Brothers of Detroit introduced an ana- 
tomical articulator having adjustable condyle paths and a 
lateral movement. The first frame was arranged with hinges 
about on the same plane as the occlusal plane of upper cast 
when mounted, the idea being to copy the center of rotation 
of the mandible in wide open movements. 
For obvious reasons this was found incorrect, and the de- 
sign of the frame changed to the form shown on page 1120. 
THE KERR ANATOMICAL ARTICULATOR 
Christensen’s work 
In 1902, Dr. Carl Christensen of Copenhagen, Denmark, 
discovered a simple method of recording the condyle paths in 
Fig. 1024.— The Christensen Anatomical Articulator 
the living subject, and devised an articulator having adjust- 
able condyle paths which could be set according to such regis- 
tration. (See page 337.) 
In 1906, Dr. Snow improved the Gritman articulator by 
converting the fixed into adjustable condyle paths, applv- 
ing a tension spring which permitted a greater range of move- 
ment without impairing the stability of the frame 
Christensen’s method of registering the condyle paths in 
snow’s anatomical articulator 1122 
A BRIEF HISTORY OF PROSTHETIC DENTISTRY 
conjunction with the use of the Snow “New Century Articu- 
lator,” and the face bow, supply the means for constructing 
dentures anatomically and is to a great extent the system 
most generally practiced and taught in this country. 
Fig. 1026.— Cut Showing Compensating Curve (Christensen) 
Dentures constructed by this method, when introduced in 
the mouth, will perform essentially the same functions as the 
natural teeth, and are capable of reducing food with less 
effort than are those in which hinge action alone is possible. 
Furthermore, they are much less liable to displacement when 
Fig. 1026.— The New Century Articulator (Snow) 
in use, as oalancing contact is one of the essential features 
tnat in practically all cases can be attained. 
The Snow Articulator, like the Christensen. Walker and 
Bonwill appliances, has its rotation centers placed four inches 1123 
A BRIEF HISTORY OF PROSTHETIC DENTISTRY 
apart, which, according to Bonwill’s measurements, corre- 
sponds with the average distance from center to center of the 
human condyles. 
Walker clearly proved that the lateral rotation centers of 
the mandible, in some individuals at least, were located, not in, 
but between the condyles at varying distances in different 
cases. Others have since proven the truth of Walker’s find- 
ings, and in addition have shown that the rotation centers may 
lie outside of the condyle centers as well. 
Excepting the efforts of Christensen, as noted, this de- 
scription has been confined to what has been accomplished by 
men in this country. It will now be in order to mention some 
of the contributions to this subject by the members of the pro- 
fession in Europe, whose interest was aroused by Bonwill’s 
work. 
In 1890, Graf von Spee, a German anatomist, called atten- 
tion to the curved arrangement of the occlusal planes of the 
natural teeth and of corresponding curves in the condyle 
paths. (See page 302.) 
schwarze's articulator 
In 1900, Dr. Paul Schwarze of Leipsic constructed an 
articulator somewhat on the order of the Bonwill appliance, 
Fig. 1027.— The Schwarze Anatomical Articulator 
but having both a forward and downward movement to, the 
condyles. 
In 1901, Tomes and Dolamore made a series of recordt 
of condyle paths as disclosed by the hinge action, or opening 1124 
A BRIEF HISTORY OF PROSTHETIC DENTISTRY 
and closing mandibular movements. These were of no special 
value in a practical way, further than to verify the research 
work of Walker and others in reference to the downward pitch 
as well as variations in the condyle paths. (See page 275.) 
Parfitt, Constant, Campion, Warnekros, Peckert and others 
have contributed in various ways and at different times to 
this most interesting subject. 
Recently Bennett has shown that there is an actual bodily 
side movement to the mandible, which, although caused by the 
muscles that induce lateral rotation, cannot be classed as ro- 
tary. This is a most important recent discovery in mandibu- 
lar movements, and one which, in some cases, might, with 
profit, be reckoned with in denture construction. 
gysi's WORK 
In 1910, there appeared in the Dental Cosmos a series of 
es by Dr. Alfred Gysi of Zurich, Switzerland, describing 
Fig. 1028. — "'he Gysi Condyle Register 
in detail various ro~i« ring devices for recording mandibular 
movements, togetner with many records, secured by means 
of them. 
The principal appliances shown are an articulator, a con- 
dyle path register, and an incisor path register. A BRIEF HISTORY OF PROSTHETIC DENTISTRY 
1125 
The articulator has adjustable condyle paths, and also 
adjustable rotation centers, the maximum distance between 
which is five and one-fourtli inches, while the minimum dis- 
tance is about two and three-fourths inches. 
The condyle register, as its name indicates, records the 
inclination and curvature, if any exists, of the condyle paths, 
on cardboard, in such manner that the angular inclination 
Fig. 1029.— Lateral Path Register 
may be read and the condyle ]1h:ths of the articulator set ac- 
cordingly. 
The condyle register also frrTTlls the same purpose as a 
face bow in mounting casts on the occluding frame. 
The incisor path register consists o a metal plate, attached 
to the occlusal surface of the lower oc' ' the upper 
surface of which is covered with a thin film of carbonized wax. 
A small steel point, backed by a fine spring within a socket, 
and attached to a small plate, is fixed to the labial surface of 1126 
A BRIEF HISTORY OF PROSTHETIC DENTISTRY 
the upper occlusion model in such manner that when the 
mouth is closed the point rests upon the waxed surface of the 
incisor path register, which extends somewhat forward of the 
labial surface of the baseplate. In lateral and protrusive 
movements of the mandible the point marks upon the waxed 
surface the lines of travel of the mandible in the incisal region. 
Later on, when the occlusion models are returned to the casts 
on the articulator, the rotation centers of the frame are moved 
to such position that the marker on the upper occlusion model 
will follow the same lines it marked on the waxed register 
during mandibular movements. By this means the lateral 
rotation centers of the mandible are determined and the cen- 
ters of the articulator set accordingly. 
Since 1910, Dr. Gysi has devised a lateral condyle path 
register, which records the bodily side movement of the man- 
dible. The articulator condyle paths are so arranged that 
they may be set to reproduce this movement to a fairly accu- 
rate degree. (See page 465.) 
The Gysi Adaptable Articulator, with accessory appliances 
enable the careful prosthetist to register more of the essen- 
tial mandibular movements than can be accomplished by any 
other available means. 
Consequently, with such registration possible, and with 
the generally improved methods in denture construction that 
have recently been and are being developed, prosthetic den- 
tistry is rapidly advancing into the field of an exact scientific 
specialty. 
Fig. 1030.— Lower. Se ' Luce Articulator, Showing “ Tracing 
Knobs ” in 1 .on Lower Occlusion Model 
Dr. C. E. Luce has designed an articulator in which cer- 
tain anatomic movements may be reproduced as follows: 
Round head tacks, or “tracing knobs,” are pressed into 
the lower occlusion model, the wax rim of the upper model A BRIEF HISTORY OF PROSTHETIC DENTISTRY 
1127 
softened, and introduced in the mouth and the mandible sub- 
jected to lateral movements. The round heads of the project- 
ing tacks mark lateral paths in the upper wax rim. 
Fig. 1031.— Upper Section of Frame, Showing Paths Traced 
in Upper Occlusion Model 
To use this appliance successfully, the casts should be 
mounted on it by means of a face bow. 
When so mounted, the hinge pin of the articulator is re- 
moved, the cup situated immediately in front and between 
Fig. 1032.— General Vie’’ >ce Frame 
the hinges filled with softened modeling compound, the upper 
bow of the frame carrying the cast and occlusion model 14,set 
in position and subjected to lateral movements, the round- 
head tacks guiding the direction of movement. During this 1128 
A BRIEF HISTORY OF PROSTHETIC DENTISTRY 
lateral movement, projections on the underside of the upper 
bow, immediately over the hinge cup, form paths in the model- 
ing compound. 
These paths in the cup represent shorter arcs of circles 
than those in the occlusion rims. They have, however, com- 
mon centers, viz., the centers of rotation of the mandible. 
On removing the tacks from the occlusion rim the pins of 
the frame, resting and moving in the grooves in the compound, 
Fig. 1033.— Details of Articulating Cup 
within the hinge cup guide and control the lateral movements 
of the lower against the upper occlusion model on much the 
same principle as a pantagraph works. 
Crown Work 
The placing of artificial crowns on the roots of natural 
teetli has been practiced for hundreds of years, yet it is only 
within the last half century that much advancement has been 
made over the primitive methods of Fauchard’s time. 
Pivot teeth of porcelain were mentioned by De Chemant 
in 1802, although for many years after his time, teeth carved 
PIVOT TEETH OF DE CHEMANT 
Fig. 1034.— Porcelain Crown 
(De Chemant) 
from bone, ivory and various substances were used in single 
crown replacements. Frequently, sound natural tooth crowns 
were also used for this purpose. A BRIEF HISTORY OF PROSTHETIC DENTISTRY 
1129 
THE GROOVED FLAT-BACK FACING 
In the early part of the last century, a porcelain facing, 
grooved on the back, and with small strips of platinum baked 
Fig. 1035.— Grooved Facings Formerly Employed in 
Crown and Denture Construction 
in the porcelain along the sides of the groove for attachment 
to the wire pivot, was used both in Europe and this country 
in crown work. 
THE ASH TUBE TOOTH 
The Ash Tube tooth, introduced about 1840, was used in 
both denture construction and, to a limited extent, in crown 
replacements. (See page 529.) 
The recent articles, within the last two years, by Dr. Gird- 
wood, have shown the modern application of this type of tooth 
to prosthetic restorations. (Dental Cosmos, 1914-1915.) 
THE WOOD PIVOT TOOTH 
A full contoured porcelain crown, with a circular opening 
in the base for the reception of a wood pivot, was introduced, 
probably between 1850 and 1860. This crown was attached 
to the root by means of a wood pivot which fitted tightly into 
both crown base and root canal. The pivot was forced to 
Fig. 1036.— Porcelain Crowns Designed for Use 
with Wood Dowels 
Fig. 1037.— Prepara- 
tion of Root for Re- 
ception of Crown and 
Dowel. Labial View 
place while dry, and on absorbi g moisture swelled and firmly 
held the crown in position. The writer a number of years ago 
removed two central incisors wlr h had been set in this man- 
ner eighteen years previously, neither of which, in that time, 
had required resetting. 
THE SMITH CROWN 
In 1844, Dr. J. Dodge Smith devised a crown which was 
of similar form to the one just described, but in which a wood 1130 
A BRIEF HISTORY OF PROSTHETIC DENTISTRY 
Fig. 1038.— Dr. J. Dodge Smith’s Crown 
pivot containing a metallic tube for a core to strengthen it 
was used. 
THE CLARK CROWN 
In 1849, Dr. F. H. Clark devised a removable crown, which 
was attached to the root by means of a metal dowel, split to 
Fig. 1039.— Dr. F. H. Clark’s 
Crown 
form a spring, for bearing against a metal tube firmly fixed in 
the root canal. It was so formed as to afford drainage for pus 
or vent for gas which might accumulate in the pulp chamber. 
THE LAWRENCE-FOSTER CROWN 
In 1849, Dr. Henry Lawrence invented a porcelain crown 
having an opening extending through from base to lingual 
Fig. 1040.— Dr. Henry 
Lawrence’s Crown. Af- 
terward Called the “ Fos- 
ter ” Crown 
surface. It was held in place by means of a screw anchored 
within the root canal. 
This crown was afterward known as the “Foster” Crown. A BRIEF HISTORY OF PROSTHETIC DENTISTRY 
1131 
THE DWINELLE CROWN 
In 1855, the American Journal of Dental Science con- 
tained a description by Dr. W. H. Dwinelle of a gold band 
with floor, fitted to a tooth with vital pulp, and held in place 
Fig. 1041.— The Dwi- 
nelle Crown for Vital 
Teeth and Non-Vital 
Teeth 
by means of two screws passing through the floor and into the 
dentin. The “tubbing,” or gold-bound cavity, was filled with 
crystal gold, while to the labial or buccal surface of the band 
a porcelain facing was affixed. 
This same principle was also applied in the crowning of 
pulpless teeth, the crown being held in position by means of 
Fig. 1042.— The Dwinelle Crown for Vital Teeth 
a screw anchored within the pulp chamber. The five cuts 
show the Dwinelle method of attaching a porcelain-faced fer- 
rule crown to the stub of a vital tooth with crystal gold. 
This work of Dr. Dwinelle is about the first reference 
found of combining gold and porcelain in the restoration of 
lost natural crowns. 
THE WOOD CROWNS 
In 1862, Dr. B. Wood describes the restoration of defec- 
tive teeth by the application of enamel caps. These were 
Fig. 1043.— B. Wood’s “ Enameled Cap ” Crowns 
formed by fusing to platinum caps, previously fitted to the 
teeth, some form of enamel, probably such as jewelers used. 1132 
A BRIEF HISTORY OF PROSTHETIC DENTISTRY 
These caps were cemented in place with oxychlorid of zinc or 
attached with gutta percha. 
Dr. Wood also constructed thin gold crowns with interior 
staples by means of which anchorage to the teeth was secured 
Fig. 1044.— Thin Gold Crowns Described by Dr. B. Wood 
with cement. These crowns, because of their thin walls, were 
more or less unstable. 
THE MORRISON CROWN 
In 1869, Dr. W. N. Morrison described in the May number 
of Missouri Dental Journal a gold shell, two-piece crown. 
Fig. 1046.— Gold Shell Crown Constructed and 
Described by Dr. W. N. Morrison 
in 1869 
This crown was substantially the same as is constructed to- 
day and is quite generally known as the “Morrison Crown.” 
THE BLACK CROWN 
In the June number of the same journal. Dr. G. V. Black 
described and illustrated the construction of a porcelain-faced 
Fig. 1046.— Crown Constructed and Described by 
Dr. G. V. Black in 1869 
crown for an anterior tooth, held in place by means of a screw 
passing into a gold-lined root canal. 1133 
A BRIEF HISTORY OF PROSTHETIC DENTISTRY 
The similarity between this and the crown Dr Richmond 
patented years afterward is obvious. 
THE BEAN CROWN 
In the July number, 18G9, of the American Journal of 
Dental Science, Dr. J. B. Bean described a porcelain-faced 
Fig. 1047.— Crown 
Constructed and De- 
scribed by Dr. J. B. 
Bean in 1869 
removable crown the dowel of which was split and received 
within a permanently fixed tube in the root canal. 
THE MACK CROWN 
In 1872, Dr. Clias. H. Mack designed a pivot tooth having 
a dovetailed depression in the has f the crown 
Fig’. 1048.— The Mack Crown 
Metal pins, roughened, were first fixed in the root of the 
tooth and the crown attached with cement or amalgam. 1134 
A BRIEF HISTORY OF PROSTHETIC DENTISTRY 
THE BEERS CROWN 
In 1873, Dr. J. B. Beers of California patented a gold cap 
crown practically the same as described some four years pre- 
viously by Dr. Morrison. 
Fig. 1049.— The Beers Crown 
An 1875, Dr. W. H. Gates devised a “vertically open con- 
tour crown,” composed of metal and porcelain, designed to 
be held in place with cement. Tn this, as in the Mack crown, 
THE GATES CROWN 
Fig. 1050.— The Crown 
the dowel was first permanently set in the root canal and the 
crown adjusted and attached later. Manufacturing difficul- 
ties, however, prevented its introduction and use. 
THE RICHMOND CROWN 
In 1880, Dr. C. M. Richmond designed a porcelain-faced 
crown backed with metal and held in place on the root by 
means of a screw similar to the crown designed by Dr. Black. 
An internally and externally threaded tube was fixed in 
the root canal, the crown formed with a groove in its lingual 
surface for the passage of a screw which entered the tube 
within the root, and by means of which it was held in place. A BRIEF HISTORY OF PROSTHETIC DENTISTRY 
1135 
Figs. 1051 and 1052.— The Richmond Crown 
Fig. 1053.— Sketch of One of Dr. Rich- 
mond’s Earlier Crowns 
' Fig. 1054.— The Improved Richmond 
Crown 
A cap diaphragm rested upon the root end and over this 
the crown base, also of cap form, telescoped. 
THE GATES-BONWILL CROWN 
In 1881, Dr. W. G. A. Bonwill designed a crown wholly of 
porcelain having a central opening slightly enlarged at either 
end for the reception of metal dowel. 
Fig. 1055.— The Gates-Bonwill Crown 
These crowns were set with an amalgam specially pre- 
pared by Dr. Bonwill. Both three-sided and triangular metal 
dowels were used. 
The specifications of the Mack patents, issued six years 
previously, were so broad that they covered the principle of 
this crown. Therefore, when placed upon the market it was 
given the name of the “Gates-Bonwill Crown.” 1136 
A BRIEF HISTORY OF PROSTHETIC DENTISTRY 
THE BUTTNER CROWN 
In 1881, Dr. W. H. Biittner patented a set of appliances 
for reducing the root periphery of a tooth to a uniform cylin- 
Fig. X05C.— The Buttner System of Crown Construction 
der, fitting a deep-sided dowel cap to same and root canal and 
attaching a porcelain facing to the base so formed. 
In 1883, Dr. W. S. How designed what was called the 
“four-pin crown.” These pins, set within a depression on the 
lingual surface of the facing, were folded around a threaded 
THE HOW CROWN 
Fig. 1057.— The How Four-Pin Crown 
dowel fixed in the root canal and the lingual contour of the 
tooth developed in amalgam. 
Dr. How also designed the Dovetail Crown in 1889. 
In 1883, Dr. Henry Weston designed a “porcelain pivot 
crown” having two pins located in a depression on its lingual 
surface for the reception of a cross-head dowel. The dowel 
and facing were attached with solder and the crown attached 
to the root by gold, cement or amalgam. 
THE WESTON CROWN A BRIEF HISTORY OF PROSTHETIC DENTISTRY 
1137 
Another form of crown devised by Dr. Weston consisted 
in a more fully contoured porcelain facing, in which the dowel 
Fig.‘ 1058.— Weston’s Cross-Head Dowel 
Crown 
' Fig. 1059.— Weston's Fixed Dowel 
Crown 
was baked. This crown was secured to the root in the same 
manner as was the preceding crown. 
THE LOGAN CROWN 
In 1885, Dr. M. L. Logan devised a full contoured porce- 
lain crown having a platinum dowel permanently fixed within 
its base. 
Fig. 1060.— The Logan Crown 
This crown has, almost from its introduction, been exten- 
sively employed and has proven most serviceable as a substi- 
tute of the fixed dowel type. 
In 1890, Dr. E. Parmly Brown designed a crown very 
similar to the “Logan,” but with a convex instead of a con- 
cave base. 
THE BROWN CROWN 
Fig. 1061.— The E. Farmly Brown Crown 
Within recent years many forms of detached dowel crowns 
have been introduced, which, because of comparative ease of 1138 
A BRIEF HISTORY OF PROSTHETIC DENTISTRY 
adaptation, are fast comiug into favor, both as crown replace- 
ments and for use in bridge and denture work as well. 
Among these may be mentioned the Davis, S. S. White, 
Justi, Brewster Twentieth Century, illustrations of which are 
found elsewhere. 
An analysis of the various means by which crowns, both 
ancient and modern, are fixed to natural teeth and roots shows 
but two general principles of attachment, viz., with dowels, 
the telescoping principle, or a combination of the two methods. 
Much of the material contained in the foregoing history of 
crowns has been obtained from a monograph published by 
the S. S. White Dental Manufacturing Company, entitled 
“Origin and Development of Porcelain Teeeth,” and from 
various articles which have appeared from time to time in the 
Dental Cosmos. 
Bridgework 
Modern bridgework, of a practical character, is of very 
recent origin as compared with dental procedures in general. 
Dental literature of modern times contains scarcely any 
reference to bridgework previous to 1869. 
In addition to the three greatly improved crowns pre- 
sented by Drs. Morrison, Black and Bean in that year, Dr. 
Bennett described, in the Dental Cosmos of October, 1869, a 
method of bridging in the space of a single missing tooth as 
suggested by Dr. B. J. Bing of Paris. 
THE BING BRIDGE 
This method consisted in preparing cavities in the teeth 
proximating the space, fitting a square bar across the space, 
its ends resting within the cavities, and by suitable steps 
Fig. 1062.— The Bing Bridge 
Tooth, 1869 
adapting and soldering a facing to the bar. The appliance 
was fixed by packing gold foil into the cavities and around 
the bar ends. 1139 
A BRIEF HISTORY OF PROSTHETIC DENTISTRY 
dr. webb’s work 
In 1873, Dr. Marshall H. Webb suggested a modification 
of the Bing method, consisting of a flattened “two stop back- 
ing and saddle,” and in 1879 a “stop post,” consisting of a 
Fig. 1063.— Modification of the Bing Bridge (Webb) 
facing attached to a rigid wire staple, the ends of which are 
anchored within the root canals of the proximating teeth. 
In both cases the stops were surrounded by and anchored 
within gold foil filling in the cavities of the adjoining teeth. 
DR, LITCH’s WORK 
In 1880, Dr. Wilbur F. Litch suggested two modifications 
of the Bing bridge. The first was called a “wing plate,” in 
which the backing was extended beyond the dummy so as to 
rest upon the lingual surfaces of the proximating teeth. Per- 
forations were then made in the wings and corresponding 
Fig. 1064.— Dr. Litch’s First Modification of the Bing Bridge 
holes in the teeth, through the enamel, and as deeply in the 
dentine as practicable, without endangering the pulp. 
Headed platinum pins were passed through the plate into 
the holes, the relation between backing and pins secured, the 
case invested and the pins soldered to the wings. The sub- 
stitute was set with cement. 
The second modification consisted in devitalizing either 
one or both teeth and extending dowels through the wings into 1140 
A BRIEF BlSTORY OF PROSTHETIC DENTISTRY 
the root canals. It will be noticed that both Drs. Webb and 
Litch increased the anchorages of the dummies by root dow- 
Fig. 1065.— Dr. Litch’s Second Modification of the Bing Bridge 
els, being impelled to do so because of failures in their first 
attempts. 
DR. WILLIAMS* WORK 
In 1884, Dr. J. Leon Williams, in the Dental Cosmos, called 
attention to the necessity for more stable anchorage for 
Fig. 1066.—Modified Richmond Crown (Williams) 
bridges and suggested the use of a modified, so-called, Rich- 
mond crown, which, in a general way, represents a common 
type of porcelain-faced crown of to-day. 
Fig. 1067.— Four-Tooth Anterior Bridge 
(Williams) 
Fig. 1068.— Two Bridges Described by Dr. 
Williams in 1884 
This article was followed, the next year, with illustrations 
and descriptions of two very practical bridges by the same 
writer. A BRIEF HISTORY OF PROSTHETIC DENTISTRY 
1141 
Dr. Williams remarks, in January Cosmos, 1884: “As the 
single crown is the beginning and the end of all bridgework, 
a description of that particular form, which is of the greatest 
practical value, will be necessary. This is known as the Rich- 
mond crown, though not the crown he claims as his invention. 
It consists essentially of three parts — a pin [post?] which 
enters the root canal; a root cap of gold; and a porcelain 
face, which is the ordinary plate tooth.” 
It is evident that our modern system of bridgework could 
not have been possible without the evolution of suitable 
crowns for supporting the same. 
DR. STARR’S WORK 
In the Dental Cosmos, 1886, Dr. R. Walter Starr described 
a difficult case of restoration in which two removable bridges 
were successfully applied. The telescoping crown principle 
is here mentioned for the first time. 
Fig. 1069.— Removable Bridges by Dr. Starr, 1886 
In 1887, Dr. Starr suggested a modification of the Bing 
bridge tooth, consisting of a porcelain tooth with two parallel 
bars extending through it by means of which the projecting 
ends of the substitute were anchored within fillings placed in 
the proximating teeth. 
The names of Drs. Cryer, Starr, Hodgkin, E. Parmlv 
Brown, Hollo Knapp, Stowell, and Rhein are associated with 1142 
A BRIEF HISTORY OF PROSTHETIC DENTISTRY 
the early history of recent bridge methods, nearly all of whom 
presented modifications of the Bing bridge. 
Drs. Williams, Richmond and Knapp seem to have been 
among the first to recognize the necessity for the use of 
Fig. 1071.— Starr’s Modification of the 
Bing Bridge, 1887 
stronger and more hygienic abutments in bridge appliance, 
although no doubt many others were coming to recognize the 
same fact. 
In 1888, Dr. Sidney S. Stowell described an extension stop- 
supported bridge, similar to those frequently constructed to- 
Fig. 1072.— Two-Tooth Stop and Saddle Bridge 
day, except that with present methods the stop rests in a 
depression within an inlay instead of being enclosed within a 
filling, as described by Dr. Stowell. 
BASIS OF OUR PRESENT SYSTEM OF BRIDGEWORK 
The crowns of Wood and Dwinelle in the <<50,s,> formed 
the basis. The great improvements by Morrison. Black and A BRIEF HISTORY OF PROSTHETIC DENTISTRY 
1143 
Bean, in crowns, and the appearance of the Bing bridge tooth, 
all of which were presented in 1869, although crude, furnished 
the necessary elements which had previously been lacking. 
Further improvements in crowns, the development of 
various forms of dummies, together with simplified technical 
procedure, gradually followed, but only after many failures 
and a considerable lapse of time. 
It is singular to note that practically all of the pioneers 
in bridgework failed to recognize the heavy stress in masti- 
catory effort delivered against bridge replacements. Neither 
were the limitations in regard to resistance of stress of the 
materials employed well understood. 
This lack of knowledge of the strength of materials used, 
together with an indefinite or exaggerated idea of the capacity 
of natural teeth or roots for performing their own work and 
carrying the additional burden imposed by the replaced teeth 
were some of the discouraging features. 
Peridental troubles, the splitting of roots and recurrent 
decay of the abutment and pier teeth and roots were of fre- 
quent occurrence. 
A recognition of these facts, which could only be gained 
by experience, led to further improvements in crowns of 
greater strength and of more hygienic form and in more judi- 
cious selection of cases for substitutes of this type. 
PORCELAIN BRIDGE 
Baked porcelain crown and bridge work went through a 
similar process of trial, failure and development before the 
limitations in this field were finally determined. The principal 
Fig. 1073.— Platinum Framework for Porcelain 
Bridge (Schwartz, 1902) 
failures were due to insufficient strength to the metal sub- 
structure and deficient bulk of porcelain. One of the pioneers 
in this field was Dr. G. W. Schwartz of Chicago, who was en- 
gaged in the production of porcelain crowns, bridges and in- 
lays as early as 1893. 1144 
A BRIEF HISTORY OF PROSTHETIC DENTISTRY 
While to-day, the application of fixed bridge work is not 
as extensive, the results of such application at the present 
time are generally far more satisfactory than in the past. 
REMOVABLE BRIDGES 
Bridges of the removable type, and partial dentures sup- 
ported by saddles resting upon the alveolar process, retained 
in position by some of the various forms of fractional appli- 
ances, are now introduced in many cases where formerly 
bridges of the fixed type were applied. 
Inlays 
An inlay, in its dental meaning, refers to a filling com- 
posed of some dense material, constructed outside the tooth 
cavity, and which is held in position in the cavity by some 
adhesive medium. 
FIRST RECORDED ATTEMPTS IN FILLING TEETH 
The first attempts at filling teeth must naturally have been 
extremely crude, and the results of the pioneer efforts in this 
field have proved but temporary in character. Because of 
the difficulty in adapting dense materials, the first fillings were 
undoubtedly of the pasty, plastic or pitchy class. 
Mastic and alum, a substance of this class, was recom- 
mended for filling carious cavities, by Rhazes, a Persian phys- 
ician, about 850 A. D. (Guerini). Frequently medicinal agents 
were incorporated with the mastic base for the purpose of 
arresting the progress of decay, myrrh, sulphur and turpen- 
tine being mentioned in this connection. The comfort derived 
from the use of such stoppings, although only of temporary 
nature, gradually led to the general practice of filling, and the 
use of more permanent materials. 
Mesu, an Arab surgeon, in the latter part of the eighth 
century recommended the use of gold foil for filling teeth, 
while from the thirteenth century on various writers mention 
the use of both gold and lead for this purpose. 
FIRST MENTION OF INLAYS IN DENTAL LITERATURE 
In 1690, Pierre Dionis, a surgeon of Paris; in discussing 
the filling of teeth, says: “For this purpose, gold or silver 
leaf is made use of; but this method of stopping is not dur- A BRIEF HISTORY OF PROSTHETIC DENTISTRY 
1145 
able, because gold or silver leaf is apt to become loosened and 
fall out. It is therefore preferable to make a stopping with 
a piece of gold or silver corresponding in size and shape to 
the cavity. Many prefer lead on account of its softness, while 
others simply use wax.” (Guerini.) This is the first definite 
reference to the inlay method of filling teeth, so far as the 
writer knows, in any of the old-time treatises on dental pro- 
cedures. 
In 1718, Lorenz Heister, a German surgeon recommended 
the filling of teeth with various substances. In reference to 
crown cavities in molar teeth he recommends gold or lead leaf, 
or a piece of the latter fitting into the cavity. (Guerini.) 
Unfortunately, few specimens of ancient inlay work are 
in existence, and the genuineness of such as are preserved is 
questionable. 
PREHISTORIC INLAY WORK 
In the Peabody Museum of Harvard University is a pre- 
historic skull, in the central incisors of which are inlays of 
green stone. This specimen was found a few years ago 
among the Aztec or Toltec ruins, near Copan, Honduras, by 
Professor Owen. Whether these inlays were placed in the 
teeth to correct the ravages of decay or merely for ornamental 
purposes cannot, of course, be determined. 
THE BEGINNING OF MODERN INLAY METHODS 
Authentic records of inlay work in modern times date back 
only about one hundred years. At the beginning of this 
period, tin, lead and gold, in the form of foil, were the only 
metallic fillings in use. Amalgam had not yet been introduced. 
It came into vogue as a filling material, under the name of 
“silver paste,” about 1825, but for years was looked upon 
with disfavor and used to a very limited extent. Cohesive 
gold was not introduced until 1855, and therefore, since none 
of the foils were cohesive, extensive contour restorations were 
impossible. Added to these difficulties, the general dislike on 
the part of patients to the display of metals in the mouth, 
rendered the filling of teeth a discouraging, and oftentimes 
unsatisfactory, procedure. 
It is not surprising, therefore, that efforts were early made 
to find a material for filling operations less objectionable in 
appearance, and easier to manipulate than the metals. The 
records of these attempts are scattering and difficult to find. 1146 
A BRIEF HISTORY OF PROSTHETIC DENTISTRY 
Many efforts in inlay work, and probably some reasonably 
successful results, were without doubt never disclosed, be- 
cause, as a rule, the pioneer practitioner kept his methods a 
secret. 
Such early records as are available are usually found in 
little handbooks, published in the early days by the practi- 
tioner, and intended for circulation among prospective pa- 
tients. Later on, the dental journals from time to time con- 
tained descriptions of inlay methods, as they developed. 
BRIEF SUMMARY OF INLAY WORK, BEGINNING WITH 1820 
In 1902, Dr. Walter W. Brack of Breslau, Germany, in 
the Items of Interest, presented an outline of the history of 
inlay work, gathered from common and obscure sources. A 
portion of the following brief description of the progress of 
this work is based upon the article mentioned. 
In 1820, C. J. Linderer filled teeth by the “fournieren” 
(inlaying) method and the “plattieren” (veneering) method. 
The first procedure consisted in preparing a cavity in circu- 
lar form, and from the tooth of some animal shaping a cylin- 
drical rod to fit. This was driven into the cavity, the project- 
ing portion cut off and polished even with the tooth surface. 
The expansion of the inlay, due to absorption of the oral 
fluids, caused it to swell and thereby furnish retention. Some- 
times both inlay rod and cavity walls were threaded to fur- 
nish positive mechanical retention. 
The plattieren method was adapted to shallow cavities and 
consisted in shaping small, flat pieces of rhinoceros teeth to 
fit the prepared cavity. These veneers were usually held in 
place with dowels of the same material. Difficulty in match- 
ing the shades of the natural teeth, discoloration from use 
and general lack of permanency, were the principal objections 
to the Linderer inlays. 
In 1837, Dr. Murphy of London conformed a platinum mat- 
rix to the prepared cavity, and in this matrix a glass inlay 
was fused, which was held in place with amalgam. 
In 1857, Dr. A. J. Volck reccmmended the use of porcelain 
for filling cavities in the front teeth. The inlays so formed 
were held in place by packing ropes of gold foil around their 
peripheries. 
In 1862, Dr. B. Wood shaped porcelain blocks to tooth cav- 
ities by grinding to form. A BRIEF HISTORY OF PROSTHETIC DENTISTRY 
1147 
In 1870, Dr. Hickman formed inlays from sections of por- 
celain teeth, shaping the pieces to fit the cavities by grinding. 
Fig. 1074.— Dr. Wood’s Method of Forming Inlays from Blocks of 
Porcelain by Grinding 
In 1870, Dr. Starr designed “cavity stoppers,” small 
pieces of porcelain of various shapes and sizes, which were 
fitted to cavities by grinding. The pieces were provided with 
platinum pins for retention purposes. 
In 1870, Dr. C. H. Land constructed inlays by “fusing 
pieces of artificial teeth in a platinum impression of the outer 
borders of the cavity.” This method, as he later on modified 
it by pulverizing the teeth before fusing, represents the basic 
principle of our porcelain inlay system of to-day. 
DR. C. H. land's METHOD OF PORCELAIN INLAY WORK 
Fig. 1076.— Dr. Fisk’s Method of Veneering Carious 
Teeth 
In 1876, Dr. Bogue described a method suggested by Dr. 
Fisk of veneering a carious tooth with small gold caps, which 
he likened to “little gold toadstools, set with gutta perclia, 
somewhat resembling an umbrella.” 
Fig. 1076.—i F Bing’s Metallic 
Facing 
In 1877, Dr. B. J. Bing recommended the use of “metallic 
facings” for protecting fillings of cement or gutta-percha. 
These facings were usually made of pure gold or platinum, 
DR. BINGES METALLIC FACING 1148 
A BRIEF HISTORY OF PROSTHETIC DENTISTRY 
and when set very much resembled in appearance the metallic 
inlays of the present time. 
Dr. Wilber F. Litcli describes these facings quite fully in 
the American System of Dentistry, p. 949. Of their practica- 
bility, he says: “In large crown cavities they have an in- 
definite durability, and in the writer’s practice large numbers 
of proximal facings have been in use for three and four years 
and still give no s.gn of failure.” This system, although 
crude, proved m incentive to many to attempt the restoration 
of badly decayed bicuspids and molars by these or similar 
m»ans. The writer constructed and placed a number of fac- 
i& ? this type for patients in th, clinic of Washington 
University Dental School in 1891. (M Cental College.) 
ROLLINS ’ METHOD OF INLAY *■ ORK 
In 1885, Dr. W. Hollins, in the Archives of Dentistry, de- 
scribed as follows a method of inlay work employed by him- 
self for a number of years previous to tb- date mentioned. 
An impression of the tooth with cavity . taken in 
a material composed of two parts mastic, one purt paraffin, 
and one part graphite. The tooth and cavity surfaces should 
be previously oiled with vaseline. When secured, the impres- 
sion should be placed in a bath of copper sulphate, and a film 
of copper deposited by electrolysis, the process usually requir- 
ing from two to three days to develop a sheet about 1 y2 m.m. 
thick, or sufficiently rigid to obviate distortion in handling. 
The impression was then removed, and a hole bored in the 
bottom of the cavity in the copper reproduction of the tooth, 
to facilitate the removal of the matrix. Into the cavity a piece 
of No. 30 gold foil was adapted with pellets of cotton. The 
matrix thus formed was filled with enamel powder and fused 
in a gas muffle furnace. Before the mass hardened it was 
pressed into the copper mold with a platinum instrument. 
After cooling, the enamel was removed from the mold by 
pressure through the opening in the base of the copper pat- 
tern, and the gold matrix peeled off. It was set with a mix- 
ture of zinc oxide and gutta-percha, the excess being removed 
with chloroform. 
In 1885, Dr. C. W. Dunn, in the British Journal of Dental 
Science, described a method practiced by himself since 1868, 
of taking a wax impression of the tooth and cavity, from which 
DR. DUXX's METHOD OF INLAY WORK A BRIEF HISTORY OF PROSTHETIC DENTISTRY 
1149 
a model in plaster was secured. This was painted with a mix- 
ture of wax and rosin, to prevent friability of the cavity mar- 
gins. Into the cavity a filling was fitted by repeated grinding 
and trial, until satisfactory adaptation had been secured, after 
which it was set with cement. Various substances were used 
by him for inlays, such as mineral and natural teeth, as well 
as the teeth of cattle and lambs. 
DR. STOKES’ METHOD 
In 1887, Dr. J. L. Stokes, in the Southern Dental Tournal, 
described a method of making the inlay, and shapir 
cavity to receive it. ter setting, he removed the har _ d 
cement from the to a slight depth, and filled between 
the cavity walls a 1 inlay with gold. A similar method of 
retention had been previously introduced by Dr. Essig of 
Philadelphia some time in the seventies. 
■i, 
DR. AMES METHOD OF GOLD INLAY WORK 
In 1888, Dr. W. V. B. Ames of Chicago constructed gold 
inlays by adapting a foil matrix of platinum to the tooth cav- 
ity, and fusing in it gold plate or solder to the required con- 
tour. The inlay was then cemented in position. Shortly after 
this he demonstrated the method at a meeting of the Illinois 
State Dental Society, a description of which is found in the 
Proceedings of 1890. 
So far as the writer is able to learn, this was the begin- 
ning of the gold inlay methods by the matrix system. It de- 
monstrated the practicability of fillings of this type. 
VARIOUS METHODS OF INLAY PRODUCTION IN RECENT YEARS 
In 1889, Dr. W. Storer-How, in the Dental Cosmos, de- 
scribed in detail the method of constructing inlays by grind- 
ing sections of porcelain teeth of suitable shade, to the desired 
form. 
In 1889, Dr. Herbst described a method of making glass 
inlays. An impression of the tooth with cavity prepared was 
secured in Stent’s Compound, from which a plaster model 
was formed. To ma’re the base of the inlay rough, for reten- 
tion purposes, grains of sand were placed in the bottom of 
the cavity of the plaster tooth, and the latter, while moist, was 
filled about two-thirds full of powdered glass. The moisture 
was then absorbed and the glass fused. This was then re- 
peated until the inlay was of the desired contour 1150 
A BRIEF HISTORY OF PROSTHETIC DENTISTRY 
In 1890, Prof. Sachs recommended making a matrix of 
Williams’ gold foil No. 00, or of platinum foil, and fusing the 
glass directly into this reproduction of the cavity. Sachs also 
described an excellent method of making inlays from porce- 
lain teeth of suitable shade. From a porcelain tooth a piece 
nearly cylindrical in form and slightly larger than the cavity 
was cut. This cylindrical section was mounted with melted 
shellac on the end of an engine mandrel. The mandrel was 
revolved in the engine and the porcelain held against the face 
of a lathe stone revolving in the opposite direction. The man- 
drel was held at a slight angle to the face of the lathe wheel, 
so as to form the mounted block into a slightly tapering cone. 
The cavity was prepared in circular form by means of suitable 
wheel burs. The inlay, still mounted on the mandrel, was 
introduced into the cavity with emery powder or pumice stone, 
and revolved rapidly to secure close adaptation at the mar- 
gins. When closely adapted a groove was cut near the per- 
ipheral base of the inlay for retention purposes After set- 
ting, the surplus, or projecting end, was reduced to a level 
with the tooth surface with stones and discs. Copper tre- 
phines charged with diamond dust were also used for cutting 
the section from the porcelain tooth, while cylindrical burs 
corresponding in size to the section cut by the trephine were 
used for forming the cavity. 
In recent years the supply houses have introduced rods 
of porcelain for inlay work, of varying sizes and tints, with 
trephines of corresponding sizes for cavity preparation. This 
system obviates grinding the periphery of the inlay. A sec- 
tion of rod, slightly longer than the depth of the cavity, is cut 
nnd cemented to place, and the surplus reduced with stones 
and discs. 
Fig. 1077.— Steps in the Construction of an Incisor 
Inlay (Alexander’s Matrix Method) 
hi 1896, Dr. C. L. Alexand r described a method of inlay 
construction, the substance of which is as follows: Prepare 
dr. Alexander’s inlay methods A BRIEF HISTORY OF PROSTHETIC DENTISTRY 
1151 
cavity with definite margins. Make holes for retaining pits 
in dentin. Adapt platinum foil to tooth surface. Insert re- 
taining posts through matrix. Take impression of posts and 
Fig. 1078.—- Pin Inlay for Molar Tooth 
foil; remove, invest and unite with pure gold. Return to 
tooth for final adaptation and trimming. 
Fig. 1079.— Various Views of Incisor and Molar Inlays 
When fitted, a wax or modeling compound bite is taken, 
occlusion casts are formed, the bite removed, and the desired 
restoration developed in wax. 
Fig. 1080.— Restorations for the Anterior Teeth 
Over this restoration in wax, gold or platinum foil is bur- 
nished. 
Invest, leaving one side op m for removal of wax with hot 
water and into the metal-lined matrix thus formed gold is A BRIEF HISTORY OF PROSTR. JENTISTRY 
fused. The various illustrations here , rn are from the 
Dental Coomos. 
Fig. 1081.— Bridge with Pin Inlay Attachments 
Fig. 1082.— Upper Bridge Supported by Three Pin Inlays 
In 1897, Dr. M. S. Finley described a similar method of 
restoring the occlusal surfaces of bicuspid and molar teeth. 
Heavy gold, however, instead of foil, was used For adaptation 
to tooth surfaces. When swaged on a die dapted to the 
Fig. 1083.— Pin Inlay (Finley) A BRI 
tooth, the cusp fc 
tion. ! 
Gold inlays were made by prep, 
under cuts, and into this Watts’ 0 
condensed, the filling being built to general .. 
means. It was then removed and the cavity suriaces .. 
inlay painted with rouge and alcohol to prevent the ot 
der, . Jch afterward into the interstices, fm*v- 
spr* "ing and rr ' Tying th form of the inlay. The origina- 
te" of this etlmd is not kno.vii to the writer. Dr. W. M. Gris- 
wold of Hamburg, Germany, described it a number of years 
ago, and stated that he had been using it since 1898. 
lulay work advanced slowly because of the prejudice ex- 
ing in regard to the use of cement as a retention medium for 
iings of this class. The objections urged against inlays in 
general, both porcelain and metallic, were, first, the liability 
of the cement to solution by the oral fluids, and second, the 
tendency of such fillings to become displaced under stress. 
Three factors contributed largely to the production of both 
classes of inlays under consideration: First, the introduction 
of the Custer electric furnace in 1894. and of improved porce- 
lain bodies, revolutionized and simplified the making of porce- 
lain inlays; second, the methods of cavity preparation in 
general, suggested by Dr. Black, of opening up cavities in 
order to gain access to all parts, and of developing flat seats 
and parallel walls so as to furnish resistance form, largely 
overcame the liability to displacement, of inlays of both gold 
and porcelain, when set and subjected to stress; third, ob- 
servation of cases where properly adapted and correctly set 
inlavs had been subjected to stress and the action of the oral 
fluids for a considerable length of time, disclosed the fact that 
cement, although not ideal, was a reasonably good retaining 
medium, not liable to solution as rapidly as was at first deemed 
probable, and that under favorable conditions there was no 
recurrence of decay. 
The improvements mentioned in porcelain bodies, and 
neans of fusing the same, together with the beautiful results 
accomplished bv experts in this field, developed a widespread 
wave of enthusiasm in ceramic dental art. Like all new things 
which ,,iuuji.se reasonablv good results, porcelain became a 
fad and w ossly misapplied, not only in the construction 
of inlays, hyt crown and bridge work as well. Tn limited 
SLOW PROGRESS OF INLAY WORK 1154 
A BRIEF HISTORY OF PROSTHETIC DENTISTRY 
bulk, porcelain is inherently weak, friable and extremely liable 
fracture under stress. These facts were overlooked, or not 
recognized by many, with the result that many discouraging 
xdilures occurred. Warpage of the matrix, resulting in im- 
perfect adaptation of inlays to cavities, difficulty in matching 
the tints of natural teeth, with fracture and displacement of 
the fillings under stress, were some of the discouraging fea- 
tures of porcelain inlay work. 
From flood to ebb tide, the wave of enthusiasm in ceramic 
work lasted about ten years, beginning about 1895, just fol- 
lowing the advent of the Custer electric furnace. It reached 
its highest level in 1903-4. Since the latter date mentioned, 
as time and service disclosed the limitations of porcelain as 
a filling material, its use has gradually declined. Its value in 
favorable locations is unquestioned. 
PROGRESS OF GOLD INLAY METHODS 
Meanwhile, although less desirable from an esthetic stand- 
point than porcelain, the production of gold inlays rapidly 
increased, because of their great inherent strength and wide 
range of application. During the period from 1900 to 1907, 
the method of gold inlay production by means of a matrix 
gained in favor, technical steps improved, and the value and 
permanence of this system of filling teeth was practically 
established. 
One of the greatest difficulties met with in the making of 
gold inlays by the methods then in vogue was in warpage of 
the matrix while fusing the gold in it to the desired contour. 
In 1905, Dr. Barnes of Cleveland, Ohio, demonstrated that by 
substituting 1-500 platinum foil for the 1-1000 gold or plati- 
num foil then in use, warpage could be practically eliminated. 
While the matrix method of inlay production had ap- 
proached a stage bordering on perfection, the technical steps 
involved were at times tedious and sometimes complicated, 
depending on the form and location of the cavity to be filled. 
The production of the matrix itself, although much less try- 
ing on both patient and operator than tedious filling opera- 
tions, required time and skill to secure the desired results. 
Some easier method, therefore, was sought. 
INCEPTION OF THE WAX MODEL METHOD 
The idea presented of making a model of the filling by 
pressing wax into the tooth cavity, or a reproduction of it. A BRIEF HISTORY OF PROSTHETIC DENTISTRY 
1155 
This model, when properly carved and contoured, was invested 
and cast in metal. Where or when this idea originated, or to 
whom credit for it belongs, cannot now, and probably never 
will, be determined. 
An Analysis of the Casting Process 
By analysis, the casting process, as applied to dental opera- 
tionsr may be set forth as follows: 
First, forming in a plastic material as wax, or in wax and 
metal, a model or pattern of the object it is desired to repro- 
duce by casting. 
Attaching to the model, before investment, a wax or metal 
sprue former to form a pouring gaine, or sprue, for the injec- 
tion of the metal into the mold. 
Enclosing the pattern with sprue former attached, in a 
single mass, or a sectional mass of refractory material, capa- 
ble of setting in a short time and of withstanding heat with- 
out material change. 
Eliminating the wax from the investment by some form of 
applied heat, thus freeing the mold for the introduction of the 
metal. 
Fusing the metal in a crucible-like depression in the invest- 
ment, which is connected with the mold, through the sprue; 
or melting the metal in a crucible and pouring it directly into 
the enlarged outer extremity of the sprue, through which it 
is conducted into the mold. 
Applying pressure to the molten metal to force it into all 
parts of the mold, to insure the production of a sharp casting. 
Some of these various processes will now be considered in 
detail, after which their application in the production of pros- 
thetic restorations of different kinds will be presented some- 
what in chronological order. 
FORMING MODELS IN WAX OF THE CASTING TO BE PRODUCED 
The construction of a plastic model, usually wax, of the 
object it is desired to reproduce in metal. 
This principle is centuries old among artisans, and even 
among uncivilized people, with some of whom it was custom- 
ary to form in wax a model of an implement and enclose it in 
a clay investment. On heating the clay, the latter was hard- 1156 
A BRIEE HISTORY OE PROSTHETIC DENTISTRY 
ened and the wax dissipated, thus leaving a matrix or mold 
into which the molten metal, usually copper, was cast. 
METHODS OE FORMING A SPRUE Oli POURING GATE 
A sprue is defined as follows: “in casting metal, one of 
the passages leading from the ‘skimming gate’ to the mold; 
also, the metal which fills the sprue or sprue-gate after solidi- 
fication, same as dead-liead.” (Century Dictionary.) “A 
piece of metal or wood used by a molder in making the ingate 
through the sand.” (E. H. Knight.) 
For many years, in prosthetic procedures it was custom- 
ary, and is, even at the present time, in two-piece molds, to cut 
the sprue after investment of the model. More often, how- 
ever, a piece of wax is attached to the pattern leading exter- 
nally to the outside of the investment fiask, so as to form a 
groove in both parts of the investment. When the matrix 
is separated and the wax removed, the groove thus formed 
may be enlarged if necessary for the injection of the metal. 
In single investments, a piece of wax, metal or wood, of suit- 
able size for the sprue is attached to the model before invest- 
ing, and removed after the investment has hardened. When 
wax is used, its removal is effected by heat. 
In Harris, Ed. 1873, the first suggestion of “small cylin- 
drical wax gates” is mentioned in connection with the Bean 
process of casting. These were enclosed in a single invest- 
ment to serve as sprue formers through which the metal was 
cast in attaching the teeth to the aluminum base. 
In Richardson, Ed. 1880, mention is made of a tapering 
sprue former of wax, in connection with Reese’s cast base den- 
tures. The name pouring-gaine is there applied to it. In the 
final investment of a pattern, the wax sprue former was en- 
tirely enclosed, and subsequently dissipated in heating the 
case. 
ENCLOSING THE WAX MODEL IN A SINGLE INVESTMENT 
The object in enclosing a wax model in a single invest- 
ment rather than in a sectional matrix is to prevent fracture 
of the margins of the mold, which nearly always occurs in 
opening a matrix formed in two or more pieces. 
Rough margins of the mold result in rough castings, while 
oftentimes, even though the margins may not be fractured, 
slight contraction in the investment material, or failure of the A BRIEF HISTORY OP PROSTHETIC DENTISTRY 
1157 
several sections of the matrix to register correctly, will permit 
the fused metal to escape into the joint areas. 
This fact has been recognized by many and for the past 
twenty years or more the single investment has been gradu- 
ally coming into favor. 
ELIMINATING THE PATTERN BY HEAT 
This is a logical outcome of the use of wax for a pattern 
and of its enclosure in a single investment. 
FUSING THE METAL IN CLOSE PROXIMITY TO THE MOLD 
The principal cause of failure in casting operations is due 
to the metal when fused becoming chilled and more or less 
sluggish in injecting it into the mold. This difficulty is spe- 
cially noticeable when the metal is melted in a separate recep- 
tacle from which it is poured into the mold. 
To cast sharply, a metal or alloy must be superheated 
sufficiently so that after injection into the mold it will be in a 
liquid, conformable condition, in order to become adapted to 
irregular surfaces. 
APPLYING PRESSURE TO THE PUSED METAL TO INDUCE SHARPNESS 
OP DETAIL IN THE CASTING 
The necessity for applying pressure in some manner to 
the fused metal to insure sharpness of detail in castings was 
recognized by Blandy in 1855, and many others since his time. 
The manner of applying pressure to eliminate the air in 
the mold and permit the metal to fill it perfectly varies greatly, 
as will subsequently be seen. 
Briefly summed up, some of these methods are as follows: 
Gravity, vibration, mechanical pressure, compressed air or 
gas, partial vacuum, centrifugal force and steam. 
PIONEERS IN THE PRODUCTION OP CAST VIOREL 
The casting of denture bases of tin, as stated on page 1108, 
was first attempted by Dr. Edward Hudson of Philadelphia 
in 1820, by Dr. W. A. Royce of Newburgh, N. Y., in 1836, and 
by Dr. George E. Hawes of New York in 1850. 
Tin does not cast sharply by the ordinary or crude meth- 
ods employed in those days and therefore the production of 
dentures by this method was not very satisfactory. 
The introduction by Dr. A. A. Blandy of an improved tin 
alloy gave a decided impetus to casting methods since his time. 1158 
A BRIEF HISTORY OF PROSTHETIC DENTISTRY 
THE BLANDY CAST BASE DENTURE 
The Blandy Process of casting metal base dentures, which 
was presented in 1856, was described in Harris, Ed. 1873, in 
substance as follows: 
A wax model of the required denture was formed in which 
the teeth were arranged, much as for vulcanite cases, a special 
tooth being used for this purpose. 
The waxed case was enclosed in a two-piece investment 
composed of plaster and feldspar. On separating, the larger 
portion of wax was removed, but the smaller portions between 
the teeth were allowed to remain, being subsequently dissi- 
pated in the heating process. 
A channel was cut in the back of the case, at least two 
inches long, to serve as a sprue, and on either side vents for 
the escape of the air were formed. A deep sprue was sug- 
gested so that when filled, the weight of the metal therein con- 
tained would insure density in the casting. In addition to this 
means, it was suggested that jarring the flask as soon as the 
metal was poured would aid in the production of a sharp 
casting. 
Fig. 1084.— Teeth Designed for Use with the Blandy Process, 1855 
bean’s method of casting aluminum 
In 1867, Dr. J. B. Bean of Baltimore formed denture bases 
in wax, arranged gum section teeth in occlusion and alignment 
and carved the denture to required form. The gum sections 
were then removed and a recess of dovetailed form was carved 
in the wax baseplate to the lingual of the pins to afford an- 
chorage for the gum sections in final attachment 
The wax model, minus the teeth, was then enclosed in a 
special flask, in an investment composed of plaster and pumice 
stone previously boiled, so treated to form a denser mass than 
would result from an ordinary mix. 
When the investment was hardened, the flask was opened, 
the wax removed, the flask again closed and thoroughly heated 
to evaporate the moisture. 
The flask was supplied with three openings, one centrally 
located to serve as a sprue for the introduction of the fused 
metal, and a smaller one on either side for the admission and 
exit of hydrogen gas at the moment of casting. At the time of 1159 
A BRIEF HISTORY OF PROSTHETIC DENTISTRY 
clearing the matrix of wax, grooves were cut from these open- 
ings to the interior of the mold. 
The terminal end of the sprue on the flask was cone-shaped 
to receive an extension sprue, some six inches long, which was 
heated and set in position just before pouring the metal. 
Fig. 1085.— The Bean Appliance for Casting 
Aluminum (Reproduced from 
Harris, Ed. 1873) 
When the aluminum was fused, hydrogen gas was intro- 
duced in the mold through one of the lateral openings in the 
flask, to expel the air and thus prevent oxidation of the heated 
metal, the extension sprue set in position and the metal cast 
into the hydrogen filled mold. 
As the metal filled the mold, the hydrogen escaped through 
the other lateral opening. Both lateral openings were par- 
tially obstructed by fine wire which, although permitting the 1160 
a brief history of prosthetic dentistry 
introduction of gas in one and the escape of gas and air 
through the other, prevented the escape of the metal under 
pressure of that contained within the long sprue. 
When cast, the baseplate was finished, the porcelain blocks 
adjusted in position and attached by a second casting process 
in which a more fusible alloy was injected into the dovetailed 
groove previously mentioned, and around the pins of the 
teeth. 
In this second step the use of “small cylindrical wax 
gates’’ was mentioned.> These served the purpose of sprue 
formers, were enclosed with the baseplate and teeth in a sin- 
gle investment, subsequently dissipated by heat, and through 
them the low fusing alloy was cast under gravity pressure 
into the groove and around the pins of the teeth. 
In these two operations described by Dr. Bean are pre- 
sented several of the fundamental processes of casting, viz., 
in the first steps are mentioned a wax pattern; its investment 
in a sectional matrix of refractory material; injection of the 
molten metal into the mold under gravity pressure; in the 
second steps are mentioned “cylindrical wax gates,” or sprue 
formers, a single investment, or one piece matrix, and dissi- 
pation of the wax by heat. 
On page 630 of the Dental Cosmos, 1873, is illustrated an 
apparatus designed by C. Sauer of Berlin, for casting alum- 
inum denture bases. This appliance resembles in many re- 
spects the Bean apparatus which had been introduced a few 
years previously. 
The points of interest in this article are the use of an alloy 
of aluminum, recommended because it cast more sharply than 
the pure metal, the application of a deep sprue to the flask to 
increase the pressure on the metal within the mold, and the 
casting of the fused metal directly against the teeth. 
sauer's method of casting aluminum 
reese's method of casting tin alloys 
Tn 1879, Dr. G. P. Reese introduced a new alloy of greater 
hardness than that previously in use, which was designed for 
upper denture bases. A special flask of his own design was 
recommended for the investment of the case. 
HAYFORD's METHODS AND APPLIANCES 
Tn 1884, Dr. J. W. Hayford of Xenia, 0, patented an 
appliance for casting Watt's, Weston's and other fusible A BRIEF HISTORY OF PROSTHETIC DENTISTRY 
1161 
alloys then in use. This appliance consisted of a press and a 
flask having an opening in its upper side through which the 
fused metal was poured into the sprue and mold. 
Fig. 1086.— Dr. Hayford’s Casting Appliance 
By means of a lever a plunger was pressed downward into 
the flask and against the fused metal and in this manner it 
was forced into all parts of the mold by mechanical pressure. 
THE WATT'S FLASK 
In the latter part of the 80’s, Dr. Geo. F. Watt designed 
a Mask having two extensions in which the sprues were formed. 
When the cast metal was injected into the mold the weight of 
that contained within the sprues condensed that within the 
mold by gravity pressure. (ISee page 224.) 
DR. martin's METHOD OF CASTING 
Beginning about 1889, and for a number of years follow- 
ing, Dr. G. M. Martin of Indiana demonstrated and taught the 
method of casting inlays, crowns and bridges in the Indiana 
Dental College, and in post-graduate work in Indianapolis. 
The method was substantially as follows: 
Formation of the pattern in wax, investment in refractory 
material within a cuplike receptacle, eliminating the wax with 
heat, melting the metal in a crucible-like depression, which 
was connected with the mold by a sprue, and casting the fused 
metal by mechanical and later by centrifugal force. No mat- 
rix was used in forming the pattern in wax for an inlay. 
The crucible and sprue were formed by attaching a piece 
of wire in case of inlays, or a strip of metal plate in bridge- 
work, to the curved side of a section of cork, mounting the 1162 
A BRIEF HISTORY OF PROSTHETIC DENTISTRY 
pattern at the outer extremity of the sprue former and apply- 
ing the investment around the pattern and over the curved 
cork base. 
THE CARROLL METHOD OF CASTING ALUMINUM 
In 1888, Dr. C. C. Carroll patented an apparatus for cast- 
ing aluminum denture bases, bridges and crowns. The prin- 
cipal improvement of the method over those preceding it was 
Fig. 1087.— The Carroll Casting 
Appliances 
in the use of a sealing cap for closing the crucible, and casting 
the metal by means of compressed air. 
Dr. Carroll demonstrated his appliances and method of 
casting aluminum at the World’s Columbian Dental Congress 
in Chicago, in 1893, as well as at previous times. 
THE ZELLER CASTING APPLIANCES 
Tn 1891, the Zeller appliances were introduced These con- 
sisted of a flask for investment of the case, burners for heat- 
ing- the flask and fusing the aluminum, and a suction tube by 
means of which a partial vacuum could be created in the mold. A BRIEE HISTORY OE PROSTHETIC DENTISTRY 
1163 
When the case was heated and the metal fused, it was drawn 
into the mold by mouth suction or a suction bulb. 
In 1893, the Eenner appliances were introduced. These 
consisted of a flask with attached crucible for investment of 
the case and holding the metal while fusing, of a stove and 
jacket for heating the case, a sealing cap fitted with a packing 
by means of which the metal could be forced into the mold by 
compressed air. The writer used and demonstrated both wax 
and metal sprue formers with this appliance as early as 1895. 
THE EENNER CASTING APPLIANCES 
DR. harper's CAST CROWNS AND BRIDGES 
In 1894, Dr. W. E. Harper of Chicago constructed cast 
aluminum bridges by the following method, one special type of 
abutment of which will be outlined: 
A molar tooth having a proximo-occlusal cavity was pre- 
pared by reducing its occlusal and axial surfaces in the usual 
manner required for the reception of a shell crown. 
The cavity in the tooth was prepared as for the reception 
of a filling, but without undercuts, the axial walls flaring out- 
ward slightly. 
An axial band of aluminum was then fitted to the tooth, be- 
ing carried slightly under the gingiva, the occlusal end being 
left open. 
Wax was pressed into the open end of the band, directly 
into the cavity against its various walls, and over the reduced 
occlusal areas of the tooth, without the interposition of a 
matrix. 
The patient was instructed to bite into the wax to develop 
occlusion, after which the cusps were carved to required form. 
This wax-metal abutment was then united to the dummies, 
which were of wax, or, in some cases, of wax and porcelain 
combined, a wax sprue former attached, the whole piece in- 
vested in a Zeller flask, and heated to dissipate the moisture 
and wax. 
The aluminum was then fused in the attached crucible and 
drawn through the sprue into the mold by partial vacuum 
force. 
In specimens shown the writer in 1896 and subsequently, 
there appeared to be perfect union between the cast metal and 
the band. 1164 
A BRIEF HISTORY OF PROSTHETIC DENTISTRY 
This abutment might appropriately be termed a crown 
inlay, since it constituted not only a crown, but an accurately 
fitting inlay as well. 
Dr. Harper frequently demonstrated and described this 
method of crown-inlay construction at various clinics and to 
different individuals as well. He stated to the writer as early 
as 1896 that he had been successfully following this plan of 
bridge construction in his practice. 
By analysis this method embodies the pressing of wax 
directly into the tooth cavity, and against various tooth sur- 
faces, in the formation of the crown-inlay pattern, without the 
interposition of a matrix, the use of a sprue former of wax, 
investment of the pattern in refractory material, dissipating 
the wax by heat, casting the fused metal into the matrix by 
vacuum force. 
THE ALEXANDER METHOD OF CASTING INLAYS 
Reference has previously been made to Dr. C. L. Alex- 
ander’s method of forming inlays. His first paper on “Cast- 
ing Fillings and Abutments for Bridges” was reported at a 
meeting of the Southern Dental Association, held at Asheville, 
N. C., in July, 1896. The discussion which followed clearly 
brought out the fact that the durability of the cement by which 
inlays were held in place was still a point not yet determined 
by experience, and many in the profession opposed the ap- 
plication of inlays on this ground. 
The “casting of fillings,” however, was “in the air,” and 
the possibilities in this field were beginning to be recognized. 
THE HOLLINGSWORTH METHOD OF CASTING 
In the American Text Book of Prosthetic Dentistry, pages 
669-70, Ed. 1896, is described the Hollingsworth method of 
casting bridge dummies, the patterns of which were composed 
of wax, wax and paraffin, or wax and gutta percha. 
The pattern after being carved to correct occlusion and 
form between the two abutments, was removed. To one end 
was attached a cylindrical piece of wax about one-eighth of an 
inch in diameter, to serve as a gate or sprue former. 
A shallow, oblong, sheet iron pan, to which a handle was 
attached, was used as a table on which to invest the case. 
The investment, composed of a mixture of plaster and 
marble dust, was mixed to medium thin consistency, the pan A BRIEF HISTORY OF PROSTHETIC DENTISTRY 
1165 
filled with it and the wax pattern with sprue former attached, 
laid on it near one end, and covered over to the depth of about 
one-half inch. 
The investment in the other end of the pan was not con- 
toured but left flat, and when hardened a depression or shal- 
low crucible was formed in this surface and connected by a 
groove with the exposed end of the sprue former, the invest- 
ment around which was removed to form a funnel-shaped 
opening for the ready entrance of the gold into the mold. 
All surfaces were cleared of debris and the case heated to 
dissipate the moisture and wax. 
In the crucible depression, gold scrap or plate was placed 
and with a blowpipe, brought to a thoroughly liquid condition, 
when, by tipping the pan in an upright position, the gold was 
cast into the mold by gravity. 
In 1902, Patent No. 708,811 was issued to Dr. M. W. Hol- 
lingsworth for a machine for forcibly casting dental bridges. 
The fundamental principle of this machine resembled some- 
what his first crude appliance, previously described. 
This appliance consisted of a base provided with a hinged 
table, on which the investment rested. Through the bottom of 
the table projected a sprue former of brass, having a reduced 
upper extremity to which the wax model was attached. A 
metal hood for supporting the sides and outer end of the in- 
vestment was adjusted to the table, and which, being adjust- 
able, permitted the investment to be closely applied to the 
pattern and thus exclude the air, after which, while the invest- 
ment was still soft, the hood was adjusted and filled. 
Fig. 1088.— The First Hollingsworth Appliance for Casting Gold Dummies 1166 
A BRIEF HISTORY OF PROSTHETIC DENTISTRY 
When hardened, the sprue former was removed and a 
stick of carbon of corresponding size was inserted into the 
opening. 
In investing a case in this appliance, the crucible for melt- 
ing the gold was formed in one end of the table, being con- 
nected with the sprue by a lateral groove and opening. 
When the investment was thoroughly dry and heated, and 
the wax dissipated, gold was placed in the crucible, where it 
was fused. 
Fig. 1089.— The Hollingsworth Pressure Casting Appliance 
By means of a lever device the hinged table was raised to 
an upright position. This movement cast the gold into the 
sprue and mold by gravity. 
When the table was in nearly an upright position the outer 
end of the carbon was brought in contact with a cam surface 
of the base, thus pressing it forward into the sprue and forc- 
ing the gold into the mold by mechanical pressure. 
These processes involve a wax model, enclosed in a sin- 
gle investment of refractory material, a removable metal 
sprue, formation of a crucible depression in the investment, 
dissipation of the wax model by heat, fusing and casting the 
gold under both gravity and mechanical pressure. A BRIEF HISTORY OF PROSTHETIC DENTISTRY 
1167 
In 1900, the writer designed a flask for casting aluminum 
in which a metal sprue former was used in conjunction with a 
wax model enclosed in a single investment. 
The metal was melted in an attached crucible and forced 
into the mold with a metallic piston which fitted the interior 
of the crucible. Because of difficulty at times resulting from 
the piston becoming locked within the crucible chamber, a 
sealing cap, with tube attached, was substituted and by this 
means the fused metal was injected into the mold with com- 
pressed air, and also steam pressure. These flasks were used 
for some time in the technic laboratories of the Northwestern 
University Dental School by Dr. Waldberg, Dr. Metliven and 
the writer. 
FLASK DESIGNED BY THE WRITER 
Between 1896 and 1905, Dr. B. F. Philbrook, of Dennison, 
la., developed a system of casting inlays which in substance 
was as follows: 
In his first efforts, between the period from 1896 to about 
1898, he formed a model of the desired filling by pressing wax 
into the cavity of a tooth, reproduced in the usual way, in 
plaster. This is known as the indirect method. From 1898 
and thereafter he formed the filling by pressing the wax di- 
rectly into the natural tooth cavity, without the interposition 
of a matrix, and carved it to the required form. 
To each extremity of the inlay a cylindrical piece of wax 
was attached, one to serve as a sprue former, the other to 
form a channel through which to clear out the wax. 
The pattern and extensions were then invested in refrac- 
tory material in a ring in such manner as to exclude the air, 
the sprue former occupying a central position, the other ex- 
tension situated near one side. 
When the investment had set, it was trimmed out around 
the sprue former to form a crucible-like depression in which 
to melt the metal. 
With a bulb syringe, hot water was forced into the sprue 
and mold, and out the side channel, thus freeing the mold and 
openings leading to it of the greater bulk of wax. 
The invested case was heated to expel the moisture and 
any remaining wax present, the metal placed in the crucible, 
fused with a blowpipe, and forced into the mold as follows: 
A sealing cap consisting of a metallic disc of larger diam- 
eter than the investment ring, having attached an asbestos 
DR. PHILBROOK’s METHOD OF CASTING INLAYS 1168 
A BRIEF HISTORY OF PROSTHETIC DENTISTRY 
packing for sealing against the escape of air, was pressed 
firmly and evenly down upon the upper end of the ring. 
Through a tube of metal which was attached to the upper 
central side of the disc, air was forced by mouth pressure into 
the crucible containing the fused metal, thus injecting it 
through the sprue into the mold. 
By 1904, several important modifications in the above 
methods were made by Dr. Philbrook, viz., the use of a metal- 
lic sprue former, the designing and use of a metallic crucible 
former, dissipation of the wax by dry heat or flame, a sealing 
cap containing moist asbestos, the steam from which, when 
heated and confined, injected the fused metal into the mold. 
The methods and appliances employed by Dr. Philbrick, 
from 1896 to 1905, inclusive, may be briefly summed up as 
follows: 
A model formed without a metal matrix; both by the in- 
direct method of pressing wax into a plaster model of the pre- 
pared tooth and cavity, and by the direct method, by pressing 
the wax directly into the natural tooth cavity; the use of both 
wax and metal sprue formers; a metallic investment ring; 
metal as well as wax sprue formers for supporting the pattern 
and forming the sprue; investment of the wax pattern in a 
single mass of refractory material; dissipation of the wax by 
hot water in some cases, dry heat or flame in others; fusing 
the metal in the crucible depression of the investment in the 
upper end of the ring; injecting it into the mold by com- 
pressed air or by steam pressure. 
DR. SCHLOTTER’S CLINIC 
In 1904, Dr. Jacob Schotter at Manitowoc, Wis., gave a 
clinic before the Wisconsin State Dental Society on cast gold 
inlays, in which successful castings were shown, made by grav- 
ity pressure. This clinic demonstrated the method he em- 
ployed in his practice. 
In August, 1905, Dr. John A. Lentz of Phoenix, Ariz., 
applied for a patent for a “ process for forming dental struc- 
tures,” which patent was granted in October, 1906. Briefly 
described, his processes are outlined as follows: “My inven- 
tion relates to such dental work as making inlays, onlays, 
crowns, bridges, artificial dentures and other dental structure, 
or certain parts of the foregoing.” 
He mentions specifically his method of preparing a molar 
THE LENTZ CASTING PROCESS A BRIEF HISTORY OF PROSTHETIC DENTISTRY 
1169 
tooth for a crown in the usual manner, to which was fitted 
a properly contoured band. A plastic impression material 
was then placed on the occlusal end of the band, forced be- 
tween its inner walls and the axial surfaces of the tooth and 
against its occlusal surface as well, without the interposition 
of a metal matrix. By closing the jaws in various positions, 
clearance paths for the opposing cusps were developed, after 
which the cusps were carved to desired form. 
The crown was then removed and inclosed in a suitable 
investing material in a two-piece ring. On warming and sep- 
Fig. 1090.— The Lentz Casting Appliance 
arating tlie latter, the plastic material which lined the in- 
terior of the band and of which the cusps were formed was 
removed. In one portion of the ring the root sides and end, 
reproduced in investment material, were thus exposed within 
the enclosed gold band, while in the other part of the ring the 
investment presented the reverse of the carved cusp surfaces. 
The casting was accomplished by drying and heating the 
investment in the two halves of the ring, placing an excess 
amount of gold in the cusp depressions, where it was fused, 
while pressure, sufficient to force it into all parts of the mold, 1170 
A BRIEF HISTORY OF PROSTHETIC DENTISTRY 
was developed by dropping the lever of the molding machine 
down until the two halves of the ring touched and registered. 
By this process the fused gold was adapted to all the in- 
equalities of the root surfaces, as represented in the invest- 
ment material within the ring, and when properly finished, 
fitted the root closely. Modeling compound or wax was used 
as the impression material. 
THE OLLENDORF CASTING PROCESS 
In 1906, or previously, Dr. Ollendorf, of Breslau, Ger- 
many, presented appliances and described a system for cast- 
ing crowns, bridges and dentures under pressure. lie used the 
disappearing wax model, enclosing it in an investment of silex 
and plaster. Gravity force for producing pressure on the gold 
in casting was employed, as in some of the preceding methods 
mentioned. This method was described by Dr. Sachs in a 
paper read before the American Dental Society of Europe, 
August, 1906. (Dental Review, March, 1907.) 
SUMMARY OF PROGRESS IN CASTING OPERATIONS 
Thus it appears that the five fundamental principles in- 
volved in the casting process as practiced to-day were widely 
known and utilized prior to 1907 in crown, bridge and denture 
construction, and the casting of inlays was practiced by a con- 
siderable number of individuals with greater or less success. 
That experiments had been and were being conducted 
along these lines by a considerable number of individuals is 
unquestioned. The results of these efforts were frequently 
gratifying, but sometimes disappointing, due largely to a lack 
of exact knowledge of the physical properties of materials 
employed. 
CAUSES OF FAILURES IN CASTING OPERATIONS 
In the light of present knowledge, the causes of failure in 
some of the pioneer efforts with cast inlays were due to 
dimensional changes in the wax model during and after form- 
ing it, this material being very susceptible to temperature 
variations, to impurities present in the wax which remained 
as a residue in the matrix, and failed to volatilize on heating; 
to changes in the investment under heat; but principally in 
failure to render the gold sufficiently plastic to cast sharply. 
Although it is possible to superheat gold to a sufficient 
degree to cast sharply, by means of the ordinary blowpipe, 
still, under some conditions, it is a difficult task. A BRIEF HISTORY OF PROSTHETIC DENTISTRY 
Fig. 1091.— The Ollendorf Casting Appliances 1172 
A BRIEF HISTORY OF PROSTHETIC DENTISTRY 
Had the pioneers, in the casting of prosthetic substitutes 
in gold, recognized the great value and efficiency of the Knapp 
nitrous oxide and gas blowpipe which was introduced about 
Fig. 1092.— Knapp’s Nitrous Oxide and Gas Blowpipe 
1890, work in these lines would have progressed rapidly, and 
the problem of casting inlays and various prosthetic appli- 
ances would have been practically solved. 
dr. taggart’s method of casting inlays 
In 1907, Dr. W. H. Taggart of Chicago made application 
for patents on various processes and “Apparatus for making 
models for the casting of dental inlays and the like,” “Method 
for making models for dental inlays and the like,” “Method 
for making dental inlay fillings and the like,” “Apparatus for 
making castings.” The first two patents 'granted in 
1907, the last two mentioned in 1911. 
Briefly, the steps of producing an inlay v j the Taggart 
method are as follows: 
A pattern of the desired filling is made by pressing wax 
directly into the prepared tooth cavity, without the interposi- 
tion of a matrix, and carved to required form. 
The pattern is mounted on a metallic sprue former, which 
rests in and is supported by a metallic, dome-shaped crucible 
former. A BRIEF HISTORY OF PROSTHETIC DENTISTRY 
1173 
A mix of refractory investment material is made and care- 
fully applied around the wax model in such manner as to elim- 
inate the air. 
The investment ring or flask is then set on the crucible 
former and its interior filled with investment material, thus 
surrounding the previously coated model. 
Fig. 1093.—- The Taggart Casting Appliances 
When he investment has hardened, the crucible former 
and sprue ner are removed. 
The invested case is then heated to expel the moisture and 
dissipate the wax. 
The flask or investment ring is then set in the depressed 
base of the casting machine, the metal placed in the crucible 
depression of the investment and fused with the flame from 
an attached blowpipe of the nitrous oxide and gas type. 
When fused, the plunger which carries a sealing cap on 
its lower end is brought forcibly down upon the upper end of 
the flask, thus preventing escape of the nitrous oxide gas, 1174 
A BRIEF HISTORY OF PROSTHETIC DENTISTRY 
which is automatically admitted at the time of sealing the 
crucible space. 
Under compression of the gas, the fused metal is forced 
through the sprue into the mold. 
The essential principles involved in this process may be 
briefly summed up as follows: 
A wax model formed with or without a metallic matrix, 
an investment ring, a metallic sprue former, a metallic cru- 
cible former, a sealing cap for confining the compressed gas, 
a single investment matrix, dissipation of the wax pattern 
by heat, injecting the fused metal into the mold by compressed 
gas. 
The discovery by Dr. Taggart that in order to cast sharply 
gold must be superheated, constitutes the most valuable 
contribution to the casting process introduced within recent 
years. 
This he accomplished and demonstrated by means of his 
casting appliances to which a blowpipe of the Knapp pattern 
was adapted. With the Taggart appliance or the Knapp blow- 
pipe, gold in small quantity can be readily heated several hun- 
dred degrees above its melting point. 
In using either of these appliances, care must be observed 
not to overheat the gold or burn it. When excessively over- 
heated, even pure gold is slowly but gradually dissipated, 
while if composed of an alloy some of the lower fusing con- 
stituents will be oxidized or volatilized, thus impairing the 
quality of the metal for specific purposes. 
Again, in superheating the gold excessively, the invest- 
ment deteriorates, resulting in rough surfaces in the mold, 
change in form of the latter, and in some cases intimate union 
of the investment with the casting. 
By means of an ordinary gas blowpipe, with a free inlet 
for both gas and air, and means for controlling the same, to- 
gether with a strong pressure of air such as can be developed 
with a large foot bellows or power pump, equally good results 
may be accomplished without danger of dissipating the gold 
or impairing the investment. (See page 1026.) 
RECENT APPLIANCES 
Within recent years many devices in which some of the 
older methods of pressure mentioned were employed have 
been introduced, two of which will be described. A BRIEF HISTORY OF PROSTHETIC DENTISTRY 
1175 
THE SOLBRIG CASTING PLIERS 
This device consists of plier handles; to the shorter end 
of one is attached a pad containing moldine or moist asbes- 
tos. The opposite beak contains a depression in which rests 
the investment ring. When fused, the metal is forced into the 
Fig. 1094.— The Solbrig Casting Appliance 
mold by closing the plier handles, thus bringing the pad at- 
tached to the opposite beak in contact with the ring margins 
and sealing the crucible chamber. (Ash’s Quarterly, 1910.) 
THE BIBEE CASTING APPLIANCE 
This consists of a base for supporting the investment ring, 
and a cup device containing moldine or clay. 
Fig. 1095.— The Biber Casting Appliance (Ash’s 
Quarterly, 1910, Slightly Modified) 
When the gold is fused, the cap is applied to the ring and 
the metal forced into the mold by hand pressure. 
From this brief outline of casting operations in the past, 
the names of a number of men who engaged in this work, to- 1176 
A BRIEF HISTORY OF PROSTHETIC DENTISTRY 
getlier with a description of tlieir methods and appliances, 
have been omitted for lack of time and space. 
The writer has attempted to present in a concise and dis- 
passionate manner those facts which he has been able to care- 
fully gather from reliable sources, pertaining to the inception 
and growth up to present development of the five fundamen- 
tal principles of the casting process. 
That the science of precision casting is yet imperfect is 
evident, since the control of dimensional changes in the ma- 
terials used has not yet been accomplished. 
By simplest means and with crudest appliances some are 
able to secure results equal to the best. Others, equipped with 
the most convenient and improved apparatus meet with fre- 
quent failures. Personal equation in this as in many other 
fields largely determines the quality of results attained. 
From this outline it will also be seen that the development 
of the five fundamental principles of casting as practiced to- 
day is the result of the composite effort of many men, extend- 
ing over a period of many years. Practically all of the proc- 
esses had become, and most of them were long ago recognized, 
as heritages of the profession, since time and use had rendered 
them more or less common methods of procedure. INDEX 
Absorption of alveolar borders 18-22 
irregular 191 
under stress 49 7 
unequal 320 
Abutments, in engineering bridge con- 
struction 783 
in dental bridge work 786 
preparation of roots and teeth 
for 795 
selection of suitable roots and 
teeth for 790 
Acid for pickling 169 
Adaptation, denture, comparative re- 
sults with different bases 126 
Adhesion, physics of 24 
useful in denture retention 24 
Adjusting the face bow to occlusion 
models and face 330 
to occluding frame 332 
Affinity of metals for each other 976 
Alabaster 43 
Alexander, Dr. A. C., denture repair... 573 
Alexander, Dr. A. C., method of repair- 
ing vulcanite 573 
Alexander, Dr. C. L., inlays 1150-1152 
Allen, Dr. John, continuous gum 
590, 877, 878, 881 
Alloys 975 
affinity of metals for each other.. 976 
binary 990 
copper amalgam 978 
dental amalgam 977 
eutectic 977 
for crown bridge and plate work..1002 
for inlay casting 1006 
for prosthetic casting 1004-1005 
for tempering 1043 
Matthiessen’s theory of .'. . . 975 
specific gravity of 978 
triple 135 
Alloying metals, object in 976 
Alpha rays of radium 939 
Alumino-thermy 968 
Aluminum 1055 
denture bases 120 
cast 191 
swaged 212 
physical properties of 1056 
Alveolar borders 18 
absorption of 18-22 
adapting base plates to 313-320 
reduction of flabby 19-20 
selecting and fitting trays to 64 
Amalgam 977 
dental, history of 1145 
dies, in crown work 664 
restoration of badly decayed teeth 
with 736 
Ambler, Dr. H. L 1087 
Ames, Dr. W. V B., inlays 1149 
Anaesthetics, local 630 
Analysis of the casting process 1155 
Anatomic and esthetic forms of teeth. 
631-633 
Anatomic method of denture construc- 
tion 304-463 
masticatory mechanism 269 
Anchorage, of teeth to various bases 535 
of plastic substances to metal 
bases 174 
in restorations for crowns 736 
for inlays 910 
Ancient, prosthesis history of 1077 
records of 1086 
prosthetic appliances 1081 
Anderson, Dr. C. L., bridge 796-816 
Angle, Dr. E. H., impression trays.... 73 
Annealing metals 168-960 
An outline of metallurgy 936 
crowns for 640 
palatine foramina 11 
typal forms of 362 
Antimony 1066 
Antiquity of Ebers’ papyrus 1078 
Aphrodite facial outlines 371 
Appliances, in die and counterdie con- 
struction 128 
anatomical, Gysi 465-1124-1125 
Snow 308-1120-1121 
Application, of bridge restorations.... 786 
of crown replacements 625 
of full dentures. 304 
of heat in soldering 971 
of occlusion rims to base plates.. 314 
of porcelain 609-864-872-898 
of face bow 330 
Aqueous solutions, separating mediums. 94 
borax and shellac 94 
soap 95 
Arch, alveolar 291 
bar, palatal 522 
in engineering 783 
palatal 10 
Argol 1034 
Arranging and occluding the teeth in 
full dentures 382 
Arrhenius, Prof. Svante, nebular tem- 
peratures 952-970 
Articulation, tempero-mandibular .... 274 
of sound 401 
Articulators 
Bonwill 1114 
Christensen 1121 
Evans 1113 
Gariot 1112 
Gritman 1119 
Gysi 465 
Hayes 1115 
Kerr 1120 
Luce 1126-1127 
Plain line 1114 
Plaster 1112 
Schwarze 1123 
Snow 1122 
Starr 1115 
Walker 1117 
Artificial, dentures, physical and me- 
chanical problems involved in their 
construction 23-304 
stone 110-495 
Artistic judgment necessary in devel- 
oping wax model dentures 396 
Asbestos, for investment 689 
Ash’s tube teeth 538 
Assembling bridge, structural parts 
of a 805 
crown 687 
Atmosphere 24 
aid in denture retention 25 
pressure exerted by 25 
Atomic weight 956 
unit of 956 
Atomic relation of elements to each 
other 947 
Atoms 947 
vibration of 947 
Attaching, bite fork to occlusion model 
326 
anchorage loops to metal base 
dentures 177 
casts to occluding frame 333 
clasps to baseplate 188-268 
facings to crowns and bridge, in 
repairs 839 
peripheral shoulder wires to metal 
bases 175-489 
eeth to baseplate, by soldering... 188 1178 
INDEX 
Attachments, for retention of partial 
dentures 233 
clasps 236-500 
specialized frictional appliances.505-525 
for bridges 808 to 834 
Carmichael 808 
modified 811 
Corcoran 811 
Goslee, inlay clasp 827 
Heddy 816 
split dowel crown 821 
St. John inlay 912 
telescoping crown 820 
Autogenous soldering (sweating).... 871 
Automatic, blowpipes, Knapp, Taggart 
834 
flask closing devices 446-454 
gas regulators 452 
safety valve 453 
Babbitt metal 134-1063 
Backing, porcelain facings, in crown 
and bridge work 682 
Bailey flask 129-156 
Baking of porcelain.616-854-861-864-8 73-902 
Balancing contact. .299-307-317-354-391-404 
Banded, crowns 
640-721-733-735-820-824-849-857-861 
Bar, forms of lingual bars 491 
contact 606 
lingual, combined with gold sad- 
dles 496 
palatal arch 622 
Barium 944 
Barns, Dr., inlays 1154 
Bartlett, Dr. Walter M 38-622 
Base metals 956 
Baseplates 118 
celluloid 125 
ideal 126-230 
metal 119-126-166-180-208-222-588 
requirements of 313 
Bases for artificial dentures 118 
aluminum 120 
alloys of tin 120 
celluloid 125 
comparative results in adapta- 
tion 126-127 
gold 118 
platinum 119 
vulcanite 121-127 
Basic ingredients of porcelain 880 
constituents of rubber 436, 439 
Bean, Dr. J. B 218-1134, 1158 
Beauty, science of 360 
Beeswax 59-922 
Bennett, Dr. N. G 299-1124 
Benson, Dr. C. W 750 
Bequerel Radium 939 
Berdmore 1099 
Beryllium 943 
Bessemer steel.... 1042 
Beta rays 939 
Bevan, Dr., experiments in vulcaniz- 
ing 438 
Beveling 681 
Biber 1175 
Bilious 356 
Binary 990-1002 
Bing 1138-1143-1147 
Birkland, Dr. J. W 769 
Birmingham wire gauge 1070 
Bismuth 1060 
Bite fork 326 
modified 675 
Bite, meaning of term 327 
difficulty in taking 327 
practical method for securing. . . . 329 
various methods of such 327-330 
Black, Dr. G. V 
.18, 125, 278, 305, 306, 907, 1132 
Blanch Barkley, nugget 981 
Blandy, Dr. A. A 227-1158 
Blocks, porcelain... 532, 620, 621, 622, 1103 
Blowpipe 
flame, structure of 972-1174 
Knapp’s nitrous oxide 934 
Stiver’s gas 692 
Bodily functions 7 
impairment of 8-397 
Bogue, Dr. E. A 1147 
Bonwill, Dr. W. G. A 
238-273-308-1113-1114-1117-1118-1135 
Borax 1133 
Boron 943 
Boser’s rule 986 
Bowditch 283 
Brantt 436 
Brass 1064 
Bridgeford, Dr., rubber paste for re- 
pairs 586 
Bridges (Engineering) 783 to 786 
arch 783 
cantilever 785 
girder 784 
Howe truss 784 
pontoon 785 
suspension 785 
Bridges (Dental) 786 to 832 
fixed 786 
classification of 786-798 
extension 789, 1142 
saddle 787 
sanitary 789 
removable 817 
repair of 832 
Bridgework (dental) 786 to 832 
fixed 786 to 817 
abutments and piers 790 
preparation of teeth and 
roots for 796 
selection 791 
constructive technic 799 
factors to be considered in 
planning 790 
history of 1138 
means of attachment other 
than crowns 
Carmichael 808 
modified 809 
Corcoran 809 
Heddy 816 
inlays 773, 915 
St. John 912 
removable 817 to 832 
attachments 818 
inlay 827 
lingual half crown 829 
split dowel 821 
telescope crown 8 20 
modifications of 831 
repair of 832 to 848 
Brief outline of recent discoveries.... 938 
Britannia 36-1066 
Bromine 943 
Bronze 1055 
Brophy, Dr. R. C 220 
Brown, Dr. E. P 837 
Brown and Sharp...'. 1070 
Briick, Dr. W. W 1046 
Bryant repair system 837 
Buckingham, Dr 64 
Bunsen burner 973 
Burchard, Dr. H. H 19 
Cadmium 1060 
Caesium 943 
Cajaput 930 
Calcar 129 
Calcium 942 
Calipers 460-654 
Calorie, the unit of heat energy 121 
Candle flame 872 
Cantilever bridge 786-789 
Caoutchouc, the basis of rubber 436 
Cap, in crown work 651 
construction of 661-662 
direct method 651 
indirect method 662 
Carat, use of term 986 
Carbon 943 
Carmichael attachment 808 
modified 811 
Carroll, Dr. C. C., casting aluminum 
219-1162 
Case, Dr. C. S., enamel cleavers 644 
Cassius, purple of 882 INDEX 
1179 
Cast, definition 33 
crowns 770 
cusp of 769 
denture bases 120-190 
aluminum 120-190-1158 
Watts metal 120, 222 
trays, impression 38 
iron .1041 
Casting Counterdies 159-759-760-761 
clasps 264-827-828 
crowns 770 
dies 153-256 
inlays 933 
materials used in inlay work.... 
920 to 929-1023 
plaster 33 
rings for molding 129 
root restorations 737 
Casts, production of 90 
change of form under stress 100 
construction of 100 
distinction of term, from model... 33 
forms for 96-98 
materials used for 101 
necessity for use of resistant ma- 
terials 101 
partial cases 104 
removal of impression from 
106, 107, 109 
strengthening isolated teeth on... 105 
treating surfaces of, for vulcanite 432 
treatment of impressions for.... 105 
warpage 106 
Cavity preparation for inlays 888 
gold 907 
porcelain 888 
Celluloid 551 
dentures 551 
casts for 97, 560 
technic of construction .... 555-559 
Cement, as an impression material.. 57 
as a medium for setting crowns 
and inlays 694-886-889-906-935 
general composition of 117 
shadow problem in inlay restora- 
tion 904 
Cementation process 1042 
Cementum 625 
Cerium 944 
Change of volume in rubber during 
vulcanization 447 
color, in porcelain due to metal 
backing 682 
dimensional in material employed 
in casting 920 
Chase’s molding sand 129 
Chaser 183, 763 
Character of emanations from radio- 
active substances 939 
Chemical constituents of rubber 440 
changes in rubber due to vulcan- 
ization 441 
formulae of wax and paraffin.. 922-923 
of plaster of Paris 43 
Chemistry of vulcanization 441 
photography 1057 
Chlorination process 984 
Chlorine 942 
Christensen, Dr. Carl....275, 308, 337, 1121 
Chromium 944 
Cicero, facial outlines 369 
Cinnabar 1063 
Clamps, soldering 185, 186 
Clapp, Dr. G. W., color analysis 379 
Clark, Dr. F. H., crown 1130 
Clark, F. W., unequal distribution of 
elements 946 
Clasp metal 1009 
formulae for (Weinstein) 1010 
gauges commonly used 241 
Clasps 236 
advantages and objections 236 
application of 246-249 
indications and contra-indications 
governing 246 
requisites of 237 
Clasps—Continued. 
technic of construction 250-264 
types most commonly used 
242-249-500-505 
Classification, bridgework. 
natural teeth (Williams) 362 
temperaments 356-367 
Clay 878 
Clearing, matrix of wax in vulcanite 
work 414 
mold of wax in cast base dentures 204 
in inlay work 932 
Cleavers 644-645 
Cocaine 630 
Coefficient of expansion 965 
Coin gold 986, 994, 1036, 1037 
Coke furnace, for baking porcelain.. 1006 
Collodion 93-1110 
Colloids 436-437-945 
Color problems in tooth selection.... 373 
complementary 377 
principles, synopsis of 374 
primary, secondary, ter- 
tiary 375-3T6 
chart of Frontispiece 
Columbium 944 
Compensating curve, meaning of the 
term 300 
development of, on occlusion 
models 343 
fundamental principles of.... 344 
omitting 353 
practical steps in .. 348 
Ulsaver’s method 352 
Wilson’s method 354 
- modification of 302 
Composition, alloys of gold plate...... 
987-1002, 1003-1014 
artificial stone 110 
Babbitt’s metal (Haskell’s).. 134-1063 
beeswax 922 
celluloid 561 
clasp, metal 988-1024 
dental rubber 439 
flux, oxidizing 1035 
reducing 834 
soldering 1032-1036 
gold, for casting 1005-1006-1008 
investment materials ..1044-1046-1047 
Melotte’s metal 135-136-1065-1066 
modeling compound 68 
plaster 43 
porcelain continuous gum body.. 880 
gum enamel 882 
solders gold 987-1012-1014 
platinum 988 
silver ...1057 
tinner’s 1062 
Compressibility of plaster 56-428 
Condit, Dr., attachment 612 
Conductivity, denture base material.. 121 
electricity 963 
heat 962 
Condyles, articular surfaces of man- 
dible 274 
form of 272 
location of 272 
paths of t 274 
lateral \ 297-472 
methods of registering. ... 336-466 
protrusive 296-466 
variation in pitch of 275 
Conic forms of natural bicuspids and 
molars 633 
method of band construction.. 635-745 
Constitution, Kinetic, of matter 944 
Construction of, dentures 304 
aluminum 190-208 
celluloid 661 
continuous gum 588 
wax model 405 
weighted 221 
vulcanite 304-463-476 
bridges ...783-825-867-876 
casts 96-97-100 
cores 99 
counterdies ...139-159-165-769-760-761 
crowns. .625-782-820 to 832, 849 to 869 1180 
INDEX 
Construction of—Continued. 
dies 139-153-165-256 
inlays 877-935 
occlusion models 314 
Continuous gum, body and enamel.... 
608-880-882 
dentures 388 
advantages 588 
disadvantages 588 
sequent step in construction.. 
588-619 
Contouring, shell crown band 749 
cast crowns 770 
continuous gum dentures 688 
occlusion models 322 
patterns for seamless crowns... 773 
pliers 268-750-751-876 
wax model dentures 395 
Contour models in anatomic work... 313 
construction of 314 
Copper 1053 
alloys of 1054 
amalgam 978 
as a hardening agent in gold 
alloys 1002 
Corcoran attachment in bridgework.. 
787-811-814 
Cores 99-142-147 
Coronium 952 
Counterdies 159 
construction of, by casting 159 
dipping '. 161 
metals and alloys 136 
fusing points of 136 
for partial denture bases 164 
partial 162 
requirements of 136 
Countersunk, pin teeth 538 
retention holes, aluminum bases 
210-218 
root cap 669 
Cradle, in placer mining 982 
Crowns, artificial, various forms. . .625-782 
banded, baked porcelain 850 
Bean 1133 
Beers 1134 
Black 1132 
Bonwill 1135 
Brown 1137 
Buttner 1136 
cast 770 
Clark, F. H 1130 
Davis, plain 725 
banded 733 
cast base 731 
DeChemant 1128 
Dwinelle 1131 
Foster 1130 
Fauchard 1092 
Gates 1134 
How 1136 
Johnson & Bund 716 
.Tusti 730 
Logan, plain 717-1137 
banded 721 
Land, jacket 861 
lingual half 828 
Mack 1133 
Morrison 735-1132 
porcelain faced 640 
jacket 8 56 
Richmond 1135-1 140-11 41 
shell, two piece 735 
seamless 772 
shoulder 771 
Smith 1129 
split dowel 821-825-1130 
telescope 820 
tube, Ash’s 529-1111 
Twentieth Century 716 
Weston 1136 
White, S. S 1138 
Wood 1131-1132 
wood pivot 1129 
replaceable porcelain teeth and 
facings for 696 to 725 
diatoric 716 
Dimelow 833 
Crowns—Continued. 
Evslin 702-703-704 
flat back, Asli’s 538-540 
grooved 1129 
Gardiner 712-713-714 
Goslee 707 
long pin 700 
Merker 714 
Steele 697-698-834 
technic of construction 697 
cap and dowel 641-662-663 
cast base . 731 
plain base 726 
shell 739 
various repair methods for 832 
crown slitter 846 
post puller, Skinner 844 
White, S. S 845 
systems, Bryant 838 
Steele’s 834 
Crucible, in steel production 1042 
chamber 1175 
former 201 
space in investment 1174-1175 
Crystallization, of plaster 47 
effect of cohesiveness on metals.. 
959-960-961 
Crystals of plaster, size of 48 
Cupellation 1050 
Curie, Madame 939 
Curve, compensating 300 
Spee, Graf von 302 
Cushing, Dr. George H., clasp 241 
Cusps, development of in crown 
work 755-772 
adapting to axial band 763-766 
developing in plaster 754 
metalline compound 761 
wax 755-764 
reproducing in gold, casting 769 
swaging 759 
Custer, Dr. L. E., furnace 902-1162 
Cutting, bands in crown work651-744 
conic method ..635-746 
compensating curve on occlusion 
models 343 
Cyanide process 984 
David (facial forms) 371 
Davis crown 725 
Debasement of elements 940 
DeChemant, early porcelain work.... 1101 
Decomposition oxides of aluminum... 969 
radium compounds 939 
Deglutition, the tongue as an aid in 14 
Dental amalgam alloy 977 
alloys 978 
arch 291 
bridgework 786-848 
organs 288 
Dentimeter for root measurement.... 649 
Dentin 625 
Dentures, anatomic method.... 304 to 475 
full cases 304 
Gysi system 465 
technic 465-475 
Snow-Christensen method.... 304 
technic of 304-466 
partial 475 
balance of 624 
technic of 475 to 625 
repairing 561-687 
Developing, balancing contact 391 
cusps in gold 759 
metalline compound 761 
plaster 754 
wax 764-766 
in crown work.. 641 
Diatomaceous earth 1020 
Dies, definition 33 
for clasp construction 256 
for denture construction 153 
metals used for 132-134-136 
purpose of 126 
Differential limit 299 
Digestion 7-8 INDEX 
1181 
Dimelow facing 539-540-857 
Direct method of casting denture 
bases 200 
counterdie construction 759-761 
inlay, matrix and wax model for- 
mation 896-918-929 
root cap construction 659-661 
Discoloration of pink vulcanite in re- 
pair 567-571 
Discoveries, recent, in chemistry and 
metallurgy 938-945-952-968-969 
Dispersion of light 374 
Distal margins of upper denture, out- 
line form of 30-312 
Distribution of elements, unequal.... 946 
Dobereiner, triads of 948 
Donham flask spring 433-434 
Dovetailing, preliminary in vulcanite 
repair work 576 
Drawing split dowels 823 
Draw-plate 823 
Du Chateau, first efforts in porcelain.. 1101 
Ductility 959 
Duff, Prof. A. Wilmer, Kinetic consti- 
tution of matter 946 
Dummies, various forms of 
801-802-803-804 
Dunn, Dr. C. W., inlays 1148 
Dwinelle, Dr. W. H., crown 1131 
Early efforts in porcelain 1101 
records of dental prosthesis 1086 
specimens of denture replacements 
1081 to 1086 
Edge tools, table for tempering 1043 
Effect of X-ray on various substances 941 
Eka-aluminum 952 
Eka-boron 952 
Eka-silicon 952 
Elasticity in metals 962 
modulus of 962 
rubber 439 
Electricity, conductivity of metals.... 963 
exceptions 962 
Electrons 945-946-952 
Electro-welding 967 
Elemental gases 938 
electricity 970-971 
Elements 937 
outline of recent discoveries 938 
table of, in order of discovery.... 942 
atomic weight 943 
periodic table of 951 
their atomic relation to each other 947 
Elgin casting machine 935 
Eliminating -wax patterns in casting.. 
204-225-932-1155-1157 
Emery lathe bands 457 
Eminentia articularis 274 
Enamel, removal of from roots 644-739-741 
Enameling metal caps in crown re- 
placements 1131 
Engineering, principles of bridge 783 
Enlarged raphe 11 
Equalizing denture bearing 105 
Equilateral triangle of Bonwill 273 
Esthetics of denture construction 2 
tooth selection 355 
Etching porcelain inlays 906 
Ethereal solution 93 
Etruscans 1081 
dental art of 1082 
Eucaine 630 
Eutectics 977 
Evans, Dr. Daniel T 1013 
Evslin tooth in crown and bridge con- 
struction 702-703-704 
Expansion, coefficient of 965 
compensating for 29-133 
control of . 53 
of investment materials 
925-1016-1023-1024-1029 
of plaster 51-52-1019 
silex 1020 
wax 921-1029 
Expression, muscles of 279 
Extension, bridge (see cantilever).. . 
785-789-1142 
Extraction of gold 983 
metals 936 
Eye, color functions of 377 
Face bow 309-1116-1120 
adjusting to occlusion models.... 330 
occluding frame 332 
bite fork of 326 
application to occlusion mod- 
els 326 
object accomplished by its use... 309 
Facer, root, Ottolengui 659 
Roach 660 
Facial outlines 360 
profile 322 
Facing gum porcelain..542-544-608-617-882 
granular 440 
vulcanite, pink 439 
in repairs 567 
Facings, teeth, Dimelow 539-540-833 
Evslin 702-703-704 
flat back, Ash’s 540 
grooved 1129 
long pin .....680, 715, 839 
Steele 697, 698, 834 
Factors to be considered in crown- 
work 626 
bridgework 790 
denture construction 23 
Facts, hypothesis, theories and specu- 
lations 937 
Farragut, Admiral 367 
Fauchard, bridgework 1092 
crown work 1091 
dentures 1093 
summary 1095 
Feldspar 879 
Fenner 1163 
Ferrite 975 
Fine, Dr. W. M 459 
Finishing, bridges 806 
crowns 693, 725, 767, 781 
dentures 456-461 
inlays 935 
Finley, Dr. M. S 1152 
First reference to prosthesis 1086 
Fixed dowel crowns 640-716-721 
Flame, structure of 971-974 
Flare of axial surfaces of bicuspids 
and molars 633 
average 634 
greatest 634 
least 634 
Flasks, casting 11 
Bean’s 1159 
Carroll’s 1162 
Fenner’s 1163 
Hayford’s 1161 
Watts 224 
molding 129 
Wood’s 203 
Zeller 1162 
Bailey 129-156 
Hawes’ 129-156 
Lewis’ 129-157 
rings, nest of 129 
vulcanite 408 
Flashing, aluminum, wax models 
for 196-201 
celluloid 566 
vulcanite, full cases 410 
partial cases 481 
Flexure, elasticity of 239 
Flow of metals under stress 962 
Fluorine 944 
Flux, oxidizing 1035 
reducing 1034 
soldering 1032 
Fogg’s interstitial gum facings.... 480-620 
Fonzi, teeth 1103 
Force of mastication 271-306 
Forms of matter 955 
Formulae for casting gold “A,” “B,” 
“C,” “D” 1005-1008 
clasp gold 988-1010 
dental alloy 1048 1182 
INDEX 
Formulae for casting gold—Continued. 
amalgam alloy 977 
gold solder 987-1014 
gold plate No. 1-2 1002-1003 
investment compounds (casting).. 1028 
investment compounds (solder- 
ing) 1022 
oxidizing flux 1036 
platinum solder 988 
reducing flux 1034 
silver solder 1051 
soldering flux 1032 
specific gravity 957 
Foster crown 1130 
Fracture of enamel 645 
Fractured bridge 847 
vulcanite dentures 661 
Freezing of metals 957-1007 
French’s impression plaster 52-101 
Friability of porcelain 885 
Frictional or working surfaces of the 
teeth 288 
Full dentures (see dentures) 
Furlong’s plastic rubber 686 
Furnaces, porcelain 613-614-873-874 
Fusible metals (Hall’s formulas).... 1066 
Fusing point of metals 957 
Gadolinium 943 
Gallium 943 
Gardiner, replaceable facings 712 
Gariot, Dr. J. B 1112 
Garretson bite guide 328 
Gas and nitrous oxide blowpipe 934 
regulator 451-452 
Gasoline furnace 874 
Gates crown t 1134 
Bonwill crown .* 1135 
Gates, for surplus rubber 417 
Gauges, steam 450 
Gauging amount of rubber 427 
General classification of bridgework.. 786 
Genese, Dr., developing lingual forms 
of teeth in vulcanite 459 
German silver trays 39 
Germanium 944 
Gilmer, Dr. T. Ij., suggestion for cor- 
rect mounting of casts 1116 
Gilmorej Dr. Steele, frictional attach- 
ment 514 
Gingival, termination of cementum. . 626 
Girder, in bridge engineering 784 
Glaesenapp, Prof. M., plaster 45 
Glands, salivary, function of 15 
Glass inlays 1046-1049 
Glazing porcelain 618-928 
Glenoid fossa 274 
Gold 1016-1039 
alloys of, see index 
carat, meaning of term 986 
extraction 983-984 
formula, see index 
mining 981 
preparation of pure 985 
reduction of (Boser’s rule) 986 
solders, see formulae 987 
treatment of scrap 985 
Goldschmidt, Prof 969 
Goslee, Dr. H. J 193, 827, 930 
tooth 707 
technique of application 708 
Graphite 925-1029 
Gravity, specific, formula for estimat- 
ing 957 
casting. . .222-1158-1160-1161-1164-1170 
Greene, Dr. J. W 27, 87 
Grinding porcelain crowns 717, 728 
facings 680-693-863 
Grinding to correct occlusion 388 
Griswold attachment 624 
Griswold, Dr. W. M 1153 
Gritman, Dr. A. D 1119 
Groove, rectangular 288-290 
Ground gypsum 44 
Guerini, Dr. Vincenzo 1077 
history of dentistry 1079 
Gum, sandarac 93 
Gutta percha 62 
Gysi, Dr. Alfred 308, 460-465, 1124 
Half band crown 821 
crown 828 
round wire clasps 243 
for split dowels 822 
Hammond furnace 614 
Hancock, Thomas, vulcanite 438 
Hard, bite wax 60 
solder 971 
Hardening steel 1042 
Harmony defined 368-374 
laws of, applied in tooth selection 360 
Harper, Dr. W. E 741-1163 
Haskell, Dr. L. P 134-135-1063 
Hawes, Dr. G. E 129-148-1160 
Hayes, Dr.' R. S 1116 
Hayford, Dr. J. W 1160 
Head, Dr. Joseph 306 
Heat 962-964-965 
Heating, flask in vulcanite work 419 
investment for soldering 1030 
for casting inlays 1030 
Hebrews, dentistry among the an- 
cient 1087 
Heddy, Dr. 816 
Helium 943 
Heinrichsen appliance 504 
Herbst, Dr 1149 
Herder, reference to mouth 3 
Herodotus, reference to ancient den- 
tists 5 
Hickman, Dr., inlays 1171 
High and low fusing porcelains 885 
lip line 324 
temperatures 969 
Hindu prosthetic specimens 1085 
Hinge tray 677 
Hippopotamus, dentures of 1086-1090 
Histology 626 
History of dentistry (Guerini’s) 1079 
Holder, cotton roll 768 
crown 767 
Hollingsworth, Dr. M. W. 1164 
Horn, mallet 171 
pene hammer 262 
Hot and cold molds 
933-1025-1026-1030-1063 
How, Dr. W. S., crown 1136 
Hutchinson, Dr., on temperaments.... 356 
Hydro-carbon, rubber 440 
Hydrogen, debasement of other ele- 
ments into 940 
Hygienic requirements of crowns 639 
Hyperaemia, duo to mechanical irrita- 
tion 124 
Hypothesis in reference to elements... 937 
Impression 33 
materials 42 
beeswax 59 
beeswax and paraffin 59 
cements 67 
classification of 42 
gutta percha 61 
modeling compound 58 
plaster 43 
of clasp, teeth and baseplate 267 
of root in crown wprk 663 
of teeth to be clasped 252 
rebuilding 254 
relieving 27-31 
technic of taking 63-68-69-71-72-74 
difficult cases 79 
modeling compound 81-86 
partial cases 73-495 
plaster 63 
tray 34 
fitting 36-38-64 
hinge 677 
nomenclature 36 
special 38-39-40 
treating and filling of 90-105 
Incisor teeth 288 
path 295 
registering 469 
Im’ia rubber (see caoutchouc) 436 INDEX 
1183 
Indirect method of constructing cast 
aluminum bases 193 
counterdie 760 
inlay matrix and wax model... 918-919 
root cap 662-836-856 
Indium 943 
Individual saddles 788-802 
Infection, the mouth as a focus of.... 8 
Inflammatory mucous tissue under vul- 
canite 122 
Inlays 877-935 
gold, cast 920 
cavity preparation 907 
matrix method of production 918 
direct 918 
indirect 919 
technic of construction 929 
physical properties of ma- 
terials employed 920 
porcelain 877-884 
basic ingredients 878 
properties 880 
cavity preparation 889 
technic of construction ...895-907 
Insoluble constituents of rubber 440 
Inter-articular fibro-cartilage 274 
Interchangeable teeth 706 
diatoric 716 
Evslin (posterior) 702 
Gardiner 712 
technic of application 712 
Goslee 707 
technic of application 708 
Merker 714 
Steel, posterior 697 
tooth facings 697 
Ash 631 
Dimelow 640, 833 
Evslin 702 
long pin 700 
Steele’s 697 
application 697 
Internal lateral ligament 286 
Investing, aluminum, wax pattern for 
..196, 203 
banded, Logan 724 
bridge, for soldering 806 
cap and dowel 672 
celluloid 556 
continuous gum, for soldering.... 600 
Richmond crown 690 
vulcanite, wax model denture for.. 410 
wax model inlay for casting 931 
wax model for weighted lower.... 223 
Investment, compounding of 1028 
compounds for casting 1023 
soldering 1016-1020 
directions for use 1029 
for aluminum cases 203 
heating of 1030 
Iodine •. .. . 631 
Iridio-platinum 999 
Iridium 999-1048 
Iron ores 1038 
haematite 1039-1040 
magnetic 1039 
occurrence 1039 
pyrites 1040 
reduction of 1040 
spathic 1040 
forms of 1039 
cast 1041 
steel 1041 
wrought 1041 
Ivory appliances 1086-1090 
Ivory, Dr. J. W 644-768-819 
Jacket crowns, porcelain 856 
Land 861 
Jenkins’ porcelain 883 
Jewelers’ gauge ...1071 
gold plate ..1087 
Johnson and Lund crowns 716 
Joint, tempero mandibular 274 
bevel in vulcanite repairs 564-565 
Juno, facial outlines 371 
Justi crown 730 
impression trays 65-74-87 
porcelain body 883 
teeth, gum sections 621 
plain 526 
Justi, H. D„ teeth .536-621 
K plier for inlay work 900 
Kaolin 373 
Kelly attachment 623 
Kennedy, Dr. E., modified Carmichael 811 
Kerr articulator •...1120 
impression trays 82-85-88 
metal forms for casts 96 
soldering tweezers 766 
Kieselguhr 1020 
Kinetic, constitution of matter 944 
Kingsley alloy 227 
scrapers 29-468 
Knapp, Dr. J. Kollo, blowpipe... 934-1172 
bridgework 1142 
Knight, E. H., definition of a sprue..1166 
Koch, Dr. C. R. E., history of den- 
tistry 1087 
Krypton, discovery of 837, 838 
Labial, contouring of occlusion mod- 
els . 316 
Ladles, melting 131-266 
Land, Dr. C. H., porcelain inlays.... 847 
jacket crown 865 
Lane, Dr. J. G., silica 1024 
Lanthanum 943 
Lathe, polishing 456, 457-461 
Lavater, discourse on the mouth 3 
Lawrence-Foster crown 1130 
Lead method in silver reduction 1160 
physical properties of 1161 
Le Gro, Dr. A. L., cavity of prepara- 
tion 917 
Lever, the mandible as a 271 
Leverage on denture bases 26 
Lewis flask for molding 129-157 
Ligaments, the mandibular 284 
capsular 286 
lateral 286 
external . . . 286 
internal 286 
spheno-mandibular 286 
stylo-mandibular 286 
Lime block, in fusing platinum 1047 
Lingual muscles 14 
marginal ridges 388 
Lips as a feature of the face 9 
as a guide in establishing plane of 
occlusion 320 
Liquation 976 
Liquid silex in vulcanite work..... 417, 432 
Lithium 943 
a product of debasement of cop- 
per 940 
Litigation, dental vulcanite 1109 
Lixiviation, in recovery of gold 984 
Locating high and low lip lines. ... 318-324 
median line 318-324 
outer ends of condyle3 318-325 
Logan, Dr. M. L., crown 1137 
Loop clasps 500-501-503-504-606 
Loose pin anchorage for inlay abut- 
ments 917 
Lower jaw (mandible) 270 
Luce. Dr. C. E., condyle movements, 
and articulator 283-1126 
Lymphatic temperament 356 
Magnesium 942 
chloride 113 
in alumino-thermy 968 
Magnetic iron 1039 
Malleability 969 
Mallet, horn 171 
horn pene 262 
Mallett, Dr., experiments in vulcan- 
izing 438 1184 
INDEX 
Mandible 270 
analysis of lateral movements . . 29 7 
articulation with temporal bone .. 274 
auxiliary functions 271 
centers of notation 297 
governing factors in movements of 295 
muscles which control 282-284 
Mandibular ligaments 284-286 
governing factors in movements.. 295 
Manganese 944 
Manufacture of celluloid 552 
dental rubbers 436-441 
gutta percha 61 
plaster 14 
porcelain 878-883 
steel 1042 
wrought iron 1041 
Marble dust 129-1019-1164 
Martin, Dr. G. M., casting 1161 
Mash bite 188-478-576-579-673 
Mason spacing calipers 683 
Mastication muscles of 284 
restoration of function of 1-304 
Masticatory apparatus 269 
mechanism 269 
movements 273 
muscles of 277-284 
Matrix counterdies 163 
contour, In continuous gum cases. 598 
direct method of production 918 
Indirect method of production.... 919 
packing in vulcanite denture con- 
struction 418-426 
production of platinum, In porce- 
lain inlay work 887-905 
sand 139 
seamless crown method 773 
Matter, forms 9 55 
mutability of 937 
Matthiessen’s theory of alloys 975 
McClelland, Dr., rose pearl 551 
McJjeod. Dr. W. Bowman, expansion 
of plaster 54 
Measurement, angular divergencies of 
axial walls of bicuspids and molars. 634 
compressibility of plaster 56 
cutting band according to 651-745 
expansion of plaster 52 
plate and wire 1068 
root, in crown work 649-743 
width of band 744 
Mechanical and physical problems in- 
volved in denture construction .... 23 
Medieval bridgework 1092 
Mediums, separating 92-95 
Melotte’s metal and other fusible al- 
loys 135-10616 
Melting point, explanation of 957 
Mendeleeff, Dimitri, periodic system 
°* 950-952 
Mercury 1063 
Merker, Dr. M. K., tooth 714 
Metabolism 7 
Metals, alloys of 975 
a new series of 1001-1016 
binary 990-1001 
alloying 976-978 
base 956 
native 956 
noble 956 
physical properties of 966-974 
Metallography 935 
Metalloid 955 
Metallurgy 936 
Methven, Dr. H. F 814 
Meyer, Dothar 959 
Michaels, Dr. W., translation of Glae- 
senapp’s work 45 
Micro-structure of metals 976 
Micrometer caliper 1073 
Microm 945 
Miller, Dr. H. C., celluloid flask 656 
Millimeter 946 
Mineral, first reference of, for teeth.. 1089 
Minerals, occurrence of, in nature.... 965 
Mixing: cement 694 
investment 931 
plaster 66 
porcelain 899 
Model, use of term 33 
of tooth for seamless crowns.. 773-771 
wax contour and occlusion 313 
denture 313 
for inlay 929 
Modeling compound 58 
composition 58 
manipulation 81 
Molar tooth forms 288-293 
typical forms of 756-757 
Mold, eliminating wax from 932-1157 
-variation in method of 932 
expansion of 927 
formation of single 1156 
Molding sand 129 
Molecular tension 169 
disturbance 211 
theory of matter 944 
Molecule 944 
Molybdenum 942 
Morgan attachment 509-510-511-512 
Morrison, Dr. W. N., crown 711-1132 
Mouth, a focus of infection 8 
examination of 18 
Mucous membrane of the palate 12 
plaques 124 
Muscle marking impressions.. 37, 67-71-86 
Muscles of mastication 277 to 284 
action, summary of 284 
Native metals 966 
Natural denture 288-289-290 
Necessity for use of face bow 309, 330 
Neodymium 943 
Neon 943 
Nero, facial outlines 372 
Nervous temperament 356 
New elements 938-952 
Newlands, octaves of 950 
Newtonium 952 
Nickel 1065 
Nitrogen 943 
Nitrous oxide blowpipe, Knapp’s. . 934-1172 
Noble metals 956 
Nomenclature tray 35 
Nonconductivity of vulcanite 122 
Noyes, Dr. Frederick B., histology ..10-626 
Occlude, definition of the term 288 
Occluding frame 307-308 
adjusting condyle paths of .... ‘M2 
applying face bow with occlusion 
models attached to 332 
arranging teeth to occlusion mod- 
els on 382 to 390 
Gysi and appliances 466-1124 
mounting casts on 332 
removing casts from 406 
Snow, and appliances 
308-332 to 353, 382 to 393, 1122 
various types of the 1109-1128 
Occlusal plane, meaning of the term 293 
curvature of 293 
determining correct 319 
Occlusion, anatomical, of natural den- 
tures ' 289-290-294-301 
models 313 
adjusting bite fork and face 
bow to 330 
arranging the teeth on 382 
construction of 314 
developing compensating curve 
on 343 
restoring dis' rbed facial con- 
tour by means of 322 
rims, approximate depth of. . . 315 
bucco-lingual relation of, 
to borders 315 
establishing height of in- 
dividual 319-320 
requirements of 314 
trial of, in the mouth 318 
points determined by.... 
318 to 327 
retainer 412 INDEX 
1185 
Occurrence of metals in nature 955 
Octaves of Newlands 950 
Offset crowns 632 
dowels 727 
Ollendorf casting appliances 1170 
Onlays 1168 
Opaque porcelain 905 
quality of cement ... 904 
vulcanite gum facing 440 
Oral cavity 9 
boundaries of 9 
contents of 9-14 
teeth 9-288 
tongue 13-14 
mucous membrane of 10 
epithelium of 10 
palatine vault 10 
bony structure of 10 
foramina of . 11 
rugae of 13 
vestibule of 9 
cul de sacs of 9 
Ores 956 
Osmium 944-1000 
Ottolengui, Dr. R., root-facers 659 
Outline, an, of metallurgy 936 
Overbite 301-535 
Owen, Prof., prehistoric inlays 1145 
Oxides, reduction of, with flux.. 971-1031 
(See noble and base metals) 956 
Oxyacetylene blowpipe 970 
Oxychlorid of magnesium 110 
zinc 20-117 
Oxygen 943 
Oxyhydrogen flame 970 
Oxyphosphate of zinc 20 
Packing rubber in vulcanite cases... 
418 to 428 
Palatine vault 10 
epithelium of 10 
Palladium 944-997-1002-1003-1005-1010 
Papyrus, Ebers’ 1077 
antiquity of 1078 
Parabolic arrangement of the teeth in 
the dental arches 292 
Paraffin 59-922-923 
Parker shot swager 163-164 
Partial dentures 476 
baseplates for 476 
gold, technic of 180-189-488-490 
lingual bar 496 
vulcanite 477-484 
lingual bar 490-491 
flasking of 481 
planning of 476 
protrusive bite for 478 
retention of 187-233-236-476 
settling of. from use 497 
specialized frictional appliances for 
500 to 524 
Pathological conditions, oral 628 
treatment of 629 
Peeso. Dr. F. A., removable bridge 
methods 818-989-1023-1032-1037 
removable crown and bridge work 989 
Pepperling, Dr. T. D , .. . 931 
Peridental membrane 625 
Periodic table of the elements (Men- 
deleeff) 950 
law 954 
Peripheral outlines of derftures 400 
Perlite in micro-structure of steel.... 975 
Permanent dentures, when to introduce 21 
Philbrook, Dr. B F., inlays 1167-1168 
Phoenician dentis. ;* 1080-1081 
Phosphor bronze 1055 
Phosphorus 944 
Photography, chemistry of 1051 
Physiological relations of teeth and 
surrounding tissues 627 
Pickling, acid bath for ..169-170 
Pier, definition of 783 
Piers and abutments 790 
preparation of teeth and roots for 795 
selection of 790 
Pig iron 1041 
Pigments 375 
Pink gum facing, porcelain 608-882 
protesyn 6?7 
granular 440 
vulcanite 439 
Pivot crowns, De Chemant 1128 
Fauchard 1092 
wood 1129 
Placer mining 981 
Plain line articulator 1114 
Plaster models to arrest expansion of. 133 
Plaster of Paris, accelerators for 101 
advantages of, for impressions.... 56 
as a binder in investments.... 97-1019 
chemical composition of 43 
compressibility of 56 
contraction of 52 
deleterious properties of 101 
deterioration when heated 101 
expansion of 51 
control of 51 
warpage as result of 53 
indications for use in impressions 63 
influence of mixing on quality. ... 51 
manufacture of 44 
setting, time required for 45 
size of crystals 48 
use in cast production 103 
Plate and wire gauge 1075 
gold for denture bases 167 
annealing 168 
carat of used 167 
for crown, bridge and plate 
work 1002 
gauges used 168 
Platinum 1043 
alloys of 995-1048 
fusing of, Custer’s method 1046 
in clasp metal 1009 
physical properties of 1045 
uses 1047 
Pliers used in crown, bridge, denture 
construction 258-750-751-876 
Plumpers for facial contour restora- 
tion 317, 323 
Polishing vulcanite dentures 456 
Polyprene-india rubber 441 
sulphides, formation of, in vulcan- 
ization 442 
Pontoon bridge (engineering) 785 
Porosity in porcelain 619-904 
in vulcanite 441 to 445 
Portland cement 101 
Possible stellar temperatures 970 
Potassium sulphate as an accelerator 101 
Pouring gaine 1156 
Melotte’s metal 256 
metal dies 154 
counterdies 160 
Watts 225 
Powder, glass 1146-1149 
silex 1020 
talcum 352 
Praseodymium 943 
Prehension 296 
Preliminary considerations in crown 
work 625-736 
dovetailing of denture base in re- 
pairs 576 
steps in flask closing 428 
impression taking 64 
packing the matrix 418 
securing anchorage of teeth to 
metal bases 174 
Preparation of cavities, special 912 
continuous gum body 608 
pure gold 985 
roots or teeth for abutments 
642-739-771-795-867 
Preparing impression for cast produc- 
tion 74 
ingredients for porcelain 879-880 
Pressure, atmospheric 25 
applied in flask closing 428 
metal casting 1157 
Price, Dr. W. A 883-927-1067 
Principle, object sought in denture 
construction 1 to 6-304 
Principles, a synopsis of color 374 
...1041 1186 
INDEX 
Primary colors 375 
Prismatic colors 374-376 
Pritchett, Dr. T. W 1-299 
Production of casts 90 
aluminum bases by casting 200 
swaging 212 
Profile, facial 320-321 
Proportionate parts of teeth. 644 
Prosthetic dentistry, definition and 
scope of J 
Prout’s hypothesis 947 
Providing for escape of surplus cellu- 
loid 
rubber 417 
settlement of dentures under stress 
497-517 
uniform bearing of dentures on 
tissues 27 to 30 
Proximal cavities for inlays, prepara- 
tion of 890 to 895-908 to 917 
contact restoration of 632-738 
surfaces reduction of 479 
views of bicuspids and molars.... 
756 to 759 
Pruyn, Dr. C. P 20 
Pterygoid muscles 278-280-284 
Pulp devitalization in crown work. .627-641 
Pumice 460 
Punch, anchorage loop 217 
Mason 634 
ordinary plate 342 
perforating 217 
riveting 343 
Young 634 
Purple of Cassius 882 
secondary color 376 
Pyrometer furnace 614-964 
Pyroxylin, basis of celluloid 651 
Quartz 880-1020 
Quicksilver - 1063 
Radio-active substances 939 
Radium 939 
Ramsay, Sir William... 937-938-940-941-946 
Ransom and Randolph, vacuum cast- 
ing machine ••• 935 
Raphe 11-18 
Rawlinson, Dr. John, dentures for.... 468 
Rayleigh. Lord 938 
Rays, alpha 939 
Wta 939 
'gan-nfia 939 
X 938-939 
Reaming 667 
Rebuilding an impression for die cast- 
ing 264 
Recent discoveries, a brief outline of.. 938 
Recording the condyle paths 336 
Red, color principles 376 
rubber 439 
Reducing flame 974 
flux 1033 
Reduction, alloys of mercury 1064 
aluminum 1056 
copper 1064 
gold 986 
rule for (Boser’s) 986 
iron 1040 
lead 1061 
silver 1049 
tin 1062 
Reinforcing partial baseplates of gold 180 
detailed methods 180-181 
platinum bases 591-594 
Reese, Dr. C. N., pin shaver 687 
Reese, Dr. C. N., casting 1160 
Refining gold 986 
Reflection gold base against teeth 182 
Refractory materials 1016 
Registering condyle path....' 336 
Regrinding of teeth 462 
Reheating modeling compound impres- 
sions 83-84-85 
Relation, atomic, of elements 947 
root cap and dowel in crown work 671 
securing of, between clasps, teeth 
and baseplates 266-267-483 
Relief of dentures over hard palatine 
areas . 27 
border crests of lowers 31 
Removable bridge work 817 
attachments 818 
Removal of a banded dowel crown.... 842 
dowels from root canals 844-845 
natural crowns 642 
shell crowns by leverage force... 846 
slitting 836 
temporarily set crowns 696 
Removing the enamel from teeth and 
roots 644-739 
whx from matrix in inlay work.. 932 
vulcanite cases 414 
dowels from root canals 844 
Repairing crowns and bridges 833 
dentures of vulcanite 561 
Replacing crown and bridge facings.. 
833 to 843 
Replaceable teeth and facings 696-734 
Reproducing cusp surfaces in gold in 
crown work 759-769 
gum surfaces in porcelain 617 
natural denture in porcelain teeth 
and wax 547 
Reproduction of natural tooth forms 
in porcelain 364 
of wax model dentures in perma- 
nent materials ... 407 
Requirements of an impression mate- 
rial 42 
of a partial denture 233 
of a base plate 313 
of an occlusion rim 314 
Requisite of die metal 131 
counterdie metal 136 
clasps 237 
models 97 
denture bases 118 
Residual ridges 18 
Resiliency of clasps 238 
Resistance to stress of casts, necessity 
for 110-428 
dies 132 
Restoration of facial contour 322 
masticatory function 1-269, 463 
Reswaging partial gold bases 186 
platinum bases plates 95 
Retainer occlusion 412 
Retention of dentures, full 23 
partial 233 
Rhodium 944-1000 
Richmond. Dr. C. M., crown 1134 
Rideout, J. B 832 
Ridge lap 544-545 
Rigid baseplates, necessity for ....118-313 
Rim occlusion, requirements of 314 
Ringer’s solution 630 
Roach. Dr. P. E 235-265-500 
attachment . . .503-505-508-660-769-818 
Roentgen. Prof. William 938 
Rollins. Dr. W. H., inlays 1148 
Rolling mill for gold 1069 
Roman, lady, facial outlines 372 
history of prosthesis 1086 
prosthetic specimen 1086 
Root preparation for dowel, crowns. . . 
641 to 650 
shell 736-743 
porcelain jacket 856 
Rouge and alcohol as an anti-flux.... 1153 
as a polishing agent 693 
Rubber, composition of dental 439 
derivation 436 
vulcanization o’ 454 
chemistiy ot 441 
Rubidium 943 
Ruthenium 943 
Saddle bridges 787 
indiv: ual for dummies 788 
with ingual bar 496 
Saliva, function of 15 1187 
INDEX 
Salivary glands 15 
Salts of radium 939 
Samarium 911 
Sand, molding 129 
Sandarac varnish 93 
Sanford 378 
Sangufne temperament 366 
Saphira facial outlines 368 
Sauer, Dr. C., casting 1160 
Scandium 913 
Schimmelpennick, Mine., facial forms 
360-361 
Schottler, Dr. Jacob, inlay 1168 
Schwartz, Dr. G. W 623-1143 
Scrapers, vulcanite 457-458 
Screw estimating force of, in flask 
closing 428 
presses 433-434 
Seamless crowns, matrix method 772 
die method 776 
Sectional molds in vulcanite work.... 407 
Watts’ metal casting 223 
seamless crown work 777 
Second vulcanization effect on pink 
vulcanite 667 
Secondary contraction in gold in cast- 
ing operations 928 
Selection of impression trays 36-64 
teeth, esthetics of 355 
suggestion in 380 
Selenium 944 
Sense of harmony 369 
taste 14 
Separating mediums 92 
Separation of impressions from casts 
106-107-108-109 
die and counterdie 161 
Setting crowns and bridges.... 767-807-826 
inlays 906-935 
Shade guide in tooth selection 546 
Shadow problem in inlay work 904 
tooth selection 379 
Shears for crown and bridge technic. . 658 
Shot swager, 'Parker’s 164-165 
Shoulder crowns, cast gold 771 
porcelain jacket 856-857 
Shrinkage of metals in passing from 
liquid to solid state 132 
Shut (proportionate parts of teeth). . 
644-646 
Sieve in molding 130 
Silex, powdered, as an ingredient in 
nvestments 925-1020 
Sinca, fused utensils of 1020 
Si""on 944 
Silver, a.ioys of 1050 
conductivity of 963 
ores of 1049 
photovaphie uses of 1051 
soldeis 1051 
reduction of 1049 
Slag, in iron smelting 1040 
Slow, mutation of elements 947 
Sluice, in placer mining 982 
Smelting of copper ores 1054 
iron 1040 
Smith, Prof. Alexander 941-946 
Smith, Dr. J. Dodge, crown 1129 
Snow, Dr. Geo. B., anatomical appli- 
ances 308-309-338-339-1120-1121 
Soapstone in fusing porcelain 902 
in smoothing models 130 
Sodium . 944 
Soft palate, extent to which denture 
should rest upon 30 
Solarizing pink vulcanite 440 
Solbrig casting pliers 1175 
Solder, gold 1012 
silver 1051 
soft .’ 1062 
Soldering 970 
conditions essential to successful.. 971 
temperatures applied in some 
cases -*.... 970 
Soldering jack 609-510 
Solutions, alcoholic varnishes 93 
aqueous 94 
Solutions—Continued. 
ethereal 93 
Sonorousness in bell metal 977 
Spar, fluor, in alumino-thermics 969 
Spathic iron ore 1040 
“Special” Ideal baseplate 230 
Specialized frictional appliances 
236-500 to 525 
Specific gravity 957 
heat 965 
Spectroscope 937-946 
Spectrum 937-939-952-953 
Spence, Dr. Stewart J., plaster 
101-102-103-432 
Spiral springs for denture retention.. 
1093-1097-1107 
Split dowel 821-1037 
Spillers resin 441 
Spongy borders 19-21 
Sprue, definition of 1156 
Staining fluids 91 
Staining porcelain teeth. 718 
Starr, Dr. E. .1 1115-1147 
Starr, Dr. R. W 1141-1142 
Steam pressure, table of 450 
Steel, hardening and tempering of.. 1042 
Steele, teeth and facings 697 to 700 
repair outfit 834 
Stellar bodies, temperature of the 
larger 970 
Stiver, Dr. D. S., blowpipe.... 692 
Stomatitis 17 
Stokes. Dr. J. L..... 1149 
Stowell, Dr. Sidney S., extension 
bridge 1142 
Strontium 944 
Structure of flame 972 
Stuck, Dr., vulcanizing rubber be- 
tween metal surfaces 1111 
Submaxillary glands 15 
Sublingual glands 15 
Substituting artificial for lost natural 
teeth in repairs.... 578 
Substitution of a baseplate in repairs 579 
Substructure of a bridge 783 
application of stress to 783 
Sulphur 944 
Sulphuric acid pickle 169 
Summary, brief, of recent discoveries 941 
Superheating gold in casting opera- 
tions 928-1025-1026-1027-1157-1174 
Superstructure 783 
Support for continuous gum case 612 
Suspension bridge 785 
Swaged crowns, seamless 772-776 
cusps for crowns 759 to 765 
Swager, Parker shot 164 
Swaging denture bases.166-178-180-208-590 
Sweating 971-1004-1037 
Sykes, C. A 458 
Synovial sacs 274 
Table of alloys, binary (Weinstein). . 990 
casting gold, “A,” “B,” “C,” 
“D” 1005-1008 
clasp metal 1010 
hardness and elasticity of. 1012 
gold and silver 993 
copper 995 
palladium 998 
platinum 996 
plate No. 1 1002 
No. 2 1003 
solders 1014 
melting points of "New Se- 
ries” 1036 
triple (fusible metal) 136 
color, analysis of individual face. 379 
conductivity of heat and elec- 
tricity 987 
constituents of dental rubber 439 
gum body and enamel.... 881-882 
coefficient of expansion 966 
divergence of bicuspid and molar 
crowns 634 
elastic force of steam 461 
elements in the order of discovery 942 
for estimating thickness of dou- 
bled gold baseplate 182 1188 
INDEX 
Table of alloys—Continued 
high and low fusing porcelains.. 883 
mandibular muscles 284 
masticatory action on food 306 
oxides used in coloring porcelain. 881 
shrinkage of metals 132 
specific heat 964 
screw force in flask casting 428 
steam pressure 450 
temperature as displayed by color 958 
temperaments 356 
tensile strength of metals 962 
thermal conductivity of substances 122 
unequal distribution of elements. 946 
welding under pressure 967 
Table of the periodic law 951 
thermal conductivity of substances 122 
measured in calories 122 
fusible alloys 136 
the temperaments 356 
screw force in flask closing 428 
unequal distribution of the ele- 
ments 946 
the triads of Dobereiner 9 49 
weldin*, ■... nressure 967 
I t,•’ •Dr. W. in.., -?§. 
—■ 926-930-933-93t A.. 11 72-1173-1174 
Taking bites 327-329 
impressions t- -495 
Tantalum . 944 
Taste sense 14 
Technic of bridge construction.... 799-867 
crown work 641 to 78.. 
full denture construction..308 to 475 
partial denture construction.. 476-524 
celluloid 551 
continuous gum 688 
repairing dentures 561 
crowns and bridge repairs..832 to 848 
Teeth, formula of human 288 
natural form of 755 
porcelain forms of 535 
Telescope crowns 820-821 
Tellurium 944 
Temperaments, table of the 366 
Temperatures common and extraordi- 
nary .' 969 
Temporary dentures 21 
Tempero-mandibular articulation .... 274 
Tenacity 961 
Tensile strength 961 
Terbium 944 
Testing balancing contact 391 
base plates and occlusion models. 318 
impressions 85 
occlusal surfaces of teeth for 
working efficiency 387 
root preparation in crown work. 649, 743 
parallel relation of crown and 
bridge abutments 819 
Thallium 944 
Theoretical belief in regard to new 
elements 952 
Therapeutic methods of treatment... 629 
Thermal conductivity of various den- 
ture bases 121 
Thompson, Prof. .T. ,T., experiments in 
the debasement of elements. 941 
Thorium 944 
Three point contact, in denture con- 
struction 393 
Thulium 944 
Time a factor in fusing porcelains... 614 
Tin 1062 
Tint, definition 374 
Titanium oxide 881-944 
Tolstoi, statue of 398 
Tone definition 374 
Tongue, muscles of 14 
Tongs, muffle 901 
Tooth, natural forms reproduced in 
porcelain 362 
shade guide 645 
Tray nomenclature 36 
selection 36 
Treatment of diseased conditions 629 
after setting crowns and 
bridges 631-695 
Triads of Dobereiner 948 
Trial base plates 311 
Truss in bridge engineering 784 
continuous gum dentures 605 
porcelain bridge work 869-1143 
Tube teeth, Ash's 529-1111-1129 
Tungsten 1067 
Turner gasoline furnace 874 
Tweezers, K, for inlay work 900 
Types of True Bite Teeth 363-364 
Typal forms of natural teeth (Wil- 
liams) 362 
Ulsaver, Dr. E. S., method of 352 
developing the compensating curve 352 
Ultra-microscope of Zsigmondy 945 
Undercut areas, use of cores in 99 
swaging gold in 179 
Unequal distribution of the elements. 946 
Uniform bearing of dentures essential 26 
Unilateral mandibular movements.... 297 
Unit of thermal conductivity 122 
Upper dentures, retention of 26-27 
outline form of distal 30 
margin of 30 
Uranium, compounds of 939 
the initial element in 939 
tho debasement scale 941 
Use of the face bow 330 
Utility rne of the three prime objects 
in denture construction 1 
Vacuum casting machine .. 935 
chamber 28 
Vanadium 944 
Vanderpoel, Emily, the relation of 
color to light. - :T 373 
Van Horn. C. S 1024 
Van Woe it Dr. P. T 854-919 
Variations in the pitch of condyle 
paths 275 
lateral pat v,- the condyles.... 474 
Various forms teti.li 636 
Varnish for impressions 93 
Vault, palatine 10 
Vegetable bases 651 
Vein gold 983 
Veneers for denture gums, granular 
facing 440 
pink vulcanite 439 
porcelain 608 
inlay, Linderer’s 1146 
Vestal virgin, facial outlines 370 
Von Wardroff, Prof. R., thermal con- 
ductivity 121 
Voick, Dr. A. J., inlays 1146 
Vulcan facial outlines 368 
Vulcanite conductivity of thermal 
changes 121 
denture bases 121 
advantages and disadvantages 
of 121 
double vulcanizatio- process. 
227 to 486 
inflammatory conditions re- 
sulting from use of 122 
dentures, full upper and. lower 
sequent steps in construction 
of 310 to 475 
partial 477 to 488 
repairs of 561 to 587 
finishers (Wilson) 457 
lathe burs 456 
Vulcanization of lubber, chemistry of. 441 
dimensional changes during 447 
contraction 447 
expansion 447 
in automr ■ closed flasks.... 454 
clor lted flasks 454 
time 465 
Vulcani- danger from improper 
ham 4 449 
sat. y devices for 449 
gas regulator 461 
safety valve 462 
steam gauge 450 
thermometer 449 
time regulators 451 INDEX 
1189 
Walker, Dr. W. E ...1116 
Ward, Dr. M. A 917-1017 
Warming oven for flask separation.. 413 
Warpage of casts and impressions. 53-55 
Watt’s flask and metal.. 223-224-227-1161 
Wax, bees 59 
and paraffin 69-922-923 
rosin 60-1149 
composition of 922 
hard bits 60 
inlay 922-923 
eliminating from mold 932 
temperature required to ren- 
der plastic 930 
Weaver cleavers 644 
Webb, Dr. Marshall H., bridge 1139 
Webber, Carl O., Ph. D 441-443 
Wedge of vulcanite 484 
Wedging to regain lost contact 738 
Weighted lower dentures 221 
of vulcanite 221 
with metal core 221 
cast metal bases 222 
Weinstein, Dr. L. J., artificial stone.. 
495-1023 
refractory materials 927-1016 
some recent work concerning gold 
alloys 98»9 to 1039 
spring for absorbing shock....... 500 
Welding of metals 966 
copper to iron (new process) 968 
alumino-thermv 968 
temperatures, common and ex- 
traordinary 969 
Weston, Dr. Henr crown 1136 
metal for cast bases. .i*j 227 
Wet method for recovering silver.... 1064 
Whetting hone, aluminum as a 1058 
White, Dr. J. D., platinum frame for 
crown 855 
Wbite, Samuel S., -vulc ;te litigation.1110 
tooth manufacture 1105 
White, S. S., White Dental Mfg. Co. 
monograph on origin and develop- 
ment of porcelain teeth 1138 
Wildman, Dr. E 439-881 
Williams, Dr. E. Lloyd 68 
Williams, Dr. J. Leon 
362-364-365-396-795-1140-1141-1142 
Wilson, Dr. George H 
35-312-354-360-433-454-4 57 
Wire and plate gauge table 1075 
Wiring denture bases, full gold. 175 
partial 489 
platinum 593 
Wood, Dr. B., crowns 1131 
inlays 1147 
metal, fusible 1066 
Wood, pivot, teeth 1129 
Wood, Dr. W. W., casting appliances 200 
Wrinkles, removing from metal bases 179 
platinum matrix 920 
Wrought iron 1041 
X (Newtonium) . -. 95° 
Xenon alL „c. 
X-ray tT> qigen) 938 
Yell (primary color) 375 
Yttrium 944 
Young plate perforator 684 
Zeller casting appliances 1162 
Zero, absolute, conductivity of met- 
als at 964 
Zinc 1058 
for dies 132 
Zirconium . . . 944 
Zsigmondy, ultra-microscope of 945 
Zygomatic arch, muscular attachment 
to : 278 
Zylonlte 551