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Oil-Cloth, $4.50; CI., 35.00; Sh., #6.00 8@° Catalogues of Medical and Dental Books sent upon application. ' ^Wl# £§§SK ':-^lfeS^ -3 ^X&t^^-^K 13- -..:. iH .-.loTltohiLl.;'.;: .... ;:.--.3r,.x Oi ^ei-rn C ;. -.a. papilla, otcerrr : sleiim of inferior it. a: :>^ rra^1.ila. .-.irv csr.al con.laming THE PRINCIPLES AND PRACTICE OF DENTISTRY INCLUDING ANATOMY, PHYSIOLOGY, PATHOLOGY, THERAPEUTICS, DENTAL SURGERY AND MECHANISM. BY CHAPIN A. HARRIS, M.D., D.D.S. R 01 RY." LATE PRESIDENT OF THE BALTIMORE DENTAL COLLEGE, AUTHOR OF "DICTIONARY OF MEDICAL TF.RMINOLOGY AND DENTAL SURGERY." REVISED AND EDITED B ^^./f^p y^ FERDINAND J. S. GORGAS, A.M., M.D. D.D.sTT * AUTHOR OF "DENTAL MEDICINE," EDITOR OF HARRIS' "DICTIONARY OF MEDICAL TERMINOLOGY AND DENTAL SURGERY," PROFESSOR OF THE PRINCIPLES OF DENTAL SCIENCE, DEN- TAL SURGERY AND DENTAL MECHANISM IN THE UNIVERSITY OF MARYLAND. WITH ONE FULL-PAGE PLATE AND ONE THOUSAND AND TWENTY-EIGHT ILLUSTRATIONS. PHILADELPHIA: P. BLAKISTON, SON & CO., No. 1012 Walnut Street. 1889. V^\3p Entered according to Act of Congress, in the year 1889, by P. BLAKISTON, SON & CO., In the Office of the Librarian of Congress, at Washington, D. C. SHERMAN for instance, that of speech. Who does not knoAV that THE TEMPORARY TEETH. 97 when any of the teeth are wanting, the palate cleft, or there is a hare-lip, Iioav much the speech is impaired? And so Avith all the other functions of the body; the relations between them and the mouth, and the mutual dependence of each on the other, is equally demonstrable. CHAPTER IX. THE TEETH. Fig. 30. The teeth in the human mouth are the prime organs of mastica- tion, are the hardest portion of the bod}', and are implanted in the alveolar cavities of both the upper and lower jaw. A tooth is composed of four distinct struct- ures: 1. The pulp, occupying the chamber in the crown and the canal extending through the root; 2. The dentine, which constitutes the principal part of the organ; 3. The enamel, Avhich forms the covering and protection of the croAvn; 4. The cementum,, or crusta petrosa, Avhich covers the root. (See Fig. 30.) Tavo sets of teeth are developed in the mouth, one of first dentition and one of second denti- tion. The teeth of first dentition, termed the milk, temporary, or deciduous teeth, are designed merely to supply the Avants of childhood, and are replaced with a larger, stronger, and more numerous set. The teeth of second dentition are termed the permanent or adult teeth, and are intended to continue through life. The anatomical divisions of a tooth are: 1. The croAvn or exposed part, situated above the gum; 2. The root, occupying the alveolar cavity or socket; 3. The neck, Avhich is the con- stricted portion betAveen the croAvn and root. a. The coronal surface divested of enamel; b. the dentine ; c. the pulp cav- ity; d. the cementum, or crusta petrosa; e. the enamel. THE TEMPORARY TEETH. The temporary teeth are divided into three classes: first, the in- cisors; second, the cuspids, or canine teeth; third, the molars,Avhich 98 PRINCIPLES AND PRACTICE OF DENTISTRY. are succeeded by the bicuspids or premolars, which are not repre- sented in the temporary set. The temporary teeth are twenty in number, ten in each jaAv, namely: four incisors, two cuspids, and four molars. Fig. 31. Fig. 32. FRONT OR LABIAL VIEW OF THE TEM- PALATINE AND LINGUAL VIEW OF THOSE PORARY TEETH OF THE LEFT SIDE. ON THE RIGHT SIDE. The incisors of the upper jaw are implanted in the pre-maxillary bones, which early in life unite with the maxillaries. The pulp-cavity in a temporary tooth is also larger in proportion to the size of the organ than in a permanent tooth. The pulp- Fig. 33. Fig. 34. LATERAL OR SIDE VIEW OF TEMPORARY SECTION OF DITTO, EXPOSING THEIR PULP TEETH. CAVITIES. cavities of the central and lateral incisors are of the same general shape, like that of an elongated tube, while those of the canines and molars correspond with the form of these teeth. DESCRIPTION OF TEETH BELONGING TO EACH CLASS. 99 THE PERMANENT TEETH. There are thirty-tAVO teeth in the permanent set, sixteen to each jaAv—being an increase of twelve over the temporary, designated as follows: incisors, four; cuspids, two; bicuspids or premolars, four; molars, six—in each jaAv. The surfaces of the teeth covered by the lips are called "labial;" by the cheeks, "buccal;" toward the roof of the mouth on the upper jaw, " palatal;" toAvard the tongue on the loAver jaw, "lingual." The name "proximate" is given to the sur- faces next to each other; the surfaces looking toward the centre are called "mesial;" and those looking from the centre, "distal." DESCRIPTION OF TEETH BELONGING TO EACH CLASS. Each tooth, as has already been remarked, has a body or croAvn, a neck, and a root or fang. In describing these several parts, I shall begin Avith The Incisors (four to each jaw, and so called from the Latin word incidere, to cut; on account of their sharp, cutting edges (Fig. 35), Fig. 35. a a, a a. Front view of the incisors; b b, b b. palatine or lingual view ;cc,cc. side or lateral view. a a, a a). They occupy the anterior central part of each maxillary arch. The body of each is wedge shape—the anterior or labial sur- face is convex and smooth; the posterior or palatal is concave, and presents a tubercle near the neck; the palatal or labial surfaces come 100 PRINCIPLES AND PRACTICE OF DENTISTRY. \ together, and form a cutting edge. In a front view, the edge is generally the Avidest part; it diminishes toward the neck, and con- tinues narroAving to the extremity of the root. The crown of an incisor has four surfaces; tAvo proximate, one labial, and one palatal or lingual—the term palatal being applied to an upper, and lingual to a loAver, incisor. It also has four angles; namely, a right and a left labio-proximate, and a right and left palato- proximate, or lingua-proximate. The iavo large incisors Avhich are situated one on each side of the median line, are termed the central incisors; the other tAvo, the lateral incisors, or laterals, because they occupy a position on either side of the centrals. The croAvns of the upper central incisors are about four lines in breadth, and the laterals three. In the lower jaAv, the crowns of the central incisors are only about two lines and a half in Avidth, Avhile the laterals are usually a little Avider. But the width of the croAvns of all the incisors varies in different indi- viduals. The length of a superior central incisor is usually about one inch, and that of a lateral is half of a line less. In the lower jaAv the central incisors are only about ten lines in length ; the laterals are about one line and a half longer. The length of the crown of an incisor is exceedingly Arariable. That of an upper central varies from four and a half to six lines; and there is the same want of uniformity in this respect with the crowns of all the incisors. The superior central incisors are somewhat more prominent than the lateral incisors, OAving to the curve of the alveolar process. The neAvly-erupted incisors have three points or cusps on their cutting edges, which soon disappear through wear, leaving such edges smooth and uniform. The labial aspect of the crown of a superior central incisor is convex, and the \rertical diameter is greater than the transverse. Of the lateral surfaces, the mesial is generally flat, Avhile the distal is more rounded. The lateral incisors are more slender in shape and smaller than the central incisors, but have the same general form, Avith someAvhat more convexity of the labial surface. The roots are all single, of a conical form, flattened laterally, and slightly furrowed longitudinally. Those of the lateral incisors are more flattened laterally than the roots of the centrals, slightly longer and more gradually tapering towards the apex. The pulp-cavities of all the incisors have the same shape—like that of an elongated tube. The enamel is thicker before than behind, and thinnest at the sides. THE CUSPIDATI, OR CUSPIDS. 101 The function of this class of teeth, as their name imports, is to cut the food, and for the performance of this office the}'' are admirably fitted by their shape. As age advances, their edges often become blunted ; but the rapidity with Avhich they are worn aAvay depends altogether upon the manner in Avhich those of the upper and loAver jaAv come together. THE CUSPIDATI, OR CUSPIDS. The Cuspidati, Canini, or Cuspids, so called from the Latin Avord cuspis, " a point," because they terminate in a point, are commonly known by the name of canines (Fig. 36). They are situated next to the incisors, and occupy the space betAveen the lateral incisor and first bi- cuspid, tAvo to each jaw, one on either side. They somewhat resemble the upper central incisors Avith their angles rounded. Their croAvns are conical, \Tery convex externally, and their palatal surface more uneven, and have a larger tubercle than the incisors. They are stronger and generally more durable teeth than the incisors, and their roots form a vertical ridge on the external surface of the alveolar process. Their roots are also larger, and of all the teeth the longest; like the incisors, they are also single, but have a groove extending from the neck to the extremity, shoAving a step toward the forma- tion of two roots. A cuspid, like an incisor, has four surfaces and four angles, designated by the names already giAren. The breadth of the crown of an upper cuspid is about four lines, that of a loAver is about three and a half; but, as in the case of the incisors, the Avidth of the croAvns of these teeth is variable. The length of a cuspid is greater than that of any other tooth in the dental series—it being about thirteen lines. The breadth of the neck of one of these teeth is about one-third greater in front than behind, and from before backward it measures about four lines. The upper cuspids, Avith no good reason, are sometimes called eye teeth; the loAver are termed stomach teeth. The inferior cuspids have a shorter root than the superior cuspids, and the median cusp is not so pointed. These teeth are for tearing the food, and in some of the carnivorous animals, Avhere they are very large, they not only rend but also hold their prey. The incisors and cuspids together are termed the oral teeth. a a. Front view of the cuspids; 6 b. palatine and lingual view ; c c, side view. 102 PRINCIPLES AND PRACTICE OF DENTISTRY. THE BICUSPIDS. Fig a a, a a. Buccal view ot the bicuspids; bb,bb I palatine and lingual view; cc,cc. side view. The Bicuspids, so called from the Latin words bis, " twice," and cuspis, " a point" (Fig. 37), four to each jaAv, and tAvo on either side, are next in order to the cuspids. They have two distinct promi- nences or cusps on their grinding surfaces, one ex- ternal and the other inter- nal, and separated by a deep depression or notch. In the superior bicuspids the exter- nal cusp is somewhat larger than the internal cusp, while in the inferior bicuspids the internal cusp is larger than the external, and the root is more cylindrical in form. They are also named pre- molars or the small molars, but are more commonly designated as the first and second bicuspids. They are thicker from their buccal to their palatine surface than either of the incisors, and are flatter on their sides. The buccal surfaces are very convex, and the crowns of the second bicuspids are generally somewhat larger than those of the first bicuspids, and more of a square form. A biscuspid has five surfaces: namely, two proximate, one anterior and one posterior; one buccal; one palatal or lingual surface, as the tooth may be in the upper or lower jaw, and one grinding surface. It has also four angles; one anterior and one posterior palato-proxi- mate and one anterior and one posterior bucco-proximate angle. The size of these teeth, like that of the incisors and cuspids, is variable. The buccal surface of the crown of a superior bicuspid of ordinary size at its broadest part is about three lines in breadth, while the anterior and posterior proximal surfaces are about four lines. The palatal is quite as wide as the buccal surface. All the diameters of the crown of a lower bicuspid are usually a little less than those of an upper. The entire length of a bicuspid is ordi- narily about eleven lines. The superior bicuspids have generally tAvo roots, but sometimes a single root, Avhich is often deeply grooved, while the inferior bicus- pids have but one root. The deeply-grooved root is indicative of THE MOLARS. 103 tAvo pulp-cavities, which may unite at the central portion of the root and form a narrow transverse fissure at the neck of the tooth. Of the tAvo roots of the superior bicuspids, the inner or palatal is smaller than the outer or buccal, each root having an opening for the vessels and nerves to enter. THE MOLARS. The Molars, so called from the Latin word molaris, " grinding," and designated as first, second, and third molars (Fig. 38), occupy the posterior part of the alveolar arch, and are six in each jaAv, three Fig. 38. a a a, a a a. Outer view of the molars; b bb, bbb. inner view; ccc,ccc. side view; on either side. The first, OAving to the period of their eruption, are called the sixth-year molars, and the second, for the same reason, are called the twelfth-year molars, while the third are called the dentes sapientise or Avisdom teeth, from the Latin words dens, " a 104 PRINCIPLES AND PRACTICE OF DENTISTRY. tooth," and sapientia, " wisdom," being erupted at a period when maturity is reached. The molars are distinguished by their greater size—the first and second being the largest; the grinding surfaces have the enamel thicker, and are surmounted by four or five tubercles or cusps, with as many corresponding depressions ar- ranged in such a manner that the tubercles of the upper jaAV are adapted to the depressions of the lower, and vice versa. A molar, like a bicuspid, has also five surfaces and five angles, designated by the names already given. The upper molars have three roots, sometimes four, and as many as five are occasionally seen; of these roots two are situated exter- nally, almost parallel Avith each other, and perpendicular; the third root forms an acute angle, and looks toward the roof of the mouth. The former are called the buccal roots, and the latter the palatcd. The roots of the first two superior molars correspond with the floor of the maxillary sinus, and sometimes protrude into this cavity, their divergence securing them more firmly in their sockets. The lower molars have but tAAro roots—the one anterior, the other pos- terior; they are nearly vertical, parallel with each other, and much flattened laterally. The last molar, or wisdom tooth, is both shorter and smaller than the others; the roots of the upper Avisdom tooth are, occasionally, united so as to form but one; while the last molar of the loAver jaw is generally single and of ft conical form. The roots of the molar teeth, both of the upper and lower jaw, after diverging, sometimes approach each other, embracing the inter- vening bony partition in such a manner as to constitute an obstacle to their extraction. The bucco-palatal diameter of the croAvn of an upper molar is usually a little less than the antero-posterior. In the lower jaAv, the bucco-lingual and antero-posterior diameters are generally about the same. The crown of the first molar is generally larger than the second, and the second larger than the third or wisdom tooth; and the croAvn of the last-named tooth is always smaller in the upper than in the loAver jaw. The pulp-cavities correspond to the external form of the roots and at the necks of these teeth they unite into a common cavity called the pulp-chamber which often ends in cornua corresponding to the cusps. The length of a molar tooth varies from eight to tAvelve and a half or thirteen lines. TEMPORARY" AND PERMANENT TEETH. 105 The molars and bicuspids together constitute what are termed the buccal teeth. The use of the molars, as their name signifies, is to triturate or grind the food during mastication, and for this purpose they are admirably adapted by their mechanical arrangement. ARTICULATION OF THE TEETH. The manner in Avhich the teeth are confined in their sockets, is by a union called gomphosis, from the resemblance of this kind of articulation to the Avay in which a nail is receiA'ed into a board. Those teeth having but one root, and those Avith two perpendicular roots, depend greatly, for the strength of their articulation, on their nice adaptation to their sockets. Those having three or four roots have their firmness much in- creased by their divergence. But there are other bonds of union ; by the periosteum lining the alveolar cavities, and investing the roots of the teeth ; also by the bloodvessels entering the apices of the roots; and finally, by the gums, Avhich will be noticed in another place. DIFFERENCES BETWEEN THE TEMPORARY AND PERMANENT TEETH. The temporary and permanent teeth differ in several respects, and on this point I will give Mr. Bell's observations : " The temporary teeth are, generally speaking, much smaller than the permanent; of a less firm and solid texture, and their charac- teristic forms and prominences much less strongly marked. The incisors and cuspids of the loAA^er jaAv are of the same general form as in the adult, though much smaller; the edges are more rounded, and they are not much more than half the length of the latter. The molars of the child, on the contrary, are considerably larger than the bicuspids Avhich succeed them, and resemble very nearly the permanent molars. " The roots of the tooth in the molars of the child are similar in number to those of the adult molars, but they are flatter and thinner in proportion, more holloAved on their inner surfaces, and diverge from the neck at a more abrupt angle, forming a sort of arch." In the temporary teeth the union of the enamel and cementum is distinctly marked by a Avell-defined ridge of enamel at the base of the croAvn, which forms a constricted neck ; Avhereas in the per- manent teeth the union of the enamel and cementum at the base of the croAvn is very indistinct. 106 PRINCIPLES AND PRACTICE OF DENTISTRY. RELATIONS OF THE TEETH OF THE UPPER TO THOSE OF THE LOWER JAAV, AVHEN THE MOUTH IS CLOSED. The crowns of the teeth of the upper jaAv generally describe a rather larger arch than those of the loAver. The upper incisors and cuspids usually shut over and in front of the loAver; but sometimes they fall plunib upon them, and at other times, though rarely, they come on the inside. The external tubercles or cusps of the superior bicuspids and molars generally strike on the outside of those of the corresponding inferior teeth. By this beautiful adaptation of the tubercles of the teeth of one jaw to the depressions of those of the other, every part of the grinding surface of these organs is brought into immediate contact in the act of mastication; which operation of the teeth, jn consequence, is rendered more perfect than it Avould be if the organs came together in any other manner. The incisors and cuspids of the upper jaAv are broader than the corresponding teeth in the loAver; in consequence of this difference in the lateral diameter of the teeth of the tAvo jaAvs, the central in- cisors of the upper cover the centrals and about half of the laterals in the loAver, Avhile the superior laterals cover the remaining half of the inferior and the anterior half of the adjoining cuspids. Con- tinuing this peculiar relationship, the upper cuspids close over the remaining half of the lower and the anterior half of the first inferior bicuspids, while the first superior bicuspids cover the remaining half of the first inferior and the anterior half of the second. In like manner, the second bicuspids of the upper jaw close over the posterior half of the second and the anterior third of the first molars in the lower. The first superior molars cover the remaining two- thirds of the first inferior and the anterior third of the second, Avhile the tAVO-thirds of this last and anterior third of the loAver dentes sapientise are covered by the second upper molars. The dentes sapientise of the superior maxilla, being usually about one third less in their antero- posterior diameter, cover the remaining tAvo-thirds of the cor- responding teeth in the lower jaw. (See Fig. 39.) Thus, from this arrangement of the teeth, it will be seen, that when the mouth is closed, each tooth is opposed to tAvo ; and hence, MALFORMED TEETH. 107 in biting hard substances and in mastication, by extending this mutual aid, a poAver of resistence is given to these organs which they would not othenvise possess. Moreover, as an English Avriter, Mr. Tomes, very justly observes, if one, or even two adjoining teeth should be lost, the corresponding teeth in the other jaw would, to some extent, still act against the contiguous organs, and thus, in some degree, counteract a process, first noticed by that eminent dentist, Dr. L. Koecker, which nature sometimes sets up for the expulsion of such teeth as have lost their antagonists. CHAPTER X. MALFORMED TEETH. Peculiarities in the Formation and Growth of the Teeth.—In the development and growth of the various parts of the body, curious and interesting anomalies are sometimes observed; but in no por- tion of it are they more frequent in their occurrence or diversified Fig. 40. Fig. 41. iTto^ «nrr\ WJ m) Fig. 40 shows the front view of the lateral incisor and canine from the left side of the under jaw, united throughout their entire length, but with the line of junc- tion well marked. The age at which they were removed was seven years. The corresponding teeth on the opposite side of the jaw were similarly united. Fig. 41 shows the representation of the lateral incisor and canine from the left side of the lower jaw of a patient aged nine years. In this example the line of junction is less distinctly marked than in the preceding illustration, and is alto- gether wanting near the base of the enamel. in their character than in the teeth. But aberrations in the forma- tion and groAvth of these organs are, for the most part, confined to the teeth of second dentition. Although the deciduous teeth are much more exempt from devia- tions in form, size and number, than the permanent teeth, yet they are not altogether free from such irregularities. One form of irregularity of these teeth may consist in a greater number than tAventy ; while in other cases there may be a numerical deficiency. Deciduous teeth, especially the molars, are occasionally met with having more than the normal number of roots. A more common 108 PRINCIPLES AND PRACTICE OF DENTISTRY. form of irregularity is the union of tAvo, or sometimes even three, deciduous teeth, generally incisors, or an incisor and a canine, either by a union in the cementum, or in the dentine and enamel. When the union is in the cementum, the roots only are united, but where it is in the dentine and enamel there is a fusion of both the croAvns and the roots, and one pulp common to the two teeth (geminous). Fig. 42x represents two specimens of triple fusion of the decidu- ous right superior lateral incisor and cuspid, Avith a supernumerary tooth between the two, taken from the mouth of a boy three years of age. Fig. 422 represents another specimen of triple fusion of de- ciduous teeth from the mouth of a little girl, Avhich occupied the same position as that represented by Fig. 421, and Avas composed of the same teeth. Both of these specimens were extracted by Dr. Isaac Douglass. Malformed Permanent Teeth.—Irregularity in the forms of permanent teeth is much more common than is the case with de- ciduous teeth ; some of the former differing so much in size, either above or beloAV Avhat is normal, as to occasion disfigurement; in the same mouth very large teeth may be associated Avith others ex- Fig. 42. Fig. 43. Fig. 44. tremely small, or the malformation may be confined to a single tooth of the set. But examples of this kind are not very frequent; for where there is an increase or diminution in the size of the teeth of one class, there is generally a corresponding change in that of the other. Aberrations of this character are probably dependent upon some diathesis of the general system, Avhereby the teeth, during the earlier stages of their formation, are supplied Avith an excessive or dimin- ished quantity of nutriment. Again, the malformation may be confined to the root, Avhile the croAvn of the tooth is of the normal size. A superior central incisor may have a root Avhich is abnormally small, Avhile the crown is of the usual size. Another malformation consists in an excess of the normal number of roots, the superior molars sometimes having four or six slender malformed teeth. 109 roots, and the inferior molars three and four, the inferior canines tAvo, and the superior bicuspids three roots Figs. 43, 44. The varia- Fig. 45. Fig. 46. tions in form of the permanent teeth are beyond enumeration; in some cases teeth Avith single roots are bent at different angles. The croAvns of the teeth, also, frequently present deviations from the natural shape equally striking and remarkable. Figs. 45, 46 and 47 represent molar and incisor teeth Avith mal- formed roots. Teeth Avith flexed roots are also met Avith. Figs. 48 and 49 repre- sent superior central incisors Avith single and double flexions of the roots. Fig. 47. Fig. 48. Fig. 49. Mr. Fox gives a draAving of a tooth very much resembling the letter 8. The author has also met Avith several examples of teeth similarly deformed, and from like causes. Some very remarkable deA'iations have been knoAvn to take place in the groAvth of the teeth. The most singular case on record is that related by Albinus. " Tavo teeth," says he, " between the nose and the orbits of the eye, one on the right side and the other on the left, were inclosed in the roots of those processes that extend from the maxillary bones to the eminence of the nose. They Avere large, remarkably thick, and so very like the canines that they seemed to be these teeth, Avhich had not before appeared; but the canines themselves Avere also present, more than usually small and short, and placed in their proper sockets. The former, therefore, appear to have been neAV canines, which had not penetrated their sockets, because they were situated where these same teeth are usually ob- served to be in children. But Avhat is still more remarkable, their points Avere directed toward the eyes, as if they were the neAV eye 110 PRINCIPLES AND PRACTICE OF DENTISTRY. teeth inverted. And they were also so formed that they Avere, con- trary to what usually happens, convex on the posterior and concave on the anterior." A case of a somewhat similar character is men- tioned by Mr. John Hunter. The following case is in the words of Mr. G. Wait: " While I was prosecuting my anatomical studies, I Avas struck Avith the appear- ance of a cuspid of the upper jaw; it Avas short, and appeared as if the body of the tooth Avas in the jaw, and that it Avas the tip of the root that presented itself. Upon further examination I found this verified, and after the cranium and loAver jaAv Avere properly macerated and cleansed, I found one of the loAver bicuspids in the same position." The folloAving is one of the several cases of deviation in the growth of the teeth, that have come under the author's observation: In 1840, he was requested to extract a tooth for a lady of Baltimore, under the following circumstances. She had, for a time, experi- enced a great deal of pain in her upper jaAv, and supposed it to originate from the second molar of the right side, but AArhich was perfectly sound. Meanwhile her general health became impaired, and her attending physician, thinking that the local irritation might have contributed to her debility, advised the extraction of the tooth. On removing it, the cause of the pain at once became apparent. The dens sapientise, which had not hitherto appeared, Avas discovered Avith its roots extending back to the utmost verge of the angle of the jaw, Avhile its grinding surface had been in contact Avith the posterior surface of the crown and neck of the tooth just extracted. On the removal of the Avisdom tooth, the pain ceased. About the middle of December, 1849, a youth aged sixteen applied to the author to extract a right superior bicuspid, AAdiich, he said, was ulcerated at the root. On examining his mouth, he discovered only one bicuspid, but above and between the root of this and that of the first molar, he observed a small fistulous opening. On in- troducing a small probe, it immediately came in contact with the crown of a tooth looking toward the malar process of the superior maxillary, which, on extraction, proved to be the second bicuspid. The author has in his possession several molar and bicuspid teeth which have small nodes upon their necks, covered Avith enamel; and there is a jaw in the Museum of the Baltimore Dental College which has five teeth presenting this anomaly. The author has two teeth in his possession of most singular shape, presented to him by his brother, the late Dr. John Harris. They were extracted in July, 1822, from the right side of the upper jaw of a young gentleman, nineteen years of age, by the name of Craw- ford. They occupied the place of the first and second bicuspids, MALFORMED TEETH. Ill and their croAvns are almost wholly imbedded in lamellated den- tine, that should have constituted their roots, but which are entirely wanting. Judging from their appearance, one would be inclined to suppose that, their sacs failing to contract, they remained sta- tionary in their sockets, and as the base of the pulps elongated, they came in contact with the bottom of the alveoli, and Avere caused to bulge out and to be reflected upon their crowns, to the enamel of Avhich, nearly to their grinding surfaces, they are per- fectly united. For some time previously to the extraction of these teeth, they had been productive of considerable irritation and pain in the gums and jaw, and it Avas for the relief of the suffering Avhich their presence induced that they were removed. Since the above was AA'ritten, the author has seen a still more remarkable deviation in the groAvth of a tooth. It is in the upper jaAv of an adult skull in which the natural teeth are all Avell formed and regularly arranged in the al- veolar border, but between the extremities of the roots of the superior central incisors, in the substance of the jaw, there is a supernumerary tooth the crown of Avhich looks upAvard toAvard the crest of the nasal plates of the two bones. The whole tooth is about one inch in length, and the apex of the crown is nearly on a level Avith the floor of the nasal cavities. There is also in the Dental Museum of the University of Maryland a central incisor of the upper jaAv, Avith the root bent upon, and in contact with, the labial surface of the croAvn (Fig. 50). United Teeth.—Inclosed as each tooth is in a distinct sac, and separated on either side by a bony partition, from the adjoining teeth, until after the completion of the formation of the enamel, it may be difficult to conceive how osseous union could take place betAveen tAvo of these organs, but so many examples of such union are met Avith, that there is no longer any question concerning its possibility. Tavo or more teeth, generally the molars, may be permanently joined together by a union in the cementum of their roots, occa- sioned by diseased action, such as exostosis, taking place after the complete development of the teeth. The term " osseous union" has been applied to such cases. Fig. 51 represents united second and third molars, the one figure presenting the buccal aspect, and the other the palatal. Fig. 52 also represents the osseous union of superior second and third molars. Many years ago we had an opportunity of seeing tAvo interesting cases. One consisted in the union of the croAvns of the central 112 PRINCIPLES AND PRACTICE OF DENTISTRY. incisors of the upper jaw, the palatine surface of which presented the appearance of one broad tooth, while anteriorly they had the semblance of two teeth; the other case consisted in the union of the right central and lateral incisors of the loAver jaAv. A professional friend informed the author, in a conversation some years since, that he had met Avith a case of osseous union betAveen a second bicuspid and the first molar of the loAver jaAv, which was so palpable that there could have been no doubt of its existence. Cases of this nature are not very common, and a connection of the roots of two teeth, by an intervening portion of the alveolus, is Fig. 51. Fig. 52. very easily mistaken for osseous union of the roots themselves. A few years since, in extracting a second molar of the upper jaw, the author brought the dens sapientise along with it. At first he thought there Avas osseous union of the roots, but upon close examination found a very thin portion of the alveolar Avail betAveen, to Avhich their roots were firmly attached. Such a case as this Avould, in many instances, be set doAvn as an example of osseous union. An osseous union of the teeth is, fortunately, of rare occurrence • if it were otherwise, it would be productive of many accidents in the extraction of teeth. Apart from this consideration, it can be of but little importance either to the practitioner or to the physiologist. Since the publication of the first edition of this work, a number of cases of osseous union of the teeth have fallen under the obser- vation of the author. Among them are a number of examples of osseous union of the temporary teeth. Gominous or Fused Teeth.—When two teeth are united by a union in the enamel and dentine throughout the entire length of their croAvns and roots, they are termed " geminous " or " fused" teeth, as the malformation is occasioned by a fusion of their pulp, from close proximity and pressure, one pulp being common to the tAvo teeth. The tAvo central incisors, and the lateral incisors and canines are more commonly joined together in this manner than any of the other teeth. Fig. 53 represents geminous central and lateral in- MALFORMED TEETH. 113 cisors, shoAving the labial and palatal aspects, these specimens being in the Dental Museum of the University of Maryland. Other cases occur-where the union or fusion is confined to the croAvns of the teeth, the roots being separate. Fig. 54 represents tAvo geminous central incisors, the croAvns of Avhich are united while the roots are separate. Fig. 53. Fig. 54. Supernumerary Teeth.—The development of supernumerary teeth is usually confined to the anterior part of the mouth, and more frequently to the upper than to the loAver jaAv. They sometimes, hoAvever, appear as far back as the dentes sapientise, and Hudson says he has seen them behind these teeth. We have hoav in our anatomical collection, tAvo supernumerary teeth that Avere extracted, one from behind and the other at the side of one of the upper Avisdom teeth.* The croAvns of supernumerary teeth Avhich appear in the anterior part of the mouth are usually of a conical shape, and for the most part situated betAveen the central incisors; they usually have short, knotty roots; sometimes, however, they bear so strong a resemblance to the other teeth that it is difficult to distinguish the one from the other. We once saw tAvo lateral incisors in the loAver jaw, both of Avhich were so Avell arranged, and perfectly formed, that it was impos- sible to determine Avhich of the two ought to be considered as the supernumerary. Mr. Bell mentions a case in Avhich there were five lower incisors, all of Avhich Avere Avell formed and regularly arranged. Such teeth, hoAvever, are more properly knoAvn as " supplemental." Supernumerary cuspids rarely if ever occur, but supernumerary bicuspids are occasionally met with. Delabarre says he has seen them ; and Ave have met Avith three examples of the sort; in each of these instances the teeth were very small, not being more than one-fourth as large as the natural bicuspids, with oval croAvns, and placed partly on the outside of the circle and partly betAveen the bicuspids. We extracted one of them, and have it still in our possession. Its root is short, round, and nearly as thick at its ex- tremity as it is at the neck of the tooth. * These teeth were removed by Dr. Chewning, dentist, of Fredericksburg, Ya. 8 114 PRINCIPLES AND PRACTICE OF DENTISTRY. The supernumerary teeth that appear further back than the bicuspids, though much smaller, bear a strong resemblance to the dentes sapientise. Supernumerary teeth, although generally imperfect in their forma- tion, are less liable than other teeth to decay. This may be at- tributable to the fact that they are harder, and, consequently, not so susceptible to the action of the causes that produce the disease. Although the occurrence of supernumerary teeth rarely disturbs the arrangement of the others, their presence is sometimes pro- ductive of the Avorst form of irregularity (Fig. 55 represents a case of Fig. 55. this kind); and even when they do not have this effect, they impair the beauty of the mouth, and, for this reason, should be extracted as soon as their croAvns have completely emerged from the gums. To the practitioner of dental surgery, the occurrence of supernu- meraiy teeth is interesting only in so far as it affects the beauty of the mouth and the relationship Avhich the teeth of the upper jaw sustain to those of the loAver; but to the physiologist it involves the question, what determines their development? In propounding this interrogatory, hoAvever, it is not our intention to enter upon its discussion in this place, as it forms no part of the design of the present treatise. (See " Origin of Permanent Teeth.") Supplemented Teeth.—The term supplemental is employed to desig- nate teeth which resemble in shape and size those of the regular series, as a third lateral incisor or canine, or a fifth biscuspid in either the upper or lower jaw, the additional teeth being perfectly normal in form. Such teeth are extremely rare, but we have met with several examples in Avhich supplemental teeth so closely re- semble the natural incisors that no difference could be discerned betAveen them. We have also met Avith three superior lateral in- cisors where it Avas impossible to determine which Avas the supple- mental tooth. Nodular Teeth.—Occasionally teeth are found having small white pearly nodules on their necks, or upon the roots near the termina- tion of the enamel. These enamel nodules consist of a thick layer MALFORMED TEETH. 115 of enamel covering a cone of dentine, Avhich projects from the neck or root of the tooth, and contains dentinal tubuli. They are simi- lar to the excrescences in the form of extra cusps, Avhich are some- times found on the croAvns of the teeth, especially the molars, and the enamel covering them is formed by a true enamel organ. These nodules are of physiological interest only, as they do not give rise to any pathological symptoms. They are a variety of dental exostosis Avhich is extremely rare and difficult to account for. Sometimes they may be mistaken for supernumerary teeth, and an attempt to remove them may result in the extraction of the tooth to Avhich they are attached. Fig. 58. Figs. 5G and 57 represent permanent teeth wTith nodules of enamel attached to the necks and sides of the roots. Odontomes.—This term has been generally applied to tooth tumors developed from the hard tissues of the teeth, but it is noAV restricted to those irregular masses of dentinal tissues Avhich result from some hypertrophied condition of the tooth papilla or formative pulp. In such cases the irregular mass consists of dentine and enamel, bear- ing little or no resemblance to a tooth; and it originates after the commencement of calcification. Fig. 58 represents an odontome consisting of an irregular mass of tooth tissues. The teeth described by Salter, Wedl and others, under the name of " Warty Teeth," and Avhich are composed of tissues hypertrophied and folded together into an irregular and complicated mass, afford a fair example of odontomes. It is not unusual for odontomes to remain in the mouth for a considerable time Avithout causing trouble, but sooner or later they may give rise to inflammation folloAved by suppuration in the adjoining parts, Avhen their immediate removal is necessary. Mr. John Tomes refers to a case where the body of the sphenoid bone Avas found to be the seat of a tumor containing dentine. Figs. 59, GO represent dental anomalies extracted from the 116 PRINCIPLES AND PRACTICE OF DENTISTRY. mouth of an old woman seventy years of age, one of the hairy Burmese family, by Dr. J. A. Daly, and are described as folloAvs by Dr. C. T. Caldwell: " I find two very remarkable instances of gemination or organic union of two neighboring teeth. The measurements and outlines of the drawings are as near as possible correct. Figs. 59 and 60. " The lines A B and C D are intended to shoAv the position of the teeth in the jaw, the portions above A B and below C D indicating the parts exposed above the gum. They were covered by a thick layer of dark-brown concretion, the exact nature of which I have not yet determined. " Fig. 59 shows the right second molar and wisdom-tooth of the, lower jaw so completely joined together that both crowns and roots are united throughout their entire length. The two roots of the second molar may be easily made out in the specimen, and just behind them, and completely fused Avith them, is the connate root of the Avisdom-tooth. Fig. 5P. Fig. 60. " Still more remarkable than this is the specimen represented by Fig. 60, Avherein the union of two upper molars is confined to the roots, Avhich are so welded or blended together as to leave but little trace of the several fangs. This specimen Avas at first supposed to be a large-sized molar with an enormous exostosis, but a section through the parts shown in the drawing disclosed a pulp-cavity, and close examination revealed the fact that this portion of the mass is in reality the crown of a tooth, made up of enamel, dentine, and pulp-cavity, filled Avith nerve and nutrient vessels, as in ordi- nary teeth. The tubercles or cusps, having never been subjected to Avear, are in a perfect condition on what should have been the top or free surface of the crown, while the roots had become coalescent Avith those of its neighbor in such a manner that only one of the united teeth could assume an upright or natural position in the jaw, the other being forced into a horizontal position, Avith only a side protruding abo\re the surface of the bone. " This gemination or coalescence of contiguous teeth occurs during an early stage of their development, and is due to absorption of the MALFORMED TEETH. 117 intervening bony tissue caused by pressure, where as in this case several very large teeth croAvd themselves into a very small mouth." Sypliilitic Teeth.—Mr. J. Hutchinson Avas the first to call attention to a class of malformed permanent teeth, the result of inherited syphilis, and he asserts that certain deviations in the forms of teeth are valuable as diagnostic marks of the existence of syphilis of congenital constitutional type, and he classes them Avith syphilitic interstitial keratitis. This author describes syphilitic teeth as fol- lows : " In those Avho had cut their permanent teeth the condition of the incisor teeth was very peculiar, both in form, color and size. As a diagnostic of hereditary syphilis, various peculiarities are often presented by the others, especially the canines; but the upper central incisors are the test teeth. When first cut, these teeth are short, narroAV from side to side at their edges, and very thin. After aAvhile a crescentic portion from their edge breaks aAvay, leaving a broad, shallow, vertical notch, Avhich is permanent for some years, Fig. 61. Fig. 62. A. B but betAveen twenty and thirty usually becomes obliterated by the premature Avearing down of the teeth. The tAvo teeth often con- verge, and sometimes they stand Avidely apart. In certain in- stances in Avhich the notching is either wholly absent or but slightly marked, there is still a peculiar color and a narroAV squareness of form, which are easily recognized by the practiced eye...... Indeed, there can be no doubt Avhatever as to the truth of the assertion that malformed upper incisors (permanent set) are all but invariably coincident Avith this disease." Henry \V. Williams, M.D., Professor of Ophthalmology in Har- vard University, confirms Mr. Hutchinson's observations, and says: "The central incisors of the second dentition have a peculiar cre- scentic notch at their loAver margins, and the lateral incisors and canines, as Avell as the molars, are often small, peg-shaped, and with 118 PRINCIPLES AND PRACTICE OF DENTISTRY. tuberculated prominences upon their surface. They are, perhaps, also irregularly set in the jaw, and of bad color, or prematurely decayed." Figs. 61 and 62 represent syphilitic teeth in a boy and two girls, aged respectively tAvelve, fourteen and seventeen years. Mr. John Tomes describes these teeth as being of "a dusky, opaque appearance, and are small relatively to the size of the jaAVS, so that distinct intervals are left between them; moreover, they are of a very soft character, so that they speedily become worn doAvn, and the characteristic transverse notch obliterated." Mr. Hutchin- son remarks: " Inasmuch as specific inflammations do not occur during the period of intra-uterine life, the teeth belonging to the deciduous series are not liable to be affected, though they may be lost by exfoliation consequent on stomatitis and periostitis. On the other hand, the occurrence of specific affections of the mouth soon after birth may be readily supposed to affect the permanent teeth which are at this time developing, and certain characters are enumerated as indicative of such interference Avith the groAving teeth." Deviations of the teeth from the normal condition are so numer- ous and varied in their character, that it Avould be impossible to describe all of them. Under the title of " dilaceration," Mr. John Tomes describes a con- dition of tooth resulting from displacement of the calcified portion of a tooth from the tissues Avhich Avere instrumental in its produc- tion, the development being continued after the normal position of the calcified portion Avas lost; for example, the croAvn of an incisor Avhen partly formed may move from its position upon the pulp, and be turned outAvard or imvard, or to either side, and there remain in a state of rest, the development of the tooth continuing Avith the displacement of one-half of the croAvn permanently preserved. Fig. 63 represents three cases of dilaceration, tAvo incisors and a bicuspid. Teeth have also been found with the root at its apex ex- panded into a cup-shaped disk, on the margins of Avhich are several openings or foramina for the entrance of the nerves and vessels. Also teeth Avith dentine excrescences in the form of nodules growing from the wall of the pulp chamber. Sometimes these nodules of secondary dentine almost fill the pulp-chamber, Avhile the parenchyma of the pulp is extensively occupied by small MALFORMED TEETH. 119 granules. Such excrescences frequently cause pain of a neuralgic character. The devitalization of the pulp is the only treatment. Dilated roots of teeth are caused by the dentinal pulp becoming hypertrophied into a globular structure of considerable size, and Avhen calcified forming an osseous mass, often larger than the tooth itself. Such tumors are composed of an outer layer of cementum, and a thin shell of dentine enclosing a A'oluminous pulp, Avhich may or may not be calcified. Dilated roots of teeth may occasion pain Avhen the jaws are opened, Avith expansion of the jaw at the alveolar portion. Malformed teeth also result from interrupted development of the dental tissues, Avhich is manifested by the croAvns irregularly grooved or pitted and smaller than the natural size. The incisors are generally thin and atrophied, and the cusps of the canines and molars sharp-pointed, such teeth being deficient in quantity and quality of their tissues, and of a yelloAV, opaque color. Malformed teeth are sometimes, though rarely, met Avith Avhere the roots are perfectly developed while the crowns present a peculiar deficiency, and consist of rudimentary formations Avhich appear like small irregular masses of dentine without any enamel coA'ering. These croAvnless teeth, as they may be styled, are sometimes found worn level with the gum line. Another anomaly of tooth-structure, and one that is also very rare, consists of teeth with crowns flattened in an antero-posterior direction, the jaAvs presenting an edentulous appearance. The sulci of such teeth are misshapen, and the cusps are like narrow ridges. Exostosed teeth are also included in those that deviate from the normal form, one of the most re- markable instances of Avhich Avas a case exhibited by Mr. Tomes — a molar of the upper jaAv, removed from a patient aged forty-one, who had long suffered pain in the jaAV, from Avhich a fistulous passage led through the cheek. Fig. 64 represents this case. (See "Exostosis of the Teeth.") Unerupted or Impacted Teeth are often malformed, and may cause dentigerous cysts. (See " Dentigerous Cysts.") Organic Defects of Structure.—That peculiar structural defect of the teeth, which Avas formerly designated atrophy, is less frequent in its occurrence than any other disease to which these organs are liable; but as the progress of the affection usually terminates Avith the action of the causes concerned in its production, it has scarcely 120 PRINCIPLES AND PRACTICE OF DENTISTRY. been deemed of sufficient importance to merit serious consideration. Hence its etiology and pathology have not been very carefully in- vestigated. Fig. 65 represents superior and inferior front teeth with crowns disfigured by irregular grooves and pits. This affection consists in a congenital defect of structure in teeth rather than in the wasting, for want of nourishment, of any of the dental tissues. The congenital form of the disease is evidently the result of altered function in a portion of one or more of the forma- tive organs—if not of absolute degeneration, from vicious nutrition. Teeth presenting these organic structural defects may very properly be divided into three varieties. Each has characteristic peculiarities Avhich distinguish it from either of the others. Tavo are always congenital, and the other, although most frequently con- genital, sometimes occurs subsequently to the eruption of the tooth. First variety.—The peculiarities that distinguish this variety from either of the others are, that it never impairs the uniformity and smoothness of the surface of the enamel, and is characterized by one or more Avhite, or dark, or light brown, irregularly shaped spots upon the labial or buccal surface of the tooth. It occurs oftener than the third variety, and less frequently than the second. It rarely appears on more than one or two teeth in the same mouth though several are sometimes marked by it. It is seen on the molars more frequently than the bicuspids, and much oftener on the in- cisors of the upper jaw than any of the other teeth. We do not MALFORMED TEETH. 121 recollect to have ever observed it on the cuspids of either jaAv, nor on the palatine or lingual surfaces of the incisors. The enamel is much softer on the affected than on the unaffected parts of the tooth, and may be easily broken and reduced to powder with a steel instrument. It seems to be almost Avholly deprived, in these places, of its animal constituents, and to have lost its con- nection Avith the subjacent dentine. The size of the defective spots is almost as variable as their shape, but the only harm resulting from them is the unsightly aspect they sometimes give to the tooth. As Ave have before remarked, this variety is sometimes accidental, occurring subsequently to the eruption of the tooth, but in a large majority of cases it is congenital. It is rarely seen on a temporary tooth. In all the cases which have come under our observation, it was confined, to the best of our recollection, to the teeth of second dentition. Second variety.—This may be very properly denominated per- forating or pitting defect; it gives to the enamel an indented or pitted appearance, the irregular depressions or holes extending trans- versely across and around the tooth. The pits are sometimes more or less distinctly separated one from another by prominent lines; at other times they are confluent, and form an irregular horizontal groove. Sometimes the}' penetrate but a short distance into the enamel; at other times they extend entirely through it to the den- tine. Their surface, though generally rough and irregular, usually presents a glossy and polished appearance—a peculiarity which ahvaj's distinguishes this variety of the affection from erosion. The pits often have a dark-broAvnish appearance, though sometimes they ha\re the same color as the enamel on other parts of the tooth. This \rariety is never confined to a single tooth. Tavo, four, six, or more corresponding teeth are always affected at the same time in each jaAv; and the corresponding teeth on either side precisely in the same manner and in the same place. When more than tAvo are marked, the distance of the pits from the coronal extremity of the tooth varies, according to the progress made in the formation of the enamel at the time of the operation of the causes concerned in the production of the affection. For example, when the line of pits in the central incisors is situated about two lines from their cutting edges, it will scarcely be one line from the cutting edges of the laterals, and only the points of the cuspids Avill be marked. When the indentations are nearer the edges of the central incisors, they Avill be on the edges of the laterals, and the cuspids Avill have entirely escaped. 122 PRINCIPLES AND PRACTICE OF DENTISTRY. Sometimes the teeth are marked with two or three rows of pits, and when this is the case, the patient has either two or three relapses; or has been attacked two or three times in succession with some disease capable of interrupting the progress of the formation of the enamel. Although the incisors are more frequently marked Avith these in- dentations than any of the other teeth, the cuspids, bicuspids, and even the molars, are sometimes affected with them. When the dis- ease attacks the molars, its effects are generally located on the grinding surface. The permanent teeth are more liable to be attacked than the temporary. We have known but one instance in which the latter Avere affected Avith the disease. This variety occurs oftener than either of the others, and though it sometimes gives to the teeth a disagreeable and unsightly appear- ance, it rarely increases their liability to decay. Third variety.—In this variety the whole or onty a part of the crown of a tooth may be affected ; the dentine being often implicated as well as the enamel. The tooth usually has a pale-yelloAvish color, a shrivelled appearance, and is partially or wholly divested of enamel. Sometimes the crown is not more than one-half or one- third its natural size. Its sensibility is usually much increased, and its susceptibility to pain from external impressions is wonderfully excited by acids. It is also more liable than the other teeth to be attacked by caries. The root of the tooth is sometimes, though rarely, affected, and presents an irregular knotted appearance. The disease is often confined to a single tooth, but it more fre- quently shows itself on tAvo corresponding teeth in the same jaw. According to our observation, the bicuspids are more liable to be attacked than any of the other teeth. The temporary teeth are rarely affected with it. This variety occurs less frequently than either of the others; and, although it increases the liability of the affected organs to caries, they sometimes escape until the twentieth or thirtieth year of age. In the description Avhich we have given of the three varieties of defective structure, we may have omitted to mention some of the peculiarities belonging to each, but we have pointed out their prin- cipal characteristics with sufficient accuracy to enable them to be distinguished one from another, and either from erosion. The first variety is evidently produced by some cause capable either of preventing or destroying the bond of union between the enamel and subjacent dentine. When the affection is congenital, as it almost always is, it is de- MALFORMED TEETH. 123 pendent upon some disease in the pulp or intermediate membrane, Avhich constitutes the bond of union between the dentine and enamel, subsequently to the formation of the latter, either simple local irritation, or general constitutional disturbance. One would be likely to suppose, if the defective spots were occasioned by dis- ease of the pulp or intermediate membrane, the morbid action would scarcely confine itself to such narrow and circumscribed limits. But, Avhether the destruction of the intermediate membrane of the affected parts results as a consequence of actual disease, or merely from vicious nutrition, or Avhether from unknown causes it has failed to be developed here, it is certain that the fibres of this portion of the enamel are not united to the subjacent dentine; thus, not receiving a supply of nutrient fluid or vital principle, their animal frameAvork partially or Avholly perishes, leaving but little else than their inorganic constituents. The cause of this variety of congenital atrophy, it must be confessed, is very obscure; and, in the absence of positiAre knowledge, Ave can only infer the cause from the nature of the affection. If it does not result from one or other of the above-mentioned causes, it is difficult to imagine in Avhat way it is produced. The cause of the second variety may be due to some constitu- tional disease Avhich may interrupt the secretion of the earthy salts deposited in the enamel cells or secretory ducts of the enamel mem- brane, for the formation of the enamel fibres; occurring at the time Avhen this process is going on, it might prevent them from being filled, and cause them to Avither or Avaste away, giving to this portion of the enamel the pitted appearance which characterizes this variety. In other Avords, the secretion of the inorganic con- stituents of the enamel being interrupted for a short time the hori- zontal roAv of cells in the enamel membrane, into Avhich it should be deposited, Avill not be filled ; consequently, as might readily be sup- posed, they will Avaste aAvay, leaving a circular row of indentations around the croAvn of the tooth. But as soon as the constitutional disease has run its course, the secretion of the earthy salts will be resumed; and unless the child experiences a relapse, or has a second attack of disease, capable of interrupting this secretory process, the other parts of the enamel will be well formed. Some writers ascribe the formation of these pits in the enamel to the chemical action of a corrosive fluid, or to an acidulated condi- tion of the fluid contained in the dental sacs; but they have evidently confounded this affection Avith erosion. We believe, hoAvever, it almost always occurs as a consequence of some erup- 124 PRINCIPLES AND PRACTICE OF DENTISTRY. tive disease or catarrhal fever occurring during the formative pro- cess ; and there are many facts Avhich go to sustain the correctness of this opinion. In nearly all the cases that have fallen under our observation, it Avas clearly traceable to measles, scarlatina, chicken- pox, catarrhal fever, or small-pox. It may, hoAvever, occasionally be produced by other constitutional diseases. The third variety, so far as our observation upon this subject has permitted us to form an opinion, ahvays results from altered or vicious nutrition, caused by disease of the pulp or enamel mem- brane, or both, during the secretion of the dentine or enamel, according as one or both are affected. We are inclined to believe that the disease in the dental pulp or enamel membrane may be produced either by local or constitutional causes, or both. But the information Avhich we have been able to obtain in the cases that Ave have seen concerning the state of the general health, and that of the mouth at the time of the dentification of the pulp and the secre- tion of the enamel, have not been as satisfactory as we could have Avished. Since Avriting the foregoing, the following interesting case of dental atrophy has fallen under our observation : Mrs. C. called to consult us concerning her daughter's teeth, which, from congenital defect, presented a most unsightly appear- ance. The girl Avas betAveen nine and ten years of age. The cut- ting edges of the upper central incisors Avere badly pitted and very rough ; the corresponding teeth in the loAver jaw had a transverse row of pits passing around them, about a sixteenth of an inch below their cutting extremities. Another roAV of pits, so close together as to form a rough groove, encircled the upper central incisors, about an eighth of an inch below the gum, and the laterals a little nearer their cutting edges ; the loAver incisors were similarly marked, but not quite so near the gum. The enamel, near the second trans- verse row of pits, and between it and the cutting edges of the teeth, Avas thin and of a light-broAvn color. A little above the first toav, on the central incisors, Avere two or three brown or opaque spots. The first permanent molars Avere also encircled Avith a toav of in- dentations, about half-way betAveen their grinding surfaces and the gums. On inquiry, we learned from the mother that the child had a light attack of measles Avhen between eleven and twelve months old, of scarlet fever when about fifteen or sixteen months of age and dysentery at about the tAventy-first or tAventy-second month. Now, here Ave have the three varieties of defective structure on ORIGIN AND FORMATION OF THE TEETH. 125 the same teeth; and the occurrence of constitutional diseases about the time Avhen the affected parts of the teeth must have been re- ceiving their earthy salts, which Avould seem to establish very con- clusively the connection of the one Avith the other. The nature of this affection is such as not to admit of cure. The treatment, therefore, must be preventive rather than curative. All that can be done is to mitigate the severity of such diseases as are supposed to produce it, by the administration of proper remedies. By this means their injurious effects upon the teeth may, perhaps, be partially or wholly counteracted. In some forms of this affection the teeth may not decay more readily than others, so that the only evil resulting from the affection is a disfiguration of the organs ; but in others, and especially in the pitted variety, it may be necessary to insert fillings at an early age. When the cutting edges of the incisors only are affected, the diseased part may sometimes be removed Avithout injury to the teeth. CHAPTER XL ORIGIN AND FORMATION OF THE TEETH* Of all the operations of the animal economy, none are more curious or interesting than that Avhich is concerned in the pro- duction of the teeth. In obedience to certain developmental hnvs, established by an all-Avise Creator, it is carried on from about the sixth Aveek of intra-uterine existence, with the nicest and most Avonderful regularity until completed, and excites in the mind of the physiologist the highest admiration. From small papillse, observable at a very early period of foetal life, the teeth are gradually developed, and as they increase in size, the papillse assume the shape of the croAvns of the several classes of teeth they are respectively designed to produce. Having arrived at this stage of their formation, they now begin to dentinify, first upon the cutting edges of the incisors, the apices of the cuspids, bicuspids and eminences of the molars; from thence the process is continued over the Avhole surface of their crowns, until they * The study of the "origin and formation of the teeth " should begin with the "development of the bones of the head and face," and the "description of the mucous membrane," to which subjects the reader is referred. 126 PRINCIPLES AND PRACTICE OF DENTISTRY. become invested Avith a complete layer of dentine; and so layer after layer is formed, one Avithin the other, until the process of solidification is completed. Before the appearance of the dentinal germ or papilla, hoAvever, the enamel of the teeth begins to form, and Avhen the enamel organ or cord has acquired the appearance of a hood or cap, and contemporaneous Avith this change, the dentinal papilla is deA'eloped, and this formative operation is gone through Avith previously to the completion of the dentinification of the pulp. In the meantime, and in anticipation of the loss of the temporary teeth, a second set is forming, and as the teeth of the one series are removed, they are promptly replaced by those of the other. Thus, by a beautiful and most admirable pro\rision of Nature, the first set of teeth, intended to subserve the wants only of childhood, Avhile the jaAvs are too small for the reception of such as are re- quired for an adult, are removed and replaced by a larger, stronger, and more numerous set. The older Avriters, regarding a knoAvledge of the earlier stages of the development of the teeth as not of much importance, paid little attention to the subject, and hence this most curious and interesting department of developmental anatomy has remained, until recently, measurably uncultivated. Eustachius, Ave believe, Avas the first to notice the position and arrangement of the teeth in the jaAvs pre- vious to their eruption. But his researches Avere confined to the examination of the jaAv after birth, at Avhich period he speaks of having discoArered, by dissection, the incisors, cuspids, and three molars on each side, in each jaw, partly in a gelatinous and partly in a solidified condition. He also discovered the incisors and cuspids of the permanent set behind the first. Eustachius Avrote in 1563, and nineteen years later Urbian Her- mard, a French anatomist and surgeon, although unacquainted with the Avork of the former, gave a very similar description of the situation of the croAvns of the incisors and cuspids of both sets in the jaAvs of an infant at birth. He represents them as partly bony and partly mucilaginous. He also discovered the bicuspids; but he was unable to find the molars at so early a period as at birth. The researches of Albinus threw no additional light upon the manner of the formation of the teeth, and little Avas known con- cerning the earlier stages of the development of these organs until the time of John Hunter, who informs us that in the alveoli of a foetus of three or four months " four or five pulpy substances, not very distinct, are seen." Although Mr. Hunter gives a more minute description of the pro- ORIGIN AND FORMATION OF THE TEETH. 127 gress of the formation and arrangement of the teeth in the jaAvs previously to their eruption than any previous writer, yet, Avith re- gard to their origin and appearance during the earlier stages of their development, he is unsatisfactory. Xor do the researches of Jour- dain, Blake, Fox, Cuvier, Serres, Delabarre, Bell, and other writers, throAV much additional light upon the subject. In fact they could not, as their researches, except those of Mr. Bell, do not seem to have been commenced at periods sufficiently early in foetal sub- jects; and even from the time Avhen they were first instituted, the progress of the organs does not appear to have been traced through the subsequent stages of their formation Avith the requisite degree of care and accuracy. It is not, therefore, necessary to notice the descriptions given by these authors of the progress of the formation of the teeth. The theories of Arnold and Goodsir, and especially the latter, Avere formerly universally accepted, but the later researches of Waldeyer and Dursy have shown them to be erroneous, and the theory of Waldeyer is now generally adopted.* Commencing the description of the development of the teeth Avith the condition of the jaws of the embryo at the period of the for- mation of the organs. Avhich compose the " dental follicle," namely, the enamel organ, the dentinal germ or papilla, and the follicular Avail or sac, there is at an early period no trace of osseous tissue in the lower jaAv, the maxillary arch having Avithin its component elements a symmetrical cartilaginous band, Avhich extends its entire length, as far as the frame of the drum of the ear, and which is knoAvn as " Meckel's cartilage." This cartilage acts a transitory part only, until osseous tissue is developed, when it disappears, first by calcification, and afterward by ossification. (See Development of the Bones of the Head and Face. Figs. 2, 3, and 4.) As regards the upper jaw, the same period of evolution as that of the loAver jaAv marks the union of the maxillary germs with the median or inter-maxillary germs, Avhich occurs in the human embryo about the fortieth or forty-fifth day. On the surface or * According to the theory of Goodsir, at an early period of foetal life there ap- pears a continuous open groove running around the whole circumference of the jaws. From the bottom of this groove, which he styles the primitive dental groove, there arise isolated and uncovered papillse corresponding in number to the decidu- ous teeth. These papillae become covered in by. the deepening of the groove and the coming together of its two edges over their tops, while at the same time trans- verse septa are formed, so that the several papillae become enclosed in separate follicles. 128 PRINCIPLES AND PRACTICE OF DENTISTRY. Fig. 6P. rounded portion of the tAvo maxillary arches thus formed, and Avhich later constitute the alveolar border or process, a depression or groove, called the " dental groove," appears, Avhich, hoAvever, is so completely filled or " heaped up " Avith a bed of epithelial cells as to form a protuberance or smooth ridge, desti- tute of any fold or depression AAThatever. This ridge (Fig. 66) is composed of a thick bed of epithelial cells, which, however, on its sides form a coat of a feAV rows of cells only, and does not include any other well-defined tissue unless it be some vessels, nerves, and muscle-fibres in process of deA^elopment. The principal structures of the teeth are derived from such elements as compose the epithelial structure and the tissues beneath Avhich represent the corium and cellular tissue of the mucous membrane, beneath which is the ossifying substance of the jaw—the enamel being formed from the epithelium Avhich fills the dental groove and constitutes the rounded projection or smooth ridge, and the dentine and cementum (crusta petrosa) from the deeper structures of the mucous membrane. Development of the Enamel.—First, as to the deArelopment of the enamel, which is very similar to that of the hair follicle. About the sixth or seventh week of foetal life, the epithelium fills the groove Fig. 67. d. A mass of epithelium —the "dental ridge;" 6. younger layer of epithe- lium ; c. deepest layer of epithelium—theprismatic or columnar stratum ; e. enamel germ. a. Flat layer of epithelium; b. proliferation of cuboidal layer, forcing columnar layer down- ward, producing V-shaped appearance. The removal of these upper layers leaves the " primitive dental groove;" c. lamina from which arise the epithelial cords of enamel organs. or depression on the surface of the jaw so full that a small, rounded projection or ridge is formed, from the under surface of which a process sinks into the tissue beneath, the outlines of which resemble in shape the letter V with the apex slightly inclined toward the inner surface (Fig. 67). This epithelial process or band is simply a prolongation of the natural covering of the mouth, which sinks ORIGIN AND FORMATION OF THE TEETH. 129 Fig 68. into the embryonic tissue of the jaAv, and forms for itself a groove Avhich it completely fills, and is composed of the same histological elements as the epithelium of the mucous membrane of the mouth. When this epithelial band is fully formed it presents two sur- faces, an external and an internal, and from the latter a process is given off Avhich forms the epithelial lamina. This epithelial lamina is a continuous process extending over the entire epithelial band, being an inflection of the band itself, and its elements are the same, namely, polygonal cells inclosed by a layer of prismatic cells. The " dental follicle " Avhich, as Avas before stated, consists of the enamel organ, the dentinal germ or papilla, and the follicular A\rall, is developed from points on the free extremity of the epithelial lamina. These follicles appear as small tubercles arranged at inter- Arals on the free margin of the lamina, and correspond in number and location to the future decidu- ous teeth, being the primitive germs of the dental follicles Avhich retain their connection Avith the lamina by means of a slender cord, which gradually increases in length as the development of the germ at its extremity progresses. This germ constitutes the enamel organ, while the neck or cord in its pro- gressive lengthening merely serves as a temporary connection with the lamina. This germ presents a spherical form in its early stage (Fig. 68), and is composed of an external layer of prismatic cells (ameloblasts) including a mass of polygonal cells. The younger layer, described as " infant cells," owing to the active cell-multipli- cation which takes place at the point where the epithelial cord for the tooth is to arise, sinks into the substance of the tissue beneath the epithelium in the form of a pouch. Some contend that the cells of this infant layer are not columnar, but are oval or spheroidal. The enamel organ at about the fourth month of the development of the embryo has undergone very considerable changes, the primi- tive polygonal cells Avhich compose the central mass or middle region of this organ have been transformed into stellate bodies dif- fering in appearance from the primitive cells, a process, hoAvever, which is confined to the cells of the enamel germ, and which does not take place in the cells of the epithelial cord or lamina, thus 9 PRISMATIC DENTAL FOLLICLE. c. Prismatic or columnar cells ; d. large polygonal cell of the epithelial band; e. small cells of the epithelial laminae. 130 PRINCIPLES AND PRACTICE OF DENTISTRY. affording evidence that the constitution of the one differs from that of the other. These stellate cells (Fig. 69) are composed of a central nucleus surrounded by a transparent or finely granular mass, which mingles with the neighboring elements. They occupy at first only the centre of the enamel organ, and those near the periphery preserATe their primitive polygonal form, but be- Fig. 69. Fig. 70. stellate cells of the enamel Represents the hexagonal organ. form assumed hy the base (Diagrammatic, from Frey.) of the stellate cells. come stellate as the organ increases in size, and are formed from the original elements composing the internal mass of the enamel organ, being epithelial in their nature. After a, time the base of these stellate cells presents the regular prismatic form of a hexagon (Fig. 70). During this modification of the enamel germ, no change appears to take place in the epithelial lamina. The primitive enamel germ at length loses its original spherical form, and becomes somewhat cylindrical, pursuing a horizontal course until it undergoes a considerable increase in length, Avhen, by an abrupt turn it takes a vertical direction and sinks into the tissues of the jaw. During such a progress the cord acquires a length in accordance with the requirements of the j#av. After the epithelial cord has changed its course from a horizontal to a vertical direction, its extremity expands and assumes a club- shape, on account of the multiplication of the polyhedral cells of Avhich its greater portion is composed, and also of the prismatic cells that surround it. This expanded extremity also becomes some- what spherical, and its upper portion corresponds to the point of connection Avith the cord, while the lower portion points toAvard the base of the lower jaw. This condition represents a fully formed enamel organ, Avhich is ORIGIN AND FORMATION OF THE TEETH. 131 the first trace of the dental follicle. Very soon the loAver portion of the enamel organ becomes concave, and assumes the form of a cap or hood, although still retaining its connection Avith the epithelial cord. At this stage in the deA-elopment of the enamel organ, the dentinal germ or papilla makes its appearance. During the development of the primitive epithelial cord, lateral germs similar to small rounded nodules, in the form of varicosities, Fig. 71. make their appearance, and Avhich, according to Magitot, resemble an irregular chaplet or chain. These lateral germs are composed of small polyhedral cells, like those of the cord itself, with walls formed of a layer of prismatic cells in continuation of the Malpig- hian layer of the epithelium. From these lateral germs or masses, at a later period, after the cord is ruptured, epithelial prolongations arise. 132 PRINCIPLES AND PRACTICE OF DENTISTRY. The primitive cells during the early stage of evolution present the same characteristics on all parts of the periphery, but as soon as the dentinal germ or papilla begins to appear these primitive cells on the concave surface lengthen, while those of the convex surface decrease in size until they disappear entirely, before the atrophy of the enamel pulp; and those of the internal surface re- main for the formation of the enamel organ. Besides increasing in length, the prismatic cells of the concave surface of the enamel organ undergo changes, their extremities, directed toAvard the centre of the enamel organ, forming slender Fig. 72. enamel organ and "nasmyth's layer" of cells, drawn under a magnifying power OF 1800 diameters. a. Portions of the reticulum which lie exactly in focus; the points of intersection are seen to be made up of a finer and more delicate reticulum; b. parts which lie a little beyond focus; c. granular matter held in the meshes of the reticulum,; d. " Nasmyth's membrane," or layer of flat cells, just outside of enamel cells. processes, which either unite, or are continuous with filaments from surrounding cells, Avhich constitute the portion of the enamel organ designated as the stratum intermedium. The stratum intermedium consists of cells, which, according to Mr. Tomes, are intermediate in character between those of the bordering epithelium and the stellate reticulum, being branched, but less conspicuously so than the stellate cells, with Avhich they are continuous on the one hand, and on the other with the enamel cells. According to W'aldeyer, Hertz and Hannover, since the enamel cells may be frequently seen connected at their loAver extremities with the cells of the stratum intermedium, a multiplication of enamel cells from the cells of this stratum, in the direction of their length, may be admitted to occur. ORIGIN AND FORMATION OF THE TEETH. 133 Fig. 73. E.E. According to Dr. G. V. Black, and quoted by Dr. M. A. Dean, "just before the calcification, and even before the odontoblasts make their appearance, the ameloblasts (prismatic cells), and the tissues of the pulp are separated by a Avell-marked double pellucid layer, Avhich in sections appears as a double band." This double band is represented in Fig. 73 by the tAvo Avhite parallel lines, A A, the upper one being the tissue which is identical Avith the membrana prseformativa of Hux- ley, Avhile the loAver one represents the basement membrane of Ladd and Bow- man, and the membrana prseformativa of RaschkoAV. After the epithelial cells are changed into hexagonal prisms, these anastomose and form the hexagonal rods character- istic of fully matured enamel. The epithelial covering on the outer surface of the enamel remains distinctly perceptible, and after the eruption of the croAvn of the tooth, this layer, Avhich is knoAvn as the " dental cuticle"— cuticula dentis, and also as " NasmATth's membrane," may be separated from the enamel surface beneath it by strong acids, Avhen the hexagonal depressions of enamel prisms are apparent, and on the application of nitrate of silver the char- acteristics of epithelium appear. Dr. J. L. Williams, in an able article on " embryology," dissents from the opinion of Legros and Magitot concerning the function of the membrana prseformativa of RaschkoAV, and positively denies that it has any modifying influence in the process of the development of the teeth; and, while he is not prepared to deny in toto the ex- istence of this membrane, says, that an examination of many speci- mens failed to discoA'er this structureless, transparent tissue; and he asks, " Hoav is it possible that the odontoblasts, Avhich are more than ^Vo of an mcn m diameter, can be developed in a membrane Avhich Beale says is " certainly less than the ^l^ of an inch in thickness." Dr. Williams also remarks: " It has been supposed that the so-called ameloblasts, or enamel cells, are formed directly A. A. B. M. Basement membrane; N. neck; S. sac or follicular wall; 0. enamel organ; B. bulb; E. E. ex- ternal epithelium of the enamel organ and the basement mem- brane; E. C. epithelial cord: C. T. connective tissue surrounding the enamel organ; Ep. epidermis or oral epithelium. The parts embraced between the points where the divergent lines A A terminate are : (1) The concave face of the enamel organ, lined with a layer of ameloblasts, or the "internal epithelium." (2) The membrana prseformativa of Hux- ley, or the tissue composed of the basal coverings of the ameloblasts. (3) The membrana prseformativa of Raschkow, or the basement mem- brane. (4) The dentine bulb itself. Diagrammatic. 134 PRINCIPLES AND PRACTICE OF DENTISTRY. from the layer of columnar or prismatic epithelium, which covers the face of the enamel organ." But preceding the development of the enamel cells, the original prismatic cells break up or divide into round, nucleated corpuscles, which change is denominated by by Professor Heitzmann and Dr. Atkinson a return to an embryonal condition." Fig. 74. THE SPECIMEN FROM WHICH THIS DRAWING WAS MADE WAS PLACED UNDER A ONE-TENTH- INCH IMMERSION LENS, MAGNIFYING ABOUT 800 DIAMETERS. a. Connective tissue of tooth-sac; b. capillary vessels cut transversely and longitudinally, and filled with blood-corpuscles; c. reticulum of enamel organ ; d. round and flat layer of cells, forming the so-called " Nasmyth's membrane ;" e. ameloblasts, or enamel cells. " From these embryonal corpuscles are developed the enamel- forming cells, and also an outer layer of smaller cells, from which is formed Nasmyth's membrane." The same author also regards the enamel organ as a " true secreting organ," and that the material for the formation of enamel has no other evident source. Development of the Dentine.—As the epithelium is undergoing this peculiar development into the enamel organ, a projection of the corium of the mucous membrane of the fcetal jaw rises up to meet ORIGIN AND FORMATION OF THE TEETH. 135 it out of the dental groove. This projection is the dentinal papilla or germ, which is described, after Dursy and Waldeyer, as a ridge, " the intervening parts of which are atrophied so as to leave papillse Fig. 75. DRAAVN UNDER THE SAME MAGNIFYING POAVER AS FlG. 46. o. ConnectiA'e-tissue cells of tooth-sac; 6. reticulum of enamel organ. In this drawing it is seen that the reticulum holds in its meshes very large, soft, granular corpuscles, heretofore knoAvn as the gelatinous fluid of the enamel organ; c. breaking down of columnar layer of cells into embryonal corpuscles, from which ameloblasts are developed. or germs which become coated all over by the enamel organ, and thus the saccular stage of the teeth is produced, the papillse Avhich 136 PRINCIPLES AND PRACTICE OF DENTISTRY. are to form the bulk of the teeth being coated Avith a vascular con- nective tissue, isolated by the enamel organ and separated from each other by the growing (osseous) tissue of the foetal jaw." Dursy, according to Waldeyer, says : " The first germ of the den- tine appears in the dental sacculus, as a dark semi-lunar area at the bottom of the dental groove—that is to say, of the enamel germ— coetaneously and continuously with Avhich it is developed along each half of the jaAv. At certain points corresponding to the position of the subsequent teeth, the young structure develops in the form of papillse, projecting against the enamel germs, Avhile the remainder Fig. 76. a. Meckel's cartilage ; b. traces of ossification ; c. lowest layer of Malpighian stratum ; d. oral epithelium; F. ameloblastic or prismatic layer; lower F. external layer of enamel organ; g. stellate reticulum of the enamel organ; H. dental germ or papilla; I. follicular Avails. atrophies. The two horns of the semi-lunar mass (as seen in sec- tion) extend from the base of the dental papilla some distance upAvard, and embrace the dentine germ and enamel organ." According to Dr. Sudduth, the epithelial cord does not penetrate the underlying tissue searching for a dentinal papilla, but it has the poAver to superintend the differentiation of a papilla for itself. As the dentinal papilla or germ increases in height, it assumes a slightly oblique direction in relation to the axis of the follicle and and at the same time becomes constricted at its base, thus forming a neck at the line where the enamel organ is reflected back upon itself (Fig. 76). ORIGIN AND FORMATION OF THE TEETH. 137 Fig The follicular Avail, AArhich forms a part of the dental follicle, first appears as a process arising from the base of the papilla, to the neck of Avhich it is attached like a slight collar. Its development begins as soon as the small mass Avhich constitutes the dentinal germ assumes a hemispheric form. The follicular Avail, by its gradual upAvard groAvth, at length embraces and isolates both the enamel organ and the dentinal papilla, and during its evolution, from being composed of embryoplastic elements, b}7 degrees assumes the appearance of a distinct laminated membrane, Avhich may be separated from the adjacent tissue, except at the base of the papilla to which it remains adherent. According to both Kolliker and Huxley, the transparent stra- tum (membrana prseformativa) Avhich invests the dentinal papilla, reflects itself back on its internal surface, and thus lines the whole inner surface of the follicular Avail. As the evolution of the follicular Avail progresses, it closes over the contents of the dental follicle, Avhich, besides the wall, consist of the enamel organ and the dentinal papilla; the enamel organ being sub- jacent to the follicular wall, to which it conforms in such a manner that, Avhile the ex- ternal face of the organ is in relation Avith the wall, the a. Wall of the sac, formed of connective tissue, i „^.,„,,.^ fnn.^ ir, 4v^ ;m Avith its outer stratum a1 and its inner a2; b. loAver concaAe lace is in lm- . .„. .. ... . ... *w v, v- ^ enamel organ, Avith its papillary and parietal mediate contact Avith the layer of cells ; c. d. the enamel membrane and papilla. The dentinal papilla en*mel Prisms; e- dentine cells; {• den^ f ™ r r i J- an(i capillaries; g. i. transition of the wall of the OCClipieS the loAVer and Central follicle into the tissue of the dental germ. portion of the follicular sac. The enamel organ fills the entire space betAveen the sac wall and the papilla, terminating at the base of the latter in a rounded mar- gin Avhich forms the dividing line between the prismatic cells Avhich cover its concave and convex surfaces (Fig. 77). The dental follicle is of an ovoid form, and varies in size according to the class of tooth to be developed from it; and Avhen it is completely formed, it re- mains inclosed Avithin the embryonal tissues of the jaAvs, Avith Avhich it is at first only slightly connected. 138 PRINCIPLES AND PRACTICE OF DENTISTRY. When the rupture of the epithelial cord occurs, it loses its com- munication with the mucous membrane, and forms no connection Avith the maxillary bone, as the alveolar processes are not developed until a later period. The rupture of the epithelial cord, which brings about the isola- tion of the dental follicle from the mucous membrane, is due to the upward groAvth of the follicular Avail, Avhich closes over the top of the enamel organ, beneath Avhich is the papilla, the union of the edges of the wall producing compression or strangulation of the cord at that point. At this period of eA*olution, the saccular stage, the dental follicle is completed, and from the cells of the dentinal papilla a soft matrix of animal matter is formed, which becomes impregnated with calcareous matter to form the complete dentinal tissue, while in the interior of the cavity of the dentine, cells are formed, Avhich continue to form neAV matrix for a considerable time. After the dentinal papilla has become coated over by the enamel organ, and the saccular stage of the teeth is produced, and the papillse have become separated from each other by the developing tissue of the embryonic jaAv, odontoblasts (dentine cells) begin to form. These odontoblasts are large nucleated cells of elongated form, containing numerous processes deA'eloped from the cells of the dentinal papilla, Avhich at that early period consist of fine fibrous tissue with numerous cells. The odontoblasts send out processes Avhich, as they develop, calcify externally, the calcified portion forming the dentine, and the uncalcified part the dentinal fibrillse, and the lateral branches of anastomosis whereby the tubuli or canals of the dentine anastomose. The remains of the odontoblasts form a cellular layer which con- stitutes the investment of the pulp lying between its nerves and vessels and the dentine. This cellular layer is known as the " ivory membrane "—membrana eboris of Kolliker. The enamel organ is non-vascular, but a network of vessels is fur- nished to the follicular wall and the dentinal papilla from the surrounding tissues. At the period when the epithelial cord is ruptured, the cells com- posing the epithelial lamina become greatly increased in number, and irregular proliferations or u buddings " occur, Avhich wander In- different courses into the deeper portions of the embryonal tissue. These buddings differ in form, sometimes in that of cylinders Avhich retain their connection with the primitive lamina; but frequentlv this connection is absorbed, and an epithelial mass is set free. Clusters of these masses occasionally take the globular form, resem- bling those in the lamina itself, but frequently they become absorbed ORIGIN AND FORMATION OF THE TEETH. 139 and disappear before the development of the tooth is completed. At the time the absorption of the epithelial lamina is taking place, changes precisely analogous are transpiring in the severed epithelial cord. From the remains of this cord processes are given off, Avhich at times become quite numerous, and may remain almost to the time of the eruptive stage of the tooth. The direction of these processes is toAvard the epithelium, and they consist of the same polyhedral cells as the cord and lamina, but are never invested Avith prismatic cells. All these epithelial Fig. 78. a. Meckel's cartilage; b. traces of ossification; c. loAvest layer of Malpighian stratum : d. oral epithelium ; ^.ameloblastic layer; lower F. external layer of enamel organ; //. dentinal papilla; I. follicular Avail; K. buddings of epithelial cord. proliferations finally disappear by absorption, unless some such masses may become detached and wander into the deeper tissues; for it is considered by some eminent histologists that a dentinal papilla or germ may originate from any point of the dentinal sheet of tissue Avith Avhich the epithelial mass comes in contact, and that it is solely through the influence of the enamel organ upon this tissue that the development of the dentinal papilla is induced. Immediately after the rupture of the epithelial cord, the forma- tion of the secondary follicle of the permanent tooth begins. There is no trace of the osseous tissue of the ja\v at the time of the origin of the primitive epithelial cord. Bone first makes its appearance J^llO PRINCIPLES AND PRACTICE OF DENTISTRY. near the base of the follicles, forming a horizontal layer, and sepa- rating the groove of the follicles from the canal reserved for the vessels and nerves. From the layer or floor, lateral processes arise and form the dental groove, in which the follicles remain for some time without being separated by transverse partitions, and it is only after the development of the crowns of the teeth has commenced, Fig. 79. FROM THE UPPER JAW OF A KITTEN, ABOUT THE TIME OF BIRTiI. a. Oral epithelium ; b. bone of jaw ; c. neck of enamel organ ; d. dentinal papilla; r. enamel cells ; /. stellate reticulum ; h. germ or papilla of permanent tooth, the enamel organ of which is derived from the primary cord. that bony processes are throAvn across the groove, forming recepta- cles for the lodgment of each follicle Avith an opening in the direc- tion of the epithelial surface (Fig. 79). Development of Cementum (Crusta Petrosa).—There appears to be a difference of opinion among histologists concerning the origin of the cementum. Magitot, in 1858, and again Robin and Magitot, in 1861, described a neAV tissue, Avhich, some time before the formation of .the first dentine cap, was supposed to exist betAveen the follicu- lar wall and the organs within it—the enamel organ and the papilla—differing from the other tissues in color, consistence and structure, and upon which the formation of the cementum de- pended. On the other hand, Kolliker, Waldeyer, Hertz, Kollman, and others, deny the existence of such a membrane or tissue, and as- cribe the formation of the cementum (Avhich resembles ordinary bone, as it contains canaliculi and lacunse), to a periosteal origin— that it is developed from the deeper tissues of the foetal jaAv by periosteal ossification, the process being similar to that of bone for- mation in other parts of the body. ORIGIN AND FORMATION OF THE TEETH. 141 Origin of the Permanent Teeth.—While Goodsir held that the folli- cles of the permanent teeth originate from a fold of the sac of the primitive or deciduous follicle, the later investigations of Kolliker and Waldeyer have shoAvn that the permanent follicles of teeth that have deciduous predecessors arise from certain prolongations of the primitive epithelial cord. The germ of the permanent follicle originates at a point Avhere the primitive epithelial cord merges into the enamel organ of the tem- porary tooth, and is an outgroAvth of this cord (see Fig. 80). The permanent cord takes a vertical direction, and passes betAveen the bony alveolar wall and the primitive follicle, and then along the inner or lingual face of the follicle, its elements being the same as those of the primitive cord. The permanent dentinal papilla or germ sinks to the bottom of the osseous dental groove, where it soon loses its connection with the primitive follicle, though still retaining its relation with the epithelial lamina. The primitive follicle, hoAV- ever, by the severance of its cord at a point just below Avhere the germ of the perma- nent or secondary cord arises, loses all connection Avith the epithelial lamina, and develops as an independent body or organ. The sinking of the follicle of the permanent tooth is soon folloAved by the entire series of phenomena Avhich characterize the groAvth of every dental fol- licle; and Avhile the permanent follicle is being developed, the remains of the ruptured primitive cord Avhich continues to be attached to the primitive follicle, are subject to that " budding " process Avhich invariably commences at the moment this cord is severed—about the fourth month, or quickening period. The direc- tion of the permanent cord being vertical, its length is governed by SECTION OF THE LOAVER JAAV OF A HUMAN FC3TUS, 9% inches in length ; corresponding to about the eighteenth week. (Magnified 80 diam.) K. Cord or bourgeon of the secondary follicle ; L. point where its separation from the primitive cord is being effected ; a. Meckel's cartilage dimin- ished by absorption ; 6. bone of the jaw; e. (upper) dental artery, (lower) dental nerve; d. epithelium; E. originally the cord of the temporary follicle, but now the sole property of the permanent one. 142 PRINCIPLES AND PRACTICE OF DENTISTRY. the height of the alveolar border, and the direction of the primitive follicle. When sinking into the substance of the jaw, the perma- nent cord always assumes a spiral form, and to such a degree that it can be readily distinguished from the primitive cord, as this latter is never so distinctly spiral in form as the former. This spirality of form peculiar to the permanent cord is occa- sioned by the greater distance this cord must traverse in the more VERTICAL SECTION OF THE LOWER JAW OF A HUMAN F03TUS, Measuring 18% inches ; corresponding to nearly the thirty-ninth week of gestation. The fig- ure represents a cut passing through the follicle of a bicuspid. b. Bone of the jaAv ; d. oral epithelium ; g. enamel organ: H. dental bulb ; K. debris of the cord of a permanent follicle : K' K7. epidermal globules. Follicle for the permanent tooth connected Avith th« debris of its cord, A". developed tissues of the jaAv, to permit the permanent follicle to ac- complish its passage to a point under the temporary tooth, and thus prevent the stretching of the cord and the disturbance of the parts with Avhich the cord and enamel organ are connected. The spiral nature of the cord continues from its origin towards its termination in a rounded or club-shaped enlargement, similar to that of the extremity of the primitive cord, this enlargement representing the enamel organ of the permanent tooth. At the period in the evolution of the permanent follicle when the 00000102010600000201010000000202010202010101010000020091020000020202010002 ORIGIN AND FORMATION OF THE TEETH. 143 dentinal papillse becomes unicuspid for the incisors and canines, and multicuspid for the molars, the permanent epithelial cord, Avhich has already been for some time severed from the primitive cord and follicle, also loses its connection Avith the permanent follicle, and has no communication aftenvards with the epithelial lamina. This severance is soon folloAved by the separation of the permanent cord into fragments, Avhich, as was before stated, bud and lengthen in different directions, and become mingled and confounded with those of the primitive cord, anastomosing with them to form a sort of plexus. Finally, all these epithelial masses atrophy and disappear. The above description applies to the deArelopment of the perma- nent teeth that have temporary predecessors. But the origin of the permanent teeth that appear back of the temporary teeth, and have no deciduous predecessors, is entirely different. The first permanent molar, the follicle of Avhich makes its appear- ance during the fifteenth Aveek of embryonal life, and only a feAV days after the greater number of those of the deciduous teeth, and yet does not erupt until about the sixth year, originates directly from the epithelium of the mucous membrane, the epithelial cord from Avhich penetrates the foetal tissue in a region Avhere no follicle has preceded it. The second permanent molar originates from an outgroAvth of the epithelial cord of the follicle of the first permanent molar, resem- bling in this respect the twenty anterior permanent teeth, but differ- ing in the direction of its course. While the teeth deri\red from the temporary follicles pass over the lingual face of the latter to a posi- tion beneath them, that of the second permanent molar takes a horizontal direction for some distance, and then by an inflection takes its position at the posterior side of the follicle of the first molar, where it is developed in a line Avith those anterior to it (Fig. 54). The origin of the third molar or Avisdom tooth is effected in the same manner as that of the second permanent molar, as the epi- thelial cord that forms its enamel organ emanates from the cord of the second permanent molar. Hence we find the cord of the first permanent molar originating from the epithelium ; that of the second permanent molar from the cord of the first permanent molar; and that of the third molar from the cord of the second permanent molar. Dr. G. V. Black, whose extensive researches in dental histology are Avorthy of all praise, is of the opinion that, " although the epithelial cords of the tAventy anterior permanent teeth generally arise from those of the temporary follicles, yet they do sometimes emanate directly from the epithelium of the mucous membrane. If such is the case, the secondary or permanent epithelial cords 114 PRINCIPLES AND PRACTICE OF DENTISTRY. may originate from either the primary cord, the temporary follicle, or the epithelial lamina. The follicles of the temporary teeth are developed during the period betAveen the latter part of the third month of gestation and the beginning of the fourth year—Avithin forty -tAvo months, Avhile the follicles of the permanent teeth require a much longer time for their evolution. It Avould seem quite reasonable to suppose that the dentinal papilla acts as an organic mould upon which the elements of the enamel are coated, but Magitot asserts that as the epithelial cord which represents the future enamel organ ahvays precedes the appearance of the papilla, Fig. 82. SECTION ON A LINE AA^H THE FOLLICLE OF THE FIRST PERMANENT MOLAR Human subject, three months after birth. Magnified 80 diameters. ft. Maxillary bone; c. c. dental artery and nerve; E. cord of the follicle of the first per- manent molar; g. enamel organ ; H. bulb of the first permanent molar; K. bourgeon of the enamel organ of the second permanent molar. Avhich is never formed until the cord has advanced a certain dis- tance, this cord decides not only the place of genesis, but the form and function of the corresponding tooth. According to Dursy, a dentine germ or papilla may be developed from any point of the semi-lunar area which is found below the enamel organ, as soon as such a point is reached by this organ, and the dentine germ de- pends upon the course Avhich the enamel organ takes. For example, if the epithelial cord of a canine should take an unnatural course, so as to come in contact Avith the dentinal tissue at a point betAveen the bicuspids, the canine Avould be developed betAveen those teeth ; THE DENTAL PULP. 145 hence it seems reasonable to conclude that the enamel organ deter- mines the form and character of the future tooth. Although the proliferations or buddings of the remains of the epithelial cord, after its severance from the enamel organ, usually disappear by absorption, yet it is possible that some such masses, meeting Avith dentinal tissue, may become the enamel organs of sup- ernumerary teeth. THE DENTAL PULP. The pulp, occupying the pulp-cavity in the centre of the tooth, is the shrunken condition to which the tooth-germ, or dentinal papilla, is permanent^ reduced after it has normally accomplished the work of dentinification, and affords the vascular and nervous supply of the dentine. In the development of the dentine-dentinification, Fig. 83. A PORTION OF THE BODY OF THE PULP, SHOAV- A PORTION OF THE SUPERFICIAL LAYER OF ING THE CELLULAR ARRANGEMENT. THE PULP, SH OAVING THE APPEARANCE OF VESICLES. the thickening of the dentinal wall is produced by the primary single layer of odontoblasts, and this thickening is not only at the expense of the pulp-cavity, but of the pulp itself, Avhich gradually diminishes in size as the dentine increases in bulk. The dental pulp is an exquisitely sensitive, highly vascular substance, of a reddish-gray color, enveloped in an exceedingly delicate and appa- rently structureless membrane, continuous with the alveolo-dental periosteum, and adherent to the Avails of the pulp-cavity. This is designated by Mr. Thomas Bell " the proper membrane of the pulp," and by Purkinje and Raschkow, " the preformative membrane; " because, in the formation of the dentine, the deposition of earthy salts, according to these authors, commences in it. The pulp, according to the two last-mentioned authors, is com- posed of minute globules. SchAvann describes it as consisting of globular, nucleated cells, Avith vessels and nerves passing betAveen them, the cells having the same radical course as the fibres of the dentine. According to the microscopic observations of Mr. Nas- 10 Fig. 84. 146 PRINCIPLES AND PRACTICE OF DENTISTRY. myth, it is principally composed of minute vesicular cells, varying in size from the ten-thousandth to the one-eighth of an inch in diameter, disposed in concentric layers; these, Avhen macerated, have an irregular, reticulated appearance, and are found to be inter- FlG. 85. a. The vessels of the pulp of an upper central incisor injected, as seen under the scope, very highly magnified; b. the natural size of the pulp. spersed with granules, the parenchyma being traversed by vessels having a vertical direction. See Figs. 83 and 84, copied from Mr. Nasmyth. Mr. Tomes describes it as consisting, from its earliest appearance THE DENTAL PULP. 147 Fig. 86. of a series of nucleated cells, united and supported by plasma; also, prior to the commencement of the formation of the dentine, of delicate areolar tissue, occupied by a thick, clear, homogeneous fluid or plasma. The pulp is liberally supplied with bloodvessels, furnished by the trunk which enters its base. The ramifications of these vessels are distributed throughout its entire substance, form- ing a capillary net-Avork Avhich terminates in loops upon its surface. Three or more arteries enter at the apicial foramen, and supply the pulp, dividing into branches, which, after pursuing a parallel course, form a capillary plexus, immediately beneath the cells of the membrana eboris, or ivory membrane. The nerves of the pulp enter the apicial foramen by one large and three small trunks, and, like the arteries, pursue at first a parallel course, and then form in the bulb a rich plexus beneath the membrana eboris. The nature of the terminations of the nerve fibres in the pulp is yet uncertain. Magitot states that he has fully satisfied himself that the nerves become continuous with the blanched, some\\rhat stellate cells, which form a layer beneath the odontoblasts, and, through the medium of these cells, Avith the odontoblasts themselves. Con- cerning this, Mr. Charles Tomes remarks: " If this vieAV of their relation to the nerves be correct, the sensitiveness of the dentine Avould be fully accounted for Avithout the necessity for the supposition that actual nerve fibres enter it, for the dentinal fibrils Avould be, in a measure, themselves prolongation of the nerves." The distribution of the vessels of the pulp is represented in Fig. 85, copied from the work of Mr. Nasmyth, and made from an injection preparation of an upper central incisor. The communica- tion of the arteries Avith the veins by means of a series of looped capillaries, presenting a densely matted appearance upon the surface, is beautifully repre- sented. THE NERVES OF THE PULP OF AN UPPER ADULT BICUSPID, MAGNIFIED The nerves of the pulp have a t^ty DiAMEters. very similar arrangement in their distri- bution, having apparently looped terminations (Fig. 86). Kolliker describes the pulp as consisting of an indistinctly fibrous connec- 148 PRINCIPLES AND PRACTICE OF DENTISTRY. tive tissue, containing many dispersed, rounded and elongated nuclei, with, occasionally, narrow bundles somewhat like imperfect foetal connective tissue filled Avith a fluid substance. Immediately beneath the structureless membrane in which these tissues are en- closed, there is a layer composed of many series of cells, cylindrical or pointed at one end, Avith long and narrow nuclei, arranged perpendicularly to the surface of the pulp, like a cylinder of epithe- lium. This layer is described as being from two to four one-hun- dredths of a line in thickness. These, in regular series proceeding internally, become less and less distinct; " but the cells, without losing their radial arrangement, are more intermixed, and pass finally, by shorter and rounder cells, without any sharp line of demarcation, into the vascular tissue of the pulp." His description of the distribution of the vessels and nerves of the pulp is similar to that given by Mr. Nasmyth and Mr. Tomes. The dental pulp undergoes considerable change in adAranced age, diminishing in size by its progressive calcification. Further degeneration sIioavs an atrophied condition of the odonto- blastic layer, and coincidently with the diminution in the quantity of the cellular elements, an increase of the fibrillar connective tissue. At last the capillary system becomes obliterated, accord- ing to Mr. Charles Tomes, " by the occurrence of thrombosis (effusion of blood into the cellular substance) in the larger vessels, the nerves undergo fatty degeneration, and the pulp becomes a shrivelled, unvascular, insensitive mass." CHAPTER XII. TOOTH STRUCTURES. Enamel.—With regard to the formation of the enamel, the dental follicles have their origin in a cord which emanates from the epithelial layer of the mucous membrane of the mouth. These cords arise directly from a process of the oral epithelium, those of the permanent teeth, which succeed the deciduous ones, being out- growths from the primitive cords. Concerning the cords of the other permanent teeth, those for the first molars originate directly from the epithelium of the mucous membrane, and the remaining ones from the cords of the preceding molars. The enlarged ex- tremity of the cord constitutes the enamel organ of the future dental follicle. (See Origin and Formation of the Teeth.) TOOTH STRUCTURES. 149 When the enamel is first deposited upon the surface of the den- tinal papilla, it is of a chalky appearance, and aftenvard attains the glossy hardness by Avhich it is characterized, with a Avhite appearance, like porcelain. Fig. 87. Fig. 88. ^yfrOm. Erm^rT-rTrTrrrTT^ wypyuaiaa|rynVi tLTTT444-UrHTrl 11V H^^rUrTTTrrn raJHES&XQ^^^^J A SIDE VIEW OF THE ENAMEL FIBRES ; "B^B^^E^^^^vS MAGNIFIED 800 TIMES. ^S^^^^^^^^W 1. The enamel fibres; 2 2 transverse striee «^SIl!i^§!£§P' upon them. THE HEXAGONAL TER- MINATION OF THE FIBRES of a portion of the sur- The enamel forms a smooth, dense layer en- FACE OF THE ENAMEL; , . ,, ,. .-. ., j. ., highly magnified. veloping the croAvn of the tooth as tar as the At 1,2, 3, the crooked neck, Avhere it insinuates itself betAveen the crevices between the hex- cementum and dentine. It is thickest on the strongly mSed* m°TQ cutting edges and grinding surfaces of the teeth, tapering to a thin edge at their necks. In color it is rather translucent than white. The analysis of enamel con- sists of Calcium Phosphate,.........85.3 Calcium Carbonate, ......... 8.0 Calcium Fluoride,.........3.2 Magnesium Phosphate,........1.5 Sodium Salts,..........1.0 Animal Matter and Water,.......1.0 Von Bibra gives the following : Adult Adult Man. Woman. Calcium Phosphate and Fluoride, .... 89.82 8163 Calcium Carbonate,.......4.37 8 88 Magnesium Phosphate,......1.34 2.55 Other salts,.........88 .97 Cartilage,.........3.39 5.97 Fat,...........20 a trace Organic..........3.59 5.97 Inorganic,.........96.41 94.03 Enamel consists of hexagonal or polygonal fibres or rods arranged in Avaved lines perpendicularly to the dentine. Those fibres or rods 150 PRINCIPLES AND PRACTICE OF DENTISTRY. Fig. 90. FlG« 89. situated on the most promi- nent part of the crown are arranged in a vertical di- rection ; those upon the side are placed horizontally, whilst the intermediate fibres present all degrees of obliquity. As these fibres necessarily diverge from the dentinal to their free sur- face, the upper space thus human enamel from the masticating surface of occasioned must be filled by the gradual enlargement of The figure is merely intended to show the general ., ~, P .,i . direction of the fibres. the fibres from Within out- ward or by the addition of supplemental fibres. The latter assumption Mr. Tomes thinks the correct one, although difficult of demonstration. The enamel rods are marked by trans- verse striae, Avhich indicate, according to Mr. Beale, the successive layers of calcifi- cation, and are much more strongly pronounced in some specimens than in others, being most markedly so in the enamel of un- healthy subjects. Upon opening a dental sac from a foetal jaAv, inter- posed between the inner surface of the sac and the coronal surface of the tooth, a semi-fluid, gelatinous sub- stance will be found, com- posed of nucleated cylin- drical columns with more or less spherical nucleated cells enveloped in fluid. Similar columns will be cavities in human enamel, found on the inner surface Which communicate with the dentinal tubes. of the Sac. This is the TOOTH STRUCTURES. 151 enamel organ, or enamel pulp, and from it the cells found in the gelatinous fluid have become separated. Columns of a like kind are also found on the surface of the enamel. When the tooth makes its Avay through the gum, and before it has suffered from friction, by the action of hydrochloric or acetic acid, a mem- brane-like surface may be raised from the surface of the enamel, Avhich is seen under the microscope to consist on one side of "columns of the enamel pulp, and on the other of decalcified enamel fibres," joined end to end, but easily separated at the point of junction. This membrane, to which Mr. Nasmyth first dreAV attention, is described as the persistent dental capsule; but Mr. Huxley thinks it is identical Avith the membrana prseformativa. The enamel differs from dentine in its greater density; the much earlier period at which entire calcification takes place; the absence, except in abnormal conditions, of any uncalcified portions; the direction in which calcification progresses; and in the fact that it is the least constant of the dental tissues. In pathological condi- tions irregular cavities are sometimes found in the enamel near to the surface of the dentine, and in such cases the dentinal tubes may communicate with them (Fig. 92.) In some cases the den- tinal tubes ma}'' enter the enamel, but this condition is more common to some animals than to the human subject. " It is more frequently absent than present in the teeth of the class of fishes ; it is wanting in the entire order Ophidia among existing reptiles; and it forms no part of the teeth of the Edentata, and many cetacea among mammals." (OAven's " Odontography," xxiv.) Dentine.—With regard to the manner of the formation of the dentine, the first step in this process is the development of the odontoblasts, which have the same relation in the development of the teeth as osteoblasts have in the formation of bone. The odontoblasts are large nucleated cells, of elongated form, provided Avith numerous processes developed t from the dentinal papilla, which at that early stage consists of fine fibrous tissue containing many cells. The odontoblasts send out processes, Avhich, as they develop, become calcified externally, the calcified portion forming the dentine, and the uncalcified part the dentinal fibrillse, and the lateral processes the branches of anastomosis through Avhich the tubuli or canals of the dentine communicate. The remains of the odontoblasts themselves form the investment of the pulp, situated betAveen its nerves and vessels and the den- tine, a cellular layer known as the membrana eboris, or ivory mem- 152 PRINCIPLES AND PRACTICE OF DENTISTRY. brane of Kolliker. (See Origin and Formation of the Teeth.) The dentine is deposited around the fibrils of the odontoblasts, the latter occupying a position nearly at right angles to the sur- face of the dentine, the deposition being in the protoplasm which is found in the interspaces betAveen the fibres. Lime salts being deposited in the protoplasmic basis-substance, the odontoblast, as the process of secretion proceeds, becomes enclosed in a thin spherule of formed material, known as " calcoglobulin,"* and the dentine substance or tissue assumes the form of a homogeneous mass, traversed by tubes which contain the dentinal fibrils. The greater portion, or body of every tooth is composed of den- tine, Avhich is a yellowish-Avhite, semi-transparent, hard, elastic substance, and intermediate in consistence betAveen the enamel and the cementum. In a normal condition the dentine is never ex- posed, being covered in the crown of the tooth by the enamel, and in the root by the cementum. In a fresh specimen the human tooth is found to consist of 62 per cent, of its Aveight in organic salts, 28 per cent, of tooth cartilage (organic matter), and 10 per cent, of Avater. Berzelius gives the folloAving analysis of dentine: Calcium Phosphate,.........62.00 Calcium Carbonate,.........5.50 Calcium Fluoride,.........2.00 Magnesium Phosphate,........1.00 Sodium Salts,..........1.50 Gelatin and Water,.........28.00 Von Bibra gives— Calcium Phosphate and Fluoride,......67.54 Calcium Carbonate,........7,97 Magnesium Phosphate,........2.49 Salts,...........1.00 Fat,.....*........58 Cartilage,..........20.42 While the organic basis of the matrix of dentine is similar to that of bone, yet it is not identical, being of firmer consistence, and does * Calcoglobulin is a term applied to a thin layer of partially calcined tissue found between the organic and inorganic tissue in the development of bone den- tine or cementum. TOOTH STRUCTURES. 153 Fig. 91. not yield gelatine Avhen boiled. A fresh section of dentine presents a satiny aspect, but Avhen submitted to the microscope it is found to consist of a multitude of fine tubes, known as the dentinal tubuli, with an intertubular substance. These minute tubes permeate the entire structure of the den- tine, their direction varying in the different parts of the tooth. Each tube originates by an open, circular mouth or orifice upon the surface of the pulp-cavity, where it runs toward the peri- phery of the dentine in a direction usually perpendicular to the surface, just before reaching Avhich it divides into branches. Proceeding in a wavy and radiated manner throughout every portion of the dentine to its periphery, these tubes, although gen- erally terminating at that point, in some instances extend beyond transverse section of dentine. dentine and cementum from the root of a human incisor; copied from kolliker. a. Dentinal fibres or tubes; b. interglobular spaces, having the appearance of the lacunx in bone; c. smaller interglobular spaces; d. commencement of the cementum, with numerous canals close together; e. its lamellae: f. lacunx; g. canals. and encroach upon the enamel or upon the cementum. When the latter is the case, they may communicate with the canaliculi and lacunae. ToAvard the grinding surface of the crown of a tooth, when occlusion is received, these tubes have a vertical direction, and a horizontal direction when the pressure of adjoining teeth has to be 154 PRINCIPLES AND PRACTICE OF DENTISTRY. resisted; and thus the shock of occlusion and pressure is more generally distributed over the entire tooth structure. These dentinal tubes, instead of pursuing a straight course, describe curves, the longer ones less abruptly defined than the others, and are termed " primary curvatures," the latter being more common to the croAvn than to the root. The secondary curva- tures, although smaller than the primary, are much more numer- ous. The coincidence of the primary curvatures of adjoining den- tinal tubes, or the presence of rows of what are known as " inter- globular spaces " (Fig; 92), may occasion a striated or laminated appearance of the dentine, the lines thus formed being at nearly right angles with the tubes and known as the contour lines of Owen. They proceed in an arched manner, someAvhat parallel to each other. The dentinal tubes are cemented together by a sub-granular matter, radiating from the cavity to the surface of the tooth. From these tubes branches are given off in great number in the roots and as the enamel approaches the dentinal surface. In the croAvn these branches are few in number. They anastomose freely with each other and with the superficial dental tissues. They terminate in loops or are lost in the enamel. By their extension into the super- ficial dental tissues a close union is formed between them and the dentine, notwithstanding the fact that each tissue is developed from a distinct formative pulp. Kolliker thought these tubes contained clear fluid in the fresh state. In the dried preparation they are empty, and are readily permeated by colored fluid. These facts pIG 93 give rise to the opinion, that their sole purpose Avas the con- duct of nutrient fluids. Mr. Tomes, however, following Nasmyth, objected to this the- ory on purely physiological grounds. The extreme sensi- tiveness of an exposed coronal termination of a dentinal tube in the midst surface from which a portion of the dentine-human. of enamel has been broken; the fact that in operations for the removal of carious dentine the sensitiveness was found to be greatest just beneath the enamel; and furthermore, that when the pulp was broken up or destroyed by escharotics, this sensibility Avas lost, led him to conclude that the sensibility of the dentine depended on its connection Avith the pulp, and to suppose that these tube-contents might be in some TOOTH STRUCTURES. 155 Fig. 94. A FRAGMENT OF DENTINE, a, through which run the softer fibrils, c, which seem to be continuous with the odontoblast cells, 6 (after Dr. Lionel Beale). wa}r associated Avith the sensibility of the structure in which they were found, serving to establish connection between it and the pulps, to which supposition fluid contents opposed an insurmount- able difficulty. Led by this train of reasoning to a careful exam- ination of the tubes, he found " each dentinal tube tenanted by a soft fibril, which, after passing from the pulp into the tube, folloAvs its ramifications, and (Tomes's Dental Surgery, 327) that these fibrils may be traced into the dentinal pulps." Professor Kolliker and M. Lent had previously seen processes extending from the " peripheral cells of the dentinal pulp;" but had supposed them " organisms for the development of the den- tinal tubes." Mr. Tomes was unable to de- termine the manner in Avhich the fibrils ter- minated in the pulp, Avhether by cells or by any communication Avith nerves; but does not, therefore, question the function he has assigned them, since, Avhen their connection with the pulp is cut off, all sensibility is lost to the dentine. He adds, " It is by no means necessary to assume that the dentinal fibrils are actually nerves before alloAving them the power of communicating sensation. Many animals are endowed Avith sensation Avhich yet possess no demonstrable nervous system;" whilst, at the same time, it has been impossible to demonstrate nerves in the human body so numerous as to warrant the assumption that at every prick of a needle the point must touch a nerve fibre. Again, the greater sensibility of the dentine immediately beneath the enamel is satis- factorily accounted for by the law Avhich refers to all nerves the greatest sensibility at their terminal extremities. Mr. Tomes also thinks "the foregoing facts will warrant the conclusion that the dentinal fibrils are subservient, not only to sensation in the den- tine, but that they are also the channels by Avhich the nutrition of this tissue is carried on," and argues very forcibly that they do convey nutrient fluids, from the fact that the tubes are capable of undergoing structural change, and that the fibrils may also become calcified at their distal extremities, and that the calcifying material SECTION OF DENTINE, From the edge of which hang out the dentinal sheaths, and beyond these again the fibrils (after Boll). 156 PRINCIPLES AND PRACTICE OF DENTISTRY. Fig. 96. must be derived from the pulp, reaching the place of deposit through the fibrils. Differing in this from Dr. Beale, Avho, Avhilst agreeing Avith Mr. Tomes as to the presence of these fibrils, Avhich he has himself succeeded in demonstrating, is of the opinion that the so-called dentinal tubes " are not tubes, nor are they canals for the transition of nutrient substances dissolved in fluids." He con- siders these fibrils as simple germinal matter communicating with the germinal matter on the surface of the pulp, and that the tubes are the formed material of this fibrillar germinal matter. " The wall of the tubes Avith the matter betAveen the tubes corresponds to the ' wall' of an ordinary cell, or to this and the intercellular substance (my formed material), and the central part of the con- tents Avith the nuclei (my germinal matter). If you look at the tissue of the pulp just beneath the surface of the dentine you find a number of OAral masses of germinal matter colored intensely red by carmine. These are nearly equidistant, and separated from each other by a certain quantity of material which is very faintly colored, and in cases Avhere the solution was not very strong it remained color- less. This colorless matrix is continuous with the intertubular or dentinal tissue, Avhile the in- tensely red germinal matter, or rather, a pro- longation from it, extends to the dentinal tubes." (Beale on the Structure and Growth of Tissues, 155.) Dr. Beale admits that the dentinal tubes do convey nutrient fluids, but contends that they Ave re not designed for that purpose. He says, "As in the formation of bone already described, spaces or pores are left, through Avhich nutri- ent matter passes toward the germinal matter. In this way very fine channels result, which may be seen in the dry tooth passing from one dentinal tube to the other." (Structure and GroAvth of Tissue, 167.) The dentinal fibrillse appear to be formed by the peripheral por- tions of the processes of the odontoblasts, after the latter become long and narrow, attaining considerable length. The formation of dentine begins about the fourth month of foetal life, at the summit of the papilla. The superficial portion of the crown is first formed, and afterward undergoes no alteration in size all subsequent groAvth taking place on the surface adjacent to the dentinal pulp. The growth of the root takes place from above, TRANSVERSE SECTION THROUOH THE DEN- TINAL TUBULI OF THE ROOT OF A HUMAN TOOTH. Magnified 350 diame- ters, showing their nu- merous anastomoses. TOOTH STRUCTURES. 157 dowmvard into the alveolus destined to receive it. Placed at right angles to the outer surface of the pulp, between it and the dentine already formed, or before any dentine is formed, is situated a layer of " elongated cylindrical bodies or cells, Avith nuclei" someAA'hat resembling nucleated, columnar epithelium. With regard to the exact share taken by the pulp in the formation of dentine, Kolliker saj^s a layer of cells forming the peripheral portion of the pulp are immediately concerned in its formation. He says, that from the base of the dental sacs the dental pulp proceeds, rich in vessels, and finally also in nerves, with a non-vascular external portion. The latter is bounded by a delicate, structureless membrane, the mem- brana pra'formativa (Raschkow), Avhich has no further relation to the formation of the tooth. Beneath this lie cells of 0.016 to 0.024"' in length, and 0.002 to 0.0045 in breadth, Avith very beautiful vesic- ular nuclei, and distinct single or multiple nucleoli. They are arranged close together over the Avhole surface of the pulp, like an epithelium, though not so closely defined as it Avould be, but gradu- ally passing, at least apparently, by smaller cells into the paren- chyma. In vascular pulps an additional boundary line may be traced, inasmuch as the capillary loops in Avhich the vessels ter- minate do not penetrate betAveen the cylindrical cells, but end close to one another upon their inner surfaces, so that," considering that the dentine is produced by the cells in question, we might be justi- fied in terming them the dentinal membrane or membrana eboris. The internal portion of the pulp, he thinks, consists of a granular matrix, subsequently becoming more fibrous, and that when ossification of the dentine begins numerous vessels are developed, and a little later numerous nerves also make their appearance. According to this obseiwer, it is " only the most external epithelium-like layer of cells," and not the entire pulp, Avhich is engaged in the production of den- tine, and these maintain a constant thickness " by the elongation of the original cells, accompanied by a continual multiplication of their nuclei." He does not consider that the " same cell suffices for the whole duration of the dentine," but that neAV cells may from time to time be formed; and denies that the whole pulp is progres- sively changed into dentinal cells, and thinks its only purpose is to support the vessels essential to the groAvth of the dentinal cells, from Avhich alone the dentine is formed, by the gradual re- ception of calcareous salts. (From " Tomes's Dental Surgerv," 388.) M. Lent refers the formation of the dentinal tubes to a " series of delicate processes extending from the dentinal pulp, to AArhich Kol- 158 PRINCIPLES AND PRACTICE OF DENTISTRY. liker assents, and thinks it probable that a single cell may generate an entire tube. He also recognizes the existence of an intertubular substance, which he believes to be " excreted by the cells in common, without structural relation to individual cells or their prolonga- tion." The theory adA'anced by Mr. Beale is, that on the dentinal sur- face of a tissue lying on the pulp are found certain " cells like columnar cells," which are in relation with the nerves and blood- vessels of the pulp into Avhich they send prolongations, and that from these cells alone is developed the dentine, agreeing in so much with Kolliker and Lent, but does not hold with them that the " canals are direct processes of the whole dentinal cells," nor that the intertubular substance is a direct secretion from the cells. His vieAvs are, briefly, that these cells or " elementary parts " are situated on the surface of the pulp; that they consist, as cells do everywhere, of germinal matter and formed material, and that the so-called in- tertubular substance is but the oldest part of the formed material, in Avhich, by the gradual deposition of mineral matter, the dentine is formed; growth taking place here, as elsewhere, from within out- ward, from nuclei or germinal matter to cell-Avail or formed material, while calcification takes place in the opposite direction, from the oldest and most distant formed material toward the germinal matter. We have said calcification takes place gradually, probably during the life of the individual or until the pulp-cavity is obliterated; hence we have a central mass of germinal matter, the so-called dental fibrils, surrounded by calcified formed material, giving rise to a tubular appearance, the dental tubes; and since the calcifying process takes place from Avithout inward, the germinal matter is made to present the appearance of an attenuated fibre gradually enlarging as it approaches the pulp. Upon this fibrillar mass the calcifying process continually encroaches, until the so-ealled tube is obliterated. Until this is accomplished, however, the germinal matter must be nourished and mineral matter must be conveyed to its most distant part for deposition, and if this conduct of nutrient fluid constitutes a claim to the name, they may still be called tubes. NotAvithstanding Mr. Tomes's inability to trace any communi- cation betAveen this fibrillar matter and the nerves of the pulp, such connection must be supposed to exist—Prof. Christopher Johnston, of Baltimore, succeeded in tracing nervous communica- tion with the dentine—and to it we must refer the sensibility of this tissue. TOOTH STRUCTURES. 159 Fig. 97. INTERGLOBULAR SPACE8 IN DENTINE. Fig. 98. On account of the tubes dividing into minute branches, as they approach the surface of the dentine, they appear to end in very fine pointed extremities. Some of these tubes anastomose Avith the branches of others, forming loops near the periphery, Avhile others terminate deeper in the tissue. The inner walls of the tubes surrounding the fibrillse constitute the dentinal sheaths, Avhich are apparently of fibrous structure. The intertubular tissue con- tains the greater part of the earthy constituents of the den- tine, and under the microscope presents a granular appearance. What are known as inter- globular spaces, are indicators of arrested development of the dentinal tissue, and are not considered to be normal. These spaces are dark and irregular, and are most com- monly observed a little dis- tance beloAV the surface, in a discolored and imperfectly developed tooth; they have a ragged outline. According to Bodecker, soft living plasm is found in the smaller interglob- ular spaces. According to Krause, den- tine has a specific gravity of 2.080, and contains less earthy matter than the enamel, but more animal substance, Avhich accounts for the rapid progress of caries Avhen the dentine is exposed. Cementum.—Cementum is developed from the deeper tissues of the foetal jaAv, precisely like bone is produced in other parts of the body, by periosteal ossification. It contains canaliculi and lacuna?, and, according to Salter, Haversian canals in the thicker portion. It is not so dense as the dentine, and approaches more nearly in THICK LAMINATED CEMENTUM. From the root of a human tooth. 160 PRINCIPLES AND PRACTICE OF DENTISTRY. character true bone, which is necessary in order that the tooth may be tolerated by the more highly vitalized structures in relation with it. The analysis of cementum is as follows: Calcium Phosphate and Fluoride,.......58.73 Calcium Carbonate, ......... 7.22 Magnesium Phosphate, .......•• 0.99 Salts.............0.82 Cartilage,...........31.31 Fat,............0.93 The Cement, or Crusta Petrosa, is the most highly organized of the dental structures. It covers the roots of all the teeth, encroaching slightly upon the crown, where it overlaps the enamel. Its purpose is to bind the teeth securely in the alveoli, forming the vital bond between the bone and the commonly unvascular constituents of the teeth. It is thickest about the terminal part of the root, gradually thinning as it approaches the croAvn. According to Mr. Tomes, "its structural character depends upon the amount of tissue present." In the thicker parts the canaliculi are seen anastomosing freely with each other, and establishing vascular relations between the several lacunae; and they " occasionally become connected with the ter- minal branches of the dental tubuli." This communication, though doubted by many observers, Mr. Tomes considers demonstrated " beyond cavil" by preparations in his possession. Haversian canals, as was before remarked, are also found in very thick sections of cementum ; but M. Morel is of opinion that these canals are only found where cementum has been morbidly developed ; but Mr. Tomes is of a different opinion, and says that where two roots are united by cementum a vascular canal will not unfrequently be found in it, and that this appearance " is not necessarily an evidence of disease." The lacunae and canaliculi of cementum are distributed lengthAvise around the root, those in proximity to the dentine joining with the terminal branches of the dentinal tubuli, while those upon the external surface radiate toward the investing membrane. By such a provision, even after the devitalization and removal of the pulp, the vitality, not only of the cementum, but of the dentine of the teeth, is maintained. Fig. 99. LACUNA OF CEMENTUM, Which communicates with the termination of the dentinal tubes. TOOTH STRUCTURES. 161 From irritation of the dental periosteum the cementum often be- comes hypertrophied, the affection being known as " dental exos- tosis." Cementum contains more animal matter than the dentine, and becomes very sensitive when exposed by the recession of the gum about the neck of the tooth. Osteo-Dentine.—Osteo or secondary dentine is a substance par- taking more of the nature of cementum than of ordinary dentine, as it possesses no true dentinal tubes, but canals similar to the canaliculi of bone. It is generally formed in the teeth of persons of advanced age, Avhere the pulp-cavity is very much diminished in size, and it also forms a protection against the exposure of the pulp of the tooth Avhich has been denuded of its natural tissues by mechanical abrasion, the action of caries, or by fracture. In other cases secondary dentine is deposited in isolated nodules scattered throughout the substance of the dental pulp, Avhich may unite and form larger masses and become adherent to the Avails of the pulp- cavity. Some of these masses are occasionally penetrated by blood- vessels, and surrounded by concentric lamella?, like the Haversian canals of bone. The dividing line between the primitive and secondary formations of dentine is char- acterized by numerous irregu- lar spaces and globular con- tours, Avhile deeper in the mass of lately formed second- ary dentine tubes or canals may exist. Not infrequently, hoAvever, the tubuli of secondary den- tine are arranged in a very irregular manner, either " in tufts or in bundles, and Avith- out any apparent reference to points of radiation." Osteo- dentine is also usually very transparent, on account of this tissue being devoid of light - refracting tubes, its canals being so completely filled up Avith the secondary deposit that they permit the transmis- sion of light. The tubuli of normal dentine are frequently filled 11 SECONDARY DENTINE, Filling up one of the cornua of the pulp cavity, From a human molar affected by caries. 162 PRINCIPLES AND PRACTICE OF DENTISTRY. Avith a secondary deposit, especially in the roots of teeth, and to which the name " horny dentine " has been given. The formation of secondary dentine appears to depend upon irritation of the pulp, of long continuance but restricted as to degree, and during the time " that the sIoav conversion of the organ is taking place the dentinal fibrillae also become impregnated with calcareous matter and solidify." PART SECOND. DENTAL PATHOLOGY, THERAPEUTICS CHAPTER I. GENERAL CONSIDERATIONS. The susceptibility of the human body to morbid impressions differs in different individuals. In some, its functional operations are liable to derangement from the most trifling causes; in others they are less easily disturbed. Nor do the same causes always pro- duce the same results. Their effects are determined by the tendency of the organism and the susceptibility of the part on Avhich they act; both Avith regard to constitutional and local disease, this is true of the organism generally, and of all its parts separately con- sidered, but of none more than the teeth, gums and alveolar pro- cesses. The teeth of some persons are so susceptible to the action of corrosive agents, as to become involved in general and rapid decay as soon as they emerge from the gums; Avhile those of others, though exposed to the same causes, remain unaffected through life. A similar difference of susceptibility also exists in the parts Avithin Avhich these organs are contained. With the teeth these differences of susceptibility to morbid im- pressions are implanted in them at the time of their formation, and are the result of the different degrees of perfection in Avhich this process is accomplished. In proportion as these organs are perfect, is their capability of resisting the action of destructive agents in- creased, and as they are othenvise, it is diminished. This is true of every part of the body; but as the teeth are formed, so they con- tinue through life, if not impaired by disease, except that they gradually acquire a very slight increase of density, Avhereby their liability to caries is correspondingly lessened. Not so, however, with the other parts of the body. They may be innately delicate or imperfectly developed, and aftenvard become firm and strong, or be at first healthy and Avell-formed, and subse- quently become impaired ; and in proportion as they undergo these changes, is their susceptibility to disease increased or diminished. But the teeth are not governed by the same laAvs, either physical or vital, that regulate the operations of the other parts of the animal economy. Not only the manner of their formation, but their dis- eases, also, are different. The other tissues of the body, not except- ing the osseous, are endowed Avith recuperative powers, whereby an injury is repaired by their OAvn inherent energies; but the teeth do not possess such attributes. Assuming these propositions to be true—and that they are, especially those Avith regard to the teeth, Ave shall endeavor to shoAY 166 DENTAL PATHOLOGY, THERAPEUTICS. —it becomes an object of considerable importance to discover the signs by Avhich the susceptibility of the human organism to disease may be determined. But to do this, except in so far as the teeth, gums and alveolar processes are concerned, is not our present object; yet, in the prosecution of the task we have undertaken, Ave shall have occasion to advert to certain constitutional and local tendencies indicated by the appearance and condition of the teeth and other parts of the mouth. M. Delabarre affirms that, by an inspection of the teeth, Ave can ascertain whether the innate constitution is good or bad, and our OAvn observations go to confirm the truth of this opinion; but, as this author adds, these are not the only organs that should be interrogated. The lips, the gums, the tongue, and the fluids of the mouth, should also be examined, to discover the health of the organism, and ascertain whether the original condition of the con- stitution has undergone any change. Those Avho have not been in the constant habit of closely observ- ing the appearances met Avith in the mouth, may be skeptical Avith regard to the information that may thus be derived; but those Avho have studied them with care will not hesitate to say that they are, in many instances, more certain and accurate than any which can be obtained from other physical appearances. For example : the periods of the dentinification of the different classes of both sets of teeth being known, we are able to infer Avhether the innate constitu- tion be good or bad, from the physical condition of these organs; for, as the functions of the organism are at this time healthily or unhealthily performed, will they be perfect or imperfect, or, in other Avords, will their texture be hard or soft. It is well knoAvn to writers on odontology, that the teeth of the child, like other parts of the body, usually resemble those of its parents; so that when those of the father or mother are bad or irregularly arranged, a similar imperfection is generally found to exist in those of the offspring; but this does not necessarily follow, and when it does, it is the result of the transmission of some con- stitutional impairment, Avhereby the formative operation of these organs is either disturbed or prevented from being effected in a per- fect and healthy manner. The quality of the teeth of the child, therefore, may be said to depend on the health of the mother, and the aliment from which it deri\res its subsistence. If the mother be healthy, and the nourishment of the child of good quality, the teeth will be dense and compact in their texture, generally Avell- formed and well-arranged, and as a consequence less liable to be acted on by morbid secretions than those of children deriving GENERAL CONSIDERATIONS. 167 their being from unhealthy mothers, and subsisting upon aliment of a bad quality. Temperament, also, exercises an influence upon the functional operations of the body. The Temperament in Relation to the Teeth.—Before proceeding fur- ther, it may be Avell to notice the individual conditions or qualities knoAvn as temperaments. The word temperament is derived from the Latin tempero, " to mix together," and implies the constitution as determined by the predominance of certain constituents of the body. For among the ancients it was supposed that the manifesta- tions of the functions were tempered or so determined by the pre- dominance of any one of the three humors then recognized, namely: blood, lymph, bile, and atrabilis, or black bile. Dunglison, in his Medical Dictionary, defines the temperaments to be those individual differences which consist in " such disproportion of parts, as regards volume and activity, as to sensibly modify the Avhole organism, but Avithout interfering Avith the health; " in other Avords, a physiological condition in which the functions of the different organs are so regu- lated as to impress certain characteristics upon each individual. Others contend that these individual differences, " though they can scarcely be called morbid, yet certainly give a proclivity to disease in the direction indicated by the temperaments." Dr. James W. White, on this subject, remarks: " Temperament may be defined as a constitutional organization, depending primarily upon heredity—national or ancestral—and consisting chiefly in a certain relative proportion of the mechanical, nutritive, and nervous systems, and the relative energy of the various functions of the body—the reciprocal action of the digestive, respiratory, circulatory, and nervous systems. The stomach, liver, lungs, heart, and brain —digestion, assimilation, respiration, circulation, and innervation —are all factors in the differentiation of temperament; and accord- ing to the congenital predominance of one or the other, and the relative activity of these functions, is the modification of the char- acteristics of the individual Avhich determines his position as to temperament. Each temperament is the result as well as the indi- cation of the preponderance of one or another of these systems, and of relative functional activity. " A perfect equilibrium of the different systems is rarely if ever presented in any individual. One having a balance of all the tem- peraments Avould be temperamentless,or of no special temperament. It is difficult, in some cases, to decide positively to Avhich variety a special case belongs, the several temperaments being combined and blended in such ever-varying proportions. Not infrequently the indications are even contradictory, and the blending of several tern- 168 DENTAL PATHOLOGY, THERAPEUTICS. peraments requires a nice discrimination to define the admixture. The primary elements of temperament are susceptible of such mani- fold combinations ; the determining forces are so complex, and our knoAvledge of their comparative values is so limited, that no rule can be given Avhich will not fail in numerous instances to apply in all respects to individual cases; but that there is a general relation between constitutional qualities and external signs does not admit of question. " Temperaments are readily divisible into four basal classes— bilious, sanguineous, nervous, and lymphatic; then again into sub- classes of mixed temperaments—a combination of two or more of the primary divisions. In these combinations one or other of the so-called basal temperaments predominates, and a compound term is used to express the complexity, as, for instance, thenervo-bilious, signifying that the bilious base—the foundation temperament—is qualified by an admixture of the nervous element, and so throughout the series. Twelve varieties of temperament, in addition to the four basal, may thus be designated by the combination in pairs of the original four. The admixture of the peculiarities of three or of all four of the basal temperaments results in what are denominated respectively ternary and quaternary combinations, Avhich call for nice discrimination in diagnosis; but even such complexities are registered in the size, form and color of the dental organs." The sanguineous temperament is characterized by a fair, ruddy complexion, yellow, red or light auburn, or light-brown hair, a good class of teeth, a full muscular development, large, full veins and active pulse, indicating an abundant supply of blood, and warm extremities, all showing perfect health, and in females a tendency to voluptuousness. The mind is hopeful and elastic, yet at the same time fickle and volatile, with little determination and perseverance. Although indicating perfect health, yet in this temperament diseases are prone to assume the acute form, and speedily run their course either to recovery or a fatal termination. The bilious temperament is characterized by a preponderance of bile, indicated by a dark or sallow countenance, black hair, generally luxuriant, a slow or moderate circulation of the blood, shown by a hard, strong pulse, dark eyes, strong teeth, with a yellow tinge over the entire crown; and the body, instead of the roundness of form peculiar to the sanguine temperament, is angular ; Avanting in ease and grace of manner; there is restlessness, but at the same time great force of character and quickness of perception and power of will. The digestive organs, however, are more liable to derange- ment than in other temperaments, indicating some defective action GENERAL CONSIDERATIONS. 169 in these organs; the liver, of course, being the principal one affected, and necessitating the use of mercury as a stimulus. The lymphatic temperament is characterized by a predominance of lymph or phlegm in the system; and persons possessing it have a general softness or laxity of the tissues, the proportion of the fluids being too great for that of the solids, the lymphatics and ab- sorbents not acting so thoroughly as to prevent the cellular tissue from being filled Avith humors ; so that there is a Avant of sensi- bility. The complexion is fair, but not ruddy, and the hair, either light or dark, is not luxuriant, but thin and straight. The eyes are light, generally blue, the circulation feeble, and the pulse, as a con- sequence, Aveak, and a want of tone in the system. The skin is pale, flabby, and moist, and the body is heavy and rounded, Avhile the teeth, although they may often appear comparatively good, yet are sensitive and not highly organized. Although the expression denotes a Avant of activity, yet there is a clear and active mind, characterized by prudence and sound judgment Avithout enthusiasm. OAving to the predominance of lymph, there is a tendency to dropsy and chronic disease. The nervous temperament is characterized by the predominance of the nervous element, and by great activity or susceptibility of the great nervous centre—the brain. Persons possessing this tem- perament are distinguished by their impressibility, susceptibility to intense feeling or intense excitement. There is great irritability, anxiety, and agitation, which peculiarities enable us readily to recognize it by the tone of voice and manner of speaking. The body is slender, though Avell formed, the complexion pale and soft, and the muscles small and yielding. In illness, symptoms are often complicated Avith those of nervous disorder, and the mind desponding. There is Avant of power and endurance. Upon the temperament the constitutional health depends to a greater extent than pathologists generally admit; and hence it is that that of the child usually partakes of that of one or other, or both, of its parents. "This," says M. Delabarre, "is particularly observable in subjects that have been suckled by a mother or nurse, Avliose temperament Avas similar to theirs." To obviate the entail- ment of this evil, he recommends mothers having teeth constitu- tionally bad to abstain from suckling, and that this highly im- portant office be intrusted to a nurse having good teeth ; asserting at the same time, that by this means the transmission of so trouble- some a heritage as bad teeth may be avoided. Dr. J. Foster Flagg gives the following tabular presentations of the relation of the temperament to the teeth : THE TEETH AS INDICATED BY TEMPERAMENT. GENERAL DIVISIONS. BILIOUS. SANGUINEOUS. NERVOUS. General Color and Quality Bronae-yellow, with strength or power of coloring. Cream-yellow, and inclined to translucency. Pearl-blue or gray; inclined to General Form.................... Large and inclined to angular; rather long in proportion to breadth. Well proportioned; abounding in curved or rounded outlines; cusps rounding. Length predominating over breadth; fine, long, cutting edges and cusps. Surfaces of the Teeth........ Inclined to transverse ridges,and abounding in strong lines ; neither brilliancy nor transparency of sur-face, but slight translucency. Smooth, or nearly so; elevations and depressions rounded ; cutting edges and cusps translucent. Fair degree of brilliancy. Brilliant and transparentdepres-sions and elevations; abounding in long curves. Firm and close ; well locked. Moderately firm; jaw inclined to rotate in mastication. Very long and penetrating. Gum Margin or Festoon Heavy and firm, but inclined to angularity. Round and full, as regards both breadth and depth. Delicate, shapely and fine; oval in curve. Heavy and rugged in shape; squarely set. Numerous and graceful in out-line ; not heavy, but well rounded. Close, not numerous ; small and long. LYMPHATIC. Pallid and opaque, or muddy in coloring. Large, but not shapely; breadth predominating over length; cusps poorly defined. Surface of incisors devoid of de- pressions or elevations; opaque and dead in finish, even to cut- Ling edges. Loose and flat. O Thick and undefined in shape. Sparse and flat. GENERAL CONSIDERATIONS. 171 Depending, then, as the physical condition of the teeth and the organism generally confessedly do, upon the quality of the nourish- ment from Avhich subsistence is derived during infancy and child- hood, it is highly essential that this be good; and that that especially, derived from the breast, be from those only who are in the enjoyment of perfect health and possess good constitutions. The teeth, Avhile in a pulpy state, partake of the health of the organism generally. As that is healthy and strong, or unhealthy and Aveak, so will the elementary principles of which they are then composed be of a good quality, or deteriorated; but after dentini- fication has commenced, the solid parts cease to be influenced by, or to obey the hiAvs of, the other parts of the body. If the general health be good at the time this process is going on, it will be evidenced by their density and color; if bad, in the looseness of their texture, etc. This is a subject to Avhich we have paid some attention, having for a long time been in the habit of carefully noting the differences in the appearance of the teeth of different individuals, and of both dentitions; and, though Ave have been able to conjecture in some instances Avhat had been the state of the mother's health during the first months of pregnancy, candor compels us to confess that Ave have never been able to find any signs in the peculiarity of their shape, size, density, or arrangement that indicated it. But from the moment that the part of the formative process of these organs Avhich is not influenced by subsequent changes in the general economy commences, certain peculiarities of appearance are impressed upon them that continue through life, and about the certainty of the in- dications of Avhich, in regard to the general health, Ave think there can be no doubt. With regard to the information concerning the innate constitu- tion, to be derived from an inspection of the teeth, it has been well remarked by Delabarre, that physicians may derive much advantage in pointing out the rules of domestic hygiene for the physical education of children ; for, says this eminent dentist, " Can he admit of but one mode ? Has he not, then, the greatest interest in being Avell assured of the innate constitution of each child for Avhom ad- vice is required, to enable him to recommend nutriment suited to the strength of its organs ? Will he report only on a superficial examination of the face, its paleness, the color of the skin, all of which are variable ? Will he not regard the repletion or leanness of the subject, the state of the pulse, etc. ? Surely he will make good inductions from all these things ; but the minute examination of the mouth Avill give him beyond doubt the means of confirming 172 DENTAL PATHOLOGY, THERAPEUTICS. his judgment; for, besides what we already know of the teeth, the mucous membrane of the buccal cavity receiAres its color from the blood, and varies according to the state of that fluid." This is a matter Avhich the observation of the dentist has an opportunity of confirming almost every day; and Avhich, Avhen taken in connection with the physical characteristics of the teeth, together Avith those of the salivary and mucous secretions of the mouth, constitute data from which both the innate and present state of the constitu- tional health may be determined Avith accuracy and certainty. The symptoms of actual disease have been minutely and repeat- edly described, but the physiognomical signs by which the suscepti- bility of the human organism to morbid impressions is determined, and the kind of malady most likely to result therefrom, do not appear to be so well understood. " Whatever," says the author last quoted, " may be the knowledge Avhich a practitioner may acquire of the changes which a disease, or even any tendency to disease, may effect in the functions of some organs, it is, at least, advanta- geous to be able to conjecture what has happened in the whole of the system at some other time. In fact, can a physician, when about to prescribe for a slight indisposition of a person Avhom he hardly knows, rely entirely upon the symptomatology of the tongue ? Do not its aspects singularly vary ? Is it not notorious that in certain persons it is always red, white, yelloAv, or blackish ? I, as well as others, have had occasion to make these observations on persons with whom it was ahvays thus, yet without their being subject to any of those indispositions that are so common in the course of life." The signs are as variable in sickness as in health, and, con- sequently, can only be relied upon as confirmatory of the correct- ness of other indications Avhich manifest themselves in other parts of the body. The physical changes produced by, and characteristic of, disease have been described, both by ancient and modern medical Avriters • but the works Avhich have appeared upon this subject do not com- prise all that is necessary to be knoAvn. For example, if Ave examine the lips, tongue and gums of a dozen or more individuals Avho are regarded as in health, differences in their appearance and condition will be found to exist. The lips of some will be red, soft, and thin • others, red, thick, and of a firm texture; some will be thin and pale • others, red on the inside and pale on the edges ; some are constantly bathed Avith the fluids of the mouth; others are dry; and these differences of appearance and condition are as marked on the tongue and gums as they are upon the lips, and are supposed to be attributable to the preponderance or want of existence in suf- GENERAL CONSIDERATIONS. 173 ficient quantity of some one or more of the elementary principles of the organism. Hence may be said to result the differences in temperament and susceptibility of the body to the action of morbid excitants. If the quality and respective proportions of the materials furnished for the groAvth, reparation and maintenance of the several organs of the body be good, and in proper proportion, all the organs will be Avell formed andendoAved Avith health, and, as a consequence, capa- ble of performing their respective functions in a healthy manner. But if their elementary ingredients, to use an expression of the author from Avhom we have just quoted, be bad, their functions will be more or less feebly performed. These materials are furnished by the blood. From this fluid each organ receives such as are necessary to its oavii particular organization. The blood, therefore, exercises an important influence upon the Avhole system, determining the health of all its parts, which, as Delabarre says, " is relative to the quantity of the blood, and the general health results from that of all parts of the system." In order to do this, harmony must exist betAveen all the organs; but in consequence of the great variety and intermingling of tempera- ments, it rarely does, except, perhaps, in those in Avhom the sanguine predominates, and Avho have not become enervated by irregular and luxurious living. Even when it does exist, Ave are by no means certain that it will continue to do so; for, exposed, as the body is, to a thousand causes of disease, its functional operations may, at almost any moment, become disturbed. Among the civilized nations of the earth, the peasantry of Great Britian probably possess as good constitutional temperaments as are anywhere to be found ; and yet, Avith these people, Ave are told, that although the sanguineous pre- dominates in a majority of cases, it is combined and intermingled, in a greater or less degree, Avith others, In all these modifications the blood plays an important part; it determines the temperament of the individual, and, by consequence, the physical condition of all the tissues of the body subject to the general laws of the economy, But the dependence between the solids and this fluid is mutual; it, also, is dependent upon them, and the condition of one is relative to that of the other. The solids, if we may be permitted the use of the metaphor, are the distillery of the fluids, Avhile they, in turn, nourish, repair, and maintain the solids. A change, then, in the condition of one is folloAved by a corresponding change in the condition of the other, If the blood be of an impure quality, or any of the ingredients entering into its composition exist in too great or too small a quantity, it will fail to 174 DENTAL PATHOLOGY, THERAPEUTICS. supply the solids Avith the materials necessary to the healthful per- formance of their functions, and, if not actual disease, a tendency to it, will be the result. And, again, the purity of the blood is de- pendent upon the manner in Avhich the solids perform their offices. While, therefore, duly appreciating the importance of this fluid, and its existence in a pure state, to the general health of the economy, we cannot ascribe to it, regardless of the functions of the solids, a controlling influence over the organism. To distinguish all the nice and varied shadings of temperament, or states of the constitutional health, by the physiognomical ap- pearances of the body, is perhaps impossible, or can only be done Avith great difficulty, and by those who have been long exercised in their observance; but to discover that Avhich predominates is not so difficult a matter, and the indications are nowhere more palpably manifested than in the mouth. By an inspection of the several parts of this cavity, together with the fluids and the earthy matter found upon the teeth, Ave believe inductions may be made, not only Avith regard to the innate constitution, but also with regard to the present state of health, serviceable both to the dental and medical practitioner; and, in the further prosecution of this inquiry, we shall endeavor to point out some of the principal of the indications here met with, to state the appearances by which they are distin- guished, and to offer such other general reflections as the subject may, from time to time, seem to suggest. CHAPTER II. DENTITION. The term " dentition " implies the eruption of the teeth, and is a process which consists of tAvo stages, namely, first dentition and second dentition. At about the seventh week of intra-uterine exist- ence the process of development of the teeth of first dentition begins, and shortly after birth the outlines of the forms of the deciduous teeth may be observed on the external aspect of the jaAvs • but as age advances, owing to the increased development of the mucous membrane and alveolar processes, these outlines become less appa- rent. As the period of dentition approaches, a slight ridge on the summit of each jaw is seen, which is attributed to the dipping down of the process of epithelium Avhich forms the enamel organ. Prior to the sixth month of age (first dentition commencing generally DENTITION. 175 betAveen the fifth and seventh months after birth), small promi- nences are observed on the summits of the alveolar processes, AAThich gradually become more distinct and almost as light in color as the teeth themselves. As soon as the tooth has penetrated the mucous membrane, the latter contracts so as to permit the crown of the tooth to project above its level. The deciduous teeth begin to erupt betAveen the fifth and seventh months, and at the age of two years and a half all of the first set have appeared, the corresponding teeth of the tAvo sides of the jaAv erupting at the same time. The two inferior central incisors appear at the age of six or seven months, in the order in which they are named, followed by the superior central incisors, the superior lateral incisors, the inferior lateral incisors, the four first molars, the four canines, and last, the four second molars. The usual order of the eruption of the deciduous teeth is as folloAvs: Central incisors between the 5th and 8th months. Lateral incisors " " 7th and 10th " First molars " ;i 12th and 16th " Cuspids " " 14th and 20th " Second molars " " 20th and 30th The loAver teeth generally precede the upper teeth by a feAV weeks, appearing in the same order. This order, however, is not invariably folloAved, for teeth may be prematurely erupted so as to be seen at birth. But the cases of retarded eruption are much more common than those of premature eruption, owing to constitutional debility or the existence of some constitutional disease. During the eruptive period, there is a gradual elongation and protrusion of the teeth, and a coincident dissolving aAvay of both the hard and soft tissues Avhich overlie them. The approximal edges of the alveolar borders of the maxillary bones disappear by an absorptive process, the teeth rise in their cavities, and their roots lengthen to such a degree that the crowns press upon the opposing gums, Avhich under such pressure, become thinner and thinner, until finally the crowns escape. Henry SeAvell, M.R.C.S., gives the following concise description of the process of eruption : " The eruption of the teeth is a process of gradual elongation of the teeth on the one hand, and the simul- taneous absorption of the super-imposed tissue on the other. The absorption commences, first, in the overhanging margins and front Avails of the alveoli, Avhich gradually disappear until room is afforded for the passage of the advancing tooth. The growth of the tooth keeps pace with this absorption, and the crown of the tooth 176 DENTAL PATHOLOGY, THERAPEUTICS. at length pressing against the membranous coverings, these undergo atrophy, and becoming by degrees thinner, and at last transparent, give Avay and disclose the advancing crown." The exact relation of dentition to infantile diseases is not generally recognized, and many affections have been erroneously ascribed to this process. There is no doubt, however, that the condition of the system at the period of first dentition is such that the infant is very suscep- tible to nervous impressions, and hence the symptoms of any con- stitutional disease that may be present are greatly aggraArated. OAving to the predominance of the nervous system in infancy, there is a greater sympathy between distant organs than in adult life, and considerable disturbance may be excited early in life by even slight functional disorders. The brain is proportionally larger and less perfect in structure than in the adult; the tissues of the body are also softer and more vascular, the skin is more sensitive, the abdomen, glands, kidneys, liver, pancreas and lacteal vessels, are disproportionately large, and functional activity depends chiefly upon the nutritive processes. Such peculiarities, therefore, account for the susceptibility to disease in infants and the tendency of their diseases to become inflammatory, and to involve organs not originally affected. The evolution of the teeth is commonly attended Avith more or less inflammation of the parts in relation Avith the dental follicles, and this turgescence is greater Avith some teeth than with others; sometimes it is present to such a degree that the gums are greatly SAvollen and extremely tender, presenting a very red appearance, more so than in ordinary dentition. The indications of the eruption of the teeth are an increased flow of saliva, Avhich tends to keep the mouth moist and cool, and is due to the irritation of the trifacial nerve which gives sensation to the teeth and nutrition to the salivary glands; an itching of the mouth Avhich causes the infant to keep its fingers on the gums, as a slight pressure evidently gives some relief; the irritation continuing, the mouth, as a result, becomes hot and dry, and there is more or less febrile excitement. Diarrhoea frequently ensues, Avhich, if not too great, is beneficial; one or both cheeks may become unusually red, which is a symptom of nervous disturbance; eruptions may appear on the face or head, and sometimes on the entire body • ulcera- tions may occur on the lips, gums, inside of the cheeks, and on the tongue; itching of the nose, twitching of the muscles, disturbed sleep, wakefulness, dilatation of the pupils, thirst, loss of appetite all indicate an increase of the irritation; the temper becomes very DENTITION. 177 irritable, and delay in the eruption of a tooth may cause congestion of the gum Avith SAvelling of the cheek; nausea and vomiting, diarrhoea, fever, thirst, and other system disturbances such as con- vulsions, etc., may soon succeed these symptoms. A premature eruption of the teeth is more liable to give rise to constitutional symptoms than a tardy or delayed eruption. The salivary secretion, Avhich is very scanty prior to the period of the eruption of the teeth, ahvays increases as dentition approaches, and in cases of difficult dentition, becomes very profuse. A decided form of stomatitis may be present, and in some cases, even abscesses have formed, which could only be relieved by incisions. As a general rule the degree of irritation present depends upon the number of teeth erupting, but owing to the difference of suscepti- bility, one tooth may give rise to more irritation than the simul- taneous eruption of several teeth will in other cases A perfectly healthy child, properly cared for, may erupt its teeth Avith little or no suffering, although there may be some restlessness, a slight decrease of appetite, and a slight elevation of the tempera- ture of the mouth. At other times a mere local uneasiness may be experienced, Avhich will induce the infant to place its finger in the mouth, or to bite upon some foreign substance, which apparently affords relief. In such cases as these the processes of the develop- ment of the teeth, and the absorption of the tissues confining them, are equal, and the result is that the teeth perforate the gum Avithout causing either pain or irritation. Where, however, there is a differ- ence in the progress betAveen the groAvth of the teeth and the absorp- tion of the opposing structures, then these different forces produce irritation, and a difficult dentition results. When the eruptive period arrives, the roots of the teeth are yet incomplete, for instead of a conical end and the small opening or foramen Avhich a completed tooth presents, there is a voluminous pulp occupying a cavity with an incomplete termination almost as large as the root itself; hence any considerable increase of vascular and nervous action produces a hypersemia of the pulp which may cause its protrusion and induce thereby constitutional disturbance. The immediate cause of the irritation is conceded to be due to the downward pressure of the root upon the nerves and vessels of the pulp of the tooth, such pressure being caused by the opposing gum, and giving rise to congestion and swelling, Avhich have the effect of increasing the induration of the opposing tissues. Constitutional as Avell as local symptoms result from such irritation, some of Avhich are of the most serious character. The cerebro-spinal system may become affected, giving rise to restlessness, sleeplessness, pain in the 12 178 DENTAL PATHOLOGY, THERAPEUTICS. head, convulsions or paralysis ; also the respiratory system, a con- dition which is manifested by cough, catarrh, bronchitis, pneu- monia, or spasmodic croup; also the alimentary canal, Avhen there may be nausea, vomiting, loss of appetite or diarrhoea; also the skin may become affected, and such forms of skin disease may manifest themselves as eczema, acne, etc. Therefore, the period of dentition may be a dangerous one, for many infants die at this time, either from convulsions, from Avhooping cough, or cholera infantum. Difficult dentition is more frequently a predisposing than a direct cause of infantile convulsions. At such a period a sensitive state of the nervous system, or an afflux of blood to the head, may re- sult in convulsions, although such an affection may be the direct consequence of the irritation caused by the efforts of several teeth to erupt at the same time, especially in the case of weakly children. The premonitory symptoms of convulsions are depression, restless- ness, and fretfulness for some days before the paroxysm ; the eyes have a wild, unnatural appearance, the sleep is disturbed, and some- times there is unusual heat of the head, Avith a sudden starting or twitching of the limbs. In general convulsions, the paroxysm is characterized by a hot head during its early stage, and a flushed face, while in sympathetic convulsions the head is cool and the face pallid ; the pulse is accelerated, as well as the respiration, Avhich is also irregular, especially if the respiratory muscles are involved, Avhich is usually the case. The muscles of the face, eyes and eye- lids, and limbs, are in a state of rapid involuntary contraction and relaxation ; the features are distorted ; the mouth is draAvn out of shape, and the teeth become tightly closed, owing to the tonic con- traction of the masseter muscles; and if the paroxysm is prolonged, frothy saliva may issue from the lips. The eyelids are usually open, and in severe cases the pupils of the eyes are concealed under the upper lids, or the eyeballs may be forcibly draAvn from side to side. The head is strongly retracted, or turned to one side; the thumbs and fingers are convulsively flexed, so that the former are turned across the palms and covered by the fingers; the great toe is adducted and the other toes are flexed, and with the legs move spasmodically ; consciousness is lost. The dura- tion of the paroxysm varies from a few minutes to several hours, generally averaging from five to fifteen minutes; and Avhen it ter- minates favorably, the spasmodic movements gradually cease, and are followed by a deep inspiration and quiet or sleep, with a return of consciousness. The temperature and respiration become natural, although dulness and bewilderment of mind may continue for several hours. In severe cases, the respiration is so embarrassed DENTITION. 179 and the circulation so retarded that congestion of various organs results. Death does not usually occur from one paroxysm, but from several at intervals, during the last of which convulsive movements cease, and there is no return of consciousness; the limbs grow cold, the pulse feeble, and coma supervenes. The treatment of convulsions consists in first removing the irrita- tion by the use of the gum-lancet, by emesis, purgatives, etc., accord- ing to the indications; the feet, as soon as possible, may be put in hot water, to which mustard is added; or a warm bath may be used; such measures have a soothing effect upon the nervous system, and cause muscular relaxation and derivation of blood from the cerebro-spinal axis. They also prevent passive congestion and oedema of the brain and lungs. Antispasmodics and nervous seda- tives are indicated after the cause of the irritation has been removed. Cold applications, in the form of a cloth frequently wrung out in cold water, should be made to the head, to reduce its temperature, which will have the effect of contracting the vessels and membranes of the head, and diminishing the cerebral congestion. An aperient is useful, unless there has been previous diarrhoea. An enema of soap and water will produce free and speedy evacuation, as it is often necessary to relieve the digestive canal of irritating substances. For the relief of the paroxysm, and to lessen its duration, chloro- form has been successfully employed as an anaesthetic, but as it is a dangerous agent, the bromide of potassium is preferable, in doses of three grains for a child one year of age, or four or five grains for a child of two or three years of age, dissolved in cold water, and administered every ten minutes; after the convulsions cease, there should be longer intervals betAveen the doses. In very severe cases, Avhere the bromide of potassium may not act Avith the required promptness, the hydrate of chloral may be employed in doses of five grains for a child of one year of age, and ten grains for one of four years of age, dissolved in two or three drachms of Avater, and injected, by means of a small syringe, into the rectum. The bromide of potassium may be combined Avith the chloral as folloAVS: R. Potassi bromid. gr. xvj.; Chloral hydrat. gr. iv. to vj.; Sodii bicarb. gr. xv.; Aquse menth. pip. £§j. M. This remedy is generally successful in controlling the spasmodic movements in five or ten minutes, unless recovery is impossible. During such premonitory symptoms of difficult dentition as fretful- ness and nervous excitement, the bromide of potassium is a useful and safe remedy. Demulcent and soothing lotions are useful to reduce the swelling and tenderness of the gums; and an ivory or rubber ring, for the child to bite upon, will afford great relief. 180 DENTAL PATHOLOGY, THERAPEUTICS. The practice of rubbing the gums with a thimble or ring is in- jurious, as the swelling and tenderness are increased. Unless the tooth is on the point of protruding, the operation of lancing the gum is by many thought to be unnecessary, for the reason that the gum is not rendered tense by the pressure of the advancing tooth, and too much importance has been attached to the supposed tension and resistance of the gum. When the symptoms are local and the gums are somewhat con- gested and swollen, scarifying them lightly with a very sharp lancet Avill often afford relief; but if the gums are very tender, this opera- tion should not be performed. Others, again, advocate the operation of lancing the gums in difficult dentition, even Avhen no single local indication exists in the mouth, by making free incisions over the teeth Avhose eruption is anticipated, the cuts extending through the gum to the presenting surface of the tooth, and thus affording manifest and complete relief. Xo injury results to the erupting tooth, or to the germ of the developing permanent one, if the lancet is carried to the surface of the crown, without undue force is employed. Partially erupted canines and molars sometimes require the use of the lancet to re- lieve the pressure of the enclosing band of gum tissue. Such ob- jections against lancing the gums, as the infliction of great pain and uncontrollable hemorrhage, are of little moment, as is also the assumed increased resistance of cicatricial tissue; for, although the Avound made by the lancet should heal before the appearance of the tooth, this cicatricial tissue is easier absorbed, and consequently less resistant. For lancing the gum over an incisor, a single incision in the line of the arch will ansAver; the molars generally require a crucial in- cision, and the gum of the canines, even after the point of the cusp has emerged, may require severance on the lateral, anterior and posterior surfaces, in order to relieve the tension and liberate these teeth. The illustrations (Fig. 101) show the necessary incisions for the different classes of teeth. Should undue bleeding result from such an operation, it can be arrested by means of a little finely powdered alum applied to the incisions; should such a remedy fail, more powerful astringents or styptics can be employed, such as tannic acid, styptic colloid, matico, poAvdered resin, etc. Nitrate of silver and the iron preparations are liable to cause slough and secondary hemorrhage; hence should never be employed in such cases. As the act of sucking may promote persistent bleeding, in such cases the child should be either placed at the breast of the nurse, or a gag of soft linen be introduced in such a manner as will DENTITION. 181 prevent the infant from sucking its gums. Internal remedies in case of a hemorrhagic diathesis are indicated to correct an abnormal or depraved condition of the blood and promote contraction of the orifices of the bleeding vessels; but their use is seldom necessary. When such remedies are indicated, tincture of the muriate of iron, acetate of lead, aromatic sulphuric acid, gallic acid, and tur- Fig. 101. ^?-\- pentine are the agents to be employed. Dr. James W. White gives the following formula Avhich will meet all the indications in such cases R. Tinct. ferri chloridi, Acid, acetic, dil., Liq. ammonii acet., Ext. ergot, fid., Syr. simp., Aquae, . f^ss. • f-5'j- . fSss. ad f|iij. Dose, a teaspoonful every three hours for a chikl six months old M. It is not unusual for some children to be affected Avith diarrhoea during the period of dentition, and Avhich may be accompanied Avith irritability of the stomach. Where not too debilitating and protracted, the diarrhoea is beneficial, but, on the other hand, it must not be neglected and permitted to become a source of danger. But there are often other causes for this affection than those Avhich can be attributed to dentition, such as improper food and clothing, residence in unhealthy localities, and exposure to cold. The diarrhoea, when severe, should be controlled by proper remedies, capable of reducing the number of evacuations to tAvo or three daily, as a greater number may result in danger to the child. The treatment of the diarrhoea of dentition consists in a change in the diet, the adoption of hygienic measures, and, Avhen medicines are necessary, the administration of the milder purgatives in small 182 DENTAL PATHOLOGY, THERAPEUTICS. doses. Where the dejections are acid, as is shoAvn by the green color, half a teaspoonful to one teaspoonful of castor oil or calcined magnesia will prove beneficial. According to Dr. West, if there be neither much pain nor tenesmus, and the evacuations, though Avatery, are fecal, and contain little mucus and no blood, very small doses of the sulphate of magnesia and tincture of rhubarb are more useful than any other remedy. R. Magnesiae sulphatis, ...... %}. Tinct. rhei........3J. Syr. zingiberis,.......£j. Aquae carui,...... gix.. ^- SiG.—One drachm three times a day, for children one year old. Dr. Christopher Elliott recommends half to one drachm doses of the infusion of chamomile-flowers for infantile diarrhoea of denti- tion, Avhen the evacuations are greenish in color or are slimy and streaked Avith blood. For the diarrhoea of infants due to indigestion, and attended Avith acidity, Prof. J. L. Smith recommends the folloAving: R. Pulv. ipecac,......gr. ss. Pulv. rhei,.......gr. jj. Sodae bicarb.,......gr. xij. M. Divide into chart. No. xij. One powder every four to six hours, for an infant one year old. The same author also recommends the folloAving in the non- inflammatory diarrhoea of infants: R. Tinct. opii deodorat.,.....gtt. xvj. Bismuth, subnitrat.,.....gij. Syr. simplic,......^ss. Mistur. cretae.,......^iss. M. Shake well, and give one teaspoonful, from three to four hours. For increased excitability of the intestine due to dental irrita- tion, Avhich is indicated by frequent stools of semi-solid matter con- taining undigested food, Dr. Lees recommends the use of bromide of potassium in from three to five-grain doses every three or four hours for a child one year of age. Persistent constipation may be treated with ten-drop doses, three times daily, of cod-liver oil, in- creasing the dose if necessary to a half drachm. For the skin affection attending dentition, such as eczema in the acute form, Avith a Avatery discharge and an irritable skin, oxide of zinc, used as a dusting poAvder, will prove serviceable, but the parts should not be Avashed Avith Avater. SECOND DENTITION. 183 When the discharge is thicker and more purulent, and forms scabs, they may be removed by bathing the part Avith oil and Avash- ing it with soap and water, and a salve applied, composed of equal parts of vaseline and simple lead plaster; or less of the lead plaster may be used with the vaseline, if the salve should prove too strong; or an ointment may be employed, composed of oxide of zinc, five grains, and simple salve, one ounce. When the gum over an erupting tooth appears SAvollen and con- gested, and at length ulcerates, even after the tooth is protruding, a condition to which the appellation " odontitis infantum " has been applied, the ulcers may be touched Avith a crystal of alum, and a lotion composed of sage tea and honey used, with decided advan- tage. For a sloughing condition of the mucous membrane over an erupting tooth, the careful application of strong carbolic acid will prove efficient. During infancy, and especially during the period of dentition, the clothing should consist of fine, soft flannel next to the skin, to protect the body from variations of temperature, and all changes be made gradually. The food for some months after birth should be confined exclusively to milk, that of the mother being prefer- able Avhen she is in good health. For artificial food, Avhen such is necessary, an excellent preparation is that of Dr. J. F. Meigs, which consists of equal parts of milk, cream, lime-water, and oatmeal, barley- or arroAvroot-Avater, to which a little sugar of milk is added. SECOND DENTITION. The design of nature is to preserve the deciduous teeth until their roots are absorbed and they become loose, and are removed to make room for their permanent successors. But the eruption of the permanent teeth begins before any of the deciduous teeth are removed. BetAveen the ages of five and a half and six years, the first permanent molars make their appearance; hence they are commonly called " sixth-year molars," and their germs, with those of the remaining permanent teeth, are progressing with the devel- opment of the deciduous teeth. When the permanent teeth are developing, and their croAvns, on account of the growth of the roots, are approaching the alveoli of the deciduous teeth, a process of absorption commences, by which the roots of the latter teeth are gradually destroyed, the dissolving process going on until only the croAvns of the deciduous ones remain. The process of absorption affects the roots of the decidu- ous teeth in the order corresponding to their development and eruption; the inferior central incisors are first shed, then the 184 DENTAL PATHOLOGY, THERAPEUTICS. superior central incisors, then the lateral incisors; and this order is preserved until all of the deciduous teeth have been removed or have become so loose that they are easily extracted. The absorptiA'e process commences in the alveoli of the decidu- ous teeth, and then attacks the apices of their roots, and in some cases progresses until it involves a large portion of the croAvns. The loss of substance commences generally upon the side of the root, near the apex, toAvard the advancing croAvn of the permanent tooth, and the surface of the root acted upon presents pits, grooves, or irregular facets, Avith rough surfaces and sharp edges, such as Avould result from corrosion. If a deciduous tooth undergoing this process of absorption be extracted, a loose, spongy substance is Fig. 102. ILLUSTRATES THE JAWS OF A CHILD BETWEEN SIX AND SEVEN YEARS OF AGE, SHOWING THE RELATIONS OF THE TWO SETS OF TEETH. found adherent to it, which Laforgue and Bourdet supposed to be an absorbent organ secreting a fluid capable of dissolving the tooth- structure. According to Wedl, a fluid is secreted by the cells of this organ Avhich dissolves the hard substance, and referring to the theory held by some, he says " that these cells are of a parasitic nature, that is to say, that the dental substances are eaten up, as it were, since the cells absorb the latter, and he remarks that " possi- bly amoeboid movements may be the occasion of the Avasting of the tissues;" he is also of the opinion that the organ of absorption is developed from the connective tissue of the root membrane of the deciduous tooth. According to a microscopic examination made SECOND DENTITION. 185 by Mr. Tomes, the surface of this absorptive organ is made up of peculiar multiform cells, each one being composed of several smaller cells, the number varying from tAvo or three to as many as fourteen or fifteen. Some have regarded the method employed b}r nature for the re- moval of the roots of the temporary teeth as sui generis, but there is a better reason for considering it to be the effect of an inflammatory process that brings about a proliferation of cell-groAvth, Avhich may at one time act as an absorbent and at another be reparative. As to the precise manner in Avhich these cells of the absorbent organ act, much remains to be learned, but that it is a physiological pro- cess, and occasioned by the action of cells knoAvn as " osteoclasts," or " odontoclasts," and is not a mechanical force, is noAV quite gen- erally admitted. These cells secrete what has been termed " a soluble ferment," or " fluid of exudation," which dissolves out the lime salts from the hard tissues Avith which it comes in contact, the surface acted upon presenting a series of pits and cup-shaped depressions. Dr. C. N. Peirce, in an excellent article, entitled " Calcification and Decalcification of the Teeth,"* and Avhich is illustrated by the folloAving instructive figures (Fig. 103), in treating of the absorption or decalcification of the roots of the deciduous teeth, regards this process " as being both physiological and someAvhat obscure " and he further states: u The evidence that it is the result of a physiological action is the fact that it matters not to what extent absorption has progressed, the very moment vitality of the pulp ceases that instant this retro- grade metamorphosis terminates. What induces this molecular dissolution it is difficult to state, though the several conditions Avhich are ahvays present are readily recognized; but the part they play is so obscure that it is not readily ascertained. The manner of its commencement Avhen successful—always at the end of the root—and the presence of a vascular papilla in close proximity to the absorbing surface, are, Avith the retention of pulp vitality, three essential accompaniments, and the absence of any one of them Avould militate against the completion of the process. " The statement that the presence and pressure of the permanent tooth are essential, cannot be sustained, for frequently the decalci- fication of the deciduous tooth is successfully accomplished in the absence of its successor; and again, how often do we find the per- manent tooth impacted against or Avithin the bifurcated roots of * Dental Cosmos, August, 1884. Fig. 103. CALCIFICATION AND DECALCIFICATION OF THE TH. Fig. 1. Fig. 3. 22 months after birth 18 months alter birth 12 months after birth 0 months after birth 40th week (birth) 30th week embryo 18th week embryo 17th week embryo 12 years 10 years 9 years 8 years 7 years 6 years 5 years 4 years 3 years 2 years 1 year At birth Calcification of the Deciduous Teeth. A Decalcification of the Deciduous Teeth. Tho numbers on Fig. 3 indicate years. Fig. 2 Calcification of the Permanent Teeth. From a Paper by Db. C. N. Phirce, in the Dental Cosmos for August, 1884. SECOND DENTITION. 187 the deciduous molar, or pressing down by the side of its single- rooted predecessor, both being more or less displaced by the per- sistence of the deciduous tooth Avithout absorption. That the organ has served its purpose, and that the nourishment which had pre- viously been appropriated by it is diverted or relegated to its suc- cessors, is probably the most plausible explanation Ave can give of this interesting physiological process." J^b> The average time and order for the eruption of the permane^pF teeth are as follows : First molars,........5 to 6 years. Central incisors,...... 6 " 8 " Lateral incisors,.......7 *' 9 " First bicuspids,........9 " 10 " Second bicuspids,.......10 " 12 " Canines,.........11 " 13 " Second molars,........12 " 14 " Third molars, or wisdom teeth,. t . . . 17 " 21 " Usually little or no difficulty attends the eruption of the perma- nent teeth, Avith the exception of the third molars of theloAver jaw, Avhich may cause considerable trouble and suffering, on account of their being croAvded between the second molar and the ramus or ascending portion of the jaw, the space left being insufficient to accommodate the third molar. Inflammation from such a cause may extend to the soft tissues, such as the muscles, and render the act of SAvalloAving difficult and painful, and that of mastication im- possible. The inflammation thus caused may also terminate in suppuration, and the pus discharge at remote points, internal or external. Such maladies as neuralgia, hysteria, epilepsy, St. Vitus' dance, disordered vision, earache, deafness, tetanus, etc., have been caused by the eruption of the third molar. Occasionally the erup- tion of the molars anterior to the third molars may be attended with some constitutional disturbance, such as headache, slight neu- ralgic pains, impaired appetite; and also local symptoms, such as SAvollen gums, increased heat of mouth, and an increased fioAV of saliva. The extraction of the third molar may be necessary in some cases; in others, that of the second molar, although the re- moval of a carious first molar may sometimes relieve the crowded condition of the arch, Avhen the trouble is owing to a want of space betAveen the second molar and the ramus of the jaAv. The lancing of the gum over a third molar not yet protruded often relieves. The most common period of suffering from second dentition, apart from that of the third molar, is from the tenth to the thirteenth 188 DENTAL PATHOLOGY, THERAPEUTICS. year, and it is characterized by such affections as obstinate and pro- tracted cough, Avith paroxysms of long duration, also diarrhoea, Avasting of flesh, nervous diseases, loss of spirits, headache, and morbidly sensitive and painful e}^es. The obstinate cough has disappeared Avhen the molar teeth pierced the gums; and a mixture of iron and nitric acid Avas successful in ""immediately curing a patient of seven years of age in the practice of Dr. James Jackson, Avho recommends the folloAving remedies as being most useful: " First, a relief from study or from regular tasks, yet using books so far as they afford agreeable occupation or amusement. Second, exercise in the open air, preferring the mode most agreeable to the patient, and in more grave cases the removal from toAvn to country." Fig. 104 represents an instrument, the invention of Mr. Wood- house, and introduced by Dr. L. D. Shepard, designed for the re- Fig. 104. moA'al of the overlying gum which covers the masticating surfaces of the first and third molars, very often for months after the cusps have appeared through the gum, and thus promotes, if it does not cause, the decay so frequently accompanying these teeth upon their erup- tion. An incision is made with a lancet, through the gum, along the anterior margin of the tooth, and the thin flat blade of the cutter is inserted; then, by closing the handles, the section of gum the size of the blade is instantly removed. The operator Avill find this process much more effectual, and far easier to the patient, than the usual practice of cutting the gum in different directions. THIRD DENTITION. That nature sometimes makes an effort to produce a third set of teeth is a fact Avhich, however much it may be disputed, is now so well established, that no room is left for cavil or doubt. THIRD DENTITION. 189 The folloAving interesting particulars are taken from " Good's Study of Medicine:" " We sometimes, though rarely, meet Avith playful attempts on the part of nature to reproduce teeth at a very late period of life, and after the permanent teeth have been lost by accident or by natural decay. " This most commonly takes place between the sixty-third and eighty-first }Tear, or the interval Avhich fills up the tAvo grand cli- macteric years of the Greek physiologist; at which period the constitution appears occasionally to make an effort to repair other defects than lost teeth. . . . " For the most part, the teeth, in this case, shoot forth irregularly, feAV in number, and Avithout proper roots, and, even Avhere roots are produced, Avithout a reneAval of sockets. Hence, they are often loose, and frequently more injurious than useful, by interfering Avith the uniform line of indurated and callous gums, Avhich, for many years, perhaps, had been employed as a substitute for the teeth. A case of this kind is related by Dr. Bisset, of Knayton, in which the patient, a female in her ninety-eighth year, cut tAvelve molar teeth, mostly in the lower jaw, four of which Avere throAvn out soon after- Avard, while the rest, at the time of examination, Avere found more or less loose. " The German Ephemerides contain numerous examples of the same kind ; in some of Avhich teeth Avere produced at the advanced age of ninety, a hundred and even a hundred and tAventy years. One of the most singular instances on record is that given by Dr. Slade, Avhich occurred to his father, Avho, at the age of seventy-five, reproduced an incisor, lost twenty-five years before, so that, at eighty, he had hereby a perfect row of teeth in both jaws. At eighty-tAvo, they all dropped out successively; two years afterward, they Avere all successively reneAved, so that at eighty-five he had once more an entire set. His hair, at the same time, changed from a Avhite to a dark hue; and his constitution seemed, in some degree, more healthy and vigorous. He died suddenly, at the age of ninety or a hundred. "Sometimes these teeth are produced Avith Avonderful rapidity; but in such cases with very great pain, from the callosity of the gums through Avhich they have to force themselves. The Edinburgh Medical Commentaries supply us with an instance of this kind. The indi\udual Avas in his sixty-first year, and altogether toothless. At this time his gums and jaAvbones became painful, and the pain was at length excruciating. But within the space of tAventy-one days 190 DENTAL PATHOLOGY, THERAPEUTICS. from its commencement, both jaws were furnished Avith a neAV set of teeth, complete in number." A late physician of Baltimore informed the author, in 1838, that an example of third dentition had come under his own observation. The subject, a female, at the age of sixty, he assured him, erupted an entire neAV set in each jaw. The following extract of a letter from a professional friend* de- scribes another very interesting case : " I have just seen a case of third dentition. The subject of this ' playful freak of nature,' as Dr. Good styles it, is a gentleman resid- ing in the neighborhood of Coleman's Mill, Caroline County, Vir- ginia. He is noAV in his seventy-eighth year, and as he playfully remarked, ' is just cutting his teeth.' There are eleven out, five in the upper and six in the lower jaw. Those in the upper jaw are two central incisors, one lateral and two bicuspids, on the right side. Those in the lower are the four incisors, one cuspid and one molar. Their appearance is that of bone, extremely rough, Avithout any coating or enamel, and of a dingy brown color." Two cases somewhat like the foregoing have come under the author's observation. The subject of the first was a shoemaker, Mr. M., of Baltimore, who erupted a lateral incisor and cuspid at the age of thirty. Tavo years before this time he had been badly sali- vated, and, in consequence, lost four upper incisors and one cuspid. The alveoli of these teeth exfoliated, and at the time he first saw him, were entirely detached from the jaw, and barely retained in the mouth by their adhesion to the gums. On removing them, he found two white bony protuberances, which, on examination, proved to be the crowns of an incisor and cuspid. They were per- fectty formed, and though much shorter than the other teeth, yet up to 1845 they remained quite firm in the jaAv. The subject of the other case was a lady residing near Fredericks- burg, Virginia, who erupted four right central incisors of the upper jaAV successively. One of her temporary teeth, in the first instance, had been permitted to remain too long in the mouth, and a per- manent central incisor, in consequence, came out in front of the dental arch. To remedy this deformity, the deciduous incisor was, after some delay, removed ; and about two years after, the permanent tooth, not having fallen back into its proper place, was also extracted. Another two years having elapsed, another tooth came out in the same place and in the same manner, and, for similar reasons, Avas also removed. To the astonishment of the lady and her friends, a Dr. J. D. McCabe. THIRD DENTITION. 191 fourth incisor made its appearance in the same place, two years and a half after the extraction of the first permanent tooth. When it had been out about eighteen months, the author was called in by the lady, Avho Avished him, if possible, to adjust it. Finding that it could not be brought Avithin the dental circle, he advised her to have it extracted, and an artificial tooth placed in the proper place in the arch. In the second number of the eighth volume of the " American Journal of Dental Science," the history of a case of four successi\re dentitions of the upper central incisors is given* The following interesting case is related by Dr. B. H. Catching in the Southern Dental Journal for October, 1886. The patient Avas a girl, born August 6th, 1871, very small and delicate, having been a six-months' child. At the age of six months the eruption of the teeth began, and at seven months she possessed a full set of diminutive teeth, all of which were shed Avithin three months. When eleven months old, teeth again began to erupt, and at the age of fifteen months a second full set Avas in her mouth. These soon crumbled aAvay, and her mouth Avas Avithout teeth until she had arrived at the age of tAvo and a half years, Avhen a third set began to erupt. The child weighed at this time but ten pounds, and this third set of teeth caused her so much trouble that the mother endeavored to have them extracted, and not being able to induce a dentist to perform the operation, she extracted tAvelve of the teeth herself in order to give relief to her child ; and all of the third set were removed prior to her fourth year of age. She remained without teeth until her eleventh year Avhen her last and permanent set began to erupt, nearly all of Avhich were, at the date of Avriting this account, in her mouth, sound and firm. Her last set is deficient in one superior central incisor, one superior left bicuspid, two inferior right bicus- pids, and an inferior left cuspid and bicuspid. At seven years of age this child Aveighed but thirty pounds, but at fifteen years of age she had developed into a stout, strong girl. Dr. T. T. Moore, of S. C, verifies this case, as the child was under his care also, both himself and Dr. Catching haAring carefully observed the conditions and development from the beginning to the end. Concerning the manner of the origin and formation of teeth of third dentition, adopting Wedl's vieAvs, germs may lie dormant for many years in the animal organism, until they are subjected to favorable conditions which enable them to develop. The croAvns of * Dr. W. H. Dwinelle. 192 DENTAL PATHOLOGY, THERAPEUTICS. such teeth only being formed, Avhile the roots are stunted, is clearly due to the small depth of the jaws in old age. CHARACTERISTICS OF THE TEETH. Most dental physiologists have observed the marked differences that exist in the appearances of the teeth, gums, lips, tongue, and secretions of the mouth of different individuals; and of that earthy substance (commonly called tartar), deposited in a greater or less abundance on the teeth of every one; and, although all may not have sought their etiology, many have had occasion to notice, at least, their local indications, and to profit by the information which they have thus obtained. Nor have they failed to observe that the size, color, length and arrangement of the teeth vary, and that these are indications of their susceptibility to disease. There are five principal classes or descriptions of teeth, each of Avhich differs, in some respects, from the others, a knowledge of Avhich is very essential to the dental practitioner, in order that he may determine their liability to decay, strength of attachment, and the form and size of their roots. Class First.—The teeth belonging to this class are Avhite, with a light cream-colored tinge near the gum, Avhich becomes more and more apparent as the subject advances in age, of a medium size, rather short than long, with thick, square edges; those of each class of uniform dimensions, and very hard. This description of the teeth is most frequently met with in persons of sanguineous tem- perament, or, at least, those in whom this predominates; they rarely decay, and generally occupy their proper position in the dental arch ; the most common deviation, and one most peculiar to this class, is that of the superior incisors antagonizing with the inferior, causing the form of abrasion knoAvn as mechanical. They are not as easily acted upon by corrosive agents, and caries attacking them, usually of the black variety, makes but slow progress, and often exists for a considerable time Avithout causing pain or inconvenience. Operations performed upon teeth of this class are those, above all others, on Avhich Ave can predict the most perfect success. They in- dicate, if not perfect health, at least a state which bordered very closely on it at the time of their dentinification. This first description of teeth is occasionally found among persons of all nations. They are very common in cold and temperate climates, and especially in the middle classes of the inhabitants of England, Ireland and Scotland. They are also frequently met with in some parts of the United States, the Canadas, the mountainous districts of Mexico, and so far as we have had an opportunity of CHARACTERISTICS OF THE TEETH. 193 informing ourself, in France, Russia, Prussia and SAvitzerland. Those who haA'e them usually enjoy excellent health, and are seldom troubled Avith dyspepsia or any of its concomitants. It is this kind of teeth Avhich, Lavater says, he has never met Avith except in " good, acute, candid, honest men," and of whose possessors it has been remarked, that their stomachs are ahvays Avilling to digest Avhatever their teeth are ready to masticate. In confirmation of Avhat has before been said with regard to the influence Avhich the state of the constitutional health, at the time of the solidification of the teeth, exerts upon the susceptibility of these organs to morbid impressions, it is only necessary to mention the fact, wellknown and frequently alluded to, of the early decay of a single class, or a pair of a single class of teeth, in each jaw, Avhile the rest, possessing the characteristics just described, remain sound through life. Thus, Avhen it happens that a child of excellent constitution is affected with any severe disease, the teeth which are at the time receiving their earthy salts are found, on their eruption, to differ from those which have received their solid material at another time, Avhen the operations of the body were healthfully performed. Instead of having a white, smooth, and uniform sur- face, they have a sort of chalky aspect, or are faintly tinged with blue, and are rougher and less uniform in their surfaces. Teeth of this description are very susceptible to the action of corrosive agents, and, as a consequence, rarely last long. But, not Avilling to rest the correctness of these views upon mere hypothesis, we, in a great number of instances, where Ave have seen teeth thus varying in their physical appearance, have taken pains to inquire of those Avho had an opportunity of knowing the state of the general health of the individuals at the different periods of dentinification; and in every case where we have been able to pro- cure the desired information, it has tended to the confirmation of the opinion here advanced. Nor have Ave neglected to improve the many opportunities that have presented, in the course of a some- what extended professional career, of making these observations. Although the operations of the economy are so secretly carried on that it is impossible to comprehend their details fully, it is known that the phenomena resulting therefrom are influenceVi and modi- fied by the manner in Avhich they are performed. If they are deranged, the blood, from Avhich the earthy materials forming the basis of all the osseous tissues are derived, is deteriorated, and fur- nishes these salts in less abundance and of an inferior quality. Hence, teeth that solidify Avhen the system is under the influence of disease, do not possess the characteristics necessary to enable them 13 194 DENTAL PATHOLOGY, THERAPEUTICS. to resist the assaults of corrosive agents, to which all teeth are more or less exposed, and Avhich rarely affect those that receive their solidifying ingredients from pure blood. The calcareous salts of these organs are furnished chiefly by the red part of this fluid, the gelatine is derived from the white or serous part; " whence," as Delabarre remarks, " it results that the solidity of these bones varies according as one or other of these principles predominates," and the relative proportions of these are regulated by the state of the blood at the time the teeth are under- going solidification. Class Second.—Having digressed thus far, Ave shall noAV proceed to notice the teeth belonging to the second class. They have a faint, azure-blue appearance ; are rather long than short; the incisors are generally thin and narrow, the centrals being frequently a little longer than the laterals. In some cases the lateral incisors are very small and pointed. The cuspids are usually round and pointed; the bicuspids and molars small in circumference, with prominent cusps and protuberances upon their grinding surfaces. Teeth possessing these characteristics are usually very sensitive, caused, doubtless, by a superabundance of animal matter, and are more easily acted upon than teeth of the first class, by corrosive agents, and to the ravages of which, unless great attention is paid to their cleanliness, they often fall early victims. The variety of caries almost peculiar to this class is known as the Avhite, the parts attacked being rendered soft and humid ; and as they retain their natural color, it but too frequently happens that such teeth are almost irretrievably ruined before its presence is suspected. They are, also, more frequently affected with atrophy, or have upon their surfaces Avhite, brown, or opaque spots, varying in size and number; several are sometimes found upon a single tooth, and in some in- stances every tooth in the mouth is more or less marked with them.. But this is not the only description of teeth liable to be affected Avith this disease. These spots are occasionally met Avith on teeth of every degree of density, shape, shade and size; but they are, probably, more frequently seen on teeth of the second class than on those first described; besides Avhich, it often happens that they are affected with erosion on emerging from the gums, and sometimes so badly as to place either their restoration or preservation beyond the reach of art. This species of erosion, or that Avhich occurs pre- viously to the eruption of the teeth, is caused by some diseased condition of the fluid which surrounds them before they appear above the gums, and is denominated congenital. Teeth like those now under consideration are indicative of a CHARACTERISTICS OF THE TEETH. 195 weakly constitution, of a temperament considerably removed from the sanguineous, resembling the lymphatic, and of blood altogether too serous to furnish materials such as are necessary for building up a strong and healthy organism. They are more common to females than to males, though many of the latter have them. They are met Avith among people of all countries, but more frequently among those Avho reside in sickly localities, and Avith individuals whose systems have become enervated by luxurious living. In Great Britain they are more rare than in the United States, and those Avho have them seldom attain to a great age. Nevertheless, some, under the influence of a judicious regimen and a salubrious climate, though innately delicate, do acquire a good constitution, and live to a great age; Avhile the teeth, less fortunate, unless the most rigid and constant attention is paid to the use of the means necessary for their preservation, generally fall early victims to the ravages of disease. Class Third.—The teeth of this class, though differing in many of their characteristics from those last described, are, nevertheless, not unlike them in texture and sensibility to disease. They are pecu- liar to those Avho have inherited a scrofulous habit or diathesis. In this state of the system we find a sufficient supply of blood, but it is usually of a pernicious character; the Avhole organism is affected by it and rendered very susceptible to disease, more especially to that class superinduced by cold. Teeth developed under constitu- tional defects of this nature are larger than teeth of the first or second class; their faces are rough and irregular, Avith protuberances arising, not only from the grinding surfaces of the bicuspids and molars, but also not unfrequently from their sides, Avith correspond- ingly deep indentations. They have a muddy white color. The croAvns of the incisors of both jaAvs are broad, long, and thick. The posterior or palatine surfaces of those of the superior maxilla are rough and usually deeply indented. In the majority of cases their arrangement is quite regular, though frequently found to project. The ahTeolar ridge usually describes a broad arch. The excess in size, both here and in the teeth, seems to consist more of gelatin than calcareous phosphate. Teeth of this description decay rap- idly, and in some instances appear to set at defiance the resources of the dentist. They are liable to be attacked at almost every point, but more particularly in their indentations and approximal surfaces. The caries to which these teeth are liable is in color and consistence betAveen the two kinds mentioned in connection Avith the first and second classes. The author is .acquainted Avith a family, consisting of seven or 196 DENTAL PATHOLOGY, THERAPEUTICS. eight members, most of Avhom are adults, all having this sort of teeth. The most thorough attention has been paid by each, and yet all have lost most of their teeth. They are usually first attacked in their approximal surfaces and indentations, but neither their labial faces nor most prominent points are exempt from caries. No sooner is its progress arrested in one place or part than it appears in an- other. The author has had occasion to fill a single tooth in as many as four, five, and even six different places; and in this Avay, though his efforts at the preservation of any considerable number have proved unavailing, he has been able to save some of them. But it is not necessary to particularize cases. Every dentist has seen teeth of this description. The corrosive properties of the fluids of the mouth, hoAvever, are sometimes so changed by an amelioration of the constitution that, notwithstanding the great susceptibility of the teeth to disease, they are sometimes preserved to a late period of life, or until the general health relapses into its former or some other unfavorable condition. This has happened in several instances that have come under the author's immediate observation, and it should be borne in mind that the solvent qualities of these juices are influenced by the state of the constitutional health. Class Fourth.—Teeth of this class usually have a white, chalky appearance, are unequally developed, and of a very soft texture. They are easily acted upon by corrosive agents, and, like the teeth last noticed, generally fall speedy ^victims to disease, unless great care is taken to secure their preservation. Persons who -have teeth such as described in this class, generally have what Laforgue calls lymphatico-serous temperaments. Their blood is usually pale, the fluids of the mouth abundant, and for the most part exceedingly viscid. They do not have that Avhite, frothy appearance observable in healthy, sanguineous individuals. As teeth that are neither too large nor too small, and that have a close, compact texture, and tinged with yelloAv, are indicative of an originally good constitution, Avhatever it may be at the present time, so those that are long, narrow, and faintly tinged Avith blue, as Avell as those that greatly exceed the ordinary size, and that are irregular in shape, and have a rough, muddy appearance, furnish assurance of a constitution originally bad. The first of the latter descriptions of teeth are more frequently met with among females than males, and among those of strumous habit, than those in whom this dia- thesis does not exist'. Class Fifth.—-The teeth belonging to this class are characterized by whiteness and a pearly gloss of the enamel. They are long and CHARACTERISTICS OF THE TEETH. 197 usually small in circumference, though sometimes well developed. They are regarded by many as denoting a tendency to phthisis pul- monalis, and are supposed by some to be very durable; but the author has observed that individuals who have this sort of teeth, when attacked by febrile or any other form of disease having a ten- dency to alter the fluids of the body, are very subject to toothache and caries; and that when this condition of the general system is continued for a considerable length of time, the teeth, one after an- other, in rapid succession, crumble to pieces. It would seem, from this circumstance, that the fluids of the mouth in subjects of strumous habit, if free from other morbid ten- dencies, are less prejudicial to the teeth than they are in most other constitutions, and the author is of the opinion that it is owing to this that they are so seldom attacked by caries. M. Delabarre, in speaking of persons Avho have teeth Avhich, though beautiful, from having smooth and apparently polished sur- faces, present shades intermixed with a dirty white, says, they " have had alternations of good and indifferent health during the formation of the enamel. These teeth," he continues, " ordinarily have elongated crowns, and many present marks of congenital atro- phy." Again he observes, "-Teeth of this sort deceive us by appear- ing more solid than they are; they remain sound until about the age of fourteen or eighteen; at this period a certain number of them decay, especially when in infancy the subject was lymphatic, and continued to be so in adolescence. This description of teeth is fre- quently met Avith among the richer classes, in Avhich children born feeble reach puberty only by means of great care, and, consequently, owe their existence solely to the unremitting attention of their pa- rents and the strengthening regimen that the physician has caused them constantly to pursue. Having reached the eighteenth or twen- tieth year, their health is confirmed, but the mucous membranes ever after have a tendency to be affected; the redder color of the mouth, more especially its interior part, and that of the lips, and the upper part of the palate, Avhich, by degrees, discovers itself as the subject gradually advances in years, shoAving an ameliorated condi- tion. It is thus that numerous persons, having gained a sanguineous temperament, Avould deceive us, if it were not that some marks of erosion are seen on the masticating surfaces of the first permanent molars, Avhich informs us that the present health is the result of amelioration." There are other cases in Avhich the teeth are of so inferior a quality that they no sooner emerge from the gums than they are attacked and destroyed by caries, while the subjects who possess them are 198 DENTAL PATHOLOGY, THERAPEUTICS. enabled, by skilful treatment, to overcome the morbid constitutional tendencies against Avhich, during the earlier years of their existence, they had to contend, and eventually to acquire excellent health. But in forming a prognosis, it is essential to ascertain whether the general organic derangement which prevented the teeth from being well formed, and thus gave rise to their premature decay, is heredi- tary, or whether it has been produced by some accidental cause subsequent to birth. The procurement of health in the former case will be less certain than in the latter, for when the original elements of the organism are bad, the attainment of a good constitution is more difficult. Persons of sanguineo-mucous temperaments, having suffered in early childhood from febrile or inflammatory diseases, often have their teeth affected with what Duval calls the decorticating process (denudation of their enamel), resulting, no doubt, from the destruc- tion of the bond of union between it and the dentine. There are other characteristics which the teeth present in shape, size, density, and color, and from Avhich valuable inductions might be made, both Avith regard to the innate constitution and the means necessary to their own preservation; but as the limits assigned to this part of our subject will not admit of their consideration, Ave shall conclude by observing that the appearances of these organs vary almost to infinity. Each is indicative of the state of the gen- eral health at the time of their formation, and of their own physical condition and susceptibility to disease. CHAPTER III. DISEASES OF MUCOUS MEMBRANE. STOMATITIS. The diseases of the mucous membrane lining the mouth, very common at the periods for the eruption of the teeth and later in life, are comparatively rare during foetal life, and differ, as regards symptoms, in accordance with the nature of the affection and the part of the mucous surface in which it may have its origin. The most common affection of the membrane lining the mouth is knoAvn by the general term stomatitis, from the Greek Avord aro/ia " mouth," and itis, " a suffix denoting inflammation," and is de- scribed by Prof. Wood as follows: "Inflammation of the mouth appears in reddened, somewhat DISEASES OF MUCOUS MEMBRANE. 199 elevated patches, or occupies large portions of the surface, some- times extending apparently over the whole mouth. In some cases it is superficial, Avith little or no swelling, and may be designated as erythematous, from the Greek word epuftpos, 'red;' in others it occupies the Avhole thickness of the membrane, extending some- times to the submucous tissue, and even to the neighboring struc- tures, as the sublingual and submaxillary glands, and the absorbent glands of the neck, and occasions considerable tumefaction in all these parts. In the erythematous form it is characterized by red- ness and sense of heat, and sometimes considerable tenderness, but is not usually attended with acute pain; when deeper in the tissue it is often very painful. " Portions of the epithelium sometimes become opaque, giving an appearance of whiteness in streaks or patches. Occasionally this coating is elevated in blisters, or even detached, like the cuticle, from the skin, in scales. Superficial ulcerations not unfrequently occur, Avhich may spread over considerable portions of the mem- brane. In certain states of the constitution the ulcerative tendency is very strong and deep, and extensive sores occur, Avhich are some- times attended with gangrene. "There is often a copious flow of saliva; though, in some in- stances, this secretion, as well as that of the mucous follicles, is checked, and the mouth is clammy or dry. The sense of taste is usually more or less impaired, and speech and mastication are often difficult and painful. When the tongue is affected, its surface is, in general, first covered Avith a Avhitish fur, through Avbich the red and swollen follicles may often be seen projecting. This fur sometimes breaks off, leaving the surface red, smooth and glossy, with here and there prominent follicles; or the surface may be hard, dry, or gashed Avith painful fissures. When the gums are in- volved, they swell, and rise up betAveen the teeth, around the necks of Avhich they frequently ulcerate. In some cases this ulceration does not cease until it has extended into the sockets, and destroyed altogether the connections of the teeth, which become loosened and fall out, after Avhich the gums Avill heal. " Ordinary inflammation of the mouth is seldom so Auolent as to induce symptomatic fever. This form of inflammation is more fre- quently a complication of other diseases than an original affection. When of the latter character, it is generally caused by the direct action of irritant bodies, as by scalding drinks, acrid or corrosive substances taken into the mouth, or unhealthy secretions from decayed teeth. The sharp edge of a broken tooth sometimes gives rise to much inflammation, and even deep and obstinate ulcers, 200 DENTAL PATHOLOGY, THERAPEUTICS. especially of the tongue. Inflammation of the mouth may also result from the reaction which follows the long contact of very cold substances, such as ice, Avith the interior of the mouth. It some- times proceeds from the propagation of inflammation from the fauces, and is a frequent consequence of gastric irritation produced by sour or acrid matter in the stomach. Drunkards seem peculiarly predisposed to it. Of the constitutional causes none are so frequent as the state of fever, which, whatever may be its peculiar character, is very apt to affect the mouth, and not unfrequently occasions inflammation." Catarrhal Stomatitis.—Catarrhal stomatitis may be either acute or chronic, and a simple form is common to children under the age of one year; Avhile this simple form gives rise in itself to no seArere symptoms, yet it may be connected with other serious maladies, and hence is often overlooked. Acute catarrhal stomatitis first appears in the form of bright-red patches at the angles of the mouth and on the inside of the cheeks, which increase in size and some- times unite, Avhen the entire mucous surface of the mouth may be- come inflamed. While it is more intense in one part than in another, it may be confined to the tongue alone, or be uniA7ersally diffused over the whole mucous membrane of the mouth. It is characterized by an increase of the heat and redness of the part affected, rapid proliferation and exfoliation of epithelial cells, and more or less dryness of the surface, as there is but little mucus secreted, Avith a high degree of sensibility, and pain when the lips or tongue are moved. The pain is of a smarting, burning character, the result of irritation on a denuded surface. OAving to the limited extent of connective tissue, the swelling of the inflamed mucous membrane is generally slight. In severe cases the gums become SAvollen and spongy, and bleed readily, and the entire surface of the mouth and tongue is covered with a white, viscid mucus; there is an increased flow of saliva, that is acrid and irritating, which may dribble from the corners of the mouth, causing a greater degree of congestion, Avhich is apparent by the dark red color of the affected membrane. A fetid condition of the breath is not common to the acute form of catarrhal stomatitis unless shallow ulcers are present, which result from the rapid loss of the superficial cells and a failure in the development of others to supply their places. The engorge- ment of the vessels of the mucous membrane is folloAved by the exudation of Avhite blood-corpuscles. The intensity of this affection varies in different cases, sometimes existing in such a slight form as to cause little uneasiness, and DISEASES OF MUCOUS MEMBRANE. 201 quietly disappearing, while at other times it may cause intense pain, and continue for Aveeks or months.' In a severe form it may extend to the oesophagus and stomach, or the larynx and trachea, and at last prove fatal, especially if there is present a decided state of cachexia, or a severe co-existing disease. When it occurs during the period of dentition, to which it is com- mon, it is often accompanied with fever, and sometimes, especially when long continued, by a profuse Aoav of saliva; occurring pre- vious to dentition, it is seldom accompanied with fever. When caused by dentition, the gum over the erupting tooth be- comes inflamed, and the inflammation may extend over the entire buccal surface. But when due to the irritation of dentition, this form of stomatitis is generally more circumscribed than Avhen it arises from a constitutional cause. It may also result from a mer- curial course of treatment, exposure to cold, hot and stimulating food, or a diseased condition of the alimentary canal. In adults catarrhal stomatitis may result from long-continued irritation of the mucous membrane of the mouth, or from injuries to the gums, such as may result from laceration in the extraction of teeth ; also from the sharp edges of fractured teeth and roots, and constitutional derangement. In very young children, among the early symptoms are restless- ness and fretfulness, Avith refusal to take food, or, when attempting to do so, suddenly ceasing on account of the pain experienced. Chronic catarrhal stomatitis is characterized by the structural changes Avhich ensue on account of the stroma becoming affected. The mucous surface affected becomes indurated and thickened, the mucous glands are obstructed, and, as a result of their secretion being arrested, they become encysted and present a granular ap- pearance on the surface of the membrane. The breath is more or less fetid owing to the secretions of the mouth becoming vitiated, and the teeth are coated Avith sordes. The papilla? of the tongue become hypertrophied, but the substance beneath is less affected than in the acute form of this affection. The duration of the acute form is from three to six days as a general rule, Avhile the chronic form is more persistent. Simple stomatitis of children is readily relieved by means of emollient Avashes, such as solutions made from the slippery elm bark or the pith of sassafras, in cold water. When severe, a leech or tAvo applied to the angle of the jaAArs will prove serviceable, and as a wash, the acetate of lead, in a solution composed of three grains to one fluidounce of AArater. A few doses of bromide of potassium may relieAre the nenTous excitement and fretfulness. One 202 DENTAL PATHOLOGY, THERAPEUTICS. part of borax to three of honey, or a drachm of borax to an ounce of glycerin and water, or a weak solution of alum, may prove useful local remedies. The treatment of catarrhal stomatitis consists in first removing the cause of irritation, when such is present, and the use of alkaline washes, or, in more obstinate cases, a solution of either chloride of zinc or nitrate of silver, one grain to the ounce of water. Phenol sodique or phenate of soda will correct the fetor of the breath, when used in the form of spray. For the chronic form the following may be applied to the inflamed mucous surface, either in the form of a gargle or spray: &. Acidi carbolici,......3J- Olei gaultheriae,.......^U- Glycerini,........3U- Olei menthas piperitae,.....3iij-—M. When the inflammation of the mouth is symptomatic of a dis- eased condition of the alimentary canal, the remedies adapted to such a condition are necessary. Ulcerous Stomatitis, also knoAvn as " Noma," is another affection of the mouth which is common to childhood, the premonitory symptoms being the same as in simple stomatitis. The inflamma- tion usually begins upon the gums and extends along the buccal surface. An examination of the mouth, hoAvever, at this stage of the disease, reveals one or more small, inflamed and slightly ele- vated points or pimples, which, sometimes within a few hours, but more commonly after one or tAvo days, present a softened and yel- lowish apex, and at length a small ulcer, superficial at first, but gradually becoming deeply excavated, with often an inflamed and elevated margin. The surfaces of these ulcers are covered with an ash-colored or a yellowish matter, in the majority of cases; but sometimes, instead of b^ing thus covered, their surfaces are bare, and bleed readily. Some of the ulcers may unite and form large, irregular ulcera- tions, while others remain isolated. The ulceration, Avhen severe, gives rise to considerable swelling, especially around the ulcers, and the swollen part is soft, and not very tender on pressure. The soft, yielding nature of the SAvelling enables this form to be dis- tinguished from gangrenous ulceration, as there is more induration in the latter affection. These ulcers result from acute phlegmonous inflammation, and may attack any part of the mucous membrane lining the mouth, but are most commonly found on the sides of the frsenum, along the inferior margin and edges of the tongue, and inside the lips. DISEASES OF MUCOUS MEMBRANE. 203 It is but seldom that they are found on the upper surface of the tongue: but Avhen they do appear, on this surface, they are generally superficial, and not deeply excavated. When the ulcers in this form of stomatitis are fully formed, there is usually a profuse Aoav of saliva, and a decrease of the febrile ex- citement. The boAvels, which in the first stage of the disease are costive, now become loose, and often very much so during its con- tinuance. A simple form of ulcerous stomatitis is characterized by but one or tAvo small ulcers, Avhich in a little time fill up Avith granulations and soon heal over. In a more severe form of this disease a considerable number of these ulcers exist, in some cases covering almost the Avhole of the mucous membrane of the gums, the inside of the cheeks, arch of the palate, sides and inferior sur- face of the tongue. During the early stage of ulcerous stomatitis the mouth becomes hot and painful, and the submaxillary glands swollen and tender. The breath becomes very offensive as soon as the ulceration is well established, and there is a tendency to keep the mouth open. Another form of this disease is sometimes met with, where but one or two ulcers exist, but Avhich gradually extend over the mucous surface, at the same time increasing in depth, and with no appearance of healing. This form of the affection is attended Avith hectic fever, the exacerbations occurring night and morning, and rapidly Avearing away the strength. There is yet another form of ulcerous stomatitis occasionally met Avith, which consists of a softening of the mucous membrane of the palate in its centre, either on the median line or outside this line. The membrane appears to be softened into a kind of pulp, of a red or faAvn color, Avhich, on its removal, discloses an ulcer with per- pendicular walls; the bone, hoAvever, forming its base, is found to be perfectly healthy. It is the opinion of some that ulcerous stom- atitis is contagious ; that is, that it may be communicated by using the same spoon in eating, and also that it is endemic and epidemic. Ulcerous stomatitis is common to the period of dentition, especially Avhen there is disorder of the digestive organs. The causes of ulcerous stomatitis are uncleanliness, poor food, residence in damp, dirty places, mercury, a cachectic condition, enfeebled system, and contagion. The treatment of ulcerous stomatitis consists in a change of resi- dence and diet, cleanliness, the use of tonics, ferruginous or vege- table, such as the liquor ferri nitratis, Avith tincture of calumba, given in simple syrup, tincture of chloride of iron and sulphate of quinine, or coddiver oil, and such local remedies as dilute chloride 204 DENTAL PATHOLOGY, THERAPEUTICS. of zinc, carbolic acid, nitrate of silver, muriatic acid, with an alter- nate wash of honey and borax, equal parts; or the chloride of lime applied dry to the ulcerated surface twice daily, and simple water used during the interval, and continued until a healthy appearance is apparent, Avhen a Aveak solution of chloride of lime, one grain to forty-five of water, is employed. Chloride of lime one drachm, with honey one ounce, is also recommended. Chlorate of potassium often acts like a specific, employed internally and externally, the dose of which is tAvo or three grains, dissolved in Avater Avith sugar, or in syrup. The following formula may be employed : R . Potass, chlorat.,......^ss to j. Mellis.........£ss. Aquae,........^ij.—M. One teaspoonful every two hours, and also applied as a lotion. Dr. Condie recommends the following treatment Avhere the ulcers are slow in healing: A solution of borax, gr. xv to the ounce of water, or a Aveak solution of the nitrate of silver, gr. j to the ounce of water, or sulphate of copper, gr. v to the ounce of water, or acidum nitricum dilutum applied by means of a camel's hair pencil to the Avhole of the ulcerated surface, which will improve the character of the ulceration and arrest its progress. " Any apparent cause of irritation, such as a decayed tooth, should be removed." When there is great derangement of the ali- mentary canal accompanying ulcerous stomatitis, or this disease occurs during the course of other acute and chronic diseases, such as pneumonia, scarlet fever, smallpox, etc., the proper remedies adapted to the removal of these diseases are necessary. Aphthous Stomatitis.—This form of stomatitis, sometimes called "follicular stomatitis," and also "canker sore mouth," although it is not confined to the seat of the follicles, is common to all ages, but is most frequent during childhood. The seat of the aphtha? is usually the inner surfaces of the lips and cheeks, the gums, the tongue, and sometimes the roof of the mouth. They commence with a vascular injection, Avhich is folloAved in a few hours by a whitish exudation immediately below the epithelium and upon the corium, in the form of small, round or oval, isolated spots, the smallest being of the size of a pin's head, but the greater number of a diameter of one or tAvo lines, causing slight vesicle-shaped elevations, on the surface of the mucous membrane. The vesicles have a whitish appearance with an inflamed ring about their base ; after their rupture an irregular gray surface is exposed, and the ulcers resulting are shallow and painful. After a feAV days the ex- DISEASES OF MUCOUS MEMBRANE. 205 udation softens, and the points become denuded of epithelium, presenting superficial, painful ulcers, but without indurated edges. After an existence of one or two weeks the aphtha? disappear, leaving red spots, which, hoAvever, soon fade. Besides being very painful to the touch, and also to food and liquids, they are attended Avith an increased secretion of saliva. Two or more of the ulcers may coalesce, forming one large ulcer- ated patch, to the edges of which vegetable fungi may adhere; in rare cases, it may become gangrenous, Avhen the affection is usually complicated with gastro-intestinal disease. The constitu- tional symptoms are generally slight, except Avhen there is a ten- dency to gangrene, Avhich may cause a feeble pulse, pallid counte- nance, wasted body and limbs, and great prostration. The causes of aphthous stomatitis may be bad hygienic condi- tions, uncleanliness and privation, but it is usually owing to some derangement of the digestive organs, when it may also be accom- panied with diarrhoea. It differs from ulcerous stomatitis in form of the aphtha?, and the inflammation being confined to the immediate vicinity of the ulcers, and not extending over the mouth. The treatment of aphtha? consists in the application of demulcent drinks, such as the mucilage of gum acacia, flaxseed or marsh- malloAV. Mel-boracis, honey of borax, is an efficient application applied Avith a camel's-hair pencil, and a small quantity of some opiate to relieve the tenderness of the ulcers, and the restlessness. When the ulcers, besides being painful, are not disposed to heal, they may be touched Avith nitrate of silver, or with hydrochloric acid in honey of roses, or nitric acid applied on the sharpened end of a stick of orange Avood. The application of chlorate of potassium is also effective in some cases. The constitutional treatment con- sists in the administration of citrate of magnesia or rhubard to cor- rect the intestinal trouble, and tonics of sulphate of quinine or other vegetable bitters, or of the tincture of the chloride of iron, to keep up the strength. When there is a great number of the ulcers, with considerable fever, and symptoms of cerebral congestion, or of con- vulsions, the administration of laxatives, and the bromides, with a Avarm foot-bath, will prove beneficial. Thrush.—This affection,also knoAvn as "sprue" and "muguet," is characterized by a form of inflammation which consists of points and patches of a curd-like appearance on the surface of the mucous membrane of the mouth, its common seat, as the fauces, pharynx and oesophagus are only occasionally affected. Thrush commences as simple inflammation of the mucous sur- face, which is followed by the appearance of minute semi-trans- 206 DENTAL PATHOLOGY, THERAPEUTICS. parent points or granules, which soon become white and opaque. While some remain as points, others extend, and by coalescing form patches, the surfaces of which are not uniform, but unequally elevated. The central part of the points and patches project but little above the surrounding epithelial surface, being not more than a line in height, They resemble in color and consistence portions of curdled milk, for which they may be mistaken. Being very easily detached, they are rapidly reproduced, and their white color may change to a yellow hue. Composed of epithelial cells and a parasitic vegetable groAvth, of the oidium albicans variety, each point consists of roots, branches and sporules, the roots being transparent, and penetrating the epithelial layer, and sometimes even as far as the basement mem- brane. The branches divide and subdivide, and consist of elon- gated cells with one or two nuclei. Around the branches are numerous sporules. Thrush, in its mildest form, appears in points or small patches; and if the patches are of large extent, Avhich, however, rarely occurs, the affection is attended by a state of great prostration and danger, from some concomitant disease. Often it occurs as the sequel of pneumonia, or gastro-intestinal inflamma- tion, in the latter case being caused by neglect, improper food, or a deprivation of the maternal milk. In the mildest cases, the symp- toms are similar to those of simple stomatitis. When the inflamma- tion is more extensive, and especially if the fauces and oesophagus are involved, the inflamed surface becomes very hot, red, and pain- ful, and there is fretfulness and fever. In the severest forms, the surface becomes dry and parched, the inflammation more extensive, and there is thirst, loss of appetite, vomiting, and frequently diarrhoea, with an anxious, pallid countenance, rapid emaciation and extreme prostration. When thrush is complicated with aphtha?, small, white, flocculent patches appear on the surface of the mucous membrane, which in- crease in size and finally coalesce. In such patches some form of vegetable parasite exists, more commonly that known as oidium albicans. The causes of thrush are bad hygienic conditions, constitutional feebleness, indigestion and improper food. It is common among emaciated children in crowded institutions, or Avher© there is ex- posure to dampness. Foul nursing-bottles are also a common cause of this affection. It appears to be more prevalent during the summer months, and to occur more frequently under the age of three months. DISEASES OF MUCOUS MEMBRANE. 207 Even children of eighteen months, suffering from debilitating diseases, are subject to it. The stools are greenish and acrid, giving rise to excoriations of the parts with which they come in contact. When this disease occurs in adults, it is attended with an increased flow of saliva and a dry, hot state of the mouth, rendering degluti- tion painful. The treatment of thrush should commence with an improvement in the diet and locality, if these are at fault, and the administration of an alkali to correct the acidity of the secretions Avhich is usually present. Saccharate of lime added to the milk is very beneficial. The following combination is recommended by Dr. Sudduth : R. Infusi rhei,......^iij. Potassi bicarb., ...... £j. Tincturse cinnamomi,.....gij. Syrupi simp., ...... ^vj.—M. Dose. A teaspoonful every three hours for an adult. Quinine in one-grain doses every three hours will prove beneficial for infants. The quinine may be combined Avith tincture of the chloride of iron to produce a tonic effect, one drachm of the quinine Avith one ounce of the iron, in doses of fifteen drops every three hours. Dr. Trousseau recommends the following alterative tonic Avhich is very effective : R. Hydrarg. chloridi corrosivi, . . . . gr. j-ij. Liq. arsenici chloridi,.....f^j. Tinct. ferri chloridi, Acid, hydrochlorici dil. . . . aa f.^iv. Syrupi.........fgiij. Aquam,......ad f ^vj.—M. Dose. One dessertspoonful in a wineglassful of water after each meal. The local treatment consists in the application of borax with honey—mel-boracis, or borax Avith powdered sugar, or dissolved in water. Some object to the use of sugar, as it promotes the growth of the parasite. Prof. J. L. Miller recommends the following: R. Sodii borat.,.......3J. Glycerinae,.......gij. Aquae,........£vj.—M. Sig.—To be applied with a camel's hair pencil four or five times a day. If such an application fails, which is rarely the case, then recourse must be had to a solution of nitrate of silver, or sulphate of zinc. R. Zinci sulph.,......gr. ij-iv. Aquae rosae,......^ij.—M. When thrush is complicated Avith other diseases, the proper treat- ment for such diseases may render its treatment easy and effectual. 208 DENTAL PATHOLOGY, THERAPEUTICS. Gangrene of the Mouth.—This disease, characterized by such names as "Cancrum Oris," " Gangra?nopsis," "Canker of the Mouth," " Water Canker," is common to children of debilitated constitutions and a decided lymphatic temperament, the result of scanty nourish- ment, improper clothing, and damp, unhealthy places of abode, or Avhere many children are crowded together in charitable institutions. There are several forms of this affection, the most common, perhaps, being preceded by inflammation of the gums, Avith such premonitory symptoms as great languor and listlessness, indisposition to any exercise, irritable temper, loss of sleep and appetite, and increase of thirst. The countenance becomes pale and dejected, and a peculiar puckering of the cheeks is observed about the corners of the mouth. Emaciation and night-sweats are not uncommon. These premonitory symptoms may continue for several days, or even Aveeks, when an acute pain is felt in the mouth and gums, with a sense of heat and itching about their margins, the free edges of Avhich become congested and thickened, spongy, and of a dark red or purple hue, bleeding readily. The floAV of saliva increases greatly, and is frequently mixed with blood. From about the necks of the teeth a muco-purulent matter is discharged, which after a time becomes thin, Avatery and acrid, rendering the breath very offensive. In the majority of cases this disease is confined to one side of the mouth and to the lower jaAv, and if allowed to progress, the gums separate from the necks of the teeth and alveolar processes, and become ragged, flabby, and livid; the teeth on the affected side loosen, and at length drop out, and at this stage there is an increase of the febrile symptoms and night- sweats. In such a state the gums may continue for weeks or even months, but usually after a few days a number of ash-colored vesicles make their appearance, which rapidly increase in size and become confluent, the divided gum presenting a gangrenous ap- pearance. The dead portions separate, a gangrenous ulcer folloAvs, and soon the entire part is destroyed, and the inferior maxillary bone exposed. The ulceration is more common to the labial surface than to the lingual, and commences in the front part of the mouth, extending to posterior parts. The ulcers, before becoming gan- grenous, are covered with a yellow or gray secretion, which, on being removed, exposes many small, red papilla?, Avhich correspond to imperfect granulations. After a time the gangrenous ulceration extends to the mucous membrane of the cheek and lips, causing pain and difficulty in attempting to open the mouth, Avhich is some- times impossible. In a short time the whole of the mouth becomes affected, and DISEASES OF MUCOUS MEMBRANE. 209 death usually occurs at about the eighth or, at the furthest, upon the fourteenth day from the commencement of the gangrene. Mr. Tomes remarks, that although the disease is usually confined to children during the shedding of the temporary teeth, yet adults are not Avholly exempt from its attacks. There is another form of this disease Avhich differs considerably from that just described, from the fact that it is not preceded by inflammation of the gums, but commences in the cheek, usually at the angle of the lips, and comes on abruptl}', without the pre- monitory symptoms characteristic of the first form described. There is first seen a hard, indolent tumor, about the size of an almond, in some part of the lips or cheek, Avhich is deeply seated, the skin covering it being someAvhat redder than natural. This tumor gradually increases in size for a feAv days, Avhen the mucous membrane covering it presents a gangrenous appearance, Avith an offensive odor. Before this occurs, hoAvever, the external redness of the skin covering the tumor becomes pale, then livid, then of a grayish hue, surrounded by a red circle, Avhich spreads rapidly, and in a feAv hours changes to a black color. The gums nearest to this tumor then become gangrenous, and the teeth loosen, and at length fall out. Death usually occurs before the death of the bone of the jaAv. There is also a superficial form of gangrene sometimes met Avith in the form of spots of a dark- broAvn color surrounded by a red margin, Avhich vary in size, and have for their seat the corners of the lips and inner surfaces of the cheeks. These spots may first appear in the form of slightly red- dened patches, but in this mild form are ahvays superficial, confined to the mucous membrane alone, the sloughs separating Avith little loss of substance, soon to be folloAved by healthy granulations and cicatrization. Gangrene of the mouth may occur at any period betAveen the first and tenth year of age, but is more common betAveen the second and fourth years; and the children subject to it are those of a lymphatic temperament, delicate constitution, soft, flaccid muscles, pale skin, and Avhose digestive organs are deranged. It usually occurs in those Avhose systems are much reduced or cachectic, and is more common to children croAvded together in asylums, and those deprived of pure air and proper nourishment, or enfeebled by disease. It sometimes follows the eruptive fevers, and such diseases as pneumonia, scrofula, whooping-cough, typhus fever, ague, etc. In the treatment of gangrene of the mouth no little depends upon the time this is instituted. Before the gangrene makes its appear- ance much may be clone in the Avay of preventive treatment, in 14 210 DENTAL PATHOLOGY, THERAPEUTICS. order to remove the existing predisposition. A dry, pure air, clean- liness, and a nourishing diet adapted to the condition of the diges- tive organs, are very essential. The preparations of iron and bitter vegetable tonics are required. The administration of the sulphate of quinine, and the local ap- plication of a strong decoction of Avhite oak bark, is thought, by Dr. Condie, to be beneficial in preventing gangrene of the mouth in cases in which there is every reason to anticipate its speedy occur- rence. For local treatment solution of sulphate of zinc (one drachm to the ounce of water), to which is added honey and tincture of myrrh, two drachms of each, will prove serviceable. Nitrate of silver, either in the solid form or in solution, applied to the affected part, has been successfully employed in a large number of cases. When the disease is established, the first indication in the local treatment is to arrest the progress of the gangrene, and hasten the detachment of the slough, and for such purposes highly stimulat- ing or escharotic agents are required. The affected parts should be well cleansed, and then sprayed Avith carbolized water and strong acetic, sulphuric, nitric or hydrochloric acids, nitrate of silver, acid nitrate of mercury, or chloride of antimony, applied, by means of a brush, on and about the slough, to be at once folloAved by the application of dry chloride of lime, when the mouth is to be thor- oughly Avashed out with water, by means of a syringe. By such applications to the edges of the ulcers, the diseased tissue is de- stroyed and healthy granulations promoted. After the separation of the slough the escharotic is to be discon- tinued, and the chloride of lime alone employed. Some, hoAvever, prefer milder remedies than the strong acids, such as the nitrate of silver, if the slough is small in extent; if larger, muriated tincture of iron is applied, undiluted, and after the progress of the gangrene is arrested, the use of astringent stimulants, such as tincture of myrrh or the French aromatic Avine. Dr. Coates found sulphate of copper, according to the folloAvino- formula, to be successful: R. Cupri sulph..........^ij. Pulv. cinchonse,...... . . 5ss. Aqusp,..........giv.—M. To be applied twice a day to the entire ulcerations and excoriations. In milder cases a solution of sulphate of zinc, gj to an ounce of Avater, by itself or combined with tincture of myrrh, is found to be useful. If the milder agents, after tAvo or three days' use, do not prevent the gangrene from spreading, strong hydrochloric acid, ap- DISEASES OF MUCOUS MEMBRANE. 211 plied by a camel's-hair pencil, may prove efficacious, and its use immediately followed by lime Avater made turbid by lime. To cor- rect the fetor, chlorine or carbolic acid, properly diluted, may be employed alternately Avith the sulphate of copper, or Labarraque's solution of chlorinated soda, one part to eight or ten parts of Avater. The tincture of myrrh, Avith tonics and a nutritious diet, should complete the treatment, Dr. Condie recommends the administration of sulphate of qui- nine during the time the local remedies are being applied, as folloAVS: R. Qniniae sulphat., . . . . . . . . gr. x. Acid, sulph. dil.,......."Nix. Sacch. alb.,......... giv. Aq. cinnamom., ........ 51 v.—M. Dose: A teaspoonful every three hours. The free internal use of the chlorate of potassa, one to three scruples in tAvelve hours, according to the age of the child, has been employed Avith advantage. For the diarrhoea accompanying the disease, and especially Avhen it is profuse, Dr. Condie recommends acetate of lead, as folloAvs: R. Acetat. plumbi,...... . gr. xvj. Cretae praep.,........Qiiss. Ipecacuanhae, ........ gr. iv. Opii pulv.,........gr. ij.—M. To be divided in xvj portions; one to be given every three or four hours. Syphilitic Ulceration of the Mouth.—Syphilitic ulcers are the secon- dary results of constitutional syphilis, and are usually found on the tongue, the lips, or the tonsils. Although the syphilitic ulcer is usually superficial, little irritating and attended Avith the discharge of a small amount of pus, it is occasionally phagedenic in charac- ter. Such ulcers, as a result of constitutional syphilis, may be in- cited by abrasions and injuries caused by fractured and carious teeth upon the sides of the tongue, and they may appear on the lip as the result of kissing. These ulcers also appear upon the tonsils and pharynx. These syphilitic ulcers may be distinguished from more malignant ones by their improvement under specific medica- tion, and the other indications of constitutional syphilis generally present and recognizable. The glands of the neck are often found enlarged Avhen syphilitic ulcers exist in the mouth or on the lips. Local and constitutional treatment is required in the majority of cases. The local treatment consists in the application of a solution of chromic acid—ten grains to the ounce of Avater,—by means of a camel's-hair brush, three times a day. When such applications 212 DENTAL PATHOLOGY, THERAPEUTICS. fail, the administration of mercury is necessary; and in all cases a total abstinence from alcoholic drinks and tobacco is required. Mercurial Stomatitis.—The employment of mercury as a medici- nal agent causes increased watery eAracuations, increased Aoav of bile and saliva, and, as a consequence, increases the Aoav of blood to the secreting part. But when administered in excess other effects folloAV. It is capable of producing inflammation, especially the acute, phlegmonous, adhesive variety. The effects of its use depend upon the quantity administered and the susceptibility of the patient to its action. When carried to excess, the mucous mem- brane of the mouth becomes tender, red, and swollen, the glands beneath the jaw become painful, and at length ulceration occurs, which spreads from the gums—Avhere the effects of the drug are first observed—to fauces and throat, and, in extreme cases, the parts affected may perish. Prof. Wood describes this disease as folloAvs: " Among the first indications of the action of mercury are often a metallic taste in the mouth, like that of brass or copper, and some increase of saliva. At the same time a close examination will detect a slight redness and sAvelling of the gums, particularly about the necks of the lower incisors, while somewhat beloAV their edge a broad, white line may be observed, depending on opacity of the epithelium. " The patient soon begins to feel some uneasiness, complaining of soreness Avhen the gums are pressed, and of pain Avhen the teeth are forcibly closed together. There is also a sense of stiffness about the jaws when the mouth is opened, and they feel as if projecting above their proper level. The flow of saliva increases, the inflam- mation extends, the gums and palate become obviously swollen and the tongue covers itself Avith a yellowish-white or broAvnish fur, and is often so much enlarged as to exhibit the impression of the teeth upon being projected from the mouth. The throat frequently becomes sore, and the cheeks and salivary and absorbent glands SAvollen and painful. There is often severe toothache or pain in the jaws. A whitish exudation along the edges of the gums is very common. " The breath, which sometimes from the beginning, and some- times even before the appearance of anyone of the symptoms men- tioned, has a peculiar, disagreeable odor, noAv becomes extremely offensive, and in bad cases almost intolerable. Ulceration often occurs, especially about the necks of the teeth, which are conse- quently loosened, and in the cheeks, lips and fauces. The ulcers often have their origin in a vesicular eruption. The Avhole mouth, with its appendages is sometimes so swollen that it can scarcely be DISEASES OF MUCOUS MEMBRANE. 213 opened, and the tongue so much enlarged as to project beyond the lips. " The patient is now nearly or quite unable to articulate or to masticate his food, and sometimes can scarcely swallow. Hemor- rhage is not an unfrequent attendant upon the bad cases, and is sometimes so profuse as to be alarming. Sloughing also takes place, and portions of the jawbone are occasionally laid bare. There is ahvays in the severe cases more or less fever, which is partly symp- tomatic of the local affection and partly the direct effect of the mer- cury. Death, from the exhausting influence of the irritation, want of nourishment, and hemorrhage, has occurred in numerous in- stances, but the patient usually recovers from the worst forms of the affection, though sometimes with a deformed mouth. " The tongue and cheeks have occasionally adhered at points where their ulcerated surfaces were in contact, and a surgical oper- ation has been necessary to remove the evil." For the treatment of mercurial stomatitis, see " Treatment of Mercurial Inflammation of the Gums." Scurvy-Srorbutus is a disease characterized by spongy gums, offen- sive breath, livid spots on the skin, great general debility, and a pale, bloated countenance. " Scurvy," remarks Prof. Wood, " is generally very gradual in its approach, so that it is scarcely possible to say, in an}^ particular case, Avhat Avas its precise time of attack. Attention is commonly first attracted by an unhealthy paleness of complexion, a feeling, on the part of the patient, of languor and despondency, Avith an in- disposition to bodily action, and unusual fatigue after exercise; a sensation of Aveariness and aching in the limbs, as from over-exer- tion, though the patient may have been at rest; and some swelling, redness, and tenderness of the gums, Avith a tendency to bleed from slight causes. With the advance of the disease, the face becomes paler, and assumes a someAvhat salloAv or dusky hue, and often a degree of puffiness; the lips and tongue become pallid, and contrast strikingly Avith the gums, which are purple or livid, especially at their edges, rise up between and around the teeth, are soft and spongy, and bleed from the slightest touch; the breath is offensive; purplish spots or blotches appear upon various parts of the surface, beginning usually upon the lower extremities, and afterward ex- tending to the trunk, arms, and neck, though seldom affecting the face ; hemorrhage frequently occurs, most commonly from the nose, gums, and mouth, but sometimes from the stomach, bowels, and urinary passages; the feet become oedematous and the legs SAvollen and painful; the general debility increases, and muscular exertion 214 DENTAL PATHOLOGY, THERAPEUTICS. is apt to be attended Avith palpitation of the heart, panting, vertigo, dizziness, and a feeling of faintness. The petechial spots are evi- dently OAving to the extravasation of blood Avithin the cutaneous tissue. Occasionally portions of the surface look as if bruised Avithout having suffered any violence; and bloAvs which, under ordi- nary circumstances, Avould produce no effect, noAv give rise to exten- sive ecchymosis. Should the disease continue, all the symptoms become aggravated; the complexion assumes often, Avith its pale- ness, a livid or leaden hue ; the gums swell greatly, and put forth a blackish, fungous groAvth, so as sometimes to conceal the teeth ; blood continually oozes from them; sloughing occasionally takes place, laying bare the necks of the teeth, and extending, in very bad cases, even to the cheek. "The teeth become loose and sometimes fall out; the patient is unable to cheAV solid food, in consequence of the state of his gums. The breath becomes intolerably offensive; hard and painful tume- factions occur in the calves of the leg, among the muscles of the thigh, upon the tibia? and loAver jaAv, and in the hand, Avith stiffness and contraction of the joints, especially the knee, and severe pain in the extremities upon every attempt at movement; and the de- bility, before so prominent a feature in the case, noAv becomes ex- cessive, so that the least exertion is dangerous, and the patient sometimes dies suddenly upon rising from bed, or upon being con- veyed, Avithout great caution, from one place to another. Wounds, even slight scratches, degenerate into unhealthy ulcers; old cica- trices break out afresh, and existing ulcers assume a neAV and much Averse aspect. The bones are said to be softened, united fractures are again opened, and in the young the epiphyses separate some- times from the shaft. "Throughout the complaint the tongue is usually clean and moist; and the appetite and digestion remain unimpaired almost to the last, unless the disease, as sometimes happens, should be complicated Avith fever. Indeed, there is often a craving for food, especially for fresh vegetables and fruits; occasionally. hoAvever, there is vomiting, Avith epigastric distress, and other evidences of stomachic disorder. The bowels are mostly costive, and in some cases obstinately so, but diarrhoea not unfrequently intervenes, Avith black or bloody and offensive evacuations. The pulse is generallv small, feeble, and sIoav ; but cases occur in Avhich it becomes very frequent, and the surface of the skin febrile, probably from the sympathy of the system with various local irritative congestions. " Great emaciation usually attends the disease when severe or lasting, but not invariably. Little cerebral disturbance is ordinarily DISEASES OF THE GUMS. 215 observable, and the patient often retains full possession of his senses and intellect to the last." In regard to the cause of scurvy, it is the general belief that it results from the absence of fresh vegetables and fruits. Prof. Ham- ilton says, " In regard to the pathology of scurvy, the belief prevails that it is due essentially to the absence of certain staminal prin- ciples from the blood, and especially potash; as all, or nearly all, the remedies Avhich have been employed successfully in the pre- vention or cure of scurvy, contain potash, such as potatoes, cabbage, celery, lettuce, lime, lemon, and orange juice." As regards the treatment, both local and constitutional are required. The local treatment being the same as is recommended for " mercurial stoma- titis," need not be repeated. The constitutional treatment consists in the administration of the vegetable acids, such as lemonade, for example. Turner's antidote, composed of potassa? nitratis 3ij, and acidi acetici, oviij, in tablespoonful doses, three times a day, is a favorite remedy. In connection with this, Dr. Garretson recom- mends saturating a sheet Avith water moderately Avarm and moder- ately salt, Avhich is throAvn around the body each morning immedi- ately on rising, and rubbed against the flesh until a ruddy glow is excited. CHAPTER IV. DISEASES OF THE GUMS. Little can be ascertained concerning the innate constitution from an inspection of the gums. Subject to the huvs of the general economy, their appearance varies Avith the state of the general health and the condition and arrangement of the teeth. Although the proximate cause of disease in them may be specified as local irritation—produced by depositions of tartar upon the teeth, or decayed, dead, loose or irregularly arranged teeth, or by a vitiated state of the fluids of the mouth, resulting from general organic derangement, or any or all of the first-mentioned causes—their susceptibility to morbid impressions is influenced to a considerable extent by the constitutional health; and the state of this deter- mines, too, the character of the morbid effects produced upon them by local irritants. For example, the deposition of a small quantity of tartar upon the teeth, or a dead or loose tooth, would not, in a healthy person of a good constitution, give rise to any- thing more than slight increased vascular action in the margin of the gums in contact Avith it; Avhile in a scorbutic subject, it 216 DENTAL PATHOLOGY, THERAPEUTICS. Avould cause them to assume a dark purple appearance for a considerable distance around, to become SAvollen and flabby, to separate and retire from the necks of the teeth, or to grow doAvn upon their crowns, to ulcerate and bleed from the slightest injury, and to exhale a fetid odor. In proportion as this dis- position of body exists, their liability to be thus affected is in- creased ; and it is only among constitutions of this kind that that peculiar preternatural morbid groAvth takes place by Avhich the Avhole of the croAvns of the teeth sometimes become almost entirely imbedded in their substance. But, notwithstanding the dependence of the condition of the gums upon the state of the constitutional health, they are occasionally affected Avith sponginess and inflammation in the best tempera- ments, and in individuals of uninterrupted good health. The Avrong position of a tooth, by causing continued tension of the gums investing its aWeolus, sooner or later gives rise to chronic inflamma- tion in them and the alveolo-dental periosteum, and gradual Avasting of their substance about the mal-placed organ. The causes of tooth- ache, too, often produce the same effects; the accumulation of sali- vary calculus upon teeth, hoAvever small the quantity, is likeAvise prejudicial. All of these may occur independently of the state of the general health. A bad arrangement of the best constituted teeth, and toothache may be produced by a multitude of accidental causes disconnected with the functional operations of other parts of the body. While, therefore, the appearance and physical condition of this peculiar and highly Avascular structure are influenced in a great degree by habit of body, they are not diagnostics that ahvays, and Avith unerring certainty, indicate the pathological state of the gen- eral system. It can, however, in by far the larger number of cases, where the gums are in an unhealthy condition, be readily ascertained Avhether the disease is altogether the result of local irritation, or Avhether it is favored by constitutional tendencies. In childhood, or during adolescence, Avhen the formative forces of the body are all in active operation, and the nervous suscepti- bilities of every part of the organism highly acut-, the sympathy betAveen the gums and other parts of the system, and particularly the stomach, is, perhaps, greater than at any other period of life. The general health, too, at this time is more fluctuating, and Avith all the changes this undergoes, the appearances of the gums vary. Moreover, there are operations carried on beneath and Avithin their substance, Avhich are almost constantly altering their appearance and physical condition; and which, being additionally influenced DISEASES OF THE GUMS. 217 by various states of health and habits of body, it may readily be conceived that those met with in one case might be looked for in vain in another. Having arrived at that age Avhen all the organs of the body are in full vigor of maturity, and not under the debilitating influences to Avhich they are subject during the earlier periods of life, the gums participate in the happy change, and, as a consequence, present less variety in their characteristics. The general irritability of the system is not noAv so great, the gums are less susceptible to the action of irritating agents, and, as a consequence, less frequently affected Avith disease; but as age advances, and the vital energies begin to diminish, the latent tendencies of the body are reawakened, and they are again easily excited to morbid action, and exhibit a darker color and thicker structure, Avith a tendency to bleed, and such Conditions in an exaggerated form in dyspeptic persons and those subject to glandular struma. In the most perfect constitutions, and during adolescence, they present the folloAving appearances: they have a pale rose-red color, a firm consistence, a slightly uneven surface, their margins form along the outer surfaces of the dental circle beautiful and regular festoons, Avith a very thin edge around the teeth and firmly attached near their necks, with the interstices so filled up that but little food can collect betAveen the teeth, and the mucous membrane here, as Avell as in other parts of the mouth, has a fresh, lively, roseate hue. The time for the eruption of a deciduous tooth is announced some Aveeks before it takes place, by increased redness and slight tume- faction of the edges and apices of the gums surrounding it. The eruption of a tooth, whether of the first or second set, is also pre- ceded by similar phenomena in the gums through which it is forcing its Avay, and these will be more marked as the condition of the system is unhealthy, or as the habit of the body is bad. If the health of the subject continues good, and the teeth are Avell arranged, and the necessary attention to their cleanliness be strictly observed, the characteristics just enumerated will be preserved through life, except there will be a slight diminution of color in them after the age of puberty until that of the climacteric period of life, Avhen they will again assume a someAvhat redder appear- ance. But if the health of the subject becomes impaired, or the teeth be not regularly arranged, or wear off, or are not kept free from all lodgment of extraneous matter, their edges, and particu- larly their apices, will inflame, swell, and become more than ordi- narily sensitive. The gradual wasting or destruction of the margins of the gums around the necks of the teeth, Avhich sometimes take place in the 218 DENTAL PATHOLOGY, THERAPEUTICS. best constitutions, and is supposed by some to be the result of gen- eral atrophy, is ascribable, we have no doubt, to some one or other of these causes, favored, perhaps, by a diminution of vitality in the teeth, Avhereby they are rendered more obnoxious to the more sen- sitive and vascular parts Avithin Avhich their roots are situated. That these are the causes of the affection (for it is evidently the result of diseased action in the gums), is rendered more than prob- able by the fact that it rarely occurs Avith those Avho, from early childhood, have been in the regular and constant habit of thor- oughly cleansing their teeth from four to five times a day. Although possessed of a good constitution, a person may, by in- temperance, debauchery, or long privation of the necessary comforts of life, or by protracted febrile or other severe kinds of disease, have his assimilative and all the other organs of the body so enervated as to render every part of the system highly susceptible to morbid impressions of every sort; but still this general functional derange- ment rarely predisposes the structure noAv under consideration to any of the more malignant forms of disease occasionally knoAvn to attack it in subjects of less favorable constitutions. The margins of the gums may inflame, become turgid, ulcerate, and recede from the necks of the teeth, and the Avhole of their substance be involved in an unhealthy condition; but they Avill seldom be attacked Avith scirrhous or fungous tumors, or bad-conditioned ulcers, or affected Avith preternatural morbid groAvths; and in the treatment of their diseases Ave can always form a more favorable prognosis in persons of this description than those coming into the Avorld Avith some specific morbid tendency. But the occurrence of severe constitutional disease, even in these subjects, is folloAved by increased irritability of the gums, so that the slightest cause of local irritation gives rise to an afflux of blood to, and stasis of this fluid in, their capillaries. The teeth of persons thus happily constituted are endoAved Avith characteristics such as have been represented as belonging to those of the best quality. They are of a medium size, both in length and volume, white, compact in their structure, generally Avell arranged, and seldom affected Avith caries. Another constitution is observed, in which the gums, though par- taking somewhat of the characteristics just described, differ from them in some particulars. There color is of a deeper vermilion ; their edges rather thicker, their structure less firm, and their surface not so rough, but more humid. The mucous membrane has a more lively and animated appearance. They are more sensitive and more susceptible to the action of local irritants, with morbid tendencies DISEASES OF THE GUMS. 219 more increased by general organic derangement, than Avhen possessed of the appearances first mentioned. When in a morbid condition the disease, though easily cured by proper treatment, is, nevertheless, more obstinate, and Avhen favored by constitutional derangement, assumes a still more aggravated form. Their predisposition to disease is so much increased by long con- tinued disturbance of the general system, and especially during youth, and by febrile or inflammatory affections, that not only their margins, but their Avhole substance, sometimes become involved in inflammation and sponginess, followed by ulceration of their edges, and recession from the necks of the teeth, Avhich, in consequence, loosen, and often drop out. But gums of this kind, like those first described, seldom groAv doAvn upon the croAvns of the teeth. Neither are they very liable to be attacked Avith scirrhous or fungous tumors, or any form of disease resulting in sanious or other malignant con- ditioned ulcers. Indeed, Avith diseases of this kind, they are not, perhaps, ever affected, except in those cases Avhere every part of the body has become exceedingly depraved by intemperance, debauchery, or some other cause. The teeth of those Avhose gums are of this description, if Avell arranged and kept constantly clean, and if the secretions of the mouth be not vitiated by general disease, will, in most cases, remain healthy through life. It is only among sanguineous persons that this description of gums is met Avith, and the teeth of subjects of this kind are gener- ally of excellent quality, and though more liable to be attacked by caries than those first noticed, they are seldom affected Avith it. In sanguineo-serous and strumous subjects, the gums are pale, and though their margins are thin and Avell festooned, often exude, after the twenty-fifth and thirtieth year, a small quantity of muco- purulent matter, Avhich, on pressure, oozes from between them and the necks of the teeth. Their texture is usually firm, and they are not very liable to become turgid. They often remain in this condi- tion to a late period of life, without undergoing any very percepti- ble change. Their connection Avith the necks of the teeth and areolar processes appears Aveak, but they rarely separate from them. In individuals ha\dng such constitutions, dyspepsia, chronic hepa- titis, and diseases in Avhich the prima1 vise generally are more or less involved, are not unfrequent, and are indicated by increased irrita- bility, and sometimes a pale, yellowish appearance of the gums. In jaundice, the yelloAvish serosity of the blood is very apparent in the capillaries of this structure. 220 DENTAL PATHOLOGY, THERAPEUTICS These constitutions are more common in females than males, in the rich than the poor, and in persons of sedentary habits than in those Avho use invigorating exercise. If at any time during life the health is ameliorated, the gums assume a fresher and redder appear- ance, and the exudation of muco-purulent matter from betAveen them and the necks of the teeth ceases. In mucous dispositions, the gums have a smooth, shining appear- ance, and are rather more highly colored than the preceding. Their margins, also, are thicker, more flabby, and not so deeply festooned ; they are more irritable, and, consequently, more susceptible to mor- bid impressions. If, Avith this disposition, there be combined a scorbutic or scrofu- lous tendency, the gums during early childhood, in subjects wdiich, from scanty and unAArholesome diet, have become greatly debilitated, are liable, besides the ordinary forms of disease, to another—char- acterized by their separation from, and exfoliation of, the alveolar processes, accompanied by a constant discharge of sanies. This form of disease, however, though peculiar to childhood, and wholly con- fined to the indigent, is by no means common. These constitutions are rarely met with, except among persons Avho live in cellars, and damp and closely confined rooms in large cities, and in Ioav, damp, and sickly districts of country. The mucous membrane in subjects of this kind is exceedingly irritable, and se- cretes a large quantity of mucus. Persons even thus unhappily constituted do, sometimes, by change of residence and judicious regimen, acquire tolerably good constitu- tions. Little advantage, hoAvever, is derived from these, unless they are had recourse to before the twenty-fifth or thirtieth year of age, though they may prove beneficial at a much later period. The gums in scorbutic persons have a reddish-brown color; their margins are imperfectly festooned and thick; their structure rather disposed to become turgid, and ever ready, on the presence of the slightest cause of local irritation, to take on a morbid action. When thus excited, the blood accumulates in their vessels, Avhere, from its highly carbonized state, it gives to the gums a dark purple or brown appearance; they swell, and become spongy and flabby, and bleed from the slightest touch. To these symptoms supervene the exhala- tion of a fetid odor, the destruction of the bond of union betAveen them and the necks of the teeth, suppuration and recession of their margins frorn the same gradual wasting of the alveolar cavi- ties, loosening, and, not unfrequently, the loss of several or the whole of the teeth. These are the most common results, but sometimes they take on other and more aggravated forms of diseased DISEASES OF THE GUMS. 221 action : preternatural, prurient groAvths of their substance, fungous and scirrhous tumors, ichorous and other malignant and ill-condi- tioned ulcers, etc. The occurrence of alveolar abscesses in dispositions of this kind is often followed by necrosis and exfoliation of portions of the max- illary bone, and the effects Avhich result to the gums are always more pernicious than in habits less depraved. The development of the morbid changes Avhich take place ill this structure even in subjects of this kind, Avhile the character 01 the disease is influenced, if not determined, by a specific constitu- tional tendency, is, nevertheless, referable to local irritation as the immediate or proximate cause, and were this the proper place, we could cite numerous cases tending to establish the truth of this opinion. In scrofulous habits, the gums have a pale bluish appearance, and when subject to local irritation, they become flabby, exhale a nauseating odor, detach themselves from the necks of the teeth, and their apioes groAV down betAveen these organs. The blood circulates in them languidly, and debility seems to pervade their Avhole substance. They are exceedingly irritable, and not. unfre- quently take on aggravated forms of disease, and as often happens to this, as Avell as to the preceding habit, there are combined tendencies which favor the production of ill-conditioned tumors and ulcers. The indications furnished by the gums during the existence of a mercurial diathesis of the system are morbid sensibility, increased A'ascular and glandular action, foulness, bleeding from the most trifling injuries, pale bluish appearance of their substances, turgidity of their apices, and sloughing. The effects, hoAvever, resulting to these parts from the employment of mercury differ in different in- dividuals, according to the general constitutional susceptibility, the quantity taken into the system, and the length of time its use has been continued. In persons of very irritable habits, a single dose Avill sometimes produce ptyalism, and so increase the susceptibility of the gums that the secretions of the mouth, in their altered state, Avill at once rouse up a morbid action in them. The effects of a mercurial diathesis upon these parts is not unfre- quently so great as to result in the loss of the Avhole of the teeth. But Avith these effects both the dental and medical practitioner are too familiar to require any further description. Finally, A\*e Avould observe, that the indications of the several charactei'istics to Avhich we have noAv briefly alluded may not be correct in every particular, and there are others Avhich we have not mentioned; yet Ave think they AArill commonly be found true. As a 222 DENTAL PATHOLOGY, THERAPEUTICS. general rule, persons of a full habit, though possessed of mixed temperaments and in the enjoyment of what is usually called good health, have gums Avell colored, with rather thick margins, and very susceptible to local irritation. With this description of individuals, inflammation, turgidity, and suppuration of the gums are very com- mon. To prevent these effects, constant attention to the cleanliness of the teeth is indispensable. Prof. Schill says, the "gum is pale in chlorosis ana?mia; of a purple red color before an active hemorrhoidal discharge and in cases of dysmenorrhcea; of a dark red color, spongy, and bleeding readily in scurvy and diabetes mellitus, and after the use of mercury. Spongy groAvths indicate caries of the subjacent bone." Regular periodical bleedings of the gums in dysmenorrhcea, and particularly in scorbutic and mucous subjects, are not unfrequent, nor in any case where they are in a turgid condition. Spongy groAArths of the gums in scorbutic and scrofulous persons often result from irritation produced by decayed teeth, and are not, therefore, ahvays to be regarded as an indication of caries of the subjacent bone. Dr. T. Thompson, of London, says that the reflected margin of the gums of a large majority of phthisical patients is deeper in color than the other portions usually presenting a vermilion tint. Mr. George Waite says," A change of residence to a damp climate will often rouse up in the gums a great degree of vascularity. In the damp places of England and Ireland the appearances Avhich the gums present are of a turgid and vascular nature. In the damp countries of France, these conditions of the gums run a much greater length, from the circumstance of the difference in the con- stitutions of the tAvo nations. In the damps of Germany and Swit- zerland persons also lose their teeth early in life; the climate engenders malaria and Ioav fevers, enfeebles the poAver of digestion, and^brings on rheumatic affections, with languor and general con- stitutional debility." Of the correctness of Mr. Waite's observations there can be no question, and they go to establish Avhat has been said in regard to the predisposing cause of disease in the gums; namely, that the enervation of the vital powers of the body, from whatever cause produced, increases their susceptibility to morbid impressions. INFLAMMATION OF THE GUMS. The gums and alveolar processes, from apparently the same cause, frequently assume various morbid conditions. An unhealthy action in one is almost certain to be followed by disease in the other. The most common form of disease to which these parts are INFLAMMATION OF THE GUMS. 223 subject is usually, though A-ery improperly, denominated scurvy, from its supposed resemblance to scorbutus, a disease to Avhich, how- ever, it bears no resemblance. Instead, therefore, of continuing the use of this term, Ave propose to treat the disease under the name of chronic inflammation and tumefaction of the gums, attended by recession of their margins from the necks of the teeth, which seems to express more clearly the condition of the parts and the nature of the disease. The gums sometimes, though less frequently, become the seat of acute inflammation. The other affections to Avhich they are liable Avill be noticed in their appropriate place. The diseases of the gums and alveolar processes are diA'ided by Mr. Bell into tAvo classes : those Avhich are the result of local irrita- tion, and those which arise from constitutional causes. Were it not for local irritation in these parts, the constitutional tendencies to disease Avould rarely manifest themselves ; and, on the other hand, Avere it not for constitutional tendencies, the effects of local irritation Avould seldom be of a serious character. " Thus," says Mr. Bell, "the same cause of irritation Avhich, in a healthy person, Avould occasion a simple abscess, might, in a different con- stitution, result in ulceration of a decidedly cancerous type, or in the production of fungous tumors, or the formation of scrofulous abscesses." Kach constitution has its peculiar tendency; or, in other words, is more favorable to the development of some forms of disease than others ; and this tendency is always increased or diminished accord- ing to the healthy or unhealthy performance of the functional opera- tions of the body generally. Thus, derangement of the digestive organs increases the tendency, in an individual of a mucous habit, to certain forms of diseased action in particular organs, and especially in the gums. A local irritant, Avhich Avould othenArise produce only a slight inflammation of the margins of the gums, Avould iioav give rise to turgidity and sponginess of their Avhole structure. The same may be said with regard to a person of a scrofulous or scorbutic habit. The susceptibility of the gums to the action of morbid irritants is ahvays increased by enfeeblement of the vital powers of the body. Hence, persons laboring under excessive grief, melancholy, or any other affection of the mind, or under constitutional disease tending to enervate the vital energies of the system, are exceedingly sub- ject to inflammation, sponginess, and ulceration of the gums. But, notwithstanding the increase of susceptibility which the gums de- rive from certain constitutional causes and states of the general health, these influences may, in the majority of cases, be counter- acted by a strict observance of the rules of dental hygiene; or, in 224 DENTAL PATHOLOGY, THERAPEUTICS. other Avords, by constant and regular attention to the cleanliness of the teeth. A local disease, situated in a remote part, often has the effect of diminishing the tendency in the gums to disease ; but when, from its violence or long continuance,'the general health becomes impli- cated, the susceptibility of these parts is augmented. Although deriving their predisposition to disease from a specific, morbid constitutional tendency, they, nevertheless, Avhen diseased, contribute in no small degree to derange the Avhole organism. Their unhealthy action vitiates the fluids of the mouth, and renders them unfit for the purposes for Avhich they are designed ; hence, Avhen these parts are restored to health, Avhether from the loss of diseased teeth, or the treatment to which they may have been sub- jected, the condition of the general health is ahvays immediately improved. Thus, Avhile the susceptibility of the gums to morbid impressions is influenced by the state of the general health, the latter is equally influenced by the condition of the former. And not only is a healthy condition of the gums essential to the general health, but it is also essential to the health of the teeth and alveolar processes. From the intimate relation that subsists between the former and the latter, disease cannot exist in one Avithout in some degree affecting the other. Caries of the teeth, for example, often gives rise to in- flammation of the gums and alveolo-dental periosteum ; on the other hand, inflammation of these parts vitiates the fluids of the mouth and causes them to exert a deleterious action upon the teeth, and also excites more or less constitutional derangement. ACUTE INFLAMMATION OF THE GUMS. Acute inflammation of the gums frequently occurs in connection Avith stomatitis, or general inflammation of the mucous membrane of the buccal cavity, Avhich appears under a great variety of forms. In this case the inflammatory action does not ahvays extend to the subjacentfibro-cartilaginous structure; but the local disease is often complicated with other disorders, the treatment of which comes more properly within the province of the medical than that of the dental practitioner. Ulitis, or acute inflammation of the gums, is, in most cases, a purely local disease, arising usually from the irrita- tion of dentition, or as a consequence of periodontitis. It often extends to the submaxillary glands and muscles of the face, and is attended by swelling and other morbid phenomena. But as this form of inflammation of the gums is treated of in connection Avith other subjects, it will not be necessary to repeat Avhat we have said elsewhere concerning it. INFLAMMATION OF THE GUMS. 225 CHRONIC INFLAMMATION AND TUMEFACTION OF THE GUMS ATTENDED BY RECESSION OF THEIR MARGINS FROM THE TEETH. Chronic inflammation of the gums may exist for years without being attended Avith suppuration or recession of their margins from the necks of the teeth ; but these phenomena are sooner or later developed, according to the amount of local irritation and the state of the constitutional health and habitof body. With the occurrence of inflammation the margins of the gums gradually lose their fes- tooned appearance, become thick, spongy, and rounded, and ulti- mately, on being pressed, purulent matter is discharged from betAA'een them and the necks of the teeth. Their sensibility is increased, and they bleed from the most trifling injury. The diseased action usually first develops itself in the gums around the loAver front teeth and the upper molars, opposite the mouths of the salivary ducts, also in the immediate vicinity of aching, decayed, dead, loose, or irregularly arranged teeth, or in the neighborhood of roots of teetli ; from thence it extends to the other teeth. The rapidity of its progress depends on the age, state of the general health, temperament and habit of body of the individual, and the character of the local irritant Avhich has given rise to it. It is ahvays more rapid in persons addicted to the free use of spirituous liquors, and in individuals in Avhom there exists a scorbutic tendency, or who have suffered from venereal disease, or from the constitutional effects of a mercurial treatment used to cure this or other diseases. The inflammation may be confined to the gums of two or three teeth, or it may extend to the gums of all the teeth in one or both jaAvs. As the disease advances, the gums begin to recede from the necks of the teeth, and the alveoli to Avaste, and the teeth, as they lose their support, loosen and ulti- mately drop out. In Fig. 105 is represented a case in which nearly one-half of the roots of the loAver incisors have become exposed by this devastating process. But the loss of the teeth, though it puts a stop to the local disease. is not the only bad effect that re- sults from it. Constitutional symp- toms often superArene, more vital organs become implicated, and the health of the general system is sometimes very seriously im- paired. Hence, the improvement often observed after the loss of 15 226 DENTAL PATHOLOGY, THERAPEUTICS. the teeth, in the general health of persons Avhose mouths have for a long time been affected Avith this disease. No condition of the mouth has a greater tendency to deteriorate its secretions and impair the functions of mastication and digestion, than the one under con- sideration. In forming an opinion of the injury likely to result from the disease, the dentist should be governed not only by the health and age of the patient, and the local causes concerned in its production, but he should also endeavor to ascertain Avhether it is connected with a constitutional tendency, or is purely a local affection. Some have been led to believe that the Avasting of the gums and alveolar processes may sometimes take place without being connected Avith any special, local, or constitutional cause; that it is identical Avith that process by which the teeth of aged persons are removed, and that when it occurs in persons not past the meridian of life, it is symptomatic of a kind of premature old age. The loss of the teeth, from the Avasting of the gums and alveolar processes, although occurring frequently in advanced life, is not a necessary consequence of senility, for Ave occasionally see persons of seventy, and even eighty years of age, whose teeth are as firmly fixed in their sockets, and their gums as little impaired, as in indi- viduals at twenty. We do not recollect ever to have seen a case of this kind in Avhich there Avas not evidently some diseased action of the gums. But it is of little importance Avhether it be the result of old age, a constitutional tendency, functional derangement of some other part, or local irritation, since the consequences resulting from such loss are always the same. The gums, after having been once the seat of chronic inflamma- tion, are ever after more susceptible to the action of morbid irritants. CAUSES. The immediate or exciting cause of inflammation of the gums is local irritation, produced by salivary calculus, by carious, dead, loose or aching teeth, or roots of teeth, or by teeth Avhich occupy a Avrong position, or that are croAvded in their arrangement. It may also be produced by very hard teeth, which, in consequence of their density, possess only a very low degree of vitality; for cases of re- cession of the gums, in which a very slight inflammatory action exists, are frequently met Avith in individuals having teeth of this description. This can only be explained, by supposing a want of congeniality between these organs and the more sensitive and highly vitalized parts Avith Avhich they are in immediate contact. The INFLAMMATION OF THE GUMS. 227 same thing is observed Avhen the vitality of the teeth is Aveakened by age. The secretions of the mouth, especially the mucus, are often ren- dered, by certain conditions of the general system, so acrid as to become a source of irritation to the gums. Dr. Koecker, Avho had the most ample opportunities of observing this affection in all its various forms, says that he has never seen a case in Avhich tartar was not present. That this is so in a large majority of the cases, there is no question ; but that it is in all, is certainly a mistake. The author has met with many in which not the smallest deposit could be detected. The disease attacks persons of every age, rank and condition; and in every country, climate and nation. It is, however, more frequently met with in the loAver than in the higher classes of society. Persons who pay no attention to the cleanliness and health of their teeth are particularly subject to it. With sailors, and those Avho live principally on salt provisions, it is very common. " Persons of robust constitution," says Dr. Koecker, " are much more liable to this affection of the gums than those of delicate habit; and it sho\Ars itself in its worst form after the age of thirty oftener than at any earlier period." To the causes of irritation Avhich haATe already been enumerated, may be added, uncleanly habits Avhich cause the accumulation of extraneous matters on the teeth and along the edges of the gums, which decompose, producing irritation and increased vascular ac- tion, folloAved by congestion, stagnation and general breaking down of tissue, and the secretion of pus; also mercurial poisoning; scurvy; syphilis ; a croAvded dental arch ; malignant impressions; artificial teeth badly inserted, or made of improper material; and dental operations badly performed. The use of improper tooth-brushes and powders, especially charcoal, may be reckoned among its ex- citing causes. The irritability of the gums is sometimes increased by the use of acids; at other times it is diminished. Every condition of the general system tending to increase the susceptibility of the gums to the action of local irritants favors the production of the disease. Everything that tends to induce such conditions may be regarded as a predisposing cause; such as bilious and inflammatory fevers, the excessive use of mercurial medicines, the venereal virus, intemperance and debauchery. Any deteriora- tion of the fluids of the body is peculiarly conducive to it. Persons of cachectic habit are far more subject to it, and generally in its worst forms, than those individuals in the enjoyment of good health. Strumous individuals sometimes have an affection of the gums 228 DENTAL PATHOLOGY, THERAPEUTICS. which differs in many respects from the one just described. The gums, instead of being purple and SAvollen, are pale and harder than ordinary, and, on being pressed, discharge muco-purulent matter of a dingy white color. They often remain in this condition for years, Avithout appearing to undergo any structural alteration, or to affect the alveolar processes. This form of the disease is prin- cipally confined to persons who have very Avhite teeth ; it is much less likely to attack males than females; and has never, so far as we have been able to ascertain, been mentioned by &.ny dental Avriter. It rarely occurs before the age of eighteen or tAventy ; and it seems to be the result of impaired nutrition. The gums exhibit no signs of inflammatory action; on the contrary, they are paler, less sensi- tive, and possess less warmth than usual. It is never attended Avith tumefaction or absorption, except in its advanced stages. TREATMENT. In the treatment of inflamed, spongy, and ulcerated gums, the first thing claiming attention is the removal of the exciting causes. If there are dead or loose teeth in the mouth, or teeth which, from their position, act as mechanical irritants, they should be at once extracted. The remaining teeth should, at the same time, be freed from tartar, and all other irritating depositions, in such a thorough manner as to permit none to remain, either about the necks or be- neath the margins of the gums; and, if necessary, all deposits should be removed from about the very ends of the roots of the teeth, so far, at least, as the separation of the gums from the teeth extends. All necrosed portions of process should also be removed, and the entire surfaces of the exposed portions of the roots of the teeth be well polished. Besides removing the tartar, if the gums are much congested, they should be scarified around the necks of the teeth and all hypertrophied groAvths in the interstices cut aAvay. The bleeding Avhich follows such operations should be promoted by frequently rinsing the mouth Avith Avarm water. It is essential, in the treatment of the disease under consideration, that a decided impression be made upon it at once ; consequently, no time should be lost in the removal of local exciting causes. " The advantage derived from this operation" (extraction of dead, loose, or irritating teeth), says Dr. Koecker, " would be either partly or wholly lost, Avere it performed at different periods." This observa- tion has been verified by the author more than once. When he has been prevented, by the timidity of his patient, from extracting all the offending teeth at the first sitting, he has ahvays found the cure much retarded, and, in some instances, almost entirely defeated. INFLAMMATION OF THE GUMS. 229 Several sittings, however, are often required for the complete re- moval of the salivary deposit. The cure may be hastened by Avashing the mouth seAreral times a day Avith some tonic and astringent lotion. The author has found the folloAving to be very serviceable: R. Powdered nutgalls, Peruvian bark, each . ... 2 drachms. orris root, ...... 1 drachm. Infusion of roses, ....... 4 fluidounces. The infusion to stand for a day or so upon the powders, with frequent stirring; then decant and filter. In mild cases of inflammation of the gums and mucous mem- brane of the mouth, iodine in glycerine—saturated solution—is an excellent application. For acute inflammation of the mucous membrane, the folloAving recipes will prove very serviceable as gargles: R. Potas-a? chloras, Soda? boras, aa . Aqua?, R. Potassa? chloras, Alumina sulphas, I Aqua?, R. Acidum tannicum, Potassa? chloras, Mel. rosa, . Aqua bulliens, . R. Aqua? Cologn., . Tinctura capsici comp Soda? boras, Tinct. cinchona?, Tinct. pyrethri, . Aqua?, a- gij.-M. 3J- .—M. 33- si- Oj.-M. Si- s'- o'j- o.i- §iij—M. — Garretson. We haA^e, in cases where there Avas much soreness and ulceration of the gums, prescribed the folloAving: R. Borax,.........2 scruples. Honey,.........1 fluidounce. Sage tea.........4 fluidounces. This is a favorite and very general domestic remedy, and will be found very soothing and healing. For ulceration of the gums and mucous membrane of the mouth, the folioAving will pro\re excellent applications : 230 DENTAL PATHOLOGY, THERAPEUTICS. o« —M. o'j- o.i- 3iv —M. gtt. v. SJ- gtt. v.-M si- oJ-" -M. R. Acid, carbolic. Glycerini, . R. Sod re boras,. Glycerini, . Aqua?, . R. Acid, carbolic, Glycerini, . 01. caryophylli, R . Soda? sulphis, Glycerini, . As a wash for the mouth, Dr. Fitch recommends a decoction of the green inner bark of white oak, which we have found beneficial. The folloAving are recommended by Dr. Koecker as being very ser- viceable : " Take of clarified honey, and of the tincture of bark, two ounces each. Mix and dilute in the proportion of three tablespoonsful to a pint of warm sage tea or water. It may be used frequently during the day. " Take of honey, and of the tincture of myrrh, tAvo ounces each. Mix and use as above." For soft, SAvollen and spongy gums, the French preparation knoAvn as Phenol Sodique—phenate of soda—a teaspoonful to a tumbler of Avater, Avill prove beneficial. The pleasantest, and at the same time the most efficacious, mouth- wash which the author has ever employed is the folloAving : R. South American soap bark, Pyrethrum, each Orris root, Benzoic acid, Cinnamon, Tannic acid, Borax, Oil of wintergreen, Oil of peppermint, Cochineal, White sugar, Alcohol, . Pure water, 8 ounces. 1 ounce. 4 drachms. 4 scruples. 2 fluiddrachms. 4 3 drachms. 1 pound. 3 pints. 5 " Mix the ingredients thoroughly; digest for six days, and filter. If, notAvithstanding the use of the means here recommended, matter still be discharged from around the necks of the teeth, and should the gums continue spongy, and manifest no disposition to heal, their edges may be touched with a solution of the chloride of zinc or nitrate of silver. This will seldom fail to impart to them a INFLAMMATION OF THE GUMS. 231 healthy action. Either remedy may be used in the proportion of from one to three, or even six grains to one ounce of Avater. The most convenient mode of applying them, is with a camel's-hair pencil, and they will often succeed Avhen other remedies fail. In those cases where the matter discharged from the edge of the gum has a nauseating and disagreeable odor, a preparation composed of carbolic acid f .3ij ; oil of gaultheria, f 3ij ; and aqua rosse, f ,^iij ; of which ten to tAventy drops may be added to a wineglass of Avater and used as a gargle, or applied on lint to the inflamed surface, is an excellent remedy for rendering the mouth comfortable. An excellent disinfectant in such cases is a gargle made by diluting a teaspoonful of chlorinated soda (Labarraque's solution) in four or eight ounces of Avater. Or it may be used much stronger, and applied Avith a small mop to the diseased parts; phenol sodique is also an excellent disinfectant. While the means here directed for the cure of the disease are be- ing employed, a recurrence of its exciting causes must be studiously guarded against. Tartar and foreign matter of every kind should be prevented from accumulating on the teeth, by a free and frequent use of a suitable brush and Avaxed floss-silk, until a healthy action be imparted to the gums; these should be used at least five times a day, immediately after rising in the morning, after each meal, and before retiring at night. The application of the brush may at first occasion some pain ; but its use should nevertheless be persisted in, for, Avithout it, all the other remedies will be of little avail. The friction produced by it, besides keeping the teeth clean, is of great service to the gums, in imparting to them a healthy action. Treatment different from that here described is necessary in that form of disease Avhich Ave noticed as being characterized by preter- natural paleness and discharge of muco-purulent matter from be- tAveen the edge of the gum and the neck of the tooth. In the first case of this disease treated by the author, he directed astringent and detergent lotions to be used ; but these did not produce the desired effect. Having been led, from his observation in this case, to suspect that the disease Avas connected with some constitutional derange- ment, and Avas probably the result of a debilitated condition of the general system, he recommended, in the next case, the use of tonics and free exercise in the open air. This course, though attended with evident improvement of the general health, seemed to be productive of no benefit to the gums. They still appeared debilitated, and on being pressed discharged matter from beneath their edges. He ad- vised a continuance of the tonics and exercise, and, with a view of exciting inflammation, touched the edges of the gums, with nitrate of silver. This had the desired effect, and, as he had anticipated, a 232 DENTAL PATHOLOGY, THERAPEUTICS. neAV disease Avas substituted for the old one; for the cure of Avhich he directed the mouth to be Avashed, five or six times a day, Avith the mixture of sage tea, alum and honey, and at night and morning with salt Avater. This treatment was perfectly successful. In about three Aveeks the gums assumed a healthy appearance, acquired their natural color, and the discharge of muco-purulent matter entirely ceased. He has since had occasion to treat several other cases, in all of which he adopted the same treatment, and Avith like success. HYPERTROPHY, OR MORBID GROAVTH OF THE GUMS. The structural changes which take place in the gums, as a conse- quence of increased vascular action, are almost as various as are the constitutional tendencies of different individuals. Those character- izing the affection last noticed consist, for the most part, in increased thickness and recession of their edges from the necks of the teeth ; but in the one of which Ave are noAv about to treat, there is morbid growth, Avhich is sometimes so considerable, that it almost covers the crowns of the teeth, thus interfering very seriously Avith the function of mastication. When thus affected, the gums have a dark purple color, Avith thick, smooth and rounded margins; and dis- charge almost constantly from their inner surface a thin purulent matter, Avhich exhales an exceedingly offensive odor. They bleed profusely from the slightest injury, and are so sensitive that the pressure even of the lips is sometimes attended Avith pain. They are also affected with a peculiar itching sensation, Avhich at times is a source of great annoyance. The accompanying engraving (Fig. 106) will convey to the reader a more correct idea of the appearance of the gums, Avhen thus affected, than any description which can be given. It will be perceived from this that the morbid growth extends to the gums of all the teeth, as it usually does in this variety of diseased action. Among the local and consti- tutional effects arising from the disease are offensive breath, vitiated saliva, destruction of the alveoli, with loosening and ultimate loss of the teeth, impaired digestion, Avith all its disagree- able concomitants, enlargement of the tonsils and bronchitis, together Avith a long train of other phenomena. INFLAMMATION OF THE GUMS. 233 CAUSES. The exciting cause of this peculiar affection is local irritation, produced by salivary calculus, dead, diseased, or irregularly arranged teeth ; but the character of the structural alteration is evidently determined by some cachectic habit of body or constitutional ten- dency. It often attacks the gums of individuals AArhose teeth are sound and Avell arranged; but the author has never met Avith a case in Avhich tartar Avas not present though, in some instances, the quan- tity was so small as almost to lead one to doubt Avhether it could have had much agency in the production of the disease. But the susceptibility of the gums to morbid impressions in individuals liable to this affection is usually so great, that an irritant, Avhich under other circumstances would scarcely excite an increase of vascular action, gives rise, in cases of this sort, to the rapid development of an aggravated form of disease. TREATMENT. The first thing to be attended to in the treatment of the disease is the removal of all dead teeth, and such others as may in any Avay irritate the gums. The morbid groAvth should be next removed, by making a horizontal incision entirely through the diseased gums to the croAvns of the teeth. This should be carried so far back as the morbid groAvth extends. After this the gums should be freely scari- fied by passing a lancet between the teeth doAvn to the alveoli, in order that the vessels may be completely divided, and discharge their accumulated blood. This should be repeated several times at intervals of four or fh*e days. Meanwhile the mouth may be Avashed three or four times a day with some astringent and detergent lotion, and occasionally mopped Avith a weak solution of chloride of zinc or nitrate of silver, one grain to the ounce of Avater. Phenol Sodique—Phenate of Soda—either in its full strength or diluted with from one to tAvelve times its bulk of Avater, according to indications, proves very serviceable as a lotion, causing the rapid absorption of the extravasated blood, preA^enting fetor, and speedily healing and hardening the gums. The tartar should be removed as soon as the gums have sufficiently collapsed to admit of the operation. In severe cases a permanent cure cannot be effected by the local treatment above described, for, in addition to the removal of the enlarged gum tissues, it may be necessary to excise the edge of the alveolus. Particular attention should be paid to the regimen of the patient and such general remedies prescribed as the peculiar nature of the case may indicate. Excess and intemperance of every kind 231 DENTAL PATHOLOGY, THERAPEUTICS. must be avoided. In cases of an inflammatory type, the diet should be chiefi}' vegetable; but Avhere there is debility, or other cachexia, animal food should be used, taking caretoaAroid all young meats, as veal or lamb, all gross meats, such as pork, and all salt meats or shell-fish. Fruits and acid beverages, such as infusions of malt and vinegar, lemon-juice, spruce beer, etc., may be used Avith advantage. The teeth should be kept perfectly and constantly clean. Not a particle of foreign matter should be permitted to remain betAveen them or along the edges of the gums. A scrupulous attention to this precaution is indispensably necessary, as it constitutes one of the most important remedial indications. MERCURIAL INFLAMMATION OF THE GUMS. Small and repeated doses of mercury, when carried to the point of salivation, frequently give rise to the development of peculiar morbid phenomena in the gums and other parts of the mouth. The first indication of the specific action of this poAverful medicinal agent upon the animal economy consists in a slightly increased redness and tumefaction of the free edge of the gums, around the necks of the inferior incisors. There is a characteristic bluish color along the edge of the gums, while the investing mucous membrane of the adherent portion, a little loAver down, often assumes a white color owing to the opacity of the epithelium. These appearances are folloAved by increased secretion of saliva; a strong metallic taste; soreness of the teeth and gums; inflammation and SAvelling of the mucous membrane of the roof of the mouth, fauces and cheeks, and the salivary glands; swelling of the tongue, Avith increased redness of its edges, and a peculiarly offensive odor of breath. In the mean- time, the edges of the gums about the necks of the teeth savcII and assume an increase of redness; the saliva becomes viscid, and is secreted in such abundance as to Aoav from the mouth, and the movements of the jaAvs are attended with pain. The alveolo-dental periosteum is thickened, and the teeth raised from their sockets and loosened. A vesicular eruption sometimes appears, folioAved by ulceration and sloughing of the gums, and very frequently by necrosis of large portions of the alveolar process and maxilla. We Avere shoAvn, a feAv years since, the entire alveolar border of both jaAvs, the necrosis and exfoliation of AA'hich had been occasioned by severe mercurial salivation ; and Ave have frequently had occasion to remove portions both of the superior and inferior maxillary bones—the necrosis having been occasioned by the use of this medicine. By the prudent administration of mercury, salivation may be in- INFLAMMATION OF THE GUMS. 235 duced, Avithout causing the deplorable effects just described. But the specific action of this agent upon the constitution is ahvays attended by more or less tumefaction and sponginess of the gums, and Avhen once brought under its influence, hoAvever perfectly its effects may have subsided, they are ever after more susceptible to morbid impressions. Again, it should be remembered that very many of these deplorable symptoms folloAV the use of mercurials, even Avhere there is no intention to salivate. It is a powerful agent, capable of much good ; but one which has been productive of untold mischief, especially upon the mouth and teeth. Doubt- less life must be saved at the expense, if necessary, of the teeth. But the peculiar specific action of this medicine should forbid its constant and indiscriminate employment. TREATMENT. It is scarcely necessary to say, that until the use of the mercury is discontinued, it will be impossible to control or even counteract its effects upon the gums; but in mild cases these usually soon disappear after the action Avhich it has produced on the general system has completely subsided. When the gums continue spongy, the boAvels should be kept open Avith Seidlitz poAvders or other saline cathartics, the patient restricted to a fluid farinaceous diet, and the mouth gargled several times a day with mild astringent lotions, to which it may sometimes be advisable to add a little laudanum. Benefit may be derived from the application of the officinal tincture of iodine in a solution composed of one-half Avater. For internal use, chlorate of potash and iodide of potassium are considered the best remedies in mercurial poisoning. The chlorate of potash is also of very great service as a lotion, in the strength of one drachm to the ounce of AArater. For internal use, ten grains of the chlorate of potash may be dis- solved in half an ounce of water, and administered in four or five closes during the day. For an adult, Dr. Garretson recommends the following lotion as very beneficial in cases Avhere the tumefac- tion is very great and indolent looking: R. Potassse chloras, . gss. Soda? boras, Alumen pulv., aa . . . 3ij- Potass, permang., grs. xxv Aqua cologn., .... 3ss. Tinct. cinchonae, SU- Tinct. myrrha?, 3J- Infus. quercus (fort.), 3iv.-M Sio.—Gargle the mouth pro re nata. 236 DENTAL PATHOLOGY, THERAPEUTICS. The iodide of potassium may be given in doses of from three to five grains, three times a day, in some bitter infusion. The following gargle will be found very serviceable in mercurial salivation: R. Tinct. iodinii,.....giij to vj. Potassse iodidi, .... grs. xv. to xxx. Aquae,......Oss.—M. After the action of the medicine upon the system has subsided, and the disease assumes a chronic form, the gums, as directed by Mr. Thomas Bell, should be freely scarified by passing a lancet entirely through their substance, between the teeth ; and this opera- tion should be repeated as often as every few days, until they are completely restored. The use of astringent washes should at the same time be continued, and if there are any teeth which, from the loss of their vitality, or from having become very much loosened b}^ the partial destruction of their sockets, act as irritants, they should be removed. For correcting the fetor arising from the ulcerated surfaces, a gargle may be used composed of two or three drachms of charcoal suspended by agitation in a tumbler of water. After retaining a portion of this gargle for a short time, the mouth should be rinsed with Avarm water, to remove the particles of charcoal. A solution of the permanganate of potash, in the strength of from two to ten grains to the ounce of water, as a gargle, or of phenol sodique in the form of spray, or permanganate of potash solution Avill prove effective for the removal of the fetor; also washes made from chlorinated soda or lime. ULCERATION OF THE GUMS OF CHILDREN ATTENDED AVITH EXFOLIA- TION OF THE ALVEOLAR PROCESSES. The gums and alveolar processes of children are occasionally attacked by a very peculiar form of disease, which occurs more frequently during the shedding of the temporary and the eruption of the permanent teeth than at any other period of childhood. We have never known adults to be affected Avith it, and to the ordinary spongy, inflamed and ulcerated gums it does not appear to be at all analogous. It bears a much closer resemblance to cancrum oris, yet differs in many particulars from this disease. Among the symptoms which characterize the affection, are itch- ing and ulceration of the gums and their separation from the necks INFLAMMATION OF THE GUMS. 237 of the teeth and alveolar processes; there is. at first, a discharge of muco-purulent matter from betAveen the gums and necks of the teeth, which ultimately becomes ichorous and fetid. The teeth loosen, and the alveoli lose their vitality and exfoliate. Ulcers are formed in various parts of the mouth, and the gums and lips assume a deep red or purple color. In the exfoliation of the alveolar pro- cesses, the temporary, and sometimes the croAvns of the permanent teeth, are carried away. The constitutional symptoms are: skin, for the most part, dry; pulse, small and quick; the bowels gen- erally constipated, though sometimes there is diarrhoea; and to these symptoms may be added lassitude and a disposition to sleep. These may be regarded as the prominent phenomena of the dis- ease in its most aggravated form. When exfoliation of the alveolar processes takes place, the symptoms usually abate, and sometimes wholly disappear. Delabarre says: " Among the great number of children that are brought to the orphan asylum, he has had fre- quent occasion to notice singular complications of the affection, as modified by the strength, sex and idiosyncrasies of the different subjects." The gums and lips, in some, he describes as being of a beautiful red color; in others, the lips are rosy and the gums pale, and sometimes very much SAvollen. He also enumerates among the symptoms, burning pain in the mucous membrane of the cheeks, and ulceration, pain and swelling in the submaxillary glands. In the majority of cases the disease is confined to one jaw and to one side, though sometimes both are affected by it. The effect on the permanent teeth, in all the cases Avhich have fallen under the notice of the author, Avas injurious, though Delabarre says that in children Avho have reached their seventh or eighth year the teeth are not injured, except that they may be badly arranged, in con- sequence of the want of a proper development of the jaAv. The author enumerates the folloAving symptoms of a very aggra- vated form of this disease: inordinate appetite, burning thirst, a small spot on the cheek, or about the lips, resembling an anthrax, Avhich rapidly increases in size, turns black, separates, discharges an ichorous fluid, and its edges roll themselves up like flesh ex- posed to the action of a brisk fire ; the flesh separates from the face, the bones become exposed, hectic fever ensues, and in the course of fifteen or tAventy days death puts an end to the sufferings of the child. Delabarre asserts that this affection is more common among females than males, and that the bones of the jaw are so much soft- ened that they may be easily cut A\ith a knife. 238 DENTAL PATHOLOGY, THERAPEUTICS. CAUSES. The disease seems to be the result of general debility or defecth'e nutrition and a cachectic habit of body. It appears to be almost wholly confined to children of the poor and destitute, and, so far as the author's observations extend, to those who reside in cellars or small and confined apartments. Children of scorbutic habit seem to be the most subject to it. From the great debility of all the organs of the body, their functions are languidly and imperfectly performed. That the disease is determined by general enfeeble- ment of the functions of the body, there is, we think, little doubt; but Avhether it would develop itself independently of any local cause, is a question which we do not feel ourselves able satisfac- torily to answer. It is not at all improbable that local irritants are the exciting cause ; and we are the more inclined to this belief from the fact that in all the cases which have fallen under our observa- tion the teeth Avere considerably decayed, and had previously given rise to pain; and in some instances they were coated with tartar. While, therefore, the character of the affection is determined by some peculiar constitutional tendency and general enfeeblement of the A'ital poAvers of the body, it is not unlikely that local irritation is the immediate cause of its development. TREATMENT. As the treatment of this affection comes more immediately within the province of the medical than of the dental practitioner, we shall not dAvell long upon the subject. The local treatment should consist of acidulated and astringent gargles. The ulcerated parts may be occasionally touched Avith a solution of the nitrate of silver, or chloride of zinc, from three to eight grains to the ounce of Avater; phenol sodique or permanganate of* potash solution may be employed to correct the fetor. As soon as the alveolar process exfoliates, it should be removed. After this takes place, a cure is generally speedily effected under proper con- stitutional treatment. This last may consist of mild alteratives, a generous nutritive diet, consisting of succulent vegetables, and, in the absence of fever, of wholesome meats, tonics, and exercise in the open air. (See " Ulcerous Stomatitis.") ALVEOLAR PYORRHOEA. Alveolar Pyorrhoea, commonly designated " Riggs's disease," de- notes suppurative inflammation of the gums, attended Avith the INFLAMMATION OF THE GUMS. 239 destruction of the alveolar processes. It usually commences with an uneasy sensation in the gums and teeth, Avhich soon become painful. At an early stage of this disease the margin of the gum presents decided inflammatory action, and bleeds from slight causes. As the disease progresses, the inflammation extends deeper into the substance of the gum, which becomes greatly congested with venous blood, SAvollen, and exhibits a tendency to separate from the necks of the teeth, Avhich gives rise to the formation of small sulci filled Avith pus. There is also a loss of substance of the gum, and the destruction of the margins of the alveolar processes is folloAved by the death of the thicker portions beneath, and, as a consequence, the teeth become loose and change their positions. There is fre- quently a separation and protrusion of the superior and inferior front teeth, Avith a thick, fetid discharge from about their necks, Avhich causes a disagreeable taste and a very offensive breath. The gum at this stage of the disease, is of a dark purple or livid hue, Avith a congested margin, and in some cases, on account of its being denuded of its epithelium, its surface presents a polished appearance ; it may also become granular, and covered Avith fungous excrescences. At an extreme stage of the disease, complete destruc- tion of the alveoli, and of a considerable portion of the gum occurs, and the teeth are held in place by a tough, ligamentous attachment, Avhich Avas formerly the alveolo-dental periosteum. The roots of the teeth become coated Avith a layer of calculus, often of a greenish- brown color and great hardness, Avhich adheres tenaciously, render- ing its removal very difficult. Although the tAvo forms of calculus, the salivary, which is derived from the saliva, and the sanguinary from the serum that exudes from the gums when diseased, cause inflammation of the peridental membrane, yet the latter form of calculus appears to be more com- monly associated with this suppurative inflammation than the former. The congestion and consequent recession of the gum from about the necks of the teeth, permits the salivary form of calculus to be deposited on the roots, by the ready access afforded to the fluids of the mouth; Avhile the pathological condition of the tissues in con- nection Avith the teeth, causes a serous exudation, the result of Avhich is the deposit of the harder variety of calculus. The nature of this calcic deposit is no doubt modified by the serous fluid from the gum. 240 DENTAL PATHOLOGY, THERAPEUTICS. CAUSES. Although alveolar pyorrhoea is a disease depending almost wholly upon local causes, such as the irritation of salivary and sanguinary calculus, and especially this latter form of calcic deposit, and a per- verted condition of the secretions, yet its peculiar manifestation, no doubt often depends upon some unfavorable diathesis, which enables the local causes to produce more serious effects than might be pos- sible in better systemic conditions. If the teeth are perfectly free from irritating accretions, and present smooth, polished surfaces, at points Avhere the more highly vitalized surrounding structures come in contact Avith them, no inflammatory action will occur in such structures. On the other hand, if the teeth, on account of calcic deposits about the margin of the gum and along their roots, act as irritants, inflammatory action, folloAved by such effects as the disease under consideration presents, may ensue. Loav vitality and all diseases Avhich affect the circulation may be named as predisposing causes of alveolar pyorrhoea. Dr. Black, in describing this disease under the title of " phage- denic pericementitis," maintains that it is of local origin, Avhile Dr. Atkinson ascribes it to constitutional causes. There is good reason, hoAvever, for believing that there are both predisposing and exciting causes for this disease. TREATMENT. In the early stage of alveolar pyorrhoea all salivary deposition should be carefully removed, and the surfaces beneath well polished ; a decided change for the better may occur in a very short time, as the inflamed gum will lose its congested appearance, and assume a lighter color and a firmer consistence, and become reduced to its normal thickness. In the more advanced stages of this disease, the treatment consists in reaching, by means of narroAV, sharp instru- ments, the extreme limits of the diseased action, removing all de- posits, and breaking up the diseased tissue and necrosed bone, and polishing the surfaces roughened by depositions of calculus. The diseased margin of the alveolar process must be removed to such an extent that the firm and resistant bone is reached by the edge of the cutting instrument, Avhich a nice sense of touch Avill determine. A nice sense of touch, only acquired by practice, Avill enable the operator to distinguish, with the instrument, foreign and dead sub- stance from tooth structure and living bone. It is especially necessary that every particle of salivary calculus and necrosed bone should be removed, as their presence will be indicated by a reddened INFLAMMATION OF THE GUMS. 241 patch of tissue, someAvhat larger than the irritant beneath. As the remoAral of such irritants causes both pain and hemorrhage, such an operation will require several sittings, and the frequent application of carbolic acid, by means of a properly shaped piece of orange Avood. After this operation is completed an application of dilute aromatic sulphuric acid Avill prove serviceable. The effect of such treatment is to promote the reproduction of neAV bone, and cause the gum to become firmly attached to it, and thus restore the stability of the teeth, and in many cases the only therapeutic treat- ment necessary will be the use of an astringent wash, such as tinc- ture of myrrh in its full strength, applied to the gum about the necks of the teeth. When constitutional disturbance exists in con- nection Avith the local effects, after perfectly removing all irritants, a dilute solution of chloride of zinc may be applied to the ulcerating surfaces by passing it under the gum, about the necks and roots of Fig. 107. the teeth, by means of cotton wound on a broach, and alternating Avith dilute aromatic sulphuric acid and tincture of iodine, applied to the surface of the gum. Chlorate of potash solution should be used as a mouth-wash after each meal and at night, Avith as thorough use of the brush as the condition of the gums will permit. The use of a solution of common salt is recommended during the in- tervals betAveen the applications of the more powerful remedies; also phenol sodique. For the Avorst stage of this disease, Avhere the teeth are held in the mouth by means of the tough, ligamentous attachments only, their removal is inevitable. The above illustration represents Dr. J. M. Biggs's set of instru- ments for the thorough remoA'al of all salivary, sanguinary, and other deposits from the roots of the teeth, in the treatment of this disease. Some prefer instruments Avith slender points, which require a 16 242 DENTAL PATHOLOGY, THERAPEUTICS. pushing motion, instead of the curved hook or hoe-shaped instru- ments so commonly used for the removal of calcic deposits from the teeth, and which necessitate a motion toAvard the hand. Whatever form of instrument is used, the thorough removal of all concretions from the teeth is absolutely necessary in this treat- ment, as all soft tissues are rendered unhealthy by the contact of calcic deposits. Dr. Cushing's set of scalers (Fig. 108) are well adapted for the removal of all calcic deposits from the teeth. For the removal of slight deposits in the form of thin scales, Dr. Gilmer recommends that the gum be first expanded so that it may stand off from the tooth, by packing under its free margin salic}dized cotton, which is allowed to remain for twenty-four hours. Fig.108. A method of treatment recently recommended by Dr. A. W. Harlan, is as folloAvs: For the acute form, the pockets formed by the separation of the gum should be first filled with iodoform and eucalyptus, iodoform and oil of cinnamon, or be thoroughly syringed with a one to three-grain solution to the ounce of water, of chloride of alumina, Avhich is a good disinfectant and astringent. In three or four days the sanguinary deposits may be removed, as Avell as the edges of the alveoli. The pockets should then be syringed with peroxide of hydrogen, for the purpose of thoroughly cleansing them and also to destroy the micro-organisms present. After drying the gums, the pockets should be injected with a solution of iodide of zinc, grs. xii. to grs. xiv. to the ounce of water, two or three drops or more to eaeh pocket. After several days have elapsed, the gums should be carefully dried, and a fine cone of cotton or bibulous paper moistened with peroxide of hydrogen gently pressed into each pocket; if any pus is present effervescence will take place, Avhen each pocket must be again injected with the iodide of zinc solution. In chronic cases, after the removal of the diseased bone INFLAMMATION OF THE GUMS. 243 and the careful cleansing of the roots, the pockets should be syringed Avith peroxide of hydrogen, followed by the injection of a xxiv. gr. solution of the iodide of zinc, in the same manner as be- fore described. In very bad cases, a stronger solution of the iodide of zinc is recommended, xxviii. grs. to the ounce of Avater; and Avhen the margins of the gums present a ragged border or cone- shaped slit, pure granular iodide of zinc is applied to the edges of the slit once in three days, the injection into the pockets being re- peated every fourth day. Combinations of iodoform and eucalyptus; iodoform and oil of cinnamon ; iodoform and eugenol, chloride of aluminium in the form of a solution composed of one to three grains to the ounce of Avater; sanitas, three parts to one part of eugenol, have also been employed with benefit, in the form of paste and injections once in four days. A strong solution of chloride of zinc, 20 to 30 per cent,, applied with care about the teeth by means of an abscess-syringe will prove beneficial by relieving the congestion and constringing the soft tissues. The after-treatment consists in the use of stimulating appli- cations, such as cinnamon-Avater, or carbolic acid combined Avith oil of cinnamon and oil of gaultheria, in the proportion of one drachm of the former and four to five drachms each of the latter. Cleanliness should also be observed, and in the use of the tooth-brush the motion should ahvays be lengthAvise instead of across the teeth—a soft brush being preferable to a stiff one. It is advisable, in cases Avhere the destruction of the alveolar process has not been great, to preserve the gingival margin, in order that a perfect restoration of the peridental membrane may take place. Such an operation may be performed by introducing through the ginghral aperture a bent chisel, or a hoe-shaped excavator, and the diseased structure removed as high up as it may extend toward the apex of the root. In cases Avhere the cutting instrument cannot be introduced in such a manner Avithout injury to the gingival margin, a flap of the soft tissue over the diseased bone may be raised, and all carious struc- ture removed, as well as calcic deposits from the denuded root, through such an opening Avithout destroying the gingival margin. After the parts are thoroughly cleansed by injections of tepid water, stimulating applications may be made of carbolic acid (in crystals) one part, oil of cinnamon tAvo parts, and oil of gaultheria three parts. Dr. Gilmer recommends for obstinate cases the use of car- bolic acid and camphor, in the form of " phenol camphor," which consists of equal parts of carbolic acid and gum camphor, prepared by melting such a mixture on a sand bath until an oily liquid is obtained; it is applied by means of a syringe, to the pus-pockets. 244 DENTAL PATHOLOGY, THERAPEUTICS. Before the application of disinfectants and antiseptics, the parts should be cleansed Avith the peroxide of hydrogen, either alone or combined with the bichloride of mercury. \ ADHESIONS OF THE GUMS TO THE CHEEKS. The gums and inner walls of the cheeks sometimes contract ad- hesions which interfere seriously Avith the functions of the mouth. The affection may be congenital, but in the majority of cases it occurs subsequently to birth. The extent of the adhesion may be small, or it may occupy the gums of the entire alveolar border of one or both sides of the mouth, and of one or both jaws. Desira- bode relates the case of a young man, Avho, in consequence of a venereal ulcer, had his upper lip united to the gums of the four incisors in such a Avay as to form a sort of loop above the teeth, which, by the retraction of the lip, Avere caused to project outward* Adhesion of the gums to the cheek or lips results from ulceration, caused either by constitutional disease or local lesions. But that it arises more frequently as a consequence of the immoderate use of mercury than from any other cause, is a universally admitted fact. The author has met with several cases, however, in Avhich the affec- tion has resulted from ulceration of the gums around necrosed tem- porary teeth, and of the corresponding wall of the cheek, caused by excoriation of the mucous membrane, produced by the sharp points of the protruding roots. But the extent of the adhesion, in cases of this sort, is never very considerable. The proper remedy is to separate the parts which have groAvn to- gether with a sharp bistoury. This done, reunion should be pre- vented bjr keeping a pledget of cotton or lint in the Avound, until the process of cicatrization is completed. CHAPTER V. TUMORS OF THE MOUTH AND JAAVS. Tumors of the gums are of various kinds; some interesting cases of simple hypertrophy are reported by Dr. Gross and Mr. Salter and Mr. Erichsen, Avhich are reproduced by Mr. Heath in his ad- mirable " Essay." Mr. Salter's case was found to consist of a pink- * Author's translation of Desirabode's " Complete Elements of Science and Art of the Dentist," p. 227. TUMORS OF THE MOUTH AND JAAA^S. 245 ish, corrugated and lobed mass, composed of an expansion of the alveolus, with " immense hypertrophy of the fibrous gum, and an exuVrant groAvth of the papillse of the mucous membrane." Dr. Gross's case AA'as someAvhat similar. Mr. Erichsen's Avas found, " on section, to consist of firm, fibrous stroma, containing much glan- dular tissue in its interstices, and covered on its surface by very large and vascular papilla?. The epithelial layer was of unusual thickness, but no abnormal epithelial structures were found in the growth, Avhich Avas an example of true hypertrophy." (Heath's " Jacksonian Essay," 190.) A peculiarity of this case was that the teeth were also hypertro- phied. In each of these cases the diseased tissue was removed and the exposed surface cauterized. Polypus is a simple hypertrophy of the interdental gum, or dental pulp, and is generally occasioned by the irritation of a Avorn-out or broken tooth witli a ragged edge. In structure these groAvths are like the gum from Avhich they arise. They seldom give much pain, except ulceration should take place. If simply cut away, they are very likely to return; but if the tooth is removed, and astringent or cauterant applications be made, they give but little trouble. Continuous pressure, by gutta percha or other means, Avill also control them. Mr. Salter reports two cases of " Papillary Tumors of the Gums," consisting almost entirely of epithelium, arranged in filiform papillse resembling those of the tongue. It is described as " a curious Avhite mass, consisting of coarse, detached fibres, pointed and free at one extremity and attached at the other; in fact, it Avas a mass of papilhe, many of them nearly an inch long, and similar in shape to the ' filiform ' papillse of the tongue; their surface was shreddy and broken ; among the elongated processes Avere a feAv rounded eminences like ' fungiform' papillae, and these had a smooth and broken surface." The term Epulis is usually applied to tumors springing from the margin of the gums, Avhatever their structural character. They most commonly spring from the gum, betAveen tAvo teeth; as they continue to groAV, the base may increase also in size, till it covers the alveolar bone, or it may undergo superficial development, the point of attachment undergoing but little change; in other Avords, it may possess a broad, flattened base or a narrow pedicle. In structure it bears a close resemblance to the gum, and sometimes has imbedded in it spiculse of bone, which may have been detached from the alveolar bone, constituting the source of irritation which gave rise to the morbid groAvth ; or it may have been a true osseous 246 DENTAL PATHOLOGY, THERAPEUTICS. development; a portion of germinal matter, having escaped from its true osseous relation, has been here arrested, established a false centre of groAvth, and undergone development, in obedience to the primitive impulse of the parent cell from which it was derived. The accompanying figure, from Mr. Heath, is a typical epulis of the most common variety. It is Fig. 109. __^_ seen to be a " firm, fibrous tumor," Avith " some fibro-plastic cells in- termingled." This variety of epulis is not unusually attached to the periosteum of the alveolus, Avith pro- jecting spiculse of bone entering it from the maxilla. Left to themselves, these tumors will often continue to groAV, encroach- (Fig. 90 of" Heath on the Jaws.") . ,. , , , . , ing upon the tongue, hard palate, and teeth. They are thus made liable to injury by the teeth, and an ulcerated surface is in this way established, which discharges freely, occasions considerable pain, and may become the seat of hemor- rhage. A softer and more vascular variety is described by Mr. Hutchin- son as consisting of fibrous tissue, in which are imbedded a large number of polynucleated cells of the myeloid variety. In the " Transactions of the Pathological Society," he thus describes them: " The epulis presented all the characters of myeloid growth in a most remarkable degree. Its section was very vascular, and showed hues varying from a deep-red to buff, and a peculiar light-greenish tint of yelloAV (xanthoid of Lebert). Scattered in its structures Avere some detached masses of soft, spongy bone. Under the mi- croscope were seen an abundance of the large polynucleated bodies characteristic of these groAvths, many of them being very irregular in shape and much branched." This form of epulis is most fre- quently connected with the interior of the alveolus, and hence more closely resembles the endosteal structures. When presenting an ill-conditioned and ulcerated surface, it closely resembles a malig- nant growth, but does not, as has been thought by some writers, pass into cancer. Mr. Heath also describes a variety which he calls " giant-celled epulis," consisting of " large, irregular, disk-like cells containing numerous beard-like nuclei interspersed among the fibrous tissue." It presents a surface of uniform smoothness, of a dark-gray color, with numerous purple spots upon it. He considers it as holding a position intermediate betAveen " fibro-cellular and myeloid tumors," TUMORS OF THE MOUTH AND JAWS. 247 and of a similar nature to the growths described by Otto Weber as " giant-celled sarcoma," and as a " fibrous form of cancer arising from bone," by Wedl. Another form of epulis, resembling epithelioma, and of interest, as showing that epithelioma may be developed in the gum as else- where, is thus described in a report by Mr. Bruce to Mr. Heath: " The surface of the tumor is covered with healthy mucous mem- brane. The interior of the tumor is whiter, firmer, and more com- pact than the surface, but there is no line of demarcation between the tumor and its mucous covering. The structure of the growth is distinctly glandular, very much resembling some form of compact adenoid tumor of the breast. " At the point of attachment of the tumor to the parts beneath, a remarkable transformation of the glandular into the epithelioma- tous structure is seen. In one part of the section may be seen the cut ends of gland tubules, whilst in their immediate neighborhood are most distinct nests of true epithelioma, consisting evidently of concentrically arranged cells compressed from the centre upAArard." Mr. Adams reports a similar case Avhich resulted in death, the disease having reappeared in the skin after its removal. It is often difficult to determine the causation of epulis, but they may often be referred to the irritation of broken or unsound teeth, or to fragments of the alveolar bone which become detached, or to outgrowths from the alveolus; most frequently, however, to roots of decayed teeth ; hence Mr. Heath thinks the greater frequency of these tumors in women—five to three—they, having a greater dread of all surgical operations, are more likely to permit useless roots to remain in their mouths. It is rarely fatal, but sometimes attains such size as to'produce great deformity, pain, and embarrassment of the functions of mas- tication and deglutition. For the treatment of epulis, nothing short of the entire removal of the tumor, with its periosteal attachments, together Avith all de- cayed teeth, or even sound ones—when the disease seems inclined to reproduce itself—promises any good result. After excision, the actual cautery should be freely applied, for the double purpose of destroying all trace of the disease and of arresting hemorrhage. Tumors of the hard palate are closely related to epulis, and papil- lary and epithelial forms are reported—the former presenting but little difference from tumors of the same character arising on the gum. An epithelial tumor occurring on the hard palate is reported by Dr. Andrew Clark, Avhich Avas described as "soft, elastic and vas- 248 DENTAL PATHOLOGY, THERAPEUTICS. cular. The cut surface is of a dead-Avhite color, distinctly granular, like rough honey, crumbly-looking, and studded with red or pink blotched parts sunk beloAV the general level. On further examina- tion, it appears to be permeated by a kind'of glairy substance (col- loid matter), which helps, seemingly, to give coherence to the tumor. To the naked eye the tumor resembles in some respects a cephaloid or myeloid mass. To the latter it bears the greatest resemblance in general character, seat and structure. The microscopic characters are those of epithelial cancer, epithelial cells in all stages of devel- opment and of the most various forms, together Avith a few nest-cells and fat. The mucous membrane over the tumor, though not con- tinuous with it, presents the same structural characters. This de- cides the doubt betAveen the epithelioma and myeloma." (Heath's " Jacksonian Essay," p. 208.) Encysted tumors of the hard palate are also sometimes found,-but they are rare, and require no special description in a Avork of this character. These tumors, Avhen epuloid in character, are to be treated in the manner already described. When the bone becomes affected, it also must be removed to such an extent as will leave an entirely healthy surface. Unerupted teeth may also give rise to osseous tumors, requiring surgical interference. This is more peculiarly the case with the Avisdom tooth, for a reason easily understood : the space nominally allotted it, betAveen the second molar and the terminal point of the alveolar ridge, is often too limited for its eruption; endeavoring to make its Avay through the bone, under such circumstances, the opposition it encounters is often sufficient to occasion great irritation and pain, and occasionally to entirely prevent its eruption. The retained tooth thus becomes a centre of irritative action, and may serve, not only to determine the site, but the fact of such tumors. Mr. Tomes also relates a case in Avhich the Avisdom tooth was bound down by a " mass of enamel, dentine and cementum, throAvn to- gether Avithout any definite arrangement," Avhich occupied the place of the second molar. Mr. Heath also records a case, reported by Dr. Forget, in which a tumor about the " consistence of ivory," cov- ered everywhere with enamel, and about the size of an egg, occupied that portion of the jaAv betAveen the ramus and the first bicuspid. It Avas composed chiefly of enamel and dentine, with portions of cementum " dipping into the crevices " here and there, and was re- garded by Dr. Forget as a " fusion and hypertrophy of the last tAvo molars." Again, one of the anatomical elements of the tooth may become TUMORS OF THE MOUTH AND JAAVS. 249 so hypertrophied as to constitute a troublesome disease, and call for surgical interference. The cementum is most likely to undergo such change. M. Maisonneuve reports a case cited by Mr. Heath, in Avhich the hypertrophied cementum attained the size of a pigeon's egg- it is desirable,if possible, to remove all such morbid growths AA'ith- out injury to the bone in which they are implanted ; but it may be- come necessary to excise that part of the jaAv in Avhich it is. All neighboring teeth Avhich may possibly be associated with it should be removed. Tumors of the antrum and upper jaw may be appropriately de- scribed together, the distinguishing characteristics being pointed out. Poly pus.—GroAvths of this character occasionally occur in the antrum, and are closely allied to the small cysts occurring in its mucous membrane; both are essentially a " hypertrophy of some element of the mucous or sub-mucous tissue. When the connective or areolar tissue predominates, the fleshy polypus is produced ; Avhen the glandular element is especially affected, we have the cystic form produced. Intermediately, when the fibrous element is very loose, and Ave have some glandular hypertrophy, the semi-gelatinous poly- pus is produced, which closely resembles the nasal polypus." (" Jacksonian Essay," p. 210.) Antral polyps are very vascular, and are sometimes the ushers of malignant disease. The diagnosis is exceedingly difficult until they have acWanced sufficiently to break doAvn the osseous Avail some- where ; this most frequently takes place into the nose, through the thin nasal Avail. They should be removed as soon as ascertained to exist, and the troublesome hemorrhage Avhich is likely to occur should be arrested by injections of a reliable styptic in any strength which is not likely to give rise to trouble, if the opening is sufficiently large to permit its ready escape. A single instance of a peculiar form of fibroid growth of the antrum is recorded by Mr. Heath, from whose work we take the fol- loAving description by Mr. Bruce : " It appears to consist of a fine, soft, fibrous stroma, in which very numerous nuclear bodies, and a feAv elongated fibre-cells are distributed. Its structure resembles that of the upper strata of a mucous membrane, from Avhich it is probably an outgrowth. It consists of neAvly-formed fibrous tissue, and of the elements from which fibrous tissue is developed, and may, therefore, be classed 250 DENTAL PATHOLOGY, THERAPEUTICS. among the simple fibro-plastic growths as distinguished from the true myeloid tumors." Fibrous tumors of the upper jaw are not unlike fibrous tumors found elseAvhere. They are slow of groAvth, dense in structure, with interlacing, slender bundles of fibres, and are frequently lobulated. They commonly spring from the interior of the antrum, or from the alveolus, and sometimes attain to an enormous size, crushing in the antrum or obliterating its walls by absorption, encroaching upon the orbit, destroying its floor, penetrating the nasal cavity, and, extend- ing outward, conceal the teeth on the same side from view. Mr. Liston removed a tumor of this kind from the face of a lady, Avhere it had arisen six years before, apparently from a blow received on the face, and had attained to an enormous size, covering the whole of. that side of the face. Its smallest diameter was six inches. This tumor became of increased vascularity after the cessation of the catemenia at the regular monthly period, and bled slightly at these times, from the adjacent parts of the gum. They are usualhy of an OAral or rounded form, freely movable, and painless. When laid open they present a Avhite, shining, ligamentous structure, and are composed of nucleated fibres. If left to themselves they may be- come softened in the centre and undergo disintegration, though Mr. Heath thinks they never suppurate, except where they have been punctured in establishing a diagnosis. They may also undergo cal- careous degeneration, but are never ossified. Mr. Paget reports a case in which distinct pulsation, synchronous with the radial pulse, was felt. They rarely recur after removal, perhaps never when entirely removed. Mr. Weber thinks " they are usually connected with the lining of the Haversian canals," and ad- vises that a portion of the bone be remoAred in all operations. Their origin is usually referred to the irritation of decayed teeth, or to direct violence. Fibro-cellular tumor, or osteo-sarcoma, is of softer consistence than the simple fibrous tumor; they are smooth, round, elastic tumors, of a yelloAvish color, and are infiltrated Avith a serous fluid. Unlike the simple fibrous tumor, they exhibit a strong tendency to ulceration, Avhich sometimes serves to confound them with malignant growths, from Avhich they are to be distinguished by the history of the case, and the non-implication of the lymphatic glands. They are thus described by Sir Philip Crampton: " In the earlier stages of the dis- ease, the tumor consists of a dense, elastic substance resembling fibrocartilaginous structure, but the resemblance is more in color than consistency, for it is not nearly so hard, and is granular rather TUMORS OF THE MOUTH AND JAAVS. 251 than fibrous, so that it' breaks short.'' On cutting into the tumor, the edge of the knife grates against spicula, or small grains of earthy matter, Avith Avhich its substance is beset." Fibro-cellular tumors may undergo fatty or calcareous degeneration. Recurring fibroid tumors occur, if at all, so rarely in the upper jaAv, that any description is unnecessary in a work of this kind. The same may be said of vascular tumors. Myeloid tumors are described by Mr. Paget as occupying an inter- mediate position betAveen fibrous and fibro-cellular tumors. They are composed of parallel fibres, with fibro-plastic cells, and bear a close resemblance to "granulation cells in process of development into fibro-cellular tissue." On section they present a smooth, shiny, semi-transparent appearance; are of a pinkish or bluish color and of brittle texture. They usually occur in the young; are painless, and seldom recur. Externally, they present a dark maroon color, quite characteristic. An excellent description of a tumor of this class is furnished Mr. Heath by Dr. Tonge, from which we make the folloAving extract: " It Avas of firm consistence throughout, and on section presented a Avhitish appearance, with a small pink patch or tAvo, and a Avhitish, creamy-looking juice could be scraped from the cut surface. . . . The fibrous element Avas much less abundant than the cellular, and consisted of Avhite fibrous tissue, Avith numerous fine curling fibres of yelloAV elastic tissue, and many small oval and rounded nuclei were imbedded in the fibrous struct- ure. The greater portion of the tumor seemed to be composed of cells. These Avere mostly of an irregularly rounded form, often Avith pointed processes; and some shuttle-shaped and spindle-shaped, of a someAvhat trapezoidal form, Avere not uncommon, Avhile a few cells presented the character of those distinctive of myeloid tumors. All the cells contained one, and often tAvo, very large, and generally oval nuclei, Avith one, tAA'o, or three nucleoli, and a variable number of oil globules. The myeloid cells observed Avere of irregular outline, and contained from three to five nuclei, Avith single or double nucleoli; one very large cell contained six nuclei." Their formation takes place slowly, after the manner of cyst forma- tion, or other simple tumors. When the bone has been removed by absorption or otherwise, they may be recognized by their character- istic color, and when a cyst forms Avithin them, as sometimes happens, myeloid cells may be found in the fluid that escapes Avhen it has been punctured; thus distinguishing it from c}',stic formations. Cartilaginous tumors are of tAvo kinds : simple, innocent or benig- nant tumors ; and tumors presenting a malignant appearance. Those of the first class present a round or OAroidal form, are smooth, hard, 252 DENTAL PATHOLOGY, THERAPEUTICS. of sIoav growth, and painless. Those of the second class grow Avith great rapidity, to a large size, and are of a malignant appearance. Cartilaginous tumors occur on the upper jaw, but may affect it secondarily by extension from other parts. Mr. Heath describes several specimens taken from St. George's and St. BartholomeAv's Hospitals, in one of Avhich the disease occurred on the inner side of the orbit, and tAvo years later had pressed the superior maxilla? fonvard nearly an inch beyond the inferior, while the " bones of the face and orbit were extensively absorbed." In the other, the superior maxillary bones were entirely absorbed, the cav- ity of skull was invaded, and the brain pressed aside; it is attached to the soft palate beloAV, and presses fonvard the walls of the nose in front. Mr. Paget relates a case in Avhich the disease had existed nine years, was remoA'ed, but returned, and the patient died seven years after. UA section of the tumor shoAved that it was composed of an outer, hard, thin shell of bone, completely inclosing a morbid growth of spongy, cancellated structure, devoid of all appearance of carcinomatous or spongy disease." These growths are usually verysloAV, andAvhen removed exhibit but a slight tendency to recur. Cases are reported in Avhich the free local use of iodine has effected the absorption of tumors of this kind that had not yet attained a large size. They sometimes soften, disintegrate, slough, and establish fistulous openings, through Avhich a jelly-like mass escapes. Osseous tumors in their simplest form are but a hypertrophy of previously existing bone tissue. They are predisposed to by syphi- litic and scrofulous affections, and sometimes their immediate origin may be traced to the irritation of imperfect teeth ; in general, Iioav- ever, it is difficult to refer them to a determinate cause. They are of sIoav groAvth, painless, and closely resemble true bone in structure. Their sloAvness of groAvth, hardness, painlessness and fixity, are the characteristics on Avhich a diagnosis may be based, though they are occasionally movable. Occasionally they ulcerate, and troublesome fistulous openings are established. When of a large size they may invade important organs, occasioning great trouble, as in the case reported by Mr. Hilton, Avhere it invaded the orbit, and by its pres- sure burst the ball of the eye. Cancerous tumors of the upper jaAv are, in Mr. Heath's experi- ence, limited to the medullary form ; other observers have, however, occasionally met with scirrhus. Mr. Hancock adA^anced the vieAV that medullary disease does not begin in the antrum, but in the bones at the base of the skull. This view is refuted by the observa- tion of Mr. Liston and others, who have shoAvn that it unquestion- ably begins in the antrum very often. They are characterized by TUMORS OF THE MOUTH AND JAAVS. 253 rapid development, softness to the touch, and, Avhen fully established, by a peculiar expression and salloAv, putty-like appearance of the skin. In this situation it is seldom accompanied by glandular en- largement. By pressing upon the nasal duct it may occasion con- siderable oedema of the loAver eyelid, Avith enlargement of the facial veins, from obstructed circulation. For the cure of all solid tumors of the upper jaAv, there is but one remedy on Avhich we can rely—the knife. All operative procedures should be resorted to at the earliest practicable moment, before the facial structures have been extensively invaded by the disease. When the disease is entirely removed, in eAren malignant groAvths, Ave may sometimes entertain a hope of permanent relief. To effect the removal of tumors in this situation various methods have been devised. Until 1826, surgeons usually contented themselves with the removal of so much of the disease as could be effected Avith the gouge and chisel; but about this time Mr. Lizars, of Edinburgh, proposed the removal of the entire superior maxilla, having pre- viously secured the carotid artery. An opportunity to carry out his suggestion did not offer until December of the following year, Avhen, in attempting this operation, the hemorrhage, notwithstand- ing the ligation of the carotid, Avas so great as to necessitate the discontinuance of the operation. In the meantime, Avithout any knoAvledge of Air. Lizars's suggestion, Mr. Gensoul successfully re- moved the upper jaw without securing the artery, and with but little hemorrhage. Mr. Lizars afterward operated successfully, and the operation is noAv an established one. His incision Avas carried from the angle of the mouth to the malar bone, Avhere, when more space Avas required, it Avas met by a short, vertical incision, and an incision was also made from the middle line of the lip to the nostril. Mr. Gensoul employed a vertical incision from the inner canthus to the angle of the mouth, Avhich was met midway by another at right angles to it, letting fall on its outer extremity another vertical incision. The bone Avas then removed with the mallet and chisel. An obvious objection to these operations AAras the great deformity occasioned, and the division of the facial nerve. To obviate these difficulties, Sir William Fergusson suggested a plan, Avhich has since been very generally adopted. It consisted solely in an inci- sion from the middle line of the lip to the nostril, Avhen, by stretch- ing the integument, sufficient space Avas usually gained. If more, hoAvever, Avas required, the incision Avas carried up alongside of the nose to the inner canthus, and beloAV the eye to the outer canthus; thus the facial nerve and artery Avere divided so high up as to give but little trouble, Avhile the scars are most favorably situated (see Fig. 110). 254 DENTAL PATHOLOGY, THERAPEUTICS. After deflecting the skin, a small saw is passed into the nostril, with which the hard palate and alveolus are divided. The nasal and malar processes of the superior maxilla are next sawed nearly through, and the division completed Avith bone forceps. The bone is then grasped by the power- ful forceps devised by Sir William Fergusson, and forcibly wrenched from its attachments to the ptery- goid process and palate bones. The infra-orbital nerve is then divided, the soft palate carefully dis- sected from the detached bone, which is ready for re- moval, after which hemor- rhage is arrested by liga- tures and the actual cautery, and the Avound closed with silver sutures. When the palate bone and orbital palate are not involved, they may be spared by saAving horizontally above and below them respectively. Sir William Fer- gusson noAv prefers to avoid the removal of all healthy tissue by attacking the disease from centre to circumference with strong curved and angular bone forceps. Both superior maxillse have occasionally been removed ; but it is an operation so seldom required that a description of it is not called for in a Avork of this kind. Tumors of the lower jaw do not differ in essential particulars from those already described. They are more readily diagnosed and safely removed than those of the upper jaw. Deaths are com- paratively rare from operative procedures here. When the tumors are small, they may be removed without incision of the lip, by simply dissecting it from its attachment to the bone, turning it clown, and removing the diseased portion with bone forceps. When a large body is to be removed, the incision should be carried beneath the margin of the jaAv, Avhere the scar shall afterward be concealed from view. When the bone is exposed, we should endeavor carefully to ascertain if the disease may not be removed with the external plate of bone alone; if this may not be done, the saAv should be brought into requisition, and the diseased structure removed. Amputation of the lower jaw is far more readily effected than of the upper; for TUMORS OF THE MOUTH AND JAAVS. 255 a detailed account of this operation the student is referred to more exclusively surgical Avorks. CYSTIC TUMORS, DENTIGEROUS CYSTS. It must be remembered, in connection with diseases of the antrum, that it is of variable size, Avith Avails of variable thickness. In youth the Avails are thick and the cavity small. After attaining its maximum size in the adult, it is found again to diminish Avith old age; it is larger in males than in females. But in adult life its capacity varies in different subjects, from one drachm to eight drachms, the average capacity being about two and a half drachms. Suppurative inflammation,or abscess of the antrum, is commonly due to extension of inflammation from the teeth to the lining mem- brane of its cavity. The roots of the first and second molars not infrequently present prominences at the antrum, and sometimes the first molar roots are found extending into this cavity entirely un- covered by bone. It Avill, therefore, be readily seen hoAV disease of the roots may prove a source of irritation and inflammation to the lining membrane of this cavity ; but such direct communication is not necessary; and disease beginning in alveoli not in immediate relation Avith the antrum may extend through intervening bone and establish communication. Direct blows upon the face may also in- duce suppurative inflammation of its membrane, and it may also arise from "pressure during birth." The symptoms are, pain of a dull character, shooting up the side of the face and head, rigors succeeded by irritati\Te fever, Avith ten- derness and SAvelling of the cheek. As the pus accumulates, the pressure to Avhich it subjects the Avails of the cavity, together Avith the vitiated nutrition occasioned by its presence, determines absorp- tion of the bone and the discharge of the contained fluid through the opening thus established either into the orbit or by the side of the teeth. Before an opening is established, however, the orbital Avail may become so dilated as to occasion partial blindness by dis- placement of the eye, or it may even induce an amaurosis which shall result in permanent blindness. Sometimes extensive necrosis is occasioned, affecting all the adjacent bones, as in the case reported by Mr. Salter, in which the " floor of the orbit, the upper-cheek portion of the superior maxilla, and the infra-orbital, and a large plate of bone from the inner (nasal) wall of the antrum, Avere in- volved." Dr. Mair, of Madras, reports a case in which death re- sulted in sixteen days, though apparently beginning as a simple oza'na. The post-mortem examination in this case revealed a con- dition of things that led Dr. Mair to conclude that it began as a 256 DENTAL PATHOLOGY, THERAPEUTICS. " disease of the antrum, originating in degeneration of the mucous membrane lining its cavity, or, perhaps, connected with the soft tumors which grow from the apex of the tooth and from the lining membrane of the root; secondarily, involving the ethmoid, lach- rymal, palatine, and inferior turbinated bones of the left side, caus- ing suppuration and disintegration, the purulent matter filling the cavity of the antrum extending toward the left nostril, causing oztena, and upward into the orbit, behind the globe of the eye, push- ing the eye outward and forward, the matter finding its way through the optic foramen to the anterior surface of the left hemisphere of the brain, there acting as a foreign body, exciting inflammatory action, terminating in cerebral abscess, pausing convulsions, coma, and death." (Edinburgh Medical Journal, May, 1806.) Cases of such severity are, fortunately, rare; but they indicate the possibili- ties of the apparently most simple cases, as well as the line of treat- ment most likely to obviate such conditions and result. Treatment.—In the simplest cases in Avhich suppuration of the antrum is strongly suspected, we should at once remove all decayed teeth or roots, and even sound teeth, when found to be tender. If matter has not yet formed, the disease may then subside under the use of simple fomentations. It is safer, however, in most cases, to penetrate the antrum, preferably through the socket of the first molar, because of the greater depth of the socket; and this too, without delay, care being taken to regulate the force so as not, by too great violence, to injure the floor of the orbit, Should the teeth be sound, and it be desired to save them, an opening may be made through the alveolus above the gum. The cavity should be freely injected with tepid water, and subsequently with some slightly stimulating and antiseptic lotion ; and care must aftenvard be taken to prevent the admission of foreign substances into the cavity. In the more chronic forms of this disease, the purulent accumula- tion takes place so slowly, and the consequent expansion is so gradual, that it is often mistaken for solid growths; and in many cases the diagnosis is of extreme difficulty ; surgeons of distinction, having begun an operation for the removal of a solid groAvth, have been surprised to find their hands bathed in pus Avhilst the supposed tumor disappeared from beneath them. In all cases in Avhich the diagnosis is not perfectly clear, an exploratory puncture should be made, and thus the difficulty is at once resolved. Sometimes the pus is inclosed in a second bony investment, due to the ossification of the antral periosteum. When this occurs, it occasionally happens that the bone remains thickened long after the evacuation of the pus and the entire cure of the abscess, the TUMORS OF THE MOUTH AND JAAVS. 257 deformity, of course, remaining unaltered. It then becomes neces- sary to open the antrum and remove this ossified periosteum. A clear or yelloAvish serous fluid is not unfrequently found in the antrum, Avhich the older Avriters took to be a secretion of mucus, which, having failed to make its escape by the aperture between the antrum and the nostril, accumulated in such quantity as to occasion Avasting of antral walls to such an extent as to permit the fluctuat- ing mass to be felt at certain points. This fluid Avas found on ex- amination to contain numerous flakes of cholesterine, as is the case in Avell-defined cystic groAvths, and, as it in no respect resembled mucus, recent Avriters have referred this form of disease to cystic formations. The most recent and able writer on this subject, Mr. Heath, thus describes their mode of origin: " It is certain, however, that some of these cases, and very probably all of them, originate in the groAvth of a cyst, or cysts, Avithin the antrum, or in connection Avith the fangs of the teeth, which either groAV to such a size as to be mis- taken for the cavity of the antrum Avhen opened, or break into the antrum by absorption of the cyst-Avail, so that on subsequent exami- nation no evidence of the cyst formation can be discovered." These cyst formations are also occasionally mistaken for solid groAvths; and Mr. Heath relates an instance in Avhich " a very able surgeon remoATed the upper jaAv before the mistake Avas discovered." And Sir William Fergusson relates a case in Avhich a similar error Avas avoided by an exploratory puncture, which should in no case be omitted. They may be single or multiple; sometimes there appears to be a " cystic regeneration of the entire mucous membrane." Mr. Gi- raldes, Avho Avas the first Avriter on this subject, thinks they are due to " dilation of the glandular follicles of the mucous membrane, and that, in such cases, it Avill be necessary to open the antrum, so as to remoye the entire mass; it being useless in such cases to pursue the customary plan of tapping the antrum." Cysts of teeth are divided by Mr. Heath into two classes : " First, cysts connected Avith the roots of fully developed teeth; and, sec- ondly, cysts connected Avith imperfectly developed teeth—to Avhich the term 'Dentigerous Cysts' has been applied in modern times." They occur indifferently in either jaAv; in the upper, hoAvever, are sometimes complicated with collections of fluid in the antrum, which they have secondarily affected. When of very small size they give but little trouble, and are frequently found attached to the roots of teeth after extraction, where their existence had not before been suspected. They seem to occur most frequently in con- 17 258 DENTAL PATHOLOGY, THERAPEUTICS. nection Avith the incisor teeth, and sometimes attain a very large size, even Avhen not communicating with the antrum. They are commonly associated Avith the disease of the root about which they are formed, Avhether as cause or effect, it is difficult to determine, the majority of observers holding the latter opinion. Mr. Paget relates a case in Avhich the cyst contained as much as an ounce of fluid, and Avas received in a ^^)m fjjff deep depression in the alveo- ^|§f f^ lar border of the jaw. And Delpech reports one contain- ing so much as three ounces, without connection with the antrum. They consist essen- tially of a serous bag growing CYSTS CONNECTED WITH ROOTS OF TEETH. „ " , i , i • from the dental periosteum at the extremity of the root, filled with a clear or yellowish fluid Avith bright shining particles of cholesterine floating about in it, Ac- cording to Mr. Tomes the morbid process is probably identical with that resulting in the formation of alveolar abscess, but being less acute, a serous cyst is formed instead of a suppurating one. Mr. Heath remarks that " large cysts produce more or less ab- sorption of the outer wall of the maxilla, and are very common consequences of diseased teeth, but seem to give surprisingly little inconvenience to the patients, even when of large size and produc- ing considerable deformity of the face. They are commonly con- founded with cystic distention of the antrum." Mr. Heath says " the clinical history of cysts connected with the teeth is that of painless expansion of the alveolus, more frequently of the upper jaw, with crackling of the bone on pressure and ulti- mate absorption of the bony Avail. The cyst then presents a bluish appearance through the distended mucous membrane, and if large, gives distinct evidence of fluctuation." When an incision is made into the cyst a dark-colored clear fluid escapes, but when inflam- mation is present the contents become purulent. The treatment of such cysts consists in cutting away the thin outer wall, so that the cavity may granulate up. Dentigerous cysts occur in connection Avith teeth, most commonly permanent teeth, in which the process of evolution has been ar- rested, and is due, Mr. Tomes thinks, to the accumulation of fluid between the enamel and soft outer tissue at the time when the en- amel is completed, which fluid is usually discharged when the tooth is erupted; but when the tooth remains within the jaw, this dis- TUMORS OF THE MOUTH AND JAAVS. 259 charge cannot take place, and it continues to increase in quantity until a cyst is established. We are thus enabled to account for the presence of cysts in those cases in Avhich neither the tooth nor ad- jacent bone presents any appearance of disease. In illustration of this theory, Mr. Tomes relates a case in Avhich, "instead of having the two fangs common to second molars of the loAver jaw, the im- planted portion of the tooth Avas dilated into one large concavity, in Avhich Avas placed the crown of a second tooth, perfectly invested Avith well-developed enamel, and with the masticating surface di- rected toAvard the jaAv. The two teeth appear to be united by dentine at one point, and to have one common pulp-cavity.....I consider that in the case cited, fluid collected betAveen the enamel of the Fig. 112. dentigerous cyst of lower jaw. b. Showing position of tooth. inverted tooth and the remains of the enamel organ, situated within the socket of the second molar. As the cyst enlarged, the contigu- ous bone Avas absorbed to make room for it, and new tissue Avas concurrently developed on the outer Avails of the socket till, at last, a large cup of bone Avas formed." (" Dental Surgery.") When cysts of this kind occur in the lower jaw, they present more obvious deformity. Sometimes the cyst undergoes calcification, and is exceedingly difficult to diagnose from a solid tumor. Mr. Heath remarks that " the diagnosis of dentigerous cysts from other cysts is exceedingly difficult until they are opened, as indeed is the recognition of any form of cyst. A careful examination of the mouth may reveal the absence of a permanent tooth, or may 260 DENTAL PATHOLOGY, THERAPEUTICS. shoAV a temporary tooth occupying a permanent position. On the other hand, hoAve\'er, it must be remembered that teeth may be wanting without being connected with any disease." Many errors of diagnosis, leading to operations for the removal of supposed tumors, have been made by able and distinguished surgeons, Avho have had the courage and candor to confess their mistakes, among whom may be mentioned Gensoul, Syme, Feavu, and Lisfranc. The two latter gentlemen each remoA'ed half the jaw. It is only when the osseous walls have become so wasted as to give under pressure a parchment-like crackling that the diagnosis may be made with any approach to certainty. In every case an explo- ratory puncture should be insisted on before proceeding to operate. The existence of a cyst determined, and communication with the antrum suspected, the first molar tooth should be removed and the Avail of the antrum be perforated through the socket, and if a super- numerary tooth is found in the cavity, it should, of course, be re- moved. In many cases it is necessary to remove the front wall of Fig. 113. inverted crowns of teeth between expanded roots of other teeth, causing dentigerous cysts. the antrum and stuff the cavity with lint, thus inducing granula- tions, before a cure can be effected. This can generally be effected Avithout incision of the integument. When feasible, the plate of bone removed should be left attached to the periosteum, and be replaced after removal of the cyst. Cysts in the lower jaAv present some peculiarities Avhich make a separate description necessary. They may occur in connection with fully developed teeth, or without any direct connection with the teeth. They may be multilocular, and in rare instances may con- tain one within another. Mr. Coote reports a case in an infant of six months—which resulted in death from exhaustion occasioned by continued discharge after an operation—in Avhich, covered by a thin shell of bone, a perfect nest of cysts connected Avith the an- trum have been shoAvn to arise in the glandular structure of its lin- ing membrane, but in the loAver jaAv Ave have no such membrane. Instead thereof, we have two layers of laminated bone enclosing a cancellated structure lined by the endosteum alone. Mr. Heath is TUMORS OF THE MOUTH AND JAAVS. 261 of opinion that it is in these calculi the disease is developed, " A cancellus expanding and producing gradual absorption and obliter- ation of its neighbors until a cyst of considerable size is produced." The causation of cystic formations in the loAver jaw is very obscure, though they are probably associated in some way with the irritation from adjacent roots. They may continue to reproduce themselves, from time to time, until the cancellated tissue is entirely destroyed. Cysts in connection Avith undeA^eloped teeth—dentigerous cysts— which are common to both jaws, may suppurate and form abscesses. Fig. 114. Fig. 115. DENTIGEROUS CYST DUE TO NON-DEVELOPMENT OF CANINE TOOTH. They generally occur, in the case of unerupted teeth, from some irritation, and are more common to permanent than to deciduous teeth. Inversion of the tooth also appears to be a cause of these C}rsts. Mr. Heath remarks that "when dentigerous cysts occur in the loAver jaAv they form more isolated and prominent tumors than in the case of the upper jaAv, and in some cases the projecting bony Avail has been removed." The treatment of dentigerous cysts consists in a free incision and the removal of the uneruptcd tooth, as a simple puncture will not answer. The front Avail of the cyst should be removed, and the cavity filled with lint, " so as to induce granulation and gradual obliteration." This may be accomplished in the majority of cases Avithout any incision of the integuments. After the removal of a 262 DENTAL PATHOLOGY, THERAPEUTICS. portion of the cyst wall, in the case of dentigerous cysts of the lower jaw, the plates should be pressed together as much as possible; and the same may be accomplished in the case of the upper jaw by the pressure of pads and bandages. Mr. Heath directs that the cyst should always be reached by dividing the mucous membrane Avithin the mouth, and without incising the cheek; but if necessary, a single line of incision only should be made, so that as little after- deformity as possible may be produced. Unilocular cysts are to be treated simply by extracting adjacent teeth, and, after evacuating the contents, when the walls are thin, crushing them in so as to diminish the size of the cavity. Accord- ing to Mr. Eve multilocular cysts, so far from haA'ing a dental origin, are produced by an ingrowth of the epithelium of the gum. They may result from injury, the irritation of decayed teeth, or long con- tinued inflammation. They are of slow growth, and present ATery little tendency to implicate surrounding parts. Multilocular cysts are found in the lower jaw, consisting of cells varying in size from that of a pea to others occupying the entire thickness of the bone. Multilocular cysts may be treated according to the plan of Mr. Butcher, which consists in dividing the mucous membrane over the cyst freely, and then with a gouge and the bone-forceps removing the expanded external plate of the bone, with the contents and lining membrane of the cyst, interfering with the teeth as little as possible, and avoiding the facial artery. Dr. Mason Warren recom- mends a more conservative practice than that of Mr. Butcher. His treatment consists in the puncture of the sac within the mouth, and at the same time obliterating its cavity by crushing; then to keep up, by injections, etc., a sufficient degree of irritation to favor the deposition of new bone. CHAPTER VI. CALCIC DEPOSITS ON THE TEETH. SALIVARY CALCULUS. The color, consistence, and quantity of salivary calculus, or tartar, as it is most commonly called, vary in different temperaments, and upon all of them the state of the general health exercises consider- able influence. The characteristics of this substance, therefore, fur- nish diagnoses, important both to the physician and dentist. Their indications are, in many cases, less equivocal than the appearances SALIYARY CALCULUS. 263 of any other part of the mouth ; but, like those of the gums, should not, perhaps, be alone relied upon. It is necessary to interrogate eA-ery part from which information can be derived concerning the pathological condition of the several organs of the body. Salivary calculus is composed of earthy salts and animal matter. Phosphate of lime and fibrine, or cartilage, are its principal ingredi- ents ; a small quantity of animal fat, however, enters into its com- position, and the relative proportions of its constituents vary accord- ingly as it is hard or soft, or as the temperament of the individual from Avhose mouth it is taken is favorable or unfavorable to health. Hence it is that the analyses that have been made of it by different chemists differ. No two give the same result, The black, dr}^ calculus deposited around the necks of the teeth of such only as have good constitutions, is never in large quantities; it is dissolved in muriatic acid Avith difficulty, while the dry, light- brown calculus found upon the teeth of bilious persons dissolves more readily in it; but the soft, Avhite calculus, found upon the teeth of individuals of neuro-lymphatic temperaments, is scarcely at all soluble in the acids, but is readily dissolved in the alkalies. All persons are subject to deposits of salh'ary calculus, but not alike; it collects on the teeth of some in larger quantities than on those of others, and its chemical and physical characteristics are exceedingly variable. It is sometimes almost wholly composed of calcareous ingredients; at other times these constitute but about one-half, or little more than one-half, of its substance, the remainder being made up of animal matter. Nor is its color more uniform. Sometimes it is black, at other times it is of a dark, pale, or yel- lowish broAvn, and in some instances it is nearly Avhite. It also differs in density. In the mouths of some it has a solidity of tex- ture nearly equal to that of the teeth themsehres; in others, it is so soft that it can be scraped from the teeth with the thumb- or finger-nail. The black kind is the hardest, the Avhite the softest, and its density is increased or diminished as it approaches the one or the other of these colors. Salivary calculus collects in very small quantities on the teeth of persons possessed of the most perfect constitutions, and even on these it is seldom found except on the inner surfaces of the lower incisors next the gums. It is then black, or of a dark brown, very dry, and almost as hard as the teeth, to which it adheres Avith great tenacity. It rarely happens that any unpleasant effects are produced by the presence of this form of calculus upon the teeth. The general health is never affected by it, and the only local injury that results 264 DENTAL PATHOLOGY, THERAPEUTICS. from it is slight turgiditv of the edge of the gums in immediate contact with it. The indications, therefore, of this description of calculus are favor- able, both with regard to the teeth, gums, and organism generally. The teeth upon which it is found are of an excellent quality, and rarely affected by caries. They have the characteristics represented as belonging to the best kind, and teeth of this description are only found among persons having good innate constitutions. There is another form of black calculus, differing from this in many particulars. It is found in the mouths of those having good constitutions, but Avhose physical powers have been enervated by privation or disease, or intemperance and debauchery, and most frequently by the last named. It is found in large quantities on the teeth opposite the mouths of the salivary ducts; it is exceed- ingly hard, and agglutinated so firmly to the organs that it is re- mo\Ted Avith great difficulty; it is very black, has a rough and uneven surface, and is covered with a glairy, viscid, and almost in- sufferably offensive mucus. The presence of this kind of salivary calculus is attended Avith very hurtful consequences, not only to the gums, alveolar processes, and teeth, but also to the general health. It causes the gums to in- flame, swell, suppurate, and recede from the teeth, the alveoli to Avaste, and the teeth to loosen and frequently to drop out. The secretions of the mouth are also vitiated by it, and rendered unfit to be taken into the stomach. Hence, as long as it is permitted to remain on the teeth, neither the skill of the physician nor the best regulated regimen, though they may afford partial and temporary relief, Avill fully restore to the system its healthy functions. As this form of calculus is seldom if ever met with except in con- stitutions naturally excellent, the teeth on which it is deposited are generally sound, but they are often caused, by the disease Avhich is produced in the gums and alveoli, to loosen and drop out. The dark-broAvn caculus is not so hard as either of the descrip- tions of black. It sometimes collects in tolerably large quantities on the loAver front teeth and on the first and second superior molars; it is also often found on all the teeth, though not in as great abundance as on these. It does not adhere with as much tenacity as either of the preceding kinds, and can be more easily detached from them. It exhales a more fetid odor than the first variety, but is less offensive than the second. The persons most subject to this kind of calculus are of mixed temperaments, the sanguineous, hoAvever, always predominating. They may be denominated sanguineo-serous and bilious. Their SALIVARY CALCULUS. 265 physical organization, though not the strongest and most perfect, may, nevertheless, be considered very good. But, being more sus- ceptible to morbid impressions, their general health is less uniform and more liable to impairment than those possessed of the most perfect constitutions. The effects arising from the accumulations of this description of salivary calculus, both local and constitutional, are less hurtful than the variety last noticed; but, like that, it causes the gums to inflame, swell, suppurate, and to retire from and expose the necks of the teeth, the alveoli to waste, the teeth to loosen and sometimes to drop out. It also gives rise to a vitiated condition of the fluids of the mouth. Salivary calculus of a light or pale yelloAvish-broAvn color is of a much softer consistence than the darker varieties, and is seldom found upon the teeth, except of persons of bilious temperament, or those in Avhom this predominates. It has a rough and, for the most part, a dry surface; it is found in large quantities opposite the mouths of the salivary ducts, and sometimes every tooth in the mouth is completely imbedded in it. It contains less of the earthy salts and more of the animal matter than any of the foregoing descriptions, and from the quantity of vitiated mucus in and adher- ing to it, has an exceedingly offensive smell. It is sometimes, though not ahvays, so soft that it may be crumbled betAveen the thumb and finger. Inflammation, turgescence, and suppuration of the gums, inflam- mation of the alveolo-dental periosteum, the destruction of the sockets and loss of the teeth, and an altered condition of the fluids of the mouth, are among the local effects produced by the long- continued presence of large collections of this variety of tartar. The constitutional effects are not much less pernicious. Indigestion and general derangement of all the assimilative functions are among the most common. When the deposit is not large, inflammation and sponginess of such parts of the gums as are in immediate con- tact with it, and fetid breath, are the principal of the unpleasant effects produced by it. White calculus rarely collects in very large quantities, and though most abundant on the outer surfaces of the first and second superior molars and the inner surfaces of the lower incisors, it is nevertheless frequently found on all the teeth. Its calcareous ingredients are less abundant than those of any of the preceding descriptions. Fibrine, animal fat and mucus constitute by far the larger portion of its sub- stance. It is very soft, seldom exceeding in consistence common cheese-curd, to Avhich in appearance it bears considerable resem- 266 DENTAL PATHOLOGY, THERAPEUTICS. blance. Although it exerts but little mechanical irritation upon the gums, it keeps up a constant morbid action in them. Its effects, however, upon the teeth are far more deleterious than any other description of calculus. It causes rapid decay of the organs, and the fluids of the mouth are also vitiated by it. It is only upon the teeth of persons of mucous habit, or those who haA^e suffered from diseases of the mucous membranes, or those in whom these tissues have been more or less involved, that this kind of calculus accumulates. Salivary calculus sometimes accumulates in very large quantities, giving to the mouth a most disagreeable and repulsive aspect, and imparting to the breath, not unfrequently, an almost unsufferably offensive odor. Fig. 116 represents a set of teeth incrusted with it, and Fig. 117 a single tooth, presented to the author by Dr. W. Allen, Fig. 116. Fig. 117. of Massachusetts, with the largest accumulation of this substance he has ever seen in one mass. Its longest diameter is an inch and an eighth, its shortest seven-eighths, and its thickest five-eighths of an inch. Imbedded in its substance is the entire crown and neck of a loAver dens sapientise, which was removed Avith it. It is of a light-brown color, and weighs two drachms and seventeen grains. The late Prof. Austen described an interesting case where every tooth, above and below, had been loosened by alveolar absorption caused by this deposit; no tooth having more than an eighth of an inch depth of socket, and some of them held only by an exceedingly tough attachment to the gum and periosteum. The calculus upon the lower incisors Avas equal to five times the size of the teeth, most of it being on the inside, and three-quarters of an inch thick at the base. A singular peculiarity in this case was the excessive pain of extraction. Small as Avas the attachment, it was uncommonly firm; and the patient, a working-man, was laid up with nervous prostration for tAvo weeks after the operation. CHEMICAL CONSTITUENTS OF SALIVARY CALCULUS. Salivary calculus is composed of phosphate of lime and animal matter; combined in various proportions, accordingly as it is SALIVARY CALCULUS. 267 hard or soft; consequently no tAvo analyses will yield the same result. Schehevetskey gives the following analysis. He found one hun- dred parts to contain: Water and organic matter,.......22.07 Magnesium phosphate,........1.07 Calcium phosphate,.........67.18 Calcium carbonate,.........8.13 Calcium fluoride,.........1.55 100.00 Dr. Stevenson furnishes the folloAving : Friable soft calculus Hard calculus from from molars. lower incisors. Water and organic matter, .... 21.48 17.51 Phosphate of magnesia,.....1.31 1.31 Phosphate of calcium, with a little carbonate and a trace of fluoride, .... 77.21 81.18 100.00 100.00 Hard, dry tartar contains more earthy and less animal matter than the soft, humid tartar. Chemical analysis reveals a large proportion of mucus, as is shown by the folloAving table of Vaquelin and Langier: Phosphate of lime and a little magnesia, .... 66 Carbonate of lime,.........9 Salivary mucus (including ptyalin),.....13 Animal matter soluble in hydrochloric acid, .... 5 Water and loss, . •.......7 100 An analysis of saliva reveals water, ptyalin, fat, chloride of so- dium, chloride of potassium, phosphate of lime, and sulphocyanide of potassium. The infusoria of which M. Mandl says tartar is composed, have their origin in the vitiated mucus which is always mixed Avith it. Scherer detected with a microscope infusoria in large numbers, in the saliva of a girl laboring under a scorbutic affection of the mouth ; but the author is inclined to believe that they had their origin in the mucous secretions of this cavity, which are ahvays mixed with the former fluid. They are more or less numerous, as the tartar is hard or soft, or in proportion to the quantity of mucus that enters into its composition.* * Dr. Dwinelle gives a minute description of their appearance in the first num- ber of the fifth volume of the American Journal of Dental Science. 268 DENTAL PATHOLOGY, THERAPEUTICS. ORIGIN AND DEPOSITION OF SALIVARY CALCULUS. There formerly existed much diversity of opinion as to the source Avhence salivary calculus is derived ; but it is now generally conceded that this deleterious concretion is a deposit chiefly from the sahva, with an admixture of mucus, as the analyses of both these secre- tions reveal the necessary materials in sufficient quantity to form it. Bidder and Schmidt make the phosphates and carbonates amount to very nearly one per cent, in the saliva. All that is necessary, therefore, is that the surfaces of the teeth should have a sufficient affinity for the substance in question to cause a nucleus, which, Avhen once formed, the secretion continues until serious secondary effects are liable to result. In most varieties of salivary calculus there is a notable supera- bundance of the phosphates and carbonates, while in others there is nearly forty per cent, of purely animal matter. Hence the differ- ence in action upon them by acids and alkalies. Of the animal matter entering into the composition of salivary calculus, fibrin, animal fat and mucus are in the largest proportion. Of the existence of the elements of the composition of calculus in the saliva there can be no question. Chemical analyses of this.fluid, direct from the glands, place all doubt upon the subject at rest. Thus it is seen that the chief earthy constituents which enter into the formation of this substance are contained in the saliva. It may also exist in solution in the mucous fluid of the mouth. That the deposition of tartar may take place on one side of the mouth without a similar deposit on the opposite side, furnishes no evidence in support of the doctrine which has been advanced, that it is an exhalation from the capillaries of the mucous membrane of the gums. The mastication of food is, with most persons, performed more on one side of the mouth than on the other; that this function prevents, in a great degree, the accumulation of tartar on the organs immediately concerned, is a fact with which every dentist must be familiar. Hence its frequent collection on the teeth of one side and not on those of the other. And that it is ascribable to this circum- stance is susceptible of positive proof. If, on the removal of the tartar from the teeth of a person in Avhose mouth it has collected only on those of one side, mastication be aftenA'ard altogether per- formed on this side, it will not reaccumulate on them ; and if requi- site attention to the cleanliness of the teeth on the other side be not observed, it will soon collect there, although these teeth had before remained free from it. Again, it often happens that disease of a severe character is ex- cited in the gums by the use of mercurial medicines and other SALIVARY CALCULUS. 269 causes, and yet but a small quantity of tartar collects on the teeth ; but that any condition of the general system, or of the mouth, tend- ing to make the fluids of this cavity more viscid, promotes its for- mation, is undeniable. There are, hoAvever, some temperaments much more favorable to its production than others ; and it is a well- established fact, that the mucous membrane of those in whose mouths it accumulates in largest quantity is the most irritable, and the buccal most viscid. Again, if it were deposited by the mucous fluids of the mouth, it would collect in largest quantities on those teeth which are less abundantly bathed in the saliva; as, for ex- ample, the anterior surfaces of the upper incisors and cuspids, while those opposite to the mouths of the ducts which discharge this fluid into the mouth Avould be less liable to deposits of tartar than any of the other teeth; whereas the contrary is found to be the case. The conclusion, therefore, appears to us irresistible, that this earthy matter is chiefly a salivary deposit, and takes place in the following manner: It is precipitated from the saliva, as this fluid enters the mouth—especially when the secretion is sluggish—upon the surfaces of the teeth opposite the openings into the ducts from which it is poured. To these its particles become agglutinated by the mucus ahvays found, in greater or less quantity, upon them. Particle after particle is deposited, until it sometimes accumulates in such quantities that nearly all the teeth are almost entirely in- crusted Avith it. As regards the points of deposit of salivary calculus, the greatest quantities are found opposite the mouths of the ducts of the sali- vary glands, upon the lingual surfaces of the inferior incisors, cus- pidati and bicuspids, and the buccal surfaces of the superior molars. The necks of the teeth, about the free margins of the gums, afford favorable points for its collection, as here the saliva is longer retained and its calcareous ingredients precipitated, than upon more exposed parts. It first collects about the necks of the teeth in semi-circular or crescent-like lines close to the enamel, under the edge of the gums, and a nucleus being once formed, it rapidly encroaches upon the crown, Avhere it is deposited more abundantly. Certain varieties of salivary calculus adhere to the necks of the teeth Avith great tenacity, and often progress as far as the apex of the root, until the teeth are deprived of their support, and their roots left denuded and exposed. Salivary calculus is never deposited on the flesh, but only upon such substances as represent the teeth or form nuclei, as artificial teeth, for example. It is sometimes de- posited in the ducts, which may be, owing to a sluggish condition 270 DENTAL PATHOLOGY, THERAPEUTICS. of the saliva, in a form known as ranula, and has been removed in a mass as large as a hazelnut. M. Robert presented to the Anatomical Society of Paris a hog's bristle, which had been forced into the duct of Wharton, densely covered with a thick salivary concretion. From the fact that salivary calculus is often found upon parts where the saliva cannot be retained for any length of time, it is evident that it is sometimes precipitated as soon as this fluid enters the mouth. EFFECTS OF SALIVARY CALCULUS UPON THE TEETH, GUMS, AND ALVEOLAR PROCESSES. Although salivary calculus does not directly act injuriously upon the substance of the teeth, but, on the contrary, preserves the part it covers from the action of chemical agents, yet the effects of the presence of this substance are ahvays pernicious, though sometimes more so than at others. An altered condition of the fluids of the mouth, diseased gums, and not unfrequently the gradual destruc- tion of the alveolar processes, and the loosening and loss of the teeth, are among the consequences that result from it. But besides these, other effects are occasionally produced, among which may be enumerated tumors and spongy excrescences of the gums of various kinds, necrosis and exfoliation of the alveolar processes and of por- tions of the maxillary bones, hemorrhage of the gums, anorexia, derangement of the whole digestive apparatus, and foul breath, catarrh, cough, diarrhoea, diseases of various kinds in the maxillary antra and nose, pain in the ear, headache, melancholy, hypochon- driasis, etc. So irritating is its presence that, wherever it comes in contact Avith the gums and alveoli, it causes their absorption, Avhich in some cases may, at first, be attended with little or no incon- venience to the parties ; while in others considerable inflammation, ending in suppuration of the gums, may result, extending to the mucous membrane of the mouth. Periostitis and necrosis of the alveolar processes are also results of the irritating action of this substance. The character of the effects, hoAvever, both local and constitutional, depends upon the quantity and consistence of the tartar, and upon the temperament of the individual as Avell as the state of the general health ; the two former of these are determined by the tAvo latter, and by the attention paid to the cleanliness of the teeth. If this last be properly attended to, salivary calculus, no matter how great the constitutional tendency to its formation, will not collect in large quantity upon the teeth. The importance, therefore, of its constant observance cannot be too strongly im- SALIVARY CALCULUS. 271 pressed upon the patient, especially in those in AArhom there exists a great tendency to its deposition. The teeth and their contiguous parts suffer more from accumula- tions of this substance, than almost any other cause. Caries is not much more destructive to them. "When permitted to accumulate for any great length of time, the gums become so morbidly sensi- tive that a tooth-brush cannot be used without causing pain ; con- sequently, the cleanliness of the mouth is not attempted, and thus, no means being taken to prevent its formation, it accumulates with increased rapidity, until the teeth, one after another, fall in quick succession victims to its desolating ravages. It sometimes not .only undermines the constitution, by occasion- ing discharges of fetid matter from the gums, and corrupting the fluids of the mouth, but it also renders the breath exceedingly un- pleasant and offensive. So nauseating and disagreeable is the odor Avhich some descriptions of tartar exhale, that the atmosphere of a Avhole room is contaminated by it in a feAv minutes. MANNER OF REMOVING SALIVARY CALCULUS. This is an operation of great importance to the health of the gums, alveolar processes, and teeth. But from a misconception of its nature, rather than from fear of pain, many are much opposed to it; and, notAvithstanding the universal admiration in which clean and Avhite teeth are held, they will suffer the beauty of these organs to be destroyed rather than submit to its performance. There are some, indeed, who, though scrupulously particular in everything that regards dress, seem, nevertheless, to consider cleanli- ness of the mouth as unworthy of notice. For the removal of tartar from the teeth, a variety of instruments are necessary, which should be so constructed that they may be easily applied to every part of every tooth. Those in common use among dental practitioners are so very similar in their shape and so Avell known, that we do not deem it necessary to point out the minute differences of construction, or even to give a general descrip- tion of the instruments themselves. The instruments should be light, made Avith ivory, ebony, or cocoa handles, and tapering from a little above the ferule, both ways ; and the points of the instru- ments should be delicately shaped, so as readily to pass below the free edge of the gum. The success of the operation depends much upon the careful removal of every particle of deposit, for which a heavy, clumsy, or large-bladed instrument is wholly unsuited. If any particles of tartar be suffered to remain, they will irritate the gums, and serve as nuclei for immediate re-accumulations. 272 DENTAL PATHOLOGY, THERAPEUTICS. Drs. F. Abbott's and How's sets of scalers, represented in the following figures, are well adapted for removing salivary calculus from all parts of the teeth. Fig.118. The adhesion of salivary calculus to the teeth is sometimes so great that considerable force is required for its removal, even when the sharpest and best-tempered instruments are employed; but or- dinarily it may be removed with ease. Considerable tact, hoAvever, is necessary to perform the operation in a skilful manner; more than most persons, from its apparent simplicity, imagine. This skill can only be acquired by practice. Calculus may be taken from the outer and inner surfaces of the teeth without much diffi- culty ; but the removal of it from between them is more trouble- some, and can only be effected by means of very thin, sharp-pointed instruments. Many, however, prefer scaling instruments with slender points, such as are represented by Fig. 119, which are used Avith a pushing motion in a direction from the hand, instead of toward the hand. Fig. 120 represents a set of five scalers suggested by Dr. How. In removing this substance from the teeth, the point or edge of SALIVARY CALCULUS. 273 the scaling instrument should be applied beloAV the deposit, between it and the gum, and passed A\'ell under, until it comes in contact Avith the surface of the tooth, and the mass scaled off in the direc- tion of the cutting edge or grinding surface. Care is necessary that the edge of the instrument does not roughen the tooth substance, especially the dentine, beyond the enamel. After the removal of the greater part of the deposit, the instrument should be lightly passed over the surface, to detach any particles Avhich may remain, especially upon the approximal sur- faces. After the use of the scaling instruments, finely pulverized Fig. 120. C pumice or silex should be applied on a piece of orange wood so shaped as to reach all parts on Avhich the deposit has collected. The wood-points of various forms, charged with finely-poAvdered pumice or silex, and rotated by means of the dental engine, are very useful for removing the discoloration caused by salivary calculus and the dark mucous deposit, Avhich often cause the teeth to present quite an unsightly appearance. The small tooth-polishing brushes represented by Fig. 121, and 274 DENTAL PATHOLOGY, THERAPEUTICS. the soft-rubber polishing cups suggested by Dr. J. B. Wood, Fig. 122, both operated by the dental engine, will cleanse teeth from remains of calculus after use of scalers and from discoloration even under the free borders of the gums. The cervical margins of fillings may also be polished by the small brushes and cups. Where the surface of the enamel or dentine is found to be rough and without the natural polish, after the use of the pumice or silex, Fig. 121. Arkansas stone and the burnisher may be applied with advantage and a finely polished surface obtained. Several sittings are sometimes necessary for the completion of the operation, especially when the calculus has accumulated in very Fig. 122. large quantities. In all cases of this sort, it should be first removed from betAveen the edges of the gums and the necks of the teeth. During the intervals betAveen the several operations the mouth should be gargled, several times a day, with some cooling and astringent Avash ; but on this subject more particular directions will be given in another chapter. SANGUINARY OR SERUMAL CALCULUS. 275 During the removal of calculus from the teeth, the gums often bleed very freely ; and Avhen much SAvollen and spongy, it may be Avell to promote it by holding tepid Avater in the mouth. When the lower incisors are loose, as is often the case, the operation should be proceeded Avith very cautiously, and the teeth supported by the fin- gers of the left hand holding the jaw, especially Avhen the calculus is very hard and adheres Avith great tenacity. Chemical agents are sometimes employed for the remoA^al of sali- vary calculus, especially such of the vegetable and mineral acids as are supposed to have less affinity for the lime of the teeth than the phosphoric acid Avith Avhich it is combined; but it is scarcely nec- essary to say that any acid capable of dissolving tartar will act upon these organs. The use of all such agents should be most scrupul- ously avoided. Nearly all acids, both mineral and vegetable, as has been shown in another part of this work, are prejudicial to the teeth. Their careless administration by physicians is a fruitful source of injury to the teeth. And they certainly should form no part of any dentrifice, or be in any Avay used for the removal of stains of any kind from the teeth. SANGUINARY OR SERUMAL CALCULUS. By this title Dr. L. C. Ingersoll designates a structureless calcare- ous deposit found at the apex of the root of a tooth, or sometimes extending in a line of granules along the root from the apex to the neck of the tooth, or again encircling the root immediately beneath the free margin of the gum. Being of a sanguinary origin, it is found only where the serum of the blood is present, Avhich, being decomposed, gives up its lime salts, and affords material for the de- posit, Avhich is stained Avith the hematin of the blood. This form of calculus is derived from the serum that exudes from the diseased tissue, and its superior hardness is due to its being more purely min- eral than salivary calculus, and it is generally of a black or dark- green color. Sanguinary calculus is deposited upon the roots of the teeth, and not upon their crowns, as with salivary calculus, being often found upon the very apex of the roots. It also differs in an- other respect from salivary calculus; the sanguinary, resulting from the disorganization of blood, and ulceration of tissues, is in the form of dark, hard granulations approaching crystallization. The root of the affected tooth is denuded of its cementum, and the granular deposit so closely adheres that its removal is quite difficult. Some- times it is found immediately beneath the margin of the gum, in the form of a dark, hard, rough, ring, Avhich may occasionally be visible through the gum, in the form of a dark circle. A viscid, 276 DENTAL PATHOLOGY, THERAPEUTICS. serous fluid may exude from about the neck of the tooth under slight pressure, the result of the ulceration which gives rise to the deposit. This fluid is not of the same nature as the pus from an abscess, being watery and nearly odorless, and composed, in a great part, of the serum of the blood. While salivary calculus causes inflammation, sanguinary calculus is a result of inflammatory ac- tion, and is found upon teeth affected with ulceration. The method of removing sanguinary calculus is referred to in the treatment of alveolar pyrrhcea. MUCOUS DEPOSIT ON THE TEETH. While persons of all ages are subject to deposits of salivary cal- culus, there is a mucous deposit, to Avhich the teeth of children are especially liable, in the form of a brown or a green stain, which has been erroneously called green tartar. This deposit is generally found upon the labial surfaces of the front teeth, more especially upon those of the upper jaw, and varies in color from a light brown to a dark green. From its not collecting upon the posterior teeth and upon the lingual surfaces of the inferior front teeth opposite the mouths of the ducts leading from the salivary glands, there is every reason to conclude that this deposit is not precipitated by the saliva, and hence is altogether different in its origin from salivary calculus. It is generally considered to be a deposit from the mucus, Avhen this secretion is in a more acid condition than is natural. From its effects upon the teeth, when it is alloAved to remain on them for a considerable time, and also from the fact that it is most abundant Avhen the mucus is secreted in large quantities and of a decidedly acid reaction, there is little doubt as to its origin from this secretion. That it is not deposited on all parts of the teeth, is no reason for doubting the correctness of this theory, Avhen Ave consider that the parts upon Avhich it is found are those protected from the friction of food and the movements of the tongue and the flow of the saliva. This form of discoloration of the enamel is indicative of an irrita- ble condition of the mucous membranes and viscidity of the fluids of the mouth. Sour eructations, vomitings, diarrhoea and dysentery are not unfrequent with those whose teeth are thus affected. While the presence of this green stain on lately erupted teeth is almost a certain indication of softened enamel, this is not the case Avhen it is deposited on adult and very dense teeth. It does not appear to be a precipitate from the mucus, as salivary calculus is from the saliva, but is rather a groAvth of fungi upon the surface, and it is yet an open question whether it develops its own acid, as in the case of the MUCOUS DEPOSIT ON THE TEETH. 277 "sprosspilz" lately described by Dr. Miller, or Avhether it retains the neutral secretions to the acidulated stage. According to Wedl, it may " readily be demonstrated that the de- posit is a green, greenish-yellow, uniformly minutely granular mass Avhich is morphologically identical Avith the matrix of leptothrix." In regard to the effects of this mucous deposit upon the teeth, Avhile salivary calculus tends to preserve the portion of tooth-sub- stance on Avhich it is precipitated, this green stain so erodes the enamel that decay advances in the part which it covers, more or less rapidly, according to the quality of the teeth and the length of time it is alloAved to remain. The removal of this mucous deposit re- quires more skilful manipulation than that of salivary calculus, on account of its being a thin film entering into the substance of the enamel, rendering it difficult to detach Avithout injury to the tooth substance; Avhereas salivary calculus is deposited in such quantities as to leave thick incrustations, which are readily scaled off from an uninjured surface. Where the erosion caused by this mucous de- posit is but slight, it may be removed by Arkansas or Superior stones, or by finely powdered silex or pumice stone and Avater ap- plied on a stick of hard, fine-grained Avood, such as orange Avood or hickory; the point of the piece of Avood being so formed as to adapt it Avell to the surface on which it is to be used. The wood-points or small brushes, or soft rubber cups, charged Avith either of the poAV- ders referred to, and rotated by means of the dental engine, Avill prove very serviceable for such an operation. After all the dis- coloration is removed by the means just referred to, the surface should be Avell burnished Avith a steel burnisher and a solution of pure Castile or Avhite Windsor soap. When, hoAvever, the effects of this mucous deposit are more serious, the enamel not only being discolored but deeply eroded, it is necessary to make use of the co- rundum point, rotated by means of the dental engine, the enamel chisel or file, to remove the injured surface. The enamel chisel is to be preferred to the file in all cases Avhere it is applicable; and the plain surface thus obtained should be polished Avith fine silex or pumice stone, Arkansas or Superior stones, and the burnisher. Care is necessary in the use of the enamel chisel, to avoid wounding the neighboring soft tissues. To prevent the possibility of such an accident, and to enable the operator to have control over his instru- ment, the chisel should be held firmly with the hand in such a manner as to alloAV the thumb to rest on an adjoining tooth. When the dentine is very sensitive, as is frequently the case, a proper agent for allaying the sensitiveness may be applied from time to time to the surface, as the operation of cutting it away proceeds. (See " Treatment of Sensitive Dentine.") 278 DENTAL PATHOLOGY, THERAPEUTICS. CHAPTER VII. THE FLUIDS OF THE MOUTH. In treating upon the physical characteristics of the fluids of the mouth, it will not be necessary to dwell at much length on their ef- fects, when in a morbid condition, on this cavity. Concerning their agency in the production of caries of the teeth, Ave shall add one or two remarks. Saliva, in healthy persons having good constitutions, has a light frothy appearance, and but little viscidity. Inflammation of the gums, from whatever cause produced, increases its viscidity, and causes it to be less frothy. In a healthy state, it is inodorous, floats upon and mixes readily Avith water, but Avhen in a viscid or diseased condition, it sinks and mixes Avith it with difficulty. Irritation in the mouth, from diseased gums, aphthous ulcers, in- flammation of the mucous membrane, the introduction of mercury into the system, or taking anything pungent into the mouth, in- creases the flow of this fluid, and causes it to be more viscid than it is in its natural and healthy state. In treating on the symptomatology of saliva, Prof. Schill says, " The sympathetic affection of the stomach in pregnancy is some- times accompanied by salivation, which, in this case, mostly takes place after conception, and sometimes continues to the time of de- livery. It is also observed to occur in Aveakened digestion, in gastric catarrhs, after the use of emetics, in mania, in Avhat are called ab- dominal obstructions, in hypochondriasis and hysteria; salivation occurs during the use of mercury or antimony. " In confluent smallpox, salivation is a favorable sign. If it cease before the ninth day, the prognosis is bad. In lingering intermit- tents, salivation is sometimes critical; more frequently in these affections it precedes the termination in dropsy. " Diminution of the salivary secretion, and, in consequence of this dryness of the mouth, is peculiar to the commencement of acute disease, as also to the hectic fevers occasioned by affections of the abdominal organs. If the Aoav of the saliva stop suddenly, there is reason to apprehend an affection of the brain. " Thick, viscid sahva occurs under the same circumstances as the diminution of the salivary secretion, especially in smallpox, typhus, and in hectic fevers. It is thin in ptyalism. In gastric diseases, where the liver participates, it becomes yellow or green; by the ad- mixture of blood it may assume a reddish color; in pregnant or lying- THE FLUIDS OF THE MOUTH. 279 in Avomen, it is sometimes milky; an icy-cold saliva was observed by the author in face-ache. " Frothy saliva from the mouth is observed in apoplexy, epilepsy, hydrophobia, and in hysterical paroxysms." Dr. Bell, of Philadelphia, in a note to the work from Avhich we have just quoted, says, "Acid saliva is regarded by M. Donne as indicative of gastritis or deranged digestion. Mr. Laycock," he observes, " on the other hand, infers from numerous experiments on hospital patients that the saliva may be acid, alkaline, or neu- tral, Avhen the gastric phenomena are the same. In general, Mr. L. remarked that it was alkaline in the morning and acid in the even- ing." We have had occasion to observe that the acid quality of the saliva Avas more apparent and more common in lymphatic, mucous and bilious dispositions, than in sanguineous or sanguineo-serous persons, and that weakened or impaired digestion ahvays had a tendency to increase it. M. Delabarre says, " When this fluid" (the saliva) " has remained in the mouth some moments, it there obtains new properties, accord- ing to each individual's constitution and the integrity of the mucous membrane, or some of the parts Avhich it covers. " In subjects Avho enjoy the best health, Avhose stomach and lungs are uninjured, the saliva appears very scarce, but this is because it passes into the stomach almost as soon as it is furnished by the glands that secrete it. It only remains long enough in the mouth to mix with a small quantity of mucus, and absorb a certain portion of atmospheric air, to render it frothy. " On the other hand, the saliva of an individual whose mucous system furnishes a large quantity of mucus, is stringy and heavy; is but slightly charged Avith oxygen, contains a great portion of azote and sulphur, and stains siher." Increased redness and irritability of the mucous membrane of the mouth is an almost invariable accompaniment of general acidity of these fluids. Excoriation and aphthous ulcers, and bleeding of the gums, also, frequently result from this condition of the salivary and mucous secretions of this cavity. Anorexia, languor, general depression of spirits, headache, diar- rhoea, and rapid decay of the teeth, are very common among persons habitually subject to great viscidity of the buccal fluids. It is like- Avise among subjects of this kind, and particularly when the vis- cidity is so great as to cause clamminess of these secretions, that the green discoloration of the enamel of the teeth is most frequently met Avith. 280 DENTAL PATHOLOGY, THERAPEUTICS. CHAPTER VIII. CHARACTERISTICS OF THE LIPS. The indications of the physical characteristics of the lips are more general than local, and the observations of Laforgue and Dela- barre on this subject leave little to be added. We cannot, therefore, do much more than repeat Avhat they have said. " The lips," says Delabarre, " present marked difference in differ- ent constitutions. They are thick, red, rosy, or pale, according to the qualities of the blood that circulates through their arteries." Firmness of the lips, and a pale rose color of the mucous mem- brane that covers them, are, according to Laforgue, indicative of pure blood, and, as a consequence, of a good constitution. Redness of the lips, deeper than that of the pale vose, is also mentioned as one of the signs of sanguineo-serous blood. Soft, pale lips are in- dicative of lymphatico-serous dispositions. In those subjects the lips are almost entirely without color. When there is a sufficiency of blood, the lips are firm, though variable in color, according to the predominancy of the red or serous parts of this fluid. Both hardness and redness of the lips, and all the soft parts of the mouth, are enumerated among the signs of plethora. Softness of the lips, without change of color in their mucous membrane, is spoken of by the last author as indicative of deficiency of blood; and softness and redness of the mucous membrane of the lips are signs that the blood is small in quantity and sanguineo-serous. Deficiency in the red corpuscles, and in the nutritive qualities of the blood, is evidenced by the want of color and softness of the lips, and general paleness of the mucous membrane of the Avhole mouth. " The fluids contained in the vessels," says Laforgue, " in forms of anaemia, yield to the slightest pressure, and leave nothing between the fingers but the skin and cellular tissue." In remarking upon the signs of the different qualities of the blood, the above-mentioned author asserts that the constitution of children about six years of age cannot be distinguished by any universal characteristics; but that the lips, as well as the other parts of the mouth, constantly betoken "the quality' of blood and that of the flesh;" and, " consequently they proclaim health or disease, or the approach of asthenic and adynamic disorders, Avhich the blood either causes or aggravates." Again, he observes that the blood of all children is "super- abundantly serous," but that it is redder in those of the second con- CHARACTERISTICS OF THE TONGUE. 281 stitution than in those of any of the others, and that this is more distinctly indicated by the color of the lips. "The quality of the blood," says he, "is necessary to dispose all the parts to elongate in their growth. When the proportions of the constituent elements of the blood are just, groAvth is accomplished Avithout disease. If the proportions are otherwise than they should be for the presenta- tion of the health, or if one or more of its elements be altered, health no longer exists, growth is arrested altogether, or is performed irregularly. The nutritive matter is imperfect, assimilation is pre- vented or impaired. On the other hand, its disintegration decom- poses the patient; if death does not sooner result, it will consume him by the lesion of some vital organ." The changes produced in the color of the blood by organic de- rangement are at once indicated by the color of the lips. The accuracy of Laforgue's observations on the indications of the physical characteristics of the lips has been fully confirmed by subsequent writers. " The secretion of the lips," says Prof. Schill, " has a similar diag- nostic and prognostic import to that of the tongue and gums. They become dry in all fevers and in spasmodic paroxysms. A mucous Avhite coating is a sign of irritation or inflammation of the intes- tinal canal; accordingly, this coating is found in mucous obstruc- tions, in gastric and intermittent fevers, in mucous fever, and before a gouty paroxysm. A dry, brown coating of the lips is a sign of colliquation in consequence of t^yphus affections; it is accordingly observed in typhus, in putrid fever, in acute exanthemata, and inflammations Avhich have become nervous." The lips, however, do not present so great a variety of appearance as those of other parts of the mouth, for the reason that they are not as subject to local diseases; but their general pathological indi- cations are, perhaps, quite as decided. CHAPTER IX. CHARACTERISTICS OF THE TONGUE. The appearance of the tongue, both in health and disease, is re- garded by physicians as furnishing more correct indications of the state of the constitution and general health than any of the other parts of the mouth. It is asserted, hoAvever, by others, and by those,, too, Avho have the very best opportunities for inspecting the various 282 DENTAL PATHOLOGY, THERAPEUTICS. parts of this cavity, that the lips and gums furnish as marked and reliable indications as the tongue. That the state and quality of the blood can be as readily ascertained by an examination of these parts as by that of the tongue, is, Ave believe, undeniable; but that the pathological condition of the body can be inferred is a question we leave for others to decide. So far as the quality of the blood and the temperament of the subject are indicated by the color of the tongue, the preceding re- marks concerning the lips Avill be found applicable, the one being as much influenced by them as the other. It Avill, therefore, be un- necessary to recapitulate Avhat Ave have before said upon the subject. The effects produced upon the mucous membrane of the tongue by disease in any other part, are said to be analogous to those pro- duced on the general integument. So, also, are the changes of its color, consistence, humidity and temperature, similar to those of the skin. We are likewise told that the changes of its coating agree with the analogous changes of the perspiration, and that these phe- nomena are more decided in acute than in chronic affections. But the diagnostic and prognostic indications of the tongue vary according to the temperament and constitutional predisposition of the individual. The physician should acquaint himself Avith its appearances in health, to be able to determine correctly its indica- tions in disease. He should likeAvise inform himself of the changes produced in its appearance by certain morbid conditions of the body. In some subjects it is ahvays slightly furred and rather dry, especially near its root; in others it is always clean and humid ; in some, again, it is always red, and in others pale. Prof. Schill divides the signs of the tongue into objective and subjective. " To the objective belong the changes of size, form, con- sistence, color, temperature, secretion, and of power and direction of motion; and to the subjective belong the anomalous sensations of taste." In enumerating the pathognomonic signs of the tongue, this author says that hypertrophy, inflammation or congestion, may occasion its enlargement; and that inflammatory SAvelling of it, when arising from acute diseases, such as " angina, pulmonary in- flammation, measles, plague, or variola, yields an unfavorable prog- nosis. Even non-inflammatory SAvelling of the tongue is a danger- ous phenomenon in acute diseases, especially cerebral, Avhich are combined Avith coma. If it be the consequence of mercury, of the abuse of spirituous drinks, of gastric inflammation, of chlorosis, of syphilis, or if it occur in hysteria or epilepsy, the prognosis is not dangerous; but the disease is ahvays the more tedious where the CHARACTERISTICS OF THE TONGUE. 283 tongue swells than Avhere it does not. It is enlarged, also, by de- generescence and cancer. " Diminution of the size of the tongue takes place where there is considerable emaciation. In this case it continues soft and movable. If, in acute states, the tongue becomes small, and is, at the same time, hard, retracted and pointed, the irritation is very great and the prognosis bad. This sign occurs more especially in typhus, in the oriental cholera, in inflammation of the lungs, and in acute cerebral affections. In hysteria and epilepsy this phenomenon has no unfavorable import." Internal maladies, he says, seldom cause the form of the tongue to change; but that the simplest change arising from chronic irri- tations of the stomach, chronic dyspepsia, and acute exanthemata, is enlargement of its papilla?. In cases of protracted dyspepsia, the edges of the tongue sometimes crack, and in paralysis and epilepsy it becomes elongated. In acute diseases, a soft tongue is a favorable indication ; and flaccidity of it is symptomatic of debility. Humidity of the tongue, he tells us, is a favorable sign, and that dryness of it occurs in acute or violent inflammations and irrita- tions, and more particularly Avhen seated in the intestinal canal and respiratory organs. "This also happens in diarrhoea, typhus, pneu- monia, gangrene of the lung, pleuritis, peritonitis, enteritis, catarrh us gastricus, gastritis, inflammation of joints, etc. Among the higher degrees of dryness he enumerates the rough, the fissured and burnt tongue as furnishing still more unfavorable indications, informing us, at the same time, that if these be not accompanied by thirst, they prognosticate a fatal termination. The abatement and crisis of the disease is indicated by the tongue becoming moist." Dr. Bell, of Philadelphia, in a note to Prof. Schill's observations on the tongue, says, " A rough and dry, and even furred tongue is seen in some dyspeptic persons Avho sleep with the mouth open; and although it indicates an irritation of the digestive organs, it is not a bad augury." Bilious persons, not unfrequently, though not troubled Avith any manifest symptoms of gastric or intestinal de- rangement, or any other apparent functional disturbance, have a furred tongue in the morning. Paleness of the tongue, says Prof. Schill, is a sign of a serous con- dition of the blood, of chlorosis, of great loss of blood, of chronic disorders, of sinking of the strength in acute maladies assuming a " nervous form, as typhus and scarlatina maligna. It is also found," says he, " in enteritis and dysentery, Avhen but little fever is present." He infers from this that paleness of the tongue is caused bv the 284 DENTAL PATHOLOGY, THERAPEUTICS. " drawing of the fluid downward ;" but it is often observed in per- sons Avho enjoy tolerably good health. Lymphatic dispositions, as has been before remarked, are peculiarly subject to it. Again he observes that a very red tongue is indicative of " vio- lent inflammation, mostly of the intestinal canal, but also of the lungs and pharynx, also of acute exanthemata. He regards the prognosis as bad, when a furred tongue, "in acute diseases of the intestinal canal, becomes clean and very red," if the change is not accompanied Avith the return of the patient's strength. " But," he continues, " if the debility is not considerable, and the tongue becomes clean and very red while other febrile symptoms continue, a new inflammation may be expected." But even in affections like these, the redness of the tongue is always more considerable in sanguineous than in lymphatic or lymphatico-serous subjects, so that in forming a prognosis from this sign, the temperament of the individual should never be overlooked." Proceeding with the description of the signs of this organ, he says, '" The tongue becomes a blackish-red and bluish-red in all serious disturbances of the circulation and respiration, as also in severe diseases of the lungs and heart, as catarrhs, suffocations, asthma, extensive inflammations of the lungs, carditis, Asiatic cholera, confluent smallpox, and putrid fevers. It becomes black and livid in cases of vitiation of the blood, more especially in scurvy, at the setting in of gangrene, and in phthisis, Avhen death is near at hand." Among the diseases mentioned as giving rise to an increase of the temperature of the tongue, are glossitis, violent internal inflamma- tion, and typhus fever; and coldness of this organ is observed to take place in Asiatic cholera, and at the approach of death. The signs from the secretion of the tongue are thus enumerated: A clean and moist tongue are favorable indications, but a clean, dry and red tongue, as seen in sIoav, nervous fevers, acute exanthemata and plague, are bad auguries. A furred or coated tongue is said to occur chiefly in intestinal disorders, diseases of the lungs, skin, and in rheumatic affections. The coating is said to vary in " color, thickness, adherence, and extent," and different kinds of secretion from the mucous membrane of this organ are mentioned as occur- ring in different diseases, and it should have been added in the same disease in different temperaments. After describing the various kinds of coating on the tongue, together Avith their respective indications, Avhich it is not necessary here to enumerate, the occurrence of false membranes and pustules, resulting from peculiar forms of mucous secretion, are next men- DISEASES OF THE DENTAL PULP. 285 tioned. The former shoAV themselves either as small Avhite points, or large patches and sometimes they are said to envelop the Avhole tongue. The color is " sometimes Avhite, sometimes yelloAv, and sometimes red," and the greater the surface covered by them, the more unfavorable is the prognosis regarded. " Pustules on the tongue," says our author, "are sometimes idiopathic, but in most cases symptomatic. They are either distinct or confluent; the con- fluent are the worst. Those Avhich are hardish and dry, and also those which are blue, and those of a blackish appearance, Avhich sometimes occur in acute disease, are of an unfavorable import." On the other hand, those Avhich have a AA'hitish, soft, moist, and semi-transparent appearance, are less unfa\rorable, and Avhen the aphthae, or eruption, are repeated, it portends a longer continuance of the malady. The pustules or aphthae are mentioned as being frequent accompaniments to the folloAving diseases, namely : gas- tritis, catarrhs, enteritis, metritis, dysentery, cholera infantum,peri- tonitis, intermittent and typhus fevers, pleuritis, pneumonia, and the third stage of pulmonary consumption. Their prognosis is said to be favorable Avhen they "appear with critical discharges after the seventh day," and unfavorable Avhen they occur as a consequence of a general sinking of the physical powers of the body. But it is unnecessary to enumerate all of the pathognomonic indi- cations of the various morbid phenomena described by semeiolo- gists; we have noticed more of them than Avas our intention to have done. We shall, therefore, conclude the present inquiry, by simply observing that the indications furnished by the physical charac- teristics, not only of the tongue, but by those also of the teeth, the gums, salivary calculus, the lips, and fluids of the mouth, are, as Ave have endeavored to shoAV, essential to the successful exercise of the duties both of the dental and medical practitioner. CHAPTER X. DISEASES OF THE DENTAL PULP. The pulp of a tooth, from the high degree of vitality Avith Avhich it is endoAved, is one of the most sensitive structures of the body, and, like other parts, is liable to become the seat of various morbid phenomena. Its susceptibility to morbid impressions is influenced by a variety of circumstances, such as temperament, habit of body, the state of the constitutional health, the condition of the hard 286 DENTAL PATHOLOGY, THERAPEUTICS. structures of the tooth, etc. A cause, which under some circum- stances would not be productive of the slightest disturbance, might, under others, give rise to active inflammation, with all its painful and disagreeable concomitants. Increased irritability (hyperesthe- sia) may exist independently of any organic change, either in the pulp, dentine, or enamel. Examples are often met with in females during gestation; but it arises more frequently as a consequence of caries than from any other cause connected with the teeth. Even before the disease has penetrated to the central chamber of the organ, the pulp often assumes a most Avonderful and marked in- crease of irritability, either from functional disturbance arising from decomposition of the dentine, impaired relationship between the tAvo, or from being more exposed to the action of external deleteri- ous agents. Impaired digestion, as Avell as a disordered state of other functions of the body, frequently produces the same effect. The susceptibility of the pulp to impressions of heat and cold, and of acids, is ahvays increased by heightened irritability. When this exists to any considerable degree, the mere contact of these agents Avith the tooth is often productive of severe pain, which, on their removal, usually very soon subsides. The pulp, hoAvever, may remain in this condition for months, and even years, Avithout be- coming the seat of inflammatory action. Preternatural sensibility of the dentine, whether in a sound or partially decomposed state, augments very appreciably the irrita- bility of the pulp. The sensibility of dentine is sometimes so much increased that the mere contact of any hard substance Avith a part which has become exposed by the destruction of a portion of the enamel, is often productive of severe pain. Impressions of heat and cold convej^ed through the conducting medium of a metallic filling, or through a thin covering of dentine, as sometimes happens when a considerable portion of the tooth has been worn away, is a very fre- quent cause of heightened irritability of the pulp. W7ith its sus- ceptibility thus increased, the impressions produced by these agents are often a source of irritation, and even of inflammation and sup- puration, causing the death of the entire crown and inner walls of the root of the tooth. At other times, the irritation is only followed by slight increase of vascular action and an effusion of plastic lymph over the affected part of the pulp, Avhich is gradually converted into osteo-dentine; and thus a barrier is interposed betAveen it and the irritating agents. Hyperasmia and Irritation.—The pulp of a tooth may become the seat of severe pain even when there is no inflammation. The slightest increase of vascular action, a condition knoAvn as hypersemia, when DISEASES OF THE DENTAL PULP. 287 this organ is in a preternaturally irritable condition, is productive of more or less irritation. The pressure of even slightly distended vessels upon the nervous filaments distributed upon it, at such times, is sufficient to cause great pain. Hyperemia of the dental pulp may exist in any degree, accord- ing to the increased amount of blood which expands its vessels. Tin- coronal portion of the pulp, what is generalhy known as its " bulb," exhibits the greatest distension under such conditions, and the pain resulting is often sharp and lancinating, and even paroxys- mal in character. The pain from hyperemia is often referred to other organs, such as the ear, face, and in fact to any part of the distribution of the fifth pair of nerves. Hyperemia ma}T result in diffuse inflammation of the pulp Avhen the red blood-globules escape through the pulp-tissue, Avhich generally occurs at the point Avhere the distension is greatest. This condition is liable to occur in sound teeth as Avell as in carious ones. Within certain limits hyperemia is a physiological condition, an impression induced by a temporary excitant, which soon passes away Avithout injury to the parts involved. But Avhen the cause is sufficient to bring about repeated attacks, the vessels of the pulp fail to contract, and remain distended Avith blood, and the affected organs become very suscep- tible to even slight thermal changes, and the hypersemia becomes pathological instead of physiological. The treatment for hyperemia of the dental pulp consists in the removal of the cause of irritation and the protection of the tooth from all thermal and other influences which may cause repeated distensions of its vessels with blood of more than the normal quantity. In the case of carious teeth, the use of non-conducting filling-materials is indicated; in cases of other- Avise healthy and sound teeth, they should be protected from thermal changes until the susceptibility to such influences has passed away. Dr. G. V. Black recommends for the latter cases a closely-fitting gutta-percha cap as a protection. Impressions of heat and cold are conveyed more readily to the pulp when the dentine is in a morbidly sensitive condition, and Avhen this is the case, they produce a more powerful effect. The remedial indications of pain in a tooth arising simply from irritation of the pulp, consist in the remoA'al of the primary and exciting causes. When produced by impressions of heat and cold conveyed to it through the conducting medium of a metallic filling and intervening super-sensitive dentine, if the severity and con- tinuance of pain is such as to warrant the belief that it will give rise to inflammation, the filling should be removed and some non-con- ducting substance placed in the bottom of the cavity before replac- 288 DENTAL PATHOLOGY, THERAPEUTICS. ing it. If this is done before inflammation actually takes place, it will prevent subsequent irritation from these causes. It is worthy of remark, hoAvever, that the pain thus produced is in proportion to the sensibility of the subjacent dentine. If this is destroyed pre- viously to filling the tooth, irritation of the pulp will be as effectually prevented as by the interposition of a non-conducting substance. But in the application of agents for this purpose, there is danger of destroying the vitality of the pulp. The employment of them, however, is resorted to more frequently to prevent pain during the removal of caries than to relieve any subsequent irritation from impressions of heat and cold. (See Sensitiveness of Dentine.) Although a frequent cause, yet a metallic filling is not the only medium through which impressions of heat and cold are conveyed to the dental pulp. When the dentine on the coronal extremity or side of a tooth becomes very thin from loss of substance, occasioned by mechanical or chemical abrasion, by the use of the file, erosion, or other cause, the pulp sometimes becomes painfully susceptible to the action of these agents. Loss of substance from any of these causes is also often attended by exalted sensibility of the exposed dentine; and Avhen this is the case, the contact of acids with it is productive of more or less pain. Nature, hoAvever, usually prevents the painful consequences that would naturally rise from continued abrasion of the coronal ends of the teeth, and the consequent ex- posure of their nervous pulp, by the gradual ossification of this organ ; so that by the time it would become exposed, it is converted into osteo-dentine. But this does not always take place in time to prevent irritation and pain. When irritation of the pulp occurs in a tooth that has been cut away on one or both sides, so much so as to leave only a thin cover- ing of dentine, the best known means of preventing morbid sensi- bility is to keep the filed surface constantly clean by frequent fric- tion Avith a brush and waxed floss silk, or with some other suitable substance. This operation should be repeated after each meal, and in the morning immediately after rising, and at night before going to bed. The application of nitrate of silver, for sensitiveness aris- ing from loss of substance or from exalted sensibility of exposed dentine, has proved successful. The nitrate in the solid form may be applied by enveloping a portion of the stick Avith wax, which will enable the operator to handle it with impunity. Or the end of a silver wire may be dipped in nitric acid and the application be thus made to the sensitive surface, taking care to protect the adja- cent parts. Some are in the habit of applying salt, as soon as the DISEASES OF THE DENTAL PULP. 289 sensitive surface has been touched Avith the nitrate, to neutralize its effects. To prevent contact with the gum, Avhen it is necessary to apply the nitrate to the necks of the teeth, a coating of collodion may be painted on them with a camel's-hair brush. Chromic acid has also been used in these cases with success. The careless use of the burr, and also of sand-paper disks, in the dental engine, may also induce irritation of the dental pulp on account of the heat generated by such agents. When caries has extended to the central cavity, irritation is often produced by contact of partially decomposed portions of dentine or other foreign matter with the pulp. The proper remedial indi- cation in such cases, it is scarcely necessary to say, consists in the removal of all matter from the teeth that can either act as a me- chanical or chemical irritant. This done, the cavity in the tooth, supposing the pulp to be in a healthy condition, should be properly filled. But Avhen the irritation arises as a consequence of exalted irrita- bility and increased vascular action of the pulp, dependent upon disease or altered function of some other part or parts of the''body, the remedial indications are different. The treatment then should be addressed to the primary affection. Examples of this sort are of frequent occurrence. They are met with almost daily, particularly in females during gestation, in dyspeptic individuals, and in persons affected Avith gout and chronic rheumatism. They are also some- times met Avith in individuals who have been exposed to miasmatic emanations of marshy districts, when the irritation assumes an intermittent form, occurring at stated intervals of tAventy-four, forty-eight, or seventy-tAvo hours, and continuing from one to three hours. Some of the worst forms of toothache are produced by one or other of these causes. The local disturbance, when it occurs in females during pregnancy, may generally be removed by mild aperients, warm foot-bath, and anodynes at night on going to bed. When it depends upon other kinds of derangement of the uterine organs, treatment suited to the peculiar indications of the case should be instituted. When it occurs in a person affected with dyspepsia, rheumatism, or gout, the constitutional treatment required by the particular disease con- stitutes the proper remedy. Wrhen the irritation assumes an inter- mittent form, an emetic or cathartic, followed by quinine, will generally put a stop to the local disturbance, provided it has no con- nection Avith caries of the crown of the tooth. 19 290 DENTAL PATHOLOGY, THERAPEUTICS. INFLAMMATION—PULPITIS. The pulp of a tooth, when healthy, has a grayish-white appear- ance, and its capillaries are invisible to the naked eye, but when it becomes the seat of acute or active inflammation, they may be dis- tinctly seen, as the organ then assumes a bright red color. Inflam- mation, having established itself, soon extends to every part of the pulp, and even to the alveolo-dental periosteum. When permitted to run its course uninterruptedly, it usually terminates in suppura- tion in from three to eight or ten days. The unyielding nature of the walls of the cavity in Avhich it is on all sides inclosed renders expansion of the pulp impossible, and as its capillaries become distended with blood, they press on the ner- vous filaments AAdiich are everywhere distributed upon it, causing at first constant gnaAving pain; which afterward, as the distention of the vessels increases, becomes severe, deep-seated, throbbing, and sometimes almost insupportable. Inflammation may attack the pulps of sound teeth as Avell as those affected with caries ; but it occurs more frequently in the latter than in the former, and it is oftener met with before than after the pulp has become actually exposed. The severity of the pain, however, is determined by the condition of the tooth, the state of the general health, and the causes concerned in its production. The pulp, Avhen in an irritable condition, is more liable to become the seat of acute inflammation than when in a perfectly healthy state, and the occurrence of suppuration is soon folloAved by alveolar abscess, unless an opening is made immediately through the crown, neck, or root of the tooth, for the escape of the matter. The effusion of lymph, which takes place during the inflammatory stage, and which, under other circumstances, and Avhen the inflam- mation is less severe, is made to play an important part in the reparation of the injury, compresses the pulp into still narrower limits as it accumulates in quantity, and thus becomes an additional source of irritation, adding fuel to the flame already lighted up. Inflammation of the pulp may be caused by a bloAV on the tooth ; by impressions of heat and cold conveyed to it through the enamel and dentine, or through a metallic filling; or by the pressure of a filling, or the direct contact of external irritating agents, such as disorganized portions of the tooth, particles of alimentary substances, acrid humors, etc. But, as Ave have stated in another place, inflam- mation of the dental pulp is not always a necessary consequence of impressions of heat and cold; pain may be produced by them INFLAMMATION--PULPITIS. 291 Avhen it does not exist; but in this case it usually subsides soon after the remoA'al of the irritant. The exposure of the pulp by decay is a common cause of inflammation of the organ, also abra- sion and the careless preparation of a cavity for the insertion of a filling, although in rare cases the pulp of a tooth may be exposed for months, and subjected several times a day to the actual contact of foreign bodies, Avithout becoming the seat of acute inflammation. The irritation and increased vascular action thus occasioned are, no doubt, removed by the effusion of lymph to Avhich they give rise, and the pulp, after it has become exposed, having room to expand as its vessels become distended, does not suffer irritation from the pressure to AAdiich it Avould otherAvise be subjected. When suppuration takes place, the pain very nearly ceases, but the tooth for a time remains sore to the touch, and its appearance is changed. It has no longer the peculiar animated translucency of a living tooth, but has assumed an opaque, muddy, or brownish aspect. With the disorganization of the pulp, the entire crown and inner Avails of the root lose their vitality ; still, if the alveolo-dental periosteum has not become seriously involved in disease, the vas- cular and nervous supply furnished to the cementum is often suf- ficient to prevent the tooth from exerting any injurious influence upon the surrounding and more highly vitalized parts. The cemen- tum, being more analogous in structure to true osseous tissue than dentine, iioav plays an important part in the animal economy. It being more liberally supplied Avith vitality and with nutrith7'e juices, and not being sensibly affected by the death of the other parts of the organ, it keeps up the living relationship of the tooth with the alveolo-dental periosteum, at least sufficiently to prevent it from acting perceptibly as a morbid irritant. Inflammation of the pulp of a tooth, besides the local pain with Avhich it is attended, often gives rise to a train of constitutional morbid phenomena, usually of a mild, but sometimes of an aggra- vated and even threatening character. Among these are headache, constipation of the bowels, furred, tongue, dryness of the skin, quick, full, and hard pulse, earache, ophthalmia, disease of the maxillary sinus, etc. The amount of constitutional disturbance arising from inflamma- tion of the pulp of a tooth depends on the state of the general health, and the nervous irritability of the system at the time. In the majority of cases it occasions but little inconvenience, and disap- pears as soon as the inflammation ceases, but sometimes it, assumes a very alarming character. A fatal cases of tetanus, produced by inflammation of the pulp of a lower molar, occurred, a number of years ago in Baltimore. The subject Avas a young, lady about. 292 DENTAL PATHOLOGY, THERAPEUTICS. eighteen years of age. The system at the time, from great bodily fatigue and mental excitement, was in an exceedingly irritable condition, but in other respects, though constitutionally rather del- icate, she was in the enjoyment of good health. There is not an organ or tissue of the body in which acute inflam- mation is more intractable in its nature and rapid in its progress, than in the pulp of a tooth; and when we take into consideration its situation, and its physical and vital peculiarities, it is not to be Avondered that it should, in so large a majority of the cases, termi- nate in the disorganization of the part. Still, it may sometimes be arrested, and the remedial indications here, though they cannot be as readily and fully carried out, are the same as for inflammation in any other part of the body. The first and most important one consists in the removal of all local and exciting causes. For simple exposure of the pulp, without sloughing, the first step, after removal of all irritants from the carious cavity, is to attempt the reduction of inflammation and the prevention of the effusion of serum or lymph, by cleansing the exposed surface Avith tepid Avater, and, after care- ful drying, to bathe it with dilute tincture of aconite, Avhen it may be covered with a thin coating of a solution of gutta-percha in chloroform, or glycerine, or collodion carefully applied, and the tooth protected from irritation. Some prefer the use of a prepara- tion composed of crystallized carbolic acid rendered fluid by a small quantity of chloroform. This preparatory treatment, if successful, is to be folloAved by the process of "capping the pulp," as described in another place. If it be the result of irritation produced by the pressure of a filling, the plug should be immediately removed, leeches applied to the gum of the affected tooth, and, if the patient be of a full habit, blood may be taken from the arm, and a brisk saline purgative prescribed. The removal of the filling, however, when the inflammation has previously made much progress, will not prevent suppuration, but it may keep it from extending to every part of the pulp. When an external opening is made for the escape of the matter, the moment suppuration takes place the remaining portion of the pulp will be relieved from the pressure Avhich caused the irritation, and then the inflammatory action may cease. But if the matter remains in the central cavity of the tooth, the part of the pulp Avhich has not suppurated will still be subjected to pressure, and the inflammation and suppuration will go on until the entire organ perishes. Nor will the disorganizing process stop here. The alveolo- dental membrane at the extremity of the root will soon become implicated, and in a short time alveolar abscess will form, thus ter- minating the acute stage of the disease. INFLAMMATION—PULPITIS. 293 There may be no indication of irritation or inflammation for several weeks, or even months, after a tooth has been filled ; but at the expiration of this time, the pulp, from increased irritability, caused perhaps by some change in the state of the patient's general health, may be attacked by inflammation. Although this very sel- dom happens, it does, nevertheless, sometimes occur. When there is reason to apprehend that it is about to take place—and it may be suspected if pain is felt in the tooth AArhen anything hot or cold is taken into the mouth, or if it becomes the seat of gnaAving or gradually increasing pain—the filling should be removed. If the pain now ceases, a thick layer of gutta-percha dissolved in chloroform, or Hill's stopping, or os-artificiel, or oxy-phosphate of zinc preparation, may be placed in the bottom of the cavity, and the filling replaced ; using the precaution, as before directed, to introduce the gold in such a way as to prevent the liability of depressing the floor of the cavity ; or a temporary filling of some plastic non-irritating sub- stance, such as Hill's stopping or the oxyphosphate of zinc, may be inserted and permitted to remain for some time, Avhen a more dura- ble filling may be introduced. But if the pain and inflammation continue unabated, and the application of such escharotics as car- bolic acid, chloride of zinc, nitrate of silver, and chromic acid, fails to reduce the congestion, it may be necessary to extract the tooth, or expose the pulp, and destroy its vitality by applying to it some powerful escharotic. When this is done, it is usually Avith the view of securing the retention and preservation of the tooth by filling the pulp-cavity and root, an operation now very frequently performed by dentists. The abstraction of blood directly from the pulp, one might sup- pose, would often be successful in arresting the inflammation; but Ave do not think this has been resorted to for this purpose sufficiently often to determine its therapeutic value. At any rate, it seems rea- sonable to suppose that if, by this means, the congestion of the capillaries could be removed, the tumefied pulp would be reduced to its natural size, and be relieved from the pressure to which, as a consequence of its distended condition, it is subjected. To obtain the largest amount of benefit capable of being derived from the operation, the opening should be made in that portion Avhere one of the principal arteries Avould be most likely to be punctured; and this, it seems to us, Avould be just where the canal of the root enters the chamber of the crown of the tooth. But in making the puncture here, the pulp being very small at this point, there is danger of cutting it off; and as reunion might not take place, the portion in the central cavity would necessarily perish. 294 DENTAL PATHOLOGY, THERAPEUTICS. If the pulp were exposed, there would be a better opportunity of relieving the congested condition of its capillaries by the abstraction of blood ; but the difficulty of obtaining free access to the organ by drilling a hole through the intervening dentine is very great; the tooth, Avhen suffering from inflammation, being usually so sore to the touch that the slightest pressure is productive of great pain. Depletion of the pulp may be accomplished by means of a fine, sharp-pointed instrument; or Dr. Allport's method of treating ex- posed pulps may be resorted to, namely, that of excising a portion of the pulp at the orifice of exposure, and then draAving the edges together so as to induce union by first intention. If the tooth is an incisor or cuspid, and the pulp cannot be restored to health, its vitality should be destroyed ; or, if suppuration has preATiously taken place, an opening should be made into the chamber of the tooth as before directed, for the escape of the matter. Should it be found, after this has escaped, that disorganization has not extended to even'' part of the pulp, the remaining portion may be destroyed in the manner hereafter to be described. This done, the pulp-cavity and root may be filled, as soon as the inflammation of the socket has completely subsided. Dr. Black takes exception to the statement of C. A. Harris, Wedl, Tomes and Salter, that inflammation of the pulp is of frequent oc- currence before the exposure of the organ, and he is of the opinion that the great mass of the cases occur coincidently Avith the exposure or afterward. Chronic inflammation of the dental pulp often occurs where the chamber of a tooth has become gradually exposed by caries of the dentine; and Avhen this happens, the action of the fluids of the mouth, and of other foreign substances which obtain access to the cavity, as Avell as of the decomposed portions of the tooth-substance, causes an increase of vascular action in the exposed part, followed very often by a slight discharge; but the morbid action thus induced is comparatively seldom accompanied by pain. The pulp may re- main thus partially exposed for months, and even years, Avithout causing any other inconvenience than a momentary twinge of pain Avhen some hard substance is accidentally introduced into the cavity of the tooth, which subsides immediately after its removal. Sooner or later, hoAvever, the pain thus excited will become more permanent, continuing, each time it occurs, from five to ten minutes to one or more hours after the cause of the irritation has been removed. If a tooth be filled under such circumstances, the pressure of the fluid upon the pulp, which is poured out from its exposed surface beneath he filling, will give rise to a more general and active form of in- INFLAMMATION--PULPITIS. 295 flammatory action. Pain is often experienced before actual exposure of the pulp occurs. The liability of the tooth to ache increases as the pulp becomes more and more exposed by the gradual decomposition of the den- tine ; and the inflammation may ultimately assume a more active form, Avhen the pain becomes very acute, owing to the consequent effusion into tissue surrounded by unyielding Avails, or the pulp may become the seat of fungous groAvth or it may be absorbed or de- stroyed by ulceration, or by gangrene and mortification. Cases sometimes occur in Avhich the disease is attended Avith severe dart- ing pains, often occurring several times in the space of tAvo or three minutes, succeeded by intervals of perfect ease for many hours. At other times it is attended by dull, aching pains, aggravated by taking SAveet or acid substances into the mouth. In cases of this sort, the application of heating or stimulating substances to the exposed sur- face of the pulp will usually procure relief. Permanent exemption from pain, hoAvever, is not always obtained and sooner or later it may become necessary either to destroy the pulp or to extract the tooth. In some cases, hoAvever, where the pulp becomes exposed by the action of caries, no pain is experienced except by contact of foreign substances with the exposed surface. The body of the pulp, when the organ becomes exposed from a decayed opening in the grinding surface of a molar, is sometimes absorbed, Avhile its prolongations in the roots often remain unchanged for tAvo or more years. Exposure of the pulp is usually attended with ulceration—a disor- ganizing process, which often causes the destruction of a large portion of the part occupying the central chamber of the crown of the tooth, making in it numerous little excavations. The ulcerated surface usually presents a yelloAvish appearance, that of an irritatable ulcer, with the exudation of a serous or sanguino-serous fluid, a condition hoAvever, Avhich must not be confounded Avith a state of suppuration. The exuded fluid is very offensive, as it rapidly decomposes, and its reaction is alkaline; Avhen the disorganizing process is arrested before it has effected the destruction of any very large portion of the pulp, it usually becomes covered Avith healthy granulations. When the inflammation occurs in cachectic individuals it often assumes an acute form, and sometimes terminates in gangrene and mortification. The loss of vitality may be confined to the body of the pulp, or it may extend to every part of the organ. In the former case the pain continues, but in the latter it ceases as soon as morti- fication takes place. When this happens, the entire pulp, Avhich 296 DENTAL PATHOLOGY, THERAPEUTICS. has now a dark-brown or black color, may be removed. But this is not a very common termination. The symptoms of chronic as well as acute inflammation are always modified by the state of the general health, habit of body, and the temperament of the individual. The pain attending the former, hoAvever, is periodical, occurring at irregular and uncertain intervals, and constitutes that variety of toothache so often relieved by local applications; whereas, in the latter, it is constant. In chronic inflammation, Avhich implies a state of ulceration, the pulp is either actually exposed or only covered by decomposed or partially decomposed dentine, and the diseased surface rarely em- braces a larger circumference than that described by the bottom of the decayed caAdty. The inflammation, therefore, is local as Avell as chronic, but nevertheless, it is often of so persistent a character as to render its removal exceedingly difficult. The dentist, how- ever, is not so much restricted in the application of remedies as in the treatment of acute inflammation, and to the action of which it yields more readily. But notwithstanding all this, he will neces- sarily encounter difficulties in his efforts to subdue it. A greater length of time is sometimes required than the patient is willing to give; and the opening through the crown to the central cavity is frequently too small, previously to the removal of the partially de- composed dentine, to admit of the direct application of the neces- sary remedial agent to the inflamed surface of the pulp. Again, it often happens, that the situation of the tooth and cavity are such as to prevent a complete view of the diseased part. It is important that the operator should get such a view to enable him to determine whether the inflamed surface is ulcerated, or pours out a serous fluid; or whether the morbid condition is simply one of irritation, produced by the presence of acrid matter, or of partially or wholly decomposed dentine. Unless his diagnosis is correct, his prescription will be as likely to do harm as good; but, having ascertained the exact character of the disease, he may often be able to institute treatment that will result in the restoration of the pulp and the preservation of the tooth. It is important, too, to understand the part which nature plays in the curative process; for cure here, as in other parts of the body, is effected by that internal force which, as Chomel says, " presides over all the phenomena of life, contends unremittingly Avith physi- cal and chemical laws, receives the impressions of deleterious agents, reacts against them, and effects the resolution of disease." This vital force is sometimes exercised in the cure of disease in the pulp INFLAMMATION—PULPITIS. 297 of a tooth, but more frequently in its prevention; as is shown by the gradual ossification of the organ in those cases where it would othenvise become exposed by mechanical or spontaneous abrasion of the solid structures Avhich inclose it; and occasionally by the formation of secondary dentine upon the surface of the original or primary dentine at a point toward Avhich the caries is advancing. Nature, no doubt, would always provide in this Avay against the exposure of the pulp, if the occurrence Avere ahvays long enough preceded by sufficient irritation or increase of vascular action in it to call her energies into operation. But the formation of osteo- dentine, Avhich constitutes the protective Avail of defence, is a tardy process, and, as a general rule, proceeds more slowly than the caries in the tooth, Avhich causes the exposure of the pulp. Besides, it often happens that its approach is not announced by the slightest irritation, a condition necessary to the new formation, until it reaches the central cavity. At other times, the approach of the disease gives rise to too much irritation, a condition equally unfavorable to the dentinification of the pulp. Thus, no protective covering being formed, it soon becomes exposed, when it is subjected to the action of such irritating agents as may chance to be brought into contact Avith it. Hence, its liability to become the seat of chronic inflam- mation as Avell as other forms of diseased action. If the disease is attended Avith pain, the removal of this must first claim attention, and should be effected Avith as little delay as possible; othenvise the morbid action may extend to every part of the pulp and peridental membrane, and assumes more active and unmanageable form. If the pain is the result of irritation produced by the direct action of mechanical or chemical agents, the cavity in the tooth should at once be carefully freed from all extraneous sub- stances and decomposed portions of dentine. This done, a dossil of raAV cotton or lint—saturated Avith spirits of camphor, laudanum, sulphuric ether, chloroform, creosote, or some one of the essential oils—may be applied. The folloAving anodyne application has been employed Avith advantage to relieve the pain arising from congestion of the pulp : Cotton saturated with a solution composed of alcohol, 1 ounce; chloroform, 2 ounces; ether, f ounce; gum camphor, i ounce; tincture of opium, i ounce; and oil of cloves, 1 drachm. When the pain is relieA'ed another application, consisting of carbolic acid and oil of cloA^es, is made and permitted to remain for some fifteen minutes. A paste composed of iodoform and glycerine is also employed after the active symptoms of congestion have sub- sided. For the treatment of Avounded and irritated pulps the tincture of 298 DENTAL PATHOLOGY, THERAPEUTICS. calendula proves a very useful remedy. Such agents as glycerole of thymol, carvacrol, oil of eucalyptus, tannic acid, lead water, mor- phine, creosote, chloral, and tincture of aconite, have also been found serviceable in the treatment of inflamed conditions of the pulp. When the irritation is produced by acidulated buccal fluids, the application of carbonate of soda, or some other alkali—tepid water containing sufficient carbonate of soda to make it slightly alkaline —Avill often give immediate temporary relief; but as the condition of the secretions of the mouth, especially the salivary, is usually owing to gastric derangement, the correction of this constitutes the first and most important remedial indication. When any applica- tion is made to the pulp for the purpose of removing irritation and pain, its full effect will not be obtained unless the fluids of the mouth are excluded from the cavity of the tooth ; this may be done by closing the orifice with softened wax, or cotton saturated with the sandarach solution, using the precaution not to force it so far as to press the application previously made upon the exposed pulp. Suppuration of the Pulp.—Independent of the condition knoAvn as alveolar abscess, the pulp of a tooth is liable to suppuration when exposed for a considerable time, by the formation of either an ab- scess Avithin its substance, or, more frequently, by a superficial sup- puration on its surface. In such cases, layer after layer of the substance of the organ is destroyed at the point of exposure, and inflammatory elements or products take their places. The layer of odontoblasts is disorgan- ized as a result of superficial inflammation, and becomes a mass of sanious pus filled with micro-organisms. Deep pockets are formed in the substance of the pulp by the suppurative process, and a sec- tion of the organ is progressively destroyed from the exposed sur- face in the direction of the root. This progressive suppuration and destruction may continue until a small portion only remains in the apical portion of the root-canal, or the entire organ is destroyed. Many histologists are disposed to question the theory that the dental pulp ever recovers after suppuration is once established in it, while some contend that cicatrization and ability to perform its functions are possible after such attacks. Suppuration of the pulp generally commences in the form of small collections of pus within the layer of odontoblasts Avhich may retain their distinct forms for some time, when they may coalesce. Deeper in the structure of the pulp a large abscess may undermine the layer of odontoblasts, and if the pus generated under such cir- INFLAMMATION--PULPITIS. 299 cumstances is greater in quantity than the cavity for its retention, compression and strangulation of the pulp result, causing the de- struction of the organ. The pain accompanying abscess of the pulp generally commences Avith a slight gnawing sensation, Avhich per- sistently increases in severity until it becomes very excruciating. When decomposition of the entire pulp occurs, gas is generated Avhich, by its pressure, gives rise to severe pain, and the trouble is only relieved by a vent being made for the escape of the gas and secretion. It is seldom, however, that gas is formed within the liv- ing pulp, although there are cases sometimes met with Avhere gas is generated in a closed pulp-cavity during the progress of the suppu- ration in the pulp. A small amount of pus in a pulp-chamber may undergo absorption, or even fatty degeneration, but such cases are rare. The causes of suppurative pulps may be enumerated as follows: Mechanical ATiolence,such as bloAvs; the careless regulating of teeth; the rapid separation of teeth by wedges, screAVS, etc., or separation by any method Avhen the condition of the system contraindicates such an operation; thermal influence through a metallic filling, and especially in the case of young teeth; exposure of the pulp to irri- tating agents. A dead pulp may remain quiet for months, or even years, and if not exposed by caries, even for many years, but the action of the atmosphere may in a very short time cause inflamma- tion of the peridental membrane; hence it is often a question Avhether teeth in Avhich dead pulps are quiescent should be inter- fered Avith. But as all such teeth are liable to cause periodontitis and alveolar abscess the treatment of such cases, Avhere no expo- sure exists, is to make an opening with a drill into the pulp- chamber, the entrance of the instrument being easily recognized by its sudden opening into such a space. When this is effected, an antiseptic agent, such as oil of eucalyp- tus, iodoform in the form of an etherial saturated solution, or per- manganate of potash, should be introduced into the pulp-cavity, taking care to leave a vent through the temporary filling Avhich is to confine the antiseptic agent. The remains of the devitalized pulp should be removed at a second sitting, by means of a barbed broach, and a second application of the antiseptic made. Such treatment should be continued until all odor of decomposition has disappeared, and the cavity will permit of being closed tightly Avithout trouble ensuing. The antiseptic agent must be thoroughly applied, so that it may pass into ever}'- part of the pulp-cavity and the dentinal tubes. It should be remembered that the product of 300 DENTAL PATHOLOGY, THERAPEUTICS. decomposition, which is principally sulphuretted hydrogen exhib- ited in the form of gas, is not only rapidly developed, but exerts great pressure in the apical space; hence the roots of a tooth thus affected should not be filled until there is every reason for believing that the decomposition has been overcome. It may be necessary in these cases to continue the antiseptic treatment for several weeks before filling the pulp-cavity, although immediate root-filling, even in such cases, has its advocates. Degeneration of Structure.—This condition may result from a low degree of inflammation of the pulp Avhen long continued, which has the effect of so reducing its volume that it presents a shrivelled ap- pearance, and to which the term " mummified " has been applied. The pulp-cavity in such cases is entirely free from any products of decomposition, and the tooth retains its natural color. This affection appears to be more common to teeth of a dense structure, and has been ascribed by writers on this subject to a gradual oblit- eration of the tubuli by a deposit of secondary dentine, which in- terferes Avith nutrition to such a degree as to produce attenuation. The original cells of the tissue disappear and are changed into fine fibres, and areolae are developed in the matrix, and the sensibility of the pulp is either greatly diminished, or altogether destroyed, the latter being the condition of completely mummified pulps. Dental pulps in such a condition never become a source of irrita- tion, and the only treatment required is the removal of the remains of the attenuated organ and the filling of the pulp-cavity. Spontaneous Disorganization.—The spontaneous destruction of the pulp of a tooth is an affection which seems to have been for a long time overlooked by Avriters on dental pathology; and, although it is one which rarely occurs, examples of it are met with sufficiently often to entitle it to a place among the diseases of the teeth. The first case which attracted the attention of the author occurred in 1836, and he has subsequently met with six or seven others. In each of them the disorganization had been carried on so insidiously, that neither the presence of disease nor structural alteration Avas suspected, until the teeth had assumed a dull broAvnish or bluish- brown appearance. The death of the pulp had not been preceded in any of these cases by the slightest indication of inflammatory action. It had apparently resulted from want of sufficient vital energy to sustain the nutritive function. The alveolar cavities of the affected teeth in these cases were, seemingly, in a healthy condition—a circumstance A\dnch, when Ave take into consideration that the parts of the extremity of the roots INFLAMMATION—PULPITIS. 301 Avere exposed to the action of the disorganized remains of the dental pulps, may appear somewhat strange. But this may have been owing, partly, to diminished excitability in the alveolo-dental peri- osteum, and partly to the smallness of the quantity, and the innoc- uous character of the matter contained in the central cavities of the teeth. The gums of that portion of the alveolar border occupied by the affected teeth had a pale, grayish-purple appearance, but ex- hibited no indications of actual disease. They Avere as thin and their margins as distinctly festooned here as in any other part of the mouth. In some instances, the teeth had been in this condition for seven or eight years. On perforating the crowns, only a drop of dark-brown matter, about the consistence of thin cream,and having but little odor, escaped from the pulp cavity of each. In all the cases which the author has seen of this remarkable affection, the loss of vitality had taken place previously to the tAventieth year of age, and, according to his observations upon the subject, it seldom confines itself to a single tooth, but occurs sim- ultaneously in corresponding teeth. The pulps of several usually perish at about the same time. In the first case to Avhich his atten- tion Avas called, six had lost their vitality. The affection, too, seems to be principally confined to the incisors and cuspids, and sound teeth appear to be as subject to it as those AA'hich are carious. Noav, as the disorganization of the pulp, in cases of this sort, is not the result of inflammatory action, it must be dependent upon constitutional rather than local causes—upon some peculiar ca- chexia, Avhich causes the function of sanguinification to be imper- fectly performed. This inference, too, seems to be fully warranted by the appearance of the subjects in all the cases Avhich the author has had an opportunity of examining—characterized by an ex- tremely pale and slightly bloated aspect of countenance, indicating a serous condition of blood. The remedial indications in cases of this sort are the same as in necrosis produced by inflammation and suppuration of the lining membrane and pulp. Fungous Groivth.—The pulp of a tooth, when exposed by decay of the croAvn, sometimes becomes the seat of a fungous groAvth, in the form of a small Arascular tumor, the formation of Avhich is caused by constant irritation. These morbid growths sometimes attain the size of a large pea, completely filling the cavity made in the croAvn of the tooth by decay; at other times they do not exceed that of a small elderberry. The former have little sensibility, and bleed freely from the slightest injury; the latter are less vascular, but are nearly as sensitive as the pulp in a healthy state. 302 DENTAL PATHOLOGY, THERAPEUTICS. It often happens that a fungous groAvth of the gum or dental periosteum, finding its way through an opening in the side of the neck or root of a decayed tooth, appears in the central cavity, and is sometimes mistaken for a morbid growth of the pulp. But the character of a fungous growth or polypus of the pulp can be readily determined by its attachment to the portion of the organ occupying the pulp-chamber by a constricted neck. Such fungous growths have a dark-red color and a fleshy or spongy consistence. Such fungous growths are more common to the pulps of the inferior molar teeth when caries has hollowed out the crowns to a con- siderable degree. Such tumors usually grow very fast, and some- times attain the size of a hickory nut. They are exceedingly vas- cular, bleeding profusely when wounded, and are soon reproduced after removal. The author has met Avith tumors of this kind which had originated in the alveolo-dental periosteum of the extremity of the root. The only remedy in many cases of fungous groAvth of the pulp is the removal of the tooth. A cure cannot be effected by extirpating the morbid growth. The author has frequently removed them nearly to the extremity of the root, but they have ahvays reap- peared in a few days or weeks after the operation. A pulp in this condition resists the action of arsenious acid when applied for its devitalization. Where there is a tendency to fungous growth of the pulp, the ap- plication of an escharotic has proved serviceable. Of these agents chromic acid appears to be very effective. Another method is to apply carbolic acid freely to the fungous growth, to obtund its sensitiveness, excise it, and then make an ap- plication of nitric acid on a disk of card-board. A method of treat- ing such fungous groAvth is described by Dr. Maercklein as follows: After carefully removing all foreign substances and carefully dry- ing the cavity, apply the tincture of iodine with a pledget of ab- sorbent cotton or bibulous paper until the entire growth is covered with the iodine; after Avhich seal the cavity in the usual manner. This should be repeated every twenty-four hours until it has been completely destroyed. If the fungous growth should fill the entire cavity, take small pledgets of the paper or cotton saturated with the iodine and place them between the fungoid and the walls of the cavity until as much pressure has been made as is consistent with the comfort of the patient, but in no case giving pain. This dress- ing is repeated daily until sufficient room has been obtained to proceed as in the first case. It frequently happens, however, that teeth in this condition are too far gone to justify their retention. INFLAMMATION—PULPITIS. 303 Ossification.—Allusion has been made several times, in the course of this Avork to the ossification of the dental pulp, as a means em- ployed by nature to prevent the exposure of this most delicate and exquisitely sensitive structure. But examples of it are occasionally met with in teeth Avhich have suffered no loss of substance, either from mechanical or spontaneous abrasion, or from the decay of the dentine. The occurrence, whatever may be the circumstances under which it takes place, is evidently the result of the operation of an established law of the economy, dependent upon moderate irrita- tion and a slight increase of vascular action ; ossification having commenced, it usually goes on until every part of the pulp is con- verted into a substance analogous to cementum. We infer, then, that when the pulp of a tooth becomes the seat of a sufficient amount of irritation, ossification must folloAV as a necessary conse- quence ; but if the irritation be succeeded by active inflammation, a different result may be expected. The irritation necessary for the ossification of the pulp of a tooth sometimes arises from constitutional causes; but in the majority of cases, it results from the action of local irritants, and most fre- quently from impressions of heat and cold, communicated through the medium of a metallic filling or a thin layer of dentine. During the ossification, a sensation is occasionally experienced in the tooth somewhat similar, though altogether less in degree, to that Avhich attends the knitting of the fractured extremities of a broken bone. A numb, vibratory pain, barely perceptible, is first felt passing through the tooth several times a day, but only lasting a second or tAvo at a time. It is often scarcely sufficient to occasion any annoyance, or to attract anything more than momentary attention. As the ossified deposit increases in size, pain of a neuralgic char- acter may ensue, and similar to the sensation Avhich results from the knitting together of the fractured extremities of a bone,but not constantly severe. At times, however, the pain becomes sharp and darting, affecting the side of the face and head. The treatment consists in the application of an anodyne, such as lead Avater, about the affected root and the opening of the pulp-chamber, in order to remove the affected pulp, Avhich should be completely extirpated. With the ossification of the pulp, the crown and inner walls of the root lose their vitality, but the appearance of the tooth is not, as is the case of necrosis arising from the disorganization of the pulp, materially affected. The central cavity being filled Avith semi-translucent osteo-dentine, the croAvn retains its natural color. 304 DENTAL PATHOLOGY, THERAPEUTICS. The discoloration and opacity attending necrosis produced by other causes result partly from the presence of putrid matter in the pulp- cavity, and partly from its absorption by the surrounding dentinal wall. Odontalgia.— Pain in a tooth, toothache, or odontalgia,* as it is technically termed, is a symptom of some functional or structural disturbance, either of the organ in which the pain is seated, or of some other part or parts of the body, but more frequently of the former than of the latter. So variable is the character of the sensa- tion, that any description Avould fail to convey to one who has never experienced it a correct idea of its nature. The pain sometimes amounts only to slight uneasiness; at other times the agony is almost insupportable. It may be dull, deep-seated, boring, throb- bing, or lancinating. It may be slight at first, gradually increasing in severity until it amounts to the most excruciating torture, or it .may come on without any premonition whatever. It may be con- fined to a single tooth, or it may affect several at the same time. It may commence in one tooth and pass from thence to another, and continue until every one in turn has been attacked. It may continue for hours and days Avith scarcely any cessation; or it may be intermittent, the paroxysms recurring at stated or irregular intervals, and each lasting from thirty minutes to one, tAvo or more hours. The causes of odontalgia are almost as numerous as are the varie- ties of character which it exhibits. Irritation and inflammation of the pulp, and inflammation of the investing membrane, are among the most frequent; but it is sometimes referable to a morbid condi- tion of the nerve or nerves going to a single tooth, or of the trunk from which several teeth are supplied; also to derangement of the digestive organs, to increased nervous susceptibility of the uterus resulting from pregnancy, amenorrhcea, etc., and to certain diatheses of the general system. Inflammation of the peridental membrane and pulp may be pro- duced by a blow upon a tooth, or by powerful impressions of heat and cold communicated through the enamel and dentine, or through a metallic filling ; but it is more frequently occasioned by pressure, or by the direct contact of irritating agents, such as carious portions of the tooth, particles of food, acrid humors, and other irritating * So much has been said upon this subject in the consideration of the different forms of inflammation of the pulp in the preceding pages, that but little remains to be noticed. INFLAMMATION —PULPITIS. 305 external substances. But inflammation is not always a necessary consequence of such impressions. Pain maybe produced by them Avhen inflammation does not exist; in this case it usually subsides soon after the remo\ral of the irritant. Indeed, the pulp of a tooth may be exposed for months, and subjected seA'eral times every day to the contact of foreign substances, without becoming the seat of inflammatory action; and in the absence of this, the pain, though coming on Avith the suddenness of an electric flash, and often of the most excruciating kind, is seldom of long duration. But Avhen inflammation exists, the pain, Avhich at first amounts only to a slight gnaAAung sensation, is more constant; after a Avhile it assumes a throbbing character, and if not promptly arrested, it increases in severity, and continues until suppuration of the lining membrane and pulp takes place. So long as it is confined to the parts Avithin the pulp-cavity, the pain is not increased by pressure on the tooth, nor is the tooth started from the socket, as in period- ontitis. The locality of the inflammation may also be distinguished by the fact that cold Avater or ice applied to the tooth generally gives relief. But the inflammation rarely confines itself long to the in- terior of the tooth ; it usually soon extends to the periosteum of the root and its socket, Avhen a someAA'hat different train of phenomena are developed. Suppuration, hoAvever, having taken place, an abscess soon forms at the extremity of the root. The severity of the pain attending pidpitis (as inflammation of the pulp is technically termed), is doubtless, owing to the fact that this exceedingly sensitive structure, as its vessels become injected, is prevented from expanding by the unyielding nature of the Avails of the cavity in AA'hich it is situated. Its capillaries being thus dis- tended, must, as a necessary consequence, press upon the nerves Avhich are everyAvhere distributed through it, and the excruciating painful, throbbing sensation, by Avhich this variety of odontalgia is characterized, is produced by the pulsation of these vessels. Hence, increased action of the heart and arteries, from Avhatever cause pro- duced, augments the pain ; it is also more severe at night, Avhile the body is in a recumbent posture, than during the day, because this position gives an increased fulness to the arteries of the head. The phenomena attending the inflammation, however, are influenced very much by the condition of the tooth and the habit of body of the patient. When the inflammation is acute, it extends to every part of the pulp and lining membrane. It also occurs more frequently before than after these tissues have become exposed, and generalh7 termin- ates in suppuration. Chronic inflammation usually arises from 20 306 DENTAL PATHOLOGY, THERAPEUTICS. partial exposure of the pulp, and may exist for months Avithout being attended Avith pain; but the pulp, when thus affected, is more susceptible of injury by heat or cold, and by irritating substances; and the liability of the tooth to ache, especially at night, is greatly increased. Odontalgia, caused by acute inflammation of the investing mem- brane, is characterized by pain, at first dull, afterward acute and throbbing, soreness and elongation of the tooth, redness and tume- faction of the gums, and sometimes by swelling of the cheek; indi- cating the formation of alveolar abscess. In this variety of odon- talgia, the tooth is often so much raised in its socket as to interfere more or less Avith mastication. The pain attending the foregoing pathological conditions, Avhen severe and protracted, is often accompanied by constipation, head- ache, dryness of the skin, flushed cheeks, fulness and increased rapidity of pulse, and other constitutional symptoms. The nervous susceptibility of the teeth is sometimes so much in- creased by organic and even functional disturbances of other and often remote parts, that the mere contact of the minute nerves of the pulp and the lining membrane against the Avail of dentine which encases them is attended Avith severe pain. This variety of odontalgia is termed sympathetic, and is supposed to be the result of the transfer of nervous irritation, or more properly, of exalted sensi- bility of the dental nerves, arising from a morbid condition or func- tional disturbance of some other part. If this hypothesis be true, it is probable that with this heightened nervous excitability there is a slight increase of vascular action in the pulp, \vith a correspond- ing increase of size in its capillaries ; in consequence of which, it is fair to presume the nervous filaments supplying these tissues Avould be apt to respond painfully to the undue pressure. Though pain arising from this cause may have its seat in sound as Avell as in decayed teeth, it occurs more frequently in the latter than the former, OAving to the fact that any structural alteration in the den- tine adds to their already increased nervous excitability. Persons of highly excitable nervous temperaments, pregnant fe- males, and individuals laboring under derangement of the digestive organs, are particularly subject to this variety of odontalgia. Odon- talgia, arising from pathological conditions or functional distur- bances of other parts, assumes a great variety of forms. The pain may be continued, but more frequently it is periodical; it may be confined to a single tooth, or it may attack half a dozen or more at the same time. It sometimes also alternates Avith the paroxysms of rheumatism or gout, the pain in such cases assuming the specific character of these diseases. INFLAMMATION—PULPITIS. 307 Mr. W., aged forty, for fifteen years the victim of gout, came to me in 1830. The first right upper molar was carious, but the pulp not exposed. Ten or twelve days before each attack of gout, recur- ring every three or six months during the last five years, this tooth Avas the seat of a peculiar grinding, lancinating pain, becoming gradually more severe, but ceasing entirely as the gout-symptoms came on ; it returned as these subsided, and continued for tAvo Aveeks. Filling the tooth gave temporary relief only, and it Avas found necessary to extract it. In Avhat is termed neuralgic odontalgia, " the pain," says Dr. Wood, "is usually of the acute character; sometimes mild in the beginning, gradually increasing in intensity, and as gradually declining, but usually very irregular; at one time moderate, at another severe, and occasionally darting Avith excruciating violence through the dental arches. Not unfrequently it assumes a regular intermittent form. Instead of pain, strictly speaking, the sensation is sometimes of that kind which is indicated Avhen Ave say that the teeth are on edge, and is apt to be excited by certain harsh sounds, such as that produced in the filing of a saAv, or by mental inquietude, and by the contact of acids or other irritant substances. Neuralgic toothache sometimes persists, Avith intervals of exemption, for a great length of time. The diagnosis is occasionally difficult. When, however, it occurs in sound teeth, is paroxysmal in its character, is attended Avith little or no swelling of the external parts, occupies a considerable portion of the jaAv, and especially Avhen it alternates or is associated with pain of the same character in other parts of the face, there can be little doubt as to its real nature." This variety of sympathetic toothache is perhaps induced by caries, or by the manner in Avhich the teeth are arranged in the alveolar arch, or by some peculiar susceptibility of the parts; as is sIioavii by the fact that the pain usually ceases on the removal of all such causes of irritation. But Avhile, on the one hand, pain in the teeth may be caused by a morbid condition of other organs, these organs, on the other hand, frequently sympathize with the diseased condition of the teeth, and become, to quote the language of Mr. Bell, "the apparent seat of pain. I have seen this occur not only in the face, over the scalp, in the ear, and underneath the loAver jaAv, but doAvn the neck, over the shoulder, and along the Avhole length of the arm." Cases of this sort are frequently met Avith. In treating of odontalgia, Dr. Good observes: " This is often an idiopathic affection, dependent upon a peculiar irritability (from a cause Ave cannot easily trace) of the nerves subservient to the aching tooth, or of the tunics by Avhich it is covered, or of the periosteum, 308 DENTAL PATHOLOGY, THERAPEUTICS. or the fine membrane that lines the interior of the alveoli. But it is more frequently a disease of sympathy, produced by pregnancy, or chronic rheumatism, or acrimony in the stomach, in persons of an irritable habit. It is still less to be wondered at that the nerves of the teeth should often associate in the maddening pain of facial neuralgia, or tic douloureux, as the French Avriters sometimes term it; for here the connection is both direct and immediate. In con- sequence of this, the patient, in most instances, regards the teeth themselves as the salient points of pain (as they unquestionably may be in some cases), and rests his only hope of relief upon ex- traction ; but when he applies to the operator, he is at a loss to fix upon any particular tooth. Mr. Fox gives a striking example of this, in a person from whom he extracted a tooth which afforded little or no relief; in consequence of Avhich his patient applied to him only tAvo days aftenvard and requested the removal of several adjoining teeth, Avhich were perfectly sound. This he objected to, and sus- pecting the real nature of the disease, he immediately took him to Sir Astley Cooper, Avho, by dhuding the affected nerve produced a radical cure in a feAv days." The author is acquainted with a gentle- man similarly affected. He has had all his teeth on the right side of both jaAvs extracted Avithout obtaining any relief. There is still another cause of odontalgia, Avhich Ave should not omit to mention—exostosis; but from the obscurity of the diagnosis, the existence of the affection can seldom be determined with positive certainty, except by the removal of the tooth. As Ave have already had occasion to treat of this disease, it is unnecessary in this place to dAvell upon the subject. Finally, some teeth, from peculiar constitutional idiosyncrasy, are more liable to odontalgia than others. It sometimes happens that every tooth in the mouth is destroyed by caries without being affected Avith pain, while at other times teeth apparently sound become the seat of the most agonizing torture. The first thing to be attended to in the treatment of odontalgia is the removal of the causes which have given rise to it; this can only be done by carrying out the curative and remedial indications of the morbid conditions and functional disturbances with Avhich it is connected. While these continue, it will be impossible to obtain permanent relief. The sensibility of the nerves supplying a tooth may often be obtunded, and the pain palliated by the application of stimulating and anodyne agents to the exposed pulp; but the relief thus procured is seldom of long duration. Wrhen their effects subside, the pain usually returns Avith increased severity. W7hen the pain arises from chronic inflammation and irritation, produced by external agents on an exposed portion of the lining membrane, INFLAMMATION—PULPITIS. 309 such applications may often be employed Avith great adATantage: and among those AAdiich have been used for this purpose are creosote, the oil of cloves, cinnamon, etc., laudanum, spirits of camphor, tan- nin, ether, and chloroform. But of all the remedies prescribed by the author, he has found none more useful in allaying the pain than the folloAving: R. Sulphuric ether, . . 5J. R. Sulphuric ether, . . . ,^j. Powdered camphor, . gij. Creosote, .... ,^ss. Powdered alum, . . ^ij. Ext. of nutgalls, . . . gj. Sulphate of morphine, . gr. ij. Powdered camph, . . . .^ss. The alum should be very finely powdered, and all the ingredients well mixed before use. R. Chloroform. R. Chloral. Tinct. opii, aa . . ,^ij. Camphor, aa . . 3J. Tinct. benzoin, . . ^viij.—M Morphine, . gr. ij. Oil of peppermint, . ^ij.—M. After removing all foreign matter and carefully drying the cavity of the tooth, a small bit of cotton or lint dipped in either of the above mixtures may be applied, and renewed several times a day, if necessary. The relief obtained is, in the majority of cases, almost instantaneous; but, as the effect is only temporary, the pain is apt to recur. The author has sometimes used a thick solution of gutta- percha in chloroform. The application of a drop or two of this to the exposed pulp is usually followed by the immediate cessation of pain, and as the chloroform eAraporates, a thin layer of gutta-percha remains, and serves for a time as a sort of protection to the pulp. It often becomes necessary to have recourse to the destruction of the pulp, as there are many cases in which the patient cannot be prevailed upon to submit to the former, and as there are others in Avhich the retention of the organ is called for by some peculiar. necessity. This may be effected either by immediate extirpation with a small, sharp-pointed elastic stilet or probe, by the actual cautery, arsenious acid, carbolic acid, cobalt, or chloride of zinc. Immediate extirpation, or the application of devitalizing agents, are the means usually employed for the purpose. Pain in a tooth arising from acute inflammation of the pulp and lining membrane, can only be relieved by the extraction of the tooth, the destruction of the pulp, or by subduing the inflammatory ac- tion ; the last can seldom be done except by the most energetic treatment in the very beginning, in cases Avhere the decay has not penetrated to the pulp cavity. The propriety or impropriety of ex- traction Avill be determined by the amount of pain, the progress made by the inflammation, the condition of the parts Avith Avhich the tooth is immediately connected, the effect of local disturbance 310 DENTAL PATHOLOGY, THERAPEUTICS. upon the general system, the situation and importance of the tooth, and the extent of structural alteration which has taken place in the crown. If the retention of the tooth, on account of its location, or the loss of several other teeth, is of great importance to the patient, and the circumstances of the case justify a well-grounded belief that it can be preserved and rendered useful, without acting as a morbid irritant, the operation, if possible, should be avoided. In this case, supposing the inflammation to have proceeded too far to be arrested, the pulp may be destroyed and the tooth treated in the manner de- scribed in another chapter. When the inflammation is produced by other causes than exposure of the pulp and the contact of external irritants, it may perhaps be successfully combated. The treatment is similar to that for local inflammation in other parts of the body ; the administration of sal- ine cathartics, the application of leeches to the gum of the affected tooth, abstinence from animal food and stimulating drinks. If the pulse is full and hard, blood may be taken from the arm Avith ad- vantage. Diaphoretics are often beneficial, such as Dover's Powder, or Spirit of Mindererus. Bromide of potassium, in doses of gr. v. to gr. xl., Avith a mustard plaster to the back of the neck and a hot foot-bath, Avill also be found efficacious. Should these means fail to arrest the inflammation, and suppuration take place, the formation of alveolar abscess may be preA^ented by promptly perforating the crown of the tooth for the escape of the matter; but such cases usually terminate in periodontitis, Avhich perhaps arises as frequently from this as from any other cause. As the treatment of periodontitis or inflammation of the investing membrane is described in another chapter, it is unnecessary to re- peat it. But when the formation of alveolar abscess is threatened the removal of the tooth, in many cases, will be found necessary. If it be an incisor or cuspid, hoAvever, the operation should be per- formed as a last resort. Odontalgia, assuming a rheumatic or gouty character, calls for a someAvhat different plan of treatment. In addition to the local means already described, it may be necessary to adopt the consti- tutional treatment applicable to rheumatism and gout. When the pain arises from increased vascular action and nervous irritation of the pulp, occasioned by a disordered condition of the digestive or- gans, and assumes an intermittent form, an emetic or cathartic, followed by the use of quinine, will generally afford relief proAuded caries has not penetrated to the pulp cavity. If dependent on gen- eral nervous irritability of the system, tonics, exercise, change of air, or such other constitutional measures as the peculiarities of the case may indicate, should be recommended. DEVITALIZATION AND REMOVAL OF THE PULP. 311 The extraction of the tooth is the only remedy that can be relied upon for relief of pain arising from exostosis of the root. Dr. Good, hoAvever, thinks it may be cured in the early stages by the use of leeches and mercurial ointment, and others recommend the internal use of iodide of potassium. DEVITALIZATION AND REMOVAL OF THE PULP. With regard to the best means of destroying the pulp of the tooth, Avhen it is impossible to preserve it, there exists much diversity of opinion. There are tAvo methods by Avhich this may be accom- plished, one by immediate extirpation Avith an instrument, and by actual cautery; the other, by the application of some devitalizing agent, as arsenic. Each method has its advocates. For the removal of the pulp by extirpation, there are different forms of instruments employed, such as a three- or four-sided broach, barbed for some distance from the point, Avhich is thrust as far up the pulp canal as is possible, then rotated and AvithdraAvn, bringing the pulp Avith it. Fig. 91 represents a broach of this kind, Avhich may be used with or without a holder. Another form of broach is used for this operation Avhich is not barbed, but thrust into the pulp for the purpose of so lacerating it that it may after- Avards be removed Avith nerve instruments Avithout much pain. A fine, round, steel Avire, from Avhich the temper has been draAvn, and having a flat point bent on an angle of about forty degrees, is also used for extirpating the pulp. The edge of the point, in introducing this instrument, is pressed against one Avail of the canal and gradually forced up as far as it Avill enter, when it is suddenly turned so as to excise the pulp, and on AvithdraAving the instrument bring the severed organ Avith it. Figs. 124 and 125 represent excellent forms of instruments de- vised by Dr. R. B. Donaldson for cleansing pulp-canals and re- moving pulps. For extirpating the pulps of the molar teeth, a larger instrument is required, which is thrust into the pulp-chamber and rotated so as to sever the body of the pulp from the branches filling the root canals. The small nerve instruments are then employed for re- moving these branches. The operation of extirpation should depend upon the tempera- ment of the patient, and the condition and class of the tooth. Where such an operation avouIcI cause a severe shock, OAving to a nervous, irritable temperament, it is best to employ the therapeuti- cal method; on the other hand, Avhere there is great poAver of endur- ance, and the tooth is of a frail, chalky consistence, or threatened Avith periosteal inflammation, it is preferable to remove the pulp by 312 DENTAL PATHOLOGY, THERAPEUTICS. an operation. The pain, hoAvever, can be greatly mitigated by the previous application of some obtunding agent, such as sulphate of atropine, aconite, cocaine, or chloroform. Fig. 123. Firc. 124. Fig. 125. DEVITALIZATION AND REMOVAL OF THE PULP. 313 In all cases, and by Avhatever method, the orifice of exposure should be large, and nearly on a line Avith the axis of the tooth, so as to admit of easy manipulation, especially if the barbed broach or bent Avire are employed ; and when a pulp is removed by such an operation, the Avound usually heals by first intention, and no peri- osteal irritation results. The actual cautery consists in thrusting a Avire, heated to a white heat, up the canal; but as this is considered a barbarous method,it is not resorted to by practitioners in this country. Besides, peri- osteal inflammation is often a result of its use, and the pain folloAv- ing its application is sometimes very seA'ere. The galvanic cautery is preferable to the actual cautery for the destruction of pulps, ap- plied by means of a bent platinum Avire maintained at a white heat. Arsenious acid* has long been used in connection Avith acetate of morphine and creosote, or carbolic acid, to devitalize the pulp; the arsenic and morphine being mixed in equal parts, and taken up on small pellet of cotton saturated with creosote, which is introduced directly upon the exposed portion of the pulp, and the cavity filled with Avax or cotton saturated Avith a solution of gum sandarach and alcohol. *The morphine Avas formerly supposed to modify the irritating action of the arsenious acid; but since this has been dis- covered not to be the case, its use has been dispensed with by many AA'ho prefer no other combination than creasote or carbolic acid. Water, alcohol, and ether haA'e also been employed as substitutes for the creosote. The arsenious acid is at times combined Avith an equal part by Aveight of pulverized charcoal, on account of the anti- septic properties of this latter agent, and also on account of its mechanical action in preventing the dentine from absorbing Avhat is intended for the pulp alone. A favorite mixture is knoAvn as " nerve paste;" but Avhen a definite quantity of the arsenious acid is desired for application to a pulp, it is better to employ the dry form. Various formula? are in use for the preparation of devital- izing mixtures, such as equal parts by Aveight of arsenious acid and acetate of morphine; three parts by weight of arsenious acid to two parts of morphine; tAvo parts of arsenious acid and one part of morphine. Creosote, or carbolic acid, is generally employed to combine the ingredients, and also to act as a sedative. Although the thirtieth part of a grain of arsenious acid is the average quantity generally employed to devitalize the pulp, yet the amount may be * The employment of arsenious acid for the destruction of an exposed dental pulp, and the relief of the pain arising therefrom, originated with the late Dr. Spooner, of Montreal; and in 1835 it was recommended to the profession by his brother, Dr. S. Spooner, of New York, in an excellent popular treatise upon the teeth. 314 DENTAL PATHOLOGY, THERAPEUTICS. reduced to the T^ of a grain in many cases when judiciously used. The length of time the preparation should be alloAved to remain varies from six to twenty-four hours. Dr. J. F. Flagg recommends the folloAving formula: R . Arsenious acid,.........gr- J- Acetate of morphine, .......• gr- 'J- Carbolic acid,.........gtt. iij. A very convenient form of devitalizing mixture is that knoAvn as "nerve fibre," which consist of a combination of arsenic, creosote, tannin, and opium incorporated in the fibres of cotton or lint, Avhich is afterwards dried and cut up into shreds. Dr. Jas. Gordon has suggested the folloAving method of devitalizing pulps, Avhich is claimed to be less painful than that heretofore employed : after care- fully cleansing the cavity saturate a very small pledget of cotton, held by a foil carrier, with benzole and then apply to the cotton a little nerve paste, and place the Avhole directly upon the exposed pulp, and cover it by loosely filling the cavity AArith cotton saturated with sandarach varnish. If a solution of caoutchouc in benzole is employed to saturate the first pledget of cotton to which the nerve paste is applied, the preparation Avill better retain its place in the cavity, and is less liable to be displaced Avhen the retaining pledget of cotton saturated with sandarach is introduced. When arsenious acid is applied to temporary teeth, the quantity employed should be very minute, and many are disposed to question the safety of its application to such teeth, as the agent may be ab- sorbed by the very vascular structure and injure the surrounding membranes. Not unfrequently cases are met Avith where repeated applications of the preparation fail to destroy the vitality of the pulp, which is doubtless owing, in cases where the organ is fairly exposed, to its inflamed condition at the time the application is made, which enables it to resist the absorbent action of the arsenic. In such cases a preparation composed of tannin and creosote has proved serviceable. Arsenic Avhen applied to a pulp excites inflammation, and as this condition passes off the agent is absorbed and devitalization follows. Too great a quantity of arsenic will defeat the object, and in many cases its devitalizing action is prevented by the high degree of in- flammation present, so that it is necessary to reduce the inflamma- tory condition before a successful application of the devitalizing agent can be made. The time the arsenious acid is permitted to remain in the tooth is important, and should be determined by the condition of the pulp, the class of tooth, the structure of the tooth, the age of the patient, DEVITALIZATION AND REMOVAL OF THE PULP. 315 and the susceptibility to the influence of the agent. The time ne- cessary for the action of arsenious acid varies from six to tAvelve, and in some cases tAventy-four hours, when minute quantities are employed. As the degree of inflammation excited by the arsenic depends upon the quantity of the agent employed, it is much the safer and better plan to apply small quantities than an amount which will devitalize the pulp by one application; for in the latter case there is danger of the effects being carried to the peridental membrane through the apical foramen. It is often very difficult to retain the devitalizing agent on frac- tured teeth, Avhen it becomes necessary to destroy their pulps. A method pursued by some is to apply a minute quantity and cover it Avith gutta-percha, Avhich is held in position by ligatures. An- other method suggested by Dr. Rich, is to secure the arsenical preparation by surgeon's rubber plaster, passing it around any por- tion of the croAvn Avhich remains. The late Dr. Harwood, of Boston, Avho Avas strongly opposed to the use of arsenious acid as a devitalizing agent described his plan of accomplishing this object by the surgical method as follows: " I first effect such an opening as Avill enable me to approach the exposed pulp in the line of its axis, or as nearly so as circumstances Avill permit. Then, having carefully but sufficiently exposed the surface of the pulp, I pass doAvn to the apex of the root, through the pulp, a small untempered steel instrument, with a trocar-shaped point, and revolving it once or twice sever the vessels and nerve. This, as any one knoAvs Avho is accustomed to inserting artificial teeth, produces but a slight and momentary pain. I then, by means of minute instruments, adapted to the purpose, endeavor to remove every portion of the severed pulp and lining membrane, and, as soon as the hemorrhage ceases, dry and fill the cavity. " It should be borne in mind, that at the point where the vessels and nerve in question enter the root, the passage is much smaller than it is immediately Avithin. This strait Avill be easily recognized Avhen reached, by the touch, the instrument appearing to be arrested by an obstacle, and not by being Avedged in a narroAV passage. Care should be taken, I think, that the instrument is not alloAved to pass through the strait, either by being too small, or by being revolved there till it cuts its Avay through. For, by Avounding the parts Avith- out the tooth, and forcing particles of bone out upon the parts ex- ternal to the root, the danger of an unfavorable result would be greatly increased." Dr. E. C. Kirk suggests the folloAving devitalizing mixture, Avhich 316 DENTAL PATHOLOGY, THERAPEUTICS. he states has given uniform satisfaction as a prompt obtunder, and immediate relief from pain : R. Acid, arsenic pulv., cocaine hydrochlorat, iia . . . gr. xx. Menthol cryst.,........• gr- v- Glycerine,.......• • . q. s. M. To make a stiff paste. Dr. James Truman recommends the following devitalizing mixture as prompt and painless : Take the amount of arsenic it is proposed to employ and add an equal quantity of iodoform, and on a glass slide by means of a 5 per cent, solution of carbolic acid, make a paste. The Avhole is carried to the pulp on a piece of cotton the size of a pin-head in which it is incorporated, and covered with a cap of platinum or of red gutta-percha, and over this a temporary filling of Avax or cotton saturated with sandarach. On the different methods of destroying the nerve, Dr. J. H. Foster says : " It is a difficult matter, and I have generally found it utterly futile, to attempt to induce patients to submit to the removal of the pulp by extraction or excision Avith instruments, in those cases in which it becomes necessary to destroy vitality before the teeth can be filled. To obtain the consent of the patient by a representation of the ad- vantages, in its immediate effects, of this mode of treatment by extirpation as contrasted with the more sIoav and uncertain practice, by the aid of chemical agents, has been my earnest endeavor. I do not remember a single case of the removal of the dental pulp by an instrument—the gold being inserted into the dental cavity im- mediately after the hemorrhage has been checked—Avhich has re- sulted in alveolar abscess." Dr. Foster, however, generally employed arsenious acid, with mor- phine, one part of the former to four of the latter, applied on a small pellet moistened with creosote. After applying this directly over the pulp, he covered it Avith a cap, to avoid pressure; then filled the external cavity Avith some soft material Avhich will ex- clude moisture. At the end of forty-eight hours he enlarged the dental cavity, removing its contents to the apex of the root; then, after waiting another forty-eight hours, he proceeded to. fill the canal, leaving the cavity in the croAvn to be filled at a subsequent sitting. In performing this operation on molar teeth, Avhere there is a prob- able chance of a favorable issue, and the preservation of these teeth is particularly called for, he thought it important that the excavation should be clone at intervals, so as to cause as little irritation at each sitting as possible, and that the filling of the different cavities in the tooth be also proceded Avith in like manner. DEVITALIZATION AND REMOVAL OF THE PULP. 317 Dr. Maynard Avas the first to perfect the method of using arsenious acid as a devitalizing agent and many years ago he adopted the folloAving plan: Expose the pulp as much as possible, apply the arsenic and cap the orifice Avith a cup-shaped plate of lead, the convex side outAvard. Keep this cap carefully in place, and fill the cavity over it Avith cotton, into Avhich Avhite Avax has been Avorked, in such a Avay as not to shut in and compress any air which might press upon the pulp. This packing will keep the arsenical prepara- tion perfectly dry for tAventy-four hours, or longer. After removing this packing and the preparation, he proceeds to remoATe the pulp. Instead of attempting to do this at once, he be- gins by cutting on every side of the orifice, so much enlarging it as to be enabled to remove the pulp Avithout pressing the contents of the cavity upAvard. His probes Avere objects of peculiar interest, especially those for extirpating the pulp. Some of them were made from the main- spring of a Avatch, by filing or grinding them sufficiently narroAV to enter the smallest space which he Avishes to probe. In this Avay he secured the most perfect spring temper, a point not easily attained in so frail an instrument as a probe adapted to this purpose. These probes Avere bearded by cutting them with a sharp knife—the beard pointing backAvard. With different sizes of these and other probes, and by enlarging the cavity from time to time, he removed the pulp to the extremity of the root. In the destruction of the pulp of a tooth, the late Prof. C. A. Harris employed both mechanical and chemical agents. He had been in the habit, for more than twenty years, of occasionally ex- tirpating the pulp to the extremity of the root by introducing a very small untempered instrument, Avith spear-shaped point; though not at first Avith the vieAv of aftenvard filling the pulp cavity. He had also used the actual cautery and arsenious acid. To the last-named agent, as used by most dentists for destroying the vitality of teeth, he was at one time strongly opposed, and believed a vast amount of injury Avas produced by it; but he aftenvard concluded that Avith proper care and judicious after-treatment, it might be used Avith safety, and, in most cases, with advantage. He employed it for de- stroying the vitality of the pulps of the molar and bicuspid teeth, and occasionally applied it to the incisors and cuspids. As a gen- eral rule, however, Avhen he Avished to destroy the pulp of one of the last-named teeth, he extirpated it by thrusting a small instru- ment up the pulp-cavity to the extremity of the root. When he used arsenic, he applied about the thirtieth or fortieth part of a grain Avith an equal quantity of morphine; placing it on a small piece of 318 DENTAL PATHOLOGY, THERAPEUTICS. raw cotton, moistened with creosote or spirits of camphor, and sealed up the cavity with white or yellow wax. At the expiration of seven or eight hours he removed the Avax and arsenic, and after- ward the pulp of the tooth. If the portion in the root was still sensith-e, he applied it a second time; but he seldom found it neces- sary to do so. There is comparatively little objection to the use of arsenious acid, provided it is judiciously and carefully employed. and not allowed to come in contact Avith the gums, as it is the only agent that will destroy the pulp effectively and with the least pain in a comparatively short time. Such agents as nitric acid and carbolic acid are also employed to destroy pulps. The method being first to apply the carbolic acid to the exposed surface of the pulp, and then the nitric acid on a small disk of card-board cut a little larger than the orifice of expo- sure and retained for half a minute. After this is removed a second application of the carbolic acid is made, and the pulp remoAred from the cavity by means of a barbed broach. Some employ a fine splinter of Avood dipped in nitric acid, which is thrust into the pre- viously obtunded pulp. Repeated applications of carbolic acid, chloride of zinc, nitrate of silver or caustic potash are also preferred by some to arsenious acid, for devitalizing agents. A piece of hard elastic Avood, shaped to conform to the pulp-canal, and suddenly forced up on the pulp by the bloAV of a condensing hand-mallet, is recommended by some as being almost painless. CHAPTER XL SENSITIVENESS OF DENTINE. While inflammation of the soft tissues exhibits such symptoms as pain, redness, heat and SAvelling, the dentine of a tooth in a similar pathological condition does not indicate all such manifesta- tions ; for, OAving to its peculiar structure, there is no redness, on account of a want of red globules, nor swelling, on account of the density. There is, however, exalted sensibility, and to such a con- dition the the term inflammation has been applied. Inflammation of the dentine is due to exposure of this structure consequent upon the breaking down of the enamel or protective covering, and its degree will depend upon the organic structure of the teeth, suscep- tibility to irritation and the nature of the irritating agents. Teeth that are very vascular and highly organized are often extremely sus- ceptible to the action of irritating substances, and such a state of SENSITIVENESS OF DENTINE. 319 exalted sensibility may at times be occasioned by disturbance of other and remote organs, such as the uterus, for example. The direct cause of inflammation of the dentine is irritation of the fibrilla? Avhich occupy the dentinal tubuli, and are processes from the odontoblasts, and proceed through these tubules to the periphery of the dentine, and, in some cases, even beyond this struc- ture. The odontoblasts are arranged in a layer on the outer surface of the pulp, and slight irritation of the ends of the fibrillse, AA'hich proceed from these cells, results in the formation of secondary de- posits of dentine. The greatest sensitiveness is generally found Avhere the union of the dentine Avith the enamel occurs, for the reason that at this point the nerve fibres terminate, and Avhich accounts for the greater sen- sitiveness of dental caries in its incipient stage. A tooth is sometimes exceedingly sensitive Avhen the pulp is not exposed; but, in the majority of cases, this need not deter the oper- ator from removing the decayed part and filling the cavity, for the inflammation of the dentine may be confined to a thin lamina di- rectly beneath the carious matter, and the only inconvenience it Avill occasion the patient will be a little suffering during the opera- tion, and slight momentary pain for a few days, Avhenever anything hot or cold is taken into the mouth. But Avhen the sensibility is so great that the patient cannot bear the removal of the diseased part, as occasionally occurs, it may be allayed by the application of chlo- ride of zinc to the cavity of the tooth, for from three to six minutes. When this is done, care should be taken to prevent it from coming in contact Avith any of the soft parts of the mouth, on account of its active escharotic properties. For the destruction merely of morbid sensibility in the solid structures of a tooth, chloride of zinc, according to the author's ex- perience, although someAvhat less certain in its effects, is superior to any preparation dependent for its active properties upon the the presence of arsenic. With this agent it rarely happens that more than five minutes are required to obtain the desired effect. Although a poAverful escharotic, it does not, as all arsenical prepa- rations are liable to do, produce any deleterious effect on the pulp of the tooth. It is thought, hoAvever, in some cases to modify the texture of the dentine; and, in the opinion of some practitioners, so much so as to render it more easily acted upon by decaying agen- cies. When first applied, it excites a sensation of heat, folloAved by burning pain ; but these soon subside, and on removing it from the tooth, the parts of the cavity Avith which it Avas in contact will, in a large majority of the cases, be found totally insensible to the touch of an instrument. 320 DENTAL PATHOLOGY, THERAPEUTICS. The chloride may be applied directly to the cavity of a sensitive tooth, without being combined Avith any other substance, on a little raAv cotton or lint; or it may be made ink) a paste by mixing it Avith an equal quantity of flour, the moisture which it absorbs from the atmosphere being sufficient for the formation of the paste; or it may be mixed Avith a little pure anhydrous sulphate of lime, in an impalpable poAvder, and then applied to the tooth. But before this is done, as much of the decomposed dentine as possible should be removed, and the application should be held firmly in contact Avith the part of the cavity on Avhich it is intended to act. A single application Avill generally suffice to destroy the sensibility to a suffi- cient depth as Avill enable the operator to remove any remaining portions of decayed dentine Avithout pain; but repeated applica- tions are sometimes necessary. The fortieth or fiftieth part of a grain of arsenic is sometimes ap- plied, and allowed to remain from one to three hours; but there is great danger of destroying the vitality of the pulp by the use of this agent, even though it be permitted to remain for only a short time ; hence its use is not recommended. Tannin or tannic acid in alcoholic solution, or in creosote and glycerin, are valuable applica- tions for this pathological condition of the dentine. Nitrate of silver, chromic acid, and the terchloride of gold are also used for the same purpose—the nitrate being applied in either a solid form or in a concentrated solution; and Avhile it affects the dentine to a greater depth than either the tannic acid or chloride of zinc, yet its action is not so painful as the latter. Creosote and carbolic acid are extensively used for this condition of dentine, and are among the safest of these agents. Chloroform applied to the cavity on a small piece of cotton will often give a temporary insensibility, and has the merit of being quite harmless; which cannot be said of chloride of zinc, arsenic, or cobalt—the first sometimes acting injuriously upon the dentine, the tAvo latter upon the dental pulp. A mixture of chloroform and aconite, equal parts, is also recom- mended ; also, carvacrol, oil of cloves, oil of cedar, oil of eucalyp- tus, glycerine and tannin, creosote and tannin, camphor and chloral solution, camphorized ether, oxide of calcium (this latter. hoAvever, causes considerable pain when first applied), carbonate of sodium, menthol, thymol, the sesquichloride of chromium, a mixture of equal parts of tincture of aconite and a saturated solution of iodine, carbonate of potash, equal parts of sulphate of morphine and gum camphor, ethylate of sodium, carbonate of potash and glycerine, equal parts of crystallized carbolic acid and caustic potasli, made by mixing into a crystalline paste, and knoAvn as the " Robinson SENSITIVENESS OF DENTINE. 321 120. Remedy," and the insertion of temporary fillings composed of oxy- chloride of zinc or oxyphosphate of zinc, or Hill's stopping. An efficient means for the application of heat as an obtunder of sensitive dentine is the " Dento-Electric Cautery," represented in Fig. 126. The looped-wire of this instrument is rapidly F passed across the sensitive surface, and obtunds it to , such a degree as to produce an immunity from suffer- ing of considerable duration. In the instrument a platinum loop, A, is held by set- screws, B, in contact with metal conductors which pass through a hard-rubber handle. The battery Avires are coupled to the tAvo terminals, C. The appliance is held in the hand somewhat in the same manner as a pen or pencil in Avriting, and the circuit is closed by pressing upon the spring, D,AArith the forefinger, when the resist- ance of the loop causes it to become heated. The pla- tinum loop Avhen destroyed is readily and inexpensively replaced. A safe way of meeting the difficulty in slight cases, is to have the excavators and burrs very sharp and Avell tempered, and to cut firmly and decidedly (for the scraping of a dull instrument is quite as painful as the cut of a sharp one), making cuts "Avhich sweep the circumference of the cavity," or in a direction from the pulp chamber. Friction, by means of a burnisher, is also recom- mended as being effectual Avhere the position of the sensitive surface will permit of its use. When painful escharotics are employed, the sensi- tiveness of the dentinal surface should first be obtunded by the application of a solution of sulphate of atropine, or other local anaesthetic. Having noticed the agents usually employed for de- stroying morbid or hyper-sensibility in dentine, we will proceed to notice a feAv of the non-conductors against thermal influences that have been used for the accom- plishment of the same object. Among the substances Avhich have been employed for this purpose are as- bestos, gutta percha, cork, oiled silk; also such filling materials as IIUPs stopping, the oxychloride and oxyphosphate of zinc. Asbestos, as a non-conductor of caloric, certainly possesses every desirable property, and is as indestructible in a tooth as gold. When used for this purpose, the purest variety should be selected. A 21 MET Q 322 DENTAL PATHOLOGY, THERAPEUTICS. small pellet made from the filaments of this mineral, placed in the bottom of a cavity previously to filling, will effectually prevent irritation of the pulp from impressions of heat and cold. The cavity, hoAvever, should be first properly prepared, washed with tepid Avater, and made perfectly dry. The asbestos may occupy from one-fourth to one-sixth of the depth of the cavity after the filling has been introduced and consolidated. A thin layer of gutta percha placed in the bottom of the cavity, previously to introducing the gold, is as effectual in preventing the transmission of impressions of heat and cold as asbestos, and can be more conveniently applied. There is, hoAvever, a preparation of it, known as " Hill's stopping," which is better than the simple article for a temporary filling. Cork is an equally good non-conductor of caloric, but some object to its use on account of its being more destructible than asbestos or gutta percha; but cut off, as it necessarily Avould be in the bottom of the cavity beneath the filling, its liability to undergo any change would seem to be rendered wholly impossible. But it is of a more porous nature than gutta percha, and cannot be adapted as perfectly to the inequalities of the floor of the cavity. There is also danger, in introducing the filling, of forcing some portions of the gold through it, unless a very thick piece be used. Oiled silk has also been used in some cases very successfully, but it is not as good a non-conductor as either of the afore-mentioned agents. The filling materials knoAvn as oxychloride of zinc and oxyphos- phate of zinc often prove effectual in preparing a sensitive cavity for a more durable metallic filling. For the method of applying these agents, and also Hill's stopping, the reader is referred to the chapter on " Materials Employed for Filling Teeth." Should it, hoAvever, be necessary to fill the cavity with a more permanent material, such as metal, and the inflammation is con- fined to a portion of the dentine, this may be protected by a layer of the non-conducting material, and the metal introduced over it. CHAPTER XII. PERIODONTITIS. Periodontitis, pericementitis, dental periostitis, peridentitis, as the affection is variously named, denotes inflammation of the in- vesting or peridental membrane of the roots of the teeth, a tissue highly vascular and very susceptible to inflammatory conditions, PERIODONTITIS. 323 and may, in a great majority of cases, be regarded as a premonitory stage of alveolar abscess, as it rarely occurs before the pulp has been deprived of its vitality. Although the death of the pulp generally precedes the inflamma- tion of the peridental membrane AA-hich usually originates in the apical space, yet this inflammation may arise before devitalization takes place; but in such cases the pulp is involved to such a degree that its recovery is impossible. The peridental membrane is con- fined between the Avails of the alveolar cavity and the root of the tooth, and as a consequence is incapable of expansion when its vessels are engorged Avith blood ; and endowed with a large supply of nerves Avhich render the membrane very sensitive even in a normal condition, it becomes excruciatingly painful Avhen inflamed. Inflammation of the periosteum of a tooth may be acute or chronic, the acute form being generally due to direct local irritation, and the chronic form to systemic influences. Each variety is modified in its character by the state of the constitutional health, and by the causes concerned in its production. The premonitory symptoms of the acute variety are a slight sensation of uneasiness and tension, a feel- ing of fulness about the affected part, and a desire to press the teeth together. Pressure appears to afford temporary relief, but the uneasy feeling returns on the pressure being withdraAvn. The symptoms are soon folloAved by a dull, heavy and continuous pain, and the affected tooth appears to be longer than the adjoining ones, and is really so, OAving to the increased thickness of the invest- ing membrane of the root. Occlusion of the teeth gives rise to severe pain, and there is an inclination to keep the jaws apart. The appearance of the gums at this stage of the affection also indicates the existence of disease in the investing membrane; they become very tender and SAvollen, and change from a pale rose color to a deep red or purple opposite the root of the affected tooth. At first the inflammation is confined to the free margins, but soon it becomes more general, until the Avhole of the gum about the root of the tooth is involved. Although the pain increases in severity, it yet preserves the same character, and even Avhen not continuous, it seldom ceases for any great length of time. At length suppuration occurs, and Ave have the condition known as alveolar abscess; this process sometimes extending to nearly every part of the periosteum, causing the entire death of the tooth, and often followed by erosion of the root and necrosis of the alveolus. When favored by a ca- chectic habit of body, it often extends to the periosteum of the jaw, followed by suppuration and necrosis. The following case Avillgive some idea of the severity it occasionally assumes : 324 DENTAL PATHOLOGY, THERAPEUTICS. In 1840, a poor girl, aged fourteen, was brought to the author. About three months before she had been taken to a barber tooth- drawer for the purpose of having the first left inferior molar ex- tracted. The crown was broken off, the roots left in the socket. In- flammation supervened. This soon extended to the periosteum of the entire bone from the second bicuspid to the coronoid process; as it was permitted to run its course uninterruptedly, it ter- minated in necrosis and exfoli- ation of all this portion of the bone (Fig. 127), the anterior extremity of Avhich, Avhen first seen by the author, had passed through the integuments of the loAver part of the face, and protruded externally. A feAv days after it Avas removed without difficulty. Acute inflammation of the peridental membrane having termin- ated in suppuration, sometimes, instead of subsiding altogether, degenerates into a chronic form, and when favored by some consti- tutional vice, as the scorbutic, venereal, or scrofulous, it often gives . rise to the destruction of the socket and loss of the tooth. The acute form of periodontitis is readily diagnosed by the pain caused by pressure on the affected tooth, which distinguishes it from such diseases of the dental pulp as irritation and inflammation or pulpitis. Besides, the pain of periodontitis can ahvays be definitely located, Avhereas in pulpitis its exact location is often doubtful; again, the dental pulp is influenced by thermal changes to such a degree as to very greatly increase its sensibility when diseased, Avhereas, the peridental membrane is not so influenced and its sensitiveness is not increased to any marked degree by thermal changes, except when the pulp-cavity contains gas which expands from heat and induces pressure on the tissues beyond the apical foramen. Chronic inflammation of the peridental membrane is generally preceded by the active form of the disease, but it may assume the chronic form at the commencement. In this case it is complicated with tumefaction of the gums, and discharge of puriform matter from betAveen their edges and the necks of the teeth. Chronic peri- dontitis is but a modified form of the acute, and is manifested by soreness of a tooth, which may either be so slight as to occasion very little annoyance, or be very considerable, Avith apparent congestion of the gum about the tooth, and sensitiveness of a greater or less degree when the organ is pressed upon. PERIODONTITIS 325 After the loss of vitality in the pulp of a tooth, the peridental membrane is very susceptible to inflammation, owing to the irritation to Avhich it is subjected, and also to the Aveakened condition of this membrane, and its increased function in supplying the cementum and dentine Avith nourishment, CAUSES. Periodontitis, in most instances, is the result of inflammation of the pulp of a tooth, either from direct exposure or the presence of an irritating substance, such as the remains of a dead or decompos- ing pulp, salivary calculus, the free use of arsenious acid, the in- judicious use of agents employed for obtunding the sensitiveness of dentine, the action of mercurial remedies, etc. It may also result from the loss of an antagonizing tooth, violence, proximity of a metallic filling to the pulp, overhanging portions of a filling, and the presence of caries beyond the margin of the gum. Besides the local causes enumerated, there are also constitutional causes, such as a syphilitic taint through an infiltration of lymph and serum into the periosteum, or betAveen it and the root of the tooth or al- veolar Avails of the socket; also rheumatism, especially in those who have been subjected to an excess of mercury, and scrofula, which produces a form of periostitis common to children. This affection may also extend from the periosteum of one tooth to that of adjoin- ing teeth. TREATMENT. The treatment of periodontitis will depend upon the causes pro- ducing and influencing the disease, and the condition of the general system. The first thing to be attended to is the removal of all irri- tants from the pulp-cavity, such as a decomposing pulp, after Avhich the congestion of the affected part may be relieved by the use of such agents as produce counter-irritation, or by depletion. When the pulp of the tooth is inflamed it should receive imme- diate attention, and if the pulp is dead, all the debris should be re- moved from its pulp-cavity by means of nerve instruments, and syringing Avitli tepid Avater. All deposits of calculus should be re- moved from the teeth, and also all dead teeth and roots Avhich are useless and cause irritation. The pulp-cavity should then be thor- oughly disinfected by iodoform, eucalyptus, iodine, carbolic acid, salicylic acid, or sanitas, etc. After the application of the disinfect- ing agent, the pulp-cavity should be loosely filled Avith cotton satu- rated with an antiseptic agent, but sufficiently close to prevent the entrance of fluids. If a secretion of pus is present the application may 326 DENTAL PATHOLOGY, THERAPEUTICS. be frequently changed, and thus prevent the pressure of the secretion from causing pain. In severe cases Avhere the above treatment does not prove effectual, counter-irritation may be resorted to ; the gums may be scarified, or such agents be applied as iodine and creosote, tincture of capsicum, and tincture of iodine. An excellent application is composed of equal parts of the officinal tincture of iodine and tinc- ture of aconite root applied to the gum two or three times daily, in the acute form of the affection. Previous to the application, the gum should be dried, and afterwards the cheek kept from coming in con- tact with it until a metallic pellicle is formed. Cantharidal collodion is also an excellent counter-irritant, and is applied to the gum, after the surface is dried with a napkin, by means of a camel's-hair brush, taking care to protect the lip, and to prevent moisture from inter- fering before the ether in the preparation evaporates and an artificial cuticle is formed. Within a few hours blistering results, and the periostitis is effectually relieved. Another method of producing counter-irritation is to make a deep incision in the gum over the affected root, and to introduce into this a small pellet of cotton or lint saturated with creosote, or carbolic acid, which is retained for from one to five days, the time depending upon the persistence of the inflammation, taking the precaution to change the dressing every day. The application of a solution composed of equal parts of tincture of aconite, tincture of opium, and chloroform, is often very serviceable; also a small linen bag containing capsicum, one side of the bag being covered Avith leather, to protect the cheek. Lead-Avater, in the proportion of a fluidounce to two fluiddrachms of laudanum, applied in the same manner as the agent before named, has also been successfully used. Depletion may be ac- complished by means of the gum lancet, or by the use of leeches or cups. Hypodermic injections of morphine have also been resorted to for the relief of the intense pain of this affection, such as a solution of morphine or tincture of opium, some ten to twenty drops being in- jected Avith a suitable syringe beneath the mucous membrane; also, with good effect, the application of rhigolene or ether spray until the gum about the affected tooth is blanched. As a topical applica- tion, rhigolene has been recommended, applied to the gum on a pellet of cotton after free scarification. Constitutional treatment is also serviceable, such as the adminis- tration of saline cathartics. Bromide of potassium in a dose of twenty-five grains, or the same quantity of the bromide combined with five drops of the tincture of veratrum viride, and repeated every four hours, will often prove serviceable in incipient alveolar ALVEOLAR ABSCESS. 327 periostitis. A preparation known as mercurius virus, the third deci- mal trituration, given in small doses two or three times a day, has been recommended by Prof. Chase, and used successfully by others in relieving acute periostitis. During the treatment, a cap of gutta- percha, moulded to the croAvns of one or tAvo teeth on the opposite side of the jaAv, Avill protect the affected tooth from any irritation Avhich may be caused by the occlusion of the opposing ones, and thus facilitate the restoration. For the treatment of the chronic variety of periodontitis, the reader is referred to " Chronic Inflam- mation and Tumefaction of the Gums." CHAPTER XIII. ALVEOLAR ABSCESS. An alveolar abscess is a collection of pus in a sac attached to and closely embracing the root of a tooth, and isv the result of inflam- mation of the tissues of the apical space, where its inception in- variably occurs. The peridental membrane having become the seat of acute inflammation, plastic lymph is effused at the extremity of the root. This is condensed into a sac or cyst, which closely em- braces the root near its apex, the walls of lymph become vascular, and perform the functions of secretion and absorption, and as sup- puration takes place, pus is formed in the centre of the sac. The inflammation, in the meantime, having extended to the gums and neighboring parts, they swell and become painful, and as the pus accumulates in the sac, it distends and presses upon the surrounding walls of the alveolus, Avhich, by a chemico-vital process, are gradu- ally broken doAvn. By absorption, through pressure, an opening is ultimately made through one side of the alveolar cavity, Avhen the pus, coming in contact with the investing soft structures, presses upon them and causes their absorption also, or it may follow the side of the root to the margin of the gum, and thus outlets are effected for the escape of the accumulated matter. In some cases the pus may separate the periosteum from the bone of the alveolar cavity and form a receptacle for itself betAveen the membrane and alveolar wall, and if not promptly discharged may cause necrosis of the bone. The pus of an alveolar abscess, in the case of young persons, usu- 328 DENTAL PATHOLOGY, THERAPEUTICS. ally finds an exit through the root canal of the tooth, especially when the abscess is formed upon the apex of the root, owing to the large size of the foramen of a deciduous tooth. In adult persons the escape of the pus generally takes place through the alveolar Avail and the soft tissues opposite the root of the affected tooth. The secretion of an alveolar abscess, especially when an inferior molar is affected, may find its way to the surface of the cheek or neck, and considerable deformity be caused from the cicatrix re- sulting. In some cases the sinus of an abscess may invade the duct of a salivary gland, and necessitate the operation for salivary fistula, before a cure can be effected; but the secretion may escape from a more remote point. It may make for itself an opening through the cheek or through the base of the lower jaw, and be discharged externally; or it may pass up into the maxillary sinus, or through the nasal plates of the superior maxilla, or form a passage between the two plates of the bone, and escape from the centre of the roof of the mouth. The formation of abscess in the alveolus of an inferior dens sapi- entia1 is sometimes attended with inflammation and swelling of the tonsils and of the muscles of the cheek and neck. The author has knoAvn trismus to result from this cause. The pain attending the formation of alveolar abscess is deep- seated, throbbing, and often so excruciating as to be almost insup- portable. But as soon as suppuration takes place, it loses its severity, and Avith the escape of the pus nearly or altogether ceases; but the tooth, from the thickened condition of the alveolo-dental periosteum, particularly at the apex of the root, often remains sore and sensitive to the touch for several days. The energies of the disease, hoAvever, having been expended, the secretion of the pus, in the majority of cases wholly ceases, and the opening in the gums closes. From the increased susceptibility in the alveolo-dental periosteum to morbid impressions, occasioned by the presence of a tooth deprived of a large portion of its vitality, a recurrence of the inflammation is liable to take place, when pus will be again formed and the passage for its escape re-established. But the pain attending any subsequent attack is seldom so severe as in the first instance. There are some cases, however, in Avhich the inflammation, instead of subsiding altogether, degenerates into a chronic form. In this case, the sac at the extremity of the root continues to secrete pus, though the quantity is usually small, and the opening in the gums remains unclosed. Persons of a scrofulous diathesis are very liable to this affection, Avhich, in these cases, very soon assumes a chronic form. ALVEOLAR ABSCESS. 329 In the extraction of a tooth which has given rise to the formation of abscess, the sac is often brought away Avith it. Two teeth in which this had happened, taken from the upper iaw— •V i\i xi. ^ x i Fir. 128. Fig. 129. one a cuspid, and the other a first molar—are represented in the accompanying cuts (Figs. 128 and 129). In the case of the molar, the sac is attached to the palatine root. Both of these teeth Avere extracted previously to the formation of an external opening for the escape of the matter. Although in the majority of cases the sac is attached to the apex of the root, yet it is not un- usual for the point of attachment to be on the side of the root, as in the case of the superior front teeth, and bicuspids, or in the bifurcation of the roots, in the case of the molars, for example. When the sac is situated upon the side of the root of a superior front tooth, it is generally upon the labial surface, and Avhen it is situated at the apex of the root of a molar tooth, the palatine root is the one generally affected. The temporary teeth are much more liable to this disease than the permanent teeth, and the superior incisors more susceptible than the inferior teeth of the same class. But the treatment of inferior teeth affected Avith abscess, especially the bicuspids and molars, is often more difficult than that of the superior, on account of the gravitation of the pus, and the impossi- bility in many cases of making an opening through the alveolar process so low as the extremity of the root, OAving to the muscular attachment being so high on the ridge. The character of the secretion differs considerably in different cases; instead of the yelloAvish-white appearance that pure or laud- able pus presents, and Avhich may be present in some cases of alveo- lar abscess in good constitutions, a highly vitiated, acrid fluid, Avith either a diminished supply of pus corpuscles or an entire absence of such corpuscles, usually distinguishes the secretion, which some- times becomes very irritating in its effect upon living tissue. The systemic condition of the patient modifies the character of the secretion, as also does the nature of the local irritants. The time required for the formation of alveolar abscess varies from three to ten or fifteen days, according to the violence of the in- flammation. But a collection of pus may be detected by fluctuation under the finger, if applied to the tumefied gum one or two days be- fore an external opening is spontaneously formed for its escape. The size of the cavity formed by an alveolar abscess depends upon the severity of the disease, and the susceptibility of the parts 330 DENTAL PATHOLOGY, THERAPEUTICS. involved. In some cases it is quite small and confined to the point of irritation, while in others it may be very extensive. Very severe pain accompanies this affection when the abscess is rapidly formed, owing to the distention occasioned, and the inability of the secreting pus to escape. As soon as an opening is effected, however, the ten- sion is relieved and the pain subsides. A great susceptibility to alveolar abscess exists in case of an inflammatory diathesis, and after a time it may assume a chronic character, when the secretion and discharge of the pus is continuous. Although the pain may not be more than a slight uneasiness, the acute form is productive of intense pain. There is also a difference in the extent of the in- flammation affecting neighboring tissues, depending upon the ac- tivity of the irritants present, as in some cases of alveolar abscess the inflammation of adjacent parts may be very limited, Avhile in others it may be very extensive. The inflammation and pain attending the formation of abscess in the alveolar cavity of a tooth often gives rise to general febrile symptoms, headache and constipation of the bowels. In the acute form of this disease, the pain is intense, Avhile in the chronic form, where the pus is constantly secreting and discharging, the sensation experienced is soreness and an uneasy feeling, with slight pain upon a change of temperature. Chronic alveolar abscess generally follows the acute form, and re- sults from a subsidence of the acute symptoms into others less pain- ful, but more persistent. The chronic form is generally accompanied Avith a fistulous opening Avhich in its position and the direction of the canal presents quite a variety of forms. The fistulous opening is usually, hoAvever, upon the gum over the root of the affected tooth; but in some cases the fistulous opening may close and the secretion from the abscess appear at a different point some distance from the original one. In other cases a chronic abscess may again assume acute symptoms, which may continue until a neAV exit for the secre- tion manifests itself at a more remote point. These chronic cases often cause a feeling of stiffness, caused by the pus burroAving through muscular tissue, as the secretion will generally follow a course which presents the least resistance. The direction of the pus is also influenced by gravitation, especially in abscesses connected Avith the inferior teeth. Abscesses connected with the inferior molar teeth sometimes discharge into the antrum and produce serious complications. Abscesses discharging on the face are generally con- nected Avith the inferior molar teeth, and are influenced in this re- spect by gravitation, and the least resistance the pus in its burrowing course may meet Avith. The closure of a fistulous opening of a ALVEOLAR ABSCESS. 331 chronic alveolar al >scess may lead to the retention of the pus, Avhich, on account of gravitation, in the case of an inferior tooth, penetrates to the surface along the border of the loAver jaw. Abscesses connected Avith the superior teeth, when pointing on the face, generally discharge beneath the prominence of the malar bone, and the deformity result- ing after the healing of the fistula is caused by the formation of a dense cord of neAV tissue which binds the skin permanently to the bone, and Avhich must be severed in the treatment for correcting such a deformity. CAUSES. The immediate cause of alveolar abscess is inflammation of the peridental membrane which is frequently incited by inflammation of the pulp and its subsequent death and decomposition, irritating mat- ter being thus formed, which sooner or later affects the tissues of the apical space through the apical foramen of the tooth. Such a condition is often the result of filling the cavity in the croAvn of a tooth, and permitting a dead and decomposing pulp to remain in the pulp-cavity. It may also be produced by mechanical violence, the irritation of a dead tooth, or by a drill accidentally passing from the canal through the side of the root into the periosteum, or by the presence of a portion of a gold filling forced through the root of a tooth. TREATMENT. The treatment of alveolar abscess should be preventive rather than curative, for it often happens, after it has occurred, that the integrity of the parts is so impaired as to cause a recurrence of the affection. Although the secretion of pus may cease for a time, and the opening in the gums become obliterated, the tooth, being deprived of a large portion of its vitality, is liable, Avhenever the excitability of the peridental is increased by any derangement of the general system, to give rise to a recurrence of the disease. Especially is this the case Avhen the disease has assumed the chronic form. The formation of an abscess, therefore, should, if possible, be preArented by the use of such means as are referred to in the treatment of u periodontitis," a common termination of this disease being alveolar abscess. But should these means fail to prevent the formation of pus, we then have to resort to either therapeutic or surgical treat- ment, consisting in the removal of the irritant matter from the pulp-cavity. An alveolar abscess of recent origin will yield more readily to treatment than one of long continuance, and the chronic form is 332 DENTAL PATHOLOGY, THERAPEUTICS. much more difficult to arrest, especially after the adjacent parts have become involved, than the acute form. When constitutional derangement is present, general treatment, such as the particular condition indicates, must be resorted to. The local or surgical treatment consists in breaking up the sac of the ab- scess, and the evacuation of the pus as soon as possible, and ready access must be had to the point of accumulation in order to success- fully accomplish such a result. A sharp-pointed bistoury or small trephine, may be employed to enlarge the fistulous canal, Avhen the pus has made an opening through the process and gum to the surface opposite the root of the tooth, and the sac broken up by means of nerve instruments, its remains being thrown off, and healthy granulations developing Avithout further treatment. In many cases, however, therapeutic treatment must follow the surgical, before a perfect cure is accom- plished. The therapeutic treatment consists in first removing all irritating substances from the pulp-cavity, Avhich should be freely opened to the apex of the root, and the application of disinfectant and antiseptic remedies. For cleansing the root, chloride of sodium injected into the canal answers a good purpose, to be folloAved by such agents as will cause the absorption or destruction of the sac containing the pus, such as creosote, carbolic acid, salicylic acid (applied in the solid form), nitrate of silver, iodine, etc. When a tumor appears on the gum from the presence of the pus which has penetrated the bone, the contents of the abscess should first be dis- charged by making an opening in the tumefied gum with a sharp lancet, provided the disease has been allowed to progress to such a degree as to render this operation necessary. The opening in the gum should not be allowed to close until the pulp-cavity has been exposed, and the decomposed contents removed, Avhen this cavity should be thoroughly disinfected by such agents as were referred to in the treatment of periodontitis. If no opening has been formed through the alveolar process, the decay in the croAvn cavity should be removed, and the orifice of the pulp canal be so enlarged as to admit a nerve instrument or small broach, by means of which it can be cleaned out, and thus allow the matter to escape through the tooth. Tepid water should then be injected into the pulp canal by means of a small syringe until all decomposed matter is removed, Avhen one of the remedial agents mentioned above may be substi- tuted for the tepid Avater, or applied on a strand of floss silk, Avhich is carried to the apex of the root by means of a nerve instrument or broach. At the end of twenty-four or forty-eight hours, accord- ing to the character of the symptoms, this treatment is repeated, the ALVEOLAR ABSCESS. 333 croAvn cavity during the interval being filled with cotton. A com- bination of seAreral of the remedial agents is serviceable in obstinate cases, such as creosote and tincture of iodine, carbolic acid and tincture of iodine, or creosote and tannin in alcohol, Avhich can be Fig. 130. applied daily on floss silk, folio Aved by clean silk introduced daily for tAvo or three days, until the discharge ceases. Figs. 130 and 131 represent Dr. J. N. Farrar's alveolar abscess syringe, for injecting iodine, carbolic acid, etc., and also an ordinary hard rubber syringe for the same purpose. 334 DENTAL PATHOLOGY, THERAPEUTICS. The following solution of Dr. Percy Boulton possesses therapeutic virtues of superior efficiency, especially after creosote, carbolic acid, eucalyptus, iodoform, iodine, or salicylic acid, have been employed to stimulate and disinfect the secreting surfaces to a healthy action : R. Tr. iodin. comp.,.........^ x|v- Acid, carbolic, crygt. (fusa),......."X VJ- Glycerinse, ...••••••• 3 V11J- Aq. destillat.,..........3 v-~M- This solution possesses antiseptic and stimulant properties. This surgical treatment consists in making an opening, or enlarg- ing the fistulous one, through the alveolus, opposite the extremity of the affected root, by means of a small trephine, drill, or chisel, first making a vertical incision in the gum with the lancet, and thus gaining access to the seat of the disease. The attachment of the sac to the root is then broken up by means of a delicate instrument Avhich permits of being passed about the extremity of the root, and the wound in the gum kept open for a feAv days by inserting a tent, in order that the remains of the sac may escape, and such agents as tannin and glycerine, carbolic acid and glycerine, etc., may be ap- plied. It rarely happens that this surgical treatment can be made through the pulp canal of the root and without an opening in the alveolar process. During treatment, to prevent the occlusion of the teeth, where this may be necessary, a cap of gutta-percha can be moulded over the adjoining teeth by first softening this material in warm water. The excision of the apices of the roots of teeth, by means of a small trephine, and thus bringing away the sacs also, has been recommended as successful surgical treatment of alveolar abscess. Dilute aromatic sulphuric acid is a very reliable application, either alone or combined with a small quantity of tincture of cap- sicum, in chronic cases of alveolar abscess of long standing associ- ated with a necrosed condition of the margins of the processes. Replantation is also resorted to, and in many cases may prove efficient, if care is exercised to remove all coagulated lymph and diseased membrane, and also to fill the canal permanently before returning the tooth to its cavity. Under favorable circumstances a tooth thus treated may become firmly attached within a few days. Wrhen escharotic agents are injected into the pulp-cavity and through the fistulous opening in the process and gum, their contact with the mucous membrane may be prevented by the introduction of a Hill's stopping filling in the crown cavity, in the centre of Avhich an opening is made to admit closely the point of the syringe, Avhile at the same.time the parts about the fistulous opening are protected ALVEOLAR ABSCESS. 335 by bibulous paper, cotton, and napkins. When there is a tendency of the accumulated pus in the sac of an abscess upon one of the inferior teeth to discharge through an external opening in the cheek, or beneath the jaw, this result may be prevented by a free incision in the gum opposite the root of the affected tooth ; should the dis- charge, however, through an external opening be inevitable, the im- mediate extraction of the tooth is necessary. The application of fomentations and emollient poultices externally are rarely productive of any adA^antage, and may do harm by pro- moting the discharge of matter through the cheek or loAver part of the face. When this occurs, a depression, with puckering of the skin, is apt to remain after the escape of pus through the opening ceases and the orifice has closed, causing disfiguration of the face, which is caused by the formation of a strong cord of neAV tissue Avhich binds the skin firmly to the bone. It rarely happens, however, that anything more is necessary for the cure of the external opening than the extraction of the tooth Avhich has given rise to the formation of the abscess. The formation of an abscess in the alveolus of a loAver Avisdom tooth is sometimes productive of very serious and even alarming consequences. The following is one of several similar cases which have fallen under the observation of the author: In 1832, he was sent for in great haste to visit a physician who resided thirty miles in the country. He had been attacked two Aveeks before Avith severe pain in the left dens sapientise of the lower jaAv. At the expiration of three or four days, a physician Avas called in, avIio made several unsuccessful attempts to extract the tooth. The inflammation now extended rapidly to the fauces, tonsils, and muscles of the jaAv and face. Obstructed deglutition and a constant fever supervened, upon Avhich repeated blood-lettings, cathartics, and fomentations applied to the face had little effect. His respiration Avas difficult, and the muscles of his jaws soon be- came so rigid and firmly contracted that his mouth could not be opened. This was the condition of the patient when the author first saAv him, Avhich Avas the morning of the day following the one on Avhich he was sent for. In addition to the treatment which had previously been pursued, an injection with two grains of tartar emetic was administered. About seven o'clock in the evening the fever Avas succeeded by alternate paroxysms of cold and heat. An effort was now made to force open his mouth Avith a wooden wedge. This was partially successful, but his teeth could not be forced asunder suf- 336 DENTAL PATHOLOGY, THERAPEUTICS. ficiently to admit of the introduction of the smallest-sized tooth- forceps. But while his jaws Avere thus partially separated, he attempted to swallow some warm tea; in the effort an abscess burst and discharged nearly a tablespoonful of pus from his mouth, and it Avas supposed that double that quantity passed doAvn into his stomach. This gave immediate relief, but it was not until about three o'clock in the afternoon of the next day that his jaws could be forced apart sufficiently to permit the extraction of the tooth Avhich had caused the trouble. To the roots of this, which Avere united, there Avas attached a sac, about the size of a large pea, filled with pus. The patient recovered rapidly, and in a few days was quite Avell. The folloAving is the most singular case of alveolar abscess Avhich has ever fallen under the observation of the writer. The subject was a lady about thirty years of age. She had been troubled with a dripping of pus from behind the curtain of the palate for about twelve months, and becoming somewhat alarmed at its continuance, she called the attention of her family physician, Prof. Thomas E. Bond, to it, Avho carefully examined the case, and endeavored to ascertain the place from Avhence the matter came. He soon satisfied himself that it was from the socket of a diseased tooth. Upon pass- ing his finger around on the gums covering the superior alveolar border, he discovered a protuberance over the root of each upper central incisor, nearly as large as a hazel-nut. This tended to con- firm the opinion which he had formed as to the source from Avhence the matter came, and he requested us to visit the lady Avith him, which we did on the following day. On examining the case Ave ad- vised the immediate removal of the affected teeth, and the more strongly, as they were found to be in a necrosed condition. The lady readily consented to the operation, which was performed on the following day. The discharge of matter from behind the curtain of the palate immediately ceased, and the patient was re- lieved from an affection which had been a source of great annoyance. The pus from the abscess, in this case, instead of passing out through the nasal plates of the superior maxilla, passed back over the roof of the mouth, and escaped in the manner described. The author Avas once consulted in a case of a similar character to the one last noticed. The pus had found its way from the socket of a first superior molar to about the centre of the palatine arch, thence passed up into the posterior nares, and was discharged from behind the velum palati. Inflammation of the investing membrane of the roots of an in- ferior dens sapientise may produce equally serious effects, Avithout NECROSIS AND EXFOLIATION OP ALVEOLAR PROCESSES. 337 occasioning the formation of an abscess in the alveolus. The erup- tion of these teeth is sometimes attended Avith like consequences. The irritation has, in some instances, extended to the lungs, and even been, in decidedly consumptive persons, the exciting cause of consumption. The occurrence of alveolar abscess in the cavity of a temporary tootli is often folloAved by exfoliation of the sockets of several teeth, and sometimes of considerable portions of the jaw-bone, seriously injuring the rudiments of the permanent teeth, and sometimes caus- ing their destruction. The author saw a case, a few years since, in which an abscess of the alveolus of the first lower temporary molar had occasioned exfoliation of the sockets of a cuspid and two molars. About one-half of the alveolar cells of the two bicuspids and the cuspid of the second set were also exfoliated, thus leaving their im- perfectly formed crowns entirely exposed. The treatment of the chronic form of alveolar abscess is generally confined to the removal of the cause of the affection, or at least to that of the secretion, which in simple cases consists in the cleansing of the pulp-cavity of all irritating matter Avhich by its decomposed condition promotes the formation of pus. The application of dis- infecting agents is then indicated, such as eucalyptus, iodoform, iodine, carbolic acid, salicylic acid, etc., etc. Peroxide of hydrogen or sulphuric ether answer as good cleansing fluids in the form of injections by means of an abscess syringe. The entire tract of the abscess and fistulous opening should be subjected to the action of the disinfectant. Dr. G. V. Black has successfully em- ployed a combination of carbolic acid 2 parts, oil of cinnamon 1 part, and oil of gaultheria 3 parts, as a stimulant disinfectant in the form of an injection. The presence of sanguinary calculus on the root of a tooth affected with the chronic form of alveolar abscess, may retard or prevent the successful treatment, until such an irri- tant is removed. CHAPTER XIV. NECROSIS AND EXFOLIATION OF THE ALVEOLAR PROCESSES. The alveolar processes, as well as other osseous structures, are liable to necrosis or loss of vitality. When their connection with the periosteum—the source from Avhence they derive their nourish- ment and vitality—is destroyed, death folloAvs as a necessary con- sequence The loss of vitality may be confined to the socket of a 22 338 DENTAL PATHOLOGY, THERAPEUTICS. single tooth, but more frequently it extends to several, and sometimes to the alveolar border, occasionally including a part or the whole of the jaw. It may occur in either jaw, but it is more liable to take place in the lower than in the upper.. When confined to the alveoli, the dead part is never replaced Avith new bone, but examples are on record of the regeneration of a part, and even the whole of the lower jaw. When one or more of the cavities of the teeth lose their vitality, nature exerts all her energies to separate the dead from the living bone; this process, technically termed exfoliation, is supposed by some to consist in a sort of suppurath'e inflammation, but there is reason to believe it is effected by the action of a corrosive fluid poured out from the fungous granulations of the living bone in im- mediate contact Avith the necrosed part. During the process of exfoli- ation, a thin acrid matter is discharged from one or more fistulous openings through the gums or from between them and the necks of the teeth; the gums, having lost their connection with the ne- crosed bone, become soft and spongy, and assume a dark purple ap- pearance, are preternaturally sensitive to the touch, and bleed from the most trifling injury. In the admirable work of Mr. Fox, on the Natural History and Diseases of the Teeth, the case of a gentleman is related whose left lateral incisor became carious ; inflammation and pain ensued, to- gether with swelling of the gums and lip. Instead of consulting a physician, he applied poultices to his face, until suppuration in the alveolus took place, causing the formation of an external opening through the gums for the discharge of the matter. After his mouth had remained for some time in this condition, he applied to Mr. Fox, who, upon examination, found that not only had the decaA^ed tooth become loose, but also one on each side of it. The first he extracted, and discovered that the alveolus, from the destruction of the peri- osteum, was quite rough. The adjoining teeth, still continuing loose, were in a feAv Aveeks removed, and the slight force that was applied brought Avith them the alveolar process of the whole of the three teeth, and also a considerable portion of the jaw-bone. The author has met Avith several very similar cases, although all Avere not produced by the same cause, and he has several specimens in his possession, two of which were presented to him by his brother, the late Dr. John Harris. He has also met Avith two cases of necrosis and exfoliation of the alveolar processes, which are worthy of special notice. The subject of the first case was a gentleman of a strumous habit, about thirty years of age; the necrosis and exfoliation extended to NECROSIS AND EXFOLIATION OF ALVEOLAR PROCESSES. 339 the cavities of all the teeth in the upper jaw. He had the nerve destroyed in the second bicuspid, on the right side of the superior maxilla. We believe it Avas aftenvard remoA'ed, and the pulp-cavity and root filled. About six Aveeks after, as nearly as we could ascer- tain, the cavity of the tooth became slightly painful, but as his suffering Avas not constant, he supposed it would soon cease. The pain ultimately, hoAvever, began to increase, and by the latter part of the following September was so severe, and attended by so much constitutional disturbance, that he Avas induced to consult a physi- cian. After having been under medical treatment for about two weeks, the author was requested by the medical attendant to see him. The affected tooth wTas found to be loose, and its cavity in a necrosed condition; inflammation had extended to every part of the ahreolar border ; the gums were very much swollen, and nearly all the teeth sensitive to the touch. As the patient Avas laboring under con- siderable cerebral derangement, and as no advantage could be de- rived from the removal of the tooth at this time, it was deemed advisable to let it remain until exfoliation of the necrosed cavity should take place. Without going into a detailed description of the local and consti- tutional treatment subsequently pursued, it will be sufficient to state that necrosis extended to the cavities of all the other teeth, except those of the second and third molars, on each side of the mouth. In the course of about tAvo months tAvelve teeth, together Avith their exfoliated cavities, and several large pieces of the maxillary bone Avere removed. It was hoped that the disease Avould stop here, but in three or four Aveeks the four remaining molars became very sore to the touch, and as purulent matter began to be discharged from their sockets, it became necessary to remove them. Several small pieces of bone were exfoliated after the last operation, but at the expiration of about four months from this time his mouth Avas suf- ficiently restored to enable him to wear a temporary set of artificial teeth. The subject of the second case was a lady of a cachectic habit, about thirty-five years of age. The necrosis resulted from inflam- mation of the alveolo-dental periosteum, oc- casioned by irritation produced by the roots of four incisors, upon which pivot teeth had been placed, which, howeA^er, had been removed some tAvo or three Aveeks before the author saw the patient. At this time necrosis had ex- tended not only to the sockets of these teeth, but also up to the nasal crest of the maxillary bone, and the pro- 340 DENTAL PATHOLOGY, THERAPEUTICS. cess of exfoliation had already proceeded so far, that he Avas enabled to remove the entire piece, the appearance of which is represented in Fig. 182. A few weeks after the removal of this piece, he again saAv the patient, and, on examination, found a large portion of the palatine plate of the bone in a necrosed state; but the process of separation had not yet proceeded far enough to enable him to remove it. The accompanying engraving, made from a drawing furnished the author by Dr. Maynard, represents a case of necrosis and exfoliation of a portion of the outer Avail of the alveolar ridge, and the conse- quent protrusion of the roots of the teeth on one side of the mouth. The only facts Avhich Dr. Maynard had been able to procure in relation to this case were contained in the patient's statement: " That in 1818 he took a cold, which settled in his upper jaw, and a large piece of the jaw-bone came aAvay." The cast from Avhich the drawing Avas made was taken in 1840, at which time the doctor cut off the apices of several roots which projected from the gums. The alveolar process in relation Avith the superior central incisors appears to be more susceptible to necrosis than other portions, and this may be ascribed to such causes as diminished vitality occurring during conditions of depression and debility, the liability of such a prominent part to mechanical injury, and the effect of suppurative inflammation upon a portion of the process which possesses a less degree of restorative power than other portions better protected by muscular tissue. Phosphor-Necrosis.—Necrosis of the bones of the jaAvs may also result from exposure to the fumes of phosphorus, as in the manu- facture of matches, for example. The disease, when due to such a cause, usually commences about a carious tooth, or in an alveolar cavity opened by the extraction of a tooth, and is sometimes complicated with affections of the lungs and air-passages. In phosphor-necrosis there is a peculiar pasty appearance of the face, puffiness of the cheeks, and considerable pain and swelling in the affected jaw. Instead of the separation of a sequestrum, the dead bone becomes incrusted with a pumice-stone-like material, which adheres very firmly to it. Abscesses form and discharge ex- ternally through the skin of the cheek, and leave fistulous openings for the escape of the matter. NECROSIS AND EXFOLIATION OF ALVEOLAR PROCESSES. 341 CAUSES. The immediate cause of necrosis is the death of the periosteum, occasioned by inflammation. The cause of this, as has already been shown, is, in a large majority of the cases, dental irritation. Necrosis of the alveolar process occurs Arery frequently Avhile the system is under the influence of mercurial medicines, and during bilious and inflammatory fevers, and certain other constitutional diseases, as syphilis, small-pox, etc. It may also result from me- chanicalinjuriesandthedevitalizingeffectof such agents as arsenious acid and chloride of zinc, when applied to destroy pulps of teeth, and to obtund the sensibility of dentine, etc., etc. TREATMENT. The treatment of cases of this kind consists in the removal of the sequestra, strict attention to cleanliness, and the free use of chlori- nated washes. As soon as the dead portions of bone become sepa- rated from the living, and can be easily removed, they should be taken away Avith a pair of forceps. Should the removal of a con- siderable portion of the bone of the jaAv be requisite, it is seldom necessary to interfere with the skin, or make an external incision. The whole of the lower jaw can be removed in this manner by di- viding it at the chin, and after separating all the attachments of the soft parts with the knife, drawing out each half at a time. To correct the offensive odor and disagreeable taste occasioned by the constant discharge of fetid matter, Avashes of chloride of sodium may be employed. There is no remedy, perhaps, that gives more satisfaction in the treatment of necrosed alveolar process and carious bone, than dilute aromatic sulphuric acid, combined with a small quantity of tincture of capsicum, using alternately the antiseptic known as "listerine." Prior to the application of such agents, the diseased parts should be syringed Avith tepid water, and this cleansing process continued throughout the entire course of treatment. While cold AArater will coagulate pus and unhealthy secretions, Avhich are irritating by their pressure, Avarm Avater will produce the opposite effect, and is a use- ful adjunct to the antiseptic remedies. The removal of teeth in cases of necrosis of the areolar process, should only be resorted to after mature consideration, for it frequently happens that the affec- tion is confined to the labial walls, and if it is arrested new bone may he formed to such a degree as to give stability to the teeth in relation Avith the affected part. Condy's fluid, or a solution of permanganate of potash, a weak solution of carbolic acid, or a solution of chlorinated soda, will 342 DENTAL PATHOLOGY, THERAPEUTICS. ansAver as disinfectants, and correct the fetor. The strength of the patient should be supported by stimulants and tonics, and good nourishment. CHAPTER XV. ABSORPTION OR GRADUAL DESTRUCTION OF THE ALVEOLAR PROCESSES. This disease, to which the term " phagedenic pericementitis " is also applied, is a destruction of the walls of the alveolar cavities of the teeth, by a process of absorption which is always preceded by a corresponding loss of the peridental membrane, which is apparently caused by a chronic form of inflammation. WThen treating of inflammation and tumefaction of the gums, the author adverted to the Avasting of the alveolar cavities of the teeth, taking occasion to express a doubt that such operation of the econ- omy ever manifested itself in the absence of all local disease. It is always accompanied by a slight increase of redness, tume- faction, and a shrinkage of the edges of the gums (ulatrophia); but the diseased action here is so inconsiderable as often to attract little attention. It is also attended by a slight discharge of purulent matter from betAveen the margin of the gum and the tooth; but the quantity is so small that it usually escapes observation. The peri- dental membrane participates also in the diseased action, but this is so often confined to the corresponding wall of the process which is absorbed away, that the tooth often remains quite firmly articu- lated, after the Avasting of its socket has proceeded even so far as to expose more than half of the root. Indeed, the affection appears to be closely allied to chronic inflammation and tumefaction of the gums. The progress of the disease is often so slow that ten, fifteen, or tAventy years are required to affect very Fig. 134. perceptibly the stability of the teeth in their cavities. The commencement of this destructive process is usually first observed around the cuspid teeth; sometimes it makes its first appearance on the alveoli of the palatine'roots of the first and second upper molars, and occasionally it goes on here for years before it affects the cavities of any of the other teeth. The teeth, after their roots have been partially exposed, become, ABSORPTION OF THE ALVEOLAR PROCESSES. 343 as might naturally be supposed, more susceptible to impression from heat and cold, and more easily affected by acids or saccharine mat- ters ; but this is about the only manifest inconvenience experienced from the disease, until the teeth begin to loosen in their cavities and are gradually displaced. In Fig. 134 is represented a case in which the roots of the teeth have become considerably exposed by the gradual wasting of their sockets—the destruction being, as is usual, greatest toAvard the median line. It appears to be questionable whether the destruction of the al- veolar walls precedes or folloAvs that of the peridental membrane, but from the nature of the latter tissue and its important functions in relation to the bone, we are of the opinion that the absorption of the latter occurs as a consequence of the destruction of the peridental membrane. CAUSES. The cause of this peculiar affection has never been very satisfac- torily explained. Some have supposed that, inasmuch as it occurs most frequently in persons of advanced age, it results from a decline of the vital powers of the body, independently of local causes. But as it is often met with in middle-aged persons Avhose constitutional health is unimpaired, Ave doubt the correctness of the opinion. In , all cases which have come under our observation, whether in middle- aged or very old persons, the teeth indicated an excellent innate constitution, whatever may have been the state of the general health at the time. In every instance these organs AA'ere possessed of great density, and this fact is particularly noticed by Mr. Fox, Avho says: "In a majority of cases in Avhich this disease occurs,the teeth are perfectly sound, and from numerous observations, Ave think Ave may venture to assert that persons Avho have had several of their teeth affected Avith caries in the earlier part of life, are not liable to lose, by an absorption of their sockets, those which remain sound ; but where the teeth have not been affected with caries in the early part of life, persons, as they approach the age of fifty, and often much earlier, have their teeth becoming loose from absorption, or a Avast- ing of the alveolar process." Noav it is evident that teeth endowed with the poAver of resisting to so late a period of life the action of the causes of decay, to Avhich all teeth are more or less exposed, must be possessed of extreme density, and, necessarily, a corresponding low degree of vitality. In vicAV of this fact, we have been led to the opinion that the teeth themselves may act, to some extent, as mechanical irritants to the 344 DENTAL PATHOLOGY, THERAPEUTICS. more highly vitalized parts Avith Avhich they are immediately con- nected, causing an increase of vascular action in the periosteum of the thin edges of the alveoli and margin of the gums. This abnormal condition is attended by a slight secretion of purulent matter ob- served betAveen the edges of the gums and teeth. It is to the corrosive action of this purulent matter that the gradual destruction of the alveoli has by some been attributed ; but it is more probably a result of the obscure disease than its cause. This affection has been ascribed to the presence of salh^ary and sanguinary calculus, the use of charcoal powder as a dentifrice, and the application of a very stiff brush for cleaning the teeth ; but Avhen caused by these tAvo latter agents, the absorption does not progress to such a degree as when it is owing to a Avant of congeniality be- tween the tooth and the more highly vitalized structure surrounding its root, or the other causes before referred to. A later theory as to the cause of this affection has been advanced by Dr. Arkoevy, who believes that it is caused by a certain fungous formation found in close connection Avith the wasting of the alveoli and the gingival margin, as well as the subsequent loosening of the teeth; and that it is quite different from leptothrix buccalis, although it is in developmental relation with it. Dr. G. V. Black also states that it is probable that the disease is caused and maintained by the presence of some peculiar fungus or form of micro-organism and that it is infectious, this tendency being shown by the loss of the neighboring teeth. Others have ascribed this affection to a peridental inflammation arising from a gouty or rheumatic diathesis. TREATMENT. From what has been said concerning the cause of this affection, it is obvious that a cure cannot always be effected; its progress, however, may sometimes be arrested. The first step in the treatment is to remove all irritants, such as deposits of calculus from the necks and roots of the teeth, and correct the nature of the fluids of the mouth, abnormal in character, by constitutional treatment, the use of lime-water, and a detergent dentifrice. Should such means prove ineffectual, the application of a solution of iodine and creosote or carbolic acid to the margins of the gums will often be of benefit in retarding the absorption, and inducing a more healthy action. The secretion of the purulent matter, to the action of which some attrib- ute the destruction of the alveoli, is the result of a disease in the alveolo-dental periosteum and the edges of the gums, arising from some peculiar physical condition of the teeth, the progress of which may be retarded by cleaning the teeth frequently and thoroughly, HYPERTROPHY OF WALLS OF ALVEOLAR CAVITIES. 345 using the precaution each time to remove the purulent matter from betAveen the edges of the gums and teeth, lest, if allowed to remain it should become putrescent, and in this condition act as an irritant to the gum. For this purpose the parts should be washed Avith a solution of peroxide of hydrogen and bichloride of mercury (one grain of the latter to the ounce of the former), after which much benefit will be derived by applying a 30 per cent, solution of chlo- ride of zinc, by means of a camel's-hair brush, to the margins of the gums. As the margin of the gum is inflamed, and a sulcus or pocket formed between it and the tooth, the use of the agents above referred to, will promote health}7 granulations. The judicious application of pressure upon the gum has in some cases restored the receded portion, to a degree, at least. Dr. G. V. Black suggests that when there is rapid destruction of the tissue and a considerable portion of the alveolar wall has been destroyed, and much of the peridental membrane detached from the root of the tooth, it is better to cut away some parts of this with in- struments until firm bone is felt, but that care should be taken not to injure the gingival margin in any manner. The soft tissue farther up, however, may be lacerated without evil result, but the margin of the gum should be preserved so that it ma}7 close around the neck of the affected tooth. Where it is desirable to preserve a valuable tooth, one of the roots of which has been denuded of gum and process, such root may be amputated by the use of a fissure-burr operated by the dental engine. The root should be cut off as close to its union Avith the croAvn as possible and the surface made smooth. It is advisable to fill all the roots, with gold before amputating. CHAPTER XVI. HYPERTROPHY OF THE WALLS OF THE ALVEOLAR CAVITIES. A tooth is sometimes sloAvly forced from its place by a deposit of bony matter in the bottom or on the side of the socket. Two, or even three teeth, may be gradually displaced at the same time, by exostosis of the alveoli. The deposition usually proceeds so slowly that one or tAvo years are required to effect a very perceptible change in the situation of a tooth. The upper central incisors are more frequently affected than any of the other teeth, and the deposit oc- curs oftener at the bottom than on the sides of the alveoli. In the 346 DENTAL PATHOLOGY, THERAPEUTICS. first case, the tooth is gradually protruded from the socket; in the other, it is either pressed out of the arch, or against one of the ad- joining teeth. Irregularity in the arrangement of the teeth is, in this manner, sometimes produced, especially when more than one socket is affected at the same time. The central incisors are sometimes forced apart; at other times they are forced against each other, and caused to overlap. The deposition of bone, however, being generally con- fined to the bottom of the sockets, the teeth are more generally thrust from their alveolar cavities. When this occurs Avith a person whose upper and lower teeth strike directly upon each other, it oc- casions much inconvenience; for the elongated tooth must either be thrown from the circle of the other teeth, or, by striking its antagonist, prevent the jaws from coming together. CAUSES. So little is known concerning the cause of exostosis of the sockets of the teeth, that it may seem almost useless to attempt an explana- tion of it. That it results from some irritation of the lining mem- brane is very generally believed, but what causes the irritation does not seem to be Avell understood. We have thought that it might sometimes be produced by pressure on the bottom of the alveolus, especially Avhen the extremity is nearly as large as any other part of the root of the tooth. The susceptibility of the lining membrane to morbid impressions may sometimes be so great that the pressure of a very conical root may be sufficient to produce this effect; or, it may be produced by the pressure of a tooth which possesses only a very low degree of vitality. But in connection Avith this class of cases must be taken another, in which absence of all pressure would seem to be an inciting cause of alveolar exostosis; as Avhere a tooth has lost its antagonist tooth or teeth, and in consequence becomes elongated. A diseased state of the gums can have no agency in the production of the exostosis, for it most frequently occurs in indi- viduals whose gums are perfectly healthy; and if it were the result of any constitutional tendency, all the teeth would be as likely to be affected by it, as those we have mentioned. TREATMENT. When the exostosis is on the side of the alveolar cavity, the tooth cannot be restored to its natural position; but when it is in the bottom of the cavity, the elongated organ may from time to time, as it is forced from the alveolus, be filed or ground off even Avith the other teeth; but in doing this, care should be taken to avoid as much as possible the unpleasant jar Avhich the file or corundum disk is so NECROSIS OF THE TEETH. 347 apt to cause, and Avhich might, in such cases, excite the periosteum to increased activity and a more rapid deposit. This Avill remove the deformity and prevent its displacement by the antagonizing tooth. By this simple operation, repeated as occasion may require, it is preserved for years, and rendered almost as useful as any of the other teeth. Steady pressure in the proper direction, applied to the croAvn of a tooth so affected, may also prove serviceable at an early stage. CHAPTER XVII. NECROSIS OF THE TEETH. By the term necrosis, Avhen applied to a tooth, is meant the death of the entire organ, or of the croAvn and inner walls of the root; for it often happens that a degree of vitality is kept up in the outer portion of the dentine and the investing cementum by the peridental membrane long after the destruction of the pulp and lining mem- brane. When other bones are affected with necrosis, the dead part is throAvn off and the loss supplied by the formation of neAV bone. But the teeth are not endowed Avith the recuperative power which the process of exfoliation calls for. The density of a tooth is not sensibly, if at all, affected by the mere loss of vitality; but so great a change takes place in the ap- pearance of the organ, that it may readily be detected by the most careless obsener. After the destruction of the lining membrane, the tooth gradually loses its peculiar semi-translucent and animated appearance, assuming a dingy or muddy broAvn color; and this change is more striking in teeth of a soft than in those of a hard texture. The discoloration, too, is ahvays more marked when the loss of vitality has resulted from a blow, than when produced in a more gradual manner. The discoloration is partly owing to the presence of disorganized matter in the pulp-cavity, and partly to the absorption of this matter by the surrounding walls of dentine. After the destruction of the lining membrane, the tooth may re- ceive a sufficient amount of vitality from the alveolo-dental perios- teum to prevent it from exerting a manifest morbid influence upon the parts with which it is immediately connected. Teeth have been retained under such circumstances Avith apparent impunity for many years. But Avhen every part of a tooth has lost its vitality, it be- comes an extraneous body. When this happens, inflammation of the cavity ensues, the gum around it becomes turgid and spongy, and bleeds from the slightest injury, and the organ gradually loosens 348 DENTAL PATHOLOGY, THERAPEUTICS. and ultimately drops out. In the meantime the diseased action frequently extends to the cavities and gums of the adjoining teeth. The front teeth, being more exposed to injuries from violence, are more liable to necrosis than the molars. CAUSES. Necrosis of the teeth may be produced by a variety of causes, such as protracted fevers, the long-continued use of mercurial medicines, by caries and by external violence. The immediate cause, however, when not occasioned by a blow sufficient to destroy the vascular connection of the tooth with the rest of the system, is inflammation and suppuration of the lining membrane; but it may result from deficiency of vital energy and from impaired nutrition; for the author has met with several cases in Avhich the loss of vitality could not be accounted for in any other way. TREATMENT. When a tooth, deprived of vitality, is productive of injury to the gums and to the adjacent teeth, it should be immediately removed; for, however important or valuable it may be, the health and dura- bility of the others should not be jeopardized by its retention. When necrosis of a tooth is apprehended, Ave should endeavor to prevent its occurrence, by the application of leeches to the gums, and by gargling the mouth with suitable astringent washes, and the employment of such remedies as are useful in the treatment of alveolo-dental periostitis. If this plan of treatment is adopted at an early period, it will sometimes prevent the loss of vitality; but if long neglected, a favorable result need not be anticipated. When the loss of vitality is confined to the crown and inner walls of the root, if the former is not seriously impaired by caries, it may be perforated, and the pulp-cavity and root cleansed and filled in the manner as directed in another part of this work. If the necrosed tooth is an incisor, the perforation should be made from the palatal surface, provided the proximate surfaces are sound. But previously to the introduction of a filling, the decomposed surface of the walls of the pulp-cavity should be completely removed, and if this does not restore the tooth to its natural color, the process of bleaching should be resorted to. Bleaching Necrosed Teeth—To improve the appearance of a necrosed tooth which has become discolored from the dentinal tubuli absorb- ing the coloring matter from the blood, the following method may be pursued : First, remove all decayed matter from the crown-cavity, where such a cavity exists, taking care, hoAvever, to leave the enamel NECROSIS OF THE TEETH. 349 uninjured, and also as much of the dentine as is necessary for the strength of the tooth. Pursue the same course with regard to the canal in the root, cleansing this carefully by means of a syringe and tepid Avater, after the removal of decomposed matter with the nerve canal instruments. When the discoloration is recent, and not more than a red tinge in degree, such treatment as has been described may prove sufficient; should it not be, however, owing to the length of time the discoloration has existed, and the hue is a broAvn, dark broAvn or black, it is then necessary to resort to such agents as contain chlorine. Solutions of chloride of soda, chloride of lime, chlorate of potash, decompose organic substances by removing the hydrogen of their coloring matter. One of the most reliable of these preparations is the solution of chloride of soda, known as " habarraque's Disinfecting Fluid," which may be introduced on- a pellet of cotton, and alloAved to remain in the tooth from thirty to sixty minutes, according to the 'degree of discoloration present. Repeated applications may be necessary in some cases before the object desired is accomplished. To prevent the caustic action of these agents on the soft parts, the canal in the root should be partly filled prior to their introduction, and care taken to prevent their coming in contact with the mucous membrane of the mouth. The chloride of lime is introduced in the same manner as the chloride of soda, and is allowed to remain for five, ten, or fifteen minutes at a time, and its application repeated if necessary, the croAvn-cavity during the interval being protected by a temporary filling of Hill's stopping. Dry, fresh chloride of lime made into a paste with dilute tartaric acid has given satisfaction in many cases as a bleaching preparation; and in recent cases, or in slightly discolored teeth, the plastic filling material known as oxychloride of zinc, introduced into the crown cavity and worn as a temporary filling, has been effective in im- proving the appearance of a discolored crown. Oxalic acid care- fully applied and protected, is also effective as a bleaching agent, applied in the form of a crystal introduced into the carious cavity and dissolved by applying to it a drop of water. Cyanide of potassium in solution will remove the stains caused by old amalgam fillings, but must be employed with great care, as it is a very active and deadly poison. In the use of all these agents, it must be re- membered that upon the cause of the discoloration will depend the efficacy of the chemical agent, and that chlorine will answer in some cases, owing to the nature of the agents instrumental in pro- ducing the discoloration, Avhile cases of discoloration arising from the action of other agents, will require such preparations as oxalic acid, etc. 350 DENTAL PATHOLOGY, THERAPEUTICS. After the action of the bleaching agent is no longer required, a good practice is to fill the crown cavity of the tooth with either prepared chalk, or carbonate of magnesia, which may be secured by a tem- porary filling, and permitted to remain for several days ; or a filling of the oxychloride of zinc may be temporarily used, and a more permanent filling be subsequently introduced. Chloride of zinc in the form of crystals may also be employed as a bleaching agent; also chlorine water injected repeatedly by means of a syringe; also chlorate of potash and chloride of alumina. The peroxide of hydro- gen has also been used successfully for bleaching discolored teeth, and its disinfectant properties add to its value. The folloAving directions are given by Dr. A. W. Harlan : " After the root has been filled and the tooth is free from tender- ness, apply the dam, dry the cavity, and remove all discolored den- tine. Wash the cavity several times Avith fresh peroxide of hydro- gen and place a feAv crystals of chloride of alumina in the cavity, moisten Avith the peroxide of hydrogen, and wait from three to five minutes; wash the cavity thoroughly with distilled water, then apply a solution of 30 grains of borax to the ounce of Avater until the acid is entirely neutralized. Dry the cavity Avith hot air, and paint the interior Avith copal-ether varnish. When it is dry mix oxychloride of zinc of the desired color and fill the cavity full; allow it to harden, then prepare the cavity for the gold filling and fill it at once." In the incisor teeth it is recommended to glue white unruled note paper to the labial walls with varnish and cover it with oxychlo- ride, and afterwards fill Avith gold as a sequel to the bleaching operation. The active agent is oxygen, and even when chlorine is used to bleach discolored teeth the cavity should be moistened Avith Avater, as the latter is essential, for the chlorine, having a great affinity for the hydrogen of the Avater, unites with it and liberates the oxygen, which is the active agent. Electrolysis is also applied to the bleaching of discolored teeth by placing nascent oxygen in contact with the discolored surface. It is applied, according to Dr. W B. Ames, as follows : First fill the root and moisten the cavity Avith acidulated Avater (one drop to the ounce of water, in order to render it a more effectual electrolyte), then apply a metal electrode connected with the negative pole of the battery in contact with the moistened surface of margin of cavity and pass a platinum needle, connected with the positive pole of the battery, over the surface to be bleached. Upon closing the circuit the oxygen of the water is liberated at the positive pole near HYPERCEMENTOSIS—EXOSTOSIS OF THE TEETH. 351 the surface to be bleached, and the hydrogen is liberated at the negath-e electrode outside the cavity. Electrolysis is also recom- mended for the treatment of alveolar pyorrhoea. It should be remembered that the effect of these agents is to remove the organic or animal matter from the tooth-structure, and that their repeated application may cause the crown of the tooth to become frail and brittle. CHAPTER XVIII. HYPERCEMENTOSIS—EXOSTOSIS OF THE TEETH. This disease is common to all bones, but it attacks no other part of a fully formed tooth than the root; for in the cementum alone, of the three osseous dental tissues, do we find that degree of vascu- larity which is a necessary condition of groAvth—normal or abnormal. It usually commences at or near the extremity, then extends upward, covering a greater or less portion of the external surface. It some- times, hoAvever, commences upon the side of the root and forms a large tubercle; at other times the deposit of the new bony matter is spread over its surface, often uniformly, but more frequently unequ- ally. When it exists in a nodular form upon the roots, this deposit offers a very serious obstacle in the extraction of such teeth. The osseous matter thus deposited, has usually the color, consistence and structure of the cementum, though sometimes it is a little harder and assumes a yellower tinge. The enlargement is in fact an hypertrophied condition of this sub- stance. Mr. Tomes, alluding to normal cementum, remarks: " When it is limited to a thin layer, the lacunae are altogether absent, and even canaliculi do not appear until a certain thickness is attained. In a longitudinal section of a front tooth the cementum near the neck will present a thin layer of transparent tissue, marked with faint indications of granularity, accompanied in some cases with an obscure linear appearance, suggestive of the idea that the calcification of parallel fibres had contributed to its production. Proceeding in the direction of the root the cement thickens, and is traversed here and there by canaliculi; and still farther doAvn lacunas make their appearance, first as a single series, then, with an increased Fig. 135. 352 DENTAL PATHOLOGY, THERAPEUTICS. thickness of the cementum, in numbers; the number generally de- pending upon the thickness of the tissue." Those singular anom- alies, occasionally met with, where enamel, dentine and cementum are mixed up in a shapeless confusion, are no exceptions to the rule that exostosis is confined to the cementum ; for though classed under this head, these cases arise from the disruption of the formative membranes (possibly the result of violence), each secreting its pecu- liar tissue. The deposit of osseous matter is sometimes so considerable that the roots of two or more teeth are firmly united by it. Fig. 135 represents some common examples of hypercementosis. Fig. 136. Fig. 136 a represents the circumscribed variety, and Fig. 1366 the diffused variety. Hypercement is a product of the peridental membrane, and is formed in layers the first of which is attached to the primary ce- mentum, in the same manner as the first layer of this latter sub- stance is attached to the peripheral surface of the dentine. W^hen the normal cementum is fully formed, the peridental membrane becomes inactive as a hard tissue producer, until some pathological condition causes it to again assume such a function. An extraordinary case of dental exostosis Avas sent to the author for examination, by Dr. V. M. Swayze, of Easton, Pa. The tooth apparently is a dens sapientise, and the formation of the exostosis must have commenced with the dentinification of the pulp. It had spread over every part of the tooth, the croAvn as well as the root; it had ruptured and penetrated every part of the enamel membrane, but had not wholly destroyed the function of this organ, as nodules of enamel are seen in various parts of the exostosis. The tumor, including the tooth, is about as large as a common-sized hickory nut. In one instance, the author was compelled to extract four sound teeth and nine roots; yet the pain Avas not at any time severe, but it was constant, and a source of great annoyance to the patient. The HYPERCEMENTOSIS—EXOSTOSIS OF THE TEETH. 353 following is one among the many cases which have fallen under his observation: Mr. S., of Baltimore, in the fall of 1845, called upon us for adATice. Having for some time suffered pain in the first left superior bicuspid, he had applied tAvo years before to a dentist for the purpose of hav- ing the tooth removed. In the operation, the root, about three- sixteenths of an inch from its extremity, was fractured and left in the socket. In consequence of this, the gnawing pain with which he had for a long time before been troubled, continued, and at the expiration of tAvelve months the gum over the remaining portion of the root became very much swollen, puffing out the lip to the size of half a hen's egg. The tumor, after a feAv days, was opened, and a large quantity of dark-colored, fetid, purulent matter was dis- charged, which, for a short time, gave considerable relief. The tumor, hoAvever, Avas re-formed, and opened some four or five times in as many months. At this time his gum Avas swollen, and the upper lip puffed out in the manner just described. On opening the tumor, about three tablespoonfuls of black matter, resembling thin tar, escaped. We then found, upon examination, that the outer wall of the antrum, immediately over the remaining portion of the root of the first bicuspid, Avas destroyed, and there Avas an opening through it large enough to admit the forefinger. Believing that the extremity of the root left in the socket was the cause of the disease, Ave immediately proceeded to extract it, which Ave succeeded in doing after removing the outer wall of the alveolus. The root was found, on removal, to be enlarged by exostosis to the size of a very large pea. The operation proved perfectly successful, the secretion of purulent matter soon ceased, and in a feAv weeks he Avas completely relieved from the troublesome affection under which he had so long labored. Several }7ears ago, Prof. Gorgas, while demonstrating practical anatomy, discovered all the teeth in the mouth of one of the sub- jects (a negro girl about tAventy-five years of age) to be in an ex- ostosed condition. On the roots of one of the superior molar teeth the deposit of osseous matter measured three-fourths of an inch in diameter. Teeth affected with hypertrophy of the cementum may be free from tenderness even under pressure or percussion, although the gum may, in some cases, be slightly congested ; but the diagnosis of this affection is extremely difficult unless the enlargement of the root causes a prominence on the alveolar ridge, which is not often the case. 23 354 DENTAL PATHOLOGY, THERAPEUTICS. In many but not in all cases of this affection, more or less dis- comfort and pain attend this deposit, owing to the enlargement of the cementum with consequent pressure upon the nerves. When such an enlargement is in proportion to that of the alveolus, little or no pain may be experienced. The pain arising from the enlarge- ment of the cementum is at times moderate though persistent, but in some cases it may be excruciating, and may be referred to distant parts of the face and head or ear and about the terminal branches of the fifth pair of nerves, thus resembling neuralgia. CAUSES. Most writers concur in attributing the proximate cause of hyper- trophy of the cementum to irritation of the peridental membrane; but this is not, as some suppose, necessarily dependent upon any morbid condition of the crown itself, for it often attacks teeth that are perfectly sound. It seems rather to be attributable to some peculiar constitutional diathesis. It never makes its appearance on the roots of temporary teeth, nor upon permanent teeth until the sixteenth or twentieth year when the dental tissues are completely calcified. TREATMENT. When it is possible to discover the existence of dental exostosis at an early stage, iodide of potassium in large doses, and painting the gum over the affected root with such counter-irritants as a saturated tincture of iodine, or cantharidal collodion to produce a blister. The disease having established itself does not admit of cure, and when it has progressed so far as to be productive of pain and incon- venience to the patient, the loss of the affected teeth becomes inevi- table. When the enlargement is very considerable and confined to the extremity of the root, and has not induced a correspondent enlargement of the alveolus around the neck of the tooth, the ex- traction of the affected organ is often attended with difficulty, and can only be accomplished by removing a portion of the alveolar wall of the cavity, or fracturing it. Some are of the opinion, however, that the deposit of osseous matter may be arrested and absorption excited so as to make room for that already deposited, by the administration of iodide of potassium, as referred to above. EROSION OF THE TEETH. 355 CHAPTER XIX. EROSION OF THE TEETH. Tins is one of the most remarkable affections to which the teeth are liable, and occurs without any recognized cause. It consists in the gradual loss of substance on the labial surfaces of the teeth, and it attacks the incisors more frequently than the canines and some- times extends to the bicuspids and first and second molars. It first appears as a slight cup-shaped depression and increases over a limited space until it forms a continuous horizontal groove, as regu- larly and smoothly constructed as if it had been made with a file, about one line or less beloAV the free margin of the gum, the eroded surface being generally very sensitive. (See Fig. 137.) After it has removed the enamel, it commits its ravages upon the subjacent den- tine, sometimes penetrating to the pulp-cavity. It rarely changes Fig. 137. Fig. 138. the color of the enamel, but the dentine, after it becomes exposed, assumes first a light, and aftenvard a dark broAvn color, retaining, however, a smooth and polished surface. This destructive process does not ahvays commence at merely one point on the labial surface of the central incisors, as just described; it sometimes attacks several points simultaneously. (See Fig. 138.) As it spreads, these unite, and ultimately a deep excavation is formed, Avith walls so smooth and highly polished that the tooth presents the appearance of having been scooped out with a broad, square, or round-pointed instrument. It is often confined to the incisor and canine teeth and in some cases to the teeth on one side of the mouth only. The progress of the affection is exceedingly variable. It is some- times so rapid that the dentine becomes exposed within two or three years from the commencement of the disease; at other times its effect upon the enamel is scarcely perceptible for the first six or eight years after it makes its appearance. In the case of a lady whose teeth Avere thus affected, the denuding process did not per- forate the enamel for nearly twenty years. The dentine, after it is denuded of enamel, is generally quite sensitive, and very susceptible to heat and cold. CAUSES. The cause of this singular affection has never been satisfactorily explained. It Avas first noticed by Mr. Hunter, who called it decay 356 DENTAL PATHOLOGY, THERAPEUTICS. by denudation, and supposed that it was a disease inherent in the tooth itself, and not dependent on circumstances in after life, for the reason that it attacks certain teeth rather than others, and is often confined to a particular tooth. Some writers suppose it is occasioned by chemical action, to Avhich, however, there appears to be many valid objections. Mr. John Tomes and also Mr. Salter ascribe it to the vigorous use of the toothbrush or other friction, but such a cause is improbable. That this may increase the size of the horizontal groove is more than probable ; that it may even in some cases determine the commence- ment of the groove, is just possible. But no conceivable action of the brush could be an inciting cause of that form of the disease shown in Fig. 138. There is better reason for believing that this affection is due to a condition of enamel deficient in vital resistance, owing to some modification at the period of its formation, thus ren- dering it susceptible to the action of agents which it might, under more favorable circumstances, successfully resist, such as an acid contained in the mucus. Others have regarded it as dependent on faulty tooth structure, but microscopical examinations have failed to establish such a theory, as, according to Dr. Black, the erosion does not follow the developmental lines, which would be the case if portions of the teeth could be worn away on account of any soft- ness from faulty development. The generally accepted theory is that this affection is caused by the action of an acid secretion, abnormal in character, produced on the inner surface of the lip, the motion of the latter assisting in the solution of the tooth-substance. Dr. \V. D. Miller records the following experiment, which he regards as definitely settling the question as to whether or not ero sion occurs in pulpless teeth: " We have all seen pulpless teeth Avhich presented extensive erosions, but we have not been able to say that these erosions were not produced while the pulp of the tooth was still alive, and, as far as I am aware, no one has succeeded in refuting beyond all doubt the assertion that erosion attacks only teeth with living pulps. On the 7th of April, 1886, a piece of ivory was set, by means of cement, in the cavity of a right inferior bicus- pid, Avhere the loss of substance by erosion was so extensive that it would have exposed the pulp if the latter had not been protected by secondary dentine. On the 23d of April, 1888, the piece was removed for examination, and showed two very distinct parallel horizontal furrows. The surface had a very fine polish, character- istic of abraded dentine. No one examining the piece of ivory would hesitate for a moment to pronounce it a typical case of erosion." EROSION OF THE TEETH. 357 TREATMENT. In advanced stages of the affection, its progress may be arrested by properly preparing the cavities, and afterwards filling them Avith gold ; or if the defective spaces will permit, porcelain sections or facings may be inserted. This, in the majority of cases, will prove successful. Should the grooves or pits when superficial, become dis- colored, it will be proper to use occasionally pumice or silex applied on a point of wood. Erosion associated with Abrasion.—This process was formerly treated under the title of " Chemical Abrasion " but as it appears to be an affection of the teeth in which the effects of both erosion and abrasion from mechanical causes are combined, it is considered under the head of erosion. It is of rare occurrence, and commences on the central incisors, proceeding thence to the laterals, the cuspids, and sometimes, though very rarely, to the first bicuspids. Teeth thus affected have, when the jaws are closed, a truncated appearance ; the upper and lower teeth do not come together, and they are rather more than ordinarily susceptible to the action of acids, or of heat and cold. In other respects, little or no inconvenience is experienced until the croAvns of the affected teeth are nearly destroyed. Its progress, as in the case of simple abrasion of the labial sur- faces, is exceedingly variable. It sometimes destroys half or tAvo- thirds of the croAvns of the central incisors in two or three years ; at other times seven or eight years are required to produce the same effect. In one case which came under our OAvn observation, the abrasion had'extended to the bicuspids, and the central incisors of both jaAvs Avere so much AA'asted, that on closing the mouth they did not come together by nearly three-eighths of an inch ; yet two years only had elapsed since its commencement. In another case, Avhere it had been going on for seven years, it had not extended to the cuspids, and the space between the upper and loAver incisors did not exceed an eighth of an inch. The subjects of these two were gentlemen—the first aged about "About fourteen months since (1831), this gentleman perceived that the edges of the incisors, both above and beloAV, had become slightly Avorn down, and as it were, truncated, so that they could no longer be placed in contact with 358 DENTAL PATHOLOGY, THERAPEUTICS. each other. This continued to increase and extend to the lateral in- cisors, and, afterward, successively, to the cuspids and bicuspids. There has been no pain, and only a trifling degree of uneasiness, on taking acids, or any very hot or cold fluids, into the mouth. W'hen I first saAv these teeth, they had exactly the appearance of having been most accurately filed clown at the edges, and then perfectly and beautifully polished ; and it has now extended so far that Avhen the mouth is closed the anterior edges of the incisors of the upper and lower jaAvs are nearly a quarter of an inch asunder. The cavi- ties of those of the upper jaw must have been exposed, but for a very curious and beautiful provision ; they have become gradually filled by a deposit of neAV bony matter, perfectly solid and hard, but so transparent that nothing but examination by actual contact could convince an observer that they were actually closed. This appear- ance is exceedingly remarkable, and exactly resembles the trans- parent layers which are seen in agatose pebbles, surrounded by a more opaque mass. The surface is uniform, even, and highly polished, and continues, without the least break, from one tooth to another. It extends at present to the bicuspids, is perfectly equal on both sides, and when the molars are closed, the opening, by this loss of substance in front, is observed to be Avidest in the centre, diminishing gradually and equally on both sides to the last bicus- pids." The same causes may be ascribed for this affection as for those of erosion and abrasion. There is apparently some defect of struct- ure, which renders the central portions of the tooth-surface suscep- tible to both erosion and mechanical abrasion, and the latter process may account for the smooth and polished surfaces Avhich are invari- ably present. • * From the fact that teeth thus affected continue to lose structure much more rapidly than the unaffected teeth of the same mouth do from mastication, and this too even after they cannot be brought in contact with each other, we cannot ascribe the affection to mechani- cal abrasion alone ; and careful observations have failed to find any cause for such loss of substance in the dentine structure. Dr. Black remarks that: "the effect is certainly that of erosion, and is identical with that process as seen on the labial surfaces of the teeth and occurring independently of mechanical abrasion. The only treatment for such cases is that of restoration, either by means of capping Avith gold, or the attachment of sections of porce- lain croAvns; as no therapeutic treatment will control or arrest this singular disease. ABRASION OF THE TEETH. 359 CHAPTER XX. ABRASION OF THE TEETH. Were it true, as declared by Richerand, that the loss of the enamel occasioned by friction is repaired by a new growth, it would never suffer permanent loss from mechanical abrasion. But enamel and dentine, once formed, pass beyond the sphere of that reparative power found in other bony tissues where red blood circulates freely. NeAV enamel is therefore never formed after the eruption of the tooth ; and new dentine only within the pulp-cavity by the action of the odontoblasts. The teeth rarely suffer much loss of substance from friction when the incisors of the upper jaw shut in front of those of the lower. It is only Avhen the former fall directly upon the latter, that mechani- cal abrasion of the cutting edges of the front teeth can take place, and when this happens, they sometimes suffer great loss of sub- stance. The croAvns of these teeth are occasionally worn entirely off, while those of the molars and bicuspids are, comparatively, little affected. The lateral motions of the jaw, being in these cases unrestricted—and this motion being, of course, greater at the anterior than at the posterior part of the mouth—it necessarily happens that the front teeth suffer the most abrasion. Sometimes all the teeth are worn off alike ; at other times, OAvingto the peculiar manner in which the jaws come together, the abrasion is confined to a few. Abraded surfaces of teeth often become very sensitive, and the irritation affects the dental pulp in such a manner as to often favor the deposit of secondary dentine. The rapidity of the abrasion depends greatly upon the manner in which the teeth antagonize, as sliding movements when the jaws are closed cause abnormal wear of the two surfaces. No doubt the grinding together of the teeth during sleep, the effect of nervous- ness, also facilitates the abrasion. Abrasion is frequently caused by the loss of a number of teeth, which necessarily brings the entire Avork of mastication upon the remaining ones to such a degree as to rapidly Avear them away, especially Avhen the latter are feAv in number. Mr. Bell believes that certain kinds of diet tend, more than others, to produce abrasion of teeth; in proof of Avhich he tells us that sailors who, the greater portion of their lives, live on hard biscuits, have only a small part of the crowns of their teeth remaining. But the antagonism of the teeth has much more to do with it than the 360 DENTAL PATHOLOGY, THERAPEUTICS. nature of the food; though, of course, when they do not strike in such a way as to wear the cutting surfaces, very hard or gritty ar- ticles of food would make the abrasion more rapid. When the front teeth of the lower jaw strike against the pala- tine surface of those of the upper, the latter are sometimes Avorn aAvay more than three-fourths, and in some instances entirely upon the gums. We have seen the teeth of some individuals so much abraded, in this way, that little of the crown remained, except the enamel on the anterior surface. The Avearing away of the crowns of the teeth would sooner or later expose the pulp, Avere it not that nature, in anticipation of the event, sets up an action by which layers of odontoblasts of the pulp resume their functional activity, and a portion of the organ, or the entire mass of it, at times is transformed into osteo-dentine. By this beautiful operation of the economy, the painful consequences that Avould otherwise result from the exposure of the pulp are Avholly prevented. TREATMENT. The early correction of irregularities in the arrangement of the teeth, so that a proper antagonism of the teeth is secured, by which the cusps will fit into sulci of the opposing teeth, may be suggested as preventive treatment in many cases. After the abrasion has occurred, the adaptation of caps of gold or other metal, or gold in the form of contour fillings, or enamel sections, to the cutting edges and grinding surfaces thus worn away, Avill often preserve and render useful teeth in such a condition. CHAPTER XXI. FRACTURES AND OTHER INJURIES OF THE TEETH FROM MECHANICAL VIOLENCE. The injuries to which teeth are subject from mechanical violence are so variable in their character and results as to render a detailed description impossible. The same amount of violence inflicted upon a tooth does not always produce the same effect. The nature and extent of the injury will depend as much upon the physical condition of the teeth, the state of the constitutional health, and the susceptibility of the body to morbid impressions, as upon the violence of the blow. Thus, a blow sufficiently severe to loosen a tooth might not, in one case, be productive of any permanent bad INJURIES OF THE TEETH FROM MECHANICAL VIOLENCE. 361 consequences; while in another, it might cause the death of the organ and inflammation of the adjacent parts, as well as necrosis of the alveolus. A tooth of compact texture, and in a healthy mouth, may be de- prived of a portion of its substance without any serious injury ; but a similar loss of substance in a tooth not so dense in structure Avould be likely to produce inflammation and suppuration of the lining membrane, and possibly of the alveolo-dental periosteum. Hence, in order to form a correct opinion of the result of injuries of this sort, Ave must take into consideration not only the character of the tooth upon Avhich the bloAV has been inflicted, but also the state of the mouth and the health of the individual. If the tooth is not loosened in its cavity, any injury resulting from a loss of a small portion of the enamel, or even of the dentine, may be prevented by smoothing the fractured surface Avith a file, that the juices of the mouth and particles of extraneous matter may not be retained in contact Avith it. But if the tooth is loosened, and inflammation of the investing membrane has supervened, leeches should be applied to the gums, and the mouth Avashed several times a day with some astringent lotion, until the inflammation subsides. For more detailed treatment, the reader is referred to the chapter on periostitis. When a tooth has been displaced from its cavity by a 1)1oav, and its vascular connection Avith the general system destroyed, necrosis must, as' an almost necessary consequence, be the result. An im- perfect union betAAreen the tooth and alveolus may sometimes be re-established by the effusion of coagulable lymph, and the forma- tion of an imperfectly organized membrane ; but the tooth will ever after, from the slightest cold, or derangement of the digestive organs, be liable to become sore to the touch, and in most cases will ulti- mately assume a muddy broAvn, unhealthy appearance. The author has, on several occasions, replaced teeth that had been knocked from their cavities; and in some instances the operation was attended Avith success. The subject in one case Avas a healthy boy, of about thirteen years of age, who, Avhile playing bandy, re- ceived a bloAV from the club of one of his playmates, Avhich knocked the left central incisor of the upper jaAv entirely out of its ca\dty. He saAv the boy about fifteen minutes after the accident. The alve- olus Avas filled Avith coagulated blood. This he sponged out, and after having bathed the tooth in tepid Avater, carefully and accurately replaced it in its socket, and secured it there by silk ligatures at- tached to the adjacent teeth. On the folloAving day the gums around the tooth Avere considerably inflamed, to reduce Avhich in- 362 DENTAL PATHOLOGY, THERAPEUTICS. flammation he directed an application of three leeches and the frequent use of diluted tincture of myrrh as a wash for the mouth. At the expiration of four weeks the tooth became firmly fixed in its socket, but from the effusion of coagulable lymph, the alveolar membrane was thickened, and the tooth, in consequence, protruded someAvhat. A slight soreness, on taking cold, has ever since been experienced. Dr. Noyes, of Baltimore, mentioned to the author a case of a somewhat similar character. The subject was a boy about ten years of age. One of his front teeth Avas forced from its socket by a fall. It was replaced shortly after, and in a few weeks became firm in its alveolus. Mr. Bell also mentions a case attended with a like result. The alveolar processes and jaAV-bones are sometimes seriously in- jured by mechanical violence. The author was requested by the late Dr. Baker, of Baltimore, to visit, with him, a lady who, by the upsetting of a stage, had her face severely bruised and lacer- ated. All that portion of the lower jaw Avhich contained the six anterior teeth was splintered off, and was only retained in the mouth by the gums and integuments with which it was connected. The Avounds of her face having been properly dressed, the detached portion of the jaw was carefully adjusted and secured by a ligature passed around the front teeth and first molars, and by a bandage on the outside, around the chin and back part of the head. Her mouth was washed five or six times a day with diluted tincture of myrrh. The third day after the accident Dr. Baker directed the loss of twelve ounces of blood; and in five or six weeks, with no other treatment than the dressing of the wounds, she perfectly recovered. It often happens that the crown of a tooth is broken off at the neck. Wre have known Jie croAvns of four, and in one case of thir- teen, teeth to be fractured by a single blow. The subject of the last case was a fireman, who, received an accidental bloAV on his mouth from the head of an axe, which broke off the crowns of all the upper and lower incisors, tAvo cuspids, and three of the bicus- pids of the inferior maxilla. The subject in the other case was a boy about twelve years of age, who, from a similar accident, occa- sioned by running up su Idenly behind a man who Avas chopping wood, had the crowns of his upper incisors broken off. In both of these cases the inflammation which supervened Avas so great as to render the removal of the roots necessary. The crowns, roots, and alveolar processes are sometimes ground to pieces, or the teeth driven into the very substance of the jaw. Mr. Bell says he once found a central incisor so completely forced into the bone, that he thought it to be the remains of a root; but, on removing it, found it to be an entire tooth. CARIES OF THE TEETH. 363 When the crown of a tooth has been broken off by a Woav, and destructive inflammation results, the root should be extracted. When, however, the injury has not been sufficient to cause such a degree of inflammation, an artificial crown may be engrafted on the root; but it is very necessary that the inflammation should be en- tirely subdued previous to the operation of pivoting. If the tooth is to be replaced with an artificial substitute attached to a plate, the root should be first extracted, unless it is adapted to serve as a sup- port for a section of bridge-Avork. In some cases, however, the root may be filled and be permitted to remain ; but the practice is usu- ally a bad one. The possibility of a fractured tooth reuniting was formerly doubted, but Wedl, in his "Pathology of the Teeth," refers to some fifteen cases in which union took place, some of Avhich were due to the formation of secondary dentine, and others to that of cementum. CHAPTER XXII. CARIES OF THE TEETH. The teeth are more liable to be attacked by caries than by any other disease, and this will now claim our attention. Caries of a tooth is the chemical decomposition of the earthy salts of the affected part, sometimes, but not ahvays, accompanied by disorganization of the animal frameAvork of this portion of the organ. There is no affection to which these organs are liable more frequent in its occurrence, or fatal in its tendency, than this. It is often so insidious in its attacks, and rapid in its progress, that every tooth in the mouth is involved in irreparable ruin before even its existence is suspected. Its presence is usually first indicated by an opaque or dark spot on the enamel; and, if this be removed, the subjacent dentine will exhibit a black, dark-broAvn, or Avhitish appearance. It usually commences on the outer surface of the dentine of the crown, be- neath the enamel, at some point Avhere it is imperfect, or has been fractured or otherwise injured; from thence it proceeds toward the centre of the tooth, increasing in circumference until it reaches the pulp-cavity. If the diseased part is of a soft and humid character, the enamel, after a time, usually breaks in, disclosing the ravages the disease has made on the subjacent dentine. But this does not ahvays happen; the form of the tooth sometimes remains nearly perfect until its whole interior structure is destroyed. 364 DENTAL PATHOLOGY', THERAPEUTICS. Fig. 140. No portion of the croAvn or neck of a tooth is exempt from this disease; yet some parts are more liable to be first attacked than others; as, for example, the depressions in the grinding surfaces of the molars and bicuspids, the approximal surfaces of all the teeth, the posterior or palatine surfaces of the lateral incisors, and, in short, Avherever an imperfection of the enamel exists. The enamel is much harder than the dentine, and is by far less easily acted on by the causes that produce caries. It is sometimes, hoAvever, the first to be attacked, and when this happens, the disease develops itself more frequently on the labial or buccal surface, near the gum, than in any other locality; often commencing at a single point, and at other times at a number of points. When the enamel is first attacked, it is usually called erosion; but as this tissue does not contain so much animal matter as the subjacent dentine, the diseased part is often washed aAvay by the saliva of the mouth; while in the dentinal part of the tooth, it, in most instances, remains, and may be removed in distinct laminae, after the earthy salts have been decomposed. In very hard teeth, the decayed part is of a firmer consistence, and of a darker color than in soft teeth. Sometimes it is black; at other times of a dark or light brown; and at other times, again it is nearly white. As a general rule, the softer the tooth, the lighter, softer and more humid the caries. The color of the decayed part, hoAvever, may be, and doubtless is, in some cases, influenced by other circumstances ; per- haps by some peculiar modification of the agents concerned in the production of the disease. Commencing externally beneath the enamel, the disease proceeds, as before stated, toAvard the centre of the tooth, de- stroying layer after layer, until it reaches the lining membrane, leaving each outer stratum softer and of darker color than the subjacent one. The dentinal tubuli become less dis- tinct near the margin of the carious structure than is the case in the perfectly normal tissue in proximity with the pulp-chamber, and, according to Mr. John Tomes, has a zone-like form (the zone of Tomes), Avhich he regards as a consolidation of the dentinal tubuli, an effort on the part of nature to place a line of demarcation between the healthy and carious structure. *A transparent zone of dentine removed a short distance from and surrounding that which is under- going decomposition consequent upon caries. CARIES OF THE TEETH. 365 Other writers, however, consider this zone of transparency to be the result of diseased action causing a complete exclusion of air from the tubuli, thus rendering them invisible when viewed by transmitted light. The terms deep-seated, superficial, external and internal, simple and complicated, have been applied to the disease. These distinctions only designate different stages of the same affection. By complicated decay is meant caries which has penetrated to the pulp-cavity of the tooth, accompanied by inflammation and suppuration of the lining membrane, and the death of the organ. The lining membrane, however, is not always inflamed by exposure, nor is inflammation invariably followed by suppuration. The roots of the teeth frequently remain firm in their sockets for years after the croAvns and necks have been destroyed, shoAving that they are less liable to decay than the croAvns; but nature, after the destruction of the last, as if conscious that the former are of no further use, exerts herself to expel them from the system, Avhich is effected by the gradual wasting and filling up of their sockets. After this operation of the economy has been accomplished, they are frequently retained in the mouth for months, and even for years, by their periosteal connection Avith the gums. The effort of nature is confined more to the back than to the front teeth; it often happens that the last remain, after the destruction of their crowns, for many years, and sometimes without much apparent injury to the parts within Avhich they are contained. DIFFERENCES IN THE LIABILITY OF DIFFERENT TEETH TO DECAY. Having explained at some length, in a preceding part of this Avork, the manner in which the physical condition of the teeth is influenced, it will not now be necessary to dAvell upon this portion of the sub- ject. It Avill only be requisite to state, therefore, that teeth Avhich are Avell-formed, well arranged, and of a firm texture, seldom decay, and Avhen they are attacked, the progress of the disease is not rapid; Avhereas, those that are imperfect in their formation, and of a soft texture, are more susceptible to the action of the causes Avhich produce it; and when assailed, if the progress of the affection is not arrested by art, they usually fall speedy victims to its ravages. Just in proportion as the dentinal structure of the teeth is hard or soft, the shape of the organs perfect or imperfect, their arrange- ment regular or irregular, is their liability to caries diminished or increased. The density, shape and arrangement of the teeth are influenced by the state of the general health, and that of the mouth at the time of their dentinification. If, at this period, all the functions of the 366 DENTAL PATHOLOGY, THERAPEUTICS. body are healthily performed, these organs will be compact in their structure, perfect in their shape, and usually regular in their ar- rangement. That the teeth should be thus influenced will not appear strange, when we consider, as Richerand remarks, " that there exist amongst all the parts of the living body intimate relations, all of which correspond to each other, and carry on a reciprocal inter- course of sensations and affections. Hence, if there is a morbid action in one part, other parts sympathize with it, rallying, as if sensible of the mutual dependence existing between them, all their energies to rescue their neighbor from the power of disease." Increased action in one portion of the system is generally followed by diminished action in some other part; thus, for example, gastritis may be produced by constipation of the bowels; pueperal fever by diminished action in the heart, with an increased action in the uterus, etc. Hence, we may conclude, that if the body, at an early age, be morbidly excited, its functions will be languidly performed, the process of assimilation checked, the regular and healthy supply of earthy matter in the bones interrupted, and, consequently, that the teeth which are then formed will be defective. Other parts of the body, in which constant changes are going on, if thus affected at these early periods, may afterwards recover their healthful vigor; but if the teeth are badly formed, they must ever, because of their low degree of vascularity, continue so; hence they will be more liable to decay than when dentinified under other and more favor- able circumstances. Capillary bloodvessels form a large part of every organ, the char- acteristic tissue of each being strictly extra-vascular (literally, outside of the vessels). Where the bloodvessels are most abundant, as in the nervous and muscular structures, growth and change take place rapidly and constantly ; since almost every particle of the extra- vascular or interstitial tissue is in contact Avith the circulating fluid, the function of which is to supply material for growth and carry off waste matter. Hence such organs have great recuperative power, and are modified by the varying conditions of the body. But the dentine and enamel of the teeth are vascular only during the period of development. These structures, once formed, pass beyond the reach of the capillaries, except the layer of dentine in contact with the dental pulp. Hence the dental pulp may deposit new bone as a barrier against caries; but the carious dentine itself is incapable of self- restoration. " That the teeth acquire this disposition to decay," says Mr. Fox, "from some want of healthy action during their formation, seems to be proved by the common observation, that they become decayed in CARIES OF THE TEETH. 367 pairs; that is, those which are formed at the same time, being in a similar state of imperfection, have not the power to resist the causes of the disease, and therefore, at nearly about the same period of time exhibit signs of decay; while those Avhich have been formed at an- other time, Avhen a more healthy action has existed, have remained perfectly sound to the end of life." Most Avriters are of opinion that the power of the teeth to resist the various causes of decay is sometimes weakened by a change brought about in their physical condition through the agency of cer- tain remote causes, such as the profuse administration of mercury, the existence of fevers and all severe constitutional disorders. Severe constitutional disorders, and the administration of certain kinds of medicine, may not act directly on the teeth, by altering their physical condition, and thus rendering them more susceptible to the action of corrosive agents; but they are indirectly affected in proportion as the secretions of the mouth are vitiated and their cor- rosive properties increased. The folloAving considerations establish, to our mind, the truth of Avhat we have just stated. Artificial teeth of bone or ivory decay more rapidly after the profuse administration of medicine, or during the existence of any disease that tends to vitiate the secretions of the mouth, than at other times. Furthermore, teeth of so dense a text- ure as to be capable of resisting the action of the acidulated buccal fluids are not affected by constitutional disease; yet they are just as liable as those of a spongy texture, to any structural disease com- municated from the general system. The following is the result of our OAvn observations: the gums and alveolar processes are sometimes destroyed by the use of mer- cury, so that all the teeth loosen and drop out, without being affected by caries. The teeth of persons in Avhom a mercurial diathesis has been a long time kept up, or Avho have been for years suffering from dyspepsia, phthisis, feA'ers, or other severe constitutional disorders, often continue perfectly sound; while other teeth, under similar circumstances, frequently decay. Noav, all this goes to prove, not that changes are effected in the structural condition of the teeth, Avhereby their predisposition to decay is increased, but that there are differences in the capabilities of different teeth to resist the action of the secretions of the mouth, made acrid by the affections just enumerated. The author has noted the effects of mercury and of other medi- cines, as Avell as of constitutional diseases of the severest and most protracted kinds, and has ahvays observed that—occurring after the development of the teeth—it Avas only as they impaired the healthy qualities of the fluids of the mouth that they affected these organs. 368 DENTAL PATHOLOGY, THERAPEUTICS. In fact, their density, their exposed situation, their functions, all would seem to indicate that such changes as take place in other parts of the body are not only unnecessary, but many of them are impossible, and designedly so, that they may more fully answer their purpose. Dr. Good says " that caries of the teeth does not appear to be a disease of any particular age or temperament, or state of health." It is true it is not a disease of any particular state of health, further than that certain constitutional affections exert a deleterious in- fluence upon the secretions of the mouth, and thus become indirect causes of decay of these organs. That it is not a disease of any par- ticular age seems to contradict common experience, for it compara- tively seldom happens that caries appears after the age of forty. The reason of Avhich is obvious. Teeth of a loose texture, or othenvise imperfect, cannot resist the action of the causes of delay to Avhich all teeth are, up to this period of life, more or less exposed; while those which from their greater density remain unaffected thus long, are generally enabled, by the increased solidity they gradually ac- quire, to resist them through life. Teeth sometimes, though rarely, decay at fifty, or even at a later period ; but caries of the teeth, generally, may be said to be confined to youth and middle age. The formation, arrangement, and physical condition of the teeth are sometimes influenced by hereditary diathesis, affecting the parts concerned in their production, or the general system. That a mor- bid condition of the system, on the part of either parent, often pre- disposes their progeny to like affections, is an axiom fully recognized in pathology, and a fact of which we have many fearful proofs. That there is an hereditary tendency in the teeth to decay, cannot, we think, be denied. But we believe it to be the result of the trans- mission of a similarity of action in the parts concerned in the pro- duction of these organs; so that the teeth of the child are, in form and structure, like those of the parent whom it most resembles, and from whom it has inherited the diathesis. The teeth of the child, if shaped like those of the parent, possessing a like degree of den- sity, and similarly arranged, are equally liable to disease; Avhen ex- posed to the action of the same causes, they are affected in like manner, and, usually, at about the same period of life. Such being the fact, is it unreasonable to conclude that judicious early attention may so influence the formation and arrangement of the teeth that their liability to disease may be diminished ? Medicinal remedies and sickness have a powerful influence upon the dental tissues; first, through hereditary transmission of an impaired constitution; secondly, by their action upon the process of development, if given while the teeth are being formed. It is, then, to the differences in CARIES OF THE TEETH. 369 the physical condition and manner of arrangement of these organs —Avhether in different individuals or in the same mouth—that the difference in their liability to decay is attributable. Dr. John Allen remarks : " The nutritious substances in the food that Ave take are intended to build up all parts of the system—the hard tissues as well as the soft tissues. Of the food intended to build up these organisms, certain portions make bone and teeth. Noav the particles of matter are deposited atom by atom, and the system is gradually built up. Wrhen Ave take food into the system, it is converted into blood. This blood is conveyed through all parts in little corpuscles, which are freighted with the proper constituents to sustain and build up these organisms. These little corpuscles convey such constituents as are necessary for the production of bone, teeth, flesh, and the fat, and these various substances are deposited just where they should be. Now it is essentially necessary that we have these little vesicles freighted with the proper constituents, and duly freighted. Hoav shall we know this ? By taking the food just in the proportion that it is provided for us by our Creator, and as it comes from nature's laboratory. " Noav Ave take this ground from the fact that, as a nation, we have worse teeth than any other on the earth. Now why is this ? Simply because we change the proportions of these various constituents that our Creator has provided for us, by separating away Avhat has been put there for the building up of the hard tissues. " To prove this, let us look to other nations. They that do not change the proportions of the various constituents that enter into their bodies do not have decayed teeth. " There is a constant change going on, and particles of matter are deposited atom by atom, and the system kept fully charged with the mineral elements of Avhich these structures are built up. When you look at nations that do not change the proportions, you see no decayed teeth, and the history of these nations proves that their teeth are sound and beautiful to old age. What is the condition in our country ? W^e do change these proportions. We do ignore the mineral elements provided for us, and we do have decayed teeth. We find that there are over twenty millions of teeth SAvept from our population every year. We do not take the material into our system that carries back, atom by atom, and keeps the hard tissues built up until the old particles pass away. The old particles pass aAvay after they have served their purpose, and new ones then take their places. " It is estimated that every child uses half a barrel of flour every year; and it is estimated that there are forty pounds of the bone- 24 370 DENTAL PATHOLOGY, THERAPEUTICS. forming material thrown out from every barrel that Ave use. The child takes its food on fine flour, and is deprh^ed of twenty pounds in a year of this mineral element, which should be taken into the system in order to make those hard, flinty substances that our Creator intended. Now, by the time that child is twenty years of age, it has been deprived of four hundred pounds of the elements which should have been taken into the system, and Avould have kept it charged sufficiently to have presented these substances hard and flinty, as they should be. " We sweep from our American population over twenty millions of teeth every year, and this should proA'e the theory that our tis- sues do undergo a change, and that, particle by particle, they pass away. As it is now, the teeth are becoming Avorse and worse every year; and not only this, but it becomes hereditary, and is trans- mitted from parent to child." CAUSES OF DENTAL CARIES. Predisposing Causes.—The causes of dental caries are divided into predisposing and exciting; among the former may be enumerated a defective constitution, either innate in the child as derived from the parent, or acquired from accidental influences to which the child has been exposed. Any condition of the system that will interfere with the proper elimination and application of the materials neces- sary for the formation of perfect structures may haA*e a deleterious influence upon the teeth. Hereditary defects are quite common, the teeth of the child exhibiting the peculiarities of those of the parents. Impaired or diminished vitality from constitutional or local causes is also a predisposing cause of dental caries. Febrile conditions not only impair or diminish vitality, but change the nature of the fluids of the oral cavity to such a degree as to cause them to act upon the teeth very injuriously. Dr. George Watt remarks : " That all diseases tend to weaken the dental organs, and thus are predis- posing causes of decay. The most virulent are the eruptive fevers, such as typhus, typhoid and scarlet fevers, measles, smallpox, ery- sipelas, etc. These fevers, and perhaps all diseases, predispose to decay in two Avays. Weakening the entire constitution, they cor- respondingly impair the vitality of the teeth, and thus they have less power to resist the encroachments of the exciting causes of decay. And further, they deprave the secretions of the salivary glands and the oral cavity, rendering them liable to such decompo- sition as will result in the formation of exciting causes." The same author also remarks: " That the condition of the teeth is influenced by heredity, no obsenung dentist can doubt. We have seen a family in AA'hich its female members, for four generations, C ARIES OF THE TEETH. 371 lacked the left upper lateral incisor. Sometimes one parent has good teeth, and good dental organs pertain to the family history, and the ease Avith the other parent is just the reverse; we see chil- dren not usually having dental organs of an average betAveen the tAvo parents, but some of them copying one parent and some the other. The constitution of the parents, and especially that of the mother, may be unable to impart due vigor, or proper materials in requisite quantities, to the process of developing the teeth. From some cause, hereditary or otherwise, there may be a lack of lime salts in the system, or a lack of physiological ability to appropriate them and build them in properly with the organic matter of the teeth. Another condition may sIioav the very best formed teeth, while the alveolar processes, periosteum and mucous membrane may be defective. A defective periosteum cannot give efficient nutrition ; deficient development of the alveoli results in ineffectual support; Avhile if anything is Avrong Avith the mucous membrane Ave may have to contend Avith defective or depraved secretions." Dyspepsia affords an example of both a predisposing and an excit- ing cause of caries, as its effect is to generate an acid in the stomach which, by eructation, is brought into direct contact with the teeth. Malaria is a predisposing cause of dental caries, on account of the unfavorable conditions it induces; also such medicinal agents as vitiate the oral fluids and irritate the mucous membrane and perios- teum, and interfere with the functions of the mucous follicles and salhTary glands—mercury, for example; also salivary calculus, by its irritating effects upon the soft tissues in connection with the teeth, and its influence upon the oral secretions; also Avant of exercise, which affects the stability of the teeth, and causes absorption of the alveoli; also Avant of cleanliness, Avhich may be regarded as one of the most common of the predisposing causes of dental caries; also artificial teeth improperly inserted or composed of bad materials; also improper dental operations, both as regards manner and time ; also diseased teeth and roots AAdiich are productive of irritation to the periosteum and gums; also sudden changes of temperature, which may cause an exalted sensibility of the dentine, diminish the vitality of the teeth, or produce checks in the enamel of frail teeth. The fissures and grooves on the crowns of the molars and bicus- pids are ascribed by some to an arrest of development, a failure of the enamel covering in its formation from the cusps toward the centre of the crown to come together and coalesce. Others, however, ascribe these defective places to be due to a rupture of the enamel oruan at these points—a separation of the ameloblastic layer, thus separating the enamel rods and forming a fissure; such fissures being more common in teeth Avith prominent cusps. 372 DENTAL PATHOLOGY, THERAPEUTICS. Exciting or Immediate Causes.—The exciting or immediate cause of- dental caries is conceded to be the action of agents chemically disin- tegrating the hard structures of the teeth, and which have their source in the vitiated secretions of the mouth, abnormal secretions from the stomach, the saliva, the mucus, and the decomposition of animal and vegetable substances. Fauchard, Auzebe, Bourdet, and other French writers of the eighteenth century, expressed the belief that dental caries is, for the most part, the result of the action of chemi- cal agents; and the existence of an acid in the mouth capable of decomposing the teeth was conclusively proven by Dr. S. K. Mitch- ell, in 1796. The theory that the decay of the teeth is the result of the action of external agents was first distinctly suggested to the dental profession of the United States, about the year 1821, by Drs. h. S. and Eleazer Parmly. The late Professor Westcott, by a series of experiments made in 1843, found that " acetic and citric acids so corroded the enamel in forty-eight hours, that much of it was easily removed with the finger-nail, and malic acid or the acid of apples, in its concentrated state, also acts promptly upon the teeth." Dr. W. D. Miller, an American dentist practicing in Berlin, deserves great credit for many careful investigations made to determine the cause of dental caries. He has lately given the results of over three hundred experiments, and has cultivated bacteria in order to deter- mine the nature of a new fungus Avhich is always found in the mouth and in carious dentine, and which is always said to be ac- companied by a strong acid. Dr. Miller maintains that caries are caused either by the casual introduction of strong acids into the mouth, or by the weaker acids formed by the fermentation of farinaceous or sac- charine particles of food. After the destruc- tion of the enamel, the process of disinte- gration attacks the organic matter, and first of all the micro-organism, which causes an endless variety of changes in the dentine, until finally it presents the appearance of a mass of decomposed matter intersected in every direction with fungi. Dr. Miller as- serts that he has been convinced by an ex- amination of several hundreds "nf specimens, that after decalcification has taken place, the only change of any importance whioh occurs is produced by micro-organisms. And he further says that he sees " the need of little or nothing more than Fig. 141. Longitudinal section carious bicuspid of CARIES OF THE TEETH. 373 organic acids and fungi to account for all the phenomena of dental caries." " Give me these two factors and I can produce caries Avhich Avill deceive the most experienced operators and microscopists." Dr. Miller sums up in the following propositions the results of his investigations on the subject of dental caries : First. The contact of saliva with amylaceous or saccharine food (not to speak of nitrogenous food), or a solution of sugar or starch in saliva, kept at body temperature, invariably gives rise in four or five hours to a strong acid reaction, due to the generation of an organic acid. Second. There must consequently be in the human mouth a con- stant, though variable, generation of acid, because of the impossi- bility of keeping the mouth perfectly free from food and from solu- tions of amyloids in saliva, which penetrate cracks, pits and fissures, or are held by capillary attraction between the surfaces of the teeth in contact, and there become acid by fermentation. Third. The degree of acidity depends somewhat upon the length of time AA'hich has elapsed since partaking of food, and will be found greatest on rising in the morning. Fourth. A cavity of decay in Avhich saccharine or amylaceous food has remained for some hours must, and will be found, always and Avithout exception, to have an acid reaction. Fifth. The extent to which any tooth suffers from the action of the acid depends upon its density and structure, but more particu- larly upon the perfection of the enamel and the protection of the neck of the tooth by healthy gums. What we might call the per- fect tooth Avould resist indefinitely the same acid to which a tooth of opposite character would succumb in a few weeks. Sixth. An occasional possible absence of an acid reaction in a cavity of decay is no indication that acid has not participated in the production of the cavity. Little or no value can be attached to tests of the saliva alone. Seventh. Any general or special disorder or condition of the sys- tem which results in the withdrawal of lime salts from a tooth, or in a loAvering of its density, or in a weakening of the chemical union betAveen the organic and inorganic matter of the tooth, ren- ders it more liable to decay. Eighth. Strong acid and corroding substances brought but momen- tarily into the human mouth, may give rise to lesions of the enamel at points Avhere the ordinary agents alone could never have begun. Ninth. All the microscopical appearances and characteristics of caries may be produced with the greatest exactness out of the mouth, simply by subjecting teeth to those acid mixtures Avhich are con- stantly to be found in the mouth. 374 DENTAL PATHOLOGY, THERAPEUTICS. Tenth. The superficial layers of carious dentine undergo an almost if not absolutely complete decalcification, Avhich decreases as we approach the normal dentine. The same is true of dentine decal- cified in saliva and bread. Eleventh. The destruction of the organic constituents follows (not precedes) the decalcification, and is evidently, for the most part, to be ascribed to the action of fungi. Twelfth. The fungi found in the human mouth do not participate directly in the process of decalcification. The exact part which they perform in the production of an acid reaction requires further investigation. Thirteenth. The fungi produce the most manifold anatomical changes in the softened dentine, resulting in the complete oblitera- tion of the structure and final disappearance of the tissue in a mass of debris and fungi. Fourteenth. The invasion of the micro-organisms is ahvays pre- ceded by the extraction of the lime salts. Fifteenth.. The destruction of the tissue remaining after decalcifi- cation is effected almost Avholly by fungi alone. Sixteenth. Inflammation can hardly be looked upon as a very important factor in caries of the teeth. Seventeenth. Caries of the enamel is purely chemical, the decalci- fication resulting at once in the complete dissolution of the tissue. Eighteenth. Caries of cement runs a course analogous to caries of dentine, a softening of the tissues by acids, and following this its destruction by fungi; a slight inflammatory action on the part of the living matter in the corpuscles, is not to be excluded. Dr. George Watt, in his " Chemical Essays " on " Caries of the the Teeth," remarks: " It is evident that the acids do not all act alike on the teeth. Indeed, some exert no influence Avhatever on them, while others act with great energy on each and all of their constituents." In his notice of the agents which ordinarily act chemically on the teeth, producing caries and chemical abrasion, he accounts for the presence of certain acids in the mouth as fol- lows: "Oxygen and nitrogen uniting in the mouth, in whatever proportions, nitric acid must be the ultimate result, as air and mois- ture, the only agents necessary in the transformation, are here always present. Mucus and particles of nitrogenous food lodged about the teeth undergo decomposition, and yield nitrogen to the oxygen of the atmosphere, or of the fluids of the mouth. Organic nitrogenous bodies contain hydrogen and oxygen, as Avell as nitro- gen ; consequently by their decomposition these elements are all liberated. The mutual affinities of hydrogen and nitrogen take CARIES OF THE TEETH. 375 precedence, and the result is the formation of ammonia, NH3; am- monia exposed to the action of oxygen is ahvays decomposed ; oxide of nitrogen is formed, and nitric acid is the result." If buccal mucus as well as particles of nitrogenous food remain around, upon and between the teeth, till decomposition is effected, the Avhite va- riety of caries is produced. Nitric acid is also sometimes formed in the mouth by the agency of galvanic action, which may be gen- erated by two metals placed in the mouth in close proximity to each other, and the fluids of the mouth acting on one of them. And if they are so situated that the mucous membrane forms a connecting conductor, by being in contact Avith both, a current may be estab- lished sufficient to decompose any of the binary compounds con- tained in these fluids. The liberated nitrogen, hydrogen and oxygen, will form ammonia, and then nitric acid. But galvanic action in the mouth is more likely to develop hydrochloric than nitric acid. Some Avriters, hoAvever, contend that nitric acid is never formed in the mouth, for the reason that they have not found it present in a free state, because in such a state its effects Avould not be confined to carious tooth structure. The advocates of its presence in the mouth contend, on the other hand, that it combines atom by atom, as rapidly as it is generated, with the elements of the tooth struct- ure, and that all conditions necessary for its formation exist in the mouth. From the fact that putrefying animal substance has been found in carious ca\dties, and an alkaline reaction instead of an acid, has been obtained from the tests of the carious matter of cavities, Dr. Miller also disputes the presence of nitric acid, and its influence in producing " Avhite decay." The presence of sulphuric acid in the mouth is accounted for as folloAvs: Albumen is a constituent of mucus, and is contained in many articles of food. Sulphur, if not a constituent of, is ahvays united with albumen. Its ordinary presence in the mouth is there- fore easily explained. Sulphur and oxygen unite directly, under various circumstances, as in the combustion of sulphur, but it is probable that the union here is effected by indirect means. Hydro- sulphuric acid, or sulphuretted hydrogen, is one of the results of the putrefactive decomposition of albuminous substances. The oxygen of the atmosphere rapidly decomposes this acid by taking its hydrogen to form Avater. The sulphur is therefore set free, and being in its nascent state, its affinities are increased in energy, and it also unites Avith oxygen, forming sulphurous acid, SO,, Avhich in the presence of the saliva is rapidly converted into sulphuric acid, or S03. The quantity of sulphur, however, present in the 376 DENTAL PATHOLOGY, THERAPEUTICS. mouth at any one time, is very minute, and a great proportion of this is exhaled by the breath before it has time to undergo decom- position. Sulphuric acid has a weaker affinity for the constituents of the tooth than some others; and the black decay resulting is not so common as some other varieties, and progresses less rapidly; and as from the nature of the chemical action the texture of the tooth is not so entirely broken up, the carbonized portion protects the parts beneath it, as the slow and prolonged action of this acid on the gelatinous portion of the tooth results in its carbonization, the carbonized gelatin being " animal charcoal." Sulphuric acid does not break down the texture of the tooth to the extent that some other acids do, because it cannot unite with, or, under ordinary cir- cumstances, decompose the principal earthy salt of which it is com- posed. Sulphuric acid is frequently administered as a medicine. The escharotic power of hydrochloric acid depends mainly on its affinity for water, which is very active, and on its ability to coagu- late albumen. When concentrated, it dissolves animal tissues, but in this respect is far inferior to nitric acid; its chemical action is generally inferior to that of either nitric or sulphuric. When much diluted, and mixed with dried mucous membrane, it dissolves co- agulated albumen, fibrin, etc. Concerning the action of hydro- chloric acid on the tooth: the carbonate of lime and the acid are mutually decomposed, the results being chloride of calcium, water, and carbonic acid. The carbonic acid escapes as a gas, and the chloride being very soluble, is dissolved in the saliva, and thus re- moved from the tooth. The phosphate of lime, though not decom- posed by, is highly soluble in, hydrochloric acid. It is dissolved and thus removed from the organic portion of the tooth. Hydro- chloric acid is also administered as a medicine; it is also an ingre- dient of the gastric fluid, and is often present in abnormal quanti- ties in the stomach, from which it is thrown into the mouth by eructation and vomiting. It may also be present in the saliva when the latter is in an abnormal condition, as it may originate in the decomposition of the soluble chlorides contained in the saliva and mucus. When the chlorine of these is liberated it takes hydrogen from the water of the saliva, and this acid is the result of the union. It is also sometimes directly furnished by the salivary glands, either as a secretion or an excretion; and it is usually found in the mouth when the mucous membrane is inflamed, as well as in patients who indulge in the excessive use of salted meats. Galvanic currents in the mouth always result in the formation of this acid. What is known as the "septic theory," is explained as follows by Dr. C. S. Stockwell: " We will suppose an absolutely perfect tooth, CARIES OF THE TEETH. 377 the enamel absolutely intact, and no defects whatever. The enamel in such a case forms a perfect protection against the micro-organisms. There are many places about the teeth, however, where food collects and remains undisturbed. Noav the organisms of fermentation oper- ate upon the food and saliva, and the result is an acid. This acid may erode the enamel in time, so that a portion of the organic tissue of the tooth becomes exposed; organisms may then act directlv upon the fibrils or organic tissues; by absorbing the protoplasm they weaken its vitality or resisting force, disturb nutrition, set up inflammatory action, and the result is stasis and death of the organic tissue; after which the putrefactive and fermentative stage comes in, Avhich disposes of both the organic and inorganic portions of the tooth. We, then, first have a killing of a portion of the organic tissue as a result of the action of organisms—a disease. Secondly, the disposal of the organic and inorganic by putrefactive and fermenta- tive processes—caries." He also believes that the putrefactive and fermentative processes may be simultaneously going on, and that they are essentially identically alike; and the result of one is alkali accompanied by an odor—putrefaction; and the other process results in an acid Avithout the odor—fermentation ; and that these processes have a common cause—organisms. The generally accepted theory at the present time of the cause of dental caries is the "chemico-parasitic ;" according to this theory it progresses as follows : The enamel is first decalcified by the action of fermentation on some favorable point on the crown of the tooth, and the decalcification progressing involves the dentine. As soon as the enamel is removed the cavity affords lodgment for the micro-organ- isms, which, at this stage of the affection, can penetrate the dentinal tubuli and the process of decalcification not only continues but is facilitated by the acid formed by these micro-organisms, until the tooth-cartilage, or organic portion of the structure, alone remains, which at length undergoes putrefaction. Deposits of food upon the teeth are soon invaded by micro-organisms constantly found in the mouth. Dr. Miller has discoArered no less than twenty-two different fungi in the human mouth, of which sixteen are capable of produc- ing acids in substances prone to fermentation, Avhich substances are decomposed and lactic acid, according to Dr. Miller's analysis, is generated. When the fluids of the mouth are acid, the acid formed by the micro-organisms acts in its full strength, Avhereas, if the oral fluid is normal in character the acid of the organisms is neutralized. The foregoing theory of the cause of dental caries explains the rationale of the treatment at present adopted for arresting its pro- gress. By the removal of the decomposed part, and filling the cavity 378 DENTAL PATHOLOGY, THERAPEUTICS. Avith an indestructible material, the contact of those agents upon the chemical action of which the disease depends, is prevented, and the further progress of the decay arrested. PREVENTION OF CARIES. It is an old adage, no less true than trite, that " an ounce of pre- vention is better than a pound of cure," and in the present instance it may be applied Avith its full force. Were more attention paid to the practical instruction thus conveyed, many of the diseases of the teeth might be avoided. Most of the remarks that might be made on this subject have been anticipated; consequently, it will only be necessary to observe, that if the teeth are Avell formed and Avell ar- arranged, all that will be required is to keep them clean ; if any irregularity occurs, it should be remedied by the means before de- scribed. For cleansing the teeth, when they are in a sound condition and free from calcareous deposits, the gums healthy, and the secretions of the mouth normal in character, the regular and frequent use of pure water by means of a proper brush and waxed floss silk will, in most cases, be sufficient. But when the enamel is stained and discolored, and the secretions of the mouth inclined to acidity Avith a tendency to calcareous deposits, then the employment of a denti- frice is necessary. Dentifrice—from dens, a, tooth, and frico,fricare, to rub—is a medi- cinal preparation, in the form of a powder, for cleansing the teeth. An almost numberless variety of dentifrices are in use, and many of them highly injurious. In the preparation of an agent of this kind, the object should be to obtain a compound pleasant to the taste, altogether free from acids and acrid substances, and soluble or in- soluble, according to the nature of the case in Avhich it is to be used; one capable of neutralizing and removing acrid and fermenting mat- ters secreted between the teeth, and also allaying irritation. A denti- frice, then, should be anti-acid, and, moreover, a poAvder; and the more simple the preparation the better. A preparation composed of orris root, prepared chalk, and pure Castile or Avhite Windsor soap, to which may be added very finely poAvdered cuttle-fish bone or pumice-stone, for the removal of calcareous matter, when there is a tendency to deposits of this nature, will answer every purpose. W7hen the gums are in a healthy condition, there is no use for such ingredients in a dentifrice as Peruvian bark or myrrh, and as for liquid dentifrices, they are of very little use, for the object in using the brush is friction, and as these liquid preparations are generally lubricating alkaline substances, they cause the brush to pass so easily CARIES OF THE TEETH. 379 over the teeth as to render them almost useless. In many cases an unhealthy condition of the gums is owing to the irritation produced by local irritants, and their removal is all that is needed to restore them to health. Soap alone will not cleanse the teeth, for it prevents friction ; and charcoal, notwithstanding its detergent and antiseptic properties, is injurious as a dentifrice, or as an ingredient of one, on account of its insinuating itself under the free margin of the gum, and causing it to recede from the neck of the tooth, no matter how finely it may be pulverized. Either of the following dentifrices may be used: R. Prepared chalk, • • 3iv. Powdered orris root, . |iv. Powdered cinnamon, . 3 iv. Sup. carb. of soda, . . 3 ss. White sugar, .... • • 3j. Oil of lemon, . gtt. XV Oil of rose, .... . gtt. ij. Prepared chalk, • • gij- Powdered orris root, • • 3>'j. Pumice stone, • • n R. Ingredients in both prescriptions to be thoroughly pulverized and well mixed The importance of keeping the teeth clean cannot be too strongly impressed upon the mind of every individual. Proper attention to the cleanliness of these organs contributes more to their health and preservation than is generally supposed. Against caries it is a most poAverful prophylactic. " When the teeth," says Dr. h. S. Parmly, " are kept literally clean, no disease will ever be perceptible. Their structure Avill equally stand the summer's heat and winter's cold, the changes of climate, the variation of diet, and even the diseases to Avhich the other parts of the body may be subject from constitu- tional causes." The configuration and arrangement of some teeth is such, however, as to preclude the possibility of keeping them clean; but this should not deter any one from using the proper means, for if disease is not Avholly prevented, they will, at least, contribute Arery greatly to the preservation of the organs. The subject of "food in relation to the teeth," has claimed the at- tention of eminent writers, many of whom are convinced that strict attention on the part of the mother to hygienic laAVs, from the time of conception, Avill influence for good the structural quality of the developing tooth-tissues of the child. As phosphate of lime is an important ingredient of the tooth-tissues, it is urged that the requisite 380 DENTAL PATHOLOGY, THERAPEUTICS. quantity of this lime salt should be supplied with the food, and that due attention to the laws of health in regard to exercise, rest, venti- lation, bathing, etc., will cause the lime salt to be assimilated and properly appropriated in the formation and development of tooth- tissues. Many also believe that foods prepared by artificial means are very serviceable in supplying such elements as fail to be assimi- lated in the ordinary manner ; hence the use during pregnancy and lactation of preparations of the syrup of the lactophosphate of lime, Avheat phosphate, and such articles of diet as oatmeal, cracked wheat etc., are recommended as being of great benefit. No doubt the amount of phosphate to be used by the system will depend in a great measure upon the digestion. PART THIRD. DENTAL SURGERY. Besides the operations of General Surgery which are performed upon the mouth, in common with other parts of the body, Dental Science gives specific directions for those operations of Special Surgery demanded in the— 1. Correction op Irregularities in the Arrangement of the Teeth. 2. Treatment of Dental Caries. 3. Extraction of Teeth. 4. The Use of Anaesthetic Agents. 5. Dislocation and Fracture of the Jaw. 6. Diseases of thic Maxillary Sinus or Antrum. 7. Caries of the Maxillary Bones. CHAPTER I. IRREGULARITY OF THE TEETH—ORTHODONTIA. Method of Directing Second Dentition.—To properly direct second dentition a knowledge of the relative position of the permanent and temporary teeth at a period soon after the appearance of the first teeth of the permanent set, is necessary. Fig. 142 represents the jaAvs of a child between six and se\ren years of age, all of the temporary teeth being in position, and the six-year molars erupting. Fig. 142. The developing crowns of the permanent teeth occupy a higher place than the temporary teeth, and the superior central incisors have a more outAvard inclination, on account of their size and the increased Avidth of the arch they are to occupy Avhen erupted. The croAvns and a small portion only of the roots of these teeth are com- pleted, and they are placed directly under and in contact Avith the floor of the nares. The superior lateral incisors are not so far ad- Aranced in their development as the central incisors, and their crowns are situated beneath the angle of the nares and back of the roots of the temporary laterals and canines. The canines are situated on a higher plane than either the central or lateral incisors, not more than one-fourth of an inch beloAV the infra-orbital canals, and along the sides of the outer walls of the nares, Avith their croAvns about completed. The croAvns of the first and second superior bicuspids are situated on the same plane as the 384 DENTAL SURGERY. lateral incisors, being embraced by the roots of the first and second temporary molars, and are but partly developed. The croAvns of the first permanent molars of both jaws have erupted and are about antagonizing Avith each other, but their roots are only one-half formed. The crowns of the permanent second molars are but partly developed, and are situated above and posterior to the roots of the first permanent molars, their grinding surfaces having a direction dowmvard and slightly backward toward the lower por- tion of the external pterygoid processes. The dentes sapientise of the upper jaAv are represented by small crypts only, in a higher plane in the maxillary tuberosities. The inferior permanent central incisors are situated directly be- hind the roots of the temporary incisors, and have their croAvns completed Avith about one-fourth of their roots. The roots of the permanent lateral incisors are not so far developed, and are situated someAAdiat back of the crowns of the permanent central incisors and canines. The permanent central and lateral incisors, as do all of the inferior teeth, occupy a vertical position in the jaws, on account of the inferior dental arch being smaller than the superior. The inferior permanent canines occupy a loAver plane than the incisors, and their partly developed roots extend very near to the under sur- ' face of the bone of the jaw. The position and stage of development of the inferior permanent bicuspids and first molars are about the same as those of the corresponding teeth of the upper jaAv. The developing croAvns of the permanent second molars occupy a higher plane than that of the bicuspids, and their grinding sur- faces have a direction upAvard and forward. The inferior dentes sapientise are represented by small crypts only, in the coronoid processes. There is nothing more destructive to the beauty, health, and durability of the teeth, and no disturbance more easily prevented, than irregularity of their arrangement. Also, in proportion to the deviation of these organs from their proper position in the alveolar arch, are the features of the face and the expression of the counte- nance injured. It also increases the susceptibility of the gums and alveolo-dental membrane to morbid impressions. It is important, therefore, that the mouth, during second dentition, should be properly cared for; and so thoroughly convinced is the author of this, that he does not hesitate to say, that if timely pre- cautions were used, there would not be one decayed tooth where there are now a dozen. Much harm, it is true, may be done by improper meddling with the'teeth during this period, but this, so far from inducing a total neglect, should only make those having the care of children more IRREGULARITY OF THE TEETH—ORTHODONTIA. 385 solicitous in securing the services of scientific, accomplished prac- titioners. For the judicious management of second dentition, much judg- ment and a correct knowledge of the normal periods of the erup- tion of the several classes of teeth are required. All unnecessary interference with these organs at this early period of life should certainly be avoided, as it will only tend to mar the perfection at Avhich nature ever aims. The legitimate duty of the physician being, as Mr. Bell correctly observes, " the regulation of the natural func- tions AArhen deranged," he should never anticipate the removal by nature of the temporary teeth, unless their extraction is called for by some pressing emergency, such as a deAuation of the permanent ones from their proper place, alveolar abscess, or exfoliation of the alveolar processes. The mouth should be frequently examined from the time the shedding of the deciduous teeth commences until the completion of second dentition ; and Avhen the growth of the permanent teeth so far outstrips the destruction of the roots of the temporary, that the former are caused to take an improper direction, such of the latter as have occasioned the obstruction should be immediately removed. In the dentition of the upper front teeth this should never be neglected ; for, Avhen they come out behind the temporaries, as they most frequently do, and are permitted to advance so far as to fall on the inside of the lower incisors, a permanent obstacle is offered to their subsequent proper adjustment. When a Avrong direction has been given to the growth of the loAver front teeth, they are rarely prevented from acquiring their proper arrangement by an obstruction of this sort. They should not, Iioav- cver, on this account be permitted to occupy an erroneous position too long ; for the evil will be found easier of correction while recent than after it has continued for a considerable length of time. The irregularity should be immediately removed. The permanent central incisors of the upper jaw being larger than the temporaries of the same class, it might, therefore, be sup- posed that the aperture formed by the removal of the one would not be sufficient for the admission of the other, Avithout an increase in the size of this part of the maxillary arch. It should be recol- lected, hoAvever, that by the time these teeth usually emerge from the gums, the croAvns of the temporary lateral incisors are so much loosened by the partial destruction of their roots, as to yield suffi- ciently to the pressure of the former to permit them to take their proper position Avithin the dental circle. When this does not happen, the temporary laterals should be extracted. 25 386 DENTAL SURGERY. Under similar circumstances, the same course should be pursued with the permanent lateral incisors and the temporary cuspids, and also with the permanent cuspids and the first bicuspids. But from the fact that the bicuspids are erupted before the per- manent cuspids, the premature extraction of the temporary cuspids is often the cause of the projection of one or more of the front teeth; sometimes to such a degree as to produce considerable deformity. The removal of the temporary cuspids should therefore be avoided Avhen there is reason to believe that the growth of the jaAv will pro- vide sufficient space for a deviating permanent lateral incisor to take a proper position within the dental arch. The bicuspids being situated betAveen the roots of the temporary molars are seldom caused to take an improper direction in their groAvth. Nor are they often prevented from coming out in their proper place for want of room. In the management of second dentition much will depend on the experience and judgment of the practitioner. If he be properly in- formed upon the subject, and gives to it the necessary care and atten- tion, the mouth will, in most instances, be furnished with a healthful, Avell arranged and beautiful set of teeth. At this time, " an opportu- nity," says Mr. Fox, " presents itself for effecting this desirable ob- ject " (the prevention of irregularity)," but everything depends upon a correct knowledge of the time when a tooth requires to be extracted, and also of the particular tooth, for often more injury is occasioned by the removal of a tooth too early than if it be left a little too long ; because a new tooth, which has too much room long before it is required, will sometimes take a direction more difficult to alter than a slight irregularity occasioned by an obstruction of short duration." The temporary teeth, by remaining too long are likely to affect the arrangement, and consequently the health, of the permanent teeth, and they should be extracted, because, in that case, their presence is a greater evil than any that would be occasioned by their removal. As a general rule, they should be suffered to remain until their presence is likely to injure the permanent teeth and their con- tiguous parts. When the permanent teeth are crowded, the lateral pressure is fre- quently so great as to fracture the enamel. If this cannot be pre- vented in any other Avay, one on each side should be extracted. It is better to sacrifice two than permanently to endanger the health of the whole. The file or revolving discs and points upon the dental engine should never be used with a view to remedy irregularity; the ex- traction of two teeth, one on each side of the jaw, however small IRREGULARITY OF THE TEETH--ORTHODONTIA. 387 the space required to be gained may be, is far preferable. The second bicuspids, cseteris paribus, should always be removed rather than the first, but sometimes the extraction of the first becomes necessary. By the removal of the teeth, ample room Avill be gained for the arrangement of all the remaining ones, and the injury resulting from a crowded condition of the organs prevented. The author does not, hoAvever, wish to be understood as convey- ing the idea that filing the teeth necessarily causes them to decay, for, Avhen the file is used for any other purpose than to gain room, the apertures may be made large enough to prevent the approxima- tion of the organs, and thus the bad effects resulting from the opera- tion Avill be prevented. The extraction of the root of a superior front tooth, a central in- cisor, for example, when the croAvn has been greatly disfigured or Avholly destroyed by mechanical violence, may cause the superior front teeth to fall behind the inferior teeth. Should such a deformity not occur, it frequently happens that an unsightly space is left, too small for the insertion of an artificial tooth to correspond in size Avith the adjoining natural ones. To avoid such results, the root should be allowed to remain, and the proper treatment instituted to subdue the inflammation, the pulp removed Avhen exposed, and the root filled to the apex Avith gold or other suitable material. By pursuing such a course, the root is retained until such a time as its removal will not affect the adjoining teeth. In some cases the portion of the crown destroyed may be restored Avith gold, or an artificial crown inserted on a pivot. When the deciduous canines are extracted on the approach of the permanent lateral incisors, the first bicuspids will move fonvard and occupy the space necessary for the reception of the permanent canines, Avhich may erupt over the laterals, and by their pressure cause these latter teeth to shut within the loAver teeth. Fig. 143 illustrates the mischief attending the premature extrac- tion of the deciduous canines. Nature, Avhen permitted to proceed Avith her Avork without inter- ruption, is able to perform her operations in a perfect and harmo- nious manner. But the functional operations of all the parts of the body are liable to be disturbed from an almost innumerable num- ber and variety of causes, and im- pairment of one organ often gives rise to derangement of the Avhole organism, for the relief of Avhich the interposition of art not unfrequently becomes necessary, and it 388 DENTAL SURGERY. is fortunate for the well-being of man that it can in so many in- stances be applied with success. In sound and healthy constitutions, the services of the dentist are seldom required to assist or direct second dentition. In remark- ing upon this subject, Dr. Koecker observes, u that the children for whom the assistance of the dentist is most frequently sought are those who are in a delicate, or at least imperfect, constitutional health; in Avhom the state not only of the temporary teeth, but of the permanent also, is to be considered ; and Avhere both are found diseased, the future health and regularity of the latter require the greatest consideration of the surgeon. " Irregularity of the teeth is one of their chief predisposing causes of disease, and never fails, even in the most healthy constitutions, to destroy, sooner or later, the strongest and best set of teeth, unless properly attended to. It is thus not only a most poAverful cause of destruction to the health and beauty of the teeth, but also to the regularity and pleasing symmetry of the features of the face; always producing, though slowly and gradually, some irregularity, and not unfrequently the most surprising and disgusting appearance." Though nature is generally able to accomplish the task assigned her, yet there are times when she requires aid, and it is then, and then only, that the services of the dentist are needed. Therefore, whilst, on the one hand, we should guard against any uncalled-for interference, Ave should, on the other, always be ready to give such assistance as the nature of the disturbance presented to our notice may require. The progress of caries in the temporary teeth is very rapid, as a general rule, owing to the large proportion of organic matter com- pared with the inorganic. Alveolar abscess is, therefore, a common result of the loss of vitality, and the absorption of the alveolar pro- cesses from such a cause may expose the apex of the root of one or more temporary teeth. In the case of the necrosed roots of the superior incisors present- ing such a condition, and it is necessary that such teeth should be preserved in order to prevent an irregular arrangement of the suc- ceeding permanent ones, which is very prone to occur from the pre- mature loss of the temporary teeth, the exposed ends of the roots of the necrosed temporary teeth may be excised and carefully rounded off with the file or corundum point. By such a method the necrosed teeth may be retained in the mouth until the period of shedding has arrived, and the space necessary for the reception of the corresponding permanent teeth be preserved. The eruption of the permanent teeth begins before any of the IRREGULARITY OF THE TEETH—ORTHODONTIA. 389 temporary teeth are shed, the first of the permanent teeth to appear being the sixth-year molars, between the five and a half and six and a half years. These teeth are often mistaken for temporary teeth, and being prone to decay, on account of defective structure, and the early period of their eruption, they are frequentlv lost early in life. But as the sixth-year molars perform an important part in the preservation of the integrity of the arch, their retention is desirable if possible. Cases, however, occur Avhere they cannot be permanently preserved, Avhen every effort should be made to pre- serve them up to a certain period, namely, until the twelfth-year molars are about to erupt, or until a period betAveen the tenth and twelfth years. If the sixth-year molars are lost earlier than the period Fig. 144. Sixth-Year Molar. named, the adjoining teeth will close up, and cause irregularity when the other teeth appear. On the other hand, if the sixth-year molars are lost later than the time named, the space they occupied is never compactly closed, and the adjacent teeth will incline toAvard the vacant space, and the continued occlusion in mastication will cause them to tip over to such a degree as to result in a decided impairment of the occlusion. Such irregular teeth may also be- come painful and loose, on account of the recession of the gums and the absorption of the alveolar processes, and even the adjoining teeth may suffer in a similar manner. Fig. 144 represents an adult lower jaAv, side view. 390 DENTAL SURGERY. Irregularity of Arrangement of the Teeth.—The causes of the various forms of irregularity of the teeth are divided into accidental—those occurring after the eruption of the teeth, and congenital—those occurring prior to their eruption. The accidental forms of irregularity are most commonly caused by the presence of temporary teeth beyond the proper time of shed- ding, OAving to the process of absorption of their roots not being commensurate with the development of the permanent teeth, or to the presence of necrosed roots of temporary teeth which are not absorbed. The congenital forms of irregularity are generally caused by a want of development of the jaws commensurate with the size of the teeth. In some rare cases the excessive development of the maxillse may result in abnormal spaces between the teeth. The temporary teeth seldom deviate from their proper place in the alveolar arch; but irregularity of arrangement is of frequent occurrence in the permanent teeth, especially the cuspids and in- cisors. The first and second molars are seldom irregular; for, like the teeth of first dentition, they rarely encounter obstruction in their growth and eruption. The sixth-year molars being the first of the permanent set to appear, the ten anterior teeth are limited to that part of the arch occupied by the ten temporary teeth ; if this space is too small, irregularity must of necessity ensue. The dentes sapientise are sometimes irregularly erupted, in conse- quence of a want of correspondence between the development of the tooth and the growth of the maxilla. The tooth in such cases takes usually the direction of least resistance, the croAvn presenting more or less obliquely forward, backward, outward, or inward. Of these four positions, the first and fourth are found usually in the lower jaw; the second and third are most common in the upper jaw. When a bicuspid is forced from its proper place, it turns inward toward the tongue, or outward toward the cheek, accordingly as it is in the upper or lower jaw; or it may be so turned in its cavity by the occlusion of the teeth in the opposite jaAv, the loss of an adjoining tooth giving the necessary space, as to present one of its proximate surfaces toward the cheek. The cuspids, when prevented from coming out in their proper place, make their appearance either before or behind the other teeth. When they come out anteriorly, which they do more frequently than posteriorly, they often become a source of annoyance to the upper lip, excoriating and sometimes ulcerating the mucous membrane. The incisors of the upper jaw present a greater variety of abnor- IRREGULARITY OF THE TEETH--ORTHODONTIA. 391 mal arrangement than any of the other teeth. The centrals come out sometimes before and sometimes behind the arch ; at other times, their median sides are turned either directly or obliquely for- Avard toAvard the lip. The laterals sometimes appear half an inch behind the arch, looking toward the roof of the mouth ; at other times they come out in front of the arch, and at other times, again, they are turned obliquely or transversely across it. When any of the upper incisors are transversly inclined toward the interior of the mouth, the lower teeth, at each occlusion of the jaAvs, shut before them, and become an obstacle to their adjustment. This form of irregularity often interferes with the lateral motion of the jaw. The lower incisors sometimes shut in this manner, even when there is no imvard deviation of the upper teeth. In this case the irregu- larity is owing to preternatural elongation of the lower jaw, which arises more frequently from some fault of dentition than from any congenital defect in the jaw itself. Sometimes the superior maxillary arch is so much contracted, and the front teeth in consequence so prominent, that the upper lip is prevented from covering them. Cases of this kind, however, are rarely met with; but when they do occur, it occasions much deform- ity of the face, and forms a species of irregularity very difficult to correct. From the same cause the lateral incisors are some- times forced from the arch, and appear behind the centrals and cuspids, the dental circle being filled with the other teeth. An abnormal promi- nence of the superior incisors may be either congenital or accidental, and Avhen of the former origin it is almost invariably accompanied Avith a contracted arch, especially betAveen the bicuspids of the right and left sides of the mouth, the incisors occupying a V-shaped posi- tion (Fig. 145). When this form of irregularity has an accidental origin, it is 392 DENTAL SURGERY. generally caused by a pernicious habit of thumb, tongue, or artificial nipple-sucking.* Figs. 146 and 147 represent the form of irregularity caused by thumb-sucking. An unusual prominence of the superior incisors, attended Avith a diminution of space betAveen the bicuspids and an abnormally high cheeks over the lateral parts of the mouth, while the median portion escapes the controlling pressure which would be exercised when the mouth is closed. * Such a habit as thumb-sucking may be prevented by the application of some bitter substance, such as aloes, to the thumb, tying the arms close to the body at night, or the wearing of coarse, heavy gloves. IRREGULARITY OF THE TEETH—ORTHODONTIA. 393 Dr. Kingsley is of the opinion that the Y-shaped arch is nearly always of congenital origin—that is, an inherited tendency, while the broad or rounded form of arch is often due to mechanical causes. Inflammation of the throat early in life in children of a strumous diathesis, will not only produce deformity of these parts, but irregu- larity of arrangement of the teeth, by causing tension of the muscles, which has the effect of contracting the oro-naso-pharyngeal space by pressing the lateral portions of the walls inward. The retention in the jaw of permanent teeth is also a cause of irregularity, as in some cases bicuspids and molars may not erupt sufficiently to meet the opposing teeth. There are many other deviations in the arrangement of the incisors. Mr. Fox mentions one that was caused by the presence of two supernumerary teeth of a conical form, situated partly behind and partly between the central incisors, which, in consequence, were throAvn fonvard, while the laterals were placed in a line with the supernumeraries. The central incisors, though half an inch apart, formed one row, and the laterals and supernumeraries another. Mr. Fox says he has seen three cases of this kind. This description of irregularity is rarely met Avith. M. Delabarre says that cases of transposition of the germs of the teeth occasionally occur, so that a lateral incisor takes the place of a central, and a central the place of a lateral. A similar trans- position of a cuspid and lateral incisor is, also, sometimes seen. Two cases of this sort have fallen under the observation of the author. The incisors of the loAver jaAv being smaller than those of the up- per, and in other respects less conspicuous, do not so plainly show an irregularity in their arrangement, nor is the appearance of an individual so much affected by it. Still it should be guarded against; for such deAdation, Avhether in the upper or lower jaw, may prove injurious to the health of the teeth and the beauty of the mouth. The groAvth of the inferior permanent incisors is sometimes more rapid than the destruction of the roots of the corresponding temporaries. In this case the former emerge from the gum behind the latter, and sometimes so far back as greatly to annoy the tongue and interfere Avith enunciation. At other times the permanent cen- trals are prevented from assuming their proper place, because the space left for them by the temporaries is not sufficient. The irregu- larity in the former of these two cases is greater than in the latter. The same causes in like manner, affect the laterals. M. Delabarre mentions a defect in the natural conformation of the 394 DENTAL SURGERY. jaws, by which the upper temporary incisors on one side of the me- dian line are thrown on the outside of the loAver teeth, while the corresponding teeth on the other side of the same line fall Avithin. The same arrangement, he says, may be expected, unless previously remedied, in the permanent teeth. The author has met with but two cases of this sort, and the subjects of these he did not see until after they had reached maturity. Referring to an ingrafted tendency in all living matter to repro- duce itself, Dr. Kingsley remarks: " I am of the opinion that such deformities, even when transmitted for generations, may have the tendency stamped out by being corrected immediately on their de- velopment; that is, before the deformity has made its fixed impres- sion upon the individual." Mr. Mummery is of the opinion that a large amount of dental disease is originated by overtaxing the brain action of children, and Dr. Kingsley remarks that "the next generation will see more ab- normality in dental development, and an increase of nervous and cerebral diseases, and that the two are correlated and spring from the same cause." Treatment of Irregularity.—Orthodontia, or the treatment of irregu- larity, should accord with the indications of nature. When the irregularity is neither great nor complicated, and its causes are re- moved before the nineteenth or twentieth year, the teeth, without the aid of art, will, in many cases, assume their proper position. When, however, the efforts of the economy are unavailing, recourse should be had to the dentist, who can, in most instances, bring the deviating organs to their proper position in the arch. The general rule is, that as soon after the eruption of a tooth as it becomes cer- tain that it will assume an irregular position, interference is justifi- able, as every year not only increases the difficulties, but impairs the stability of the dental organs. Teeth incline to return to their place on the removal of the cause of irregularity. They may be also made to change position under the influence of pressure. The pres- sure must be constant; it must be sufficient to "cause motion, yet not so great as to set up destructive inflammation; lastly, it must be continued until the teeth can be kept in place by antagonism with the opposing teeth; or in case there is no such antagonism, a retain- ing appliance must be worn more or less constantly for a year, or even longer. The regulating appliance should be as simple in its con- struction as is possible to accomplish the purpose, so that both time and labor may be saved, and the patient be able to attend to its re- moval and adjustment when it becomes necessary to cleanse it; this should frequently be done. IRREGULARITY OF THE TEETH—ORTHODONTIA. 395 Teeth artificially regulated change position chiefly, if not entirely, by the double process of absorption from one side of the socket, folloAved by the slower process of ossific deposit on the opposite side. It is therefore essential to success that the tooth be retained in its neAV position, either by the other teeth or by mechanical appliance, until such deposit is formed. Many cases fail from a want of persistence on the part of patient or dentist. How far, and in what direction a tooth may be moved, will depend partly upon the position of the apex of the root; partly upon the antagonism of the opposing teeth. Cuspids growing out far upon the alveolar arch will usually be found to have short and curved roots. The attempt to move them might cause the curved apex to pierce the alveolus. Even Avhen not curved, the root is short, and the regulated tooth will not possess that durability which is characteristic of the cuspids. It should always be borne in mind that in regulating teeth the crown is the movable point, whilst the apex of the root is the fixed point, and must determine in great degree the extent and direction of motion. Again, the natural or artificial movement of bicuspids backAArard to make room for front teeth may be aided or hindered by the opposing teeth. An upper bicuspid, for instance, once carried back, so that the posterior slope of the lower bicuspid strikes it, will re- tain its position or may be throAvn even further back. Upper incisors striking inside the lower, or lower incisors unnatu- rally prominent, may be regulated, and the opposing teeth will tend to keep them in their corrected position. But it will require long and patient use of the regulating apparatus to keep in place upper incisors Avhich project outward, or loAver incisors inclining inAvard. In deciding upon the removal or extraction of an irregular tooth, it should not be forgotten that a tooth moved by mechanical appliance, especially if the change in position is considerable, will not prove as durable as if no moArement had been necessary. Hence it may some- times be advisable to extract irregular cuspids in cases where their correction requires much change in their position and that of the bicuspids, and the arch is completely and regularly filled by the remaining teeth. In a case presented to the late Prof. Austen, the superior arch was perfectly regular and closely filled ; but both cuspids had come out aboAre the arch. The cuspid roots were normal, and it seemed prac- ticable to bring these teeth doAvn into the places of the first bicus- pids. But the four bicuspids Avere sound, and the first bicuspids 396 DENTAL SURGERY. gave very much the appearance of the natural arrangement. Hence, as in point of expression there would be no great gain, and in point of durability a probable loss, it was not thought advisable to subject the patient to the tedious annoj^ance of regulation. In describing the treatment of irregularity, we shall notice the means by which some of its principal varieties may be remedied ; otherwise, the application of the principles of treatment would not be well understood, since it must be varied to suit each individual case. As a general rule, the sooner irregularity in the arrangement of the teeth is remedied the better; for the longer a tooth is alloAved to occupy a wrong position, the more difficult will be its adjustment. The position of a tooth may sometimes be altered after the eighteenth, twentieth, or even the thirtieth year ; but it is better not to delay the application of the proper means until so late a period. A change of this kind may be much more easily effected before the several parts of the osseous system have reached their full development, and while the formative process is in vigorous operation, than at a later period of life. The age of the subject, therefore, should ahvays govern the practitioner in forming an opinion as to the practica- bility of correcting irregularity. Previously to the twentieth year, the Avorst varieties of irregularity may, in most cases, be successfully treated. The first thing claiming attention in the treatment is the removal of its causes. Whenever, therefore, the presence of any of the tem- porary teeth has given a false direction to one or more of the perma- nent, they should, as a general rule, be extracted, and the deviating teeth pressed several times a day with the finger, in the direction they are to be moved. This, if the irregularity has been occasioned by the presence of a deciduous tooth, will, generally, be all that is required. But when it is the result of narrowness of the jaw, either con- genital or acquired, a permanent tooth on either side should be re- moved, to make room for such as are improperly situated. All the teeth being sound and well formed, the second bicuspids are the teeth Avhich should be extracted; but if, as is often the case, the first permanent molars are so much decayed as to render their preserva- tion impracticable, or, at least, doubtful, these teeth should be removed in their stead. After the remoA'al of the second bicuspids, the first, usually, very soon fall back into the places which they occupied, and furnish ample room for the cuspids and incisors. But if they fail to do this, they may be gradually forced back by inserting wedges of wood or rubber betAveen them and the cuspids, IRREGULARITY OF THE TEETH—ORTHODONTIA. 397 or by means of a ligature of silk, or rubber, securely fastened to the first molar on each side, or by other proper appliances. These should be renewed every day, until the desired result is pro- duced. The most frequent kind of irregularity, resulting from narrowness of the jaAv, is the prominence of the cuspids. These teeth, with the exception of the second and third molars, are the last of the teeth of second dentition to be erupted; consequently they are more liable to be forced out of the arch than any others, especially Avhen it is so much contracted as to be almost entirely filled before they make their appearance. The common practice in such cases Avas to remove the projecting teeth. But as the cuspids contribute more than any of the other teeth, except the incisors, to the beauty of the mouth, and can, in almost every case, be brought to their proper place, the practice is injudicious. Instead of removing these, a bicuspid should be extracted from each side. When the space be- tween the lateral incisor and the bicuspid is equal to one-half the Avidth of the croAvn of the cuspid, the second bicuspid should be removed,but Avhen it is less, the first should be taken out; because, although the crown of the latter may be carried far enough back after the remo\ral of the former to admit the crown of the cuspid between it and the lateral incisor, the root of this tooth will remain in front and partly across the root of the first bicuspid; leaving a more or less prominent vertical ridge on the anterior part of the alveolar border, which, to some extent at least, acts as an irritant to the gums and periosteum. As the incisors of the upper jaw are more conspicuous than those of the loAver, and when Avell arranged contribute more to the beauty of the mouth, their preservation and regularity are of greater rela- tive importance. Hence, the removal of a lateral incisor, Avhen it is situated behind the dental arch, as is often done with a view to remedy the deformity produced by false position, is a practice Avhich cannot be too strongly deprecated, provided sufficient space can be made for it betAveen the cuspid and central incisor by the removal of a bicuspid from each side of the jaw. Dr. Kingsley remarks that " cases are of frequent occurrence which shoAV that a pair of any of the teeth in the mouth may be remoA^ed to correct an irregularity, excepting the canines of both jaAvs and the superior central incisors." " It Avould be an inconceiv- able case Avhich would justify the extraction of the superior central incisors; but the upper lateral incisors and any pair of the loAver incisors may be removed, in certain cases, without any serious detri- 398 DENTAL SURGERY. ment to the appearance of the mouth." "It is not necessary to the contour, symmetry, or harmony of the features that everyone of the masticating organs should be retained in the mouth." " The articu- lation of masticating organs is of much more importance than their number, and a limited number of grinding teeth fitting closely on occlusion Avill be of far greater benefit to the individual than a mouthful of teeth with the articulation disturbed." " It is a dis- puted point as to which of the teeth behind the six front teeth can be best spared from the mouth." " If the sixth-year molars are badly decayed, their removal would be indicated. If they were sound, and also the bicuspids, there might be no greater reason for their removal than either of the bicuspids. In fact, sound molars in the jaw are of more value as masticating organs than equally sound bicuspids." The same writer is also of the opinion that extraction of any teeth from a V-shaped jaw before it is Avidened, Avould be likely to prove bad practice. Many different forms of appliances are necessary in correcting an irregular arrangement of the teeth, as almost every case presents its oavii peculiarities. It is therefore not only impossible to describe every form of irregularity to which the teeth are subject, but also the forms of appliances necessary. The attention of the reader will, therefore, be directed to the treatment of the most common forms, and the necessary appliances for their correction, modifications of which can be constructed according to the peculiarities presenting themselves. The most simple appliances for correcting irregularity consist of rings cut from rubber-tubing, and silk or rubber ligatures, which have their uses in the management of some of the easily manipulated cases. The value of such simple appliances, however, depends upon the skill exercised in applying and securing them. A simple band or ring cut from rubber-tubing, and prevented from slipping up to and injuring the gum, by means of waxed floss-silk tightly tied about the necks of the teeth, will answer for drawing two teeth, incisors for example, together, between which there is an unsightly space. A similar ring may be employed for correcting an irregular front tooth which projects beyond the arch. The folloAving figures represent some of the most useful knots for applying silk ligatures: Fig. 148 represents 13 forms of the most useful knots : 1, thumb- knot; 2 (12, 15, 16), various stages of the clove-hitch; 3, drag-rope, or lever-hitch; 4, draAv-knot; 5, garrick bend; 6, common or sheet- bend; 7, running-knot; 9, men's harness-hitch; 10, sheep-shank; 11, double bowline-knot; 12, first stage of clove-hitch ; 13, single bow- line-knot ; 14, half-hitch ; 15, second stage of clove-hitch. IRREGULARITY OF THE TEETH--ORTHODONTIA. 399 In describing the treatment of irregularity, we shall commence with an incisor occupying an oblique or transverse position across the alveolar ridge; so that the cutting edge of the tooth, instead of being in a line with the arch, forms an angle Avith it of from forty to ninety degrees. This variety of devia- tion is rarely met with in both centrals, but often occurs Avith one. Some den- tists have recommended in cases of this kind, when the space between the adjoining central and lateral incisor is equal to the width of the deviating tooth, to turn the latter in its socket with a pair of forceps, or to extract and immediately replace it in its proper position. It is scarcely necessary to say that if a tooth is turned in its socket, without great care is exercised and the operation gradually performed, the ves- sels and nerves from which it derives nourishment and vitality are strangu- lated ; hence, though its connection Avith the alveolus may be partially re-estab- lished, it will be liable to act as a morbid irritant, and be subject to inflamma- tion from comparatively slight causes. The tooth, hoAvever, may be brought to its proper position, Avithout incurring the risk of injury, by accurately fitting a gold ring or band, Avith knobs on the labial and palatine sides; to each of these a ligature should be attached. Thus fastened to the ring, each end should be carried back, one on either side, in front and behind the arch, and secured to the bicus- pids as represented in Fig. 149, so as to act constantly upon the irregular tooth. The ligatures should be reneAved from day to day, until the tooth assumes its proper position. Should the space not be sufficient to permit the use of the band, the method practiced by Mr. Tomes is shoAvn in Fig. 150. A plate is fitted to the inside of the arch, and a band carried in front and soldered to projections from the plate, Avhich pass between the bicuspids. On each side of the irregular tooth a metallic dovetail is fastened, and pieces of com- pressed wood inserted into them. The swelling of the wood grad- Fig. 148. 400 DENTAL SURGERY. ually turns the tooth. In a few days the metal sockets will require to be changed in position, and in a few weeks the tooth may be thus brought nearly or quite to its natural place. If the space permits, these two methods may be advantageously combined. Use the plate as in Fig. 150, with the inner dovetail; but for the long outside band substitute the band (Fig. 149) around the tooth, with a loop on the median side ; from this pass an elastic ligature to a hook soldered on the plate. The tooth is turned on its axis by the combined pull of the ligature and thrust of the wood. Fig. 149. Fig. 150. For turning or twisting a tooth upon its axis, Dr. J. F. Flagg rec- ommends the clove-hitch, Fig. 148'', over which the ends of the liga- tures are passed and then tied tightly with a surgeon's knot, which holds so firmly to the tooth that it will not slip; the ends are then carried to a rubber ring attached to a neighboring tooth, and by its elasticity keeps up a constant torsion force. For rotating a single tooth as well as drawing out teeth that in- cline within the arch, the screws represented in Fig. 151, and de- signed by Dr. Farrar, will be found as useful as any other means. Before attempting to turn the deviat- ing organ, it should be ascertained if the aperture between the adjoining teeth is sufficient to admit of the operation. If not, it should be increased by the extraction of a bicuspid from each side of the jaw, and moving the teeth in front of them backAvard until sufficient room is obtained. The time required to do this will vary from three to eight or ten weeks, depending upon the number of teeth to be acted on, and the age of the patient. A sufficient space may sometimes be gained by pressing outward the adjoining teeth in cases where they fall within the normal cun^e of the arch. IRREGULARITY OF THE TEETH—ORTHODONTIA. 401 This may be done by the use of the " Coffin Split Plate," or by the " Norton-Talbot Regulating Springs," both of Avhich appliances are described further on. Figs. 152, 153 and 154 represent favorite devices of Dr. J. N. Farrar for rotating teeth, the simplicity of which requires no further Fig. 152. Fig. 153. explanation except that it is constructed entirely of gold or plati- num, and bound upon the tooth to be rotated by a slip-noose as thin as writing-paper, and about one-twelfth to one-fifteenth of an inch wide, Avhich is tightened by means of a nut screAved against a small strip of plate, resting against other teeth. Fig. 155. Fig. 156. Irregular and protruding front teeth may be partially rotated and drawn into position by a very simple, but at the same time ingenious appliance devised by Dr. S. H. Guilford. Figs. 155, 156, 157. 158 and 159 represent two cases of the kind referred to, and Dr. Guil- ford's appliance. According to Dr. Guilford's description, this ap- 26 402 DENTAL SURGERY. Fig. 157. -3 Gr- Fig. 158. \*^N^ pliance is made on a model of the teeth, and is constructed as fol- lows : " A piece of gold backing cut an eighth of an inch wide, and of sufficient length to extend along and a trifle beyond the palatal surfaces of the centrals, is bent to conform as closely as possible to the lingual sur- faces of these teeth, and for- ward so as to slightly clasp the disto-palatal angles, as shown in a, Fig. 157. To this are sol- dered tAvo strips cut from upper plate scrap, a little narrower than the first piece, and bent in the form of b, and c, Fig. Fig. 159. 157, respectively, which are sufficiently long to extend slightly over the anterior and posterior surfaces of the teeth. After being properly shaped to fit the model, their backs are soldered together, and, in turn, soldered to the part (a), as shown in Fig. 157. The only thing then to be done is to reduce with a file the thickness of the part b, c, which passes between the teeth, Fig. 158. Before applying such a fixture, it may be necessary to place a piece of wood between the teeth for a few hours, to separate them sufficiently to admit the ap- pliance. The labial part of the apparatus should rest against the teeth just at, or slightly above the most prominent part of their convexity; while the lingual portion should be near the gum (not quite touching it), and the slightly curved ends of this part Avill catch just above the little nodule usually found on the disto-palatal angle near the gum. When thus secured it cannot easily be dis- placed by the action of the lip or tongue. Bend the long palatal arms slightly toAvard the short labial ones daily, and spring it back into position on the teeth. The elasticity of the gold stiffened by the solder will do the work. To guard against its accidental loosen- ing, tie it to the tooth with a thread." Fig. 160 represents an appliance designed by Dr. Kingsley for twisting the central incisors. After the arch was expanded, as it was a case of contracted arch, a vulcanite plate was required to re- tain the teeth in their spread condition, and its presence was made available for attachments for elastic ligatures. A small hook of gold IRREGULARITY OF THE TEETH—ORTHODONTIA. 403 Avire Avas inserted opposite the canine teeth, and a little staple or loop of the same Avire at the apex of the plate betAveen the centrals. Previous to insertion a ring of rubber cut from tubing was caught over one hook, passed through the loop at the apex and Pig- m caught on to the other hook. The plate was then introduced into the mouth, and the elastic band draAvn over each lateral incisor, as seen in the figure. The tendency of the elastic band to contract in a straight line, operated only on the in- verted corners of the centrals, and by this means the cen- trals Avere turned into their proper positions. Figs. 161 and 162 represent a case of irregularity before and after treatment, where the overlap- ping central incisors Avere turned, and a deviating lateral incisor forced outward, by the appliances just described. The operation known as " torsion," which has been recommended by Mr. Tomes, consists in forcibly turning a tooth in its cavity by grasping it near its neck Avith a pair of forceps, FlG lfi1, the beaks of Avhich are guarded with chamois- skin or other substances, to prevent injury. Where the deviating tooth, such as an incisor, requires but one-fourth of a turn or twist, or less, this is ac- complished by one ope- ration : but Avhere one-half turn is required, several operations, after intervals of a few days, are neces- sary. The tooth is then secured in its neAV position by means of ligatures until a retaining plate is constructed, and the necessary antiphlogistic treatment pursued. The danger of such an opera- tion as torsion is the injury likely to occur to the vessels and nerves resulting in devitalization, and in no case should it be attempted 404 DENTAL SURGERY. until the root of the deviating tooth is fully formed, and sufficient space exists for its reception. The use of vulcanized India-rubber is of great value in the correc- tion of irregularities. The peculiar manipulations it requires will be found in another portion of this work ; it is only necessary, there- fore, in concluding this chapter, to briefly mention the properties which fit it for this important branch of dental practice. It admits of absolutely perfect adaptation to the teeth. If only a part of the crowns of the teeth require fitting, a wax impression will be sufficiently accurate. But if the gum and under-cut surfaces of Fig. 162. the teeth are to be fitted, a plaster impression is necessary. Prof. Austen's method of taking plaster impressions in gutta-percha cups will enable a skilful operator to take an accurate impression of any mouth, however irregularly the teeth may be arranged. A closely-fitting vulcanite plate can be worn Avith comfort; hence the patient is not tempted to remove it. It has no motion ; hence does not wear the teeth or irritate the gums. Its firmness of adapta- tion makes it an excellent "fixed point," from which to make pres- sure or traction in any required direction upon the irregular teeth; the counter-pressure, being distributed all over the regular teeth, is not felt. When it is necessary to cap the molars, a layer of varying thickness should be carried over them all, to prevent the soreness caused by mastication upon any one tooth. Any variety of appliances may be used in connection with the plate that the judgment of the operator suggests as best adapted to bring about the required change. The plastic nature of the crude material nermits enlargement or extension in any direction, without IRREGULARITY OF THE TEETH--ORTHODONTIA. 405 the necessity of soldering, as in metallic plates, and with sufficient exactness. Thus, prominences may be left behind teeth which are to be moved outAvard, in which may be made dovetails for the insertion of com- pressed Avood; slits or holes for India-rubber, which makes more rapid pressure than the wood; or holes for the insertion of small screws. These screws may bear directly against the tooth, and be turned slightly each day or two. Or the portion of the plate next the tooth or teeth to be moved may be separated with a delicate saw from the plate; the ends of the screAV or screws playing into this move the tooth or teeth by a broad bearing, which will, in certain cases, be better than the point of the screw. Or a small piece of vulcanized rubber may be taken ; one end fit- ting against a molar or bicuspid, and into the other end a screw thread cut to receive a delicate screw; on the head of this screw a second piece of rubber may be fitted against the tooth, to be moved so as to allow the screAV to be turned Avithout changing its position on the tooth. This combination forms a miniature jack-screAV sim- ilar to those recommended some years since by Dr. DAvinelle, and will often be found useful. It may be used in combination with the rubber plate by attaching one end to the plate instead of resting it against a tooth. If it is desired to move a tooth by the elasticity of a spring, a vulcanite plate is made to fit closely to the mouth and teeth ; one end of a metal spring is fitted tightly into a groove cut in the plate, so that the free end shall bear Avith the requisite force against the tooth. The elastic slip or spring, when made of vulcanized rubber, can readily be bent by means of a Avarm burnisher, so as to press with greater or less force, as the case may demand. Fig. 163, taken from Mr. Tomes' work, Avill illustrate one variety of the application of metal springs on a vulcanite plate ; in this case pressing outward and laterally the left central and right lateral incisors. This mode of making pressure will be found very useful. It acts steadily, is under control, and does not need renewal so often as the wedges of wood or rubber. What are known as seamless collars -can also be employed for rotating teeth as folloAVS : " To rotate a central incisor, take a fine wire and wrap it around the tooth close to but not under the gum, and cut the wire so that its ends exactly meet to measure the circumference of the tooth. Straighten the wire Avithout stretching it; find its equal in length on the collar diagram, and select the medium Avidth collar numbered under that line. Take a piece of thick gold plate, shape it like Fig. 164, and solder it to the collar as seen in Fig. 165, using 406 DENTAL SURGERY. only solder enough to unite the end of the lever, without flowing any solder over the collar to prevent it from fitting close on the tooth. Dry the tooth, smear its neck all around with oxyphosphate cement, and force the collar over the tooth so that the lever will be in position to be pulled by a ligature, or rubber ring, after the cement has become hard, Avhich should take at least ten minutes. Fig. 163. FrG. 164. Fig. 165. The applied fixture is shown by Fig. 166. A bar regulator that is to be anchored to molars or bicuspids may be likewise soldered to collars, which can then be cemented on the anchor teeth ; or the bar may be adjustably connected with the collars, which are then fixed by cement on the teeth." " Such fixed collars also serve as fulcra for jack-screws, the points of which will take on the metal of the collars so as not to slip, and yet leave the enamel uninjured. Other similar functions will be found available in the collars for regulating purposes." Where ligatures are required, the vulcanite plate affords an easy means of attaching them in any desired position; passing them through holes and tying; looping them over projecting knobs of vulcanite, or over small metal hooks set in the plate; or stretching them through slits sawn in the plate. If a band is to be carried for any purpose in front of the arch, it may be connected with the plate on the inside of the arch, through any spaces occurring between the bicuspids or molars ; if there are no such spaces, or if they are to be closed up in the process of regu- lation, the cap which is often required to pass over the molars will connect the two. But the outside band is not often necessary. The inside plate is less awkward to the patient; it is out of sight; and almost, if not quite every required movement can be obtained from it. IRREGULARITY OF THE TEETH—ORTHODONTIA. 407 Fig Where the irregularity consists in some of the teeth projecting Avhile others incline imvard, such a case can be advantageously treated by the use of a vulcanite plate; the various stages progress- ing nearly at the same time. The impression in this case to be taken in plaster; the plate capping the second molars; first molars and first bicuspids carried outward by wooden or elastic wedges, or by a double spring of vulcanite fastened to the plate opposite each space of the extracted second bicuspids; the left central and right lateral carried out by wedges or screws; the right central and left lateral brought in by ligatures looped over hooks in the plate. At the com- pletion of the work a new impression to be taken, and the plate worn until the teeth become firmly fixed; the use of a retain- ing plate preventing a return of the teeth to their old positions. Ligatures in connection with a vulcanite plate can also be employed for drawing irregular projecting front teeth to their normal positions, after the re- moval of posterior teeth (the second right and left bicuspids, for example), to afford the requi- site space. Fig. 167 represents a case of torsion and retraction of the central incisors, Avith pins im- bedded in the vulcanite plate for the attachment of the ends of the ligature. Fig. 168. Fig. 171. © Fig. 169. Fig. 170. Studs of vulcanized rubber or celluloid, Figs. 168, 169, 170, 171, can be attached to rubber plates for the support of elastic rings 408 DENTAL SURGERY. and moved from one position to another, as suggested by Dr. S. J. ShaAV. The late Prof. J. H. McQuillen recommended a strip of thick gold plate, similar to what is used for clasps, and curved to suit the arch, and so applied by means of rubber ligatures or rings, as to draw forward irregular teeth. The ends of the bar are screwed to the bicuspid or molar tooth on either side, and the rubber ligatures or rings pass over the dovetail-shaped parts and the irregular teeth. Fig. 172 represents portions of metallic bars, a and b, with holes and slits for elastic ligatures or rings; cef, portions of bars with hooks and prominences for ligatures; d, plate, Avith holes for ligatures (Farrar). Where the irregularity consists in one or more of the superior front teeth shutting within the inferior teeth, various appliances have been rec- ommended, the oldest, perhaps, being the grooved plate of Duval, and inclined plane of Catalan, which consisted of a simple circular bar or plate of gold, passing in front of the teeth, from the first molar on one side to the first molar on the other, to which the inclined plane was soldered. In the application of this principle for the cor- rection of irregularity, the author has been in the habit of constructing the apparatus somewhat differently. With a metallic die and counter-dies, he has a plate of gold struck up over all the teeth, when practicable, as far back as the first or second Fig. 173. Fig. 174. molar, completely encasing them and the alveolar ridge. An encase- ment of this sort (Fig. 173) possesses greater stability than can be obtained for an appliance like the one invented by Catalan. The inclined plane represented by Fig. 173 can be more conveniently constructed of vulcanized rubber, which possesses advantages over metal for such an appliance. IRREGULARITY OF THE TEETH—ORTHODONTIA. 409 If considerable time is required for the wearing of such an appli- ance as an inclined plane, injury may result, as the masticating teeth are prone to elongate, and the proper articulation of the teeth be im- paired ; again, if the patient refuses to press the deviating teeth, on account of their sensitive condition while moving upon the inclined plane, the result desired will not be accomplished. In Fig. 175 the letters A and B show a combination of an inclined plane Avith elastic ligatures, designed by Dr. N. W. Kingsley, to correct an irregularity of both upper and lower incisors, and the same apparatus was used as a retaining plate when the change Avas completed. Two things are necessary in the treatment of this form of irregu- larity : first, to prevent the upper and lower teeth from coming Fig. 175. Fig. 176. entirely together, by placing between them some hard substance, so that the overlapping incisors may not interfere Avith the necessary outAvard movement. The second is the application of some fixture that Avill exert a constant and steady pressure upon the deviating teeth, until they pass those of the lower jaw. Fig. 176 represents another appliance of Dr. Farrar for correcting a form of irregularity Avhere the teeth incline to the inside of the arch. The bar (d), in Fig. 176, is made of thick plate, about one- eighth of an inch Avide, and is secured at one end (c) to a molar or bicuspid (or both), by means of a clamp-band (a c or g), while the other extremity rests upon a lateral incisor. This forms a bridge of the bar, Avhich is pierced midAvay by an oblong hole through Avhich is passed a flat screAV (b b), made by filing two sides, which prevents 410 DENTAL SURGERY. its turning, one end of which is soldered to a thin plate (or it may be hammered thin) at the free extremity of which is soldered a thin band (b b), which fits tightly around the crown of the cuspid to be moved. To prevent the band from slipping, a metallic pin-point may be soldered on its inside to fit into a little hole drilled into the tooth (or the band may be at- tached to the crown by the oxychloride or oxyphosphate of zinc preparations, and no hole drilled into the tooth). A nut (h) is then tightened, Avhich draws the cuspid into position, and at the same time forces the lateral incisor (which, in the case repre- sented by the cut, is projecting) inward. Fig. 177 represents another appliance designed by Dr. Farrar for drawing irregular front teeth outward, Avhich needs no explanation. Fig. 178. For drawing irregular projecting teeth, such as canines, into posi- tion, the following appliance of Dr. F. H. Lee, which was designed as an improvement on a somewhat similar appliance designed by Dr. Littig, answers the purpose admirably : The Pull-back Jack-screw's special use is for drawing in obstinate canines which have erupted outside of the line of the arch, but it will work with equal satisfaction on any of the other teeth. The post or nut is set in position and held by vulcanizing into a rubber plate fitting the mouth as shown in the cut (Fig. 178); the screw-bolt is then placed through the post, and a wire or ligature IRREGULARITY OF THE TEETH—ORTHODONTIA. 411 (wire preferred) is passed around the tooth, the ends being secured to the holes in the cross-head or swivel-block. The wire is then tightened from time to time as the tooth is brought to its place. To prevent the plate from being moved out of position by the strain upon it, it should be fastened to the teeth of the arch. Figs. 179,180, and 181 represent a form of irregularity consisting of the misplacement of the superior canines and lateral incisors, Fig. 179. Fig. 180. and the appliance designed by Dr. Joseph Richardson for correcting it, the principle of which was suggested a number of years ago by Dr. Redman. In addition to the malplacement of the lateral incisors and canines, there Avas some lateral contraction of the arch. After the extraction of the first bicus- pids a narrow band of vul- canized rubber (Fig. 180) was constructed, embracing the six anterior teeth. Pressure Avas made upon the misplaced teeth by means of Avooden pegs inserted in holes drilled through the band, at such points as Avere indicated by the direction in which it was desired the teeth should take. The pegs rested against the posterior mesial angles of the lateral incisors in such a way as to force them outward and backward, Avhile those inserted into the opposite or labial por- tion of the band carried the canines backward and inward. These pegs projected but slightly at first, and were lengthened from time to time, as the teeth moved. What is knoAvn as the " Lee-Bennett jack-screw " is an appliance suggested by Dr. G. W. Bennett (Fig. 182). It combines a swiveled- jack-screw Avith the forked post-nut of Dr. Lee's Pull-back (Fig. 412 DENTAL SURGERY. ITS), so that any tooth may be pushed outward into line, as shown by the cut. On occasion both devices may be fixed in the same plate, and be simultaneously operated, the Lee to pull back one Fig. 182. tooth, and the Lee-Bennett to push out another. Both of the oper- ating screws may be turned by the same lever. Figs. 183, 184, 185 represent a simple yet effective appliance sug- gested by Dr. E. S. Talbot, for forcing out a tooth situated inside the arch, and Avhich is described as follows : Fig. 183 represents a second inferior bicuspid Avithin the arch, and the appliance, which consists of a thin, narroAV, close-fitting vulcanite plate, with a hole drilled through its middle, opposite the centre of the tooth to be moved. In the other side is another hole, but not drilled quite through the plate. Fig. 184 represents a IRREGULARITY OF THE TEETH—ORTHODONTIA. -113 spring made of piano-wire, having a single coil, A, Avith the ends of its arms bent at a right angle. One of these ends, C, is cut short to enter the corresponding hole in the plate, and the other end, B, is left long enough to go through the plate and press upon the lingual surface of the irregular bicuspid, leaving a full eighth of an inch between that arm of the spring and the plate, as is shown in Fig. 188, Avhich represents the spring in position. The plate and spring, being separate, can be readily removed for cleansing, and to increase the power by spreading the arms of the spring. Fig. 185 represents a spring for the same appliance, having two long ends, B, B, which are designed for a case where two such teeth are to be likewise moved in opposite directions; the two holes in this case to be drilled entirely through the plate, so that the ends of the springs can be made to press against the lingual surfaces of the tAvo deviating teeth. Dr. Richardson also designed the following appliance, represented by Fig. 186, for shortening teeth elongated during the treatment for irregularity. It consists of a plate affording fixed points of resistance and hav- ing clasps attached and pinned to the centrals Avith Avooden pegs Fig. 186. Fig. 187. resting against their anterior, and the plate against their posterior surfaces, as represented in Fig. 186. To this plate firm elastic cords were attached, stretching across the openings for the elongated teeth. When this plate was pressed firmly to its place upon the teeth and held securely by the means already referred to, the con- tractile force of the cords produced the necessary shortening of the elongated teeth. Fig. 181 represents the elongated laterals as shoAvn in Fig. 187 in their proper positions. A system of regulating teeth, designed by Dr. Jno. J. R. Patrick, is simple and also effectual, and differs from any heretofore referred to. No cast of the mouth is required, and the appliances can be 414 DENTAL SURGERY. readily cleansed, and may be used for an indefinite number of times. The power employed is the elasticity of a bow-spring (see Fig. 188), which consists of a half-round gold wire and platinum bar (A A), curved to correspond with the shape of the arch, having upon it a number of sliding rings, by means of which anchorage is secured and attachment made to the teeth to be moved. The bar is bent with its flat surface inward, and is of sufficient length to allow its ends to rest gently on the external lateral surfaces of the first and second molars, as desired. The slides are fitted accurately, so as to move steadily. Two of these, which are made longer for the pur- pose, are used to secure anchorage, by soldering to their inner sur- faces thin gold bands (B B), previously fitted to the teeth selected. The bar is held in position by set-screws (C C), passing through them. Small buttons are soldered to their external surfaces, through Avhich the screAvs pass, to give them greater purchase. To the Fig. 188. smaller slides the different appliances for moving teeth are attached, as Avedges, hooks, v-bars, loops, and bands (D E F G H I), of various sizes and shapes, as required. The apparatus acts as a lever, of which the power is the elasticity of the bow-spring, the fulcrums the points used for anchorage, and the resistance the tooth or teeth to be moved. If these are outside the arch, the bow-spring is adjusted so that its .flat surface touches all of the projecting teeth, and is firmly set with the set-screws. The wedges are then forced together between the teeth to be moved and the bar; should the wedges cease to act before the teeth are properly placed, the set- screws are loosened, the wedges separated, and the bar taken up until its inner surface is again pressed against the projecting teeth, Avhen it is again set firmly, and the wedges are again brought into play. To move teeth outward, the elasticity of the bow-spring is made to draw upon them by means of the proper appliance. IRREGULARITY OF THE TEETH—ORTHODONTIA. 415 Rubber bands or ligatures may be made useful auxiliaries. This appliance can be used on either jaAv. Should the bar at any time Fig. 189. Fig. 190. Fig. 191. Fig. 192. Molar Bow, A. Molar Coupler. Molar Yoke. Bicuspid Bow, B. exhibit a tendency to slip toAvard the gum, it can be held in place by snapping one of the slides provided with a hook over the cutting edge of a tooth. Fig. 194. Fig. 193. Bicuspid Coupler. Molar Yoke iu place as an anchorage for a spring or rubber ring or ligature. What are denominated " Yoke Regulators " are designed for use with Dr. Patrick's appliance. The yokes can be immediately fixed Fig. 195. Molar and Bicuspid Yoke Regulators with Patrick's bow-spring, wedges, and hook in place. upon the teeth, and the manner of applying them is described as folloAVS: The bow is to be passed from behind and between the teeth, hoAV- 416 DENTAL SURGERY. ever close together these may be. The coupler is then put over the bow ends, a nut placed in the end of the key and carried to place on the bow. When the nuts have been screwed on, if the bow ends project, they can be dressed off with a corundum point, or be covered by a section of small rubber tubing stretched from nut to nut, or be wound with ligature silk. Figs. 189, 190, 191, 192, 193, 194, and 195 represent these yokes, bows, couplers and their application to Patrick's bow-spring. As comparatively feAV cases of irregularity occur which in their treatment do not require expansion of the arch, a number of appli- Fig. 196. Figs. 196 and 197 are typical appliances for the upper and lower jaws. The wire in Fig. 196 shows the form best adapted for expanding the anterior portion of the arch ; that in Fig. 197 the form adapted to enlarging the posterior portion. The additional wire on the left of Fig. 196 was used, in the case above mentioned, to force the lateral incisor outward. ances have been designed to accomplish such an object, such as a hinged metallic plate, the jack-screws, either by direct force or acting on split plates. One of the most satisfactory appliances, however for expanding the arch is the invention of Dr. Coffin, of London, Eng., AAdiich is rep- resented by Figs. 196, 197. It consists of a thin vulcanite plate capping some or all of the bicuspids and molars, and fitting the palatal or lingual surfaces of the anterior teeth, but divided along the IRREGULARITY OF THE TEETH—ORTHODONTIA. 417 median line into tAvo distinct halves, connected, however, by a steel- wire spring, so arranged that, while guiding and limiting the relative motion of the tAvo halves of the plate, its tension exerted between them may be perfectly varied in direction and magnitude. The im- pression of the mouth should be obtained with gutta-percha, as it is elastic, and by its slight contraction in cooling, affords a tightly- fitting plate, Avhich, however, is not inserted in the mouth until it is divided. The steel spring is made of piano-forte Avire, and is of the form shoAvn in Fig. 198. To construct the spring two pairs of pliers are necessary, and a pair of clasp-benders. After cutting the proper length of Avire, from one to two and a half inches in average cases, the wire being of Fig. 198. a diameter betAveen three- and four-hun- dredths of an inch (about 0.035 inch), it should be bent first in the centre, and then back on each side, with the clasp-benders, holding it with the pliers, and thus giving the spring (as a serviceable form) the shape of a three- or five-curved serpentine figure, like a rounded capital W. It should also be bent to fit as nearly as possible the palatal surface of an upper model, or the lingual surface of a loAver model, and its ends should be flattened and roughened, Avithout being softened by heat, for half an inch from the extremities. The plate being mod- elled in wax, the spring is placed on the surface, with its ends buried Fig. 199. Fig. 200. within, and when removed by the counterpart, protected from the rubber by tin-foil before packing. In making the spring the flat- tened ends should be coated with tin; some are in the habit of coat- ing over the entire spring, but this is not necessary, as the Avire after it is worn becomes discolored with a polished appearance. Some recommend the insertion of a small piece of zinc in contact Avith 27 /W\ 518 DENTAL SURGERY. three cells of a Bunsen battery. The cells of the battery supplied with the electro-magnetic mallet are excellent for the purpose, or three or four cells of any bichromate battery will answer. Fig. 350. r 1 If U \ f ^r The circuit should be broken occasionally during a prolonged examination,, and also whenever the lamp is not in use, to prevent its becoming so hot as to be unbearable in the mouth. TREATMENT OF DENTAL CARIES. 519 For the examination of posterior cavities a mirror, set at an angle of 45 degrees, is attached to the end of the guard. With the mirror attachment the electric mouth lamp forms a perfect laryngoscope. Instruments for Forming the Cavity.—Fig. 349 represents a set of instruments called "Explorers," useful for examining the teeth to determine the presence of caries. For the removal of the diseased Fig. 351. part of the tooth, and the formation of a cavity for the proper re- ception and retention of a filling, a variety of instruments are re- quired, Avhich should be constructed of the best steel, and so tempered as to prevent them from either breaking or bending. Their points should be so shaped that they may be conveniently applied to any part of a tooth, and made to act readily upon the portion Avhich it is necessary to remove. Fig. 352. The instruments employed for this purpose are excavators and chisels. Fig. 350 represents some of the many forms of excavators in use, and Fig. 368, page 528, the various forms of chisel-excavators. Ill Fig. 363. LI They may be formed either with handle and point in one piece or fitted to separate handles made of Avood, ivory, pearl or cameo ; or be made to fit into one common socket handle. The introduction 420 DENTAL SURGERY. 207. The collars are attached to the teeth by oxyphosphate of zinc, after a hole is drilled in the side of each, and the spring is bent into form, and the ends turned at a sharp angle so as to enter the holes in the collars. These springs can also be used for pressing out the central incisors when they shut Avithin the inferior front teeth. A rubber plate is made to fit the mouth as shown in Fig. 208, and two of these springs are vulcanized into it at the lateral incisor region. The arms are turned into loops at the extremities to secure a liga- ture. When the plate is adjusted the arms are bent horizontally Fig. 208. and brought in close proximity to the labial surfaces of the deviat- ing central incisors, and securely tied. Fig. 209 represents appliances of Dr. Farrar's to move irregular teeth—the first to draw teeth together, and the second to separate irregular teeth in making space for another. Fig. 210 represents an appliance, also, of Dr. Farrar's, in position, for drawing a cuspid toward a second bicuspid, after a first bicuspid has been extracted. For moving a projecting incisor or cuspid backward, a gold spiral spring was formerly employed. It was found to be more efficient than a ligature of silk, inasmuch as it kept up a constant traction IRREGULARITY OF THE TEETH—ORTHODONTIA. 421 upon the deviating tooth. But it is objectionable, on account of the annoyance it causes the patient. A ligature of rubber is far prefer- Fig. 209. Fig. 210. able, and this material is noAV very generally employed in the treat- ment of every description of irregularity in which simple appliances 422 DENTAL SURGERY. are required. The difficulty of tying India-rubber ligatures is ob- viated by the use of several sizes of delicate elastic tubing (French manufacture), from which sections may be cut, more or less thick, according to the required length and power of the ligature. Each strip becomes thus an endless band which may be readily passed from one tooth to another or to a hook on the plate. Where the superior central incisors project beyond the inferior so much as to give a pointed appearance to the lip, Dr. Kingsley rec- ommends the folloAving regulating appliance (Fig. 211): a rubber plate fitting the roof of the mouth is constructed on a plaster model, taken from a plaster impression, in the same manner as any other vulcanized rubber plate would be made. This plate, which is made as delicate as strength and durability will permit, is cut away op- posite the irregular incisors, so that there may be room for these to Fig. 211. be pressed in. The pressure, which is brought to bear in such a manner as not only to move these incisors, but act more or less upon the whole arch, is made by means of a very simple contrivance, such as a piece of gold, formed in the shape of a T, about a quarter of an inch in length, and with a staple or ring at the bottom of the up- right portion of the T, through which a ligature may be passed. This ligature is a rubber ring, cut from a piece of small rubber tubing, and is passed through the eyelet in the T and then attached to the plate, reaching directly to the second molars on either side. The plate being introduced into the mouth, the T is brought for- ward and passed between the central incisors, so that the cross-bar of the T is brought to bear upon their labial surfaces. If the incisors are in close contact, space is made for the gold bar forming the part of the T which projects into the mouth, by wedging. The effect of IRREGULARITY OF THE TEETH--ORTHODONTIA. 423 this appliance will be to draAv the central incisors inward, and at the same time to force the side teeth outAvard. To prevent the in- cisors from returning to their abnormal position, delicate rubber rings may be used, being slipped over the incisors and attached to a close-fitting retaining plate of rubber covering the roof of the mouth. Fig. 212. Figs. 212 and 213 will represent a case of irregularity before and after treatment, in the treatment of which the appliance above de- scribed is applicable. Fig. 213. Fig. 214 represents a similar appliance for correcting a form of irregularity consisting of the projection of the superior front teeth, where the force is applied to all of the projecting teeth at once. Fig. 215 represents a vulcanite plate with an alloyed gold and platinum band attached by means of screws, suitable for moving back projecting front teeth, after the necessary space is obtained by 424 DENTAL SURGERY. extraction of a bicuspid on each side. This appliance is very ef- fectual, and can be regulated by the patient using a common watch- key, or one made for the purpose, in order to increase the pressure Fig. 214. of the band upon the projecting teeth. Small hooks attached to the front portion of the band, and passing over the cutting edges of the incisors, prevent the band from slipping up to the gum. Fig. 215. Fig. 216 represents a form of special loop for draAving back the canines, and which is attached to the same plate, the band being re- moved until after these teeth are moved. A special plate may be constructed for the moving of the canines, or but one plate be employed, made of the form represented by Fig. 215, and which can be afterwards modified, as in Fig. 217. Dr. B. S. Byrnes has suggested a method of correcting certain forms of irregularities of the teeth by the motive-power of the IRREGULARITY OF THE TEETH--ORTHODONTIA. 425 " spring " or elastic force of thin gold bands, which he described at a meeting of the Southern Dental Association, as follows: " My preference is gold of 20k. to 22k. fine, and, as a rule, the thinner the bands the better the result. It frequently occurs, of course, that for special cases or for a special purpose during the progress of any case the band must be doubled in thickness, but this fact does not change the rule as stated. The pressure exerted by the bands is gentle but constant, and the teeth upon which they operate are moved rapidly, with only the slightest inconvenience to the patient. No plates are used, the fixed points for the applica- tion of the motive power being supplied by such of the teeth as are suited to the purpose. " The method of application is in a general way as follows: The fixed points having been determined, the tooth or teeth to be regu- Fig. 216. Fig. 217. lated are connected to them by means of a thin gold band. In se- lecting the fixed points care should be observed to choose teeth which Avill offer greater resistance to the force to be applied than those which are to be moved will. The band is then manipulated so as to form it into a spring or series of springs so adjusted as to bear most poAverfully on the misplaced tooth. Thus, suppose a projecting su- perior central incisor is to be drawn inward to align properly with the remainder of the teeth in the arch. A continuous gold band embracing the first molars on both sides is fitted around the outside of the arch. With a dull pointed instrument like a burnisher the ribbon is then pressed into the interstices of the teeth over which it passes, thus forming it into a series of small springs. The incisor being the most prominent point will naturally be most affected by the pressure exerted by the springs, and in a short time it will be found to have moved away from the band so that it is no longer 426 DENTAL SURGERY. affected by the tension of the springs. As soon as this occurs the apparatus is removed, the ribbon is annealed, straightened, and a small portion, say a thirty-second to a sixteenth of an inch, as may be required, is cut out of it. The ends are then soldered, and the appliance is replaced upon the teeth, the connecting band being formed into a spring as before. Tension is thus kept up until the tooth has assumed the desired position. " This is the plan of procedure in ordinary, simple cases of irregu- larity; but the method is equally applicable to more complex con- ditions. I have not yet seen a case since my adoption of this devdce where it could not be made to do the work of moving the teeth readily. Sometimes the spring of the band may be advantageously supplemented by other aids, as the insertion of a rubber Avedge at points where a particular gain is desired, in accordance with the recognized principle that in regulating teeth the movement is greatest where the elasticity is greatest. " One of the most importat points to observe in the treatment of a case of irregularity is to always have the fixture so tight that it is not necessary to tie it on to the teeth. I frequently apply fixtures by degrees; that is, after making a snug fit, force the appliance partially to place, then allow an interval, sometimes of half an hour, before proceeding to complete the adjustment. I find this plan lessens the severity of the operation to the patient, not onty because of the rest afforded, but because the teeth seem more in- clined to yield, and thus allow the fixture to be placed more readily. " To apply the rubber wedge, select a strip of rubber of the desired thickness. Place the gold fixture, which should fit perfectly tight, in position, and insert the rubber behind the band opposite to one of the interstices. Take the ends of the rubber in either hand ; stretch it to its fullest extent, and gradually work it to the desired spot; then clip off the ends. Press the teeth forcibly in the direc- tion in which you Avish to move them with one hand, Avhile with the burnisher in the other the band is pressed into the interstices. " Case I.—The first case which I shall describe is that of a young lady who at the time she came to me was in her eighteenth year. The condition of her teeth at that time is well shown in Fig. 218. The missing right superior central had been extracted when the patient was about eleven years old, as the only relief from the un- endurable pain following devitalization of the pulp at the hands of an itinerant dentist. To supply the deficiency a partial plate of vulcanite had been worn for the last three and a half years. The re- maining anterior teeth of the upper jaw had been gradually forced IRREGULARITY OF THE TEETH—ORTHODONTIA. 427 outAvard until at the time I first saAv them they protruded at an angle of forty-five degrees. In the lower denture the incisors stood Avithin the arch, the cuspids inclining fonvard. As a result of this conformation the chin Avas somewhat wrinkled and slightly up- turned. The lips wore a constant pout, the mouth being what may Fig. 218. be termed ' peaked.' The molars being the only teeth Avhich oc- cluded properly, the mouth Avas never naturally closed, and the patient Avas unable to make an incisive bite. " In treating this case I aimed to compass four principal points : 1st, the destruction of the ' peakedness ' by producing a broader or more oval arch; 2d, the reduction of the projecting teeth to their proper position ; 3d, the improvement of the articulation; and, 4th, the closure of the space caused by the loss of the right superior central. " The last mentioned was first undertaken. For the first tAvo days a heavy band Avas used to force the ends or cutting-edges of the right lateral and left central together. A very thin, narrow gold band Avas then fitted to embrace the necks of these tAvo teeth, and a Avedge of wood was inserted under Fig. 219. it on the side toAvard the cutting-edges, causing the C—«—- -n^ teeth to move vertically towards each other. The band being placed around the necks, and the wood spreading it toward the cutting-edges, caused very great pressure at the apex of the root. Another band (Fig. 220) was then constructed to move the incisors backAvard and bring them into a more vertical position. This Avas placed in position without removing the first (Fig. 219). It consisted of two bands embracing the cuspids and bicuspids of each side, connected by another band of the same material passing outside of the incisors. The connecting band wras then pressed into the interstices between the teeth, and rubber wedges were inserted. 428 DENTAL SURGERY. This fixture caused constant pressure backward on the anterior teeth, and an outward pressure on the cuspids and bicuspids. The gold band acted as a lever, the lateral teeth as the fulcrum, and the posterior teeth as the weight to be moved. The connecting band was cut and shortened every other day, the patient having a sitting every day to allow the gold to be sprung more as the teeth moved away from it, " At the end of three weeks the narrow band at the necks of the incisors was discarded, its work having been accomplished, and that shown in Fig. 220 was substituted by another, which passed around the outside of the whole arch from the first molar on one side to the corresponding tooth on the other. This appliance (Fig. 221) was required to do little actual work, its principal office being to hold the gain already made, and to close the spaces between the teeth, which were now about equal in extent, and to bring the teeth to a vertical position. The gold was doubled in thickness over the Fig. 220. Fig. 221. incisors and cuspids to prevent its yielding while the backward movement was progressing, which would allow the arch to again assume the peaked appearance which the treatment was undertaken to correct. The small hook or catch was to prevent the band from slipping up toward the gum, Avhich it showed a tendency to do when first applied. The patient now Avears a similarly shaped band, but only one-third as wide, as a retaining piece, which she removes and reapplies at pleasure. " The treatment of the irregularity in the lower anterior teeth was begun about a week after work on the upper jaAv was commenced, and was completed in three weeks. A band, constructed as shown in Fig. 222, was applied, clasping the first molars on both sides, and passing around the cuspids and behind the incisors. A wooden wedge was placed between the incisors and the band and springs formed by pressing the band into the interstices betAveen the cus- pids and bicuspids, cutting and re-adjusting as before. In two weeks this fixture Avas substituted by another (Fig. 223). This IRREGULARITY OF THE TEETH—ORTHODONTIA. 429 was a plain band clasping the incisors, with wings tipping upon the cuspids, and having the portion behind the incisor doubled in thickness. A little block of rubber inserted under each of the wings completed the Avork in a Aveek's time. The wings were then Fig. 222. Fig. 223. pressed back to hold the gain, and a piece given to the patient to wear as a retaining-plate. " Fig. 224 is an accurate representation of a cast of the mouth taken at the conclusion of the operation. The correction of the irregularities in this case was accomplished in a month, work being carried forward simultaneously in both jaAvs after the treatment of Fig. 224. the lower teeth Avas commenced. The work of moving the upper teeth Avas pushed so rapidly as to slightly ' spring ' the maxillary at the attachment of the compressor nasi and the depressor alse nasi, so that the Avings of the nose were pulled laterally inward and doAvnAvard, causing a slight bulging or bridge on the centre of the nose. But I saAv the patient some six months after the case was dis- missed, and the muscles had adjusted themselves, and no deformity was visible. The patient then informed me that she had never had any trouble Avith either of the retaining fixtures. 430 DENTAL SURGERY. " Case II.—Patient, a lady, aged twenty-seven. The occlusion of the teeth was very faulty (Fig. 225). The lower cuspids closed in front of those in the upper jaw, giving to the chin an angular shape, and the deformity was becoming more conspicuous from day to day. The dentes sapientise Avere just erupting into a croAvded arch, Fig. 225. causing considerable pain throughout the denture, and pushing the lower cuspids still further forward. As the wisdom-teeth were well deAreloped, I decided to extract the first bicuspids to make room for them, and this was accordingly done. The threatened trismus dis- appeared promptly, and the work of bringing the cuspids back into position was begun. Two gold bands (Fig. 226) were applied, one Fig. 227. Fig 226. on each side, embracing the first molar and cuspid. The bands were sprung into the interstices on both the buccal and lingual sur- faces of the teeth. During the early portion of the treatment heavy bands were used, which were made to fit tight and forced to place, each cuspid being pressed backward with the thumb of the left hand Avhile the gold band was pinched into the interstices Avith a pair IRREGULARITY OF THE TEETH—ORTHODONTIA. 431 of root forceps. The molars were capped the first week to permit the cuspids in the opposing jaAvs to pass each other freely. As ab- sorption proceeds slowly at the age of this patient, it was deemed inadvisable to push the work rapidly, and the bands were therefore cut and tightened only twice a week. As soon as the cuspids were brought back from their inclined position, the case became a very simple one to treat; as the arrangement and shape of the teeth enabled me to put on very tight bands. The treatment was com- pleted in ten weeks. Fig. 227 is from a cast made after the conclu- sion of the Avork. " As illustrating the convenience with which the apparatus was worn, I may mention that the patient was a vocalist of considerable Fig. 228. merit, and during the whole period of the treatment was enabled to sing with perfect accuracy of tone and enunciation. " Case III. was corrected in eight sittings. The patient was a lady aged tAventy-two years. When about ten years old she fell, strik- ing upon the teeth of the upper jaw in such a way as to knock out the right lateral and dislocate the other incisors, the left central re- maining at an angle of 35° after its attachment to the alveolus Avas renewed. The incisors gradually separated from each other, the space between the centrals at the cutting-edges being more than an eighth of an inch. The cuts give a very accurate idea of the ex- tent of the deformity, which was very marked. Previous to my seeing the case, a dentist in Ohio had attempted to bring the teeth into proper position by means of a rubber band passing from the left central over the little lug seen on the plate between the centrals (Fig. 228); but this attempt failed, as the resistance Avas almost equal to the power employed. The appliance I used in correcting 432 DENTAL SURGERY. this case is shown in Fig. 229,—a simple gold band extending from the second biscupid and first molar on the right side as base across the mouth to the central to be moved. Here there were no teeth to be utilized in forming the connecting-band into a series of springs, but this was readily accomplished by crimping the band as shown. Fig. 229. " Fig. 230 shows a somewhat more complicated apparatus than any of those previously described. It was used in a case where the right central overlapped the lateral. It illustrates how the method Avhich I advocate may be applied to turn a tooth where the force must be applied directly across the mouth. After the necessary room was provided, this fixture was applied. It accom- Fig. 230. plished its work in four days, after which a retaining device was applied, consisting of a simple band, clasped tightly around the central which had been rotated, and provided with wings tipping on the left central and under the right lateral. " There are very few forms of irregularity of the teeth to the cor- rection of which the method I have endeavored to describe may not IRREGULARITY OF THE TEETH—ORTHODONTIA. 433 be applied. So far, since I began to use it I have found none, and I have treated many cases." Figs. 231 and 232 represent an ingenious appliance of Dr. Farrar for laterally moving the apices of the roots as well as the crowns of teeth. It consists of gold clamp-bands operated Avith a screw ; ful- crums are placed between the teeth, to prevent the crowns from Fig. 231. Fig. 232. moving faster than the entire roots, these fulcrums being replaced by smaller ones as the teeth, under the pressure of the clamp-band, approach each other. Retaining plates are generally required after the operation of mov- ing teeth from irregular to regular positions is completed. For the Fig. 233. greatest difficulty in correcting irregularity of the teeth is often caused by the tendency of such teeth to return to their old positions. It is necessary,therefore, that retaining plates should be worn until the corrected teeth become firmly fixed ; and no definite time, al- though the average time may be stated as that of one year, can be 28 434 DENTAL SURGERY. given for the completion of such a process. Before permanently re- moving a retaining plate its use may be dispensed with for a short time, an examination being made daily, to determine if there is any tendency of the corrected teeth to return to their irregular posi- tions. A simple form of retaining plate, to be worn after the correction of an irregularity caused by the projection of the superior front teeth, is represented by Fig. 233, which is a simple vulcanite plate with a small gold wire attached to it, and passing to the outside of the front teeth, through a small opening betAveen the canine and bicuspid teeth on each side. After the correction of a contracted arch, a simple vulcanite plate, such as is represented by Fig. 234, Fig. 234. Fig. 235. will answer as a retaining plate. A plate of this kind should be adapted to the palatal surfaces of all the superior teeth. Fig. 235 represents an ingenious application of the rubber dam for the retention of replanted teeth, and which may also be utilized for the retention of one or more irregular teeth after treatment, Avhich is the suggestion of Dr. Herbst. The idea is so plainly shown by the illustrations that further description is unnecessary. Wedges of elastic rubber are often useful in cases Avhere the loAver teeth shut outside the upper ones. They should be used of such a thickness as will exert a gentle pressure only. Fig. 236 represents a case of this kind, with the Avedges in position. The jack-screw is also a valuable appliance for regulating teeth. Its use was first suggested by Dr. William H. Dwinelle, and it has been applied alone, or in connection with a split-vulcanite plate. Figs. 237 and 238 represent different styles of jack-screws, the old and new, which are operated by holes in the middle bar; other holes render them capable of being secured to a tooth, thus avoiding the danger of being swallowed if accidentally detached. In some cases, IRREGULARITY OF THE TEETH—ORTHODONTIA. 435 one end of the first style of screw has been permanently imbedded in the rubber plate. Fig. 236. Dr. M. H. Cryer has designed an appliance by the use of which no injury results to the teeth while the jack-screws are in operation. Fig. 237. Fig 238. Fig. 239. It consists of thin platinum bands or clasps fitted to the teeth, the ends either soldered or held together by a small screw. The clasp Avhich encircles the tooth to be forced outward contains a small hole for the reception of the point of the jack-screAv, and upon the 436 DENTAL SURGERY. other clasp, which may encircle several teeth used as a fulcrum, small lugs are soldered, between which the other end of the jack- screw, which is of the form of a crotch, fits tightly, and is thus pre- vented from slipping. Fig. 239 represents a vulcanite split-plate with a jack-screw in position. Fig. 240 represents a screw which is a combination of the two forms already alluded to, having upon its end a revolving crutch. Fig. 241. Levers are also used with advantage on the outside of the arch, to press with a gentle force a deviating tooth, and thus move it into a proper position. Fig. 241 represents a plate of vulcanized rubber with levers or" Shortening the teeth has already been referred to in several of the cases presented, and it remains only to allude to an apparatus de- IRREGULARITY OF THE TEETH—ORTHODONTIA. 437 signed by Dr. Kingsley for such an object. It consists of a frame of gold adapted to the cutting edges of the incisors and lapping on to the canines, to which is added a stud or post about half an inch in length, soldered to it opposite the canines, and coming out of each corner of the mouth. This apparatus is shown by Fig. 242. The arms extend upward, passing outside the cheeks, and consist of metal connected by elastic ligatures to a skull-cap. Fig. 243 rep- resents the entire apparatus in action. For lengthening a short tooth, Dr. J. D. White suggests the simple method of tying a thread ligature tightly around the neck of the tooth, under the free margin of the gum, and if much irritation and Fig. 243. Fig. 244. pain result, to remove the ligature, and, keeping the tooth at rest, apply a little pounded ice in a bag to the gum. After a Aveek's rest, the same treatment is to be pursued every alternate week, until the end is accomplished. But great care is necessary to keep the irri- tation Avithin proper bounds, this treatment being applicable only to growing teeth, although occasionally to matured teeth also. The folloAving is an appliance designed by Dr. Farrar to bring into its proper place in the arch an impacted canine, represented by Fig. 244, which will also prove effectual for elongating a tooth. It consists of a narrow gold plate (see Fig. 245), swaged to fit the palatal margins of the gum and surfaces of the lateral incisors and bicus- pids, with thin cross bars, or a clasp around the first bicuspid con- 438 DENTAL SURGERY. necting this plate with a smaller one adapted to the labial margin of the gum. To the small plate or pad, as it is termed, a smooth nut is soldered, through which passes a screAV, its lower end bent so as to enter a small hole drilled into the croAvn of the short tooth, which by means of a thread-nut is forced downward. The elongated tooth is retained in its new position by the delicate apparatus represented by Figs. 246 and 247. The action of an elastic spring, the free end of which acts upon the short tooth while the other is imbedded firmly in a rubber plate, will often answer the purpose of elongating a tooth. Dr. A. E. Matteson has suggested an appliance to force the erup- tion of teeth which are impacted in the jaw in such a manner as to Fig. 245. Fig. 246. prevent their occluding or meeting with the opposite ones when the jaws are closed. It is described as folloAvs : A rubber plate is made to cover the roof of the mouth and to fit the necks of the teeth closely. A French clock spring is adjusted to the rubber plate in such a manner that one end is riveted into the central posterior part, so that when the spring is forced up against the plate, its distal end touches the necks of the teeth to be drawn out. Ligatures are then fastened to the necks of the teeth, and the spring carried up to the plate and secured to the teeth (Fig. 248). With a sufficiently power- ful spring, from two to four teeth may be operated upon at one time. Fig. -249 shows a similar appliance for operating upon impacted lower teeth. IRREGULARITY OF THE TEETH—ORTHODONTIA. 439 For the same purpose, Dr. E. S. Talbot suggests the following ap- pliance : A rubber plate is made to fit the jaw and the teeth, into which a hole is drilled at a point in the centre of the space made by the missing or impacted tooth, smaller than the one arm of the coil-Avire spring it is to hold. The other arm of the spring, upon Fig. 248. the end of Avhich is a loop (Fig. 250) meets the neck of the tooth to be moved, and is there secured Avith a ligature. When the tooth is so imbedded in the process that a ligature cannot be fastened to it, a platinum band Avith a hook soldered upon it may be forced up under the gum and secured with oxyphosphate of zinc. If this fails, a hole may be drilled into the crown of the tooth, and an eye- Fig. 250. bolt fastened in with cement, to which the spring can be secured by means of a ligature. By drilling the hole in the rubber plate at a longer distance from the impacted tooth, a greater spring is given to the wire. Deformity from Excessive Development of the Teeth and Alveolar Ridge of Lower Jaw.—When the teeth of the lower jaw form a larger arch than those of the upper, the incisors and cuspids of the former shut in front of those of the latter, causing the chin to project, and other wise impairing the symmetry of the face. Figs. 251 and 252 present 410 DENTAL SURGERY. a front and a side view of this deformity. It may result from a want of correspondence in the development of the teeth and alveoli of the two maxilla, the upper jaw being defective in size, while the lower jaw is natural; or the former being natural, the latter may be in excess. It may also arise from a simple eversion of the lower teeth or inversion of the upper. Treatment.—The remedial indications of the deformity in question consist in diminishing the size of the dental arch, which is always a tedious and difficult operation, requiring great patience and per- severance on the part of the patient, and much mechanical inge- nuity and skill on the part of the dentist. The appliances to be employed have of necessity to be more or less complicated, requir- Fig. 251. Fig. 252. ing the most perfect accuracy of adaptation and neatness of execu- tion ; they must also be worn for a long time, and, as a natural con- sequence, are a source of considerable annoyance. The first thing to be done is to extract the first inferior bicuspids. Sufficient room will thus be obtained for the contraction which it will be necessary to effect in the dental arch for the accomplishment of the object. An accurate impression of the teeth and alveolar ridge should be taken Avith wax, softened in warm water, and from this impression a plaster model is procured, and afterward a metallic die and counter- die, in the manner to be described in a subsequent chapter. This done, a gold plate of the ordinary thickness should be swaged to fit the first and second molars (if the second has made its appearance, and if not, the second bicuspid and first molar on each side), so as completely to encase these teeth. If these caps are not thick enough to prevent 'the front teeth from coming to- gether, a piece of gold plate may be soldered on that part of each which covers the grinding surfaces of the teeth. Having proceeded IRREGULARITY OF THE TEETH—ORTHODONTIA. 441 thus far, a small gold knob is soldered to the inner and outer front corners of both caps, and to each of these a ligature of silk or rubber is attached. These ligatures are to be brought forward and tied tightly around the cuspids. When thus adjusted, the lower arch Avill present the appearance exhibited in Fig. 253. By this means the cuspids may, in fifteen or twenty days, be taken back to the bicuspids. If in their progress they are not carried toward the inner part of the alveolar ridge, the outer ligatures may be left off after a few days, and the inner ones alone employed to complete the remainder of the operation. After the positions of the cuspids have been thus changed, a cir- cular bar of gold should be made, extending from one cap to the other, so as to pass about a quarter of an inch behind the incisors, and be soldered to the inner side of each cap. A hole is to be made through this band, behind each of the incisors, through which a ligature of silk may be passed and brought forward and tied tightly Fig. 253. Fig. 254. in front of each tooth. These ligatures should be renewed every day until the teeth are carried far enough back to strike on the inside of the corresponding teeth in the upper jaw. Fig. 254 represents the appearance which the lower jaw presents with the last-named apparatus upon it, and will better convey an idea of its construction, the manner of its application, and its mode of action, than any description which can be given. An appliance of this sort may be made to act with great efficiency in remedying the deformity in question; but, in its application, it is necessary that the caps be fitted with the greatest accuracy to the teeth, and they should be removed every day and thoroughly cleansed, as well as the teeth they cover. If this precaution is neg- lected, the secretions of the mouth, which collect between the gold caps and teeth, will soon become acid, and corrode the latter. 442 DENTAL SURGERY. The remarks made in the previous chapter upon the use of the vulcanite are applicable here. Such a plate, for this class of cases, is readily made, and inflicts no injury upon teeth or gums. Elastic, instead of silk, ligatures might be used, and the retraction of the in- cisors carried on simultaneously with that of the cuspids. The use of vulcanized rubber instead of gold is of great value in correcting irregularities of this nature, the form of the appliances being the same. The employment of elastic rubber ligatures in connection with vulcanite plates is generally found to be effectual in correcting the irregularity of the inferior front teeth. The following appliances, from designs of Dr. Kingsley, will be found serviceable: Fig. 255. Fig. 255 represents an appliance for correcting an irregularity where the inferior canine teeth stand outside the arch, Avhich is some- what narrow; the first permanent molars being first extracted. Hooks of gold wire are inserted in the plate as points of attachment for the elastic bands, which are drawn forward and attached to the canines by silk or linen threads. By such means the canines were drawn into position and the arch Avidened. Fig. 256 represents other forms of attachment for elastic bands and ligatures. Fig. 257 shows an appliance for correcting the irregular arrange- ment of the four inferior incisors. Gold wire hooks (A A) pass over the arch between the canines and adjoining teeth, in order to give an independent attachment for the elastic ligatures outside as well as within the arch, and movements in almost any direction can be IRREGULARITY OF THE TEETH—ORTHODONTIA. 443 obtained. For cleansing purposes such appliances can be removed and replaced by the patient. Protrusion of the Lower Jaw.—This deformity, although produced by a different cause from the one last described, is similar to it, and gives to the lower part of the face an unnatural and sometimes dis- agreeable appearance. It also interferes with mastication, and often Avith prehension and distinct utterance. It wholly changes the relationship which the teeth should sustain to each other when the mouth is closed. The cusps or protuberances of the bicuspids and molars of one jaw, instead of fitting into the depressions of the corresponding teeth of the other, often strike their most prominent points ; at other times, the outer protuberances of the lower molars and bicuspids, instead of fitting into the depressions of the same Fig. 256. Fig. 257. class of teeth in the upper jaw, shut on the outside of these teeth. The trituration of aliments is consequently rendered more or less imperfect. This protrusion of the lower jaw is supposed by some to be the result of a "natural partial luxation." In fact,its causes are by no means clearly understood. It is often hereditary, and would seem to be caused by that mysterious agency Avhich impresses peculiarities of growth and shape not only upon the loAver maxilla, but upon every bone in the body. The agency is so constant and overruling, that avc must be prepared to find the jaw returning to its position after the discontinuance of treatment; unless, by the interlocking of the cusps of the upper teeth and the overlapping of the upper incisors, Ave can restrain the tendency. It is of more frequent occurrence than the one which results from excessive development of the teeth and alveolar ridge, and requires, as before stated, an en- tirely different plan of treatment. It rarely occurs previously to second dentition. 444 DENTAL SURGERY. Fig. 258. as could be safely applied. Treatment.—The plan of treatment formerly adopted consisted in fastening on each side a cap of vulcanite on one of the loAver molars, thick enough to keep the front teeth about a quarter of an inch apart when the jaAvs were closed. Fox's bandage was then applied. This was buckled as tightly as the patient could bear with convenience, pressing the chin upAvard and backward. A piece of tough Avood, slightly hollowed so as to fit the arch of the lower teeth, made narrow at the upper end, was intro- duced between the teeth several times a day, the concave portion resting upon the outside of the lower and against the inside of the upper, em- ploying at each time as much pressure By continuing this operation from day to day, for several Aveeks, the natural relationship of the jaws would, in most cases, be restored. The description of bandage here alluded to, and the manner of its application, is represented in Fig. 258. When the protrusion of the loAver jaAvis accompanied by irregularity, means should at the same time be employed for remedying it. The earlier the treatment is instituted, the more easily will the deformity be overcome. It may, however, be successfully remedied at any time previously to the tAventieth year of age, and sometimes at a much later period; but after this time the operation becomes more difficult. An appliance designed by Dr. G. S. Allan (Fig. 259), and which he employed successfully, consists of a brass plate to fit the chin, having arms with hooked ends reaching to a point just below the point of the chin. The arms are arranged in such a way that the distance between them can be altered at will by simply pressing them apart or together. The upper part consists of a simple net- work going over the head, and having two hooks on each side, one hook being above and the other below the ear. The network and the chin-plate are connected by four elastic rubber ligatures exerting pressure in such a manner as to force the lower jaw almost directly backward. The upper elastics are used simply to keep the mouth closed so that the lower elastics will not pull it open; the upper be- ing made just strong enough so that the muscles of the mouth need not be strained to keep the jaw open during the operations of eating and talking. IRREGULARITY OF THE TEETH--ORTHODONTIA. 445 In cases where the lower front teeth close OATer the upper, and thus cause a deformity of the face, it is important to discriminate correctly between those AAdiich result from malformation, and a protrusion of the jaw occasioned by partial luxation, as the remedial indications in the two are entirely different. Those which would prove suc- cessful in the one would prove unsuccessful in the other. But, fortunately, deformity arising from the last-mentioned cause is, Fig. 259. comparatively of rare occurrence; hence, the dentist is seldom called upon to exercise his ingenuity and skill in its treatment. Dr. EdAvard Angle's system of correcting irregularities of the teeth is described by him as folloAvs: " In studying the conditions by which we may best accomplish the movements of the teeth, we may simplify the process if we re- member the movements in the line of the arch, which are five : for- Avard, backward, inward, outward, and partial rotation. These, and their slight modifications, Avith the exception of elongation and de- pression, which are rare, are all we are called on to perform. The principles governing all of these movements are the same. So that, by understanding the principles governing one, we may compre- hend all. " In applying force to a tooth, it should be sufficient to accom- plish the movements as rapidly as is consistent with physiologi- 446 DENTAL SURGERY. cal law. When pressure is once applied, it should be continued without relinquishment, for there should be no retrogression of the tooth. " The appliance for accomplishing the movement of a tooth must be so perfect in design, construction, application, and operation, that there should be no need for its removal till its object is accom- plished. " After the mal-posed tooth has been moved into the desired position and proper occlusion secured, it should be firmly sup- ported and retained till it has become firm in its neAV socket. " A strip of 32 to 36 gauge platina about J of an inch wide, is made into a loop and slipped over the tooth to be banded. The ends are now grasped close to the tooth with a pair of flat-nosed pliers, and the band drawn tightly around the tooth, a strong burnisher being Fig. 260. applied at the same time to still further make it conform to the shape of the tooth. A small bit of solder is now placed on the band at the junction, and all carried in contact with the flame of the soldering lamp. After it is soldered the ends are chipped off, and the band is now complete and ready for any attachments which may be made; after which it is cemented in position on the tooth. " For accomplishing the different movements of the teeth, I use the folloAving simple appliances: " Fig. 260 shows two forms of the screw: one for pushing, as shown at 1; one for pulling, as shown at 2; and a lever for rotating, as shown at 3. For making and using these appliances, use Stubb's steel-wire of two sizes. You will also need jewellers' gold-plated wire and hollow wire, or, as it is knoAvn among jewellers, 'joint-wire,' which may be of either gold or silver, and a few pieces of piano wire. The screw for pushing is made by cutting a thread on a piece of IRREGULARITY OF THE TEETH—ORTHODONTIA. 447 Stubb's steel wire of the desired size and length. One end of this screw is beaten flat, and to the other end is screwed a small nut made of platinized gold. This complete is shown at 4. A piece of the joint Avire is now sawed off the desired length. The screw is slipped into this pipe, and the whole is now complete and ready for use, as shoAvn at 1. This style of screw may be made any size or length ; the largest I have yet made being 2} inches in length, the shortest J inch. " The traction screw is made of Stubb's steel wire, in a similar manner to thescreAV just described, with the exception that one end of the screw is bent sharply at right angles. The screAV complete is shown at 2. The entire length of the screw is about I of an inch, the angle or bent portion, -332 of an inch. " The lever is made of a piece of piano Avire (No. 13), about 2? inches in length, bent at one end into the form of an eye. It is shown complete at 3. " Rotation by means of this instrument is accomplished by band- ing the tooth to be rotated. Before cementing the band in position Fig. 261. on the tooth, a piece of joint-wire 4 inch long is soldered on to the band on the labial or buccal surface at right angles to the axis of the tooth. The band is noAV cemented in position on the tooth. The straight end of the piano wire is inserted into the little pipe in the band; the other end sprung round and made fast by a Avire ligature to the tooth nearest the eye in the end of the leA^er. Fig. 261 shows an incisor being rotated b}' this method. "After the tooth has been moved into position it is retained by removing the spring and inserting a piece of the gold-plated Avire 448 DENTAL SURGERY. into the tube from the opposite side, long enough for the end to rest on the labial surface of the tooth adjoining, as shown in Fig. 262. The piece of Avire is prevented from turning or working out, by passing a fine drill through the pipe and one side of the Avire, and inserting a neatly-fitting piece in the hole thus made. " For accomplishing the movements of a tooth from within out- ward into the line of the arch, the screw first described is used in the following manner: The tooth to be moved is banded and piped in the same manner as described in rotation; then into the palatal side of the band is formed a slot, into Avhich is inserted the flat end of the screAV. Resistance is gained for the base of the screw by selecting a sufficient number of teeth to completely resist the press- ure of the moving tooth. " These teeth are banded and piped close to the gum, and on a line Avith it. A piece of the gold-plated wire is threaded through these little pipes, either before or after cementing the bands in Fig. 263: position. Against this Avire is placed the base of the pipe encircling the screw. A suitable notch is fitted into the end of the pipe to fit the wire and prevent it from slipping; or, if this wire of resist- ance is placed on the outside of the arch, as may be done with ad- vantage in many cases, the base of the pipe is rested against one of the bands encircling one of the teeth. It is prevented from slipping by soldering it in position, or by plugging the end of the pipe, and filing it to a sharp point. The point rests in a pit formed in the band. Fig. 263 shows the screw in position in moving an inlocked cuspid. " Force is applied by tightening the nut with a small wrench after the tooth has been moved into the line of the arch. If the IRREGULARITY OF THE TEETH—ORTHODONTIA. 449 movement of rotation is necessary the lever is applied, after which it is retained by inserting a piece of the plated wire into the little pipe. The end of the Avire resting against the outer surface of the tooth on each side is shoAvn in Fig. 264. " The movement of a tooth inward into the line of the arch is accomplished by banding the tooth. To the palatal side of the band, close to and on a line with the gum, is soldered one of the little pipes -j32 of an inch long. Into this pipe is hooked the angle of the traction screAV. Resistance is gained by banding piping on one or more teetli on each side of the tooth to be moved, the pipes being soldered close to and on a line with the gum. Through these little pipes, either before or after cementing in position, is threaded a piece of the plated wire. " Pressure is noAV exerted by the screAV pulling through, and the nut working against the end of another of these little pipes soldered to the Avire of resistance. Fig. 265 shoAVS a lateral incisor being draAvn into line. The nut is tightened as often as necessary. The end of the screAV is snipped off from time to time to prevent its chafing the tongue. " After the tooth has been draAvn into line, the wire of resistance and the traction screw are removed, and the tooth is retained in position by inserting a piece of the plated Avire into the little pipe before occupied by the angle of the traction screAV, the wire being long enough for the ends to rest against the palatal surface of the tooth on each side, as shoAvn in Fig. 266. The retaining wire is held in position as shoAvn in Fig. 262. " The movement of a tooth backAvards in a line of the arch is accomplished by banding the tooth to be moved. To the outAvard 29 450 DENTAL SURGERY. surface of the band is soldered one of the pipes -fa of an inch long, at right angles to the tooth, and line of the arch. Into this pipe is hooked the angle of the traction screw. The other end of the screw passes through, and the nut works against, the end of the pipe soldered to the bands encircling the teeth to be used in overcoming the resistance of the tooth being moved. Fig. 267 shows a cuspid being drawn backward. It will be seen that the' movement, tip- ping, Avhich is the ideal, is thus gained, and though the pressure is exerted on one side of the tooth only, yet rotation is impossible, as it moves backward. It will also be seen that the resistance is complete, as the teeth used for this purpose cannot tip, but must be dragged fonvard bodily through the alveolus. The screw is snipped off from time to time as it emerges through the pipe and Fig. 267. chafes the cheek, or the cheek may be protected by covering the end of the screw Avith a piece of Avarm gutta-percha. " After the tooth has been moved backward the desired distance, it is retained there by the screw being kept in position, or it may be removed and a piece of gold Avire inserted in its place. " The movement of the tooth forward in line of the arch is accom- plished in the same way, only selecting teeth from the opposite side to be used in overcoming the resistance of the teeth being moved. " The expansion of the arch is accomplished by placing a bar of heaviest piano wire against the palatal side of the arch, one on each side. They are held in position by the ends in front passing through little pipes soldered to bands encircling the cuspids. The IRREGULARITY OF THE TEETH—ORTHODONTIA. 451 posterior ends are kept in position by the ends of the wire being bent sharply at right angles, and hooked into little pipes attached to bands encircling the last molars. " Thus it will be seen that tAvo rigid bars of steel, one on each side, are held firmly in contact with the teeth. As shown in Fig. 269, pressure may be exerted by placing the screw first described directly across the arch, the opposite ends resting against the bars of steel; expansion is gained by tightening the nut on the screAV. " A better method of applying pressure against these two bars is to bend a piece of heavy steel wire to conform to the curve of the arch across from bar to bar. At the side near one end is filed Fig. 269. a notch fitting neatly one of the bars which it is to rest against. The other end is beaten slightly flat and a hole drilled through at a point directly opposite the other bar on that side of the arch. Through this hole is placed the screw for pushing, as shoAvn in Figs. 260 and 263. The screAV should not be over I of an inch in length. " This appliance is now ready to place in position, as shoAvn in Fig. 268. It is in position in Fig. 269. " Pressure is exerted by tightening the nut. After the nut has travelled the length of the screw, the bent wire is removed and straightened a little that the screw may have more action. It Avill be seen in the engraving that two of these screws and braces are used, one to remain in position Avhile the other is being straightened, thus preventing the teeth from moving back, as would be the case if but one Avas used. 452 DENTAL SURGERY. " These braces are moved along the bars forward or backAvard according as pressure is needed. After the sides of the arch have been pressed apart the desired distance, they are retained by a straight bar passing across the arch from cuspid to cuspid, the ends being bent sharply at right angles and hooked into little pipes, soldered at right angles to the pipes already described as attached to bands encircling cuspids. " The incisors are drawn into line by means of the lever and trac- tion screAV, this cross-bar serving as the wire of resistance for the traction screw to pull to. " This method of expansion may be applied to the lower arch as well, as little interference is offered to the movement of the tongue. If several teeth are to be retained in position, one molar on each side of the arch is banded and piped on a line parallel with their Fig. 270. axis. Into this pipe is hooked the ends of a piece of the plated wire, bent to conform to the shape of the arch and snugly encir- cling it. To this wire is attached by bands and pipes such teeth as should be supported. Fig. 270 shows such a retaining appliance. " Such is the general method of using these three appliances, but the different ways in which they may be applied are almost innu- merable, each case requiring some slight modification. " The greatest care and accuracy should be observed in the con- struction, application, and use of these appliances. The little tube should be of gold and fit snugly the different parts of the appliances passing through them. The rubber dam should always be adjusted about the teeth before fitting and cementing the bands into posi- tion, and the cement used should be of the finest quality. The BONAVILL SYSTEM OF CORRECTORS FOR IRREGULARITIES. 453 screws may be made of platinized gold, or, if of steel, they should be nickel-plated." THE BONWILL SYSTEM OF CORRECTORS FOR IRREGULARITIES. BY AV. G. A. BONWILL, D.D.S. To do justice to a subject of such vast importance, and do credit to myself, Avould demand more space. I shall, therefore, deal more in description of the apparatus and cases, leaving the new theory of etiology in its completeness to the near future in a monograph. To make my OAvn history more replete, I must shoAV what I did in this line of work from 1854. My first essay Avas on orthodontia in 1862, which, from its length, Avas not published in the Cosmos. As the apparatus was then entirely new and the practice rather radical for the time, and as it has since been revived by others, I shall briefly present it. It will be observed that the " Talbot spiral spring " is a true re- production of the figures 271 to 276. These I used for several years, until I abandoned them for the present simple devices shown in figures 277 to 280. Only occasionally I use the spiral spring. From the folloAving language it will be seen that I anticipated the " Coffin plate " of rubber, except that I used silver wire made spiral, and made them adjustable or detachable from the plate. " If the inferior jaAv, I clasp, Avhere possible, and when not, strike up a plate to cover the deciduous or permanent teeth, as they may be, and operate from this. From the inAvard inclination of the in- ferior bicuspids and molars (or molars alone of the temporary set) there will be sufficient firmness gained by making it to press out- Avard at these points." " If there are no other means of holding, in the inferior jaw, an india-rubber plate made to fit accurately either the teeth or palate, or both; and if you desire, the surface of the vulcanized plate can be roughened to enable the patient to masticate thereon, and screAV the spiral springs into this."* This I seldom used, being bulky and dirty, and far more liable to injure the faces of the teeth. I could do more with the spiral spring soldered to a metal plate. The same principles of action I then held I still adhere to, to wit: 1st. To commence as soon as possible after the seventh year, or as soon as there is evidence of decided irregularity. 2d. To Avatch all children's teeth from the third year and deter- mine by an exploring needle, every three months, the exact position * Extract from my essay on Orthodontia read before Delaware Dental Society in 1862 or 1863. 454 DENTAL SURGERY. of the coming permanent teeth as soon as the first permanent molar has appeared. 3d. To preserve, by early treatment, the first and second molars —temporary—even to the treatment of their pulps, if they were not brought in time to obviate it. 4th. To be sure the first permanent molars are preserved with- out loss of pulp and allow nothing to interfere Avith their full and free development in the arches, as upon these teeth more than any others are due the irregularity, by coming too far forward in the arch from decay of approximal surfaces of temporary molars, or from the tardy eruption of the permanent incisors. The sixth-year molar drives the arch into smaller space when the incisors have appeared out of or inside the arch. If the arch is once interfered with the area is not so great, and consequently there will be a deeper underbite and the permanent molars will move forward and always keep them so, causing the permanent teeth which are yet undeveloped in the maxilla, and lying over each other and not in line, to roll over and shorten the whole maxilla in front of the permanent molar. Therefore, keep this tooth as far back towards the ramus as possible. 5th. That all apparatus should be simple and, if possible, firmly fixed, that the patient can have no control over it, and then see the case every few days. 6th. That constant and uninterrupted pressure is preferable. The antagonism of the opposite jaw will ahvays be exerting a force to make them move back and forth in the sockets, which makes - sufficient intermittent pressure. 7th. That while one plan, without change somewhat to each case, Avill not do, yet the infinite number of such apparatus is a greater nuisance to patient and operator. 8th. That impressions of both jaws in plaster and a duplicate from the first; that the plaster teeth could be cut off and rearranged to see the effect, and these models placed in my anatomical articu- lator, where it could be studied in the lateral movements, so necessary. That this should be studied carefully; and, before action is taken, have the patient call and study the case in rela- tion Avith the plaster model; and if doubt existed as to the extrac tion of a tooth or teeth, better postpone a few days and send for patient again rather than make so great a blunder. 9th. That a tooth should be held as sacred as an eye; and, while extraction is sometimes demanded, Avhen the greater good of the patient is at stake—when of weak constitution—yet do not too hastily resort to it. BONAVILL SYSTEM OF CORRECTORS FOR IRREGULARITIES. 455 loth. That Avithout the combined assistance of parent and child, better not commence. 11th. That nothing should be withheld from the child or parent, but every detail, every risk, and the amount of patient endurance needed, the long time and, Avhen all is corrected, to allow of stay plates, that the work gained may be retained. 12th. Not least of all the factors, I must mention (which I did not at first see) to place such valuation on the services as will insure your interest and will drive the parties concerned up to their duties. To these points I would noAv further insist on the great importance of utilizing as factors or fulcrums the temporary molars. 1st. By shaping them with a disk on all their sides or surfaces, so that a gold clasp can be securely placed thereon. Figs. 291 and 292. 2d. Where a ligature only is needed, to cut a groove with the disk on the buccal and palatal and lingual surfaces near the cervix, in which to place the silk ligature to keep it from working doAvn under the gum. Fig. 291, C C. These teeth will soon be lost, and no injury is done by shaping and grooving them. 3d. By the use of gutta-percha (Figs. 280 and 281), Avarmed and placed on the palatal or lingual side of the tooth, around which a ligature is to be placed and carried slightly up over the grinding surface to prevent the ligature from pressing doAvn under the gum. This I use on permanent teeth. 4th. Where the tooth cannot be cut or gutta-percha used, then gum sandarach varnish or a thin solution of oxyphosphate zinc placed on the tooth will prevent the ligature from slipping when the tooth is being rotated, or to keep it from pressing up under the gum. 5th. The immense importance of the Anatomical Articulator, with the geometrical and mechanical laws governing it. The study of this alone will lead to the anticipation of so many irregularities, and will teach one to commence very early. It shoAvs hoAV invariable is law and, when violated, where the cause is and how to obviate it. It sIioavs Avhat is an archetype, and demonstrates clearly how the highest efficiency is reached in the equilateral triangular jaw of man, and that nothing can be made more perfect by nature or man. Noav to make my application of this to orthodontia I must unravel much that you can see in the American System of Dentistry, vol. ii., page 486. Presuming upon your having read the article, I will take advantage of it to save time and Avork and concisely put it. What we Avant to get at is the significance of the grinding surfaces of the bicuspids and molars Avith the curve at the ramus and the- 456 DENTAL SURGERY. particular angle formed by the palatal surfaces of the superior incisors. We want to know exactly hoAV much the superior incisors should overlap the inferior, and how far up on the palatal surfaces of the superior incisors and cuspids the inferior should go—or the under- bite—before we can understand what is a deviation from the normal standard, and how to intelligently correct it. I have asserted that the length of cusps of the first superior bicus- pid governs the whole thing. Give me such tooth from any pre- historic age, and I will tell you how deep the underbite of inferior incisors. It is no guessAVork ! You see hundreds of mouths with the inferior incisors going so far up that they touch the base of the superior and in many cases the gums. Why is it not normal ? No one can tell without this law governed by the first superior bicuspid. Every one will assume that the upper should close OATer the lower incisor, and their only reason for it is because the inferior being smaller in width must form a smaller arch, and must work within the superior arch of larger incisors. There are several other reasons that this model will reveal, and could only be known and seen, first, in it. Unless there were an underbite, and that regulated to a given depth by the teeth in the rear of the arch, the superior would be thrown so far forward, while the inferior would be thrown inward, as to lose their usefulness and be a deformity, as Ave so often see when the bicuspids and molars are gone and no antag- onizing surfaces are left as abutments. When we look at the cur- vature at the ramus Ave are reminded that there is an overbite, for were there no curve just here the muscles would act more forcibly on the side opposite to that upon which you are cheAving, and the normal relation of compensation and efficiency Avould be destroyed. Then I say the highest efficiency cannot be reached, or, in other words, to get the greatest results from the least expenditure of force with least wear to the teeth, except by folloAving this design; and when this is fully realized, you will see where but little change of position of the first permanent molar forward, from the extraction of a temporary molar, the normal bite is made much deeper, as it alloAVS the jaws to approach each other very much faster. If nature intended to have given man a deep underbite, then we would have seen such an arrangement of the back teeth as carniv- orous animals, where but one long cusp is used to get the greatest amount of shearing surface. Instead, then, of the bicuspids having cusps greater than the RON AVILL SYSTEM OF CORRECTORS FOR IRREGULARITIES. 457 angle of an equilateral triangle, they would have all been cuspid teeth in order that the cusps Avould be of any value in the lateral movements. When they reach beyond an angle of 45° their effi- ciency is no longer gained, but a direct loss and danger of fracture by the long wedge-shaped cusps that would have to enter it. A cuspid Avould be much more powerful to pierce and cut, and no danger of loss from fracture. Then I assert, when the overbite or rather underbite rises higher than one-eighth of an inch abnormality commences; since the incisors Avould not permit the bicuspids and molars to come into contact Avhen the incisors Avere touching on their edges. But, by this arrangement, no matter in what lateral position you place the lower jaw, the teeth of both jaAvs will be touching at their separate points of the equilateral triangle at once. We Avill take a natural superior first bicuspid and measure the length of its cusps, place it at the point on the tAvo lines a and e in its relation in distance from the condyles Avith the superior Fig. 270a. £^ centrals. This will be about one-fourth the distance from the cen- trals to the line running from the condyles. Do you not now see that if these tAvo lines a and e diverge from the point of motion at the condyles at T until they reach the superior bicuspid at b at the depth of groo\Te, that carrying the lines still further to the left until they strike the palatal surface of the superior incisor, the lines must be further apart there than anyAvhere else? Fig. 270a. By this I knoAV exactly, Avhen I am grinding on artificial teeth, that if my overbite at e and a is one-eighth of an inch, the depth of cusps of all the teeth backAvard until I reach T would be of less depth, and at T Avould have no cusp at all. Were it not true, only certain teeth Avould touch at any lateral movement, and deeper than this the bicuspids and molars not touching but little of the time Avould throAV much more force on the palatal surfaces of the upper incisors to press them out of the 458 DENTAL SURGERY. arch and contract the arch of inferior incisors and crowd them into a lesser arch as so many bricks, one over the other. Then you must surely see that the permanent molars must be in a position that their length out of the jaw must be such as to allow the inferior incisors to occupy a larger arch, and only under such plan can they be regular and fill their highest function. To make the application. If Ave extract the first temporary mo- lar too soon after the sixth year, the second temporary molar will be thrown forward on this scale and on these lines a, e to T, that will alloAV the jaws to come closer together and force the inferior incisors further in under the wedge-shaped palatal surfaces of the superior incisors until they begin to overlap each other, since the arch be- comes less as they are driven backward by the inclined plane of the palatal surfaces of the superior incisors, and until the first molars again touch on their grinding surfaces, Avhich is only after they have been moved forward between these lines a and e. The same result folloAvs should the first permanent molars not come up as fast as do the incisors in the inferior jaw. The latter are in advance, and consequently there is no prop long enough to hold the jaAvs from a deep underbite or the inferior incisors touch- ing the gum. Besides, if the inferior permanent incisors should be forced within the arch by non-absorption of the roots of the temporary teeth, they would have no guide from the superior incisors and the result would be too deep an underbite. Now all this is with the temporary teeth and the first permanent molars at the seventh year. Should the second temporary molar be extracted too soon, the deformity becomes more marked by the forward movement of the first permanent molar. Aside from direct loss by extraction, see how much approximal surface is lost on all the temporary molars and on the incisors from caries, which allows the first molar permanent to move forward and the loss of it to keep the jaws apart, at this early age so necessary. Still further is this increased by the rapid decay of the first perma- nent molars allowing the jaws to approximate still nearer, forcing the loAver incisors into a much smaller arch, and consequently higher up under the superior permanent incisors. Add to all this the croAvning climax of blunders: the extraction of the first permanent molar or molars too soon. One is enough to break up the masticating surface on that side, and how great a loss, as the force of mastication is thrown upon the incisors, which, at this early age, must drive the upper out and the lower in and crowd worse than ever. BONAVILL SYSTEM OF CORRECTORS FOR IRREGULARITIES. 459 To add the straw. See now the condition of the permanent teeth in the jaAvs, not yet to the surface (bicuspids and cuspids), with a contracted arch, from the full complement of teeth, but the loss of mastication in the proper region has prevented the expansion of the arches Avhich is so necessary at this early age. Even if none are extracted, look at the many deciduous teeth that give untold pain from exposure of pulp and abscesses which pre- vent the use of the jaws on hard food, such as is needed to develop size and bring more nutrition to the parts to make the processes, but also the sad effect on the nutrition of the teeth themselves. Is it at all Avonderful that Ave have increasing abnormality Avith increase of caries? Can we not see from this pen picture what a grand field Ave have for shaping the destiny of individuals who are certainly doomed to greater deformity as the ages come? That your duty lies, above all else, in Avatching each child with scrupulous care, making it a part of a forced education to go to the dentist every three months and submit to a close examination Avith an exploring needle to find the coming tooth in advance of loose- ness and also to give your best efforts to the saving of the temporary before pulps are exposed. The principal causes of irregularity are diverted and polluted nutrition. Nutrition is diverted when the jaAvs and teeth are not actively and normally used, and it is taken up by those organs that are demanding it from their constant action before it can be applied to the bones. Polluted nutrition is where diseases of various kinds contaminate the fluids and render inactive by their poisons the organs as to cause irregular deposits of bone in the teeth and maxilla, retarding their groAvth, consequently their arrangement, in the arch. The choice of proper food and its mastication has a powerful effect in not only diminishing the supply of phosphates but their application to the jaAvs and teeth from Avant of proper action. The trigeminus nerve is not a factor. If, then, nutrition by perversion, pollution, or diversion be what I say, a prime factor in the cause of irregularities, let us draw upon our imagination the first effort that nature makes to supplant the temporary set. The first permanent molar in both jaws should be present and to their full height or place, or in contact -before the central incisors are lost. Early decay of the temporary teeth is potent in irregularities. The injudicious use of the forceps, by too early or late extraction, ac- cidents, and, not least, the meddlesome dentist. We find it almost entirely confined to civilized life. Never found in the lower animals. The muscles are becoming, or should be, stronger every day, as the 460 DENTAL SURGERY. most active parts gain the most nutrition and at once. Unless the teeth are in full contact and well propped in position by alveolar borders calculated to resist the coming force to be exerted thereon, the arches in front being now the weaker of all, must be forced out of position by the jaws being forced nearer each other. This is most possible, for if nutrition has not been plentiful and not used greedily by the alveolar processes, the results must be as I say. Then look at the average set of teeth of the child at six that comes to us. The further the sixth year molar goes forward between these two lines a, e, and T, the less room all the coming permanent teeth have, and, the jaAvs necessarily coming closer together than if the molars had remained at their place in the alveolar border, where the greatest resistance is offered, we can see how the bicuspids are rolling over each other and in the circle or arch in front Avhere the teeth are in advance in the loAver jaAv, but not growing as fast as they should from want of nutrition by perversion or pollution, the props,—the temporary incisors—being no longer of value, the jaAvs approximate too closely, and when the laterals make their appearance is it any surprise to us that they should be inside the arch in most cases? Hoav could they arrange themselves regularly when the arch is so wanting in firm bone to hold them in bounds, and from caries of all the posterior teeth and those not yet above the surface croAvding forward as the resistance is taken aAvay from the condition of the temporary molars and lack of energy in the tis- sues, both soft and bony? It would be marvellous if they, in their normal state, Avhich is apparently not in curve, should not be found one upon the other, overlapping in the border before eruption. To add to the horror, the irregularity of their periodicity is so great and out of order or proportion that the inferior permanent incisors are crowded into a smaller arch than the third of a circle, and there is not room for them. The malady increases as the inci- sors of both jaAArs come into place. If any irregularity at all in the superior jaAv, it becomes greater in the lower, for as the inferior reach the normal point, Avhere they should stop going up under the supe- rior on the palatal side, they fail to do so for Avant of that proper resistance which a perfect arch alone in the loAver would insure. But one tooth inside the arch of the loAver jaAv and at once, as the superior come into place later from requiring more nutrition and want of full use from the pain of mastication, they are retarded, and the lower arch becomes smaller than the third of the circle, and, as a sequence, are croAvded by the superior imvard and upAvard until in so many instances they reach the gums at the base of the superior incisors, because, as I said previously, the loAver arch had collapsed from the many causes which should have been prevented. BONAVILL SYSTEM OF CORRECTORS FOR IRREGULARITIES. 461 This can occur in jaws where the temporary are in perfect condi- tion as Avell as the sixth year molars, from a contracted alveolar border and absorption not keeping time with the advance teeth. But it is not so often found. Instead of contracted jaws from extraction and caries, it is compressed alveolar borders, and the want of resistance in them when the man- dibular action cannot be performed and no healthy nutrition be the result; that is the condition of the parts. Keep back the first permanent molars, and, if possible, push them further back toAvard the condyles, that there may be no intrusion on the domain of the coming permanent teeth. Have the temporary teeth in such condition that free mastication can be performed. (rive the child all the nutritious food he needs, Avith plenty of exer- cise and sleep. Keep saccharine matter far from him in the shape of cake and candy. Make him eat his food without any Avater or drink. Have the salivary glands of value by compelling them to secrete from the use of dry food, and food Avill be SAveet enough without sugar. The food is kept longer in the mouth. The jaws are used their full time. The muscles become stronger and the alveolar borders firmer, and the nutrition is plentiful, and is utilized without any part having to cry out for want of it. The nutritious supply will then always be in advance of the demand, and well laden Avith everything that can give life to an organism, and my word for it, good teeth and a well-arranged mouth result. I have had the greatest satisfaction in the use of gutta percha on the approximal surfaces of the temporary molars, Avhich, as long as it can be kept in them, spreads the jaAvs or keeps the permanent molars from croAvding forward. Invaluable. The trouble has ahvays been how to get hold of any of the tem- porary teeth as a fulcrum. It has been my practice for years to first make use of the silk ligature and rubber bands, Avithout plates. To do so, hoAV shall I prevent the ligature from slipping off the permanent tooth, and from slipping down over the temporary tooth used as the fulcrum? I argue that as the temporary cuspids and first molars will soon be lost after the permanent lateral incisors have come, and are high enough to get hold of, to cut a slot Avith a small hard-rubber disk on their buccal and palatal surfaces deep enough to hold the liga- ture Avhich keeps it from ever passing down under the gum, Fig. 291. If I must make a plate of rubber or metal for the inside, I use the same grooves to hold the plate in position. If I must have a clasp, Avhich is now most frequently the case in the use of this neAV appliance, which I will presently shoAV you, I 462 DENTAL SURGERY. cut the first temporary molar on its mesial and distal surfaces a little under parallel, as at Fig. 292, and the strain is so slight it is not uplifted before the lateral incisor has been drawn into the circle. If there is any danger from the ligature wounding the gum, I place underneath gutta percha. If I want to pass a ligature around a permanent tooth (Figs. 281 and 286), as a fulcrum, I simply warm a small piece of gutta percha and press it on the palatal or lingual side of the tooth, letting it extend slightly down on the gum, and when cold and rigid, cut two holes through it to let the ligature pass, and then betAveen the teeth, and tied outside to the rubber band. This little adjunct cannot be overpraised ; for it is so soon adjusted, is pleasant to the patient, and non-irritating to the tissues. I cannot tell you how much I love gutta percha, and especially just here to save me so much plate work and irritation, and for keeping my children in good humor. If a metal wire or band is pressing into the gums, and a hook cannot be used on the grinding surface, the gutta percha fills the need; and it answers well as a Fig. 272. Fig. 271. csa^ ^feJ«" fulcrum by letting the band directly into the gutta percha or by at- taching it to the wire or silk ligature that holds the former. The figures from 271 to 292 show all the appliances and their ap- plications for irregularities. Figs. 271 to 276 show the spiral spring in various phases. Fig. 271 is a silver plate to fit the loAver incisors tied on to a cen- tral to correct a superior central from the inclined projection on the right, and the end of spring acting on the right inferior central to throw it out of the arch. Figs. 272, 273, 274 are metal bands with clasps, Avith the spiral spring soft-soldered under a metal loop hard-soldered to the bar.d. This retains the temper. These are used on many teeth in either jaw. Fig. 274 is a metal plate with half clasps fitted to the bicuspids to hold it in position. The spiral spring is soft-soldered to plate. This can be changed to various positions on plate, and is applicable to cases where it is difficult to place clasp entirely around a tooth. Fig. 275 was made for drawing backward the four incisors of in- BON AVILL SYSTEM OF CORRECTORS FOR IRREGULARITIES. 463 ferior jaAv Avith spiral springs, adjusted not to interfere with the tongue or superior teeth. The piece at A goes-over the incisors, and is held by ligatures tied to one or more of the teeth. Fig. 273. Fig. 274. Fig. 276 is a jack-spring for constant pressure. It may be made in a curve to conform to the hard palate. It is very powerful and effective, and superior to a, jack-screw. In all these spiral-spring appliances, the spring is tied to the tooth to be acted upon to hold it from slipping; or, in some cases, a hole drilled into the tooth is better. Fig. 276. Fig. 275. The appliances that Avith me have superseded all others are seen in Figs. 277 to 292. Fig. 277 is a curved bar of platinized gold with four holes punched therein for the passage of silk ligatures. It is Fig. 277. Applied in Fig. 285. Fig. 278. Applied in Fig. 289. another Avay of applying Fig. 278 Avithout band and used mostly for a single tooth in either jaw. The principle of action will be seen in Fig. 285, Avhere two inferior lateral incisors are to be drawn from 464 DENTAL SURGERY. within out. To do so requires expansion of the jaws. This is effected by making the holes in the end of the plate over the centre of each cuspid, and by carrying the silk ligature from the mesial side of the laterals around back and up between the lateral and cuspid and through the hole in plate at either end, and attached to a rubber band Avhich is stretched between the holes. This pushes the cuspids backAvard or opens the arch, and the centrals move for- ward someAvhat, and the laterals easily fill the breach. Once in position and they are retained without apparatus. If the holes through Avhich the ligatures pass were made exactly opposite laterals, no good would be effected, because the pressure would be as much doAvn as out, and compressing the arch. But the ligatures applied as directed force the jaws apart, although the band is resting hard on the cuspids. The ligature is a loop or slip- knot, and must be applied so as to come out between the lateral and cuspid. Gum sandarach varnish will keep it from slipping Fig. 279. Fig. 280. o n Figs. 281 and 286. Bar shown as applied, Fig. 281. around the tooth. The band as heretofore applied has not ex- panded the arches, because the holes were not in the right places —over the cuspids. Fig. 278 is this same bar with a clasp on one side of the arch. The bar is lengthened beyond the clasp to allow of the rubber tubing tied at B being attached far enough away from A for getting.poAver. It is applied, Fig. 289, by clasping a first molar. The right central has to be twisted, and the lateral also, but in the opposite direction. The bar rests upon the mesial buccal edge of the lateral Avhile the silk ligature is carried twice around the central, bringing it up next the lateral, and over it through the hole in the bar in the point Avhere it rests on the lateral, and is now drawn through the rubber band which has been tied opposite the molar. The rubber is stretched to the full length of the bar. The cuspid Avas also draAvn outward on the same bar by boring a hole directly opposite, which can be made to tAvist the cuspid as well as to draw it outAvard. Fig. 279 is the same bar applied to Fig. 281 for draAving out both Applied i BONAVILL SYSTEM OF CORRECTORS FOR IRREGULARITIES. 465 superior laterals and expanding the arch. The right cuspid is just emerging and the first bieuspid is clasped. The ligature Avith a slip- loop is carried over the right lateral, coming up from its distal side and through the hole in bar at A, and tied to the rubber band near the first bicuspid. The left lateral is ligated the same Avay, coming up through the hole at B, which is over the centre of cuspid. The ligature pressing the left cuspid backAvard is tied to the rubber band at C. Where the bar is too short to stretch the rubber band, it can be lengthened on one side of the clasp or carried back to the right bicuspid. The loAver jaAv partially shows the application of the gutta percha stay-plate (see Fig. 280) for keeping the ligature from off the gum at Fig. 281. cervix, on the first molar. The loAver jaw being too large an arch for the upper, I extracted the first right bicuspid, and as the right lateral inferior incisor Avas too far in the arch, and the right cuspid very far outside, I simply ligated the first inferior molar on the same side. A piece of pink base-plate gutta percha was warmed and pressed up against the molar, letting it rest partially on the adjoin- ing teeth (see Fig. 280); Avhen cold, two holes Avere made in it for the passage of the ligature Avhich Avas tied on the buccal surface of the molar. A rubber band Avas tied to the inside before adjusting. A ligature is iioav cast around the right lateral, carried up between it and the cuspid, and over it through the space Avhere first bicuspid was extracted, on the lingual side of the first bicuspid, and tied to the rubber band attached to the gutta percha stay or helmet on the first molar, and stretched over the buccal surface of the cuspid. This dreAV the lateral out very forcibly. The ligature Avas lastly 30 466 DENTAL SURGERY. placed on the cuspid alone, and remained for six weeks without change. . Fig. 280 is also applied in Fig. 286. This was a very contracted lower arch with a deep underbite. The arch was first expanded by the fixture shown in Fig. 282, made of piano wire, with half clasps Fig. 282. Fig. 283. Applied to Fig. 286—Expander of bicuspids, Lower. Shown as applied, Fig. 284. of platinized gold at A A, made with small ears to rest on the grind- ing surfaces of the first bicuspids to prevent slipping down upon the gums. These clasps are soft-soldered to retain the full temper of the piano wire as a spring. It is a very cheap and easy way of making such ah apparatus and with a powerful spring which such cases demand. Fig. 284. In this case I could not afford to extract any teeth, because the incisors Avere already touching the gums on palatal side of the su- perior centrals. In expanding the loAver arch I obviated this deep over and underbite. The left lateral was very far inside the arch, and the cuspid so far as to nearly allow the bicuspid to touch the BONWILL SYSTEM OF CORRECTORS FOR IRREGULARITIES. 467 lateral. The silk ligature was now placed over the lateral and carried up next the cuspid. The first bicuspid was ligated with a stay-plate or helmet of gutta percha on its lingual side with the ligature, running through both holes and carried around the first bicuspid and tied on buccal side. This prevented entirely the slip- ping of ligature upon the cervix. A rubber band was now stretched betAveen the lateral and bicuspid and secured. This expanded the arch in front and drew out the lateral in a very short time. Had to change once for a broken or slipping ligature. These little gutta percha caps or helmets work admirably, and are not worn or dis- placed in mastication. Fig. 283 is another modification of Fig. 279, or single bar, and is applied in Fig. 284, where the four superior incisors are to be moved fonvard from one-fourth to three-eighths of an inch and the whole Fig. 285. arch expanded to meet the more perfect and larger arch in the loAver. It is made of two flat bars of platinized gold sliding over each other for at least two (2) inches. A loop is soldered to the end of each flat bar as guides to hold them in place while sliding through. A rubber band is shown attached to the end of each bar at A A, which, in contracting, enlarges the circle, and consequently not only throws out the incisors, but the bicuspids and cuspids as Avell. The attachments are made on either side to a molar or bicuspid, OAving to the ease of clasping. I have utilized the decay on anterior surface of a molar by filling Avith amalgam, and cutting a hole into it for one end of the bar to rest instead of a clasp. The apparatus is shoAvn applied in Fig. 284 Avith the bars some distance away from the incisors to be attacked. Before the apparatus is placed permanently in position, the four incisors are ligated Avith a loop as shown in Fig. 291, using gum 468 DENTAL SURGERY. sandarach varnish to prevent slipping or turning on the tooth. The ligature should be so adjusted as to twist the tooth if needed, while drawing it forward. These are noAV tied to the sliding bars, bringing them closely in contact with all the teeth in the arch. The rubber band is now tied between the two points A A, and the appli- cation is complete. It is easy to see not only its simplicity but its great effectiveness. It can be used equally well for contracting an arch. Fig. 286. Fig. 287 shows the Avorst case of protrusion of the upper jaw I ever saw. It was not done by an acquired habit, nor did it have any precedence in heredity. The temporary teeth had proper arches. No cause could be assigned. They came as you see in Fig. 287. The lower incisors, when I first saAV the case, were three-eio-hths of an inch from the superior incisors on their palatal surface, andAvere imbedded into the gums on the hard palate. BONAVILL SYSTEM OF CORRECTORS FOR IRREGULARITIES. 469 Before attempting to draAv in the incisors I made a rubber plate (Fig. 288) to cover the hard palate thickened where the lower teeth Avould touch, and opened the jaws at the bicuspids at least one- eighth of an inch. This Avas not only to drive the inferior incisors Fig. 288. up further into their sockets, but to allow the bicuspids and molars to come down and antagonize before the plate Avas removed. Tavo years Avere consumed in this. To this plate I now attached a rubber band carried entirely around the arch with a silk liga- Fig. 289. ture, and at the central incisors I made a metal hook, carried o\Ter their cutting edge Avith tAvo holes, through which the ligature passed. This kept the ligature doAvn on the incisors near the cut- ting edges, and Avhile it was aiding in drawing in the arch, it did 470 DENTAL SURGERY. another important thing: forced the centrals up into the alveolus. This was done by the tendency of the rubber band to work up towards the gums, and at the same time it pressed them up and made them shorter without grinding. This was a parallel case with the one delineated by Dr. Kingsley in " Oral Deformities," but without any of the treatment given there. The sliding band in Fig. 283 would have done well here, but I adopted the simpler one of liga- ture and rubber. To secure it a gold band running over the arch from the second bicuspids, which were soldered to clasps around the latter which could be adjusted or removed by patient. The rubber plate was removed as soon as I commenced to draw the incisors into the arch to give room for them to fill a smaller arch. Fig. 290 shows the application of the band in the lower jaw Fig. 290. MB where the temporary molars are still in place. The permanent laterals are far inside the arch. The temporary cuspids also re- mained. The first molar has had all its sides squared to retain a clasp. A platinized gold bar similar to Fig. 279 with clasps is used with a hole at the end of bar C; and then opposite the right central incisor, with another over the centre of the right temporary cuspid at G, and the fourth hole at the end of bar near the first molars at B. The principal feature about this is, aside from the bar, the cutting so heroically the temporary molars for retaining the plate. This does no injury, and if it was likely to, they would soon have to be extracted for the bicuspids. The ligatures are applied as in all former cases of this bar, so as to press backward as well as drawing outAvard. In this case two separate pieces of rubber band are used. Fig. 291. The feature about this case Avhich makes it novel and unique is the utilization of the superior temporary cuspids for holding the ligature. To place a ligature on the temporary teeth BONWILL SYSTEM OF CORRECTORS FOR IRREGULARITIES 471 insures their removal or extraction Avithout this plan. It is to keep the ligature on the body of the tooth I take a small hard-rubber corundum disk and make a groove on both the labial and palatal sides of the cuspid, deep enough for the ligature to rest securely. If necessary, I should do it to the first or second temporary molars if a ligature could be gotten around the incisor to be turned into place. Fig. 291. The rubber band is draAvn through and between the centrals, which gives it more poAver over the incisors. The left superior lateral was soon placed in the arch. Fig. 292 shoAvs the cut surface in first temporary molar on the left and as applied on the right with the clasp around it attached to the bar. The ligature passes between lateral over central and through hole in bar at A, pressing central to the left and molar to right. I must repeat—the utilizing of the temporary molars in cutting them for clasping, or by grooving, for ligatures cannot be OA'er- estimated. It permits of fulcrums early in the case, which hereto- fore baffled our skill. The sooner we commence to correct irregu- larity the easier and more complete. 472 DENTAL SURGERY. The explanation of geometrical huv, and the value of the ana- tomical articulation in showing how the first permanent molar plays so important a part in making the lower incisors roll over each other, and make a smaller arch and with so deep an under- and overbite of three-eighths of an inch, as to destroy the pure law of one-eighth of an inch as the normal one. I am almost quite ready to say, never extract the first permanent molar. Keep down the inferior incisors. Have the permanent molar take its place soon and rapidly in the arch. Drive it backward toward the ramus rather than have it move forward to make the underbite too deep. To a mind of any comprehension these are simple devices and plain rules ; the application can be made to any case of irregularity. Any one can surely make the apparatus. Whoever hereafter will under- take this branch of practice, should first read my article on the geometrical Liav of articulation and study the principles invoked, and not attempt wildly to do what but few men have even truly fathomed. Really, in every city some one should make of this a special practice, and the profession should encourage such b}r send- ing cases for their inspection and consultation. And such specialist should do all he can in return to teach by example and demonstra- tion by clinic, to enlighten those who are so pl?ced from large cities they are compelled to take such cases. When we can have that understanding betAveen us, then we may feel as banded brothers more fully equipped for these hitherto difficult and almost thank- less operations. In conclusion, to sum up brief!}T, do not interfere where by simple extraction the case will correct itself; when teeth must be moved, do it decidedly, to avoid tedious delay ; but take care not to be so rapid as to excite inflammation; do not move teeth with deformed or defective roots; do not sacrifice sound and regular bicuspids to bring into the arch teeth Avhich will require to be moved through a great space, for this movement materially impairs their durability ; lastly, do not attempt to bring teeth to a position where you cannot keep them until firm ossific deposit makes them permanent in their new positions. Dr. Kingsley is of the opinion that a correct judgment can rarely be formed of the proper treatment necessary in any case of irregu- larity which necessitates a change in the expression of the mouth from plaster models alone, as an opinion formed by the most expe- rienced observer on a cursory examination, may be changed upon a more careful study of the features, the family type, and the model of the teeth. The same writer remarks : " It is not always advisable TREATMENT OF DENTAL CARIES. 473 to attempt to change the expression of a mouth where the condition is an inherited peculiarity, a part of the family type, and Avhere the change would involve a very prolonged effort, possible breaking up of a good articulation of masticating organs, and with the knoAvl- edge that nature Avill be constantly making an effort to return to the hereditary type." CHAPTER II. TREATMENT OF DENTAL CARIES. The treatment of dental caries is one of the most important opera- tions in dental surgery, because of the usefulness of the organs to be saved ; the universality of the disease; also, the complex and difficult nature of the treatment required. The caries may be slight and superficial; or it may be more or less deep-seated ; lastly, it may penetrate even to the pulp-cavity. The difficulties of treatment in- crease in the same order, and in this order they will be taken up. Caries, Avhen superficial, may be arrested by the same means used for deeper caries; but in a large number of cases it will require for its rerinwal only the use of files, enamel chisels, or disks. These instruments are also often used preparatory to the operations nec- essary for the arrest of deep seated caries ; hence their use demands our first consideration. Treatment of Superficial Caries.—There is no operation in dental surgery against Avhich a stronger or more universal prejudice prevails than that of filing the teeth; yet, when judiciously and skilfully performed, there is no one more beneficial or effectual in arresting the progress of caries. Although productive of much good, it is, in the hands of unskilful operators, a source of incal- culable injury. Dr. John Harris says:* "Filing the teeth is one of the most im- portant and valuable resources of the dental art; it is one that has stood the test of experience, and is of such acknowledged utility, as to constitute of itself, in the treatment of superficial caries on the lateral surfaces of the teeth, one of the most valuable operations that can be performed on these organs. And even after caries in the localities just mentioned has progressed so far as to render its removal by this means impracticable or improper, the use of the * These remarks are applicable to all instruments employed for the same purpose as the file, such as enamel chisels, corundum and diamond disks, etc., etc. 474 DENTAL SURGERY. file, in most cases, is still necessary in order to the successful em- ployment of other remedial agents. But in either case a failure to accomplish the object for which it is used would only be equivalent to doing nothing at all. "The use of the file, then, may very justly be considered a sine qua non for the removal of superficial caries from the sides of the teeth Avhich come in contact Avith each other, as can be attested by thousands of living witnesses; and in preparing the way, in deep- seated caries, for the thorough removal of the disease, and filling successfully the cavity thus formed. " The fact that the croAvns of the teeth are covered with enamel is alone sufficient evidence of its importance and utility in shielding and protecting the bony structure which it envelops from mechanical and morbid influences ; so that it would seem that its removal or loss would necessarily expose the organs to certain destruction. But we have satisfactory evidence that teeth, after having suffered the loss of large portions of the enamel, have been restored to health, and preserved for many years, and often through life. " The rapidity with which caries progresses after the exposure of the dentine by the loss of the enamel, depends upon the physical peculiarities of the teeth, and upon local and constitutional influ- ences ; hence the difficulty, and oftentimes impossibility, of obtain- ing the object for which dental operations are instituted Avhile such influences are suffered to exist. If special regard is not had to the curative indications, most if not all the operations upon the teeth which have for their object their ultimate preservation, are sure, to a greater or less extent, to augment all of the previously existing local affections, by increasing the irritability of the parts, and by rendering them more susceptible of being acted upon, both by local and constitutional causes. "There is no instrument so well adapted as the file for the removal of the disease when situated in these parts of the teeth, especially when the organs are in close proximity with each other ; or for the removal of rough and Aveakened edges of the enamel in deep-seated caries, and for making sufficient space or room for the removal of the diseased parts preparatory to plugging. " It may be laid down as a rule, from Avhich exceptions should never be taken, that the file should not be used Avhile the teeth or their contiguous parts are suffering general or local, acute or chronic, inflammation. Therefore, Avhen this is the case, the treatment of the general and local affections should precede the operation filing. Upon the removal of all the acute or chronic diseases of the mouth greatly depends the success of the dentist in the treatment TREATMENT OF DENTAL CARIES. 475 of affections of the teeth calling for the employment of the file. As much importance, therefore, is to be attached to an enlightened and discriminating judgment as to tact in the performance of the operation. " In fact, the removal of all local causes of irritation—such as dead roots of teeth, teeth occasioning alveolar abscesses, or such as exert a morbid influence upon the surrounding parts, and all depositions of salivary calculus or other foreign matter—should precede all other operations upon these organs. " The length of time necessary for the restoration of the parts con- tiguous to the teeth may vary from a few days or weeks to as many months, depending upon the nature and extent of the disease, the general health of the patient, and the constitutional as well as local treatment to Avhich they are subjected. " In assuming the position that filing the teeth does not, of neces- sity, cause them to decay, it is by no means to be inferred that the operation can, in all cases and under all circumstances, be per- formed with advantage or even impunity. Its effects, like .those of most other operations upon the teeth, when the curative indications are disregarded, or not properly carried out, are most injurious. The employment of the file at an improper time and in an im- proper manner increases the liability of teeth to decay; it augments the irritability of all the parts adjacent to them, and consequently their susceptibility of being acted upon by local and constitutional causes. "Notwithstanding the utility and value of the operation, filing the teeth may be regarded as a predisposing cause of caries. If this be true, it may be asked, Avhy file at all? I answer, in this country, OAving to the prevalence of the immediate or direct cause of caries, the operation is only performed as remedial, for the purpose of re- moving actual disease or as preparatory to plugging. It does not, of necessity, folloAV that caries of the teeth, after having been judi- ciously removed or treated, although the organs be predisposed to the disease, will ever again occur. The general system often escapes the development of those diseases to Avhich it is predisposed through life; so also do the teeth. If the operation be properly performed, and the filed surfaces kept thoroughly clean, a recurrence of the dis- ease, notAvithstandingthe increased predisposition thus induced, will never take place. The immediate cause of dental caries being the contact of corrosive agents with the teeth, the necessity for this pre- caution is obvious. The bony structure of these organs is more easilv acted upon by such causes than the enamel; for this reason, when it becomes necessary to expose it Avith a file, for the removal 476 DENTAL SURGERY. of disease, it should be done in such a way as to admit of its being kept thoroughly and constantly clean; so that, if it afterward be- comes carious, it will be owing altogether to inattention of the pa- tient. In vieAV of this, whenever it becomes necessary to file the teeth, Avhether for the complete removal of caries, or as only preparatory to plugging, we should always impress upon the patient the im- portance of cleansing the surfaces thus operated upon at least three or four times every day. The future preservation of the organs will depend upon the constant and regular observance of this precaution especially when they are of a soft or chalky texture, for they are then far more easily acted upon by decomposing agents than when hard. "The cases requiring the use of the file vary so much that it Avould be difficult to lay down precise directions with regard to the extent to Avhich the operation should be carried. This must be de- termined by the judgment of the operator. The design of the operation may be defeated either by filing too much or too little. Either extreme should be avoided; but it is my opinion that by far the greater number of unsuccessful results are attributable rather to the too moderate than to the too great use of this instrument espe- cially where the circumstances of the case have nothing to do in determining the result." In filing the front teeth and those on the right side of the mouth, the operator should stand to the right and a little behind the patient, in order to steady the head, as it rests against the back of the oper- ating chair, Avith his left arm ; while Avith the fingers of the left hand the lips are raised and the teeth properly exposed for the operation. In filing the teeth on the left side of the mouth, it may be necessary for the operator to stand upon the left side of his patient. The file, firmly grasped between the thumb and middle finger of the right hand, with the end of the forefinger resting upon its outer end should be moved backward and forward in a direct line, as any deviation from this would immediately snap the instrument. The first opening bet Ay ecu the teeth, when the approximal edges of the two are carious, should be made Avith a flat file, about one-fourth of a line in thickness, cut on both sides and both edges; this done a file cut on one side and both edges should be employed for the com- pletion of the operation. If only one tooth is decayed, the opera- tion may be commenced and completed with a safe-sided file. The file, during the operation, should be frequently dipped in tepid water, to prevent it becoming heated or clogged Avhile in use ■ espe- cially should the water be warm or tepid where the teeth are sensitive TREATMENT OF DENTAL CARIES. 477 Fig. 293. When the files become so much clogged that the water or a brush will not cleanse them, a brass or steel scratch-brush may be used, or they may be dipped in sulphuric or chlorhydric acid, and then washed Avith the greatest care, to remove every trace of acid. Fig. 293 represents vari- ous forms of the thin sep- arating file. To secure the success of the operation, it is some- times necessary to cut away a considerable portion of the tooth; but in doing this, the operator should be careful not to destroy the symmetry of the labial surface. The aperture, anteriorly, should only be wide enough to admit of a free oblique or diagonal motion of a safe-sided file of about one-fourth of a line in thickness, or a correspondingly thin corundum disk. In this way, one-fourth or more of a tooth may be removed Avithout materially altering its ex- ternal appearance. But a tooth should not be filed entirely to the Fig. 294. HMS1# 'ED gum ; a shoulder should be left, to prevent its approximation to the adjoining tooth. Sometimes the decay is of such size and so situ- ated, that it may be removed by means of enamel chisels, with less alteration in the external or labial surface of the tooth. These very valuable instruments will also be found useful for rapid cutting pre- paratory to the sloAver action of the file. A rounded form can be given by them to the inner angles of the teeth, for which purpose they may either follow or take the place of the file. Fig. 294 represents a set of enamel chisels, strait and curved, by which the operation of removing a portion of the crown of a tooth 478 DENTAL SURGERY. can be performed much more rapidly than by the file, and also with more comfort to the patient. Fig. 295 represents a set of Dr. Louis Jack's Double-end Enamel Chisels. Fig. 296 represents Dr. W. W. Evans's set of Enamel Chisels. When operating upon the front teeth with the enamel chisel, the instrument should be firmly grasped in the hand, near to its cutting edge, and the edge applied to the surface of the portion to be re- Fig. 295. moved, while at the same time the point of the thumb uses as a fulcrum the cutting edge of the tooth or the one adjoining. For operating upon the bicuspid and molar teeth, heavier enamel chisels are required than in the case of the front teeth, and with either straight or oblique cutting edges. The curved form of chisel is useful when the mouth is small, and it is difficult to reach the point desired with the straight form. When the decay occupies a large portion of the approximal sur- face, and has penetrated into the tooth to a considerable depth de- stroying the enamel anteriorly, and causing it to present a ragged and uneven edge, it will be necessary to form a wider exterior aper- ture than mere regard for appearance would dictate. When the approximal surfaces of the two front teeth are affected Avith caries about an equal portion should, if circumstances permit, and it is necessary to cut away tooth substance, be filed or cut from each TREATMENT OF DENTAL CARIES. 479 tooth. In the case of delicate front teeth, or teeth slightly loose in their cavities, it will be Avell before filing, to mould a small piece of gutta-percha, or modelling composition, around or against the inner surfaces of the tooth to be filed and several adjoining ones. It gives support to frail teeth, and greatly lessens the danger of irritation from the motion imparted by the file to the teeth which are not firmly set in their sockets. Some use for this purpose plaster; but Fig. 296. we think the gutta-percha, or modelling composition, as suggested by Prof, (iorgas, Avill be found altogether more conveniently applied and more agreeable to the patient. When the file is employed for separating the superior incisors and cuspids, the operation may be completed with a bevel-edged file, as no sharp angle should be left near the gum. In separating the bicuspids by filing, a space should be made somewhat in the form of the letter V; it should not, hoAvever, form an acute angle at the gum. This space should also be slightly Avider to Avar d the palatal and lingual surfaces. For its formation, a V- shaped file, Avhich is one bevelled on both sides, will be found most suitable. A space shaped in this manner will prevent the approxi- mation of the sides of the teeth, and if filling be necessary, it will enable the operator to do it in the most perfect manner. Fig. 297 represents knife-edge or bicuspid pointed and blunt files. Fig. 21)8 represents a file designed by Dr. E. Parmly BroAvn, for contouring the approximal surfaces of molars and bicuspids. It is three-sided, and cut on all sides. When the separation of the molar teeth in this manner becomes necessary, the same shaped space should be formed. But as these teeth are situated far back in the mouth, it cannot often be done Avith 480 DENTAL SURGERY. a straight file; to obviate this difficulty, an instrument, Avith Avhich every dentist is acquainted, denominated a file-carrier, is usually employed. Fig. 297. Kig. 298. Fig. 299 represents Dr. J. E. Line's file-carrier, which i its construction, as well as very serviceable. TREATMENT OF DENTAL CARIES. Fig. 300. 481 482 DENTAL SURGERY. Fig. 300 represents Dr. W. B. Miller's file-carrier, Avith three heads, as shown, Avhich admits of changing direction and slant very quickly. Fig. 301 represents a cheap and simple file-carrier, the device of Dr. D. M. Clapp, either straight or curved, Avhich will carry a thin separating file, and also finer ones for cutting metal. A file-carrier attachment for use with the dental engine, has also been devised, but is not so readily controlled as the hand instrument. A great variety of V-shaped separating files are now to be found in the dental depots, from English, French, and American manu- facturers. Fig. 302 Avill give a correct idea of some of these shapes. Fig. 304. Fig. 303. Disks composed of different substances, and attached to mandrels, for use with the dental engine, are employed for separating teeth that are affected with superficial caries on their proximate surfaces. Figs. 303 and 304 represent the diamond disk, composed of a thin plate of metal, such as nickel, in which diamond powder is thor- Fig. 305. oughly incorporated. The corundum disks, Fig. 305, introduced by the late Dr. Robert Arthur, of Baltimore, are noAV used, to the almost entire exclusion of files, in separating teeth, especially molars and bicuspids. Although often employed for separating the incisor teeth they are not so well adapted for such delicate operations, on account TREATMENT OF DENTAL CARIES. 483 of being less readily controlled than the chisel or file. The incisor teeth, being much smaller than the posterior teeth, should never be cut in the same proportion. When the disk is used for separating the anterior teeth, the greatest care should be exercised to avoid too much cutting, especially of the labial angles. These disks are similar in composition to the ordinary corundum avheels used for grinding porcelain teeth, being composed of emery poAvder and gum shellac, which, being softened by heat, is rolled into Fig. 306. a great variety of shapes to suit the different operations to be per- formed by them. The disks thus formed are mounted on mandrels (Fig. 307), for use with the dental engine, an instrument which will hereafter be described. Fig. 306 represents a feAv forms of Dr. A. L. Northrop's corundum points for cutting and polishing. Fig. 307 represents different forms of mandrels, with and without shoulders, for mounting corundum, diamond, rubber, celluloid, box- wood, emery-paper, sand-paper and cuttle-fish paper, disks and points. After a sufficient portion of the tooth has been cut away, the sur- face should be made as smooth as possible, with a very fine or half- Avorn file, or Avith Arkansas, Hindostan or Scotch stones, Avood polishing points, disks of soft or hard rubber, boxwood, felt, emery, sand, or cuttle-fish paper, carrying poAvders such as pumice, silex, emery, buck-horn, corundum flour, Hindostan, Arkansas, etc., etc., or with tape charged Avith such poAvders. 484 DENTAL SURGERY. Fig. 308 represents hard rubber disks, for carrying powders for polishing the natural teeth and finishing fillings. Fig. 309 represents boxwood disks. Fig. 310 represents corrugated soft rubber disks and points for carrying poAvders for polishing. Fig. 311 represents emery, sand, and cuttle-fish paper disks. Fig. 308. Fig. 309. Fig. 312 represents points of Arkansas, Hindostan and Scotch stones mounted on mandrels for polishing the natural teeth and fillings. Fig. 313 represents wood polishing points, which are screAved into a mandrel for use with the dental engine. These points are also Fig. 311. serviceable for removing discoloration from the teeth, such as results from depositions of calculus. Dr. George H. Cushing's Changeable Angle Disk Carrier, Fig. 314 is easily attached and removed from the dental engine hand-piece its angular range being indicated by the dotted lines. A fountain mouth protector (Fig. 315), while protecting the tongue and cheek from injury, serves also to keep the disk wet. A supply of water is stored in the rubber bulb of reservoir b, by compressing and immersing it in water, and is fed as required through the small TREATMENT OF DENTAL CARIES. 485 Fig. 316 represents Dr. F. Herrick's fountain drip-point, intended for keeping up a continuous dripping of water upon corundum points, engine burrs, and other rapidly revolving instruments. Fig. 314. When removing superficial caries, all edges and sharp corners should be rounded and made smooth, and when the operation is completed the patient should be directed to keep the excised surfaces of tooth-structure perfectly clean, for if the secretions of the mouth or extraneous matter be permitted to adhere to such surfaces, a re- currence of the disease will take place. Prior to removing superficial 60 4 486 DENTAL SURGERY. caries from the approximal surfaces, and especially of the front teeth, such teeth may be separated by pressure made Avith avoocI, cotton, tape or rubber, so that unnecessary cutting of enamel may be avoided, and but little more of the tooth-structure be removed than the de- calcified part. When a portion of the approximal surface of a tooth is cut aAvay, the excised surface should be left free and exposed to the friction of the tongue and lips, which will prevent food and other extraneous matters, as well as the secretions of the mouth, from lodging and remaining in contact with it. The portion cut away should be as much as is possible from the posterior part of the approximal surface, especially in the case of the front teeth, so Fig. 315. Fig. 316. as to prevent any noticeable disfigurement. When superficial caries is located on the approximal surfaces of the bicuspids and molars, and near to the grinding surfaces, it may be removed by cutting out a V-shaped space between such teeth. When enamel chisels are employed for removing superficial caries, the instrument should be grasped near its cutting edge, which should be applied in the line of the enamel fibres, using the adjoining tooth as a fulcrum for the thumb, in order to prevent the instrument from slipping and wounding the soft part adjacent. Having in such a manner removed the overhanging enamel, the softened or decalcified dentine should be cut away with a scoop-shaped excavator, the use of which will also determine the depth to which the caries has penetrated and if not too extensive, the enamel chisel can again be employed until the surface is made level or uniform. All edges and sharp corners should be rounded and made smooth, and it may be necessary in order to complete the cutting process, to use a curved fine-cut file Corundum disks operated with the dental engine may be found mor' TREATMENT OF DENTAL CARIES. 487 convenient for the removal of superficial caries, and especially in the case of the bicuspids and molars, to be followed by strips of emery eloth, or paper of the fine grades ; also disks of fine sand- paper. 'When a perfectly smooth and normal surface is obtained, it should be highly polished with pulverized pumice, or silex applied on linen tape, or on disks of flexible rubber, boxAVOod, or celluloid, completing the operation Avith polishing putty (peroxide of tin). The corundum and Arkansas or Hindostan stone points, followed by the use of Avood points for the application of the polishing putty, Avill be found useful for removing superficial caries from exposed surfaces. When the operation of removing superficial caries is com- pleted, the patient should be directed to keep the excised surface of tooth-structure perfectly clean. Caries upon the approximal surfaces of the teeth may be prevented by occasionally polishing such sur- faces, and passing floss silk between the teeth in connection Avith the use of the tooth-brush. Since the introduction of the dental engine, the removal of super- ficial caries, and the preparation of the excised surface can be A'ery effectiA'ely performed; and it should be remembered that such a sur- face should be left self-cleansing, so that deleterious substances may not lodge and remain in contact Avith it. For separating the teeth to obtain space for the free use of the instruments employed in preparing and filling cavities on the ap- proximal surfaces, the reader is referred to the " Treatment of Deep- seated Caries." Skparation of the Teeth.—Before a cavity can be prepared in the approximal surface of a tooth, it is usually necessary to separate it from the adjoining one. This may be done either Avith a file, enamel chisel, corundum disk, or by the pressure of some interposed elastic substance, or by Avedges of Avood driven between the teeth, or by metallic Avedges or separators. Each of these methods has its advantages. When caries has extended over nearly the Avhole ap- proximal surface, so that, after the remo\Tal of the diseased part, the orifice of the cavity Avill be surrounded by a thin, brittle, and irreg- ular Avail, the former is the preferable method ; especially in indi- viduals haAdng a decided scorbutic tendency, or Avho have suffered from the use of mercurial medicines or syphilitic disease, and in aged persons. But Avhen the caries has spread over only a small portion of the surface of the tooth, and is surrounded by sound, healthy enamel, the latter method should be adopted; especially in individuals in Avhom there is no manifest tendency to inflammation or sponginess of the gums, and in young subjects. The manner of separating teeth with cutting instruments has been alread}r described; 488 DENTAL SURGERY. it Avill only be necessary, therefore, in this place, to offer a few remarks on separating by pressure, which Avas first adopted by Dr. Eleazer Parmly. The following are its advantages, where it can be resorted to Avith safety : after the removal of the pressure, the teeth almost immedi- ately come together, leaving no space to injure their beauty; Avhat is of still greater importance, the dentine around the external surface of the filling is not exposed to the action of the secretions of the mouth, or other agents capable of exerting upon it a deleterious ac- tion. On the other hand, some are of opinion that when the teeth come together again a lodgment is afforded to corrosive agents, upon the presence of Avhich the disease was,in the first instance, produced, and which would soon cause a recurrence of it. In replying to this objection, it is only necessary to observe that the parts of teeth first attacked by caries Avere the points in contact Avith each other, Avhere the enamel may be supposed to haAre sustained some injury by pressure, thus rendering them more vulnerable at these points to the action of the causes that produced the disease. By properly re- placing the diseased parts with gold, the external surfaces of the fillings will be the only parts that come in contact Avith each other; and if of gold will not be liable to injury from the above-mentioned mechanical causes. The enamel around the fillings, if proper at- tention to cleanliness be observed, is not so liable to be acted on by chemical agents as the dentine Avhich the cutting instrument Avould expose. But teeth cannot always Avith impunity be separated by pressure; it can only be done Avith safety in certain cases. As a general rule, the Avriter is of the opinion that it ought not to be attempted after the thirtieth or fortieth year of age, though it may sometimes be done Avith safety at even a later period. The diseased action excited for the time in the sockets of the teeth does not so readily subside at a later age; and it has in some instances been knoAvn to result in the loosening and ultimate loss of the organs. In one case Avhich came under the observation of the author, the inflammation ex- tended to the pulp, causing its disorganization, and the consequent death of the tooth. The pressure ought never to be too actively exerted; it should be gradual and constant. From three to five days are usually required for the separation of tAvo teeth sufficiently for the removal of the decayed part and the introduction of.a filling. After they have been separated in this Avay, they should be kept apart, without any in- crease of pressure, until the soreness in the cavities shall have sub- sided, before any further steps are taken in the operation. Cotton TREATMENT OF DENTAL CARIES. 489 saturated Avith sandarach ATarnish, or white gutta-percha, or zinc fill- ing materials, may be used to retain teeth after being separated Avith other substances, or by the rapid method. Only two teeth should be separated in the front part of the mouth, in the same jaw, at the same time. As soon as the cotton or tape, or other substance used to sepa- rate teeth, has afforded the desired space, it should be removed, and the space retained for one or two days by cotton saturated with sanda- rach \rarnish,or white gutta-percha, or one of the zinc filling materials pressed betAveen them, Avhen the teeth may be Avell enough to per- mit of being operated on. The pressure is usually made by introducing between the crowns of two teeth a thin wedge of soft wood, a piece of India-rubber, tape, a little raw cotton or ligatures, replacing the first-named sub- stances every day or two with thicker pieces. While some prefer India-rubber to any other substance employed for the purpose, the object may be readily attained Avith other substances. Cotton or tape pressed firmly between the teeth and renewed daily, also gutta- percha, will in the course of a few days separate teeth, and with less soreness than India-rubber, to the use of which many object, on account of the irritation it causes. Many operators prefer gradual pressure in separating teeth, but others, on account of economy of time, consider it better for the separation to be made at once, and not prolonged through several days. It is also urged that the pa- tient suffers less, and that there is also less danger to the teeth, in rapid separation than Avhere this process is gradual. The degree of pressure, and the method by Avhich the separation is to be accom- plished, should, hoAvever, be determined by the susceptibility of the parts to inflammation. The operation of rapidly separating the teeth consists in the use of two Avedges of fine-grained Avood, either orange or boxAvood. The first Avedge is forced betAveen the necks of the teeth, care being taken not to lacerate the gum, while the second Avedge, Avhich tapers more than the first, is inserted betAveen the points of the teeth, the wedges being driven alternately by mallet force, until sufficient space is obtained, Avhen the second wedge is remoA'ed. Very great care should be exercised in driving the second wedge between the points of the teeth, on account of the force exerted by it. This description applies to the front teeth, as it is not advisable to attempt the separation of the molar teeth in this manner. Fig. 317 represents a set of the Jarvis Separators, by means of Avhich adjacent teeth can be forced apart without delay, or appreci- able pain to the patient. This separator consists of a piece of steel, nickel-plated, bent upon itself, having the tAvo ends formed to fit the 490 DENTAL SURGERY. outer portions of the approximal surfaces of tAvo adjoining croAvns. These jaws are forced apart by the action of the screw which passes through one and against the other. The compound forms consist of tAvo wedges approaching or passing each other, and are applicable to the incisor teeth, the first forms being applicable to the bicuspid and molar teeth. Fig. 317. TREATMENT OF DENTAL CARIES. 491 they are to be turned to spread the separator. Figs. 321, 322, and 323 represent Dr. W. A. WoodAvard's separators, the blades of which Fig. 318. Fig. 319. act independently, which is an advantage Avhen the teeth are irregular. Fig. 324 represents Chase's Dental Wedge Forceps, by which Avooden wedges can be forced between adjacent teeth for the purpose of separating them, and by the use of this appliance it is claimed that there is less danger of irritation and subsequent inflammation than by the method of driving a Avedge with the hand-mallet. Fig. 321. Fig. 322. Fig. 323. Dr. Corydon Palmer recommends the folloAving method of rapid wedging : A Avedge made from a thin piece of wood or quill is first introduced between the teeth, to protect the gum. Next to the first Avedge, a square, tapering one of orange or boxwood is introduced at the gum, in such a manner as not to interfere with the view of the Avail of the cavity, and Avhich is permitted to remain during the operation of filling, being driven to hold the space gained by a broad Avedge, introduced by hand-pressure or mallet force between the cutting edges of the teeth, its point being directed toward the gum. The separation is gradually accomplished, in order to allow the tis- sues to accommodate themsehres to the pressure to which they are subjected. It is recommended that the rapid process for separating teeth be restricted to cases Avhere but little space is required, and 492 DENTAL SURGERY. Fig. 324. TREATMENT OF DENTAL CARIES. 493 Avhere the structures are soft and spongy. Fig. 325 represents a Avedge-cutter, for removing the projecting portions of the wooden Avedges. A f'ter separating teeth by rapid wedging, the Avooden wedges should not be permitted to remain between the teeth, Avhen more than one sitting is necessary to complete the operation of filling, but removed, and the space maintained by cotton saturated with sandarach var- nish or by gutta-percha, until the next sitting. There is a difference of opinion among many prominent and skil- ful operators, in regard to the permanent separation of the teeth ; the advocates of contour fillings objecting to the removal of so much tooth-substance Avithout substituting for it a non-destructible sub- Fig. 325. stance, such as gold, Avhile the advocates of the permanent separation method contend that self-cleansing surfaces, properly prepared, are preferable to the labor, pain, time, expense and general strain for both patient and operator in perfecting contour work. Dr. T. F. Chupein, an advocate of the permanent separation of the teeth, describes his method as follows: "The mode of treating the upper incisors and cuspids is indicated by the following diagram, Fig. 326. " It will be noticed that there are semilunar spaces cut from the palatal surfaces of each tooth. These spaces are cut for the removal of incipient decay, for its anticipation as Avell as to obtain room to fill when decay is deep-seated. To make these spaces Avithout muti- lating the outer faces of the teeth, we proceed as follows: Tavo teeth are Avell wedged apart by the introduction of wooden Avedges, floss cotton or rubber, Avhichever seems best to the operator. When separated about the thirty-second of an inch or more, a thin disk is 494 DENTAL SURGERY. used on the dental engine. The Arthur disk, D, is about the proper size, and this is used on the palato-mesial and distal aspects of the teeth being operated on, and the cutting so shaped that the outer Fig. 326. faces of the teeth are not encroached upon. After the enamel from these surfaces is removed, a curved file, like the following, may be Fig. 327. used to curve out the surface begun by the disk, or, Avhat is still better, a small corundum point, mounted on the right-angle attach- ment of the dental engine, and applied be- p-rfi Q98 tween the tAvo teeth to be operated on; the n i------- head of the patient being well thrown back, ---_______ so that these surfaces may be readily reached. Should either of the teeth thus separated need filling, the filling should be done at once, as more room is had iioav, than if the teeth are permitted to fall back into their old places. When two are thus separated (and filled, if they need filling), two more are Avedged apart, and the spaces cut, as has been described." Concerning the treatment of the bicuspids and molars, Dr. Chu- pein says: These teeth are so concealed by the lips, that even Avhen pretty wide separations are made betAveen them they present no revelation of their having been operated upon at all. To separate the molars and bicuspids, we do not Avedge them apart, as we recommend the incisors and cuspids to be done (although it Avould be no detriment to do so), but Ave leave the teeth in the relation, one to the other that we find them, and separate them, so as to leave a small point of contact near the gum margin. This point of contact, though TREATMENT OF DENTAL CARIES. 495 minute, is sufficient to keep the surfaces that have been deprived of the enamel by the disk or file from again approaching each other, and also serves to protect the gum from being irritated by the im- paction of food. Fig. 329 will illustrate this idea. It will be seen that the filed surfaces are entirely kept apart, and that though the tooth may change its position or turn in its socket (Avhich is not likely), the cut surfaces Avould be still kept from close proximity. It also permits a free space, Avhich is readily kept clean by simply rinsing the mouth. We fear that it is the careless man- ner in Avhich this operation has been performed that has brought it into disrepute, and which, from this carelessness, has made many Avho tried the system abandon it as being ineffectual, Avhen the fault lay more in the manner of its performance than in the integrity of the operation. Particular stress must be laid on the non-removal of this point of contact, otherwise the operation becomes ineffective. Indeed, if it is removed, Ave consider that the operation Avould be Avorse than if nothing at all had been done. To make it entirely effective, it should be done in anticipation of decay, or when decay is Fig. 329. in its first stages—Avhen it has not or scarcely has pierced the enamel. If attempted later, the very point of contact we wish to preserve Avill be encroached on by decay, or completely destroyed by it. If in anticipation of decay, the cutting need be done only from one tooth, and that from the mesial surface of the furthest back tooth. Fig. 330 Avill illustrate this. We Avould recommend that after the teeth are separated a waxed thread be passed through the separations down to the gum, and that this should pass the point of contact easily, and with a snap, to in- dicate that the teeth are just held apart, but yet touch sufficiently that their relation, one to the other, should not have been changed. The thread or silk thus used should not be frayed. This would in- dicate roughened edges of enamel or too close contact. If the former, it should be polished or cut smooth ; if the latter, the point of con- tact should be lessened so that the string Avill pass through readily and Avith a snap. We recommend, too, that the rubber dam be ap- plied on these teeth after these separations are made. It will often Fig. 330. 496 DENTAL SURGERY. appear that all decay has been removed. This deception is caused by the gloss left on the cut surfaces by the saliva, but when the dam Fig. 331. ^ **9 FlG" 333- Fig. 332. Fig. 334. Fig. 335. I CO: Fig. 336. ro is applied, and the surfaces dried and critically examined, we can know for certain if all the disorganized tissue has been removed or not. TREATMENT OF DENTAL CARIES. 497 We proceed to make these separations by arming the dental en- gine with a disk like that represented at Fig. 326 d. We cut the teeth through from their buccal to their palatal aspect, if in the upper, and from their buccal to their lingual aspect if in the loAver jaAv. We stop from time to time as Ave proceed, to see if Ave have not gone too far. When nearly doAvn to the point of contact, near the gum, Ave stop Avith the engine and finish with a file having a round edge, like Fig. 331; or, in case of molar teeth, with a file like Fig. 332. When finished, the buccal aspects of the teeth have the appearance represented by Fig. 333, while the teeth vieAved from their masticating surfaces are represented by Fig. 334. Should it be found neceesary to fill the teeth thus separated, an easy approach to the cavity is had, and the fillings as well as the filed surfaces can be left highly polished. The class of teeth shown at Fig. 335 are such as we recommend to be treated as we have described, for they present broad surfaces of contact on their buccal, masticating and palatal aspects, and are thus rendered more prone to decay from the ready lodgment of particles of food betAveen them. The other class of teeth, represented by Fig. 336, rarely decay, be- cause, as Avill be seen, they touch only by minute points of contact, and are thus not liable to decay. We do not recommend teeth of this form to be separated. If they decay they should be Avedged apart and filled, and alloAved to fall back in their old position. De- cay in teeth of this class will generally be found above the point of contact toward the gum. Should permanent separation be at- tempted with teeth of this class it might prove ruinous, or if effec- tive, the teeth must, from their shape, be considerably mutilated and cut aAvay, to prevent the cut surfaces from again falling in close apposition. Judgment, therefore, must be used in the separation of the teeth, although, as we have said, the operation is comparatively simple. But Avhether the teeth be separated Avith cutting instruments or by pressure, the space should be sufficiently wide to enable the dentist to operate with ease, otherwise, it will be impossible to re- move the caries and fill the teeth in a proper manner. TREATMENT OF DEEP-SEATED CARIES. Filling teeth is one of the most difficult operations the dentist is called upon to perform ; it often baffles the skill of operators who have been in practice many years. It is advisable only under cer- tain circumstances, and when the operation is performed without due regard to these, it may be productive of injury rather than 32 498 DENTAL SURGERY. benefit. It is the only certain remedy that can be applied for ar- resting the progress of deep-seated caries ; but to be effective, it must be executed in the most thorough and perfect manner. The pre- servation of a tooth may be regarded as comparatively certain when well filled, and with a suitable material, if it be afterward kept con- stantly clean. At any rate, it is not likely ever again to be attacked by caries in the same place. On this highly important operation, Dr. E. Parmly thus remarks: " If preservation is as good as a cure, this is as good as both; for the operation of filling, when thoroughly performed, is both pre- servation and cure. And yet it must never be forgotten, that this assertion is true only in those instances in which the operation is well and properly done; and perhaps it is imperfectly and im- properly performed more frequently than any other operation on the teeth. "There are reasons for this fact, into which eATery ambitious and honorable practitioner will carefully inquire. Although the books are explicit on this point, I deem it sufficiently important to deserve a few additional remarks. The following considerations are essen- tial, and, therefore, indispensable to success in this department of practice. Firstly. The instruments used must be of the proper con- struction and variety. Secondly. The material employed must be properly prepared as well as properly introduced. Thirdly. The ca\dty AAdiich receives the filling must be so shaped as to retain it in such a manner as to exclude not only solids, but all fluids, and even the atmosphere itself. Fourthly. The surface of the filling must be left in such condition as to place it beyond the reach of injury from food and other mechanical agents with which it necessarily comes in contact. Fifthly. The tooth thus filled should be free from pain and every known cause of internal inflammation." It is important that the operation be performed before the disease has reached the pulp-caAity ; after this,the permanent preservation of the tooth may be regarded as more or less questionable. Still, under favorable circumstances, the author believes it may, in the majority of cases, be performed with success. But, as the propriety and manner of filling a tooth after the pulp has become exposed will hereafter come up for special consideration, as well also as the operation of filling the pulp-cavity after the destruction of the pulp, it will not be necessary to enlarge upon these subjects at this time. Materials Employed for Filling Teeth.—Among the articles which have been employed for filling teeth, are gold, platina silver tin, lead ; fusible alloys of tin, lead, bismuth, and cadmium ; amal- TREATMENT OF DENTAL CARIES. 499 gams, gutta-percha, oxychloride of zinc, oxyphosphate of zinc, and various preparations of the gum resins. Of these no single one can be said to unite all the requirements of a perfect material for filling, Avhich may be enumerated: 1. Resistance to the mechanical action of mastication. 2. Resistance to the chemical action of the mouth. 3. Facility of introduction and consolidation. 4. Harmony of color. 5. Absence of all galvanic, chemical, or vital action upon the teeth or the general system. 6. Absence of all heat-conducting property. 7. Absence of shrinkage. Gold Foil.—To the use of this material, when properly prepared, there is the least possible objection; perfectly answering the first, second, fifth, and seventh requirements; to a great extent the third, if in skilful hands ; but deficient in the fourth and sixth. No better material is Avanted for the operation. A tooth may be so filled with it as to secure, in almost every case, its permanent preservation. It should, hoAvever, be perfectly pure, be beaten into thin leaves, and Avell annealed by the manufacturer, before it is used. When pre- pared in this manner, it may be pressed into all the inequalities of the cavity, and rendered so firm and solid as to be impermeable to the fluids of the mouth. Although there may be no difference in the purity of the gold and the thickness of the leaves, yet a marked difference will be found to exist in the malleability and toughness of the foil of different beaters. The art of preparing gold for filling teeth is an exceedingly nice and difficult one, and is believed to have attained greater perfection in the United States than in any other country; at least, this fact is so generally admitted, that many of the most eminent European practitioners procure nearly all they use from America. (See process of manufacture in Harris' Med. and Dent. Dictionary.) The principal preparations of gold used for filling teeth are the non-cohesive, the cohesive, and the sponge or crystal gold. Non-cohesive or Soft Gold Foil.—This is a preparation of leaf gold Avhich does not possess the property of cohesion to such a degree that the leaves can be firmly united on being pressed together with moderate force, and is introduced on the Avedging principle, the cavity for its reception being made of such a form or shape as will retain the mass after it has been properly introduced and con- solidated. Non-cohesive gold foil is employed in different forms, such as the rope, the tape or ribbon, the cylinder, the pellet, and the mat or block. The thickness of the leaves is determined by the number of grains 500 DENTAL SURGERY. each contains, and is designated by numbers on the books betAveen the leaves of Avhich they are placed after having been properly an- nealed. These numbers range from 3 to 240. A book containing a quarter of an ounce of No. 4 will have thirty leaves in it. Some dentists use foil varying in numbers from 4 up to 20, and even, of late, to 120, while others confine themselves to a single number. If but one number of the non-cohesive be used, 5 will perhaps be found better than any other. The author has used Nos. 4, 5, 6, 8, 10 and 15, but he prefers 4 and 5, and is decidedly of opinion that, in a large majority of cases, a better filling can be made with the first tAvo numbers than any of the others. There may be cases in which higher numbers can be more advantageously employed; as, for in- stance, in cavities which are very large, and where the operation of filling has extended beyond the walls of the cavity, owing to the difficulty of securing a perfect adaptation. Cohesive Gold Foil.—This is a preparation of leaf gold Avhich possesses the property of cohesion to such a degree that the leaves readily and firmly unite on being pressed together with moderate force. Although one or tAvo others claim priority in the discovery of the advantages now derived from the use of cohesive gold foil, yet the credit is certainly due to Dr. Robert Arthur, as he was not only the first to demonstrate the applicability of this form of gold in filling teeth, but in a series of Avell Avritten articles* he overcame the objec- tions which Avere at first urged against it, and proved that its great cohesive property rendered it a valuable adjunct in the preservation of the teeth. This form of foil is so cohesive that any number of pieces may be welded one to another; thus a part, or even the whole of the croAvn of a tooth may be built up with it. The same prop- erty may to a limited extent, also be imparted to foil manufactured in the ordinary Avay, by re-annealing. This property is peculiarly valuable in many cases where it becomes necessary to build up a large portion of the crown of a tooth; but when it is used, instru- ments having serrated points are required, like those employed in the use of crystal or sponge gold. Crystal or Sponge Gold has been employed by dentists for filling teeth for a number of years. The author has used it in a number of cases with very satisfactory results. Since the publication of the fifth edition of this work, the properties of crystal or sponge a0ld have been more thoroughly and extensively tested, and the result * A Treatise on the Use of Adhesive Gold Foil 1857. TREATMENT OF DENTAL CARIES. 501 has fully confirmed the favorable opinion entertained by us Avith regard to its value. The author is acquainted with several of the most skilful operators in the United States who have used it almost exclusively in their practice for several years ; and has seen fillings made by some of these gentlemen, which, for beauty and solidity, he does not think could be surpassed. This form of gold has a spongy texture, being composed of crystals, and widely differs from foil or leaf gold. The crystals possess the property, Avhen pressed firmly against each other, of welding and becoming as solid and almost as incapable of disintegration or crumbling as a piece of bullion or coin. This property enables a skilful manipulator to supply almost any loss Avhich a tooth may have sustained, even to the building up of an entire croAvn. Still, it will neArer supersede the use of cohesive and non-cohesive gold foils, as there are many cases in Avhich leaf gold can be used more advantageously and Avith more facility. Nor Avill the employment of it, in the opinion of the author, ever become universal; for the reason that more care and skill are required to make a good filling Avith it than with leaf gold, especially when the cavity in the tooth is difficult of access. Filling Avith crystal gold is more tedious than the same operation Avith ordinary foil. Experiments have been made with silver, platinum, and aluminium; but Avith unsatisfactory results. They are less malleable than gold, and therefore cannot be made so thin ; at the same time they have not the softness of tin; hence they Avork harshly under the plugger. An additional objection to silver is its liability to undergo chemical change, being in this respect greatly inferior to pure tin. Platinum, Avhile it possesses indestructihility, in this respect being even superior to gold, is deficient in other properties as a filling material, as it can- not be Avelded Avith facility, is difficult to manipulate in the form of foil, on account of its stiffness and harshness, and hence cannot be adapted and condensed in such form to the surface of a cavity. A form of platinum known as platinum sponge has been employed with greater facility than platinum in leaf form, but it requires skilful manipulation, and its cohesive property is readily destroyed by the slightest degree of moisture. Platinum has also been used in the form of foil coated with a considerable thickness of pure gold, and it is claimed that by such a combination a denser filling can be made, and also one conforming to the color of the tooth in Avhich it is placed. The peculiarity of aluminium, in this relation, is the im- possibility of Avelding its leaves by pressure; even under the gold- beater's hammer it forms loose scales, which no annealing can make adherent. 502 DENTAL SURGERY. Tin Foil.—This, when chemically pure and properly prepared, is less objectionable for filling teeth than most of the articles hereafter enumerated. Under favorable circumstances, if skilfully introduced, it Avill prevent the recurrence of caries. The greatest objection, per- haps, to the use of tin foil^s a filling material, is its softness and consequent inability to Avithstand the friction of mastication for many years. When used in cavities not so exposed it answers a good purpose as a filling material, as it is unalterable by reagents. Being an inferior conductor of heat it is tolerated in sensitive teeth in cases where a better conductor, such as gold, would not be. It is also regarded as valuable in soft teeth, and some regard it as pos- sessing advantages over gold for filling in such teeth, and also in the temporary teeth, being easy of introduction, and in accord with the tooth-structure. On account of the qualities referred to, tin foil is sometimes employed for lining cavities to be filled with gold. It is prepared as a filling material in the form of foil, the leaves varying in thickness from No. 4 to No. 20. The numbers from 4 to 10 are mostly used, and it is manipulated in the same manner as non-cohe- sive gold foil. Lead is far more objectionable than tin, as it is more easily decom- posed by the secretions of the mouth; its introduction into the stomach might be productive of serious injury to the general health of the patient. But, happily, this article is now seldom if ever used. Amalgam, formerly known by the name of mineral cement, or lithodeon, is usually composed of about equal parts, by weight, of pure tin, silver, and varying proportions of zinc and platinum—and sometimes gold and copper—the zinc, about one to three per cent., constituting a most important element in controlling shrinkage and preventing oxidation. The gold is not especially valuable, and when used in an amalgam, from one to four per cent, is sufficient. These metals are melted in a crucible and poured into ingots, which are then cut up with a file into filings. These filings are mixed, after the cavity in the tooth is prepared for the filling, with about thirty- three and one-third per cent, of distilled mercury, and incorporated to the consistency of a thick paste. The mass is then thoroughly washed with alcohol, to Avhich is added a few drops of a strong solu- tion of chloride of zinc. The excess of mercury is then removed by twisting the mass in a piece of chamois skin or strong muslin. It is also recommended to press the mass quite thin, after it is re- moved from the chamois skin, with a strong pair of flat pliers in order to remove still more of the mercury. Caution should, hoAvever be used, to avoid pressing out too much mercury. The mass Avlien TREATMENT OF DENTAL CARIES. 503 introduced, should be about the consistency of ordinary putty. The cavity should be prepared with as much care as for a gold fill- ing, and moisture prevented from coming in contact with it. When the cavity approaches near to the pulp, some non-conducting sub- stance, as Hill's Stopping, should be applied between the amalgam and the bottom of the cavity. After the filling has become suffi- ciently hard, its surface should be carefully finished by filing and burnishing. Dr. BonAvill gives the following directions for working amalgam composed of silver, tin, and gold ; from 5 to 7 per cent, of the latter he considers sufficient, condemning the use of zinc: " As soon as the first piece of alloy is inserted a wad of bibulous paper (Japanese) as large as the cavity is placed thereon, and an oval-pointed steel instrument is pressed upon it Avith great force to croAvd out the superabundant mercury. Go on adding alloy and more paper until the cavities are crowded full from cuspid to molar, leaving no intervening space. Direct pressure is not as efficacious as rubbing the amalgam in Avith a burnisher over the paper, which drives the mercury out at all points. No rough-faced instrument should be used; smooth burnishers and oval-faced only, on the same principle as in rubbing in gold by the action of the mechani- cal mallet. When you have reached nearly the proper fulness, use the flatter burnishers entirely, to not only add the alloy, but to be sure that the mercury is carried to the edges. To do this, you must not lose a moment; and the alloy should not have too much gold in it, or you cannot undertake so much at one sitting." Describing the operation of filling with amalgam the superior cuspid decayed on its distal surface, Avith the first and second bicus- pids on the anterior distal, and grinding surfaces gone so far as to leave nothing standing but the buccal and palatal walls; and to this add the first molar Avith its anterior wall, croAvn and distal sur- faces as seriously involved, the same Avriter continues: " By the time you have gotten all the cavities full, you must com- mence at once to divide between each and contour. " It will be found that when the opposite teeth are made to an- tagonize Avith it, great care must be used to keep from dislodging any portion of this large mass; therefore, before the division on the approximal surfaces is made, see that the articulation is absolutely correct, Then Avith a broach with small point turned, scratch aAvay all the cervix until the tool reaches from both buccal and palatal surfaces, and the divisions are clear to nearly the grinding surface. Now, Avith a very thin knife or saw you can carefully divide the fillings to make each tooth distinct. In this proceeding great care 504 DENTAL SURGERY. must be exerted or the contour will be broken. When this has been done, shape with proper instruments, leaving all the grinding surface in contact as broadly as possible, so that when the teeth go back again to their positions from Avhich the gutta-percha had moved them, the food cannot wedge doAvn between them. Where cavities are obscure on approximal surfaces, get the alloy as nearly in place as you can, and a Avad of paper will be sure to force it down. Besides those cases with more or less Avails for support, in those where much of the cusps of either wall is gone the alloy can be added and compressed easily and surely. Entire or partial crowns can be secured in a feAv minutes. Be sure that the alloy is not allowed to remain projecting over the free margin of the contour Fig. 337. before the patient leaves. Then but little dressing of the contour is necessary when the operations are filed and finished." Fig. 337 represents a set of what are knoAvn as Arrington's amal- gam instruments. Amalgam becomes hard by the crystallization of the mass and the evaporation of the mercury; hence, without a Avell-prepared form is used, and great care exercised in its amalgamation and introduction, a filling of this material may either contract or become porous; and when the latter is the case, the oxidation extends to the tooth-struct- ure, which becomes, as a consequence, discolored. Amalgams, unlike the plastic gutta-percha and zinc preparations, do not adhere to the walls of the tooth-cavity; hence, in their use it is necessary that attention should be paid to the form of cavity into which they are to be introduced; and as they are often employed for filling cavities of a shallow form, and with frail walls, under-cuts TREATMENT OF DENTAL CARIES. 505 and dovetails are required for the retention of such fillings. From the tendency of the amalgams of mercury to assume a spheroidal shape and separate from the margins of a cavity, sharp angles and pits are objectionable. The addition of palladium to an amalgam may prevent such shrinkage, but adds to the discoloration, and the rapidity of its setting is such as to evolve a sufficient amount of gas to cause an explosion with emission of light. Such an accident may be avoided by gradually adding the palladium poAvder to the compound, and using very small pieces for introduction, and their rapid insertion, each piece being Avell compounded as it is added to the mass. It is claimed that Avhile the surface of a palladium amal- gam changes to a black color, it does not stain the tooth-structure, and that it is the most durable of the amalgams. An excess of sil- ver Avill also cause an amalgam to blacken and stain the tooth- structure. Silver and copper control the change in form, as the solid particles of copper which remain, have an amalgamated sur- face only, Avhich prevents the change in form common to a homo- geneous mass. Platinum imparts toughness and edge-strength to an amalgam. Cold makes an amalgam composed of tin, silver and mercury, unclean; although an amalgam of pure gold and mercury alone is white and clean, but is not adapted for a filling material. A better class of amalgams has been recently introduced, Avhich appears to change bulk to a less degree, and to preserve their light, silvery color much better than the older forms; hence, the former objections to this filling material appear to fuove, in a great measure, been overcome. The ease Avith which amalgam fillings can be in- troduced, no doubt often leads to carelessness in the manipulation of this material, but it should be remembered that to obtain the best results from it, the caAdty in Avhich it is placed should be as carefully prepared as for a gold filling; and also that perfect dryness is essential to its adaptation and durability. There exist some differences of opinion concerning the necessity for washing amalgam, prior to its introduction, with alcohol and other fluids, some contending that by so doing it is impossible to remove all of the moisture in time for its insertion. Sufficient mercury sliould be alloAved to remain in the mass as will permit of its being manipulated Avithout crumbling, and when it is inserted over a sensitiATe surface, or in proximity to the pulp of a tooth, some intervening substance, such as Hill's Stopping, or oxyphos- phate of zinc, should be placed between the sensitive surface and the filling. It is claimed that continuous pressure Avith the burnisher upon the surface of an amalgam filling during its setting, will prevent its 506 DENTAL SURGERY. tendency to separate from the walls of the cavity, and insure better results from its use. It is also very necessary that the margins of amalgam fillings should be well defined, as, owing to its brittle na- ture, thin, overhanging portions are liable to break away, leaving imperfections Avhich may soon prove injurious to the filling. After an amalgam filling has become hard (and during this hardening process the patient should be warned against masticating upon it), the surface should be as carefully prepared and polished as that of a gold filling. The objections, therefore, urged against amalgam are, that it oxi- dizes and blackens; that the tooth-structure with which it remains in contact becomes discolored; that it contracts in hardening, alloAV- ing the secretions to make their way around the filling. Of late years it has been urged that it is imcompatible with tooth-structure, and that the mercury might act injuriously on the system. These objections are characteristic of most of the amalgams iioav on the market, although in a few notable exceptions they have been almost entirely overcome; but there is no good reason why amalgam should be incompatible Avith tooth-structure, or that the small amount of mercury imprisoned in this alloyed mass should possibly produce any mercurial effects. There is good reason, therefore, for believing it to be, in these respects, perfectry inert. The use of amalgam is contra-indicated, in all teeth which can be filled Avith gold ; in the front teeth, on account of its color ; and in pulp-cavities, on account of the difficulty of introduction into small canals. Various opinions are held as to the indications for the use of amalgam. In our OAvn opinion it is one of the most valuable materials for some operations, as, for instance, in cavities so difficult of access as to render the in- troduction of a perfect gold filling doubtful, and Avhere the opera- tion would be long, tedious and difficult, to both patient and operator, Avere gold used. Fig. 338 represents a number of amalgam Carriers and Fillers. Of these instruments, Nos. 1, 2, and 3 are constructed with fixed points, covered by a tube, which projects to form a cup for the amal- gam, and recedes so that the points work through as Pluggers to force it into the cavity ; No. 1 being half curve, No. 2 double-end giving tAvo angles, and No. 3 straight. No. 4 has a fixed tube with spring plunger, to force in the amalgam. The Loadstone Carrier and Plugger, No. 5, is a double-end instrument, one point of which is so prepared as to attract amalgam, Avhich will adhere to it while being conveyed to the cavity in the tooth; the reverse end is made as a Filler. TREATMENT OF DENTAL CARIES. 507 Fig. 338. 508 DENTAL SURGERY. Fig. 339 represents a Mercury Holder for convenient preparation of amalgam. Fig. 340 represents a set of Weston's Amalgam Pluggers. Robinson's Textile Metallic Filling has been in use for several years, and, on account of its containing no mercury, has, with some prac- titioners, taken the place of amalgam in a large per cent, of cases. It is not advisable to introduce it in very large pieces, as they can- not be manipulated with accuracy, and a filling of this material should be commenced Avith a cylinder or mass, and the remaining portion packed in the form of strips. It is necessary that it should be thoroughly malleted throughout the Avhole process of filling, as otherwise it may disintegrate under mastication. When it is com- bined Avith gold, and both metals are exposed to the fluids of the mouth, the textile filling will become black, Avhich, however, is said to occur on the exposed surface only, and not inside the tooth. Gutta-percha and HilVs Stopping,—Gutta-percha is an excellent material for temporary fillings. It may be made harder, whiter, and less contractile by incorporating with it some very fine poAvder of feldspar, silex, lime, or magnesia. A very excellent preparation knoAvn as HilVs Stopping is made by mixing gutta-percha with as much of the folloAving poAvder as it will hold without becoming brittle: quicklime,tAvo parts, very fine quartz and feldspar, one part each. Of all temporary fillings this is probably the best yet known. Prepared gutta-percha and Hill's Stopping are introduced in small pieces by first Avarming on a porcelain or metal-slab, over an alcohol lamp, until they become plastic enough to be readily pressed into the cavity and to adhere to its Avails. As soon as the cavity is filled, an instrument having a condensing point large enough to cover the entire surface of the filling should be applied and kept in position until the mass has become cool. Fig. 341 represents a cup for heating gutta-percha fillings, devised by Dr. Flagg. It is made of brass, silver or nickel-plated, to be filled with water and warmed over a spirit-lamp. The pellets are placed upon the top of the heated cover, from which they are taken up Avhen introducing them into the cavity. The surface of the filling is then cut down and burnished, after which a little chloroform may be applied, by means of a camel's-hair brush, to complete the fin- ishing process. The preparations of gutta-percha now used for filling materials possess different grades of plasticity, so that a filling may be com- menced Avith one that softens at a low temperature, and finished with TREATMENT OF DENTAL CARIES. 509 another which requires more heat to render it plastic, and hence becomes harder. For cavities situated on the approximal surfaces ©fc(v Fig. 340. Fig. 341. of the teeth and extending below the margin of the gum, gutta- percha preparations appear to answer a good purpose in resisting 510 DENTAL SURGERY. the dissolving action of the acid from the inflamed gum. When the gutta-percha preparation is made plastic enough to adhere to the Avails of a cavity, by passing it through the flame of a spirit- lamp, care is required that it should be evenly heated and not burnt. By using the loAver grade over sensitive portions of a cavity, less pain is experienced from the heat, and after the cavity is filled Avith the higher-grade material, the surplus can be removed Avith thin steel or platinum spatulas heated to the required degree, and the surface made smooth by passing over it a burnisher. Chloroform applied to the surface of a gutta-percha filling will give a smooth finish, but may render such a surface less durable, on account of its dissolving action. Fig. 342 represents a set of Dr. W. A. Bronson's gutta-percha in- struments. Zinc Preparations.—A mixture of chloride of zinc and oxide of zinc has been much used under the various names of oxychloride of Fig. 342. 0 zinc, os-artificial, osteo-dentine, osteo-plastic, mineral paste, etc. Quack- ery has seized it with eagerness, and plastered up many teeth with a mortar even more conveniently used than amalgam. Although in some few cases it may resist the action of the secretions of the mouth, it will not answer for a permanent filling. The friction of mastica- tion soon destroys it, and in approximal cavities it frequently crumbles aAvay in a few weeks or months. . Still, as a temporary filling, it may, if employed with caution and judgment, be found useful, and for certain cases very valuable. It has been used with success for filling the pulp-cavities of the teeth. It has also been applied to exposed nerves, and in some favorable cases successfully but its use for such a purpose is very uncertain, as the escharotic action of the zinc chloride will almost certainly produce death of the pulp. In the combination of the oxychloride ingredients the oxide TREATMENT OF DENTAL CARIES. 511 of zinc is usually mixed Avith some siliceous substance, to increase the hardness, and the chloride of zinc is diluted Avith water. When the powder and liquid are combined a cement results, which forms hydrated oxychloride of zinc, by the taking up of some of the Avater as a base. Some prefer" mixing the oxychloride in the form of a thin paste, and after adapting it carefully to the bottom and sides of the cavity, or over a sensitive surface, to complete the operation Avith a paste of thicker consistency. A warm burnisher will hasten the setting of the oxychloride, and apparently increase its hardness. The application of talc (soapstone), in the form of a properly-shaped point, which may be heated, or in the form of powder, appears to improve the surface of such a filling, by rendering it less permeable to moisture. On account of the oxychloride preparation being acted on by weak acid and even alkaline solutions, it cannot be depended upon for a permanent filling material, and will frequently dissolve aAvay in a few weeks or months, especially if introduced near to or beneath the margin of the gum. It often answers a good purpose Avhen applied to sensitive dentine, but, like the chloride of zinc, one of its ingredients, its application causes considerable pain for a short time. It has also been employed for bleaching discolored dentine, and as an interposing substance between a thin wall of cavity and darker but more durable filling material, such as amalgam. Of late years, various preparations, known as oxyphosphates of zinc, have been introduced, composed of the basic oxide of zinc and glacial phosphoric acid. One of these preparations is said to be composed of the nitrate of zinc and phosphoric acid. The oxyphos- phate preparations are preferable to the oxychlorides,.on account of their being less irritant to the pulp and more durable, especially Avhen placed about the necks of the teeth. They have also the ad- vantage over the oxychlorides of greater hardness; but it should be remembered that all of the zinc preparations are liable to be dis- solved by the fluids of the mouth, and hence are not so reliable for temporary fillings as gutta-percha, especially the form known as Hill's Stopping, particularly where such fillings extend beneath the margin of the gum to the cementum. The oxyphosphates mix less readily than the oxychlorides, and require more care in the combination of the powder and liquid. If mixed too thin, a sticky, unmanageable mass results, and if too thick the mass will crumble in pieces; it is therefore recommended to so prepare it that it may be rolled between the thumb and finger Avithout adhering to them, or, on the other hand, crumbling to pieces. 512 DENTAL SURGERY. Fig. 343. Fig. 344. Fig. 345. r \ TREATMENT OF DENTAL CARIES 513 On account of the oxyphosphate setting very rapidly, the cavity should be ready to receive it before it is mixed, by being free and protected from moisture by the application of the rubber-dam. Like the oxychloride, it is necessary that the surface of a filling of this material should be protected from moisture for some minutes after its introduction, and the same substances may be used to coat over the surface, as in the case of the oxychloride. Unlike the oxy- chloride, however, a Avarm instrument cannot be employed to hasten its setting. A number of forms of these cements are in use under the names of those originating them. Oneform,knoAvnas Poulson's is the pyrophosphate of zinc, the pyrophosphoric acid being in crys- tals, Avhich require to be melted in a platinum or porcelain spoon, held over a spirit lamp, care being taken that ebullition does not occur. When reduced by heat to the consistency of glycerine, it is dropped upon a Avarm porcelain slab, and is ready for introduc- tion into the cavity. Exposure of this preparation to the air causes its deterioration, hence it should be kept in hermetically sealed Ares- sels. Some of these plastic zinc preparations appear to be much less soluble in some mouths than in others, and considerable importance is attached to the manner in which they are mixed and inserted into the cavity. In using any of these preparations, the cavity is prepared as usual; then a small quantity of the liquid (either the chloride of zinc or the phosphoric acid) is dropped upon a piece of glass or porcelain, and enough of the poAvder (oxide of zinc) added to make a paste so thick that the surface Avill not appear Avatery. The cavity is then perfectly dried and protected from saliva and the material quickly introduced, after Avhich it is kept free from moisture for ten or twenty minutes. When sufficiently hard, the surface is finished by scraping and pol- ishing. The longer the surface is kept dry, the harder these materials become. Coating the surface with sandarach varnish (or gutta-percha dissolved in chloroform, or melted wax) will afford protection for some time. In all cases Avhere these preparations are introduced near a pulp, or as a capping over exposed pulps, the cavity should ahvays be previously Aviped out Avith a solution of gutta-percha and chloroform, to prevent the escharotic and irritant effect. Fig. 343 represents platinum points for oxychloride and oxyphos- phate filling. Fi°". 344 represents the agate burnisher, which is considered to be superior to any other burnisher for surface finishing of oxychloride and oxyphosphate fillings. 33 DENTAL SURGERY. Fig. 347. Fig. 345 represents the points of different forms of spatulas for mixing the zinc prepara- tions, which is conveniently done on a porcelain palette, such as is used by artists. Fig. 346 represents a common form of mouth mirror, of which both plain and magnifying are used in examining the teeth. Dr. Maynard, of Washington, has recently .made an improve- ment in mouth mirrors, by substituting pebbles for glass, which more clearly reflect the objects they picture. Fig. 347 represents reflectors for attachment to rubber-dam clamps, so that while providing a strong light, both hands of the operator are left free for manipulation. They are useful in operations upon posterior cavities in molars. By means of a ball-joint the mirror can be ad- justed to concentrate the light upon the cavity or any portion of the mouth required. Instruments knoAvn as stomatoscopes have been devised for the purpose of obtaining a perfect light for operations on the distal sur- faces of molars and bicuspids, and are found to be especially useful Avhen the sky is cloudy, and for night Avork. Such instruments as the Grohnwald and Beseler stomatoscopes, Avhich are capable of being so adjusted as to throw, light to any part of the mouth necessary in filling teeth may be used. Dr. C. F. W. Bodecker as- serts that by aid of a stomatoscope he Avas en- abled to see up to near the apex of the pulp-canal of a palatal root of a first u pper molar, the cavity being on the distal and grinding surface. The electric light has also been utilized for the same purpose, and alsofor examinations of the throat, and even of the stomach. Mr. E. T. Starr, of the S. S. AVhite dental establishment, TREATMENT OF DENTAL CARIES 515 has recently succeeded in obtaining highly satisfactory results in this direction. His instrument consists of a lamp formed of a delicate glass bulb, from Avhich the air has been AvithdraAvn and as nearly a perfect vacuum created as possible. The bulb varies in shape, being spheroidal, flat and compass-shaped, and also cylindri- cal, with a conical termination. Through the thin wall of the lamp run the conducting Avires, connected l>y a carbon arc, on which the electricity centres, and which thus becomes the place of light. The glass lamp is very small, the cylindrical-shaped being scarcely half an inch in length, and with a diameter much less than that of an ordinary lead pencil. The compass-shaped lamp is about one- quarter of an inch thick, and has a diameter of three-quarters of an inch to an inch, while the spheroidal is scarcely larger than a good-sized pea. The lamp is attached to a handle from seven to nine inehes long, and about half an inch thick, through which rim the wires connecting Avith the battery. The intensity of the poAver and the brilliancy of the arc of light can be regulated by moving along the handle a ring which connects with the wires. The handle has several joints, and its position can be arranged so as to adapt it to the shape of the cavity it is to illuminate. .Mirrors can also be fastened to the lamp, and light reflected to places where the lamp cannot be introduced. To prevent the too great radiation of heat and the-diffusion of light, the lamp may be partially covered Avith a hard rubber or gutta-percha case. When the lamp is placed in the mouth of a patient, every portion of the throat, even to the loAvest parts, and every recess of the upper places, can be plainly seen. Placed behind the teeth, the intense light renders not only the teeth but even the gums above, highly transparent. If the teeth are good and free from caries, no lines will be visible, but the presence of a filling, or the beginning of caries may at once be seem When the lamp is placed within the mouth, and the lips are closed, the entire front structure of the mouth is brought to view. No unpleasant sensations are experienced, even in cases of protracted use. Fig. 348 represents the "Electric Mouth Lamp," or "Stomato- scope." The electric mouth lamp will be found an invaluable assistant to the dentist in diagnosing lesions of the teeth and associate parts. especially in those obscure cases where, although there are unmis- takable symptoms of serious pathological disturbance, careful ex- amination with the-appliances heretofore in vogue fails to discover the exact location of the trouble. Sound teeth are sometimes need- lessly sacrificed in fruitless endeavors to find the seat of neuralgic pains for Avhich, OAving to the insufficiency of the means of diag- 516 DENTAL SURGERY Fig. 348. TREATMENT OF DENTAL CARIES. 517 nosis, no satisfactory cause can be established. The electric mouth lamp illuminates the oral cavity so brilliantly that any departure from normality, whether it be a hidden caAdty of decay, an unsus- pected dead pulp, or even the slight thickening of the tissues which is the precursor of decay, is unerringly detected. This apparatus will also be found very useful in the operating room in other directions. In the preparation of inaccessible cavities it is often difficult to tell when the excavation has proceeded far enough, but the electric mouth lamp will show at once whether all the dis- integrated tooth-substance has been removed. In use the lamp is placed behind the object to be illuminated— that is, so that the object is interposed between the lamp and the eye of the observer. Thus, in examining the teeth the lamp is placed within the arch, so that its light falls upon the lingual or palatal surfaces of the teeth, while the eye of the operator is directed to the labial or buccal surfaces. So lighted, every portion of the teeth Fig. 349. r r7^\ III! III! fill IIII 1111 II n IIII ». Fig. 611. 764 MECHANICS—DENTAL PROSTHESIS. to the tapering form shown; the walls being subsequently grooved with an oval burr, No. 90. The enlarged section, Fig. 610, shoAvs the crown adjusted on the root by means of cement or gutta-percha, which surrounds the post and fills all the spaces in the root and crown. Fig. 611 shoAvs the completed crown. Fig. 612 exhibits a, Fig. 612. Fig. 613. Fig. 614. Fig. 615. bifurcated bicuspid root, its end appearance, and a Logan crown adjusted to the root. Fig. 613 illustrates the best manner of bend- ing the post. Fig. 614 shows a split post, and its adaptation to a bifurcated bicuspid root is seen in Fig. 615. Figs. 616 and 617 Fig. 616. Fig. 617. Fig. 618. Fig. 619. exhibit the mode of mounting the Logan crown on a superior molar root, and Figs. 618 and 619 the same crown in its relation to an inferior molar root. " In the preceding description the figures clearly present to the mind's eye of the expert dentist the essential features of the new Logan crown and the method of mounting it; yet further explana- tion with reference to the figures will perhaps prove serviceable to such as may not be familiar with all the details of root-crowning. " In every instance where a root is deemed ready to receive its filling, it should first be measured through its canal from the cervi- cal opening to the apical foramen, and this may be accurately done with a gauge adjustable on a delicate canal explorer, Fig. 620. The CROAVN AND BRIDGE-AVORK. 765 same device serves to measure the distance from the apex to which the canal should be then filled (Fig. 621). It also gauges the depth to which the drill may be carried. The proper degree of enlargement from the bottom of the drilled hole will, of course, depend on the observed size and character of the root, and every dentist should familiarize himself with generic tooth-forms, so that when the length of an incisor, cuspid, or other tooth-root is known, he can so nearly determine its hidden outlines as to form with precision a corre- sponding enlargement of the pulp canal such as is shown by the several cuts. The suitable preparation of the bifurcated roots of some bicuspids and of all the molars is a matter involving diffi- culties and judgment of an unusual character. An instance of the Fig. 620. Fig. 621. Fig. 622. Fig. 623. Fig. 624. Fig. 625. feasibility of splitting the post of a Logan crown to adapt it to the bifurcated root of a bicuspid is shoAvn by Figs. 614 and 615. This example directs attention to the peculiar shape of the new post, in Avhich there is effected such a distribution of its metal that its greatest strength is in the line of the greatest stress that will in use be brought to bear on the croAvn, while the least metal is found at the point of the least strain; the applied part of the post being in outline nearly correspondent to that of the root itself. The pulp- canal is likewise conformably enlarged to receive the largest and stiffest post compatible Avith the size and shape of the root to be croAvned. " The fitting of a Logan crown to a root is best done by the use of a Avet stump wheel in the engine hand-piece, which affords the 766 MECHANICS—DENTAL PROSTHESIS. greatest facility for the slight touches required to abrade the thin cervical borders of the crown, Avhich may thus be made Avithout encroachment on the post. " By the old method of adapting pivot teeth to roots, the close fit- ting of the crown precluded the use of a plastic packing, because its thinness over the surface of the joint made such packing liable to break loose under the shock and strain of use. The recess in the Logan croAvn obviates this defect by providing a receptacle for a considerable interior body of cement that will be deep enough to be self-sustaining internally, and yet allow the peripheral portions of the root and crown to approach each other so closely that, though only a film of packing remain, it will still be strong enough to in sure the persistent tightness of the joint. Such annular boss of cement when formed of amalgam also adds strength in some cases to the mount. " When enough of the natural crown remains, it is well to leave standing some of the palatal portion, and cut the root under the gum-margin at only the labial part, as shown by Fig. 622. Thus, the labial-joining of the root and crown will be concealed, and the other parts of the joint will be accessible for finishing and keeping clean (Fig. 623). The Logan crown may be ground until a large part shall have been removed for adaptation to the occluding tooth or teeth without greatly impairing its strength (see Fig. 624). This crown also in such cases maintains the translucency which is one of its peculiar excellences, owing to its solid porcelain body, and the absence of a metallic backing or an interior largely filled with cement or amalgam. " The distal buccal root of the natural superior molar is in nearly every instance too small to receive a post of any useful diameter, and therefore the Logan superior molar crown has but two posts, Avhich, like those of the inferior molar crown, are square, and thus may be easily barbed, as may also the ribbed posts of the crowns for the anterior tooth-roots. These posts are in all the Logan crowns large enough to answer in any given case, and can, of course, be easily reduced to suit thin or short roots. " Any of the cements or amalgams may be used in fixing these crowns, but good gutta-percha, softened at a low heat and quickly wrapped around the heated crown post, Avhich is at once seated in the root, forms the best mounting medium, and has the great ad- vantage of permitting a readjustment, or if need be the ready re- moval of the crown by grasping it Avith a pair of hot pliers or for- ceps, and holding it until the gutta-percha is sufficiently softened. " An excellent combination for some cases is accomplished by fit- CROWN AND BRIDGE-WORK. 767 ting a narrow seamless gold collar over the neck of the root pre- pared like that of Fig. 623, and then adjusting and mounting in the manner described a Logan crown, with the results shown by Fig. 625."* For reaming out and grooving the walls of the root-canals, Fig. 626 represents what is known as the " grooving burr engine-bit." This burr is intended for cutting grooves in the walls of root-canals to provide retaining-points for plastic materials in setting porcelain crowns. The grooves are made by SAveeping the burr, while in motion, around the walls of the canal, which should be made large enough to permit the burr end to reach the bottom of the cavity. Tavo or three grooves, as may be desired, can be cut in thin roots with safety, one size of the burr answering for all cavities. The Fig. 626. Fig. 627. Fig. 628. Fig. 629. canal is then filled with gutta-percha, oxychloride, amalgam or other plastic, and, before it sets, the barbed pin of the crown is in- serted, with the effect of forcing the material into the grooves, thus adding greatly to the strength of the operation. Fig. 627 represents Dr. Ottolengues' root-reamers and facers. The root-reamers are of the size and taper of the Logan crown- pins Nos. 1, 2, 3, and have corresponding numbers. With a drill just the diameter of the smooth end of the reamer, the root should be drilled to the proper measured depth, and the bored canal be then enlarged Avith a suitably numbered root-reamer, which, having a smooth end, cannot be forced beyond the end of the drilled hole. Dental Cosmos. 768 MECHANICS—DENTAL PROSTHESIS. There are five sizes of the root-facers, so that one may be chosen of such width that the root end can be smoothly, quickly, and safely faced to fit the crown. Dr. C. M. Richmond has devised a modified form (Fig. 628) of the last described crown, which consists in making the pin square instead of round, to prevent the crown from rotating, and in form- ing an opening on the palatal and lingual surface of the basal cavity, for the free escape of the filling material when placing the crown in position. Dr. Richmond suggests that a quick-setting material, such as oxyphosphate of zinc, be used in the bottom of the cavity, and amalgam at the surface. Fig. 629 shows the modi- fied crown in position. A new crown has recently been invented by Dr. Richmond, and the mode of mounting it is described by Dr. How as follows: " A superior central incisor root will serve as a typical case, and its projecting end is to be shaped as seen in Figs. 630 and 631. This can be rapidly done with a narrow, safe-sided, flat or square file, Fig. 630. Fig. 631. Fig. 632. the angles of the slopes being such that the gum on the labial and palatal aspects will not interfere with nor be disturbed by the operater in this preliminary work, for the root-end is not at this time to be cut quite down to the gum. A root-reamer is then em- ployed to bore out the root to receive the crown-post, which is of the same size and shape as the Logan crown-post for a central in- cisor. Fig. 632 shows in section the relation of the reamer to the root. The new Richmond crown, Fig. 633, is then put on the root (see Fig. 634), and its position relative to the adjacent and occlud- ing teeth noted. If the cutting-edge of the crown is to be brought out for alignment with its neighbors, the root can be drilled a little deeper, and the reamer pressed outwards as it revolves to cut the labial wall of the cavity. The palatal root-slope must then be filed to make the V correspond to the changed inclination of the crown. CROAVN AND BRIDGE-AVORK. 769 " Thus, by alternate trial, and reaming, and filing, the crown may be fitted to the root and adjusted in its relations until the post has a close, solid bearing against the labial arid palatal Avails of the enlarged pulp-cavity, and the croAvn-slopes separated from the root- slopes by the thickness of a sheet of heavy Avriting-paper. This space can be accurately gauged, and the root-slopes conformed to the crown-slopes by warming the crown and putting on its slopes a Fig. 633. Fig. 634. Fig. 635. Fig. 636. little gutta-percha, so that an impression of the root-end may be taken, and the root-slopes dressed with a file until the film of gutta- percha proves to be of equal thinness on both slopes. After thus completing the adjustment, with due attention to the alignment and occlusion, the crown and the root are to be dried as thoroughly as possible. "' To do this effectively in the root, it should first be SAvabbed and Avashed out Avith absolute alcohol, and then continuously flooded Fig. 637. Fig. 638. Fig. 639. with Avarm air, until the root is not merely dry, but dried through- out as far as possible, and made so Avarm as to render the patient conscious of its heat. A little gutta-percha is then put on the sides of the post and over the slopes of the croAvn, which is then pushed into place, the exuding gutta-percha cut aAvay, and the joint smoothed Avith a Avarm burnisher. The film of gutta-percha should be very thin. The crown and root may be quickly cooled by the use of the syringe with cold water, and the patient then enjoined to let 49 770 MECHANICS—DENTAL PROSTHESIS. the crov»n rest for a few hours in order that the gutta-percha may become quite set. Fig. 635 shoAvs the completed croAvn. " Dr. Richmond usually takes a thin, perforated disk of gutta- percha, pushes the post through it, warms the crown, presses it into place, and Avhen cooled removes the crown, and with a sharp knife trims aAvay the gutta-percha close to the crown-neck. He then Avarms the crown, puts a very little oxyphosphate cement on the post, and presses the croAvn home. " The obvious advantages of the device are the readiness Avith Avhich the slopes of the root-end may be shaped Avith a file; the facility Avith Avhich these slopes may be given any angle to set the croAvn out or in at the base or at the cutting edge, or to ghre it a twist on its axis; the certainty that, once adjusted, the final set- ting Avill exactly reproduce the adjustment; the assurance that in use the crown will not be turned on its axis,—a most common cause of the loosening of artificial crowns; the firmness of its resistance to outAvard thrust in the act of biting. This fact is made apparent by Fig. 636, Avherein it will be seen that in an outward movement the crown B would rock upon A as a pivot, and the dotted line D shoAvs hoAV the crown slope is resisted by the root-slope, Avhich ex- tends so far towards the incisive edge that a much firmer support is given to the croAvn than if the resistance should be, as it usually is, on the line of the gingival margin C. " The cases for which the neAV crown seems specially adapted are such as have some considerable portion of the natural crown re- maining, and for these it would seem that no better artificial sub- stitute has yet been made accessible to the profession. " For roots that have become wasted below the gum-surface the new crown is not suitable, except in such cases as are decayed under the labial or palatal gum-margin only, but haA'e yet project- ing the approximal portions of the crown (see Fig. 637). " The sectional view (Fig. 638) and the perspective plan vieAvs (Fig. 639) illustrate the manner of mounting these crowns on this class of roots. The finished crown appears as in Fig. 639." Fig. 640 represents different forms of crowns, and the nut-drh^er and screw-nut for setting porcelain croAvns on natural roots. The all-porcelain croAvns, such as the Foster, Gates-Bon will, dove- tail crown, and others, have been set in various Avays, prominent among Avhich has been the use of solid-headed screAvs; but we find that much more satisfactory and firmer work can be done by first fixing the screw-post in the root, thus permitting the croAvn te be slipped over the end of the post and properly adjusted to the root, after which the cavities in both root and crown may be partly filled CROAVN AND BRIDGE-WORK. 771 and a nutscreAved on the end of the post to condense the filling and firmly secure the crown in its place. These appliances are very simple. They consist of a nut-driver, over Avhich is placed a split tube for carrying the nut (see sectional Adew). The sole object of this tube is to hold the nut and prevent its falling into the mouth or on the floor during the process of attaching or detaching it from the post. The substitution of pieces of porcelain for the portions of croAvns of teeth destroyed by caries, by a process of inlaying, was suggested Fig. 640. Foster Crown. Gates-Bonwill Crown. Dove-Tailed Crown. How Screw-Posts. (b with nut.) Headed Screws. Nut-Driver with Split Tube. many years ago by Dr. EdAV. Maynard, and successfully practiced by Dr. A. J. Volck, of Baltimore, and also by Dr. B. Wood. Dr. W. Storer Hoav describes a method as follows :* " One of the chief obstacles to success in many of these operations has been the difficulty of exactly fitting the inlay to the tooth. There is, hoAvever, a class of cases Avhich, by methods that will be now described, may be repaired Avith the certainty of gratifying results. * Dental Cosmos, August No., 1888. 772 MECHANICS--DENTAL PROSTHESIS. "A typical instance is that illustrated in Fig. 641, and the filling of gold usually inserted in such a cavity is a glaring disfigurement, endurable only by reason of the necessity of preserving the life and usefulness of the tooth. Fig. 641 also shoAvs the oval-shaped cavity about to be converted into a circular one by means of a Avheel burr, as, say, No. 208. A fine-cut burr is essential for this Avork, which requires skill and delicacy with firmness of touch in order to the making of a truly circular cavity of the smallest diameter consist- ent Avith the inclusion of all the borders of the original cavity. When this has been nearly done, and the cavity suitably deepened by an excavating Avheel-burr, as No. 22, the barrel-burr, say No. 239, is to be used with steadiness and due attention to the holding of it, so that Avhen pressed quite to the bottom of the cavity the margin Avill be exactly circular, Avhenever that is possible. (See Fig. 642.) In some cases the differences between the diameters of the succes- sive or even the same numbers of the finishing burrs will be found too great, so that Avhile one size is not quite large enough, the next size is much too large. It is best, therefore, to be prepared Avith Fig. 641. Fig. 642. Fig. 643. some hard-Avood points, in shape like the wood polishing-points No. 3, and of closely graded sizes to be used in the porte-polisher No. 307. A thin strip of bone or ebony or vulcanite should also be at hand having a series of holes that may be made Avith the barrel burrs, each of which Avill make three different sizes, and the strip serves as a very useful gauge. Selecting then a hard-wood point (one made of copper, or of tin solder, would be even better) a very little larger than the cavity, put in it some corundum polishing- paste and carefully grind the cavity larger, circular, and true doAvn to the bottom. Of course, it is next to be thoroughly washed out with alcohol and dried with warm air. With a wheel burr No. 15, or oval No. 91, cut small grooves in the upper and lower walls, but not on the thin side-walls, Avhich Avould thus be needlessly Aveakened. Select from the stock of broken or whole porcelain teeth, whether plain-plate, vulcanite, or gum teeth, one which will match the color of the natural tooth, and, Avith a corundum disk or other AAdieel, cut out a section somewhat larger than the cavity. But when a stock of cavity-stoppers is accessible, one of these will be preferable CROAVN AND BRIDGE-WORK. 773 because made wholly of enamel, and therefore likely to take a better polish in the process of finishing. "It is Avorth Avhile to spare no trouble or time or expense in matching as near as possible the exact shade of the tooth to be inlaid, because the success of the substitution will greatly depend upon the closeness of its resemblance to the natural tooth. In an emer- gency, choose the lighter rather than the darker shade. When the suitable tooth has been found, and ground to an approximate di- ameter and thickness, cleanse thoroughly its enamel face Avith alco- hol, and then Avith shellac melted but not burned, stick the face of the porcelain to the flat-faced end of a A\'ood-point in the porte- polisher. After the porcelain has become quite cool, try it severely to be sure that it has stuck fast, because it will be annoying and cost valuable time if it shall be dislodged and need to be re-set when nearly finished. For the purpose of illustration, a cavity-stopper is selected, and is shown mounted with shellac on a Avood-point. The porte-polisher is put in the engine hand-piece and rotated in contact Avith a corundum Avheel, or slab, Fig. 613. For more rapid grinding it may be rotated in contact with a revolving corundum wheel. The gauge previously mentioned will serve for frequent trials in the successive holes until the inlay fits the hole next larger than the cavity. Then the successive trials must be made in the cavity itself until, after grinding on a piece of Arkansas stone, the inlay exactly fits the cavity. In some instances it will be best to Avet the inlay Avith a very fine polishing-paste and grind it in the cavity. This is, however, someAvhat hazardous, because of the liability of the inlay to get stuck fast in the cavity, and so endanger the cavity-Avails. It is then best to grind on the corundum slab the bottom of the inlay, to allow it to settle in the cavity and take up the space previously occupied by the paste betAveen it and the cavity-Avails. A fitted inlay will resemble Fig. 644, and for greater security after it shall have been mounted, it will be necessary to cut with a sharp corundum disk notches on opposite sides of the inlay; and to insure the coaptation of these notches with the grooves in the cavity, and at the same time be sure that the inlay shall shade properly with the tooth, it will be best to detach the inlay from the avooc! before cutting the notches (Fig. 645). Both the cavity and inlay must be perfectly clean and dry before the inlay is lightly placed in the cavity, to determine Avhich is its upper and which its under edge, so that the notches may be correspondingly cut with a clean, sharp, dry disk. Another reason for so cutting the notches is found in the fact that sometimes the lateral curve of the surface of the tooth will be so great that a groove on the lateral 774 MECHANICS—DENTAL PROSTHESIS. Avail of the inlay Avould jeopardize the closeness of the joint on the surface at that point. " It Avill, of course, be understood that the process described Avith reference to the porcelain cavity stopper is applicable to the prepara- tion of any section from a porcelain tooth, and at this stage of the proceedings it is assumed that the clean, dry, notched porcelain inlay closely fits the clean, dry, grooved cavity.. These are to be fastened to each other mainly by a locking-bit of cement or gutta- percha in each of the notches and grooves, in addition to a mere film of such plastic material betAveen the cavity and inlay walls. This is the critical period of the operation, because of the extreme difficulty of so nicely proportioning and evenly distributing the cement or gutta-percha that the joining of inlay and tooth shall be complete in the actual contact of the marginal walls, excepting only the interstitial porosities which are to be filled with the cement or gutta-percha. « " It is probable that the generality of operators will do best with the phosphate of zinc cement, but in any case, Avhatever the mate- rial of union is to be, the invariable prerequisites are,—perfect dry- ness of both the cavity and the inlay, and some degree of warmth in each of them. These conditions may be best accomplished by a thorough washing of both with absolute alcohol, and the use of the hot-air syringe immediately preceding the mixing of the cement. This should be mixed quickly and thin, and a mustard-seed bit of it taken on the blade of a small excavator and placed in the two grooves of the cavity, as also in the tAvo grooves of the inlay ; to be instantly followed by the rubbing of the walls of the inlay all over with the least possible cement on the tip of the finger. The inlay is then at once seated in the cavity and with a quick back-and- forth grinding motion pressed firmly into place (taking care that the notches are in right relations to the cavity-grooves), and held under pressure fully five minutes. In cases wherein the inlay has been ground into the cavity, it may be better not to remove the inlay from the mandrel, but to thinly coat its walls with cement, and, using the porte-polisher as a handle, turn the inlay into its seat (as a ground stopper into its bottle) with such firmness as to detach the inlay from its shellac attachment to the Avoocl-point, and leave the inlay stuck fast in the tooth. A little Avhite wax is then melted around the joint with a hot burnisher, and the patient dismissed for a subsequent sitting, at least five or six hours later; for it is of great importance that the cement be alloAved to get hard before any strain is put upon the inlay. It is also essential to the proper seat- ing of the inlay that no cement be allowed on the floor of the cavity CROAVN AND BRIDGE-AVORK. 775 or the bottom of the inlay, because no amount of pressure will bring the walls into contact if there is a body of cement between those tAvo flat surfaces; and continued pressure for a short time after the seat- ing is necessary lest the elasticity of possibly occluded air lift the inlay from its seat before the cement or gutta-percha shall have stiffened sufficiently to hold it in place. " The rough grinding of the protruding portion of the inlay (Fig. 646) may be clone Avith a stump or croAvn corundum Avheel, until the margins are nearly flush Avith the tooth-surface, and then a 1 levelled corundum point like No. 7 or No. 12 may be used, as shoAvn in Fig. 647, to make the inlay conform closely to the contour of the tooth, and the final finish will best be given by an engine Arkansas stone bevelled like 'R' or 'T' and used Avith its further side in contact Avith the inlay or tooth, or both as the case may be (Fig. 647). Such use of the side of a grinding or polishing Avheel avoids Fig. 644. Fig. 645. Fig. 646. Fig. 647. Fig. 648. the hollowing or waAry lines Avhich commonly result from the peripheral contact of wheels or points Avith the convex surfaces of the tooth. Indeed, the preferable polishing instrument Avould be a device like the old engine reciprocating porte-polisher, if it could be given poAver enough to be effective. A magnifying-glass Avill aid in making sure that the finish leaves the inlay border quite flush with the enamel at every point. " A small bevelled Arkansas stone wheel is almost a necessity for making the inlay flush Avith the enamel, because the hard stone not only cuts the porcelain smoothly Avithout acting also upon the enamel by its detritus, as is the case Avith the soft stones Avhen the enamel and inlay surfaces are nearly in the same plane, but it has a peculiar feel under the hand when cutting the porcelain, and also emits a peculiar sound, so that, although the water and debris may hide the joint from vieAV, the operator can know by the touch when the wheel is acting upon the inlay or the tooth. This is of great consequence in order that only so much, and yet every Avhit of so much, porcelain may be cut aAvay as shall suffice to make the best possible joining, Avhile preserving all the enamel essential to a flush contact Avith the inlay and a suitable contour of both at the finish. " Previous to attempting this method of repair, it is advisable that 776 MECHANICS—DENT4L PROSTHESIS. there should be some preliminary practice in setting inlays in teeth which have been extracted, or in pieces of ivory or bone; because there will thus be developed practical points Avhich cannot be here described and yet are essential to the proper performance of the operation. Fig. 649. Fig. 650. " The completed inlay, Fig. 648, when suitably adapted and finely finished, may well be considered as exemplifying the nearest ap- proach to perfection in the accomplishment of dental repair that has as yet been achieved." Dr. S. D. Rambo has suggested a method of restoring broken croAvns of teeth Avith pieces of artificial teeth in connection with pivots, which he describes as folloAvs : " Beginning Avith a central incisor, Avith one-third of the crown broken off, as in Fig. 651 a, I fill the root with lead-wire, as folloAvs: From a piece of sheet-lead I cut a strip and pass it through a draw plate until it is reduced to the size of a medium pin; cut the wire into pieces one inch long and roll one end to fit the foramen at the apex. If, in passing it up, I find that it goes through (Avhich I as- certain from the pain produced), I take it out and cut the point off Fig. 651. A. B. C. D. E. F. G. H. a little and try it again. When I find that it has closed the apex exactly, Avhich I knoAV from the touch, I pass doAvn by the side of it a nerve-plugger the same shape as the lead needle intro- duced, making room for another wire, and so on until I find the first third of the root filled. I then fill the middle part with gutta-percha, cutting the Avires off as far up as I can, otherwise CROAVN AND BRIDGE-AVORK. 777 the lead might discolor the tooth at the margin of the gum. I then fill the last third of the root Avith oxyphosphate cement, to prevent the tooth from turning dark. Before introducing the lead Avires I moisten them Avith phenic acid or creasote. Lead is less irritating in the flesh than any of the other metals. I have found buckshot in deer that had long since healed over, with no sign of inflammation or ulcers. For the reason that flesh will kindly heal around lead, I think it the best material that can be employed for filling the roots of teeth. Next, drill a hole, as if for a pivot, and shape the rough edges of the crown more or less as in Fig. 651 a. Select a plate tooth having pins parallel Avith the sides, the exact shade of the tooth to be operated upon, and grind it to fit the part to be replaced. (See Fig. 651 b.) Back the piece of arti- iicial tooth Avith a thin platinum plate, cutting the pins off smoothly with the backing, and secure it by splitting the heads of the pins. Then put the platinum Avire into the hole drilled for the pivot, in- serting it loosely, and bending to such a shape as to touch against the Avails so that it may occupy the same position when replaced. Attach the piece of tooth to the Avire (which is already in the tooth) with Avax, leaving a space the thickness of a 00 file betAveen the natural and piece of artificial tooth. Now draAv the wire out very carefully, to guard against displacing the piece of tooth ; invest in plaster and solder Avith pure gold. Make the backing thick enough to give the necessary finish to the tooth. Next, dry the hole Avith hot air; put the piece of tooth in its place Avith enough plastic filling (either gutta-percha or oxyphosphate) around the Avire to fill the interspaces ; then cut out the material in the joint to the depth of tAvo lines, fill in with gold, and finish Avith disks, etc. The crown is iioav restored (see Fig. 651 c) with something that does not attract so much attention, Avhich is more lasting and is far more artistic, Avith less fatigue to patient and operator than if it had been restored Avith gold. "Fig. 651 D represents a central incisor having tAVO-thirds of the croAvn, parallel to the cutting edge, broken off. In a case of this kind fit a point to the croAvn, and proceed in the same manner as described in the preceding case. Fig. 651 e shows the piece of por- celain tooth prepared, and Fig. 651 f a side vieAV of the restored croAvn. All except that portion of the broken surface of the natural tooth that is not covered by the artificial piece must be coveredl Avith a thin platinum plate, Avith a hole through it to permit the Avire to pass. This is done in order to have a Avail to Aoav the solder against, and to make the piece the required thickness at the joint.. Cases like Fig. 651 a sometimes require similar treatment... When. 778 MECHANICS—DENT A L PROSTIIESIS. there is plenty of space on the palatal surface, retaining pits niav be made, and the shape restored by building gold against the backing of the artificial tooth. The latter requires more time, and is, perhaps, no better if as good as the former. " Many, no doubt, Avould cut off the remainder of the crown in a case like that shown in Fig. 651 d and pivot. But I consider tooth- structure too valuable to be thus lost, to say nothing of the difficulty of making a joint beneath the gum so perfectly as to prevent the accumulation of vitiated secretions around it. I, therefore, save all I can, not being particular where the joint is made. Another advan- tage in having the joint at a distance from the gum is, that the root is less liable to decay. Still, even when the crown is entirely lost see Fig. 651 g and h), I find the above method a good one for pivoting, using gutta-percha to secure the tooth in position, and to prevent the secretions from entering the joints, trimming smoothly the excess of gutta-percha around the joint. " Bicuspids and molars (see Figs. 652 and 653), having very large buccal or approximal cavities extending into the grinding surface, can be easily managed by fitting pieces of artificial teeth into cavi- ties. If the teeth are dead the pieces may be more perfectly secured by soldering a Avire and extending it doAvn the root. In operating on a superior molar, use a long Avire for the palatal root, and a shorter one may be placed on the opposite side as a brace. Exca- vate the material as described, and fill around Avith gold." It remains briefly to refer to the application of vulcanite to the pivoting of teeth. The following method admits of variations to suit a metal pivot, rubber pivot, or the usual hickory pivot. Prepare the root as usual, being careful to drill the canal with utmost uniformity and smooth- ness. Have a set of very smooth aluminum pins, about a half-inch long, to suit the canals made by different-sized drills; select one which will fit accurately into the root, yet can be easily removed, and press it to the bottom of the canal, letting it project beloAV the root a fourth of an inch. Carefully take a plaster impression of the root and two adjoining teeth in a small Avax or tin-foil cup ; Avhen quite hard, break it in the line of the arch, and remove. The pin may come with the plaster or remain in the tooth ; sometimes the break in the plaster will be just at the pin; but Avhen pressed together the hole will be entire. Into this hole place the pin, if yet in the tooth. CROAVN AND BRIDGE AVORK. 779 Soap this impression and make, with great care, a model, using the finest plaster; Avhen the plaster has fully set, remove the impres- sion piecemeal, so as not to injure the model, which should then be hardened Avith dilute soluble glass. The model, with its projecting aluminum pin, is uoav ready for fitting and attaching the tooth; this may be retained—1. By a hickory pivot; in Avhich case seleet a plate or rubber tooth, Avhich Avill not interfere with the pin; fit it to the root, the front edge alone touching; arrange the Avax, and set in flask for vulcanizing. When finished, draAv the aluminum pin; in the hole insert a compressed hickory pivot, and proceed as Avith a porcelain pivot tooth. There are three advantages in this kind of pivot tooth: it fits the root accurately, canals in root and tooth are of same size, and are also exactly in line—three points which cannot always be secured in an ordinary porcelain pivot tooth. If a plate tooth is used, a loop or hook must be soldered to the tooth pins, passing around the alumi- num pin. 2. By a metallic pivot; in Avhich case, fit a crown to the root as lie fore. If an aluminum pivot is preferred, the one already in the plaster may be retained, the projecting part roughened with a file, and the wax then arranged and the piece prepared for vul- canizing. If a gold pivot is preferred, carefully draAv the aluminum pin and replace with a gold one of exactly the same size. 3. By a vulcanite pivot; in which case a plain vulcanite tooth may be used, first carefully drawing the aluminum pin^ then set a small Avire in the hole, extending downAvard behind the tooth, to strengthen the pivot. Apply Avax and prepare for vulcanizing. Lining the root canal Avith a gold cylinder, filling a eonical-cavity Avith foil, or any other preliminary preparation of the root, does not modify the processes just described; but, among the advantages of the vulcanite pivot tooth, is the readiness Avith Avhich it fits an irregular surface; hence, a root hollowed by decay need not be filled, provided there is sufficient length of sound root for the canal. Another advantage is the firmness given to the close fitting of the rubber to the base of the root. A method of applying hard or vulcanized rubber to pivot work has been suggested by Dr. J. Richardson, and is briefly described by Dr. J. E. Dexter, as folloAvs : " An ordinary pivot croAvn is loosely fitted up Avith a Avood peg, Avhich also fits loosely the canal in the root. The crown is ground from before backAvard so as to leave a space betAveen the posterior portions of root and crown. Wax applied to the root and croAvn at once holds the crown and pivot in proper relative position, and gives an impression of the root end. The Avhole is Avithdrawn, and so invested in plaster that the crown, 780 MECHANICS—DENTAL PROSTHESIS. peg and Avax may be removed, and the crown be capable of accurate replacement on the model. The hole in the root and root model are now properly drilled by the same drill to receive a gold Avire pivot; the latter being long enough to project above the root into the crown, and being smaller than the holes in both root and croAvn, to alloAV of vulcanite enwrapping it Avithin these spaces. Now the hole in the root model is packed Avith vulcanite gum, the gold pivot heated and pushed through the gum to its place, the hole in the crown also packed, and the crown forced to its position on the model over the projecting end of the gold pivot. More gum is packed in the palatal groove between root and croAvn, the Avhole flasked and vulcanized, and the finished croAvn forced to its place on the root, a few folds of gold foil being interposed to fill the joint tightly. " Dr. Richardson also made vulcanite tubes for pivot sockets, to replace those of gold commonly used, by vulcanizing a layer of gum around a gold wire, Avhich should afterward form the pivot. The wire, being Avrapped in a single layer of tin foil, Avas readily draAvn from the tube after vulcanizing, the tin being removed Avith muriatic acid. A proper length of the vulcanite tube Avas inserted in the root, either by force and a tight fit, or by aid of plastic cements, and the pivot, vulcanized to a porcelain croAvn, Avas made to take up the extra space in the tube caused by the removal of the tin foil, by bending, or by splitting and springing it open." Also, Dr. H. C. Register's variation of this method, which " is to use an ordinary plain rubber-tooth, and form its palatal contour with vulcanite. Through this a hole is drilled, in line Avith that in the root, the latter being filled Avith hickory Avood. The crown now being held in position, a drill is passed through the hole in the vulcanite into the wood in the root, and a gold screw pivot is passed through the crown into the wood root socket, holding the two firmly together. The details need no further description." A method of pivoting a bicuspid is suggested by Dr. Bishop and described as follows by Dr. Dexter:. " The root being a first bicuspid, both canals were opened, and a thin'Avire set loosely in each, the projecting ends being bent together like a staple over the root face. Gutta-percha was then packed upon the root face, around and under the wire staple. A plain rubber tooth Avas now ground to fit, and held in place while the gutta-percha was continued over its pins and shaped to contour. " The whole was now removed together, invested, vulcanite gum substituted for the gutta-percha and vulcanized. The tooth AA'as set in place with plastics in the canals around the pins. CROAVN AND BRIDGE-AATORK. 781 " This method appears to have much value for certain cases. Variations of it may be noted; for instance, using oxyphosphate, oxychloride, or fossiline. in place of the gutta-percha, and leaving the tooth in place, for a temporary purpose, instead of removing and vulcanizing. Also, using heavier wires of platinum and iridium alloy for the pivots, and springing them apart, after vulcanizing, so as to obtain their spring pressure in maintaining the tooth in place." Banded or Fe/ruled Pivot Teeth. — Dr. W. H. DAvinelle, in the American Journal of Dented Science, April, 1855, was the first to sug- gest the banded or ferruled pivot tooth in connection Avith crystal gold, for restoring lost or fractured croAvns. Fig. 654 represents the shape or mould into Avhich crystal gold is packed, a plate tooth being first backed Avith gold, to which is soldered a band. The tooth is fastened to the root by a screw passing through a horizontal plate at the base of the backing into the dentine, and a somewhat larger screAV having been placed and secured in the pulp canal, with the free end projecting into the cap on the crown, gold is built around this end and the cap filled. What may be more properly termed a " cap croAvn" than a pivot tooth Avas suggested by Dr. Wm. N. Morrison, in the Missouri Dental Journal, May, 1869. No screAvs or pivots are used in this method, but a cap of gold is made in the form of a tooth crown, by being SAvaged on a model or die of a natural tooth, its sides encircling the root, and extending under the gum to the edge of the alveolar pro- cess. A bar is soldered across the inside of the cap, to afford a support for the oxychloride of zinc (the oxyphosphate will answer also). The root is then prepared for the reception of the cap, Avhich is filled Avith the zinc preparation and pressed into place on the root. Dr. B. Beers, in 1873, suggested a method of forming a gold crown from a flat strip of gold by stamping it in the centre on a block of lead, Avith a punch. The gold is then annealed, and the tAvo ends bent around the tooth (the stamped surface representing the labial surface of a front tooth), and these ends soldered together. The " bite " is then adjusted by means of a half-round file, so that the tooth articulates properly Avith its antagonists. A thick flat piece of gold is then bent to suit the form of tooth required and soldered on the top of the gold croAvn, Avhich is fastened to the root by inserting headed gold screAvs into the canal and then filling the cap with oxychloride of zinc, Avhen it is forced over the root to its proper place. Fig. 655 represents Dr. Beers' crowns and method of attachment to the roots of teeth. Dr. E. S. Talbot has improved upon the method of Dr. Beers, by 782 MECHANICS—DENTAL PROSTHESIS. a band fitted to the root, and extending to the alveolus, across the inside of which a partition or floor of gold is soldered. In this floor holes are made opposite the pulp canals underneath. Wires are loosely inserted in these canals, and the space in the band beneath the floor is filled Avith gutta-percha or one of the zinc preparations Fig. 655. and the band or collars forced into position on the root, the Avires projecting through the holes in the floor. After the gutta-percha or cement has become hard, the wires are drawn out, and headed screws are substituted, which fasten the band or crown to the root. The work is completed by filling the band Avith gold, or by swaging Fig. 656. Fig. 657. Fig. 658. a gold croAvn or cap, which is slipped over or within the edge of the band encircling the root, the cap being previously filled with cement. Fig. 656 represents Dr. Talbot's method. Fig. 657 represents root trimmers or reducers, suggested by Dr. R. W. Starr. They are intended for trimming the edges or reducing the diameters of roots over which collars are to be placed. The shoulder keeps the instrument on the root and limits the penetra- tion of the spur, which, by its knife edge, scrapes the side of the CROAVN AND BRIDGE-AVORK. 783 root (Fig 658a), so that it may easily and quickly be given the shape of Fig. 6586, or any similar form. They are made right and left; the straight pair (Nos. 1 and 2) for use on the superior roots anterior to the molars, and the curved pair (Nos. 3 and 4) for use in all the other natural roots. Dr. C. M. Richmond's method of making what are known as the "Richmond CroAvns" is as follows: This crown consists of a close- fitting band or ferrule of coin gold plate, to which a cap or surface, corresponding to the grinding surface of the class of tooth it is designed to crown, is soldered. The root is prepared by making the exposed surface flat, by means of the file or corundum disk. A strip of gold plate, about No. 27 American gauge, is then cut, of such a width as will extend from the alveolar process to a height sufficient to give the proper length of gold croAvn. To determine the proper width of the strip or ferrule, a pattern of tin or sheet lead, adapted to the tooth, may be used. The strip of gold plate is then bent Avith the pliers, and filed to the proper form, and the overlapping ends soldered together, the ferrule being made slightly smaller than the root it is to encircle, so as to secure a tight fit. After the band or ferrule is completed, it is capped by a piece of plate large enough to cover the croAvn end, and the tAvo soldered together, and properly finished by smoothing the sharp edges with a file and burnisher. The cap or crown is then adapted to the festooned margin of the gum and septa, by filing the approximal edges concave. The margin of the gold croAvn, Avhere it comes in contact with the neck of the root, is slightly bevelled from the out- side, in order to make a thin edge, Avhich Avill adapt itself to the surface of the neck under the pressure necessary to force the crown to its place on the root. The crown is then forced over the root, and the position of the artificial cusps yet to be made determined by the antagonism of the opposing teeth. Small, flattened buttons, made by melting scraps of plate, and slightly flattening them by blows Avith a hammer, are soldered on the grinding surface of the gold crown, Avhich is filled and invested during the soldering pro- cess Avith moistened sand, to Avhich is added a little plaster. After thus attaching the cusps and contouring the grinding surface, the gold croAvn is ready to be adjusted to the root. A small hole is first drilled through the side or top of the crown, to allow the surplus cement, by Avhich the crown is secured, to escape. The concavity of thecroAvn is then filled Avith either the oxychloride or oxyphos- phate of zinc, mixed someAvhat thinner than for a temporary filling, and the crown forced over the root, and the patient directed to bite upon it, in order to secure the proper occlusion of the teeth. The 784 MECHANICS—DENTAL PROSTHESIS. croAvn is then firmly held in place until the cement has hardened, when the small hole through which the surplus has escaped can be filled with gold. Any slight defect in the articulation can be remedied by grinding Avith corundum points. The method of Dr. H. W. F. Buttner is a combination of the ferrule, or band encircling the root, and a central pivot, and is described as folloAvs by Dr. J. E. Dexter: " A special set of instruments is used in this process. Those for preparing the root are drills, reamers and trephines (Fig. 659 6 cd). The drill bores out the root canal. The reamer cuts the face of the root level, being guided by a central pin. The trephine turns the neck truly cylindrical for a certain distance up or doAvn its sides, being also guided by a centre pin. The root, thus prepared, is shoAAm in Fig 660. The drill, reamer and trephine are in various and exactly corresponding sizes. "A steel wire is noAV placed in the root, projecting half an inch. An impression is now taken, the wire projecting through it; a cup with an opening over the root being used for that purpose. The Fig. 659. Fig. 660. Fig. 661. wire is withdraAvn carefully before removal of the impression from the mouth, but is afterward replaced. OATer it, on the impression, is now slipped that one of a set of brass root models (Fig. 659a) which corresponds to the drill and trephine used, and the model is then made, and holds the brass root model in its place, Avith the wire projecting. The latter is now removed, and plaster cut from around the root model to a depth sufficient to accommodate the cap which is to follow. This is of gold, struck out of the solid, on that one of the accompanying steel dies which accords Avith the trephine and root model used. It also has a central pin, to cor- respond with the drill Avhich enlarged the root canal (Fig. 660). CROAVN AND BRIDGE-WORK. 785 This cap is set on the root model, and a plain plate tooth, ground IioIIoav on the inner surface, to cover the outer Avail of the gold cap, is backed, and soldered in place on the cap—of course, after re- moval from the brass root model—the solder forming the palatal contour. The Avhole is iioav polished, placed on the root, and driven home Avith a mallet (Fig. 661 \ "The perfectly accurate fitting of this operation is secured, be- yond cavil, by the set of drills, reamers, trephines, dies and root models Avith Avhich it is performed. Probably—indeed, almost certainly—this is the strongest method of attachment of artificial crowns to natural roots which can be devised. Indeed, the only thing breakable about any given case of this method seems to be the porcelain crown or face. The end and interior of the root, also, are absolutely preserved from moisture for, at least, a very long time." Another method of forming banded root-croAvns is described as follows by Dr. C. S. W. Bakhvin :* " Select a Logan crown slightly shorter than Avould be used for setting Avithout a ferrule. Countersink and prepare the inside of a root as for a Bonwill or any ordinary crown. If the outside of the root at the margin of the gum presents an irregular surface, then Avith Dr. Walter Starr's reducers (Fig. 657) shape it to such a size that the ferrule may be perfectly adapted to all parts. Take an impression, and produce in zinc or Babbitt's metal a die, to form which take a plaster model of the root-end, an eighth of an inch long, and shellac it to the point of a cone, Avhich can be easily made by turning doAvn a large spool, thus making the deep mould in sand into Avhich the metal is poured. With this die strike the gold (22-caret, No. 30 gauge, is most commonly in use), laid upon soft lead. A feAV blows will produce a seamless and per- fectly-fitting cover and ferrule. After trimming this to fit the fes- toon of the gum, drill in it from the loAver side a hole for the pin of the croAvn, leaving the ragged edge produced by the drill. Then fill the countersunk portion in the porcelain croAvn with oxyphos- phate of zinc, and Avith the gold ferrule or cap in place, adjust the croAvn as you Avould Avish it Avhen completed. AYhen the oxyphos- phate is hard, you Avill find the ragged edge on the upper side of the cover will materially aid in removing and keeping the cap where it belongs. Unite the cover to the platinum pin in the crown with a small amount of soft solder,—tin and lead,—using muriate of zinc as a flux, a feAV blasts from the blowpipe being all the heat required. Then fill the root Avith oxyphosphate and firmly * Dental Cosmos, vol. xxviii. 50 786 MECHANICS—DENTAL PROSTHESIS. press to place. These caps might be made up at leisure, providing a few variations for double and single rooted teeth. When a case is met that you cannot fit from your stock, choose a cap larger than the end of the root, and with a single clip of the shears cut to the centre of the cap, and with pliers spring together, lapping the edges until the size required is obtained. Solder with gold solder by holding over the spirit-lamp, and proceed as before. " Fig. 662 shows a root, cover, and Logan crown ready to be assem- bled for the soldering of the croAvn-pin to the cover; Fig. 663 shoAvs Fig. 662. Fig. 663. Fig. 664. the cap cemented and soldered to the crown, and Fig. 664 the com- pletely crowned root." Dr. H. C. Merriam describes a new form of artificial crowns as follows :* " We need a crown that can be ground on its sides as well as against the root, with a straight hole through it, similar to that of the English tube teeth, excepting that the hole should come out at a greater distance from the cutting edge in the incisors and cuspids. After the crown is ground, to place the hole through, it may be formed as we desire with a copper drill and corundum, or with hard-rubber points dipped in corundum. " There are now made, for use in machine-shops, wheels the cor- undum of which is united with a flux, and baked at a temperature of nearly three thousand degrees. These wheels hold a true edge, and when made small enough will be a great step in advance of what we have. I have had small points made in this way, with Dental Cosmos, January, 1887. CROWN AND BRIDGE-AVORK. 787 which I can grind out a crown to any of the forms illustrated in Fig. 665. " I iioav shoAV you some of the different varieties that can be made by grinding the crown just referred to (Fig. 666), the advantages of Fig. 665. Fig. 666. which have already been stated. With these crowns it is expected that dowels will be used, set in either cement or gutta-percha. " We will noAV pass to forms which are to be secured by metal bands fitted either to the root or to the crown itself (the strongest, of course, being held at their periphery), and I will detail my method of applying the same, for it enables me to avoid the trouble and delay of investing or soldering. For these the crowns given in Fig. 665 may be used, as well as those shoAvn in Fig. 666. "The band is fitted to the root, and the crown ground into the band after proper occlusion with its antagonist has been obtained. If a molar, a fine groove is ground around it, and the band, after being corrugated on its inner surface with a small lining burr, is placed on a lead anvil and the tooth driven into it, thus partially securing the advantage of union by gomphosis. The common glass stopper is a good illustration of how little more than its fit would be required to retain it firmly in place. For this little I have draAvn on the tube-teeth Avorkers of England. A few small pieces of sul- phur are then placed inside the band, and all held over a small flame until the sulphur melts and Aoavs into the groove between the band and the croAvn. Zinc phosphate may be used before the crown is forced in, or some flux—borax, for instance, which melts at a Ioav temperature, though this would probably require invest- ing. We then have a crown which, if a molar, I do not fear to attach with gutta-percha without dowels; but others may not have this confidence, and dowels may either be put into the roots or set 788 MECHANICS—DENTAL PROSTHESIS. in the crown with cement, and aftenvards secured to their places in the root as usual (Fig. 667). It is evident that if cement is strong enough to hold a dowel in the root it must be equally serviceable in securing the crown to the dowel. Some like the hardest way best. These may fit a fine platinum or pure gold wire into the Fig. 668. Fig. 670. Fig. 671. groove around the crown (Fig. 668). Drive in as before; invest and solder (Fig. 669). A gold amalgam may be used, such as Avas em- ployed by old plate-workers for banding a plate over the teeth. I have not tried this, but suggest it as of possible use, the dowels being Fig. 672. Fig. 674. put in as before. For the incisors the groove should not run around the anterior face of the crown, and I have not soldered these teeth in (Fig. 670). I have entire confidence in any form for the incisors and bicuspids where the root is Avell banded, the dowel put into the centre, and the crown forced to place in gutta-percha (Fig. 671); while for the molars, if quite short, I do not care for the doAvels. CROWN AND BRIDGE-AVORK. 789 You Avill notice that this method does away with much of the show- ing of gold in molars Avhere such a result is desired (Fig. 672). " When cohesive gold Avas first used Ave thought nothing could be more beautiful,—the more conspicuous the better,—but Ave gradu- ally learned that the perfection of art was to conceal art. So it is Avith tooth-croAvns, and Ave shall learn soon to omit great backings, etc., Avberever possible; not only because they are conspicuous, but because a tooth backed up by any substance is no longer trans- lucent. " I Avill present one more form for molars, and although it shows more gold than any of the others, it is perhaps the strongest of all. The band is made full Avidth down to occlusion, and any large, strong tooth is ground to fit the space to be filled in the arch. This is driven into the band so as to be even Avith its edge; cemented Avith sulphur as before, and I think we have a croAvn that is made for all time (Fig. 673). " Setting.—I first varnish the band inside with Canada balsam dis- solved in ether; then fill the crown with gutta-percha and crowd it up against the root several times to get an impression. When sure that I have the right amount of gutta-percha, I place the doAvels in the root (if I am to use them); heat the croAvn; dip it into cajeput or any essential oil, and croAvd it to place. The doAvels I fit in the same Avay, Avrapping them Avith gutta-percha and Avorking up and doAvn in the root until I get the impression before the final forcing to place. I thus have the advantage of the dowel and hard centre of gutta-percha to act as a plunger, and the soft, semi-dissolved gutta-percha comes back on the outside of the mass, forming, I think, the tightest root filling known. I fill roots in this Avay with gutta- percha points Avhen I do not use a doAvel. The dowels used are made by Avrapping a piece of platinum and iridium Avire with about one-third of a sheet of gold foil, Avhich is melted on and the com. bination made true by being drawn once through a Avire gauge. A piece of piano-wire is then Avound around it three or four times to serve as a guide, and a fine platinum wire, previously drawn square, is caught and turned through the wire-guide a feAV times, Avhen the Avinding may either be finished by hand, or the end, after being started, may be placed in a lathe-chuck and wound up at once (Fig. 674). A piece of gold foil is then wrapped around the Avhole and the fine Avire soldered on. A dowel made in this manner is not strained by having its thread cut, and the thread, being square and coarse or fine as you wish, is strong and possesses plenty of grip. " Should these forms prove as valuable as I hope, those at a dis- 790 MECHANICS—DENTAL PROSTHESIS. tance from the cities, without gas, will find that the labor of crown- ing roots has been much lessened. " When a root has broken off far under the gum it should be filled with gutta-percha, and a temporary plate worn—if the loss be in the front of the mouth—until the root works down, Avhen it may be croAvned and the plate given up. " In preparing roots after a large portion of the crown is broken away, I enlarge the pulp-chamber with a large, round burr, and, when even Avith the gum, follow with the reA'olving saw here shoAvn (Fig. 675). With this saw I often cut off the remnants of a croAvn from the inside without wounding the gum or drawing a drop of Fig. 675. Fig. 676. ® II I t\ blood, and am saved the unpleasantness of running a stump cor- undum wheel in the mouth. The outside of the root can sometimes be formed Avith the instrument here shown (Fig. 676)." Fig 677 represents porcelain cusp-crowns. These porcelain cusps are designed for use with a gold band representing the body of the tooth. The band or collar is first fitted to the suitably prepared root, and the cusp-crown is then fitted in the collar. The collar is then filled with gutta-percha, cement, or amalgam, and the crown pressed into place. 1 shows in section a molar root, collar, and cusp-crown. 2 shows the same mounted. In cases where it is desirable to show as little of the gold collar as possible the forms indicated in 3 and 4 may be employed, the gold band being cut away on the buccal side, as shown in the cuts. Dr. E. T. Starr, in the Dental Cosm,os, describes an improved " die- plate " and " hubs " for shaping metal cap-crowns of his own sug- gestion : CROWN AND BRIDGE-WORK. 791 " In the construction of metal cap-crowns to cover natural teeth or teeth-roots there are many methods Avhich result in good work, hut in most cases the caps do not articulate as Avell as they might, for the reason that means for embossing the bicuspid and molar cusps are not at hand, or available Avithin the short time at the dis- posal of either the patient or the dentist. With the object of pro- viding an easy and quick Avay of Avorking under such circumstances, Fig. 677. I have made a single plate (Fig. 678) in which are four groups of in- taglio dies representing Avith distinctive correctness the peculiar cusps of the upper and loAver right and left bicuspids and molars. These are indicated by the Hillischer notation, so that each form may be easily identified in practice. " The hubs A B (Fig. 679) are of the sizes shown, and are made of an alloy composed of tin one part, lead four parts, melted together. The mould C should be Avarmed, the melted alloy poured in every hole, and the overfloAV Aviped off just before the metal stiffens. This will make the butts of the hubs smooth and flat. After a minute or tAvo the mould may be reversed, the hubs shaken out, and the casting process continued until a considerable number of hubs shall have been cast. " In Fig. 680 a molar hub is shoAvn in place on a piece of No. 32 792 MECHANICS—DENTAL PROSTHESIS. gold plate, Avhich lies over the 6- (upper right first molar) die. A succession of blows on the hub, Avith a four-pound smooth-faced hammer, will drive the plate into the die, and at the same time Fig. 678. spread the hub metal from the die centre to its circumference in such a manner that the plate will be perfectly struck-up with the Fig. 679. least possible risk of being cracked. The flattened hub is seen in Fig. 681, which also shows at D the obverse of the struck-up hub, CROWN AND BRIDGE-AVORK. 793 and at E the cameo of the struck-up plate having every cusp and depression of 6- sharply defined. " The counter-die plate (Fig. 678) is made of a very hard cast metal, Avhich will admit of the striking up of many croAvn-plates by Fig. 680. the means and methods described, if the croAvn-plates be not too thick and stiff. Of course they should be annealed before they are placed over the die. In careful hands, the die-plate should give clear cusp definitions after years of use. " For the reason that the counter-die plate is in some respects similar to a stereotype plate for printing, the struck impressions on Fig. 681. tAvo strips of thin plate will appear as in Fig. 682, Avherein their regu- lar order is noticeable as seen from the cameo surface of the struck plates. The peculiar action of the hub in forming first the centre of the croAvn plate, and spreading from the centre outAvards, as the hub is shortened under the hammer, until the die is overspread by the plate and hub, Avith the result shoAvn in Fig 681, is an essential feature of this process for obtaining easily and quickly the superior 794 MECHANICS—DENTAL PROSTHESIS. styles of coronal cameos shown. If a cusp or fissure should chance to crack in hubbing, a small piece of plate may be struck over it, or another croAvn plate be struck over the first and the two soldered together. " The depressions in the struck plate can be partly or wholly filled with scraps of plate or solder, and the surplus plate cut away from the cameo. " The fact is noteworthy that, by means of the Knapp bloAvpipe, the coronal intaglio may even be filled Avith melted scraps cut from the identical plate out of which the cameo was struck. The better Fig. 682. RIGHT. left. right. LEFT. way, however, is to fill, say a twenty-caret cameo with eighteen- caret plate scraps. The fitting and soldering of the doubled or filled cameos to suitable collars is a simple matter, and need not be described. " It only remains to add the statement that, by this counter-die and hub process, gold, platinum, silver, or other metallic cap-crowns having finely-formed and solid cusps for proper occlusion and re- sistance to wear, can be made with little trouble and in a very short time." Artificial Crowns Attached to Natural Teeth, without Plates or Clasps.— These operations are of comparatively recent date, and are gen- erally known as " bridge work " or " grafting," which is simply an extension of artificial crowns over the spaces made by the loss of �5949759 1799999 CROWN AND BRIDGE-WORK. 795 natural teeth. The credit of first inserting artificial croAvns to ad- joining natural teeth, by fillings of cohesive gold foil, is due to Dr. B. J. Bing, Avho describes his method as follows : " In the ease of inserting a central incisor, a cavity must be made in the palatine depression of the adjoining central, and also the lateral, and one in the approximal surface of either of these teeth, about the place where we usually find decay on these surfaces. An impression is then taken which will show these cavities, and a gum or plain plate tooth carefully fitted and backed Avith gold, observ- ing the precaution of allowing a small point of the backing to extend into the approximal cavity. Two little griffes (bars) are then Fig. 683. Fig. 684. Fig. 685. Fig. 686. Fig. 687. soldered to the base of the backing, the ends of which are carefully plugged into the palatine cavities Avith gold foil, in such a manner as Avill tend to draAv these teeth very slightly together." Figs. 683, 684, 685, 686, 687 represents Dr. Bing's bridge-teeth. Fig. 683 represents porcelain crowns having two strong pins of platinum baked in each side, the pairs of pins being so placed that the tooth when fixed in position is held firmly in proper relations to the adjacent teeth. Fig. 684 shows the supporting teeth pre- pared to receive a lateral incisor. Fig. 686 is a face view of the same in position. Figs. 685 and 687 show the same in the case of a bicuspid croAvn. 796 MECHANICS—DENTAL PROSTHESIS. These croAvns may be soldered to each other, or to collars and to cap-crowns, in the construction of every form of bridge denture. Dr. W. F. Litch has modified Dr. Bing's method, an abridged description of which, by Dr. Dexter, is as follows: " Supposing a left upper lateral to be inserted: Take an accurate impression of the parts (canine and central, and gum betAveen), and make metallic dies from the model. Swage gold or platinum plates to very exactly fit the palato-approximal surfaces of the canine and central. Fit into the interspace a plain plate lateral incisor, slightly Avider than the space to be filled, bevelling and grinding the sides posteriorly, so that the tooth cannot be forced backward betAveen its neighbors; the neck fitting accurately, but lightly, upon the gum. Back the tooth with gold. Place the prepared tooth and the struck plates upon a perfect model of the parts, and adjust the tooth backing accurately to the plates on each side. Cement together Avith shellac or other resinous cement; remove and complete the final adjustment in the mouth. Invest, and solder the tooth and plates together in their exact relath'e positions, observing to accu- mulate a large portion of solder over the joints (Fig. 688). The apparatus, if now placed in the mouth, will be found self-support- ing against any force except the perpendicular; for it cannot be forced backAvard into the mouth, OAving to the extra Avidth of the lateral; nor forward out of the mouth, OAving to the Avings or plates extending over the backs of the neighboring teeth; nor upward toward the gum, owing both to the porcelain tooth resting thereon, and to the converging planes of the plates or wings and the postero- approximal surfaces of the artificial tooth. " The methods of final attachment are two, depending upon the case: 1. If one of the neighboring teeth is devitalized, attaching a pivot to the plate on that tooth and inserting it with gutta-percha, the plates themselves being covered with a film of the same sub- stance on their dental aspects (Fig. 689). 2. If the teeth are both alive, a modification of Bing's plan of filling, performed as follows: CROWN AND BRIDGE-WORK. 797 "The denture being constructed as before described, and polished, drill a cavity in the centre of the palatal face of each tooth covered by the plates, slightly larger in diameter than the head of the pin in an ordinary rubber tooth, no deeper than the enamel, and under- cut (Fig. 690 b). To each of these openings fit a platinum one- headed rivet, the head being very thin and perfectly flat on each side. Split the shanks of the rivets nearly to the head (Fig. 690 a). Make openings in the plates to exactly correspond wdth those in the teeth, and countersink them deeply on their palatal aspect. Place the gutta-percha on the dental surfaces of the plates, as described, and j tress the denture to its place in the mouth. When the cement is cooled and hard, remove that portion pressed into the holes in the plates and teeth, pass the rivet heads through the holes in the plates to their seats in the tooth cavities, and fill them in position with gold. When the fillings have reached the level of the tooth Fig. 690. Fig 691. Fig. 692. surfaces, spring open the split rivet shanks and continue packing gold around and between the separated parts and into the counter- sinks in the plates until flush Avith the plate surfaces. Cut off the surplus pivot shanks and finish (Fig. 690)." Dr. Litch's method can also be adapted to the restoration of fractured angles of incisor teeth, as shown in Figs. 691 and 692, and which need no further description. Fig. 693 represents a case of two bicuspid croAvns secured to one root and two adjoining teeth. The late Dr. M. W. Webb also modified the methods of Dr. Bing by forming an undercut groove in the porcelain croAvn in each side and along the cutting-edge, and filling gold foil solidly in the groove and slightly over the cutting-edge, to make the porcelain croAvn more secure than the platinum pins hold it, and to protect the edge from the occlusion of the loAver teeth ; also to build the croAvn into the approximal surfaces only. 798 MECHANICS—DENTAL PROSTHESIS. Dr. Webb also described a method by which a croAvn Avithout plate or clasps and where no root remains can be inserted : " After suitably forming the cavities in the proximate wall of each tooth next the space left by the loss of the one that had been extracted a plain porcelain croAvn Avas fitted to the place and backed Avith gold plate. A portion of the backing extended about one and a half lines from each side of the croAvn for insertion in the cavities prepared in the adjoining teeth, and to these parts a gold Avire Avas soldered to fit into the pulp-chambers of the adjoining teeth. A small gold plate was then formed to fit upon the gum, covering as much space as was taken up by the neck of the natural tooth. When the backing was riveted to the pins in the crown and this placed in position, and Avhile the whole rested on the small plate Fig. 693. upon the gum, the backing and plate were so secured by Avax that they could be removed intact and soldered. Each extended side of the backing and the surface of the wire was barbed, so that the gold foil would the better secure the crown when filled into every part. The crown Avith the gold attachments being ready for inser- tion, oxychloride of zinc (or oxyphosphate) was placed in the pulp chambers of the adjoining teeth and the crown at once pressed to place. Wh*en the cement had hardened, a portion of it was cut away, so as to make proper anchorage for light, cohesive gold foil, which was impacted in small pieces around part of the wire and that portion of the plate extending into the cavities, and the crown was then secured." To avoid any danger of the porcelain crown being broken from the platinum pins, Dr. Webb suggested that a groove be cut in each CROAVN AND BRIDGE-AVORK. 799 side, and along the cutting-edge of this crown (Fig. 694 d), so that gold foil may be impacted into it by means of a fine-edged corundum disk, after a heavy backing of gold plate and the wire have been fixed in place and soldered (Fig. 695, a). Into this groove the Avire to connect the artificial crown Avith the natural teeth is to be placed (Fig. 694 a). When the operation of contouring the palatal surface of the crown with gold foil is completed, the case presents the appearance shown by Fig. 696. Dr. Webb also made use of a stout wire (No. 13), with a screw thread cut upon one end, for insertion into a devitalized tooth, and Fig. 695. bent to receive the porcelain crown which was soldered to its free end, the Avire being secured in place in the natural tooth by filling around it with gold foil (Fig. 697). Figs. 698, 699, and 700 show an extensive operation performed by Dr. M. W. Webb, in which he made use of gold wire (No. 13) for bridging a lateral incisor, the natural tooth having been lost, and also the crown of the left cuspid, and disintegration having taken place in many of the teeth, and the front teeth abraded to the den- tine. Fig. 698 shoAvs the cases as prepared for filling, with the arti- ficial croAvn attached to the gold Avire in position, and gold screws inserted in the pulp-chambers of the cuspid and bicuspid teeth. Fig. 699 shoAvs the labial contour of each croAvn after the lost portions Avere restored with gold foil. Fig. 700 shoAvs the finished case. What is knoAvn as the " mandrel system " of bridge-denture is described as follows: * In all of the various systems of crown and bridge-work which have been brought to the attention of the dental profession, one very important point seems to have been overlooked, viz., the compara- * Dental Cosmos, Aug., 1886. 800 MECHANICS—DENTAL PROSTHESIS. Fig. 698. Fig. 699. Finished case—a, b, d,f, g and h, pulpless teeth ; g, whole crown restored with gold ; aj and h, almost entire gold crowns; the teeth b and d support the gold crown faced with por- celain, c, and fully one-fourth of the crown of each of these is restored with gold, as is also that of e, the pulp of which is living, CROAVN AND BRIDGE-AVORK. 801 five conformation of the necks of different classes. The general forms of the croAvns of teeth have long been Avell-knoAvn, but so far as we are informed no systematic classification of the shapes of the necks has heretofore been made. It Avould appear that such a clas- sification ought to form the basis of any system of crown and hridge-Avork claiming a scientific foundation. To lay the ground- work of the system here described a large number of human teeth of the various classes Avere secured, their croAvns cut off, and the shapes of the stumps accurately determined ; thereby devoloping the fact that, no matter how great differences may exist in the ap- parent shapes of the crowns of individual teeth of a given class, there is a remarkable uniformity in the configuration of their necks. That is, the necks of upper cuspids, for instance, Avere found to have a fixed type, from Avhich the variations were very slight as to shape, though there appeared to be no exact standard of size. So of the other classes, Avith the single exception of the superior molars, in which hvo distinct forms Avere found, the first being those in which the buccal roots Avere Avider than the palatal; the second, those in which the reverse condition Avas found, the single palatal root being wider at its junction with the croAvn than the tAvo buccal roots. The occurrence of roots of the second class being rather exceptional, the first class Avas accepted as the type. The configuration of the necks of all the teeth having been de- termined, a set of mandrels for shaping collars to fit them Avas de- vised. The set (Fig. 701) consists of seven mandrels, six of Avhich are double end. Their shapes are modelled upon the general typal forms of the necks of the teeth Avhich they represent, and they are made tapering to provide for all required variations in size. The illustrations are about t-Avo-thirds actual size, the longest instruments being nine inches in length. The cross-sections shoAV the shapes and proportionate sizes at the greatest and least diameters. The long taper permits the most minutely accurate adjustment of the collars. No. 1 is a double-end mandrel, for superior molars, right and left; No. 2 is a single mandrel, for superior bicuspids, right and left; No. 3 is a double-end, for superior cuspids, right and left; No. 4, double-end, for superior centrals, right and left; No. 5, double-end, for inferior molars, right and left; No. 6, double-end, for the infe- rior centrals, laterals, cuspids, and first bicuspids, right and left; No. 7, double-end, one end for the superior lateral incisors, the other for those bicuspids in Avhich a bifurcation of the roots, or a ten- dency in that direction, extends across the neck to the croAA'n, in the form of a depression on one or both approximal sur- 51 Fig. 701. Right Inferior Central, Lateral, /sss Cuspid, and First Bicuspid. Left QO O to Bifurcated Bicuspid. Superior Lateral and Inferior Second Bicuspid. Mandrels for Shaping Seamless Tooth-Root Collars, Fig. 702. o O O O O O s' 1 2 9 Q 3 4 5 6 V 8 9 lO 11 12 13 14 15 o q © and fV inch) are made (Fig. 702), Avhieh it is be- lieved Avill cover all requirements. These collars, although devised as a part of the system, can be used in all methods of crown and bridge-Avork which require bands, and possess many advantages over any others. They are really labor-saving devices, as their use saves the time and trouble of making, and there is no danger of their coming unsoldered when the pins or the backing of the croAvn is being soldered; and there are no hard spots to give trouble in burnishing, as, for instance, close to the root, after the collar has been shaped and placed in position, the whole surface being uniformly soft. The seamless collars are also especially adapted to remoA'al or detachable bridge-Avork. They are so constructed that Nos. 1, 16, and 31 exactly fit into or telescope AAdth Nos. 2, 17, and 32, and so on through the entire set, each collar fits into the series next higher; so that a root may be banded with one size and the size next larger used to form the tube for the telescoping croAvn. Their advantages for the construction of cap-croAvns are obvious. The other appliances specially devised for this system are, a re- ducing-plate or contractor, a pair of collar pliers, and a hammer. The contractor (Fig. 703) contains holes Avhich are complemen- tary in shape to the mandrels. The mandrels being applied to the inner circumferences of the collars, while the contractor must admit the collars themselves, the short taper of the holes in the contrac- tor necessarily covers a somewhat greater range of size than is shown in the mandrels. With this appliance collars can be evenly and ac- curately reduced in size at the edges, Avithout burring or buckling. The illustration is actual size. The collar pliers (Fig. 704) are for contouring the collars to shape, one beak being made convex and the other concave to corre- spond. With this appliance the slightest changes required in the contour of the collars are easily made. About a half inch from the extremity of the concave beak a small bar of flat steel is attached to it by means of a screAV. The free end of the bar has a minute projection upon one face, the other being reinforced to fit into the concavity of the beak. In the centre of the face of the convex beak CROWN AND BRIDGE-WORK. 805 is a depression, into Avhich the projection on the steel bar strikes, making a very efficient punch for forming guards or stops to pre- vent the collars from being forced too far under the gum. The de- pression in the convex beak being slightly larger than the projection Fig. 704. or punch, the metal is not cut through, but merely raised on the side opposite to the punch. The punch attachment being pivoted can be swung to one side Avhen not in use. Fig. 705 is a mallet or hammer, with steel face and horn peen. The handle is 9 inches long. One of the appliances required is a lead anvil, Avhich being only a piece of soft lead, say 2x3 inches and an inch thick, is not illus- trated. The female die of an ordinary case will ansAver very Avell. 806 MECHANICS--DENTAL PROSTHESIS. To illustrate the uses of these appliances, take a case in which two inferior bicuspids of the left side are missing, and the crowns of the cuspid and first molar so badly decayed that the probabili- ties are that they Avill soon fall victims to the forceps. The old-time way Avould have been to extract the molar and cuspids, and make a partial plate. Examination, hoAvever, sIioavs that the roots of these two teeth are in good condition, affording an excellent oppor- tune for the construction of a piece of bridge-work. With a corundum point or rotary file, cut off the remaining por- tions of the crowns level with the gum margins. Prepare the roots in any of the well-known ways, thoroughly cleansing the apical portions and filling them with whatever material is desired, being careful only that the work is well done. For the better retention of the filling-material to be placed in the pulp-chamber, retaining- grooves can be made or retaining-posts inserted. Take a piece of binding-Avire (No. 26, American gauge), say 2J inches long, pass it around the neck of the molar stump, cross the free ends, and, hold- ing the wire in place with one finger, twist the ends Avith a pair of flat-nose pliers until the wire clasps the neck closely at every point (Fig. 706). Where there are irregularities in the contour of the tooth, it is necessary to press the wire into them Avith an ap- proximal burnisher. It is obvious that the ring thus formed Avill show the exact size and shape of the neck of the tooth. Remove the ring carefully, lay it on the lead anvil, put over it a piece of flat metal, and with a smart blow from a hammer drive the Avire into the lead (Fig. 707). Upon removing the wire an exact impression of the ring will be left in the lead anvil. (This part of the work, as indeed all others, should be done carefully as described. The wire ring may be driven into the lead by a direct blow of the hammer face, but the blow might not strike equally, and the interposition of the flat metal held level insures an even impression. A piece of an old file is best, as the file-cuts keep the wire from slipping) Next, cut the wire ring at the lap, straighten out the Avire, and select a suitable collar by comparing the length of the wire with the straight lines in the diagram (Fig. 702) which show the inside diam- eters of the various sizes. Should none of these correspond exactly, take preferably the next size smaller. It will be remembered that the collars are No. 30 in thickness, Avhile the wire with which the conformation is secured is No. 26. This difference permits the collar when contoured to shape to enter the lead impression readily, a decided advantage in fitting. Having selected the collar, fit it to mandrel No. 5, with the peen of the hammer, holding it upon the lead anvil, and using a slight pushing force to help in stretching Fig. 705. CROAVN AND BRIDGE-WORK. SO, Fig. 707. Fig. 708. Fig. 709. wwm'Z 73 808 MECHANICS—DENTAL PROSTHESIS. and forming it (Fig. 708). Having driven the collar to form, remove it from the mandrel and try in the lead impression. If it does not fit exactly, return it to the mandrel and stretch it a little, Avhen it will usually fit perfectly, as the mandrels have been designed care- fully to the average shapes Avhich obtain in the great majority of tooth-necks. In the exceptional cases where the collar does not fit it can be readily contoured to the exact shape Avith a pair of flat-nose pliers. Of course, if it fits the impression in the lead, it Avill fit the neck of the tooth, ahvays provided the measurement and the impression have been carefully made. If the collar or band has been accidentally stretched too much, or if for any reason when brought to shape it is too large, its root end can easily be reduced to the proper size by the use of the con- tractor. Place the edge of the collar which is to fit the root in the proper hole ; hold it level Avith a piece of file as in taking the lead impression of the ring, and tapping lightly on the file drive the collar into the plate (Fig. 709) until the proper reduction is made. The collar is next " festooned " to correspond to the shape of the maxillary ridge. Lay it, gum edge up, on the lead anvil, and with the piece of flat file and the hammer drive it into the lead. A feAv cuts with a fine half-round file across the approximal diameter will conform the edges to the surface of the ridge (Fig. 710). Then place the collar in position, and, having ascertained just how far it should go down on the root, remove it, and with the small spring punch in the collar pliers form projections on the inside of the band at the proper points to serve as stops, which, resting on the top of the root, will prevent the collar from being forced further doAvn upon it than is desirable (Fig. 711). A collar for the cuspid is then fitted in the same maimer, using mandrel No. 6 for shaping, after which the case is ready for the building of the bridge. Place both collars in position and take ah impression of the parts, including the interiors of the excavated pulp chambers, from which make a cast in the usual way. Bend a short piece of half- round gold or platinum wire into the form of a horse-shoe, the two extremities of which shall fit into the roots of the molar. Then take a longer piece of the same Avire, somewhat more than enough to extend from the toe of the horse-shoe Avhen in position to the cuspid root; bend one end of it at a right angle, or nearly so, to fit the root of the cuspid, and (cutting off any excess of length) solder the other end to the toe of the horse-shoe. The bar extending between the tAvo roots is the truss of the bridge. Next, place the appliance on the cast (Fig. 712), holding it in position with Avax, CROAVN AND BRIDGE-AVORK. 809 and select the teeth to take the place of the missing bicuspids and molar. The best form for this purpose is a tooth having holes extending through it vertically from the neck to the grinding surface similar to the Avell-knoAvn Bomvill croAvn. The crowns used should be large enough to fill the space rather tightly, even if their sides have to be flattened slightly to let them in. If the teeth do not fill the space tightly, a small portion of Fig. 710. Fig. 712. plastic filling material croAvded betAveen them, as mortar betAveen the granite blocks in the arch of a railway bridge, will greatly in- crease the strength of the Avork. > After the teeth are ground to fit and the proper length for occlu- sion is ascertained, the truss is covered Avith a thin film of Avax, upon Avhich the croAvns are again pressed to their positions. Upon the removal of the croAvns the impression of the holes running through them will be found in the Avax. At these points drill holes through the bar Avith a small twist-drill run by the engine, and into these fit and solder the pins for the support of the crowns. The bridge is iioav ready to be attached permanently. Set the crowns in position upon their supporting pins to secure the proper alignment. (If the operation Avere upon the upper jaAV they Avould have to be held Avith Avax.) Put into the canals of the supporting roots (the cuspid and first molar) a sufficient quantity of some 810 MECHANICS—DENTAL PROSTHESIS. quick-setting plastic, as oxyphosphate, to about half fill the pulp- chamber, but not enough to prevent the supports of the truss from being forced home. Force the bridge supports to place, and after allowing the filling material to become set remove the crowns. Fill the remainder of the pulp-chamber and the whole of the collar Avith gold or Avith amalgam, gutta-percha, oxyphosphate, or any suitable plastic (Fig. 713). Set the crowns permanently, the molar and cuspid first, as this affords greater facility for the trimming off of any ex- cess of the filling material used in the attachment. For attachment of the crowns, gutta-percha is probably the best material, as croAvns set with it are readily removed for the correction of any inaccuracies of occlusion or alignment, by grasping them between the beaks, previously warmed, of a pair of universal lower molar forceps. The heat Avarms the gutta-percha and releases the tooth, Avhich can then be re-set properly. In attaching croAvns AVith gutta-percha the holes in the croAvns are first filled Avith the material, after Avhich the croAvn Fig. 714. is warmed and forced to place. Any of the other plastics ordinarily used in setting Bonwill crowns can be employed at the discretion of the operator. Fig. 714 shoAvs the case completed. In securing the occlusion of a piece of bridge-work it is Avell to make the artificial teeth a little short, so that the natural teeth on both sides will meet the first shock of mastication. Nature will correct the occlusion in time by slightly elongating the roots sup- porting the bridge. If the artificial crowns are permitted to strike the natural teeth from the first, the undue strain upon the two sup- porting roots may cause soreness and perhaps more serious conse- quences. When a sound tooth is to be used as one of the supports of the bridge, a modification of the method just described is necessary. Take a case where it is desired to bridge the space caused by the loss of the right inferior bicuspids and first molar. The crown of the right cuspid is nearly gone, but the root is sound and capable CROWN AND BRIDGE-WORK. 811 of supporting one end of the bridge. The other end will be attached to the second molar, Avhich is a sound tooth. Prepare and band the cuspid root as before ; dress off the second molar crown until it is slightly smaller than the neck, so as to permit a cap to be tele- scoped oA'er it, and take the measure of the crown Avith the binding- Avire. Select a suitable seamless collar of sufficient Avidth to extend from the neck to a little beyond the grinding surface, and drive it up on the proper mandrel to get the general shape, but not the full size required to fit the tooth, leaving it so that the edge having the larger circumference will just pass over the end of the croAvn ; place the collar on the tooth, and with a block of wood and the mallet tap it to place just beyond the free margin of the gum. This method Avill make a close fit, as the collar will readily stretch all that is necessary. With a sharp-pointed instrument mark the length of the crown, remove the collar, and cut it to the proper width as indicated. Then in a piece of gold plate of the thickness used for caps form four little depressions of the general character of an im- Fig. 715. pression of the molar cusps. An easy Avay to do this is to lay the plate on the lead anvil; then with the ball on the end of an ordi- nary socket-handle and the hammer the depressions are made in a moment. Set the collar on the plate, borax it, charge with solder, and heat till the solder flows. Cut off the surplus plate, and a perfect cap for the molar is made. Place it on the tooth and take an impression, and thereafter proceed as before directed to make the truss of the bridge and mount the teeth, except that in this case the posterior end of the truss is to be soldered to the molar cap. For the final attachment place a little oxyphosphate or any other plastic filling material in the cap to secure it firmly (Fig. 715), first cutting a slot in the crown end of the cap for the escape of the excess of material. Pressure upon the filling material hastens its hardening. 812 MECHANICS—DENTAL PROSTHESIS. Detachable Bridge-work. A description of two or three methods of constructing detachable bridges Avill suffice to indicate the general principles involved. Having these, each operator will find it an easy task to devise the modifications necessary to adapt a method to individual cases. The first method is especially applicable to cases Avhere both ends of the bridge are attached to roots,—as, for example, the inferior cuspid and second molar roots of the right side, the intervening teeth having been lost. The operation is conducted as described in the first case of fixed bridge-work doAvn to the construction of the truss, for Avhich in this method square gold wire is used. Having cut the wire of the proper length, lay it upon a piece of gold plate (about No. 26, American gauge) of the same length and full three times as wide, and placing the two upon the lead anvil, Avith a hammer and the piece of file before used drive them into the lead. This will form the plate into what Ave may call an open trunk, Avhich fits the square Avire. Remove the tAvo from the lead together, and, without separating them, curve to the proper shape to form Fig. 716. the truss. Grind croAvns having vertical holes, like the Bomvill, to fit, and having determined the proper points for the supporting pins, by the method already described, drill through both trunk and bar at these points. Separate the bar from the trunk, and fit and solder pins to the bar. Construct small tubes to fit the pins, ream out the holes through the trunk to admit them, and set the tubes with solder in the enlarged holes (Fig. 716). Fix the crowns permanently upon the tubes. They may be mounted in any of the approved ways, by vulcanizing or by the use of a plastic filling material. When they are firmly set, place the trunk Avith the teeth upon the bar, and CROWN AND BRIDGE-AVORK. 813 anchor permanently as already described. Fig. 717 shows the com- pleted Avork. In this method the truss consists of the bar and the open trunk which covers three sides of it. The bar is of course permanently attached to the roots of the molar and cuspid, but the trunk Avith the teeth can be remoA^ed at any time. The second method of constructing a detachable bridge is appli- cable to cases Avhere one or both of the supports or piers are sound teeth. In the case adduced for illustration the right inferior cuspid crown was decayed, and both of the bicuspids and the first molar Fig. 717. Avere absent. The supports for the bridge were the sound second molar and the cuspid root. After the cuspid root Avas prepared and banded, the crown of the molar Avas reduced very slightly,—not sufficient to destroy the enamel, but just enough to permit a collar properly fitted to pass over it. A collar somewhat Avider than the length of the crown from grinding surface to neck was fitted and cut to the proper Avidth. Tavo lugs Avere then soldered upon the anterior and posterior sides and bent to fit into the approximal fissures, which Avere slightly cut out to admit them. An impression was taken, the collar coming aAvay in the plaster, and a cast Avas made with the collar in position. A coned tube Avas then made for the root of the cuspid and a coned pin fitted into it. A truss of half-round Avire Avas made, to Avhich the coned pin and the molar collar were soldered ( Fig. 718). A half-clasp to grasp the lateral was next soldered to the end of the truss to be supported by the cuspid. The object of this clasp was to guard against the teeth being throAvn out of proper alignment by the force of mastication. Bomvill croAvns were then vulcanized to the truss, after their sup- porting pins had been fitted and soldered to it. (Countersunk crowns can be used as Avell in the same Avay. Plain plate teeth may also be used in this style of Avork, in which event they are to be 814 MECHANICS—DENTAL PROSTHESIS. soldered to the truss.) The bridge was then ready to be set, which was accomplished in the following manner: The cuspid rqot was nearly filled with oxyphosphate, and the coned tube Avas placed upon the pin. The band Avas put on the molar, and the coned pin with the tube upon it was forced into the plastic in the cuspid. As soon as this became set, the tube was held permanently, Avhile the bridge itself could be removed whenever desired (Fig. 719). This method of fixing the tube allows considerable range in its adjustment. In soldering the coned pin to the truss, care should be Fig. 719. taken to set it at an angle exactly parallel to the axis of the molar; otherwise there will be difficulty in removing the bridge. The third style of detachable bridge-work to be described involves the use of cusp crowns (Fig. 720) for supporting posts or piers. Suppose a case where both ends of the bridge are to be attached to inferior cuspid and second molar roots, the intervening teeth having Fig. 720. been lost; the bridge is, therefore, required to extend from the right inferior cuspid to the right inferior second molar, with only the roots of the two teeth named as supports. Prepare the roots and pulp- chambers. Set screw-posts into the dentine for anchorage or as re- taining-pins, and fit the collars, using sizes Avide enough to form the walls of the crowns. Fill the pulp-chamber and about tAvo-thirds of the depth of the collars with a plastic filling material, packing it well around the retaining posts. Select suitable cusp crowns for the Fig. 718. CROAVN AND BRIDGE-WORK. 815 molar and cuspid and place them in the ends of the bands to ascer- tain the occlusion. If too long, shorten the cusps or reduce the bands with engine corundums or rotary files, and when the correct articula- tion is found form a small square shoulder in the lingual edge of the cuspid and in the posterior grinding surface of the molar. Fill the remaining portion of the collars Avith plastic mixed somewhat thinner than the first lot, and set the cusp crowns in position. If there are antagonizing teeth the mere closing of the patient's jaAvs will force the croAvns to place. If there are no antagonizing teeth the croAvns can be readily tapped to place with the mallet, using a piece of Avood as a driver. AHoav the filling material to set firmly, trimming off any excess Avhich may exude around the collars. bridge supports or piers constructed on this plan are strong and durable, and likely to AAdthstand any strain. Take an impression, and proceed to fit seamless collars to telescope over those alreadj' Fig. 721. set upon the cuspid and second molar roots. It Avill be remembered that these collars are so made that each size telescopes into the next higher series. If the proper sizes are selected for the outside or female bands, the Avork of fitting is readily and quickly accom- plished, forming tubes Avhich slide easily over the supporting piers, and at the same time fit closely. It is only necessary to take care in shaping the tubes not to drive them too far up on the mandrels and thus stretch them so as to destroy the fit. To the outer end of each of the tubes solder a small piece of gold plate, forming partial caps so placed as to rest Avhen in position upon the shoulders pre- viously cut in the cusp croAvns. Adjust a truss bar of half round gold Avire, to the ends of which solder the tubes (Fig. 721). The 816 MECHANICS—DENTAL PROSTHESIS. truss is noAV ready for the teeth, Avhich may be of any of the forms used for this purpose, and they may be attached to the bar in anv way desired. One of the strongest attachments is vulcanite. An easy modification of the plan just described is readily adapted to cases where only a small space is to be filled and one end of the bridge is to be supported by a sound tooth. Thus, suppose it is desired to bridge a space formerly occupied by the tAvo inferior left bicuspids, the croAvn of the first molar being a mere shell. The operation Avould be essentially the same as in the previous case, except that the sound cuspid Avould be utilized for one of the piers as follows: Fit a seamless collar, cut out a portion of it so that it will embrace only about two-thirds of the cuspid croAvn, and solder a partial cap or cover to it, as illustrated in Fig. 722. Or, if deemed preferable, the cuspid may be separated from the lateral incisor with the corundum disk and the collar allowed to embrace the whole crown. The great desideratum in constructing a piece of bridge-Avork is, of course, the securing of perfect usefulness in mastication and speech, combined with absolute comfort and cleanliness. The closer a bridge approaches that condition Avhere its Avearer loses consciousness of its presence in his mouth, the nearer perfection it is. Scarcely less important, hoAvever, is the necessity of providing for repair. Accidents will occur, and the system AA'hich superadds to usefulness, comfort and beauty, ready facilities for repairing breakages, is by so much superior to those Avhich make no such proAdsion. A croAvn broken from a bridge constructed by any of the methods above described can be easily substituted, and the piece when repaired will be as strong and serviceable as it Avas originally. It has not been deemed necessary to detail the construction of a single croAvn separately, as all the steps are included in the building of bridges, Avhich have been described minutely. Porcelain cusps of the general form illustrated in Fig. 723 have been designed spe- cially for these cases. In mounting them the gold band is cut away on the buccal side as shown in Fig. 724 to permit the porce- lain to show. Dr. C. M. Richmond, of NeAV York City, in making removable dentures of the entirely soldered kind, employs a zinc die made from a cast of the anchor tooth Avith its cap on. He makes of crown metal (platinum faced Avith gold) a collar somewhat smaller than the tooth-cap, and deep enough to reach from the gum to about a sixteenth of an inch above the cap. He then drives the die into the collar so far that the extra sixteenth of an inch can be ham- CROWN AND BRIDGE-AVORK. 817 mered OATer and burnished doAvn on the die-end to form a flanged collar. Outside of this, in the same manner, he forms another flanged collar, and then solders the two together, thus obtaining a close-fitting stiff collar, that will not stretch in being telescoped on and off the anchorage, and is kept by the flange from being forced Fig. 723. too far over the tooth-cap. A denture of this kind is illustrated in Fig. 725, Avhich also shoAvs his post and roof device in another form than that pre\dously described. It may be well to add that, in the use of an impression cup for holding the plaster and sand around the parts to be subsequently Fig. 724. Fig. 725. remoAred from the mouth, the inside of the cup should first be slightly oiled, to allow a separation of the cup when the mass is being prepared for the soldering. A removable bridge-work is suggested by Dr. T. S. Waters, which is described as folloAvs: " The natural molars and bicuspids, one or more of each class, are capped with gold croAvns, each molar being double capped, and the outer cap containing two small springs constructed of small strips of elastic metal (gold and platinum), one end of each-spring being soldered to the inner surface of the cap near its base at the neck of the crown, and the other end free to press on the side of the inner cap. Such springs retain the outer cap fitting over the inner one on the prepared natural crowns, by their pressure on the sides of the inner, caps, the latter being cemented to the natural croAvns. " The band for the natural bicuspid crowns has two shoulders on the inside which fit into grooves cut in the mesial and distal sur- faces of the gold forming the croAvn." 52 818 MECHANICS—DENTAL PROSTHESIS. Dr. James W. Loav, the inventor of Avhat is known as the " Low- method of bridge-denture," describes it as follows: " My experience has convinced me that, as a rule, a tooth firm in the jaAv need not be extracted. There are but few exceptions. When the treatment is followed persistently, and proper judgment used, nearly all the partial loss of the teeth can be restored without covering the roof of the mouth, and made as valuable for masticating food as the natural teeth, I am positive, and wdth less injury to the remaining teeth, than by any other method. The method referred to is that known as the ' Low method,' or bridge-work. " Bridge-work consists in supplying vacancies between teeth or roots with artificial teeth, attached to the adjoining natural teeth or roots by means of bands or croAvn, and held in such position Fig. 726. that there is no contact with or pressure on the gums beneath, and thus no opportunity for secretions or other foreign matter to be held there and thereby become offensive. "There is really but one kind of bridge-work, and but one way to make bridge-work to insure success. There are many ways of making teeth without plate, but this is not bridge-work. I will here try to explain in detail my manner of making and adjusting bridge-work. " For the first illustration, as seen in Fig. 726, Ave have a case where all the teeth have been extracted, except the two cuspids and two second molar roots. " We first proceed to prepare the roots by crowning. I use gold croAvns on the molar teeth, and what is known as the Low crown on the two cuspids. CROAVN AND BRIDGE-AVORK. 819 "The preparation of the two cuspids consists in making the croAvn ready for adjustment. I always measure the tooth to be croAvned Avith gold Avith a strip of block tin, 35 thick stub gauge or thereabouts. Place the tin around the tooth, and with pliers care- fully measure the full size of the same. " Should you be measuring a tooth, or part of a tooth, on which there are projections, take the engine, and, with a stone, grind off the same, making a smooth surface, so there Avill be nothing to in- terfere Avith the fitting of the bands properly. After cutting the tin measures by the marks made by the pliers you have the measures ready to make the gold bands by. Cut the bands and bevel the edges, and solder together, and you are ready to fit. After fitting all the bands, and finishing the crowns in the usual Avay, I place each in position in the mouth, having previously regulated the articulation of each crown as desired, in the process of making. We iioav take a deep articulation in wax, and impression in plaster of Paris; remove before it gets too hard, and place all the croAvns in their positions in the impression; varnish, oil and pour in the usual way ; separate the cast from the impression and place in the articu- lator. Then pour plaster. After the plaster has hardened, remove the wax and we have the articulation proper, and are ready to select and grind our teeth, having previously selected our shade. My experience has long ago taught me that no porcelain teeth can stand the pressure for bridge-work, the strain on them being tAvice as great as with teeth on plates, which rest on the gums that give to pressure. In order to prevent breakage of teeth and give strength, I have for many years been making a tooth with gold cusps. I will here describe my manner of doing so. I had some shells of bicuspids and molars made, or rather teeth, without the croAvn. They can noAv be found in some of the depots. " For the first step, I use 28 gauge platinum for a covering of the inside of the shell or just where you wish gold to flow. Then I bend the pins down to hold the platinum in position, and with a file remove all overlapping platinum to prevent breaking of our tooth in heating. The tooth is made flat on the crown surface with the express intention of restoring with a gold croAvn. This croAvn need not be very thick, but should perfectly resemble the cusps on the natural tooth, for the purpose of mastication. As these cusps are not on the market, and every dentist making bridge- work cannot make it in a Avay to stand, without putting gold cusps on the grinding surface of the bicuspids and molars, I will here describe for the benefit of those Avho do not know hoAV to make them, how they can be made Avith very little trouble. Pick out a 820 MECHANICS—DENTAL PROSTHESIS. natural tooth with cusps the exact shape you Avish to haA'c your gold cusps, mix some fire clay in a thick paste, then press your tooth into it a little deeper than you Avish the cusps. Having made the proper impression, remove the tooth, and set the impression over the gas stove to dry. After it is dried and reasonably hot, lay your pieces of gold in the impression and, with a bloAV-pipe, melt them. When melted, press with a piece of steel on the gold till cool. This mould wdll do to make many from. If you have not the fire clay and can get charcoal that is burned from fine-grained wood, and is soft, you can simply press your tooth into the charcoal and melt in the same way, or you can carve your teeth as you desire in a block of carbon. . Of course the little steel dies are handier, as we can swedge up our gold cusps in them, either solid or thin. " Having described our manner of making the cusps, we will now return to the manner of finishing our tooth. We left off by saying we covered the inside and bent down the pins and filed off the over- Fig. 727. Fig. 72S. lapping platinum. We noAV place the cusp on the top of the tooth, and place in the position desired, holding it there Avith wax, and with a spatula trim the wax the exact shape we wish our tooth to be, V-shape, tapering from the croAvn down. We now encase in plaster and sand, which gives us a box. When hard, remove the wax and place over the stove, and when sufficiently dry fill in with icoin gold, using the blowpipe to melt it in a solid mass, and then our tooth is ready to file up and place in position on the articulator. Fig. 727 shows the tooth in this condition. " After our teeth are all arranged we hold the same in position with wax, remove from the articulator, encase with plaster and sand or asbestos in the usual way. That we may have a strong case, I always use platinum wire between each tooth, and then proceed to heat and solder. Be sure that all the gold cusps are so arranged that you can get all soldered together, as this gives us great strength. My formula for solder, which I have used for many years and CROWN AND BRIDGE-WORK. 821 which will be found very easy-floAving and almost the exact color of the gold you are using, is as folloAvs: Ahvays figure from the carat of gold you are working. Take 1 pennyweight coin gold, 2 grains of copper, and 4 of silver. We now have our case soldered ; after filing as desired, commence to finish with felt wheels and pumice stone, after which we use rough buff wheels. We are now ready to adjust in the mouth. In Fig. 728 we see the case ready for adjustment. " Have the assistant dry all the teeth or roots to be operated upon Avhile you are mixing the cement. Be sure and use a kind which does not harden very rapidly, or your cement will set before you get your teeth adjusted. Use sufficient cement to fill all the gold croAvns perfectly when the case is driven to place. Moisten the step plugs and cap Avith cement, touching every portion, and Avith an instrument place a little cement in the bottom of the caAdty. Fig. 729. Wc now adjust our case, using the little rotor for the low crowns, and a piece of ivory for driving on the gold crowns. Fig. 729 represents the case when in position. " It Trill be seen by looking at the previous cut (Fig. 728) that the teeth, after having been soldered, are all spaced fully one-third of the distance from the place of contact with the gums and the grind- ing surface of the teeth, so that secretions could not possibly lodge there. I have given you a description of my manner of making a full upper case of bridge-work, where there are roots to be croAvned to support the bridge. I will noAV describe my manner of operating upon a case where the four centrals are missing, as seen in Fig. 730. To supply these four teeth where the cuspids are intact, I use a gold band. "I first measure the tooth with strips of tin and make the gold bands as before described, cut out the outside lower portion of the band before beginning to fit. In fitting, as the band is being driven 822 MECHANICS—DENTAL PROSTHESIS. doAvn, cut away any of the band that touches the gum before all touches; never drive the band under the gum, as inflammation would probably follow. " I mention this as I have seen many attempts to get rid of the band by driving up under the gums and cutting them out on the front, until they Avere too narrow for strength. It is hard work to make something out of nothing. The bands should be heavy and strong, and the patient made to understand that if he expects to get rid of the annoyance of the plate he must sacrifice his dislike to shoAving gold. After driving the bands up close to the margin of the gums, as the cuspid teeth are very tapering, the bands will have to be taken in at the bottom. To do this I slit the band about a third of its length up, then place it on the tooth again, lap it over enough to bring it to a close fit, and then take it off and solder. " Continue taking it in wherever it does not perfectly fit the tooth, and after a good fit is obtained proceed as before described by tak- ing an articulation and impression. In adjusting first try the case on to see that it fits and that the articulation is all right. Fig. 731 sIioavs the case ready for adjustment. " Next, have the assistant dry the teeth upon which the bands are going, and then mix your cement. This should be mixed to about the consistency of thick cream. It must be neither too thick nor too thin, or the adhesion will not be strong enough to hold. Cover your teeth with cement and then the inside of the bands. Place these on the teeth and carefully mallet up into position. For this purpose I use a steel instrument Avith a crease or groove in the end. The teeth must be kept dry after the case is in position until the cement is well set. After this is done bevel the edges of the bands and burnish close to the teeth, and if properly done they "will be made to resemble gold fillings. CROWN AND BRIDGE-WORK. 823 " In Fig. 732 Ave have the case completed. " I am aAvare that in a case like this, porcelain crowns instead of gold bands could be used, and I should consider it much preferable to do so Avhere Ave have roots or unsound teeth to operate upon, but do not advise the destroying of nerves where the teeth are intact to supply such a case with croAvns, as the bands will answer every pur- pose for many years. " If they should give out in after years the roots can then be croAvned. I have man}' of these cases that have been in use seven and eight years, some of which have never loosened, and some I Fig. 732. have re-set nearly every year. I ahvays impress upon the patient the necessity of having them re-set immediately, should they be- come loose, and advise them to have their cases examined at least once a year. Should parties insist upon having croAvns used to supply a case like the one just described on perfectly sound teeth, I should begin by using an aluminum disk, with corundum, cutting deep as possible, both on the labial and lingual sides. Then use the excising forceps. This can be done under the influence of an anaes- thetic or othenvise. It is not by any means so painful an operation as one AArould think. If the nerve does not come out Avith the piece of tooth cut off, I take a piece of orange wood which I have previously cut the proper shape to drive into the nerve canal. I place it in creosote and let it soak a feAV minutes before beginning to operate. Immediately after severing the tooth, drive this into the canal, then remove, and dip in creosote and drive in again. This will perfectly fill the nerve canal; all sensitiveness will disappear, and you can begin to operate at once. I do not recommend this treat- ment for sound teeth, but I have treated many exposed nerves in this Avay; also many teeth broken by accident, and think this the 824 MECHANICS—DENTAL PROSTHESIS. most satisfactory way to dispose of such cases. I have never had any unfavorable results folloAV after operating upon teeth in this way, and I can hardly say as much in favor of any other treatment. I speak of this manner of treating exposed nerves as one of the operations that sometimes become necessary in adjusting a bridge properly. I do not claim any originality in this mode of treatment. I knoAV several dentists who use this method, all of whom report satisfactory results. We now have Fig. 733, shoAving the roots pre- pared to receive the case. Fig. 733. "I have many of these cases in use that are giving entire satis- faction. The instrument selected for preparing these roots should Fig. 73o. be one with small inside cutters and large bevellers, so as not to cut away any more tooth-substance than possible. " Fig. 734 represents the case ready for adjustment. " Fig. 735 represents the case after adjustment. " In this article I have described my manner of making teeth for CROAVN AND BRIDGE-WORK. 825 bridge-work, and I am now using a tooth made expressly for this Avork. " The following Fig. 736 shows us a socket. These are ready made in various sizes in bicuspids and molars with corresponding shells. " Figs. 737 and 738 represent the shells placed in sockets. Fig. 737 is a molar tooth showing the shell in position, and 738 is a central reversed. " Fig. 739 represents the socket as made for the four central and two cuspid teeth. The advantage of these teeth can readily be seen, not only for bridge-Avork but all gold plates. A tooth, if broken, can readily be replaced without removing the bridge or cracking by soldering, and with only a small expense. " Fig. 740 represents the shell placed in position in the socket, Avhich can be used for bridge or crown-work, and will greatly re- duce the labor in making either." Dr. G. W. Melotte describes his system of bridge-denture as fol- lows :* " Fig. 741 illustrates a case for the supply of a lateral and a bicuspid. In this instance the cuspid could be cut off, and the root collared Fig. 741 and capped in combination Avith a pin entering the enlarged pulp- canal ; but, as there may be grounds for objection to cutting off sound teeth, I obviate the necessity by cutting a shoulder on the lingual portion of the cuspid, and suitably shaping its sides to per- mit a close fitting collar just under the free margin of the gum. A narroAV strip of pure pattern tin, bent tight around the tooth-neck, and cut through Avith a knife at the lap on the labial surface, will serve as a measure for the length of a strip of 22-carat gold plate, * Dental Cosmos, Decern. No., 1886. 826 MECHANICS—DENTAL PROSTHESIS. No. 29 thick, and as wide as the length of the distal side of the cuspid. The ends of the gold are then squared, and with round- nosed pliers brought evenly together, to be held in flush contact by the soldering-clamp shown in Fig. 742. The soldered collar, with its joint side inward, is then adjusted on the tooth as accu- rately as possible, giving slight bloAvs Avith a mallet until the collar touches the gum, when it should be marked to indicate the neces- sary trimming to conform it to the gum contour. After it has been thus trimmed, the edges bevelled, the labial part swelled with con- touring pliers, and the lingual part cut down to about one-tenth of an inch in width, the collar is again driven on, and will appear as seen in Fig. 741. A stump corundum wheel is then used to grind a shoulder on the lingual surface of the tooth, grinding also the edges of the collar flush with the shoulder. The collar is again Fig. 742. removed, and a piece of thin platinum plate, about No. 32, sufficient to cover the lingual surface of the tooth, is caught on the lingual edge of the collar by the least bit of solder, and all put in place on the cuspid (see Fig. 743). The platinum should now be burnished on to the shoulder, and over the tooth and collar to the extent shown by the lines in Fig. 743. After trimming to those lines, and careful replacement and burnishing on the tooth, the collar and half cap are removed, filled with wet plaster and sand, and the platinum soldered to the gold. It is then placed on the tooth, bur- nished into all the inequalities of the tooth, very carefully removed, invested, and enough solder flowed o\'er the platinum to cover and give it strength. Fig. 744 shows it complete on the cuspid. " I have feared that a detailed statement would imply a long and tedious process, but I have often made such collars in less than an hour, and in any case time must be made subservient to exactness of fit and adaptation to the end in view. " In the preparation for fitting a collar on the first molar (Fig. 741), I should have wedged or otherwise separated it from the second CROWN AND BRIDGE-AVORK. 827 molar, so that a piece of sheet brass might be put in place, as shown by Fig. 745, and an impression taken in plaster, which if allowed to get hard would bring away the metal. If not, it could be replaced in the plaster. Melted fusible metal, when near the cooling point, is then poured into the impression, and Avhen cold will allow the safe removal of both the plaster and the metal strip. On this metal model a collar can be formed that will accurately fit the molar, as seen in Fig. 741. If the molar has no antagonist, a cap may at once be struck up on the model; but if there be an antagonist the cusps Fig. 743. Fig. 744. Fig. 745. Fig. 746. of the natural molar should be removed by grinding at points Avhere the occluding tooth will admit of sufficient thickness of the gold cap. An exact copy of the ground cusps can then be made in less than five minutes, by the use of moldine with its accessories, and the process is as follows: Make the tooth perfectly dry. Put the collar on it. Nearly fill the cup (Fig. 747) Avith moldine, and coat it Avith soap-stone poAvder. Press the compound on the tooth and collar firmly to about one-fourth the depth of the tooth. Carefully Fig. 747. Fig. 748. remove the cup; trim off any overhanging material, and place the rubber ring over the cup to about one-half the depth of the ring. Melt the fusible metal and pour it as cool as it will run from the iron ladle. As soon as the metal is hard, remove it with the ring (Fig. 748), taking care not to impair the impression, which can be used again if the die is found imperfect or gets injured in use. 99999999� 828 MECHANICS—DENTAL PROSTHESIS. Place the die and ring in cold water, to remain until quite cooled. While the die is wet and held over a basin of Avater, pour into the ring fusible metal which has been stirred until it begins to granu- late, and quickly immerse all in the water. The die and counter- die should separate readily by tapping them Avith a hammer but if they stick others can be quickly made from the same impression by the same method, using more care. With this die and its counter-die, a piece of No. 29 or 30 gold plate is SAvaged to fit per- fectly the cusps and collar, which, when removed, can be held to its place on the cap by the soldering-clamp, using spring pressure enough merely to hold them together for careful soldering with the pointed flame so as not to unsolder the collar. The seamless collars are excellent Avhen care is used in selecting the proper size, as directed on the diagram. " The caps being in place on the cuspid and molar, an impression is taken Avith plaster; the caps accurately set in the impression, and hard wax melted with a hot spatula around the edges of the caps. The impression is then thoroughly coated with sandarac varnish, after Avhich it is dipped for a moment in water, and filled Avith a wet mixture of one part marble-dust Avith two parts of plaster; using great care to perfectly fill the caps and moulds of the teeth. Wait until this mixture has become quite hard; remove the cup, and Avith a suitable knife chip off the plaster without marring the cast; secure a good articulating impression, and transfer it to the cast to obtain an exact reproduction of the relative occlusions of all the teeth in- volved. With such an articulation in hand, and Avith the means already described for swaging gold or platinum plate to fit the cusps and articulating surfaces of either the natural or artificial teeth, it should be within the capacity of any competent dentist to complete1 a suitable bridge; although there are practical points that can only be imparted by clinical instruction and actual demonstration in the mouth. Such a bridge is shown in position by Fig. 746." Dr. R. Walter Starr describes a bridge-denture which can be removed for repair in case of injury, as follows :* " It will doubtless be admitted that in some cases bridge-Avork has advantages over the ordinary plates for partial dentures. It will also be conceded that the security and permanence of the fix- ture enhances its practical value to the patient so long as all goes well. But if for any reason it shall become necessary to remove the bridge, for repairs or treatment of the roots used as anchorage, its fixedness proves a serious objection. * Dental Cosmos, vol. xxviii. CROAVN AND BRIDGE-WORK. 829 " In the endeavor to provide a remedy for this defect, the struct- ures noAv to be described originated, and will, it is hoped, be found applicable in many instances in such cases as are typified by the accompanying illustrations. " In the construction of such bridges the first thing to be done is to grind with engine-corundums the overhanging edges and sides of the teeth which are to serve as abutments so that the crown-ends shall be slightly smaller but of the same shape as their necks. This can be demonstrated by bending a piece of fine binding-Avire around the tooth-neck, and tAvisting the free ends together to form a close- fitting loop, which, if the tooth has been suitably shaped, may be slipped from the tooth without changing the form of the loop, thus giving an exact outline of its form and size. Such a loop is shown in Fig. 749. The loop is then laid upon an anvil, and the squared end of a short piece of wood placed over the wire, and a blow struck to drive the loop into the wood as a guide in shaping the wood to the precise size and form of the inside of the loop, as in Fig. 750. Fig. 749. Fig. 750. Fig. 753. The free end of this wooden mandrel must subsequently be slightly reduced so as to conform exactly to the natural crown. In lieu of this method an exact impression of the tooth may be taken in plaster to serve as a mandrel. About a sixteenth of an inch is then ground from the occluding cusps of the abutment teeth, and an impression taken of the teeth and surrounding parts to obtain a model as shown in Fig. 753. A piece of gold plate, say 22-carat fine, number 30 gauge, is cut and fitted closely around the mandrel, and its ends soldered to make a collar, as in Fig. 751. This is laid with the crown end upon a piece of lead, and a piece of wood or metal laid over it and struck with a hammer to drive the collar into the lead so as to hold it securely and maintain its form, while with a smooth, half-round file the 830 MECHANICS—DENTAL PROSTHESIS. neck end is shaped as seen in Fig. 752. The other end of the collar is then cut so that the depth of the collar shall a little exceed the visible length of the tooth, thus allowing the neck end when placed upon the tooth to pass beneath the free edge of the gum. A piece of gold plate, either plain or struck up in cusp form, is then soldered to the crown end of the collar. If a seamless collar is used it can be laid upon the plate for soldering without an investment or a clamping wire. A piece of thin platinum plate, No. 36 gauge, a little AAdder than the space to be covered Avith the teeth, is fitted and burnished over the space between the abutment teeth, which have been so trimmed that the caps described will slide on and off easily. These caps are now cemented to the platinum plate, and collars made and fitted to properly fill the space between the abut- ment teeth. They are held in contact with each other and Avith the platinum plate by running melted white Avax in and between Fig. 754. Fig. 755. Fig. 756 them. The whole piece may then be transferred from the model to the mouth, and stiff mixed plaster and sand pressed into and over the collars and caps. When the plaster has set the mass may be removed, trimmed, and the wax melted aAvay Avith a result as shoAvn in Fig. 754. The lines of contact of the collars Avith each other, with the caps, and with the plate are to be neatly soldered, when the investment may be removed, leaving the bridge as shown by Fig. 755. The free edges of the plate may then be trimmed to the margins of the collars or caps, and the whole denture polished. The bridge may now be slipped on and off the natural abutment teeth with just enough of friction to retain the denture in position and yet allow of its ready removal. " Suitable cusp-crowns (see Fig. 756) are now selected, the cups partly filled with wax, and the cusps placed in position. The den- ture is then tried in the mouth and the proper occlusion obtained by grinding or filing the edges of the cups. The piece is now to be thoroughly cleansed and dried; the cups nearly tilled with insoluble cement, or hot gutta-percha; the cusp crowns set in the cups; the bridge put quickly in place, and the patient directed to firmly and repeatedly close the jaws to properly determine the occlusion. It CROWN AND BRIDGE-WORK. 831 will be found best to place a piece of paper the thickness of a postal card o\rer the porcelain cusps when forcing the denture to place, so as to insure that they shall be a little short, and thus avoid irrita- tion of the anchorage teeth in mastication. These anchorage teeth or roots will in time elongate and form a close occlusion. Fig. 757. " When the cement is properly hardened the piece may be removed. A hole should now be drilled through the metal caps to allow escape of surplus filling material. A small quantity of gutta-percha thoroughly warmed should noAV be placed in the caps, and Avith a Fig. 758. piece of card placed betAveen them and the occluding teeth, the caps should be forced home. " The completed case is represented in Fig. 757. "The bridge may at any time be removed with Avarmed forceps beaks held long enough on the caps to soften the gutta-percha. The cusp croAvns may be removed if desired by the same method and replaced Avithout detaching the bridge. " A modified bridge is shoAvn in Fig. 758. It will be observed that collars have been firmly fixed with cement or gutta-percha on the 832 MECHANICS—DENTAL PROSTHESIS. abutment teeth, which have their occluding surfaces ground flat on their inner aspects, so that the partial cap shown may thus prevent the telescoping collars from being forced too far doAvn on the teeth. By means of a frame saw, a narrow tongue is cut on the outer face of each telescoping collar, the free portion serving as a spring clasp to hold the bridge securely on the abutment teeth, and still alloAV the removal of the piece Avhenever so desired. Fig. 759 shoAvs such a bridge in place. It is obvious that if in this instance the roots only of the cuspid and second molar had been present, they could by means of the collar and cusp-crown devices, have been put in shape to serve as abutment teeth for the telescoping bridge shown in Figs. 758 and 759. The second molar roots so crowned are seen in Fig. 760. When it is desirable to shoAV the faces of the porcelains to a greater degree, the collars may be cut away on the buccal sides Fig. 759. Fig. 760. Fig. 761. and the countersunk crowns be used as illustrated by Fig. 761. The platinum base may either rest broadly upon the gums or be sloped so that only the buccal border shall touch the gums, or it may be so shaped as to be entirely free from the gum. This is done by building upon the plaster cast, and bending the platinum plate and shaping the gold tubes to the surface so made, depending wholly for support on the abutment teeth or roots. " Briefly stated, the points of excellence in this bridge are strength, lightness, avoidance of liability to breakage of the porcelain in sol- dering, ease of construction and adaptation, and the facility Avith which it may be reorganized, or for any reason be removed and re- placed. This last feature is of special value in the not infrequent event of subsequent alveolar abscess, for in cases such as are shown in Fig. 757 the bridge may be removed, the involved teeth drilled, medicaments applied, the bridge replaced, and this process repeated without depriving the patient of the use of the denture." In the Dental Cosmos, Dr. Dexter describes a removable-bridge denture or " cap-plate," as follows: 7240 CROAVN AND BRIDGE-AVORK. 833 " Take a case where, on the loAver jaw, there are standing in the mouth a third molar, a canine and first bicuspid on each side,—six teeth in all. These teeth are shortened, by breakage and masti- cation, so that the upper incisors close to Avithin an eighth of an inch of the gum line between the canines; added to this, they are so tipped and twisted in their places as to make it very difficult to properly adapt an ordinary denture to the spaces between them; and, lastly, let the patient evince entire abhorrence of, and a fixed resolution not to permit, the resting or pressure of any appliance upon his gum-tissue. Such a case is the one for which I have con- structed this cap-plate. Such cases are often treated by building up or doAvn the natural teeth with gold, in order to open the bite, and then replacing lost teeth with an ordinary plate. My apparatus, however, accomplishes both these desiderata in one operation, Avhile simultaneously avoiding any and all pressure upon, or irritation of the gum. " The appliance which I shoAV you (Fig. 762) is constructed as folloAvs: Caps of gold and platinum alloy, of about 26 to 28 U. S. Fig. 762. standard gauge, are struck up to fit over and down the sides of the natural teeth selected for the piers, fitting closely. If all the sup- porting teeth stand perpendicularly, and parallel with each other, thus creating no ' undercut' (so to say), the sides of the caps may encircle the teeth as far as possible (not, however, impinging upon the gum-line), and be simply slit (in tAvo or more places on each tooth) perpendicularly, so as to spring apart and alloAV of sliding the Avhole over the natural convexities of the teeth, the sides coming together again Avhen in place and thus holding the whole apparatus firmly. But "should the teeth be tipped or leaning, and not par- allel, the sides of the caps must then extend over only such parts as can be closely fitted and yet be sufficiently perpendicular and par- 53 834 MECHANICS—DENTAL PROSTHESIS. allel, to allow of removal and replacing of the appliance. Of such a character is the case now shown you, there being only one place on the six caps where a slit is of value; the sides of the caps being so fitted as to hold partly by their own elasticity, and partly by that of the whole apparatus. Such a case, of course, will most severely try the capabilities of any artificial denture; and not the least merit of the present piece is its triumph over, and perfect and practical adaptation to, the obstacles of an exceptionally difficult case. " The caps, when struck up, will not cling to the teeth Avhen in place; nor should they, for they must be capable of easy removal during succeeding processes. But, when the piece is ready for final insertion, the sides of the caps must be sprung inward sufficiently to hold to their supports with firmness. " The caps being now made, it is in order to determine the length of ' bite' needed. Place the caps in position in the mouth, and build wax on their grinding surfaces to a proper length and con- tour, both side and grinding. Invest, remove wax, and flow into its place eighteen-carat gold. Shape the grinding surfaces, by trial in an articulator or the mouth, to the proper occlusion. Next, take an impression with the caps in place, pour the model, select and back plain plate-teeth, and wax them in place. Invest the whole, remove the wax from the backs of the teeth, and fit in the spaces between the caps, bands, or bars of irido-platinum alloy (or gold, as circumstances may determine), being careful that the bars fit ac- curately to the backings of the porcelain teeth, and to the caps at each end. In fitting the bars to the caps, select such points of attach- ment as will not interfere with the spring of the slit sides of the caps. If necessary, let the bars avoid the sides of the caps, and reach, by curving, to the tops or grinding surfaces. Should you desire to ar- range the porcelain teeth irregularly, you need not hesitate to do so. Set them just as you would for rubber or celluloid, and then, simply taking a ' finger impression ' of their backs Avith modelling compo- sition or wax, when invested as above stated, and making dies, you can readily ' strike up' your bars to fit the irregular positions of the backings. But, should this be difficult, on account of great irregularity, or stiffness of bars, then construct the bars of two or three thicknesses of metal, each struck up separately, -and then ' sweated ' into one. Next, solder the bars to the backed teeth, but not to the caps, as yet. The reason is that perfect adaptation of the bars to the caps is absolutely necessary to the success of the piece. Therefore, now place the caps in place in the mouth, and wax the bars with their attached teeth in the spaces between them ; filling, CROWN AND BRIDGE-AVORK. 835 grinding, and adjusting until all is exactly as required. Then (and not until then) take an impression of the whole in place, the appa- ratus coming away with the plaster. Pour the impression Avith plaster and pumice, sand, or asbestos (sand is best), carefully re- moA'e the impression plaster, invest outside the model with its sus- tained apparatus, and then solder the caps and bars together. In doing this, as little solder as possible should be used, to prevent warping of the whole. The bars should have a broad, firm hold on the caps; but the contour of their union should be made on the bars before they are united to the caps, and not by flowing on a body of gold while uniting the bars and caps sufficient to attain the de- sired hold and shape of union. On the contrary, the bars should be properly shaped at their ends, and carefully fitted to the surfaces to Avhich they will be attached, when a small amount of solder floAved into the joint will make a perfect union and give all the strength possible. This is not plumbing work. All that iioav re- mains to do is to spring or bend slightly imvard, as before directed, the sides of the caps so that they may grasp their supporting teeth firmly, yet not too much so to create difficulty in removal or in- sertion ; then finish and polish. Burnishing is generally objection- able, since it gives, in some lights, a black shine to the piece, adding greatly to the prominence of the appliance as a part of the view Avhenever the wearer opens his mouth. " Should it be desired to produce the best possible results with the piece, the interstices between the artificial teeth and any other crevices to be found may be filled with gold or amalgam,—I prefer the former; or vulcanite may be packed in such places (which may be, if necessary, cut out to proper dimensions by burring), and finished up smoothly. The piece shoAvn you contains no less than seventeen gold fillings, Avhich signifies that no debris, or even moisture, has any foothold of concealment about it, and that it is, therefore, as clean in itself as is possible for any artificial denture to be. This, you will say, is rather expensive Avork. Very true. The Avhole method is expensive in both money and labor. But I am quite consoled for this fact by the thought that it will not, therefore, be likely to do much harm to the public, since the ' cheap-jacks ' and ' incompetents ' will probably let it alone. " In the piece shoAvn there are six caps, three on a.side. There are five incisor teeth placed betAveen the canines, tAvo of Avhich are capped Avith gold to break up the uniformity of porcelain in front, as contrasted with the uniformity of gold behind, and thus help to evade artificiality of appearance. Between the molar caps and the double caps for canine and bicuspid, the connecting-bar is horizon- 836 MECHANICS—DENTAL PROSTHESIS. tally placed, dipping doAvnward to parallel the gum line, as Avell as to evade an encroaching molar above. When necessary, an artifi- cial tooth or teeth can be ground and soldered to these bars. Gen- erally, however, the connecting-bars should be perpendicularly placed, to insure resisting strength in the line of the attacking force." Dr. R. Walter Starr, in the same journal, describes the folloAving case of removable bridge-denture: " The case of Mr. W. presented difficulties of an unusual char- acter, as may be seen by inspecting the illustration, Fig. 763, which renders detailed description unnecessary. " It will be observed that the molars and the left second bicuspid overhang to a degree that would make the taking of an accurate impression by ordinary methods well-nigh impossible. After a Fig. 763. careful study of the case, it Avas decided that tAvo separate pieces of removable bridge-Avork should be attempted, and, as an essential preliminary step, the overhanging sides of the molars and bicuspids were ground with engine corundum Avheels and points until those sides Avere made much less inclined, Avhen plaster impressions were taken, first of one-half, and then of the other half, of the jaw. Gold cap-crowns were closely fitted over the molars, left second bicuspid, right first bicuspid, and cuspid stump. Gold crowns were made to telescope over all the caps, which Avere then, by means of oxyphos- phate cement, fixed firmly on the teeth. Suitable plate-teeth were selected, fitted, backed, and hard-waxed in place between the tele- CROAVN AND BRIDGE-WORK. 837 scoping crowns. After hardening the Avax A\dth cold Avater from a tooth-syringe, the pieces Avere carefulby removed, invested and sol- dered. The tAvo completed bridges Avere easily replaced on or removed from the supporting capped teeth, and their appearance Avhen detached is correctly shoAvn by the illustration, Fig. 764, Avhich also shows the capped teeth and stumps. This figure likeAAdse shows the results of the novel method employed in croAvning the incisors. Gold collars Avere fitted tight on the necks of the incisor stumps, and the ncAv-stylc porcelain caps adjusted in the collars, and set in Fig. 764. the oxyphosphate cement which had been packed into the collars; thus at the same time fastening the collars on the stumps and the caps in the collars, as shoAvn completed in Figs. 764 and 765. " Fig. 765 illustrates the finished croAvns and bridges, which latter Avere secured in position by placing a small piece of gutta-percha in each of the telescoping cap-crowns, which were then warmed and carefully pressed in place,—the gutta-percha filling only the spaces betAveen the flat tops of the caps of the natural teeth and cusped caps of the bridges. '' Whenever for repair, or for any other purpose, it shall become desirable to remove one of the bridges, that may readily be done by 838 MECHANICS—DENTAL PROSTHESIS. applying a hot instrument or hot air to the caps to soften the gutta- percha sufficiently to permit the telescoping bridge to be taken off. " A full upper vulcanite denture Avas made to replace the old one, which, by improper occlusion, had throAvn the full force of mastica- tion on the anterior teeth of the lower jaw, and produced the de- structive action that resulted in the deplorable loss of tooth-substance shown in Fig. 763. "The prosthetic devices thus briefly described have so far proved perfectly satisfactory to both patient and dentist. The obvious dif- ficulties of the case, and the somewhat novel means employed in supplying useful and secure dental substitutes, seem to justify the writer in bringing the case to the attention of the profession." Fig. 765. A bridge of this form can also be made removable by cementing it on the natural crowns or roots with gutta-percha, and by still further securing it by screws entering the body of the croAvns or roots through the gold forming the occluding or grinding surface portion. Dr. H. C. Register has devised the folloAving method, which, in the eArent of a porcelain crown being broken, possesses the advantage of allowing the place to be filled by a new crown without disturbing the main appliance. The following concise description of this method is by Dr. Dexter : " Taking a typical case (Fig. 766), a rim or saddle of gold, plati- num, or iridinized platinum is struck to fit the spaces between the CROAVN AND BRIDGE-WORK. 839 teeth a and b. To this are attached bars, x, Fig. 768, to enter the fillings at z, z (Fig. 767). Posts or pivots (d, Fig. 768) are soldered upon this saddle Avhere the artificial teeth are to be placed, their Fig. 766. free ends being threaded to carry the nut e. HoIIoav crowns, count- ersunk for the nut at g, and having the necks ground to reach over the saddle and press upon the gum, are fitted over each post. Fig. 767. Fig. 768. Amalgam is used to fill in the space betAveen the post and the tooth- wall, as in a Bomvill setting, and the crowns are drawn to place and held with the nut. The saddle is fixed in its place in the mouth, before the croAvns are finally attached, by filling into the cavities z the bars x x." 840 MECHANICS—DENTAL PROSTHESIS. Dr. J. L. Williams suggests the following methods for the single croAvn and for " bridge-work," which he describes as follows : " It consists essentially of three parts: a square pin of platinum and iridium which enters the enlarged pulp-canal, a cap of gold, and the porcelain face, which is the ordinary plate tooth. " This crown is made in the following manner: After the end of the root is made perfectly smooth with corundum wheels and properly shaped scalers, a gold ferrule or band is fitted around it. If it is desirable that this band should be entirely concealed, the labial surface of the root should be bevelled a little above the margin of the gum, and after the band has been soldered it may be placed in position, and the line of contour of the margin of the gum marked upon the front of the band. The proper bevel can then be cut and the edges squared upon a corundum Avheel, leaving the Fig. 769. lingual portion of the band a little longer than the front. Pure gold, rolled to No. 34 of the standard gauge (American), is used for soldering upon the bevelled surfaces, thus making a closed cap for the end of the root. A suitable tooth is now selected and backed with pure platinum or pure gold. The cervical end of the tooth is then ground to the proper position on the front bevel of the cap, all of the fitting being done Avhile the cap is in position on the root. " After the fitting is completed the cap is removed and the tooth attached by strong resin Avax and again placed in position AA'hile the wax is warm. Any slight change in position which is necessary can then be easily made. The tooth and cap are noAV removed together, invested, and united at the back by solder. It is well to use a solder for the cap with a higher melting point than that used for the back- ing, as it obviates the danger of unsoldering the band Avhen the backing is flowed on. After finishing and polishing the work, the end of the root is made perfectly dry, a sufficient quantity of oxy- phosphate cement, mixed somewhat thinner than for filling pur- poses, is placed in the enlarged pulp-canal and also in the cap. The crown is then carried to place with firm, steady pressure, held CROAVN AND BRIDGE-AVORK. 841 a feAv minutes until the cement is sufficiently hard to prevent dis- placement. The surplus cement Avhich has oozed out around the band should be carefully removed, and the work is then completed." Fig. 770. Fig. 771. Fig. 772. Dr. Williams's method can be applied to "bridge-work," as the above Figs. 770, 771, and 772 will shoAV. In this method, special croAvns, Figs. 773 and 774, for molars and 842 MECHANICS—DENTAL PROSTHESIS. bicuspids, with porcelain faces, are made, Avhich are backed with gold or platinum and the tips ground squarely off. Zinc pattern dies are made from the grinding surfaces of molars and bicuspids to be used for SAvaging from pure gold a tip or cap for the protec- tion of the porcelain face. The conca\-e surface of these tips is filled by melting coin gold into them, and this surface is then ground smooth and fitted to the squared surface of the porcelain face and waxed in position. Triangular pieces of platinum are then cut of the proper size to fit the sides of the tooth, waxed in position, and the whole invested, leaving the back open, which is filled with coin gold. Dr. Williams also describes other forms of bridge-denture, in one of which there are no supporting roots, and in the other the sections are united by bands of gold. * " Figs. 775 and 776 illustrate a method of inserting extensive pieces of bridge-work in cases where there are no natural teeth Fig. 775. or roots for supporting one end of the bridge. The work from which these draAvings were made was constructed by Dr. H. A. Parr. By this method bridges may be inserted in cases Avhere all of the teeth on one side of the mouth have been lost, or Avhere all of the teeth anterior to the molars on both sides are want" ing. Crowns are first fitted to the teeth which remain. These crowns being in position, an impression is taken. From this a cast is obtained with the crowns in their proper positions. A second impression is also taken of that portion of the mouth where there is no natural support for the bridge. From this impression metal- lic dies and counter-dies are obtained, from which is 'struck' a * Dental Cosmos, December, 1885. CROAVN AND BRIDGE-WORK. 843 small gold plate about three-fourths of an inch in length and Avidth, the size of the plate varying according to position and other condi- tions. After this little plate or ' saddle ' has been perfectly fitted, it is waxed in the proper position on the model, with the crowns. The interArening teeth are now placed in position, and the work in- vested and soldered. To provide for the possibility of shrinkage or absorption at the point where the plate or saddle rests, it is sug- gested that it be not soldered to the bridge, but attached by means of an adjustable screAV. " Fig. 777 illustrates another device for obviating the necessity for removing the croAvns of natural teeth in preparing the mouth Fig. 778. for bridge-work. CroAvns are fitted in the mouth to the points of attachment in the usual manner. An impression is taken, bringing the croAvns away in their proper positions. From this the cast or model is obtained. Heavy bands of half-round gold or platinum 844 MECHANICS—DENTAL PROSTHESIS. bars are now fitted around the necks of the natural teeth on their lingual surfaces. These bands, being Avaxed in position, serve to connect the different parts of the bridge, uniting them in one piece without the loss of any of the natural croAArns. I have found this a highly satisfactory method of inserting extensive pieces of the Avork. Fig. 778 shows the mouth as presented for Avhich the piece shown in Fig. 777 was constructed. Fig. 779 shoAvs the piece in position. Fig. 779. " Fig. 780 illustrates a case which is a type of a class of frequent occurrence. Alternate molars and bicuspids in the upper and lower jaws are lost until the occlusion.is somewhat changed, and the force of mastication is gradually brought upon the front teeth. Fig. 780. Rapid wearing of these teeth results. These cases are among the most difficult that the operator is called upon to treat by the ordi- nary methods. In the case herewith illustrated, the loAver bicus- pids with a molar on one side were in good condition, but the loss of the upper bicuspids and molars made them useless. As usually CROAVN AND BRIDGE-WORK. 845 happens, the upper incisors had suffered most. The lower incisors Avere restored by capping them with cohesive foil. The bridge shown at Fig. 781 was constructed for the right side of the upper jaAv, Avhile the teeth on the left side were restored by contour work, as shoAvn at Fig. 782. "The superiority of the condition of this patient's mouth, Avhich resulted from this work, over anything which could have been ac- complished by plate work is almost inconceivable to one not familiar Avith these methods. " The only annoyance Avhich bridge-work is likely to cause patient or operator is the occasional breaking of a porcelain, an accident of not frequent occurrence. While the replacing of a broken porcelain has never been a matter of extreme difficulty, yet I have always regarded the methods hitherto employed as more or less imperfect and uncertain in their results. This led me to devise a method of Fig. 782. replacing broken porcelains which leaves the Avork fully as strong as before; a method Avhich makes the operation a very simple one, requiring less than an hour for its performance; and after the por- celain has been replaced, an expert would not discover any traces of an accident. After removing all traces of the broken porcelain, the projecting pins are cut off, and two holes drilled through the backing in the exact position occupied by the pins. The narrow space of metal noAV intervening between these tAvo holes is cut out Avith a fissure-burr. This leaves a groove which should not be Avider than the diameter of the pins. The length of this groove should now be increased on the lingual surface, but not on the front. The object of this is to give a dove-tail shape to the groove, Avhich is easily effected by the use of the same fissure-burr above referred to. The lingual appearance of this groove when properly shaped is shoAvn in Fig. 783. The proper tooth is selected, the pin passed tn rough this hole and bent outAvards into the dove-tail groove. It iioav remains but to fill the space betAveen the pins Avith any form of cohesive gold (I use crystal gold), and with corundum, Arkansas, 846 MECHANICS—DENTAL PROSTHESIS. and rubber points in the engine the surface is finished and polished. The wedge-shaped filling of crystal gold acts as a keystone betAveen the pins, and makes a most perfect method of repair." Porcelain veneers or facings for bridge-work are represented by Fig. 784. These facings of molar and bicuspid forms have two long plati- num pins (cross-wise) for attachment. They are specially designed Fig. 784. for use in bridge-work operations. The long pins afford facility of repair when a tooth has been broken in use. Incisor facings of the same character are also employed. Dr. H. W. Howe recommends the following flux that is exceed- ingly useful in bridge-work, and is prepared as follows. Put in a cup: Boracic acid, ..........1 oz. Ammonia,..........\ oz. Carbonate of ammonia,........\ dwt. Bicarbonate of soda,........2 dwt. Water,...........4 ozs. Boil until the fumes of ammonia are no longer given off. Coat the bridge or other work all over the gold with the flux. Heat it over a spirit-lamp to dry it on. Give it another coat, if needed, leaving no part exposed. Then scrape off where it is desired that the solder shall flow, and it will go nowhere else. The Avork will come out of the heating as bright as when it went in, and the solder will be smooth. The polished surfaces will not be corroded or blackened. CROAVN AND BRIDGE-WORK. 847 Dr. C. H. Land has devised what he calls " metallic enamel coat- ings and sections," which he describes as follows :* " The accompanying engravings, Figs. 785 and 786, are taken from practical cases that have at this date been in use for one year. In the case represented by Fig. 785, the patient- was about sixty years of age. The right lateral incisor was prepared with a HoAve post, shown in its relative position. The five remaining teeth, after the cavities were prepared, contained tooth substance as represented by the dark surfaces, the Avhite representing the lost portion of each tooth, restored Avith sections of porcelain made to imitate the exact color and contour of the original tooth substance. The cavities are prepared as for gold filling, when a thin piece of annealed platinum plate, No. 35 standard gauge, is placed over the tooth, and by Fig. 785. Fig. 786. means of burnishers made to take a perfect impression of the outer rim of the cavity, after which platinum pins are attached, as shoAvn at A. The object of the pins is to serve as a fastening, both for the porcelain paste or body and as retainers to hold the completed sec- tion in the cavity of the tooth. The porcelain paste or body is built upon the platinum disk and made to imitate the lost portion of the tooth. It is then baked in a gas furnace, requiring but tAventy minutes for the first buscuit and fifteen for the second, and Avhen finished appears as shown at B, ready to be cemented with oxyphosphate. C and D are modifications for the other teeth, and Fig. 786 illustrates porcelain facings for molars. " The especial feature of this system is the large amount of tooth substance preserved above the gum, there being no necessity for telescoping the root so far beloAV as to sever the tissues. This mode of practice also dispenses with the long operations and protracted use of the rubber dam; it almost entirely obviates the use of amalgam, and saves the necessity for large gold fillings; there is * Independent Practitioner, February and August, 1887. 848 MECHANICS—DENTAL PROSTHESIS. no malleting, no long and tedious operation either for the patient or dentist, while at the same time teeth are perfectly restored, both in appearance and usefulnesss. " There is another advantage in the use of the enamel coatings which is not, in my opinion, a trivial matter. When large metallic fillings are inserted, the constant thermal changes consequent upon their alternate heating and cooling must exercise an unfavorable influence upon the tissues about the tooth. Even if the pulp be dead and the root be filled, there will be a checking and fracture of the tooth in time, from the continually varying changes of tempera- ture. An inflammation of the membranes will also be likely to occur from the same cause, and thus the tooth will in time be lost from the mere influence of the presence of a large mass of metal. " It is also a fact that large gold fillings cannot be inserted Avith- out so much malleting that the strength of the tooth is gone, and frail walls are cracked beyond the possibility of repair. These dangers are all obviated by the use of the porcelain facings, while teeth so restored are much more natural in feeling and more grate- ful to the touch of the tongue than any metallic filling can be." Dr. Land describes his metallic enamel sections as follows: " By reference to Fig. 787, Nos. 2, 7, 10, 12, and 15, there will be seen characteristic conditions of decay suitable for this class of work. 2 and 7 are the prepared cavities on anterior sides of molars. The manner of procedure is to burnish a thin piece of annealed plati- num plate into the cavity. This takes a perfect impression of its outlines. The surplus edges are trimmed off and platinum pins attached, using pure gold leaf for solder. (See 3 and 4.) The pins serve as a fastening, both to secure the completed section in place and as retainers for the porcelain body. 5 and 8 illustrate the com- pleted sections, showing the contour of the original shape of the lost portion of the natural tooth. Nos. 1 and 6 are prepared sections cemented in place. " Having secured the prepared sections as shoAvn in 3 and 4, por- celain paste or body is built upon them and carved so as to imitate the original contour of the lost portion of the tooth, as shown in 5 and 8. They are then placed on a bed of silex and fused in a gas furnace. This requires tAventy minutes for the first biscuit, and fifteen for the second. When completed, they will be a reproduc- tion in porcelain of the lost parts of the natural organs, resembling nature perfectly, both in color and shape. They are then cemented in the cavity, either Avith gutta-percha filling or oxyphosphate cement. When the anterior side of a molar or bicuspid is decayed, as shown in 11 and 15, the enamel front or veneer, 13, is added to CROWN AND BRIDGE-WORK. 849 the porcelain body, and when completed it will appear as shown in 14. This veneer serves as a ready and efficient means of securing Fig. 787. the proper shape and contour of each class of teeth. To those who are not familiar with the use of a gas furnace this class of work may 54 850 MECHANICS—DENTAL PROSTHESIS. seem difficult, but a little experience with the modern appliances now within the reach of every dentist, makes the operation a com- paratively simple and easy one. 17, 18,19, and 20 are a modification. 17 represents a tooth filled with gold, having two pins attached. 18 is a platinum disk, with tubes adjusted to correspond to the po- sition of the pins in 17. Porcelain body is built about the tubes, and when fused in the furnace the whole will form a porcelain crown as shown in 19. 20 illustrates the relative position of the tubes, which are designed to form countersinks for the pins in 17. When cemented in place, it makes a very durable and beautiful piece of work. 16 is an incisor constructed in a similar manner. From this will be seen the great advantage of being able to have the porcelain in a plastic state, as it enables the dentist to perfectly adapt the form of each peculiar case with the utmost precision, and this could not be so admirably done with manufactured crowns. Fig. 788. Fig. 789. " I wish to call especial attention to the large amount of tooth- substance preserved. In nearly all the modern systems of crown- work there seems to be too much good tooth-material cut away, and I think a careful investigation will demonstrate this neAV pro- cess to be far superior, making it possible to save the greater portion of the crown, it not being necessary to cut beneath the gum. In nearly every case, sufficient tooth-substance can be retained to preserve the .pulp alive, and when the teeth are devitalized the major portions of the crown can be left intact, serving for retaining purposes and making it unnecessary, in the majority of. cases, to resort to screws or posts. 16 illustrates a section of porcelain ad- justed to a central incisor which, when carefully done, makes a very acceptable piece of work. Although the joint may sometimes be conspicuous, it is not nearly as much so as a glaring piece of gold." Figs. 788 and 789 represent a practical case before and after the insertion of the sections. In concluding the subject of artificial crowns attached to natural roots and teeth, it remains only to briefly refer to the advantages CROAVN AND BRIDGE-AVORK. 851 and disadA'antages of each method. As regards what is strictly pivot work, all methods are objectionable in which the exposed sur- face of the root is not protected from such agents as disintegrate tooth structure; as regards the ferrule or band crown, such work is objectionable where it causes irritation of the gum and periosteal tissues, or permits of the disintegration of the supporting roots or teeth, or is temporary in its nature, on account of the use of the plas- tic preparations in connection with it; and lastly,all "bridge"or " graft" Avork is objectionable where it cannot be kept perfectly clean and free from accumulations of fluid and other substances beneath it, and Avhere it cannot be repaired in case of accident without breaking up the entire appliance. The effects of thermal changes on tooth tissues when brought directly in contact with large masses of metal, and the exceedingly frail nature of many of the porcelain crowns and facings required by some of the methods in use, should also be considered. Fig. 790. /"v\ /ir** z^ *^ in £?± fm>r\ /"v^ 1 2 3456 78 Fig. 791. 9 10 11 12 13 14 15 ' 16 To grind the Logan tooth-crown, it has been suggested to take a holloAV mandrel and, while in a hand-piece, heat the end and mount on it a corundum wheel, such as No. 00, being careful to make its outer face true and leave the hole in the end of the mandrel free for the pivot or post of the tooth-crown to enter. The neck of the Logan crown can then be ground without the risk of grinding the post or pivot, which enters the socket of the mandrel and is pro- tected. Solid gold cusps made of twenty-two carat gold and designed to 852 MECHANICS—DENTAL PROSTHESIS. be soldered to gold bands fitted to natural roots, and also for form- ing the masticating surfaces of porcelain crowns in bridge-work, can be obtained at the dental depots or be made by stamping thick gold plate Avith hard metal dies. Figs. 790 and 791 represent gold cusps for crown and bridge-Avork. CHAPTER VI. MANNER OF REFINING AND ALLOYING GOLD, AND CALCULATING ITS FINENESS. Gold is the best metal, and for general use the best material that can be used for the attachment of artificial teeth. When used of proper fineness, it resists the most acrid secretions of the mouth, and undergoes, during the long years of use, no change in its strength, form, or texture. Other metals and materials have a special utility, but none have so wide a range of usefulness, and none can take the place which this royal metal holds in dental prosthetics. Although the manner of refining, alloying and manufacturing gold into plate, solder, etc., may not, perhaps, be regarded as com- ing properly within the province of the dentist, yet, as he often experiences great difficulty in procuring them of the right quality, a brief description of these several processes is necessary. Espe- cially is this necessary, since the dental depots seldom keep on hand any gold plate finer than eighteen carats. This we consider dis- creditable to the profession which calls for so inferior a quality of metal rather than to those whose business it is to supply their de- mands. Twenty-carat plate can as readily be kept on hand by manufacturers as twenty-four carat foil. Moreover, some practition- ers are so situated that they cannot use gold plate, unless they know how to prepare it from coin. Gold in its pure state, free from alloy, is too soft and yielding to serve as a suitable support for artificial teeth ; but if it contains too much or an improper alloy, it will become tarnished by the secre- tions of the mouth, rendered too brittle for service, through those molecular changes which take place, with greater or less rapidity, if the plate is less than twenty carats fine. It is, therefore, of the utmost importance that the gold used in connection with artificial teeth should be of the proper fineness, and possessed of the requisite malleability. To secure these qualities, it is necessary to know the REFINING AND ALLOYING GOLD. 853 kind and quantity of metal with which to alloy it before it is made into plate or other forms necessary for the purposes for which it is to be employed. Gold clippings, filings and other scraps and parts of old gold pieces, as found in the laboratory, are apt to become mixed with base metals, such as iron from the wearing of files, and occasionall}7, small particles of lead, tin, or zinc. If these are melted with and permitted to remain in the gold, they wdll destroy its ductility, s and render it unfit for use. Iron, less objectionable than the lead or tin, may always be removed with a magnet before the gold is melted; but to free it perfectly from the others, it will sometimes be necessary to refine it in the manner presently to be described. A two-thousandth part of tin or lead destroys the ductility of gold, and even exposure to the fumes of red-hot tin or lead renders it ex- ceedingly hard and brittle. Antimony, or bismuth, Avhen mixed Avith gold, exerts upon it a very similar effect. So marked is the influence of antimony in injuring one of the most valuable proper- ties of gold, that its original name regulus (little king), by which it is best known in commerce, was given in view of this controlling effect upon the king of metals. It is of the utmost importance to bear in mind the action of minute quantities of these four metals, so much used in the laboratory, upon gold, platina and silver. Platina, united Avith gold in certain proportions, has the effect of hardening the latter metal and making it very elastic, but does not materially affect its ductility. The affinity 'of the alloy for oxygen, hoAvever, is so great that it is readily acted on by nitric acid. The acids of the mouth will often make this alloy very brittle. But for this, the tAvo metals, combined in the proportion of fifteen parts of gold to one of platina, would form an exceedingly useful alloy for the construction of spiral springs. That a combination of two metals should be thus easily acted on by an agent incapable of acting on either when in a separate state, may appear somewhat remarkable, but it is, nevertheless, true. We have in the effect of platina upon steel an analogous case. It makes the steel exceed- ingly hard and fine-grained; but although itself totally insensible to the action of oxygen, when alloyed in minute quantity with steel, it causes this latter metal to oxidize with such readiness as to make it unfit for use. Hence may be seen the fallacy of the idea entertained by many that because platina is a more indestructible metal than silver or copper, it must necessarily make a purer plate. The properties of alloys are, in fact, so often and so widely different from those of their component metals that they can be ascertained only by ex- 854 MECHANICS—DENTAL PROSTHESIS. periment. Of the three metals, platina, silver, and copper, specula- tive theory might select the first and purest as the best alloy for gold; whereas, actual experience demonstrates that copper, itself the most injurious to the mouth, imparts most perfectly to gold, if kept within proper limits, those qualities which are required in a dental plate. In view, then, of the importance of having gold Avhich is to be placed in the mouth of the right quality, every dentist who has connected with his practice a mechanical laboratory should have the necessary fixtures for melting and wrorking this metal into the various forms required for dental purposes. The principal of these are, a small furnace, with crucibles and tongs, ingot-moulds, an anvil and hammers, and a rolling mill; a plate gauge, draw plate, and bench vise; fluxing and refining chemicals, etc. REFINING GOLD. It is not our intention, in describing the manner of refining gold, to enter into a minute detail of the various methods employed for assaying or refining this metal, but to point out as briefly as possi- ble the manner of separating it from the several metals with which it is most frequently combined in the dentist's laboratory. The method usually employed by assayers for separating gold from silver is to roll the alloy out into very thin plates, and put it in nitric acid; this will dissolve most of the silver, and leave the gold behind in the form of brown plates, scales, or powder, which, after being thoroughly washed, is put into a crucible with borax and melted down into an ingot of pure gold. But this method will not succeed unless the quantity of silver be equal to two or three times that of the gold; for the nitric acid, which acts only upon the silver (and copper), cannot eat out all the alloy if its particles are too much surrounded with the particles of gold. From the old rule—one- fourth gold, three-fourths alloy—came the name given to this process, quartation; it is also known as the nitric acid process. It is well adapted to the purification of gold upon a large scale, and is the process used in the U. S. Mint. But it does not remove the platina so generally found in dentists' scrap ; and is not so well adapted for gold of 18 carat fineness and upwards as the next process. The nitro-muriatic or aqua regia process dissolves all the metals of the alloy, but immediately precipitates the silver. The gold is subsequently precipitated in a state of purity, thoroughly washed, dried, and melted down with borax. The process is, briefly, as follows : Melt the scrap to be refined; roll into a thin strip and curl it up into what is technically termed a cornet; place in a porcelain REFINING AND ALLOYING GOLD. 855 vessel and pour on the aqua-regia, three or four ounces to the ounce of alloy, which must be mixed at the moment of using, in the pro- portion of one part of pure nitric acid to two, two and a half, or three parts of hydrochloric acid; quicken the solution by heat from a spirit-lamp, setting the vessel where the nitrous fumes can escape from the room; decant or filter the solution so as to separate the precipitated silver; evaporate the clear solution over a spirit- lamp, nearly to dryness, add hydrochloric acid and evaporate a second time, so as to get rid of all nitric acid. The concentrated orange-colored solution is the chloride of gold together with the chloride of platina and other metals, from which it must be separated by precipitation. Dilute largely with water, and add, little by little, a solution of the proto-sulphate of iron (green-vitriol), until the dark olive-brown precipitate, which in- stantly appears, ceases to form. Pour on this precipitate some sul- phuric acid, to remove all traces of iron, and then wash several times Avith hot Avater, dry it, and melt Avith borax in a crucible. If the presence of much platina is suspected, the solution should be treated Avith muriate of ammonia (sal ammoniac) after the gold has been removed. This will precipitate the platina, Avhich should be AArashed, dried, and sold, inasmuch as the dentist has no heat sufficiently intense to melt it. If the alloy to be refined consists simply of gold and platina, the aqua-regia solution, after being made neutral by twice evaporating nearly to dryness, should be di- luted with water and the platina precipitated by muriate of ammo- nia ; then decant the gold solution from the platina and precipitate the gold .by the proto-sulphate of iron. A third method of refining is the sulphuric acid process, which it is unnecessary to describe further than to say that it resembles the quartation process. Gold is melted with five to seven times as much silver, granulated, and then boiled three or four hours in a platina or iron retort with sulphuric acid. By any of these three processes, but most conveniently by the second, dental scrap may be refined to a purity sufficient for every practical purpose. The assayer resorts to other methods to obtain the absolute purity required in analyses. Gold still containing traces of silver may be treated Avith sulphuret of antimony. This is done with a strong heat in a covered crucible, and after the gold has been kept in a state of fusion for some thirty or forty minutes it should be poured into an ingot-mould, and sep- arated from the antimony, Avhich will lie at the top. It may be necessary to melt it in this way two or three times, adding, each time, a less quantity of antimony; at the last melting, a current of 856 MECHANICS—DENTAL PROSTHESIS. air, from a pair of bellows, should be thrown upon the surface of the fused metal, to evaporate the antimony, and after the vapor ceases to escape, a little refined nitre and borax should be throAvn into the crucible. It should then, in a few minutes, be poured into the ingot-mould; should it crack in hammering or rolling, it must be again melted, and a little more nitre and borax thrown on it. Still another process for refining gold is occasionally used, called cementation. It consists in first rolling the gold out into exceed- ingly thin plates, then placing it in a crucible with a mixture of four parts of brickdust, one of calcined sulphate of iron, and one of chloride of soda. A bed of this mixture or cementing powder is first placed in the bottom of the crucible; the gold is then put in and covered with it. The crucible is covered with another crucible; the joints well luted with clay, and gradually raised to a red heat, at which temperature it should be kept from twenty to tAventy-four hours. The crucible is then removed from the fire, the top broken off, and after it has cooled, the gold may be separated from the cement and washed, or, what is still better, boiled in hot water. The form of furnace for melting gold depends much upon the kind of fuel. Charcoal, coke and anthracite are the three kinds used; bituminous coal is inadmissible until converted into coke. The plumbing stores and stove factories now furnish so many con- venient forms for the use of gas and any of these fuels that we shall not occupy time or space in their detailed description. A pipe six feet high will give to the oridinary " preserving furnace " a draft sufficient to melt gold with charcoal; coke gives a very intense heat, but needs a stronger draft; anthracite requires a powerful draft, but gives a more steady heat, needs less frequent renewal, and hence is better for long-continued heats. As regards the shape and size of the stove, the following points should be attended to : convenience of access to the crucible; suffi- cient depth and width to surround the crucible with a good body of fuel, without unnecessary waste of material. Fletcher's small and convenient blast crucible furnaces, for melt- ing gold by the use of gas and refined petroleum, are very service- able in laboratory work. The Ceylonese goldsmiths use a blast furnace of very rude and simple construction. It consists of a small, low, earthen pot, filled with chaff or sawdust, on which a little charcoal fire is made, which is excited with a small bamboo blowpipe, about six inches long, the blast being directed through a short, earthen pipe or nozzle, the end of which is placed at the bottom of the fire. By this simple con- REFINING AND ALLOYING GOLD. 857 trivance, a most intense heat may be obtained, greater, it is said, than is required for melting gold or silver. For separating iron, copper, tin, lead, or zinc from gold, the fol- loAving simple method may be adopted : After passing a magnet a number of times through the filings or fragments, to remove all traces of iron or steel, put the gold in a clean crucible, covered with another crucible, having a small opening or hole through the top; lute the two together with clay ; place them in a bed of charcoal in the furnace; ignite the coal gradually; afterward increase the com- bustion by means of a current of air from a pair of bellows, or by turning on the draft; after the gold has melted, throw in, at inter- vals of about ten minutes, several small lumps of nitrate of potash (saltpetre) and sub-borate of soda (borax), and keep it in a fused state for thirty or fort}r minutes; then remove the crucible, and plunge in water to cool it; break it and separate the lump of gold from the dross; then put into another crucible; melt with a little borax, and pour into an ingot-mould, of the proper size, previously warmed and oiled. Bichloride of mercury (corrosive sublimate) is sometimes used instead of or after nitre, for the purpose of dissi- pating the base metals, and often Avith more certain and better re- sults, especially where the presence of any tin is suspected. If the gold cracks on being hammered or rolled, it should be melted again, and more nitre and borax thrown in; the inside of the cru- cible should also be well rubbed with borax before the metal is put in. It is sometimes necessar}^ to repeat this process several times, and if the gold still continues brittle, a little muriate of ammonia (sal ammoniac) may be throAvn into the crucible when the gold is in a fused state; after the vapor ceases to escape, the metal should be poured into an ingot mould, warmed and oiled as before directed. This last method of treatment will make the gold tough, and pre- vent it from cracking under the hammer, or Avhile being rolled, pro- vided it is, from time to time, properly annealed during the process. By this method of refining gold, known as the dry process, or " re- fining by fire," sufficiently accurate results will be obtained for many of the practical purposes of mechanical dentistry; since the variation of an eighth or a quarter of a carat in the fineness of gold plate is not often a matter of much consequence. Comparing the two classes of refining processes—the humid, by acids, and the dry, by fire—the first is the more accurate, and the only way to remove platina or silver; but it is the most troublesome, and requires a familiarity with chemical details, AAdiich, unfortunately, many dentists are totally ignorant of. The second may remove the lead, tin, zinc, antimony and bismuth, if in small quantity; and if con- 858 MECHANICS—DENTAL PROSTHESIS. tinued for a sufficient length of time, with a free use of nitre, may remove a large proportion of copper. It can scarcely be depended upon if the object is to make an ingot of pure gold, but will ansAver admirably if the purpose is merely to lessen the alloy or remove certain impurities. As the dry process is one that the dentist will often have occasion to resort to, we shall give (from the seventh volume of the American Journal of Dental Science) the folioaving description of the very excel- lent method pursued by Dr. Elliott, of Montreal: " The following implements are necessary for this purpose: a small draught furnace ; a quantity of fine hard-wood coal; a clean crucible, with a sheet-iron cover (a lump of charcoal is better); a light pair of crucible tongs ; an ingot mould, made of soapstone; a little nitrate of potash, carbonate of potash, borax and oil. The fireplace of the furnace should be about ten inches in diameter, and eight or ten deep; this should be connected by means of a pipe with the chimney, so that a powerful draught may be made to pass through the coal. A blast-furnace is objectionable, for the reason that the bellows burns out the coal immediately under the crucible and it is, therefore, constantly dropping down, which is not the case with the draught furnace; besides, the draught furnace produces a more even fire, a quality equally indispensable. " In preparing for a heat, the furnace should be filled about half full of coal, and after it is well ignited, it should be consolidated as much as practicable without choking the draught. The crucible containing the metal and a little borax may then be set on, and more coal placed around and over it, the door of the furnace closed, and the damper opened. It should remain in this way until the gold is perfectly fused. The coal may then be removed from over the crucible, and a bit of nitrate of potash dropped in, in quantity equal to the size of a pea to every ounce of gold, and the crucible immediately covered Avith a plate of iron. More coal may then be placed over and around the crucible, and the gold kept in a fused state at a high temperature, until the scoria ceases to pass off, which it will do in the course of five or six minutes. The ingot mould, having been previously warmed, should be placed in a convenient position for pouring, and filled about half full of lamp oil. The cover should now be thrown off quickly, the crucible seized with the tongs, and at the same instant another small bit of nitrate of potash should be thrown into it, and the gold rapidly, but carefully, poured into the mould. " The ingot always cools first at the edges, and shrinks away from the middle. On that account, the mould should be a little concave REFINING AND ALLOYING GOLD. 859 on the sides, so that the shrinking will not reduce the ingot thinner in the centre than at the edges. " Moulds of the best form will sometimes produce ingots of irregular thickness. Such ingots should be brought to a uniform thickness under the hammer, using the common callipers as a gauge. If this be neglected, the plate will be found imperfect at those points Avhere the ingot was thinnest. The plate should be annealed occasionally during the process of hammering and rolling, and should be reduced about one number in thickness each time it passes between the rolls. If any lead, tin, or zinc be mixed with the gold, the nitrate of potash must be used in much larger quan- tities, and, in that case, it is better to let the button cool in the bottom of the crucible. Then break the crucible and melt it in a clean one for pouring, using borax and nitrate of potash in very small quantities for the last melting. " In case the subject of assay be in the form of filings or dust, a magnet should be passed through it, so as to remove every particle of iron, and then, instead of melting it with borax, it should be melted first with carbonate of potash, and afterward Avith nitrate of potash, in quantities proportioned to the necessities of the case, as before directed. Carbonate of potash is the only flux that will bring all the small particles of metal into one mass. Without it, a great portion of the gold will be found among the scoriae, adhering to the sides of the crucible, in the form of small globules. This pro- cess of refining ansAvers equally as well for silver as gold." ALLOYING GOLD. Gold, Avhen in an unalloyed or pure state, as before stated, is too soft to be used as a support for artificial teeth ; consequently, it has been found necessary to combine with it some other metal, in order to harden it. Silver and copper are the alloys most frequently em- ployed. Many dentists prefer the former, erroneously supposing that it does not increase the liability of gold to tarnish as much as the latter. But this opinion is sustained neither by facts nor expe- rience. Gold, when alloyed Avith copper, unless reduced altogether too much for dental purposes, will resist the action of acids as effect- ually as when alloyed Avith silver, and the former renders it much harder than the latter. Besides, it renders the gold susceptible of a higher and more beautiful finish. If, therefore, but one of these metals is used, copper may be regarded as preferable to silver. The gold employed in mechanical dentistry by most practitioners is altogether too impure for the purpose, it being not more than 860 MECHANICS—DENTAL PROSTHESIS. eighteen carats fine, and sometimes it is reduced even to fourteen. When not above these standards of fineness, it is disc6lored by the buccal secretions, imparts a disagreeable taste to the mouth, and becomes brittle after it has been worn for a few years. The plate which is to serve as a basis for artificial teeth should never be re- duced beloAV twenty carats; and as that for the upper jaw does not require to be more than one-third or one-half as thick as that of the lower, the gold for the latter may be a little finer than that em- ployed for the former, as it is necessary that it should be more malleable. The following standards of fineness may be regarded as the best that can be adopted for gold used in connection Avith arti- ficial teeth: plate for the upper jaw, twenty carats; for the lower, twenty-one; and for clasps and wire for spiral springs, eighteen. In reducing perfectly pure or twenty-four carat gold to these standards, first make an alloy of copper and silver, which may be either in the proportion of copper 4, silver 1, or copper 9, silver 1, according to the qualities required in the plate. The effects of the two metals are in strong contrast—copper giving hardness and elas- ticity, and deepening the color into a red; silver preserving the softness, and giving a greenish-white shade to the original yellow of the pure gold. Of these alloys take—to twenty-one grains of pure gold, three grains; to twenty grains of pure gold, four grains; and to eighteen grains of pure gold, six grains; to make, respectively, twenty-one, twenty and eighteen carat gold. In the latter case, the alloy should be used containing most silver, as so large a percentage of copper makes the gold too hard and elastic, and gives it rather too red a color. The gold should be first melted in a clean crucible, and as soon as it has become thoroughly fused, the silver and copper alloy may be thrown in, with two or three small lumps of borax. After keeping the whole in a melted state for some five or ten minutes, it should be quickly poured into an ingot mould of the proper size, previously warmed and oiled. If the gold cracks during the process of ham- mering or rolling, it must be melted again and a few small pieces of borax with a little muriate of ammonia thrown in, and in five or ten minutes recast into an ingot. When scraps and filings are to be converted into plate, they should first be refined, afterward properly alloyed. This may also be neces- sary with all gold the quality or fineness of which is not known; but with national coins having a known fixed standard this will not be necessary. When they are above these standards of fineness, the amount of alloy necessary to reduce them to the required fine- ness may be readily found by calculation. It is often unnecessary REFINING AND ALLOYING GOLD. 861 to change the fineness of either American (21.6 carat) or English (22 carat) coin; especially when the depth of the plate in upper cases, or the prominence of the ridge in lower, gives additional stiffness to the plate. There are tAvo principles upon which plates are alloyed. The first, and common one, is to add as much alloy as the gold will stand ; the second is to add the least possible quantity. The first results in eighteen carat gold, and uses mainly silver, lest the six grains of alloy should make it too brittle. The last results in twenty or twenty-tAvo carat gold and uses chiefly or exclusively copper; since the least quantity of this gives the greatest stiffness. The simple rule is to have the purest plate which the form of the mouth Avill permit. For shallow mouths, requiring increased stiff- ness, a twenty-carat plate may be used; but better practice still is to increase the rigidity by greater thickness, or sometimes by doubling some part of the plate. In connection with the alloying of gold, it is proper to make some remarks upon the terms in which the fineness of alloys is expressed, and the means of ascertaining it. Pure gold being taken as the starting-point, it may be expressed by unity (1), or by 24, or by 1000. In the first case, fineness is given in fractions. In the second case by parts called carats, which, for convenience, may be considered as equivalent to a grain; thus representing pure gold by 24 grains, or 1 dwt. In the third case, value is expressed in decimals, and is the most convenient system, although the second is the most customary with jewellers and den- tists. The following table, prepared by the late Prof. Austen, will show the relative value of these three systems in a few of the most usual forms of gold alloy : Fractions. Carats. Decimals 1. 24. 1000. 22. 916.6 9 21.6 900. 5 5 20. 833.3 4 ~5 19.2 800. 3 1" 18. 750. 5 15. 625. 1 12. 500. 1 3 8. 333.3 Pure gold.................... English coin................ American coin.............. Dentists' gold, best......... " " good....... Jewellers' gold, best....... *' " good...... " " common, Commonest solder......... The table gives the amount of pure gold; subtracting which from the number at the head of each column will give the amount of 862 MECHANICS—DENTAL PROSTHESIS. alloy. For example: best jewellers' gold contains 18 carats of pure gold and 6 carats of alloy; or three-fourths pure gold and one- fourth alloy; or 750 parts pure gold and 250 parts alloy. To know hoAV much alloy is required to reduce gold from one fineness to another, Prof. Austen gives the following rule: Divide the lower carat (c) by the difference between the lower carat (c) and the higher (C) ; divide the weight (W) of the gold by this quotient (c -=- (C— c)), and it will give the amount of alloy (A) to be added. He also gives the following table of divisors which will be found con- venient, as saving the necessity of much calculation : Carats. 22. 21. 20. 19. 18. 16. 14. 12. 24. 11. .7 .5 3.8 3. 2. 1.4 1. 22. 21. 10. 6.3 4.5 2.6 1.7 1.2 21.6 35. 12.5 7.3 5. 2.8 1.8 1.3 20. 19. 9. 4. 2.3 1.5 18. 8. 3.5 2. The first vertical column represents the fineness before alloying; first horizontal column the fineness after alloying. Example: To reduce a double eagle (weighing 516 grains, 21.6 carats fine) to 20, 18, and 12 carat plate, divide the weight by 12?, 5 and H; this gives the amounts of alloy to be added—for the first, 41.3 grains; for the second, 103.2 grains ; and for the third, 387 grains. When it is required to know the fineness of the plate or solder made from known quantities of gold and alloy, multiply the weight (W) of gold, before alloying, by its carat valuation (C) ; divide this product (CW) by the weight of the gold after alloying (W + A); the quotient Avill be the carat value (c) of the alloyed gold. This and the preceding rules may be also expressed by algebraic formula?: c CW (1) A = W-*----- (2) c=----- C—c W+A The fineness of any mixture of alloys of known value may be found by a simple arithmetical rule. Multiply each weight by its carat (pure gold being 24), divide the sum of the products by the sum of the weights, and the quotient will be the carat value of the mass. The following formulas may be employed for manufacturing gold plate from pure gold for dental purposes : Nos. 1, 2 and 3 for the base, and No. 4 for clasps: INGOT MOULDS, ROLLING MILLS, SOLDER. 863 No. 1. No. 2. Gold Plate 18 Carats Fine. 18 dwts., .... pure gold, 4 dwts., .... pure copper, 2 dwts., .... pure silver. Gold Plate 20 Carats Fine. 20 dwts., .... pure gold, 2 dwts., . . . • pure copper, 2 dwts., .... pure silver. No. 3. No. 4. Gold Plate 21 Carats Fine. 21 dwts., .... pure gold, 2 dwts., .... pure copper, 1 dwt., .... pure silver. Gold Plate 20 Carats Fine. 20 dwts., .... pure gold, 2 dwts., .... pure copper, 1 dwt., .... pure silver, 1 dwt., .... platinum. The following formulas maybe employed for manufacturing gold plate from coin gold : No. 1 for the base and No. 2 for clasps: No. l. No. 2. Gold Plate 18 Carats Fine. i Gold Plate 20 Carats Fine. 20 dwts., .... gold coin, 20 dwts., .... coin gold, 2 dwts., .... pure copper, j 8 grs......pure copper, 2 dwts., .... pure silver, i 10 grs......pure silver, ' 20 grs., .... platinum. Gold plate 20 carats fine according to formulas No. 4 and No. 2 is suitable for clasps, backings, and irregular appliances where great strength and elasticity are required. The folloAving formula of Johnson Bros, gives an 18 carat gold plate: United States gold coin,......64£ dwt. Pure silver,........13 dwt. CHAPTER VII. INGOT MOULDS, ROLLING MILLS, SOLDER. The gold, after being refined or alloyed, should be remelted in a clean crucible, Avell rubbed on the inside Avith borax, and poured into an ingot mould (Figs. 792, 793) of proper length, width and thickness. Ingot moulds may be of iron, soapstone, asbestos, charcoal or car- bon. The first is perhaps most convenient. The second gives, with the same gold, a tougher ingot; the asbestos ingot block, Avhich may also be used for melting, is a perfect non-conductor, and is 864 MECHANICS—DENTAL PROSTHESIS. represented by Fig 794; it is 1\ inches wide and \ inch thick. With the charcoal ingot mould the greatest toughness of metal is obtained, so far as the nature of the ingot mould can modify it. Pig-iron, from the same furnace, run into iron moulds, may be white and brittle; or into sand moulds, gray and less brittle; or into charcoal, dark gray and soft. Some such modification of the molecular arrangement of gold, due to its manner of cooling, is Fig. 792. Fig. 793. probably the correct explanation of the fact that a charcoal mould yields, other things being equal, a tougher ingot than iron. An apparatus is now in use, which combines the crucible and ingot mold, in which a crucible, or moulded carbon, communicates Fig. 794. with an ingot mould, both held in position by a clamp underneath, and SAviveling on a cast-iron stand. The metal to be melted is placed in the crucible, and the flame of a blowpipe is directed on it until it is perfectly fused. The waste heat serves to make the in- got mould hot, and the whole is tilted over by means of an upright handle at the back of the mould. A sound ingot may be obtained at any time in about two minutes. The charcoal ingot mould is easily made. Select a fine-grained INGOT MOULDS, ROLLING MILLS, SOLDER. 865 piece; saw in half and make smooth by rubbing the surfaces to- gether. Then make the matrix in one of three Avays : either cut the shape required out of one-half, with the proper gate; or bend a heavy wire into shape of the ingot and gate, and bind it between the surfaces; or saw off a charcoal slab, and after cutting out the shape of the ingot and gate, bind it between the surfaces. Those who have once used a charcoal ingot, will seldom use any other. After it has become sufficiently cool, it may be placed on an anvil, and its thickness reduced to about an eighth of an inch, Avith a hammer weighing from one to one and a half pounds. It should then be well annealed by being placed in the furnace, lightly covered with small pieces of charcoal, and heated until it assumes a uniform cherry-red color; or it may be annealed AAdth a blowpipe. It may be necessary, during the operation of hammering, to subject it once or twice to this process, to prevent the gold from cracking. If, notwithstanding this precaution, it should crack, it must be again melted, and refined with muriate of ammonia. Sudden cooling does not make it brittle. On the contrary, some jewellers maintain that if plunged in alcohol and water, it is softer than Avhen sloAvly cooled. A little sulphuric acid in the water will give a bright sur- face to the plate, by cleansing off the oxide of copper; but this acid pickle is only necessary for removal of the metal of the dies used in swaging, or of the borax used in soldering; in all other cases we prefer to have the oxide coating. After the gold has been reduced to the thickness just mentioned, and well annealed, it may be placed between the rolls of the mill, previously so adjusted as to be the same distance apart at both ends, and not so near to each other as to require a great effort to force it between them. The rollers, however, should be brought a little nearer to each other every time the plate is passed between them; and during this process they should be kept well oiled, so that there may be as little friction as possible. Many roll the ingot without any previous hammering. In the process of rolling care must be had to anneal often, and to roll in one direction until sufficient width of plate is obtained; then, before cross-rolling, be sure to anneal, else the plate will be very apt to crack. Rolling mills for gold are variously constructed. Some are very simple, while others are quite complex, have a great deal of ma- chinery connected Avith them. The rollers also vary in length, from three to five inches. For the gold plate used by dentists, they need not be more than three or three and a half inches long. Fig. 795 represents a simple form of rolling mill, Avithout the cog-gear- ing, as seen in Fig. 796. The latter is a strong but simple mill, and 55 866 MECHANICS—DENTAL PROSTHESIS. is very well suited to the dental laboratory. The set-screws at the top are turned with a rod, and must be both moved alike, else the plate will be thicker on one side, and will curve laterally in rolling. Fig. 797 represents a more complicated mill, designed for those who do much or heavy rolling. With such a mill, all the heavy roll- ing of a laboratory could be done without the aid of an assistant. The thickness of the plate may be determined by a gauge plate. That which is to serve as a basis for artificial teeth for the upper jaw may be reduced until it fits the gauge at 25, 26 or 27, according to the quality of the plate and the depth or irregularity of the arch. For the loAver jaw, and for backings and clasps, it may range from 21 to 24. When the whole alveolar border and a portion of the roof of the mouth is to be covered, it may be a little thinner Fig. 795. Fig. 796. than when applied only to a small surface; also thinner when the arch is deep or irregular. The purer the gold is, the thicker must be the plate. When very wide clasps, too, are employed, it is not necessary that the gold should be as thick as if required for narroAV ones; and low or wide backings need not be so thick as long or narrow ones. Lower plates, if wired around the edge or doubled over the middle third, may be made of the same thickness as an upper plate. But these are matters which the judgment of the den- tist alone can properly determine, and, consequently, no rules can be laid doAvn upon this subject from which it will not sometimes be necessary to deviate. Gauge plates are, unfortunately, not uniform. For many years the most reliable were those manufactured by Stubbs. But it is difficult to procure them. At the same time it is very important that some standard should be adopted in the profession. Under these circumstances we approve the suggestion of the late Dr. S. S. White, who recommended the gauge plate given in Fig. 798, which INGOT MOULDS, ROLLING MILLS, SOLDER. 867 has been adopted by the principal brass manufacturers of this country. Fig. 797. Fig. 798. It may be necessary sometimes to make gold wire for spiral springs or other purposes, also hollow-tube wire. A draw plate Fig. 799. (Fig. 799), strong pliers and bench vise (Fig. 800) are the necessary tools for this purpose. The draw plate should be of the hardest 868 MECHANICS—DENTAL PROSTHESIS. steel, with the holes diminishing very gradually. The pliers should be rough at the end, for grasping the wire, which must be often annealed during the process. Tube wire may be obtained from the jewellers, by Avhom it is known as joint wire. But it is seldom over sixteen carats fine. For use in the mouth it should be not less than twenty carats; but for many purposes, pure gold or platinum tubing is better. It is easily made as follows: Take a small strip of plate one-fourth of an inch wide, one or two inches long; slightly taper one end; bend it around a mandrel or common knitting needle, and pass it into one of the larger holes of the draw plate. Then with the pliers draw it through and repeat until the edges of the strip meet. Remove the mandrel and solder the seam with fine gold or else pure gold. Lastly, select a mandrel or needle, the size of the required tube, and draw the Fig. 800. wire until it has the proper thickness. If the bore is to be smaller than any needle at hand, the last drawing may be done without the mandrel. The simplest method of winding wire into a spiral spring is to secure it between two blocks of wood, held between the jaws of a small bench vise, as shown in Fig. 800. The upper end of the wire is then grasped by a hand vise or sliding tongs, in connection with a spindle or steel wire the size of a small knitting needle, six or eight inches in length. The spindle, resting on the blocks of wood, is made to revolve, and by this movement the gold wire is drawn through the blocks and wound firmly and closely round the steel rod. INGOT MOULDS, ROLLING MILLS, SOLDER. 869 GOLD SOLDER. In making gold solder, the materials employed for the purpose, if not pure, should be refined separately. Unless this is done, it Avill be difficult, and often impossible, to ascertain their relative purity, which should be known, to insure the desired result. The gold is placed in a clean crucible with a little borax, and as soon as it has become perfectly melted, the silver, and afterward the copper, are added. When all are melted, the alloy may be immediately poured into an ingot mould, previously warmed and oiled. The process of hammering and rolling the solder is the same as that described for gold plate. In consequence of the large amount of alloy in solder, it is sometimes so stiff, and even brittle, as to be Avith great difficulty rolled ; this difficulty is increased by the fact that its Ioav fusibility makes it not very easy to anneal Avithout melting. This is especially the case with solders in which zinc or brass is used. In making solder into the composition of which zinc enters, the other ingredients must be thoroughly melted, then the zinc (or brass) introduced at the last moment, rapidly stirred, and the metal quickly poured. A piece of charcoal will be found better for making small quantities of solder than a crucible. The solder employed for uniting the various parts of a piece of dental mechanism should be sufficiently fine to prevent it from being easily acted on by the secretions of the mouth. If pure gold is used, the solder will be of finer quality than if twenty-two carat gold is used, but will not Aoav quite so readily. But tAventy-two-carat plate may be used, if its alloy is known, by making due allowance for the amount, which is easily calculated by use of preceding rules. The following makes a solder sixteen carats fine, and may be used for eighteen- or twenty-carat gold plate; it floAvs very freely. No. 1.—Pure gold,........6 dwts. Fine silver,........1 " Roset copper,........2 " By adding one or two grains of zinc, a solder may be made that will floAV at a loAver temperature than that made by recipe No. 1. It will also have a finer gold color; but it is apt to impart to the piece a brassy taste, and for this reason the author rarely uses it. Zinc solders are apt not only to have a brassy taste, but also to become brittle after long use. The folloAving formulas will give solder fourteen carats fine; the first from Johnson Bros. 870 MECHANICS—DENTAL PROSTHESIS. No. L. 1 No. 2. Pure silver, . . 2i dwts. American gold coin, . $10 " copper, . 20 grs. Pure silver, . . 4 dwts " zinc, . 35 " ' " copper, . 2 " The following formulas from the American System of Dentistry, are suitable for bridge- and crown-work, and are twenty carats fine: No. 1. American gold coin (21.6 carats fine) ($10 piece) . . 258 grs. Spelter solder (composed of equal parts of copper and zinc) 20.64 " No. 2. Pure gold,.........• . 5 dwts. " copper,.........6 grs. " silver,.........12 " Spelter solder..........6 " Dr. D. H. Goodno's formula, which is said to give a gold solder which is remarkably tough, Aoaa'S readily, and does not discolor in the mouth, is composed of the following alloy: Pure gold...........40 grs. " silver...........2J " " copper,.........2\ " " zinc,..........3 " In the melting process the zinc is rolled in gold foil and placed in the crucible and covered with borax. The copper and silver are then added and also covered with borax, and the whole melted. To use this alloy for a twenty-carat plate 5 dwts. of pure gold are added to 1 dwt. of the alloy; for eighteen-carat plate, 5i dwts. of pure gold to li dwts. of the alloy. The following formulas, taken from Dr. Richardson's work on " Mechanical Dentistry," furnish solders (No. 4) over fifteen carats fine, and (No. 5) eighteen carats fine. Gold coin, Silver, . Copper, Brass, . No. 4. No. 5. 6 dwts. Gold coin, . . 30 parts 30 grs. Silver,. . 4 " 20 " Copper, . 1 " 10 " . 1 " Other recipes might be added, but the foregoing have been found with us to answer every purpose. More difficulty arises in the use of solders from a wrong method of soldering than from defect in the solders themselves. Almost every dentist will be found to have his MATERIALS FOR IMPRESSIONS OF THE MOUTH. 871 favorite recipe, which " invariably flows smoothly." The very fact that so many hundred different solders work so well goes far to prove Avhat Ave have said. Some "will boast of using a solder as fine as the plate. This may be true if, b}r " fineness," we mean simply carat valuation. But a solder containing two grains of zinc to the dwt. is in no true sense as fine as a plate alloyed with that amount of copper; yet both are tAventy-two carat metal. Rules for the management of solder, plate and blowpipe, in the act of soldering, will be hereafter given. CHAPTER VIII. CUPS AND MATERIALS FOR IMPRESSIONS OF THE MOUTH—PLASTER MODELS. In the construction of a dental substitute, mounted upon a plate or base, it is necessary to obtain an exact model of the parts upon which it is to rest, and to which it is to be attached. For this pur- pose a perfect impression of these parts must be obtained, involv- ing—first, the choice of a suitable impresssion cup; secondly, the selection of an impression material. IMPRESSION CUPS OR TRAYS must be of such size and shape as to permit their easy introduction into the mouth; also must they folloAV, as nearly as possible, the Fig. 801. Fig. 802. outline of the surfaces to be copied, allowing a uniform space of one-fourth or one-eighth of an inch for the material. These cups 872 MECHANICS—DENTAL PROSTHESIS. are sometimes called mouth cups; but we think the name given, and now generally used, is greatly to be preferred. They are of two kinds, metallic and gutta-percha. Metallic cups were formerly made of sheet tin, cut into shape and soldered, and were so imperfect that it was very often necessary to swage metallic cups to suit special cases. The depots now sup- ply an excellent assortment of well-shaped Britannia impression cups, of which sixteen will constitute a full set; namely, six sizes MATERIALS FOR IMPRESSIONS OF THE MOUTH. 873 for full upper cases, and three for full lower; three sizes for partial upper cases (in these the outer rim rises at a right angle), and four for partial loAver (these cups have a depression, or a place cut out to receive the front teeth). Figs. 801 and 802 illustrate full upper and lower impression trays. Figs. 803 and 804 illustrate partial upper and lower impression trays with flat bottom and square sides. Figs. 805 and 806 illustrate adjustable impression trays. In tak- ing impressions of deep, narrow mouths, or where a masticating tooth standing alone widens the jaw at a particular point, it is sometimes desirable to be able to readily adjust the size and shape of the tray used. Upper, Fig. 805, and lower, Fig. 806, impression trays have been designed to meet this want. Either of these can be made into a partial tray by cutting off one side. Fig. 807 illustrates Southwick's upper impression tray with raised palatine edges to prevent the plaster from slipping off. Fig. 807. Fig. 808. Fig. 808 illustrates a partial loAver tray with an opening to allow the front teeth to pass through and the tray to pass down to the maxillary ridge. A piece of Avet paper is placed over the opening when the cup is filled Avith the plaster-batter. Fig. 809 illustrates Dorr's loAver impression tray with posterior lingual wings, which enable the operator to obtain an accurate impression of the jaw on either side of the tongue. These wings may easily be spread apart, or brought towards each other, or twisted, or cut away to adapt the tray to nearly any size or shape of the edentulous lower jaw. Fig. 810 represents Dr. Franklin's cup for full lower impressions; the slot and upper groove permit secondary pressure of the wax or 874 MECHANICS—DENTAL PROSTHESIS. plaster, after the surplus material is forced up, as it is pressed on the alveolus. " This cup, or rather double cup, has a groove or space in its centre all the way round. The advantages of this groove are, that, when the lower part of the cup is filled, and the upper part one- fourth full of plaster, and placed in position over the ridge, the operator, with the end of the finger or other suitable means, can gently agitate the whole mass of plaster in the cup, and thus pre- Fig. 809. vent air-bubbles, blanks, or other imperfections on the surface of the impressions. The peculiar shape of the outer flanges of this cup is such as to distend the cheeks, while the lower inner edges, press- ing upon the submaxillary and sublingual glands, depress them sufficiently to prevent any fold or ligamentous attachments from being embraced by the impression." Fig. 811 represents the Wardle cup, which is supplied with a movable palate plate, so adjusted that it is capable of forcing the centre of the impression material against the highest part of the arch, as well as laterally against the palatal sides of the necks of any remaining teeth. Fig. 812 represents Fouke's impression cup, by Avhich it is claimed MATERIALS FOR IMPRESSIONS OF THE MOUTH. 875 a correct impression in all variety of cases, both partial and full, can be obtained. It consists of a metallic portion with a canvas lining. Fig. 811. The design of the cup suggests of itself the manner of using it; which consists of the ordinary pressure against the metallic part of the cup, in connection with a proper distribution of pressure with Fig. 812. the fingers and compressing instrument A, against the canvas lining of the cup, C C; the latter pressure must be made with a degree of firmness and steadiness sufficient to compress thoroughly all parts of the mouth. 876 MECHANICS—DENTAL PROSTHESIS. Exceptional cases, which no form of purchased cup will suit, may require a swaged brass, zinc, copper, of silver cup; or a cup cast out of Britannia metal, or other tin alloy. The process of SAvaging will hereafter be described; also, the method of moulding a cup from a pattern of Avax. Most of these cases, however, may be met by bending, hammering, or cutting the ordinary Britannia cup; remembering always that a wise economy never hesitates to sacrifice the cup, to sucure excellence of the impression or the saving of time. Without this adaptation of the cup to the form of the alveolar ridge and palate it is impossible, in certain mouths, to get a good wax or gutta-percha impression. Fig. 813 illustrates a partial upper tray for one or two teeth, which is useful in pivot- ing and bridge-work. Fig. 814 illustrates Mathews's partial upper or lower tray. Cups similar in shape to the Britannia, but not in so many varie- ties of size, are also made of hard rubber and porcelain. The first cannot easily, and the latter cannot at all, be modified in shape to Fig. 814. suit special cases. The porcelain cups are handsome and clean looking, but they are easily broken; and when plaster is used, it will sometimes leave the glazed surface and cling to the mouth. We, therefore, prefer the Britannia cup, unless the case requires Prof. Austen's gutta-percha cup. These cups were originally devised to meet a difficulty incident to vulcanite partial pieces. Perfect impressions of dove-tailed inter- dental spaces, and the lingual side of molars and bicuspids, often undercut, are impossible in wax or gutta-percha. Yet, Prof. A. regarded this as essential to the proper construction of a partial vul- canite set of teeth. They are thus made: Take a wax impression and make a model; in partial cases, brush over the teeth of the model one or two layers MATERIALS FOR IMPRESSIONS OF THE MOUTH. 877 of thin plaster, to fill up all undercuts, and to make the plate fit loosely ; saturate the model with water, and mould over it a gutta- percha cup. This last is done, not by using the gutta-percha in sheet, but by first making into a ball; then working it from the palate outward, leaving a thick mass in the centre. It should be, on the inside, from one-fourth to one-half of an inch thick, so as to be stiff and unyielding; but on the outside not more than one- eighth or one-sixteenth thick, so as to be slightly elastic and yield- ing. The Avhole inside of the cup must be roughened up Avith a scaler or excavator in such a Avay that the plaster can take firm hold. In most partial cases, the impression will have to be re- moved in sections ; the inside remaining entire, but the outside and the parts betAveen the teeth coming away separately. In certain cases, it is necessary to partially cut through the cup before putting in the plaster, and usually upon the thick masses of gum Avhich fill the interdental spaces. A cut on the inside, in line with the ridge, gives pliancy to an otherwise rigid cup, and permits its easy removal. When it is desirable to extend the cup around the entire arch, so as to get an exact plaster impression, not only of the gum but of all the remaining teeth, this rim of gutta-percha must be slit at two or three points, to give that pliancy which is a chief merit in this form of cup. These cups have no handle, but are removed by inserting a plugging instrument into a small hole previously made in the back part of the cup, where it is thickest. IMPRESSION MATERIALS Must possess the folloAving properties: (1) Plasticity in sufficient degree to copy mucous tissues, avoiding the extremes of softness, Avhich permits them to flow from the cup, and of hardness, which requires excessive pressure. (2) The property of hardening within a short time, and under conditions not incompatible with the mouth. (3) Absence of expansion or contraction, except in very moderate degree. It may also be added that the materials should not be such as, in taste, smell, or appearance, are calculated to dis- gust the patient. There are four materials ansAvering to these requirements, and possessing properties as distinctive as the sources whence they are derived. From the Animal kingdom, Beesavax ; from the Vegetable kingdom, Gutta-Percha and Modelling Composition; from the Mineral kingdom, Plaster. After their separate description, a brief revicAv of their distinctive properties will be given. No one of the four can be dispensed Avith; no one should be exclusively used. 878 MECHANICS—DENTAL PROSTHESIS. Beeswax.—Formerly the only material used, and is yet very use- ful for certain cases, and is absolutely indispensable for other dental purposes. The best wax is from virgin combs, and has a rich golden color. Commercial adulterations with tallow, etc., injure it, and mixture with resin makes it harsh and difficult to manage. Gutta- percha is sometimes incorporated with it to give hardness in warm weather; bleached or white wax is also used for the same purpose. A very valuable addition is paraffine. Pure paraffine is very plastic, softening at a low temperature (100°); but the folds of soft paraffine have no tendency to reunite, and consequently the mass is full of easily separated flakes or layers. It imparts this property to wax, if in too large proportion ; but its moderate use greatly im- proves the wax. It causes it to soften at lower heat, makes it more plastic when warm, and harder when cool. The depots furnish wax and its compounds in very pure, neat and convenient forms ; so that there is now little necessity for the den- tist to spend the time once demanded to reduce the thick cakes into serviceable shape. It may be well, however, to state briefly how to prepare wax for impressions. Melt and pour into cakes one-quarter of an inch thick; cut into pieces about two inches square ; and Avhen nearly cold roll on a wet board, with a wet wooden roller, to one- half or one-fourth this thickness. This breaks down the crystal- lization, and reduces it to a form very convenient for softening when wanted for use. It may be softened OArer a broad flame, or before a fire or stove, or in warm water. In using dry heat be careful not to melt the surface, or give the peculiar Avhitish appearance that precedes melting. In using water, have a large quantity, to secure uniformity of temperature, and keep it at 120°-130° Fahrenheit. Below this it will not yield readily to the gum; above this it becomes adhesive. Some practice is necessary in knowing the proper quantity of wax to use in the cup; the usual mistake is to take too much. Select a cup of proper shape and size; if the arch is a deep one, put some hard wax or gutta-percha in the centre to force up the wax at that point. This is much better than to have a hole in the cup through which to make pressure Avith the finger. Such cups are worse than useless, for it is impossible to make secondary pressure without in- jury to other parts of the impression ; except in case of wax pro- jecting above the cup, outside the ridge. Put the wax in the cup; smooth the surface, which should be a little softer than the body of the wax; then introduce and press against the gums or teeth with a steady, uniform, and moderately strong pressure; also, as nearly MATERIALS FOR IMPRESSIONS OF THE MOUTH. 879 as possible, in a direction at right angles to the plane of the alAreolar ridge. The Avax above the cup is pressed against the gums on each side, so that an exact impression may be obtained of all the depressions and prominences on the outside of the arch. But this must be done with great care, holding the cup firmly and pressing the finger against the cheek or lip, rather than directly upon the wax. It is much better in all cases to have the sides of the cup high enough to give the wax support at all points. For this purpose, it becomes necessary sometimes to swage or cast a special cup. Very perfect wax impressions can be taken in such cups. On the removal of the cup and wax from the mouth, the greatest precaution is necessary to prevent injuring or altering the shape of the impression. Holding the handle firmry, it must be drawn directly downward, in case there are front teeth, in the direction of the axes of these teeth. Impressions of a full upper arch sometimes adhere very tightly. They can generally be loosened by draAving up the cheek and lip on one side or both sides alternately; or by a slight cough,, which, acting upon the palate, admits air behind and above the impres- sion. Any violence or tAvisting motion injures the impression ; in Avax or gutta-percha such defects cannot be detected until, on com- pletion of the plate, maladjustment creates suspicion of its cause. The Avax must be kept in the mouth long enough, to cool and harden. A small piece of ice in a napkin, held against the under side of the cup, Avill rapidly harden it. This simple plan is preferable to the use of double cups, into which a stream of cold water is injected. The latter are not only expensive and troublesome to use, but they endanger the accuracy of the impression. All wax impressions, unless for models on which other cups are to be made, should be hardened by artificial cold; it greatly helps to prevent change of shape on withdrawal. If the surplus wax, by contact with the lips or teeth, injures the impression, then, if it is a full case, cut off the surplus, dip into warm water, and introduce the same impres- sion a second time; but if it is a partial case, it must be taken; aneAv, for the teeth cannot, with any accuracy, enter their wax im- pressions. Gutta-Percha.—This very valuable material will be found useful in taking impressions of the lower jaw and in some partial cases, also frequently in full upper cases where the teeth are set on a vul- canite base. The manipulations are different, accordingly as we Avish to make the gutta-percha adhere to the eup, or wdsh it to part from the sides of the cup as it shrinks on cooling.. In the first case, soften in AArater heated to 180°-200° Fahrenheit; dry off the water;; 880 MECHANICS—DENTAL PROSTHESIS. hold for a few moments over a flame, and press into a warm cup; keep the fingers wet, to prevent the gutta-percha from sticking, but do not let water get between it and the cup. In the second case, keep the surface of the gum wet, and introduce it into a cold and wet cup. When the cup is filled, place again in water at 180° ; then press it somewhat into shape, and introduce into the mouth. Press- ure must be more gentle than for wax; it must be kept longer in the mouth, and ice should be used to cool it. Be very careful, in partial cases where there is much undercut or a dovetail space between teeth, not to make the gutta-percha too hard, else it will be almost impossible to get it out of the mouth. Gutta-percha copies surfaces with all the accuracy of plaster; but, although harder than wax, it is more apt than plaster to change its shape upon withdrawing it from the mouth. Its characteristic peculiarity is contraction on cooling; but this is controlled, Avhen required, by the directions above given for making it adhere to the cup. It is less easily manipulated than wax, and not so generally useful; but its property of contraction admirably adapts it to certain cases in which plates, otherwise accurate, fail, because too large and loose. Gutta-percha for impressions is supplied in convenient form by the depots. The native color is dark, and calculated to repel fas- tidious patients. For this reason, also to give it body, it is incor- porated with about is own weight of white oxide of zinc, magnesia, or chalk, and a pinkish color given by vermilion. Thus prepared, it is less sticky when softened, and becomes harder, when cool, than the crude article. Modelling Composition or Compound is composed of gum dammar, stearine, French chalk, with carmine to color it, and a perfume to render it pleasant. Four varieties are manufactured—the soft, the medium, the hard and the extra soft, differing as to the quantity of stearine and chalk incorporated with the gum. Modelling com- position is an excellent material for impressions, as it copies very accurately, and affords a smooth model. The best manner of using it is to soften this material in boiling Avater contained in a shallow vessel. When it is thoroughly softened, and not too hot to handle, the cup for its reception should be slightly warmed, into which it is introduced in the same manner as Avax. After it is applied to the mouth, it is allowed to cool somewhat, after being pressed around the outside of the alveolar ridge. The same care is necessary in removing it from the mouth as with wax, and it should be immersed in cold water at once, to harden it. Before pouring the plaster the impression should be dipped in cold MATERIALS FOR IMPRESSIONS OF THE MOUTH. 881 Avater. To remove an impression of this material from the plaster model, both are immersed in boiling water, Avhere they should remain until the compound becomes soft, but not adhesive, when it is easily separated from the model. Plaster—Gypsum, Sulphate of Lime, or Plaster-of-Paris—consists of 28 parts lime, 40 of sulphuric acid and 18 of water; the first its mineralogical name, the second its chemical, the third its commer- cial. A beautiful translucent variety of gypsum is known as ala- baster ; the transparent crystalline variety is called selenite. That, however, used in agriculture and for calcining, is- in amorphous masses of a grayish or bluish-Avhite color. When exposed to a heat betAveen 300° and 400° Fahrenheit, most of the water of the gypsum escapes. It is then known as calcined plaster, plaster-of-Paris, or simply plaster. After being properly calcined and pulverized, if mixed with water to the consistence of thin batter or cream, it hardens in a few minutes, and acquires great solidity. The plaster has chemically reunited with a portion of the water, while another portion is mechanically held in the porous mass, and may be driven off by drying. During the process of consolidation it expands, in consequence of the absorption of the water by the particles of plaster. If the plaster is very fine-grained, this absorption takes place quickly, and the expansion occurs while the plaster is soft. But coarse-grained plaster sets before the particles become thor- oughly saturated; hence it continues to expand, more or less, for some time after solidification. There is a great difference in the quality of plaster. That used for taking impressions of the mouth (and, in fact, for all dental purposes) should be of the best descrip- tion, Avell calcined, finely pulverized, and passed through a sieve of bolting cloth previously to being used. The idea of taking impres- sions for full sets of teeth with plaster originated, we believe, almost simultaneously Avith Drs. Westcotty Dunning and Bridges, by whom, and the profession generally, it has been regarded as adapted almost exclusively to full impressions. Prof. Austen introduced a method of using it in connection Avith gutta-percha cups, Avhich makes it, in the hands of a careful manipulator, universally applicable to every case in Avhich a dental appliance is called for. He would, however, by no means recommend such universal application,, claiming only that the gutta-percha cup will give with plaster a correct impression of partial cases of greatest irregularity, where the use of wax or gutta-percha Avould be impossible. For plaster impressions in ordinary full cases, upper and lower, select a Britannia cup, about one-eighth of an inch larger than the alveolar ridge, and, in case of a deep upper arch, build up with wax„ 56 882 MECHANICS—DENTAL PROSTHESIS. so as to give support to the soft plaster; also supply Avith Avax any deficiency in the size of the cup at the back part or around the out- side edge. In exceptional cases, requiring a special cup, a gutta- percha one will be found to be much easier made than a SAvaged or cast metallic cup. If properly shaped, it will fully answer the pur- pose. The late Dr. Bean's practice Avas to take a Avax impression, make model and dies, and SAvage a plate; then solder a strip from ridge to ridge, to hold a stick, which was to act as a handle in removing the impression. He then heated the plate, and coated the palatine surface with shellac, pressing a lump of raw cotton against the ad- hesive resin. The cotton fibres caused the plaster to adhere firmly to the plate, thus avoiding the great annoyance when scales of plaster, so thin as in this kind of cup, break off. The process is troublesome, but the results are very satisfactory. To take a plaster impression, place a patient in a common chair, and after the cup is introduced, incline the head forward, holding it in place with a gentle but steady pressure upon the centre of the cup. The plaster should be very fine-grained and mixed rather thin, to get rid of air bubbles. If necessary, a little salt or a few grains of sulphate of potash should be added, to quicken sloAV-setting plaster. The necessity for salt and quantity to be used should not be left to conjecture; hence the importance of setting aside in a well-closed vessel, a quantity of " impression plaster." Also, if the plaster is " slow," set aside a large bottle of salt water of the exact strength required to make that plaster set properly. There will, in this way, be no danger of the plaster setting too quickly or too slowly. If made to set too rapidly, it hurries the operator and in- creases the risk of failure; if it sets too slowly, both patient and operator become wearied before it ft hard enough to remove. Tepid water promotes the setting of plaster. It should require about three minutes to harden after it is introduced into the mouth, which must be done when it is stiff enough to allow the plaster to be moulded into some shape, and yet soft enough to permit no sharp points or angles on its surface. If softer than this, the slightest pressure forces it out of the cup, to run sometimes out of the mouth, some- times on the tongue and fauces. This also is apt to occur if an excess of plaster is used. These unnecessary accidents are well calculated to prejudice patients against plaster, and, perhaps, against the operator. The hardness of plaster in the mouth can be ascertained by the watch, Avhen the exact time required for setting is knoAvn, or by testing some of the plaster remaining in the bowl. As soon as it breaks with a sharp fracture, it should be removed. To keep it in MATERIALS FOR IMPRESSIONS OF THE MOUTH. 883 much longer than this is apt to give unnecessary pain and difficulty in removal, OAving to the absorbing property of the hardened plaster, which causes it to cling Avith great tenacity to the mucous mem- brane. Full lower impressions are generally easy to withdraw; but some full upper ones adhere very tenaciously. Raising the cheek on one side or in front, and depressing the cup, will detach most cases. This can be done, in case of plaster, Avithout risk of injuring the shape of the impression. If this does not loosen it the patient may be requested to give a slight cough. Where there is much undercut, the plaster will break; but it can readily be replaced. Sometimes the action of the cheeks and lips, or of the soft palate, will loosen t*he impression; or an instrument may be used to press up the palate, and thus cause air to pass in at the back, when it may be easily removed. Complicated modifications of the cup to facilitate removal are of little Aralue, and make an unnecessary multiplicity of apparatus.' In partial cases, the outer rim (Avhich for this purpose is made elastic, or else in sections) is first detached, and the central portion then loosened by an instrument inserted into the back part of the gutta-percha cup. Tf there should be many broken, detached frag- ments, either loose or caught in dovetail spaces between the teeth, these must be very carefully removed; and when the surface moisture has dried off, they must, Avith the utmost nicety, be replaced in the impression.. This is sometimes a tedious and diffi- cult operation; but it is not trouble misapplied, since it is the only Avay in which perfect impressions of difficult partial cases can be obtained. Should the detached plaster be from a very irregular surface, its readjustment is made much easier by touching the gutta-percha at that point Avith a*amel's-hair brush dipped in very hot water. The fragments being all adjusted and the outside ones secured by a little resinous cement, should there be much broken surface on the inside, it is best to varnish heavily with sandarach to cement the pieces; otherAvise, let the surface be prepared, as in full sets, for preventing the plaster of the model from adhering. Wax and gutta-percha require nothing for this purpose, or, at most, a very thin layer of oil. Plaster impressions may be rendered separable: 1, by an alcoholic varnish of sandarach or shellac, or a diluted solution of soluble glass, with a little oil upon the varnished surface Avhen dry ; 2, by saturating it with as much oil as it Avill take up Avithout standing upon its surface; 3, by coating the sur- face Avith a dilute soap mixture. The varnish may be either trans- parent or colored; the transparent varnish consists of gum sandarach, 3v, alcohol, Oij; the colored varnish consists of the same propor- r 1- 884 MECHANICS—DENTAL PROSTHESIS. tions of gum shellac and alcohol. The gum is added to the alcohol and digested over a moderate heat until it is dissolved. The var- nish is best applied with a small bristle brush; the oil and soap water with a camel's-hair brush or a stiff, pointed feather. The varnish must be kept well stopped, or from time to time diluted, so as not to become thick. The soap mixture needs occasionally renewal, as the plaster gradually neutralizes its oil and renders it unfit for use. Some dentists take plaster impressions, in certain cases, thus: First, a wax impression, as usual; then enlarge, by pressure, or by cutting out the depressions formed by teeth or a prominent alveolar ridge; lastly, they pour in a thin layer of plaster, and repeat the impression. Others surround certain teeth with a collar of wax, preparatory to taking a plaster impression. The last is a troublesome method, very apt to fail, from the slip- ping of the wax collars; nor has it any superiority over a wax im- pression, to compensate the trouble. Dr. C. J. Essig suggests the folloAving method for securing a plastic impression for partial cases: " An impression should first be selected of the proper size and shape; those with the flat floor are best for partial cases; the plaster should be mixed thin, almost as thin as water, adding chloride of soda to facilitate setting. Plaster mixed in this manner does not become hard and unyielding as that mixed merely to saturation. Now oil the' cup so that it will readily separate from the impression Avhen hard, fill the cup as soon as the plaster thickens sufficiently, then, with a small spatula, place a layer of the soft plaster in upon the palatine surface; otherwise by enclosing the air in the deep portion of the arch the accuracy of the impression may be impaired. After this precaution the cup is placed in the mouth, and gently pressed up until its floor comes in contact with the teeth. When the plaster is sufficiently hardened, remove the cup, Avhich, from its having been oiled, is done without difficulty; with the thumb and index finger break off the outside walls; the portion covering the palatine surface is then removed by the use of a blunt steel spatula, curved at the end in the form of a hook. The pieces are then placed back into the cup, where they will be found to articulate with per- fect accuracy. Should the first attempt be rendered futile, by the tendency to nausea, or troublesome gagging on the part of the patient, camphor water, as recommended by Dr. Louis Jack, may be used as a gargle, which will, in nearly every case, prove an effect- ual remedy." The comparative value of the four impression materials—Avax, gutta-percha, modelling composition, plaster—can only be deter- mined by a careful study of (1) their distinctive peculiarities; (2) MATERIALS FOR IMPRESSIONS OF THE MOUTH. 885 the special requirements of different mouths; (3) the kind of base- plate, and manner of its construction. The exclusiA^e use of one is as reprehensible as the indiscriminate use of all. No one is best, nor can any be dispensed with. Disregard of this most important fact is a fruitful source of failure in impressions; failures arising neither from defect in the material nor lack of skilful manipulation in the operator, but from want of philosophical selection of re- sources. (1) Wax demands strong pressure, and is inelastic; also, it neither expands nor contracts on cooling. It copies a hard gum accurately, although it never gives the fine tracery of gutta-percha, modelling composition, or plaster. It also copies a soft gum, but not until the gum is either compressed or thrown out of shape by the strong pressure required. Gutta-percha requires moderate pressure; is slightly elastic; also has, as its marked peculiarity, ver}^ decided contraction on cooling, Avhich, hoAvever, is under control, as pre- viously explained. Slight undercuts it will take, without dragging, as Avax does ; but, on the other hand, it will occasionally pass into very narrow interdental spaces and injure the impression in the effort to Avithdraw therefrom. Modelling Composition ranks next to plaster as an impression material, and when thoroughly softened in boiling water, and when not too hot to handle, will give an accurate impression under strong pressure, and a much finer tracery than Avax. Plaster permits only gentle pressure, taking impressions of softest tissues in natural position. It slightly expands in setting; but, in a rigid cup, this makes no appreciable increase in the size of the model. It sets so hard that it Avill break before leaving the smallest undercut; but, by virtue of the same quality, in can be used in the most marked cases of dovetail, or alveolar undercut. (2) Alveolar and palatine surfaces, and their investing mem- branes, have a great variety of conditions. These must be carefully examined Avith reference to the properties, just named, of the im- pression materials. We have large or small arches; deep or flat ones ; irregular or smooth ridges. The mucous surfaces may be uniformly hard or soft; the ridge hard and palate soft; or the more difficult combination of soft ridge and hard palate; or the ridge may be irregularly hard and soft. No one material can possibly be equal to these varying conditions. (3) The mode of constructing the plate will often determine the choice of an impression material. A plate swaged upon a zinc die is smaller by the shrinkage of the die. Here—apart from shape or hardness of the parts—plaster Avould be best, wax next, gutta-percha the Avorst. A vulcanite plate is larger than the mouth, by the ex- pansion of the model. Here, the contraction of gutta-percha will 886 MECHANICS—DENTAL PROSTHESIS. often prove a very valuable compensation ; also the compression of tissue, made by the pressure of wax; special considerations must determine Avhich of these to choose. Plaster is the most reliable impression material as a general rule, and is the only material in difficult cases worthy of any reliance. It may safely be asserted that the operator Avho cannot take an accurate plaster impression of any partial case, however difficult, has a very imperfect idea of the A'alue of hard rubber. For the majority of partial cases, Avhere SAvaged work is used, modelling composition, or wax, if properly manipulated, will give ample accuracy. Where, hoAvever, the under- cut, and consequent dragging of Avax, is very great, plaster must be employed. Large, or hard, or irregular mouths are best copied in plaster; great deviations from normal size, or shape, requiring special cups. A gum of medium softness, but uniform, may be taken equally Avell in any material. This class of mouths have a wonderful adap- tation to any thing. Variations in size or form must determine the selection of the material. A gum of extreme softness, yet uniform, will give better results sometimes with one material, sometimes with another. It is often very difficult to determine beforehand; but, in case of failure, let the second impression be taken always with a different material. This is especially true of loAver sets, where the gum behind is soft and flexible; it is hard to say whether the pressure of wax, or modelling composition, or the softness of plaster leaves the ridge in best condition; gutta-percha is often very useful in these cases. Irregularity of texture in the mucous tissues is a fruitful source of trouble. A hard ridge, Avith a soft palatine surface, is easily fitted, and any impression material may be used. But the reverse con- dition will often require the firm pressure of Avax, or modelling com- position upon the ridge ; also in all cases of inequality of texture in the ridge itself. As a rule, subject to exceptions, a harder impression material than plaster is the best for these mouths, and occasionally (es- pecially for vulcanite) the contrac- tion of gutta-percha is useful. The old-fashioned upper plates, the shape of which is shown by Fig. 815,were employed to overcome this difficulty when the centra palate is very hard. Much better methods are now employed; MATERIALS FOR IMPRESSIONS OF THE MOUTH 887 that of scraping the model for a vulcanite plate, and building on a thin film of wax for a metal plate. For vulcanite plates, the model is scraped slightly on either side of the hard palatal centre. For metal plates, a thin film of Avax, about -^ of an inch in thickness, is built along the entire hard palate, terminating in thin edges, the space to be thus covered varying according to the width of the mouth. The model should also be slightly scraped at the posterior edge of the surface to be thus covered by the plate on each side of the hard portion of the palate, so that the plate may be closely adapted at such points. It is evident that an enumeration of all the complications which call for exercise of judgment in the selection of impression materials is impossible. By suggesting a few varieties, we hope to direct attention to a much neglected point, in our judgment of utmost importance. Routine practice, which inquires into the reason of nothing, and the one-idea system, wdth its " practice makes perfect" motto, are equally at fault. The future may reveal some new ma- terial ; but the four we now have are alike important and indis- pensable. PLASTER MODELS. The model is made of calcined plaster, mixed Avith water so as to have the consistence of cream ; too much AArater making the model fragile, Avhilst too little will prevent the escape of the air contained in the plaster, and the model will be porous. This last condition also greatly endangers the full floAving of the plaster into the in- equalities of the impression. The model, for convenience of description, is said to have a face, back, body and sides—terms scarcely requiring explanation. The face, corresponding Avith the mouth to be fitted, requires greatest care; and the same directions answer for it in all models. The body of the model has different shape and size according to the use to be made of it. The back should be, in all cases, parallel with the face. The sides are to be either vertical or slanting, according to its uses. In making models, we require a plaster table, with a rim to pre- A'ent scattering of waste plaster; having at least two drawers in front, a shelf at the back, also an opening for escape of waste plaster into a refuse box; a tight plaster-can and a bucket of Avater will comple the outfit of the table. The implements are tAvo or three strong boAvls, a plaster scoop, a spatula, an iron spoon, a plaster knife, a scraper, a sponge, and some camel's-hair brushes or wing- eathers of poultry. Sometimes a marble slab or slate is used for 888 MECHANICS—DENTAL PROSTHESIS. shaping the back of the model upon ; but if the table is kept clean and smooth with the scraper, this is not essential; since, in any case, a piece of wet paper should be laid down, to permit the ready removal of the model, for the purpose of shaping, whilst yet rather soft. The most troublesome models are the thick ones for sand mould- ing. The surface of the impression being prepared as above di- rected, the cup is surrounded with a rim of wax, waxed cloth, sheet lead or tin foil, fitting closely, to prevent escape of plaster, and about two inches deep. The rims should be slightly curved, to give, when placed around the cup, the requisite flare. Models made in such rims need trimming with the knife. To avoid this, and also Fig. 816. to give greatest possible smoothness and regularity to the sides, flaring rings of sheet tin may be used as follows: Set the impres- sion level on the table, and surround with some soft plastic material, such as potter's clay (wet newspaper made into a pulpy mass is perhaps the most convenient), and into this set a ring of such size as will give a proper shoulder to the model. Fig. 816 shows such a ring arranged for making such a model for plastic work, such as vulcanizable rubber, the models for which need not be very deep. For a sand model the ring should flare, should conform more to the shape of the cup, and be smaller. For the dipping process of mak- ing counter-dies and dies, the model needs no specially nice trim- MATERIALS FOR IMPRESSIONS OF THE MOUTH. 889 ming. For the fusible-metal process, the model should be cylin- drical, and not flaring. These are the three forms of thick or deep model. The shallow models are usually made without rims. The im- pression is filled, then turned down, when the plaster has set suffi- ciently to permit it, on the remaining plaster, Avhich has been poured on a strip of wet paper, placed on a smooth, flat surface. Whilst plastic it is shaped with the spatula. If for vulcanite or other plastic work, it may be taken up while soft enough to dress with a sponge. But if the shallow model is to be used in sand moulding, or in Dr. Gunning's process, it is allowed to harden and is then trimmed with the knife. In vulcanite models it will save time and insure greater accuracy in articulation to extend the model at once and make the articulating portion, if no metallic articulating frame is to be employed, as will be fully explained when describing the process of articulation. The sides of vulcanite models need no shaping except such as neatness and convenience in handling require; since they are subsequently set into the flask; but they should be no larger or thicker than strength requires. When rims are used, the impression should rest upon the plaster table; if set level, the back will necessarily be parallel Avith the face, since the thin plaster poured into the rim finds its level. In making shallow models, the impression is held in the hand, thus permitting the flow of the plaster to be aided by moving or tapping it. As before stated, wax or gutta-percha needs no oiling; plaster may be oiled or soaped, or else varnished and oiled; it must also be saturated with water just before pouring the model. Calcined plaster for models should not set too rapidly, as this will cause haste, with its attendant dangers. Coarse plaster makes a stronger model, but it has greater expansion. Gum-water, or size, retards the setting, but makes the model very hard; salt quickens the setting, but should not be used for any models which are to be kept as permanent records of the case. It is better to add the plaster to the Avater, than the reverse; it makes smoother work by permit- ting the escape of the air; it also, by the amount of unsaturated plaster, permits the operator to gauge the stiffness of the batter. In all cases the face of the model is the part first made. The thin freshly-mixed plaster is first to be carefully run into the depressions of the teeth or their ridges. A brush or feather is necessary when the cup is stationary; when in the hand, motion or tapping, or jarring, will cause the plaster to flow as desired. Perhaps the surest Avay to prevent defects on the face, from confined air, is to have a little surplus Avater in the cup. The plaster (which in this case 890 MECHANICS—DENTAL PROSTHESIS. must not be too thin) settles at once into the smallest crevice under the water, and, if not stirred, it will not be made thin and rotten by it; or the plaster-batter may force the water before it until the latter escapes at the heel of the impression. The impression once filled, the formation of the body is easy. For deep models, the remaining plaster should be poured at once, that, while thin, it may form a smooth and level back. For shallow models the plaster must slightly stiffen, lest the weight of the im- pression should make it settle too much into the plaster on the Fig. 817. Fig. 818. table. The sponge is very useful in dressing up a model; it cuts more or less according to the state of the plaster. It may be used to trim vulcanite models directly after the spatula, or to give finish to other models after the use of the knife. But when plaster is fully hardened it has no effect. Figs. 817 and 818 represent upper and lower models suitable for sand moulding; the same may be used for dipping. Fig. 819 rep- resents a shallow model in the moulding flask, shoAving how the body of the die is formed by the zinc half of the flask. The same figure may be taken to represent the position of the thin model at the bottom of an iron cup, in the pro- cess of making the counter-die by Dr. Gunning's method. Difficulties arising from undercuts, on the outside of the upper ridge and on the inside of the lower, may be overcome: (1) by filling up the undercut with Avax or plaster in all places Avhere it is unnecessary or impracticable to carry the metallic plate; (2) by using a peculiarly-constructed flask for moulding, such as the one invented by Di G. E. Hawes (Figs. 825-827); (3) by filling the undercut with movable pieces of plaster, technically known as " false cores." They should be so shaped as to admit MATERIALS FOR IMPRESSIONS OF THE MOUTH. 891 of being draAvn from the sand; at the same time they must have a decided angle, so as to mark distinctly the place in the sand for their replacement. A small nail or tack in the sand, above the core, will keep it in place while the metal is being poured. (4) By mak- ing a sectional model (Fig. 820), as suggested by Dr. A. Westcott. It may be made by filling the central third of the wax impression with the plaster, keeping it from the lateral thirds by a temporary use of clay or putty. This is removed and trimmed, leaving the back Avider than the face (Fig. 820); then replaced in the impression, and filled up on each side with plaster; the model is then removed, properly trimmed and varnished. Dr. Bean's method of making a model in two parts is equally ap- plicable to making models in three parts, and is perhaps better Fig. 820. than the foregoing. He thus describes it: " To secure a division in the model itself, the best plan is to set up in the impression a septum of thin sheet lead, forming a vertical plane in the median line of the palate, and fitted somewhat to the inequalities of the impression. This plate should have two or three small projections struck up on one side, by means of a small conical punch, and the opposite side has some cotton fibre attached with shellac, in the manner described for preparing impression cups. Fig. 821 repre- sents the shape of this plate (one-half the size), and shows the side on Avhich are the projections. Its proper position will be readily understood when applied to an impression of one of those deep palates iioav under consideration. The side having the projections is oiled, the cotton on the other side wet with water, and while fill- ing up the impression, this plate is set up in the middle, along the 892 MECHANICS—DENTAL PROSTHESIS. median line, so that when the model is trimmed to proper size and shape, it may be carefully broken apart and placed together again, in the same position." Much time may be wasted in the effort to overcome difficulties of undercut in sand moulding. The dexterous removal of shallow models will suffice for most cases of front undercut; and of all others, it may be said that no undercut on the die is of any service into Avhich the plate cannot be swaged, or in removal from which the plate is apt to be bent. Removing the impression is a fruitful source of vexation, because of the frequent breaking of prominent parts of the model, and other annoying accidents. But these are in every case the result of haste, carelessness, or forgetfulness. First, the model must have time to harden; then the impression, if of wax or gutta-percha, must be thoroughly softened. The common practice of setting the model on the stove is bad ; the smell of burning wax is often the first warning of a softening which has gone too far, injuring the model by the absorption of melted wax. It is far better to place it in water at 140° and 150° Fahrenheit, leaving it long enough for the entire mass of wax to soften; at this temperature the wax does not melt, yet is so soft that it cannot injure the most delicate point of the model. If over 150°, some portions may adhere to the model, and give trouble in removing. Gutta-percha impressions must be thoroughly softened in water at 200° ; if over this tempera- ture, portions of gutta-percha are apt to adhere to the surface. In partial cases, it is a good plan to first remove the cup, then turn up the edges of softened wax or gutta-percha, till it is free from the teeth, and then remove the entire mass. Plaster impressions require a different treatment. If the cup is wholly or partly of wax or gutta-percha, these must first be softened and removed ; a Britannia cup is loosened by light strokes of the plaster knife handle. The impression is then broken away piece- meal. Dipping it in hot water makes it rotten, and facilitates, at times, its removal. It is often necessary to cut nearly through the impression in places; in doing which, the knife or graver must be held so as to guard against injury to the model beneath. Another safeguard is to coat the impression, before pouring, with oil colored by alkanet; or, better still, to tinge the plaster with which the im- pression is taken with vermilion or Brandon red ; it gives the dry plaster a faint pinkish tinge; does not, in this small proportion, injure its setting qualities; and it makes a very distinct contrast with the pure white of the model. Few impressions can be used twice; those taken in wax or gutta- MATERIALS FOR IMPRESSIONS OF THE MOUTH. 893 percha cups, never. Partial impressions of all kinds are necessarily sacrificed to the integrity of the first model. But plaster impres- sions, in a smooth Britannia cup, may, with proper care, be replaced in the cup, and used again so as to give a model quite equal to the first. Some of these will come from the model entire; but often it is necessary to cut a groove over the alveolus, and break off the outer rim in two or three sections. Models may be partly trimmed before removing the impression; but it is always necessary afterward to trim the shoulder. Usually this is done by merely taking off the rough edges, folioAving the out- line of the edge of the impression; but for striking up a plate with the outer edge turned up, a flange, or shoulder, about the fourth of an inch Avide, is formed around the outside of the plaster model, where it is designed that the edge of the base plate shall terminate on the alveolar border. It may be shaped either in Avax or plaster, and should stand off from the ridge at an angle of about 90° or 100°, the angle of the rim being completed with pliers after swaging. A plate swaged with such a rim is used in mounting gum or block teeth, and in continuous gum work; it is stronger than a simple plate, and is susceptible of a more beautiful finish. For a lower set of block teeth, the edge of the plate may also be turned up all the way round. An objection to a SAvaged rim is the occasional difficulty of determining just hoAV far over the ridge the plate should extend; for an}' change is impossible Avithout destroying the rim. Hence the more common practice, except in continuous gum work, is to solder a gold band or wire, after adaptation of the plate to the mouth, as hereafter explained. The model, if it is to be used in sand moulding, should have several coats of shellac or sandarach varnish applied with a small bristle brush, to give it a smooth, hard and polished surface. This Avill protect it from injury by use, render it more pleasant to handle, and cause the sand to part easily from it. The gum shellac varnish may be prepared by dissolving five ounces of shellac in one quart of alcohol. In using this varnish on a damp impression, be careful not to apply a second coat until the first is hard; else it will cause the first to peel, and injure the smoothness of the surface. Sanda- rach varnish is preferable to shellac as it is harder; it is also more transparent, and, consequently, does not color the plaster. It may be made in the folloAving manner: Take six ounces of gum sanda- rach, one ounce of elemi; digest in one quart of alcohol, moderately warm, until dissolved; or the sandarach alone may be used. This is, perhaps, as good a varnish as can be used for plaster models. 894 MECHANICS—DENTAL PROSTHESIS. It is easily prepared, but the alcohol should be warmed in a sand bath or hot Avater, to pre\'ent it from taking fire. To make the finest varnish, the sandarach should be of best quality, and washed in water before being put into the alcohol. Some, hoAvever, prefer a coating of charcoal dust, or plumbago, or powdered soap-stone for sand models. Models for dipping, or pouring, or the fusible-metal process, should have no kind of varnish upon them. Vulcanite and other plastic work models may have a protecting coat of dilute soluble glass (nine parts water to one part of the glacial syrup); but if too much or too strong a solution is used, it will do more harm than good. No shellac or sandarach varnish should be applied to plaster models for either vulcanite or celluloid work. For the preparation of the surface of the plaster model to over- come the difficulty resulting from a hard ridge or prominence in the centre of the palatal portion, the reader is referred to page 886. CHAPTER IX. DIES AND COUNTER-DIES—SWAGING PLATES. Various methods have been adopted for procuring metallic dies and counter-dies. The three following are all which the author deems it necessary to describe. The first of these consists in pouring melted metal into a mould or matrix, made in sand with the plaster model. By this means the die is formed, and the counter-die is obtained by pouring metal upon it. The second consists in making the counter-die first, either by immersing the plaster model in metal, or pouring metal upon it; the die is formed by pouring metal into this. The third consists in pouring the metal for the metallic die directly into the impression. A very ingenious set of flasks for this purpose, the invention of Dr. F. Y. Clark, can be had at the dental depots. The same may be done, less conveniently, perhaps, with the usual Britannia cups and moulding rings. Take a piece of copper or brass gauze, and fit into the cup before taking the im- pression. Set the impression, thus strengthened, into a batter (asbestos or sand three parts, plaster one part), poured into a narrow DIES AND COUNTER-DIES—SAVAGING PLATES. 895 iron ring (sheet iron will answer) ; carefully work the batter around the edges of the impression; then place upon it the zinc half of a Bailey flask (Fig. 822). If the impression is thoroughly dried, the first metallic die will be perfect, no matter how much undercut there may be. A second or third may then be taken, more or less defective, but very useful for the first stages of the SAvaging process. Zinc is the metal used by Dr. Clark for the die. In this process the impression may be plaster or plaster and feldspar; but the in- vesting batter should have only enough plaster to bind the asbestos or sand together. Dr. Clark uses a copper impression cup, Avhich Prof. Austen's process dispenses with. The flask and impression must be perfectly dry, and heated nearly or quite up to the fusion point of the metal used. The second method admits of three modifications : 1. The fusible- metal process; in which the model is surrounded Avith thick paper, and fusible metal in a semi-fluid state is dashed over it with a spoon, the model being cold, so as to rapidly chill the metal. While still Avarm, the paper is removed and the counter-die trimmed with a knife; for at this temperature it can be cut as readily as cheese. The counter-die, when cold, is then smoked or coated Avith whiting, surrounded Avith paper, and semi-fluid fusible metal dashed on it, to make the die. This process is repeated, until from two to six dies are made, according to the irregularity of the case. The model should be in a ring of nearly circular shape and cylindrical; it should also be at least half an inch larger than the alveolar ridge, that the counter-die may have sufficient metal to force up the plate. 2. The dipping process consists in pouring melted lead, type-metal, or peAvter into a sheets or cast-iron cup or box, three and a half or four inches in diameter, and three or four inches deep, until it is more than half full; then, stirring the fluid mass Avith gradually in- creasing rapidity until it begins to granulate, quickly brush off the surface dross, and at once immerse the plaster model more or less deeply, as the palate is a deep or shallow one, and hold it there until the metal congeals. To prevent accident from air confined in the palatine arch, a small hole should be drilled through the plaster model. It is then removed, and the whole upper surface of the counter-die covered Avith a thin coating of whiting or lamp smoke, as before directed. After this has become perfectly dry, melted block tin, type metal or soft solder, at a temperature so low that it will not char, or even discolor white paper, is poured in, until the 896 MECHANICS—DENTAL PROSTHESIS. cup is filled. If the counter-die is so deep that the die has not suf- ficient thickness, it may be deepened by placing on the freshly- poured metal the zinc half of a Bailey flask, and continuing to pour; the metal in the two flasks will unite and form one die. When cold, the castings are removed from the iron cup, separated, and are then ready for use. 3. Dr. Gunning^s method, called also the " pouring process," in which a very thin model (made of plaster two parts, and sand or feldspar one part) is placed in the bottom of an iron box, three and a half to four inches in diameter, and about two inches deep. It is fastened there by a thin layer of plaster and sand, then thoroughly dried by gradually raising box and all to the temperature of the melted metal, which is next poured in, and the box set in a shallow vessel of water to cool it rapidly from the outside. To delay the cooling in the centre until the last moment, and to prevent con- traction at that place, a very hot pointed iron, somewhat similar in shape and size to a tinner's soldering iron, is placed upon the centre of the model before the metal is poured. When cold, this is removed, and the conical space filled with metal. The counter-die is thus made of lead, alloyed with tin or type metal. The die is made by placing over this a stout wrought iron ring, and pouring in fusible metal. Dr. Gunning uses from three to eight dies, according to the sharpness of the prominences of the model. The method gives, in his hands, very accurately fitting plates. When metallic dies are to be obtained by the first method, mould- ing flasks and sand are required. Flasks may be of wood or iron. The moulding box of wood should be about six inches square. This is to be filled with fine sand, such as is used by brass founders, in the following manner: The deep or shallow plaster model is placed on the moulding table, exactly in the centre of the box, with its face upward. Sand is then firmly packed around the sides of the model. Sand should then be sifted, covering the face of the model to the depth of a half inch, the box then filled, and the whole rammed with a firmness proportioned to the coarseness or dryness of the sand—damp or very fine or strong (i.e., with large percentage of clay) sand not permitting so much compression as sand possessing the opposite qualities, because it would become too compact to per- • mit the escape of the vapors formed during the process of pouring. But the finest sand, rich in clay and quite moist, may be used, if it is dried before pouring. Sand, mixed with olive or sweet oil, pos- sesses some advantages over that mixed with water, as it can be used a number of times without re-mixing, prevents the bubbling common to sand made too moist with water. The sand should DIES AND COUNTER-DIES—SAVAGING PLATES. 897 never be burned by pouring on it very hot metal; hence, it is better to stir the metal until it has cooled somewhat before pouring it into the mould. The metal should not be injured by overheating. Cooling the die suddenly in Avater renders it brittle. The box is then turned over and gently tapped several times with some light instrument or hammer, for the purpose of starting or detaching it a little from the matrix, and then carefully removed. Great care is necessary that this tapping does not depress first one side and then the other: this would make the die too deep in the centre, and perhaps cause the plate to rock. The model may be loosened laterally, by holding an excavator firmly upon the centre of the die and tapping it on the side. If the model be composed of three pieces, the middle section is first removed, and aftenvard the two others. There are tAvo ways of draAving the model: first, by screwing into it an excavator or gimlet, and carefully drawing it out; second, by throwing it out with a dexterous jerk of the matrix. The last is best; the excavator is apt to break through the centre Fig. 823. of the thin model, and the thick one falls out, by its oavii weight, better than it can be drawn. Fig. 823 represents the tAvo ends of a double spatula, Avhich will be found very useful in sand moulding. If the deep model is used, the matrix is noAV ready for pouring; but first remove all loose sand, and make a groove at the back part of the matrix to receive the first Aoav of the metal. If the thin model is used, a ring must be set upon the sand after the model is drawn, to give the additional size Avhich the die requires to prevent cracking under the swaging-hammer. The mould being prepared, the metal to be employed for the casting should be put into a tolerably thick wrought or cast-iron ladle, and melted in a common fire or furnace. Mr. Fletcher has invented a very useful melting apparatus, Avhich is also suitable for drying and boiling purposes. If brass is used, a blast furnace Avill be required to melt it; but if zinc, block-tin or lead, a common fire 57 898 MECHANICS—DENTAL PROSTHESIS. will afford sufficient heat. As soon as the metal has become thoroughly melted, it is poured into the furrow formed in the sand, whence it will flow into the back part of the mould. It is neces- sary to convey the melted metal into the mould in this way to pre- vent the injury which the surface of the sand might sustain by pouring directly upon it. There have been quite a number of moulding flasks devised to supersede the wooden one just described, or the common cart-wheel box, Avhich was once much used. Some of these are Avorse than useless; others are very convenient, and have the advantage of requiring only a small quantity of sand; also of permitting the sand to be dried, which cannot be well done in the Avooden box. The simplest, and perhaps best, flask is that invented by Dr. E. N. ■Bailey. Fig. 824 represents the shape and working of this flask. Fig 824. Half-flask b is placed, joint-edge doAvnAvard, over a thin model, and firmly packed Avith sand. It is then turned ; the sand com- pressed around the edge of the model; then trimmed so that the model may be easily drawn (a properly shaped model renders much sand trimming unnecessary); the model is then lightly tapped and throAvn out. All operations on the thin model must be conducted with great care, for it is easily displaced in its matrix, so as to de- stroy the accuracy of the latter. Next, pour zinc into the mould, and at once place on half flask a, and complete the pouring. When cool, remove the sand, invert the flask, Avith zinc die contained, and pour the lead (c) upon the zinc for the counter-die. In cases of moderate undercut in front, the thin model can gen- erally be drawn by a dexterous backAvard movement. But for a deeper undercut in front, also for those at the side, the moulding flask of Dr. Hawes (Figs. 825, 826, 827) will be found useful. In Fig. 825 the lower section of the flask is slightly opened, to show joints. In Fig. 827 the upper section. In Fig. 826 the loAver sec- tion is closed and confined by a pin, with the plaster model placed in it. The manner of using is thus described by Dr. C. C. Allen: " If DIES AND COUNTER-DIES—SAVAGING PLATES. 899 the "model be considerably smaller than the space between the flanges projecting inward, small slips of paper may be placed in the joint, extending to the sides of the model, so as to part the sand Avhen opening the flask for the removal of the pattern. The sand may noAV be packed around the model up to the most prominent part of the ridge. It should be finished smoothly around it, slightly descending toAvard the model, so as to form a thick edge of sand for the more perfect parting of the flask. The sand and face of the model must noAV be covered Avith dry pulverized charcoal, sifted evenly over the Avhole surface. When this is done, the upper section of the flask is placed over the loAver and carefully filled with sand. It is then raised from the loAver one, which may now be parted by re- Fig. 825. Fig. 826. moving the long pin, and the model gently taken aAvay. When closed, and the tAvo put together again and inverted, it is ready to receive the melted metal." After the metal has cooled, it may be removed and turned over, so that the face of the die shall be up- Avard, Avhile the remainder is buried in the sand. Thus placed, it is encircled Avith the ring (Fig. 827), and the metal for the counter- die poured upon it. The metals most commonly used, when metallic dies are made by sand moulding, are zinc and lead. For many reasons, these are, perhaps, the best metals for general use that can be employed. Zinc is the hardest metal that the dentist can conveniently melt. In case of deep or large arches, and for mouths where the mucous membrane is very hard, should its shrinkage prevent the close adaptation of the plate, a finishing die may be made of block tin, type metal, soft solder, or Babbitt metal (a patent alloy of copper, tin and antimony, the best formula for which is Dr. Haskell's: 900 MECHANICS—DENTAL PROSTHESIS. copper, 1 part; antimony, 2 parts; tin, 8 parts), Avhich last is nearly as hard as zinc, and has decidedly less shrinkage. When a metal softer than zinc is used, se\Teral dies will be necessary to complete the swaging. As this Babbitt metal fuses at a loAver tempera- ture than lead, it is necessary to use a counter-die in which tin forms a part; Dr. Haskell therefore recommends the following formula: lead, 5 parts; tin, 1 part. The die should be coated with Avhiting solution before pouring the counter-die. The late Prof. Austen, by careful experiment, found that an averaged-size zinc die, measuring two inches transversely, contracts 1H0 of an inch from outside to outside of the alveolar ridge, being equivalent in thickness to three ordinary book leaves. He remarks: " In the first case (upper jaw), the plate would ' bind,' and if the ridge Avere covered by an unyielding mucous membrane, it Avould prevent accuracy of adaptation. In the second case (upper jaAV), the plate Avould have too much ' play,' and consequently lack sta- bility. Again, in a moderately deep arch, say half an inch in depth, the shrinkage betAveen the level of the ridge and the floor of the palate Avill be nearly l07o0 — rather more than one leaf. In the deepest arches this shrinkage may give trouble, except Avhere the ridge is soft, and then it becomes a positive advantage. In the shalloAver cases, it is not of much moment, as there is no mouth so hard as not to yield the ToVc or tthttt oi* an inch." A counter-die should be soft. When but one metal is used, lead is decidedly the best metal for this purpose; tin may also be used if the die is made of zinc, but tin counter-dies are only employed for the final swaging, and after the use of lead counter-dies. It is desirable, if practicable, that the metal last poured (in sand mould- ing, this is the counter-die) should melt at a lower temperature than the other. In this respect zinc and lead are admirably suited— zinc melting at 770° and lead at 600°. Tin melting at 440° might be supposed, in this respect, better than lead; but such is not the fact, OAving to the tendency of tin and zinc to form alloys, while lead and zinc have no such affinity. The requisites for a die are non-shrinkage, hardness, strength, smoothness of surface, and fusibility at a low temperature. The Babbitt metal after the formula before given furnishes such qualities. Fig. 828 represents an excellent gas furnace for melting and re- fining gold and other precious metals and for melting zinc, lead, etc., of the baser metals. Fig. 829 represents a sectional diagram of the same furnace. In using plumbago crucibles, etc., they must be heated sloAvly Avhen first employed. Mr. Fletcher's small gas fur- DIES AND COUNTER-DIES—SAVAGING PLATES. 901 nace, Avhich is well adapted for melting the metals employed for dies and counter-dies, is represented by Fig. 830. In a paper on metallic dies, published in the fourth volume ot Fig. 829. the American Journal of Dental Science, Prof. Austen gives, as the result of careful experiment, the following tabular view of the Fig. 830. fusible alloys—zinc being introduced for the purpose of compari- son : 902 MECHANICS—DENTAL PROSTHESIS. 1. Zinc . . 2. Lead, 2 3. Lead, 1 4. Lead, 2 5. Lead, 5 6. Lead, 5 7. Lead, 1 8. Lead, 5 9. Lead, 2 tin, 1,........... tin, 2,........... tin, 3 ; antimony, 1, .... tin, 6 ; antimony, 1, .... tin, 6; antimony, 1; bismuth, 3, tin, 1; bismuth, 1,..... tin, 3; bismuth, 8,..... tin, 1; bismuth, 3,..... Melting Contrac- point. tility. 770° 440° 340° 420° 320° 300° 250° 200° 200° .01366 .00633 .00500 .00433 .00566 .00266 .00066 .00200 .00133 Hard- ness. .018 .050 .040 .026 .03o .030 .042 .045 .048 Brittle- The last column contains an approximate estimate of the relative brittleness of the samples given. As in the other columns, the Ioav numbers represent the metals, so far as this property is concerned, most desirable. Those marked below 5 are malleable metals; those above 5 are brittle ; zinc, marked 5, separates these two classes, and belongs to one or the other according to the Avay in which it is managed. In all cases of melting it is a safe rule to pour the metals at the lowest temperature at Avhich they will flow. It is prudent, also, to coat the metal on Avhich other metal is poured Avith a mixture of alcohol and Avhiting, to prevent all chance of adhesion. One more very important caution in the melting of zinc and lead is invariably to use separate ladles; for any lead left from a previous melting flows from the ladle with the last portions of the zinc, and being heavier (in the proportion of 11 to 7) and more fluid, falls at once to the bottom of the matrix, making the alveolar ridge more or less of a soft metal, thus totally destroying its usefulness. The elastic vapor generated by the contact of the water in the sand with the hot metal sometimes collects under or rises through the metal, and renders the casting more or less imperfect. This may be prevented: 1, by drying the sand; 2, by using coarse or loosely-packed sand, and avoiding too much moisture; 3, by mix- ing the sand with oil instead of water. The slightest moisture on one metal, previous to the pouring of another metal upon it, Avill make the latter imperfect. The folloAving method has been sug- gested to overcome this difficulty: " To prevent imperfections or bubbles in the palatal portion of metallic dies, it is not necessary to dry the mould after it is formed, or to use more than ordinary precaution as to the heat of the metal. The best result is obtained when the plaster model is quite thick and the mould consequently deep. This is then tipped forward, raising the back part or con- dyles to the highest point possible; pouring the metal in at the DIES AND COUNTER-DIES—SAVAGING PLATES. 903 front slowly, and loAvering the mould at the same time until the palatal portion is covered, and the mould filled to the top." The use of oiled sand, hoAvever, as before remarked, will prevent im- perfections by bubbling on the palatal portion of the die. In making metallic dies for partial cases, about three-fourths of the crowns of the teeth should be cut from the plaster model before using it for moulding. The plate can be fitted more easily and per- fectly than can be done when the teeth remain on the plaster model and zinc die; for, in the former case, the plate need not be cut to fit the teeth until it has been swaged, while in the latter this must be done first; consequently, in striking it up, it will be draAvn to a greater or less distance away from them. There is also danger of splitting the plate, in swaging it into the spaces between the teeth, if these are left on the metallic die. Half or partial counter- dies adapted to the palatal portion of the die only, and not extend- ing quite to the ridge, are useful in the case of a deep arch, and prevent the plate from tearing during the SAvaging process. We shall conclude the section on metallic dies by giving some practical suggestions by Prof. Austen, on the properties and uses of the metals and alloys employed for this purpose. Many of the properties of these metals, though most interesting, are not practically useful to the dentist; but there are some points, for Avhich he usually refers to his memorandum book, that should be printed on the page of his memory. The following tables pre- sent two properties of certain metals in a form coiwenient for memorizing; although not absolutely accurate, they are quite enough so for use in the dental laboratory: Order of Fusibility. Copper, Antimony, . Zinc, . Lead, . Bismuth, Tin and cadmium 2000° 900° 770° 600° 500° 440° Order of Specific Gravity. Lead, ..... 11.5 Bismuth, .... 10. Cadmium, .... 8.5 Tin...... 7.5 Zinc,..... 7. Antimony, .... 6.5 In the fusibility table, copper is given to shoAV hoAV unsuited it is for laboratory use. Remembering that 900° is red heat, the next four numbers may be easily memorized. In the specific gravity table, copper 9. and iron 8. are omitted, so as to present the table in a form easily remembered. The only pure metals suitable for a die are zinc and tin; for a counter-die, tin and lead. When one metal is used for either die or counter-die, zinc makes the best die and lead the best counter- 904 MECHANICS--DENTAL PROSTHESIS. die. Copper is too hard to fuse; antimony and bismuth are too brittle; cadmium is too expensive. All other metals used in swag- ing are alloys. Zinc and lead are valuable because : They are so unlike that they are not easily mistaken for each other; a very common error Avhen alloys are used. They have no such disposition to alloy as zinc and tin, or tin and lead'have. Zinc is so hard, one die will suffice for many cases; three are sufficient for the most difficult. The brittle- ness may be corrected by the size of the die. Its shrinkage is often a decided advantage; and in some cases, where it makes the plate bind on the alveolus, the contraction may be anticipated by coating these parts on the model Avith one or two layers of very thin plaster. Zinc, after repeated use, becomes defective, hence, a supply of neAV metal should always be kept. No metal used alone equals lead as a counter-die. Its Aveight and softness are in its favor for this purpose. A counter-die can- not be too large or heavy; convenience, of course, limits its size. A difficult plate cannot be swaged Avith a small counter-die, unless the Avork is nearly completed by partial counters, hammers, etc., before using it. As regards softness, the greater the disparity be- tAveen die and counter, the less will be the change in the die by the act of swaging. The plate is forced by the counter into the depres- sions of a die, not so much by its hardness, as by its vis inertia under the swaging blows. The little disparity in the hardness of the two dies is one serious objection to the use of the second class of opera- tions. It is a common practice to use several counters, and per- haps only one die. One die may in a few cases suffice; tAvo are better, and often three ; but good swaging never demands more than one counter-die, where that is properly made. With zinc, lead, and one fusible alloy (tin and bismuth, equal parts, or Babbitt's metab, all SAvaging operations may be completed when the dies are made by sand moulding, or by pouring zinc into the impression. But since many prefer other methods of making dies, it is important to understand the subject of alloys. Experi- ment is here the only basis of knowledge, for no a priori reasoning could deduce the singular changes caused, and new properties de- veloped, by alloying. The alloy of tAvo brittle metals is always brittle, and a brittle metal usually imparts this property to a tough one nearly in pro- portion to its percentage. But that two tough metals can make a brittle alloy is remarkable. Malleable copper, with half its weight of brittle zinc, gives hard brass, Avhich, though less tough than cop- per, is not brittle. But malleable copper, with malleable tin in the DIES AND COUNTER-DIES—SWAGING PLATES. 905 same proportions, makes speculum metal—the most brittle alloy knoAvn. A similar instance is that of lead, the softest of metals, Avhich will, in minute quantities, make gold, the most malleable of all metals, very brittle. Another remarkable property of all alloys is fusibility. Alloys fuse below the average melting point of their constituents. Ternary compounds exhibit this more strikingly than binary. The following table, in illustration of this property, will be found practically use- ful to the dentist in the selection of alloys: Alloys of Bismuth, Lead and Tin. Bismuth, 500°. Lead, 600°. Tin, 440°. Fahrenheit. 1 10 1 540° 2 5 1 510° 3 2 1 440° 4 1 1 370° 5 2 3 335° 6 1 2 340° 7 1 5 380° 8 1 4 4 320° 9 1 2 2 290° 10 1 1 1 260° 11 2 1 1 220° It will be noticed that two pounds of lead do not make one pound of tin harder to melt; Avhilst a half pound reduces its fusion point 100°. Also, Nos. 6 and 7, though containing more tin than No. 5, are harder to melt. Again, a pound of bismuth added to alloy No. 4 reduces its melting point 110°. No. 11 and all alloys containing much bismuth are brittle. The alloys of this table vary someAvhat in hardness, but all are harder than tin. Tbe " alloying metals " of the dental laboratory are copper, anti- mony and bismuth. Copper gives hardness to zinc and tin, and is sometimes combined with alloys of the two. But the high fusion point of copper renders it less useful to the dentist than the other tAvo metals. The alloy of copper, antimony and tin (Babbitt metal) is perhaps the only one of practical interest. Its advantage over zinc, in being less liable to contract, is perhaps set off by the ten- dency of most alloys to change their composition by frequent melting; and the danger of mixing different alloys, from absence of such distinctive marks as separate zinc and lead. Antimony is a more valuable alloying metal. It hardens tin, but its chief use in the laboratory is to harden lead, making type metal. Small types composed of lead 4, antimony 1, are too brittle ; 906 MECHANICS—DENTAL PROSTHESIS. and large types, lead 6, antimony 1, are scarcely fit for laboratory use. In the proportion of 9 to 1, antimony corrects the excessive contraction of lead and hardens it; yet leaves it tough so as to resist the blows of SAvaging. It is suitable only for counter-dies. The very common opinion that antimony causes lead to expand on cooling is erroneous. The alloy has a slight expansion at the moment of solidification; but after that, it obeys the universal huv of all metals, and contracts as it cools. Actual contraction depends upon the ratio of contraction and the fusion point; thus, lead con- tracts more than zinc because its high ratio of contraction more than compensates its lower fusion point. Another common error is that a zinc die poured very hot is smaller than if poured at its fusion point. Of course, contraction begins the moment cooling begins ; but so long as the metal is fluid, it necessarily fills the matrix, and contraction causes simply subsi- dence of the metal. No die begins to leave the walls of the matrix until it solidifies; hence, the amount of contraction is the same in all cases. Very hot zinc copies minutely the sand surface, and thus has not that bright, smooth appearance of cooler zinc, Avhich sets before penetrating the sand interstices; but both are equally good. Another difference is in the greater depth in the cavity on the back of the hot-poured die. But this is not as objectionable as many think ; no good mechanic strikes directly upon the die, but upon some ovoid or conical piece of metal covering the cavity in the back. Bismuth is perhaps the most valuable, to the dentist, of the three alloying metals. Antimony gives hardness, but not much fusibility; bismuth gives fusibility, but no great hardness. The table above given shows the marked effect of this metal. It is seldom used as a binary alloy, because its fluxing qualities are more fully brought out in ternary combination; also because of its expensiveness, and its tendency to impart brittleness. Type metal is rendered more fusible by the addition of .05 per cent, of bismuth. Bismuth, antimony and zinc are readily distinguished—bismuth by its great weight and characteristic pinkish color; antimony by its peculiar crystallization and its excessive brittleness. But the alloys of these metals with tin and lead have such a general resem- blance, that they must, with much care and system, be kept apart in properly labeled boxes; otherwise, if more than one alloy is used, the annoyance caused by using one for another will more than offset their utility ; in fact, such negligence defeats their usefulness. But the formula of Dr. L. P. Haskell for preparing the Babbitt metal is superior to all others for use as a die : Tin, 8 parts; copper, DIES AND COUNTER-DIES—SWAGING PLATES. 907 1 part; antimony, 2 parts. For a counter-die for such a die: Lead, 5 parts; tin, 1 part. He claims that such a Babbitt alloy for the die cannot be excelled. Dr. C. J. Essig recommends zinc for a counter-die for swaging a plate of platinum-gold or iridium-platinum; and also that such a counter-die is of especial service in partial cases Avhere a number of teeth remain. For difficult swaging he recommends three sets of dies and counter-dies, the most imperfect of the dies being furnished Avith a lead counter-die, to be first used, and the next in quality to be used with a zinc counter-die, and the nearest perfect of all with a lead counter-die as a finishing die. The following mechanical instruments will constitute an outfit: FOR METAL WORK. Two pairs of shears, one straight and Small vise and anvil. one curved. Wood or horn mallet. Hammer for swaging. Hammer for riveting. Rivet punch forceps. Saw-frame and saws. Round and half-round files. Plate-nipping forceps. Plate brush. Round and flat pliers. Solder tweezer. Long soldering pliers. Two melting ladles. Sieve and rammer. Moulding boxes, or flasks, and rings. Soldering block, plumbago, asbestos, or pumice. Glass plate for borax. Soldering-pan. Ingot mould. Crucible and tongs. Reamer. Blowpipe. Lathe and appliances. Melting furnace. Metal articulators. Acid dish, lead or copper. Plate burnisher. Soldering lamp, gas or alcohol. Polishing brushes, hand and lathe. Burrs, drills and circular saw. Rolling mill. Cutting pliers. Bending pliers. Plate gauge. Plaster knife. Plaster spatula. Plaster bowl. Tooth-holder in grinding. FOR CONTINUOUS GUM-WORK. To the above may be added: Furnace with muffles, slides and tongs; soft and stiff brushes; carving and modelling instruments. FOR VULCANITE AND CELLULOID WORK. Vulcanizer, or vulcanizer and heater Flask press. combined. Chisel or graver. Flasks for vulcanite. Rubber files. Flasks for celluloid. Callipers. Scrapers. Varnish bottle. Wax spatula. Oil bottle. Packing instruments. Scotch-stone. 908 MECHANICS—DENTAL PROSTHESIS. SAVAGING. A die and counter-die having been obtained, a piece of tin foil or sheet lead is adapted to the former, and the dimensions of the plate marked upon it. Paper is sometimes used for this purpose, but is not so good as thin sheet lead or heavy tin foil. The pattern thus made is cut out, flattened and laid upon the gold plate, and its out- line marked upon it. The outline of the plate may be marked on the plaster model and the pattern cut in conformity therewith. The margins of the plate for the upper jaAV should extend as high as possible, and especially over the position of the canine teeth, in order to restore the expression, Avhich is greatly changed by the loss of the natural teeth at such points; back of the canine teeth the margin of the plate should be lowered so as to avoid the attach- ment of the muscles and to allow the latter free motion or action. The plate should also embrace the maxillary tuberosities in order to obtain stability, and the margins at such points may extend higher than over the bicuspids and first molars. The plate should be cut a little too large, to alloAV for trimming and any accidental slipping upon the die. In partial cases the pattern should be carried partly, or fully, over the excised teeth, and no attempt made to fit it accurately around the necks of the teeth until the SAvaging is nearly or quite completed. With a pair of strong shears the portion'of plate thus marked is cut out. Fig. 831 represents a pair of shears, with long and conveniently-shaped han- dles. The blades of some shears are curved laterally ; but this form is not desirable. A fine watch-spring saAV, Fig. 548 (p. 738), should be used for curves Avhich the straight shears will not cut; curved shears may also be used for such a purpose; for very short curves, around teeth, for instance, a pair of cutting forceps Avill be found useful. Figs. 832, 833, and 834 represent nippers or cutting forceps for cutting out plate. Cutting plates to shape before swaging is, however, not only un- necessary, but is in many cases a positive disadvantage. SAvaging the square plate is greatly preferable in the lower jaw, since it permits working from the centre outward. And in both upper and lower plates, the two triangular pieces outside the ridge help to prevent plaiting, or doubling of the plate. Purchased plates are ordered to pattern, on the score of economy ; but the difference is trifling, since DIES AND COUNTER-DIES—SAVAGING PLATES. 909 good plate scrap has nearly the same value as the original plate, and every careful operator separates his plate scrap from his solder scrap and filings. After SAvaging is nearly completed, with partial Fig. 832. counters and hammers, the square plate may be quickly trimmed to shape by means of a jeweller's saw. The plate must be well annealed, and partially fitted by Avooden, horn, or leaden hammers, to that part of the die inside the ridge. Fig. 833. There is no better hammer for this purpose than lead ; but, of course, the plate must be thoroughly cleansed of all trace of the lead before annealing. The swaging is continued by the use of par- Fig. 834. tial counter-dies; these are made by placing a rim of clay or putty around the ridge and back part of the metallic die, and pouring on it fusible metal. In this way, the plate should be perfectly fitted 910 MECHANICS--DENTAL PROSTHESIS. so far as the ridge. Then, clamping the plate between the die and the partial counter, the edge is to be gradually carried over the top and outside of the ridge with hammers and small Avooden or ivory stakes. The plate may be clamped in a vise, or by means of a string passing over the die and under the foot; but a much more convenient method is found in the use of Dr. T. H. Burras's clamps, Fig. 835. Of the two forms here given, the sliding arm (No. 2) is preferable to the long screAV (No. 1). The application of the clamp is so plainly shown in No. 1, that any description is unnecessary. It is the practice of some to cut out V-shaped pieces from the front or back part of the plate, to prevent the plaiting of the metal. Fig. 835. This is very bad practice and is never called for, if due care is used in swaging and the metal is of proper fineness. To avoid plaits or folds, anneal often, and in deep arches carry the plate doAvn very gradually; also take care in such cases that the plate be thick, to allow for stretching or drawing. In swaging over the ridge, it is a very common mistake to hammer down the outside before fully striking up (with hammer and stakes) the parts nearest the partial counter-die. Ahvays make it a rule, in carrying the plate over the ridge, to swage from the centre outward, carry the plate •' home" as you proceed. In deep arches, irregular alveolar ridges, and in prominent lower ridges, SAvaging must be done slowly and Avith great care. DIES AND COUNTER-DIES—SAVAGING PLATES. 911 In the use of forceps for bending lower plates (Fig. 836), care must be taken not to bruise the metal, as Avill any steel or hard metal instruments. There is no shape of arch or of plate Avhich, by the above simple process, cannot be perfectly fitted with a 20- carat plate. The elaborate forms of a AvindoAV cornice or a jelly mould should teach any dentist hoAV poor a mechanic he is Avhen he complains of the difficulty of swaging so highly malleable a metal as gold into and over the irregularities of the mouth. And when, to save his skill, he pleads want of time, he exposes a graver deficiency—dishonesty. The fitting of the plate being thus almost completed by hammers and partial counters, it should be trimmed to its exact shape, and Fig. 836 then placed betAveen a fresh die and the full counter-die, and carried "home" by several firm blows of the hammer, given directly over the centre of the die. The hammer should not weigh more than three pounds, Avith a handle about a foot long. It is a great mis- take to use a very heavy or a very long-handled hammer. The striking-block may be an anvil, or a large wooden block set in sand or on a cushion, and the base of the counter-die must rest steadily upon it. Dr. Haskell describes a movable swaging-block to be kept under the bench as folioavs : " Eight inches wide at the top, and eleven inches at the bottom, just high enough to pass under the bench. Make it of pine with a plank bottom, to which attach heavy casters, a handle on one side, and a pocket for the hammer. Have an iron 6-inch cube cast, and filling the box nearly full of sawdust, place the iron cube in it so it will extend 2 inches above the box." It greatly facilitates SAvaging, and makes one indepen- dent of any striking block, to have a very thick and heavy lead counter. As there is ahvays a holloAV in the back of a zinc die, a conical piece of iron, steel, or other hard metal, should be placed 912 MECHANICS—DENTAL PROSTHESIS. upon it to centralize the blow of the hammer. An egg shell, filled Avith plaster, is useful as a model for making, at the time of mould- ing the die, several zinc blocks for this purpose. To a disregard of these precautions is due much of the difficulty so often complained of, in the tilting or rocking of plates and dies. Throughout the entire process of swaging, the plate must be fre- quently annealed. It may be suddenly cooled after all except the final annealing, when the cooling must be very gradual, so as to avoid warping or springing. The malleability of gold plate will permit a great deal of SAvaging without annealing; yet the neglect of this simple operation is unsafe. One broken or cracked plate gives more trouble than the annealing of a dozen. The plate, after final swaging, must be taken from the counter very carefully, to avoid change of shape. Thin paper in the counter-die makes re- moval easier; it is also easier when only one counter is used. Too much swaging gives the plate a loose fit. When block-tin, lead or fusible metal dies or counter dies are used in SAvaging the plate, any portion of these metals which may adhere to it should be removed before annealing, as their fusion upon its surface alloys them with the gold, and will render it brittle Fig. 837. and impair its ductility, or else eat holes in the plate at the spot AAdiere the particles of baser metal form an alloy, fusible at the an- nealing heat. This is done either by mechanical or chemical means. If acid is used, it should be dilute nitric, since sulphuric Avill not dissolve lead; but be very careful that the nitric acid con- tains no hydrochloric, else the plate will be acted upon. A copper or lead acid-dish may be employed, many preferring one made of thick sheet lead. Oiling the dies will also prevent the base metal from adhering to the plate, as any particles of the former can be readily wiped off. The plate, in the case of a full upper denture, should be so outlined DIES AND COUNTER-DIES--SAVAGING PLATES. 913 as to have the highest portion of the rim over the cuspids, cur\dng doAvnwards back of such points to the maxillary tuberosities Avhere it again should ascend so as to extend over these prominences. (Fig. 837.) Space should also be made for the frrenum of the lip by cutting aAvay the edge or rim for its reception. In the case of a full lower denture, the bending pliers may be used first, and its outline should be such that it does not interfere with the muscles and loose integuments. For a very flat ridge, the loAver plate should be double to give strength, and for partial lower dentures it is better to double the plate Avhere strength is required ; strength is also secured by the plate, in such cases, extending above the necks of the teeth, in some instances half Avay where the attachment of the muscles Avould otherwise necessitate a very narrow plate. Each piece of a double plate should be SAvaged separately, and the tAvo parts then Fig. 838. Fig. 839. soldered together, Avire clasps being used to hold them in position during the soldering process. If the denture is to be retained by clasps, the plate, either upper or loAver, should extend at least one- fourth of an inch beyond the clasped tooth in order to secure stability. In soldering the two parts of a double plate, the edges of one should slightly overlap the other so as to facilitate the process. Figs. 838 and 839 represent the general forms of upper and loAver plates after the SAvaging process is completed. In the upper plate is represented the proper size and position of a vacuum cavity, Avhenever it may be thought proper to use one. The question of the cavity Avill be elseAvhere discussed. If on trial of the plate in the mouth it does not fit properly, the operator must proceed to ascertain the cause of failure. And, first, Avhether it is temporary or permanent. A plate which falls because it rocks over a hard palate Avill never improve; if because it fails to go fully into the palate, it may daily improve, and ultimately adhere with great firmness. Most plates made soon after extrac- 58 914 MECHANICS—DENTAL PROSTHESIS. tion fit badly until the alveolar prominences are pressed down by wear. Some very hard mouths will not retain the plate until it has been worn for a time, especially if the mouth is very flat. Deep arches, or uniformly soft mouths, should retain the plate firmly from the first. The use of pliers, except for bending the edge into some alveolar undercut, is an evidence of bad work. The back margin of upper plates, so often adjusted in this way, is much better fitted by scrap- ing the model at the place where the plate should bind; this should be done to a depth proportioned to the softness of the membrane. Much judgment is demanded in deciding upon the necessity for a new plate. The impression may have been badly taken, or with a material not adapted to the mouth. The dies may have been care- lessly made, or the swaging imperfectly done. Trial of the plate is essential to ascertain all these points, that the articulation, solder- ing, etc., may not be so much additional labor in vain. In fitting a plate, the operator should see that its posterior mar- gin, especially at the centre, is so closely adapted as to exclude air. Dr. Haskell recommends wetting the plate before placing it in the mouth, and then by a " pumping process " watching for the escape of air bubbles. At the same time the plate should not press so hard at the centre of its posterior margin as to irritate the mucous membrane. To determine whether a lower plate infringes upon the muscles and lower integuments, the patient may be directed to raise the tongue, which will dislodge the plate if it so interferes by its depth. The lip can also be raised in front to determine if the plate extends too deep at that point. The different forms of plates, full and partial, will hereafter be considered. They are retained in the mouth by clasps or stays; by the adhesion of contact or by the vacuum cavity, the retaining force being atmospheric pressure; by the elastic spring of the Avings of the plate; by spiral springs. These will be taken up in a sub- sequent chapter, and their relative merits discussed. We pass now to the step which, in swaged work, comes next in order to the fitting of the plate—the means for securing its exact relation to the natural teeth, or, in double sets, its relation to the opposing plate. These processes come under the technical head of Articulation. ARTICULATION. 915 CHAPTER X. ARTICULATION. The term Articulation, as used in Dental Mechanics, compre- hends several distinct operations, implied in the use of the terms (1) Articulating impressions; (2) Articulating plates; (3) Articu- lating models. In many partial tests it is best, after fitting the swaged plate to the mouth, to take a wax impression with the plate in situ. This gives the precise relation of the plate to the adjacent teeth; and upon ap- plication of a model of the lower jaw, it gives the relation of the plate to the antagonist teeth. This and all other impressions of the relation of plates to the teeth, or to each other, in the mouth, we call articulating impressions. A base plate becomes an articulating plate Avhen the articulating rim is attached which has the impress of its opposite rim or teeth. In SAvaged work, it is the gold plate itself; in plastic work, it is some temporary plate of tin, lead, or gutta-percha. The articulating models make up Avhat is technically called an " Articulator," of Avhich there are many forms; all, however, comprehended under three varieties: (a) Those wholly of plaster poured into the articulating plates, (b) Those in which the model portion is poured into the articulating plates; but the back, or hinged portion, is metallic, (c) Those in which the original models are set into the articulating plates, and some complicated metallic articulator adjusted to them. Each of these classes have special advantages adapting them to ATarious exigencies of practice. Whenever, in partial cases, there are three points of contact suffi- ciently apart to give firm antagonism, Prof. Austen's plan Avas to take an impression of the lower teeth; this gives a model Avhich antago- nizes perfectly with the upper model, and makes the articulator Avithout further trouble. This plan, specially applicable to vulca- nite Avork, is adapted to swaged Avork by taking the articulating im- pression described in the second paragraph of this chapter. Such articulators require no backAvard extension or hinge, because the articulation is determined by the articulating cusps of the teeth. In partial cases, where there are only one or two points of antago- nism, and Avhere, consequently, the opposition of the corresponding teeth Avould be uncertain, the necessity exists for some third point of support. This is best given by a backward extepsion of the model, so as to permit motion of the two halves of the articulator, 916 MECHANICS—DENTAL PROSTHESIS. somewhat resembling that of the natural jaws; though many par- tial cases do not require such an extension. In putting this wax rim on the plate, it is better in all cases to trim it, as is done for full upper sets ; but Avhere there are remaining teeth, the antagonism of these determines the proper closure of the mouth, and this is not essential. The plate and adherent Avax are placed in the mouth ; the patient is then requested to close the mouth naturally, imbed- ding the teeth of the lower jaw in the wax. While the mouth is thus closed, the wax on the outside of the teeth and alveolar ridge is pressed closely against them. This done, the plate and wax impression are carefully removed, filled with plaster, and placed on a piece of wet paper, Avith the wax downward. The upper side of the plate is then oiled. As the plaster stiffens, it may be applied until it is raised half an inch above the plate, and extended back of it on the paper an inch and a half or two inches. As soon as the plaster has set, its edges may be neatly trimmed; and at the back of the surface next the paper a deep transverse or T-shaped groove should be cut, to serve as a model for the formation of a corresponding ridge on the half model with which this is to antagonize. This grooved surface must be coated with oil, or soap water, or varnish, or covered Avith a layer of tin foil or thin paper. Then partly fill the space inclosed by the wax rim with clay, putty, or wet paper, and pour on plaster to form the other half model. In running plaster into the wax impressions of the teeth, be very careful to avoid air bubbles and flaws, and do not oil the wax. After the plaster has set, it may be trimmed as before directed. Another and often more convenient method is to take a strip of sheet lead one and a half inches wide, and bend it to the required outline of the articulator. Pour this partly full of plaster, and set the plate, previously filled with plaster, upon it. Cut the grooves as before described, and pour the other half of the articulator. The lead rim saves much manipulation and trimming, which, in the other case, the plaster requires. When the half last made has become sufficiently hardened, the two pieces may be separated, after softening the wax in warm water, and the wax carefully removed. The model is then varnished, for greater comfort in handling, and when put together may present an appearance ex- hibited in Fig. 840. The artist has failed in this, and in other designs of the plaster articulator, to represent the tapering shape which it is best to give to the back half of the models, for greater convenience of holding them Avhile adapting the teeth. The fault of many plaster articu- ARTICULATION. 917 lators is that they are too large and clumsily shaped. In any given case, the proper distance of the groove or hinge is the distance from the patient's external auditory meatus to the line of the front teeth or alveolar ridge. The Avidth and thickness of the articulator must vary Avith the size or depth of the mouth, avoiding any excess of plaster not necessary to give requisite strength. For a full upper set, or where tAvo or more remaining molars have no antagonism, it is a very common practice to place on the plate a roll of wax sufficiently large to receive the imprint of the lower teeth, and to prevent these from closing too far by the insertion of a piece of wood buried in the Avax, and projecting at the median line. The closure is better arrested by tAvo lumps of sealing wax attached opposite the bicuspids, and trimmed to the required length Fig. 840. Fig. 841. before putting on the Avax. But the articulation ought to determine other points besides the single one of space. Hence the antago- nizing plate should be made by adjusting a rim of Avax corresponding in Avidth to the length proposed for the artificial teeth, and trim- ming it until all the teeth in the loAver jaw touch it at the same instant. Instead of Avax, a rim of gutta-percha may be used to rep- resent the required length and external fulness of the teeth. When this is satisfactorily adjusted, a small rim of soft wax is placed upon the Avax or gutta-percha, and the mouth closed as naturally as pos- sible until the teeth touch the latter. The gutta-percha can be readily trimmed with a sharp knife. Rims thus shaped give oppor- tunity to ascertain, by the effect on the expression of the lips, etc., exactly what length and fulness of tooth suits the particular case. Gutta-percha is better than Avax in arresting the closure of the teeth, and is decidedly best for the temporary articulating plates of plastic Avork; but the latter is more easily attached to a gold plate, 918 MECHANICS—DENTAL PROSTHESIS. and is more easily trimmed. By making the Avax cold, or by im- bedding a small block of wood opposite the bicuspids on each side, with the grain of the wood running transversely, for easy trimming, the wax rim offers a firm resistance. There is a tendency on the part of the patient to close the mouth to one side, and nearly always to project the jaw too far fonvard; it is impossible to close it behind the natural articulation. The simplest method for regulating this is to keep the body erect and throw the head backward, so as to make as tense as possible the throat muscles, which thus act as a bridle, and almost compel a correct closure of the mouth. It may also be done by careful obser- vation of repeated closures made by the patient while sitting in an erect natural position. The operator must avoid impressing upon his patient the necessity for an easy natural closure; such directions invariably defeat their object. Of course, these trials are to be made before attaching the soft Avax which receives the impress upon the final closure. A vertical median line, traced on the wax, is of ser- vice in observing the articulation, and in the subsequent adjustment of the artificial teeth. Fig. 841 represents such a rim Avith its original fulness cut away. For a double set of artificial teeth, the following method of articu- lation is often adopted. After having accurately fitted both plates, a rim of soft beeswax is placed between them, about an inch and a quarter in width. A piece of Avood, exactly corresponding in width to the proposed length of the upper and lower central incisors, is passed through the Avax between the plates at the median line; or, still better, one piece on each side between the bicuspid part of the plates. The whole is now placed in the mouth, and each plate accurately adjusted to the alveolar border. The patient is then directed to close the mouth until the plates are brought in contact with the edges of the interposed piece of wood. This done, the plate, wax and wood are together removed from the mouth. But a far better method consists in placing a rim of wax or gutta- percha on each plate, giving the length, outline, and fulness respect- ively designed for the teeth of each jaw. The two plates are put in the mouth, and the jaws are carefully closed; if the rims of wax touch at any one point sooner than another, the plates are removed and the wax trimmed; this operation is repeated until the two rims of wax meet all the way round at the same instant, and give the proper contour to the cheeks and lips. The median line is then marked, and the final closure of the mouth made with the utmost care, so that there shall be no lateral or forward deviation. The exact position being secured, the lower jaw is to be held with the ARTICULATION. 919 left hand, Avhile, Avith the right, some six or eight oblique indenta- tions are made with a wax knife across the line of contact between the tAvo rims. Some fasten them together by a warm wax knife, or by pins, or by small slips of brass plate warmed and forced into the wax. The pieces are removed jointly or separately from the mouth; if separately, they can, by the aid of these marks, be accurately readjusted. From these articulating plates a plaster articulator is made sub- stantially in the manner described for a partial case. The lead rim for shaping the models will often have to be two inches broad. If the precaution is taken to fill the space Avithin the wax rims and between the plates with paper pulp, it is not material which half is Fig. 842. filled first. Usually the lower-jaAV model will be thickest, and in this, made first, it is best to cut the grooves. Fig. 842 represents a plaster articulator with the plates removed, in which figure, from neglect of this point, the thin upper half is much weakened by the V-shaped cut. Partly to save plaster, but chiefly to permit modification of the articulation, where inaccuracy is suspected, quite a number of me- tallic articulators have been recommended. One of the first con- trived for this purpose Avas by Dr. Thomas Evans, of Paris, and made of heavy brass wire. Fig. 843 represents a very convenient form of metallic articulator. But in using this, and e\rery similar contrivance, the operator should remember that facility of changing the articulation, after the guiding wax rims are removed, is a very questionable advantage. It tempts to carelessness in articulating. Moreover, if the width of space, or other relation of the parts, is such as leads to suspicion of inaccu- 920 MECHANICS—DENTAL PROSTHESIS. racy, any change of articulation is, at best, a sort of random guess- work. The most certain correction of surmised error is, undoubt- edly, to take the articulation anew. Hence, our preference is for the old-fashioned plaster articulator, with its unaccommodating Fig. 843. fixedness, that neither offers a premium on carelessness, nor puts the careful workman at the mercy of some loose joint or screw. Fig. 844. There is another class of articulators more complicated than the above, which are very useful in those cases where the original models are used, instead of special models cast in the articulating plates. ARTICULATION. 921 Fig. 844 represents an articulator devised by Dr. J. B. McPherson, the valuable feature of which is the clamping fixture for holding the plaster model. The danger of breaking frail models in removing them from the articulator is overcome, as they can be removed by simply loosening the clamp. It has also a lateral movement resembling that of the jaw. Fig. 845 represents Dr. Genese's articulator, with set or lock pin, and interchangeable model holders. The following directions are given for using this articulator: Detach the model holder, leaving the centre screw in; paint with non-adhesive and arrange on a Fig. 845. board Avith the tube pointing away from the operator; after filling the impression, cover the holder with plaster to the hilt and reverse, the tray uppermost. Let the centre of the impression be in a line with the tube at the back, making the model slightly higher in the back than ordinary models. When set, remove the centre screw and draAv the holder out, wash in warm water, and it is ready for use again. The models can be trimmed and adjusted immediately they are hard. The entire instrument is never soiled with plaster. To Secure a Bite for Future Reference.—This articulator, as it takes the bearings of the entire surface of both upper and lower models, Avithout injury to them, and only a small quantity of plaster being 922 MECHANICS—DENTAL PROSTHESIS. used, very little shrinkage occurs, and the bite can always be re- placed on the articulator without the difference of y^- part of an inch. To Arrange a Bite for Reference.—Paint the models with non-ad- nesive; mix some plaster and pour in tissue paper, and place be- tween the models that are perfectly articulated previously; gently close the articulator until the pin enters its centre and allow it to harden; as soon as it is set, trim up, and it is then ready for any future work. Any overlapping edge or slender tooth may have a little wax or soft paper placed on it, to prevent the plaster binding too tight. Dr. W. G. A. Bonwill, who has devoted much time to the study of the geometrical and mechanical laws of articulation,Wd devised an^anatomical articulator ^Fig. 846) in accordance therewith, treats this subject as follows : " We find from 28 to 32 teeth in each jaw, arranged in such manner that no two strike directly against each other, but an- Fig. 846. tagonizing in such a manner as to prevent the whole denture from becoming very irregular, which would be the case if striking one against another. By this arrangement, when one tooth is lost, the regularity of the arch is not interfered with. As necessary as this is in nature, it is not positively necessary to follow it in artifi- cial work, although for the sake of harmony it should be done. "It will be found in 95 per cent, of cases that the upper teeth project over the lower, and the depth of overbite varies as the depth of the cusps of the bicuspids are deep or shalloAV; and the ramus will be found to come upward and backward in relative proportion to the length of the cusps and the overbite. " One point of very great importance has not been lain down in general or special anatomy—the peculiar tripod arrangement of the lower jaw forming an equilateral triangle. ARTICULATION. 923 " From the centre of one condyloid process to the other, four (4) inches is about the average; and it will be found that from this same centre of the condyloid process to the median'line at the point where the inferior centrals touch at the cutting edge, is also four (4) inches. It is strange it should have been overlooked ; but it only shows, Avhen studied in a geometrical and mechanical sense, the great wisdom in our formation. It varies slightly, but never more than one-fourth of an inch, which would make but a trifling differ- ence in describing the arc of a circle. You will perceive that in setting your artificial teeth a one-fourth inch, the radius of the circle would not materially alter the articulation. Without such an arrangement the teeth would have to be flat on their grinding surfaces to admit of lateral movement. Besides, you would not have the beautiful and Avise curvature at the ramus, for equalizing the force applied to the teeth in all directions. " Imagine the human jaw jointed at the pharynx, or as you see in the ordinary brass articulators. Do you suppose that there would be any greater wisdom displayed in such hinging or articu- lating a part destined to such varying motions and poAverful wrenching force ? No! The study of this one part of the head and jaws shows one of the most striking designs of a Great First Cause; and, when studied, you will see that every part of our frame is made by a positive law and to subserve definite purposes; such laAV being in consonance with geometry and physics and mechanics. We must see the true use or function of the jaw and the teeth, and the food destined for us, and how it should be comminuted ; there is no chance-work about it! There is law and order pervading every part; the jaw forms a perfect triangle, for the purpose of bringing into contact the largest amount of grinding surface of the bicuspids and molars, and, at the same time to have the incisors all come into action during these lateral movements. " You will also find that from the cuspids, the bicuspids and molars run in nearly a straight line instead of a curved one back towards the condyloid process, enabling them to keep the largest amount of surface ahvays presented for mastication. Another thing which has. never been explained by anatomists or naturalists, is the laAV of the normal relation of the upper to the lower incisors. The normal jaw should overjet and also have a corresponding underbite. Without such a law the incisors would lose largely their functions, that of incising on the principle of a pair of scissors. Where the incisors strike direct!}' upon each other, the power to cut off food is very much lessened. The length of bicuspids and molars proves the law. 924 MECHANICS—DENTAL PROSTHESIS. " Another unobserved fact where law is expressed, where there is an overbite and underbite, just in proportion to their depth Avill be the length of the cusps of the cuspids, bicuspids and molars. By drawing two lines from T to F, Fig. 853, or T to a and e, Fig. 847, Fig. 847. W we have the lengths of the cusps of the bicuspids, b, in the upper, and c in the lower, and also d, the second upper molar. The depth of the underbite is one-eighth of an inch from the cutting edge of the inferior central incisor e to that of the superior central incisor a. Did the teeth extend as far back as A, A, there Avould be flat surfaces at those points. But in articulating artificial teeth, when the superior second molar is reached, its distal cusp has to be raised from line T e to T a, Fig. 847, to allow the molar teeth on the op- posite side, not in mastication, to touch; for merely balancing the plate, as Fig. 850, M, N, otherwise the second molars would be of no use in lateral movement, nor would the first molars. This cur- vature at the ramus (see Figs. 851 and 852) commences at the first molar, although it shoAvs itself slightly in the bicuspids. Practi- cally, it need commence at the first upper molar. This curve, then, will always be proportioned by the underbite at a, e. The length of the cusps on bicuspids will never be more than an eighth of an inch, normally; the groove deeper than that would cut the palatal cusp off, and make of it a cuspid. It would in reality be cut in twain. This is another unobserved fact. It always has been and will be found in the archtype of human jaws. So that when you see a first superior bicuspid, it can very well be told from the length of the cusps Avhether the jaw from which it came had a depth of underbite of one-sixteenth of an inch or more. Where the teeth all strike fairly one upon the other and no overbite, then you have no occa- sion for cusps. If originally there, they would soon be worn off from the abnormal articulation. ARTICULATION. 925 " This provision of articulation is most wise, carrying out still more fully the exact law by which the anatomical movements of the loAver jaAv for perfect mastication are governed. So beautiful and so mathematical a design cannot but call forth our admiration and Avonder; and the study of no other part of the human body will give one a clearer idea of infinite wisdom. This movement we will find, in the artificial sets arranged upon this law, will prevent the plate from tilting. In the natural denture the incisors are really the first teeth to be arranged; though the first molars emerge first, to assist in the more perfect mastication of food and to keep the jaAvs at the proper distance. The incisors show a definite fixedness of purpose to arrange themselves after their typal shape, and to form the overjet and overbite at a given depth, for the accommodation of the bicuspids and molars which are soon to appear, having cuspids of a definite length, so that the law of articulation which has been premeditated to a certain typal shape and construction, be carried out. "It Avill also be found that the grinding surfaces of the bicuspids and molars have a typal shape—allowing them to meet with all their surfaces touching—for an express purpose, after a preordained and established law, from which the greatest area is gained for mastication; and that the inner cusps of the loAver teeth are as neces- sary as the outer of the superior, Avhen laterally moved. The haw is still further carried out in the curvature at the ramus, from the second bicuspid to the third molar, to permit all the surfaces on one side to be in contact (Fig. 852), while the other unused side is only partially so (Fig. 851). The nearly straight line of arrangement from the cuspids to the last molar is also in keeping with the under- bite (Fig. 847). It may Avell be asked just here: ' Will this law hold good in an artificial articulator such as I use, applied to setting of artificial teeth ? ' As soon as you once attempt to apply this prin- ciple you must certainly grasp this laAV, so wise and beautiful. There may be variations, but the general law will hold good, and Avhere there has been much latitude or varying from it by abnormal mixt- ures of races or types, if Nature is given a fair chance to right her- self, she will return to the normal standard of mathematical and mechanical precision; to do othenvise would annihilate creation. Cells free to arrange themselves must develop the original creation, and perpetuate and keep it to the perfect standard, by selecting the highest type of perfection in shape, strength, beauty, etc. " Could the reader but stand beside me while I arrange a set of teeth in this articulator, you must become converted to my system as founded on laAV and not on chance. There is no other part of the 926 MECHANICS—DENTAL PROSTHESIS. human body that will permit of thus handling and unfolding, and again rearranging. No other that stands outside its own organic workings that will permit such demonstration. It is the key to the revelation of nature's inner workings, and unfolds, without a miss- ing link, Avhat we were, absolutely perfect in cell and organism for the inception, and simply in conformity to an infinite and all-wise law which cannot be blotted out. The teeth, individually, have been a great factor in science;. and when they can be looked at from the point of view herein laid down and hitherto undeveloped, their significance will be magnified; and if we, as dentists, but take up the work as only belonging to our speciality, and scientifi- cally prosecute it, our honors and standing will be enhanced. " Upon these bases I shall found the science of articulation, and apply it to the arrangement of all artificial substitutes, changing to suit individual peculiarities. The query here naturally arises to those who have never looked into the philosophy of this matter, whether these peculiarities are necessary, and if it is possible to utilize them in our artificial dentures; and, if so, how can it be done by any of the articulators now in the market, or can it be done at all by any human device ? To all these inquiries I answer in the affirmative. " As to the necessity, it should need no argument to convince you that an artificial denture should correspond to the natural one in every respect as nearly as can be approached. It may be a ques- tion wdth you how nearly art and mechanics can imitate the natural movements and expressions. Has there ever been any rule hereto- fore given by which you can regulate your beginning and ending with any kind of design ? Have you any chart, system, or plan to go upon, such as the plot or sketches by which an architect, artist, or sculptor can bring forth his ideal ? No! I say most emphati- cally. Look at all the sets of teeth made, I care not from whose hands they come, and you will not find one made after any special law to suit the individual case. Not that no sets have ever been made that have not been serviceable or look well, or where no taste has been manifested; I have seen many, but how much more useful and life-like they can be made by following the system as found in the natural jaw. I remarked it is so strange that these points should have been overlooked so long. To have examined the human jaw critically would have led to the plan at once. But we have acted on the principle that artificial teeth can only admit of the up and down or hinge-like movement. To allow of the lateral motion is thought to be impractical, as it would throw or upset them, and render them difficult to keep in place. The regular horse-shoe shape has been ARTICULATION. 927 adhered to up to the present, for fear that if the molars were placed outside the arch, the plate would tilt, and mastication be impossible. To give to the teeth the greatest advantage, you are taught by some to let the cutting edges of the incisors meet squarely, and have no overbite. If there has to be overbite, then the arch must be so large and wide, more than normal. " It is taught that it is vandalism to grind the antagonizing sur- faces of teeth, as if there was but one magnate to see them, the manufacturer of the teeth. You are also taught that but one side or cusp of the bicuspids and molars can be made to antagonize the outer. As I have studied the matter in its manifold bearings, and as my forte is in mechanics, I speak as having authority; and, if practice is of any value in establishing theory, I am prepared to give it to you in various ways, and attest that the adaptation of such work in the mouth holds good to the law as it does in this articulator I now present. So that when you have fitted in this device on the laAV laid down here, a set of teeth for any jaAV, you can rely upon it, that if you had the jaw itself in your hands, you could not approach more nearly to what is demanded. In some cases there is need of touching a cusp here and there, but to a very trifling amount " This triangle can only be found within a perfect circle in which you have the greatest breadth and area of surface. No other geo- metrical angle Avould have given such perfect beauty and symmetry to the face. The compactness brings the largest number of teeth nearest the centre of motion. The double joint permits the greatest strength and the easiest lateral movement vVith the greatest range of this at the least expense of power and compass. It permits the largest number of teeth to antagonize at every movement, and, not least of all, this very triangle is the means by which nature develops the typal shape of the ramus., and of the formation of the jaws, the under- bite, etc. " It will be observed, that in making the lateral movement of the lower jaw to the left, the condyle of the left side stands still or does not move backAvard, it merely revolves or rotates in the socket, which is but a trifle. The right condyle moves forward in the glenoid cavity fully half an inch, when at its farthest limit, causing the outer cusps of the upper, from the centrals to the last molar, to touch the outer and inner or buccal and lingual cusps of the lower on same side—the left (Fig. 852, and J K, Fig. 850) ; and on the opposite side (Fig. 851, and M, N, Fig. 850)—the right—we find only the inner cusps of the bicuspids and molars of the upper, to come in contact with the outer of the lower, and the centrals to 928 MECHANICS—DENTAL PROSTHESIS. the cuspids do not touch. And why so little surface touching on right side when the lower jaw is thrown to the left? You cannot masticate on more than one side at once, and when you throw the jaw to the left in the act of masticating, the food is upon that side, hence there is no necessity for the right side to have so much sur- face in contact. But why should it touch at all on the right ? In order that the muscles on both sides should act equally, which could not be done if the teeth wrere not allowed to strike there, giving support to that side of the jaw, and equalizing the force brought to bear upon that side, although no food be there. If there were no touching of the teeth on that side while mastication is going on upon the left side, there would result, as a sequence, that peculiar movement of the lower jaAV at the condyloid process, which makes it difficult to place in teeth for the aged or those even in early life, who have lost all the grinders on one side. " The form of triangle is necessary again for the purpose of giving the largest number of muscles a chance to act on both sides simul- taneously and concentratedly, and thereby keeping the circle or arch of grinders down to their work, and equalizing the pressure on all sides. It enables the teeth on the side where the chewing is being done to arrange themselves when erupting, so that they will be very nearly in a line with the left condyle, which is now passive on this side, and forms one point of the dividers in forming the arc of a circle; and by this condyle being where it is—four inches from the other—the molars and bicuspids, as Avell as the central of that side, all come into the most perfect contact, for chewing and incis- ing, thereby carrying out this absolute natural law of the perfect adaptation of geometry and mechanics to her uses, and having no lost motion or function in any part. "Again, the triangle gives us an extra motion forward, which brings the lower teeth in contact with the upper to incise or cut off food presented there. This could not have been with any other ar- rangement than the triangle. One central point at the pharynx or on the median line would have been a single swivel joint, and have brought the teeth across each other in such a way that as soon as any lateral movement commenced, they would be drawn away from each other very rapidly, and but little surface be in contact. This triangle will enable you to get just the exact depth of underbite from the incisors to the last molar, and the exact shape of arches; and particularly that of the ramus, Avhich is not a matter of chance —neither is the length of cusps on the bicuspids and molars mere chance. The type has been preordained, just as the nose on your face, or the peculiar shape of the eye, or any other one part of the body. ARTICULATION. 929 And you will find that where a superior bicuspid has a cusp of a given length, the overbite will be governed and ruled by it. It cannot be othenvise. If in the arrangement of the teeth in the human jaw, no type or design were laid down in conception or embryonic life, what malformed creatures we should be, mentally and physically ! And it will be found that just in proportion as there is congenital in- sanity, or want of will or directing power, there. will be a malformation of the teeth and their arrangement. " The next step is, now that we know the exact shape of the jaw and its philosophy of form and functions, Ave must have at our command something so nearly approaching it, that we can place our models upon it, and thus again restore nature's 'lost art.' I believe I have it here so nearly that it will be found to answer our most fastidious notions of setting by a system teeth on plate. The instrument is made of brass wire one-eighth of an inch in diameter (Fig. 846), and of such shape and movements as to correspond exactly Avith the mechanism of the human jaAvs. The base with its move- ments forms one part, and the two bows another. But one base is necessary for any number of cases. The boAvs which here are sep- arated from the base, can be duplicated to any extent. They are held firmly by thumb-screAvs, and after a case is once articulated to the boAvs, they can be laid aside for future use. The lateral motion forbids the use of a prop to keep the bows apart. At first sight it Avould seem that the loAver boAV is moving in the wrong direction. Its motions are precise and correct. This has never been changed in design since first invented, in 1858. It permits of seeing whether the palatal and lingual cusps properly touch. In using it to get the lateral moA^ement, one condyle must be kept close to the point where it is held by the spiral spring, while the opposite one moves fonvard. Never use both springs at once, except in bringing the lower jaAV fonvard for incising. This method demonstrates that there is but one way to make a set of teeth articulate. " Before placing the Avax models in the articulator, it will not be out of place to say a Avord about this arrangement of the Avax on the base plate, and the selection of teeth in full sets. Always model the upper wax first, judging of the length of incisors by the trial of an artificial tooth in the mouth, such as, in shape, length and Avidth, Avould look natural and appropriate, when held under the lip. This will enable you to get the height of Avax and the contour after successful trial. The modelling of the Avax on the upper plate is not arbitrary or fixed, so far as a definite law is concerned, in being able to work after a set pattern ; here the true dental artist comes in. You get the length by trial of several blocks or single gum or 59 930 MECHANICS—DENTAL PROSTHESIS. plain teeth, as may be, as well as shade of same. As to the arch of upper you must add to and take from, making depressions, etc., until your judgment tells you it is correct. To aid amazingly in this Avork of art, draw out the patient in a smile or broad convul- sive laugh; compel him to do so; nothing tends so to relax most universally every muscle and give true expression to the counte- nance. If the wax is not in keeping with symmetry you will see where the trouble lies. Look at them in front and on either side when they are laughing as a sculptor would upon his model. Be sure that the arch at the cuspids that form a double keystone to the arch stand out more prominently than any others. The superior first bicuspid should nearly always fall back somewhat behind the cuspids. " Now that the upper wax is correct, the same rule applies to the lower. It is easy to make this conform to the upper ; you ma}7 have to change the upper in some respects when tried with the lower, but not much. The length of wax at the molars may have to be trimmed to allow of equalizing the length of the teeth on upper and lower plates. Laughing and smiling will here again tell. Be sure to mark the centre at the median line, making marks or grooves through on either side, running from upper to lower for guide; they can be removed and are now ready for.the articulator, with their bows pushed into their sockets in the base, Avhich are retained by mere friction. The plaster models or casts with the wax articula- tion or bite thereon—and all fastened together by wax or cement to prevent being displaced from the cast—are now placed on this lower bow of the articulator, and the upper bow brought over upon the upper cast. Your eye soon detects whether the median line or wax is in the centre. To get the cast in proper place, have a pair of cali- pers four inches between points, and by it place the cast in position, with centre of lower teeth just four inches from the condyles on either side. Hold in position, while with plaster you secure the upper to the bow, and when hard, the loAver bow to the plaster cast in the same way. " It may be asked where is the set screw to hold open the jaws of articulation after wax is taken off? I have never found it neces- sary in this kind of frame. Before taking off the wax, I take a pair of dividers, or a piece of wire bent with the points about one inch and a half apart, and mark, Avith one foot on plaster cast, and the other at cutting edge of wax, the bite at the median line. Do this for both jaws. To secure this height for future repairs, mark on each cast with the dividers, the distance apart or width of dividers, and this will ahvays be your guide for height. Take off all the ARTICULATION. 931 upper wax—except a section at the molars—first, and let the lower remain as a guide, for the arch of the upper. The first block or tooth fitted on the upper when backed Avith wax, answers perfectly to keep the jaAvs of the articulator apart. The set screw wTould be in the way with the lateral movements. I stated that the length or depth of underbite in full sets, is restricted to the width of the jaAvs and length of the centrals, which it is presumed have been selected to suit the individual case. KnoAving how much the underbite is to be, you can very nearly guess how much to cut out the bicuspids and molars on all the grinding surfaces, before any of them are fast- ened to the base plate, and how much arch upward at the ramus, from the second bicuspid backAvard and upAvard. If the underbite at the centrals is to be an eighth of an inch, then the bicuspids in the upper will have grooves between the cusps not quite so deep, and the molars still less. From the cuspids, then, the cusps are less to the second molar; Avere the incisors to strike equally and di- rectly on each other, there could be no cusps or they would be of no use. The inner cusps of the upper should, as a general rule, be longer or higher than the outer. (See Figs. 848 and 850.) The outer cusp is more acute, the inner rounded. The loAver the reverse —inner sharper and outer rounded, Avhere the upper closes over the loAver. For full sets you need but slight underbite, only enough to permit the loAver to come forward and act as shears for cutting; at the same time it permits of cusps to both bicuspids and molars, and gives all double amount of grinding surface; there being cusps that touch on palatal and lingual sides, at same time as the buccal Always bear in mind that the curvature upAvards at the ramus, of the upper set, is ahvays in proportion to the underbite. "If for an upper set alone, you can tell how much the upper in- cisors should overbite, by looking at the curvature of loAver molar teeth remaining. If an eighth of an inch out of line, the overbite should be fully so. This, Avhen once understood, can give no trouble. The grooves in bicuspids and molars will form with the cusps, buc- cal and lingual, an ogee, as seen in Figs. 848 and 850, to give double the grinding surface Avhen worked laterally; besides giving double cutting edges. All these grooves can be cut out before any are fastened with wax, so nearly that but little touching will be needed when the lower is articulated to upper. The first bicuspid in the lower. jaw should have but one cusp. This perfect design will be seen in the articulator why it should have but one. Two would not only be in the way of the tongue, but be of no use. Be sure that the groove in the upper is made nearer the buccal side, and for the lower or lin- gual side, for a reason Avhich you will presently have explained, as 932 MECHANICS—DENTAL PROSTHESIS. seen in Fig. 848. Now that the grooves are completed in the upper and all the teeth in place in the arch, we will articulate the teeth on the lower base. The height is soon ascertained by the dividers, and the central incisors tried on to see what changes will be needed. Fasten it temporarily with wax, and try it with the lateral motion and the points adjusted to meet all the surface on palatal side of upper teeth, when the lower is thrown to the side of the tooth being fitted. Cut from the cutting surfaces of each, whichever will make the most natural and strongest case. If for a very young subject, be careful; but for a middle-aged or elderly person do not scruple about the cutting edge and grinding surfaces, but sacrifice even the labial or palatal surface, for the sake of effect and usefulness. " I sometimes turn the buccal side of a molar inward, to save sub- stance and get effect and for better adjustment; frequently for want of room at ramus I do this; and, occasionally, turn buccal side up- wards, for the grinding surface. If using blocks before the front ones are fastened securely to the base plate, and while they are temporarily in their right place, try the bicuspid blocks, to find out how much of the joint should come off of the incisors or the bicus- pid block; or divide it. This will secure a better and more con- tinuous joint, and give the lower better chance to be arranged to the Fig. 848. Fig. 849. ........44/--. -----yU upper. Before taking off too much of the joint of either of these blocks, try the lower incisor and bicuspid block temporarily on wax, to know where the cusps are going to come. Regulate the joints by this. You can make the groove in the lower blocks the reverse of the upper, and cut them all out before much jointing is done, taking care that the groove is now on the lingual side and that the buccal cusps are rounded, and the inner more acute as in the buccal of the upper. Never cut off any of the lingual cusps of the lower bicuspid and molar teeth, such as are now made, as they are univer- sally too short, and to get them long enough for service a large por- tion of the buccal cusps have to be cut down and rounded. " The palatal cusps of the upper strike between the outer and inner of the lower (see Fig. 848) and, at the same time, these cusps should be long enough to allow in the lateral movement, the incisors ARTICULATION. 933 and cuspid on that same side, to touch simultaneously all the sur- face from the central to the last molar. If they do not, then your remedy is to make the groove deeper in both upper and lower, or perhaps the lower only, or the upper only (see J K, Fig. 850). Ex- Fig. 850. perience here will soon teach you which. When all the cusps are touching inner and outer, and the front one, take the opposite bicuspid and do likewise; and with the additional precaution, when the lower jaw of the articulator is turned to the left, to make the inner cusps of the upper strike the outer cusps of the lower (M N, Fig. 850) and vice versa, when thrown to the lateral right or left (J K, Fig. 850). The molars must have the same rule applied, with yet another additional point of great importance. " The curvature of the ramus must be made to conform to the depth of overbite (see Figs. 851 and 852), so that when the lower Fig. 851. jaw is throAvn to the right, the outer and inner cusps of both upper and loAver sets on that side come together at the same time that the bicuspids and incisors do (see Fig. 852); but the curvature should be great enough to permit on the opposite side of the second molar tooth in the lower, which slides forward to meet the first molar in the upper, apparently moving backward (Fig. 851.) If they were on a plane, they would never touch, on account of the jaws opening as they move laterally to the right or left; to mount up on the cusps of the incisors an eighth of an inch, which Avould not allow the molars to touch, if on a straight line backward. But inasmuch as 934 MECHANICS—DENTAL PROSTHESIS. on the plane of grinding surface the first upper molar stands higher in the upper plane, the sliding forward of the lower jaAV in the glenoid cavity brings the higher second molar in the lower, in con- tinuous contact wdth the first superior molar, as well as both outer Fig. 852. and inner cusps of bicuspids and molars of the upper and lower jaw (Fig. 851). This is specially done to equalize the pressure and force on both sides or parts of the dental arches. This permits of the most compensating arrangement of the teeth for equalizing the action of muscles on both sides simultaneously, and getting the greatest amount of grinding surface at each movement. This arrangement of bicuspids and molars is found in nearly all the lower animals ; the incisors, however, never touch when the jaws are in lateral movement. Turn the lower jaAV to either side and the effect is the same. As I before said, but one side of the mouth can be used at the same instant, leaving the other free to balance the other side at work. " If the upper arch of incisors of the natural teeth should be broad or deep on account of the thickness of the base or body of the in- cisors, or where they are much inclined to protrude, then the arch at the ramus is not so great. In artificial sets this need never occur, carrying out the same rule in nearly every case, of controlling the curvature at the ramus, by the depth of overbite, and length of cusps of bicuspids. This system holds good in partial sets as well. " This is all that is necessary to be said on articulation proper; it remains only to give a few points having a bearing on the per- fection of the same. Select the broadest grinding surfaces to bicus- pids and molars, that the bolus of food may be held securely on their faces, taxing less the muscles of the face engaged in mastica- tion. Narrow surface would rather tend to cut the food than grind it. This is of no mean importance in rendering artificial teeth of greatest use. " To produce the most natural effect the centrals should be the lightest in color, and the cuspids a shade or so darker, with a dif- ference in color of all the back teeth. I prefer on this account to set plain teeth wherever admissible—and nearly all lower cases are ARTICULATION. 935 so—and use different shades and arrange irregularly. The lower incisor teeth are mostly crowded, and I find to lap'them over and distort them, even to a great extent, adds very greatly to their natu- ral appearance. Don't be afraid of getting any case too irregular; very few natural sets can boast of perfect symmetry. " After the teeth are fixed temporarily on the plate they should always be tried in the mouth to see if they are perfectly correct. As the mouth is more yielding in one part than another, the closing of the jaAvs rather firmly will allow of slight readjusting of themsehres on the wax. If, when finished, they are found not to articulate properly—which is sometimes the case from the soldering or vul- canizing—have the patient bite on a strip of wax placed between the grinding surfaces to show the relation of each. Then put this back into the articulator and rearrange the grinding surface. It will be found to need but a trifling alteration. " The false movement of the lower jaw at the condyles is found in nearly all persons Avho have had but one or two teeth remaining in the front arch, to reach Avhich the jaw must be thrust forward Fig. 853. and laterally; and Avhen artificial ones are placed in, the same old movements are continued until their attention is called to it. It can be corrected Avithout any special arrangement other than follow- ing the law herein laid doAvn. " The Equilateral Triangle within the Main Triangle.—The outline draAvings in Fig. 853 may be thought ideal. But any one at all ac- quainted with geometry, who has followed me in my argument and 936 MECHANICS—DENTAL PROSTHESIS. description, must be struck with wonder at the marvelous ingenuity of the contrivance based alone on the equilateral triangle. It will be seen that perfection must be the result, since each part is com- plete within itself and the whole supporting each individual part. " How have I arrived at this divination ? The law is based upon the measurement of over two thousand human skulls. First, make an equilateral triangle, 4 inches each angle, A, A, F; draw a line from T to F. What is the guide to form the arch ? Know the actual width of the superior central, lateral and cuspid at their greatest diameter from the mesial to distal surfaces, say jf, as in Fig. 848. Measure this off with the dividers, and place one arm at F and de- scribe an arc from D to D through I. Then place dividers at I, and intersect the line just made from F and it will be found that at D will be found the extremest point of the arch D, F, D, and will be the distal surface of the superior cuspid. Place the dividers at I, and describe the arc from D to D through F, which will constitute the normal and positive arch of the superior jaw. There will be an equilateral triangle from D, F, I on either side of the mesial line at F. The same will be found the base of each superior incisor. " Next draw a line from A to D on either side, which will be the guide for the bicuspids and molars as to width and depth. Then, by placing the dividers at A and B, describe another arc to C, which will give the width of first superior bicuspid. The line from A to D passes through its palatal base, and will pass through centre of base of triangle of this tooth. Form another triangle by draAving a line from H to H, through B, which will pass through the centre of the first molar, and will give the width betAveen the palatal sur- faces or their depth or thickness. Placing the dividers at I and F, we intersect the line from F to T at Y. Draw a line through Y to E, E, forming another equilateral triangle. From B to F is now the radius of another arc, which intersects the line from D to A at V, and the line A to D at 0. A line now drawn E to E through Y intersects the centre of the second molar at E, E. " Get half the distance between the points at E on the line from D to A, and the width of the first molar is made, and also the second, which is the angle of the equilateral of each. This leaves room between the first bicuspid and first molar, and is the width of second bicus- pid ; or it is shown by placing the dividers at A and Y, and intersecting line from D to A at W, same as from B to C, for the first bicuspid's width. The distance from D to D is the same as from D to the distal surface of the second molar. P to P through Z forms another equilateral triangle, giving the Avisdom tooth's place in the arch. ARTICULATION. 937 " The arrangement of J and K (Fig. 852) on the left shows the teeth in the act of mastication, while on the right M and N (Fig. 851) the inner cusp of molars of the upper and outer of the loAver molars come in contact when not in use. There is double the surface touching at every lateral movement. Fig. 851 shows right side, as at M and N, and Fig. 852 that of left side (J, K) in action from the mesial to the last molar. Fig. 848 shows both bicuspids and molars in normal relation." The subject of articulation cannot be dismissed without a few words upon the great importance of extreme accuracy in all its de- tails. It is a very remarkable fact that some of the most pains- taking dental mechanicians practice methods of articulating in Avhich there can be no certainty, and for constant errors in which the emery Avheel is resorted to, in order to save them the mortifica- tion of making their work anew. In fact, there is no better evi- dence of the guesswork character of an immense number of articu- lations than the habitual attempts at correction by the equally guessAvork shifting of movable articulators. We assert, without hesitation, that any articulation—whether with gold plate or with the temporary plates of vulcanite and other forms of plastic work— can be taken in such manner as not to require the slightest change in the relation of the articulating models. We shall not insult the profession by attempting to prove that, if it can be done, it should be done. Next in importance to accuracy of the impression is cor- rectness of articulation. Defects in either are damaging to one's reputation. But there is this difference: that in the former the error may often be detected on trial of the plate, while in the latter case the finished work alone reveals the failure. Defective articulation is a prolific source of the disgraceful short- comings of Vulcanite Dentistry. By these terms we specialize that art and its accompanying science, which begins with Hard Rubber and ends with a Vulcanizer; which knows nothing of the uses of gold save as a circulating medium, recognizing no quality in a dental material so highly as its cheapness, no merit in a process so Araluable as its rapidity. So long as such principles rule in the dental laboratory, carelessness in articulation is of little consequence. But older practitioners, Avho are accustomed to handle the royal metal Avith a care worthy of its high character, will fully appre- ciate the great importance of a rigorously exact articulation. Dr. W. Storcr How* has described a method of utilizing plaster impressions for obtaining accurate antagonizing models as follows: * Dental Cosmos, September No., 1888. 938 MECHANICS—DENTAL PROSTHESIS. " In the process of procuring counterparts of the jaws for which dental substitutes are to be constructed, every step should be taken with the greatest degree of exactness attainable, and accurate im- pressions are therefore essential as matrices in which the Avorking models are to be cast. Impressions of edentulous jaws are commonly taken in mixed plaster, which is held in the bare tray, or in the wax impression previously taken in the tray. An elucidation of this part of the subject is not now entered upon, but it is assumed that in any case, whether the jaw be completely or partially tooth- less, an impression will be taken in plaster, and that, when practi- able, the thinnest part of the body of the impression will be not less than the sixteenth of an inch thick. Fig. 854 exemplifies such an impression of a toothless upper jaw, and Fig. 855 in like manner Fig. 854. Fig. 855. illustrates the plaster impression of an edentulous lower jaw. In both instances the trays are omitted from the cuts as not necessary to be shown. " Plaster impressions are commonly varnished Avith an alcoholic solution of shellac or sandarach, and then oiled to insure the separa- tion of the casts. The preferable way in most cases is to thoroughly brush the surface with a soft brush and strong soap-suds, and, after an interval of a feAv minutes to allow for absorption of the Avater of the suds, to fill the impression with a properly mixed batter of plaster. " Several hours should, preferably, elapse before attempting to separate the cast from the impression, which should be preserved as nearly entire as possible, and when there is not much overhang the separation may be safely effected by progressive smart tappings with a light mallet over the whole surface of the impression. If, however, the labial portions must needs be first cracked off, this may be done, after cutting a groove in the impression as near along the crest line of the cast as may be guessed, using quick, light mallet- ARTICULATION. 939 blows to knock off the sections. These are to be carefully kept, and after the separation has been accomplished are to be replaced with the palatal portion on the cast, and, with a thin-mixed plaster, built up to the approximate shape of an articulating model. When this has become quite hard it is removed from the cast, which, of course, it perfectly fits. It will also, if as an impression it was cor- rectly taken, perfectly fit the jaw, and may therefore be placed in the mouth and judiciously trimmed until the proper expression has been produced, and the exact dimensions and contour of the desired denture embodied in this plaster articulating model. Such a model is shown in Fig. 856. In like manner one may prepare a similar model of the inferior jaw. Such rigid and exact-fitting models can obviously be replaced, trimmed, and readjusted in the mouth until the best skill of the dentist shall have been expended in obtaining models at once artistic and correct. The median-line mark is then Fig. 857. made Avith a pencil or knife, and cross-lines are made on the sides of both models while they are pressed together in the mouth, after many openings and shuttings of the jaws, to be sure that at last the proper relations of the models have been obtained. The occluding surfaces are then dried, warmed, some hot wax is dropped on them, the models are instantly replaced in the mouth, and the side-marks and median-line marks made to exactly coincide, while the models are pressed together by a firm closure of the jaws until the wax has quite stiffened. The joined models can then be taken from the mouth and replaced upon the casts. These are to be fixed with care in a suitable articulator, and the result will be a precise repro- duction of the relative positions previously occupied by the models when placed on the natural jaws (see Fig. 857). Attention is here called to the fact that, normally, the horizontal line of occlusion is not straight, but curved so that the superior cuspids are at the bottom of the depression, as illustrated in the lines of the models, 940 MECHANICS—DENTAL PROSTHESIS. Fig. 857. In the construction of models for full dentures it is im- portant to maintain this curved line of occlusion, for two reasons: First, the process of mastication is facilitated by the impingement of the lower bicuspids and molars as these are occluded Avith their downward-graded antagonists by the antero-lateral movements of the loAver jaw in the act of grinding the food; second, the facial expression is improved by the rising of the respective planes of oc- clusion at those points, thus in some degree producing the effect that the limner accomplishes by upwardly-curved lines at the corners of the mouth. " Fig. 858 also shows (though imperfectly) the correctness with which the plaster models may be made to anticipate the outlines of forms which the completed dentures are subsequently to assume in becoming both useful and beautifying works of art. The thin, sharp, inflexible borders of contact with the gum along lines which provide for a firm bearing of the model, and yet permit the free play of all the muscles concerned in acts of mastication and facial expression, are noticeable in Figs. 856 and 857 as being producible in plaster models. It is likewise observable in Fig. 857 that the normal overlap of the upper incisors upon the lower may be re- produced in plaster models, and prove an important factor in sus- taining the lips in proper profile relations,—a circumstance too often ignored or overlooked in the preparation of the ordinary wax models. These are, in fact, commonly so crudely and clumsily formed, and are withal so lacking in resistance to adverse impres- sions, that not only can no dependence be placed upon them as correct representatives of the relative parts previously studied and produced in the mouth, but from the very fact that Avax forms are so easy of displacement and disfigurement, the steps in the process of obtaining such articulating models are hesitatingly and hastily taken, and of course result in faulty dentures, which, more than any other class of dental operations, proclaim the frequent failure of the dentist to so closely imitate nature as to conceal the fact that such an endeavor has been made. The practical permanence of the plaster model obviates all these defects, and, furthermore, admits of such a firm final closure of the jaAvs that, when at last the cor- responding denture is placed in the mouth, both the occlusion and the articulation are found to be correct, as could never be the case after a timid trial closure upon a soft, slippery wax model. " In Fig. 857, as in the succeeding figures, the models and casts are to be viewed as mounted on articulating frames, which do not appear because not necessary for the purpose of illustration. " Upon the removal of the models from the casts, after these have ARTICULATION. 941 been mounted on the articulator, both representatives of the eden- tulous jaAvs Avill appear as seen in Fig. 858, and in these cases the border outlines of the models are indicated to emphasize the need of making them conform to the muscle insertion lines whenever this is practicable; and that not only because of the increased stability of the dentures when they are free from liability to dis- placement by the lifting action of muscles improperly so covered, but also because the mobility of the adjacent features in the conse- quent naturalness of the facial expression will depend in great degree upon the judicious definition of the boundaries of the den- tures. " Fig. 859 shows the cast of the upper jaw in its relation to the articulating model in place on the cast of the lower jaw, and Fig. Fig. 858. Fig. 859. 860 likewise illustrates the cast of the lower jaw as related to the articulating model in position on the cast of the upper jaw. " A close observation and study of these illustrations will make clear the many points of advantage to be obtained by the employ- ment of plaster in the construction, fashioning, and adjustment of prosthetic models for full dentures. " Complete upper artificial dentures for use with more or less complete lower natural dentures constitute a large class of the cases coming within the province of the dentist, and for these the plaster articulating models are especially adapted. "Such a model as that shown in Fig. 856 may be suitably shaped to articulate Avith the natural teeth of a lower jaw, as illustrated in Fig. 861, and in the process of shaping the plaster model great satisfaction will be derived from the security of the model's reten- tion in the mouth, the firmness with which the lower teeth may be closed upon it, and the certainty Avith Avhich, by frequent repeti- tions, a natural occlusion may be obtained. When this has been 942 MECHANICS—DENTAL PROSTHESIS. done, and all the artistic conditions are complied with in perfecting the shape of the model, it is to be removed, warmed, and thus dried on its occluding surface, so that a roll of very soft impression-wax may be placed upon it, and all be quickly replaced in the mouth. " Repeated normal closures of the jaAvs are to be made, and the jaws then held tightly closed while the fingers of the operator are rapidly pressed upon the wax which covers the face of the teeth, Fig. 860. Fig. 861. so that on opening the jaws and carefully removing the model and wax there will be found an accurate impression of the teeth, which will have to pass through the wax to the model, pressing it firmly into its seat. The result is shown in the articulated model and cast. Fig. 862 shows the articulated casts when the model has been re- moved. Fig. 862. " If proper care has been taken in pursuing this process up to this point, the succeeding steps in the construction of a continuous gum, gold, celluloid, or vulcanite denture may be taken with com- plete confidence that the substitute, if made in strict conformity to the models, will exactly fit the maxilla, articulate with the natural teeth, and impart an appropriate expression to the related features of the patient. PRINCIPLES AND APPLIANCES OF SOLDERING. 943 "The foregoing method may in some cases be practiced when modelling composition has been used in taking the impression ; or the composition may be employed in building the model upon the cast Avhich has been made from a plaster impression. But for general use—and all the more so as the practice shall become fa- miliar—plaster will be found most reliable and satisfactory as a material for both the impressions and the models." CHAPTER XL PRINCIPLES AND APPLIANCES OP SOLDERING. Soldering is the union of two metallic surfaces; either by slightly fusing the surfaces themselves (technically termed sweating, or autogenous soldering), as in the union of a plate of silver to a block of copper, preparatory to rolling into Sheffield plate; or by the fusion of an alloy which melts more readily than the metals to be soldered. The conditions of successful soldering, as given by the late Prof. Austen, are: 1. A freely flowing solder. 2. Absence of oxide from the surface over which the solder is to flow. 3. Proper amount and direction of heat in flowing the solder. The first condition requires good solder; of this we have elsewhere spoken. To limit the flow of the solder, and protect all places which it should not encroach upon, a thin layer of plaster batter or a solution of whiting may be applied with a camel's-hair brush. The second calls for the use of borax, the specific action of which, as a flux, is—first, the removal of existing oxide by virtue of its poAverful affinity for it; secondly, the prevention of further oxidation by the exclusion of the oxygen of the air. The third condition demands a skilful management of the blowpipe flame; this is the principal difficulty with most be- ginners, and, indeed, Avith not a few old practitioners. The borax should be used in the lump, and rubbed with pure (distilled or rain) Avater upon a coarsely-ground glass slab until a creamy paste is formed. Into this the pieces of solder may be placed, and also some of it applied, with a small brush or feather, to the surfaces over Avhich the solder is required to flow. Hard water and the common practice of rubbing borax on a slate make it impure, and, to some extent, interfere with soldering. Too much borax is objectionable, and gold requires less than silver. The sol- 944 MECHANICS—DENTAL PROSTHESIS. der is placed along the base of the backing, and if this is short, the solder can be directed in its flow by the flame of the bloAvpipe to the holes of the pins; if the backings are long it may be best to place a small piece of solder o\Ter the holes of the pins in addition to the piece along the base of the backing. The solder should be tested before using by melting it on a piece of silver plate. In fulfilling the third condition—the management of the heat— the following points demand attention: (a) To raise the heat very gradually, until the water of crystallization of the borax is sloAvly driven off; for if this is done rapidly the borax puffs up and throws off the solder; rapid heating at the outset is apt also to crack the teeth, (by To diffuse the heat when using the blowpipe, so that the solder shall not become melted before the metallic surfaces are hot enough to unite with it; else it will roll into a ball, or flow with an abruptly-defined edge; whereas it should unite so smoothly with the plate that, except for the difference in color, its line of termina- tion cannot be detected, (c) To manage the fine point of the blow- pipe flame so as to be able to direct the flow of the solder to any given point; the rule being that, unless prevented, solder will flow toAvard the hottest point. There are two kinds of flame given by the blast of the blowpipe; 1. The broad, heating-up or oxidizing flame ; this is produced by holding the tip a little behind or at the edge of the flame. 2. The pointed, soldering or deoxidizing flame; this is produced by passing the tip more or less into the flame. A very general mistake is to use too strong a blast. The apparatus required for soldering includes a lamp to give a sufficiently hot flame; a blowpipe, to give intensity and direction to the flame; borax, brush,'glass, slate, solder and solder-tongs; investing materials and clamps, to protect the teeth, also to hold the parts in relation to each other until soldered; a receptacle to retain or give additional heat during the process of soldering; an acid (sulphuric) bath, to remove the glass of borax. As accidents sometimes occur from the flame communicating with the explosive mixture of air and alcoholic vapor in the body of the lamp, it is prudent to make a safety lamp by connecting the wick tube with the body of the lamp by a small tube, which shall be, under all circumstances, full of alcohol. Figs. 863 and 864 rep- resent such lamps. If the wick is not permitted to run below the shoulder above the horizontal tube, this tube will remain always filled with alcohol. The top of the wick tube should be bevelled off in a direction just the reverse of that shown in the drawing, so as to permit the downward projection of the flame. Fig. 865 is a very ingenious modification of the safety lamp, made by Dr. B. W. PRINCIPLES AND APPLIANCES OF SOLDERING. 945 t Franklin, so constructed as to retain the alcohol uniformly at the same level. Fig. 863. The fluid used in these lamps is usually alcohol. For all pur- poses of dental soldering alcohol gives a sufficient degree of heat, Fig. 864. Fig. 865. and is much more cleanly than the carboniferous flame of ethereal oil, sperm oil, coal oil, or gas. To give intensity and proper direction to the heat of the lamp, a bloAvpipe is necessary. The simplest is a tapering tube, fifteen to Fig. 866. eighteen inches long, and curved at the smaller end (Fig. 866). At this end the bore for the last half-inch should be perfectly cylin- drical, and about as large as a medium-sized knitting needle. This may be modified in several Avays, and made more useful. First, by 60 946 MECHANICS—DENTAL PROSTHESIS. cutting it within three inches of the flame end, and inserting a small hollow ball or cylinder, to receive the condensed moisture, which, in the plain blowpipe, often interrupts the blast. Secondly, by attaching a flattened mouth-piece, which is much less fatiguing to the lips to grasp. Thirdly, by connecting the flame end to the mouth-piece by from six to twelve inches of flexible tubing. The flame end ought to be straight, and from four to six inches long; a cigar holder makes an excellent mouth-piece. A bulb or enlarge- ment in the tube might be serviceable in retaining condensed moisture; but it is less liable to accumulate in rubber tubing than in the metal pipes. There are many forms of mouth blowpipes, and some quite expensive ones; but the pipe with flexible tube, as here described, will be found very convenient for the laboratory. Fig. 867. Fig. 868. Fig. 869. Figs. 867, 868 and 869 represent different forms of bloAvpipes devised for the purpose of preventing the moisture which accumu- lates within the tube from being blown from the orifice and inter- rupting the blast. Figs. 868 and 869 are modifications introduced by Mr. Thomas Fletcher, and for the latter it is claimed that the mouth-piece is the easiest to use, and the heaviest continued blowing causes no strain PRINCIPLES AND APPLIANCES OF SOLDERING. 947 on the lips, while the tongue has the necessary control over the opening. Being held as a pencil, the chamber on the stem stops all condensed moisture and prevents the heat ascending to the end. The mouth bloAvpipe requires in its use a peculiar management of the muscles of the chest, cheeks and palate, by virtue of which an uninterrupted and regular current of air is throAvn from the lungs through the pipe. The simplest way to learn how to do this is to first practice bloAving exclusively during /aspiration; this calls into action the cheek muscles, and involuntarily closes the opening between mouth and fauces. Then use the pipe solely during expi- ration ; this teaches control of the chest muscles in the emission of a steady, gentle blast. The art of using the blowpipe, without fatigue, consists in alternating the action of these two sets of muscles; the art of giving a perfectly steady, uninterrupted blast implies control over these muscles, and the ability to pass from one set to the other at the moment of opening or closing the entrance to Fig. 870. the fauces. After persevering practice of the tAvo methods of bloAving, the art of connecting them will come almost unconsciously ; Avhen once learned it is never forgotten. Those Avho are too indolent to master the first difficulty of learning it, become the slaves to me- chanical appliances Avhich, however useful for many purposes, can never supply the place of this simplest and best of all bloAvpipes. BloAvpipes Avorking by artificial blast may be divided into four classes: 1. Alcoholic or self-acting bloAvpipes; 2. Mechanical or belloAArs bloAvpipes; 3. Hydrostatic blowpipes; 4. Oxy-hydrogen or aero-hydrogen blowpipes. Of each of these Ave shall give an ex- ample. To enumerate all the forms that inventive talent has devised would fill too much of our space. 948 MECHANICS—DENTAL PROSTHESIS. The self-acting blowpipes derive the force of their blast from the vapor of hot alcohol, which, igniting as it passes through the flame, adds to the intensity of the heat. A someAvhat complex, but very complete, blowpipe of this class, invented by Dr. Jahial Parmly, is shown in Fig. 870. The lamp, g, supplied from the reservoir, d d, heats the alcohol in globe, i, supplied from the reservoir, j, through the pipe, n. The elastic vapor escapes at the jet, p, ghdng intensity to the large flame, l, which receives its supply of alcohol from reservoir, m j. Both upper and loAver wick tubes have movable cylinders for regulating the flame. A small charcoal furnace, r, may be brought in range of the flame for melting purposes. Smaller and more portable lamps are made, of which quite a number of different patterns are to be found in the depots. The Fig. 871. Fig. 872. principle and general plan of construction are very clearly shoAvn in Fig. 871, designed by Dr. S. S. White. All alcoholic blowpipes give intensity of heat, but are greatly inferior to the mouth blow- pipe in the control which the operator has over the force and direc- tion of the jet. The different forms of the mechanical blowpipe are almost infinite. The principle of construction is either that of the bellows 999045 PRINCIPLES AND APPLIANCES OF SOLDERING. 949 or the force pump combined with a reservoir of air to give uni- formity to the blast, Avhich would otherwise issue in jets. Fig. 873. A common house bellows, secured to the floor, will form a simple and good arrangement. A spring should separate the handles, the upper one of which forms a treadle. An india-rubber pipe should pass from the nozzle to an air-tight box, from which a second tube comes out and is attached to the blowpipe. If the bellows is made double, like a blacksmith's, the upper half forms the air-chamber, in place of the air-tight box. Fig. 872 represents the Burgess bloAvpipe, Avhich is a convenient and efficient form, a is the cylinder of the pump, which is 2? Fig. 875. Fig. 876. inches in diameter, alloAving a 3-inch stroke, b, piston rod. c is heel-and-toe treadle for driving the pump, d, the receiver, 12 inches Fig. 874. 950 MECHANICS—DENTAL PROSTHESIS. high by 3 inches in diameter, into which the air is forced. The whole height of the machine is 24 inches; the base is 12 inches by 5. Figs. 873 and 874 represent Fletcher's bellows blowpipes, capable of being adjusted in any desired position. Figs. 875 and 876 represent tAvo forms of the Fletcher automatic blowpipe, one of which is mounted on a ball-joint. These forms are very convenient for soldering, especially in the manufacture of gold crowns and bridge-work. Fig. 877. Fig. 877 represents a style of foot bellows by which the bellows and automatic blowpipes are operated. Fig. 878 represents a carbon block for use as a support in soldering. It is a perfect non-con- ductor and much cleaner than charcoal. Fig. 879 represents a Fig. 878. Fir. 879. Fig. 880. carbon cylinder, the cupped end of which answers as a good support for small cases, such as crowns, while soldering. Fig. 880 represents Macomber's gas blowpipe. The direction of PRINCIPLES AND APPLIANCES OF SOLDERING. 951 the point, 1, is regulated by the joint, 3, and the supply of gas con- trolled by the stopcock, 2. The air is supplied from the lungs, or from some form of mechanical or hydrostatic blowpipe, through the flexible tube. Fig. 881 represents a hand blowpipe, into which the air is admitted at A and conducted through a small tube to the upper end of the gas-pipe, b. The supply of both gas and air is regulated by pressure of the thumb or fingers on the rubber tubes c, c. The third class of blowpipes is sometimes combined Avith the second to regulate the blast, or with the first to intensify it. In its uncombined form it consists essentially of a blowpipe point attached by a flexible tube to an air-chamber, from which the air is forced by the steady pressure of Avater. When once set in operation, it is Fig. 881. self-acting, and in this respect has great advantage over the second class. This, Avith the perfect regularity of the blast, makes a properly constructed hydrostatic blowpipe, much the best of all substitutes for the lungs and mouth blowpipe. The gasometer of the nitrous oxide gas apparatus makes a very excellent hydrostatic bloAvpipe. Its form, and the manner of using it, are so familiar to dentists as to render any illustration or descrip- tion unnecessary. Any required force of blast may be given by detaching the counterpoise, or by adding Aveights to the descending cylinder. Prof. Austen gives the following description of a simple and in- expensive apparatus suitable for laboratories where no pressure can be had, as in cities, from public water-works. " Place in a con- venient position a strong 10-gallon water-tight oak cask, two feet from the floor. Over this, and tAvo feet above it, place a second of the same size, with a movable cover, so that water may be con- veniently poured into it. Connect the casks by a tube running nearly to the bottom of the lower cask, and having a stopcock, a, betAveen the casks. Into the top of the lower cask insert a stop- 952 MECHANICS—DENTAL PROSTHESIS. Fig. 882. cock, b, to Avhich attach the blowpipe tube, and into the bottom a larger stopcock, c, for drawing off the water. It is prepared for operation thus: close all the stopcocks, and fill the upper cask to within an inch of the top (if too full, it might chance to overflow the lower cask and force water out of the blowpipe upon the flame and Avork); then open the stopcocks, a, h, and the jet will issue with a force proportioned to the height of the water. If too strong, it may be regulated by pressure upon the elastic tube, or by partly closing the stopcock. Ten gallons of air will suffice for any ordinary case of soldering; but the process is easily renewed by closing stop a and drawing off the water, by stop c, from the lower cask, and emptying into the upper. This can be more rapidly done if stop b is left open, so as to admit air freely while drawing off the Avater." Another, but more expensive form, is shown in Fig. 882, made of copper or boiler-iron, and connected by lead pipes with the public water-Avorks, in towns and cities thus supplied. The draAv- ing, taken in connection with the previous description, makes any explanation unnecessary. The fourth class of blowpipes is analogous in its operation to the oxy-hydrogen blowpipe. The point is double, consisting of a tube, through which comes the supporter of combustion (oxygen or com- mon air), surrounded by a cylinder, through which comes the com- bustible (alcoholic vapor, illuminating gas, or hydrogen). In Count Richmont's aero-hydrogen blowpipe, the hydrogen is gener- ated in a vessel by the action of dilute sulphuric acid upon zinc, and the air forced through the centre tube, either with a bellows or from the lungs. The heat is less intense than that of the oxy-hy- drogen blowpipe, but is too great for most laboratory purposes. The gas blowpipe is a very convenient instrument; the principle is sim- ilar, and the heat very great. Fig. 883 represents an ingenious oxyhydrogen bloAvpipe invented by Dr. J. Rollo Knapp, which consists of an iron stand in which is secured by a thumb-screw a 100-gallon cylinder of nitrous oxide gas. By means of a yoke and set-screw the valve of the cylinder is connected with the tubes and valves of the blowpipe in such PRINCIPLES AND APPLIANCES OF SOLDERING. 953 manner that the proportions of the mixture of nitrous oxide and illuminating gases are under perfect regulation and control. There are tAvo pipe-nozzles, which may be used at the same time, or one at a time, according as a large or small flame may be desired. One pipe-nozzle is shoAvn as hung upon its hook, and the other as Fig. 883. if directed upon Avork held on the ph'oted bracket-table. It can be used Avherever illuminating gas is available. Any of the solder- ing operations of the laboratory, from the largest piece of croAvn- Avork to the most delicate joining of the narroAvest bands or finest wires, are accomplished Avith equal facility. With illuminating gas of good quality and sufficient pressure, a pennyAveight of 20-carat �9999999999999 954 MECHANICS—DENTAL PROSTHESIS. gold can be melted in thirty seconds. A large investment must be heated first by other means. The apparatus consists of the bloAvpipe attachments, connected to the yoke of a nitrous oxide gas-cylinder, the cylinder being set up- right, and secured by a thumb-screAV on one end of an iron base or stand, at the other end of which is pivoted a table, upon Avhich to rest the work. The bloAvpipe proper is a continuation of the outlet- tube of the gas-cylinder. A lever-valve, g, regulates the supply of nitrous oxide. Just beyond this valve is the mixing-chamber, k, to Avhich the illuminating gas is conducted from the gas-bracket by means of rubber tubing, entering the bottom of the chamber through through the valved tube, c. The lever, d, controls the supply. The mixing-chamber is provided with a gauze screen to prevent the flame from being drawn into the supply-tubes. Imme- diately beyond the mixing-chamber the pipe is branched to afford two flames of different sizes, e and f, which can be used inde- pently of each other, or both together. The valve-lever, l, regulate the flame in both. For greater convenience in manipulation the pipe-nozzles are connected with the branched pipe by rubber tub- ing. From the body of the valves, l, an arm extends, at the end of Avhich is a small scalloped disk as a holder for the flame-nozzles when not in use. In the illustration one of the nozzles is shown in the holder, the other being directed to the revolving table. In the operation of soldering, the parts to be united must be held together in their exact relative position. This can sometimes be done by simply laying them together; but usually they must be held in place, either by iron wire bound around them, or by small clamps of iron wire, or by rivets; or else by some investing mate- rial, Avhich, in dentistry, is always plaster mixed wdth some sub- stances that Avill counteract its tendency to shrink and crack under soldering heat. This substance may be coal ashes, soapstone dust, feldspar, clean sand, or asbestos. The two latter are the best, and may be mixed in proportions varying from 2 to 6 parts sand or asbestos to 4 of plaster. As a rule, the less plaster, the less shrink- age; but a very small quantity makes the investment too friable. A common mistake is to use too large a quantity of investing material. This almost invariably results in the warping of the plate; for, as all investments have some degree of permanent con- traction, and all metals must expand, if the latter is bound by a rigid, unyielding mass, it will inevitably warp. Hence, as a rule, use no more investing material than is necessary to keep the parts to be soldered in their position, and to protect the porcelain surfaces PRINCIPLES AND APPLIANCES OF SOLDERING. 955 from direct contact Avith the flame. This subject will be further considered Avhen speaking of the soldering of teeth to the plate. In selecting a suitable receptacle for the Avork to be soldered, it is important to retain the heat, especially when using the mouth blow- pipe. A funnel-shaped mat made Avith scraps of woven iron wire, or a large lump of pumice stone, or one of close-grained charcoal, Avith the outside coated over Avith a thin layer of plaster, form very simple and convenient receptacles for smaller pieces of Avork. For larger work, or for very high temperatures, it is important to receive Fig. 884. additional heat from ignited charcoal, for which purpose the solder- ing pan (Fig. 884) is a very admirable contrhrance. The movable lid remains during the heating up and the cooling off, but is, of course, removed during the act of soldering. Fig. 885 represents the form of soldering blocks which are made of either plumbago or asbestos. After soldering, the Avork should cool gradually, unless it is to be re-SAvaged. If there is any porcelain attached, the cooling must be very gradual. When cold, it may be placed in dilute sulphuric acid and slowly raised to the boiling point, kept there for a few moments, and then sloAvly cooled. This dissolves the glass of borax, AArhich is so hard that it injures the edge of files and scrapers. A few general considerations may be of service in the use of the above described appliances for soldering. It is an operation regarded by many as attended with much risk; and by students generally 956 MECHANICS—DENTAL PROSTHESIS. it is considered the pons asinorum of dentistry. Whereas, there is no process in dental prosthesis in which the desired result can be Avith more certainty obtained, provided such care and skill are exercised as alone can give success in any department of the art. Plates warp from want of support when heated, or from excess of investing batter; they are burnt, blistered, or melted, from care- less or ignorant use of the blowpipe. Teeth are broken from rapid heating or cooling; they are displaced by the shrinking of an ill-judged investment. Solder is condemned because it will not bridge a chasm one-eighth of an inch wide, will not run over plaster, will not attach itself to an oxidized surface, or will obstinately roll up into a ball, rather then flow over a surface too cold to receive it. These and all other vexations of soldering are the result of haste, ignorance, or want of skill. If there should be spaces under the teeth or backings, which, however, should always be avoided, if pos- sible, by adapting the teeth in grinding to the surface of the plate and having the backings of a proper length, such spaces should be Fig. 885. filled with gold foil. As much of the surface of the plate should be exposed as can be done by trimming away the plaster without affecting the stability and safety of the teeth, so that no obstruction is present to the flame of the blowpipe; this direction is especially applicable to a lower denture either full or partial. Good soldering depends upon the perfect heating up of the investment and plate, so that the solder can be brought by the heat of the blowpipe-flame as near the melting point of the plate as is possible without injury to the latter. In soldering two surfaces, as in the doubling of lower or shallow upper plates, the borax must contain no particles preventing con- tact of the plates; also the heat must be directed on the side opposite the pieces of solder, so that when melted it may flow be- 899999999952 ADJUSTMENT OF PORCELAIN TEETH TO THE PLATE. 957 tween the plates from one side to the other. Clamps are preferable to plaster batter for holding parts together, whenever practicable, as in soldering a Avire or band around plates; but Avhen the rela- tion must be preserved with utmost accuracy, as in clasps, the plaster investment is essential. It is also necessary for the protec- tion of porcelain from the direct action of flame. In soldering teeth to a plate, the batter must have such propor- tion of plaster with asbestos or sand as to admit of being used in small quantity, and yet be so strong Avhen heated that it will not crack, and endanger the position of the teeth. Backings and clasps must fit accurately wherever they are to be fastened. There should be no trace of plaster on a surface where solder is to Aoav ; or, in fact, substances of any kind except borax, and not too much of that. Borax must be pure and clean, and used with soft water, and the heating must be gradual, in view of its liability to throw off the solder. Solder must be of good quality and carefully placed, never putting two pieces where the position will allow the proper quantity to lie in one piece. It is a very common practice to cut solder into very small pieces, under the idea that it will flow more evenly; but if a plate is properly heated and the bloAvpipe- flame skilfully managed, the large pieces melt instantly, and flow into their proper position. It is quite possible, by careful observance of these directions, and by expertness in the management of the bloAvpipe, to solder any set of teeth so that there shall be no roughness or abrupt edges requir- ing the use of files and scrapers. In fact, these tools are never needed to ghre finish to a perfectly soldered joint; the natural flow of the solder takes a shape which cannot be improved. CHAPTER XII. ADJUSTMENT OF PORCELAIN TEETH TO THE PLATE—FINISHING PROCESS. Where vacancies between natural teeth are to be filled, it is highly important that the artificial teeth should correspond in shade and color Avith the natural organs; for in proportion as they are whiter or darker, will the contrast be striking, and their artifi- cial character apparent. Of the tAvo faults, it is better that they should be a little darker than any whiter. They should also resemble in shape those AAdiich have been lost, so far as it is pos- 958 MECHANICS—DENTAL PROSTHESIS. sible to ascertain this. Minute accuracy as to shades of color involves the necessity of a large assortment, unless one is located near a depot or agency. But the facilities of mail and express greatly lessen this necessity, provided there is time to send for the tooth or teeth required. It is desirable, in vieAV of this method of matching shades of color, to keep all refuse or broken teeth, to be used as samples in sending orders. The manufacturer supplies three varieties of plate teeth—plain, gum, and sections. The latter have the advantage of showing few joints, but are less easily repaired, and are not applicable to so Avide a range of cases. Gum teeth or sections are applicable only where there have been sufficient absorption to permit the extra fulness of the artificial gum. Many mouths are deformed by a foolish craving on the part of the patient, which the dentist is equally foolish in yielding to, whenever plain teeth are more appropriate. In point of strength, durability, and facility of repair, plain teeth are supe- rior to the others; they are also more readily adapted to the plate. The manufacture of gum teeth, in sections of two, three or four teeth, has been brought to such perfection that comparatively feAV single gum teeth are now used; especially since neAV methods of attaching these sections to the plate have rendered unnecessary that exact fitting of blocks which was one objection to their use. This perfection of manufacture has also done away with the necessity, on the part of the dentist, of devoting to the making of block teeth the very large proportion of his time formerly demanded by this difficult process. Whenever special cases demand blocks or sections made to order, it will be found more satisfactory to send proper models and descriptions, and have such teeth made by those Avho are thus constantly occupied, than to incur the disappointments and delays ineAdtably attendant upon infrequent and irregular attempts at block work. For the proper shaping of models or articulators to accompany such orders, directions will hereafter be given. These blocks, Avhen received, do not need much, if any, grinding. But all plain teeth, single gum teeth, and ordinary sections or block teeth require, after selection, to be more or less accurately fitted to the base plate. For this purpose they must be ground on emery or corundum wheels until accurately fitted, and must be so arranged, in full cases, as to meet the teeth Avith Avhich they are intended to antagonize at the same instant around the entire arch; in partial cases, the natural teeth should touch their antagonists more decidedly than the arti- ficial ones. A correct articulation will enable the dentist to antago- nize the teeth with perfect accuracy. ADJUSTMENT OF PORCELAIN TEETH TO THE PLATE. 959 The movements of the tongue, lips and cheeks must be considered in the adjustment of artificial teeth, and the expression must be carefully studied ; hence some general rules may prove serviceable. The median line of the face should exactly come betAveen the upper and lower central incisors; the centrals and laterals on each side should lean slightly toAvards the median line, the laterals a little more so in most cases than the centrals, the cuspids very slightly, and the bicuspids and molars almost perpendicular. In a full denture, the anterior teeth should lap but slightly, only enough to Fig 886 permit the cutting edges of the upper front teeth to pass over those of the lower teeth; the six anterior teeth, therefore, should not meet, but the pressure should be upon the bicuspids and molars, and be equal on both sides. Lisping is prevented by having the front teeth lap but slightly, and the stability of the denture is increased. The articulating model Avill govern the length of the teeth, especially the anterior ones. The arrangement of the posterior teeth should correspond to that of nature, the articulating surfaces of the infe- rior second bicuspids and first molars curving downward, so that the second bicuspids and first molars are somewhat shorter than the first bicuspids and second molars; by such an arrangement the denture is less liable to be forced forward in mastication. 960 MECHANICS—DENTAL PROSTHESIS. For proper expression, the anterior lower teeth should occupy a perpendicular position, as it is seldom necessary to incline them outward or inward. Even when the loAver jaAv projects someAvhat, the lower teeth should be perpendicular, and the upper teeth incline or project out to meet them. Fulness of the gum under the nose should be avoided, as the lip is given an unnatural fulness by such a thickness of material. It is frequently necessary to make consid- erable fulness of the gums of the cuspid teeth. There should be an outward curve of both upper and lower teeth when the face is observed in profile. In arranging an entire set for the upper, or for both jaws, the molars should be so adjusted that the inner or palatine tubercles come together as well as the outer ones. This precaution is neces- sary in antagonizing single as well as block teeth. If the outer tubercles strike first, the pressure there will spring and loosen the plate. For the same reason upper molars and bicuspids should not be set so that the force of mastication falls outside of the ridge. The inferior teeth should be placed well on the alveolar ridge, and not inclined iiiAvard or too much outAvard, and sufficient space be allowed for the movements of the tongue. The lower teeth of an entire denture may, Avith advantage, be longer than the upper teeth, and thus insure greater stability; hence the lower front teeth (incisors) should be arranged first, then the upper teeth of same class, and the same rule followed in regard to the remaining teeth. An unnatural regularity in the arrange- ment of artificial teeth should be avoided, as a slight irregularity will often harmonize with the features. The first bicuspids of the upper jaAv should articulate between the first and second bicuspids of the lower jaAV, so that each tooth meets two opposing teeth. The upper first bicuspids should be partially hidden by the cuspids when the denture is in the mouth, and the upper bicuspids and molars should project slightly over the corresponding teeth in the lower jaw. Placing artificial teeth outside the ridge is often a cause of failure in securing serviceable dentures. The curve of the arch in both jaws should be made by the six anterior teeth, and by these alone. The prominence of the cusps of the posterior teeth should be pre- served ; hence the necessity for careful articulation, that it may not be necessary, after the denture is completed, to grind off the masti- cating surfaces of such teeth. The greatest pressure of mastication should be upon the second bicuspids and first molars; hence the second molars may be arranged so that they are somewhat shorter than the teeth referred to. ADJUSTMENT OF PORCELAIN TEETH TO THE PLATE. 961 In partial upper dentures supplying the first and second molars, and in some cases also the bicuspids, on both sides, should a natural inferior molar remaining in the mouth have an inclination forward, as is generally the case when the teeth in front of it are wanting Fig. 887. Fig. 889. Fig such a tooth should be avoided in the articulation; othenvise the denture w liable to be forced forward by the pressure of such a natural tooth against the teeth on the denture, as such pressure increases as the jaws are closed together. 61 962 MECHANICS—DENTAL PROSTHESIS. A small space should be left between the last tooth of the upper and of the lower jaw, in those cases where the crown of the lower molar looks forward, its posterior edge being a little higher than the anterior. It is often necessary to cut away a considerable portion of a tooth, in order to make it fit accurately to the plate. This makes the pro- cess of grinding very tedious, unless the operator has a number of sharp-cutting corundum wheels, varying from half an inch to three or four inches in diameter. Fig. 886 represents an excellent form of corundum wheel (the suggestion of Dr. S. Lee), for jointing porcelain gum teeth, and is made of various grits. These wheels may be attached to a hand lathe, such as repre- sented by Fig. 887 (Coy's noiseless hand lathe). The foot lathe is, hoAvever, far more convenient for laboratory use, where much grinding is to be done. Of these, the depots furnish some excel- lent varieties. Figs. 888 and 889 represent the Snowden & Cow- Fig. 890. man and the S. S. White, which are admirable lathes for dental purposes, while in Fig. 890 we have the Amateur lathe, Avhich is a larger, stronger and more powerful lathe, capable of very rapid motion; also adapted to the making of small instruments, han- dles, etc. The lathe of Dr. Lawrence, with detached driving wheel and head, that can be attached to any convenient board, shelf or table (Fig. 891), has advantages that will make it very desirable to many. Wheels may either be set at intervals on a long spindle, or screwed singly on the end of the mandrel (Fig. 891). In the latter ADJUSTMENT OF PORCELAIN TEETH TO THE PLATE. 963 case they should be fixed with a screw chuck in the centre, so as to be quickly changed from coarse to fine, or from large to small. In grinding, the wheel should revolve toward the operator, and be kept constantly Avet with a sponge held either in a sponge-holder or betAveen the ring finger and little finger of the left hand. Fig. 891. The thumb and forefinger of each hand must be free to hold the tooth, the right wrist being steadily supported on the hand rest (Fig. 892). Two faults are very common in grinding: one is, revolving Fig.. 892. the wheel too rapidly; the other, bearing the tooth too heavily against the Avheel. The first hinders rather than helps grinding; 964 MECHANICS—DENTAL PROSTHESIS. the second is very apt to throw the tooth from the fingers, and de- stroy the delicacy of touch necessary for accurate grinding. Fig. 893 represents the cone-journal lathe head, which is also operated by a driving wheel, and can be attached to a table, and is an admirable appliance. In grinding blocks and gum teeth, and often in plain teeth, very small wheels are required to make them fit the curves of the plate. Fig. 893. Thin edges of gum teeth and blocks must be ground with very fine- grained wheels; in jointing them a three-inch wheel should be used, perfectly flat on its outer side, and running very true (Fig. 886). Wheels, when worn doAvn to small size, increase in value, because they grind out curves inaccessible to larger ones. In warm weather large and thin wheels, when not in use, should rest on a flat surface; such wheels are often warped by the softening of the shellac as they lie carelessly among other Avheels. Wheels running on the end of a mandrel, and attached by a screw chuck, can be made to run true by warming the mandrel with a spirit lamp, and at the same time revolving the wheel rapidly. The accuracy of the fit necessary depends upon the kind of work and mode of attachment to the base plate. In general terms, it may be stated that whenever any permanent plastic material is in contact with the base of the teeth, or forms the bond of union be- tween the teeth and plate, grinding is much simplified. It is some- times better, in such cases, to have a moderate space between the base of the tooth and the plate or the model, than to have actual ADJUSTMENT OF PORCELAIN TEETH TO THE PLATE. 965 contact. But in all cases the lateral jointing of block or single gum teeth requires care. The order of grinding a set of teeth is usually to fit the central incisors, then the laterals, next the bicuspids, and so on; in case of Fig. 894. Fig. 895. sections, in the same order. This order will be found most condu- cive to uniformity of arrangement; of course, it may be modified to any desired extent. In case of a double set, there is much diversity 999944 966 MECHANICS—DENTAL PROSTHESIS. of practice. Some adapt, first, the entire upper set, others, the en- tire lower.; some, again, adjust the two sets of incisors, then the bi- cuspid blocks of both pieces, lastly, the molars. Whichever method is adopted, when all or part of one of the articulating rims is re- moved, the antagonizing rim must be retained to guide in the ad- justment of the teeth. Fig. 894 represents a holder for teeth while grinding; a slot ad- mits the pins, and the side clamp holds the tooth securely. During the process of grinding, the teeth are temporarily attached to the plate in several ways. Either the articulating rim is cut away sufficiently to receive the tooth (Fig, 895), or the rim is en Fig. 898. tirely removed, and its place supplied with a mass of wax covering the plate to the top of the ridge, and to which the teeth are sever- ally attached as they are ground; others fasten the teeth to the plate with cement. Dr. Richardson gives the following formula for a tenacious wax for temporarily securing the teeth: Beeswax, ft j ; gum mastich, 3ij; Spanish whiting, 3j. For melting wax and its compounds in temporarily attaching teeth to metal plates and for " waxing up " in plastic work, the ADJUSTMENT OF PORCELAIN TEETH TO THE PLATE. 967 small Bunsen burners represented in Figs. 896 and 897 will be found very useful. Fig. 898 represents what is known as the" Duplex burner," Avhich is well adapted for laboratory use. To the usual Bunsen burner is added a large flame for the blowpipe, which is applied by rotating the upper portion upon the base. By means of a small jet either flame can be ignited, rendering it ahvays ready for use. An excellent " waxing burner " is shoAvn by Fig. 899. The tube cannot be clogged with Avax as the heat will melt it, and it will escape at the opening for the air-supply. Definite rules of arrangement, or wood-cuts illustrating various forms of teeth and manner of setting them in the arch, are not all that is necessary. This branch of dental aesthetics must, of neces- sity, be Avorked out by every one for himself. He will succeed or Fig. 899. fail just in proportion as he has the ability to observe the hundreds of models Avhich are perpetually before him; and as he has the further and rarer ability to apply his observations to the special cases that are in his laboratory. Imitation of nature is the rule. Imitations of art, and indi- vidual incapacity, make exact observance of this rule comparatively rare. We replace the sixteen teeth with only fourteen, and often make them shorter and every way smaller than the natural organs. We do not make the grinding surfaces interlock with such deep cusps as in nature. At one time cannot avoid an unnatural ful- ness of artificial gum; at other times, the contraction of the ab- sorbed arch compels the setting of molar teeth nearer the median line than the original teeth. NotAvithstanding these and many other disadvantages, the per- 968 MECHANICS—DENTAL PROSTHESIS. fection of the dento-ceramic art is such that a skilled artist, who is quick to observe what nature requires, can, in the majority of cases falling under his care, supply the lost dental organs with great accuracy, and preserve that higher order of beauty Avhich grows out of the harmony of his work with the expression of the face and entire person. But no dentist can give to his work this kind of beauty who does not systematically study the natural organs as they daily present themselves in the operating chair. Few patients would object to the pressure of a roll of wax (two inches long and about half an inch thick) against the closed teeth. A model from this impression would give the size, form, arrangement and articulation of all except the molar teeth. A well-matched porcelain tooth (more than one might be required) would add to these data the color of teeth and gum. To this add also the age, sex, physical characteristics of the face, and the physical tempera- ment. If the dentist would have a case-book for the registration of one such carefully made observation every week, he would, at the end of two years, have a collection which, as a practical guide in the selection and arrangement of artificial teeth, would prove of in- calculable value. These fixed records of minute details are made still more useful by a habit of close observation in society. In this way a set style, or mannerism, may be avoided, which so often stamps work with meaningless uniformity of expression. Artificial teeth should imitate the natural organs; yet there is a perfection of form and arrangement which it is not advisable to imitate. To disarm suspicion as to their artificial character, it is often desirable to impart a measure of irregularity. An overlap- ping lateral, a missing bicuspid, a worn canine, an incisor, bicuspid or molar apparently decayed and filled with gold, an exposed neck from absorption of the alveolus, are among the legitimate devices of the skilful mechanician who has the " art to conceal his art." If there are any defective natural teeth remaining to be matched, still higher art is required. A perfect porcelain incisor is no fit companion for one that is partly broken, decayed and discolored; and since no art can make the defective tooth perfect, and yet the patient retains it, there is no alternative but to give so much im- perfection to the artificial one as shall take away that striking con- trast which so painfully offends our aesthetic sense of fitness. In this class of operations a " diamond drill" is of great value ; in fact, so very useful is it in many ways, that we regard it as an absolutely indispensable instrument in the laboratory. Cutting away parts of teeth or blocks inaccessible to wheels; changing the shape of teeth near the gum; drilling cavities to be filled with gold, ADJUSTMENT OF PORCELAIN TEETH TO THE PLATE. 969 or holes for the repair of broken blocks, these are some of the oper- ations which the diamond drill will accomplish as no other instru- ment can. The selection and grinding of artificial teeth require, first, a high order of aesthetic culture; secondly, great patience and skilful manipulation. The latter are often taxed to the utmost to make a set of blocks answer the requirements of a given case; especially Avhen the blocks must be closely fitted to a gold plate preparatory to attachment by soldering. Single gum teeth are more easily fitted to the plate; but there are some joints; hence it is doubtful if much time is saved. The principal advantage of single gum teeth is, that a single tooth, if broken, may be replaced without in- terfering Avith the adjoining ones. Another reason why many pre- fer them is, that a small stock of teeth in this form is adapted to a larger variety of cases than blocks would be. We think, however, that dentists living at a distance from the manufacturer should depend upon a great variety of samples rather than upon duplicates of certain forms, however desirable. In jointing a set of blocks or single gum teeth, one point must be remembered Avhich has been already alluded to. In soldering, the Fig. 900. Fig. 901. metal expands, while the teeth held in the investment are brought closer together by its contraction, and in this slightly altered position they are soldered to the plate. The contraction of the plate on cooling is irresistible, and may result in one or both of the two accidents—chipping off the brittle edges of the teeth thus brought too closely together, or Avarping the plate because of the resistance which the teeth or blocks offer to the contraction of the plate. Thin letter paper slipped between the side joints will suffice to prevent these accidents. Fig. 900 gives an external view of a full upper set of single gum teeth, arranged on a gold plate, preparatory to the operations which precede soldering, or other modes of fastening them to the base. Fig. 901 is a similar view of a set of blocks, with a soldered rim covering the upper edge. Usually, in first or temporary pieces, and sometimes after the 970 MECHANICS—DENTAL PROSTHESIS. alveolar absorption is completed, the fulness of the gum is such as to forbid the addition of an artificial gum to the ten incisors, canines and bicuspids. In such cases the plate must be cut aAvay from the front of the ridge as far as the first or second bicuspid, and the teeth ground with great accuracy to fit the gum itself. Single plain teeth will usually be best adapted to such cases ; but an excellent effect can sometimes be produced by grinding a block, when the shade of gum is well matched, to fit directly upon the natural gum. In partial cases the tooth or block must invariably be fitted to the gum ; no plate should be seen above or at the side. In fitting directly to the plaster model, this should be scraped (after the tooth is ground), so that it may press firmly on the corresponding gum. The teeth or blocks being now arranged and fitted to the plate, the next step, preparatory to soldering, is to get access to the pins on the inside, for the purpose of backing them. Set the articulating model on the table with the teeth upward; bend a strip of lead (an inch Avide) outside the arch and about half an inch from the teeth; then fill the space with plaster, inserting a strip of tin foil opposite the median line, so that the plaster rim will readily break at that point when removed. In a double set do the same with each half Fig. 902. Fig. 903. of the articulator. When the plaster has set, remove all wax or cement from the teeth and plate, and proceed to examine the pins, also the relations of the teeth or blocks to the plate and to each other. This temporary plaster band we regard as essential in every case, except a few varieties of partial sets. It is equally essential in vulcanite and other forms of plastic work, as will be hereafter explained. It is a common but not good practice, where the teeth are soldered, to substitute for this temporary band the soldering investment. Fig. 902 will give an idea of the shape of this rim, except that, being here designed for a different purpose, it does not show the im- press of the teeth. Fig. 903 represents the inner surface of a set of ADJUSTMENT OF PORCELAIN TEETH TO THE PLATE, 971 blocks Avith the Avax removed, which we may suppose just Avithdrawn from the plate in the preceding figure. Blocks or sections are readily replaced in their proper positions; but single teeth are sometimes so similar, especially bicuspids, that they are apt to be misplaced. To prevent such accidents, have a circular wooden block, four inches in diameter, Avith twenty-eight cups or depres* sions, so marked that each tooth can be instantly put into and taken from its proper cup. The teeth being thus arranged, a gold plate, or backing large enough to cover the entire width, and from eight- to nine-tenths of Fig. 904. the height of the posterior surface of each, is fitted to them in the folloAving manner. Each tooth has securely fixed in the back part of it tAvo platina rivets, for the purpose of connecting it to the backing. Each backing, therefore, should have tAvo holes punched through it by means of a pair of punch forceps, as represented in Fig. 904, large enough to admit the rivets of the teeth. After hav- ing punched one hole, a rivet is inserted ; then, by moving the strip of gold plate tAvo or three times to the right and left, a mark will be left upon it, indicating the distance the rivets are apart. But pre- viously to this the rivets should be made parallel (being very careful not to strain them in the tooth), and the ends filed off level. Other- wise the pins will not go into the holes punched, and there will be an uncertainty as to which side of the pin the mark on the plate corresponds. Dr. Samuel Mallet has very ingeniously invented a punch Avhich 972 MECHANICS--DENTAL PROSTHESIS. will save much trouble in finding the proper position of the second hole (Fig. 905). After straightening the pins, one is placed in the hole, i, at the head of the punch, the other pin pressing out the movable punch, e (Avhich Avorks by the spring, g , until it slips into the slot, h; the two punches, f e, then make the holes at the exact distances apart to receive the pins. A simple form of punch, and one not liable to accident, is a piece of steel, half an inch square and three or four inches long. It con- sists of two halves riveted together at the top, each tapering nearly Fig. 905. to a point. By turning a small screw, inserted midway in one leg, the points held opposite the pins are separated to their exact dis- tance. A slight tap of the hammer marks this upon the backing, and then the holes are made with an ordinary punch. Pins often Fig. 906. set very irregularly in a tooth; they should be parallel, but not necessarily perpendicular. Too much bending of a pin close to the tooth makes it more liable to fracture in soldering, or by use in the mouth. Pins also vary much in thickness ; it is better to have the pin of the punch forceps of medium size, and to ream with a broach ADJUSTMENT OF PORCELAIN TEETH TO THE PLATE. 973 for large platina pins. A set of broaches are indispensable in back- ing teeth and in many other operations. The holes should be slightly countersunk on both sides, and after placing the backing on the tooth, it is made fast by splitting, Avith a strong knife or a wedge-shaped excavator, the ends of the platina rivets or pinching them together with pliers. If the ends of the platina rivets are hammered so as completely to fill the holes in the back- ings, it Avill prevent the solder from floAving in and uniting the two as firmly as it should do. The backings should be slightly holloAved before they are put on; by so doing, they will fit up closely to every part of the back of the tooth. Fig. 906 represents a pair of forceps designed to give a general form to the backing by punching it from a piece of gold plate of the required thickness. After the backings have been made fast to the teeth, they are to be accurately fitted to the plate, standing off from the plate enough for a very thin piece of watch spring to be passed under it. This shoAvs that the tooth is not raised, by the backing, from its place in the investment. A much Avider space makes the flow of solder un- certain ; the practice of placing scraps of gold under badly-fitting backings is a very slovenly one; and Avhere such imperfections occur it is much better to fill such spaces with gold foil. Some dentists back the teeth as they grind and fit them, and before investing ; others invest Avith the plaster and sand, and back Avithout taking them from the investment; others, again, partially invest Avith the soldering mixture, remove, and back the teeth, then replace, and add more plaster and asbestos or sand over the edges of the teeth. The last method is unsafe, because the tAvo layers of batter are apt to separate in heating, and may displace the teeth. Backings (called also stays or standards) vary much in size, shape, and thickness. Some variations are matters of taste; as, Avhether they shall be rounded, square, or bevelled at the top cor- ners ; Avhether chamfered to a thin edge, or left thick, and then bevelled or rounded. But other points often considered optional are not so, inasmuch as they affect the appearance or stability of the Avork. Backings Avhich cover the translucent edge of the tooth darken it by the refraction of the oxidized surface next the tooth, and Avhich cannot be kept bright; even if it could, the gold would impart a yelloAvish tinge. They should cover enough of the tooth, and fit so accurately, as to prevent motion of the tooth; for this Avill inevitably cause the pins, sooner or later, to break off. Back- ings, in relation to each other, must either be so far apart at their base that the solder will not flow from one to the other, forming a continuous band, or they must be in contact throughout whatever 974 MECHANICS—DENTAL PROSTHESIS. distance the solder will unite them. This rule is particularly appli- cable to backings of single gum teeth, which are often, perhaps usually) made the full width of the tooth up to the shoulder. This continuous band gives great stiffness to the plate. But the contraction of the solder will certainly warp it, unless prevented by actual contact of the edges soldered. In case of plain teeth, a heavy, continuous line of solder will almost certainly warp the plate. A block may be backed for soldering in one piece, or in parts closely fitted, or in distinct backings opposite each tooth. A block much curved is with difficulty backed in one piece; long or thin blocks are liable to be cracked by the contraction of a backing, either in one piece or made continuous by soldering. Backings should be of the same gold as the plate, but heavier, especially if long or large. Sometimes the shape of a gum or block tooth may require the re- moval of the plaster rim, which can readily be done ; then replaced after the backing is completed, for the final adjustment of the teeth. The teeth are next to be fastened to the plate Avith a small quantity of cement (resin mixed with wax, or, still better, the Avax, gum mastich and Avhiting compound), and a small roll of softened wax (not melted or made adhesive) placed over the entire surface to be soldered. In Fig. 907 the inner band Fig. 907. may be taken to represent the Avidth of this wax roll, Avhich is of great service in preventing any plaster of the invest- ment from getting accidentally upon the parts to be soldered. If the teeth have been previously soldered to the backings, this wax strip should be nar- rower : but if rivets and backings are to be soldered at the same time, the rim must be made carefully to cover every point where solder is to Aoav. The plaster band is then very care- fully removed, and the piece surrounded with the soldering invest- ment, Avhich must be no thicker than is sufficient to protect the teeth and hold them in place. The wax and cement are easily removed, leaving the surfaces perfectly clean and ready for the borax and solder. The investment should not project so far over the inner edge of the teeth as to obstruct the blowpipe flame; it should not cover the lingual surface of the plate, nor should it be thick on the palatine surface. On the palatine side it might be Avell also to cut along the median line nearly or quite through the investment; the object of this is to give play to the lateral expan- ADJUSTMENT OF PORCELAIN TEETH TO THE PLATE. 975 sion of the plate, the antero-posterior expansion being usually, from the shape of the plate, sufficiently free. This we regard the simplest and best method to prevent warping of the plate, so often caused by the very means taken to prevent it. We have said nothing of fastening the teeth Avith a firm body of cement instead of Avax, so as to try them in the mouth before sol- dering, because a correctly taken articulation makes this unneces- sary. As remarked in the chapter on articulation, this process admits of perfect accuracy. Its very object is to prevent the neces- sity of any change in arrangement after teeth are adjusted. An error of articulation will often involve a change in the jointing of blocks more troublesome than the original grinding; in fact, neatly ground blocks (or gum teeth) will not permit the slightest change of position without fresh grinding somewhere. Trial of teeth, merely to test the correctness of articulation, may in some cases be especially necessary, when used to test correctness in the selection of teeth; for it requires experience to enable us to determine, a priori, just what style of work is best adapted to the case. But the awkward and momentary retention of a plate to which the teeth are so slightly attached, is no test of its aesthetic correctness, unless the selection has been grossly misjudged. It is only after the patient has become habituated to the piece, giving time for the natural form of the lips and motions of the mouth, that we can best decide whether or not our Avork has beauty of expression as well as artistic finish, Mr. AndreAV Wilson, of Scotland, adopts the following method of backing teeth : After having partially fitted the tooth to the plate, take a piece of platina foil, as thick as can be used conveniently, and, pressing it against the tooth, perforate it where it is marked by the pins; then cut it into the required shape of the backing, and press it as closely as possible to the back of the tooth. Apply a little borax to the platina pins which come through the back; then place the tooth, with its face downAvard, upon a thin piece of pumice, covered Avith dry plaster, putting upon the platina sufficient gold for the thickness required; slowly heat it, gradually raising the heat until the gold melts, Avhen it will rapidly flow over the AAhole platina surface, uniting so firmly Avith the pins in the tooth, that Mr. W. has never, during eight years' use, seen a case in which they have loosened, even Avhere there has been sufficient violence to break the tooth. After the backing has been run, and the tooth alloAved to cool sloAvly, it is filed to the requisite thickness and shape; tooth and backing are then closely fitted and finally sol- dered to the plate. In arranging the teeth on the plate for soldering, 976 MECHANICS—DENTAL PROSTHESIS. Mr. Wilson uses an investment of white sand and plaster, equal parts, placing a thin strip of platina on the outside of the teeth, with a layer of the investment on both sides of it, so that, should the plaster crack in soldering, the platina may keep the teeth from shifting their places. The whole time occupied in heating and backing a tooth is about half an hour; Avhen several are done at once, a little longer time is required. Of course, all the backings of the set should be flowed at the same heating. Instead of using the strip of platina plate to prevent the teeth from becoming displaced, in case the plaster cracks, thin sheet-iron rings one inch deep or iron wire may be used; but platina is Fig.908. undoubtedly the neatest, and has the advantage of being inde- structible; it may be narrow and thin, so that its cost would form no objection to its use. But if the plaster is not in excess, the investment will not crack. A batter, made of three or four parts of asbestos to one of plaster, will stand the hottest fire of the labor- atory. Many prefer equal parts of plaster and sand, as forming a more solid investment in which to back up the teeth. Mr. Wilson's method might be improved, first, by completely fitting the tooth ADJUSTMENT OF PORCELAIN TEETH TO THE PLATE. 977 before backing; secondly, by running the thin platina backing, one-sixteenth of an inch on the plate, to any irregularities of Avhich it can be quickly burnished down. This flange secures a very perfect and strong attachment to the plate, and is the method of backing (Avith heavier platina) sometimes practiced in the continu- ous-gum Avork. Ordinary backings, after they have been fitted to the plate and held to the teeth by bending or splitting the pins, may be removed from the plate, set in a batter of plaster and asbestos, and soldered; the plaster should be so stiff as not to flow over the backings. The solder should be rather harder to fuse than that used to fasten the teeth to the plate. The backings, after sloAvly cooling, should be filed, and may even be Scotch-stoned. Backings can be better and more quickly finished singly than when attached to the plate. This method, or Mr. Wilson's, is much to be preferred to the common practice of soldering the backings to both teeth and plate at the same heating. A piece invested preparatory for soldering, and placed upon a lump of solid charcoal, is seen in Fig. 908. Directions for applying borax and solder have already been given. Some cut the solder into very small pieces; others use one piece to each tooth at its base, and a second for the pins unless previously soldered; in the figure the pieces are unnecessarily small. If the backings are soldered to the teeth beforehand, a more fusible grade of solder should be used at the second soldering. The Avork, as before stated, must be very gradually and thoroughly heated, up, before directing the flame upon the plate or backings. The last point to be touched Avith the flame is the solder, and this not before a slight melting of the edge shows that it is just on the point of flowing. If every preparation for soldering has been prop- erly made, the actual flowing of the solder on a full piece will take less than a minute, and will be so smooth as to require no other finish than the Scotch stone and the polishing Avheels. After sol- dering, the cover should be placed upon the soldering pan (Fig. 884), and the Avork alloAved to become quite cold before removal; when a charcoal lump (Fig. 908) or pumice stone is used the Avork must also be covered while cooling. Finishing Process.—When the piece is cold, it may be placed in Avater to soften the plastic investment, which should be carefully removed from the teeth; the set is then placed in a glass or porce- lain vessel containing a mixture of equal parts of sulphuric acid and Avater, and heat applied. As soon as the borax (Avhich, by the process of soldering, has lost its Avater of crystallization and as- 62 978 MECHANICS—DENTAL PROSTHE^I> sumed a glassy hardness is decomposed, the vessel is removed and allowed slowly to cool. This process is termed by jewellers "pickling." and requires from ten minutes to half an hour for its completion, according to the strength of the acid and the quantity Fig. 9(9. of Adtrified borax on the plate. After this the acid is washed from the piece; or it is still more effectually deprived of acid by boiling in water containing a little caustic soda. In removdng the roughness which may have been occasioned by imperfect soldering, care must be taken not to cut away too much Fig. 910. of the plate. For this purpose scrapers, files, and lathe burrs aie used, according to the position and quantity of surplus solder. Fig. 909 represents a set of solder burrs for trimming off super- fluous solder. After the work has been made as smooth as possible ADJUSTMENT OF PORCELAIN TEETH TO THE PLATE. 979 with scrapers, etc., it should be rubbed with pieces of Scotch stone and Avater until every scratch is removed; some use a fine, smooth cork attached to the lathe, and charged with water and powdered pumice or silex. The piece is then polished with Tripoli, applied by means of oil or tallow to a brush Avheel (Fig. 913), AAdiich is made to revolve rapidly against the work. Felt, rubber, walrus leather and cotton Avheels and cones are also employed in polishing. Fig. 910 represents a felt wheel and cone. Fig. 911 shows one of the various forms of vulcanite burrs for carrying polishing poAvders. As to the rapidity with Avhich a lathe should be worked: drills and burrs require a slow movement; corundum Avheels a quicker one ; rotten stone a rapid motion; and whiting, zinc-Avhite, or rouge, the most rapid of all. The piece may now be placed in a porcelain vessel containing the following mixture : nitre, 2 ounces ; salt and alum, each 1 ounce— dissolved in 4 ounces of water. After boiling for half an hour in this to decompose the copper from the surface-layer of the solder and plate, it is boiled a feAV minutes in a solution of 1 ounce of caustic soda in 4 ounces of Avater, to neutralize the acid, then washed Avith a brush in pure Avater. The removal of the copper from the surface of the plate gives to the gold the beautiful orange hue, which is its natural color, and which it will retain until the friction of mastication Avears off this surface. The secretions of the mouth Avill fail to tarnish it; and it will be free from the disagreeable taste of Avhich so many complain Avho wear artificial teeth set on metallic plate. But Avhen plate is made from coin Avithout alloy, or is of 20 carats fineness, and the solder has a corresponding quality, the pickling process may be omitted. The process of finishing is completed by polishing every part of the lingual surface of the plate, backings, and clasps with highly tempered and finely polished steel burnishers. Fig. 912 represents various forms of plate burnishers. They should be frequently rubbed on a piece of Avet Castile soap, and carried backward and forward in the same direction over the plate until every part of the gold exhibits a high polish. Burnishers of different shapes are required for different parts of theAvork; bloodstone burnishers are also used. A piece, hoAvever, can be polished in less time, if not more per- fectly, Avith brush wheels (Fig. 913). Brush wheels vary in diameter, thickness and material. Bristle Avheels vary in stiffness and length of bristle; the stiffer being used for Tripoli or rotten stone, the softer for whiting and rouge. Cotton is often substituted for bristles ; buckskin or felt are also much used for wheels or cir- cular " laps," and are especially useful in dressing up the recesses 980 MECHANICS--DENTAL PROSTHESIS. of a plate. It is of the utmost importance that wheels or laps used for different polishing substances should be kept entirely separate ; a little Tripoli or pumice poAvder on a rouge wheel may render useless the work of an hour. The brush should be set on the Fig. 911. Fig. 912. spindle of the lathe, then lightly smeared with suet, by holding a small piece against it while it is revolving. The rotten stone is applied in the same manner, and with the brush thus charged, the RETENTION OF BASE PLATES. 981 polishing may commence; but the plate must not be exposed too long to the friction, as it will rapidly wear away the pure gold surface brought out by the pickle; hence some use only the burnisher or rouge after pickling. Tripoli has a sharper grit, and cuts more rapidly than the ordinary rotten stone: but the latter gives a very smooth surface, and will, in most cases, give a sufficiently brilliant finish without rouge. A very high watch- case finish can only be given by very rapid revolution of wheels or buffers, charged with the finest quality of rouge, wet Avith alcohol. The piece must be previously washed with soap and Avater, so as to remove every trace of oil. Sometimes rouge is applied on a piece of soft buckskin, wrapped or sewed around small, blunt-pointed pieces of cork or wood. The lingual surface of the plate is the only one that should be polished. The dead color of the palatine surface throws out the polish of the other side, and greatly improves the appearance of the piece. The adhesion of a plate is frequently improved by roughening the plate Avith a file or by engraving lines upon it. The process of finishing on a gold piece, properly soldered, is a very simple matter, and one of secondary importance. A set with a Scotch-stone finish is in every respect as useful, and asthetically as beautiful, as the most highly polished plate. There is, however, no objection to this sort of appeal to the eye, provided it is not the chief merit of the Avork. There are three methods adopted for the retention of dental plates, and many modifications of form required by the various circumstances of different mouths. An enumeration of all the re- quired forms would be impossible in this work; but Ave hope to represent a sufficient variety to enable the operator to decide which is best for any given case. We think it far more important, how- ever, to endeavor to explain, as far as can be done, the principles Avhich determine these different forms and modes of retention, than to lay down any set of didactic formulas for unreasoning adoption. CHAPTER XIII. RETENTION OF BASE PLATES—THEIR SIZE AND FORM OF OUTLINE. The utility of a piece depends largely upon the firmness with which it keeps its place during mastication or in conversation. The means adopted to secure this are fourfold: The first two retain the plate by extrinsic support; the last tAvo depend upon an intrinsic 982 MECHANICS—DENTAL PROSTHESIS. quality of the plate itself. 1. Spiral springs, by constant pressure, keep the plates of a double set in position. 2. Clasps, by grasping some natural tooth, hold a partial piece firmly in place. 3. Spring plates, which are constructed of vulcanized rubber, and are available only in partial cases. 4. The close adaptation of the plate, whether of a full or partial set, causes it to adhere Avith a force which is lessened, first, by the amount of air between the surfaces ; secondly by the liability to displacement. These modes of retention Avill be considered in the order named. Spiral springs, formerly very much used, are now seldom em- ployed ; they are applied only to double dentures. Fig. 914 gives a correct idea of the position of the springs, their points of attachment, length, and direction of curvature. Fig. 915 represents the detached portions of the spring, consisting of standards, screAvs, tangs, and spiral coil. The tendency of the curved spring to straighten, presses each plate upon the alveolus, acting at the points of attachment of the standards. These points are chosen, first, in the upper jaw, as nearly as possible on the line Fig. 915. of equipoise, which will be somewhere between the centres of the second bicuspid and of the first molar; secondly, in the lower jaw, where a vertical line from the upper standard meets it. Perforated bicuspids and molars are sold, adapted to such cases; and the usual plan is to attach the standards before soldering the teeth. A more accurate method is to determine the position of the standards after the pieces are finished. The presence of the teeth makes soldering of the standards more troublesome, but not impossible; they may also be riveted to the outer rim of the plate. With the diamond drill, holes can be made through the teeth, or blocks, opposite each standard. RETENTION OF BASE PLATES. 983 Directions for making the coil have already been given; they are usually purchased ready made. Their length must be such that the curve will not irritate the ascending ramus of the loAver jaw. If too stiff, their forcible pressure will irritate the gum; if too slight they Avill fail to keep up the piece. The tangs are held in the coil by closeness of fit; when loose, they may be tightened by floss silk. The screAvs, represented in the figure, are troublesome to make, and are very apt to loosen. A better plan is, to pass a headed pin through standard, tang and tooth, and rivet or solder it in the back- ing. This plan makes the tang permanent; the pieces are separated by detaching the upper or lower tangs from the coils. It adds greatly to the strength of the pin to pass it through the tooth or block. There should also be a shoulder on the standards, to limit the movement of the tang; else the springs, by too great upward or downward motion, may irritate the mouth. It is unnecessary, in vieAV of the present limited use of springs, to describe other and very ingenious methods of attaching them. Their use is noAv confined, first, to very flatly-arched upper jaAvs, usually small, covered with hard membrane, and having the attach- ment of the facial muscles close to, or quite upon, the ridge; also to loAver cases, Avhere all trace of the ridge is gone. Secondly, to pieces inserted so soon after extraction that the rapid absorption Avill quickly destroy the adaptation. We shall speak elseAvhere of other means adopted to meet these exigencies; in failure of which,spiral springs are to be used. But they are troublesome to make, annoy- ing to Avear, difficult to keep clean and liable to accident; hence we only use them as a last resort. In conclusion, it should be noticed that the upper plate of spiral-spring pieces does not co\Ter the palate, but is shaped more like the lower piece. This is one of its com- pensating advantages; for it is an objection to the othenvise valu- able principle of atmospheric pressure that it covers so large a portion of the mucous surface. CLASPS. This method of retention, necessarily applicable only to partial pieces, has fallen into much disfavor, and given place to methods, in lieu thereof, which are really more objectionable. But, like many other time-honored practices Avhich modern dentistry has thrown in its waste basket, there are very decided advantages in this mode of re- tention, Avhich make it, in certain cases, the best possible one. The disuse of clasps has groAvn out of, first, their injurious effects, due to improper construction and injudicious application ; secondly, the difficulties of making a clasp piece. We venture the assertion, that 984 MECHANICS—DENTAL PROSTHESIS. one-half the dentists do not really know how to make a perfectly adapted clasp piece; and that, of the remaining half, two-thirds Avill not take the trouble. The tediousness of clasp adjustment is out of place in that rapidity of manipulation demanded by the cheapness of modern dentistry. Nor can Ave expect to see the easily made, but ineffectual, vacuum cavity give place, in turn, to the clasp attachment, Avhich it has to such an extent superseded, until the profession becomes awakened to the necessity of substituting good work for fast Avork—economical high-priced work for expensive low-priced work; until the mechanician so far respects himself as to value his labor more than the cost of his materials, and ceases to use certain substances because they are cheap, rather than others because they are better. Next to pivoting, the clasp is the most secure of all methods of attaching artificial teeth in partial cases. But it is not universally applicable, for reasons hereafter stated. In deciding upon the pro- priety of using clasps, the remaining teeth must be carefully ex- amined, to determine Avhether, in shape, position, texture and relation to other teeth and to the proposed plates, there are any which admit of being clasped. If there are such teeth, a perfect impression of them is necessary; then greatest accuracy in fitting the clasp; lastly, a most exact adjustment of this to the plate, to which it is to be fastened with great care. Scrupulous observance of these points, in connection with a properly fitted and shaped plate, Avill take from clasp work the force of the objections urged against it. In the selection of teeth to be clasped, the points for consideration are: 1. Their condition: never clasp loose teeth, or those where there is much alveolar absorption; or, if possible to avoid it, those which have filed surfaces. 2. Their shape: avoid all conical teeth, such as third molars and canines; also teeth considerably larger at the grinding surface than at the gum. The proper shape for clasp- ing is the cylinder, or rounded prism ; and only so much, or such part, of any tooth should be clasped as has this shape. Hence it is that thick, narroAV clasps are best, because few teeth have much breadth of cylindrical shape. 3. Their position: incisors, canines and third molars must be rejected, for this reason; and second molars are unfit, if the plate holds incisor teeth. The incisors and cuspids are, of all the teeth, least suited for the attachment of a clasp. It is exceedingly difficult to apply clasps to these teeth in such a manner as to retain even a single tooth with sufficient stabil- ity to be worn Avith any degree of comfort. We remember once to have seen a case in which a central incisor (natural tooth) was in- RETENTION OF BASE PLATES. 985 serted and kept in place by a gold wire projecting from each side of the tooth into holes drilled into the adjoining teeth. A stage of dental progress that permitted such a process, might also have al- lowed the clasping of incisors; but we know of no possible circum- stances that will justify, in the present state of dental art, the clasping of any of the six front teeth. No loAver teeth should be clasped ; but in some cases a stay (half-clasp) may be used. The best teeth, in respect of position, are the second bicuspids; next, the first molars; thirdly, the first bicuspids ; and lastly, the second molars. These eight teeth are the only ones that should ever be clasped; and, if possible, the choice should be confined to the first four. 4. Their relation to the plate and to the other teeth. Let the clasped tooth be as near the line of equipoise as is consistent Avith other considerations. For incisors alone we should, for this reason, give preference to the first over the second bicuspids; and, in case of the loss of the ten or tAvelve anterior teeth, we should use no clasp on the remaining molars. Teeth not decayed should never be sepa- rated from others with which they are in contact, for the purpose of passing a clasp. If no other tooth can be found, a stay (half- clasp) must suffice. Observance of the conditions above enumerated restrict very much the range of cases that admit of clasps. In the matter of position and relation to the plate, circumstances may compel a choice not the most favorable to success ; but in other respects it is far better to dispense with clasps than to apply them so as to incur risk of failure or injury to good teeth. The liability to decay, of the tooth around Avhich a clasp is ap- plied, is always greatly increased by the removal of any portion of its enamel. The application of clasps to diseased or loose teeth always aggravates the morbid condition of the parts, and causes the substitute, Avhich they keep in place, to become a sort of annoy- ance to the patient. Besides, such teeth can be retained in the mouth only for a short time, and Avhen they give way, the artificial appliance becomes comparatively or entirely useless; and even be- fore their loss, it is not held firmly in its place. Its instability exposes its presence to the observation of the most careless observer and this motion is injurious to all the teeth near or against which the piece comes. In the lower jaw, parts of sets are much less fre- quently called for than in the upper, and Avhen they are, the use of clasps may be dispensed Avith altogether. A clasp can seldom be applied advantageously to a lower molar. The lower front teeth are least liable to decay of any in the mouth, and therefore do not re- quire replacement, except in full sets, unless lost by a blow or by the 986 MECHANICS--DENTAL PROSTHESIS. destructive action of salivary calculus. A partial lower front piece calls for half-clasps or stays; but other partial lower pieces (replac- ing bicuspids and molars) should not depend for their stability upon any remaining bicuspid or cuspid. If the injurious effects liable to result from the application of clasps to teeth selected according to the rules given could not in any way be counteracted, dental substitutes retained in the mouth by this means would, in the majority of cases, be producthTe of more injury than benefit; but they may be in great measure pre- vented. They are not caused, as many have erroneously supposed, solely by the mechanical action of the clasps upon the teeth, but also by the chemical action of the secretions of the mouth and decomposing particles of food. The method of measurably pre- venting these deleterious effects is tAvofold: First, to prevent the chemical action, the removal of the artificial teeth, and thorough cleansing of them and the natural organs; this should be done every night and morning, and the teeth rubbed with a brush and waxed floss silk until every particle of clammy, vitiated mucus and foreign matter is removed. The inner surface of the clasps should be freed from all impurities, and the whole piece cleansed with a brush and water. Secondly, to prevent or lessen the mechanical action, the clasp should, as before remarked, fit Avith great accuracy the parts of the tooth protected with hard enamel; the whole piece should have such closeness of adaptation as to prevent motion of the clasp upon the tooth. We have elsewhere spoken of other inju- rious consequences of clasps placed too near the gums or exposed necks. Rapid decay and breaking off of the teeth, inflammation of the gums, of the peridental membrane, destruction of the alveoli and loosening of the teeth, are among the common results of the clasping of teeth as it is too often practiced. Consequences such as these have led many to an unqualified condemnation of this method; yet, as we have said, when suitable teeth are selected for clasping, and the work is properly executed, it is the best and ■most durable way in which a partial piece can be secured. Shaping and Adjusting Clasps.—The gold employed for clasps should be about one-third or one-half thicker than the plate, and as wide as the cylindrical portion of the crowns of the teeth to he fitted. Some clasps are best made of half-round wire, and narroAV; others may be broader and thinner; thick, narrow clasps are more universally applicable. In quality it is better that clasp and plate be the same, except when the plate is of pure coin. In this case. add copper (but no silver), to give elasticity. Platina, often used for this purpose, imparts too much brittleness, after the piece has RETENTION OF BASE PLATES. 987 been Avorn for some time. Some may fit the tooth close to the gum; but in other cases, the shape of the tooth, absorption of the alveolus, or morbid sensitiveness of the neck, forbid this. Enamel surfaces best resist the wearing action of clasps; dentine, exposed by the file or chisel, is more liable to abrasion or decay; cementum should in no case be brought in contact with clasp or plate. If the clasps chafe against sensitive parts, inflammation of the peri- dental membrane may be set up, followed by wasting of their sockets, and ultimate loss of the teeth. Fig. 916 represents a clasp bender. Fig. 916. With the plate in position in the mouth, a Avax impression may be taken; the plate, adhering to it, on being withdrawn, will have a correct relation to the teeth Avhich are to be clasped. Others adopt the less accurate method of adjusting the plate to the original plaster model. But as, for reasons before given, it is advisable to cut off the teeth from the model used in moulding, a second model is necessary, and usually for this purpose a second impression. Moreover, if the mouth has marked irregularities, or rugae, and the plate covers much surface, it cannot be fitted upon a plaster model so as to hold the same precise relation to the teeth as Avhen in the mouth. When accurately fitted, clasps may be at once soldered on the model, or may be attached to the plate by means of a small piece of Avax or cement composed of one part wax and tAvo of resin, softened modelling composition; this should be softened, and applied to the plate and to the inner side of each clasp. The plate and clasps thus united are carefully removed from the plaster model, and laid, Avith the convex side doAAuiAvard, on a piece of paper. Plaster is then poured on the upper side of the plate, covering it and the clasps to the thickness of half an inch. After this has set, the piece may be taken from the paper, placed on charcoal, the Avax being softened and removed, and prepared for soldering. This is the simplest Avay of fitting clasps to the plate and pre- paring the piece for soldering; but Avhen the clasp teeth deviate from a vertical position, or when the teeth are of such a shape that the wax impression does not copy them accurately, this method is 988 MECHANICS—DENTAL PROSTHESIS. in such cases, not reliable. The clasps must be fitted to the teeth in the mouth, instead of on the plaster model, and may then be attached to the plate as just directed. Often only one can be attached at a time, and after this has been soldered, the piece is replaced in the mouth, and the other made fast to the plate. The greatest care is necessary to prevent altering the position of the clasp in taking the piece from the mouth. The following is Dr. Fogle's method for securing accurate adapta- tion of the clasps. They are first fitted to the plaster model, leaving the ends straight. A narrow strip of plate, about five-eighths of an inch in length, is used as a temporary fastening, one end of which is soldered to the lingual surface of the clasp ; the plate and clasp are now both placed on the model (made from impression taken while the plate is in the mouth), and the other end fitted and sol- dered to the plate, forming a sort of semicircle or bow. Fig. 917 represents the plate, clasps and temporary fastenings on the plaster model. In Fig. 918, they are seen separate from the model. Fig. 917. Fig 918. The clasps are now adjusted to the model; however accurately this is done, it will be found, on applying the plate to the mouth, that they will not fit the teeth there. After properly adjusting them, the temporary fastenings will be found sufficient to hold the clasps in their exact position while the piece is being removed. This done, it may be invested, placed on charcoal and the other steps connected with the process of permanent soldering gone through with; detaching the temporary fastenings when the invest- ment has fixed the clasps in position. Dr. Cushman advises, in very difficult cases of adjustment, as where the clasp teeth are much inclined, and where you have to fasten to second molars, a slight modification of this plan. After soldering one end of the strip to the clasp, and having bent the RETENTION OF BASE PLATES. 989 other to touch the plate Avhen on the model, put both in their proper place in the mouth; then, with a sharp-pointed instrument, indicate the point Avhere the bow touches the plate; place them on the model again ; adjust the end of the boAV to the point marked ; con- fine it there and solder fast. Dr. Cushman considers Dr. Fogle's method of adjusting clasps so valuable that he never ventures to set clasps permanently, even in the simplest case, upon the original model, Avith the plaster teeth as the only guide for position. Dr. Lester Noble's method is as folloAvs: Place the plate in the mouth, and let the clasp bind upon the tooth with only sufficient firmness to keep it in its proper place. Then mix a small quantity of plaster from a lot which, by previous trial, you find requires four or five minutes to set; put it upon a piece of paper or sheet lead about an inch square, and just before it begins to harden, introduce it into the mouth upon the forefinger, pressing it into gentle contact Avith a portion of the plate and about one-half of the clasp. It must be held there for three or four minutes, until it is sufficiently hard to break with a sharp fracture; this point you can determine by examining the plaster left in your bowl. The plaster must then be withdrawn. Sometimes plate, clasp and plaster will be brought away together; or the plaster and clasp together leaving the plate; or the plaster Avill separate, leaving both clasp and plate in the mouth. Should the plaster by any accident break, it can readily be united at the point of the fracture, without in the least altering its shape—one great advantage over Avax. If the plaster adheres to the plate on withdraAval from the mouth, it must then be carefully detached, the plate replaced, and the same process repeated for the second clasp; or possibly the impressions for both clasps can be taken at once. Several precautions are necessary. If the clasp bind too tightly around the tooth, its ends Avill, Avhen removed, spring together; and thus it will not exactly fill the original impression made in the plas- ter. If the part of the clasp which you design to cover with plaster be so regular in shape as to make its adjustment when out of the mouth uncertain, mark it with a file or a small point of solder; this will be copied in the plaster, and remove all doubt as to its definite position. If the plaster be extended over some part of the edge of the plate, it will, in the absence of any marked irregularities of surface, give a better guide for its readaptation. Lastly, if the plas- ter cover too much of the clasp tooth, it will be more liable to break on being AvithdraAvn. Take noAV the clasps, place them each in their separate impres- sions in the pieces of of plaster, securing them, if necessary, by a 990 MECHANICS—DENTAL PROSTHESIS. small piece of softened wax. Place one end of your plate in its cor- responding bed in one of the plaster pieces. If proper care has been used, both clasp and plate will fit into the plaster with unerring accu- racy, and, of course, hold the precise relation as when in the mouth. While in this position, cover the clasp and the under surface of the plate Avith fresh plaster, or plaster and sand or asbestos; Avhen this has hardened, remove the first plaster, just as in other cases you would remove the wax, preparatory to soldering. The methods of Drs. Fogle and Noble may be thoughttoo tedious for cases where the shape and position of the teeth are such that a Avax impression Avill accurately copy them; but in the great ma- jority of cases it will be found essential to accurate adjustment to resort to one or other of them. Sealing-Avax or shellac may also be used to retain the clasps in position until they are soldered to the plate. If the clasp stands off from the tooth on its coronal edge, the food is apt to pack into the wedge-shaped space and loosen it, or even change its shape; if on the edge near the gum, it gives lodg- ment to the food and mucous se- cretions, to the injury of the tooth. Dr. Spalding recommends, as a pre- ventive against such lodgment, to use in all cases thick, narrow clasps; to attach them by two or more standards (Fig. 919), if the clasp is long; to put them well up on long teeth, and on short teeth, to cut away the plate. In this way most of the neck is exposed to the cleansing action of the tongue. The close adaptation of the clasp to the surface of the tooth is too often neglected. It is commonly done with round pliers, mak- ing trial from time to time upon the tooth of the model. This is an uncertain method in any case, and in many utterly Avorthless. Prof. Austen advised always to take a separate plaster impression of the teeth to be clasped; for which purpose a small partial impression cup is used (Figs. 813 and 814). Let the plaster get quite hard; then slightly open the impression; Avithdraw it, and close up the fissure. Make from this either a plaster or a fusible-metal tooth; if the former, harden it with soluble glass. With round pliers and a hammer, clasps can be fitted with great exactness to such a metallic tooth. Extreme accuracy of fit may most easily be obtained when the contour of the tooth is irregular,by the following method: burnish down to the tooth a RETENTION OF BASE PLATES. 991 strip of very thin platina; then on the outside of this strip lay pieces of gold (of the fineness suitable for clasps), with borax, and Aoav them Avith the blowpipe. A common error in soldering clasps is to make their union to the plates too Avide. Clasps are often called springs, but if soldered through nearly their Avhole length, they become rigid stays, devoid of elasticity. There should always be a proportion betAveen the size of the clasp and the Avidth of its attachment; in no case should it exceed three-sixteenths of an inch, and one-eighth of an inch is ample for most cases. When practicable, the t.Avo arms of a clasp should be of equal length; but in short clasps it is sometimes pre- ferable to throAV all the elasticity into a single arm. A single at- tachment is better than tAvo, as it gives more play to the arms of the clasp in the slight unavoidable motions of the plate. Again, in shaping the plate, cut it Avell off from the tooth, alloAving a tapering tongue to extend up to the clasp, for its attachment. In clasp pieces and in all partial pieces, remember that the plate should come in contact with teeth it approaches, or else stand as far off as the case Avill permit; the narroAV band of gum so often left betAveen plate and teeth is liable to irritation by compression betAveen the tAvo; this is productive of more annoyance and injury than .the direct contact of the plate against the tooth. Partied Clasps or Stays.—These differ from clasps in the absence of elastic arms grasping the tooth. Taking a short, rounded prism (triangular in case of bicuspids, in molars quadrangular) as the " type " of a clasp tooth, the clasp proper must grasp a side and tAvo angles or two sides and three angles. If it lies against two sides and one angle, or if two opposite sides are so inclined (in the line of the clasp) that it will not take hold, then it becomes merely a stay. Stays demand for serviceable action a point d\xppui ; hence they must be in pairs—lying either against the two teeth bounding an interdental space, or against teeth on opposite sides of the mouth. They have great value in all partial cases where there are no iso- lated teeth suitable for clasps. Their function is to give stability to the plate by preventing lateral motion. When the bicuspids or molars have inclined or bulging inner surfaces, the stays hold the piece after the manner of a clasp; the elastic force being given by the plate. This result can only be obtained, however, by a very carefully taken plaster impression when a vulcanite plate is made, or, in case of gold plate, by getting the exact relation of the parts by Dr. Noble's method. It is a mistake to attempt forcible reten- tion of a plate by the lateral thrust of stays; any such pressure 992 MECHANICS--DENTAL PROSTHESIS. causes the teeth to yield, and then the stays can only act as in the cases first given. It Avill be observed that when the stay on each side is double, as in Fig. 921, it not only prevents lateral motion, but the points between the teeth prevent backward motion. The stability given in this manner by stays, taken with an exact adaptation of the plate, is far more trustworthy than that given by any form of vacuum cavity. In connection Avith clasps we shall briefly notice two methods occasionally practiced for the retention of plates. First, by the pres- sure of wood against the tooth. This method was formerly much used when human or ivory teeth were set on bone. Stays were Fig. 920. Fig. 921. carved in bone (see Fig. 921); or metallic stays or clasps were riveted, or grooves and cavities were cut, holding slips of some hard wood which pressed against the teeth. This method was applied by Dr. Stokes to metallic plates—soldering gold tubes to the plate near the teeth, so that the end of the inserted wooden pivot, slightly projecting, pressed on each side of the tooth selected. Secondly, by drilling into one or two sound roots of incisors, canines or bicuspids, a short canal, and lining it with a gold tube. Corresponding pins soldered to the plate keep it in place, much as stays do; if the roots permit deep canals, they may retain it with considerable force. Such a pin may be used in combination with a clasp or stay. Directions given in chapter on crown and bridge- work easily explain how to prepare and attach such pins. In some cases it may be desirable to use such a pin in place of clasp or stay, but the plate must cover enough mucous surface to give stability. We question the propriety of subjecting the roots of two incisors to the strain of five or six teeth on a plate of this kind. When the teeth have recently been extracted, and it is designed to construct an artificial denture before much change has occurred from absorption, the front portion of the plate should terminate within the outer border of the alveolar ridge, and the edge be scal- loped to correspond with the festooned surface of the gum over the cavities from which the natural teeth have been removed. RETENTION OF BASE PLATES. 993 Size and Outline Form of Special Cases.—It is impossible to enu- merate all varieties of clasp pieces, nor could we delineate under each variety any one form as absolutely best for all its sub varieties. The more philosophical course is to find, if possible, Avhat princi- ples, mechanical and physiological, determine the best form in any case, and to illustrate by a feAv examples, the application of these principles. Upper Incisors.—The plate must not cover the front of the alveo- lus, so that, on front or side views of the mouth, its presence can be detected. This rule applies also to canines and front edges of bi- cuspids. The model at these points should be scraped, so that the corresponding die shall give a shape which will sink into the gum. The plate must also be filed to a thin edge before grinding the tooth. With these precautions a tooth or block may have the support of the plate under the centre of its base. Otherwise it becomes neces- sary to cut the plate along the line of the backings; and this is, in some cases, the best plan. Incisor teeth, if firmly bedded in the gum, may trust for stability to their hold in the standards, pro- vided they have been properly fitted and soldered. The size and shape of plate betAveen teeth and clasps Avill depend upon the number of incisors, position of clasps, presence or ab- sence of other teeth, and upon peculiarities of the mouth or of the patient. For the application of the principles already given to these several conditions we shall select a feAv particular case's. One Incisor.—A central or lateral should not be attached to a first molar on the same side by a plate clasped as in Fig. 923, Avithout Fig. 922. Fig. 923. an additional clasp, or partial stay, around one of the bicuspids, as in Fig. 922, in order that the leverage between the clasped and sup- porting tooth or teeth may be lessened. It is also desirable to have the plate extend some distance back of the tooth around which the clasp passes. When three or more natural teeth intervene between 63 994 MECHANICS—DENTAL PROSTHESIS. the clasp and artificial teeth, the latter form is preferable, because there is no possibility of irritating the teeth by the plate or by mu- cous deposits. It Avill be noticed that the curve of the plate is oppo- site that of the dental arch, thus giving proximity to the teeth only where it is unavoidable. A lateral incisor, cuspid or bicuspid may be applied in the same Avay ; and if the second bicuspid or first molar is unfit, from its shape and from decay, to be clasped, the plate may be extended to the second molar, or it may be even carried across the mouth, and clasped to a plate on the opposite side; but these modi- fications are suggested only in cases of necessity. Such plates may be made very narrow, if strength is given by increased thickness; but too narroAV plates are open to the objection of alloAving the attached tooth to bed itself too deeply under the pressure of masti- cation. When the form in Fig. 922 is adopted, it is usual to direct soldering a Avire or band along the festooned edge, to give strength. A much better plan is to gain strength by thickness of plate, and to chamfer the plate along this edge. The thin edge protects the gum equally well, does not wear the teeth more than the thick one, and has the decided advantage of giving no space for lodgment of food. This plate will permit attachment of clasp to the molar and to either of the bicuspids, accordingly as one or other of these may be best for clasping. Decision in this case is based on principles which apply to many other cases. Supposing the three teeth Avell shaped and sound, the molar is firmly implanted by its trifid root, and permits complete encircling with the clasp; but it is further from the incisor; hence there is more strain upon tooth and clasp. With the clasp to the second bicuspid, the plate having the same length as before, Ave have the best possible application of its reten- tive power; it cannot, however, pass around the outside or front angle of either bicuspid, consequently the clasp does not have so firm a hold on the tooth. The same remarks apply with even more force to the first bicuspid. There Avill usually be some modifying circumstances to determine, in this class of cases, choice of the clasp tooth. Two or Four Incisors.—Tavo incisors may be attached to a plate shaped as for one (Fig. 922), Avith the addition of a second clasp, or partial stay, when the teeth Avill not permit of a full clasp. But much the best practice is to select the second tooth on the opposite side. Fig. 924 gives the form Avhen it is decided to run the plate up to the intervening teeth. Fig. 925 represents the second form, which Avould be better suited if the plate was made larger than is shown in the figure, so as to cover more of the roof of the mouth. RETENTION OF BASE PLATES. 995 With four incisors and clasps on second bicuspids, the first form is best, because only tAvo teeth lie between the incisors and clasp; and it is better to carry the plate up to the teeth than to expose so small a portion of gum. For four teeth, the plate should be rather Avider than for tAvo. In these cases a closely-fitting plate assists so much in its own retention, that bicuspid stays will often suffice to retain them, or a clasp on one side and a stay on the other. When the adhesion of Fig. 924. Fig 925. Fig. 926. the plate to the gum is thus partly relied upon, it is not necessary to make the plate for four incisors larger than in Fig. 924. When the four incisors and the cuspids are to be replaced, the construction of the plate (Fig. 924) is upon precisely the same prin- ciple as the preceding, the only dif- ference being that the plate should be rather larger and extend further back than the clasped teeth. When the teeth on one side of the mouth are too much decayed, or are inca- pable of affording a secure attach- ment, or are missing, even this number of teeth may be held by a double clasp on one side of the mouth and a stay on the other. But the plate should be extended half or three-fourths of an inch back of the tooth to Avhich it is clasped. If this precaution is neglected, the piece, from its Aveight, may act as a lever upon the tooth, and loosen it or cause periostitis. It sometimes happens that a piece made originally Avith clasps on both sides of the mouth loses the benefit of one clasp from the loss of the tooth ; and yet the patient retains it in place as well as before. The piece is then, in part, retained by the fit of the plate to the gum; from which 996 MECHANICS—DENTAL PROSTHESIS. we learn that if only one clasp or, what is better, a double clasp. can be attached to a plate with from four to six teeth, it is advisable to cover rather more of the surface of the mouth. In this combi- nation the clasp and stay give steadiness, and the close fit of the plate to the gum gives adhesion. Upper Bicuspids.—One or both bicuspids on one side are often attached to a plate about the size of a half dollar, clasped to the bicuspid or molar behind. But such pieces are not of much service in mastication. It is better practice to leave such a space unfilled, than endanger the durability of a good tooth by clasping it. If there is a bicuspid space on either side, the plate crosses the mouth. Fig. 927 represents such a plate clasped to the first molars and fitted, as Fig. 927. Fig. 928. is very commonly done, closely to the incisors. But in this and all other cases where the four or six frorit teeth remain, if the plate does not fit closely to the palatal necks of the natural teeth, it is decidedly better to leave as large a space betAveen the plate and the teeth as possible. The strength of the plate is preserved by giving less curve to the back edge, or by doubling the plate in the middle. The design of this form is to leave uncovered as much of the rooi of the mouth as is possible. An important point is gained by having the plate fit closely to the teeth and mucous membrane immediately back of the natural front teeth: and also by having the edge of the plate made thin. The articulation of the dental letters (the mutes T, D, Th, the nasal N and the liquid L) is thickened by a plate which is left thick at such a part, or not well adapted to the mucous membrane and the teeth. When the loss of bicuspids is accompanied by that of the six front teeth, and the first molars alone remain, a good form of plate is shown in Fig. 926. The backward extension of the plate, curv- ing partly over the alveolus, is designed to prevent the Aveight of RETENTION OF BASE PLATES. 997 the piece from acting injuriously on the molars, and to assist their retentive poAver. If the second molars are also in the mouth, the extended plate must be differently shaped* If the molars are Avell shaped and firm, the plate may be narrower than here represented, being careful to make it thicker also. But if the presence of adja- cent molars prevents the use of complete clasps, or if their form renders stays necessary instead of clasps, the plate may be rather Avider. Be careful, hoAvever, not to cover the hard floor of the palate, or to attempt giving, by a cross band at the back of the plate, the stiffness Avhich is best gained by thickness of metal. Plates of this class are kept in place as much by the adhesion of contact Avith the gum as by the clasps. In many cases the force of adhesion is such, that the lateral support of stays is quite as effec- tual as clasps. Hence, after a clasp piece of this kind has been worn for some time and become perfectly set to the mouth, it may be advisable to shorten the clasps into stays; indeed, it is better practice, in all cases, to anticipate this ultimate fit of these plates, and make stays at first instead of clasps. This applies with still more force to the loss of tAvelve teeth, the second molars remaining, Avhich should in no case be clasped; stays may very properly be used to prevent lateral or backAvard motion of the plate. The presence of these second molars, by giving lateral steadiness to the plate, prevents all necessity for covering the hard palate, and makes a vacuum cavity Avholly uncalled for. A solitary molar should never be clasped, nor should it be allowed to remain in the mouth. Alternate Spaces.—It remains to consider the forms of plates for vacancies alternating Avith natural teeth. The forms given for four incisors will ansAver for all alternating A'acancies anterior to the second bicuspids, remembering to make the plate Avider in propor- tion to the number of teeth, and thicker in proportion as it is made narroAV; also, that a first bicuspid may. in many of these cases, be clasped Avith better effect than a second, or than the first molar. Fig. 929 is a good type for cases Avhere the vacancies include the bicuspids; notice in this cut the backAvard extension of the plate. Where the natural teeth are in groups of tAvo, it is best to carry the plate close up; if as many as three or four are together, the plate may be cut away, especially if they are incisors. Fig. 930 repre- sents an exceptional case, in Avhich two laterals and two left bicus- * The festooned >shape of this and similar cuts is designed to mark the number and position of the artificial teeth. The forms of the teeth are omitted, as having nothing to do with the subject of this chapter. The plates on the models are taken from the valuable work of Prof. Richardson. 998 MECHANICS—DENTAL PROSTHESIS. pids are attached, by clasping, to the right first bicuspid and molar. The left molars are supposed to be loose, or sockets much absorbed, or from some other cause forbidding clasps or stays. In this case, the undue strain on the clasp teeth will ultimately cause their loss. Whenever an unavoidable strain of this kind is thrown upon a tooth, a clasp may be used in preference to covering the palate, provided the patient is content, for the sake of the firmness Avhich it gives, to risk the loss of the tooth. Teeth are more firmly retained by clasps than by atmospheric pressure, and this, with many patients, outAveighs all considerations of injury to the other teeth. Partial pieces, Avith alternating spaces, do not acquire that adhe- sion by contact found in cases where the lost teeth lie together. The interrupted margin between the teeth so readily admits air Fig. 929. Fig. 930. under the plate, on the slightest motion, that the atmospheric pres- sure is imperfectly applied. Hence, there is continued demand for the retentive power of the clasps. The vacuum cavity does not cor- rect this difficulty, or supply the place of clasps, since, as will be explained in the next section, the vacuum acts on soft membrane and has necessarily a temporary force. When the six or eight front teeth remain, a plate holding bicus- pids and molars cannot be retained by clasps. In the first place the cuspids could not be clasped, nor would it be proper even to carry stays against them. In the latter case, the weight and lever- age of the piece would be too great for the slight clasp that a first bicuspid permits; but two stays, with the points passing as far to the front of the bicuspids as the cuspids alloAV, would tend to pre- vent the slipping of the plate backAvard. Lower Partial Pieces.—These do not properly come under the head of clasp work. In replacing one or more incisors lost by accident or calcic deposits, half-clasps may be applied to the bicuspids. RETENTION OF BASE PLATES. 999 For such cases the best style of work, beyond all question, is a vulcanite plate, made on a model from a plaster impression. Fit- ting Avith great accuracy the inner surfaces of the bicuspids, it is firmly held without injury to the retaining teeth. Partial pieces filling bicuspid and molar vacancies should not clasp cuspids or bicuspids; the position of remaining molars seldom permit clasp- ing; even stays cannot always be applied. Artificial croAvns may be inserted to support a clasped plate, and gold croAvns may be attached to roots and badly decayed teeth to support clasped plates, and thus save more valuable teeth from the strain and wear of clasps. In chapter fourth, on Preparatory Treatment of the Mouth, the question of extracting molar or bicuspid teeth, which might other- wise be used for clasping, is considered. The importance of per- manence of the Avork ouhveighs any temporary advantage resulting from clasping one or tAvo such teeth. In chapter third, and in the section on Retention by Clasps, are many remarks which it is un- necessary to repeat, but Avhich are important for the full under- standing of the details of construction given in this section. PLATES RETAINED BY ATMOSPHERIC PRESSURE. Of the tAvo methods of retaining a dental appliance already con- sidered, the first, by springs, is suited only to entire dentures; the second, by clasps, is adapted only to partial cases. The principle of retention noAV to be considered is applicable to both; Avhere prac- ticable, it is the most perfect Avay of retaining a set of artificial teeth. If the pressure of the atmosphere could be removed from mucous side of a plate, allowing its full force to be exerted upon the lingual surface, the smallest plates Avould adhere Avith a force of four pounds, the largest, forty. But, for reasons to be given, plates seldom have one-fourth of this resistance to displacement. There are tAvo methods in present use for securing the service of atmos- pheric pressure. One is by close adaptation of the plate; the other, by construction of a cavity of definite form. Both act by the more or less perfect exclusion of air from between the plate and the mouth. The first will be considered as the Adhesion of Contact; the second as the power of the Vacuum Cavity. Before describing the separate application of these to dental plates, a feAv remarks are necessary, in addition to Avhat has already been said in the last section of the third chapter, in exposition of the general principles of atmos- pheric pressure. The surfaces of tAvo pieces of highly polished ground glass, if 1000 MECHANICS--DENTAL PROSTHESIS. pressed together, will adhere firmly; so much so, sometimes, as to resist every attempt at separation. Surfaces less smooth and close- grained will also adhere with great tenacity, if their pores or irregu- larities are filled by Avetting Avith Avater. If both surfaces are rigid, they may be made to slide upon each other, but will resist a force of five to fifteen pounds for every square inch, if applied at right angles to the surface; if one surface is soft and pliant, it becomes difficult to keep it in contact around the edges. Traction upon the centre, as in the case of a disk of Avet leather upon a flat stone, Avill draiv in the edges, and create a vacuum in the centre. It might be supposed that in this vacuum space lies the power that raises the stone; whereas, it lessens the power by reducing the area of stone in con- tact Avith the leather, even if the vacuum is perfect. Still, if the entire circumference is in contact, no air enters the cavity, except what passes through the porous leather, and for a time the lifting- power of the disk is sufficient to raise the stone. If traction be made upon the disk anywhere but in the centre the flexible edge will be raised ; air enters between the surfaces, and counteracts that pressure on the under side of the stone Avhich Avas the lifting force. Hence, between two surfaces adhering by simple contact, one of which is soft and pliant, adhesion is not so persistent as where both are rigid, because of the liability to separation around the edges admitting air between the surfaces. Applying this to dental plates, we may understand their liability to become detached by a degree of motion which separates them from the gum at any one point around the edge. We learn, also, that so long as absolute contact is maintained, we have the most perfect exclusion of air practicable; hence, no force of adhesion in a limited vacuum cavity (the perfect exhaustion of which is impossible) is comparable to the adhesion of the entire surface of the plate, provided this is made as perfect as possible by accurate workmanship, and is not weakened by the admission of air around the edges. If Ave exhaust the air from the barrel of a key, and apply the lip, it will be draAvn in, and held with a force sufficient to support the weight of the key for some time. This simple experiment will prove, on examination, very instructive. The mucous and sub- mucous tissues are pressed into the key, because the fluids pervad- ing these parts, being under pressure in every other direction, tend toward the point from which the pressure is wholly or partially re- moved. The extent to which the lip is drawn into the key will depend upon two conditions: First, the softness and mobility of the tissue; secondly, the shape of the edge of the orifice. If, in addition to these tAvo points, we inquire, thirdly, Avhy the key, after a time, drops off, RETENTION OF BASE PLATES. 1001 we shall, from this simple illustration, haA-e fully explained the rationale of the vacuum cavity, as applied for the retention of a piece of dental mechanism. First: the extent to which or rapidity with which a partial vacuum becomes filled up by any yielding tissue with which it is brought in contact, depends upon the mobility of its structure. We say, partial vacuum, because the process of mechanical exhaustion can never produce a perfect vacuum. If the Avater which gives softness to mucous tissues was perfectly free to move, the cavity would be instantly filled, however deep. Parts as mobile as the tongue and lips yield readily to this fluid pressure; but the mucous membrane of the alveolar ridge and palate, being more or less tied doAvn to the bone, fills the cavity more slowly ; if too deep, it will not fill it at all, except by hypertrophy. Reverting to the experiment of the key: if violent suction is made, a purple spot is left upon the lip; the mucous tissues being prevented by their structure from filling the vacuum, the fluids still feel the impulse of atmospheric pres- sure ; the blood, thus impelled Avith a force Avhich the thin capillary walls cannot resist, is extravasated, as takes place also in the appli- cation of " dry cups." Hence, Avhere a dental-plate cavity is so deep that the tissues cannot fill it, if the degree of exhaustion is such as still to draw upon the surface, the tissues are in danger of being ruptured. Such a source of irritation will, in many persons, develop morbid action, and should forbid the use of deep cavities in any plate. Secondly: The shape of the edge modifies the rapidity Avith which the cavity fills. If the edge of a cupping glass is rounded, the skin glides under it, and is draAvn from the adjoining parts into the glass; but if the glass is ground so as to present a sharp edge on the inside, this beds itself in the surface, and prevents so much of the adjacent skin from being draAvn in. It rises to a less height in the cup, and the remaining force of the vacuum is spent upon the cap- illary vessels, which are ruptured. Hence, we learn that sharp- edged cavities fill less rapidly, but act Avith more power upon the tissues; they are consequently more apt to excite disease, if the cavity has sufficient depth to alloAV continued action. Third///: As to the cause of the final dropping off of the key: water, and all the moist tissues of the body, contain atmospheric air, Avhich they yield up under a vacuum. Hence, a mucous mem- brane, although at first draAvn strongly into a cavity, will make the vacuum less complete, by giving out the air contained in its tissue and in the blood constantly circulating through it. The adhesion of a A'acuum, therefore, over mucous membranes, requires reneAval 1002 MECHANICS--DENTAL PROSTHESIS. by occasional suction; since the blood is constantly circulating through the surface, and supplies air to the cavity. Mucous mem- branes have also the property of absorbing air; as is seen in the lining of the bronchial cells constantly, and in the poAver of the mucous membrane of the intestines to absorb the gases there gen- erated. This property acts an important part in absorbing small quantities of air unavoidably caught betAveen the plate and the mouth ; thus partly explaining the well-known fact, that plates ad- hering by simple contact become tighter after being worn aAvhile. Thus the double action of mucous membrane, absorbing minute portions of air pressed against it, and giving out its contained air to a vacuum, favors the retention of simple contact, Avhilst it acts against the efficacy of the vacuum. In either case it prevents the full force of pressure, theoretically possible. The practical infer- ence from the lesson of the key is that the Vacuum Cavity acts Avell at first, and may be useful for the temporary purpose of re- taining a plate until the changes of which the mouth is capable adapt it more perfectly to the plate; but for permanent adhesion, the only reliable application of the atmospheric-pressure principle is the Adhesion of Contact, which is fully developed only when the contact of the plate is complete. A vacuum cavity, acting as such, gradually draws the gum into it, and finally fills it by a more or less permanent enlargement; when thus filled, the plate is re- tained solely by the adhesion of contact. When a cavity, intended to hold up a plate, leaves no prominence or mark in the mouth, it unmistakably proves that it is exerting no force ; so far from aiding in the retention of the plate, it diminishes the force of adhesion by the presence of air, and has no compensating advantage, except in removing pressure from a hard palate membrane. There are, hoAV- ever, other and better ways of obtaining an air space, as elsewhere explained, without the presence of a cavity, Avhich marks the failure of its original purpose. ADHESION OF CONTACT. Full plates, Avhich are designed to adhere by force of contact, differ from those retained by spiral springs, in that the former are larger than the latter, covering more of the palate, so as to give a larger surface for the pressure of the atmosphere. They may cover the whole of the outer surface of the alveolar ridge, and a considerable portion of the roof of the mouth; but should not go as far back, nor run so high up, as some dentists are in the habit of extending them. If allowed to cover those parts of the bone where the cheek muscles on the outside of the ridge or the palate muscles at the RETENTION OF BASE PLATES. 1003 Fig. 931. thickness throughout, or by back of mouth are inserted, the gums Avill be chafed or ulcerated, the patient nauseated, and the piece rendered unstable by the action of the muscle. It is not ahvays necessary to employ a very Avide plate to give secure retention, for a comparatively narroAV one will often adhere with very great tenac- ity to the gums. But such a plate is more liable to be bent, and lose its perfect adaptation to the parts, than a Avide one, unless made thicker in proportion as it is nar roAver. As it is never necessary to make an upper plate so narroAV as a lower one, there can be no difficulty in giving the requisite strength, either by increasing the doubling the anterior half. The diagram (Fig. 931) represents half-section outlines of six modifications of form in the posterior margin of the plate, Avhere it is proposed to overcome the difficulties incident to a hard palatine membrane by cutting out the plate. The line P, curving forward from a little behind the termination of the top of the ridge (dotted line), is the extreme limit of any plate not complicated with cleft palate. The curve a or a' will give surface sufficient for the reten- tion of most plates, except in small arches. This form is more agreeable to the patient than the first, and is less apt to produce nausea; it removes the plate from all action of the palate muscles, and lessens the liability to dislodgment often caused by the forcible action of the tongue against the back of the palate, in certain efforts of deglutition. The curve b or b' may often be used solely to avoid unnecessary covering of the palate. In mouths of average size, and having moderate and regular softness, such shape will prove quite as firm as one following the line P. But these lines are more fre- quently to be folloAved, for the same reason that we take the curve c or c', to keep the plate off the hard central ridge. When this ridge is narrow, we give greatest width to the plate by following the curves on the side II of the diagram; but if the surface is broad, the space must be widened, as on the side L; and the plate made thicker. This method of relieving the central bearing of plates gives them great steadiness on the ridge, and has an advantage over other methods, in having no band or ridge of plate pressing along the line P—a point very often as hard as any other part of the palate. It is 1004 MECHANICS—DENTAL PROSTHESIS. advisable, in those cases where a vacuum cavity has been tried with unsatisfactory results, to cut out the ca\dty and part behind it, and thus try the effect of a plate folloAving curve b or c. There are other methods of taking off the central bearing of plates. When the ridge is soft, a wax impression does this by com- pressing the gum. Models from plaster impressions are scraped on the ridge for the same purpose; but this is not so good a plan, as it is difficult to do it uniformly. A much better expedient is to brush some thin plaster over the central part of the model, being careful to mark the line of the back edge of the plate, and put no plaster there; this layer must not be thicker than a card, and should have no abrupt edges. A thin layer of wax may be added in the same manner to plaster models before moulding in sand to obtain the die for SAvaged metal plates. In deep arches, the shrinkage of the zinc die accomplishes the same object; if the model is carefully scraped along the back edge of the plate, this part will fit closely, while the central portions will stand off; this is far better than the attempt to adjust the edge with pliers. In adapting atmospheric-pressure plates, the form and fit of the alveolar margin must be considered. Close adaptation of this edge is by no means so essential to firm retention of a full upper piece as in the posterior margin ; for the reason that, in most cases, the loose mucous folds which lie against the plate prevent the access of air. But closeness of fit is very desirable for other reasons: to prevent lateral motion; to avoid unnecessary fulness ; to prevent irritation of the soft parts by projecting edges of metal. The form of the alveolar edge is not essential to adhesion, provided it rises high enough to give steadiness to the plate. iEsthetic considerations, howeArer, often compel us to run the plates up as high as the muscu- lar attachments will permit; either for the support of an artificial gum or to restore sunken features. In both jaws, especially the lower, the effort to get the deepest possible edge often gives insta- bility, by subjecting the piece to the action of the facial and lingual muscles. In any case of doubt make the plate too shalloAv rather than too deep ; especially when the edge is turned over, which makes it impossible to take off any excess without spoiling the plate. Full lower plates are held by adhesion of contact; but in these the weight of the piece increases the adhesion. The surface is so small that every part of such plates should fit the gum with accu- racy. The simple rule for the form of lower plates is to extend them as far on the inner and outer edges as the muscular attach- ments Avill permit. The outer and inner edges are often rounded by soldering a gold wire, after determining the exact outline. RETENTION OF BASE PLATES. 1005 Thickness of edge is also given by doubling the plate necessary for the strength of narrow plates. The second plate is to be SAvaged precisely as the first; then, after partial trimming, the tAvo plates are swaged together over a new die. One should be wider than the other, on the outer or inner edge, to give a place for the solder; the borax cream should be free from granules, and the bloAvpipe flame directed on the edge opposite the solder. A simple and convenient clamp for binding plates together, or holding rims while being sol- dered, is made of iron (or nickel) Avire (Fig. 932). a The first bend; b the second bend ; c a side vieAV of the same; d side view of clamp, open and grasping tAvo pieces of plate. The curves should be so adjusted that the points of contact Avith the plates will be just oppo- site, else clamp or plates are liable to change position. Partial pieces may also be retained by closeness of adaptation: but there are two elements of instability Avhich usually Avill prevent them from having the secur- ity of full sets, or of partial clasp pieces—lateral movement and ex- tent of margin, admitting air on slightest motion. All such pieces should, if possible, have tAvo stays, one on each side of the mouth, to prevent lateral motion ; they should cover an extent of surface proportioned to the number of teeth ; the edges of the plate should fit Avith great accuracy. If the exact outline of the plate is deter- mined on, a good plan is to paint the model with a coat of thin plaster, keeping one-eighth inch inside the margin, and laying an extra coating over very hard places; this causes the edge to sink slightly into the gum ; yet if carefully done, it Avill not change the general contour of the surface. Partial plates, holding the eight, ten or tAvelve anterior teeth, if assisted by stays against the remaining molars, are nearly or quite as firm as full plates. But in either partial or full pieces, whenever the plate has to be cut off, for setting the six front teeth directly on the gum, this dentated margin is more apt to admit air than the upturned rim, Avhich has the folds of the lip lying against it. Partial lower plates are unstable, not from any admission of air, but because of the small extent of surface. inadequate to the pressure of mastication. Plates for partial dentures to be held in place by clasps or bands are generally made narrow, and the posterior line or edge Avithin the depression of the rugse, so as to be out of the way of the tongue, but such plates must not be made too small, or they Avill cause pain 1006 MECHANICS--DENTAL PROSTHESIS. by being forced into the mucous membrane. Partial lower plates for artificial bicuspids and molars, the six natural anterior teeth re- maining in the mouth, should extend up on the lingual surfaces of the natural teeth to prevent the too great pressure of the plate against the inner surface of the alveolar ridge, and also to give greater strength by the increased width and form of the plate back of the natural teeth, which Avould otherwise have to be made very narrow and thick. The lower inner edge of full and partial loAver plates should extend so far down as to be out of the Avay of the tongue. Carrying the edge of such a plate over the projecting sur- face of the ridge, which is generally present into the receding under- space, will prevent the tip of the tongue from getting under it; at the same time the plate should not extend so far down as to inter- fere with the frsenum of the tongue. A tongue or catch may be swaged as part of a partial loAver plate, to extend slightly over the angle of the crown of a posterior natural tooth, such as a molar or bicuspid, and catch on the grind- ing surface, and thus prevent a partial lower denture from pressing painfully on the gum. This tongue or catch should be adapted to the grinding surface of the natural tooth at a point where it will not interfere to any great degree with the occlusion of the natural teeth. Partial stays fitting as far as possible into the interspaces between such natural front teeth as remain in the mouth, will prevent par- tial lower dentures containing artificial bicuspids and molars from sliding backAvard, as all such dentures have a tendency to do. Such stays will also prevent the plate from being raised from its place by the cheeks and muscles. THE VACUUM CAVITY. In some mouths the base plate of a full upper piece adheres, from the beginning, Avith great firmness. When the gum is moder- ately and regularly soft, the palatine arch deep, and the mouth of average size, want of adherence, on trial of the plate, is positive evidence of defect in construction. But very hard, or very small, or very shallow mouths usually require time for the perfect adapta- tion of the best made plates. Dr. DAvinelle thus explains the tem- porary failure of a simple atmospheric pressure plate to fit firmly when first inserted. When the plate is applied and an effort made to exhaust the air, the gums are draAvn doAvn so as to meet it along the line and behind the edge of the plate, thus resisting every effort made from without to AvithdraAV the air from the central part of the plate; so that the pressure of the atmosphere is exerted upon only RETENTION OF BASE PLATES. 1007 a small breadth of surface along its edge, where the adhesion is con- stantly liable to be disturbed in mastication. With the view of ob\dating this difficulty, the idea of constructing a plate Avith a cavity suggested itself to the author as early as 1835, and Avas mentioned at the time to several of his professional breth- ren. The construction of the chamber then devised was found objectionable, and he abandoned its use; and it was not until the early part of 1848, when he had the opportunity of seeing a cavity plate upon a plan contrived by Dr. J. A. Cleaveland two or three years previously, that he was again induced to construct a base plate of this kind. Dr. DAvinelle made a cavity plate Avith an external open- ing and valve for exhausting the air, in the winter of 1845 ; and in the summer of 1847 or 1848 Dr. Jahial Parmly exhibited to the author a plate Avith a simple cavity struck into it by swaging. Some months after he heard for the first time of a cavity plate patented by Mr. Gilbert, of Noav Haven. The cavity now generally employed Fig. 933. Fig. 934. is formed on the median line, either far back for full plates (Fig. 933), or immediately behind the alveolar ridge for some partial plates. Dr. Flagg adds tAvo lateral cavities on the slope of the pal- ate Avith a vieAV to prevent the plate from rocking, and to give it increased stabilitv. Dr. Levett's lateral caAuties are placed directly upon the ridge (Fig. 934). With this brief history of cavity plates, Ave shall proceed to give a concise description of the manner of con- structing them. The following is the mode of construction of Dr. Cleaveland's cavity plate, Avhich, for reasons ghven beloAV, is now seldom used. A metallic die and counter-die having been obtained, a plate is SAvaged, covering the entire alveolar border and extending back as far as the line P (Fig. 931). This done, it is placed in the mouth, and if found to be accurately adapted to the parts, it is removed; a half-round gold Avire, about the size of a common knitting needle, is then soldered to the lingual side of the plate, enclosing a space shaped someAvhat as is shoAvn in Fig. 933, varying in size and form 1008 MECHANICS—DENTAL PROSTHESIS. with the differences in shape and size of the plate and alveolar ridge. The part within the Avire is next cut out with punch-forceps, or saw, and the plate placed on the model; a piece of Avax, about a tenth or twelfth part of an inch in thickness, having a circumfer- ence one-fourth greater than the hole in the plate, is then placed over the opening, extending a short distance beyond the Avire on every side. The wax at the outside is brought to a thin edge, and is also made thinner in the centre than where it covers the Avire surrounding the opening in the plate. From this model with plate and wax upon it, die and counter-die are obtained with Avhich to swage a thin plate of gold, large enough to cover the wax; its edge is chamfered off, and it is then soldered to its place on the plate, where it may be secured during soldering, either by iron Avire clamps or by gold rivets. A sectional view of the cavity is repre- sented in Fig. 935 A. The Cleaveland cavity causes the plate to adhere Avith great tenacity ; as, from its shape, it is impossible for Fig. 935. Fig. 936. the mucous membrane entirely to fill it; the traction of this cavity is constant. A serious objection to its use is the great irritation it excites in the mucous membrane, in the majority of cases. The simpler cavity plate, used by Dr. Jahial Parmly. of New York, and patented by Mr. Gilbert, of New Haven, may be formed with nearly as much ease as a plain plate. Fig. 935 B represents a sectional view of this description of plate. If it is desired to have lateral cavities, three pieces of wax, or metallic forms, are placed on the plaster model—one in the centre, as already described, and one on the slope of the alveolar ridge, on each side. When it is desir- able to make a cavity with sharply defined border, D, a second plate, a little larger than the projection, should be swaged over the base plate. From the base plate the projection is to be cut out, and the smaller plate soldered over the opening. For hard mouths, the RETENTION OF BASE PLATES. 1009 thickness of the main plate will give sufficient depth of cavity, C ; in this case no projection is to be placed on the model. Should the usual method of exhausting air from these cavities be thought insufficient, the valve of Dr. DAvinelle (Fig. 935 V) may be inserted in the plate covering the cavity. The conical portion is neatly fitted by grinding; the stem is soldered to a spring on the palatine surface. A valve of easier construction is given at V; a small rubber pad acts, by the spring, upon the outside of the hole. The size of valves and thickness of plate are exaggerated, the better to illustrate the details of construction. By means of either of these valves, a vacuum may be created, which will draw Avith great force upon the membrane over the cavity. The forms B and D, Fig. 935, necessitate a prominence in the die, Avhich is variously formed. When the die is made by sand moulding, a corresponding one, formed of wax, lead, tin, or plaster, is put on the model; a die made by dipping, or pouring, or by the fusible metal process requires plaster. Dies made by pouring into the impression require the cavity to be cut in the impression itself. A variety of shapes in tin and alloy are furnished by the depots, chiefly for vulcanite Avork; but they may be used also for the sand moulding model. Plates made by the metallo-plastic processes re- quire plaster prominences. Fig. 937. TOO The size, depth, form and position of the cavity are important considerations. In size, it must be proportioned to the plate. Fig. 936 gives a fair average size, and is excellent in form, except that it is unnecessarily pointed; all angles and sharp corners should be avoided, and fanciful shapes are aesthetic blunders; the form should appear to groAV out of some necessity; and hence it should be mod- ified to suit the form of* plate. ShalloAV cavities may be larger than deep ones; partial pieces usually have a cavity larger in proportion. Fig. 937 represents the usual forms of vacuum cavities (the shield form being objectionable on account of its sharp angles), which may be metal, such as block tin, that will not discolor the rubber; vacuum caAdties made of sheet lead are objectionable, on that account. In depth, the cavity must vary Avith the softness of the mem- brane. If soft, it quickly fills a shallow cavity, and is less liable 64 1010 MECHANICS—DENTAL PROSTHESIS. to injury by a deep one. Sharp-edged cavities fill less quickly than round-edged ones. They may vary in thickness from No. 14 to No. 24, gauge plate, page 867. When the cavity is designed, after a temporary retaining power, to act permanently in relieAdng the pressure on central hard parts, it should be very shallow. When, in very flat mouths, it is proposed to prevent lateral motion by the mucous prominence, the cavity should be deeper. Extreme depth, with a view to keep up constant action, makes a most unsightly piece, and injures the mouth. As to position, there Avould seem to be much difference of opinion, if Ave judge by the various points selected. We have never had but one opinion on this subject, and that is in favor of the central cavity. The cavity resists the greatest force of displacement when applied at right angles; as this force is ahvays nearly or quite vertical, it follows that the most effective cavities are horizontal; hence, they should only be on the roof of the palate, and limited to its level portion. Cavities covering the ruga?, or sloping walls of the palate, act at disadvantage. Again^ after the cavity ceases to act, its sec- ondary use in relieAdng pressure can be available only in this posi- tion. The very worst position for a cavity is on the ridge of either upper or lower jaw. Firm pressure on the ridge is one of the most important elements of stability in a plate. It is difficult to com- prehend what compensation for the loss of this is found in the cavity. Partial plates require, when the cavity is used, a modification of form to enable the cavity to be placed on the roof of the palate. Yet the shapes elsewhere given may be used in connection with Flagg's lateral cavities as represented by the oval in Fig. 938. If no stays can be used, as in a piece of artificial bicuspids and molars with natural incisors and canines, a central or two lateral sharp- edged cavities may be of service, to prevent lateral motion. In all other partial cases stays may be used; these, combined Avith accu- rate fitting, will give as firm a piece as any form of cavity. The vacuum cavity may also be formed in the impression, by adapting a form of wax to the roof of the mouth, in the proper position, before inserting the cup. Dr. C. H. Land has recently suggested a vacuum cavity pattern (Fig. 939), which is claimed to be of such a form as to secure the greatest advantage from atmospheric pressure, without injury to the mouth ; also to serve as a relief to the hard portions of the arch, by being of sufficient depth to allow for continued absorption of the alveolar ridge in the case of first sets; it is also claimed that its shape avoids interference with the organs of speech. SILVER, ALUMINIUM, AND PLATINUM PLATES. 1011 Dr. Joseph Spyer has devised for plastic work a thin metallic form, the surface of which is covered with minute papilliform prominences—shown in Fig. 941 magnified four diameters—which by displacement of mucus at the points of gum contact effect sur- face cohesion as if the denture were glued to the gums, yet cause no irritation and leave no marked indentations. Adapted for either upper or loAver plates. By the aid of this device it is claimed that strong cohesion can be had with a narrow plate, and thus the sense Fig. 938. Fig. 939. of taste be left unimpaired ; and that lower plates so made are very firm. They are put up in packages containing one dozen forms size of Fig. 940, which can be cut for either upper or loAver plates. Fig. 940. Fig 941. These forms are also made of gold with a thin covering of pure silver; the sulphur in the rubber, when set free by the action of vulcanizing, sulphurizes the surface, and to this the rubber adheres. Silver Plate and Solder.—The processes heretofore described, and the rules laid down, have been considered mainly in their rela- tion to artificial teeth mounted upon gold plate by the operation of soldering. But other metals may be swaged by the same pro- cesses, as platinum, aluminium and silver. 1012 MECHANICS—DENTAL PROSTHESIS. Silver is the least valuable of these, and has nothing to recommend it except its cheapness, in which questionable merit it has aluminum and vulcanite as its competitors; and hence it is now not very much used. It is manipulated in all respects like gold; except in the operations of refining by acids, the composition of solders used, and the care necessary in soldering, from the fusibility of the plate. For plates, pure silver alloyed with platinum possesses advantages over coin silver which oxidizes greatly in the mouth. The formula for such a plate is Pure silver,........1 ounce. Platinum,........1 pennyweight. Some prefer gold clasps for silver plates. A good silver solder is composed of Pure silver,..........6 parts. Pure copper,.........3 parts. Pure zinc,..........2 parts. In the preparation of such a solder, the silver and copper should be melted together and then the zinc added, pouring the molten mass into the ingot mould before the zinc volatilizes. Fine silver alloyed with one-third its weight of brass, also gives a good silver solder, as the zinc in the brass reduces the fusing point of the alloy, and makes it easy-flowing. If £ to 1 grain of zinc is added to the above formula, the fusing point is still further reduced. After pouring the alloy into the form of an ingot, it should be rolled to No. 26 or 27, annealed, and its surface cleansed by placing it in the acid-bath. Aluminium can be rolled into plate, and swaged. It requires ex- treme care in annealing, but makes a rigid, strong and very light plate. It does not Avithstand the buccal secretions as well as twenty-carat gold, nor is it as good as eighteen-carat gold. The obstacle to its general use also lies in the fact that, as yet, there is no good solder for it. Hence it is necessary to attach the teeth by vulcanite. This can be very successfully done, as vulcanized rubber adheres more closely to this metal than to any other, excepting, perhaps, pure gold or pure platinum. The process will be described in the section on Vulcanite; it is equally applicable to tAventy-carat gold and to platinum, but not at all to silver. An alloy of alumin- ium which is cast directly upon the teeth is referred to under metallo-plastic work. Platinum, if alloyed with five to ten per cent, of gold, has stiffness sufficient to be used as a base plate, in the manner previously given CONTINUOUS-GUM \ArORK. 1013 for gold. As it has no advantage over gold when used in this way, its less cost is not a sufficient offset to the inconveniences attending its use and to the color, Avhich is so objectionable to most persons that they are unAvilling to pay as much as for the same work in gold. Platinum has, however, one remarkable property possessed by no other used by dentists except palladium, which is now scarcely at all, if ever, used ; it cannot be fused in the highest heat of the forge or porcelain-baking furnace. Hence it is the only metal used for the metallic pins and other fastenings inserted into porcelain teeth; requiring for its fusion the flame of the oxyhydrogen bloAvpipe. It is also the only metal used in a remarkably beautiful style of Avork knoAvn as the Continuous Gum Work, which forms the subject of the next section. CONTINUOUS-GUM AVORK. The idea of uniting porcelain teeth to a metallic base by means of a fusible silicious composition originated in France, where the method has, to some extent, been practiced since 1820. But Dr. Fitch, Avho spent much time in Paris, and was well acquainted with the French method and Delabarre's formulae, stated, that the latter never perfected his recipes, or brought them into practical use. The composition employed there, judging specimens, cannot be used in connection with porcelain teeth containing as large a pro- portion of feldspar as those manufactured in this country. Dela- barre's compound, according to Dr. Locke, required 3761° Fahren- heit to fuse it completely. BeloAV this, it fused imperfectly, and was found too fragile. The process now known as the Continuous Gum consists essen- tially of a silicious paste, similar (except more fusible) in composi- tion to that of which the teeth are made, which is applied around the bases and fastenings of teeth previously soldered upon a plate of purest platina, and then fused at a temperature of about 2200° Fahrenheit. It takes its name from the fact that, unlike blocks or single gum teeth, it presents an unbroken continuous gum outside the alveolar ridge, as is shown in Fig. 942. It is applied in two layers—a Fig. 942. yellowish-Avhite body, giving the general contour of the gum, and an enamel, to produce that correct imitation of the natural gum, for which nothing but cera- mic materials have as yet been found suitable. Dr. Allen covered with the same material the entire lingual surface of the plate, and also certain projections outside of the molars and 1014 MECHANICS--DENTAL PROSTHESIS. above the cuspids, designed by him for the restoration of the natural fulness of the face. This falling in of the features is due to the absorption of the alveolar ridge, and cannot be fully restored by an artificial set of teeth, as usually made; since, if the molars Avere set out to the original Avidth of the teeth, the force of mastication would fall out- side the absorbed alveolus and render it practically useless. Dr. Allen's device corrects this sinking, under the malar prominence of the superior maxilla and in the canine fossa, and thus greatly aids in the restoration of the face to its original appearance. This process was patented by Dr. John Allen, in 1851; but the priority of invention was contested by Dr. William H. Hunter, in a suit, the progress and result of which were published in the dental periodicals of that period. Dr. Allen surrendered his patents of 1851, owing to certain defects in the same, and in 1856 a new patent was issued to him for the process as then improved. The process is very generally known as "Allen's Continuous Gum." The form- ulae given in this chapter are those of Dr. Hunter, and the earlier ones of Dr. Allen. As all such materials are more perfectly pre- pared on a large scale, we think it much better to purchase than to make them. A " continuous-gum " piece, made in the most perfect manner, is only surpassed in point of beauty by the occasional productions of a very few block carvers; but so rare are these specimens of per- fection in block work, that we may safely say of the continuous- gum work that, Avhen properly made, it is the most beautiful, as it certainly is the purest and sweetest, that can be Avorn in the mouth, so long as the porcelain covering maintains its integrity. It was thought, when this method of mounting artificial teeth was first adopted, that the springing of the plate in the act of mastication would cause the gum to crack and scale off; which did occur in a large proportion of the cases. Although the injury could be repaired by replacing the loss with fresh composition, and fusing it to the fractured edges of the remaining portions and to the plate, yet this at one time formed a very serious objection to its use. But later improvements in the strength of the compound, and also in the rigidity of the plate and soldered backings, or long pins, have so far corrected this evil, that it is perhaps no more liable to accident while in the mouth than any other kind of work. But, out of the mouth, its weight renders it peculiarly exposed to accident; a fall is almost certain to break one or more teeth, or crack the silicious covering of the plate. Hence, it is necessary to impress upon the patient the great importance of the most careful handling. CONTINUOUS-GUM WORK. 1015 By uniting the teeth to each other near their base, and to the plate, Avith a glazed porcelanic material, the cleanliness of the sub- stitute is most perfectly secured; as all the openings beneath and around them are completely closed, excluding the secretions of the mouth and particles of food, which have no affinity for or action upon the porcelain. In this respect they are superior to the most perfectly mounted block-teeth ; Avhile the labor of putting up a set of the former can be performed in half the time required for mak- ing and mounting a set of the latter. A person who can mount single teeth Avell may acquire a knowledge of this method, Avith proper instruction, in a feAV weeks; although much of the peculiar talent required in block-carving is needed in arranging the teeth and shaping the gum for this process, the details are comparatively simple, and may soon be taught. Of course, much practice will be required, especially in the management of the furnace heats. The necessity for such practice, to enable one successfully to manage the furnace, is the chief obstacle to its casual use by the practitioner. Unless he makes it a specialty, and does all his own work, and some for his neighbors, he will be certain to meet Avith many dis- couraging failures in the final process of baking an otherwise per fectly constructed piece. We therefore advise the dentist to swage the platina plate, select and arrange and articulate the teeth; for no one should be so com- petent to do this as the one Avhose intercourse with the patient enables him to judge exactly what form, color, and arrangement of teeth are best suited to the case; and only he can decide upon the correctness of the fit of the plate. But when all this is done, the piece should be securely packed and sent, by express or mail, to some experienced worker in the continuous- gum. The piece will be returned Avith the plate unchanged in shape, and the porcelain Avork executed in such style as can be reached only by constant practice and familiarity Avith the special details of this work. The artificial gum consists, as Ave have stated, of two parts; the first is termed the base or body, as this constitutes the princpal part of the cement, and is used for filling in betAveen the teeth and building up the gum on the plate; the other is gum enamel. The materials employed by Dr. Hunter, in the composition of his com- pounds, are silex, fused spar calcined borax, caustic potash, and asbestos. The silex and spar should be of the clearest and best quality, and ground very fine. The asbestos should be freed from talc and other foreign substances, and reduced to a fine powder. He gives the following formulae and directions. Flux.—Take of silex, 8 oz.; calcined borax, 4 oz.; caustic potash, 1016 MECHANICS—DENTAL PROSTHESIS. 1 oz. The potash is first ground fine in a wedgewood mortar, and the other materials gradually added until they are thoroughly mixed. Line a Hessian crucible (as white as can be had) with pure kaolin, fill with the mass, and lute on a cover of a piece of fire-clay slab with the same. Expose to a clear, strong fire, in a furnace, with coke fuel, for about half an hour, or until it is fused into a transparent glass, which should be clear and free from stain of any kind. This is broken and ground until it will pass a bolting sieve. Granulated Body.—Spar, 3 oz.; silex, 1$ oz.; kaolin, i oz.; completely fused. Break and grind so that it will pass through a wire sieve No. 50, and again shift off the fine particles, which pass through No. 10 bolting cloth, which leaves it in grains about the size of the finest gunpowder. It may be made of hard porcelain, fine china, or wedgewood Avare. Body.—Take flux, 1 oz.; asbestos, 2 oz.; grinding together very finely, completely intermixing. Add granulated body, 1? oz.; and mix Avith a spatula, to prevent grinding the granules of body any finer. Enamels.—No. 1. Flux, 1 oz.; fused spar, 1 oz; English rose red, 40 grains. Grind English rose red extremely fine in a mortar, and gradually add the flux, and then the fused spar, grinding until the ingredients are thoroughly incorporated. Cut down a large Hessian crucible, so that it will slide into the muffle of a furnace, line Avith a mixture of equal parts silex and kaolin, put in the material, and raise the heat to the point of vitrification, not fusion, then withdraAV from the muffle. The result will be a red cake of enamel which will easily leave the crucible, which, after removing any adhering kaolin, is to be broken doAvn and ground tolerably fine. It may noAV be tested, and, if of too strong a color, tempered by the addi- tion of covering. This is the gum which flows at the lowest heat, and is never used before soldering. No. 2. Flux, 1 oz.; fused spar, 2 oz.; English rose red, 60 grains. Treat the same as No. 1. This is a gum intermediate, and is used upon platina plates. No. 3. Flux, 1 oz.; fused spar, 3 oz.; English rose red, 80 grains. Treat as the above. This gum is used in making pieces intended to be soldered on, either in full arches or in the sections known as block work. It is not necessary to grind very fine in preparing the above formulae. Covering.—What is termed covering is made by the same for- mula? as for the enamel, omitting the English rose red. Being with- out any coloring whatever, it is used for tempering the above CONTINUOUS-GUM AVORK. 1017 enamels when too highly colored, which may be done by adding, according to circumstances, from one to six parts of covering to two of enamel, thus procuring the desired shade. When it is to be used for covering the base prior to applying the enamel, it may be covered Avith titanium, using from two to five grains to the ounce. Investient.—Take two measures of white quartz sand, mix Avith one measure of plaster-of-Paris, using just enough water to make the mass plastic, and apply quickly. The slab on Avhich the piece is set should be saturated Avith Avater, to keep the material from set- ting too soon, and that it may unite with it. Memoranda.—In preparing material, always grind dry, and use the most scrupulous cleanliness in all the manipulations. In all cases Avhere heat is applied, it should be raised gradually from the bottom of the muffle, and never run into a heat. Where it is de- sired to lengthen any of the teeth, or to mend a broken tooth, it may be done with covering, properly covered with platina, cobalt, or titanium. In repairing a piece of work, Avash it with great care, using a stiff brush and pulverized pumice stone. Bake over a sIoav fire, to expel all moisture, and Avash again, Avhen it Avill be ready for any new application of the enamel. Absorption occurring after a case has been sometime worn, by allowing the jaAvs to close nearer, causes the lower jaw to come fonvard and drive the upper set out of the mouth. By putting the covering on the grinding surfaces of the back teeth in sufficient quantity to make up the desired length, this difficulty may be to some extent remedied. Any alloy containing copper or silver should not be used for solder or plate, if it is intended to fuse a gum over the lingual side of the teeth, as it will surely stain the gum. Simple platinum backs alone do not possess the requisite stiffness, and should always be covered—on platinum with the enamel, and on gold with another gold back. In backing the teeth, lap the backs, or neatly join them up as far as the lower pin in the tooth, and higher if admissible, and in soldering be sure to have the joint so made perfectly soldered. The compositions originally employed by Dr Allen consist of— Body : Silex, 2 oz.; flint glass, 1 oz.; borax, 1 oz.; wedgewood Avare, IJ oz.; asbestos, 2 drachms; feldspar, 2 drachms; kaolin, 1 drachm Enamel : Feldspar, £ oz.; white glass, 1 oz.; and oxide of gold, lj grains. Since the publication of the early editions of this work, great improvements have been made in the composition and prep- aration of both the body and gum enamel, Avhich are furnished by the manufacturers, and may be obtained at any of the dental depots at a very moderate price. 1018 MECHANICS—DENTAL PROSTHESIS. The metals Avhich may be employed for the base in this method of mounting artificial teeth are platinum or pure palladium. The common commercial article of palladium is not pure, and is never used in this country. Platinum, alloyed with from 1 to 10 per cent. of pure gold, may also be used; but it is objectionable from its lia- bility to spring or warp. It makes a stiffer plate, and so far has the advantage over pure platinum, but for the reason given, the purest metal should be selected. Because of its softness, it must be used thicker than gold plate. The process of swaging the plate is the same as before given. It must be often annealed, and gradually carried into any deep depressions, for its softness makes it more liable than gold to be torn, made thin, or punched through. A Fig. 943. Fig. 944. narroAV rim, partially turned up, is to be left around the outside. The process of articulating, etc., is similar to that for gold. In ad- justing the teeth, accurate grinding is unnecessary ; but each tooth should touch the plate. Part of each backing, where the teeth are lined, should lap over the adjoining ones, and behind the six front teeth should also be lapped over an additional narrow band, to give greater rigidity to the plate. Continuous gum teeth with long pins are now used, the ends of the pins being bent down to the plate, to which they are soldered with pure gold : hence backing the teeth is not necessary. In this process there is great opportunity to give to CONTINUOUS-GUM WORK. 1019 the teeth that irregularity of arrangement which forms one of the characteristics of natural teeth; neglect of which gives to many otherwise excellent pieces of Avork an unnatural, artificial appear- ance, that shows great deficiency in the cultivation of dental aesthetics. Before applying the body the piece may be tried in the mouth and any inaccuracy of articulation readily corrected; careful articula- tion makes this trial unnecessary ; but if from any causes changes are found on trial to be needed, they can be made more readily in this Avork before the gum is added than in any other; since no joints or neat fitting to the plate are disturbed by changes in the position of a tooth. After this, the piece should be set in a mixture of plas- ter and asbestos or plaster and sand, resting on a muffle slide and coming up around the outside of the teeth, to keep them in place. The solder used must contain no trace of either silver or copper, as such metals will stain the gum enamel and body; but must be either pure gold, or alloyed with about 5 per cent, platina. Borax may be used, not in this case as a flux—for AA'here there is no oxi- dation no flux is required—but to hold the pieces of solder in place until ready to flow. The slide is then gradually carried in to the muffle, and the whole piece raised to the melting point of the solder. Figs. 943 and 915 represent tAvo of the most approved forms of furnaces. Fig. 944 represents Verrier's furnace for continuous-gum work. It is operated Avith the regular house supply of gas, aided by the blast from the foot bloAver (Fig. 886). It is claimed that this fur- nace will fuse gum body or enamel in from five to ten minutes, but the small size of the muffle, and its liability to " gas " the work, are objections urged against its use. Such accidents or effects are claimed to be overcome by the Com- bination Gas and Gasoline Furnace of Dr. Land, which is repre- sented by Fig. 945, in which is shoAvn this furnace thrown open, being swung on hinges at the back, exposing the muffle E. The groove P P is packed Avith asbestos fibre, so that Avhen the sections are brought together the furnace Avill be perfectly air and gas tight. It is claimed that Avith gasoline gas porcelain teeth can be enamelled in from ten to fifteen minutes, with ordinary illuminating gas in from fifteen to twenty minutes, according to quality. The rules for the management of the heat are the same as here- after given for block Avork. The heat required for this is not, how- ever, so great as that required in block work; the gold and the continuous gum materials fusing at about 2200° Fahrenheit. Having thus soldered and cooled off the piece very gradually, it must be thoroughly washed, so as to remove every particle of invest- 1020 MECHANICS—DENTAL PROSTHESIS. ment. Then, with a camel's-hair brush and small knife, such as are used in block carving, the spaces between the teeth and plate are to be perfectly filled with a finely compacted paste of body and rain water. The paste must be applied very moist, so as to exclude the air and run into all the spaces; then dried with cloth or bibulous paper, and compressed with the knife. If the lingual surface of Fig. 945. the plate is to be covered, this should be made rough by either etching the surface, or by soldering small clippings of platina over it, at the time the teeth are soldered. The natural rugae of the palate should be imitated in the thin layer of body Avhich is applied. The work must then be slowly and thoroughly dried, and the piece put on a slide with the coronal ends of the teeth downward, and im- bedded to the depth of an eighth of an inch in a thick batter of plas- CONTINUOUS-GUM WORK. 1021 ter and asbestos. But if the teeth are very securely soldered, it will be best to floAv the body Avith the plate resting, teeth upAvard, on the plaster and asbestos or sand model on which the soldering was done. The slide is then gradually introduced into the muffle, and sub- jected to a heat sufficiently high to fuse the compound—say, twenty- two hundred and fifty degrees. It is then Avithdrawn slowly, and completely cooled. Usually there will be cracks and flaws which need filling Avith paste. The outside rim is also to be turned down over the edge of the body with hammer and pliers, and any defects at this point filled up; then heat a second time, with the same care as at first. The piece, now ready for enamelling, should present a semi-vitri- fied appearance; if too highly glazed, it is too much done, and the enamel will not take so firm a hold; if too dull looking, it is not sufficiently baked, and will be deficient in strength. The enamel' must be applied moist, and is best put on with a brush; much plastering Avith a knife makes it apt to fly off in baking, and for the same reason it must be heated very gradually. The layer of enamel should be thin and irregular, the yelloAvish Avhite of the body show- ing more or less through it, so as to give the variations of tint ob- served in the natural gum. If a thick and even layer is applied, the result will be an unnatural uniform color, Avhich will destroy much of the peculiar beauty of this work. The greatest care is necessary, in applying the paste, to remove every particle from the parts of the teeth and plate Avhich are not to be covered, as it adheres with great tenacity and roughness, and disfigures these parts. Much experience is also necessary in deter- mining the exact heat necessary to develop the full beauty and strength of the work. Repeated heatings, either for the first making or for repairs, do not injure the plate or teeth, provided proper care is taken to heat and cool gradually; and provided, in case of repair, the piece is thoroughly cleansed in strong soda, to remove all trace of the buccal secretions. This work is peculiarly adapted to full lower dentures. The principles of construction are precisely the same, only the plate should be very heavy, and the extra band behind the six or eight front teeth very thick and strong. Many use it for partial cases;: for Avhich, however, it is not as Avell suited as for entire dentures.. The three distinguishing advantages of the continuous-gum work are its ready adaptability to every variety in shape of gum and arrangement of teeth, its extreme beauty, and its great cleanliness;: its three disadvantages are its Aveight, its liability to be broken by accident, and its comparative inapplicability to partial cases. 1022 MECHANICS—DENTAL PROSTHESIS. CHAPTER XIV. MOULDED PLATES OF PLASTIC MATERIALS. In the classification of operations for the Replacement of Teeth, given on pages 716 and 717, difference in the order of these operations was made the groundwork of a division of all base plates into tAvo classes: Swaged and Plastic In describing, up to the point of completion of the model, the operations common to both classes, the modifying requirements of each were duly considered. The special order and details of swaged Avork were then taken up, Avith incidental allusions to plastic work, by Avay of comparison or con- trast. Operations, materials, and apparatus peculiar to the latter will form the subjects of this and succeeding chapters. Plastic work includes all dental substitutes in which the base plate is brought into contact with the teeth and the model of parts to be fitted, whilst in a fluid, softened or plastic condition, then hardened, during continuance of this contact, either by the appli- cation or the withdrawal of heat. Plasticity, as thus used, is the property of being moulded, and has already been spoken of as an essential quality of impression materials. In them it is associated with other qualities especially fitting them for this particular use; so in plastic work, mere plasticity is of no avail, if other properties do not give to the material the qualities essential to a base plate. It must have strength and durability, and must be in harmony with the parts to which it is applied. This harmony implies that it shall not act injuriously upon the mouth, or receive injury from it; that it shall not, in form, color, taste, or smell, be repulsive to patients. It ought not, if possible, to be even objectionable; but tastes are so variable, that this contingency cannot be a positive ground for ex- clusion of an othenvise valuable material. As, in SAvaged Avork, there are four metals of which plates may be formed—gold, platinum, aluminium, and silver—in plastic work, there are five varieties of plastic material of which plates may be moulded: 1, Porcelain clay; 2, tin and its alloys; 3, sulphurated gum ; 4, celluloid and modifications ; 5, aluminium and its alloys; 6, electro-metallic. The first two have been longest in use; the third and fourth have become the most important in modern den- tistry ; the fifth and latest has yet to pass the ordeal of experience. The first is moulded by tools, not in flasks, as are the other four; it also requires intense heat to vitrify or harden it. The second is made plastic by fusion, requiring a flask, hot, to prevent cracking of teeth, and tight, to prevent escape of metal; these plates harden MOULDED PLATES OF PLASTIC MATERIALS. 1023 by cold. The third and fourth, less plastic, demand force in the act of moulding: they are hardened by heat; but the temperature to Avhich the teeth are subjected is less than in the other three. The fifth is made plastic by fusion ; but, though more plastic than the third, in its pure state it does not flow as readily as the second; its extreme lightness and sluggish flow necessitate peculiar apparatus in moulding; but some of these disadvantages have been oA^ercome by alloying it with other metals. The sixth is a process by which gold and silver are deposited upon the surface of the plaster model prepared for the purpose. Comparing them in respect of certain other properties—Aveight, durability, strength, and necessary thickness of plate; amount of change in shape, from contraction ; resistance to change by the action of the buccal fluids—vulcanite and celluloid are lightest: alu- minium, being thinner, is very nearly as light; porcelain, though a light substance, requires such bulk, that it is heavier than either: tin and its alloys are heaviest. Vulcanite plates, properly made, are strong, durable, and may be as thin as any, except aluminium; aluminium plates are thinnest and strongest; the durability of pure aluminium plates is still an open question; tin alloys are variable, some being tough and strong, others stiff and brittle, others soft and flexible; they have about the same bulk as gum, and the best are perhaps nearly or quite as durable. Porcelain plates contract very much ; aluminium much less, but still very considerably; tin alloys contract very slightly; gum has no contraction. Porcelain most perfectly resists the buccal secre- tions and substances taken into the mouth ; vulcanite nearly or quite as effectually; tin alloys undergo some change; aluminium is not changed by sulphur, as silver is, but will probably be found, in some mouths, to undergo slight change. To give uniformity of nomenclature, the four varieties of plastic Avork Avill be classed under four heads. 1. Ceramo-plastic, or porce- lain. 2. Metallo-plastic, including tin, cheoplastic metal, other tin alloys, aluminium, and gold alloy. 3. Vulcano-plastic, including caoutchouc, gutta-percha, and all vegetable substances, that by com- bination Avith sulphur, iodine, etc., have the property of hardening by heat, under the process knoAvn as " vulcanizing." 4. Celluloid, and its modification zylonite, Avhich are moulded by heat. CERAMO-PLASTIC WORK. Porcelain plates are remarkable for cleanliness, and, in the hands of a skilful Avorker in the ceramic art, may have great artistic beauty. 1024 MECHANICS--DENTAL PROSTHESIS. There are, however, several considerations that must prevent their extensive use. Like continuous-gum Avork, ceramic plates are best adapted to full sets. They are frail, occasionally breaking under the force of powerful mastication ; they will inevitably break, falling on any very hard surface. It is but just, however, to state that the feAv who make porcelain plates a specialty claim that they are no more liable to accident than other pieces; that the teeth of all, especially continuous-gum, are as apt to break as this work; and that a broken tooth or plate is more easily and quickly mended in porcelain-plate work than in any other. A second objection is the great shrinkage of any strong porcelain substance. Efforts to correct in the material itself this shrinkage, make it proportionately weak. Correction by enlargement of the model is not only troublesome, but it is uncertain ; the same is true of the correction by grinding with corundum wheels, which is very tedious, and cannot be exact. When base plates were made of ivory, and fitted to the mouth by carving, this imperfection of porcelain plates was not objected to, because the former fitted no better, if as well; but in contrast Avith the exact adaptation of other forms of plastic work, and of swaged plates, it becomes very manifest. There are many mouths in which a porcelain plate could not be retained at all; there are others which adapt themselves so readily to moderate inaccuracies, that such a plate is worn Avith entire satisfaction. A third objection is the necessity of constant practice, to keep up that skill in ceramic art which is essential to an artistic piece, and to insure uniformity of result by proper control of the furnace. This difficulty, however, can be met in the same way as in continu- ous-gum work. If the dentist will make the model, select and articulate the teeth, arrange them on a temporary plate Avith wax, to give the fulness of gum, and a sample tooth to shoAV its color, then pack securely, and send to any block carver or porcelain teeth manufacturer, he can have a porcelain plate made better, and Avith more certainty, than only an occasional practice will enable him to do for himself. If it is desired that the teeth and plate shall be carved at the same time, it will be sufficient to send correct model and articulation, with directions as to the style, color, etc., of the teeth. We think, hoAvever, that it will be safer for the dentist to select and arrange the teeth, as he can better judge Avhat is appropriate than one who does not see the patient. For details of construction, the reader is referred to other chap- ters. - Impression and model are made like any other work; articu- lating processes are the same as for other forms of plastic Avork; METALLO-PLASTIC WORK. 1025 grinding the teeth is very simple, as in continuous-gum work; en- largement of the "furnace model" and manipulation of the porce- lain mixture will be described in the chapter on Porcelain. CHAPTER XV. METALLO-PLASTIC WORK. The use of a fusible metal in the construction of base plates is by no means neAV ; but many of the metallic compounds suggested, or noAv used for this purpose, are of quite recent introduction. Ex- cept aluminium, none of them fuse above the melting point of tin, 442°. Pure tin is the oldest form of metallo-plastic base plate, and Avas used exclusively for the loAver jaw. It is objectionable on ac- count of its softness; even in a heavy lower rim, it is apt to bend, and for an upper plate it is wholly unsuited. In its resistance to chemical change in the mouth, it stands next to gold and platinum; is superior to silver, and probably to aluminium ; superior also, in this respect, to any of its OAvn alloys. The process of constructing a loAver plate of pure tin is the same as for any of the tin alloys. Tin may be made harder and more rigid by alloying Avith Gold, Silver, Copper, Antimony, Zinc, Lead, Bismuth, or Cadmium. Cop- per and lead make it unfit for the mouth; antimony, zinc, and bismuth make it brittle, unless used in very moderate proportion. Silver gives it hardness, also cadmium, without imparting the ob- jectionable properties named. Probably the best of all alloys for tin is cadmium. Closely resembling tin in its physical properties, it hardens it without making it too brittle, or imparting increased liability to the action of fluids of the mouth. The majority of tin alloys at present recommended for base plates contain cadmium, with some zinc, antimony or bismuth; they ought not to contain copper or lead. In absence of their formulas of composition, it is impossible to say that they Avill prove injurious or harmless in the mouth, or that they will undergo no change by time. Even if we kneAV the formulas, it would, in some cases, be impossible to speak positively on this point. The primary strength of any of these alloys can be easily detected; with rather more trouble, its fusion point and free flowing qualities may be learned. For all else, the safest rule is to use any or all of them "under protest," until, by personal observation, every one as- 65 1026 MECHANICS—DENTAL PROSTHESIS. certains for himself how far they are free from change, or keep their original strength after being worn. It may be thought that such distrust of the assertions of others is unprofessional. Possibly it may be; but what other course is open to any careful operator, in the face of such circulars as the one just received by the Avriter, in which a certain " rubber preparation " is recommended, as enabling the dentist to complete a set of teeth in " one hour after taking the impression." The sad truth is too notorious for concealment, that the inventors of dental "improvements' are like the discoverers of quack medicines—they magnify excellences, conceal defects, sub- stitute assertion for evidence, and claim a confidence in their inven- tions which should only be the slow growth of experience. Experiments in tin alloys, unlike those in vulcanite compounds, are easily made by any well informed dentist; he can have his favorite tin alloy, as he has his pet solder, both the result of his own experimenting. He can judge at once of certain properties; for others, he must wait the teachings of experience. If he prefers to use the labor of another, and buy an alloy which pleases him, but of which he really knows nothing, why should not full judgment upon this also be suspended until a jury of his patients have ren- dered their verdict. Cheoplastic, Wood's, Weston's and WatVs Metals.—The Cheoplastic Metal was patented by Dr. A. A. Blandy, in 1856, together with certain processes used in the construction of dental plates. The manipulations since so familiar in the working of vulcanite, were then as unknown as vulcanite itself. The peculiar merits of plastic work were at once recognized by many of the profession; and the Cheoplastic process would have passed into very general use, with such modifications as experience may have dictated, had it not been for the introduction of Hard Rubber. After some years' contest, the profession decided in favor of rubber. Dr. Blandy's departure from the States, in 1862, and the failure of the supply of his metal, led to a total disuse of the cheoplastic metal. The abuses of vulcanite, and the gross mismanagement of rubber patents, during their continuance, urged many advocates of plastic work to revert to various tin alloys, which are, in their principle of composition, and in the essential character of the processes employed, identical with Dr. Blandy's patents. The name chosen by him (signifying the making of plates by pouring a metal made plastic by heat) is equally applicable to all alloys of tin noAV used. The alloy of the cheoplastic metal was silver, with some bismuth, and a trace of antimony. The exact proportions are not known, but may be learned by reference to the patents. The alloy imparted no taste METALLO-PLASTIC WORK. 1027 Avbatever to the mouth; and its purity, so far as its capability of resisting the action of the secretions of the buccal cavity is con- cerned, was said to be equal to eighteen-carat gold. Its color became slightly darker after being worn some weeks, but could be restored by placing it in a strong solution of caustic potash. The cheoplastic metal was the pioneer of the numerous alloys of tin (stannum) which are noAV claiming the attention of the profes- sion. We have elsewhere spoken of the necessity of testing all such alloys in the crucible of " practice." We shall mention those of Drs. B. Wood, H. Weston, and George Watt. The first, because, next to the cheoplastic metal, it has been longest known to the pro- fession, particularly those alloys adapted to the filling of teeth. The last, because they are very strong, flow well and retain their color well. Of the composition of Dr. Weston's alloy, we know nothing be- yond an assurance that it contains no copper, antimony, zinc, or Fig. 946. lead. It may be better than any of its competitors closely resem- bling it; but, in ignorance of the formulae of any of them, we can only say Avhat, perhaps, if Ave knew these formulae, we might still say —submit to the test of experience that which seems to be the best. Dr. Wood's alloys are the result of an elaborate series of very careful experiments made some ten years ago. His plate alloys consist mainly, perhaps altogether, of tin and cadmium; they vary in fusibility, hardness, and rigidity, but are nearly, if not all, more 1028 MECHANICS—DENTAL PROSTHESIS. fusible than Weston's metal. Dr. Watt's metal is said to Avithstand the chemical action Avithin the mouth as Avell, if not better, than 18-carat gold, and to be strong, and to run sharp. Moulds may be made in almost any flask, but a special flask knoAvn as Watt's Moulding flask (Fig. 946), is better adapted to the use of this metal than the ordinary flask. The following instructions in connection with what remain to be given for vulcanite, will be a sufficient guide in the construction of plates made of Wood's, Weston's, Watt's, or any other stannic alloy. Teeth for rubber work are best suited for this with the folloAving precautions: First: Grind off the thin upper edge of gum teeth or sections ; the anterior band is useful in rubber, and does no harm; if of metal, it is apt to crack the block, and is unnecessary, as teeth are rather more firmly set in metal than in rubber ; hence, no metal should overlap the upper edge of the gum. Secondly : In jointing blocks, do it as squarely as possible; if merely the edges of gums touch, the slight contraction of the alloy may cause them to scale or break. If, however, from accident or necessity, this last kind of joint occurs, do as in soldering blocks to gold plate—place a thin piece of paper in the joint before securing it to the wax plate. Before drying the flasks, this slight space caused by the paper may be closed with plaster and soluble glass, to prevent metal from running in and making a metallic seam on the front of the block. Thirdly: Be careful to cover the pins with the wax which gives shape to the metal, so that in finishing up the latter they will not be exposed. Fig. 947 represents Weston's improved flask, which consists of tAvo rims without top or bottom, to permit rapid escape of moisture. It is much larger than the ordinary flasks, so as to allow room for the gate and reservoir posterior to the plate. It closes Avith tAvo small bolts with nuts, and stands on feet. It is very important to screAV the flask up well before pouring, that the weight of fluid metal may not separate the halves of the flask; the slightest space will allow much or all the metal to flow out. The plaster may be mixed with soapstone powder, pumice powder, or clean Avhite sand. Asbestos Avould prevent shrinkage, but its fibres would interfere Avith the free flowing of the batter. The same care in heating the flask is necessary as before stated, remembering that plaster confined in metal flasks takes longer to become dry. It is not safe to pour under less than three hours' drying; and this must never be done in direct contact Avith flame. Moisture is one of the products of combustion in all flame, and is largely absorbed by the plaster; hence plaster over flame can never METALLO-PLASTIC WORK. 1029 be made perfectly dry, unless contained in some box, say of sheet iron, excluding this vapor. Directions for heating, pouring, cooling off and finishing, are as folloAvs: All necessary trimming of the plaster is done before the Avax is removed, to prevent small pieces from falling in the matrix by the sides of the teeth. All of the wax is now removed, as the absorp- Fig. 947. tion of any considerable portions left in the matrix has a tendency to roughen the surface, and thus to prevent the metal from running as smoothly as it would otherwise do. After removing the wax, each half of the matrix may be held over the flame of a tallow candle, until a slight coating of lampblack forms on it. The two parts are now screAved firmly together. The flask may now be placed in a kitchen range or bake oven, 1030 MECHANICS—DENTAL PROSTHESIS. and exposed to a bread-baking heat, say from 300° to 400° Fahr., for from three to five hours, or until every particle of moisture is driven from it; then placed in an upright position, and the melted metal poured quickly into the matrix. If there is no ebullition, and the metal comes up into the vents freely, the piece will come from the matrix in a perfect condition. If it bubbles, it may be lightly tapped several times on some hard surface. When perfectly cold, the two parts of the matrix are separated, exposing one of the surfaces of the plate. When the process is properly Conducted from the beginning up to the point of pouring the metal, the piece will come from the matrix perfect in all its parts. But when the metal fails to Aoav freely around the teeth, and to cover perfectly the alveolar border and palatine arch, it is better to replace the removed half of the matrix; then, turning the gate down, heat it up ^to the melting- Fig. 948. point of the metal; place again in the sand-bath, and pour a second time. Attempts are sometimes made to patch the plate where the defects are small; but it will prove far more satisfactory in the end to pour it entirely anew. The matrix should become entirely cold before any attempt is made to remove the piece; otherwise there will be danger from the sudden exposure of warm teeth to the air. The plaster mixture is easily cut; dipping it in water will make it softer and more easily removed. If care has been used in shaping the wax plate, if the plaster has been kept free from air-bubbles, and if the joints between gum teeth or blocks have been nicely jointed and filled on their front edge, with the plaster moistened with soluble glass, the piece may be finished with little trouble. The gate and vents and irregular edges of the plate may be sawed off or removed with coarse files; fine-cut files become clogged with the metal. Scrapers (Fig. 948) may be METALLO-PLASTIC AVORK. 1031 employed for removing the roughness of surface; curved and rounded for the inner surface; flat, straight-edged, and pointed for outer surfaces or dental interstices. If carelessness in making the wax plate renders it necessary to cutaway much thickness of metal, the lathe burrs used for vulcanite will be found useful. In reduc- ing the thickness of plates, frequent use of calipers (Figs. 949, 950) Fig. 949. is necessary to avoid the accident of cutting through the plate. This is especially apt to happen in the use of lathe burrs. Fig. 950 should have the tips on one side pointed, as in Fig. 949, and they should be occasionally examined, to see if both sides come together alike. It will make the use of calipers more easy if the arms are kept permanently open by an elastic band, closing by pressure of the fingers at each trial of the plate. Graduated calipers are useful also for measuring the depth of articulating rims, the length Fig. 950. of teeth, etc., and are quite indispensable. This done, the surface is rubbed first with coarse and afterward with fine emery cloth, then washed in soap and water with a hard brush, afterward bur- nished and finished by polishing Avith chalk on a brush-Avheel; coarse Scotch stone may be used in place of the emery cloth. The upper 1032 MECHANICS—DENTAL PROSTHESIS. surface of its plate must neither be scraped nor polished, as the accuracy of the adaptation to the gums and palatine arch would be injured ; it should simply be washed well Avith a brush, using, per- haps, a little whiting. Every other part ought to be finished in the neatest and most perfect manner ; the piece is put in a strong solu- tion of caustic potash, boiled for two or three minutes, then Avashed in pure Avater, wiped dry, and finished with chalk and the brush wheel. Under no circumstances should the tin alloy be gilded. The least imperfection of the electrotype deposit, or the abrasion of any edge or prominence, or the removal of the coating by trimming the plate at any point, presents to the fluids of the mouth two metals having widely different galvanic relations; electric action is inevitable, causing decomposition of the plate, annoyance to the patient, and often ulceration of the gum. The tin alloys are quite harmless in the mouth. They all slightly tarnish, but the surface oxide seems to protect from further action, except where abraded by the masti- cation of food. The brilliant polish of new work cannot be kept so long as on a gold plate, because it is much softer; this, however, is of secondary importance, provided the metal is hard enough to resist wearing away under the necessary operations of use and of cleansing. In mounting a set of teeth for the lower jaw, the gate through which the metal is poured into the matrix should have two lateral branches, one on each side, to admit the metal more freely. The wax plate should also be thicker, to give sufficient strength and stability to the base; in other respects, the process is the same as that described for an upper set. For a partial lower set of molars and bicuspids on each side, the Avax plate should be extended behind the remaining front teeth; and two or three thicknesses should be applied here, giving stiffness sufficient to prevent breaking or bend- ing under the pressure of mastication. In making an antagonizing model for an entire set of teeth, the Avax plate for the loAver jaw is stiffened by the adjustment of a stout iron wire, bent to the curvature of the arch, and made fast to and partly bedded in the plate. The rim of wax is now arranged on the ridge, and after being properly trimmed, it is taken from the model. Upper and lower plates are then adjusted in the mouth; the articulation is obtained, and the articulator (Fig. 951) made in the manner described for a full set of teeth mounted on gold plate. Fig. 952 represents a double set of teeth arranged in wax upon a plaster articulation, ready to be placed upon their respective models preparatory to the formation of the remaining halves of the ma- METALLO-PLASTIC AVORK. 1033 trices. The cast base process is also applicable to partial sets of teeth; a single tooth, or several teeth situated in different parts of the arch, can be replaced, and retained so as to occasion no incon- venience or annoyance to the patient. The only precaution neces- sary to be observed in their construction, in addition to that of accuracy of adjustment and neatness of execution, is to thicken the projections of the wax plate between the remaining natural teeth sufficiently to give strength to the metal at these points. These portions, Avhen very narrow, should have twice the thickness of the other parts of the plate. Clasps cannot be used, as the metal itself has no elasticity, and gold clasps could not be connected to such plates. With this exception, the forms of partial pieces for this Avork are the same as for vulcanite Avork, hereafter described. After having adjusted the artificial teeth, and made them fast to the wax plate, the teeth of the model should be cut off before Fig. 951. Fig. 9"2. making the other half of the matrix, as it Avould be almost impos- sible to separate the two halves without breaking the teeth and other important parts. But if proper flasks are used, it is not necessary to cut off the teeth. In the same manner, as hereafter described for that work, the model may be set in the deep half of the flask until the edges of the teeth are nearly or quite level Avith the edge of the flask; the investing plaster supports the outside of the teeth, and prevents breakage on separating the flask. A piece from which one or more teeth have been broken can be easily repaired. If any portion of the tooth remain it is removed, and the metal that united it to the base filed away; a new tooth is selected, and ground until it corresponds with the adjoining teeth ; it is then put in place, and wax applied on the outside and inside of the tooth, smoothing it Avith the ay arm wa* knife evenly with the plate. The apex of a conical-shaped roll of wax, about an inch and a half in length, is united to the wax on the back part of the 1034 MECHANICS—DENTAL PROSTHESIS. tooth; the apex should be little more than an eighth, and the base half an inch in diameter, which latter should be half an inch above the edge of the teeth. A small stem of wax is united to the Avax on the outside of the tooth, with the free extremity half an inch above its edge. The one-half of the flask is now filled full of the plaster mixture, and the piece put immediately in it, with the base downward, first filling the irregularities of the plate with the plaster; the top or other half of the flask is then put on, and a thin mixture of the same composition is poured on top, filling the ring and cov- ering the edges of the teeth about a quarter of an inch. When hard, the projecting stems of wax are withdraAvn; the wax on each side of the tooth, and between it and the base, will be melted and ab- sorbed during the drying process. The matrix is dried in a stove or furnace, being careful hot to heat it up to the point of fusion of the plate. The alloy is then melted, and poured into it through the gate behind the tooth, and if it flows, filling the vent in front with- out bubbling, the piece will come from the matrix perfectly restored. When cold, the plaster mixture is broken from the teeth, and the metal around the new tooth finished according to the direction given for full sets. In repairing pieces, the heating of the matrix and metal must be done very carefully. If the matrix is too hot, the plate may fuse; if too cool and the melted metal too hot, porcelain may be cracked. In using tin alloys, in connection with platina pins, it should be remembered that the exposure of a single rhret to the action of the buccal fluids forms a galvanic battery, which will cause an unpleasant taste, and render the piece liable to slow decomposition; hence all pins must be carefully covered with metal, so as not to be exposed in the finishing processes. We have seen pieces made of Weston's alloy which, after cutting off the gate and vents, were ready for the emery-cloth and brush- wheels. This result can be uniformly secured by care in shaping the wax and proper attention to temperature in pouring. These alloys have a slight shrinkage, not sufficient to break blocks or chip the edges, if the directions above given are observed. The slight shrinkage may give these plates an advantage over vulcanite, in point of adaptation. Directions for repairs are the same as in other alloys. It is also recommended to mend a broken tooth by invest- ing as for gold soldering; then dry the piece, use muriate of zinc for a flux, and solder with blowpipe or soldering iron. After melt- ing one-half the pieces and disfiguring the half of the remainder, it will probably be concluded that the seemingly more tedious pro- cess is the shortest. Still, we do not object to trial of the blowpipe METALLO-PLASTIC \ATORK. 1035 and soldering iron; experience is the best of all teachers, perhaps, because she enforces her teachings by such hard blows. The strength of the Wood or Weston metal permits its use for partial pieces, and allows stays to be formed on the plate; but full clasps cannot be made, because alloys of this class are not suffi- ciently elastic. The form of such plates will be discussed in the next chapter. In preparing the above directions, Ave have discarded some innovations upon other processes, as being anything but im- provements ; such, for instance, as the recommendation to heat to 210°, or, " so that it can hardly be held in the hand," a flask con- taining teeth on to which a metal is to be suddenly poured at a temperature of 440°. This temperature may be quite sufficient, however, for some of Dr. Wood's alloys. The safest rule in all cases, except for repairs, is to heat up to the fusion point of the alloy. As an offset to this error, Ave notice a good suggestion for removing small remnants of wax by Avashing out with hot water. It has an advantage over the plan of alloAving the hot dry plaster to absorb the wax, in permitting examination of the pins and joints, and allowing closure of front joints Avith plaster; also, by enabling the mould to be thoroughly cleansed just before closing, it prevents the accidental retention of small particles of plaster, which may interfere Avith the Aoav of the metal. Aluminium Work.—This metal is, in nearly all works on chem- istry, called Aluminium, making it similar in termination to twenty- three other metallic bases discovered by modern science, and known by Latinized names ending in ium. None of these, however, have any practical value in the arts as metals, except cadmium, magne- sium, palladium, rhodium, and iridium. Sir Humphry Davy inferred, from his discovery of sodium and potassium, that alumina was the oxide of a metallic base. This conjectural metal, named Aluminium, was subsequently discovered by Wohler, but remained for more than tAventy years a mere chem- ical curiosity, until, in 1854, St. Clair Deville succeeded in manu- facturing it in large ingots by the action of sodium upon the chloride of aluminium; but the cost of metallic sodium made this an expensive process. He subsequently obtained it by the action of chloride of potassium upon the once rare mineral Cryolite—an alumino-fluoride of sodium, large deposits of which have been dis- covered in Greenland. All rocks, except limestones and some sandstones, contain alu- mina ; and it enters largely into the composition of all clay and slate rocks; hence, next to oxygen, which constitutes one-half of the globe, and silicon, Avhich forms one-fourth, alumina is the most 1036 MECHANICS—DENTAL PROSTHESIS. universally diffused of all metallic oxides, and aluminium is the most abundant of all metals. The vast beds of iron ore become insignificant compared Avith the ore beds of aluminium. As iron is noAV the most useful as Avell as the most abundant of all metals, it may not be unreasonable to anticipate the time Avhen the extent and variety of uses to which aluminium will one day be applied shall be proportioned to the vastness of its ore beds. The present use of aluminium, in dentistry and in the arts generally, bears a small proportion to its future use, when its properties shall become developed, the manner of working it better understood, its metal- lurgy simplified, and its relations to other metals ascertained by experiment. Its valuable qualities now knoAvn, and its history during the sixteen years just passed, go far to justify these expecta- tions. We shall give a brief summary of the present state of knowledge of aluminium. It is the lightest metal known except magnesium (excepting also, of course, sodium and potassium); its specific gravity is 2.56 for cast metal and 2.67 for hammered metal, about the weight of glass or porcelain. Its point of fusion is somewhere near 1000° Fahren- heit. It is malleable, laminable, and ductile in a high degree; has a hardness equal to silver, and excels it in point of tenacity; it is eight times better than iron as a conductor of electricity, being nearly equal to silver. Unlike silver, it Avholly resists the action of sulphur, also of nitric acid, unless it is boiling. Sulphuric acid does not affect it, nor do the vegetable acids, as citric, oxalic and tartaric. Its proper solvents are hydrochloric acid and chlorine. It is somewhat affected by the caustic alkalies, soda and potash; also, perhaps, by ammonia and quicklime. A solution of salt and vinegar is said to affect it, possibly due to a liberation of the chlo- rine in the salt. Its record of resistance to change by acid and alkali is a very fair one, and gives rise to the conjecture of possible impurity of metal, in explanation of the cases reported in which aluminium plates undergo change in the mouth. The conjecture is strengthened by the peculiarity of this change; it occurs in spots, seeming to indi- cate some local impurity or alloy, not by a general discoloration of the plate, such as we see on eighteen-carat gold, or silver, and on the stannic alloys. The subject of aluminium alloys in connection with the mouth and as solders is an open field of inquiry, and researches may some day be crowned with the discovery of an aluminium base plate equal in all respects to gold plate, with the peculiar advantage of its remarkable lightness. Present experience METALLO-PLASTIC WORK. 1037 is unfavorable to its power, in its pure state, of resisting the buccal secretions. Aluminium plates may be swaged, teeth backed and soldered by the bloAvpipe, just as in gold work. The best solder for this purpose is probably Dr. Starr's, containing seven parts aluminium to one of pure tin. Soldering is also done with a copper soldering tool simi- lar to that used by tinners; sometimes by the combined action of both. But the results as yet reached, in the experiment of soldering aluminium, do not justify us in recommending this form of plate ; hence Ave shall not give any description of the processes referred to, although esteeming them highly as experiments. The swaging of aluminium is done just as in case of gold or platinum, except that frequent annealing is necessary. The annealing must be done Avith extreme care, since the fusion point of the metal is so little above red heat that the slightest excess of heat will warp, blister, or melt the plate. For the purpose of annealing, it is suggested to coat the surface of plate Avith oil, and then pass it over the flame of a spirit lamp until the oil is burned off and the plate becomes white, Avhen it is instantly Avithdrawn. The extreme lightness of this metal permits the use of a plate two or three times the thickness of gold plate; hence alumin- ium plates may be the very strongest that can be made in any given case. The best method yet proposed for attaching the teeth to such a plate is by vulcanite, the details of which process will be given in the next chapter. It is a peculiarity of pure aluminium that vul- canized rubber adheres to it with great tenacity. A set of well- chosen block teeth, skilfully arranged, and secured to an accurately fitting aluminium plate, may safely be offered to the most fastidious and critical patient. It has, moreover, the great advantage that " sixty-minute " dentists will not care to imitate Avork which takes " several" hours to do even passably Avell. Another form of aluminium work, and that which has led to the present classification of this metal under the head of Plastic work, Avas the moulded or cast aluminium plate. No experiments, how- ever, seem to us to have been conducted with such care as those of the late Dr. James B. Bean, of Baltimore, who perished under an avalanche, in the summer of 1870, Avhile ascending Mont Blanc; and his process Avas not only a difficult one to pursue, but was very uncertain in its result; hence the use of aluminium is not at the present time attempted except in the form of swaged plates to Avhich the teeth are connected by vulcanized rubber, and which is referred to in the article on Vulcanite. The use of aluminium in dentistry is of comparatively recent origin, the properties of the metal undeveloped, and its most appro- 1038 MECHANICS—DENTAL PROSTHESIS. priate manipulations as yet undetermined. Although experiments thus far indicate a want of durability, they reveal properties Avhich should stimulate to reneAved effort in overcoming acknowledged difficulties. Taking lesson from the injury which the cheapness and facility of vulcanite have inflicted upon prosthetic dentistry, we may possibly find in aluminium a dental base possessed of an unsurpassed combination of excellences; requiring, hoAvever, for their development an amount of time, care and skill that will exclude it from the practice of those who are doing such discredit to their vocation. We should regard this exclusion as one of its highest recommendations to the notice of all Avho seek, by the ex- cellence of their work, to do honor to their profession. Aluminium Cast Base.—Dr. C. C. Carroll uses a prepared form of aluminium which he describes as being first made pure to prevent disintegration, and then alloyed with a small per cent, of noble metals that expand in cooling, and thus compensate the contraction of the aluminium. He describes his method as follows :* " The contraction of the metal is reduced to the one-tenth part of a line, or the one-hun- dred-and-twentieth part of an inch, practically nil, enabling us to cast directly upon the teeth without a fracture. The difficulty of making a sharp cast of aluminium by virtue of its low specific gravity is overcome by the use of our pneumatic crucible, which enables us to force the molten aluminium into every part of the matrix, pro- ducing a perfect cast of the model. " We take an impression for this aluminium cast work as we would for any other work; then from this impression make a model of plaster-of-Paris, three parts, and of fine sand or marble dust, one part. Now we proceed very much as in rubber work. For tempo- rary base plates we take common paraffine wax and roll it down to about twenty-three standard gold plate gauge. " Fig. 1 shows the temporary base plate on the model, and invested in the flask with a section of flask and investing material cut away. a b is the middle gate ; c c, gates from the heel to the middle gate; d d, perpendicular gate; ef, the flange on base plate; h, base plate cut through to shoAV position on the model; v v, direction of metal in casting. " Fig. 2 shows a denture mounted and invested in counter model of flask for Base No. 2, one-half, with the wax removed, or for Base No. 1, when to be cast directly on the teeth. " Fig. 3. //represents the line of the flange after attachment with rubber or celluloid; a a, alveolar edge of plate. * Dental Register, June, 1888. METALLO-PLASTIC WORK. 1039 " There are various forms of mounting the common rubber teeth which we used in this aluminium cast work. The simplest of which is to cast a base plate Avith a flange or undercut for the purpose of attaching the teeth by pink rubber or celluloid. Upon this cast base plate we place wax and get the bite, which we place upon the articulator and mount in the usual manner for rubber work. Then attach the teeth to this aluminium base plate, making an artificial gum of pink rubber or celluloid. " Another form of mounting is to place plain teeth directly upon the temporary wax base plate, the same as in mounting for'rubber Fig. 953. work, Avith the exception that you space your teeth slightly to allow for this slight contraction. Along the alveolar border we make an undercut in the wax base plate, which undercut is reproduced in the aluminium plate permanently when cast, for the attachment of a gum-colored facing of pink rubber or celluloid. We now invest the tooth upon the model in the two-part perforated iron flask very much after the manner of investing for rubber work, Fig. 953. Cut gates from the centre part of the base plate to the pouring point of the flask, also pockets from the heel of the base plate into which the 1040 MECHANICS—DENTAL PROSTHESIS. air is forced through the matrix in the act of casting. The wax base plate is removed by washing out Avith hot water, and the flask placed in the upper chamber of the automatic gas (or gasoline) furnace to be dried out preparatory tp casting. You will observe that by this method of mounting we intend to cast the aluminium directly upon the teeth, attaching them firmly to the plate. " Gum section teeth can be used as well as plain teeth by exercising care in the method of mounting, taking the precaution of placing a thin slip of paper between the joints before investing. " When the matrix is dry, which will be shown if no moisture appears upon a mouth mirror held OArer the pouring point, we make the cast by use of an automatic crucible, which is placed in the Fig. 954. lower chamber of the furnace and contains the aluminium to be used in casting. The crucible is placed upon the flask, connecting the nipple of the pneumatic crucible with the pouring point of the flask, and by means of a rubber bulb the aluminium is forced into the matrix, making a very sharp and well-defined cast which is a perfect counterpart of the model (see Fig. 954). As soon as the piece has cooled, the flask is opened and the denture removed. The piece is then finished up by means of sand-paper and pumice METALLO-PLASTIC WORK. 1041 stone, using fine crocus for a finer polish. It takes and retains the appearance of the finest polished nickel plate. "All forms of dentures are readily made by means of this alu- minium cast Avork, including crowns, bridges, as Avell as partial and complete dentures. " While aluminium, by virtue of its extreme lightness, having a specific gravity of 2.5, is peculiarly fitted for upper dentures, it is better to have a heavier metal for lower dentures." Gold Alloy Cast Base.—Dr. G. F. Reese has recently devised an alloy composed of gold, one part; silver, tAvo parts; and tin, twenty parts, Avhich is manipulated by a special method, as a base for artificial dentures, and Avhich hrs met Avith consid- erable favor. A brief description of Dr. Reese's method is as folloAvs: A plaster model is first obtained from a plaster im- Fig. 955. pression of the mouth, and on the model a trial plate is made of gutta-percha, paraffine and Avax, or of modelling composition. Upon this trial plate the teeth are arranged and tried in the mouth. If satisfactory, the Avaxing about the teeth is completed, and the portion of the trial plate covering the palatine surface is removed to such a degree as to nearly expose the pins of the teeth, the wax under the gums being alloAved to remain. For the portion of the trial plate removed tAvo thicknesses of French floAver wax is substi- tuted, being carefully adapted to the model. Fig. 955 represents a case carried to the stage described, the dotted lines showing the edges of the thin Avax substitute portion, and B, 66 1012 MECHANICS--DENTAL PROSTHESIS. A, and C, prominences of wax attached to the posterior border and portion of the plate covering the maxillary tuberosities, A and C being designed for the escape of the alloy which is poured in at B. The case is then placed in a brass flask, which has been oiled, to render its removal from the investment easy. Fig. 956 represents the case in the flask ready for investment. To invest the case, each section is placed upon a plate of glass and plaster poured in until it is half filled, when the model, which has been saturated with water, is pressed into the plaster batter until the teeth and gums alone remain uncovered. The counterpart of the flask is then set on and sufficient plaster poured in until the prominences of wax No. 956. along the posterior border of the trial plate are slightly covered. After the plaster has set the upper section of the flask is removed and the surface of the plaster coated with shellac varnish. The section of the flask is then returned to its place and the investment completed by filling it up to the edges Avith additional plaster. When this has set the flask is placed in hot water, in order to sep- arate the sections easily. The wax is then removed and also the sections of the flask, by gently tapping them, and communication made from the outer surface with the cavities left by the wax prom- inences along the posterior border of the plate; or, if this is impos- sible, the vents and gates may be formed at the line of division METALLO-PLASTIC AVORK. 1013 betAveen the sections, as represented by the dotted lines in Figs. 957 and 958. Externally, the openings D E and F, Fig. 958, should be enlarged by reaming out the plaster, and varnished Avith shellac, to receive the cylinders, which latter are made of wax, rolled thin, and Avrapped around a cone-shaped piece of avoocI. These cylin- Fig. 957. ders are about one and a half inches long, and about half an inch in diameter at the base, tapering to an eighth of an inch at the apex. The pouring-cylinder is usually made someAvhat smaller at its base than the others, but some two inches long. Wax covers are attached, by a Avarm spatula, to the larger ends of the cylinders, so as to make them Avater tight. Fig. 957, d e t] shoAvs the cylinders 1044 MECHANICS—DENTAL PROSTHESIS. thus prepared and attached. In case the openings have been made through the plaster investment of the lower section, as represented in Fig. 957, then the upper section, Fig. 958, need not be united to it until the openings have been formed upon the line of division, when the sections mustbe joined before the cylinders can be attached. The case is then placed in a larger flask, Fig. 959, and invested as before, allowing the end of the pouring-cylinder to rest in the open- ing of the posterior border of the flask. In this investment there is no division of the sections after the parts of the flask are filled. The case is then dried in an oven, all of the wax being absorbed by the heated plaster, until all moisture is expelled. Several grades of the alloy are used by Dr. Reese, which melt at 600° to 700° F., but a Fig. 958. higher temperature is necessary before the metal is ready to pour. A temperature of 900° F., hoAvever, will cause rapid oxidation, Avhich, of course, should be avoided. An ordinary ladle may be em- ployed to melt the alloy, which is poured at the proper temperature into the opening of the flask and investment. When sufficient time has elapsed for the metal to cool, the flask is opened and the case presents the appearance represented by Fig. 960, when it is ready for finishing; the surplus alloy being removed by a saw, and the surface of the plate polished by pumice on a wheel and brush. To repair this Avork, all edges are scraped clean, and a space cut betAveen them of about one-eighth of an inch, which is filled with wax when the set is adjusted on the model. At each end of the METALLO-PLASTIC AA70RK. Fig. 959. 1045 Fig. 960. _ S 1046 ' MECHANICS—DENTAL PROSTHESIS. space tAvo cones of wax, each about one-eighth of an inch in di- ameter, are attached, standing perpendicularly to the palatal sur- face, and the whole invested with plaster to the depth of an inch. The two sections thus made are then separated, and the Avax is Avashed out by boiling in hot water. The external ends of the spaces left by the wax cones are then countersunk and a larger wax cone is inserted into each opening, the one to form a pouring-gate, and the other to act as a vent for surplus metal, this last being en- tirely covered by the plaster of the investment. The entire piece is then invested in a repair-flask, and the plaster thoroughly dried and heated up before the alloy is poured. Fig. 961 represents a dental mould designed by Dr. Hayford, for use in manipulating Weston's, Watt's, and Hayford's alloys and by Fig. 961. which it is claimed all imperfections caused by air bubbles or failure of the material to cast sharply are overcome. The metal is intro- duced with the flask partly open, and just before crystallization commences pressure is applied by means of the leArer, which closes the flask and forces the material into every portion of the mould, producing a sharp, perfect casting. Ward's Electro-Metallic Dentures.—A process of depositing, by the action of a battery, gold and silver directly upon the surface of the plaster model obtained from the impression of the mouth, and thus securing perfect adaptation, has recently been intioduced. The surface of the plaster model is prepared for the deposit of gold by coating it Avith plumbago. A definite thickness of gold is first de- posited on the plumbago-covered surface of the plaster model, and upon the gold a deposit is then made of silver, Avhich in like man- ner is then covered by another deposit of gold. The object of using silver as an intermediate layer betAveen the tAvo gold layers is to give strength to the plate, as all deposited metals are deficient in that respect, but silver less so than gold. Sometimes a thin silver VULCANO-PLASTIC AVORK. 1047 plate is swaged and the gold deposited upon it. Any desired thick- ness of gold can be deposited. If a rim is desired on the plate, the edges of the impression are cut doAvn and shaped accordingly before the model is poured. A plate so constructed must not be soldered, as the heat will anneal it to such a degree as to render it too pliable; hence, in a set of full metal, the teeth are attached by depositing gold about and around their pins, and the backings are portions of the deposited metals, and continuous Avith.the plate. This process is applicable for full and partial dentures of all metal finish, and for combination Avith rubber or celluloid, in which case a portion of the surface of the plate—that covering the alveolar ridge, is so formed as to present projections of the metal in the form of retain- ing-points for securing the vulcanite or celluloid Avhich attaches the teeth and forms the gum portion. In can also be applied to cap- ping crowns or cusps, and to removable bridge-Avork. VULCANO-PLASTIC WORK. Under this name are included all vegetable materials which have been, or may hereafter be, incorporated Avith sulphur, iodine, or other substances, for the development of those peculiar properties so Avell knoAvn in hard rubber. Inspissated linseed oil, amber, and gum copal, etc., have thus been experimented with, but with results thus far very unsatisfactory. They are here mentioned because it is by no means improbable that among the vegetable oils, resins, or gums, hoav knoAvn or to be discovered, there will be found one Avhich shall excel any yet known in those remarkable qualities imparted by sulphur to the resinous gums, gutta-percha, and caoutchouc. These differ from some other resins, in an opacity which follows them through their combinations with sulphur, making it impos- sible to obtain even a tolerable imitation of mucous membrane. Possibly some, as yet unknown, vulcanizable transparent resin may be found, carrying into its combinations enough of translucency to give that peculiar, life-like animation which now characterizes por- celain-gum colors alone. The history of caoutchouc teaches us that it is not impossible Ave may be in daily use of some such gum or resin. The only compounds of gum (more strictly, resin) and sul- phur that have been tried to any extent are corallite and vulcanite —the trade names of sulphuretted gutta-percha and sulphurated caoutchouc; also spoken of as sulphide of caoutchouc, because the neAV properties developed by the union are such as make it appear 1048 MECHANICS—DENTAL PROSTHESIS. to be a true chemical compound, and not, like the vermilion, etc., often incorporated Avith it, a mechanical mixture. Corallite.—Gutta-percha is the resinous exudation of a forest tree, the Isonandra Gutta, found extensively in Sumatra, Borneo, and the Malayan Peninsula. It Avas first brought to the notice of the Euro- peans by Dr. Montgomerie, of Bengal, in 1842, and in a feAV years attracted much attention, for those valuable properties Avhich have since made it so indispensable to the dentist. Twelve years ago experiments Avere made Avith it in combination with sulphur. Com- bined with half its weight of sulphur, and the compound then mixed Avith half its Aveight of vermilion, it formed a substance known as " Corallite," Avhich hardened under the same conditions as vulcanite, and of Avhich it promised to become a formidable rival. Unfortunately, one property of crude gutta-percha folloAved it into this combination—its tendency to become brittle. It is well knoAvn that sheets of this substance, Avhether the pure crude gum or that prepared for dental use by large admixture of foreign mat- ter, Avill become in time so brittle as to break almost at a touch. The vulcanized gutta-percha has the same property in less marked degree, but quite enough so to be fatal to its pretensions as a rival of vulcanite. Hence, corallite is no longer avowedly used, and even its name is almost forgotten. So persistent is this injurious property that it will affect any rubber compounds Avith Avhich it may be mixed. Any suspicion of the presence of gutta-percha should condemn sulphurated caoutchouc for dental use; this last- named gum, hoAvever, may be brittle and worthless, from admixture of other substances besides gutta-percha, as will be hereafter stated. VULCANITE. Caoutchouc, formerly knoAvn as elastic resin, and still more uni- versally knoAvn as India-rubber, Avas discovered by certain French Academicians, in Cayenne, in the year 1735. For many years its only knoAvn value Avas as an eraser of lead-pencil marks. Dr. Priestley, the distinguished discoverer of oxygen, in the preface to his work on Perspective, published in 1770, speaks of it as being excellently adapted to the purpose of Aviping from paper the marks of a black-lead pencil. It Avas still many years after this that it Avas confined to this use, and to the making of rubber shoes and bottles by South American and East Indian natives, A\dio formed them on clay moulds, from the fresh exudation of the Siphonia cahuca, Jatropa elastica, or Ficus elastica. Upon discovery of a solvent, its VULCANO-PLASTIC AVORK. 1049 uses Avere extended by bringing to bear the skilled labor of civili- zation ; but the fact of its becoming hard and rigid (yet not brittle) at 48° greatly limited its value. The principal solvents of caout- chouc are spirits of turpentine, bisulphide of carbon, benzol, ether, chloroform, naphtha, and the essential oils. Mr. Charles Goodyear's discovery of the remarkable effects of sul- phur in combination Avith caoutchouc has, since 1840, extended the application of this gum to an almost infinite variety of uses. In certain proportions and at certain temperatures, the sulphur does not much impair the remarkably elastic and flexible property of the native gum, but preserves it at low temperatures. Subsequent experiments led to the discovery of hard rubber, Avhich at first Avas made into combs, buttons, etc. It Avas thus used for a number of years before its application to dental purposes. This was first at- tempted as early as 1853. Mr. Bevan, a former employee of the Goodyear Company, Dr. Putnam, of NeAV York, and Dr. Mallett, of New Haven, Avere the first persons knoAvn to the writer as engaged in these experiments; possibly others Avere at the same time thus occupied. But owing to the exceedingly cumbrous vulcanizing apparatus (Dr. Putnam's Aveighing tAvelve hundred pounds), and the absence of that knoAvledge of the material and those appliances for its manipulation which experience alone could give, it made very slow progress for the first feAV years. It has been estimated that, in 1858, not more than three hundred dentists made any use of it; in 1863 it Avas conjectured by Dr. Franklin (thendental agent for the American Hard Rubber Company) that nearly, if not quite, three thousand employed it in their practice. At the present time, the patents restricting its use having expired, it is universally em- ployed. Hard rubber possesses, Avhen prepared in greatest perfection, many qualities Avhich tit it for use as a base plate. It is impervious to the buccal secretions and unchanged by them ; it has very considerable strength, great lightness, and when properly vulcanized, a high de- gree of elasticity. For some purposes in prosthetic dentistry it has no equal, and for some few it is indispensable; but the merit of superior adaptation is shared by other plastic substances, and for manv cases Ave have shown that the fit of an old-fashioned gold plate is much to be preferred. Dental vulcanite is usually incorporated Avith vermilion, to give it a color more generally acceptable than the dark broAvn of the simple sulphurated gum. But rubber, sulphur and vermilion are all opaque substances, and can never themselves, or by combination with other materials, be made to assume any resemblance to the 1050 MECHANICS—DENTAL PROSTHESIS. natural gum, Avhich porcelain alone has, thus far, been able to imi- tate. The incorporation of such substances for this purpose has no other effect than seriously to impair the strength of the material. Ex- periments in vulcanite are much more troublesome than those with stannic alloys, and probably few Avill take the trouble of making them. A common formula for the red vulcanite is caoutchouc, 48 parts; sulphur, 24 parts; vermilion, 36 parts. The formula for a dark brown vulcanite is caoutchouc, 48 parts; sulphur, 24 parts; this gives the strongest rubber. The formula for a jet black vulcan- ite is caoutchouc, 48 parts ; sulphur, 24 parts; ivory, or drop black, 48 parts. All colored rubbers are weakened by the addition of foreign matter, as English pink vulcanite, Avhich contains 48 per cent, of Avhite clay. White oxide of zinc in the proportion of 47 per cent., will give to vulcanite mixed with sulphur and vermilion, a deep pink color. The pink rubbers are so much weakened by the admixture of foreign matter, that care must be taken when they are used to produce a more natural color of the gum portion of a den- ture, to prevent the pins of the artificial teeth from being covered by such rubber. From an extended series of very careful experi- ments, by the late Prof. Wildman, we condense the folloAving state- ments : Caoutchouc two parts, sulphur one part, form a dark broAvn rubber, Avhich is the strongest of the vulcanites. Of all additions for modification of color, purest vermilion is best; it withstands heat, resists the action of sulphur, and has an intensity of color that soonest overcomes the darkness of the rubber. Being a sulphuret, it appears to have much less effect in weakening the texture of the sulphide of caoutchouc than an equal quantity of any other sub- stance ; yet it does diminish its strength in proportion to its use. English deep red and American Hard Rubber Company's red con- tain, by Aveight, two parts sulphide of caoutchouc and one part of vermilion. To the red and brown rubbers Avhite oxide of zinc or Avhite clay are added, in proportions varying from .20 to .57 per cent., to produce grayish-Avhite or pink rubber. Of these the best is Ash & Sons' pink rubber (S. P.), containing gum sulphur and vermilion, in same proportion as English deep red, with one-fourth this Aveight of white oxide of zinc added, to tone the deep color. Black rubber is made by adding to six parts of the brown sulphide from two to four parts of ivory black. In the selection of rubbers we unhesitatingly decide in favor of the brown vulcanite, not from any absurd idea of the injurious action of vermilion, Avhich we shall presently show to be perfectly harm- less, but because of its superior lightness and strength. We are not VULCANO-PLASTIC WORK. 1051 justified in sacrificing these valuable qualities for the sake of colors, Avhich not only have no greater aesthetic harmony with the mouth, but Avhich, by the brilliancy of their color attract attention to this defect. We use Avhite platinum and aluminium and yelloAV gold ; ivory, in old times, soon darkened,, and a tobacco cheAver will blacken any vulcanite plate. Why not, then, use a brown base plate from the beginning? If the vermilion rubber is used, let it, by all means, have its natural rich mahogany color, and not the glaring brilliancy Avith Avhich students delight to invest their specimens. This does very well in shoAV cases, and is eminently adapted to those captivating exhibitions of high art, where a lovely wax face opens and closes, revealing alternately an aching void and acheless grinders ; but in the mouth such bright colors are monstrous viola- tions of good taste. Vermilion, combined Avith rubber, cannot have any deleterious effect. In no case coming under our observation, have we seen a single symptom of local or constitutional action peculiar to vulcan- ite, except a sensation of heat; this Ave take to be an electric action, due to the fact that rubber, like sealing-wax, is a powerful negative electric. It is common to broAvn, red, pink and Avhite rubbers, and there is no remedy for it. It is not a constant symptom ; some pa- tients never feel it, some often, some occasionally—dependent, per- haps, upon the state of the electric element entering into the composition of vital force. Pure sulphuret of mercury is reckoned by Orfila as medicinally inert. Fumigation, by vaporizing the mercury, gives it a medicinal activity ; but this requires a temperature of 600° Fahrenheit. There- fore, for the development of constitutional symptoms, Ave must have the presence of arsenic or of red lead, as impurities of the sulphuret,. or the existence of free mercury. - First, as to the impurities of arsenic or red lead ; they are not found in pure vermilion. But even if present, such poisonous im- purity Avould be rendered harmless, because completely invested by an insoluble coating of India-rubber. A piece of vulcanite is im- pervious to the fluids of the mouth ; hence no part of its substance can be dissolved, and thus taken into the stomach. Any supposed medicinal action must, therefore, come from such minute particles as may possibly be Avorn off the lingual surface near the teeth, Avhere bread crusts or other hard particles of food impinge. White, gray and pink rubbers have so large a proportion of foreign, matter that they are easily abraded ; but in the pure red rubbers Ave have thus an almost infinitesimally small quantity of vulcanite taken into the stomach, one-third of Avhich is is inert vermilion, adulter- 1052 MECHANICS—DENTAL PROSTHESIS. ated (we will suppose) Avith three per cent, of arsenic, and this coated with a layer of rubber, Avhich, as previously stated, is insol- uble in water, alcohol, alkalies, or Aveak acids. This very minute trace of arsenic, even if divested of its envelope of rubber, Avould have a purely homoeopathic (and, by consequence, not poisonous) action; while, if encased in rubber, Avhich pervades every part of the material, it is absolutely inert. The same may be said of the less poisonous adulteration, red lead. Secondly, as to the mercury: the researches of Prof. C. Johns- ton, Avith the microscope, and Prof. Alfred Mayer, by chemical analysis, have failed to discover the slightest trace in samples of the best rubber used. Prof. Wildman found sulphur sublimed dur- ing vulcanization, but not the smallest trace of mercury. We have failed by any mechanical force to press out any globules, nor have Ave ever, in any manipulations, seen the slightest particle of this metal, or been able Avith the microscope to detect it upon the surface of any finished piece. This question of the presence of free mercury in the vulcanized material may perhaps require a more ex- tended series of experiments. It is the only agent that can possibly exert any deleterious action upon the system. That its presence is rare is proven ; that it is never found can be confidently asserted or denied, only after the extended observations recommended, the ob- servers, hoAvever, being careful not to confound the minute crystals of sulphur Avith globules of mercury, as some have done. Impressions for vulcanite Avork may be taken in plaster, Avax, gutta-percha, or modelling composition. The minute accuracy of plaster is not so essential in SAvaged Avork, since the very fine lines of the model are partly lost in the die, and could not be impressed on the plate; but in the vulcanite the faintest scratch is faithfully copied. The finest plaster must be used, and stirred until all air bubbles are removed. Although fine plaster will give the minutest lines, yet many prefer for all laboratory use a moderately coarse plaster, Avhich becomes hard and strong Avhen it sets ; and recom- mend in all cases admissible, plaster to be mixed as thick as it Avill Avork Avell, as thin-mixed plaster expands more than the thick- mixed. The fracture of the teeth of a plaster model may be pre- vented by inserting small pieces of Avire or brass pins in the im- pressions of such teeth before pouring the plaster. The absolute necessity of plaster impressions, in most partial cases where vul- canite is used, led the late Prof. Austen to devise the method, else- Avhere described, of taking impressions with gutta-percha cups. The advantage of a partial plaster impression thus obtained are: first, the exact shape of the outside of the teeth adjoining the space VULCANO-PLASTIC WORK. 1053 to be filled permits correct adjustment upon the model; secondly, the accurate shape of the inside of the molars and bicuspids, at the point Avhere Avax or modelling composition impressions drag, allows the stays or half-clasps to be closely fitted to the teeth. But it must be borne in mind that partial impressions in plaster and partial pieces in vulcanite demand for their success the utmost care and nicety of manipulation, a care Avhich the result Avill fully re- Avard. The absolute non-contraction of rubber may make Avax, modelling composition or gutta-percha in some cases a better impres- sion-material for full sets than plaster; in fact, we recommend plaster less often for full vulcanite plates than for base plates of any other material; Avhile in partial cases, for reasons just given, we prefer its most exclusive use. Vulcanite models require no particular shaping, except the ex- tension of the back part an inch or more, so that the model itself may serve as one-half of the articulator. This not only saves time and plaster, but gives more accurate results, since there is no trans- fer of the teeth and Avax plate to a iigav wax model. When the teeth are set in the Avax plate, the model is then separated with a saAV from the back part and placed in the flask. In double sets the back part of one model is smoothed, and the T-shaped groove cut and soaped, or covered Avith tin foil; the extension of the other model is left rough, and when the articulating plates are made, the models are set into their respective plates and the space at the back part filled Avith plaster. Partial models, containing a number of teeth require no other antagonizer than a model made from a simple impression in wax of the lower teeth, Avhich wdll fit the irregularities of the teeth of the upper model. Models for vulcanite may be coated Avith very dilute soluble glass (liquid silex), collo- dion, or tin foil. The late Prof. Austen, in 1858, sent his earliest experiments in rubber to Dr. Putnam, of NeAV York, to be vul- canized. The doctor wrote to knoAV " what the varnish was Avhich prevented the rubber from sticking." It Avas this soluble glass, used originally for the purpose of hardening the surface, to prevent injury from subsequent manipulations. Antagonizing plates are made by moulding a piece of gutta-percha over the model, kept very wet, to prevent adhesions. The central part should be not less than one-eighth of an inch thick, to give stiffness to the plate; the rim on the edge should be the exact length of the teeth required, and trimmed very carefully on the outside to give the proper fulness. The gutta-percha should be first worked into a ball, using from one to tAvo sheets, according to the size of the mouth ; then, pressing from the centre outAvard,the articulating 1054 MECHANICS—DENTAL PROSTHESIS. rim is formed at the same time that the material is turned over the ridge. It is quickly done, will not injure the most delicate ridge, and gives a plate as unyielding as any gold plate. In a loAver set, the rim may be stiffened with a piece of heavy iron or copper wire. In a full, or nearly full, upper set, the impress of the loAver teeth is to be received in a thin rim of Avax set on the gutta-percha. In a double set, the rims are trimmed till they touch uniformly, and then their relation marked by decided indentations across the line of contact. It is quite possible, Avith these gutta-percha plates, to take the articulation in every case with such absolute accuracy, that no trial of the teeth is necessary, nor any grinding of the teeth upon inserting them in the mouth. Metallic articulating plates swaged for the case are much more troublesome, and are no better. The usual method of making them of sheet gutta-percha, wax, or tin- foil can never give one that full confidence in his articulation Avhich enables him habitually to dispense with the trial of the piece after grinding. As vulcanite articulations are often taken, it would be as well simply to look at the mouth and guess at them. The modelling composition is an excellent material for a base plate in securing the articulation. After being softened and adapted to the cast, a roll of softened wax is placed upon the base plate, over the alveolar ridge, and shaped to the form of the arch. After being tried in the mouth, and added to or trimmed off, if too short or too long, the patient is directed to bite into the Avax. To prevent securing too long or too short a bite, one or more small blocks of soft pine Avood, about half an inch square and thicker than the re- quired bite, may be attached to the base plate with melted wax, and trimmed off until the necessary length is obtained. The Avax rim is then applied over the block and the proper articulation secured. For an entire denture, the articulating rims may be made of model- ling composition. Preparatory to the selection and grinding of teeth or blocks, the thick articulating plates must be removed, and the model covered with thin druggist's foil, and the space inside the ridge filled Avith a mass of soft wax, pressed out until it meets the probable inside line of the teeth to be fitted; this affords a much firmer support to the teeth during grinding than the usual practice of using the thin wax or gutta-percha matrix plate. The top and outside of the ridge are left covered Avith foil alone. When blocks like Fig. 963 are to be ground, passing over the front of ridge and surmounted Avith a rubber band, it- is essential that the block shall not quite touch the model at any point; this contact is prevented by placing VULCANO-PLASTIC WORK. 1055 between the foil plate and the model a strip of foil, having four, six, or eight thicknesses, as may be desired. But Avhen blocks such as Figs. 964 and 965, or teeth like Fig. 962, are ground resting directly upon the gum, Avith no rubber above or under the upper part of the gum, the tin foil is retained only during the process of grinding, so as to receive the paint used in accurate fitting of blocks; the foil is then removed and the plaster scraped, so as to slightly bed the front blocks or teeth in the natural gums. As the teeth are ground they should be attached to the wax mass Avith softened .or melted Avax. Fig. 962. Fig. 963. In grinding, the greatest care must be taken to make close joints ; but the fitting of the base requires none of the accuracy demanded in fitting gold plates, except Avhen the tooth is to be set directly upon the gum. It is, hoAvever, a mistake to suppose that a space of half an inch can, Avith perfect impunity be left beAveen the teeth and plate ; for vulcanite has a slight shrinkage on cooling. Unlike the shrinkage of metal, Avhich is irresistible, that of vulcanite is controlled by the matrix, so that it results in no change in the shape of the plate. This is proved by the closeness with Avhich it is seen to adhere to the model on opening the matrix. But it takes place in the direction of the thickness of the plate. If, therefore, a large bulk of material is interposed betAveen the teeth and ridge, it will shrink perceptibly either from the ridge or from the teeth ; in the first case impairing the fit of the piece, in the latter case loosening the hold of the rubber upon the tooth. Thick masses of vulcanite are also apt to be porous or honeycombed, owing to the evolution of sulphur. That sulphur is evolved in all cases is evident, from the staining of the plaster, blackening of the flasks and inside of the vulcanizer, and from the peculiar smell whenever there is escape of steam. We sometimes find it makes the rubber porous, espe- cially in loAver cases, in spite of every precaution taken to prevent it. It is not impossible that subsequent modifications in the time 1056 MECHANICS--DENTAL PROSTHESIS. and manner of vulcanizing may correct this and several other diffi- culties attendant on the hardening of thick masses of rubber; meanwhile, it is safer to avoid all unnecessary thickness of material. Many cases will permit the use of a stout aluminium Avire behind and under the pins, running along the incisors and bicuspids; if so, it will reduce the bulk of rubber and strengthen the piece. We often run a heavy platinum Avire or strip of doubled plate behind the entire arch in lower sets, to add to their Aveight and strengthen them; Avhen carefully done it makes a very strong piece, and re- moves the objection of lightness, which prevents the use of rubber in many lower cases. When the teeth or blocks are ground, and the joints and outside fitting carefully examined with a Coddington lens or some other strong magnifying glass, the next point is to make guiding grooves or holes in the plaster articulator beloAV the teeth ; then place the lead band and pour the temporary investing rim, as has been already described in the investment of teeth for gold plate prepara- tory to backing (see p. 970). If it is a partial piece, Ave often pre- fer to make this rim with a roll of gutta-percha, previously wetting the model to prevent its adhesion. An elastic band or string will hold this rim in place while the Avax is being removed and substi- tuted by the matrix plate, that is, the Avax plate Avhich is to be re- placed by the rubber. The use of the rim permits an examination of the blocks or teeth on the inner side, and the correction of any irregularity in the pins or in the inner edge of porcelain where it meets the rubber, also the grinding off of any point where a block may come unnecessarily near the model. A small roll of soft wax is then to be pressed against the pins and model, holding the rim firmly to prevent the slightest displacement of the blocks. A Avax matrix plate is then slightly softened and pressed gently over the face of the model and the other Avax up to the tooth. Be careful not to thin the wax unequally, and yet to press it into all the natural irregularities of the model, and to bring out the tracings of the rugae and the central raphe. If the first wax is trimmed so as to just clear the tips of the pins and have a slight curve Avhere it joins the model, very little trimming of the Avax plate will be neccessary Avhen blocks are used. This method also enables the operator to know exactly the thickness of the plate at all points. Gutta-percha does not ansAver so well as wax as it can- not so readily be smoothed where it joins the blocks. After using the wax knife around the edges, it is well to go over the surface with a strip of oiled buckskin. VULCANO-PLASTIC WORK. 1057 The Avax plate should vary in thickness from No. 14 to No. 18, gauge plate (Fig. 798), according to the depth of the palatine arch. Vulcanite cannot safely be reduced to the thinness of gold or alu- minium plates, or even of the best stannic alloys. The elasticity of the best made vulcanite is often thought to justify great thinness of plate, and this may be alloAved in some partial pieces; but in full sets, or Avhere many teeth lie grouped together, elasticity, with thin- ness such as permits bending of the plate, is very apt to cause open- ing of joints or breaking of blocks. Elasticity of vulcanite lessens the chance of injury from an accidental fall; but as an element of strength, it is principally valuable as improving its rigidity and tough- ness ; and the plate of all full sets should be thick enough to be unyielding under the force of mastication. Fig. 966 represents the ends of a suitable wax spatula or knife. In floAving Avax Avith the heated spatula around the teeth, after they have been accurately arranged upon the model, care must be taken to keep the joints free of it; and the Avax plate should be fashioned and smoothed with either the bloAvpipe flame, benzine applied on a piece of soft cloth, or by the repeated and careful application of the Avarm spatula. The Avax plate should be as perfect a counterpart of the vulcanite plate as it is possible to make it. Fig. 967 represents a set of carving instruments, designed by Dr. W. W. Evans, for modelling Avax in vulcanite, zylonite and celluloid work. When the inside wax plate has been completely finished, the out- side plaster rim is removed, having provided for its easy removal by a break or section opposite the incisors. Again examine all joints Avith the glass, to see that they have not been accidentally opened; then apply one or more strips of wax to give the required form of edge, outside the ridge and aboAre the blocks. Plain or gum teeth or blocks, resting directly on the gum, must, of course, have no wax in front of incisors, canines, and first or even second bicuspids; in all such cases be careful, just before investing in the flask, to see that the teeth set closely down upon the model. Vulcanite blocks have a shoulder designed to receive the margin of the external rubber band; Avhen the blocks have been chosen Avith such care that no grinding of the upper edge is necessary, this gives the best finish. But it often happens that the exigencies of the case require 67 Fig. 966 \ \ ( 1058 MECHANICS--DENTAL PROSTHESIS. Fig. 1 "1 if ■ thinning or shortening of the blocks; a thin edge of wax should then slightly overlap the blocks. If the porcelain edge has sufficient thick- ness, it is sometimes a good plan to bevel it; the rubber may then be fin- ished continuously with the porcelain, and yet have a retaining edge. It is Avell to pass a very fine corundum slab over the gum just before placing the Avax rim ; it removes accidental rough- ness and makes the finishing process easier. Superfluous wax should be avoided outside as well as inside; but every undercut must be filled, else there will be danger of breaking thin or prominent ridges in separating the ma- trix. Outside surplus is more easily removed than inside; hence there is no objection in running the wax further up on the ridge than the finished plate; but unnecessary thickness is to be avoided, for reasons before given. If the original model has been ex- tended for articulation, carefully remove the plate and saAV off this portion of the model, and trim so as to fit the half flask in Avhich it is to be set. This trimming done, replace the plate, and fasten it around the edges with a hot AArax knife. It it now ready for the vul- canizing flask. All forms of teeth may be used Avith the vulcanite base, and, unlike most other work, may be used again and again. Continuous-gum teeth can be strongly and handsomely arranged, provided the patient shows but little of the tooth; and also where celluloid is used in connection with vulcanite. Single teeth, plain or gum, require either to be backed with gold strips and yi I jj \\ U soldered, or simply to have the pins ™ lengthened. For this purpose heavy platina Avire, say No. 20, should be cut I I ■ II I 1 IF VULCANO-PLASTIC AVORK. 1059 into lengths from one-fourth to three-fourths of an inch long, set between the pins in the required direction and soldered Avith pure gold. Plate teeth backed with a narroAV platina strip, similar to Fig. 968, may also be used, and are required in certain cases that will not admit of thick vulcanite teeth. The projecting tang strengthens the rubber in case of isolated teeth, and may be ser- rated Avith a file; but a pair of forceps with serrated beaks, may do this better and more quickly than the file. Occasionally some one or more under teeth strike so closely against the gum as almost to touch ; if rubber is used in such cases, these teeth must be plate teeth, with the usual soldered gold backing, having a serrated ex- tension into the rubber. The assortment of vulcanite teeth now offered to the profession is, in variety of color, size, and shape, such as to meet almost every possible case. In fact, we doubt if the manufacturers' aesthetic skill in making is not sometimes in advance of the dentist's aesthetic Fig. 968. Fig. 969. taste in selecting. Certainly the stiff uniformity and monotonous expression which so frequently meet the eye is an injustice to the present high development of the dento-ceramic art. In the next chapter we shall illustrate by wood-cuts, kindly lent to us by the S. S. White Co., some of the delicate forms which so exactly imitate Nature. Figs. 962, 963, 964, 965, 968 and 969 will give a correct idea of the special form and shape of the ping of vulcanite teeth, as at present manufactured. Vulcanizers.—A sixteen-horse-poAver boiler, communicating by twenty feet of pipe Avith a thirty-inch cubical steam chest, Avas the vulcanizer of 1857. The first one which was at all practicable as an office fixture, Avas a two-chambered affair, of cast iron, as large as a soda fountain re- servoir, heated by a coal stove. Successive improvements have since been made, and the vulcanizer of to-day is a very different thing from the huge, clumsy affair from Avhich it originated. The proper working of the vulcanizer and the satisfaction with which it is used, depend, in a great measure, upon the perfection of the workmanship put upon it; and a saving of a dollar or two in first cost, coupled Avith the possession of a poorly-made machine, will prove an expensive investment in the long run. 1060 MECHANICS—DENTAL PROSTHESIS. Copper is now almost universally employed as the material from Avhich the boiler, or body of the vulcanizer is made; a ring of brass being brazed to the edge, to form the packing joint, and the attach- ment for the cover. The flexibility of these materials render itim- Fig. 971. portant that the cover fastening should support the whole circum- ference of the edge of the boiler and bring the strain uniformly upon it, in order to preserve the truth of the face of the packing joint. If the strain is brought to bear upon the cir- cumference of the joint at intervals, as Avhen bolt or clamp fastenings are used, the result is that the boiler gradually yields to the strains at the points Avhere it is unsupported, the joint is drawn out of true, and in a short time the vulcanizer is leaky and comparatively Avorthless. For this reason, the screw-thread fastening has proved satisfactory. The Whitney Vulcanizer, Fig. 970, has a very simple fastening, the cover screwing directly on to the pot. Though the joint is not absolutely steam tight, the vulcanizer is capable of doing good Avork. It is closed by two Avrenches, Fig. 970, b and c. The bed plate and Avrench, Fig. 970, d and e, are pre- VULCANO-PLASTIC AVORK. 1061 ferable where attachment to a stationary bench can be had. The mistake is often made of oiling the screAV of this vulcanizer fasten- ing. The oil Avill burn on, causing the cover to stick, and sometimes become almost immovable. A very little black lead, very seldom applied, will keep the packing joint and thread in the best condition. The error is more frequently made of doing too much rather than too little, in this direction. Fig. 972. The Hayes Vulcanizer, Fig. 971, has a cover which is placed upon the packing joint, and is secured by a screw-collar which screws over the edge of the boiler, three set-screws in which bear upon the cover to make the joint steam-tight. This fastening, though more com- 1062 MECHANICS—DENTAL PROSTHESIS. plicated than the " Whitney," has the merit of obviating any sliding movement on the packing in tightening the joint, thus increasing the durability of the packing, and of being absolutely steam-tight. To prevent the packing from sticking to the edge of the boiler, it is occasionally dusted with pulverized soapstone. The Hays " Iron Clad " Vulcanizer resembles the one just de- scribed. The copper boiler, however, is covered by a shell of malle- able iron, Avhich greatly increases the strength. By a cold-Avater test, these vulcanizers have been found to stand a pressure of 800 pounds to the inch, Avithout injury. They are very strong, and we believe there is no instance on record of the explosion of a vulcanizer of this description. The Snowden & CoAvman Vulcanizer, Fig. 972, recently intro- duced, and an excellent apparatus, has a fastening similar to the Fig. 973. Fig. 974. Hayes. The collar has lugs upon its interior, hoAvever, engaging Avith others upon the boiler, thus dispensing Avith the screw thread. The Edson Vulcanizer, Fig. 973, and the Woodard Vulcanizer, Fig. 974, are so made that the flasks can be closed after they are put in the vulcanizer and while steam is rising. In the Edson Vulcan- izer this is done by means of a screw. In the Woodard a steam cylinder and piston form part of the vulcanizer top, and the flasks 49 VULCANO-PLASTIC WORK. 1063 are closed by the rising pressure of the steam operating upon the piston. These vulcanizers may also be used for moulding celluloid plates. Fig. 975 represents the Mann Vulcanizer. The lid, instead of being screwed on to the boiler, rests on a shoulder formed on the casting, and is secured by a heavy steel clamping-bar and screw- Fig. 975. Fig. 976. bolt. One end of the bar is hinged to the side of the boiler, the other end being slotted to receive the screAA'-bolt, which is hinged to the other side of the boiler. Rubber packing between the lid and the shoulder on which it rests makes the joint steam-tight. The lid is removed by unscreAving the nut of the screw-bolt a turn or two, when the bolt drops out of the slot and the bar is turned back, leavdng the lid free to be removed. This method, while it gives as perfect a fastening as the usual plan, affords very much greater 1064 MECHANICS—DENTAL PROSTHESIS. facility for opening and closing the boiler. Should the lid stick by reason of the packing becoming chilled (a common occurrence Avith all vulcanizers), it is easily pried off wdth very much less trouble than is required when the top screws on. Another advantage is the bail, which greatly facilitates the hand- ling of the vulcanizer, especially when hot. Thus, the boiler can be opened for the removal of one case and the placing of another. The nut of the clamping-bolt is loosened a little at a time, allowing the steam to escape gradually until the bolt is released, when the bar can be thrown back and the top of the boiler raised. The bail is also useful in removing the boiler from the jacket, in tightening or loosening the screw-bolt when closing or opening the boiler, and at all times when the boiler is to be lifted. When not in use it is readily removed. Fig. 977. Fig. 976 represents a steam gauge, to Avhich is connected a con- densing-chamber, with pipes so arranged as to form a trap. Above this trap is placed a safety-disk attachment. This gauge can be placed on any of the modern vulcanizers hav- 999999999999� VULCANO-PLASTIC WORK 1065 ing a bloAv-off or safety attachment, by simply removing the cap of same and screAving on the gauge. The " New Mode Heater," Fig. 977, invented by Dr. John S. Campbell, presents many points of difference when compared with other vulcanizers. It is made of phosphor-bronze, in a single cast- ing, Avith two chambers, the one in which the flask is placed being surrounded by an outer steam-chamber. It has screws for closing the flask as it is being heated, and is adapted to working celluloid as well as for vulcanizing rubber. Steam may be admitted to the vulcanizing chamber or not, as may be desired, and either " wet" or " dry " heat used. The use of the New Mode Heater, it is claimed, will prevent the rubber, Avhen being vulcanized, from shrinking from the teeth, and also permit of the use of plain teeth with rubber for the base and celluloid for the gum, a form of Avork to which the name of " NeAV Mode Continuous Gum " has been given by Dr. Campbell, the inventor (see Celluloid). Fig. 978 represents a transverse vertical section of Dr. Frederick W. Seabury's improved vulcanizer and celluloid press, combined in one apparatus, Avhich, it is claimed, accomplishes results never before attained in the manipulation of both rubber and celluloid, and in less than half the time usually required, and a perfect success assured every time. With this apparatus, cases can be removed from the oven and others inserted at any time during the process of vulcanization, Avith a delay not to exceed five minutes, Avhich is a great saving of time, especially Avith repair work. The draAving also represents the improved flask used in this apparatus for the purpose of uniting artificial teeth to artificial gums under pressure, Avhich is pro\dded Avith guide and locking pins, the former inclined at such an angle that Avhen the upper part of the flask is forced doAvn to im- bed the teeth into the gums it Avill be moving at such an angle as to alloAV the projecting alveolar ridge to reach its final position Avith- out breaking the plaster investment; these guide-pins can also be quickly moved from the flask by a partial rotation of the pin. The locking-pins are so placed that the upper part of the flask is forced on the loAver part; the lock-pins may be forced into place and thereby lock the flask. The cover is secured by dovetail lock-pins, and can be easily removed. In the draAving of the apparatus No. 1, A represents the holloAV body of the vulcanizer, which is sup- ported on the legs a. Within this body is placed the boiler B, Avhich is formed Avith the central inverted truncated conical flue C. The boiler and flue are supported by the tubes d, Avhich are con- nected at one end to the top of the boiler and at the other end to the chamber d3. 1066 MECHANICS—DENTAL PROSTHESIS. D designates the oven, the loAver end or base of which extends somewhat downward into the upper end of the flue C. The upper end of the oven is formed with lateral flanges d1, which rest upon the top of the case or body A, and thus support the oven in position, and also form the top of the vulcanizer. Fig. 978. E designates the pressure-cover of the oven, which is secured in position by bolts as shown. e e designate presser-screws, which work through square threaded sockets in the cover and press upon the flask F, in the oven, sup- ported upon the disk m. E1 designates two lids, Avhich are pivoted upon the cover in such VULCANO-PLASTIC WORK. 1067 manner as to be readily removed, and by uncovering apertures in the cover permit visual access to the interior of the oven. G designates a valve, Avhich is situated in the flange d1 of the oven, so as to close the channel d2, leading from the pipe d to the interior of the oven. H designates a spout; the outer end of it is tightly closed by the cap h, which leads into the tube I, entering the chamber d3 from above. The purpose of this spout is to convey water to the boiler B. i designates a pop safety-valve, Avhich is seated on the upper end of the tube I. J designates a steam-gauge connected by the siphon cock j to the chamber d3, into Avhich the tube d opens. K designates a test-cock communicating with the chamber d3, and b designates a similar cock communicating Avith the boiler B, on the Avater level. In using this vulcanizer a gas or gasoline burner is set beneath the boiler B, and the valve G is closed; but the test-cock is not closed until the escaping steam shows that all the air is out of the boiler. The heat from the burner will ascend through the flue C, and Avill act directly upon the bottom and sides of the oven, thus heating the oven and water Avhich has been previously placed in the boiler at the same time or separately. No. 2 illustrates a vertical section of the solid cover which is used at all times, except Avhen closing the flask, and occupies the same position on the vulcanizer as the pressure-cover E. It is provided with a very sensitive thermometer, immersed in a mercury bath d, Avhich projects into the oven D, and a test-cock v, used to let the air out of the oven before vulcanizing, and to blow the steam out through after vulcanizing. The bar Avrench is to be used on the cover bolts only, and must never be used on the presser-screAvs e e, for Avhich the T wrench is provided. Figs. 979 and 980 represent Dr. W. W. Evans' Ncav Vulcanizer and Celluloid Apparatus combined, Avhich is claimed to possess superior qualities for vulcanizing rubber and moulding celluloid and zylonite. Fig. 980 sIioavs a front eleATation with top attached and tools needed in the Avorking of this apparatus. Fig. 979 illustrates a transverse vertical section with one flask in position. A is a light casing, B the boiler, composed of two separate cups b b, united concentrically by screws b1 to form a water and steam space. The bottom of the boiler A is partly concave, to facili- tate ebullition and keep the steam in a state of agitation. D illus- 1068 MECHANICS—DENTAL PROSTHESIS. trates the oven composed of the inner cups b, having a cover. C is an inlet for steam, d, through the cup b, from the boiler, and an exit for steam through the cover d2, both openings being controlled by valves d1 and d3. E E represent the bolts with spherical heads at c, the point of contact with the cover C, which has a correspond- ing socket to receive it, thus making a steam-tight joint. The top of the head c2 is made to fit the T wrench, that also fits the different valves. To gain more pressure than is usually required, an addi- tional sexangular portion c1 has been made, whereby any amount of pressure can be exerted. The lower portion of the bolt is threaded for one-half its distance, and screws into or through the platen F, Fig. 979. Fig. 980. Avhich is draAvn toward the top by turning the bolts to the right, thus closing the flasks G with facility, and Avithout any strain upon the boiler, f is the thermometer, on either side of Avhich are the valves, one connecting the boiler with the oven; the other a conical safety valve, so arranged that the steam in the boiler can never go higher than the point at Avhich the safety valve is set. I is a handle to remove the top. Two large flasks may be used at a time, and it is claimed that it will readily stand from 250 to 300 pounds pressure. It is also claimed that rubber vulcanized in this apparatus is much more elastic, denser and tougher, and retains its color better than by other processes, and that it will not shrink from the teeth, and VULCANO-PLASTIC AVORK. 1069 can be vulcanized in thicker masses without becoming porous. For celluloid and zylonite, better results, shorter time of moulding (one hour and a half) and no lost steam from the boiler, are claimed. Fig. 981 represents Dr. F. W. Seabury's Dry-Steam Vulcanizer. It consists of a boiler, Avith a steam-gauge above, and a plug in the Fig. 981. top through which to supply Avater, connected by a globe valve to an oven, or vulcanizing chamber, Avhich has a capacity for three flasks. The bloAv-off cock is in the centre of the cover. An axiom of rubber manufacturers is that the drier the steam, the denser, tougher, and purer color the product will be. The advantages claimed are : Saving in rubber—the plates being sufficiently strong when made half as thick as they are required to be now. Saving in time—the plates are vulcanized and finished in less than half the time now consumed. 1070 MECHANICS—DENTAL PROSTHESIS. During the process of vulcanizing, cases may be removed from the oven and others inserted, with a delay not to exceed fhTe minutes. The flasks are in a dry, clean oven; the plaster not being immersed in water, remains intact. The plates are thereby prevented from warping, and therefore fit perfectly. The essential thing when vul- canizing is to have instantly, and retain, a pressure equivalent to the temperature. To insure this, a steam-gauge is provided. The mercurial thermometer has been almost universally employed to indicate the temperature of the vulcanizer. It is a simple and convenient device, and when protected from the action of steam upon the glass bulb, by immersing it in the " Mercury Bath " (the invention of the late Dr. Geo. E. Hayes), it has a fair durability. If accidentally broken, it can easily be replaced at a small expense. It must be remembered, however, that it only indicates the temper- ature of its bulb, and the parts immediately surrounding it, which may be different from that of the interior of the vulcanizer If a thermometer and steam-gauge are attached to the same vulcanizer, a discrepancy of as much as twenty degrees will be found at times in their indications, varying with the amount of air included in the vulcanizer in closing it. This statement is proved by the fact that when the air is expelled by blowing off a little steam, the gauge and thermometer will always agree. The uncertainty as to the results attained in different Arulcaniza- tions is thus accounted for. To obtain uniformity the air must be expelled from the vulcanizer. If there is no cock for letting off steam, the vulcanizer should only be closed after the water in it is boiling; the cover being placed loosely upon it, and allowed to remain so until steam issues freely from under it. The joint should 4hen be tightened as expeditiously as possible. There being now an atmosphere of pure steam above the water in the vulcanizer, the heat will be equal in all parts of it, and the indications of the thermometer will be correct. Care should be taken that the mercury bath has enough mercury in it to insure contact with the bulb of the thermometer; an air space between the bulb and vulcanizer cover will be as fatal to cor- rect indications as in the former case. A steam-gauge Avould be a very desirable indicator of the tem- perature, if it Avere not for its first cost, and the annoyance caused by the necessity for its connection to and removal from the vulcan- izer each time it is used. The vulcanizer is usually heated by either gas, alcohol, or kero- sene. Gas, if used in a burner which will mix the proper quantity VULCANO-PLASTIC WORK. 1071 of air Avith it before burning, is the most convenient, cleanest, and probably the cheapest fuel for the purpose. The flame should be a clear blue, with no streaks of yellow. A yellow flame results from an insufficient mixture of air, and makes smoke, soot, and a bad smell, from the production of acetylene. The use of gas also admits of the employment of the gas regulator (Fig. 982), an attachment Avhich automatically keeps the temperature of the vulcanizer at the exact point required. The steam pressure acts upon a valve to control the flow of gas to the burner, lessening the flow as the pressure rises, and keeping it at the point for which it is set. It is not liable to get out of order, and with it the supervision of the Fig. 982. dentist over the vulcanizing process is not required; and if the time cut-off is also used, the dentist is at liberty to go to his patients in the operating room, Avithout the necessity of giving a thought to the vulcanizer, knoAving that the temperature will be kept exactly right, and that the gas will be turned off at the right time. The results Avill thus be uniform; much more so than is possible with the use of the thermometer, as the regulator, operating by steam pressure, is more sensitive and exact than the thermometer can possibly be. After gas, the alcohol flame is preferable for vulcan- 1072 MECHANICS—DENTAL PROSTHESIS. izing purposes. It is clean and inoffensive. Many use the kerosene stove, but taking into account its smoke and smell, it may be doubted whether the economy secured by its use is not dearly bought. The folloAving tables, carefully collected from experiments of the French Academy, the Franklin Institute, Ure, Dalton, and others, will serve as a guide in the use of either the steam-gauge or the mercurial thermometer: No. 1. No. 2. Pressure per Square Inch. Temperature. Pounds. Temperature. Inches of Atmos- Pounds Scale Differences. Mercury. pheres. Avoirdupois. Fahrenheit. 30 1 15 212° 38° 25° 19° 15° 12° 11° 10° 10° 8° 63 300° 60 2 30 250° 73 310° 90 3 45 275° i 80 315° 120 4 60 294° 87 320° 150 5 75 309° 95 325° 180 6 90 321° 102 330° 210 7 105 332° 110 335° 240 8 120 342° 117 340° 270 9 135 352° 124 345° 300 10 150 360° 131 350° 14° 360 12 180 374° 13° 11° 11° 10° 9° 8° 420 14 210 387° 480 16 240 398° 540 18 270 409° 600 20 300 419° 660 22 330 428° 720 24 360 436° These tables shoAV the increase of steam pressure with the tem- perature up to a point much higher than the dental vulcanizer should ever be called upon to bear. The second table is prepared espe- cially to shoAV the pressure due to the temperature at different vulcan- izing points, and attention is especially called to the rapid increase of pressure Avith equal increments of heat as the temperature rises. The last column in Table No. 1 shoAvs the additional temperature required for equal increments of pressure, and it will be seen that Avhile it requires 38° to raise the pressure 15 pounds at 212°, only 4° is required for the same increase from 430°. The pressure nearly doubles Avith the addition of each 50° of heat, and alloAving a vulcanizer to run up to 400° or 420° is shoAvn to be a piece of un- pardonable carelessness, and a proceeding fraught Avith the greatest danger to life and property. VULCANO-PLASTIC WORK. 1073 Every vulcanizer should be provided with some means by which the steam will be allowed to escape before the danger-point is reached. Safety-valves have been thoroughly tried, and have proved unsatisfactory from their constant leakage. The fusible plug, consisting of an alloy of soft metal filling a hole in the vul- canizer, which would melt and blow out at 350° or 360°, Avas at one time much used, but it has the fatal defect of hardening after re- peated heating, so that its melting point is raised to 400° or even more; so that after being used a short time it is wholly untrust- worthy. The most satisfactory device for the purpose is the copper disk (Fig. 983), made of metal thin enough to give Avay under an ex- treme pressure. It is secured upon the end of a small stud,screwed into the vulcanizer cap by means of a washer and screw-cap. Long use does not impair the efficacy of this device, and no instance has yet occurred of an explosion where it has been applied to the vul- canizer and was in good order. Strange to say, there are those fool- hardy enough to deliberately plug it up and destroy its usefulness, because it has given way and warned them of their carelessness. As the copper disk gives way from over-pressure, it sometimes does so before the thermometer has reached 320°. If this is the case, it is probably because the vulcanizer has been filled too full of Avater. Allowance should ahvays be made for the expansion of water by heat; and at least one inch in height should be left, when the vulcanizer is filled, for expansion, and for steam-room. An in- stance is on record of a Whitney vulcanizer, Avith the fusible plug being stretched by successive heatings when full of water, so that its diameter Avas increased nearly a quarter of an inch. In doing this, it was subjected to a strain of nearly 500 pounds to the inch, and Avithout heating it above 320°. The blowing out of the disk at an apparently low temperature may occur from applying a strong heat to the vulcanizer Avhen it has very little water in it, the water absorbing the heat, and the pressure rising before the heat is con- ducted to the thermometer so that it can give the correct indication. All experiments in vulcanizing show that the best results are ob- tained when the temperature rises very gradually, and with some samples of rubber, and especially if some parts of the plate are un- usually thick, a rapid heating is sure to cause spongy, porous places in the plate, and necessitates its being made over. Re- peatedly tightening and loosening the cap upon the disk, as by using it for letting off steam, will cause its failure; or tightening it Avith too much force. It is only necessary that it should be steam- tight; and the copper is so thin and delicate that unnecessary force will damage it. 68 1074 MECHANICS—DENTAL PROSTHESIS. Flasks.—Of flasks there are several varieties, many of Avhich are open to some objections. The essentials of a good flask are: 1. It Fio. 984. Fig. 983. must have depth and width for the largest cases. 2. Both ends should be separate, for greater convenience of placing the model in Fig. 985. either ring. 3. The guide-fingers, about one-quarter of an inch long, should work straight and true, be strong, and yet not unnec- VULCANO-PLASTIC WORK. 1075 essarily break the regularity of inside and outside surfaces; cover flanges may be very short. 4. Inside and outside should present as unbroken a surface as possible, for facility in removing and clean- ing off surplus plaster. Both rings should taper, partly to give greatest breadth to the line of junction,partly for easier delivery of plaster. Figs. (.)84 and 985 represent the " Star " and " Anchor " flasks, the first being reversible; other flasks are also self-locking by means of flat springs on the outside of the lugs. Fig. 980 represents the " box flask," designed for extra large cases, splints for fractures, artificial palates, etc. Fig. 986. Making Matrix, Removing Wax, and Packing the Rubber.—The model of a full set is placed in the shallow half, A, of the flask (Fig. 987\ Avith Avax plate and teeth attached, as before described. The model must be saturated with water, to prevent the too rapid setting of the plaster batter with which the flask is partly filled, and Avhich, on placing the model, rises to the edge of flask and edge of the wax plate. The plaster should be mixed as thick as will pour readily, and the loAver section of the flask partly filled with it, when the model and teeth should be placed in it, bottom down, as sIioaaui in Fig. 1>S7, A, and slightly inclining in front, so as to exclude all air bubbles Avhen forcing it into place. In the case of an entire upper or loAver set the plaster should extend up to the wax, as this Avill alloAV the teeth to be imbedded in the plaster filling the upper section of the flask. As soon as the plaster has become moderately 1076 MECHANICS—DENTAL PROSTHESIS. firm, trim smoothly up to the model Avith spatula or sponge; then soap this surface, or varnish and oil it, or cover it with tin foil. When shellac varnish is used, care sliould be taken that the teeth or gums are not coated with it. Some prefer the soap solution, white soap, |j, soft water, Oj, for separating plaster surfaces. Some are in the habit of placing the lower half of the flask in water, that it may absorb as much as possible before the upper half is poured. Mix a fresh lot of rather stiff batter, and brush it carefully over the wax and into all the interstices of the teeth. Then place the upper half-flask, C, accurately upon the lower half, and quickly pour the batter, stirring it well, with a feather or small brush, into the space between the teeth and sides of the flask. Set on the cover D, and apply the clamp B, or a heavy weight. Before it fully hardens, wash off the plaster with a sponge from the outside of the flask, and let it get quite hard before separating the two halves. The object of making the batter stiff is to give it greater hardness for support of the blocks under pressure of packing. These are often displaced Fig. 987. and the joints opened under moderate pressure; because, first, the batter is too thin, and, secondly, time is not allowed for it properly to harden before packing. The flask should be set in water at about 120° for fi\re minutes before separation, so that in case of undercut or of a thin or prominent ridge, there shall be no danger of breaking the model. Dry heat may also be used to separate the flask, but the wet is preferable, as the former may melt the wax and cause it to be absorbed by the plaster; and if the base plate is gutta-percha, it will, if made too hot, adhere to the model. The wax or gutta- percha model-plate should be removed entire, if possible, and also the wax around the pins, by means of a small excavator, and what remains may be washed away by pouring over the surface a stream of boiling water, from a height of about one foot. All wax should be carefully removed in order to prevent deterioration of the rubber, and as much of it as possible be preserved for the purpose of deter- mining the quantity of rubber necessary to use in packing the piece. After the wax is entirely removed, vents or gates are cut in the VULCANO-PLASTIC WORK. 1077 plaster surface of the investments, as shown in Fig. 991, to allow the excess of rubber to escape Avhen the flask is closed. The flask will then present the appearance shown in Fig. 988; the model-half, E, separating from the teeth and Avax contained in the dental- half, H. Should the joints not be very closely fitted, place a little dry plaster over each, and touch Avith a drop of Avater or diluted soluble glass, and when hard, trim off the surplus plaster. Some prefer to pack Avith tin or gold foil. The zinc cement, in the form of the oxychlo- ride or oxyphosphate, is also serviceable, and Avhen used for such a purpose should be mixed quite thin and alloAved to become as hard as possible. Without some such precaution, the rubber Avill press into open joints, and present an unsightly appearance; of course, closely-ground joints are preferable to any of these expedients ; but neither the tightest joints nor any precautions will avail, if strong pressure is used in packing, for this invariably opens the joints and admits the gum. In partial cases, or where no vulcanite is required outside the arch and above the teeth (Avhere plain teeth are used, resting directly upon the gum), the deep half, H, must be used for the model, and the line of separation be made at the cutting-edges of the teeth; so that the plaster around the teeth may come nearly or quite level with the edge of the flask. The teeth are thus firmly fixed in their exact position, and resist displacement, which the separation of the flasks or the pressure of the rubber might possibly occasion. In this way, should the flasks chance not to come perfectly together, the result will be an extra thickness of plate, but no displacement of teeth. We consider this use of the deep-half of the flask, in all partial cases, as of the utmost importance. The teeth are neArer dis- turbed in their position on the model given them in the wax plate; also, there is no breaking of plaster teeth or splitting of the model by pressure of the rubber. To prevent the rubber from adhering to the surface of the plaster model and mould, which gives a rough surface to the palatine por- 1078 MECHANICS—DENTAL PROSTHESIS. tion of the plate, this surface, as before remarked, should be coated with either liquid silex, collodion, or tin foil. When liquid silex is used, a thin coat upon a moist plaster surface answers best; collo- dion is applied like liquid silex; tin foil is attached to the plaster surface by means of shellac varnish, and carefully adapted, by press- ure with a soft cone of leather, to all the inequalities, and its sur- face is coated with collodion, which is allowed to dry, when it is again coated with the soap solution. Such a method will render it easy to remove the tin from the vulcanized rubber, and give a polished surface. Without such precaution the use of muriatic acid may be necessary in order to remove the tin foil. Gilding the surface of the model with gold foil is also done. Clean hands and instruments are very necessary in packing rub- ber, otherwise the color and even the texture of this material are Fig. 989. impaired. The mould, as well as the rubber, should be warm during the packing process, and the latter should be cut in different sized pieces, using a large piece of the proper shape to cover the palatine surface of the model, and which may be applied by press- ure with the thumb and fingers, first dipping them in water. Fig. 989 represents a boiler suitable for heating the flasks, and having a flat top on which the rubber may be softened. In packing the smaller pieces of rubber, and especially the long strips suitable for the rim of the plate, care is necessary that all particles of plaster be excluded, and also that too much rubber is not pressed against thin margins of the gum; otherwise, fracture of the porcelain blocks VULCANO-PLASTIC WORK. 1079 may result Avhen the flask is being closed. It is safer to pack the rubber thicker in the centre, and as it yields to the pressure it Avill flow around Aveak points without danger of fracturing them. Each piece of rubber as it is added should be consolidated; and if any tooth or block has become loosened in the plaster a drop of liquid silex placed in the bottom of its plaster ca\dty will, after it becomes dry, hold it firmly in place. It is desirable in all cases and quite essential in most, that the flasks should come perfectly together. This is accomplished by at- tention to three points: 1. Softening the rubber; 2. Using a proper quantity ; 3. Having vents for the surplus. First, for softening the rubber, use a deep-covered saucepan, capable of holding the flask- press and containing tAvo or three inches of water. When the flask is thoroughly heated by the steam, the rubber is placed over the cover of the saucepan, or on a small shelf attached to the inside of the saucepan; then while soft, let it be packed, with the help of a pointed stick, or the smooth end of a straight excavator flattened for the purpose, into the dental half of the matrix. Around the teeth the rubber may be packed in the form of very narrow strips, someAvhat as foil is inserted into the cavity of a tooth with instru- ments made from excavators with blunt points bent at a right angle. The remainder is packed either in large strips or in one piece cut to the shape of the Avax plate. Secondly. It is important to use the proper quantity of rubber; too little vulcanite spoils the piece; too much requires a pressure Avhich may break the blocks, displace the teeth, and force rubber into the joints; or else requires a long time for a safe degree of press- ure to bring the flask together. In some cases the quantity can be correctly found by having the sheets of vulcanite exactly as thick as the Avax plate, removing the latter as carefully as possible and marking off its size on the former. But for some irregularly-shaped cases and most loAver cases, the following simple method will be found better. Let the plate be entirely of Avax ; remove it all from the matrix, and roll it into a sheet the thickness of the rubber; make the rubber a little larger than the wax; then cut into conveni- ently-sized strips and pack, putting most at those points where the Avax Avas thickest. Starr's measuring glass, which determines the quantity of rubber by "displacement," is a convenient instrument for this purpose. (Fig. 990.) For ascertaining the quantity of rubber required for any given case: The vessel being about half filled with water, set the lower pointer to the level of the Avater; throw in every particle of the model plate ; set the upper pointer to the rise of the water; empty 1080 MECHANICS—DENTAL PROSTHESIS. the vessel, and again fill with water to the lower pointer; add a sufficient quantity of rubber to cause the Avater to rise to the upper pointer, and there will be just enough to fill the mould. Allowance can then be made for surplus. Thirdly. Since the error in quantity should always be on the safe side of excess, provision must be made for the escape of this surplus Fig. 990. by cutting vents, that the halves of the matrix may come together without too great pressure. Fig. 991, taken from Prof. Wildmans monograph, is a fine illustration of the best method of cutting these vents. The radiating vents might, however, stop at the circular groove, taking care to make this large enough for any possible ex- cess of rubber. If these leaders are too large next the plate, the rubber may not pack so firmly as is desirable; also, the generation of gas, while vulcanizing, may force rubber too freely into the groove, and so make it porous. VULCANO-PLASTIC WORK. 1081 A good form of flask press is that of Messrs. SnoAvden & Cowman, Fig. 992. As soon as the rubber is packed, the halves of the flask are carefully brought together, placed in the press, and a moderate force applied ; the press and flask are then placed in the heater. A piece of pure "rubber-packing," about an inch thick, placed under Fig. 991. the screAV, will, as before stated, insure a constantly acting force Avhilst in the heater. Avoid using the full power of even one hand upon the lever; if the vents are free, and great excess of material is avoided, moderate pressure acting steadily in the heater will safely bring any flask together in from ten to forty minutes. Fig. 993 represents Dr. Donham's Spring Clamp which utilizes the tension of a spring for closing the flasks in vulcanizing. It gives continuous pressure and dispenses with flask-bolts. In all cases use a flask press first, and the small screw bolts, ex- *' cept in the Donham clamp, Avhen the case is ready for the vulcanizer. If pressure is applied suddenly, before the rubber is sufficiently plastic, there is great danger of fracturing the teeth, especially sec- tional blocks. When the screAV bolts alone are used to bring the sections of the flask together, no more pressure should be applied 1082 MECHANICS--DENTAL PROSTHESIS. at first than can be made with the fingers, after Avhich the flask is placed in boiling water for a few minutes, Avhen a gentle turning of the screws will suffice to bring the parts together. Clean flasks are essential to successful packing, for soiled fingers stain the rubber, which interferes with perfect union of the pieces; hence all appa- ratus handled in packing should be so simple in form as to be readily cleaned; also, it is well to keep them constantly covered with a coating of varnish. Dr. T. F. Chupein, referring to some valuable suggestions of Dr. Geo. B. Snow concerning the Physical Properties of Vulcanite, says: * Fro. 992. Fig. 993. "The writer, after giving many good points and making many valuable suggestions about vulcanite Avork and the behavior of vul- canite dental plates, recommends that when, from the nature of the case, it is found impracticable to make the plate of equal thickness, the places where the plate will be unduly thick be filled with small pieces of rubber which has been already vulcanized (an old rubber plate, for example, cut up and cleanly filed into small pieces about the size of duck-shot), to compensate for the undue thickness of the plate at these points, and to control the expansion or contraction of the material. * Physical Properties of Vulcanite, Dental Cosmos, Aug. No., 1888. VULCANO-PLASTIC WORK. 1083 " If a set of teeth be waxed up and flasked in the usual way, it Avill be extremely difficult to know where to place these pieces of vulcanized rubber; the memory being the only guide as to where they are to be put, the procedure is reduced to guess-work. " To overcome this difficulty (recognizing the value of the sugges- tion) we proceed as follows: After the case has been waxed up as usual, whether gum section or plain teeth are used, the wax is care- fully removed from the front part of the sections, or from the front part of the plain teeth, so that these are held in place only by the wax on the palatal surface. Those parts of the sections, or plain teeth, and the plaster model are then painted with rubber solution (red rubber dissolved in chloroform), and when this dries, small pieces of red rubber are packed next the sections to form the rim ; Fig. 994. or small pieces of pink rubber are packed next the plain teeth to form an imitation of the gum. This being done, the case is flasked so that the plaster of investment is brought all over the front part of the teeth as shown in the figure. Thus the small pieces of vul- canized rubber may be placed just Avhere they are needed to com- pensate for the extra thickness or volume of rubber at these points. " Fig. 994 indicates the extent of such extra thickness under the bicuspids and molars, for which spaces the vulcanized pieces are to be prepared in the present instance. "Incidentally it may be observed that by this mode of flasking the teeth are kept in their exact positions relatively to the cast, and, the gates being freely cut in the other part of the flask, the articu- lation will be found undisturbed even though the flask should not have been accurately and completely closed. " It is Avell to say that in removing the wax from the front part of the case, this should be all removed before the case is painted Avith rubber solution, and the small pieces of red or pink vulcanite that are put in place of the wax that was removed should be added to 1084 MECHANICS—DENTAL PROSTHESIS. the painted surface with a clean wax spatula, free from all grease, wax or dirt, and heated (for easier manipulation of these pieces) in the blaze of a spirit-lamp. If there is any grease on the spatula the rubber will not stick to the places where it is wanted." Time of Vulcanizing.—When the halves of the flask are brought into contact, it is taken from the press, the screws are adjusted, and it is placed in the vulcanizer, which is then filled two-thirds full of boiling water, the cover adjusted, the gas or lamp lighted, and time reckoned from the moment of closing the cover. The time occupied in heating up and vulcanizing varies with dif- ferent varieties of rubber—from fifteen minutes to one hour and a half. As thermometers vary much, and the rubber used also varies, the best plan is for every one to vulcanize trial pieces until the re- quired hardness, toughness and elasticity are obtained. It should curl under the scraper like horn, permit bending at an angle of at least 45°, and return to its original shape unchanged. When the heat is too great, or the time too long, the rubber be- comes dark and brittle. For the black rubber a longer time is necessary than for the red rubber, and the best method is to heat up very slowly until it has reached 320° F., or to use a less heat and longer time. The more foreign matters rubber contains the less time is required to vulcanize it; and where the adulteration is consider- able, as in the case of the pink rubber, the heat may be raised more rapidly, but such rubbers are weak and unfit for forming any more of the plate than the gum portion. In using the red rubbers, the heat should not rise higher than 320°, and the piece should be allowed to stand until it is cold. In a very large proportion of vulcanite pieces, the full strength of the material is lost by overheating; in others, by the opposite error of giving too much elasticity and throwing undue strain, in full cases, upon the blocks and the rim of rubber behind them. If some of the time spent in polishing up vulcanite and bringing out the of- fensively glaring brilliancy of its color were devoted to careful management of the vulcanizer, to making proper record of heatings, so as to arrive at uniform results, and to the cultivation of those habits of accuracy which alone can give success, there would be fewer broken pieces returned to the laboratory for repair. Slow heating and a perfectly tight vulcanizer full of water, with flask well bound together and vents not too free, are the best safe- guards against porous rubber; except where an unusual thickness is required, when the small pieces of hard vulcanite may be used in packing. It sometimes happens, when large and thick masses are built upon VULCANO-PLASTIC WORK. 1085 the plate, as in cases of excessive absorption, that the thick portions of the plate, when vulcanized, prove to be soft and spongy in the centre. This is the result, first, of bringing the plate up to the vul- canizing point too quickly, and the retention of the sulphurous gas. A long time, even two, three or four hours, the time depending upon the thickness of the mass of rubber to be hardened, should betaken to raise the temperature of the vulcanizer from, say 250° to 320°, if no pieces of hard rubber are used in packing. Second. Dif- ferent samples of rubber act differently when vulcanized in thick masses, depending somewhat upon the amount of earthy matter contained in them. It is very difficult to vulcanize a mass of pure rubber and sulphur even three-eighths of an inch thick, and insure its solidity. On the other hand, some of the English pink rubbers, Avhich contain large amounts of oxide of zinc and vermilion, can be vulcanized in thick masses with but little trouble. It is to be remarked, also, that rubbers which are " loaded" Avith earthy matter have less shrinkage than those which are purer. So, the expedient may be resorted to, of packing the inside of thick portions of the plate with some one of the rubbers containing more earthy matter than those usually employed, or using the same pieces of hard vulcanite as before described. The expedient of filling in parts of the mould Avhere the thickness of rubber is excessive with a mixture of small fragments of old vulcanite and new rubber Avill answer every purpose as a safeguard against porosity. If the pieces are freshly filed all over, their adhesion with the new material will be perfect, and the plate will be as strong as though wholly of new material. There seems to be a point beyond which, if rubber twice passes, it becomes inevitably brittle; hence no confidence can be placed in the old material of a repaired piece. Two flasks in the same vul- canizer cannot give the same results; loss of heat by radiation is greatest from the cover, and the supply of heat is from below; hence, necessarily, the loAver half of the oven is hotter than the upper. Uniformity of texture can be obtained, therefore, only by vulcaniz- ing one piece at a time. One who is systematic in the arrangement of his work will separately vulcanize the pieces of a double set in very nearly the same time required if both are done at once; for one piece may be in the oven, while the other is in preparation for it. Removal from Vulcanizer, and Finishing.—Upon expiration of the time determined upon, the flame is to be at once extinguished; the vulcanizer may be cooled gradually as it stands, or rapidly by the escape of the steam, or by setting the lower three-fourths of the vul- 1086 MECHANICS—DENTAL PROSTHESIS. canizer in cold water. The last method of rapid cooling is preferable; running the heat five minutes longer than when sIoav cooling is prac- ticed. Letting off steam is a very disagreeable process and makes the plaster of the flasks very hard to cut out. Flasks may, with perfect safety, be cooled by setting the vulcanizer containing them in snow or pounded ice, if desired; but in no case should the flasks themselves be cooled by contact with cold water, as some might chance to penetrate to the blocks and crack them. The flask should be opened and the piece removed from its plaster investment, within two or three hours after vulcanizing. After that time the plaster as- sumes a sand-like, granular state, and adheres with great tenacity to the plate, no matter what separating varnish may be used. Tapping the edges of the flask, after separation, will dislodge their contents in mass; the plaster can then be trimmed from the piece, taking care that it is perfectly cold. The adherent plaster in the dental half of the flask can easily be washed from the piece with a stiff brush ; but the model half leaves a coating that clings very tena- ciously, unless means are taken to prevent it; soluble glass, a dilute ethereal solution of collodion, or a layer of thin foil, have been al- ready mentioned as the proper preventives. The process of finishing is more troublesome than in the case of gold work, unless great care is used in the formation of the wax plate. Several sizes of round and half-round files are necessary for finishing up the edges and convex surfaces; for the concave sur- faces, scrapers, graving chisels and curved files. Fig. 995 represents common forms of rubber files. Fig. 996 represents several sizes of a form of scraper or finisher, suggested by Dr. Kingsley, with convex back and thin edges, which do not dull readily and are easily sharpened. Lathe burrs and file-cut wheels will be found very useful, if there is to be much reduction of thickness. Figs. 997 and 998 represent one of each; the burrs in sets of four and the wheels in sets of three. Sufficient thickness must be left in the body of the plate for strength, but the edges should be chamfered off. A pair of cali- pers (Figs. 949, 950) are required to measure the thickness of the plate, if it is to be reduced by files and scrapers, and the use of this instrument will lessen the danger of cutting through the plate. Some operators next use sand paper or emery cloth; others use pumice stone on cork wheels; many prefer Scotch stone. The third step is the use of rotten stone (not Tripoli, which cuts with too keen a grit), either on a brush wheel with tallow or oil, which is the more rapid process, or on a stick of some hard wood, with water, which is the more cleanly. A little oxide of zinc on a soft VULCANO-PLASTIC WORK. 1087 Fig. 995. Fig 998. 12204009144409 1088 MECHANICS—DENTAL PROSTHESIS. wheel, or on the finger, will give a brilliant finishing polish, but is not essential, as the rotten stone can be made to polish very highly. After trying the piece, and finding that no part of the edge requires alteration, a bright surface color may be given by placing the piece in alcohol and exposing to the sun's rays for six or twelve hours. Some regard this as an improvement; it certainly does not injure the quality of the plate, but the original mahogany color of the vulcanite is in much better taste than the bright vermilion tint thus given. In finishing partial cases, it will prevent accident if, after filling the edges, plaster, or modelling composition, or gutta- percha is fitted to the palatine surface of the plate; the subsequent operations can be conducted more rapidly and with less danger, in delicately-shaped pieces. Vulcanite is softened by heat; hence a piece is sometimes bent by revolving the brush-wheel too rapidly. A piece that has been in any way bent or Avarped may be restored by heating either in boiling salt water or in oil, to about 250°. While soft, it may be bent with the fingers; but as this guesswork method is hazardous, it is much better to bind it down upon a model, and heat to the point of softening. By pouring plaster upon the palatal surfaces of thin partial plates, and allowing it to harden, the danger of changing the shape when polishing with a revolving wheel is avoided. To give a polished surface to a vulcanite plate, and dispense with the usual finishing up and polishing process, the surface of the wax may be covered with tin foil, which is lightly, but smoothly burnished to the sur- face of the wax. To insure a polished surface to the palatal surface of a vulcanite plate also, the surface of the model may be varnished with shellac, and then covered with tin foil, evenly applied; but a better method is to obtain a block tin or other suitable metal die from the plaster model, and vulcanize upon it. When tin foil is applied to the surface of a wax plate all the wax may be removed without injury to the foil, by pouring boiling water upon it. By the use of the improved heaters to vulcanize rubber, although a longer time is necessary than with the common vulcanizers, yet the strength and color of rubber so manipulated are improved. To vulcanize red rubber with these heaters, the flask may be heated and packed in the oven; and when this process is completed the machine is closed, and the steam valve is then raised to admit the steam to the packing chamber. When the heat has been raised to 320° the case is allowed to remain in the hot box, at that temperature, for one and a half hours. To produce a pure jet-black rubber plate, perfectly pure black rubber should be used, and vulcanized by the dry process. The VULCANO-PLASTIC WORK. 1089 model and investment should be thoroughly dried before packing the black rubber, and no steam be allowed to enter the packing chamber during the operation. The time required for vulcanizing black rubber by the dry process is five hours, at 320°. To construct a vulcanite set with a celluloid gum, see chapter on Celluloid. A modification of the vulcanite process was patented, in 1868, by Dr. Stuck. Briefly described, it is the vulcanizing of rubber betAveen two polished tin-foil plates, the articulating plate being formed upon a block-tin model made directly from the impression. The plate comes out highly polished, pro\dded the tin foil has been carefully burnished into shape. On the palatine surface, this polish is objec- tionable ; hence we should prefer to vulcanize directly upon the block-tin model, the granulated surface of which is better for adhe- sion. The plate, thus made smaller than the mouth by the shrink- age of the tin, would, in most cases, fit better; the difficulty is in removing the finished plate from the metal in case of a deep arch or slight undercut, an objection, however, which is now overcome by using shell or sectional tin models. A second peculiarity of Dr. Stuck's plates is their elasticity, compared Avith pieces as ordinarily prepared and vulcanized in the same oven. This, we suggest, is due to the retention of the sulphur by the foil plates on either side. We think these elastic plates are usually made too thin, under the idea that elasticity, like rigidity, compensates for diminished thick- ness. This method, though open to some objection, is worthy of careful investigation by every worker in vulcanite. It sometimes happens that the rubber shrinks from the teeth, leaving a space in Avhich particles of food and saliva collect The cause of such shrinkage has been ascribed to the fact that the rubi ber, in cooling from a temperature of 320° to that of the atmosphere, contracts more than any metal, and the plaster of the model and investment, after boiling in sulphuretted-hydrogen Avater for sixty minutes is rendered very soft, and has not strength sufficient to hold the vulcanite in form while cooling; but, on the contrary, yielding to pressure, allows the rubber to draw away from the teeth. It is claimed that any method which will prevent the plaster model and investment from becoming soft will overcome this ob- jection. Repairing and Refitting Plates.—Vulcanite Avork may be repaired by removing the broken tooth or block, cutting dovetails in the rubber, and then fitting the neAV teeth, arranging the wax, and vul- canizing as at first. To describe this method of repairing more in detail: if a tooth or block has been broken, the fractured parts should be removed, and a dovetail or groove formed in the base 69 1090 MECHANICS—DENTAL PROSTHESIS. covering the space occupied by the tooth to be replaced. The tooth or block is then fitted by grinding and supported by wax, the dove- tail being also filled up rather fuller than is necessary to restore the surface, in order to allow for finishing. All of the set, except the portion of the lingual surface over the wax, is then imbedded in the lower half of the flask, and the plaster surface varnished and oiled, to prevent adhesion Avhen the upper section of the flask is adjusted and filled with the plaster investment. When the plaster has set, and the two halves of the flask are separated, all of the wax is removed, the piece heated up, and rubber packed into the cavity around the tooth or block. The sections of the flask are then heated and screwed together, and the process of vulcanizing com- pleted. Another method of repairing rubber plates and by which pressure is avoided, is to first cleanse the piece thoroughly, and to coat the inner surface with a little oil, to prevent the plaster which is poured upon this surface in order to form a neAV model from ad- hering. When the plate is separated from the model, dovetails are cut into the plate, and it is returned to the model, and the teeth adjusted by grinding, after which the surface under them is coated with the rubber solder, or liquid rubber, as are also such parts of the teeth and pins that are to come in contact Avith the rubber. The teeth being replaced, warm rubber is packed under them and into the dovetails, and the case is then invested in one mass of plaster, no flasks being used, and vulcanized in the ordinary manner. Wrhere the plate is cracked, or broken into tAvo pieces, the parts should be carefully adjusted and secured in place by either wax or ligatures and covered with plaster on its inner surface, so as to form a model. The plate is removed from the plaster when it has set and a groove cut out the entire length of the crack or fracture, on either side of which dovetails are formed. When the pieces are re- turned to the model, the case is placed in the lower half of the flask and invested with plaster, all portions of the plate being covered except where the new rubber is to be packed. The rubber solder is then applied to the prepared surface, and the rubber packed firmly into the groove and dovetails. The upper half of the flask is then adjusted and the investment completed, when the case is ready for vulcanizing. Instead of cutting dovetails, which are often disfiguring and sometimes impracticable, a liquid preparation may be used known as Rubber Solder. The surface of the old plate should be brushed over with it just before packing. The adhesion is so perfect that the plate Avill break through old or new rubber sooner than separate. Before cutting out the old rubber, the part of the plate under the broken teeth should be filled Avith plaster VULCANO-PLASTIC WORK. 1091 and then removed, so as to preserve the shape of the ridge; in case the process of repair requires that the plate shall be cut entirely through at this point, it is to be replaced before applying the wax. The second heating darkens the old rubber and makes it more brittle; full cases may admit of one, possibly two, such heatings. Partial cases should be repaired by replacing the entire plate Avith new rubber; although many repair as in full pieces. We decidedly prefer, in both full and partial cases, the entire re- placement of the rubber. In doing this, there are various Avays of securing the correct relation of the teeth to the new" model. To re- place a broken partial or full plate, the teeth being uninjured, attach the broken parts firmly by resinous cement on the lingual surface; soap the rubber, or very slightly oil it, and make a new model; then surround it with a plaster rim, as explained on page 970, coming fully to the edges of the teeth. Remove the resinous cement from the lingual side of the plate and take a plaster copy of this surface and of the inside of the teeth, being careful in partial cases to slope the plaster so that it may be readily drawn. The plaster now enveloping the piece is in three or four parts; remove the plaster from the lingual surface; remove the rim in one or in two pieces; then carefully remove the plate from the model. Soften the rub- ber plate and remove the teeth ; replace the plaster rim around the model and set the teeth or blocks in position, pressing a little wax under each to keep it in place. Now set model, rim, and teeth in the half-flask, first soaking in water, to prevent too quick setting of the batter. Soap or cover Avith foil the plaster surface; then saturate and put in place the remaining lingual piece of plaster; set the other half-flask and pour the remaining half-matrix. Separate flask, pick out the pieces of wax; the case is then ready for pack- ing and vulcanizing. By this process the new plate has the exact shape of the old one, and there is no necessity for moulding a new wax plate. If the plate is of such form as to endanger the model in detaching, soften it by cautious use of the blowpipe flame. If neAV teeth or block be required, let this be first fitted, and wax properly shaped around it; then proceed as above. But if some modification in the shape or thickness of the plate is required, do not fill the lingual surface with plaster; but, after making model and rim, remove plate, reset teeth, adjust a neAV wax plate, and then proceed as in a new piece. If the vulcanite rim outside and above the teeth needs modification, the plaster rim must be removed and wax placed there also, as in a new piece. Dr. George B. Snow, in an excellent article on " Repairing Vul- canite Plates," gives the following suggestions : 1092 MECHANICS—DENTAL PROSTHESIS. " It is not unusual to see vulcanite plates Avhich have been cracked or broken, and repaired by what may be termed the 'hole and plaster' system. Holes are drilled through the plate along the edges of the crack, and a new thickness of rubber superimposed upon a mass which possibly is already too thick for comfort or conven- ience ; the old crack still remaining as a weak point to occasion further breakage. No advantage was taken of any possibility of union between the old and neAV material, the dentist having been obviously ignorant of the fact that perfect union can be obtained in such cases if the surfaces of contact are freshly cut, absolutely clean, and properly roughened. " The great point to be remembered in repairing or making any addition to a vulcanite plate is, that the neAV and old material will unite perfectly, and Avith such firm adhesion that the plate will be practically as good as neAV, if the surfaces of the old plate where union with the new material is desired are freshly filed, absolutely clean, properly roughened, and of sufficient area. To insure these results, wax should not be melted upon the surfaces of union in waxing up, and removal of the wax from the mould should be ac- complished by means of instruments, and not by hot Avater, unless, possibly, for the removal of very small particles which cannot otherwise be got rid of. Any amount of the old material desired may be cut away, and its place supplied by new; and thus any change wished may be effected. In case of breakage or cracking, the plate should be cut away so that the old defects will be Avholly obliterated and new material supplied. " As a first instance, suppose a partial lower plate, supplying the loss of the bicuspids and molars on both sides of the mouth, to be broken through the bar which extends from one side of the mouth to the other behind the incisors. The fracture is generally a clean one, resembling that of glass or porcelain, and the two pieces may be brought into apposition with certainty. The dentist holding the parts together in exactly the right position, the assistant covers the lingual side of the plate at the point of fracture with a feAV drops of hot shellac from a shellac stick. A little cold water follows, and the two parts of the plate are firmly cemented together. A brace is now extended across from the molars on one side to those on the other, by laying a burnt match on the grinding surfaces of the re- spective teeth, and fastening both ends with a few drops of hot wax. By this means sufficient strength is obtained to allow of the plate being safely handled. A piece of paper or sheetewax is cut to fit and reach across the lingual space at the lower edge of the plate, and fastened therein with wax, a coat of shellac varnish is applied VULCANO-PLASTIC WORK. 1093 to the paper, the surface lathered with soap-suds and rinsed, and a model run in the same manner as in filling an impression. " After this has hardened, the plate is removed from the model, Avhich is then given a coating of liquid silex. This is always pre- ferably done in repairing plates at the time when the plate is first removed from the model. The bar may be now wholly cut away, close to the body of the plate on either side by a jeweller's saw; the cut being made diagonally, so as to make what is termed a " scarf" joint. The surfaces should be further roughened by making a series of shallow parallel cuts across them with the saw, a thick separating file or a thin-wheel engine burr. The parts of the plate are placed upon the model, waxed up and flasked; the model and buccal surfaces of the teeth being covered with plaster, and the parting made so that the plate will be retained upon the model, while the pieces of the bar can be readily removed. After the flask is opened, the pieces are removed, the usual gateways cut, and the packing, vulcanizing, and finishing done as usual. " In the case of an entire lower set broken through the centre, it Avill be seen that the same directions Avill apply, excepting as to the amount of rubber to be cut aAvay. A free cut should be made on the lingual side, extending through under the teeth, to and in- cluding the labial band; so that the broken surfaces will be entirely obliterated and at least one-eighth inch in Avidth of new rubber supplied betAveen the cut surfaces. An engine-burr will do much of this Avork nicely, and a Avheel-burr is very convenient for the purpose of scoring the surface. The making a model, flasking and packing will be done as before. " If one of the incisor-blocks be broken, and needs replacement, a new one can be fitted after the model is obtained, and the re maining steps of the process followed as has been described. " Upper plates are sometimes cracked in the centre, the crack ex- tending from under and between the incisor teeth backward over the palate. This often happens from the amount of rubber just be- hind the incisors being insufficient. It is not unusual to see it cut aAvay at this point, so that the pins are almost or quite exposed ; the plate having its usual thickness at a very short distance be- hind the teeth. A much larger amount of material will be tol- erated here than is usually employed, and often with benefit, not only to the strength of the plate, but to the articulation of the wearer. The curve of the surface of the plate should be made to. resemble that of the palate before the removal of the teeth, and it Avill be found that the extra thickness may extend for half an inch. behind the teeth without annoyance to the patient. 1094 MECHANICS—DENTAL PROSTHESIS. " A proper curvature to the surface of the plate, just behind the incisors, will do much to prevent the disagreeable Avhistling in making the s sound, and will assist in giving the correct enuncia- tion to sh, zh, and other Unguals. " If the cracked plate fits a flat mouth, a model can often be draAvn from it as it is; but if the arch is high, and the gums projecting, it is better, after thoroughly cleaning and drying the plate, to finish the cracking by breaking the plate entirely in two. The two halves may now be fastened together by dropping shellac upon the lingual side, and a model secured, from which either half of the plate can be easily removed. The whole palatal portion of the plate can then be removed by a saw-cut, leaving only a narrow margin on the lingual surface inside the teeth. The remainder of the surfaces of fracture are cut away as directed in case of the lower plate, the neAV surfaces roughened, the pieces of the old plate replaced upon the model (which has received its coating of liquid silex), waxed up, flasked, packed and vulcanized, the teeth being retained upon the model as before described. The plate, when finished, will show the old rim and a margin of the old rubber in- side the teeth. " It is sometimes desirable to change the substance of the plate entirely, as in case of supposed mercurial poisoning by red rubber; or at least to put what red rubber there may be about the plate entirely out of sight, and to reduce its quantity to a minimum. If this is to be done to the plate last under consideration, it should be prepared for flasking as described, excepting that the labial band should be cut away, and. everything arranged so that the plate can be separated from the model when flasked. The parts cut away should, of course, be replaced by Avax. The case is now set in the flask so as to leave the parting at the upper edges of the gums. The plaster is varnished and oiled, and more plaster built on against the labial sides of the teeth, extending from their cutting-edges to the edge of the flask, and again varnished and oiled, so that the appearance will now be precisely similar to a plate flasked so as to be retained upon the model. The ring of the flask is now put in place and filled, and the plaster allowed to harden. " When the flask is separated, the teeth will be found in its ring- section. A few bloAvs of the hammer will dislodge them, with the piece of plaster built against their labial surfaces. This is carefully broken away in two pieces, if possible, which are preserved, and the teeth and rubber encasing them is left. The rubber is now filed away as much as is practicable, leaving none of the old rubber in sight, and removing enough from the palatal surface to make a new VULCANO-PLASTIC AVORK. 1095 fit to the model. The teeth and plaster are replaced in the flask, and the case is ready for packing and vulcanizing, and when finished, none of the old rubber will be seen, and the plate will be practically as good as though the teeth had been removed from the old plate and reset. " It is sometimes difficult to prevent the rubber from showing at the joint between the incisors; great care should be exercised in bringing the sections together properly and in holding them in position while flasking. If there is room, a small wisp of loose cotton, not larger than a thread, may be tucked into the joint on its palatal side, the edges of the blocks being bevelled to admit of this being done. " It is evident that the change from red to black rubber just de- scribed can be made Avith a Avhole plate or a broken one indiffer- ently. If a change of articulation and a new fit to the mouth is also desired, on account of shrinkage of the gums, the plate should -be prepared so as to draAv from the model, and a few small pieces of Avax put in the palatal side to bear upon the al\Teolar ridge, and give the right articulation by trial in the mouth, the centre of the plate being cut away to facilitate the fitting of the plate to the model. A fresh model of the mouth being secured from an impres- sion, the plate is Avaxed on to it, the case is flasked Avith a false piece of plaster built against the labial sides of the teeth, as has been before described, and the plate aftenvard removed and cut away as much ,as desired; a considerable amount always being taken from its palatal surface. " This process does all and more than is specified in the Hyatt patent, as it not only gives a neAV fit, but alloAvs the material of the plate to be substantially changed. Holes and dovetails, it Avill be seen, are wholly unnecessary, and the fine serrated edge left by cross- cutting the surfaces of union Avill be found an excellent guide in scraping the plate to avoid overlaps. The use of shellac as a cement is strongly advised in repairing, as it is rigid and brittle when cold, and the broken parts, if once properly brought together, cannot get out of adjustment without at once attracting attention by the break- age of the cement. Wax does not ansAver the purpose nearly so well. " The amount of shrinkage in vulcanite from cooling after vul- canization is not so generally noticed and provided for as it should be. Plates composed of single teeth do not give trouble from this cause, but full plates, on Avhich sections are mounted, are often very vexatious to the dentist, from the change of shape they undergo from shrinkage. 1096 MECHANICS—DENTAL PROSTHESIS. " The reason of this is, that the ends of the sections abutting form an arch of porcelain, Avhich expands or contracts but slightly from changes of temperature. The rib of vulcanite immediately inside this arch, and in which the pins are imbedded, forms a second arch closely attached by the pins to the first one. The plate is moulded to the model, and hardened at a temperature of about 320°, and is aftenvard placed in the mouth, where the temperature is. in the neighborhood of 90°. Under these circumstances the con- traction, of the rubber which ensues has the effect of lessening the radius of the arch, drawing the heels of the plate together, thus rendering it a little too narrow to. fit the mouth accurately. This has the further effect of elevating the palatal portion of the plate, which, when tried in the mouth, will usually be found to rock slightly ; often so much as to interfere with its fitting. " If the plate has been made upon a model taken from the mouth, the difficulty is overcome by warming the back part of its palatal portion, pressing it down slightly, and cooling it Avhile the pressure is continued; the narrowing of the plate being too small in amount to be of itself objectionable. " This change can be accomplished Avith more certainty by making a small plaster cast of the palatal portion of the plate, placing upon the part where the change is desired a small piece of folded paper, folded so as to present a thick centre, and forcing the plate down upon it after its palatal portion has been warmed. "The shrinkage here alluded to becomes a more serious matter when the plate is re-vulcanized, in the course of repairing it. It is flasked when the change in form by its shrinkage has already once manifested itself, and again heated to 320° ; and in cooling a second shrinkage takes place, it becomes still narrower, and its fit, already defective, is made perceptibly worse. It now often becomes a matter of necessity to bring it back to its proper shape before it can be Avorn with comfort. To provide for this, a small dot should be made with a pointed instrument on each side of the plate, immediately behind the molars, and a pair of dividers set to the distance between these points. After vulcanization, the dividers can be applied to the marks, and they will indicate the amount of shrinkage the plate has experienced. Let the plate now be warmed just behind the inoisors, and in the mesial line, by repeated short puffs of a bloAvpipe flame. This must be done carefully, and the heat not allowed to extend over an area much exceeding half an inch in diameter. When the rubber is sufficiently softened, the plate should be taken by the heels, a pull made upon it sufficiently forcible to expand the VULCANO-PLASTIC WORK. 1097 arch, and a stream of cold water applied. The dividers will at once shoAV if the change made is sufficient. "When the plate is noAV tried in the mouth, it may be that the back edge will not touch the roof, and air will be admitted under the plate; in Avhich case the back edge should be warmed and forced up to its proper position. " The same remarks apply to full loAver plates as well, which often are found to have lost their fit in a measure, after having been re-vulcanized. The process above detailed will suffice to re- store them to their former fit, and render them again comfortable to the Avearer." If the teeth are to be reset, because of change, from absorption, or because of some inaccuracy in the fit of the plate, it will perhaps be best, in most cases, to proceed just as for a neAV piece, grinding the joints again for any change of arrangement. Sometimes re- jointing the blocks may be saved by bedding their cutting edges and cusps in a gutta-percha rim, before detaching from the plate; this will permit their adjustment to the new wax plate in a continuous arch. Sometimes the old plate may Avith advantage be used as an impression cup, by roughening the rubber, and using a very thin layer of Avax or plaster, Avhichever bests suits the case. In making the model, extend it backAvard, as before described under Articu- lation of Plastic Work. Before removing the piece complete the articulator, making the plaster cover the edges and crowns of the teeth one-eighth of an inch. By setting the blocks, when removed from the old plate, into their depressions on the articulator, the exact relations of blocks to the model is preserved; also, if the plaster of the impression is made accidentally too thick, the articulator may be slightly closed. The Avax plate is arranged first on the outside ; the half-articulator is then removed, and the inner part of the plate shaped. The articulating portion is then cut off, the model set in the flask, and the process completed in the usual manner. Gold, platina, or aluminium plates may also be re-fitted to suit a mouth changed by absorption. Perforate the plate with holes about size No. 22 (Fig. 798), countersunk on lingual side, regularly arranged and about half an inch apart. Fill the lingual surface between teeth Avith plaster; remove this Avhen hard and make countersinks in it, opposite each hole in the plate. Set the plate on model and fasten it Avith wax around the entire edge; then place in half flask, as usual. Replace the countersunk pieces of plaster and pour second half matrix; this piece of plaster and the wax around the edge prevent the batter of the matrix from getting betAveen plate and model. Separate flask, cut vents, put in a sheet of prepared 1098 MECHANICS—DENTAL PROSTHESIS. rubber of proper size, press matrix together and vulcanize. The impression may be taken in the usual cups or in the plate itself, and with either plaster or wax, as the case may require; if taken in the plate, cleanse this carefully after making the model. The ad- hesion of the rubber may be increased by cutting the palatine sur- face of the metallic plate with a sharp graver; it should be carefully cleansed just before packing the rubber. Dr. Richardson gives the folloAving method of refitting gold or vulcanite plates Avith a new vulcanite lining: " Perforate the palatal portion of the plate with from eight to twelve holes, at different points, and also the extreme borders, from heel to heel of the plate, at intervals of one-eighth to half an inch apart, and near the edges. These holes may be enlarged to the dimensions of a medium-sized knitting-needle; or, if the piece is of vulcanite, to tAvice or three times that size. On the lingual and buccal surfaces the holes are well countersunk with a burr drill. The plate is employed as a cup or holder to take an impression of the mouth in plaster, being pressed up closely to the parts. The plaster forced through the holes, and filling the countersinks on the opposite side of the plate, will serve to bind the plaster to the plate, and prevent the two from separating as they are detached from the mouth. When removed, the plaster impression lining the plate is trimmed even with the borders of the latter, and varnished and oiled. The lower section of the ATulcanizing flask is now filled with a batter of plaster on a level Avith its upper surface, and the impression, filled Avith the same, is turned over and placed in the centre of the flask, with the edges of the plate touching the surface of the plaster. The plate and adher- ing plaster are now carefully separated from the model. After cutting out the plaster from the holes and countersinks in the plate, the plaster forming the impression is detached from the plate, and the holes and countersinks filled Avith wax. The plate is then re- adjusted over the model, and (the surrounding surface of the plaster in the flask having been varnished and oiled) plaster is poured in upon the upper surface of the plate and teeth, filling the upper ring. When the plaster is sufficiently hard, the two sections of the flask are separated, and grooves formed, running out from the matrix to the margins of the flask. A sufficient quantity of vulcanizable rub- ber is noAV either placed upon the model, or packed in upon the palatal surface of the plate; before doing which, hoAvever, the wax filling the holes and countersinks in the plate (and which Avas placed there to prevent portions of plaster last poured, in forming the ma- trix, from filling them up) should be worked out with a small instru- ment. The Avhole being sufficiently heated, the two sections of the VULCANO-PLASTIC WORK. 1099 flask are forced together, expelling redundant material. The piece is then vulcanized." The late Dr. Wildman suggested the following method of forming a new plate, Avithout changing the articulation of the teeth : " Roughen the palatal surface of the rubber plate, to cause the plaster to adhere to it; then use it as an impression cup to take a plaster impression, being careful, when it is in the mouth, to preserve the articulation. In this impression cast the model; trim and cut conical holes at several points in its outer face. Now, before separating the impres- sion from the model, make a cast of the face of the teeth, in two or three perpendicular sections, extending to the base of the model, using a solution of soap or other parting substance on the plaster model. Remove this mould of the face of the teeth, which indicates their true position relative to the model. Then, take the impres- sion from the model. By the aid of heat sufficient to soften the rubber, remove the teeth from it. Next make a model plate with prepared gutta-percha, 'Avax and paraffine (or modelling composi- tion).' Now secure the sections of the mould of the face of the teeth to the model (their place will be indicated by the conical holes or keys) ; adjust the teeth in their proper positions in the plaster mould of them, and build up with wax to the proper form of the model set. This being done, test its accuracy of contour and articulation by placing it in the mouth. Then, using the model, proceed as for making a neAV set." " The method just described re- quires the presence of the patient; but cases occur where this is not possible, and owing to accident a neAV plate is necessary, and the articulation must be preserved. Take a case, for an example, where the plate is so fractured that it cannot be repaired, and yet is capable of being temporarily adjusted, by means of hot wax dropped from a spatula. When this is done, the palatal surface of the plate is coated lightly with oil and plaster batter poured into it to form a model. Then trim the edges of the plate and sides of the model and form holes of a conical shape to act as keys for the mould Avhich is made in sections of the outer face of the teeth. When this mould has become hard, the sections of it are removed, as well as the plate from the plaster model. Undercuts may prevent the ready removal of the old vulcanite plate, and in such a case, to prevent injury to the model, the old plate should be softened by heat. The subsequent manipulation is the same as in the previous method. When the plate is broken in half, a rubber plate may be repaired by a method suggested by Dr. Gilbert: "Remove the denture, and, with a fine SavIss saw, cut away the palatal portion of the plate to Avithin about an eighth of an inch of the inner surface of the teeth. In this re- 1100 MECHANICS—DENTAL PROSTHESIS. maining portion cut dovetails, to retain the new rubber, and also form an undercut channel in the portion which fits over the alveolar ridge in the line of the break, as far as the edge of the rim; secure the parts to the model Avith wax. The cut-out palatal portion may then be laid back in place, to aid in waxing up that part. Invest in the flask, covering the labial and grinding portions of the teeth, as in other repair work. After separating, remove the part desired to be replaced with new material; pack and vulcanize as usual." Partial pieces can usually be retained by stays and the fit of the plate. If clasps are called for, these may be made of rubber alone if the clasps are short and the rubber elastic; or of rubber strength- ened by a gold wire, which is to be curved around the clasp tooth just before packing. A gold clasp may also be fitted and re- tained in the rubber, either by a projecting slip of the same metal or by soldering into it one or two platinum pins. Fig. 999, taken from Prof. Wildman's monograph, represents these two forms of clasp; but in cases requiring clasps, we very decidedly prefer a gold plate. The larger size of vulcanite plates necessary for strength will, usually, secure adhesion, with the help of stays or half clasps ; in none of these cases do we consider the vacuum cavity of any service. Combination of Vulcanite with Metallic Plates.—Blocks or gum teeth may be secured to gold plate by vulcanite instead of by soldering. Blocks having a porcelain gum on the inside, finished to the plate and having a hole in the base opposite each tooth, present a very handsome appearance when attached to gold plate by vulcanite, and may be made very secure. The hole should be of good size (from Nos. 12 to 15, Fig. 798), but must not come so near the translucent front of the tooth as to permit the color of the rubber to darken it. In this and the subsequent modes of attachment, the swaging, ar- ticulation and grinding of blocks is done as usual, except that there is less necessity for close fitting to the plate than in case of soldered work. The temporary plaster rim, elsewhere described, must in all cases be used, so as to permit removal and correct replacement of teeth. In case of the blocks just described, press each block into place over a thin layer of wax on the gold plate. The wax projec- tion made by each hole shows where to drill the plate for the pins; then remove plate, drill holes and solder roughened or headed pins into the plate, opposite each hole; fasten the blocks temporarily with wax, then invest in the vulcanizing flask, so that on separating the matrix, the plate shall come away in one half, the teeth in the VULCANO-PLASTIC AVORK. 1101 Other. Fill the holes with rubber, and place a strip over the base of the blocks; warm and replace the two halves of the matrix, and vulcanize. Vulcanite blocks, such as those in Figs. 1000 and 1001, may be very firmly attached to metal plates by some one of the Fig. 1000. Fig. 1001. methods represented in Fig. 1002. Set the teeth or blocks in the temporary plaster rim and distinctly mark a line around the ridge, just under the head of the pins (C) ; mark across this line the posi- tion of each pin (a, b, c, d); then remove blocks and prepare the plate for the different plans of retaining the vulcanite. 1st. For an aluminium plate which can have no soldered pins, drill a row of small Fig. 1002. holes on the line between the pins; set it in the counter-die, and with a tapering punch, enlarge each hole, with the projecting burr next the tooth (C, c). Let each hole be not smaller than No. 20 (Fig. 798). In some cases a smaller set of holes may be punched or drilled in the outer edge above the gum (C). Swage the plate again, to correct the effect of this punching; then place it on model, replace blocks, arrange Avax, and prepare for vulcanizing. 2d. Ar- range the plate firmly on a piece of charcoal, set small cups of gold or platina on the line, betAveen the pins (A, a), with a small piece of solder at each, and solder them all at one heating. 3d. Or drill small holes on the line, betAveen the pins of the teeth (B, b), and insert headed platina or gold pins, and solder them. 4th. Or drill 1102 MECHANICS—DENTAL PROSTHESIS. tAvo holes between the tooth-pins (E, e) and insert a loop; only one hole is really necessary, as the other end of the loop may be short- ened so as just to touch the plate, to which the solder will attach it. 5th. Lastly, a wire may be bent in a series of Avaves (d), so as to pass under each tooth-pin (or just behind it, if the pin is too close to the plate, but never over it) and rise from the plate, between the pins. Adjust this wire accurately, with the blocks in place; mark the points of contact; then remove plate and solder the wire. The last four methods are applicable to gold and platinum, which admit of soldering. In soldering, no plaster investment must be used, and the plate must have a good support on the charcoal; with these precautions, careful soldering will not Avarp or spring the plate. If sprung, the pins and loops make it necessary to cut a deep groove in the lead counter-die before attempting to swage. After completing either of the five plans here described, re-adjust the teeth in the plaster rim and fasten them in place Avith wax, trimmed to the shape required for the vulcanite; then invest in the flask and vulcanize as before described. By avoiding excess of rub- ber, using only so much as is necessary to conceal the pins or loops, the vulcanite band may have a very neat appearance. Some dentists partly conceal the rubber by an inside and outside band; but if con- cealment is necessary, we should prefer to do it by the form of blocks above given. If the inside band is used, the simplest method is to mark the line of its position ; then, by skilful use of the hammer, a strip of gold can be paned and, Avith the pliers, bent so as to have a uniform slope and a close fit; a file will be necessary over small prominences; this method of paning is simpler than either SAvaging a band or first making a lead or tin pattern. If cast plates of alumin- ium or other metal alloys are used, it is only necessary to drill holes, as many, and of such size, as may be thought necessary, in that part of the plate next the blocks; they may pass through to the palatine surface if necessary, and be countersunk. It is very im- portant to ascertain, by trial, that the closely fitting edge of alumin- ium does not interfere with the teeth, in separating and replacing the flask. A method of attaching porcelain teeth to a metal base with vul- canite Avas devised by Dr. P. G. C. Hunt, and a process very similar was afterwards introduced by Dr. Engle. It is described by Dr. Hunt as follows: " Thus far we proceed as we do for ordinary gold plate work. We will now suppose the teeth ground and jointed, leaving as much space between the teeth and plate as the plate will admit of. We next mark with a sharp-pointed instrument, on the labial surface of the plate, each point where it is necessary to place VULCANO-PLASTIC AVORK. 1103 a loop, for purposes hereinafter described; then apply Avax to the external or labial parts of the teeth and plate, in any manner suf- ficient to retain the teeth in position; remove the wax from the lingual parts of the teeth and plate, and mark the position on the metal where it is desirable to insert the loops; remove the teeth and Avax, and with a small boAV-drill make holes through the plate at the several points previously determined on for the attachments, about the size of an ordinary plate-punch hole; take a Avire, or ordinary gold plate cut in strips, say from a half to one line in width, being Fig. 1003. governed by the amount of room there is under the base of the teeth, and with small round-nosed pliers bend the strip around; grasp both ends with square-nosed pliers; draw the round-nosed pliers from the loop, still grasping the square-nosed pliers with the left hand, and with a hammer strike the top of the loop a sufficient blow to keep the ends from springing apart; cut off the ends and dress down to fit the holes in the plate; after which solder on charcoal or other suitable substance Avithout investment. Fig. 1003 illustrates the bent or hooked Avire soldered to the base. Pickle, dress, and polish that portion of the plate to be exposed to view. Bend and flatten the pins; arrange the teeth, waxing so as to cover up the loops if practicable. The loops should be placed as near the base of the teeth as possible, the rubber forming, when finished, a part of the general concave shape which is desirable in upper dentures, and which it is not possible to obtain Avith ordinary soldered work. Then Avith silicate of soda paint the joints, to keep the rubber from forcing in where it would show after vulcanizing. Flask, vulcanize and finish as usual. Celluloid can be attached to a metal plate Avith the same loops and 1104 MECHANICS—DENTAL PROSTHESIS. hooks, by sawing out the palatal portion of the celluloid blank, and trimming away as much of the remaining portion which covers the alveolar ridge as is necessary to avoid having an excess of material. WThen investing the piece, the line of separation is made at the edge of the wax rim, thus permitting the plaster to cover the palatal por- tion of the metal. When the sections of the flask are separated, the metal plate will occupy the lower and the teeth the upper portions. The attachment of vulcanite to metal plates is an extremely useful and important application. It loses one of the peculiar advantages claimed for vulcanite, the accurate fit of the plate; but it makes very strong work, and is more cleanly than ordinary SAvaged work, because all interstices are completely closed. It also gives a shape behind the teeth more conformable to the natural shape of the teeth and gum. It obviates two of the principal objections urged against vulcanite—thickness of the plate and contact of the rubber against the gum and tongue. It dispenses with that accurate grinding of the base of blocks required in ordinary gold Avork, and obviates the risks of the soldering process. It is applicable to full sets, or to partial sets where the teeth are in groups of three or more. It is best repaired by removing the entire vulcanite attachment; but those who patch up old rubber plates can, with greater impunity, patch the " combination work; " since the strength of the piece de- pends mainly on the plate, the brittleness of second heating is of less moment. Another argument in its favor is, that it makes available to gold-dentists the beautiful forms of rubber blocks, without identi- fying them with that class of rubber-dentists who, by accommodating the style of their work to the cheapness of the material, have brought much discredit upon dental mechanism. Dr. R. M. Chase has invented what he styles " a metallic-roof plate," which com- prises a plate of gold or other metal to cover the roof of the mouth and a vulcanized extension attached to the edges of such a plate, and extending over the alveolar ridge. The edge of the metallic plate is serrated or notched, and bent upAvards at an angle so that the vulcanite portion can be attached. In such a denture, the metal portion only comes in contact with the roof of the mouth, while the vulcanite is restricted to the under and outer surfaces of the alveolar ridge. The method of constructing such a denture is described by Dr. Chase as follows: "Shape the plaster model so that it will easily drop from the sand by its own shape and weight by simply raising the flask at a right angle from the table. After shaping the model as described, mould wax and paraffine base-plate to the labial and buccal portion of the alveolar ridge of the model, filling all undercuts and irregularities, letting it extend over on to VULCANO-PLASTIC WORK. 1105 the alveolar ridge to the depth of from one-eighth to one-quarter of an inch. This should be bevelled toward the palatine aspect, this being done Avith a view to Avhere the turned-up edge of the plate will not interfere Avith the pins of the teeth. The whole model, in- cluding the wax, should be shaped on a true bevel from the base to the bevelled edge. Varnish the model, including the paraffine wax, Avith two or three coats of white shellac dissolved in alcohol. A model when prepared in this manner presents a bevelled surface at all points, which makes sand-moulding simplicity itself. When the shellac varnish is dry, mould in fine sand. Do not pack the sand over the face of the model but a trifle, rather depend upon the weight of the sand to do this. Pack thoroughly around the side and top of the flask so that when it is leA^elled off and reversed none Avill drop out. " Having secured the impression of the model, melt zinc and make a die. When the die is cool reverse it and pack sand around it nearly as high as the top of the ridge, so that only the palatine surface and the bevelled edge is exposed. Place over this a rim of iron about one inch larger in diameter than the die, and pour melted lead into the rim to the depth of one inch. Remove this counter-die and make another, but do not let the sand extend up higher than to one-half an inch of the top of the ridge. The first counter serves to shape and partially SAvage upon. When this is done trim the edge of the plate Avhere it bends over the edge of the die to the proper shape, not letting it extend beyond the top of the bevelled edge. The second counter serves for the final swaging. It is seldom necessary to make more than one die and two counter- dies as described. When the plate is shaped upon the first counter, notch the turned-up edge about one-eighth of an inch apart, cutting into the metal to about one-thirty-second of an inch—Avhere the turned up edge commences, or where it is to leave the cast, place back upon the die and smooth down the notched points which will curl up in cutting. Anneal and place upon counter No. 2 and strike the die with two or three dead pushing blows, this will finish the SAvaging process. Noav saw or trim off the base of the model, remove the wax and paraffine and adjust the trial-plate. Secure the bite or articulation, after this is done remove the trial-plate and fasten the metallic plate to the cast in position by a few drops of wax. Soften base plate, place this upon the labial and buccal sur- face of the cast, connecting it Avith the edge of the plate. Proceed to Avax up the teeth in usual manner, letting the wax-backing ex- tend on to the plate as far as desired when finished. When adjust- ment of the teeth and Avaxing process are completed, flask the same 70 1106 MECHANICS—DENTAL PROSTHESIS. as for rubber, except the plaster should cover the metallic plate, extending a little above the edge or border of the wax. Soap the plaster, adjust the upper half of the flask and fill with plaster. When hard, warm the flask and open. Remove all wax by pouring boiling hot water upon it. Now, with a pair of narrow beak-forceps, bend the notched parts every other one in opposite directions. This gives additional security against becoming detached Avhen the ex- tension is moulded to it; vulcanize and finish." A vulcanized plate may be bleached by placing it in a glass vessel containing alcohol, and exposing to the sun's rays for from four to six hours; covering the top of the vessel with a plate of glass will prevent rapid evapora- tion. The pink rubber employed to give a more natural color to the gum requires to be bleached in order to render it sightly. To remove teeth from a vulcanite plate, the piece may either be passed through an alcohol flame until the teeth become hot, or the set may be boiled in oil, or imbedded in hot sand of such a temperature as will not char the plate. The latter method is preferable when care is taken to have the sand at a proper temperature, as the teeth or sec- tional blocks can be readily detached, and all rubber adhering to the pins be removed by means of a pointed excavator. Any slight imperfections in a vulcanite plate, in the form of a small hole left by plaster particles, can be repaired by melting gum shellac and in- corporating it with vulcanite filings. A cement thus formed can be introduced in a plastic state and made smooth with a heated spatula or burnisher. Rubber can be made liquid for use as a rubber solder by cutting- it into small pieces and dissolving by either benzine, turpentine, chloroform, ether or bisulphide of carbon, all of these agents being solvents of rubber. The shape of a vulcanite plate can be changed by obtaining a correct impression and model of the mouth, upon Avhich the plate, having been previously heated, is pressed by means of a napkin or piece of chamois skin, and held in position until it is cold. To soften the rubber plate, the set may be immersed in boiling water, or placed in an oven with the teeth downward, until the rubber becomes pliable; in the latter method care should be taken that the rubber is not blistered or charred. A more certain method, hoAvever, is to reconstruct the set. For quick repair in the case of a broken tooth or sectional block, a hard, quick-setting amalgam is sometimes employed, first cutting out a suitable cavity about the space to be filled, and after the tooth is properly adjusted, packing the amalgam under it and about the pins, the tooth being firmly held in place during the operation. Wood's fusible metal has also been used for the same purpose, and VULCANO-PLASTIC AVORK. 1107 to close holes, the latter being countersunk on both surfaces, and made oblong. Spring plates consist of elastic partial pieces which are so con- structed and vulcanized as to press against certain natural teeth, and thus be retained in position. After securing the model, a little of the palatal surfaces of the plaster bicuspids and molars is scraped away, and in forming the trial plate the wax is allowed to extend some distance from the necks of the retaining teeth, upon the model, toward the grinding surfaces, in the form of partial stays. These plates are so shaped as to leave the central portion of the mouth free, no air-chambers or clasps being necessary. As the tendency of spring plates is to press the retaining teeth outward, they are not generally used. For mouths having soft places, Dr. Land recommends an air chamber covering four-fifths of the pala- tine arch, and including certain parts of the alveolar Avails (Fig. 939); and the same writer remarks: "To insure a comfortable adaptation, the pressure must be so equalized that, as the alveolar ridge recedes, undue stress will not be brought on the palate. For this reason an air space, covering almost the entire surface of the palatine arch, is desirable, as thus the pressure is better distributed and brought to bear directly on the alveolar ridge, where there will be the least danger of injuring the mouth, thus avoiding the riding or rocking of the plate on the hard palate. The conventional air chamber, Avith its acute angles invariably placed on the most rigid portion of the hard palate, soon outlines itself in the tissues, demonstrating a failure to properly utilize atmospheric pressure, and injuring the mouth by inducing absorption unnecessarily." Dr. Hurd has suggested what he terms a " flange section," for lower plates, Avhich is described as follows: An impression is first taken in wax, and this is used to obtain a plaster impression. The extreme projecting plaster at the sides of the tongue is cut off, and the surface varnished and filled up, so as to make a full model across from heel to heel, running far back upon the process, to keep the lip from pressing the plate back when the force of the muscles and lip is brought to bear upon it. After obtaining a correct articu- lation, a gutta-percha plate being used for the purpose, the teeth are set directly upon the centre of the margin, perpendicular in front, but inclined at the sides, so as to allow for a sufficient space to form an outer flange for the lip to press down upon. This flange is then made, by means of Avax, about one-third of an inch thick, with the inner surface rounded up in the same manner as the out- side but not made so thick and high, for the tongue to rest upon and keep cIoavh, thus excluding the air, the saliva which collects 1108 MECHANICS—DENTAL PROSTHESIS. under the tongue also aiding in making the vacuum. It is neces- sary that the flange should rest gently against the cheek, to give steadiness to the plate, and the teeth must be so arranged that they are level on the face. After vulcanizing, the piece is first cut aAvay by filing, at the hard margin on the under side of the outside flange, and increasing it near the edge of the plate at the cheek, and making a chamber. The inside of the plate is also cut aAvay, to free it from the sublingual muscles and glands, which tend to elevate the plate when the tongue moves upward. In cases of malformation a thin, flexible rubber flange may be attached to the plate, instead of the hard flange, so as to hold securely and conform to the movements of the muscles. Lining Vulcanite Plates with Gold.—Vulcanite plates are sometimes covered with a gold lining on the palatine surface, to prevent the contact of the rubber with the mucous membrane. What is known as the "vulcan gold lining" is composed of chemically pure gold, with a thin covering of pure silver. The flask is packed as usual and the gold is applied in one piece to the surface to be covered. The union betAveen the rubber plate and the gold covering is me- chanical ; and the sulphur in the rubber when set free by the action of vulcanizing attacks the silver, sulphurizing the surface and to this the rubber tightly adheres. If the rubber plate is covered by the gold on both sides, it is claimed that the vulcanite becomes tougher when vulcanized, for the reason that during this process the pressure against the metal gives the plate a surface more dense than it will have if vulcanized in contact with plaster. The sheets of this form of gold are of the thickness of No. 20 foil. Vulcanite for Irregularity Appliances.—Of the peculiar adaptation of the vulcanite material to the correction of irregularity mention has been made in the chapter on that subject. No further special directions'are required, except on two points: first, to have the plaster which makes the model perfectly smooth and free from air bubbles; secondly, to coat the teeth, before vulcanizing, Avith soluble glass or collodion solution. Attention to these two points will give a plate which, if the impression is correct, will fit the teeth with most perfect accuracy. Directions to Patient.—Upon the completion and insertion of a vulcanite piece, the patient should be cautioned to cleanse it thor- oughly at least once a day ; also to keep it in water when not worn in the mouth. Extreme cleanliness is advisable in all kinds of artificial work, and many patients need no such direction; the special necessity for care, in the case of vulcanite, arises from the VULCANO-PLASTIC AVORK. 1109 tenacity with which the mucous secretions adhere to the surface if, from neglect, they are allowed to collect upon it. This coating is most apt to collect at those points Avhere the friction of the tongue and of the food does not remove it; the same care is necessary for its daily removal, as is required to keep the natural teeth in good order. There is, however, this difference between cleanliness of the teeth and of the plate; that while both are essential to purity of the mouth, the secretions have no chemical action upon the plate, as they have upon the teeth. One point affecting the durability of vulcanite plates has, perhaps, not been determined by a sufficient experience. It is well known that silver and eighteen-carat gold undergo a change in the mouth, Avhich causes them to become more or less brittle; such is not the case with twenty-carat gold and with platinum. The change in these cases is partly the effect of mastication, acting as do the re- peated blows of swaging; partly a galvanic action between the molecules of the alloyed metal. A similar but much more rapid change takes place in the gutta-percha which is used for impressions; also in the vulcanized gutta-percha and in all those preparations of vulcanized rubber with which foreign substances are largely mixed for the purpose of modifying the brown or red color. The brown rubber, being purer, will probably retain its toughness and elasticity longer than the red rubber. We have some specimen pieces of red rubber which seem, at the end of tAvelve years, to possess their origi- nal strength ; and we know of one partial piece that has been Avorn constantly for ten years, which has never been repaired, and seems as strong as Avhen first made. This point, however, requires the collected experience of many observers, during a period of many years, carefully distinguishing between the brittleness of over-baking or twice vulcanizing, and that Avhich may supervene as the result of certain molecular changes in the substance of the material. It is a change which, unlike the galvanic action in gold and silver plate', may not require the presence of the buccal fluids, but which will probably take place alike out of the mouth as in ; for such is shown to be the case with gutta-percha. "Against the use of the vulcanite it is urged: 1. That it has de- graded the art by the extent to Avhich it has introduced cheap work, and by the ease with which its peculiar manipulations are performed. 2. That its medicinal action upon the system is such as to render it an unfit material to be put into the mouth. 3. That it produces an unpleasant burning or heating sensation in the mucous membrane, and a permanent sponginess of the gums, not attendant on the wearing of metallic plates. 4. That the mucous secretions require 1110 MECHANICS--DENTAL PROSTHESIS. more care for their removal from the surface of the plate than most patients are in the habit of giving; hence the liability of the piece to become unpleasant. 5. That to give the necessary strength re- quires a thickness of plate that is clumsy and interferes with dis- tinctness of enunciation. 6. That the work becomes brittle in the course of a few years. 7. That it is troublesome to repair in such a way as to maintain its original strength. "In favor of the use of vulcanite it is urged: 1. That the abso- lutely perfect and unfailing accuracy of its adaptation to the model places it, in this important respect, before every other material in use for dental plates. 2. That, being perfectly impendous to fluids and insoluble, it is a pure and harmless material. 3. That, being devoid of all galvanic action, it is more agreeable to patients than soldered and alloyed plates. 4. That it has none of the wearing action of metal upon teeth against which it becomes necessary, in partial cases, to bring it in contact. 5. That the great lightness of the material makes it very pleasant to the patient, and permits the filling out of deficiencies in the ridge with the least possible addition to the weight of the piece. 6. That this lightness, together with its peculiar elasticity, lessens greatly the danger of accidental breakage of either teeth or plate ; thus making it, when properly constructed, the strongest of all dental substitutes. 7. That the plastic proper- ties of the vulcanite and the readiness with which it may be moulded and hardened against any surface, however irregular, give it a wider range of applicability than any other substance used in dentistry." CELLULOID. Celluloid, like vulcanized rubber, a cheap base for artificial den- tures, was first introduced in 1869, and during the existence of the " rubber patents " was much used by those who objected to become licensees of the Goodyear Rubber Company. The comparatively recent improvements made in the material, and methods of manipu- lating it, have commended celluloid to professional favor as a plastic substance more in harmony with the soft tissues of the mouth, as regards natural gum color, than rubber, although it is more liable than the latter substance to change form after moulding, and to ab- sorb the oral secretions, if not properly manipulated. Celluloid is obtained from cellulose, the woody fibre which constitutes the frame- work of plants, examples of which are furnished by hemp, linen, cotton-wool, etc. In the manufacture of celluloid, the cellulose of hemp, which is the strongest, is first converted into paper by the usual method, its chemical properties during this process remaining CELLULOID. 1111 unchanged. The hemp paper is then converted into pyroxylin (gun cotton), by immersing the paper in a strong mixture of nitric and sulphuric acids, afterward being thoroughly washed. This process increases its weight about seventy per cent, and ren- ders it highly explosive, taking fire at 300° Fahrenheit. The pyroxylin is then reduced to a pulp, and a mixture made of the following ingredients: Pyroxylin, 100 parts; camphor, 40 parts : oxide of zinc, 2 parts; vermilion, 0.6 part. It will be seen, there- fore, that celluloid is composed principally of pyroxylin, with cam- phor (dissolved in alcohol) as a solvent, and that it contains less vermilion than the red vulcanizable rubbers. After the ingredients are thoroughly mixed, immense pressure is brought to bear upon the mass, by means of a hy Iraulic press of two thousand pounds to the square inch, Avhich squeezes the celluloid through a small orifice in the side, near the bottom, of a strong cylinder. This pressure is necessary to condense and solidify the celluloid, which, as it presses out of the orifice in the cylinder is cut into pieces and moulded by heat and pressure into forms suitable for dental use, called "blanks," and which, in size and shape, approximate to the bases of upper and lower dentures. These "blanks" are then sea- soned for some two months, in a room kept at a temperature of 160° Fahrenheit, when they are ready for use. To manipulate a celluloid blank into a proper denture is by no means as easy an operation as the Avorking of vulcanizable rubber, celluloid being a material that is liable to alteration in shape and character under different circum- stances. Repeated failures are the result of manipulating celluloid like vulcanizable rubber; hence perfect moulds, equal pressure, and metal dies are absolutely necessary for the usefulness and durability of such a denture. Experience proves that metal dies, which pro- duce a surface proof against disintegration, are alone reliable. The coating of the surface of a wax and paraffine plate, and also of the plaster model, with tin foil, overcome somewhat the difficulty of preventing the loss of too much of the camphor solvent by absorp- tion, and obviates the necessity of removing the original surface possessed by a celluloid plate when it is taken from the heater. In the preparation of a celluloid denture, the manipulations are the same as for vulcanized rubber, until the case is ready to invest in the flask. The plaster used for working celluloid should be of the best quality, and not mixed too thin. The pink paraffine and Avax answers better than any other material for a base plate; a thin paraffine-and-wax sheet being used for the plate, Avhich is strength- ened by adding to its surface either warmed paraffine or modelling composition, first covering the paraffine plate Avith No. 60 tin foil, 1112 MECHANICS—DENTAL PROSTHESIS. in order that the modelling composition may be removed Avithout injuring the smooth surface of the thin paraffine base plate. The teeth are arranged upon the base plate and secured by dropping Fig. 1005. melted paraffine and wax around their roots. A stick-form of paraffine and wax can be obtained, which is very convenient, the method of using it being represented in Fig. 1004. CELLULOID. 1113 The paraffine and wax compound is then carved into the shape of the gum desired, by carving instruments, such as the set of Dr. W. W. Evans, represented in Fig. 967; or a simple scraper may be used, such as is represented in Fig 1005. The surface of the paraf- fine and Avax may be made very smooth by directing upon it the flame of an alcohol lamp Avith a blowpipe, care being taken to pre- serve the outlines of the canred gum. The more perfectly the wax is carved and smoothed, the less finishing of the surface of the celluloid will be necessary. The surface of the wax is then covered Avith heavy tin foil, which is burnished doAvn lightly and smoothly. The case is now ready for investing or flasking, after which the grooves are cut for excess of material; and in every case the parting of the flask should be at the edge of the Avax, and the wax, teeth and foil removed Avith the upper half of the flask, so that the sur- face of the model or cast is left clean and entirely exposed. To prevent breaking a plaster cast, in cases of deep undercut, the method of investment suggested by the late Dr. Wildman should be followed. "It consists simply in so investing the cast that it shall occupy the position shown in Fig. 1006. If so placed, the pressure applied in moulding is brought to bear upon the mass of plaster supporting the projection, instead of upon a thin section." Cutting away the base of the cast at the heel, before investing it, will elevate the anterior part in the manner referred to. After the sections of the flask are separated, the Avax is removed by pouring boiling Avater upon it from the spout of a kettle, Avhen the tin foil Avill remain upon the plaster surface. In some cases it may be necessary to cut away the thin edge of plaster Avhich projects over the mould, in the sec- tion of the flask containing the teeth. It is recommended to cut a groove for excess of material around the inside of the flask, about one-eighth of an inch from the model, and in this section of the flask, with no cross grooves connecting the main groove with the model, as is done in the case of vulcanite. All sharp edges of plaster liable to break off should be removed or rounded, and many prefer, especially when gum teeth are used, to cut aAvay the plaster between the model and the edge of the flask, all around, about the thirty- second of an inch, to allow the surplus celluloid to escape without pressing too much upon the gums of the teeth. In using a celluloid blank, care should be taken to select one as near the size of the sur- face of the model as possible, for all folding oAvingtotoo great width at the sides will form creases in the plate; the blank may be re- duced to a proper size by cutting doAvn. Celluloid may be moulded with steam, glycerine or oil, and by dry heat, the latter giving the most perfect results. Fig. 1007 represents a sectional diagram of the 1114 MECHANICS--DENTAL PROSTHESIS. steam moulding apparatus of the Celluloid Manufacturing Com- pany. In using this steam apparatus the boiler is partly filled with water, the quantity being sufficient to cover the ribs at the bottom. The screw is turned back so far that the plunger when in position is resting against the top of the boiler, so that the model may not be injured by pressure upon the flask while the cover is being screwed down. It is very necessary that the cover should be well turned Fig. 1007. down, the gland turned back, and the screw Avorking easily, other- Avise it is impossible to determine how much pressure is exerted; for, if too much, the teeth or model may be broken, and if too little, the result is a porous plate. After the flask is placed in the appa- ratus, the screw is turned down very gently with the thumb and finger, until it is felt to touch the flask. The heat, which may be generated with alcohol, kerosene or gas, is then applied. The upper CELLULOID. 1115 portion of the safety valve, which consists of two parts, may be suspended by the pins in the lead weight, and this valve should not allow the steam to escape at a temperature of 225° F. When the steam begins to blow off, strict attention is necessary, as the plate is readily injured by too much heat without the required pressure. The time necessary from this point, with the properly regulated heat, is from fifteen to twenty minutes. When the steam escapes from the valve, its upper portion being suspended, the plate begins to soften, and the screAV is easily turned with the thumb and finger, Avhen the upper Aveight should be dropped down. The screAV is again turned very carefully, the pressure ceasing as soon as resistance is felt, and continued when it again yields. This careful screwing down is kept up, and the pressure somewhat increased as the steam rises, Avhich can be determined by raising the valve, the object being to exert an equal pressure over the entire plate, before the steam blows off very sharply and continuously on raising the safely valve. At this point in the moulding process the pressure should be increased, but an interval elapse between the turns of the screw, in order, to alloAV the celluloid, which flows very slowly, to escape under the pressure. At the end of the process, considerable pressure should be exerted by means of the screw, as much, indeed, as can be applied, or until the screw can no longer be turned. If alcohol is used to generate the heat, the cup of the apparatus is of such a size that its contents are consumed by the time the steam blows off from the safety valve, and the moulding is completed. If gas or kerosene is employed, the flame should be so regulated as to complete the the moulding process Avithin thirty to forty minutes, othenvise the celluloid may be injured. To mould celluloid in glycerine or oil, an apparatus represented by Fig. 1008 is employed. It consists of an open tank to contain the glvcerine, with a thermometer to indicate the heat, a stand on detachable legs, and a screw clamp to hold the flask. In the use of the glycerine apparatus, when the case is ready for moulding, the celluloid blank is placed in the flask, which is then put in the screAV-clamp, and the screw turned until it lightly presses upon the top of the flask. The whole case is then placed in the tank and sufficient glycerine poured in to cover the flask—about one and a half pounds. The heat (which may be generated by alcohol, gas, or kerosene) is then applied, and as soon as its effect is felt by the screw yielding to slight pressure, about 225° F., the moulding process is com- menced. The screAV should be very gently turned at first, and the pressure regulated by the softening of the celluloid, and increased 1116 MECHANICS—DENTAL PROSTHESIS. as the flask closes. The flask in the clamp can be removed from the tank at times, to note the progress of closing of the flask, Avhich should take place evenly, so as to distribute the pressure equally over the entire plate. The heat should not rise above 280° F., and if the flask is not closed completely when this temperature is reached, the flame may be reduced. Olive or lard oil may be used instead of glycerine, but the latter is preferable, on account of clean- Fio. 1008. liness. In using steam or glycerine, the flask should remain in the clamp until it has become cold; the cooling may be hastened by immersing the clamp and flask in cold water. Where the plate is of unusual thickness, or the blank is changed in shape to accom- modate it to the case, it is recommended to place the flask, secured in a clamp, near a stove, at a temperature not exceeding 140° F., for at least half a day, in order to avoid the danger of warping the plate. It is also necessary, in the use of the steam apparatus, to put sufficient water in the heater, as too small a quantity may be entirely converted into steam, which is liable to become overheated, a result which is not only dangerous, but injurious to the celluloid. In moulding celluloid by means of hot, moist air, several forms of apparatus may be used, one of the most prominent of which is the " Best" Hot Moist Air Celluloid Apparatus, represented in Fig. 1009. In using the " Best" apparatus, the plaster in the flask should be CELLULOID. 1117 made very Avet by placing it in a flask of water before it is put into the heater. After this is done the flask is placed in the clamp, the top of which is screwed down until it comes in contact Avith the flask. It is then placed in the oven of the heater and the heat ap- plied, the degree of which is determined by moistening the end of the finger and applying it to the flask. When it fizzles on contact, as a sad-iron does to the finger of a washerwoman, the flask is screwed together. Fig. 1009. RIGGED FOR GAS. RIGGED FOR KEROSENE. The point of a knife inserted between the edges of the flask will also determine the condition of the celluloid at this stage; also by experience in screAving down the flask. More pressure is applied as the celluloid softens or flows, allowing some little time to elapse betAveen the turning of the screws, until the sections of the flask are brought together, when the heat is removed in order to avoid in- juring the plate by making it porous. In the use of this apparatus the edges of the flask must not be pressed together until the cellu- loid is sufficiently softened to flow; and, on the other hand, the sections of the flask must not be kept apart too long, or the plate will become hard from the evaporation of the camphor, and ob- struct the proper closing. The case is then removed from the oven of the heater and alloAved to cool gradually, until it becomes quite cold. 9999999999955 582343 745 1118 MECHANICS—DENTAL PROSTHESIS. For moulding celluloid by dry heat, which is now considered to be preferable to either steam or glycerine, the New Mode Heater, represented by Fig. 1010, was the first apparatus invented which possessed superior advantages over the others used for the purpose, Fig. 1010. RIGGED FOR GAS. Can be adapted for alcohol by substituting the lamp for the gas-burner. GAS-BURNER. ALCOHOL LAMP". and also for vulcanizing rubber. It is a cylindrical-cast vessel, having two chambers, one within the other, the inner one being supported by piers or columns connecting its sides, top, and bottom with those of the outer chamber, the whole being made in one CELLULOID. 1119 casting. The outer compartment is the steam-chamber or boiler, and incloses the hot-air or packing-chamber on all sides except the front, where the walls of the tAvo chambers converge and become one, for the purpose of permitting access to the packing-chamber. A door, made of the same metal as the boiler, and fitted Avith lead packing to make it steam-tight, is held in place by a bridge secured Avith screws. The door is also provided Avith a plate-glass light (shown in cut), through which the operator can watch the pro- gress of the moulding in the oven. The only communication be- tween the two chambers is by means of a valve having its seat in the top of the packing-chamber, and controlled by a holloAV stem which passes through the top of the machine. B is a mercury bath ; C, thermometer; D, screw-plug; E, lam- nut; F, stem of steam-valve; G, screw-cap; H, large screw for closing the flask; I, I, I, smaller screws for the same purpose; K, K, K, L, nickel-plated caps for screws; 0, 0, steam-chamber. The New Mode Heater, Seabury's and Evans's Vulcanizers (Fig. 1010) combine in one apparatus important improvements in the means of working both celluloid and rubber, that cannot fail to commend them to the favor of the profession. It is the conviction of the inventors, which is sustained by the experience of many experts in the use of both substances, thatper- fect work in either can only be made in a dry chamber, and that where a high degree of heat is used, such as is absolutely essential in the manipulation of celluloid, the temperature must be kept uniform until the work is complete, and must not be alloAved to change suddenly. Steam is used in these machines to heat up the packing-chamber and investment, but the chamber itself can be, and for certain kinds of Avork must be, kept absolutely dry after the moulding com- mences, while the complete control which the operator has over the Avorkings of the machine enables him to maintain the heat at any desired temperature. The hot-box or packing-chamber is nearly, in one, and in the others quite, surrounded by the boiler, and steam may be admitted to or excluded from the packing-chamber at will. A case may be removed from the heater and another one inserted without reducing the temperature or letting off the steam from the boiler, thus accomplishing a large saving of time. The boiler has no steam-packed plunger or screAV to cause uncertainty as to the amount of pressure applied. The top of the boiler, in the case of the Ncav Mode Heater, is cast in one piece with the boiler; the flask is closed Avith a small key-Avrench by the thumb and finger, the screAV-bolts for closing the flask passing through the steam-chamber 1120 MECHANICS—DENTAL PROSTHESIS. in piers or columns; a steam-tight plate-glass door permits the operator to examine the work at any time during the process of moulding, enabling him to apply the proper pressure at the right time, thus reducing the liability to break the cast, investment, or teeth. The descriptions of the Seabury and Evans machines, in the article on Vulcanite, will explain their manipulation. Dry heat has no injurious effect on the celluloid material. If a piece of transparent celluloid be passed through a jet of steam, the transparency will disappear in an instant, and the material will become opaque and lose its hardness. A piece of the same trans- parent celluloid heated in a dry chamber to the same temperature as that of the jet of steam is not affected, its transparency and hardness remaining unchanged. So, too, a piece of black rubber vulcanized by dry heat is of a pure jet-black color when taken out; Avhile a piece of the same black rubber vulcanized in the ordinary method shows brownish discolorations. These simple experiments show conclusively that the action of the steam is the cause of the loss of quality. Dr. Campbell gives the following directions for the moulding of celluloid in his apparatus, which are also applicable to the others: To secure the best practical results celluloid should be moulded or pressed into the form desired at the highest possible temperature Avhich Avill not burn it. To prove this it is only necessary to mould a plate on a metal cast at the lowest temperature at which it can be done, which is less than 212°, and another on the same cast at the highest temperature possible, say 310° or 320°, and lay the two aside for a few days, Avhen it will be found that the one moulded at the lower temperature will not fit the cast, while that moulded at the higher temperature will fit as well as when first made. The reason is that the low temperature fails to overcome the tendency of the plate to return to its original form, while the high temperature ren- ders it so thoroughly plastic that this tendency is entirely eradicated. This is proportionally the case with pieces made at intermediate temperatures; the higher the temperature to which the plate is sub- jected in moulding, the more exactly will it hold its new form and the less will be its tendency to warp. Celluloid may be readily and safely manipulated in the New Mode Heater at 320°, a temperature many degrees higher than is deemed safe in other machines, and which accomplishes perfectly the result above noted, and produces a plate which is believed to be absolutely unchangeable in color, form and texture. When this very high temperature is employed the celluloid should be in the machine only long enough to permit the closing of the flask; for the reason CELLULOID. 1121 that heat vaporizes the camphor—the solvent of the material. If too much of this is driven off before the flask is closed it will be almost impossible to mould the blank to the desired form. The sooner the flask is closed after being placed in the oven, the more readily it will be done, and the better will be the result. The moulded surface of a piece of celluloid is much more durable than its interior, and will retain the color better. It is obvious, therefore, that this surface is essential to the integrity of the plate, and should be preserved intact. To insure this, the case should be so prepared that the plate, when taken from the flask, Avill require little or no labor to make it ready for use. It is possible that some surplus material at the edges may have to be trimmed off and the edges smoothed, but the case is not properly prepared if more than this is necessary. The care and trouble involved in proper prepara- tion will really save time, will absolutely avoid interference with the fit by the too free use of files, sand-paper, pumice, etc., and will in- sure a durable plate with a permanent imitation of gum-color. Moreover, the artistic taste of the operator may be exercised before the plate is moulded more readily than aftenvard. Paraffine and Avax compound is used for the base plate, according to directions before given, and the teeth arranged, the wax carved into the shape desired by means of carving tools, and made smooth. The piece is then invested in plaster, the usual grooves cut, the wax teeth and tin foil being removed Avith the upper half of the flask in parting. The Avax is then removed by means of boiling Avater, as before described, the tin foil, No. 60, used for covering the paraffine and Avax plate, remaining upon the plaster, and the investment is noAV ready to be dried out preparatory to receiving the celluloid. Drying the Cast and Investment.—To dry a plaster cast and invest- ment, and keep them free from cracks and checks, is very difficult by the ordinary means, but with the New Mode Heater it can be done so perfectly as to permit their use in casting pure gold or gold alloys. There are two Avays of drying the investment in the New Mode Heater: first, by raising the temperature to 320°, keeping the hot box dry; second, by admitting steam to the hot box. The former method can be used Avhen the investment is placed in the chamber before getting up steam. If steam is up, hoAvever, either method mav be employed. In using the dry heat method, open very slightly the screw cap of the piston or valve stem, to permit the escape of the steam generated from the water in the plaster, being careful that the steam valve is firmly seated, as otherwise all the steam made in the boiler will escape. In using steam for drying, admit the live steam 71 1122 MECHANICS—DENTAL PROSTHESIS. into the chamber Avith the investment, by raising the valve from its seat, keeping the screw cap closed. The steam quickly permeates the plaster, and in five or ten minutes the temperature of the plaster is high enough to convert the water in it into steam. As soon as the plaster is thoroughly heated, shut off the steam by closing the valve, and raise the screw cap very slightly, to alloAV that in the chamber to escape sloAvly through the small aperture at the side of the screw. In a few moments the cast will be perfectly dry, the steam escaping from the chamber, carrying with it that generated from the moisture in the plaster. Extreme care should be taken that the steam shall escape very slowly, as otherwise the plaster may be blown out of the flask into the oven, by the too rapid expansion of its vaporized moisture. The completion of the drying process is known by steam ceasing to be given off at the screw cap, G. The drying may be facilitated by placing a small chip of wood between the tAvo parts of the flask when it is put into the chamber, thus ex- posing a larger surface to the heat and allowing the moisture to escape more readily. Moulding by Dry Heat.—When the investment is dried, remove it from the chamber and insert and carefully adjust the selected blank; replace the flask in the oven immediately under the screws; see that the two sections are so placed that the guide-pins will enter properly into the lugs; open the screw cap a turn or two to alloAV the escape of the gas from the hot box; turn doAvn the large screw until it bears lightly upon the top of the flask, and close the machine. In less than five minutes the material will be sufficiently softened to permit the commencement of the moulding. The screAvs will turn readily with the thumb and finger (using the smaller key- wrench), when the blank is properly softened. Close the flask gradually, stopping occasionally if the resistance is too great. Usu- ally, if the temperature is about 300°, the flask can be closed in ten minutes; but if a very thick blank is used, the moulding must pro- ceed slowly; the small screws may be used to advantage, and more time, say thirty minutes, may be consumed. As soon as the flask is closed—unless a lock flask is used—the flame should be extin- guished, the door opened and the machine alloAved to cool. If a lock flask is used, it may be removed and thoroughly cooled before opening it, the oven being meanwhile ready for another case. The cooling may be accomplished rapidly, if necessary, by placing the flask in water. WThen perfectly cold, remove the plate from the in- vestment ; it Avill be found enveloped in the tin foil which had been burnished to the wax plate. Peel off the foil. The celluloid Avill present a hard, brightly-polished surface, received from its contact CELLULOID. 1123 with the foil, and will need no further finishing than cutting off the ex- cess of material and smoothing down the edges. The extra hardness of the surface will thus remain to preserve the integrity and color of the piece. It is claimed, also, that the contact of the foil renders the outer surface, which is always the densest portion of celluloid, much harder. Imitating Gum Membrane.—The plate produced by the above method is of the ordinary appearance, with smooth, polished gum, but a much more natural, life-life gum will result if the tin foil, after being burnished to the wax plate, is " stippled." This is done by " dotting " carefully o\7er its surface with a dull-pointed instru- ment, which should be held nearly perpendicularly to the surface to be operated on, and the strokes should be gentle—not hard enough to perforate the foil. When the foil is removed, after the case is moulded, the gums present an appearance closely resembling the natural membrane. The stippling need not occupy a great deal of time, and the result it produces is a marked improvement. Metal Casts and Deep Undercuts.—Many dentists who prefer to use metal casts have doubtless found difficulty in removing the finished plates in cases of deep undercut. The fact that a melted metal cools from the surface toAvards the centre, supplies an effectual remedy. When the metal is poured into the sand, allow it to chill only about a quarter of an inch on the outside, and then pour the balance out of the mould. This makes a holloAV cast or shell. Fill up the cavity Avith plaster and proceed as usual. After the plate is moulded, remove the plaster, place the edges of the metal cast in the jaws of a vice, and crush the shell. This will free the piece Avithout disturbing the teeth. The plaster in the shell also affords the means of attaching the cast to the articulator. A plaster core in the form of a cross may also be inserted Avhen pouring the metal die in the base, which will divide the core into four sections, which may be crushed together in a vice, and thus liberate the celluloid plate. Repairing.—If a portion of a plate has been broken away and lost, fit a piece of celluloid of the proper shape, leaving it some- what larger than the space to be fihed. Make sure that the surfaces to be united are perfectly clean; even the perspiration from the hand may cause a dark line. Flask and mould as usual. A crack in a plate, or the parts of a broken plate, may be joined by scraping the surfaces clean, or washing them with alcohol, and moulding a thin strip of celluloid into the seam. The followed method of repairing small breaks is suggested by 1124 MECHANICS—DENTAL PROSTHESIS. Dr. M. H. Cryer, and possesses the merit of extreme simplicity, and its results are in the highest degree satisfactory: Remove all portions of the broken tooth from the plate, taking care not to disturb the outlines of the socket. Select a tooth 01 proper size and shade to replace the broken one. (If the tooth is numbered, a considerable part of the trouble of selection may be saved by taking the number of the mould from the reverse impres- sion in the plate, or from the broken pieces.) Having set the new tooth partly in its place, hold it steadily over the flame of an alcohol lamp, carefully guarding the celluloid from contact with the flame. In a few seconds the tooth will begin to grow warm, and its heat will soften the celluloid sufficiently to allow the tooth to be pressed into its proper position with a napkin. This will cause a small bulge or raised spot to appear in the celluloid opposite the lingual portion of the root of the tooth. Invest in plaster, in the deeper section of the flask, covering the whole plate and the teeth, except the small portion of the celluloid raised in pressing the tooth into place. Complete the investment, part the flask, and dry the case, after which insert a piece of rather thick writing paper or heavy tin foil over the raised spot, and place in the oven. Heat up to the usual temperature for moulding and close the flask. When the case is cold the tooth will be found firmly fixed in its position, and there will be no mark to show that the plate has been repaired. In case a small portion of the celluloid is chipped away from the front of the socket—enough only to expose the end of the root when in position—drop a little wax upon the vacant spot, after placing the tooth, and carve to the shape desired. Without removing the wax, invest and mould as before described. The wax will pass off into the plaster and its place will be supplied by the celluloid, of which there is usually enough to permit the flowing of the minute quantity required without damage. If there is a similar deficiency on the inside of the plate, ex- posing the pins of the tooth, drop wax into the vacancy and pro- ceed as before, except that in this case the Avax is to be removed when the investment is made, and the bit of Avriting paper or tin foil is to be placed just below the pins, instead of over them, so as to force the flowing of the celluloid to cover them. To remove a tooth from a celluloid plate, hold the outside surface of the tooth to be removed in the flame of the lamp until the heat softens the celluloid around the pins slightly, when it may be taken off without trouble, and it will come away clean, Avithout any of the celluloid adhering to the pins. Do not move the plate back and forth through the flame, or other teeth than the one desired CELLULOID. 1125 may be loosened, or their perfect articulation may be interfered with. There is no danger of cracking the tooth so long as the flame does not come in contact with the pins. Fig. 1011 represents the first process in repairing a celluloid plate from which a tooth or block has been broken. The plate being cut away sufficiently to allow the new tooth to be adjusted by grinding a new piece of celluloid (a) is fitted to the space. The new piece is then removed and its place filled up with wax. Fig. 1012 shows the piece invested in the lower section of the flask, the space filled with Avax being the only portion visible, the entire surfaces of the plate and teeth being covered. The upper section of the flask is then adjusted and filled up with plaster. When the flask is opened, the wax is removed and the new piece of celluloid returned to its place, and upon it is placed another Fig. 1012. small piece of celluloid, or a roll of tin foil, to produce pressure upon the new piece first added, the edges of which, as well as those of the space into Avhich it is fitted, being moistened with spirits of camphor or liquid celluloid to bring about union. Liquid celluloid is made by dissolving small pieces of celluloid in spirits of camphor. The piece is then placed in the heater and subjected to the usual process. Where the plate is of considerable thickness, a new tooth or block may be added Avithout new material by cutting away as little as possible of the old plate on the lingual surface, and depending upon the thickness of celluloid pressing up, after being softened in the heater, closely to the new tooth. Loose teeth may be tightened in the same manner, wax being introduced into the \racant space and removed after the flasking. Some object to the use of a solvent in repairing on account of the 1126 MECHANICS—DENTAL PROSTHESIS. liability of the newly-added material to become porous. To cleanse celluloid plates previous to repairing, they should be placed in a solution of whiting and water, to which is added some liquid am- monia, and allowed to remain some time, when they are brushed with soap and water, and finally washed in clean water and dried. NEW MODE CONTINUOUS GUM. With reference to the second objection to the use of rubber, it is to be said that the perfect reproduction of natural effects and really artistic work cannot be made with block teeth. To obtain the proper expression, each tooth should be available for placing in any position desired, instead of being arbitrarily held in associa- tion with others, as in a block. The invention of the New Mode machine places in the hands of the profession the means for overcoming this objection by using plain teeth Avith rubber for the base, and celluloid, which is Avell suited for the purpose, for the gum, the combination forming an exquisite piece of work which the inventor calls the " NeAV Mode Continuous Gum." It is easily the nearest approach to porcelain continuous gum that has been obtained with plastic materials. Its general adoption would do away with " bad joints " and broken blocks, which are so often a source of serious annoyance. It is the only rubber plate upon which a tooth may be replaced without re- vulcanization, and which after the repair is equal in strength and appearance to the original piece; and the only one upon which repairs can be repeated any number of times without injury to the original plate. This same style of work can also be done with gold and Avith cast-alloy plates. Directions for Making the New Mode Continuous Gum.—Using teeth made expressly for continuous-gum or celluloid work, set them up in wax in the usual manner, leaving the front or outside of the roots exposed. Cut a thin strip of the wax, warm it, and attach it to the upper edge of the portion of the wax plate representing the gum, forming a rim which extends all around the outer margin. Finish the palatine surface to the form desired, invest in the flask in the usual manner, remove the wax, pack with rubber, and vulcanize. When removed from the flask the case will present the appearance shown in Fig. 1014, the front or outside of the roots being exposed and the narrow undercut rim extending all around, leaving a space with retaining grooves between the teeth for forming a gum of celluloid; looking very much as though the substance of the plate had been gouged out for the purpose. The vulcanite plate is now completed, with the teeth firmly attached to it. NEAV MODE CONTINUOUS GUM. Fig. 1013. 1127 Fig. 1014. Fig. 1015. Fig.1016. 1128 MECHANICS—DENTAL PROSTHESIS. To put on the gum, fill up the groove with paraffine and wax (this compound, not being sticky does not adhere to the instru- ment and is therefore more easily carved to the form desired), until all the space inside the rim, including the retaining grooves between the necks of the teeth, is occupied. After the wax has hardened, which may be hastened by placing in cold water, carve it into the desired form of gum. The wax may be made very smooth by throwing upon it the flame of a spirit lamp with the aid of a blow- pipe, taking care not to destroy the outline of the carved gum. Cover the wax with heavy tin foil, burnishing it lightly but smoothly to the wax. Invest the piece again in the following manner : Place the plate in one section of the flask, Avith the teeth upward, and raised at the front at a greater or less angle, as may be necessary, so that when the investment is completed the upper part of the flask may be re- moved without dragging. Imbed in plaster to the rim, and pour plaster over the palatine surface, covering the crowns, and taking care to fill the interstices between the necks of the teeth, but leaving their outer surfaces exposed. After the investment sets, pour more plaster around the inner edge of the flask ring, forming a ridge, leaving a groove or space between it and the plate. (See Fig. 1016.) Complete the investment and remove the wax from the groove and interstices between the roots of the teeth by pouring boiling water over it. Having selected a celluloid blank of proper size, saw off the outer rim (see Fig. 1013); warm this rim of celluloid in boiling water, and with the hand and a cloth press it closely about the teeth, and hold it to its place until stiff; it will then remain there until the two parts of the flask are entered upon the guide-pins. Join the two parts of the flask together and place the investment in the oven of the machine, having previously heated up the chamber. When the temperature of 280° is reached, the flask may be closed. As soon as this is accomplished, the case is ready to be removed from the oven and placed in a clamp to cool. When perfectly cold, remove the plate. The tin foil wdll adhere to it. but it can be readily removed by inserting the point of a knife under the edge and pulling it off, leaving the surface of the celluloid gum as smooth and polished as that of the foil. A surface produced by the above method presents a smooth, pol- ished gum, but if the tin foil is "stippled," as before described, a striking resemblance to the natural membrane will be produced, the finished plate presenting the appearance shown in Fig. 1015. The adjoining edges of the celluloid and rubber will be found perfectly united, each preserving its sharp outline. NEAV MODE CONTINUOUS GUM. 1129 Dr. D. Genese recommends the folloAving method of Avorking cellu- loid, Avhich Avill give a hard, smooth, polished surface to the plate Avhen it leaves the heater, regulate the size of the celluloid blank before it is moulded to the surface of the metal die or cast and about the teeth, and also form a metal cast, Avhich is easily removed from the celluloid plate after it is completed : Two perfect impressions in plaster are taken of the mouth, one of which is used to secure a plaster model, upon which the trial plate is formed, of wax and paraffine. Upon this trial plate a rim of wax is built, and the exact bite secured. In Avax, only the model of the piece desired in the finished case is then formed, Avhich is attached to a metal die, which has been obtained by moulding the plaster model in sand. The Avhole is then moulded in sand, and a zinc and lead die and counter-die obtained, by means of Avhich a tin cap (made of rolled tin, No. 29 gauge) is swaged, which will completely envelop the wax model, extend OArer ihe gum portion, and to the full height of the finished " bite.''' The edge of the tin cap, Avhich is left rough, is turned up at an angle of about forty-five degrees, so as to form a support for it in the plaster, when it is invested. The object of this cap is to form a metal mould in Avhich the celluloid blank can be shaped to the form and size desired for the case in hand. The modelled Avax is then transferred to the plaster model, which is invested in the lower half of the flask, and the surface of the investment varnished over and oiled, to ensure the required separation. The tin cap is then placed over the modelled Avax sur- face, and the upper half of the flask filled with plaster. When the flask is separated, the Avax is removed from the plaster model, the tin cap remaining firmly secured in the upper half of the flask. The celluloid blank is then placed in the tin cap mould, and the sections of the flask brought together by being piaeed in a heater. Upon removing the blank from the mould, in the flask, any excess of celluloid can be removed, and a blank of a proper size and form secured which will not press the teeth out of position in the subse- quent moulding of the plate. It is necessary to secure a duplicate bite to mount the teeth, which is done on a metal die or cast, formed as follows: The second plaster impression is removed from the impression cup, and imbedded in a sand and plaster investment as deep as it is desired to have the cast. A right-angle cross, with arms about half an inch wide at the upper surface and tapering to a sharp edge (&), is then made of plaster mixed Avith sand, and placed over the sur- face of the plaster impression, in such a manner as to bring the sharp edge almost, but not quite, in contact with the impression 1130 MECHANICS—DENTAL PROSTHESIS. surface, where it is secured by sealing the ends of the arms to the margin of the impression. A metal die or cast made in this manner is divided into four sections by the cross-core, very nearly to its surface, and is more readily removed from the celluloid plate after it is moulded, than the hollow metal cast, as the removal of the plaster core will permit of the sections of the cast being bent aAvay from any undercuts which may exist. After obtaining the form of metal die described, the teeth are mounted upon a trial plate formed over it, and according to the duplicate "bite," and the new wax plate is modelled into the form desired for the finished celluloid plate. An impression in sand of the Avhole is again obtained, a zinc die and lead counter-die poured, and a tin cap similar to the one first made is SAvaged. This tin cap forms a complete metal casing, and on flasking, is secured in the upper half of the flask by means of its turned edges. The case is then flasked in the usual manner, and on separating the sections and removing the wax, the celluloid blank, Avhich has been previously moulded into form, according to the manner described above, will be found Avell adapted to the mould. The case is then placed in one of the combination heaters, and moulded at a temperature of 300° Avhich should never be ex- ceeded ; and no pressure should be applied by the screAvs until this heat is obtained. The construction of partial sets is more difficult, but the process is the same as for entire dentures, a cap of somewhat lighter tin being used. By this process the edge only of the plate, and a slight excess of material about the necks of the teeth require trimming off, the entire surface being polished without any scraping away, by first using fine pumice and glycerine, and finally Avhiting and glycerine. The plate should be thoroughly cleansed, after re- moving it from the flask, of all particles of plaster that may adhere to it, and the entire manipulation be conducted Avith clean hands and instruments. A metal cast somewhat similar to the one above described may be made by first moulding in the usual manner, and aftenvards sawing all around the alveolar ridge with a fine saw, leaving only what will hold the parts together. Plaster is poured into the spaces made by the saw, in order to render the cast solid. When the set is finished the plaster is removed from the spaces, and pressure made by a vise upon the edges of the cast, so as to crush them in and thus free the plate. Dr. M. H. Cryer devised the filing of notches in celluloid blanks as in Fig. 1017, Avhen the counter-sunk tooth-croAvns are to be mounted in this material. The suggestion obviates the defects found to attend the mounting of these teeth in the usual way, for the con- NEW MODE CONTINUOUS GUM. 1131 fined air in the cups commonly prevents the celluloid from entering far enough to more than half fill them, and thus the pins are left untouched. As a consequence the teeth come off in the process of finishing; or, Fig. 1018 shows the effectiveness of the plan which provides for the escape of the air, Avhile the plastic promontories enter the countersinks and surround the pins, by means of which the teeth are firmly secured to the plate, on which they thus have so strong a hold that the labial necks of the crowns may, for conformity to the adjacent natural teeth, be quite uncovered by the celluloid (see Fig. 1019), and the mounting be yet a strong one, as is evid- enced by the section through plate and crown, Fig. 1020, Avhich il- lustrates a countersunk tooth crown. In this instance the short Fig. 1017. Fig. 1018. Fig. 1019. Fig. 1020. celluloid festoons (see Fig. 1019) lie close upon the gum, Avhich they much more nearly resemble than the dark vulcanite when such a base is made. When the celluloid blanks are moulded upon plaster surfaces, files, scrapers, and fine sand or emery paper, are necessary in the finish- ing process, completing the operation of polishing Avith whiting or prepared chalk, applied by means of a soft brush Avheel. Camphor, applied on a soft cloth, is also used to obtain a polish, especially betAveen the teeth and other places beyond the reach of the brush wheel. Friction with the brush wheel, sufficient to heat the plate should be avoided, on account of the danger of changing the shape of the plate and injuring the surface. Dark lines on celluloid plates are often the result of using blanks too Avide for the case, or too thin in the centre, causing the celluloid to press toward the middle of the 1132 MECHANICS—DENTAL PROSTHESIS. plate and fold upon itself. Where the arch of the mouth is very deep, the pressure by means of screws should not be applied before the blank is well softened by the heat, otherwise it may tear apart. Too little pressure, or too little material, may cause a porous plate; also overheating in the dry heat apparatus; the same condition in steam heating may result from too little pressure at the proper time. If the temperature of a celluloid plate is raised to 270°, without any pressure being brought to bear upon it, the material becomes puffed up and is ruined in texture, and cannot be restored by any subse- quent manipulation. Celluloid flows very sluggishly, hence suffici- ent material must be present to insure a perfect plate. The celluloid blank may be softened in boiling water and formed into any desired shape, and an excess at any point may be removed Avith a sharp knife. It should be remembered that there is no union between celluloid and rubber, hence when one of these materials is added to the other, it can only be done by dovetailing or drilling holes. Good, hard-setting plaster should always be used in working cellu- loid, and it should be well mixed by adding it to the water in such a manner that all is absorbed that it will take up. Care should also be taken not to mix the plaster too thin, or to use very fine plaster, as a coarse grade of strong plaster will give better results. Some are in the habit of adding clean white sand, or marble dust, to the plaster. The following directions are given in the use of the New Mode Heater, which will prove serviceable in the working of cellu- loid generally: Ahvays use good plaster, and do not mix too thin; always select a blank which nearly fits the cast, with an excess in every part; always turn the screws as soon as they will yield to the thumb and finger, and always gently; always folloAV up the rise in temperature with increased pressure; always give the material plenty of time to Aoav between the turns;.always increase the pressure toward the close of the moulding; always reduce the temperature of the piece at once after the completion of the moulding, and keep the plate under pressure until it is stone cold. ZYLONITE. A modified form of celluloid has been introduced under the name of zylonite, the working results of which appear to show a great difference in quality. Zylonite, like celluloid, is composed of pyroxylin and camphor, but in different proportions, being, it is claimed, a chemical combination, while celluloid is a mechanical mixture. PORCELAIN TEETH. 1133 Possessing translucency, the effect of zylonite in the mouth is very pleasing, and, so far as it has been tested, promises to be more durable than celluloid, Avithout the tendency to warp or to change color Avhen ordinary care is taken in its manipulation, Avhich is the same as for celluloid. The zylonite blanks are uniform in color, and although this material requires the same amount of pressure to mould, it flows with a more perfect sharpness of outline than cellu- loid, and apparently does not disintegrate. CHAPTER XVI. PORCELAIN TEETH. 9 As Pharmacy Avas once a part of Medical Practice, and instru- ment making a part of Surgery, so the manufacture of porcelain teeth Avas at one time confined to the dental laboratory. Until within the past thirty years, a practical knoAvledge of the Dento-ceramic art Avas considered an essential part of dental education. Galen com- pounded his celebrated Theriaca for two Roman emperors ; Pare and Wiseman made many of their surgical instruments ; and neces- sity has compelled physicians and surgeons in all ages to imitate these examples. But the medical and surgical Avorld have for many years committed the manufacture of drugs and instruments to those Avho, by making it a special art, can produce far better results. The time has fully come Avhen Dentistry should do the same Avith porcelain work, for tAvo sufficient reasons: 1. Manufacturers now offer to the profession porcelain teeth in such variety of beautiful forms, that not one dentist in a thousand could equal them. 2. Moderate proficiency in block-carving requires such an amount of preparatory training and of continuous experience, that the dentist's education and practice must suffer in the line of important duties Avhich cannot thus be delegated to others. Hence, nearly, if not quite all, of the most skilful block-carvers engaged in the practice of dentistry have, since the year 1850, one after another, given up this art, wThich it cost them so much to acquire. For these reasons, and also because the management of a porcelain furnace cannot be taught in books, Ave shall not attempt in this chapter to give a full and didactic exposition of the manner of making porcelain block or single teeth. Those Avho desire such knowledge with a vieAV to making it a specialty, require that which no longer comes within 1134 MECHANICS—DENTAL PROSTHESIS. the scope of a work on the " Principles and Practice of Dentistry " to teach. There is, however, on the part of all students, and probably of most practitioners, a desire to know the composition of dental por- celain, and to have some idea of the manner in which a few earthy materials and metallic oxides are made to assume such beautiful forms. Some knowledge of the component parts of porcelain is essential to a correct understanding of the necessity for their ad- mixture, as well as of the effects thus produced. PORCELAIN MATERIALS. The infusible earths, Silica and Alumina, and the fusible alkalies, Potassa and Soda, form the bulk of all porcelain. Certain metallic oxides, in small quantity, give color, and some varieties of pottery are modified by small proportions of Lime and Magnesia. Dental porcelain is made from the purest compounds of silica, alumina, and potassa, colored by metallic Gold and Platina, and by the oxides of Gold, Titanium, Manganese, Cobalt, and Uranium. SILICA. Silica (quartz, silex, silicic acid) is, next to oxygen, the most uni- versally diffused substance in nature, constituting 50 per cent, of all rocks. Granite, granitic rocks, sandstones and sand contain not less than three fourths silica ; mica schist, clay-slate and clay, not less than two-thirds; trap-rocks and lava, one-half. Silica is to the mineral kingdom what carbon is to the vegetable—the element of stability. In its purest forms (rock crystal, Brazilian pebbles, or crystals of quartz), it is free-from discoloration by iron or other oxides, it is absolutely infusible, and is insoluble in water; this is the kind selected for dental porcelain, but for other varieties of por- celain, flint is commonly used. It forms silicates with alumina, magnesia, lime, potassa and soda; the most important of which, in this connection, are the silicates of alumina and potassa. Silica, as found in feldspar and kaolin, is partly pure silica, partly the silicate of alumina. Noav the " behavior " in the furnace of silica and the silicate of alumina is different; hence, chemical analysis can esti- mate only the relative purity of these substances; experiment alone •can determine the proportions of each necessary for the develop- ment of any required property in porcelain. FELDSPAR. Next to silica, alumina (oxide of aluminium) is the most univer- sally diffused of all minerals; but, unlike silica, it is rarely found PORCELAIN TEETH. 1135 uncombined. The gem Sapphire is pure crystallized aluminium, and is the next hardest mineral to the diamond ; a less pure form is Avell known in dentistry as emery or corundum; some specimens of Avhich seem, under the lens, to be a collection of minute crystals of dark-colored sapphire. For porcelain manufacture, aluminium is never used in its purest state, but in its natural combinations Avith silica, lime, potassa and soda. For dental porcelain only two of these are used—Feldspar (known to the Chinese as Pe-tun-tse) and Kaolin. Feldspar is a silicate of aluminium and potassa, containing a little lime and a trace of iron. A less common variety of spar contains soda in the place of potassa; it makes a soft porcelain, fusible at loAver heat than the potash spar. Lime feldspar is used in some kinds of pottery, but for dental purposes potash feldspar is the only variety. It is an abundant mineral, and is often found in large masses; the purest varieties alone are used for dental porce- lain. Delaware and Pennsylvania spars are most esteemed by American manufacturers. Its most extensive dissemination, how- ever, is as one of the components of granite and granitic rocks, by disintegration of the feldspathic constituents of Avhich large beds of porcelain clay are formed, as found in China and Japan, England, Germany, and France, and also in the United States. Kaolin.—Ka-o-lin (the Chinese Avord for clay) is the purest of these mixtures of silica and silicate of alumina, prepared in Nature's laboratory, for the manufacture of porcelain. Pipe clay, potter's clay, blue clay, fire clay, and Cornish stone are similar in composition, but only the purest kaolin is used for dental porcelain. It contains nine parts of silica and eight parts aluminium ; Avhereas, spar has nine parts silica and only two parts aluminium; also spar is made fusible by its silicate of potassa—kaolin has none. Kaolin is, therefore, feldspar, deprived of its soluble silicate of potassa (or soda) Avhich has been washed out during the disinte- gration of the feldspathic rocks. It is soft and unctuous, and is highly plastic; pulverized spar, on the contrary, is granular or poAvdery, and is moulded with difficulty. Kaolin, like silex, is in- fusible ; under intense and continued heat it shrinks greatly and be- comes extremely hard, but it is ahvays porous and absorbent. Silex lessens the contraction of kaolin, spar gives it fusibility; both diminish its absorbent quality, so objectionable in any mate- rial that is to be worn in the mouth. Stone Avare, China Avare, Wedgewood Avare, Parian porcelain, and Dental porcelain vary in their properties because of the different proportions in Avhich kaolin and feldspar are combined, also in the kind of flux used. For instance, the Parian statuettes have kaolin 1136 MECHANICS—DENTAL PROSTHESIS. and spar in equal proportions, with about half as much of a flux, made of spar, quartz and potash. Dental porcelain demanding less heat, less shrinkage and a more translucent appearance, has a very much greater proportion of spar. It has required a very ex- tended series of experiments to combine silica, aluminium, and potassa in correct proportions, and to know just which of Nature's compounds it is best to use, in order to harmonize the requisites of strength and beauty, so essential to the character of a porcelain tooth. COLORING MATERIALS. The foregoing materials give a pure white porcelain of greater or less translucency. It is now required to find substances Avhich will, in the strong heat of the furnace, yield indestructible colors, by skilful combination of which the porcelain may imitate the almost endless varieties of tint in the natural teeth and gum. Of these there are three principal colors and three subordinate ones. Titanium.—The purest varieties of the oxide of titanium are se- lected ; it is found as a mineral in various localities throughout the United States. The crystals are reddish-broAvn, and have a bright metallic lustre; they give, when ground, a beautiful yellow, or yel- lowish-brown color. It is used in the coloring of all body, and is the basis of color for the class of yellowish enamels. Platinum.—This metal, precipitated from its solution in aqua regia, then washed and dried, is known as platina sponge. It gives a gray-blue color, and is the basis of color for the class of grayish-blue enamels. Gold.—Gold precipitate is used to give life and animation to the tooth, producing often a very remarkable effect. The oxide of gold, known as Purple of Cassius, and generally considered to be a mixed oxide of gold and tin, is used to impart the well-known red color of the artificial gum ; no less costly substitute has ever been found for this purpose. Oxide of Manganese gives a purplish color, and is used occasionally for some shades of tooth, but not of gum. Oxide of Cobalt gives a bright blue color. If wrapped in best blue paper, and burned in a covered crucible, it is called the ashes of cobalt, and is thought to give a more desirable tint to the enamel than the simple oxide. Ox- ide of Uranium is used in its mineral form, and gives "a greenish- yellow color; while a lemon-yellow color may be given by the oxide of silver; but this is a fugitive color at high temperatures. These colors, singly and in combination with each other, produce a great variety of colors or shades. Thus, say forty shades of body color are made by using these materials in different quantities and in PORCELAIN TEETH. 1137 different combinations; also a like number of enamel colors. Then, starting with the lightest shade of body, forty different grades may be produced, by using a different point enamel; so of each of the forty shades of body, making, if required, sixteen hundred varia- tions of shade. The following formulas will suffice to give a correct idea of the proportions in Avhich the preceding materials are combined, to give the Body and Enamel of porcelain teeth, single or in sections: Feldspar, Quartz, . Kaolin, . Titanium, . 12 oz. . 2 oz. . 15 dwts. 24 to 48 grs. Feldspar, Sponge platina, Flux, . . 3 oz. 1 to 4 grs. . 3 dwts. The Flux here mentioned is made by fusing four ounces of finely ground quartz with Glass of Borax and Sal Tartar, each one ounce; it forms a transparent glass. The following formulas show the pre- paration of Gum Enamel: GUM FRIT. GUM ENAMEL. Oxide of gold, 10 grs. Gum frit, . 1 oz. Feldspar, 1 oz. Feldspar, . 3 oz. Flux, . 8 dwts. The titanium, platina and oxide of gold must, in these recipes, of course, be modified by mixture with other colors, to produce the re- quisite varieties of shade. BODY FOR MOULDED- BLOCK TEETH. No.l. No. 2. Kaolin, . 1 oz. German clay, . 1 oz. Silica, . 3 oz. Silica, .... 3oz. Feldspar . 18 oz. Feldspar,. 18 oz. Oxide of titanium, . 65 grs. Oxide of titanium, . 65 grs. Starch, . 10 grs. to each ounce. Starch, . 10 grs. to each ounce. BODY FOR CARVED BLOCKS. No.l. No. 2. Kaolin, 1 oz. German clay, . i oz. Silica, . . 3£ OZ. Silica, .... 3£ oz. Feldspar, . . 14 oz. Feldspar,.... 14 oz. Oxide of titanium, . 40 grs. Oxide of titanium, . 40 grs. BLUE EXAMEL. YELLOW ENAMEL. Platinum blue frit, . • 1 gr- Titanium, 1 gr. Feldspar, . . 1 oz. Gold frit, 2 grs. Starch, . . 15 grs. Starch, .... 15 grs. 72 1138 MECHANICS--DENTAL PROSTHESIS. We shall now briefly describe the processes by which the porcelain teeth and sections sold to the profession are manufactured. PROCESS OF MANUFACTURE. The silex and feldspar, in their crude state, are first submitted to a red heat, then suddenby thrown into cold Avater. This is called '' Calcining," and the effect is to render them more easily broken and pulverized. All impurities having been carefully removed, they are crushed between flint stones ; when fine enough, they are put into a mill, formed of burr millstone, with chasers of the same material. They are ground in water, then floated off, and allowed to settle. The water is then drawn off or evaporated; the silex and spar, dried and sifted, are then ready for use. The kaolin, having been already pulverized in Nature's laboratory, is prepared by washing until per- fectly free from impurities, and Avhen dry is ready for use. The flux and frit are coarsely ground, but the coloring materials are reduced to an impalpable powder. All these porcelain materials are com- bined in proper proportions to form the body and the enamel, then mixed with Avater and worked into masses resembling putty. When, however, the method of biscuiting is adopted, the enamels are mixed in a much thinner state than the body. The unbaked porcelain masses are now ready for the moulding room. The moulds in Avhich single teeth or sections are formed are made of brass, and are in tAvo pieces—one-half of the tooth being represented on either side. The precise shapes desired are carved out with great care; holes are drilled to receive the platina pins in each tooth ; when the two halves are fitted accurately together, Avith guiding pins for exact closure, the mould is ready for use. The brass matrix must be made about one-fifth larger than the size desired, to allow for shrinkage of the porcelain paste. After greasing the moulds, the first operation is, by means of small tweezers, to place the platina pins in the holes made for them (there are many sizes of these pins, differing in length and thickness, to suit the different sizes of the teeth). As no piece of mechanism can be stronger than its weakest point, there should always be such a relation between the tooth substance and the pins, as to shape, size, and angle of in- sertion, that one will be as strong as the other, and both sufficient for all legitimate uses. The strength of pin, without loss of strength in the tooth, characterizes a recent and valuable improvement made by the late Dr. S. S. White, and known as the "foot-shaped pin," il- lustrated in Fig. 1021. The thickest part of this pin is at the angle, or heel; the point, or toe, runs upAvard into the thick part of the tooth, giving additional security against its being drawn out. The PORCELAIN TEETH. 1139 insertion of the pin at an upward angle beds it in the strongest portion of the tooth material; thus any weakening of the thin por- tion of the tooth is avoided, as Avhen the headed pin is inserted in a straight line; also, the greatest amount of material is found Avhere the greatest strain is brought to bear upon it. The force of mas- Fig. 1021. tication is exerted outward and toward the necks of the teeth; thus the shape and direction of this pin are best calculated directly to oppose it. It will also be noticed that its direction and unusual length of insertion permit a close grinding of the tooth, Avhich would cause the usual short and horizontal pin very soon to break away from the porcelain. The double-headed pin, a previous patented Fig. 1022. invention of Dr. White, was a very great improvement in the shape of tooth pins; but it has been superseded by this new "foot-shaped pin." Fig. 1022 represents both plain and sectional gum teeth with the lateral or cross-pins, devised by Dr. C. H. Land, Avhich, it is claimed, give greater strength to the completed denture than Avhen teeth with the ordinary pins are used. For continuous-gum teeth a complete arch is formed by tAvisting or soldering the pins together, thus lessening the strain upon any single tooth, and allowing a much lighter plate to be used. What are styled " countersunk teeth " are also manufactured, in which the pins are attached to the teeth in a depression or cavity formed in the base of each tooth. (See Dr. Cryer's method of mounting, in Chapter on Celluloid.) 1140 MECHANICS--DENTAL PROSTHESIS. The pins being properly adjusted, the enamels for the tooth and the gum are placed in the moulds by means of a small steel spatula, carefully placing them in the exact position and quantity required ; the body is placed in them in lumps corresponding to the size of the teeth; the top of the mould is then put on and the matrix placed under a press, which compacts each separate mass. They are then dried by a slow heat. When perfectly dry the top is re- moved, and the teeth will iioav drop out. In this state they are extremely tender, owing to the large percentage of feldspar, and require very careful handling. They are now sent to the trimmers' room, Avhere each tooth is carefully inspected, and all imperfections removed or filled up; the spare edges left by the union of the two sides of the mould are smoothly filed, and the arch of the gum over each tooth made rounding and true Avith a small pointed instrument. They are then placed on beds of coarse quartz sand, on trays or slides made of fire-clay, and are ready for the furnace. Formerly, there was another process, called crucing, or biscuiting, Avhich was univer- sally practiced, and is still used in some factories; it is also used in the making of blocks carved to order. It consists in submitting the teeth after moulding, to a heat sufficient to harden them so they can be cut or filed like chalkj and Avhat is called an outside enamel is then applied Avith a camel's-hair brush; but it has been found that the composition of the tooth is injuriously affected by this partial burning, subsequent cooling, enamelling and reburning. This process is unavoidable Avhen the blocks are carved by hand for special cases; but Avhenever they can be made in a matrix, the tooth is better and stronger Avhen it is enamelled in the mould and finished in a single firing. The furnace is built substantially on the principle of the dentists' furnace (Fig. 043), differing chiefly in size. The trays holding the teeth are placed in the muffle, and are thus protected against in- jury from the gases of the fuel. There is no rule Avhich can be given to determine the exact amount of time the teeth must re- main in the furnace; the practiced eye of the burner must deter- mine from the appearance of the teeth Avhen the firing is completed. If taken out before they are done the enamel Avill craze, or crack, in cooling; if a little too much done, the surface will be too glassy, and the body will not be strong. When cool the teeth are removed from the slides, placed upon wax cards, and are then ready for the dentist. The vast variety in shape, size, color, etc., of the teeth thus made gives opportunity for the selection of forms suitable to nearly every PORCELAIN TEETH. 1141 case Avhich presents itself to the practitioner. The assortment must of necessity be very large and varied to meet the wants of the oper- ator; in fact, the manufacturer has shown a better appreciation of the aesthetic requirements of the dental art than the practitioner. While the Avork of the latter too often exhibits an unmeaning mo- notony, the former has made provision for even the extreme cases which are sometimes met with; he has also given a beautiful series of those various deviations from a uniform regularity Avhich are so common in natural dentures. In some mouths these seem to be imperatively demanded to restore the familiar expression; while in any mouth, the use of some one or other of them Avould go far to disarm that suspicion of artificiality, detection of which is mortify- ing to most patients. Porcelain is a material in which the beauty of the result well re- pays the highest exercise of Art. It has been for centuries a favorite material for expressing the Poetry of Form. The famous Etruscan vases of antiquity, the exquisite gems of the Majolica of the six- teenth century, the marvellous Avork of Bernard Palissy, the prince of potters, the beautiful productions of the Sevres and Dresden manufactories, the AvellknoAvn charming designs of the Wedge- Avood ware, and the still more recent Parian statuettes, may be named in proof of the fitness of porcelain to embody the concep- tions of Genius. Dental porcelain is Avorthy of such associations; not only like them does it delight the eye and give evidence of high aesthetic cultivation, but it adds to beauty the charm of usefulness. It is customary to attribute the rapid groAvth of Dental Art, since 1840, to its associations, colleges, journals, and its didactic litera- ture—and Avith much truth. But to porcelain it OAves its very ex- istence as an aesthetic art, and the larger part of its extent and utility as a prosthetic art. It was altogether impossible for per- ishable human teeth, or their Avretched imitations in ivory, to offer sucli tempting fac-similes of nature as we meet in porcelain. By thus creating that enormously increased demand for dental service which has been the chief cause of the rapid development of its re- sources, it has made the dental profession its debtor to a greater extent than any other single influence. The depot not only renders service by the superior excellence of the surgical instruments and prosthetic materials Avhich it supplies, but it directly benefits the science and art of dentistry by releasing the practitioner from man- ufacturing toil, and giving time for the acquirement of increased knoAvledge and skill. Thus, if the time heretofore given to block making Avere deA'oted to the study of dental aesthetics, patients would have the benefit of an artistic selection from a far larger 1142 MECHANICS—DENTAL PROSTHESIS. variety of porcelain dentures than could otherwise be possibly made. The illustrations of this chapter can but imperfectly convey an idea of the beauty and expression of the originals; they will, however, assist the student in his study of those principles which guide in the selection and arrangement of teeth; they may serve also to aAvaken practitioners to the extent of the present resources of Ceramic dentistry, and to the importance of aesthetic culture in order properly to make full use of the same. The improvements in the Dento-ceramic Art have sprung from a careful inquiry into the essential characteristics which artistically formed porcelain teeth should possess. Among these are (1) Naturalness; under which term are included shape, color, and a vital appearance; the last depending upon the precise amount of translucency, the texture of the surface, and the nice blending of the colors of the body and enamel—an appearance which should be maintained as well under artificial as under solar light. Many teeth which will bear inspection reasonably well in daylight, have a very unnatural and artificial appearance when exposed in the mouth to a light under which the Avearer may be most anxious to excite ad- miration. (2.) Shape; Avhich includes a preservation of the distinc- tive characteristics of each tooth, securing the instant recognition of its position in the dental arch. There must be some defect or inaccuracy of form if, out of the twenty-eight teeth of a set, in un- assorted confusion, an experienced eye cannot tell the place of each; for every tooth has its distinctive contour. Not only should each tooth possess the individuality which belongs t'o it, but it should also indicate the character of its relation to its companions on either side, and to its antagonist. The eye trained to observe nature should not be offended by the recognition of any inharmony; should not find a second bicuspid or molar in place of a first, or incisors undistinguishable from each other, or an upper tooth in place of its corresponding loAver one; nor should it detect in the midst of one style of denture some incisor or canine characteristic of another. Figs. 1023 and 1024 exhibit very strikingly the marked peculiarities of each one of the twenty-eight teeth of an artistically designed artificial set; Avhile these and subsequent illustrations demonstrate how possible it is for modern dentistry to adapt its work to the great varieties of facial expression. Probably every reader has more than once turned at the sound of a familiar voice, to see a face strangely resembling the looked-for friend. This cor- respondence between voice and face, often so startling, is only another one of those links betAveen external and internal confor- PORCELAIN TEETH. 1143 mation, Avhich makes the study of aesthetic anatomy essential to the success of the dental mechanician. The great laAV of correspondence which enabled Cuvier to build up the entire skeleton from a single bone, makes us associate the Fig. 1023. idea of intellect with certain forms of forehead, and of character Avith certain forms of mouth, nose, and chin; it is the same law which Fig. 1024. permits us to infer from what remains, the expression of what is lost. Age, sex, temperament, and complexion; also many physi- 1144 MECHANICS—DENTAL PROSTHESIS. cal, mental, and even moral peculiarities, are suggested to the acute observer by certain characteristics of the dental organs. The artist Avho seeks to restore harmony in the facial expression should be skilled in the observance of these varied manifestations; such skill is demanded alike in the manufacture and in the application of artificial dentures. In addition to these aesthetic qualities, porcelain teeth should possess (3) Strength adequate to the legitimate use for Avhich they are intended; this strength should come from the quality of their composition, the skilful distribution of bulk to parts most requir- ing it, and from the due form, position, and proportion of the pins, Fig. 1025. Fig. 102". rather than from any increase in bulk and weight beyond that of the natural organs. They should possess, also, by reason of their conformation (4) Adaptability to the various irregularities caused by unequal absorption of the alveolar ridge, so that when judi- ciously selected they shall require little labor to adapt and antago- nize them. Special provision should be made for the results of ex- treme or very irregular absorption, or for the loss, by disease or otherwise, of parts of the maxillary ridge, so that in such cases the teeth can readily be made to articulate and afford comfort to the wearer, assisting in speech and mastication, and yet not presenting any incongruous appearance. There are, moreover, special modifications demanded by many other conditions; as, for instance, in cases having a very short ar- PORCELAIN TEETH. 1145 ticulation, requiring the pins to be set in a recess near the crowns of the teeth, and also in countersunk depressions under the base of each tooth, thus bringing the greatest resistance where there is the greatest strain in mastication; as is Avell shown in Figs. 1026, 1048. In both these blocks the full external size of tooth is given, and its characteristic form and the expression of interdental gum pre- served ; this could not be done with the usual form of blocks, ground doAvn to suit such cases. In Fig. 1025 we have front blocks for mouths where a shoulder is required to antagonize with the lower front teeth when there are no back teeth remaining. Where early contraction and protrusion of the upper maxillary arch has caused it to have a sharply curved projection, bringing the closure of the lower teeth much behind the upper ridge at the central inci- Fig. 1027. sors, or where absorption above has left a ridge prominent at its loAver edge or margin of the gum, it becomes necessary to give a peculiar tAvisted form to the front blocks. In Fig. 1027, the first tAvo blocks are for a pointed arch, accompanied in the second by a croAvded denture, so often seen in such cases. It is impossible to adapt blocks of ordinary form to such cases without destroying their true expression at one or other of the joints; in fact, much of both gum and tooth is often sacrificed to get correct articulation. The third blocks are shaded with a view to show the fulness of gum at the centrals and its falling back over the canines; this is also shown in the sectional vieAvs of the first and third blocks. For cases in Avhich the lower jaAV closes more or less in advance of the upper maxillary ridge, a large gum is often necessary, as in 1146 MECHANICS—DESTAL PROSTHESIS. Fig. 1029; but such mouths require a peculiar form of block if the loAver jaw has much projection. Where such a prominence of the gum exists from want of exterior absorption or the previous wear- ing of a plate, as to require the teeth to be set directly upon the ridge, there should be no artificial gum betAveen it and the lip. When the molar block of loAver sets extends to where the ramus of Fig. 1028. the jaAv begins to rise, a peculiar ploughshare curve of the base is required; such that, while the gum of the second bicuspid lies on the outside of the ridge, the gum of the second molar may lie partly upon the ridge, so as to give more perfect antagonism with the Fig. 1029. upper molars. The molar and bicuspid teeth from which Fig. 1028 was drawn are also marked'by a characteristic curve of the buccal surfaces, giving not only a very natural appearance, but acting as a guard to the cheek and preventing its being caught between the teeth. Fig. 1029 illustrates the difference of shape required for a mouth PORCELAIN TEETH. 1147 Avhere front absorption permits the artificial gum to overlap the alveolus, and one Avhere fulness of the natural gum requires the block to set directly upon it. In the latter case, if the color of gum is judiciously chosen and the blocks AA'ell adapted, the triangles of artificial gum will be scarcely, if at all, distinguishable from the natural; Ave regard this as an extremely useful form of block. Sectional view of the molar in the upper cut shows the curve nec- essary to bring its grinding surface directly under the ridge; the AdeAvs of grinding and cutting surfaces, together Avith front vieAVS, sIioav Iioav each tooth has a distinctive character; as, for instance, in the bicuspids so often chosen Avithout regard to the difference in form betAveen the first and second. Again, the curve of the front block shoAvs two of several variations required in the curvature of the arch ; in the upper, the sharp turn at the canine gives a square- ness across the incisors ; in the loAver, this turn is at the central, and is adapted to a pointed arch. Variations in curvature of the Fig. 1030. arch are also shown in Figs. 1024, 1037. Notice also the marked difference in the character of the bicuspids and molars in upper and loAver cuts, and the totally different expression of the front teeth. Fig. 1030 shoAvs hoAV the same intermaxillary space may be filled Avith teeth of a Avidely different size as well as character. In the - first, a very long tooth and short gum ; in the second, a very long gum and short tooth. But length of teeth is by no means the only difference here; relative size of central and lateral, direction of the axis of lateral and canine, and outline of cutting edge of the block, are three features Avhich equally mark the distinctness of these two styles ; these also are points Avhich demand that both long and short teeth shall differ among themselves as widely as these samples differ from each other. The lateral vieAV of these teeth shoAvs another marked difference in form. Fig. 1031 gives the characteristic equality of loAver incisors, or slightly greater size of the lateral; it also gives some of the diversi- ties in length, Avidth, shape of cutting edge, and form at arch of the gum. Altbough there is much less difference in the shape of the 1148 MECHANICS—DENTAL PROSTHESIS. six lower front teeth than of the six upper, it is a great mistake to suppose that a given lower block will answer for any lower case if only long enough. Side views show also a difference in the slant of the teeth, inward or outAvard, which has an important effect in modifying the expression of the lower arch. There are also dif- ferences in curvature of the loAver arch as Avell as of the upper. Fig. 1024 shows the usual upper and lower curves, and Figs. 1029, 1037 Fig. 1031. show variations of upper curvature requiring some modifications of the loAver, dependent on the character of the articulation. In Fig. 1032 are four other forms of lower front blocks, the value of which will be at once recognized. The two right-hand sets differ from those of Fig. 1031 mainly in the length and width of teeth. Fig 1032. The left lower set is well suited to patients whose natural teeth, for many years before their loss, Avere marked by exposure of the neck; this appearance may also be increased (sometimes it may be made) by judicious use of the corundum wheel, but the block here given is invaluable for such cases. The left upper block is an admirable imitation of a very usual arrangement of incisors, resulting from crowded dentition; the draAving gives a very imperfect idea of the great beauty of the original porcelain block. When the facial ex- PORCELAIN TEETH. 1149 pression indicates its use, it will have great effect in disarming sus- picion of artificiality—a very desirable quality in artificial dentures. In Fig. 1033 we have very convenient modifications to suit front spaces of two or four teeth; the set of four being in two blocks. Fig. 1033. The peculiarity of these blocks is the lateral finish of the gum; instead of a square joint, for fitting to an adjoining block, they have a rounded edge of gum color that can be adapted to the curves Fig 1034. of the absorbed natural gum. There should also be blocks of tAvo, a lateral and central, with gum shaped like the double central, as such spaces are of frequent occurrence. Besides the four forms of Fig. 1035. teeth here given there are many other varieties in size and shape of this very useful kind of block. Figs. 1034, 1035, and 1036 represent a few of the great variety of 1150 MECHANICS--DENTAL PROSTHESIS. forms of upper incisors and canines designed to meet the demands of an aesthetic discrimination. In Fig. 1034 we have, first, a long, delicate lateral, with sloping but not rounded edge, shoAving a de- cided space between it and the cuspid and central; then we find it wider, with corners and edge rounded and filling the space. Lastly, for want of space, the laterals, although long and narrow, overlap the centrals; this style is generally accompanied with a pointed arch. The fourth block, although with an overlapping incisor, has an entirely different character; it is often found in a rather flattened arch, and does not indicate a croAvded denture. In these blocks Fig. 1036. the inclination and shape of the canine as well as the shape of the incisor help to give to each block a distinctness of character which will not permit the use of one in a case demanding either of the others. The celare artem effect of overlapping or twisting laterals, like that of irregular lower incisors, is such as to tempt one to use them whenever admissible. In Fig. 1035 we have some additional varie- ties of this kind of block. In all these six cases we find differences in the size and character of the lateral, in the extent of its lapping, and in the degree of twist given to it. A careful study of the natural teeth Avill teach the dentist Avhat character of face is best suited to each of these different forms, and thus he will much increase the extent to Avhich he may properly use this kind of irregularity. In Fig. 1036 the blocks vary little in size, yet they each have a distinctive character. In the first, Ave have lateral rounded on both corners, and its axis vertical; canine, with pointed cusps and edges quite rounded. In the second we have lateral inclined, with me- PORCELAIN TEETH. 1151 dian corner pointed, lateral corner quite round; canine Avith blunt cusp, also axis inclined. In the third, surface of the canine is de- cidedly furrowed, which, with the indented edge, gives it a marked character; the lateral and central, unlike the previous blocks, have square-cut edges with corners but slightly rounded. In the fourth, the lateral is more nearly equal to the central, and none of the teeth may have any marked peculiarities; this style of block, in its dif- ferent sizes, suits Avell in many cases, and is perhaps one of the best for general use by those practitioners Avho pay no regard, in their se- lection of teeth, to the indications given by the physical characteris- tics of the face and head. The fifth block is one of that class often met with in old age, where, by the action of the loAver teeth or other causes, the arch has spread, Avidening the interdental spaces. The interdental gum is also much shorter than in youth, as is finely shown in the original from Avhich this cut is taken. In the selection of porcelain blocks, not only must the color, size, and form of the teeth be carefully considered, but reference must also be had to the cunrature of the arch. For although moderate variations in curvature can be fitted by the same set of blocks, the true expression of a porcelain denture is often lost by the attempt to adapt it to a curve for Avhich it Avas not designed. In Figs. 1024, 1029 and 1037 we have various curves of the alveolar arch, Avith corresponding variations in shape of the blocks. Sometimes the canines are made separate with a vieAV to increase the range of ap- plication of a given set; but a joint on either side is very apt to injure the effect of this important tooth. In the loAver jaw it is of less consequence because the gum is less often exposed, and it is frequently desirable to make the four incisors in one block. But in the upper jaAV it is much better to have a median joint, and another behind the canines. In Fig. 1037 the reader Avill notice that the centrals of the first set overlap the laterals, an arrangement of frequent occurrence in promi- nent and sharply curved arches. It will be observed that in Fig. 1027 the blocks are so shaped that the right or left central overlaps its felloAV. Thus Ave have three varieties of overlapping upper teeth; laterals over centrals, centrals over laterals, central over central; each of Avhich may be used with great effect if applied Avith discrimination. In the third set of Fig. 1037, and in a feAV of the preceding cuts, the gum over the cuspids is very strongly marked. This is a very characteristic feature of some mouths, and Avhen correctly used gives a fine effect; but it Avould sadly belie the expression in a timid and gentle lady's face. Yet such in- congruity is only one of hundreds constantly occurring, where 1152 MECHANICS—DENTAL PROSTHESIS. every sense of aesthetic beauty and harmony is violated; teeth of a Russian in the mouth of a Frenchman; those of a New Englander given to a South Carolinian, or those of a Canadian to a Cuban— the lips of age disclosing the teeth of youth, and no distinction Fig. 1037. made betAveen a male and female denture. These aesthetic blunders are not confined to the inexperienced tyro, but are perpetrated by many who presume to call themselves skilful mechanicians. When we consider the extensive assortment of porcelain teeth Avhich ce- ramic art has placed at the disposal of the practitioner, such mal- practice is without excuse. s PORCELAIN TEETH. 1153 These are only a feAv out of the great number of varieties, in size, form and arrangement, of porcelain teeth; they give to the dentist a much Avider range of selection than some have the ability or in- €^oo CS= clination to avail themselves of. When to variety of shape avc add shades of color, the number of sets that admit of being made, dis- tinguishable at a glance from each other, seems almost infinite. A Fig. 1039 156 Fig. 1040. 123 visit to a first class porcelain tooth manufacturer's rooms will con- vince any one that incongruity or Avant of expression in a set of teeth is the fault of him avIio selects and applies, rather than of him who designs and makes dental porcelain. 73 1154 MECHANICS—DENTAL PROSTHESIS. Fig. 1038 represents upper and lower gum sections of four, three, and two teeth, one of the upper sections having partial gums. Fig. 1039 represents an irregular gum section with the lateral out of line. Fig. 1042. I Fig. 1043. Fig. 1044. x^* Fig. 1040 represents a gum section with an extra long central in- cisor. Fig. 1041 represents a thin gum section. Fig. 1042 represents gum sections for protruding upper and lower jaws. Fig. 1043 represents a shouldered gum section. Fig. 1044 represents a festooned gum section. PORCELAIN TEETH. 1155 Fig. 1045 represents a gum section for a V-shaped protruding upper jaw; the position of the lower teeth is shoAvn by the dotted lines. It Avill be perceived that the foregoing illustrations* of the aesthetic principles of the dento-ceramic art are taken from one class of teeth, those for vulcanite or metallo-plastic work. We have done Fig. 1045. so because the art has here had its fullest recent development, in consequence of the great demand for this form of block. But dental aesthetics is quite independent of the material of the plate, so long as that Avhich is Adsible in the mouth is porcelain ; and den- tures Avhich show any substitute for the gum other than this, how- ever useful they may be, cannot rank as specimens of highest art until some material for the plate shall be discovered possessing higher claims to beauty than any yet knoAvn. * WTe are indebted to the kindness of the late Dr. Samuel S. White, and more recently of the S. S. While Dental Manufacturing Company, of Philadelphia, for the admirable illustrations by the aid of which we have been enabled to express our views upon the important subject of denial ^Esthetics. No illustrations, however, can convey a true idea of the high artistic excellence of those forms the production of which has placed Dr. White among the greatest benefactors of Dental Art. We take this occasion to ncknowedge, also, the liberality and courtesy with which onr inquiries for information on the manufacture of dental porcelain were responded to by this gentleman. 1156 MECHANICS—DENTAL PROSTHESIS. The foregoing rules will apply to the form and size of plate teeth when these are set directly upon the natural gum; but, except in case of true pivot or plate-pivot teeth, it is impossible to reproduce the precise natural arching of the gum above the tooth without some gum-colored porcelain. We must often be content in such cases with the nearest possible approach to nature. But when the plate is seen on the outside of the arch, the artist's reputation is depend- ent upon the concealment of the greater part of his work; even here, hoAvever, the cutting edge and two-thirds of the tooth permit the display of great varieties of expression. Of plain teeth Avithout gum there are four kinds. 1. Pivot teeth; shaped someAvhat like the crowns of the upper incisors and canines, with a hole in the base for insertion of a Avooden or metallic pivot. 2. Plate teeth; the oldest known form of porcelain teeth having pins for attachment of a back by Avhich to secure it to the plate. 3. Continuous-gum teeth; resem- bling natural teeth in having a root, which is more or less serrated, for better retention in the investing porcelain base; they are some- times made without platina pins ; but they are better with pins, so that they may be securely fastened to the platina plate. 4. Plain vulcanite (Fig. 1053); having a small neck, by which they are held in the vulcanite or other material in which they are set. These teeth may be set directly on the gum by grinding off the neck; they may also be used adjacent to natural teeth with exposed neck, by slight alterations of this neck, so as to give to the artificial tooth the same appearance as the natural one. There are also other forms of gum teeth besides those above rep- resented. Formerly, single gum teeth were extensively used on gold plate, and may still be occasionally required when the supre- macy of that old-fashioned material becomes once more recognized in the laboratory. The great facility of adapting blocks or sections in vulcanite work or in vulcanite attachment to swaged plates has led to the almost entire exclusion of this form of tooth except for repairing. A serious objection to single gum teeth is the number of joints; these greatly mar the artistic effect Avhich it is the design of the artificial gum to produce, especially when not kept perfectly clean, or Avhen the material of plastic plates is allowed to enter the joints. Figs. 1023 and 1046 are designed to shoAV the importance of correct and accurate grinding in order to display the true character of a set of teeth. When properly done, the joint does not inter- rupt the continuous surface of the gum more than the lines in the two loAver sets of Fig. 1046; nor should it in any case be more visible than the heavier lines of the first set. Neither should the set be so inaptly chosen as to require such grinding of joints and base as to PORCELAIN TEETH. 1157 injure its original expression. Figs. 1023 and 1046 should also be carefully studied by the student on account of the varieties of form and relation of teeth presented ; each of the four upper sets here displayed having a very distinctly marked character. Porcelain blocks Avhich are to be attached to a gold plate by soldering do not differ in external appearance from the forms already illustrated; but the shape of inner surface and the form of the pins are different. Fig. 1047 represents such a set of upper blocks in three sections. If made in four sections, the set should be divided betAveen the centrals and betAveen the bicuspids; it may Fig. 1046. also be in five sections, the four joints being in front of the cuspids and behind the bicuspids; or it may be divided into six sections, as in Fig. 1023. The line above the pins in Fig. 1047 marks the division betAveen the inner slope of gum next the teeth and the plain surface holding the pins ; this surface should be as smooth as pos- sible, for the perfect adaptation of the gold backing. Blocks may also be made in sets of three or five sections, Avith the inner surface finished in gum enamel to the plate; in this case the block is held to the plate by pins passing into holes made in its base, one opposite each tooth. The best material for retaining the pins is undoubtedly vulcanite, as described in the previous chapter; the holes should be rough, for its better adhesion. Fig. 1048 represents the "Countersunk Tooth Crowns" which alloAV of great facility of adaptation to the maxillary ridge, and (it is claimed; afford the strongest denture on a plastic base. To insure 1158 MECHANICS—DENTAL PROSTHESIS. the best results some precaution is necessary in mounting them, whether on rubber, celluloid, or metal. For a vulcanite base, the case should be flasked as usual, but each countersink should be carefully filled with small pieces of rubber; otherwise the flat rubber sheet will cover the mouths of the counter- Fig. 1048. sinks and so shut in the air as to prevent the rubber from reaching the pins and filling the cavities. When the base is of celluloid, the countersinks must be filled, in like manner, with pieces of celluloid moistened with spirit of cam- Fig. 1049 90 A phor; or preferably with a solution of celluloid, and the case heated to softness before closing the flask. For a fusible metal base, the hot flask should be jarred during the pouring to drive the air out of the countersinks. Fig. 1049 represents perforated bicuspid blocks. Fig. 1050 represents rubber bicuspid blocks with pins. 90 B PORCELAIN TEETH. 1159 The dental depots cannot keep on hand an assortment of such blocks, since the demand is too limited to justify the expense of the brass moulds. But in all our principal cities there will be found one or more dental-block carvers, Avhose experience and constant practice enable them to make any style of blocks that may be de- sired for special cases. We have elseAvhere given our reasons for thinking this a better plan than for the dentist himself to attempt occasional ceramic experiments. Let him prepare an accurate ar- ticulating model, and adapt a tin-foil plate (to avoid the risk of sending the gold one) ; then select one or more teeth, to guide the carver in the required color and character of the set. If any peculiar form or deviation from the normal arrangement is desired, this should be represented in wax ; then pack carefully, and send to the block carver. This plan is recommended to those Avho may desire, Fig. 1050. 80 A 80B for some special case, a form of blocks not to be had at the depots. Necessarily such blocks'are much more expensive than those made by the quantity in brass moulds; but if the dentist A'alues his time, the blocks would cost still more if made by himself. The true question is, however, not one of cost; if the depot can furnish the form of blocks Avhich the case requires, it is best to get them there, otherwise, they must be had elseAvhere and at any cost. Dental tradesmen, Avho sell their Avares at a moderate advance on the cost of production, may not deem it prudent to deal in such high- priced materials; but the professional dentist, who charges for "services rendered," Avill never find it necessary to hesitate incur- ring any expense requisite for the perfection of his work. The actual cost of material in single dentures has often exceeded thirty dollars; yet the mechanician Avho exercises a skill commensurate Avith this cost never has found, and never will find, difficulty in adding a just compensation for his time and skill. As a rule, patients will pay best for art Avhen exercised on expensiA'e material, except Avhere, as in painting, the effect produced is wholly irrespective of the cost 1160 MECHANICS--DENTAL PROSTHESIS. of the means employed. The true basis of professional fees lies in that which makes one man's Avork superior to another's; namely, artistic skill exercised upon materials, the quality of Avhich shall not detract from its just appreciation. As we have briefly described the processes of manufacture of porcelain dentures on a large scale—a work Avhich, of course, no practicing dentist proposes to engage in—it is proper that Ave should also give a brief description of the processes by Avhich blocks are carved for special cases, although we regard this as equally out of the line of the modern dentist's duties. We occasionally find a genius, whose gift shows that ceramic art, not dentistry, is his true profession; but men engaged in ordinary dental practice must, in justice to their patients, make use of the experience of professional block carvers, or they must use those forms offered by the ceramic manufacturer, which are the results of the highest artistic skill Avhich money can command. SPECIAL BLOCK CARVING. To make a porcelain dental arch in three sections for a full upper case antagonizing with natural teeth below, make a plaster articu- lator, as described in the tenth chapter, but having greater thickness, to permit guiding holes or grooves, as in Fig. 1051. Open the articu- lator, increasing the space one-fifth (unless this one-fifth enlargement is to be made by addition of point enamel); place on the plate a wax rim, and trim it to antagonize with the lower teeth, giving the precise external fulness required in the blocks. Mark on Avax and front edge of articulator the medial line and the lines of proposed division of blocks ; that is, between bicuspids for a four-block piece, and behind cuspids for a piece of three blocks; in either case the work is carved in three pieces. It is also well to mark, in fainter lines, the width of each tooth as determined by the size of the loAver teeth; this will be some guide in the subsequent enlargement, re- quired on account of shrinkage of the porcelain paste. Next make a plaster rim about half an inch thick (Fig. 902, on page 970, shows the height and thickness), covering the exterior surface of model and wax; making first the front section, extending a half tooth space behind the lines marked for the block joints ; then remove this, and make the tAvo side sections, extending each a half tooth space in front of these lines. The use of a leaden band and some paper pulp will expedite the making of these plaster sections; they should be trimmed to the exact length required for the crude blocks. Of course, neither in plaster nor porcelain can the front and side sec- tions be applied to the model or plate at the same time, in conse- quence of the one-fifth allowance for thickness. SPECIAL BLOCK CARVING. 1161 On removing the wax, each plaster section is a matrix to determine the external fulness of the corresponding block, on which is to be carved the shape of teeth and gum. The plate gives exact form to the base of the block; but when finished, it will require grinding, because of the derangement of fit caused by shrinkage. The thick- ness and interior form of the sections is determined by the eye, and Avill vary with the style of finish or mode of attachment, being careful, in this direction also, to make the one-fifth allowance for shrinkage. The front block is first made artd removed, then each side block separately; in a double set, both front blocks are made, then both right sections together and left sections together, so as to Fig. 1051. Fig. 1052. obtain their proper antagonism ; also, in double sets, the separation of the articulation must be sufficient to alloAV the one-fifth enlarge- ment in each set. The porcelain body is prepared as already explained; it can be compounded by the dentist, or purchased from the manufacturer. In mixing the small quantities required for single cases, two points demand special care—purity of the water and absolute exclusion of air from the mass. It must also be remembered that irregular con- traction, or Avarping of blocks in firing, is often caused by unequal compression in packing the body into the moulds, and by unequal 1162 MECHANICS--DENTAL PROSTHESIS. absorption of its moisture, by the porous plaster rim or other means used to dry it. Again, it should be remembered, in removing the rim, in carving and in all other operations on the crude paste, that the excess of feldspar gives it a tenderness very different from the tough plasticity of a kaolin mass. The putty-like body is to be carefully worked into the well-oiled mould, compressed Avith the fingers, trimmed into outline shape, and then removed, first mark- ing upon it the lines of the articulator, to guide in the carving. The block may be partly or entirely carved while on the articulator; but the delicate movements of the very delicately-shaped carving tools are, in the opinion of some, best exercised upon the free block. For carving, no directions can be given beyond what has hereto- fore been said on the necessity of a close observance and exact copying of nature. The artist requires no Avritten directions, and paper instructions never yet made an artist out of a bungler; in fact, the heaven-born genius of art cannot be created by teaching hoAvever it may be trained and directed. Many have wasted years in porcelain block carving, only to produce results surpassed by the least artistic forms offered in the depots; while on the other hand, some dental Palissy will work out a marvel of beauty that no pur- chased blocks can equal. But before one imagines himself a Ber- nard Palissy, let him read the history of that Avonderful struggle of genius; then ask, how far the routine duties of a dental office will permit an exclusiveness of devotion, Avhich ceramic art rigorously exacts as a condition of success. When carved, the blocks are thoroughly dried, then placed on coarse silex upon a fire-clay slab, and set into the muffle of the furnace, (Fig. 1052). Here they are biscuited (or cruced), that is, raised to a red heat sufficient to give some hardness, but not to vit- rify or eA'en to cause incipient fusion. They are then slowly cooled, and holes drilled for the pins, or else holes drilled into the base of the blocks, as may be preferred ; the pins are fastened in place by a little " body-slip," carefully worked in with the knife point. Slight defects of carving may now be corrected; the enamels are then ap- plied with a camel's hair brush. They must be reduced to the con- sistence of cream, and require much skill and judgment in their application, so that the point enamel shall blend properly with the body enamel; also the gum enamel must preserve its distinctness of outline, and, by its varying thickness, give those alternations of shade observable in the natural gum. It should here be remarked, that some carvers make no allowance in the body for shrinkage in length of the tooth, but compensate by the addition of point enamel. The croAvns of bicuspids and molars are usually enamelled ; also part of SPECIAL BLOCK CARVING. 1163 the inner surface of the blocks, and in some blocks the gum enamel extends to the base. When platina pins are inserted, the part of the block to be covered by the backing is not enamelled. It is scarcely necessary to remark that a large assortment of body, point, and gum enamels is required ; also that these must, with great care, be kept separate, with their respective test pieces attached; for, ex- cept by the pinkish color of gum enamel, they cannot be distin- guished Avhen in form of powder, paste or cream. The blocks are now well dried, and are ready for the furnace, Fig. 1052. (For other forms of furnaces, see article on " Continuous Artificial Gum.") Success thus far is dependent upon: 1. Thorough mixing of the body and its careful packing; 2. Skilful carvdng, so as not onby to give the required expression, but also to know Avhat allowances to make at each point for shrinkage and for the subse- quent application of the enamels; 3. Selection of enamels and their skilful blending and shaping; 4. The giving of such form, in ad- justment of the relative length and thickness of each b'ock and apportionment of material, as shall prevent warping in the furnace. These points, however, may have been perfectly attended to; yet all will have been done in vain, unless the operator has a thorough practical knoAvledge of the management of the furnace. It is this Avhich makes the ceramic experiments of the practicing dentist so often a failure; for fail he certainly will unless he knows the exact heat at which the differing fusibilities of his body and various enamels will, by their combined effect, develop the properties aimed at in their composition. Some are governed in this by test pieces; the experienced Avorkman, guided by constant practice in a Avay that he cannot explain, prefers the indications offered by looking at the piece itself. If not sufficiently baked, the body will be porous; also neither this nor the enamels will havre their true life-like char- acter. If overdone, there is an offensive, glassy, and transparent condition, equally fatal to the natural appearance; also, there is too much shrinkage and greater danger of warping. Both errors impair the full strength of the porcelain, in Avhich the ingredients are so combined as to develop greatest strength at a certain temper- ature. Furnace temperature is measured by instruments called Pyro- meters. The limit of mercurial registration of temperature is 600° Fahrenheit. Daniell's pyrometer registers by the expansion of a platina rod in a plumbago case, and is the most accurate. Wedg- wood's pyrometer registers by the rate of permanent contraction of kaolin under intense heat. A clay wedge fitting the upper part of a tapering groove will, after exposure to furnace heat, slip further 1164 MECHANICS—DENTAL PROSTHESIS. into the groove; supposing the rate of contraction uniform, this distance will be a measure of the heat after establishing its exact relation to the 600° point of Fahrenheit. But the contraction of any two pieces is not the same unless their composition is identical; also, the relation to the mercurial scale is not easy to determine. WedgAvood's zero was 1076° Fahrenheit, and he estimated one de- gree of his pyrometer equal to 130° ; on Avhich basis of calculation the highest heat of the porcelain furnace (130° to 160° WedgAvood") would range from 19,000° to 22,000° Fahrenheit). Others estimate his degree at 62.5° Fahrenheit, reducing the registration from 9500° to 11,000 Fahrenheit. Taking the fusion point of gold at 2000°, and of pure iron at 3000°, we thus have some idea of the infusi- bility of platinum and the extreme heat of ceramic furnaces. But it is evident that the correct regulation of this heat must be the re- sult of experience rather than of Avritten direction; also, that the furnace practice of different persons cannot be accurately com- pared. The muffle protects against the gases of the fire. Charcoal, coke, or anthracite are used as fuels, according to the location of the operator; the last is preferable Avhen it can be procured, because it gives the steadiest heat; charcoal requires practice to maintain a uniform heat; coke is used in all the bituminous coal regions. With either of these, after sufficient experience, a furnace may be kept regularly at the required heat for a length of time sufficient to fire the porcelain blocks. They must be thoroughly dried on the furnace-shelf before going into the muffle; the mouth of the muffle should be Avell luted, and the stopper Avithdrawn only to examine the work. The more sloAvly blocks are cooled, the more perfectly are they annealed, and hence less liable to crack from sudden changes of temperature, as in soldering. Not to interrupt the order of operations, we have deferred the description of a very ingenious method of carving devised by Dr. William Calvert. Instead of the Avax rim before mentioned, Dr. Calvert provided an assortment of teeth having all the varieties of form and size required in practice, but one-fifth larger that the given case. These are arranged in a wax gum, and the plaster mould then taken. Thus, in Fig. 1053, teeth of the first size set in wax will give, when diminished by the furnace, teeth of the second size; so in Fig. 962, each of the two lower sizes in Avax will give in the finished block the size above it. Dr. Calvert's method has three recommendations: 1. Like continuous-gum Avork, it limits the ne- cessity of ajsthetic skill (which so feAV possess in high degree) to the shaping of the gum, the judicious selection of teeth and their SPEdAL BLOCK CAR\rING. 1165 proper arrangement; leaving the details of form to the genius of the manufacturer's artist. 2. It permits the application of enamels or rather the addition of body to enamels, without the necessity of crucing, which some regard as injurious to the tooth. 3. By select- ing a variety of styles of model teeth, and by varying the relatiAre adjustment of them in the Avax, that tendency to uniformity of style is obviated, which characterizes almost every block-carver's work. Dr. Calvert's process differs mainly from the foregoing in the fol- loAving details: For a four-block piece the teeth are set in Avax shaped in exact imitation of the natural gum, omitting the second bicuspid, in place of Avhich a half-tooth space is left betAveen first bicuspid and molar, the Avax gum being carried around continu- ously. The plaster mould of the eight front teeth is then taken, a Fig. 1053. thin septum of foil being placed opposite the mesial line, so that it may be easily broken there in the act of removal, the plaster com- ino- slightly over the inside so as to give with certainty the shape of the cutting edges. Upon removing the front mould, and before making the lateral moulds, where as yet the Avax holds only two tAvo molars, it is necessary to detach the bicuspid of the front block and put it adjacent to the molar; this gives the arch its full com- plement of bicuspids. This must be done very neatly, so as not to disturb the continuity of the wax gum ; otherwise, the effect of the porcelain blocks at their joints will be injured. Dr. Calvert prefers usino- cuspids for insertion in the wax instead of bicuspids, since their external expression is similar and their form more convenient, especially in the change just described. By similarity of form we do not mean that in any mouth the canines and bicuspids are alike externally ; but, out of a collection of canines, after choosing the cuspids themselves, others may be selected, harmonizing Avith them as first and as second bicuspids. Besides overlapping the blocks at the bicuspids, to compensate shrinkage, a slight extension of each block beyond the last tooth should be made to allow for accurate grinding. If holes are made in the base, instead of platina pins in 1166 MECHANICS—DENTAL PROSTHESIS. the back, it will be best to make a continuous front block of six teeth, in which case the half-tooth space above named comes behind the cuspid. Since the carved wax of the contained teeth make carving of the porcelain paste unnecessary, the plaster moulds are varnished, oiled, and treated as are the brass moulds in wholesale manufacture. The stiff paste of point enamel is placed with a delicate spatula, into each tooth matrix, thickest at the point, and disappearing at the neck. The tooth enamel paste is then applied, with thickness re- versed ; gum enamel might also be added in the same way, but it is usually applied afterward with the brush, as this permits delicacy and uniformity of coating or easier modification of its thickness. A layer of soft body paste is now laid over the enamels, the mould is placed on the articulator and the thickness of the block is built out and shaped in the usual way, compressing it firmly, and re- moving surplus moisture with bibulous paper or the blowpipe flame. The block is next carefully removed, and while resting in its matrix, the platina pins are inserted or holes drilled in the base, or dovetails cut, as may be preferred, and the whole inner surface examined and trimmed. If the inside of the block is to be finished in gum, the enamel should now be applied; then remove the block from the matrix and apply the outside gum enamel, and trim between the teeth, where the thin edges of the plaster matrix are apt to be de- fective ; the block is then ready to be dried and placed in the fur- nace, where it is fired at a single heat without previous biscuiting. The side blocks are made in precisely the same manner. PORCELAIN PLATES. In addition to what has already been said upon this subject, it is only necessary here to consider some of the preceding properties and manipulations of the porcelain material in its use as a plate. Neither in itself, nor by known combination with any substances, can a thin porcelain plate be otherwise than frail. The fusible por- celain of the "continuous-gum work" is supported by the platina plate and the continuously soldered platina backings. Such por- celain, without metallic support, would be very frail. In endeavor- ing to give strength by decreasing the flux and increasing the refractory ingredients, we are at once met by the difficulty of shrinkage. Thus we encounter two horns of a dilemma—a very fusible porcelain with less contraction but great tenderness ; a more refractory porcelain with greater strength, but the usual one-fifth contraction, which necessarily destroys the fit of the plate, if made over the unchanged model. PORCELAIN PLATES. 1167 Dr. Allen frankly acknoAvledges the weakness of his very beauti- ful porcelain by giving it a metallic support. The dentist knows just what he is using here (see the fourteenth chapter), and can exercise his judgment upon the suitability of the Avork to any case in hand. The few dentists who make porcelain plates are more re- served in communicating their knowledge. Such unprofessional reserve is damaging to dentistry as a science; it would injure it also as an art if entire porcelain dentures had a strength equal to their beauty. It is claimed by some makers of these plates that their formulas give a porcelain which is very strong, yet has a very slight shrinkage. But until such formulas are made known to the pro- fession and an opportunity givren to test them, the general prejudice against the porcelain base must continue to be well founded. To those desirous of experimenting in this direction, we might suggest the use of silicate of magnesia and lime (asbestos) and coarsely pulverized porcelain fragments, as perhaps lessening the shrinkage of the mass. By some the ordinary dental porcelain paste is used, making pro- vision for shrinkage by enlargement of the model. One method of enlargement is as follows: With a fine stuv divide the plaster model by a cut through the median line and another on each side; separ- ate these four sections one-eighth inch and fill the joints with plaster, first saturating them Avith water; then cut the model twice at right angles to the first lines, and fill Avith plaster as before. If the back of model is perfectly level, and the work is very carefully done, Ave shall have a tolerably accurate enlargement of about one- fifth. Make a plaster matrix over this, and into it pour a furnace model, composed of three or four parts asbestos or sand to one of plaster. On this, mould and carve and bake the plate and teeth ; else transfer the plate to a pile of coarse silex, so arranged as to give it as much support as possible during the firing. Teeth and plate are sometimes carved out of the same mass on the enlarged model; or blocks may be made as already described, then transferred and united to a porcelain plate on this model. Sometimes the teeth from the depots are arranged in the porcelain paste and gum enamel applied around the teeth and over the plate. Unlike continuous-gum work, the teeth are not attached to any un- yielding plate; hence they are liable to change position by the con- traction of the plate during firing. We cannot more appropriately close this chapter on dental por- celain than by quoting some remarks of the great English ceramic manufacturer, Josiah WedgAvood, applicable to the art which he 1168 MECHANICS--DENTAL PROSTHESIS. did so much to elevate. They have a significance beyond ceramic art; and convey, in this lesson of the past, a warning to those Avho may, perhaps unconsciously, be dishonoring the profession of their choice. "All works of taste must bear a price in proportion to the skill, taste, time, expense and risk attending their invention and manu- facture. Those things called dear are, when justly estimated, the cheapest; they are attended Avith much less profit to the artist than those Avhich everybody calls cheap. Beautiful forms and composi- tions are not made by chance, nor can they ever, in any material, be made at small expense. A competition for cheapness and not for excellence of Avorkmanship is the most frequent and certain cause of the rapid decay and entire destruction of arts and manu- factures." CESOPHAGOTOMY. As the accident of swalloAving artificial dentures has occurred more or less frequently, and has in some cases resulted in death, the folloAving case Avill describe the operation of removal where all efforts of a more simple nature failed to give relief: * " On Sunday, November 14th, 1886, George K. (white), aged thirty-two years, while at dinner had the misfortune to partially swallow his set of artificial teeth, consisting of a rather narrow vulcanite plate for the upper jaw, to which Avere attached three in- cisors, one lateral incisor having been lost from the plate. The denture Avas arrested in its passage downwards, producing intense pain and partially obstructing respiration, AAdiile deglutition, even of liquids, was rendered impossible. A physician Avas summoned, Avho detected the plate in the upper portion of the oesophagus; but all efforts to remove it or force it into the stomach were futile. Sufficient opium to relieve the pain having been administered, on the folloAving day (Monday) he Avas brought by his physician to the infirmary of the University of Maryland and placed under the care of Dr. L. Mc- Lane Tiffany, professor of surgery. On the same afternoon, the patient having been etherized, careful attempts to remove the plate were made, but it Avas so firmly impacted in the upper portion of the oesophagus that all effort for its removal failed. On Tuesday, in the presence of the medical and dental classes, the patient Avas again etherized and efforts made to remove the plate through the mouth, but without success. * This operation was reported for the Dental Cosmos and Am. Journal of Dentnl Science by Prof. F. J. S. Gorgas. DEFECTS OF THE PALATINE ORGANS. 1169 " The patient lying on his back, Avith his face turned to the right, so as to render the tissues of the left side of the neck tense, Prof. Tiffany made an incision about four inches in length through the integument over the depression between the trachea and the sterno- mastoid muscle. The anterior jugular vein was cut and ligated, and the incision extended from opposite the upper border of the thyroid cartilage nearly as low as the sterno-clavicular articulation. The platysma myoides muscle and the cervical fascia were then divided. The edges of the wound being held apart by retractors, the omohyoid muscle Avas draAvn outwards, and the stemo-hyoid and sterno-thyroid muscles imvards. The carotid sheath, Avith the contained vessels, was exposed and carefully drawn outwards, Avhile the thyroid gland Avas separated as far as necessary, and drawn imvards. The larynx and trachea were drawn somewhat forward, and the finger passed behind, Avhere the foreign body could be distinct^ felt through the oesophageal Avail. u Care being taken to avoid the recurrent laryngeal nerve, an in- cision large enough to admit the finger Avas made into the oesopha- gus, through Avhich the exact position of the set of teeth Avas ascer- tained. Forceps were then introduced, and the plate removed intact. The wound, after being thoroughly cleansed, Avas dressed with antiseptic gauze and absorbent cotton, no sutures being em- ployed. On the following Thursday the patient was walking about his room, having a normal temperature and pulse. He was fed by means of a stomach-tube for sox days, after which he was able to swalloAV liquid food with little or no pain, and the external wound had nearly closed." CHAPTER XVII, DEFECTS OF THE PALATINE ORGANS. One of the most distressing deformities to which the human frame is liable is found in that defective condition of the palatine organs Avhich is known to surgeons by the name of Cleft Palate. The unfortunate sufferer is compelled, in a great measure, to be an alien among his fellow creatures; an object of compassion to the considerate, he is often made painfully conscious of notice by the heartless crowd ; and Avere he gifted Avith the poAver and eloquence 74 1170 MECHANICS—DENTAL PROSTHESIS. of a Demosthenes, or with the garrulousness of a Cleon, he could make little more use of his endowments than a mute. Fortunately this painful defect is no longer to be reckoned as one of the opprobria medicorum; for both surgical and mechanical means are now at hand by which the imperfection may at least be remedied, and often cured. Defects of the palatine organs may be divided into two classes, viz.: Accidental and Congenital. The first includes all loss of sub- stance in either hard or soft palates, whether occasioned by disease or otherwise. Such defects are not uniform in locality nor in ex- tent; consisting sometimes of simple perforations, and at others involving the destruction of the velum, a considerable portion of the os palati, the vomer and turbinated bones, and the loss of a greater or less number of the teeth. The second class includes all malformations, from the simple bifurcation of the uvula to an open- ing through the velum, palatine and maxillary bones, and a fissure of the upper lip; thus uniting the nasal passages with the oral cavity throughout their entire extent. These malformations are quite similar in character, but not uniform in extent. They may be said to begin Avith the uvula, and in the uvula and velum always occupy the median line,; but as the defect progresses anteriorly, it may deflect to one side or the other of the vomer and, following the nasal passage, divide the lip, leav- ing the vomer articulated with the palatine bone upon one side; while in other cases, the deformity seems to follow the median line, and thus involves both nasal passages, terminating in a double fissure of the lip. Congenital defects of the palate are usually accompanied by more or less deformity of the sides of the alveolar arch and of the teeth. Sometimes the sides of the alveolar ridge are forced too far apart, and at other times they are too near each other; while the teeth are either too large or too small, and are generally of a soft texture with imperfectly developed roots. Want of coaptation, resulting from defective formation in the palatine plates of the maxillary and palate bones, is the cause of congenital deficiencies of the parts in question. In the human em- bryo of about the third Aveek, the development of the face is clearly in progress. Five tubercles bud out from the front of the cephalic mass, of which the middle one (which is double) is directed verti- cally downward, and bears the appellation incisive tubercle; because the intermaxillary bones, destined to hold the superior incisor teeth exclusively, are developed in it. On either side is the tubercle, or rudiment of an upper maxillary bone, which is separated from its DEFECTS OF THE PALATINE ORGANS. 1171 fellow by a wide interval, and from the neighboring incisive process by a fissure. The fourth and fifth tubercles, also separated in front, form by their subsequent union in the median line, the inferior maxillary bone. At the same period, the palate begins to be formed by the approach toAvard the median line of two horizontal plates, or processes, springing from the maxillary process on either side. (See Development of Bones of Head and Face.) If now development proceed regularly and normally, the palate processes of the superior maxilla meet in the median line, and unite with the blended intermaxillary tubercles; Avhile the vomer grows dovraward to meet the palate processes in their line of union. The upper jaw, after the accomplishment of these changes, is complete, and the forma- tion of the lip and primary dental groove folloAvs in due course. But it sometimes happens that the superior maxillary and intermaxillary processes fail to unite with each other; whence we have the malforma- tion known as harelip, or the palate plates are arrested in their growth, and permanent^sswre of the palate is the result. Consequently, the fissure of single harelip is never exactly in the median line, but on the edge of the intermaxillary bone; Avhereas, in double harelip, a fissure exists on each side of this bone, in which the four incisor teeth are planted. Fissure of the hard palate is usually a little lateral, and not me- dian, as it results from a deficiency of one or other of the palate plates of the upper maxillary bone; and it is frequently associated with harelip and fissure of the upper jaw. The tubercles, or formative processes of the lower jaw, advance and meet in the median line, Avhile the upper maxillary processes are still separate. In man they are consolidated into a single piece; but they remain permanently divided in many of the loAver animals by a median suture. The principal effects resulting from an absence of a portion of the palatine organs are, an impairment of the functions of mastication, deglutition and speech. Distinct utterance is sometimes wholly destroyed, and mastication and deglutition are often so much em- barrassed as to be performed only with great difficulty. These effects are always in proportion to the extent of the separa- tion or deficiency of the parts. The simple act of triturating the food may not be materially impaired by the absence of a portion— however extensive—of the palatine organs, unless the natural rela- 1172 MECHANICS--DENTAL PROSTHESIS. tions of the teeth of the upper and lower jaws are changed; still, the process is more or less interfered with, as substances taken into the mouth cannot be so readily managed as Avhen the parts are in their natural state. They are liable to escape from the control of the tongue, and pass into the cavity of the nose. In cases of congenital defects of the palate and velum, it is difficult to conceive how infants manage to obtain from the breast of the mother or nurse the food necessary for their subsistence; yet, even when the anterior part of the alveolar border and part of the upper lip are wanting, the suggestions of natural instinct enable them, by a peculiar management of tongue and lip, to do it. The expedient resorted to for effecting this process is curious. The nipple, instead of being seized between the tongue, upper lip and gum, is taken be- tween its loAver surface and the under lip and gum ; and in this way it manages to extract the nourishment necessary for subsistence and growth. The tongue is thus made to close the opening in the palate, and perform the office of an obturator. By contracting the lip and depressing the tongue, the milk is drawn from the breast of the mother or nurse. At this young and tender age the child is not conscious of the imperfection of its palate; and it is not until the period arrives when it should begin to make its wants known by words, that it feels the importance of the function of speech, and begins to realize the misfortune with which it is afflicted. As the child arrives at this period, the mechanism of sucking is perfected, and is ultimately applied to the mastication of solid ali- ments. The food, when chewed, is conveyed, between the tongue and movable floor (which serves for a point aVappui), and it is brought back between the teeth. Thus it is that the complicated operation of mastication and deglutition is performed Avithout the alimentary morsel getting into the nose; or, if this does sometimes happen, it is the result of accident. But in cases of accidental lesion of the palate, the individual has not the advantage of this training of the parts during early infancy. Those who are afflicted with accidental lesions, no matter what may be their position and extent, having acquired the habit of eating by placing the aliment upon, and not under, the tongue, can take no nourishment without a part of it getting into the nose. When to this inconvenience is added a change in the natural relation of the teeth of the two jaws, mastication is rendered still more difficult and embarrassing. When this is the case, the tubercles of the teeth of one jaw, instead of being received into the depressions of those of the other, strike upon their pro- tuberances, and cannot be made to triturate the food in as thorough and perfect a manner as is required for healthy and easy digestion. DEFECTS OF THE PALATINE ORGANS. 1173 Thus, not only is the process of mastication rendered imperfect, but it is also more tedious. The process of deglutition itself, so long as the velum and uvula are perfect, is not materially affected by a simple perforation of the vault of the palate, although much difficulty may be experienced in conveying alimentary and fluid substances to the fauces and pharynx. But Avhen this curtain is cleft, or is partially or wholly wanting, deglutition is rendered very difficult; for, by the contrac- tion of the muscles of the pharynx, part of the food is forced up into the nose. The reason of this Avill appear obvious, when we take into consideration the form and function of this movable append- age. When its muscles are relaxed, it forms a slightly concave cur- tain ; but in the act of deglutition, the muscles contract, raise the velum, and close the opening from the pharynx into the posterior nares. By this valvular arrangement alimentary substances and fluids are-prevented from escaping into the nose. It matters not, therefore, whether the imperfection of the velum palati be the result of accident or disease ; its effects upon deglutition are the same. In proportion as the lesion or deficiency is great, will this operation be rendered difficult and embarrassing. There are cases where, in con- sequence of an imperfection of the palate, the patient can swalloAv no fluids AAdthout a part being returned by the nose. To obviate this inconvenience, the head is thrown sufficiently far back to pre- cipitate them into the oesophagus. This is an expedient to which many thus affected have been compelled to resort. Imperfection of speech ahvays results from an opening in the palate; it gives the voice a nasal tAvang, and renders the formation of some sounds impossible. The loss of the teeth, to a less extent, is productive of the same effect. To comprehend fully the manner in Avhich a lesion of the palate may affect the utterance of speech, it Avill be necessary to understand the agency Avhich the several parts of the mouth have in the formation of articulate sounds. Speech consists in the sounds produced by the organs of the glottis modified by the organs of the mouth. The modulation of the voice, that is, the raising or lowering of its pitch, is accomplished by the vocal cords of the glottis ; but the articulation of the consonants requires the co-operation of all the movable and fixed parts of the mouth and pharynx, palate, tongue, lips, teeth and palatine arch. Hence, if any of these be defective or Avanting, the power of forming some of these sounds is wholly lost, of others very much impaired; hence, also, the ability to sing is much less interfered with than the poAver of distinct speech. The tongue has a remarkable poAver of adapting itself to the loss of teeth and of some other parts, so as. 1174 MECHANICS--DENTAL PROSTHESIS. measurably to correct the effect on speech ; but the effect of the loss of the hard or soft palate upon the voice cannot be remedied in any such way. In both cases (accidental and congenital) the faculty of distinct articulate speech is seriously impaired by defects of any extent. In ordinary cases of congenital deformity in an adult, deglutition is not materially interfered with. The patient, having never known any other method of swallowing, is not conscious of any difficulty. Acci- dental lesions, however, coming generally in adult life, produce, in this respect, very great inconvenience. The remedy for these evils must be the closing of the abnormal passage by some means Avhich will restore to the deformed organs their functions. In perforations of the hard palate, unless of extraordinary extent, the method is very simple. In the loss of the soft palate by disease the remedy is more difficult, and in extensive congenital deformity still more complicated means must be resorted to. STAPHYLORRAPHY. The operation which is resorted to in the treatment of fissured palate is known by the name of Staphylorraphy, a Avord of Greek derivation, signifying suture of the uvula. It is an operation which has been perfectly successful in many instances, although there are numerous cases which will derive far more benefit from mechanical assistance than from the surgeon's aid. In considering the operation, a brief sketch will be given of the anatomy of the parts concerned in its performance; this will be fol- lowed by a description of the various kinds of clefts; we shall then describe the means adopted by different surgeons for their relief or cure.. To obtain success in staphylorraphy, the first care must be to gain a practical acquaintance Avith the position and relation of the muscles connected with the palate and fauces; and this can be ac- complished best by laying open the pharynx from behind, for thus the posterior surface of the soft palate is at once exposed to view. We shall find that this structure is wholly composed of muscular tissue, covered with a layer of mucous membrane continuous with that lining the hard palate. The muscles with which we have chiefly to do are: the palato- glossi and the palato-pharyngei, forming the anterior and the pos- terior pillars of the soft palate respectively ; the levatores palati, the tensores palati, and the azygos uvula?. The levator palati is a long, rounded muscle lying obliquely on STAPHYLORRAPHY. 1175 the outer side of the posterior opening of the nares. It takes its origin from the petrous portion of the temporal bone and from the cartilage of the Eustachian tube, and then descends obliquely down- ward and inward, its fibres spreading out over the posterior surface of the soft palate until they meet with those of the corresponding muscle on the opposite side. The palato-glossus is a very small muscle arising from the ante- rior surface of the soft palate on each side of the uvula, whence it passes forward and outward to be inserted into the dorsum of the tongue, thus forming the anterior pillar of the fauces. The palato-pharyngeus is separated from the preceding muscle by a space in which the tonsil lies. It arises, by two origins, from the soft palate, and descending outward and downward, is inserted into the posterior border of the thyroid cartilage. The tensor palati arises from three points, viz.: first, from the scaphoid fossa, at the base of the internal pterygoid plate; secondly, from the cartilaginous portion of the Eustachian tube; and, thirdly, from the spinous process of the sphenoid bone; it then terminates in a tendon which winds around the hamular process, which may be plainly discovered Avith the finger about half an inch behind the tuberosity of the superior maxilla; and it then passes horizontally and expands into a broad aponeurosis on the anterior surface of the soft palate. The azygos uvula? arises from the posterior nasal spine of the palate bone and from the aponeurosis of the soft palate, and de- scends to be inserted into the uvula. Having learned the attachment of these muscles, it will be well to consider their respective actions upon the palate, in order more clearly to comprehend their relations to the separated portions of a cleft palate. The levatores palati slightly raise the soft palate while it is made tense by the action of the tensor palati. The palato- pharyngei contract and bring the two sides of the palate from Avhence their fibres arise in close contact together. The action of these muscles show what an important part they must bear in regard to the operation of staphylorraphy; and when this is considered in detail, it will be seen why but little success Avas met with, until means were found to render muscular action of the parts impossible. The deficiency of the palate varies considerably, from a mere divi- sion of the uvula to a gap which constitutes a hopeless deformity. When this abnormal state is limited to the soft palate, the cleft is ahvays of a triangular shape, the apex being above and the base 1176 MECHANICS—DENTAL PROSTHESIS. below; but Avhen the soft and hard structures are involved, it is of a more or less quadrilateral shape. We shall here only consider those cases which are congenital in their origin, merely alluding to the distinction between this class of deformity and that kind Avhich may be said to be acquired, or is accidental. In congenital cleft the fissure is generally confined to the median line of the palate, because the two halves have not united at that part at the usual period. In acquired or accidental deformity, lesions are met with in all parts of the palate, to the right or left of the median line, and are usually the result of syphi- litic ulceration, or have some traumatic origin. Congenital clefts may be thus classed : Firstly, a small, triangular- shaped fissure, extending through the uvula and the posterior por- tion of the velum palati, the other portion of the palate being quite intact and sound. Secondly, the whole of the soft palate is in- volved. Thirdly, the soft palate and a portion of the palate bone is deficient. Fourthly, the cleft may be associated with abnormality in the alveolar process of the palate bone, and even with harelip. Fifthly, openings occur in the hard palate, the soft palate being un- affected. These separations may be very narrow, not exceeding a feAV lines in width, or the gap may be such that mouth and nostril seem but one. The fissure posteriorly is always on the median line; anteriorly, it generally deflects to one side or the other of the nasal septum, passing also to one side of the inter-maxillary bone. In some rare cases both nasal passages are involved, and a double harelip i&the consequence. The effects of this condition, already stated, may thus be briefly summed up. During infancy the func- tions of suction and deglutition are with difficulty performed, and at a later stage mastication and articulation are much impeded. There is also imperfect control over the muscles of the palate, both fluids and solids are liable to pass into the windpipe, and not un- frequently there is regurgitation through the nose. The speech is guttural and nasal, often so indistinct as to render it almost entirely unintelligible, and the patient is only too anxious to grasp at any chance that may be held out as being likely to grant some amelior- ation of his condition. Various methods have been suggested for the cure of this de- formity. Some have proposed to close the cleft in early infancy by means of pressure on the yielding bones; others maintain that artificial substitutes are best adapted to relieve the patient's suffer- ing ; while others as strenuously proclaim the knife to be the only means whereby success may be obtained. STAPH YLORRA PHY. 1177 The first surgeon who directed serious attention to the operation was M. Roux, a notable French surgeon, who performed it upon a young American physician, in the year 1825. Velpeau informs us that M. Colombe, another Frenchman, performed the operation on the cadaver in 1813, being probably actuated to attempt its perform- ance by reading the successful efforts of a French dentist (Le Monnier) to cure cleft palate by surgical procedure as early as 1764. For more than fifty years after this date the operation seems to have been forgotten or to have fallen into disuse, until it Avas revived by M. Roux, in France, and almost simultaneously by Dr. John C. Warren, of Boston, each of whom seems to ha\re per- formed the operation in total ignorance of what was done by the other. In 1827, Dr. SteA'ens, of New York, operated Avith success; in the succeeding year, Dr. Mettauer, of Virginia, followed in the foot- Fig. 1055. Fig. 1056. steps of his confreres in the profession, and embodied his expe- rience of staphylorraphy in a very interesting article which ap- peared in 1837. The operation also attracted attention in England, where Ave believe it was performed for the first time by Mr. Alcock, in 1822. Since then it has become one of the most frequent opera- tions in surgery, and, through the suggestions and improvements made by Hamilton and Dieffenbach, by Fergusson, Pollock, and Mason, it has served still further to enhance the benefits which it is the privilege of the surgeon's art to extend to all mankind. The operations of M. Roux and Dr. Warren were very similar in character, and we think that equal credit must be extended to the 1178 MECHANICS—DENTAL PROSTHESIS. Frenchman and to the American for the revival of staphylorraphy ; while English surgery deserves no little credit for the suggestions of men like Pollock and Fergusson, which have contributed so much to its present success. All the earlier operations of staphylorraphy consisted in paring away the edges of the cleft, and then bringing them in contact by means of sutures until union was effected. The various stages of the operation as then performed are sufficiently illustrated in the accompanying engravings, the successive steps being taken in the order of these drawings. Many modifications of this plan were made by Warren, Mettauer, Stevens, Graefe, and others; but Fer- Fig. 1057. Fig. 1058. gusson introduced a new principle of treatment in the operation which has very materially added to its successful results. We have alluded to the use of the muscles composing the velum of the palate and their important action on it, and to Fergusson must be assigned the credit of being the first to realize practically the fact that muscular action was the most frequent cause of failure of the operation; and he proved the truth of his conjecture by his method of removing the difficulty; namely, the division of the muscles of the palate, thus entirely paralyzing their action. Prior to this discovery, Sir Wm. Fergusson had adopted an opera- tion somewhat similar to Warren's and founded on that of Roux, which was performed as follows : The patient was placed in a chair with a back slightly more inclined than usual; his head being then Avell supported, and his mouth kept open by means of a gag, the ST A PH YLORR A PHY. 1179 Fig. 1059. edges of the fissured palate were pared from above downward, with a curved bistoury. Next a curved needle, with a movable eye, armed with a strong silken ligature, Avas passed through the palate, at the upper angle of the wound, at a dis- tance of about a line from the fis- sure. The other edge Avas trans- fixed in a similar manner. Two other ligatures were then inserted in the same way, the third and last being as close as possible to the ex- tremity of the wound. The threads were then seized with the fingers and tied, being very careful to avoid pressure of the knot upon the mid- dle of the wound. This earlier operation of Mr. Fergusson, which was the type of many others that have been proposed, and which is substantially the same as that illustrated by the figures before re- ferred to, has been described in order that the improvement in the modern operation may be the more fully appreciated Avhen it is sub- sequently described at length. Preparation of the Patient.—Mr. Hamilton Cartwrightof the Royal College of Surgeons, London, makes the folloAving suggestions for the preparation of the patient. Before undertaking the operation of staphylorraphy, various points have to be considered. Firstly, having decided that a surgical operation will be of more benefit to the patient than mechanical aid, cognizance must be taken of his general health ; for upon its good condition much of success must ultimately depend. Should the patient be chlorotic or anaemic, the operation must be postponed until after a proper treatment. A healthy regimen must be prescribed; frequent but not fatiguing exercise in the open air must be insisted upon, and tonics must be given, their character being determined by the patient's diathesis. Particular care must be shown in cases of struma, as there is no condition in Avhich the parts are more unlikely to heal favorably than in this. For the relief of this condition it may be necessary to devote great attention for many months. Sea air will be of much service, Avhile its effects will be enhanced by giving a course of iron. Mr. Cartwright recommends particularly two chalybeate prepara- tions. Avhich are of the greatest value in anaemia, as Avell as in that diathesis noAV under consideration. They are the syrup of the iodide 1180 MECHANICS—DENTAL PROSTHESIS. of iron and the syrup of the hypophosphate of iron and manganese. The latter acts as a tonic and an alterative; at the same time it keeps up an easy action upon the bowels; indeed, there is no medicine which he has found more rapidly successful in improving those weak and enfeebled states of the system which are owing to scrofula or to an impoverished condition of the blood. Nothing has more conduced to bring staphylorraphy into disrepute than a disregard of the physical condition of the patient; good health is the sine qua non of rapid and successful union of the parts. Having suited the treatment to the indications of the case, it is of the utmost importance that the patient be educated, so to speak, to assist the surgeon in the operation Avhich he is about to undertake; for the fauces are intensely sensitive, and were the condition of the parts forgotten, the retchings and convulsive movements so easily induced in them would probably cause a failure in the proposed cure. Various means of lessening this sensibility have been sug- gested; some have recommended rough fingering of the parts daily; and Dr. Garretson proposes to occasionally pass a tenaculum through the parts to be operated upon, a treatment which we rather think Avould make the patient more fearful than ever of the operation. As good a method as any proposed is to enjoin the friends of the patient, or the patient himself, if old enough, to irritate the fauces with the feather of a quill; in a few weeks it will be found that the parts Avill become tolerant of almost any irritation. The same re- sults may be obtained by wearing an obdurator extending far back over the palate; the irritation at first produced by it will soon dis- appear, and after wearing it constantly for a few Aveeks, all the usual symptoms produced by interference Avith the fauces will have passed away. Mr. Cartwright proposes another method of treatment, which is somewhat novel, but most successful in its results. It-has been found that the exhibition of the bromide of potassium tends to deaden the sensibility of the fauces in a very remarkable manner, and thus it may become a most useful agent preparatory to the operation. If exhibited in half-drachm doses, given thrice daily for tAvo or three Aveeks prior to the period decided upon, but little irrita- bility of the parts will be found remaining; and by the time a feAV imaginary operations on the parts have been performed, by the aid of such harmless instruments as a camel's-hair brush or the feather of a quill, the patient will be found in a fit condition to be operated upon. A fe\v days prior to the time of operating, more particular attention must be paid to the condition of the patient. Primarily, he must be well nourished, inasmuch as he will be forced to adopt STAPHYLORRAPHY. 1181 a different regimen from that to Avhich he has been accustomed for some days. His diet must be nutritious Avithout being stimulating, and the greatest attention must be given to the regular action of the boAvels, and, indeed, in all cases it is Avell to give a mild aperient before operating. The patient having been thus prepared, much of the success of the operation will depend upon his ability to remain tranquil during its performance, and to give as much assistance to the surgeon as may lie in his power. Thus he may assist the operator by opening his mouth widely, by not resisting the introduction of instruments, and, subsequently, by keeping the neAvly-connected parts as quiet as possible by restraining the movements necessarily induced by deglutition or by attempts at articulation. It will thus be seen why the operation for cleft palate must be delayed until the patient is old enough to exercise control over his movements. The best period is from nine to ten years of age, although Sir Wm. Fergusson has frequently operated much earlier, with complete success. As before observed, the pioneers who cleared the way for the suc- cess of staphylorraphy were Roux and Warren, and many modifica- tions of their plans have been made from time to time by others; but the man who introduced a neAV era in the history of the operation was Sir Wm. Fergusson, of London, who has rendered it most per- fect in all its details. This credit being generally conceded to him, we shall describe his mode of operating as the type of operations generally performed in modern days. Warren divided the pillars of the fauces empirically, with a view, as he states, of relieving the tension of the parts; but noAvhere do we find that he speaks specifically of dividing the muscles contained in them; it remained for Mr. Fergusson to point out that muscular action was the great cause of failure in most cases, and he practi- cally proved the truth of his conjecture by resorting to the operation of myotomy, dividing the muscles of the palate, and thus paralyzing their movements. He found that the tension on the line of union was principally exercised by the levator palati and by the levator pharyngeus, and he then proposed the following operation : Sir Wm. Fergusso/ds Operation—Mr. CartAvright describes Mr. Fergusson's operation as follows : He first divides the muscles of the palate by passing a curved knife around between the velum palati and the end of the Eustachian tube, thus at once dividing the levator palati. In the second stage he seizes the uvula, thus bringing for- ward the posterior pillar of the fauces, which is snipped across with round-pointed scissors, so as to divide the fibres of the palato- pharyngeus muscle; should it be deemed necessary to do so, the 1182 MECHANICS—DENTAL PROSTHESIS. anterior pillar may be divided at the same time, so as to sever the palato-glossus, though Sir William lays no stress upon the necessity of doing so. Next, the uvula is again seized, Avith a view of extend- ing the palate so that the edges of the fissure may be pared away; this is accomplished Avith a narrow bistoury from behind forward, on either side alternately, the angle of union being left for subse- quent removal. A few moments then are granted to the patient to recover, and he is permitted to swallow a few small pieces of ice, with the double vieAV of refreshing him and of staunching the bleeding. When this has sufficiently ceased, it is time to introduce the sutures, and this is done by means of a naevus-needle, armed with a silken ligature, the needle being introduced about a quarter of an inch from the edge of the fissure. Next, the extremity of the thread is pulled out by means of forceps, and another ligature is passed in like manner, until the desired number of stitches is attained. The extremities must then be tied loosely, so as just to keep the parts in apposition, and no more; after which the patient is put to bed, every care being taken to avoid all motion of the palate. He should take nothing but nourishing liquid food for a feAv days, and must be particularly enjoined to abstain from all movements involving action of the muscles engaged in deglutition, such as swallowing, coughing, sneezing, and the like, which would much endanger the success of the operation. The next stage consists in the removal of the stitches; this need not be done too soon, provided they produce no irritation; indeed, they may remain until union is perfect. The general time for their removal is about the seventh or eighth day although Fergusson often removes'them on the third or fourth. Mr. G. Pollock has introduced the following modifications in the performance of this operation: Instead of dividing the muscle with a curved knife from behind, according to the method we have just described, Mr. Pollock passes a ligature through the soft palate, so as to contract and draw it forward, and he then pushes a narrow- bladed knife through it, a little to the inner side of the hamular process of the pterygoid plate of the sphenoid bone, Avhich may be plainly discovered by passing the finger along the roof of the mouth to a distance a little posterior to the tuberosity of the superior max- illa. By raising the hand, and so depressing the point of the scal- pel, he most effectively, and in a very simple manner, divides the muscle. The parts having healed, the patient must be impressed with the necessity of practicing himself frequently in elocution, telling him that his success in articulation will depend upon him- self alone. Constant, patient, persevering effort will be necessary, and the end to be attained must be sought by distinctly articulating STAPHYLORRAPHY. 1183 every syllable of every Avord Avhich he may be called upon to utter. It is a good exercise to read a portion of some good author each day with a friend, Avho will assume the role of schoolmaster for the time being, permitting no Avord to be indistinctly uttered or slurred over, and requiring each syllable to be correctly and separately pro- nounced. Fissure of the hard palate, simple or connected with a fissure of the soft. Various means of closure have been proposed. Dr. Warren dissects the mucous membrane from the bone on either side, carrying his knife sufficiently forward toAvard the alveolar border to form a flap broad enough to meet a like one from the opposing Fig. 1060. Fig. 1061. side along the median line. When the fissure is so wide as to pre- vent the margins being brought together, Dr. Mettauer, of Virginia, recommends making several lateral incisions through the mucous membrane, Avith a vieAV of permitting the edges to be brought into close apposition. Dr. Mutter, of Philadelphia, who was very suc- cessful in the operation, also had recourse to the longitudinal inci- sion (as shoAvn by Fig. 1060), Avhich was first proposed by Dieffen- bach, with the most happy results. Dr. Warren's operation has been introduced into England by Mr. Pollock, who, with his pecu- liarly constructed instruments, proceeds as folloAvs: He makes an incision along the edge of the cleft at the juncture of the nasal and palatal mucous membrane. The soft covering of the hard palate is carefully dissected or scraped from the bones with curved knives, great care being taken that the mucous membrane and its subjacent fibro-cellular tissue are not perforated. When this has been well 1184 MECHANICS--DENTAL PROSTHESIS. loosened on either side, it Avill be found to hang down like a cur- tain from the vault of the mouth, the tAvo parts coming into appo- sition along the median line,- or possibly overlapping. The edges being then smoothly pared are brought together by means of a feAv points of suture introduced in the ordinary way, and with- out any dragging. Where the hole is not very large, Dr. Pan- coast's ingenious operation of staphyloplasty may be performed, in Avhich he raises two flaps of mucous membrane from the bone on either side, and then reflecting them across the chasm, their edges are brought together by suture in the usual manner, a plan which is so perfectly exhibited in Fig. 1061, that we do not deem any further description necessary. Recently, M. Langenbeck has sug- gested another operation, in which he proposes to dissect the mucous membrane, together with the periosteum, from the surface of the bone prior to bringing the opposed surfaces of the cleft in apposition; and the advantage claimed by him for this, Avhich he considers to be a novel method of procedure, is that the chasm is obliterated, not merely by soft tissue, but by bone, which is formed from the periosteum thus loosened from contact with the surface of the hard palate. If this theory be correct, Ave cannot but think that Dr. Warren and Mr. Pollock must have met with like results; although it is remarkable that they seem to have been unconscious of the great advances they had thus made in the treatment of cleft palate by the operation which the one proposed and the other carried out. We deem it impossible that Warren should have merely raised the mucous membrane without the periosteum at- tached to it—a dissection so difficult, that we could excuse the ablest surgeon for not accomplishing such a separation when operating on the living subject, without lesion of the mucous tissue; and until an autopsy reveals to us that real osseous tissue has filled up the breach in the continuity of the palate bone, we must confess that we shall remain skeptical as to the results now claimed by Herr Langenbeck and others for their revival of Dr. Warren's old opera- tion. There is one other treatment which we have mentioned, and to which we must make a short allusion, and that is the method of clos- ing fissure of the hard palate by means of pressure. Velpeau pro- posed to take advantage of the yielding character of young bone, by adopting mechanical means which Avould bring the parts separ- ated into closer or even perfect coaptation; this idea of his has recently been more fully Avorked out by more modern experimen- talists, who speak highly of the success which has crowned their efforts. The method of cure may be thus briefly described: A STAPHYLORRAPHY. 1185 clamp or compressor, Avith pads arranged according to the exigencies of the case, is applied on either side of the alveolar arch ; the edges of the fissure and of the bone having been pared away, the action of a screw is brought to bear upon the instrument, until the soft and pliant bones are brought together. That there are grave disad- vantages attendant on this mode of treatment cannot fail to appear to every dentist. Firstly, the alveoli of the superior maxilla are throAvn within those of the alveolar border of the inferior maxillary bone, thus laying the foundation of serious deformity in after-life. Secondly, the germs of the teeth might be so affected as to induce subsequent irregularity and malposition. Thirdly, there is danger of inflammation being excited, Avhile the delicate physique of the young child runs great risk of being affected injuriously by the irritation resulting from constant Avearing of such an instrument as that described. Lastly, we must consider the chance of fracture by exercising too much compressive poAver upon the bones. This hazard is acknoAvledged by those Avho advocate the proposed opera- tion of Velpeau; but they excuse themselves by urging that even should fracture occur it Avould be of little consequence, inasmuch as the injured parts are kept in splints, and that, therefore, the treat- ment Avhich would be correct in the one case is already provided for the other. It is to be feared that this admission will rather deter others from attempting an operation in which much evil may be done for an uncertain possible future good. The fact is more and more acknoAvledged in the humane surgery of the present day, that the gentler the means, if equal to the end proposed, the more entitled is any treatment to recognition and to praise. In the usual operation of staphylorraphy certain muscles most important to speech have to be divided ; and it is upon this very division of them that its success, in an operative point of view, so much depends, Avhile it is an important question Avhether the mus- cles are not thus in spite of their reunion, to a certain extent de- prived of power; and this, we believe, to be the reason why articu- lation is often so little improved afterthe successful performance of the operation in question. Hence, Ave propose that surgical and mechanical skill should combine to produce more perfect results in the treatment of fissured palate. We have been led to make this proposition by the success Avhich has attended our efforts in cases Avhere surgery has been but partially successful in her attempts to secure perfect union and coaptation of the opposing edges of the cleft thus leaving a gap in the anterior portion of the original fis- sure Avhile the posterior parts are Avell united. The operation Avhich avc suggest is to pare the edges of the hah'es of the bifurcated 75 1186 MECHANICS—DENTAL PROSTHESIS. uvula and the posterior portion of the soft palate nearest to them, and to bring about the union of these parts in the usual manner, by means of suture. Union having been effected, the deficiency in the anterior portion of the palate is to be filled by means of an artificial velum; the artificial A^elum at the same time extending backAvard and nearly filling the pharynx. The advantages of this combined operation are very manifest; for the muscles, being uninjured, their action is nearly normal, and the great objection of bringing about a too dense condition of the newly united palate is avoided ; this being another of the causes which prevent great improArement of ar- ticulation as a result of staphylorraphy. Noav, in the partial oper- ation just described, these disadvantages are at once removed, and the gap which still remains after the reunion of the uvula, being filled up by the artificial palate attached to an obturator, the mus- cles still have their normal play, and the palatine deficiency is better supplied than by the natural union of the separated edges of the cleft. The best results have been obtained by this most simple means of action. Figs. 1075 and 1077, being illustrations of cases occurring in the Avriter's practice, show very forcibly the man- ner of the proposed treatment, Fig. 1077 being an especially inter- esting case, because the operation of staphylorraphy, surgically considered, had been most successfully performed, but articulation seemed but little improved. The patient was Avilling to be the subject of an experiment, and the anterior portion of the reunited cleft was opened up again, and a velum, with an obturator, intro- duced in the space thus created. The results were eminently satis- factory ; the tension of the soft parts Avas at once relieved by this division, and after a little practice the patient spoke as she had never spoken before. There are many cases of abnormality in the os palati which can only be relieved by mechanical appliances, and this relief can be afforded in a most satisfactory manner; no more inconvenience being felt by the patient than he Avould experience in wearing an artificial denture, with which the false palate could be connected, were it necessary to do so. Artificial aid has been several times alluded to in reference to the operation of staphylorraphy, and, in- deed, it is still an open question whether, in a large number of cases, the greatest relief is not afforded by mechanical appliances. The surgeon's only desire should be to recommend that plan of treat- ment which he considers will ultimately render the greatest service to his patient. Undoubtedly, the operations which have been de- scribed are often, as far as mere union is concerned, most satisfac- tory in their results; but there are other considerations besides OBTURATORS AND ARTIFICIAL PALATES. 1187 these. Naturally, the chief desire of the patient is to take a footing in society on equal terms Avith other men ; and there are no means Avhich will enable him to do so, unless they can restore to him his lost or impaired poAver of speech—that divine gift which places man so immeasurably above the brute creation. This has been almost lost in many cases of cleft palate; and it is the great object of treat- ment to put the sufferer in a way of uttering his thoughts in plainly- spoken words, like those around him ; whatever means are best calculated to bestow this inestimable benefit, are those which the conscientious surgeon ought to select. There are certain cases where the opening is not large, and as there is little tension of the parts, the opposite sides come together in close proximity; staphylorraphy may here be performed with good results, for it must be recollected that it is always a desidera- tum to avoid the presence of foreign substance as a substitute for natural tissues, if these are equally effective. Allusion has been made to the liability to injury of the parts by a division of the muscles. Where an artificial palate is used, the muscles are unim- paired; and we have heard persons, Avho, when without the instru- ment could not be understood, speak fluently and distinctly the moment they introduced it into their mouths. So far as the dis- comforts of wearing such an apparatus are concerned, after a short time the Avearers becomes entirely unconscious that they are wear- ing anything artificial. OBTURATORS AND ARTIFICIAL PALATES. We have classified palatine defects as accidental and congenital; Ave shall also classify the appliances used for their remedy. The term obturator will be used for all instruments intended to stop or close all those openings in the hard or soft palate which have a com- plete boundary. Appliances made to supply the loss of the posterior soft palate, Avhether accidental or congenital, will be called artificial vela or artificial palates. Any unnatural opening betAveen the oral and nasal cavities which will permit the free passage of the breath will impair articulation. Any appliance which will close such.passage, and can be worn with- out inconvenience, will restore articulation* Obturators were formerly made of metallic plate, gold or silver being most commonly *The student will bear in mind that no cognizance is here taken of openings similar to those described in cases of congenital fissure, where the surgeon has united the soft palate, and left an opening through the hard palate to be covered by an obturator. 1188 MECHANICS—DENTAL PROSTHESIS. employed, and many very ingenious pieces of mechanism were the result of such efforts; but latterly, vulcanized rubber has almost entirely superseded the use of metals. Vulcanite has been found preferable to metals, being much lighter and much more easily formed and adapted, particularly when of peculiar shape. According to Guillemeau, obturators Avere employed by the Greek physicians; but it is to that celebrated French surgeon, Ambrose Pare, that we are indebted for the first description of an appliance of this sort. This author has furnished an engraving of an obtura- tor which he had constructed in 1585, consisting of a metallic plate, probably of silver or gold, fitted into an opening in the vault of the palate. It was held up by means of a piece of sponge, fastened to a screw in an upright attached to the upper surface of the plate. The employment of sponge, hoAvever, was found to be objectionable, as the secretions of the nasal cavities, which it absorbed, soon be- came insufferably offensive; notwithstanding which, it continued to be used for a long time. Ultimately, however, it was superseded by an obturator invented by Fauchard. This was held up by means of wings, which turned on a pivot. Both of these obturators, how- ever, exerted a hurtful influence upon the surrounding parts, as the pressure produced by the sponge and wings caused them to be gradually destroyed, and thus augmented the evil they were de- signed to remedy; consequently, their use has been Avholly aban- doned. We do not, therefore, deem it necessary to give a description of either. We will, hoAvever, quote a passage from Bourdet upon the subject. In alluding to the impropriety of having recourse to any appliance which has a tendency to counteract the curative efforts of nature, he says : " Before considering the cicatrized perforations of the palate as being of a nature incapable of diminishing in di- ameter, practitioners should satisfy themselves, thoroughly and beyond doubt, that such is the case. We do not think that this condition of permanency can exist, for positive facts attest the con- trary ; and as holes made in the cranium Avith the trepan close almost entirely, in like manner those of the palate constantly diminish." Numerous examples might be adduced, if it were necessary, to prove the impropriety of sustaining an obturator by any fixtures which act upon the lateral parts, as they necessarily tend to increase the dimensions of the opening in the palate. Where atmospheric pressure cannot be obtained,«,nd there are no teeth for clasping, the use of spiral springs, attached to a partial lower piece or to caps placed over the loAver molars, would be pref- erable to this very objectionable prominence on the upper surface .of obturators. It is of the greatest importance that an artificial OBTURATORS AND ARTIFICIAL PALATES. 1 189 palate or obturator should be executed in the most perfect manner, and be made to fit accurately to all the parts with which it is to be in contact, so that it may not produce the slightest irritation or exert undue pressure upon any of the surrounding parts. As in the case of the application of a dental substitute, the piece should not be applied while any of the teeth, especially those of the upper jaw, are in an unhealthy condition. The gums and sockets of the teeth should also be free from disease. With a view of obviating the objections which have been men- tioned as existing to the obturators of Pare and Fauchard, Bourdet proposed to employ simply a metallic plate fitted to the vault of the palate and large enough to cover the opening, Avith tAvo lateral pro- longations, one on each side, extending to the teeth, to which they are fastened by means of ligatures. This Avas also found to be ob- jectionable, as the ligatures Avere productive of constant irritation to the gums; moreover, they did not hold the plate in place Avith sufficient stability, and its use was soon abandoned. But these ob- Fig. 1062. Fig. 1063. jections Avere both obviated by an improvement made by M. Dela- barre, Avhich consisted in the employment of clasps, instead of ligatures, attached to lateral branches of the plate. To prevent these from slipping too high up on the teeth, he attached to each a kind of spur, Avhich Avas so bent as to come down over the grinding surface of the tooth to Avhich it was applied. The last-named authoi also made another modification, which consisted in the application of a drum to the upper surface of the plate (Fig. 1062). The object of this was to prevent the accumulation of mucous fluids from the nose in the cul du sac, formed by simply closing the opening below; also to prevent fluids, in sAvalloAving, from passing up between the obturator and the soft parts, through the opening into the nose. The drum evidently offers the same impediment to nature's efforts in 1190 MECHANICS--DENTAL PROSTHESIS. closing the opening as the obturator before mentioned ; on this score, therefore, it is equally objectionable. When the opening in the palate is small, and has no connection with the velum, it is unnecessary to raise the upper surface of the plate by attaching a drum or air chamber to it. If it be accurately fitted to the vault of the palate, it will effectually prevent fluids, in deglutition, from passing up in the nasal cavities, or the escape of any portion of the voice through the opening; also by frequently removing the plate, the accumulation of the secretions in the cul-de- sac will be prevented. A simple plate, like the one represented in Fig. 1063 will be all that is required to remedy the defect; and this in fact, Avill probably be found the best form in all cases, Avhether the openings be large or small. Fig. 1064 represents an obturator without teeth and without clasps for a perforation of the hard palate, being sustained in situ by im- Fig. 1064. Fig. 1065. pinging upon the natural teeth with which it comes in contact. Accuracy of adaptation and delicacy in form are all that is essen- tial in such cases, and the restoration of the speech will follow im- mediately. A clumsy contrivance Avill interfere Avith articulation almost as much as it is improved by stopping the opening; therefore, if the obturator could be confined entirely to the opening, like a cork in a bottle, it would be more desirable. As this cannot be, resort must be had to clasping the contiguous teeth, if there are any; if there are none, the obturator must extend over the Avhole jaAV, and receive its support in the same manner as Avould a set of artificial teeth. In fact, this is precisely what it becomes in such a case—an upper set of teeth bridging over and filling up an opening in the palate, thus combining an obturator with a denture. Fig. 1065 represents a more complicated obturator, adapted to an opening in the soft pal- ate. The necessity for a variation in the plan will be found in the OBTURATORS AND ARTIFICIAL PALATES. 1191 anatomical fact of the constant muscular action of the soft palate, Avhich would not permit, without irritation, the presence of an im- movable fixture. This is contrived, therefore, with a joint, Avhich Avill permit the part attached to the teeth to remain stationary, Avhile the obturator proper is carried up or doAvn as moved by the muscles. The joint, A, should occupy the position of the junction of the hard and soft palates. The joint and principal part of the appliance is made of gold; the obturator, of vulcanite. The projection, B, lies like a flange upon the superior surface of the palate, and sustains it; otherwise the mobility of the joint would allow it to drop out of the opening. This flange is better seen in the side vieAV, marked C. It is readily placed in position by entering the obturator first, and carrying the clasps to the teeth subsequently. Figs. 1064 and 1065 will illustrate the essential principles involved in all obturators. The ingenuity of the dentist will often be taxed in their application, as the cases requiring such appliances all vary in form and magnitude. The steps to be taken in the formation of an obturator are not unlike those used in making a base for artificial i teeth. It is essential that an accurate model be obtained of the opening, the adjacent palatal surface, and the teeth, if any lemain in the jaw. For this purpose, an impression taken in plaster is the only kind to be relied upon. Care must be used that a surplus of plaster is not forced through the opening, thus preventing the Avith- dravval of the impression by an accumulated and hardened mass, larger than the opening through Avhich it passed. To avoid this, beginners or timid operators had better take an impression in the • usual manner, Avith wax. If this is forced through, it can be easily removed without injury to the patient. From this Avax impression make a plaster model, and upon this plaster model form an impres- sion cup of sheet gutta-percha, using a stick, piece of Avire, strip of metal, or any other convenient thing, for a handle. This extempo- rized impression cup must not impinge upon the borders of the opening, neither should it enter to any extent. With a uniform film of soft plaster, of from one-sixteenth to one-eighth of an inch in thickness, laid over this cup, a correct impression can be taken with- out any surplus to give anxiety. Upon a correct plaster model, taken from such an impression, the obturator should be moulded out of gutta-percha, or any other plastic substance ; the subsequent steps being in principle the same as in making any other piece of vulcanite. It is desirable that it should enter the perforation, and restore, as far as possible, the lost portion of the palate; but it must not intrude into, or in any way obstruct, the nasal passage. The entire freedom of the nasal passage is essential to the purity of articulation. 1192 MECHANICS—DENTAL PROSTHESIS. That portion of the obturator Avhich occupies the oral cavity should be made as delicate as possible, consistent Avith its strength and durability. ARTIFICIAL PALATES. Before proceeding to a description of artificial palates, a brief reference to the anatomical relations and functions of the velum palati will be necessary. The palate exercises quite as important an office in the articulation of the voice as does the tongue or lips. Being a muscular and movable partition to separate the nasal and oral cavities, one edge is attached to the border of the hard palate, while the other vibrates between the pharynx and the tongue. The voice, therefore, as it issues from the larynx, is directed by the palate entirely into the mouth or through the nose, or permitted to pass both ways. A very slight deviation in this organ from its natural form will make the voice give a different sound ; so the presence of anything that clogs the natural passages, either oral or nasal, modifies the vocal vibrations. Place any obstruction in the nasal passages, par- alyze the soft palate, or let it be deficient in size, and the poAver of distinct articulation is wanting. Evidence of this statement is very frequently found after the surgeon has successfully performed the operation of staphylorraphy in case of congenital fissure. In such instances (with rare exceptions) the newly-formed palate is so defi- cient in length, and so tense, as to be deprived of its function. It cannot be raised so as to meet the pharynx and shut off the nasal passage, but hangs like an immovable septum to divide the column 4 of sound. Fig. 1066 represents a defective palate belonging to the first class, the uvula and and a portion of the contiguous soft palate being de- stroyed by disease. In such a case an obturator Avould be useless; the constant activity of the surrounding parts Avould not tolerate it. The material used for a substitute must be soft, flexible and elastic; and the elastic vulcanite is admirably adapted to this pur- pose. By observing the cut (Fig. 1066), it Avill be seen that a portion of the soft palate along the median line remains, and consequently there will be considerable muscular movement which must be pro- vided for, and which may be taken advantage of. It is desirable to make this movement available in using an artificial palate, as thereby more delicate sounds are produced than otherwise. This case presented some extraordinary difficulties in the fact that all the teeth of the upper jaw had been extracted; and it Avas ARTIFICIAL PALATES. 1193 necessary, therefore, to adapt a plate which should not only sustain the teeth for mastication, but bear the additional responsibility of supporting the artificial palate. In the choice of material best adapted as a base for the teeth in such instances, it is preferable to adopt that which will prove the most durable. There are too many interests involved to risk the adoption of anything but the best. In the case under description the patient desired duplicates, and tAvo sets of teeth Avere made, one on gold and the other on platina, with continuous gum. The plates were made like other sets of Fig. 1066. teeth, Avith the exception of a groove located on the median line at the posterior edge, to receive the attachment for the palate (marked C in Fig. 1067). Fig. 1067 will indicate the set of teeth with palate attached. The wings, marked A and B, are made of soft rubber; the frame to support them is made of gold, Avith a joint to provide for the per- pendicular motion of the natural palate, as in the case of the obtu- rator represented in Fig. 1065. When the artificial palate is in use, the joint and frame immediately contiguous lie close to the roof of the mouth; the rubber Aving, letter A, bridges across the opening on the inferior surface of side next the tongue; the wing, letter B, bridges across the opening on the superior or nasal surface, and is also prolonged backAvard until it nearly touches the muscles of the pharynx when they are in repose. Both these wings reach beyond the boundary of the opening and rest on the surface of the soft palate for a distance of from one- eighth to one-quarter of an inch, thus embracing the entire free edge 1194 MECHANICS—DENTAL PROSTHESIS. of the soft palate. This last provision enables the natural palate to carry the artificial palate up or doAvn, as articulation may re- quire. When the organs of speech are in repose there is an opening be- hind the palate sufficient for respiration through the nares. When these organs are in action, a slight elevation of the palate or a con- traction of the pharynx will entirely close the nasal passage, and direct all the voice through the mouth. The palate thus becomes a valve to open or close the nares, and to be tolerated must be made with thin, delicate edges which Avill yield upon pressure. An in- strument thus made will restore, as far as possible by mechanism, the functions of the natural organ. Fig. 1068 represents the artificial palate separated into its con- stituent parts. The frame is bent at the joint in the engraving to Fig. 1067. Fig. 1068. show a stop, marked D, which prevents the appliance from drop- ping out of position. Letter C shows the tongue, Avhich enters the groove in the plate of teeth and connects them. Letters A and B are the rubber flaps which are secured to the frame by the hooks, as seen in the engraving. The process for making rubber wings will be found described on page 1208. Fig. 1069 shows a more extensive, palatine defect of the first class. In this case the entire soft palate is gone, together Avith a small portion of the hard palate at the median line. Although this de- fect is greater in extent, the means for its remedy are more simple. The muscles of the palate are entirely gone, and, consequently, no perpendicular movement need be provided for. The appliance in this case will resemble an elastic obturator more than the valve- like palate of the preceding one. The principle here adopted is substantially that recommended by Mr. Sercombe, of London, some years since, and consists of a plate with a set of teeth in the usual ARTIFICIAL PALATES. 1195 form, and attached to its posterior edge an apron of soft rubber, which shall bridge the opening on its inferior surface, extending nearly to the pharynx. Fig. 1070 represents the set of teeth Avith the palate attached. In Mr. Sercombe's appliance this apron was made of the common sheet rubber in the market, prepared for other uses, and is objectionable for tAvo reasons: 1st. A Avant of purity in the materials of Avhich it is compounded ; in many instances substances being used in its manufacture Avhich Avould prove deleterious to the health of the patient; and, 2, its uniformity of thickness. It is far prelerable, therefore, to make a mould from which to form a palate of pure and harmless materials; one Avhich shall be of sufficient Fig. 1069. Fig 1070. thickness in the central part and at its anterior edge, to give sta- bility, and yet shall have a thin and delicate boundary Avherever it comes in contact Avith movable tissue. Such a palate may be made in a mould by substantially the same process as hereafter described. (See page 1208.) It may be secured to the plate by a variety of simple means. One, Avhich Avill give as little trouble to the patient as any other, is to make a series of small holes along the edge of the plate, and stitch it on Avith silk; or fine platina, gold, or silver wire may be used. It is desirable in this case to have the plate and palate present a uniform surface on the lingual side. In fitting the plate, therefore, it may be raised along the posterior edge from the sixteenth to the tenth of an inch, according to the thickness of the palate desired. The rubber will thus be placed on the palatine surface of the plate, and present uniformity on the lingual surface. 1196 MECHANICS—DENTAL PROSTHESIS. A little thought will show that in this case the patient must edu- cate the muscles of the pharynx alone to do the work of shutting off the nares, Avhich, in the former case, was performed by them in conjunc- tion with the muscles of the palate. Perfection of articulation Avill, therefore, depend upon the success of the patient in this new use of these muscles. In cases of accidental lesions of the palate, such as are under consideration, this education of the muscles to a new work will not be difficult. The patient at some former time has had the poAver of distinct articulation; his ear has recognized in his own voice the contrast betAveen his present and former condition; the ear will there- fore direct and criticise the practice until the result is attained. In the case illustrated by Figs. 1069, 1070, the defect had existed for tAventy-eight years, the patient, at the time of the introduction of the artificial palate, being nearly fifty years of age. The effect upon the speech was instantaneous. Articulation Avas immediately almost as distinct as in youth ; and this remarkable distinctness can only be accounted for upon the assumption that the pharyngeal muscles had undergone a thorough training in the vain effort to articulate Avithout any palate* These two cases, chosen to illustrate the application of artificial palates in accidental lesion, have required, as Avill have been per- ceived, entire upper sets of artificial teeth in connection with the palates. This selection Avas purposely made because the difficulties to be overcome are much greater. In cases where there are natural teeth remaining in the upper jaAv, the palate and its connection with a plate Avould be substantially the same, and the plate might easily be secured to the teeth by clasps in the same manner as a partial denture. Artificial Palates for Congenital Fissure.—Congenital fissure of the palate presents far greater difficulties to be overcome than cases of accidental lesion. The opening is commonly more extensive, the appliance more complicated, and the result more problematical. Nevertheless, appliances have been made in a large number of cases which have enabled the wearers to articulate with entire distinctness, so much so as not in the least to betray the defect. The first efforts made in this direction resembled obturators. They were simply plugs to close the posterior nares, and the results were far from satisfactory. It was not until it was recognized that the two classes of cases, accidental and congenital, were entirely distinct, that much progress was made. * An account of this case appeared in the Argus, of Bainbridge, Georgia, August 1st, 1868, written by the patient himself, who was the editor of that paper. ARTIFICIAL PALATES. 1197 Nearly every case of accidental lesion can be treated by an obtu- rator with considerable success; but very rarely will an obturator be of any benefit in congenital fissure, even if the congenital and accidental cases present substantially the same form of opening. For this reason much embarrassment has been throAvn around these appliances within a feAV years past. The character of the different classes has been confounded, and an instrument admirably adapted to one class has had claimed for it an equal application to the other class. Let it be understood, therefore, as a rule to Avhich there will be but few exceptions, that congenital fissure of the soft palate requires for its success- ful remedy a soft, elastic and movable appliance ; and that, Avith the most skilfully made instrument, vocal articulation must be learned like any other accomplishment. Various inventions have been made for this Fig 1071. purpose Avithin the last twenty-five years, from the most complicated one of Mr. Stearns, described in a former edition of this Avork, to the extremely simple one of bridging the gap with a single flap of rubber. The Stearns instrument, with all its complexity, embodied the only true principle, viz., the rendering available the muscles of the natural palate to control the movements of the artificial palate. The essential requisites of an artificial palate are (1) to replace, as far as possible, the natural form of the defective organs (2) with such material as shall restore their functions. Muscular poAver certainly cannot be given to a piece of mechanism, but the material and form may be such that it will yield to, and be under the control of, the muscles surrounding it, and thus measurably bestow upon it the function of the organ which it represents. Fig. 1071 represents a model of a fissured palate, complicated Avith 1198 MECHANICS--DENTAL PROSTHESIS. harelip on the left of the median line. There is a division also of the maxilla and the alveolar process; the sides, being covered Avith mucous membrane, lie in contact Avith each other, but they are not united. If it is desired, a very simple surgical operation can be performed which will unite both soft and hard tissues at this point of diAdsion. The left lateral incisor and left canine tooth are not developed. Fig. 1072 represents the artificial velum as viewed upon its superior surface, together Avith the attachment of a plate con- taining a clasp and tAvo artificial teeth to fill the vacancy. The lettered portion of this appliance is made of elastic vulcan- ized rubber; its attachment to the teeth, of hard vulcanized rubber, to which the velum is connected by a stout gold pin, firmly im- bedded at one end in the hard rubber plate. The other end has a head, marked C, which being considerably larger than the pin and than the corresponding hole in the velum, it is forced through—the Fig. 1072. elasticity of the velum permitting—and the two are securely con- nected. The process B laps over the superior surface of the maxilla (the floor of the nares), and effectually prevents all inclination to droop. The wings, A, A, reach across the pharynx, at the base of the chamber of the pharynx, behind the remnant of the natural velum. The wings, D, D, rest upon the opposite or anterior surface of the soft palate. Fig. 1073 represents a model the same as Fig. 1071, Avith the ap- pliance, Fig. 1072, in situ; the wing, D, D, in Fig. 1072, and the posterior end of the artificial velum A alone being visible in this figure. The reader will bear in mind that the essential characteristics of this appliance are a soft, elastic substance filling the gap in the soft palate, Avith a flap behind as well as before, Avhich enables it to fol- low all movements of the muscles with which it comes in contact, and thus perform, to a very considerable degree, the function of the fully developed natural organ. It is this characteristic alone Avhich made the Stearns palate a ARTIFICIAL PALATES. 1199 success, and to produce which result Stearns invented the compli- cated and, for most cases impracticable, machinery as seen in Figs. 1079 and 1080. It Avas to produce the same effect by a simple appli- ance, that the Avriter labored unremittingly for more than ten years; the appliance of to-day being no modification in any sense of the Stearns instrument, nor of that of any other author, but an indivi- dual and separate invention, so very simple that Ave can conceive of no different way by which perfection of result can be so nearly at- tained. A hundred instruments of like character now being suc- cessfully worn attest the writer's confidence in it. Simplicity has gone but one step further, and that has been to leave off entirely the posterior flap marked A, A in Fig. 1072. This has been done in England, France and Germany, and occasionally in our own coun- Fig. 1073. try, and a parade made of the fact, as an improvement on the in- ventions of the Avriter; but the experience of the past shows that in all these cases the makers have failed to comprehend the require- ments of the case, and have, in attempting to improve the instrument, dispensed with one of its essential characteristics. A later invention, and one Avhich the author believes to be of almost universal application, is represented in Fig. 1074. To ap- preciate the importance of this invention, it must be borne in mind that heretofore an instrument peculiar in form has been required for every separate case. Each appliance being made in a mould of special adaptation, has therefore entailed upon the operator a large amount of labor. With this later invention it is believed that Avith a feAV moulds, 1200 MECHANICS--DENTAL PROSTHESIS. producing a limited variety of palates adapted to the leading feat- ures in such cases, nearly every case of congenital cleft can be pro- vided for upon the same principle as other forms of surgical appli- ance are made for general use. It was only after years of experience and the observation of many cases that the characteristics Avhich were common to all could be determined. Those common features are: (a) The fissure through the soft palate is always in the median line ; (b) the variations, if any, from the median line are anterior to the soft palate in the palatine and maxillary bones; (c) thickness of the border of the fissure in the Fig.1074. remnant of the soft palate is generally uniform; (d) the sides cor- respond very nearly Avith each other in length, breadth, thickness, and contour; (e) the chief variation in nearly all clefts of the soft palate is in their size or breadth, and this is true Avithout any refer- ence as to whether the fissure extends fonvard into the hard palate or not. Figs. 1071 and 1074 represent tAvo cases of remarkable general likeness, although they differ twenty years in age and more than five years in the period of time at Avhich they were treated. The palate placed in situ in Fig. 1074 shoAvs an instrument which, with variations in size, is of almost universal application. It is nearly identical with the palate, Figs. 1072 and 1073, were that one cut across the middle. Like the other, it is made of soft rubber, and, moreover, it Avill need an additional fixture to fill the gap in the hard palate and also keep the artificial velum from being swal- lowed. In Fig. 1072 there is a projection marked B which is made of soft rubber, and is a part of the velum. This projection, as has OBTURATORS AND PALATES COMBINED. 1201 already been noticed, is intended to assist in supporting the velum in position. This is not ahvays necessary or desirable; there are cases Avhere the velum is quite as Avell sustained Avithout this pro- jection, and where, if it Avere applied, it would certainly injure the tone of the voice by clogging the nasal passage. In the case Fig. 1074, if support Avere desired by lapping on the floor of the nares, towards the apex of the fissure, it would form a portion of the hard palate or obturator instead of being part of the velum or soft palate as heretofore. OBTURATORS AND PALATES COMBINED. We shall proceed now to consider another class of cases, the proper treatment of which has been followed by the most encour- aging results. For fifty years the operation of staphylorraphy has been a favorite one with surgeons, yet the number of cases in which there has been Fig. 1075. only a partial union are largely in the majority. In many instances all that has been accomplished is simply the tying together of a small portion of the soft palate across the back part of the fissure, leaving an opening of greater or less size through the hard palate, anterior to the newly formed septum. This opening has generally been plugged with an obturator; but vocal articulation has been little, if at all, improved. To meet this emergency a new form of artificial velum was invented. Fig. 1075 Avill illustrate such a case Avith the obturator and artificial palate in s'tu. The patient Avas a man fifty years of age. The operation of sta- 76 1202 MECHANICS—DENTAL PROSTHESIS. phylorraphy had been performed twenty years previously; an ob- turator of siWer, and afterward one of vulcanite, has been worn constantly ever since. Nevertheless, the articulation was not benefited, the reason being the same as in every other case of sta- phylorraphic operation; the new fleshy palate, marked A, not being long enough to close by any muscular effort the passage to the nares. There was, however, some remaining muscular action, to utilize which power was the desired object to be attained. Letter B shoAvs the obturator, the letter C the velum. In this instance the obturator is made of soft rubber, the same as the velum, and when in use the velum is but an extension of the natural palate, as seen in Fig. 1075. Fig. 1076 shows the appliance when not in use. The plate D secures the obturator to the teeth, as in other cases of artificial palates. In order to introduce the piece, the broad flap, C, should Fig. 1076. be first passed through the opening in the roof and pushed back; the Avhole fixture will readily fall into correct position. In the case of this patient, the improvement in vocal articulation was im- mediate and very decided. Fig. 1077 illustrates another case of a similar character, but with incidental circumstances much more interesting. The patient was a lady, sixty-two years of age, for whom staphylorraphy was per- formed in 1845 by a distinguished surgeon, and the result was a remarkable success, so far asthe-union of the parts was concerned. The union was perfect throughout the entire length of the fissure, including the uvula; but although the patient had applied herself diligently to the improvement of her speech, she was unsatisfied with her progress. The fault being the same as in all other cases— too short a palate—the remedy must be the same. But here arose another difficulty. There was no opening through the roof of the OBTURATORS AND PALATES COMBINED. 1203 mouth, as in case of Fig. 1074, and there Avas no method of secur- ing the desired palate extension to the inferior surface of the natural palate. To convey to the artificial velum the action of the levatores palati was essential to success. After consultation with a skilful and distinguished surgeon of this city (Dr. George A. Peters, New \ork), it was decided to undo, in a measure, the operation of twenty-five years before, and an opening Avas made through the soft palate on the median line immediately behind the hard palate, as shoAvn in Fig. 1077. The opening Avas a simple straight incision, Fig. 1077. which Avas subsequently enlarged by Avearing a tent for a short time. There was no pain; but little bleeding ; and in a feAv days it was entirely healed. What complicated the case still further Avas the loss of all the teeth in the upper jaAV, and an entire upper denture had been worn for years. The artificial palate was attached to such a denture, and instead of proving detrimental to the den- ture, it was an advantage; serving, when in place, to keep the back edge of the plate from the possibility of dropping. The marked improvement in articulation and- the gratification of the patient were a sufficient justification for the partial undoing of such an ad- mirable surgical operation. The later experience of the writer favors the idea of a partial staphylorraphic operation, with a vieAV of making a narrow bridge across the posterior part of the fissure. Even the tying of the bi- furcated uvula together would be of far more service to the patient 1204 MECHANICS--DENTAL PROSTHESIS. than a union throughout the length of the cleft. Such a slight bridge of the gap is more easily and certainly obtained than when greater attempts are made; as the surgical operation can be supple- mented by an artificial Arelum of a very simple character, the patient thus derives the highest benefit which surgical skill can at this day give. Method of Making an Artificial Palate.—The success of these appli- ances depends very much upon the perfect accuracy of the model, since it is upon this that the parts are moulded. It is essential that the entire border of the fissure, from the apex to the uvula should be perfectly represented in the model, as these parts are when in re- pose. It is also necessary that the model show definitely the form of the cavity above, and on either side, of the opening through the hard palate; since that part of the cavity is hidden from the eye. It is desirable, although it is not essential, that the posterior surface of the remnant of the soft palate be shown; but it is especially im- portant that the anterior or under surface be represented with relaxed muscles, and in perfect repose. The impression for such a model must be taken in plaster; it is the only material now in use adapted to the purpose. An ordinary Britannia impression cup may be used, selecting one corresponding in size and form to the general contour of the jaw. This cup Avill be found too short at the posterior edge to receive the soft palate, but it may be extended by the addition of a piece of sheet gutta-percha, Avhich must be moulded into such form as not to impinge upon the soft palate, but Avhich will reach under and beyond the uvula, and thus protect the throat from any droppings of plaster. Before using the plaster, the posterior edge of the gutta-percha extension may be softened by heat and introduced into the mouth. Contact Avith the soft palate will cause it to yield, so that there is no danger of its forcing aAvay the soft tissues when the plaster is used. The first effort will be to get only the lingual surface, taking precaution not to use too much plaster. After trial, if the impression show definitely the entire border of the fissure, and the soft palate has not been pushed up by the spasmodic action of the levator muscles, it is all that is thus far desired. If, hoAvever, the soft parts have been disturbed (which, on close comparison, a little experience will decide), it is better to take a model from the impression ; and upon this model extemporize an impression cup, as described on page 1191. This temporary cup will have the advantage of the former, inasmuch as it requires but a thin film of plaster to accomplish the result, thus lessening the danger of disturbing the soft tissues. After the removal, if it is seen that any OBTURATORS AND PALATES COMBINED. 1205 surplus has projected through the fissure and spread out over the floor of the nares, it should be trimmed off. In most cases such an impression Avill be all that is required. Such an impression can be taken, with a little experience, quite as readily as a correct impression for a set of teeth. The all-important point is to have the border of the fissure closely defined, with the soft parts hanging in their relaxed condition. It is not essential to one of experience that the pharynx behind the uvula should be taken in the impression. When the model is obtained from the impression, a representation of the pharynx can be made, with suf- ficient accuracy for practical purposes, by carving. It is only when the floor of the nares is used for the support of the palate that it becomes necessary to obtain a more complicated impression, one Avhich shall represent not only a portion of the buccal cavity, but all the superjacent nasal cavity. When this is required, the next step will be to obtain, in conjunction Avith this impression of the under surface (AAdiich we call the palatal impression), an impression of the upper or nasal surface of the hard palate. This can be done by filling the cavity above the roof of the mouth with soft plaster Fig. 1078. doAvn to the border of the fissure, and, while yet very soft, immedi- ately carrying the palatal impression against it, and retaining it in that position until the plaster is hard., Avhich can be easily ascertained by the remains in the vessel from Avhich it was taken. Taking the precaution to paint the surface of the palatal impression with a solution of soap, to prevent the two masses from adhering Avhen brought in contact, there will be no difficuhy in removing it from the mouth, leaving the mass Avhich forms the nasal portion in situ. With a suitable pair of tAveezers this mass is easily carried back- Avard and AvithdraAvn from the mouth ; the irregular surface of con- tact indicates its relation to its fellow Avhen brought together. Fig. 1078 will sIioav such an impression. The portion marked A, B C Avill readily be distinguished as that Avhich entered the nasal 1206 MECHANICS—DENTAL PROSTHESIS. cavity. The line of separation from the palatal impression is plainly indicated in the engraving. The groove marked D sIioavs clearly the impression made by the delicate uvula in the soft plaster. The nasal portion is relatively large, showing an unusually large nasal cavity. The vomer lies betAveen the projections marked A, A,these projections entering the nasal passages. The surfaces marked B, B come in contact with the middle turbinated bones; the surface marked C, in contact with the inferior turbinated bone. In many instances these turbinated bones are so large as nearly to fill the nasal passages. The method of obtaining a model of the mouth from this impres- sion does not require any particular description. The process is similar to the making of a cast into any other mouth impression. The model represented in Fig. 1077 sIioavs a convenient form for such a case. When the nasal portion of the impression does not indicate the superior surface of the soft palate, the part may be represented in the model by carving. It is not essential to the success of the arti- ficial palate, that the posterior surface of the soft palate should be represented Avith the same accuracy that is required on the inferior surface or on both surfaces of the hard palate. By the aid of a small mirror and a blunt probe, the thickness of the velum and the depth behind the fissure can be ascertained ; approximate accuracy is sufficient, since the portion of the artificial palate coming in contact Avith it is so elastic that it easily adapts itself to a slight inequality, rendering absolute accuracy less important. The next step will be the formation of a model, or pattern, of the palate. Sheet gutta-percha is preferable for this purpose, although wax, or some other plastic substance, might answer. The form which should be given is better indicated by the drawing, Figs. 1072 and 1083, than it could be by written description. The Stearns in- strument, of which a cut is here given (Figs. 1079 and 1080), Avas made to embrace the edges of the fissure, and Avas slit up through the middle, so that Avhen the edges of the fissure approached each other, as they always do in SAvallowing, the tAvo halves of the instru- ment would slide by each other; a third flap or tongue was made, and supported by a gold spring, to cover and keep closed this cen- tral slit. This complicated provision for the contraction of the fissure is entirely superseded in Figs. 1072 and 1083, by making the instrument somewhat in the form of two leaves, one to lie on the inferior and the other upon the superior surface of the palate, and joined together along the median line. When the fissure contracts, the halves of the OBTURATORS AND PALATES COMBINED. 1207 divided uvula slide toAvard each other betAveen these two leaves. The posterior portion, marked A in Fig. 1072, is made very thin and delicate on all its edges, as it occupies the chamber of the pharynx, and is subject to constant muscular movement. The sides are rolled slightly upward, Avhile the posterior end is curved doAvnward. The inferior portion, marked D, D, should reach only to the base of the Fig 107P. Fig. 1080. uvula, and bridge directly across the chasm at this point (Fig. 1073); and no effort to imitate the uvula should be made. The extreme posterior end should not reach the posterior Avail of the pharynx by a quarter of an inch Avhen all the muscles are relaxed (although subsequent use must determine Avhether to increase or diminish this space), thus leaving abundant room for respiration and for the pass- age of nasal sounds. Tn cases Avhere it is desirable to make the instrument, as far as possible, independent of the teeth for its sup- port, the anterior part Avhich occupies the apex of the fissure in the hard palate may lap over upon the floor of one or both nares. Such a projection is seen in Fig. 1072, marked B, and a like process is seen in Fig. 1083, but not lettered. Were it not for this process in the first case, the palate would drop from the fissure into the mouth, the single clasp at the extreme anterior edge not being sufficient to keep the whole appliance in place throughout its entire length. Caution must be exercised that this projection entering the nares be not too large, or it will obstruct the passage, and give a disagreeable nasal tone to the voice. 1208 MECHANICS—DENTAL PROSTHESIS. All the peculiarities described must be provided for in the gutta- percha model, which, after having been carefully formed upon the cast, may be tried in the mouth, to ascertain its length or necessary variations. When its ultimate form has been determined, proAdsion must be made to duplicate it in soft rubber. A familiar illustration of the process here to be adopted is found in the parallel process employed Avhen a set of teeth is made on the vulcanite base. A model form is made of wax and gutta-percha, bearing the teeth; and in all its prominent characteristics has the shape desired in the completed denture, the rubber duplicate being vulcanized in a plas- ter mould. In like manner the rubber duplicate of the palate, as before described, may be made in a plaster mould. If plaster is used for the moulds, it must be worked so that the surface shall be free from air bubbles, or the rubber palate will be covered Avith excrescences that cannot readily be removed. By covering the surface of the mould with collodion or liquid silex, it Fig. 1081. will be much improved. But, ordinarily, plaster moulds will be found too troublesome for general use. They may be put to a most excellent use, hoAvever, by using one to make a duplicate of the gutta-percha in hard rubber. This is not necessary Avith those who have had much experience, but Avith beginners it will be difficult to work up the gutta-percha as nicely as may be desired: a dupli- cate in vulcanite will enable the operator to make a more artistic model of the palate, and one Avhich can be handled Avith greater freedom. As, in the course of a lifetime, a considerable number of elastic palates will be required, the mould Avhich produces them should be made of some durable material. The type metal of commerce OBTURATORS AND PALATES COMBINED. 1209 is admirably adapted to this use. A very complete mould is one made of four pieces Avhich will produce a palate in one continuous piece. Such a mould requires very nice mechanical skill in fitting all the parts accurately, and unless the operator has had experience in such a direction it is better to simplify the matter. Fig. 1081 shows a mould in four pieces. The blocks C, C are accurately adapted to the body of the mould marked A, and are prevented from coming into inaccurate contact Avith each other by the flanges D, D, which overlap and rest upon the sides of the main piece. B shows the Fig.. 1082. top of the mould, and the groove E provides for the surplus rubber in packing. Such a mould makes as perfect an appliance as can be produced. The palate is one homogeneous and inseparable piece. The cut Avill sufficiently indicate the form of the several parts. Each of these pieces is first made in plaster, having exactly the form desired in the type metal. They are then moulded in sand, Fig. 1083. Fig. 1084. and the type metal cast as in making an ordinary die for swaging. When in use, a clamp similar to Fig. 10S2 is placed around the mould to keep the several parts firm in their position. Fi"\ 1083 shoAvs the palate complete Avith its attachment to the 1210 MECHANICS—DENTAL PROSTHESIS. teeth. The palate is secured to the plate by a pin of gold passing through a hole of the same size in the palate; the head on the pin being larger then the hole through which it is forced. By making the palate in two pieces to be joined after vulcanizing, as shoAvn in Fig. 1084, the mould may be made in only tAvo pieces, and Avith very little trouble. When in use, the two pieces, as here represented, are bound together at the forward part by the gold pin before referred to; and a few stitches of silk secure it at the poste- rior part. The instrument then becomes identical Avith that shown in Fig. 1083. Fig. 1085 shoAA'S the mould or flask in which it is vulcanized. These flasks were made expressly for this purpose; but they are Fig.1085. not so unlike the flasks in common use in dentists' laboratories that the latter will not answer. The common flask is simply un- necessarily thick or deep. The mould is readily produced in the folloAving manner: Imbed the tAvo pieces of the palate in the plaster in one-half of the flask when the plaster is set and trimmed into form, duplicate it in type- metal by removing the palate, varnishing the surface, moulding in sand, and casting. In making the sand mould, take a ring of sheet iron of the same diameter as the flask and three or four inches high ; slip it over the flask and pack full of sand. Separate them, remove the plaster, return the flask to the sand mould, and fill Avith the melted metal through a hole made in the side or bottom of the flask. Having thus made one-half, substantially the same process will produce the counterpart. Fig. 1086 shows the mould which produces the palate illustrated OBTURATORS AND PALATES COMBINED. 1211 by Fig. 1074. It is the most simple and at the same time the most complete of any mould yet invented. The mould is made in three pieces, and is inclosed in a flask exactly the same as Fig. 1085, but with this improvement: the latter mould yields a piece formed of two separate parts of rubber, Avhich must be aftenvard joined by stitching or othenvise; while the former (Fig. 1086) produces an appliance in one piece, and as perfectly finished as by the more complicated mould of four pieces, shown in Fig. 1081. Letter A represents the base of the mould; B, the middle section, Avhich is placed on the top of A; and the third section, or top, C, com- pletes it. Fig. 1086. The mechanical process by Avhich this mould is made is sub- stantially the same as given for making those before described. The packing of the mould Avith rubber should be done in the same manner as when hard rubber is used for a dental base, with which process it is assumed that the reader is familiar. By washing the surface of the mould with a thick solution of soap previous to packing, the palate will be more easily removed after vulcanizing. The rubber used for this purpose must be a more elastic compound than that for a dental base-plate. The composition used for the elastic fabrics of commerce will answer, if made of selected mate- 1212 MECHANICS--DENTAL PROSTHESIS. rials. There is also on sale at the dental depots a soft, elastic com- pound admirably adapted to the purpose, Avith accompanying in- structions for vulcanizing; the best results being obtained by heat- ing up to 230°, and gradually increasing during four or five hours to 270°. THE END. INDEX. Single references will be found under leading word of title; many subjects are referred to under each word of title, and sometimes under its synonym. Principal subjects are alphabetically arranged: but details and subdivisions are usually given in the order of description in the text, so as to present a full synopsis of the subjects indexed. Abnormal, development and arrange- ment of teeth, 107, 383 Abrasion of teeth, 359. Abscess, alveolar, 327 ; causes and medi- cal treatment, 331 ; surgical treat- ment, 311. Absorption, of roots of deciduous teeth, 183; of alveolar walls around teeth, 342 ; time required after extraction of teeth, 736 Acids, effects on teeth, Westcott's and Miller's experiments, 372; use in refining gold, 854 ; for pickling gold plate, 978 ; after soldering, 979 Actual cautery for destroying pulp, 313 Adhesion, of gum to cheek, 244; of con- tact, 1002; of vacuum cavity, 1006: of partial pieces, 1005 Adjustment of porcelain teeth, to gold plate, 957 ; to aluminium plate, 1038; to vulcanite plate, 1058 ^Esthetics in selection and arrangement of teeth, 967, 969; rules and illus- trations, 969 Alkalies, action on teeth, 372; for cleans- ing gold plate, 979; in composition of, dental porcelain, 1137 ; continu- ous gum, 1013 Alloying gold, 859 Alloys, for gold plate, 859; formulas, 863; for dies, 904; properties and formulas, 902; of tin for plates, 1025; stannic, 1026 Aluminium, history and properties, 1035; refining, 1036; swaged plates and solder, 1037; durability in mouth, 1036 Alumino-plastic process, 1035; swaged aluminium plates, 1037 Alveolar abscess, 327 ; periodontitis, 322; Alveolar processes, anatomy, 50; necrosis and exfoliation, 337; absorption, around teeth, 342; after extraction 736; hypertrophy of walls, 345 Alveolar pyorrhoea, 238 Amalgam, for filling teeth ; instruments for using, 502 Anaesthesia, general, 659; ether and chlo- roform, 660; hydrate of chloral, bi- chloride of methylene, 666; nitrous oxide and apparatus, 661-665; bro- mide of ethyl, 666 Anaesthesia, local; congelation; hypo- dermic injection, 667; electro-mag- netism, 6ti9; spray apparatus, 670; hvdrochlorate of cocaine, 672; ob- tunders, 672 Analysis of cementum, 160; of dentine, 152; of enamel, 149 Anatomical relations of the mouth, 95 Anatomy and physiology of the mouth and' face, 39 Annealing, gold plate, 912 Antagonism of, artificial teeth, 967 ; natu- ral teeth, 105 Antimony, effect on tin, 1025; as alloy for metallic dies, 902 Antrum Highmorianum, 48 ; diseases of and treatment, 686; Dr. Abbot's treatment, 703 Aphthous stomatitis, 204 Aqua regia process for refining gold, 854 Arkansas, Hindostan and Scotch stones, 485 Arsenious acid, action on nerve pulp, 314 Arteries of month and face, 70; internal carotid, 70; external carotid and branches, 71 Articulation, Bonwill's system, 922 Articulation, of natural teeth (gompho- sis), 105; of artificial teeth, 915; importance of accuracy in, 922; HoAve's method, 937 Articulations, 69 Articulators, metallic, 920; plaster, 919 Artificial palates or vela, 1187; teeth, necessity and utility, 717 ; prepara- tion for inserting, 734; methods of in- serting, 726; different kinds of, 721 1214 INDEX. Asbestos, over exposed pulp, 610; use in soldering, 976; continuous-gum, 1013 ; porcelain, 976 Atmospheric pressure; history of appli- cation to plates, 999; illustration of principle, 1000; adhesion of contact, 1002; vacuum cavity, 1006 Atrophy of teeth, 120 Babbitt metal for dies, 899 Backing porcelain teeth ; preparation for, 970; different forms and processes for gold plate, 971-973; teeth for vulcanite plates, 1055 Bichloride of methylene for anaesthesia, 666 Bing's method of capping teeth, 795 Biscuiting porcelain teeth, 1138 Bismuth, use as alloy for metallic dies, 906 Bleaching necrosed teeth, 348 Block teeth, porcelain, 1143; manufac- ture of, 1138; special block carving, 1160 Bloodvessels of mouth and face, 70 Blowpipe, mouth, method of using, 945 ; alcoholic or self-acting, Family's, 947 ; mechanical 948 ; Fletcher's, 949; Burgess' 949; Macomber's gas, 950; Knapp's, 952 Body, porcelain, formulas of composi- tion, 1134 Bone, composition and development, 40 ; maxillary, superior, 47; inferior, 52; palate, 55 Bones, of head and face, development of, 42 Bon will's engine mallet, 559 ; articulator, 922 Bonwill's method of articulating teeth, 922 Bonwill's method of correcting irregu- larity, 453 Borax, use in melting gold, 854; in soldering, 943; in composition of continuous gum, 1013; porcelain. 1137 Bridge-work, 738, 794 Bridge-work, methods of Bing, 795; Litch, 796; Webb, 797; mandrel svstem, 799 ; detachable, 812; Rich- mond, 816; Waters, 817; Low, 818; Melotte, 825 ; R. W.Starr, 828, 836 ; Dexter, 832; Register, 838; Wil- liams, 840, etc. Britannia impression cups, 871 Broaches for nerve filling, 6.0 Bromide of ethyl, 666 Brush wheels for polishing, 980 Building up whole or part of crown of tooth, 595 Burnishers, for fillings, 565; for plate, work, 980 Burr drills, for excavating teeth, 520 Burrs for finishing fillings, 564 Calcic deposits on the teeth, 262 Calcification of teeth, 185 Calcined plaster, 881; silex and feldspar, 1134 Calculus, salivary, 262; black, 263; dark brown, 264; white, 265 ; dark green deposit. 276; excessive deposit, 266 ; chemical composition, 267; origin, 268; effects on teeth, gums and alveoli, 270 ; instruments and man- ner of removal, 271 Calculus, sanguinary, or serumal, 2"5 Calipers, 1031 Canaliculi of bone, form and function, 41 ; cementum, 160 Cancrum oris, 208 Carat valuation of gold, formulas and tables, 861 Carbolized potash, 320 Caries of the teeth, 363; liability to, 365; causes, 370; prevention, 378; surgical treatment, 473; of the max- illary bones, 709 Carriers for files, 417, 481, 564; tape, 564 Carving block teeth, 1160; Calvert's method, 1161 Cassius, purple of, 1136 Catarrhal stomatitis, 200 Cavities in teeth (see Filling), 568; va- cuum, 1006 Cells, of dentinal pulp, 145; of enamel, 149; dentine, 151; cementum, 160; follicular sac, 128 Celluloid, 1110; preparation and com- position, 1111; manipulation, 1111 Celluloid heaters and apparatus; for steam, 1114; for oil or glycerine, 1115; "Best" for moist air, 1117: Campbell's, 1118; Seabury's, 1165; Evans', 1168; drying cast and in- vestment, 1121 ; imitating gum mem- brane-stippling, 1123; metal casts and deep undercuts, 1123; liquid celluloid, 1125; repairing, 1123; new mode continuous gum, 1126; Genese's method, 1129; finishing, 1131 ; cause of imperfections, 1132; Cryer's method, 1130; zylonite, 1132 Cementation process for refining gold, 691,856 Cementum, characteristics of, 159 Cementum, origin, development, 140 Cementum, structure, 160; Ma^itot's, Robin's, Kollicker's, Waldeyer's, Hertz's, Kollman's views, 125-162 Ceramic art, dental, 1133; materials and processes, 1134 Cera mo plastic work, 1023 Chase's metallic roof plate, 1104 INDEX. L215 Characteristics of the lips, 280; of the teeth, 192; of the tongue, 281 Charcoal as fuel, 858,1164 ; ingot mould, 863 ; for soldering, 956 Chase's metallic roof-plate, 1104 Cheoplastic metal, history, 1026 Chloral-hydrate, 666 Chloride of gold, 855; zinc, 899 Chloroform, for sensitive dentine, 320; use in extraction, 659 Clamps for swaging, 910; for soldering, 100") Clasps; value and conditions of use, 983, 990; teeth suitable for, 984; shaping and adjusting, 980; method of Fogle, 988; Noble, 989; Spalding, 990; Austen, 990; gold for vulcanite plates, 1108 Clasp plates, shape of, 993 ; for incisors, 993; six front teeth; biscuspids, 994, 996 ; ten teeth, 998; alternate spaces, 998 Classification of teeth ; anatomical, 97 ; structural, 148; pathological, 107 Cleft palate, accidental and congenital, 1170 Cobalt, oxide of, coloring material for porcelain, 1136 Cohesive gold foil, 500,550 Coke, as fuel, 858, 1164 Coloring materials for porcelain, 1136 Combination of vulcanite with metal for dental plates, 1100 Condensing instruments used in filling teeth, 540 Congelation as an anaesthetic, 668 Continuous-gum work. 1013; history, 1014; properties, 1015; composition; 1016; swaging and backing, 1018; applying gum and baking, 1019 Consolidating gold in filling teeth, 543 Contour fillings, 595 Copper, as alloy, for gold, 860 ; for zinc and tin, 905 Corallite, 1048 Corundum po-nts, 483; wheels, 962 Counter dies, 900; fusible and type-metal, 902; lead, 904; tin, zinc, 907; par- tial, 903 Creasote, use in nerve operations, 273, 290 Crown and bridge-work, 738, 794 Crown of tooth ; artificial, 726; building up, with cohesive or sponge gold, 595; excising, for pivot tooth, 738 Crown-work, methods of Lawrence, 745 ; Foster, 745; Bean, 748; Richardson, 780; Buttner, 7S4; Thomas, 750; Leech, 754; Webb, 751; Williams, 840; Flagg, 752; Boice, 754; Wes- ton, 754; Carman, 754; Hunter, 754; Bonwill, 755; Davis, 757; How, 758; Logan, 762; Richmond, 763, 768; Rambo, 776; Merriam, 786; Baldwin, 785; Starr, 790 Crucibles, preparation of, 856 Crucing, or biscuiting porcelain, 113 Crusta petrosa, 140, 160 Crystal,or sponge gold,500; instruments and manner of using, 555 Cusps of gold for crown- and bridge- work 794, 852 Cuticula dentis, 132 Cylinder filling, 546 Cystic diseases, 255 Decalcification of teeth, 185 Deep-seated caries, treatment of, 497 Defects of the palatine organs, 1169 Deformity from excessive development of lower jaw. 439 Dental, caries, 363; treatment of, 473; chair, 606; engines, 523; follicle, 140; groove, 128; porcelain, 1137: prosthesis, 717 ; pulp, 145; diseases of, 285; surgery, 381 Dental follicle, 129 Dental pulp, diseases of, 285 Dentes sapientae, 103; time of eruption, 187 ; extraction of, 647 ; irregularity of, 187 Dentigerous cysts, 255 v Dentinal fibrillse and tubuli, 153 Dentine, 151; characteristics of, 151; ori- gin and formation, 134 Dentifrices, formulae, 379 Dentition, 174 Dento-electric cautery, 321 Denuding or erosion of the teeth, 355 Destruction of pulp, 311 Diamond drill, 968 Die-plate and hubs, 790 Dies and counter-dies, 894 ; fusible metal, 905; dipping process, 895; sand moulding, 896; dies, 899; partial, 903; metals and alloys suitable for, 904 Differences between temporary and per- manent teeth, 105 Dilaceration, 118 Diseases of dental pulp, 285 ; of denti- tion, 176; of mucous membrane, 198 ; of gums, 215 Disks for cutting teeth structures, etc., 482. 484 Dislocation of lower jaw, 679 Draw plate, 867 Drills for excavating teeth, 520; for labo- ratory use, 968 Drying cavities in teeth, 532 Ducts, salivary, 84 Duplex burner, 898 Electric mouth lamp, 515 Electrolysis, 375 Electro-magnetic mallet, 561 Electro-magnetism as an anaesthetic, 669 Electro-metallic plate, 1046 1216 INDEX. Elephant ivory for dentures, 723 Elevators, etc., for extracting roots, 648 Emery wheels, 964; cloth, 1031 Enamel organ, 129 Enamel: origin and foundation, 128; organ, 129; characteristics, 149; chisels for cutting, 474 Engine mallets and pluggers, 558, 562 Epithelial process.or band, 128 Epulis, 245 Erosion of the teeth, 355 Eruption, of deciduous teeth, 175 ; of per- manent teeth, 187 Ether, as an anaesthetic, 659 Ethics of dentistry (see Introductory Chapter), 33 Excavators, 518 Excising forceps', 738 Exfoliation of alveolar ridge, 337 Exostosis, hypercementosis of teeth, 351 Explorers, 519 Exposed pulps, 285, 607; destruction of, 311; extirpation, 311; filling over and treatment of, 607 Extraction of teeth, 626; temporary teeth, 655; roots, 648; teeth and roots for artificial work, 735; instru- ments of—key, 630; forceps (see Forceps), 634; indications for, 628 Face of an embryo, 43 Facial nerve, 81 Facings of porcelain, 695 Fascia, 57 Fauces, 69 Feldspar, 1134; composition of contin- uous gum, 1015; porcelain, 1136 Fibres, muscular, 57 fifth pair of nerves, 75 File carriers, 481, 564 Files, separating, 477; V-shaped, 479; for finishing filling, 563 ; vulcanite, 1087 Filling teeth, 473,479, 567: materials: gold, non-cohesive foil, 543; cohesive foil, 550; crystal or sponge, 555 ; tin foil, 502 ; amalgam, 502 ; gutta-per- cha, Hill's stopping, 508 ; zinc prep- arations, 510; textile metallic fill- ing, 508 formation of cavity, 528 ; separation of teeth, 487 ; excluding moisture, sal- iva pump, 531 ; drying cavities, 530 ; rubber dam, 533 introducing gold: non-cohesive foil; 543; roll, rope, or band, 544; cylin- ders, 546; pellets, 550; cohesive foil, 550; heavy foil, 554; crystal or sponge gold, 555 condensation with mallet, 557 ; finish- ing, 563; burnishing, 565; non- conductors over sensitive nerve, 610 filling special cavities: in superior incisors and cuspids, 568; superior bicuspids and molars, 577 ; inferior incisors and cuspids, 589; inferior bicuspids and molars, 591 ; contour filling, 595 filling over exposed or sensitive pulp, 528, 607 ; method of Foster, 608; use of zinc preparations, .609 ; Barrett's, 610; King!*., 611; Harris', 611; Webb's, 613 filling pulp chamber and root-canal, 616, 621, destruction of pulp by cau- tery and by arsenic, 313; by extir- pation, 311; methods of Foster, Dunning, Harwood, Arthur, Harris, 315; Gorgas's treatment of cavity, 618; instruments for preparing and filing pulp canals, 620 filling over exposed pulps, 607 Fineness of gold, 861 ; of gold plate and solder, 862, 869 ; formulae and tables for calculation, 862 Finishing, surface of fillings, 563; gold work, 977 ; vulcanite work, 1085 Fissure of Glasserius, 54; spheno-maxil- lary, pterygo maxillary, 47 Flask, moulding: wooden, Bailey's, 896, 898; Hawes', 899; Watt's, 1027; Weston's, 1028; Reese's, 1041 ; Hay- ford's, 1046; vulcanite, 1074; Kings- ley's, for palate, 1210 Flask press, 1082 Fluids of the mouth, 84, 278 Flux for melting and soldering gold, 957, 977; continuous gum, 1013; porce- lain, 1137; bridge-work, 846 Foil clipper, 553; spatula, 544 Foil, gold (see Filling), 499; tin, 502 Follicle, dental, 129 Follicular sac or wall, 137 Foramen, anterior mental, 52; infra- orbital, 47 ; posterior dental, 53; posterior palatine, 48 Forceps, extracting: for molars, Snell's, Harris's, AVolverton's right and left, for incisors and cuspids, for wisdom teeth, 635-641; Parmly's alveolar, with screw, Maynard's, etc., etc., 6 11 -656; excising, 726; plate cutting, 971; punch, 769; Mallett's, 972; manner of using, 643; Hullihen's screw forceps, 651 Forming the cavity, 528 Formulae for Harris's mouth-wash, 230 ; alloying gold, 861 ; gold solder, 869 ; continuous gum, 1016; porcelain body and enamel, 1137; flux and frit, 1137 Fountain drip point and month protector, 486; spittoon, 533 Fracture of the jaws, 682; of the teeth, 360 Frenum linguae, 53 INDEX. 1217 Fuel and furnaces for melting gold, 901 ; for porcelain, 1018 ; zinc, lead, 1164 Fungous growth of pulp, 301 Fused teeth, 112 Fusibility of gold solder, 861; of tin, lead, etc, 902 Fusible metal for dies, 902; allovs, 900 I Hemorrhage after extraction, 656 Herbst method of filling teeth, 548 Hickory wood for pivots, 742 Hill's stopping and instruments for using, 508 Hippopotamus ivorv, 723 Hollow wire, 742, 868 Hook for extracting roots, 649 Hot-air syringe, 540 Human teeth attached to artificial plate, 721 Hydrate of chloral, 666 Hydrochlorate of cocaine, 672 Hydrostatic blow-pipes, 952 Hyperemia of pulp, 286 Hypercementosis, 351 Hypersensitive dentine, 318 Hypertrophy of cementum, 351; of gums, 232 ; of walls of alveoli, 345 Immediate root filling, 623 Implantation of teeth, 674 Impression cups; metallic, 871 ; Frank- lin's, 873; gutta-percha, hard rub- ber, porcelain, 876; Bean's, 882; Fouke's, 874; Wardle's,874 ; swaged, 872; Sonthwick's, 873; Dorr's, 874; adjustable, 873; partial, 876: ma- terials, properties, and classification, 877 ; beeswax and compounds, 878 ; gutta-percha, 879; plaster, 881 ; modelling composition, 882; com- parative value, 884 Impressions: methods of taking, 882; preparation for model, 883; remo- val from model, 892; for vulcanite, 1047 ; for obturator, 1201; for arti- ficial palate, 1204 Incorruptible teeth, 1133 India-rubber, 1047; for regulating teeth, 398; for separating teeth, 489; sul- phurated, 1047 Inferior maxilla. 52; dislocation and fracture of, 679 ; protrusion of, 443 Inflammation of, gums, 222 ; dental pulp, 290; periosteum. 322; maxillary si- nus, 693 Ingot, method of pouring, and moulds; iron, soapstone, charcoal, 863 Injuries of teeth from mechanical vio- lence, 360 Insertion of, artificial teeth (organic prosthesis), different methods of, 726; gold in dental cavities (struc- tural prosthesis), different methods of, 543 Instruments for forming cavities in teeth, 519; introducing gold, 540; finishing fillings, 563 ; nerve-opera- tions, 564; manner of using, for extraction of teeth, 635; roots, 641 Instruments, sets of, 907 Interdental splints, 685 Ganglion ; Casserian, , o ; Meckel's ; sub- maxillary, 79 Gangrene of the mouth, 108 Gas regulator, 1071 Gauge-plate, 867 Geminous or fused teeth, 112 Genese's articulator, 921 Gingivitis, 222 Glands, salivary ; parotid, 84; submax- illary, 86; sublingual, 87; mucous, 87 Gold, for filling teeth: foil, 470,499; cohesive, 500; crystal or sponge, 500; for base plate; value, 852; ne- cessity and effect of alloys, 859 ; re fining by nitric acid process, by aqua regia process, by cementation pro- cess, by fire, 854; pouring ingot, in- got moulds, 863 ; rolling mills, 866 ; gauge and draw-plates, tube wire, 867 ; spiral springs, 868 ; soldering, 943 ; teeth attached to, by vulcanite, 1100; clasps for vulcanite, 1108; oxide of, for porcelain gum-color, 1136: Reese's gold-alloy cast base, 1041; cusps, 851; gold-alloy cast base, 1041 Gorgas's impromptu interdental splints, 685 Green stain on teeth, 276 Grinding porcelain teeth, 969 Groove, dental, 128 Gum lancets; teeth, 1142; single, 1158; blocks or sections, 1154 Gums, anatomy, 93: general pathology, 215; inflammation, 222; hypertro- phy, 232; mercurial inflammation, 234; ulceration, 236; adhesion to cheek, 244 ; tumors of, 244 Gutta-percha: over-sensitive pulps, 566; for filling teeth, 508; for impres- sions, value of, 879 ; for impression cups, 876; for articulating rims, 917 ; for palate models, 1206; for a base, 1053 Hammer, wood, horn, or lead, for first swaging iron, for final swaging, 909 Hand-lathes, 961 Hand pieces for dental engine, 525 Hard rubber (see Vulcanite). 1047 Harris's, C. H., dentifrice, 379 ; mouth- wash, 230 ' Hay ford's alloy and press, 1046 Heavy gold-foil, 554 1218 INDEX. Interglobular spaces of dentine, 159 Inter- or pre-maxillary bones, 46 Intertubular substance of dentine, 159 Introducing gold, 543 Investment, of plaster preparatory to backing teeth, asbestos (or sand) and plaster, preparatory to soldering, 976 Irregular arrangement of artificial teeth, 957 Irregularity of natural teeth, in form, 107; osseous union, 111; supernu- merary teeth, 113; third dentition, 188; in arrangement, 383; treat- ment and apparatus for, 394 ; use of vulcanite for, 409 Irregularity of teeth, treatment of, 394; by ligatures, 398 ; bands and screws, 400 ; loops, 407 ; bars, 408 ; inclined plane, 408; Farrar's methods, 400, 401, 408, 409, 410, 421, 433, 437; Tomes, 399,403; Flagg's,400; Guil- ford, 401 ; Kingslev, 402. 409, 437, 442, 443; Shaw, 407; McQuillen, 408; Lee, 410; Richardson & Red- man, 411: Bennett, 411; Talbot, 412,418, 439; Herbst, 434; Cryer, 435; Matteson, 438; Richardson, 413; Patrick, 413; Coffin, 416; Bvrnes, 424 ; Dwindle, 434 ; J. O. White, 437 ; Allan, 444, Angle, 445 ; Bonwill, 453; torsion, 403 Irritation of dental pulp, 285 Jarvis's separators, 490 Jointing blocks, 969 Kaolin, 1135; use in continuous-gum, 1016; in dental porcelain, 113 J Key of Garengeot, 630 Knapp's blow-pipe, 952 Ladles, 901 Lamps, soldering, 945; vulcanizing, 1059 Lancing the gums, 180, 644 Lands' cross-pin teeth, 1139; facings, 847 Lathes for grinding teeth, etc , hand and foot, 961 Lead for filling cavities in teeth, 502; for counter-dies, 900; alloys of, 902 ; effects of antimony, 903; forswaging- hammer, 908 Liability of teeth to decay, 365 Ligament, external lateral, spheno-max- illary, stylo-maxillary, 70 Lining root canal with gold, 750 Lips, symptomatology of, 280 Local anaesthetics. 667 Loop matrices, 583 Lower jaw, excess of teeth in, protru- sion, 443; dislocation, 679; fracture, 682 Magnet, for refining gold filings, 857 Magnetism, electro, as an anaesthetic, 669 Malformed teeth, 107 Malleability of gold, 499, 852 Mallet, force in condensation of gold, 557 ; hand and automatic, 557, 558 ; engine-pluggers, 5o0 Mandrels, 483 Manganese, oxide of, coloring material of porcelain, 1136 Manufacture of porcelain teeth, 1133 Materials : for filling teeth, 499 ; used as dental substitutes, 721; for impres- sions, 877 ; for swaged plates, 852; for plastic or moulded plates, 1137 ; for dental porcelain, 1047 Matrices for filling teeth, 583 Matrix of bone, 40; sand, for dies, 896; brass, for moulding teeth, 1138; plaster, for moulding blocks, 1139 Maxilla, superior, 47; inferior, 52 (see Lower Jaw) McPherson's articulator, 921 Mechanical abrasion of teeth, 359 Mechanics, or mechanism of dentistry, classification, 715 Meckel's cartilage, 45 Membrana eboris, 138 Membrana preformativa, 137 Mercurial stomatitis, 212; inflammation of gums, 222; amalgam, 522 ; action of vulcanite, 1052 Metal crown caps, 790 Metal tape, 566 Metallic enamel, sections and coatings, 847 Metallic impression cups, britannia, 871 ; swaged, copper, 871; dies and coun- ter-dies (see dies), 874 Metallic roof-plate. 1104 Metallo-plastic work, 1025; cheoplastic, 1026; stanno plastic, 1026; alumino- plastic, 1037 Metals, for filling teeth, 499 ; for swaged plates, 852; for plastic plates, 1026; for dies and counter-dies, 894 Method of directing second dentition, 383 Methylene, bichloride of, 666 Miller's experiments on acids, 372 Model, plaster, 887; different forms of, for swaging, 890; vulcanite, 1053; sectional model, Westcott's, 891 ; Bean's, 891 ; articulating, 917 Moulded plates of plastic materials, 1047 Moulding-flasks, 898 ; sand, spatula, 897 ; ladles, 901 Mouth, anatomy and phvsiology of, 39; bones, 40; muscles, 56; bloodvessels, 70, nerves, 75; glands, 84; mucous membrane, 90; mirrors, 514; fluids of, 84, 278 ; relations of, 39 ; washes, INDEX. 1219 230; treatment of, preparatory to artificial work, 734; impressions of, 871 Mouth-lamp, electric, 515 Mucous membrane of mouth, 90 ; dis- eases, 198 ; deposit on teeth, 276 Muscles of the mouth and face, 56 ; clas- sification of, 57 Nasmyth's membrane, 133 Necrosis of alveolar walls, 337; of the teeth, 347 Nerve exposed, filling over, and instru- ments for, 607 ; destruction and re- moval of, 311 ; inflammation of, 290; nerve broaches, 312, 620 Nerves of the mouth and face: fifth pair (trigemini), 75; ophthalmic branches, superior maxillary branch- es, 76-84; inferior maxillary branch- es, 80; facial nerve (portio dura of the seventh pair) and branches, 81 Nitrate of potash, for refining gold, 852 Nitric-acid process, 852 Nitro-muriatic acid process, 853 Nitrous oxide gas and apparatus, for an- aesthesia, 661; as a blowpipe, 952; Nitrous oxide liquefied, 661 Nodular teeth, 114 Non-cohesive gold, 499, 543 Non-conductors in fillings, 566 Obturator, 1187; Delabarre's, for hard palate, 1188 ; Kingsley's for soft pal- ate, 1189; taking impression for, 1204; combined with artificial pal- ate, 1187 Odontalgia, 304 Odontatropia, 120 Odontitis, 290 Odontomes, 115 OZsophagotomy, 1168 Operations in organic prosthesis, 715; in structural prosthesis, 473 Organic defects of structures of teeth, 119 Organic prosthesis, or replacement of dental organs, 715 Origin and formation of teeth, 125; of salivary calculus, 262; of the per- manent teeth, 141 Orthodontia, 383 Os artificial, 510 Osseous union of teeth, 111 Ossification of dental pulp, 303 Osteology, 40 Osteo-dentine, 161 Osteo-sarcoma, 244 Outline form of partial plates, 912 Oxidation of eighteen carat gold, 852 ; of tin alloy, 1025 Oxide of cobalt, 1136; gold, manganese, titanium and uranium, 1136 Oxychloride of zinc, 510 Oxyphosphate of zinc, 511 Packing vulcanite, 1078 Palate, hard, 55; soft, 68; muscles of, 67 Palates, artificial, 1187 ; Kingsley's, 1188- 1192; Steam's, 1197; Serecomb's principle, 1195 for accidental loss, Kingsley's case first, 1201; case second, 1202 for congenital fissure, 1196 ; case first, 1198 ; case second, 1199; case third, 1200; combined with staphylorraphy, 1201 preparing, introducing and consolidat- ing gold, 543 Kingsley's method of constructing: impression, 1204; model, 1205; gutta-percha pattern, 1206; matrix made of plaster, 1207 ; made of type- metal, 1208; improved forms of matrix, 1209 Palatine organs, defects of: accidental, 1169; treatment by obturators and artificial palates, 1187; by staphy- lorraphy, 1174 Palladium for base-plates, 1018 Paning (or peoning) gold band for rim- ming or backing,1102 Papillae, of tongue, circumvallate, fungi- form, 89; dental, 134 Paraffine with wax, for impressions, 878 Parotid gland, 84 Partial, counter dies,D03; clasps or stays, 993, 1108; plates: dies for, 894; swaging, 908; outline forms, 912: retention of, 728 ; of vulcanite, 1100; of stannic alloys, 1026 Pellets, 550 Pericementitis, 322 Peridental membrane, 94 Periodontitis, 322 Periosteum, alveolo-dental, 94; suppura- tion of, 327 Periostitis, alveolar, 322 Permanent teeth, 99; extraction of 626 ; separation of teeth, 474, 487 Phosphor-necrosis, 337 Physiognomy, importance of aesthetic study of, 1144 Physiological relations of the mouth, 96 Pickling gold plate, to remove borax, 977 ; lead and other swaging metals 912; surface alloy, 980 Pivot teeth (and crown): value and con- ditions of use, 726; excision of crown for, 738; treatment of pulp, 739; selection of crown, 741; wooden pivot, 742; metallic pivot, 743; Brown's method, 744; Lawrence's method, 745; Foster's method, 745; Bean's method, 748 ; Richardson's method, 779; Register's method, 780; Bish- 1220 INDEX. op's method, 780; Dwinelle's method, 781 ; Morrison's method, 781 ; Tal- bot's method, 781; Richmond's method, 780; Buttner's method, 784 ; Thomas's method, 750; Bridge work, 794; Litch's method, 754; Webb's method, 751; Williams's method, 840; Flagg's method, 752; Boice's method, 754; Weston's method, 754 ; Carman's method, 754; Hunter's method, 754; Bonwill's method, 755; Davis's method, 757 ; How's method, 758; Logan's method, 762; Rich- mond's method, 768,783; Rambo's method, 776; Merriam's method, 786; Baldwin's method, 785; Starr's method, 790 Plaster, calcined: for impressions, 881 ; manner of using, 882 ; comparative value, 884; for models, 887; for temporary investing band, after grinding teeth, 974; for soldering batter, 976 Plastic work, 1047 ; ceramo-plastic, 1023; cheoplastic, 1026; stanno-plastic, 1026; alumino-plastic, 1035; vul- cano-plastic, 1047 Plate, swaged for dental base : classifica- tion, swaging, 908; adjusting teeth to, 957 ; articulating, 915 ; soldering teeth to, 944 Platina, as alloy of gold, 853; precipita- tion of, 855 ; backings for gold-plate, 975; for ordinary swaged plate, 974; for continuous-gum work, 1018; sponge for coloring porcelain, 1136 ; pins for teeth, how inserted, 1138; White's foot-shaped, 1138 Plugging pliers, 514; instruments for sponge gold, for use with mallet, 556- 562; for nerve cavities, 620 Polishing fillings, 563; gold plate, 997 ; (see Finishing) points, 484, 485 Polypus of antrum and jaw, 249 Porcelain facings, inlaying of, 771 Porcelain facings or veneers, 846 Porcelain impression cups, 876; forms for filling cavities, 603 : plates, 848, 1166; materials, 1137; coloring materials, 1136 Porcelain teeth, 1133; kinds of, 1134; aesthetic rules for selection of, 1142; variety and beauty of, 1141; require- ments of, 1142; illustrations of dif- ferent styles of, 1144; adjustment to metal plates, 957 ; vulcanite blocks, 1055; manufacture of, 1133; in blocks carved for special cases, 1160 Portio dura of the seventh pair (facial nerve), 81 Potassium, bromide of, to deaden sensi- bility of fauces, 1180 Preparation, of nerve cavity and root for filling, 616; of mouth for artificial work, 734; of root for artificial crown, 738 Prevention of caries, 378 Primary curvatures of dentine, 153 Prismatic cells of enamel, 130 Process: alveolar, 50; malar, nasal, 49 ; palate, 55; mental, 52; coronoid, condyloid, processus gracilis, 55; orbital, 51 Prosthesis, Dental (see Introductory Chapter and 714, 717) Protection against explosion of vulcan- izers, 1073; against saliva, 532 Protrusion of lower jaw, 443 Ptyaline, 88 Pulp, enamel, 129; cavity, filling (see Nerve), 616 Pulp, dental, 145 ; diseases of, 285 ; irri- tation, 286; inflammation, 290; suppuration of, 298; spontaneous disorganization of, 300; degeneration of structure, 300; fungous growth, 301; ossification, 303; treatment of exposed, 311 ; destruction and re- moval of, 31-1; action of arsenic on, 313; cobalt, oxide of zinc, 607 Pulpitis, 290 Pumice for dentifrice, 378 ; for support in soldering, 950; for stanno-plastic model, 1028; for finishing vulcanite plates, 1086 Punch for marking backings, 971; for- ceps. 651; for extracting roots, 649 Purple of Cassius, 1136 Purulent engorgement of maxillary sinus, 696 Pyorrhoea, alveolar, 238 Pyrometer, 1163 Rapid breathing as a pain obtunder, 673 Recipes, for dentifrice, 379 ; mouth wash, 229; alloying gold plate, 859 ; gold solder, 869; continuous gum, 1015; porcelain body and enamel, 1137; flux, gum frit, and gum enamel, 1138 Reese's gold alloy cast base, 1041 Refining gold by various processes, 852 Relations of the teeth to each other, 106 Repairing continuous-gum work, 1017; stannic alloys, 1026; vulcanite, 1147 ; alumino-plastic work, 1035 Replacement of teeth(organic prosthesis), 715; order of operations, 715 Replantation,transplantation and implan- tation of teeth, 674 Retaining screws for fillings, 602 Retention of, artificial work, 726, 981; pivot, 738; clasps, 983; spiral springs, 982 ; atmospheric pressure, 999; adhesion of contact, 1002; vacuum cavity, 1006 Ring socket, for excavators, 520 Robinson's textile filling material, 508; remedy, 673 IND Rolling mills, 866 Root, orris, for dentifrice, 378 Roots of teeth, filling canals of, 616, 621 ; extraction of, 626; necessity of re- moval for artificial work, 734 ; prep- aration for pivot tooth, 726 Rubber-dam, Barnum's, 533; punches, 534; clamps, 537 Rubber, India, 1047 ; bands for correcting irregularity, 339 Saliva, composition, function, 87 ; symp- tomatology, 278; pumps for removal of, 531 Salivary calculus, 262; removal of, 271; glands and saliva, 84 Sand moulding, 897; with plaster for soldering batter, 976 Sanguinary or serumal calculus, 275 Scalers for removing tartar, 271 Scorbutus, 213 Screws for roots, 649 ; for forceps, 651 Screws for retaining fillings, 602 Secondary dentine, 161 Second dentition, 183; teeth of, 99; method of directing, 383 Selection of artificial teeth, 969 Self-acting blowpipes, 947 Sensitive dentine, 318 Separating files, 481 Separation of teeth, permanent, 493 Separators, 490 Separation of the teeth, 474, 487 Shears, plate, 908 Shrinkage of metallic dies, 894 ; of porce- lain paste in baking, 1138,1164 Silica in porcelain, 1134 Silver, as alloy of gold, 863 ; as base-plate, 1011; use in composition of cheo- plastic metal, 1026 Sixth-year molars, 389 Soapstone, ingot mould, 863; powder with plaster, 894 Socket handles, 519 ; ring, 520 Soft palate (see Palate), 68 Solder, gold, 869; formulas, 870: silver, 870 Soldering: conditions of success, 943; process, 944; clamps for, 1005; lamps for, 945; blowpipes for, 946 ; pan, 955; preparations of clasps for, 987 teeth to backings, 977; backings to plate, 975; double plates, 956; car- bon cylinders for, 956 Spar (feldspar) in porcelain, 1134 Spiral springs, 982 Spontaneous disorganization of pulp, 300 Sprav apparatus for anaesthesia, 670 Springing of plates in soldering, 956 Stannic (tin) alloys for metallic dies, 900 ; for base plates, 1025 Staphyloplasty, 1183 Staphylorraphy, 1174; history, 1177; 1221 earlier forms of operation, 1178; Fergusson's first operation, 1178; his later method, 1181 ; Cartwright's preparation of patient, 1179; com- bination with Kingsley's artificial palate, 1187; comparison of, with mechanism, 1189 Starr's measuring glass, 1080 Steam pressure, 1072 Stellate cells, 130 Steno, duct of, 85 Stomatitis, 198; simple or catarrhal, 200; ulcerous, 202; aphthous, 204; thrush, 205; gangrene of the mouth, 208; mercurial, 212; scorbutus scurvy, 213 Stomatoscopes, 515 Stratum intermedium, 132 Student's case and instruments, 607 Styptics, 657 Submaxillary glands, 86 Sublingual glands, 87 Substitutes for teeth; human teeth, 721; teeth of cattle, ivory, 722; porce- lain, 723 Substitution, or replacement of teeth (organic prosthesis), 721 ; classifica- tion of operations, 715 Sulphur, combination of, with gutta- percha, 1047; with India-rubber, 1019; action on vulcanizers, 1055 Sulphuric acid, action on teeth, 376; process for refining gold, 852; for pickling gold plate, 977 Superficial caries, removal of, 473 Superior maxilla, 47 Supernumerary teeth, 113 Supplemental teeth, 114 Suppuration of antrum, 696 Swaged work, operations of classified, 717; metals used for, 899 Swaging process, 908 Syphilitic teeth: effects of syphilis, 117 Syphilitic ulceration of the mouth, 211 Syringe, hypodermic, 667 Syringes, abscess, 333, 624 Tables: for ascertaining fineness of gold, 862; for alloying gold, 8-59; of fusi- ble alloys, 902; of fusibility and specific gravity, 903 ; of steam pres- sure and temperature, 1072; of time and temperature in vulcanizing, 1084 Tape arbor, 565 Tape carrier, 417, 418 Tartar (see Calculus), 240 Teeth : anatomical classification and de- scription, 97 ; origin and formation, 125; structure of, 148 pathological classification, 97 ; diseases of, 285; caries, 363; filling (struc- tural prosthesis), 567; extraction, 626; irregularity, 383 replacement of loss of (organic pros- 1222 INDEX. thesis), 715; substitutes for, 721 ; methods of replacing, 715; articula- tion or antagonism of, anatomical, 105; prosthetic, 717; suitable for clasping, 984; grinding and adjust- ing to plate, 957 ; manufacture of porcelain, 1138; various forms and aesthetic study of, 1142 Temperaments, classification of, 167 Temporary: teeth, 97; extraction of, 626; investing rims of plaster, after grinding teeth, 970 Temporo-maxillary articulation, 69 Third dentition, 188 Thrush, 205 Time after extraction, for insertion of artificial teeth, 736 Tin, and its alloys: for swaging, 900: for base plates, 1026 Tin-foil: for filling teeth, 502; for in- vesting impressions, 888; for pat- terns of plate, 904; for temporary articulating plates, and for tempo- rary use in grinding teeth, 1054 Titanium, oxide of, for coloring porce- lain, 1136 Tongue, 89; symptomatology of, 281 Tonsils, 69 Toothache (Odontalgia), 304 Tooth structures, 148 Transplantation of teeth, 674 Trephines for opening antrum, 702 Trial of teeth before soldering, 974; un- necessary after correct articulation, 1054 Tube wire, 742, 868 Tumors of the mouth and jaws, 244; cystic, 255 Type metal: for metallic dies, 905; for Kingsley's palate matrix, 1208 Ulceration of the gums, 236 Ulcerous stomatitis, 202 United teeth, 111 Uranium, oxide of, for coloring porce- lain, 1136 Use of anaesthetic agents in extraction, 659 Uvula, 69; loss of, 1176 Vacuum cavity: history, 999; form and position, 1009; objections to use, 1010 Varnishes for plaster impressions and models, 893, 1077 Veins of the mouth and face, 75 Vela, artificial, 1187 Voltaic narcotism, 670 Von Bonhorst's applicator, 672 Vulcanite, 1047 ; composition and varie- ties of, 1049 ; effect of the vermilion in, 1051; impressions, 1052; models, 1053; articulation, 1054; grinding and arranging teeth, 105-5; making matrix plate, 1056; packing and preparing flasks, 1078; time of vul- canizing, 1084; removal from flask and finishing, 1085; repairs of, 1089; Sttick's method, 1089; Snow's method, 1091 teeth suitable for, 1055; partial sets and gold clasps for, 1100; attaching teeth to metal plates by, 1104 ; P. G. C. Hunt's method, 1102; liquid rubber for repairs, 1106; spring plates, 1107; for pivot teeth, 1105; for correcting irregularity, 1108 durability of, 1109; Goodyear's and other patents, 1147; merits and de- merits of, 1109 Vulcanizers; Ward, Campbell, Seabury, Evans, Whitney, Hays, AA'ood, Snow- den & Cowman, Edson, Mann, 1059, 1071; flasks for, 1074, and flask press, 1082; packing boiler, 1078; safety-gauge, 1074 regulation of temperature by steam gauge, 1074 ; by thermometer, 1070; steam high-pressure tables, 1072; strength of vulcanizers, 1059; time of vulcanizing. 1084 Vulcano-plastic work, 1047 Ward's electro-metallic dentures, 1040 Warping of plates, 956 Watts' alloy, 1027 Warty teeth, 115 Wax: for impressions, 878 ; comparative value, 885; for articulating plates and rims, 917; for matrix plates, 1088; spatulas, 1057, 1058 Wedges for separating teeth, 491, 492 Wedge-cutter, 493 Wedgwood's porcelain, 1135 Westcott's experiments on acids and alkalies, 372 Weston's fusible metal, 1026 Wharton's duct, 87 Wheels for polishing, 979 Wood polishing points, 273, 484 Wood's metal for filling and base, 1026 Wounded pulps, treatment of, 297 Younger's operations, 677 Zinc: preparations for filling teeth, 510; use in gold solder; for metallic dies made by pouring in impression, made by sand moulding, 897 ; con- traction of, 904; advantages of, for die, 900 Zinc, oxy-chloride, 510; oxy-phosphate, 511; white oxide of, for polishing, 1086 Zylonite, 1132 CATALOGUE FEBRUARY, 1889. ^i CATALOGUE OF MEDICAL, DENTAL, Pharmaceutical & Scientific Publications, WITH A CLASSIFIED INDEX, PUBLISHED BY P. BLAKISTON, SON & CO., (SUCCESSORS TO LINDSAY & BLAKISTON] Booksellers, Publishers and Importers of Medical and Scientific Books, No. 1012 WALNUT STREET, PHILADELPHIA. THE FOLLOWING CATALOGUES WILL BE SENT FREE TO ANY ADDRESS, UPON APPLICATION. Catalogue No. I, including all of our own publications. A Catalogue of Books for Dental Studenis and Practitioners. A Catalogue of Books on Chemistry, Pharmacy, The Microscope, Hygiene, Human Health, Sanitary Science, Technological Works, etc. Students' Catalogue, including the "Quiz-Compends" and some of the most prominent Text- books and manuals for medical students. A Complete Classified Catalogue (68 pages) of all Books on Medicine, Dentistry, Pharmacy and Collateral Branches. English and American. "P. Blakiston, Son & Co.'s publications may be had through Booksellers in all the principal cities of the United States and Canada, or any book will be sent, postpaid, by the publishers, upon receipt of price, or will be forwarded by express, C. 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