STUDENT’S MANUAL 
CAVITY PREPARATION STUDENT’S MANUAL 
OF 
CAVITY PREPARATION 
BY 
J. E. SEVERNS, D.D.S. 
Demonstrator of Operative Technic 
Dental Department of St. Louis University 
ILLUSTRATED 
ST. LOUIS 
C. V. MOSBY COMPANY 
1915 Copyright. 1915, by C. V, Mosby Company 
Press of 
C. V. Mosby Company 
Sf. Louis PREFACE 
Realizing the need of a manual to aid the beginning 
student to acquire the proper knowledge of cavity prepa- 
ration, this volume has been prepared. Its purpose is to 
impart to the student a knowledge of the correct cavity 
form for gold and amalgam. It is not intended as a text 
to treat of operative procedure, instrumentation or 
technic. 
The illustrations are all original, but the cavity forms 
are those set forth in the standard texts on operative den- 
tistry. 
If this little manual proves beneficial to the student in 
acquiring correct ideas of cavity form, its purpose will 
have been fulfilled. 
—J. E. S. 
St. Louis, Mo. CONTENTS 
Cavity Classification... 9 
Order of Procedure 10 
Extensions for Prevention 10 
Naming of Cavity Walls, Lines, Angles, Etc 10 
Ist Class Cavity Prepared for Filling 12 
2nd Class Cavity Prepared in Upper Bicuspid 14 
2nd Class Cavity Prepared in Upper Molar 16 
Method of Cutting Convenience in Proximal Portion 
of 2nd Class Cavity 18 
3rd Class Cavity Prepared 20 
Cross-section of 3rd Class Filling „ 22 
Cross-section of Proximal Cavity 24 
Cross-section of Proximal Filling 26 
4th Class Cavity Prepared 28 
Incisal Step of 4th Class Cavity Preparation 30 
4th Class Cavity Filled 32 
sth Class Cavity Prepared 34 
Cross-section of sth Class Filling 36 
* CAVITY PREPARATION 
CAVITY CLASSIFICATION 
Cavities are classified according to the nature of the sur- 
faces upon which they occur into two general divisions. 
1. Pits and Fissure Cavities 
These occur in pits, fissures and deep grooves in the 
occlusal surfaces of bicuspids and molars; in pits in the 
occlusal half of buccal surfaces of molars; and in pits in 
the lingual surfaces of incisors. 
2. Smooth Surface Cavities 
These occur on smooth surfaces which are not kept 
clean by process of mastication, or by tongue, lips or 
cheeks. Such surfaces are the proximating surfaces of the 
teeth and the gingival third of the crown of all teeth on 
their labial or buccal and lingual surfaces. 
Cavities are also divided as to form. Dr. Black, whose 
works on operative dentistry are without a doubt our 
best authority, has classified them by number, as follows; 
Class 1. These occur in occlusal surfaces of bicuspids 
and molars, in occlusal two-thirds of the buccal surfaces 
of molars, in the lingual surfaces of upper incisors and 
occasionally in lingual surfaces of upper molars. This 
class includes all Pit and Fissure cavities; while all Smooth 
Surface cavities are included in classes 2, 3, 4 and 5. 
Class 2. Cavities in proximal surfaces of bicuspids 
and molars. 
Class 3. Cavities in proximal surfaces of incisors and 
cuspids, not including the incisal angle. 10 
Cavity Preparation 
Class 4. Cavities in the proximal surfaces of incisors, 
including the incisal angle. 
Class 5. Cavities occurring in gingival third of buccal, 
labial and lingual surfaces. 
ORDER OF PROCEDURE 
The Institute of Dental Pedagogics gives the following 
order of procedure in cavity preparation : 
First—Obtain outline form. 
Second— Remove any remaining carious dentine. 
Third—Obtain required retention form. 
Fourth—Obtain the required convenience form. 
Fifth—Obtain the required resistance form. 
Sixth—Finish enamel wall. 
Seventh—Make the toilet of the cavity. 
EXTENSIONS FOR PREVENTION 
This means the extension of the cavity wails to such 
areas as will afford self-cleansing margins, thus prevent- 
ing the recurrence of decay after a filling has been placed. 
This extension is always to be made in the preparation of 
proximal and gingival third cavities. In each case the 
extension is toward the axial line angles of the tooth for 
the reason that the regions of these angles are the least 
liable to the beginning of caries of any portion of the cir- 
cumference of the tooth near the free margins of the 
gingiva, (Black.) 
NAMING OF CAVITY WALLS, LINES, 
ANGLES, ETC. 
All cavity walls are named after the surface of the tooth 
with which they correspond. 
Ex.—Mesial wall, (M, Fig. 1). 
Lingual wall, (L, Fig. I). 
Pulpal wall, etc., (P, Fig. I). Cavity Watts, Lints, Angtts, Etc. 
11 
The pulpal wall is the wall that is placed to the occlusal 
of the pulp and at right angles to the long axis of the 
tooth. When the pulp is removed the cavity is extended 
to the floor of the pulp, and the wall is then known as the 
sub-pulpal wall. 
The axial wall of a cavity (A, Fig, 2) is one that is in 
the same plane as the long axis of the tooth and covers 
the pulp chamber. 
The names of angles of cavities are derived from the 
walls which join to form them, as : disto-buccal line angle; 
mesio-pulpal angle; mesio-bucco-pulpal point angle; 
axio-disto-gingival point angle, etc., etc. 
The cavo-surface angle of a cavity is formed by the 
junction of the surface of the tooth with the cavity wall. 
The dento-enamel junction, as the name implies, refers 
to the line of junction of dentine with the enamel. 
For purposes of description and dissection of teeth we 
have three general planes in common use: 
The horizontal plane, which is at right angles to long 
axis of the tooth. 
The axio-mesio-distal plane, which passes through tooth 
mesio-distally parallel with the long axis. 
The axio-bucco-lingual plane, which passes bucco lin- 
gually through the tooth parallel with long axis. 
The surfaces of teeth are also divided into divisions to 
aid in cavity description. These divisions are usually 
thirds, as, occlusal third, middle third, gingival third (gin- 
givo-occlusally), buccal third, middle third and lingual 
third (bucco-lingually). 12 
Cavity Preparation 
Fig. I. 
Illustrates Ist class cavity prepared for filling. Note 
extension of cavity outline buccally and lingually along 
fissures to afford smooth surfaces for cavity margins. 
Cavity walls (M F D) should all be at right angles to 
Pulpal wall (P) of cavity, thus giving box form for re- 
tention; no pits, depressions or undercuts are to be 
made. 
Cavo-surface margins of the enamel (C C C) should 
all be bevelled about one-quarter length of the enamel 
rods for gold fillings and full length of the enamel rods 
for amalgam fillings. Ist Class Cavity 
13 
Fig. I 14 
Cavity Preparation 
Fig. 11. 
Illustrates 2nd class cavity prepared in upper bicus- 
pid. The same principle of perpendicular walls and 
bevelling of margins that applies to Ist class cavity ap- 
plies to occlusal part of this cavity also. 
Note that the dove-tail of this part of cavity is made 
at expense of buccal (B) portion, while lingual (L) is 
nearly straight mesio-distally. 
In proximal portion of cavity the axial wall (A) 
should meet the pulpal wall (P) at right angles and 
also form right angles with the gingival wall (G). The 
buccal (BB) and lingual (LL) walls of the proximal 
portion should also form right angles with the axial (A) 
and gingival (G) walls, thus forming box form for re- 
tention. 
Retention form is cut along bucco-axial and linguo- 
axial line angles beginning at gingivo-bucco-axial or 
gingivo-linguo-axial point angle and cutting occlusally 
one-third to one-half the distance to the pulpal wall. 
Buccal and lingual walls of proximal portion of cavity 
should be parallel with long axis of tooth, while pulpal 
wall and gingival wall should be parallel with each 
other and also parallel with mesio-distal plane of tooth. 
Notice general curvature of cavo-surface bevel at 
gingivo-buccal and gingivo-lingual angles (HH). 
“C.” Represents convenience as cut in the cavity. 2nd Class Cavity 
15 
Fig. IT 16 
Cavity Preparation 
Fig. 111. 
Illustrates preparation of 2nd class cavity in upper 
molar where transverse ridge has not been affected. 
Retention is obtained by extending cavity along devel- 
opmental groove on occlusal sufficiently to give the dove- 
tail form. 
Proximal portion prepared as explained under Fig. 2. 
AA represents convenience as previously explained rel- 
ative to Fig. 11. 2nd Class Cavity 
17 
Fig. 11l 18 
Cavity Preparation 
Fig. IV. 
Illustrates method of cutting convenience in proximal 
portion of 2nd class cavities and in other proximal cav- 
ities when access permits. This is done by using No. 6, 
8 or 10 inverted cone bur and cutting at expense of both 
axial and buccal or axial and lingual walls along the 
line angles, thus lessening danger of weakening walls 
if cutting were all made at expense of lingual or buccal 
walls. Method of Cutting Convenience 
19 
Fig. IV. 20 
Cavity Preparation 
Fig. V. 
Illustration shows 3rd class cavity prepared; axial 
wall (A) should form right angles with gingival wall 
(G) ; also with labial (La) and lingual (Li) walls, thus 
giving the box form for retention. 
The enamel should be bevelled so as to conform with 
the direction of enamel rods, which is toward central 
portion of tooth. 
Cavo-surface bevel of enamel is similar to that ex- 
plained under Ist class cavity. Convenience for start- 
ing filling is obtained when possible as in proximal por- 
tion of 2nd class; but if proper access cannot be had 
with bur, this should be done with suitable hand instru- 
ment. 
Incisal retention (A, Fig. 6) is best obtained with 
Black’s hand instruments 3-2-28 or 5-3-28, but should 
never be made with bur. 3rd Crass Cavity 
21 
Fig. V. 22 
Cavity Preparation 
Fig. VI. 
Mesio-distal cross-section of 3rd class filling in inci- 
sor showing incisal retention (A). This is the chief re- 
tention in the 3rd class cavity, preventing filling from 
being tilted proximally. Cross-Section oe 3rd Crass Firring 
23 
Fig. VI. 24 
Cavity Preparation 
Fig. VII. 
Illustrating mesio-distal cross-section of bicuspid at 
middle third of crown, showing the box form of cavity, 
slope of enamel wall (AA) and cavo-surface bevel of 
enamel (BB). Dotted lines (CC) indicate convenience 
which is cut in gingival third of cavity as explained rel- 
ative to Fig. 2. Cross-Section of Proximar Cavity 
25 
Fig. VIT 26 
Cavity Preparation 
Fig. VIII. 
Same as fig. 7, with filling in place and cross-section 
at gingival third of cavity to show convenience grooves 
(CC) and bevels (AA—BB). Cross-Section oe Proximal Filling 
27 
Fig. VIII. 28 
Cavity Preparation 
Fig. IX. 
Illustration showing 4th class cavity prepared. 
The proximal portion of this cavity is same as the 3rd 
class, excepting that it usually extends farther on lin- 
gual and labial, owing to destruction of tooth substance. 
Fig. 10 shows details of preparation of incisal step. 
The pulpal wall of incisal step (PW) should be paral- 
lel with gingival wall of proximal portion of cavity 
(GW). 29 
4th Class Cavity 
Fig. IX 30 
Cavity Preparation 
Fig. X. 
Showing details of incisal step of 4th class cavity 
preparation. 
The bevel of labial and lingual walls are both in same 
plane (AA), while the incisal edge of the lingual wall 
(IE) is then slightly flattened (trimmed parallel with 
pulpal wall of incisal step—P). 
All cavo-surfaces of enamel slightly bevelled, 888. 
Lingual wall of incisal step should be parallel to long 
axis of tooth and meet pulpal wall at right angles, while 
the labial wall (LW) should be nearly parallel to labial 
plane of tooth, thus forming strong retention for incisal 
portion of filling. Labial plate should be left heavy or 
thick and supported with dentine, while lingual wall is 
cut much lower to afford strength and ample tooth 
structure for preparation of step. Lingual wall should 
be about one-half as high as step is wide. No pits, de- 
pressions or undercuts are necessary. 4th Class Cavity—lncisal Step 
31 
Fig. X. 32 
Cavity Preparation 
Fig. XI. 
Showing 4th class cavity filled. (Fabial view.) 
But very little gold shows on incisal, although well 
supported by the strong lingual reinforcement. 
If cavity is on mesial of tooth, incisal step should ex- 
tend to distal developmental groove, and if on distal, 
should be carried to mesial developmental groove (A). 4th Class Filling 
33 
Fig. XI. 34 
Cavity Preparation 
Fig. XII. 
Showing sth class cavity prepared in cuspid tooth. 
Retention is obtained by making a slight undercut 
with inverted cone bur along inciso-axial and gingivo- 
axial angles (AA). (See also Fig. 13, AA.) 
It is often necessary to remove all enamel at gingiva 
while the cavo-surface of enamel is bevelled but slightly. 
All walls should meet axial wall at right angles. sth Ctass Cavity 
35 
Fig. XII. 36 
Cavity Preparation 
Fig. XIII. 
Labio-lingual cross-section of tooth through sth class 
filling to show retention (AA), as explained relative to 
Fig. XII. 
Notice that cavo-surface margins are but slightly 
bevelled. sth Class Filling 
37 
Fig. XIII