Page 344 - My FlipBook

154 THE TECHNICAIj PKOCEDURES IN FILLING TEETH.

chisels. Special instruments are required for beveling the gingi-
val eavo-surface angle, the gingival margin trimmers 20 (80) -9-
12, rights and lefts, for mesial cavities, and 20(95)-9-12, rights
and lefts, for distal cavities. These instruments are made
especially for this purpose. The relation of the edge of this
instrument to the gingival cavo-surface angle of the cavity is
shown in Figure 195. They have the angle of the edge cut pur-
posely for making this bevel. A few strokes lightly made,
carried across the gingival wall and around the angle, first with
the right-hand instrument in the one direction and then with the
left-hand instrument in the other direction, are sufficient.
In the finished cavity, the dentin walls to the buccal and
lingual of the mesial portion should generally not be in the same
plane with the enamel walls, but in cavities of ordinary size
they should be very nearly parallel with each other and inclined
outward only a little from the mesio-distal plane of the tooth.
In the occluso-gingival direction, they should be parallel with
the long axis of the tooth and parallel with each other.
Toilet of cavity. The cavity now only requires the toilet
to be made to be ready for filling. The finished filling is shown
in Figure 169.
In the foregoing, the plans of doing the more important
things that must be done in the great majority of cases have been
presented, and may be regarded as general in their application.
Vaeiations. The variations of jorocedure due to position of
the teeth in the mouth and the different degrees of exposure of
the parts to view and to approach, relate mostly to the second
and third molars and to the lower bicuspids. The ujoper first
bicuspids are usually so well exposed that both the mesial and
distal cavities are easily reached, and, except that the smaller
cutting instruments, as the 15-8-12 and 10-6-12 enamel hatchets
and corresponding chisels and spoons are necessary, the instru-
ments and the instrumentation will be the same. Neither is it
often necessary to make any variation in distal cavities in the
first molar or mesial cavities in the second molar above or below.
Figures 174-177 are presented as a further study of cavity
forms. These are a representation of a molar tooth with a pre-
pared cavity, split mesio-distally and opened in order to display
all of its internal parts. Figures 176, 177 are outline explana-
tions of Figures 174, 175. A study of these will give a better
appreciation of cavity forms.
The cavity form in lower first molars will differ because of
differences in the form of the occlusal surface, most generally