Page 131 - My FlipBook

APPROXIMAL CAVITIES IN CUSPIDS.
117
In the cuspids we have the same general rules, with one or two
notable I have
exceptions. argued against any undercutting at the
incisive corner of a cavity, and also to some extent against extensive
grooving along the labial and palatal borders. This is changed in the
cuspid, for here we have proportionately more tooth- substance between
the pulp and the outer surfaces. Fig. 125 shows a cuspid having a
cavity similar to that in the central in Fig. 115. What was a quite
difficult condition in the central is much more simple in the cuspid,
so far as preparation of the cavity is concerned. Where it is the dis-
tal surface which needs attention, of course the actual is more
filling
difficult. To form this cavity in the cuspid, we need not make the
labio-gingival extension as deep as before, but as there is abundance
of tooth-substance at the palato-gingival angle we may, if we desire,
make the extension even
deeper, though it is rarely necessary. Again,
as discretion may dictate, we here may make extensive grooves along
FIG. 125. FIG. 126. FIG. 127.

both labial and palatal borders, and quite a deep undercut at the incisive
corner d is permissible where requisite. This last departure from the
former rule is allowable, first, because of the excess of dentine
rigid
in the cuspid beyond that found in the incisors, and second, because
the of the renders fracture of the corner much less
pointed cusp cuspid
liable to occur than in the incisor, which presents a broad, thin incis-
ing edge to combat the strain of mastication.
In Fig. 126 we see a cuspid needing a contour filling. When I state
that I have never seen a in which I found
cuspid it requisite to use a
screw, it is seen at once that this tooth offers a better field for extensive
operations than the incisors. In Fig. 126 the full corner may be safely
restored, depending entirely upon the internal arrangements. We
make both the labio- and extensions
palato-gingival deep. We unite
these with a deep groove, for in this tooth we may feel comparatively
safe that fracture of the gingival enamel, which makes the
against
in incisors. We make both
procedure prohibited strong grooves along
labial and palatal borders, and we make exactly the undercut at e
which was forbidden in Fig. 118. Indeed, this undercut in the
cuspids is mainly the reliance which makes us feel safe without the use