Page 129 - My FlipBook

APPROXIMAL CA VITIES IN INCISORS. 1 1
5
seen that the slight portion of the incisive edge which remained
has been
standing entirely removed, so that the two cavities become
thus united. By this procedure we have a single though extensive
cavity to deal with, and the strong retaining powers of the gingival
of the at each side
portion cavity readily retain the whole mass, oper-
ating as they do to counterbalance each other. The cosmetic effect
here is better than where an effort is made to preserve the trifling
bit of the incisive edge of the natural tooth which remained, so that
the arrangement is good both for durability and for appearance.
An analysis of the directions given up to this point discloses the fact
that in every cavity the main reliance for retention is upon the depth
and strength of the labio- and palato-gingival extensions. The latter
especially is the dependence. In making these extensions we are of
course obliged to avoid exposure of the pulp. Therefore they must be
made between that organ and the external surfaces, and distant enough
from each to avoid disaster. The pulp lies nearer to the labial surface at
this part of the tooth than it does to the palatal, for the reason that
on the palatal surface near the neck there is a considerable bulge. It
is in this thick portion of the tooth that we can anchor many fillings
which otherwise would seriously annoy us.
What, then, are we to do with those cavities which present with great
depredation about the very part in which these two important anchor-
are to be ? A
ages placed single example, choosing an extreme case,
will serve for all. Fig. 124 shows a central incisor in a condition of
almost total wreck. Caries has passed beyond the enamel line and
encroached upon the root itself at the neck. It has burrowed along
the labio-gingival angle until seemingly there is little hope for anchor-
age there. It has eaten away a good share of the palato-gingival
so that our in that
angle, mainstay position appar-
must be abandoned. In such an FIG. 124.
ently extremity
we might hope to depend upon lateral grooves,
but here we find that tooth-structure has been lost
until we are almost at the plane of the pulp-canal
itself. Even what is left of the corner is weak,
Yet the pulp is alive, and therefore if it can be
filled with gold the tooth perhaps would last longer
than were it fitted up with a crown. It can be
How are we to
filled, and well filled, with gold.
proceed in this case ? Give attention first to the labio-gingival angle,
at a. The caries passes as a sort of horn toward the labial festoon.
Use first a rose bur as wide as the cavity at a, and deepen as far as
possible without danger to the pulp. Then with a small bur undercut
this toward the gum and toward the incisive edge. This forms
place
what might be termed a dovetail. I have elsewhere said that I do not