Page 34 - My FlipBook

20 METHODS OF FILLING TEETH.

As I have made my diagrams to deal with cavities involving the re-
storation of corners, this will be an opportune place to discuss that
It has been recommended
particular subject. by recognized authority
of this character as shown the in
to form a cavity by heavy shading
To my mind this is most unfortunate We thus
Fig. 36. teaching.
both of which must become weak save in
get two sharp angles, points
the hands of the most skillful, even if this exception be allowable,
which is doubtful. In any event the result is far from beautiful. Such
a cavity coming into my hands would have been formed as shown in
Fig. 33, for the L-like extension is supposed to have been intention-
made Once I was called to refill a tooth
ally by the operator. upon
which had been operated upon according to this method, and in that
instance I formed my cavity as indicated by the dotted line, Fig. 36,
approaching my ideal as nearly as possible under the circumstances.
I could have shaped it as seen in Fig. 37, out such a form is so un-
common as to be more conspicuous than that chosen. In Fig. 38 we
see a diagram showing two corners contoured. In cases of fracture

FIG. 34. FIG. 35. FIG. 36. FIG. 37.

from falling against a curbstone or from other accident, the corner will
usually be lost, the line of fracture being a straight one. A filling placed
without alteration of the border would appear as shown at a, and the
correct border is seen at b. Let us consider these two forms aside from
esthetics. Suppose that the dotted lines/,/, give the internal retentive
shape of the cavities. The force during mastication, which will tend
to dislodge the fillings, will come in the direction indicated by the
dotted lines c, c. The border of the corner a being a straight line, it
is evident that the retention of the under strain, will be
filling, entirely
dependent upon the strength of the wall at d, of course plus the re-
sistance of the lower undercut. In the other corner (K) we have
equal strength, plus the resistance offered by a well-defined shoulder
at e. So that once more we find the curved line stronger, as well as
more attractive in appearance.
In cavities such as are shown in Fig. 39, and even where the dep-
redation has been less, it has been advised to remove the natural