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218 CLASSIFICATION OF DECAYED CAVITIES.

In filling this kind of cavity it is desirable to re-
store as much as possible the form of the tooth. The
filling should be built out from the border of the wall
almost to a line with the tooth's original proportions,
so that the whole surface of the rilling will be convex;
and should be finished with great care, the Scotch-

stone or stipple finish being preferable for that part
exposed to view.
3d Mod.—The cavity extending almost to the point
of the tooth, and terminating, or cropping out at the
surface. In the preparation of this cavity, that part
next the point of the tooth should be cut in enough
to form, a definite wall there, and to give room for
sufficient thickness and strength in that portion of
the plug. Many operators attempt to fill this kind

of cavity without such precaution, terminating that
part of the plug in a thin edge. This method is very
objectionable; for the thin edge will become more or
less separated from the tooth, and foreign substances
will be forced under it, and, becoming vitiated, induce
decay. Indeed, a defect of this kind is a sure pre-
cursor of the destruction of the filling. The introduc-
tion and finish of the filling in this kind of cavity are
the same as first described for this class; and the ad-
monition may be repeated, that there be left no thin
overlappings of the filling that may become changed
in position.