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196 CLASSIFICATION OF DECAYED CAVITIES.

condensing the last blocks by forcing in at their side
a small sharp-pointed instrument: the final portion
introduced will be the small, dense, conical roll already
mentioned. The gold being all introduced, a smooth-

pointed instrument or burnisher condenses the project-
ing portion of the filling till it is perfectly solid, when

it is finished with a fiJe, stone and burnisher, in the
manner already described. The particular shape of
the surface of the filling will be suggested by the
form of the antagonizing tooth. If there is nothing
to prevent, the surface may be slightly convex; but
if there are cusps striking upon the center of the
crown, it should be concave.

For dressing down the filling when a concave sur-
face is required, the instrument represented in Fig. 53
is very efficient. It consists of a spherical file, or bur,
Fig. 53.

finely cut, and on a proper shaft or handle ; and may
be used in the manner of the ordinary bur drill. A
variety of sizes and forms should be at hand, in order
to operate properly upon fillings of various sizes.
Adhesive Foil.—For filling these cavities with adhe-
sive foil, definite retaining points should be formed in
them, or the bottom of the cavity of such a form as to

retain firmly in position the first pieces of gold intro-