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as the pulp will permit : for as the depth of the cavity is increased, its
retentive resistance is also increased, and the change in color of the
porcelain, after it is cemented in place, is decreased. The pulpal wall
and the plane of the surface on which the cavity is located should be
parallel (Figs, lo and ii. A). This method of preparation does not en-
croach upon the pulp as readily as one that requires that the pulpal
wall should be flat. In case the cavity is almost circular or eliptical in
outline, a pit should be drilled at some point in the pulpal wall (Fig. 12).

Fig. II.

Fig. 10.

This insures a corresponding projection on the inlay, which assists the
operator in setting it in proper relation to the cavity.
These cavities should be prepared by the use of
fine-cut burs and stones. The best burs for the
technique
of Gacity preparation of cavities on the labial and buccal sur-
Preparation. faces are cylindrical in form (Fig. 4). The face
of the bur should be at a right angle to its axis.
With burs of proper size the cavity is extended in all directions to
obtain proper form and size, after which the margins should be polished
with Arkansas stones.

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