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protect the pulp b\- the remaining dentin and to retain the inlay by pre-
paring the cavity with a series of reverse curves (Figs. 39, 40 and 41).
Fig. 39 shows the cavity formation for the labial surface and Fig. 40
shows the formation of the lingual. The gingival wall should form a con-
cave surface, mesio-distally ( Fig. 39A. ) Reverse curves should be cut in the
labial and lingual plates about midway between the gingival wall and the

Fig. 40. Fig. 41.

incisal edge (Figs. 39 B, 40 B and 41 A). A third reverse curve, involving
both labial and lingual plates, should be formed at the incisal edge (Fig.
39 C). A shallow groove should be cut between the enamel plates in the
incisal region to break the plane surface, formed by the enamel plates, in
this region (Fig. 41 B).
In case the pulp is involved, the inlay may be retained by a post in-
serted into the canal. The margins should be smoothed, after which the
pulp-chamber should be so prepared that the matrix may be withdrawn.
After the matrix has been constructed, a 16 gauge irridio-platinum post
should be inserted through the matrix into the pulp canal. The post
should extend far enough through the matrix to give sufficient retention
to the porcelain and that end around which the porcelain is fused should
be roughened to give it secure attachment.

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