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are inserted in one or more canals and platinum caps are made to fit
over them. The matrix is burnished to conform to the walls of the
cavity and the caps are held in relation by sticky wax. After chilling
the wax, the matrix and caps are removed, and soldered (Fig. 6iB).
The porcelain is then fused around the caps and the matrix is read-
justed for the final burnishing. The matrix becomes a part of the inlay
and should be properly trimmed to conform to the margins of the cavity
after the inlay has been finished. After the inlay has been set the
matrix should be finished to the margins of the cavity as a subsequent
operation (Fig. 6iC).

Fig. 63.

Deep Cavities in the Occlusiil SuHace of molars.

Cavities in lower molars involving the occlusal surface to the mar-
ginal ridges leaving the axial walls unsupported by dentin and in which
there is no decay on the approximal surfaces, may be filled with por-
celain. The margins of the cavity should involve the marginal ridges
and they should be beveled in such a manner that they form obtuse
angles with the axial walls of the cavity. The pulpal wall should
be flat. The axial walls should be extended far enough to protect
the margins from stress and they should form slightly obtuse angles
with the pulpal wall. (Fig. 62.)
For pulpless molars where the entire occlusal surface is involved,
the pulp chamber is so prepared that the axial walls are slightly di-

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