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CROWN- AND 15RII>(;i':-\V()RK. 179

a system of correspc^ndiiii^' (li)\clail and groove, and a
l)rocess of nianufactnring ^^llcrel3y a porcelain facing is
made independent of its backing', has been devised. Figs.
151. 152 and 153 represent the manner of constructing a
superior cuspid crown. Fig. 151 shows the root, prepared
in the usual way for the reception of a collar crown, with
the Mason metallic l)acking adjusted to same; also the liack
face of a cuspid facing, showing the dovetail attachment,
which is baked in the body of the tooth. Fig. 152 shows
the same tooth being adjusted to the backing, while in Fig.
Fig. 151. Fig. 152. Fig. 153.

153 we have the crown complete, the same principle being
carried out in any other tooth and in bridge-work.
The tooth, with its dovetail, is fitted to the band by grind-
ing out where necessary. Then the gold backing is waxed
to the band, and, after wax is hard, the porcelain is removed
from its backing, by taking hold of extended portion of
dovetail, and drawn from same. The crown without the
porcelain, is now ready to invest for soldering. First the
dovetail groove is tilled up with Mason's investment ma-
terial, to keep out the solder, which it will do perfectly, then
the piece is invested as usual, letting the plaster come well
over the cutting point of backing. It is now ready for
soldering, and can be heated up, soldered, and cooled off