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174 MECHANICAL DENTISTRY AND METALLURGY.
on each side of the crown (B, Fig. 139), the surfaces of
which, if ch-y and shghtly warm, will be held in position
temporarily by pressing them gently against the side of the
wax. This is all now invested together (Fig. 140).
The long ends of these side pieces, after being invested,
hold them in position, as the investment should be cut away
so as to expose the sides of the crown as shown at A, Fig.
140. In the process of soldering, after the case has been
properly heated, the small pieces of solder and borax are
placed in the aperture formed by these sides of gold or mica
(the place formerly filled with wax), and the flame from
the blowpipe directed cautiously against these exposed sides
(A). The solder will then flow, uniting the several parts.

Fig. 141.

when more should be added until the proper contour with
perfect continuity of structure is secured. The crown can
be made without the gold or mica sides if great care is
exercised in flowing the solder. There will be more surplus
solder, however, to be finished off.
In finishing, the solder is brought to the contour of a
bicuspid tooth with stones and sand-paper discs, when it is
ready for the polishing process. The finished crown is
represented in place upon the root in Fig. 141.
Other Methods.—There are other methods practised, and
though some of them may not be as artistic as the one just
described, they are much simpler and quicker. For in-
stance, the palatal cusp may be built up with several pieces
of gold plate — previously melted into the form of balls and