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I30 MECHANICAL DENTISTRY AND METALLURGY.

llasked first, and the investment allowed to extend half-way
up the splint. Trim, varnish, and oil. Place the upper
model in position in the splint and finish flasking. By
allowing the tin-foil to extend beyond the wax (as at T,
Fig. 86) the investment holds it in position when the wax
is removed. Fig. 86 gives a sectional view of the flask
with the splint invested. F represents the flask; M, the
models ; P, plaster investment ; T, tin-foil coverings of the
teeth extending beyond the wax splint W, wax model of
;
splint. Before opening the flask, place it in hot water to
Fig. 87.

soften the wax. Separate the sections carefully. Remove
the body of the wax splint, with a spatula, and wash the
remaining wax out by pouring boiling water upon it; in-
struments should not be used about the teeth, as they are
liable to injure the tin-foil.
Packing and Vulcanizing.—Liberal outlets for the rubber
should 1)6 made in both sections. Cut the rubber into thin
strips and soften over boiling water. It is also advisable
to cut up a piece of previously vulcanized rubber, small
pieces of which may be packed in between the other rubber
at the thickest points, making it less liable to become porous
in vulcanizing. Pack each section carefully and thoroughly
a little more than full. Place the sections together, boil,