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202 THE GOLD AND PORCELAIN INLAY

on the articulator, in order that more exactness as to carving
of the occlusal form of the wax model may be obtained. The

principal advantage in the indirect method is the time saved
at the chair.
In the construction of the gold inlay, most of the errors
arising and misfits resulting are due to differences in the
ratio of expansion and contraction of the wax model, the

investment, and the gold at the different temperatures at
which they are handled. The secret of success in this regard

l-u Llgin casting mac.

is to keep these materials at as nearly the same temperature
as conditions will admit, throughout the process of construc-

tion. The wax should be allowed to assume room tempera-
ture before investing. The water used in mixing the invest-
ment should not be obtained direct from the water spigot,
either hot or cold, but should be kept in a bottle at room
temperature, ready for use. The investment should not be
too hot at the time the gold is cast. There is no advantage
whatever in a very hot investment, the disadvantages being