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352 THE TECHNICAL PROCEDUKES IN FILLING TEETH.

cement is gradually oozing from the margins, so that really
the inlay is sinking into the cavity, thinning out the cement
between it and the cavity walls. If the pressure is removed
too quickly, and a margin closely watched with a hand magni-
fier, it can usually be seen that the inlay rises just a little out
from its bed; hence this sustained pressure is important. This
pressure should not be with steel instruments, for these are too
liable to chip the inlay, especially if any slip should occur. Some
kind of wood point, as the toothpick mentioned above, is per-
haps best for this purpose.
Wlien the cement has become fully hard, the redundant
cement should be removed and the operation is complete. It
should, however, be protected from saliva by keeping the rubber
dam in place for half an hour longer, in order that the cement
may become as hard as possible. The qualities of the cement
should determine whether it should be kept dry or kept wet
while setting. The very hard cements usually shrink badly while
setting. This is favorably modified by moistening the cement
with water as soon as it is ready to be left to harden. This will
make the better joint. Other cements do not require this, but
are much softer. The practice of setting porcelain inlays in
cavities wet with saliva, is, to say the least, obnoxious. If, with
the cement used, it is best to have the cavity wet, let it be wet
with clean water.
The Gold Inlay.
Originally the gold inlay was made much after the fashion
of making the porcelain inlay, the difference being that the gold
was flowed into the formed matrix instead of baking porcelain
in it. In this it was an outgrowth of the plans for making por-
celain inlays. It was intended for use in positions where the
esthetic requirements did not demand porcelain, and especially
in molars and bicuspids. With the view of cheapening this,
gold shell inlays have also been made instead of solid gold, in
which the walls and exposed surface only were of gold. In the
setting of these in place, the shell was filled with cement.
Recently, however, these forms of gold inlay have been
rather suddenly displaced by the demonstration by Dr. "W. H.
Taggart of plans for casting solid gold inlays under pressure
in such a way that they will fit cavity walls much closer than those
made by the matrix plan. This casting may be done under pres-
sure of compressed air, nitrous oxide gas. steam or by a vacuum,
by which the liquid gold is forced into a healed mold so as to