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122 OPERATIVE DENTISTRY

findings of Prothero in the expansion and contraction of plaster
paris in the various periods following its mixture with water.
Finishing' the Inlay. With any of the processes of making an
inlay there are liable to be some imperfections which Avill be seen
upon removing from the investment. If these are on the cavity
side of the inlay and are of any considerable size it will probably
be necessary to make a new^ pattern. If they are only slight and
are in the form of little pedunculated masses they can generally be
removed without injury to the filling. If the contour shows that
the mold did not entirely fill the necessary amount to complete
contour, and the margin is not involved it may be sweat on using
a gold of lower fusing point than that of the inlay. Another
inethod is to make a gold amalgam and build to the desired con-
tour. Then the inlay should be subjected to heat gradually raised
ta nearly red heat when the mercury will be volatilized leaving the
pure gold fused to the position desired. This gold amalgam is
made by adding mercury to cohesive gold foil, pellets or fiber
which have been annealed, mixing thoroughly in the palm of the
liand and applying immediately to place. All exposed surfaces of
gold inlays should receive a high polish before setting, omitting
a line about one-fourth of a millimeter next to the entire margin.
Setting the Inlay. The inlay should be Mashed with Avater and
dried ; then dipped in chloroform to remove any oil that may have
adhered from the hands. The cavity should be freed from all for-
eign substance, given complete retentive form, bathed with chloro-
form and alcohol in the order named and the surface of the cavity
entirely covered with cement.
The inlay is given a coat of cement on its cavitj'- side from the
same mix and gently but firmly moved to position using hand pres-
sure assisted by light blows from the mallet. The inlay should be
subjected to pressure directed toward tlie seat of the cavity for
some minutes which v.ill in a measure overcome the tendency to-
ward displacement caused by the expansion of the cement. An in-
lay may be finished at its margins Avithin thirty minutes from set-
ting, but it is better if this step is attended to at a subsequent
time.