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354 THE TECHNICAL PKOCEDXJEES IN PILLING TEETH.

a cast that is as sharp as the original wax filling. As the shrink-
age of the gold in cooling is less than the shrinkage of porcelain
in baking, and also as there is no matrix to be stripped off, the
cast gold inlay fits the cavity more perfectly than the porcelain
inlay can be made to do. This is a distinct advantage for the
cast gold inlay. The sprue having been set in the exposed part
of the wax filling, the cast gold representing it is only to be cut
away in finishing the inlay to form. Neither is there any objec-
tion to casting the inlay from a wax filling that has been finished
a little overfull and finishing this perfectly to the margins in
every part after it has been set, as any other gold filling.
For the original practice work by students in learning this
manipulation, there seems to be no objection to using silver or
a more fusible compound of silver and tin. Silver expands at
the moment of congealing in cooling from a high melting tem-
perature, and in large masses is liable to "spouting," which is
complained of by smelters in forming silver ingots. On the other
hand, tin contracts. By making an alloy of 73 to 75 per cent of
silver to 27 to 25 parts of tin, this may be equalized by a little
careful experiment so that the cast will exactly represent the
mold. Such a cast inlay ought to do good service in the mouth
as well as good practice service.
The cast gold inlay is particularly adapted to all of those
positions in the teeth in which there is no considerable objection
from the esthetic point of view, and therefore, as heretofore
indicated, is the proper inlay for bicuspids and molars when an
inlay is called for. Some exceptions have been noted.