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102 THE TECHNICAL PROCEDURES IN FILLING TEETH.

a corner is to be built up, as in the restoration of the angle of an
incisor, or when a very solid surface is to be made, as upon the
occlusal surface of a molar that will receive severe wear. Pitting
of the surface of fillings is in a large degree the result of the
introduction of bits of gold that have not been sufficiently
annealed. To prevent the possibility of this it is well to first
anneal one part and then lay down the piece and catch it at
another point and anneal again.
W^hile the gold should be heated to redness, it should
not be heated to the melting point. This ruins the plasticity
of the foil and makes it impossible to properly condense it. To
avoid these difficulties the gold may be annealed upon a tray over
the flame of the lamp. A number of devices for this purpose
can be had, most of which are convenient and eflective. The
tray may be made of metal, of porcelain, or of mica; it does not
seem to make much difference which is used. In annealing in
this way the gold may conveniently be exposed to the heat for a
considerable time, and therefore a full red heat is not necessary
to the complete development of the welding property, so that
there is no danger of hardening the gold by melting portions of
However, the heat must closely approach the point of red-
it.
ness to be effective. Another advantage is that all parts of the
gold will become annealed.
The disadvantages of this method are, the presence of such
an apparatus upon the bracket which is needed for operating
instruments, and that the gold spread upon the annealing tray
is liable to movement by every motion, or in the eflbrt to lift
pieces from it, and roll together and stick to each other in such
a way as to cause much annoyance and delay in handling it.
Much of this annoyance can be avoided by having a tray that
is so roughened as to prevent the rolling or sliding of the gold.
Filling with Gold.
In filling teeth, cohesive gold or non-cohesive gold may be
used, or the cavity may be partly filled with non-cohesive gold
and finished with cohesive gold.
Filling with Non-Cohesive Gold.
Filling with non-cohesive gold for the entire cavity is prac-
ticed but very little nowadays, apparently for two reasons. It
requires the development of a different order of skill from that