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6o THE TREATMENT OF TEETH

during the procedure the surface of the non-
cohesive gold is depressed, an even surface of
cohesive gold will be produced. Another method
that is useful in incisors and canines is to fill the
oavity with non-cohesive gold, and then—instead of
making any holes in it with the wedge—to force the
mass in the direction of the labial wall in working
from the back, and in the direction of the lingual
Avail if working from the front, in such a way that
a sufficiently deep and broad trench-like cavity is
formed for the reception of the cohesive portion.
The success of this depends on an accurate adapta-
tion of the non-cohesive gold to the cervical, labial
or lingual, and cutting edge walls by carefully con-
densing against these walls as each piece is packed in
place, and in giving a retaining shape to the trench
that is to be filled with cohesive gold. The engine-
bur may be used to cut out some of the non-
cohesive gold if necessary. In this method either
the lingual or labial wall is left free, and is utilised
as a help in retaining the cohesive portion.
In theory, combination fillings of non-cohesive and
cohesive golds are inadvisable, because there is a
different spring, or resistance, to the stress of masti-
cation in these two kinds of gold, each differing in
rigidity or elasticity. In practice it will be found
that this combination will in many cases prevent