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170 OPERATIVE DENTISTRY

Two Methods of Combining-. There are two methods of produc-
ing this combination. One is to cast the filling and lay it into the
cement-covered cavity, which is the inlay method. The other is
to build cohesive gold into a thin mix of soft cement with which
the walls of the cavity have been coated. The essential feature of
both is that the cement be completely covered to protect it from
dissolution by external agencies, as the fluids of the mouth and the
effects of wear.
When Indicated. The inlay combination is indicated in large
cavities of easy access. The built-in method of combination is in-
dicated in small cavities of more difficult access, and where cor-
rect cavity formation is impossible or ill-advised. When using
this method convenience angles may be omitted.
Gold and Platinum. This combination adds to the many virtues
of cohesive gold fillings by increasing the resistance of the filling
to the wear of mastication. The pure gold is first used as it is capa-
l3le of more perfect adaptation to the walls, all of which should
be covered before taking up the platinized gold. The contour por-
tion should be made of the alloy. This alloy comes from the sup-
ply house in sheets which appear to be pure gold except that the
color is a little lighter. This foil comes in three numbers, 1, 2 and
3, the No. 2 being preferable for most cases.
The rules for condensation are just the same as for pure gold,
only the observance of each specific rule given on that subject is
more emphatically demanded here, and when strictly followed the
alloy will prove as easily handled.
Cohesive Gold and Non-Cohesive Gold Combined. By this com-
l)ination much time is saved as the non-cohesive gold may be in-
troduced in greater masses than the cohesive. Also the soft gold
is more easily adapted to the walls than cohesive.
The cohesive gold is used to finish the contour as it will better
resist the torsion strain and the effects of abrasion. Before the
introduction of cohesive gold all gold fillings were non-cohesive,
but since the introduction of the former the art of filling teeth
Avell with soft gold has rapidly declined, so that the making of an
entirely non-cohesive gold filling is now the exception.
Cement and Amalgam. Results similar to what might be termed
an amalgam inlay are produced by coating the prepared cavity with
cement, and immediately burnishing into this fresh cement, a por-
tion of the amalgam. The enamel margins are rendered clean