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136 OPERATIVE DENTISTRY

tions subject to great stress. Not a little trouble has been experi-
enced in the breaking of such fillings through given lines of fracture.
These should be noticed and the layers of gold leaf so placed as
to cross these lines. The tensile strength of the sheets of gold is
greater than the usual cohesion obtained giving a filling more strength
across the laminations than parallel with them.
Class Five Cavities in the Gingival Third.
Class Five cavities in the gingival third need no special mention
as they are built under the rules already outlined in Class One.
The gold is usually started in the disto-axio-gingival angle and
carried along the gingivo-axial line angle to the other gingival point
angle. The gingival wall will be the first wall to be completely cov-
ered. The mallet force should not be directed at a right angle until
that wall has been covered with a considerable layer of gold.
Class Six. Abraded Surfaces.
These cavities are built the same as large flat cavities in the same
surface, the principles of which have been given.