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54 OPERATIVE DENTISTRY

from recessional tracts, Avhich -will generally be found in the neigh-
borhood of developmental grooves. There should be at least three
of the steps or small supplemental seats. Four point suspension is
better. As the seats are small and Avill probably be required to
carry relatively heavy loads their angles should be most definite.
Second. To avoid the flattening of these pulpal walls in large
cavities of this class the operator should build the metal portion
of the filling immediately into cement which has been applied to
the pulpal wall. This renders the base of the filling adhesive to its
seat and nullifies the tendency of the filling to slip or revolve under
load.
It might be said here that the principle of the inlay is marginal

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A B
Fig. 20.—Class One filled. Cavities shown in Fig. 19.

ridge introduced into a built-in filling, a much valued feature by
many operators.
Convenience Form. There is no convenience form required in
this class of cavities when making a plastic filling. In the making
of a cohesive gold filling in this division of cavities care must be
taken that the mesial wall can be reached by direct force from the
plugger point. In some cases it will be required to move the mesial
margin well upon the mesial marginal ridge to accomplish the de-
sired result.
Convenience Point for the beginning of the first pieces of gold
should be obtained through the use of a small quantity of thin ce-
ment applied to the deepest portions of the cavity.
Finish of Enamel Walls and Toilet. The cavity should be phenol-