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FILLING BY CLASSES AND MODIFICATIONS. 219

4th Mod.—The cavity large, and the lateral walls
thin and friable. In this kind of cavity the dentine
is almost entirely removed from the lateral walls,
leaving little else than the enamel after the excava-

tion of the decay. These walls will, of course, admit
of no cutting for the purpose of giving them a more
desirable form. The cervical wall must be shaped
with special reference to a retention of the filling, to
consolidate which the requisite pressure must be ap-
plied almost exclusively toward this wall. It requires
extreme care to condense the gold in cavities of this
kind and adapt it to the lateral walls without fractur-

ing them; and various methods have been suggested
to prevent such an accident. Pluggers with very fine
points are recommended, ^as consolidating the gold
with much less pressure than would be necessary with
large-pointed instruments. But it has been maintained
that a perfect adaptation of the gold to the inner parts
of these walls is not important, provided the adapta-
tion at the border is perfect. It is certain, however,
that a filling thus imperfectly adapted, is not so good

as though the gold were in contact with all points of
the cavity; and besides, the liability of fracturing the
wall is just as great in consolidating at the border as
within. The walls may be sustained by enveloping
the tooth to the borders of the cavity with some ma-
terial perfectly adaptable to it, and capable of resisting