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216 CLASSIFICATION OF DECAYED CAVITIES.

wall, the operation of filling may be performed in one
of two ways: If the portions of the wall remaining at
each side of the fracture are thick and firm, they may
be left, and the cavity filled, so as to restore the form
of both the proximal and the palatal surface of the
tooth, the latter being thus restored with gold to the
extent of the fracture or notch. If, however, the re-
maining portions of the wall are frail, they should be
cut away till a border is reached sufficiently firm to

sustain the filling. Such cutting will leave the notch
of a circular form, and, in many cases, will remove
almost the whole of the inner wall of the cavity. As
the decay extends toward the center of the tooth,
owing to the concavity of its palatal surface, this wall
becomes very thin and easily broken, this rendering
it necessary to cut it almost all away; but, in all cases,

the excavation should be such as to leave a definite
wall, though it be but slight, all along that part of the
cavity. In such a case, good retaining points must be
made in the cervical wall, since the permanency of
the filling will depend almost entirely upon these.
The surface of the filling, when finished, may be
slightly convex from one lateral wall to the other; the
palatal portion of the surface, from the point of the
tooth to its neck, will partake of the curvature of the
border of the palatal wall; but the anterior portion
will be only flush with the anterior wall. Much care