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FILLING BY CLASSES AND MODIFICATIONS. 213

the point of the tooth the dentine often has all been
displaced by decay, leaving only the two plates of
enamel joined at the edge, and thus forming an acute
angle, the obliteration of which is always attended
with risk, unless great care is exercised, and in many
teeth it is wholly impracticable ; and still it is difficult
perfectly to fill a very acute angle. The inclination

of the inner and the outer walls of the cavity will
depend on its size: when it is small or medium,
they may be parallel, or, if necessary, slightly diverg-
ent; but when large, it is better not to cut much of
the healthy dentine from them, lest they be thus
weakened. Small grooves, however, are admissible
on these walls, near the bottom of the cavity, when
they incline to the center, and are generally, in such

case, to be preferred to pits. In the formation of
grooves or pits for anchorages, the dentine should
never be cut through to the enamel; but always den-
tine sufficient to protect the enamel should remain.
More cutting is allowable on the cervical wall than
elsewhere, as there is less danger here of weakening
the tooth by excavation. In filling with adhesive
gold, we may, if necessary, rely exclusively on this
part of the cavity for the retention of the plug; and

the best method of preparing it is, to make two or
three little pits in it at different angles with a fine,

square-pointed drill. Another method is, to form two