Page 148 - My FlipBook

144 FILLING TEETH.

labial and palatal walls are friable, and would be
easily broken ; much cutting upon such walls would
not be admissible. Again, the decay often extends

toward the point of the tooth, down to the union of
the labial and palatal plates of the enamel; in cases of
this kind, all that can be done at this point is to re-
move the decay; and fracture will sometimes occur,
even in accomplishing this.
In some instances, as in the crown cavities of the
molars, the cavity will be nearly or quite of proper
form when it is perfectly opened up, and the decay
all removed. This is the case when the decay is
confined to a simple perforation of the dentine, with-

out any lateral extensions. In proximal cavities,
there is always more or less excavation of the solid
dentine required, to give the cavity proper form.
There is no definite rule for the formation of cavi-
ties, that will be applicable in all cases. The form
will be modified by the tooth, the position of the
decay upon it, and the extent and ramifications of
the decay and the manner in which it is to be filled.
' It is given, by some, as a rule, that the depth of a
cavity should be equal to its least diameter. This is
a direction, however, of no general application, for
many cavities will be much deeper than the greatest
diameter, as in crown cavities of the molars ; and the

reverse will often occur, as in labial cavities of the