Page 184 - My FlipBook

1 68 THE TREATMENT OF TEETH

obtain these fine cavity margins is one of the most
difiicult steps in the whole proceeding. Very sharp
burs should be used for preparing the cavity, and
the small stones known as the " Gem Cavity-
Trimmers" are very useful for producing clean-cut
margins. Diamond burs and Arkansas stones are
also of great value. Ample separation of the teeth
is necessary in approximal cavities, and labial walls
may be freely cut away when necessary to facilitate
the operation. The secure retention of an inlay
greatly depends on the cavity having a certain
depth, but there are many cavities, particularly large
approximal ones in incisors and canines, in which the
absence of a great part of the lateral walls produces
a shallow cavity that cannot be deepened without
cutting into the pulp, and it may not be desirable
to destroy the pulp in order to deepen the cavity.
It may be said that any cavity that will retain
a cement filling will retain an inlay, providing the
inlay itself can be sufficiently grooved or undercut
to hold in the cement. Large restoration of con-
tour in shallow cavities will usually demand a good
cervical undercut, and a general preparation that
will enable this undercut to be taken full advantage
— particularly in the
It may also be necessary
of.
restoration of cutting edge corners—to remove part
of the cutting edge at right angles to the long axis