Page 69 - My FlipBook

EXCAVATION OF CAVITIES BY CLASSES. 65

In doing this, care should be had not to continue any single
cut so long as to develop considerable heat. Often much unnec-
essary pain is produced, and occasionally serious injury done to
the pulp of the tooth by the heat developed by rapidly rotating
burs. Also care must be had as to possible unnecessary expo-
sure of the horns of the pulp of the tooth. In very deep cavities
it may be best not to square up the whole central depth of the
ca\ity, because of danger to the horns of the pulp, but to cut a
shelf, so to speak, around the periphery to form the principal
seat of the filling, leaving the central part of the cavity deeper.
This deeper portion should then be freed of softened material
with the spoon excavators. In no case should any decayed
and softened material be left in the deeper parts of the
cavity. It is better to expose the pulp of the tooth than to
leave it covered only with softened dentin.
In many cases the squaring up of the surrounding walls, and
flattening of the pulpal wall, may be more easily done with the
hoe 1 2-5- 1 2, or 12-5-6, used with a scraping motion, than with
the bur.
When the walls of the cavity have been squared up, and the
angles of the pulpal wall, with the surrounding walls, made
sharp and definite, and all carious material removed, the enamel
walls may be planed to form, and made smooth in every part.
Unless the enamel walls approach very close to the marginal
ridges, they may be in the same plane with the dentin walls, or
parallel to the long axis of the tooth. But if they do approach
closely to the marginal ridges, the enamel rods will be inclined
toward the ridges, and the enamel wall must be similarly inclined
to be in correct form. This may always be discovered by noting
carefully the direction of the cleavage of the enamel while chip-
ping it away, and the inclination of the enamel wall should be
made to correspond with the enamel cleavage. When the
enamel wall is in correct form and planed smooth, the cavo-sur-
face angle must be slightly beveled in every part. This bevel
should not extend to more than one-fourth the thickness of the
enamel, and often should be much less.
Generally such cavities need no convenience points for starting
fillings, but when large, and the operator feels that slight con-
venience pits will aid him, there is no special objection to their
use. They should be placed in the distal portion of the cavity.