Page 73 - My FlipBook

EXCAVATION OF CAVITIES BY CLASSES. 69

Pit or fissure cavities on lingual surfaces do not occur
in the lower molars, but do occur occasionally as independent
cavities in the lingual grooves of the upper molars and rarely
in the mesio-lingual groove of the upper first molars, where
there is a fifth cusp. The instrumentation in these is on the
principles already given and requires no special description.
In pit cavities in the lingual surfaces of the incisors,
two points of special caution need to be mentioned. First, the
location of the cavity is such that the pulp is easily reached, and
accidentally and unnecessarily exposed, unless especial caution
be observed. The use of burs should be limited strictly to the
first opening of pits but little decayed. Neither inverted cone
nor fissure burs should be used in squaring up the axial and sur-
rounding walls, because the angle of approach is such that the
sharp angle of the bur is presented toward the pulp, instead
.
of its square end. This necessarily defeats the object as to
squaring up the axial and surrounding walls, and rendering the
axial line angles sharp, and especially endangers the pulp.
All of this work should be done with the hoes and the smaller
chisels.
Except in the smaller cavities, the direction of the enamel
rods will be much inclined to the incisal upon the incisal_^wall of
the cavity. This should be carefully noted in clipping away the
enamel, and the finished enamel wall should have the proper
inclination to give it the necessary strength.
Smooth-Surface Cavities.
Classes 2, 3, 4 and 5 are all smooth-surface cavities. This
distinction has been sufficiently described (page 7), but it is so
important that it will be repeated here. The special points of
distinction will also be further emphasized as the procedures are
developed.
Class 2.— Cavities in the gingival third — not pit cav-
ities — of the labial, buccal, or lingual surfaces of the
teeth.— Of these the smooth-surface cavities in the lingual sur-
faces of the teeth are so infrequent that a mention of them seems
to be all that is necessary. Difference in position calls for some
differences in instrumentation between these and smooth-surface
cavities on the labial and buccal surfaces, but the principles of
their preparation are the same.