Page 155 - My FlipBook

OUTLINE FORM I 23

I. Pit and Fissure Cavities.—If small, open and extend
full length of the fissure with a dentate fissure bur. In using,
extend the point of the bur under the enamel and cut from
within, outward. Small pits may frequently be better opened

at the beginning with the round bur. If necessary to extend
the margins much, an inverted cone bur will first under-
mine the underlying dentin, when the enamel may [then be
readily removed with the straight or bin-angle chisel, by
means of hand pressure or the mallet. In large cavities of

this class, first chisel away overhanging enamel margins.

Fig. 133.—Outline form. Occlusal cav- Fig. 134.—Outline form. Mesial cav-
ity on lower second molar. ity in the upper central incisor.

then use the inverted cone bur for extension into solid dentin,

after which use the chisel again for removal of any further
enamel.
2. Smooth Surface Cavities.—First break down all un-
supported enamel with the chisel, cutting in the direction of
the length of the enamel rods. Avoid shock by refraining
from cutting too large amounts at each thrust or blow. Then,

if necessary to extend margins further, first, undermine the
underlying dentin with the inverted cone bur, when the
enamel may then be readily removed by means of the straight

or bin-angle chisel, Black's side-cutting instruments or gini-