Page 79 - My FlipBook

EXCAVATION OF CAVITIES BY CLASSES. <0

gingival dentin wall which was left inclined to the gingi\al by
the chisel is squared up with hoe 12-5- 12 and slightly undercut
with hoe S-3-12 or 6-2-12. Then the enamel wall is finished to
the mesial and distal angles with chisel 15, and the cavo-surface
angle very slightly beveled. A convenience pit is now made,
one toward the mesial and one toward the distal in the gingivo-
axial line angle with an u> millimeter inverted cone bur, and each
extended slightly by grooving toward the central part of the
length of this line angle. The incisal dentin wall is slightly
undercut with an inverted cone bur held with its square end to
the axial wall and passed along from mesial to distal, or better,
with hatchet 8-3-23 or 6-2-23. The incisal enamel wall is
finished, being inclined slightly to the incisal and its cavo-surface
angle very lightly beveled, the straight chisel 20 being used, and
cuttmg in the direction of the length of the wall, using the
thumb and palm grasp.
This cavity as prepared in\oh'es nearly half the labial surface
inciso-gingivally, and the whole surface mesio-distally, the filling
in the mesial cavity making a portion of the wall. Upon the
distal the filling, after being made, will be cut into when the
cavity on the distal surface is prepared. It is a somewhat
extreme type of labial cavity.
Labial cavities in the upper laterals and cuspids, in the lower
front teeth, buccal cavities in the bicuspids and in the first molars,
would be excavated in the same manner and with the same
instruments. The thumb and palm grasp of instruments can not
so frecjuently be used to advantage in buccal cavities in bicuspids
and first molars, as in like positions in the anterior teeth. In
the second and third molars this grasp is usually inapplicable.
Generally the inverted cone or square-ended fissure bur may
be used with its shaft at right angles to the buccal surfaces as far
back as the first molar, and in occasional fa\orable cases in the
second molar. Usually the right-angle hand- piece must be used
if the bur is employed in excavating buccal cavities in the second
or third molars. In most cases, however, the instrumentation is
e.'isier, and the excaxation is made quicker by using chisels and
the hoe excavators. These may be effectually assisted by using
the inverted cfjne bur for making extensions toward the mesial,
chijjping tlie enamel from the occlusal wall of the slot cut, and
again undermining with the bur.