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370 THE TECHNICAL, PROCEDUEES IN FILLING TEETH.
have been opened, to remain while the cutting is being done, and
until the cavity is again freed from cuttings. Then with the
removal of this cotton the last of the cuttings will be removed.
In many cases after the tirst opening has been made, the
roof of the pulp chamber can be cut away quicker and much more
satisfactorily with the chisel and mallet.
If the exposure is from a mesial cavity, the cutting will
be, of course, to the distal and often will involve the removal
of the middle third of the occlusal surface with the whole of
the dentin intervening between it and the pulp. If a distal cav-
ity, the middle third bucco-lingually of the occlusal surface with
the intervening dentin should at once be removed to a point well
toward the mesial marginal ridge.
In the bicuspids the exposures are almost uniformly from
cavities in the proximal surfaces, and the pulp chambers are
broad bucco-lingually. The cutting for the opening of the cham-
bers must be directed first to the central part of the crown, but
later lu'oadened from buccal to lingual; for the horns of the
pulp, when long, in these teeth, spread out toward the points
of the cusps, as in Figure 419. These horns should be fully
opened so that they may be cleaned and solidly filled. The root
canals in these teeth, especially in the upper first bicuspids, are
given off from the extreme buccal and extreme lingual portions
of the chamber, as shown in Figure 419, and unless the cutting
is broad in these directions, the broach will not have direct
entrance into them.
In the incisors and cuspids, exposures are generally from
proximal cavities. In oiiening these for the removal of the pulp,
the orifice of the exposure should be first extended to the gingi-
val wall of the cavity and to the full breadth of the chamber.
The approach should be carefully considered. Generally a
broach will not readily slide into the canal without being bent
more or less. See Figure 420. This is unfavorable, and a better
approach must be made. Generally when a cavity is so large
that the pulp has been reached, the lingual wall should be cut
away, and this will improve the approach, the instrument being
passed to the lingual of the incisal edge of the tooth; rarely
the labial wall should be cut away. The approach may be
improved still more by taking a small fissure bur in the engine,
and, approaching the canal from the direction in which a broach
would be introduced, i)assing it into the canal and cutting by
lateral pressure, bi'oaden the canal in a direction to straighten
tlie approach, as shown in Figure 421. This cutting will be