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OPENING CHAMBERS AND CANALS 221

(f) Remove the contents of the pulp chamber and all

debris (Figs. 260, 261, 262 and 263).
2. Through Cavities of Decay. '
(a) Establish the outline form, remove all decay, and

make the cavity slightly retentive.
(b) If the pulp is not exposed, penetrate the dentin to the
pulp chamber, with the drills or the bi-bevelled dentate fissure
bur.

Fig. 260. Fig. 261.
Fig. 260.—Series of illustrations showing the method of opening into the pulp
chamber and canal through the lingual surface of the anterior teeth.
First drill through the enamel and dentin until the pulp chamber is reached;
then gradually enlarge the opening with burs or drills of increasing diameter.
Fig. 261,—Then increase the size of the entrance by inclining the shaft of the
fissure bur first toward the gingival and then toward the incisal portions.

(c) Remove the wall of the pulp chamber with a hoe
excavator or a dentate fissure bur, extending the cuttings
until the horns of the chamber are included.
(d) In incisors and cuspids straighten the approach to

the canal by extending the cavity in the lingual or gingival
direction with a dentate fissure bur. (See Figs. 260 to 263.)
(e) In upper molars, straighten the approach to the
mesio-buccal canal by extending the cavity with a fissure bur
toward the mesio-buccal cusp, and enlarging the pulp chamber