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226 THE TREATMENT OF PULPS

have a mesio-buccal and a mesio-lingual canal, located in the
mesial root and a distal canal situated in the distal root. The
canals in the lower bicuspids are more or less continuous with

the pulp chambers, while those in the upper bicuspids and the
upper and lower molars are separate and distinct from the
chamber, opening from its floor with more or less constricted
orifices. Owing to the presence of these constrictions, and
the small size of the buccal canals in the upper molars and

Fig. 272. Fig. 273.
Fig. 272.— Cavity of decay on the mesial surface of a central incisor opening into
the pulp chamber. It would be difficult to pass a broach to the apex owing to the
shoulders on the mesial side of the entrance to the canal.
Fig. 273.—Straighten the approach to the canal by enlarging its entrance on the
mesial side with a dentate fissure bur, a Kerr tapered canal reamer or a spiral broach
reamer. Then enlarge the cavity toward the incisal and remove the horns of the
pulp chamber. The cavity, chamber and canal are now continuous and smooth.

the mesial canals in the lowers, difficulty is frequently ex-
perienced in locating their entrances and following them with
instruments to their termination.
—
Technic. (a) Locate the entrance and explore the canals
with a small, round, smooth broach.
(b) Enlarge the orifice with a Kerr or Downie tapered
canal reamer, a small bud-shaped bur, a twist broach, spiral
broach reamer, or a Donaldson canal cleanser (Figs. 272

and 273).