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372 THE TECHNICAL, PEOCEDURES IN FILLING TEETH.

is rotating and not being held in some curved part of the canal
which would be liable to break the broach. The rotation should
not exceed one turn; it should then be withdrawn. In a good
many eases the entire contents of the canal will be brought away
with the first effort. If not, the movement should be repeated.
Often the tissue of the pulp will break up into shreds and be
but partially removed. In such cases, the smooth broach with
cotton should be used. For preparing this, the fingers should
be disinfected and a bit of absorbent cotton should be pulled
between the fingers of the two hands until a small shred is formed
containing but a few parallel fibers. One end of these should
be held between the forefinger and thumb of the right hand and
with it the broach should be grasped at mid-length, or with the
cotton wisp extending slightly past its point. With the left
hand the other end of the cotton wisp and the point of the broach
should be grasped together, and the broach rotated in the fingers
of the right hand until the cotton is wrapped firmly upon its
shaft. Wlien this is properly done, the cotton will cling firmly
to the broach and is not likely to be lost in the canal. With the
broach thus armed, dip it first in the antiseptic, press out the
surplus with absorbent cotton and then pass it into the canal,
slightly rotating back and forth. When the full depth has been
reached, turn the broach fully upon its axis and withdraw it
while in rotation. Generally the shreds of the pulp will become
entangled in the cotton and be brought away. This should be
repeated until all tissue has been removed from the canal to its
apex.
Students often have difficulty in finding the canals in the
molar teeth. This should not occur except in abnormal cases.
The difficulty generally occurs because the floors of the pulp
chambers have been mutilated with burs and the openings of the
canals filled witli chips. This should never be done; burs should
not be used in the floor of the pulp chamber.
The floor of the pulp chamber is rounded or arched in the
center and falls away toward the mouths of the canals. In upper
molars the canals are situated in the position of the angles of a
triangle (the molar triangle). Figures 422, 423, the mesial line
of which is the longest, the buccal the shortest, and the distal
the intermediate length. For the first molar, this triangle is
well shown in the illustrations representing sections a little
rootwise from th(> floor of the pulp chamber. This is best seen
in the specimen itself; and the position and the direction of the
canals, with relation to the walls of the pulp chamber and the