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376 THE TECHNICAL PKOCEDUKES IN FILLING TEETH.

similar to those of the first. The pulp chambers are usually
smaller and oftener irregular in outline. The lower third molar
has, occasionally, a very large pulp chamber.
Vakiations of the foems of pulp chambers. Many vari-
ations of form occur in the pulp chambers and root canals. The
roots of the teeth may be abnormally crooked. In many instances,
the pulp chamber will have in it secondary formations, called
nodules, which may be adherent to the walls or block the open-
ings of the canals and prevent a broach from gliding into them.
These also occur, occasionally, within the canals, partially block-
ing the way of the broach. Sometimes the pulp chamber will
be filled with nodular deposits so completely that there seems
to be no room for the tissues of the pulp. These deposits must
be removed before the root canals can be reached and entered,
after which the canals will generally be found open. Such
deposits occur within the pulp chambers of any of the teeth, but
they cause annoyance most frequently in the molars.
Occasionally lateral openings occur from the root canals to
the surface of the root. More of these have been seen from the
canals of the lower molars than any other teeth. Generally
they follow the course of the dentinal tubules and open on the side
of the root. They may diverge to one side and curve toward
the apex of the root. These can not often be detected, except in
dissections of the root, and occur so rarely they may be ignored
in practice.
Sometimes the horns of the pulp approach abnormally near
the points of the cusps of some of the teeth, as in the upper first
bicuspid, and in the mesio-buccal cusp of the upper first molar.
Then the pulp is more liable to exposure in excavating carious
cavities.
No specific directions can be given for abnormal cases.
When the pulp chamber is filled with secondary deposits, the
effort should be directed to the removal of these, preserving
the outlines of the pulp chamber, '\^^len the pulp chamber is
much narrowed by secondary dentin deposited upon its walls,
the openings into the canals should be found before any cutting
is done, and then the cutting carefully directed to straightening
them. In most instances this is done best with the barbed broach.
All small tortuous canals should be enlarged and straightened
with the barbed broach. To do this, the broach sliould be passed
into the canal as far as possible and withdrawn. The barbs will
impinge upon the walls and cut away the dentin from the promi-
nent parts of the crooks and straighten them. This should be