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45*2 THE TREATMENT AND FILLING OF ROOT CANALS.

thin. If any of those irreo;ularities be present it is important that they
be discovered and additional care be taken to eliect a complete entrance
to the canals.

Instruments for Canal Treatment.
The description thus far has included the territory to be operated
upon and its condition as regards sepsis, the agents commonly employed
to produce asepsis and antisepsis, and those applied to maintain these
conditions. The first, the condition of the root canals and dentin ; the
second, the various antiseptics employed therein ; the third, the several
materials used as canal fillings. The next study includes the instru-
ments employed and their specific applications.
The first are enamel chisels. These are employed to cut down weak
unsupported enamel walls and those portions of enamel removable by
such instruments, which interfere with direct access to the pulp canals.
The next, burs, of several forms ; the first, that known as the " dentate
fissure bur," for cutting enamel ; next rose, inverted cone, and oval forms
for enlarging cavities and removing infected dentin. Next, several
forms of broaches, canal cleansei^s, and jwohes, Gates-Glidden 7'eamers
for enlarging canals ; syringes, pluggers, and finally rubber dam and the
appropriate selection of clamps.
In relation with this latter device, it is to be recalled that demon-
strations have shown the saliva to be a highly infective fluid, for the
reason that it contains a variety of pathogenic organisms which must be
excluded from pulp canals if asepsis of these passages is hoped for. No
other single means serves so effectively as isolation by the rubber dam.
A variety of syringes will be required, a large instrument for irriga-
tion (Fig. 440), to wash away loose debris which may be present in the
cavities ; smaller syringes will be required to accurately place definite
quantities of medicaments in canals (Figs. 441, 442, and 443).
Dentate fissure burs are invaluable instruments for removing por-
tions of sound enamel walls which interfere with direct access to the
root canals. Cutting from within outward, giving the bur a sawing
motion, a groove may in a few minutes be extended across the occlusal
face of a molar from a distal cavity to a point directly over the ante-
rior root.
Large rose, inverted cone, and oval burs are employed to remove
the dentin which may obstruct direct entrance to the canals ; these are
as a rule to be used with a draw-cut, placed first in the deepest portion
of the cavity, and while revolving drawn toward the operator. Care is
to be exercised that no more than necessary of the walls, particularly
the floor of the pulp chamber, is to be burred away, to avoid mechan-
ically weakening the tooth.