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PREPARIXG ROOT-CANALS.
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may be used, though it will not always be necessary to use one, since
such a procedure would sometimes be unwise or even hazardous.
Lateral Incisors. Lateral incisors are practically the same as cen-
trals. They are, however, smaller, require smaller instruments and
greater care, and are more often found with a curved apex. A seem-
ingly straight canal in this tooth, therefore, is to be accepted with
doubt than where with the central. I have at times
greater dealing
withdrawn the Evans root-drier with a sharp crook at its end,
that it had been forced into a crooked
showing extremity.
Cuspids. The same rules apply to cuspids as to the incisors.
Whilst it is true that these are sometimes short-rooted teeth, ordi-
narily they have quite long roots, so tnat the dentist must make
a careful examination when his canal- explorers pass but a short dis-
tance into the canal of a tooth having a large crown. Where the
root is really short, the canal is usually large, the root being thick.
Thus it will not be difficult to determine that an abnormal condition is
at hand. There is not often much danger of penetrating this root
with a Gates- Glidden drill, but the end may sometimes be suddenly
attenuated, which will also be the case in the canal, so that the drill
may seem to be stopped by the apex of the root, whereas in reality it
is simply that the canal has suddenly grown so much smaller that the
tip of the drill will not enter it sufficiently to allow the blades behind
it an opportunity to cut and so enlarge it. An examination, however,
with a fine instrument after the careful removal of debris will disclose
the fact that the canal continues farther. Perhaps a smaller drill may
effect the enlargement, or if not it may be done with a reamer made
from a broken Glidden drill. The drill-head being off, the shaft
should be stoned on three sides, forming a tapering three-sided
reamer. This is a very useful instrument, because it will cut laterally,
and is pliable enough to pass curves. But as it will also drill forward,
it must be used only with the utmost caution, lest it emerge through
the root other than at the foramen. A similar instrument may
be made from piano-wire, which, because of its toughness, will not
break off in the canal, whilst it will be pliable enough to ream out
even tortuous roots to a considerable distance.
Bicuspids. Generally the bicuspids may be opened for access to
the canal either by deepening the crown cavity, or, where it is
which an extension into the sulcus
approximal decay is present,
attains the desired end. In lower teeth, however, this is sometimes
troublesome, as will be more fully explained shortly. Where in
the upper jaw the cavity is at the neck of the tooth, a new entrance
to the canal should be made by entering at the sulcus. Where a
tooth, well filled with gold approximally, presents needing to have
it will be unwise to remove the as to drill
a canal opened, filling,