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METHODS OF FILLING CANALS OF PULPLESS TEETH.
177
except as they have dealt with them in the mouths of patients, under
which circumstances failure to reach the apex may be undistinguish-
able. A study of roots, out of the mouth, and an attempt to fill the
canals, would materially alter the opinions of those who are so
certain that they always reach the apex. Nevertheless, I think that
these men
get nearer to the ideal root-filling than do those who are
"
willing to say quickly, That is as far as I dare to go," and so fill
the canal without
having made a conscientious effort to cleanse it. I
will now consider the canals of various teeth.
Central Incisors. The superior central incisor is usually a single-
rooted tooth, presenting a fairly straight canal. Nevertheless, it must
always be borne in mind that the crown of a tooth is not necessarily
a guide to the length, shape, or direction of its root. More true
of the posterior regions, this axiom is also true of teeth in the anterior
part of the jaw. Fig. 20 1 represents a central incisor whose crown
and root are about proportionate, whilst in Fig. 202 is seen another

FIG. 201. FIG. 202. FIG. 203. FIG. 204. FIG. 205
a ^_.

central which has a larger crown and a shorter root. Such short,
thick roots are by no means uncommon on central incisors. The
point of interest here is, that supposing the dentist is cleansing the
canal of a tooth such a crown as shown in
having Fig. 202, measure-
ment with a canal instrument might lead him to believe that he had
not reached the end of the canal, whereas were he to attempt to go
farther he would pass through the apex, forming an opening at the
side of the true foramen. I think it may be safely stated that in
ninety per cent, of tooth-canals there is a deviation from a straight
line just in the foraminal region, so that a drilling instrument would,
as I have said, be out to one side rather than
apt to pass directly
through the foramen. These artificially made openings are almost
always mischievous, and the mischief is greater or more uncontrol-
lable in proportion as the drill-hole is nearer the foramen and so
more inaccessible than were it nearer the coronal end of the canal.
I said that a central presents a fairly straight root and canal ; still,
there are frequent cases where the root is twisted or curved, an
example of which is shown in Fig. 203. In the illustration the
palatal aspect of a central is given, and is chosen in preference to the