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18 PATHOLOGY OF THE HABD TISSUES OF THE TEETH.
was chosen from a part showing the least discoloration. In this
case the only distortion of the crown apparent in a superficial
view of the tooth is the groove encircling the tooth and the dis-
coloration. Also, the section shows that there was not a com-
plete arrest of growth of the enamel. With a good light the
enamel rods may be traced with the microscope through the
darkest lines of the section, and they are seen to be well formed.
There is no appearance of the telescoping process. The groove
in the enamel appears much less pronounced in the section when
highly magnified as shown, than it does in the photographs of
the tooth. In the dentin, however, the injury is very severe, as
shown by the clean-cut continuous line of interglobular spaces,
which literally cut the dentin first formed from that formed later,
and in the examination of the labial line of the dento-enamel
junction in the full section, it is found to be distorted by a
recurve, showing the interference with growth to have been pro-
found and that some real shortening of the tooth must have
occurred.
As a further illustration of the possibilities in this class of
injuries, I present two photographs, Figures 19 and 20, of a
bicuspid tooth showing the separation of the telescoped parts in
an injury of this kind occurring mid-length of the root. I
extracted this tooth myself. The patient, a stranger, applied
for relief from caries of bone of the upper jaw, and this tooth
was situated on the border of the carious area in such position
that it seemed to be best to remove it, though the tooth and its
individual alveolar process were otherwise in good condition.
At the moment of removing the tooth, it was noticed ihat the
apical portion of the root did not come away, but was pulled
from its place and remained loose in the alveolus. Laying the
tooth on the bracket with the forceps, this apical portion was
picked out with the foil pliers and laid with the tooth for after
examination, because it seemed to be a very curious break. The
operation was completed and the patient dismissed with an
appointment to return later for further treatment. On exam-
ination, this tooth and root were found to have pulled apart
like a telescope tube, and the telescoping was on the lines of
growth of the dentin. Figure 19 shows the tooth and root placed
together in the normal form, in which a marks the line of break.
In Figure 20 the two parts are separated, showing how the apical
portion telescopes into the body of the root. I suppose there
was some severe illness of short duration at the time this part
of the root was developing, which prevented the deposit of cal-
cium salts, and a sharp, distinct and continuous line of inter-
globular spaces occurred. At the time, the root was developed