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DYSTROPHIES OF THE TEETH. 27

The Enamel Whorl.
Pits are a common accompaniment of the contemporaneous
accretional deformity, but in no way a necessary part of it, as is
shown by the many cases of even the severer injuries in which
they are absent. Indeed, in reckoning up the cases coming under
my notice, enamel pits seem not to have been present in more
than one-fourth of them. Further, these enamel pits occur in
teeth that are otherwise normal. It is not very rare to find a
single pit in the enamel of some one tooth of an otherwise per-
fect set of teeth. In microscopic sections, the same histological
characters are found as in pits accompanying the contempora-
neous accretional deformity. They mark an imperfection, or
partial failure, in the development of the enamel rods, confined
to a small area, usually round, and evidently are most apt to
occur in cases where there has been some marked difficulty in
enamel development. Hence, they are a very common accompani-
ment of the accretional deformity. Not infrequently, the rows
of pits in the enamel are the only signs of injury to the teeth
as a result of an illness. In this case the rows of pits form zones
on the parts of the teeth contemporaneous in development, as
one of the expressions of the accretional deformity. Aside from
conditions of general malnutrition, pits may occur in any part
of the enamel, showing no especial preference as to teeth or
locality on any tooth.
The pit marks the failure of development of the enamel rods
at a point, leaving a hole of more or less depth. This is generally
filled, or partly filled, with an amorphous material, dark in color,
varying from a yellowish hue to a deep black. I have never yet
made a section of one of these in which the dentin was exposed,
though some are as deep or deeper than the normal thickness of
the enamel. In all of these cases of very deep pits there is a
depression in the dento-enamel junction, as shown in Figure 30,
and a lining of enamel, in which the enamel rods are arranged
in a segment of a whorl, all pointing to the center like the spokes
of a wheel, in the bottom of the pit. When the enamel rods
forming these whorls have grown about a certain length, growth
ceases, and an opening is left, and this may extend as an open
pit to the outer surface of the enamel, leaving an opening the
full depth. Or this may be filled in part by a dark material
not resembling enamel. Or, again, the surrounding enamel rods
may close over it, partially or completely obscuring the pit, so
In Dr. Callow's
as to form a smooth enamel surface over it.
case, described later, the deformity consists mostly in numerous
whorls, many of them extending deeply into the dentin. These