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DYSTROPHIES OF THE TEETH. 35

I went into the examination thoroughly aroused to its
importance, and in 1909 visited a number of susceptible areas
and studied the conditions on the ground.
The essential malformation in this condition is the failure
of the cementing substance between the enamel rods in the outer
one-fourth to one-third, more or less, of the surface of the
enamel. When this exists alone the enamel is a dead paper-
white. In many of the cases a coloring matter is found in place
of the cementing substance between the enamel rods, and on this
hinges the great variety of appearances. Some of the teeth are
a paper-white that glares and impresses itself as something
abnormal whenever the person opens his lips, some are brown,
some nearly black, some quite black. Every degree conceivable
of the co-mingling of color — natural white, paper-white, yellow,
brown and black, is found.* (See Figures 40, 41, 42, 43.)

Since I commenced the study of the mottled teeth I have,
as occasion has offered, been studying the coloring matter, which
is one of the very ugly features of this condition. In this study
I have found this same coloring matter, so far as I am able to
determine, in most kinds of malformation of the enamel. Espe-
cially is it abundant in the contemporaneous accretional defor-
mities. It is a dark brown coloring matter that is deposited in
much more than half the cases in which the enamel rods are not
cemented together with the normal cementing substance. In
the enamel whorl we find this coloring deep in the enamel, some-
times actually lying against the dento-enamel junction, making
a very dark spot in a section, while the surface of the tooth is
fair. The coloring matter is the same material, and its reaction
to dissolving agents is the same in all of these various condi-
tions. I have dissolved it out and made such teeth very white.
In an effort to find a suitable name for this coloring matter
for use in dentistry I have used the word brownin, which seems
to me in good form as a nomenclature word.
* Note.— Different views have been expressed by those who have studied these
teeth as to the time at which the discoloration occurs, whether before or after the
ruption of the teeth. Dr. G. V. Black, from histological studies of a few teeth,
thought the discoloration was caused by the deposit within the open spaces between
the rods of a brownish stain before the teeth erupted. (See Dental Cosmos, Vol.
LVIII, 1916, p. 142. ) Dr. F. S. McKay, after very extensive observation of hun-
dreds of cases over a period of ten years or more, states that the teeth are white
when they erupt and the discoloration occurs very gradually afterwards. (See
Dental Cosmos, Vol. LVIII, 1916, p. 628.)