Page 95 - My FlipBook

DYSTROPHIES OF THE TEETH. 37
graphs. (See Fig. 45.) The lines of accretion in the growth
of the enamel were about as usual in normal enamel. It was
particularly notable that the lines and depths of the abnormal
condition had no reference whatever to the lines of accretion
or growth in the formation of the enamel, thus showing a
remarkable difference from the contemporaneous accretional
deformities of the enamel, in which the lines of accretion in the
growth of the tooth are very closely followed.
In the illustration, Figure 46, it will be noticed that there are
areas or lines of brownin distributed deeply in the enamel. The
yellow shades of stain seem to be caused by brownin within
the substance of the enamel which is covered by normal enamel.
In this case the modification of color is caused by the partial
showing of the brown through the translucent covering. In
other cases the yellow color appears to be caused by minute
areas of brownin too small for the naked eye to distinguish as
separate, and the mingling of this with the translucent white
gives the yellow shades. In my sections I found no yellow col-
ors whatever.
Distribution of brownin in the enamel as a whole is
extremely irregular. In the darkest areas I found in the teeth
furnished me, it was difficult to make a photomicrograph that
would show all of the spaces between the rods filled. Many
of them are empty. This character of the deposit is quite well
shown in Figures 46 and 47, which were made with low enough
power to show the whole of the incisal portion of the teeth.
The sections cut from teeth that have been mounted for
grinding in very light-colored shellac show plainly that the limit
of the imperfect enamel is not a sharp line, but that some of the
spaces are open between the enamel rods much deeper than
others. This causes the color produced by brownin to thin out
into the perfect enamel.
There are also in this enamel many places where the color
seems to be about normal, in which small groups of spaces
between the enamel rods are filled with the brownin. This is
very sharply brought out in some of the photomicrographs.
Many of these islands of color are so small as to escape obser-
vation with the naked eye, but come out prominently with the
medium powers of the microscope.
MOTTLED ENAMEL A NEW PROBLEM IN DENTAL PATHOLOGY.
Endemic white enamel, or mottled enamel, presents an
entirely new problem in dental pathology. Nothing of the kind
seems to have been discovered heretofore in any part of the