Page 120 - My FlipBook

54 PATHOLOGY OF THE HARD TISSUES OF THE TEETH.
lias been held by many persons, and in one form or otber prob-
ably has more adherents to-day than any other. How it is that
an acid can so act to cut away the substance of the tooth, leaving
a hard, polished surface which is a constant characteristic of
erosion, while in all laboratory experiment and in caries as it
occurs in the mouth the effect is a gradual softening by the
solution of the calcium salts, is left unexplained, unless Dr.
Miller's work noted above may be so regarded. As yet no acid
has been found that will remove the whole of the tissue, calcium
salts and basic substance, without previous softening.
I have made some experiments on a different plan (reported
with illustrations in the "American System of Dentistry," Vol-
ume I, page 1003). Having noticed in some experimental work
on the metals that the action of very dilute acids was different
in the still condition as compared with the action in currents, I
tried this upon teeth. Here I also found a difference. In a
rapid current of a solution of one part of hydrochloric acid to
four hundred parts of water, maintained for five days contin-
uously, teeth were cut away in forms quite similar to erosion,
the cut surfaces remaining hard and smooth, while other portions
of the teeth were not softened. I found the loss of substance to
occur only where the current broke around the teeth in a certain
way. While this experiment is impossible of comparison with
anything that can occur in the human mouth, it demonstrates
the possibility that the action of acid solutions may be modified
in some degree by conditions under which they are placed. Thus
far, however, no modification has been discovered that will in
any degree account for effects like those seen in erosion under
conditions that seem possible in the human mouth.
The fourth supposition — that erosion is caused by the
secretion of certain glands in the mucous membrane of the lips
and cheeks, that these glands become inflamed, or hypertrophied,
from some unexplained cause, and emit an abnormal secretion
which acts upon the teeth in this peculiar manner. It is certainly
true in many of the dish-shaped eroded areas in incisors par-
ticularly, that a certain part of the mucous membrane is found
to be raised in a form that fits into the excavations in the teeth.
If we touch these with blue litmus, it is instantly reddened, show-
ing the fluids in the region to be acid. Several have remarked
that this was especially true when the test is made early in the
morning, or when rising from bed.
I have personally examined many of these cases and have
found the facts as stated. I have also found in these cases the
prints of teeth not eroded clearly outlined in the mucous mem-