Page 169 - My FlipBook

EROSION. 155

spread so as to involve the neck . Again, the erosion will always pre-
sent with a sharply defined outline, and sensitiveness rarely if ever
occurs. This fact is another evidence that the
cupping-out of crowns,
which are often extremely sensitive, are not erosions. The dis-
turbance at the neck, on the contrary, is sensitive, has no distinct
borders, and the enamel is never encroached upon until caries is
present.
Siirface Cavities. Cavities upon the surfaces of teeth, other than
the approximal, may result from erosion, green-stain, or caries. The
last may have as contributory causes, abrasion, malformation, or re-
cession of the gums.
Erosion. The of erosion is still shrouded in doubt. It is
etiology
probably a distant symptom of a constitutional disturbance, which has
affected the secretions of the mucous glands so that they discharge
mucus in which there is an acid present, which has an erosive influence
upon enamel and dentine. It is rarely, if ever, seen upon the masti-
cating or approximal surfaces of teeth. It is most common upon the
and of the
labial surfaces of incisors, cuspids, bicuspids superior set,
and
and cuspids bicuspids in the inferior. It may occur, however,
upon any tooth. Its most distinctive characteristic is that the affected
is hard and Erosion also be said to
part highly polished. may
assume typical forms, of three general varieties. The most remark-
able of these is where the disease eats out an acute angle, one line of
which is at right angles to the surface of the tooth. This is made
plainer by Fig. 174, which gives a profile view of a superior bicuspid,
the erosion showing at a, whilst in
Fig. 175, a, we see the same class FIG. 174. FIG. 175.
of erosion in a lower
bicuspid.
A point which must have some
clinical significance, but which I
am at a loss to explain, is this : that
though the one tooth here is from
the upper jaw, and the other from
the lower, the erosions are iden-
tical. In each case the line of the eroded angle which is at right angles
line extend-
to the labial surface of the tooth, is at the top, the oblique
downward. In this form of the disease, the pulp-chamber is
ing
frequently reached, secondary dentine, however, being deposited, so
In a few cases the crown
that the pulp does not become exposed.
has been cut through so far that it has been lost by fracture. The
progress is usually slow.
A second, and to my mind the most dangerous form of the dis-
A with a beautiful set of
turbance is an irregular concavity. patient
teeth may come in within three months of his last visit, and show