Page 988 - My FlipBook

998 ABRASION AND EROSION OF THE TEETH.

in which the invasion of these continued to be about equal, I have never
yet seen a case that maintained a symmetrical progress in respect to the
the other teeth. The illustrations on another page will give a good idea
of this. In many cases there is a marked tendency to the formation
of a sharp angle with the surface of the enamel on the lower (toward
the crown) margin of the erosion. This is particularly noticeable in
Fig. 532. Occasionally this is seen to be next the gum (Fig. 534), but
much more rarely, and in some instances both the upper and the lower
margins are very square incuts. A few days ago I was consulted in
regard to a case in which both of the superior central incisors were cut
as if done with a No. 4 separating file, the cut extending considerably
into the dentine. This case is remarkable as being the deepest cut, in
proportion to its width, that I have ever seen. Generally the incuts
are of considerable width ; and if one margin is squarely cut in, or
nearly so, the other slopes much more gradually to the surface, as will
be seen in all the illustrations presented. More rarely cases may be
seen in which the excavations are nearly circular, with the sides equally
sloping. It will thus be observed that there is nothing definite as
relates to form. I have seen a few cases in which there was a groove
excavated lengthwise of the crown of the tooth, but these are very rare.
Dr. Cushino; of Cliicago has related to me a curious case that came
under his care, in which a groove was excavated in the labial surface
of an incisor close to the .proximal border, extending from near the
gum to the cutting edge, from which point it passed backward across
the cutting edge and then down, in the form of a groove in the palatine
surface, nearly to tiie gum. Such a form as this is certainly remarkable.
Another variety, of which two cases have come under my observation,
is the wasting of the proximal surfaces of the teeth. In each of these
round holes were formed, passing through between the teeth (each
tooth being about equally eroded), as if filed out with a rat-tail file,
the surfaces remaining hard and finely polished. When one of these
first came under my observation, the crowns of the central incisors
were almost severed from their roots, and similar openings were in pro-
cess of formation between the other teeth on one side as far back as the
space between the first and second bicuspids, while on the other it
extended to the lateral incisor and cuspid only. This effect was con-
fined to the ui)per jaw. In the other case the teeth of both jaws were
similarly affected.
In all these cases the erosion makes the greatest progress in the teeth
first attacked, and, in whatever stage of progress the case is seen, the
extent of the loss of substance gradually diminishes as it recedes from
this point in either direction. The difference in the extent of the loss
of substance generally has a close relation to the time of beginning.
Exceptions to this rule now and then occur, but it holds good in so
large a majority of cases that after seeing the ]>osition and form of the
erosion in two or three teeth we may jM'ognosticate })retty certainly the
form it will take in the adjacent teeth if the case progresses without
interruption. This progress is well marked in illustrations 532 and 533.
So far as my observation extends, the form and direction of the erosion
are not materially changed—but rarely, at any rate—after it has once