Page 108 - My FlipBook

46 PATHOLOGY OF THE HARD TISSUES OF THE TEETH.
or swollen, it is rare that it ever laps over into the eroded area,
differing markedly from caries in this respect. Some of the cases
look as though the recession of the gum may have been caused
by the erosion, but we see many cases of recession of the gum
of similar character without erosion. We also see many cases of
erosion cutting away the teeth very close to the gum without
recession of the gum. It would therefore seem that there is
no causal relation between the two. Figure 49 also has a second
complication not so frequently seen, in the squared-out projec-
tions toward the incisal from the dish-shaped portion which
were noted in Figure 48.
Wedge-shaped areas. These are the "keilformige Defecte"
of German writers. This form usually has its place of beginning
near the free margin of the guni, and if seen at its beginning
looks like a little groove cut across the crown of the tooth from
mesial to distal. These gradually deepen, and soon the case
looks as if a wedge-shaped piece had been cut out of the labial
surface of the tooth, presenting a flat side reaching toward the
gingival and a square shoulder toward the occlusal, as if filed
away with a square file. In many of the cases the cut is as square
and the angles as sharp as they could be made with such an
instrument. In others there is more inclination to rounding
of the angle in the deeper part of the cut. See Figure 50.
I had supposed that this form of erosion was the prevailing
form in Germany, for in taking up the German writers I have
found that generally they have illustrated this form only, and
generally speak of erosion as the "keilformige Defecte" (wedge-
shaped defects). Upon inquiry, however, among German den-
tists, I find that other forms are also found, but they think this
one the most common. I have seen a number of cases of this
form in which the teeth were cut through so deeply that they
finally broke away, cutting through the calcified pulp without
any distinction whatever from other parts of the dentin. These
wedge-shaped areas occur both in the upper and lower jaws,
less frequently in the incisors in the upper jaw, but more fre-
quently in the bicuspids and molars. It is not very uncommon
to see this form in the bicuspids and molars, and some irregular
forms or dish-shaped areas in the incisors and cuspids.
In Figure 51 is shown what appears to be a modification of
the wedge-shaped areas of erosion, occurring in two bicuspids.
In the deeper parts the cuts are well rounded from the occlusal
toward the gingival margins, but are flat mesio-distally. The
form is that of a segment of a cylinder.
In Figure 52 is presented a specimen of this, occurring in
the incisors of a young lady about nineteen years old. Three