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EBOSION OP THE TEETH. 47

and then the incisal edge is squarely grooved across the labial
portion of its edge. The cutting upon the fellow central incisor
has started in the same way and will follow the same course. A
case seen a number of years ago with Dr. Gushing was almost
precisely the same as this in figure, except that the groove reach-
ing the incisal surface, grooved the incisal surface and then
extended to the lingual along the mesial margin of the lingual
surface. The teeth were long cusp teeth. They were practically
unworn and there was no reason whatever to attribute the groov-
ing on the lingual surface to abrasion.
Figures 58, 59 and 60 illustrate another case of figure cut-
ting that is much more extensive. In this case there was no
grooving of the incisal edge, or along the incisal edge, only a
slight broadening of the groove on the mesial side, and it will
be noted that a similar groove is being cut upon the distal portion
of the labial surface, while there is a curious half dish-shaped
form on the distal end of the groove running mesio-distally. In
this cutting, the angles with the surface of the tooth are very
sharp, but the bottoms of the grooves are well rounded. The
depth of the cut from the transverse groove to the incisal is
shown in Figure 59, while the depth of the cut across the labial
surface is shown in Figure 60.
It was clearly apparent in examination of the tooth, that
the groove running mesio-distally had cut through the calcified
pulp. The incisal edge of the tooth had been much worn by
ordinary abrasion. The V-shaped cut in the root of the tooth
was made with a file for the examination of the pulp canal.
In all my examinations of erosion I have never seen a metal-
lic filling that seemed to have been cut away by erosion. Years
ago I made much trial of gold fillings with a view of arresting
erosion, and generally found the erosion progressing beside the
filling as though no filling had been placed. The margins of the
fillings stood up sharp and definite, showing no rounding. Dr.
W. D. Miller, in his recent articles on erosion, claimed to have
seen fillings of various sorts cut away by this process. Recently
I have met with a case which is presented in Figure 61, in which
a gold crown, which had been placed over the first bicuspid,
seems to have been cut through. The patient is a dentist, and he
tells me that this is the third gold crown that has been cut
through at the same point. It was placed over the tooth because
it had become quite deeply eroded and was extremely sensitive.
The second bicuspid below also is a gold crown, placed for a
similar reason. It has shown no signs of injury. It wiU be