Page 31 - My FlipBook

ATROPHY OF THE TEETH. 7

consists in a failure of the formation or an imperfect formation
of some specific portion of the tooth and of several teeth together.
The portion of the several teeth affected is always that portion
of each that was in process of formation or growth at the same
period in the person's existence. To understand this well one
should study closely the calcification of the crowns of the teeth
and the contemporaneous lines of calcification of the different
teeth. This will be more fully explained in considering the histo-
logical changes occurring in atrophy. In the incisors the de-
formity is oftenest seen in the form of a groove, smooth or pitted,
rimning across the labial surface from mesial to distal, and close
inspection will generally show that it encircles the tooth com-
pletely, though it is most prominent upon the labial surfaces
where the enamel is thickest. It is seen more often on the incisal
half of the length of the crown. It may be near the cutting edge
of the tooth or anywhere from that point toward the gingival
line. It is also found occasionally in the roots of extracted teeth.
There may be a single groove or pitted line, or there may be two
or even three or more of these. The teeth affected are the inci-
sors, cuspids and first molars of the permanent set, and very
rarely the first bicuspids. If it is very close to the cutting edge
on the central incisors it may not appear on the laterals, but the
occlusal surfaces of the first molars will be atrophied. This is
because these parts of these teeth are in process of formation
at the same time. If the groove is a little further removed from
the incisal edge of the centrals, the lateral incisors will also be
similarly affected. If it is a little higher still, the four incisors,
upper and lower, the cuspids and the first molars will be affected,
but the bicuspids will be free from injury. It is exceedingly rare
that the bicuspids or the second or third molars are affected by
atrophy, for the reason that the enamel and dentin of these teeth
generally have not begun to form until after the age at which
these effects are most liable to occur. But few cases occur in
which the first bicuspids are marked. The time of the occurrence
of these injuries seems to be confined mostly to the first five
years of a child's life, but some cases occur later.
In the engravings the endeavor has been to illustrate some
of the more severe types of these deformities and to explain by
illustration the histological defects. Figure 1 represents what
is known as the typical Hutchinson tooth, from the claims of Mr.
Hutchinson, a specialist in venereal diseases in London, England,
who insisted that this deformity was the result of inherited syph-
Uis. In such cases, it has formerly been supposed that the middle