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264 PATHOLOGY OF THE HARD TISSUES OF THE TEETH.
the ear to the front of the mouth, modeling out that promi-
nence of the features that makes a large part of the difference
in the cast of the countenance between the child and the adult.
It may be said that the deciduous molars act to support the
occlusion in the early part of the shedding period, but this
is readily shown to be only in part by the many cases in which
the bite is raised off from these teeth in the progress of growth
of the first molars. The models referred to previously, of the
mouth of a boy almost fifteen years old, whose deciduous molars
had not been shed and had not been lifted by the growth of the
alveolar processes, illustrates such a condition. The upper
incisors and cuspids overlap the lower in position to slide freely
upon each other and could be no support to the occlusion. The
jaws are held firmly in position by the four powerful first
molars. These, in their usual movement in the lengthening
of the face, which is clearly one of their normal functions, have
caused the stationary deciduous molars to be carried apart
about one-third of an inch between their occlusal surfaces. This
abnormal case shows plainly the function of the first molars,
not alone in holding the jaws in their proper relative positions
while the occlusion is broken up in the shedding process, but
that they also, by their movement in harmony with the general
growth of the face, cany the jaws farther apart and in this way
assist in the formation of the features by lengthening the face.
When these teeth are lost early by decay, which occurs
much too often, there is apt to be much distortion of the features
resulting. This is sufficiently apparent from careful clinical
observation, as has been noted by many men. From all of these
sources of information it seems certain that in the general growth
that is going on no part is taken by the deciduous molars after
the normal time of the beginning of the absorption of their roots.
In most cases they may be carried forward passively with the
expansion, or lengthening of the bite, but in many it seems
clearly demonstrable that their continued presence later becomes
a positive hindrance to development. In these cases at least
the normal development would not occur if the first molars had
been lost. No measurements have yet been made by which the
particular directions of distortion and the amounts have been
determined. Apparatus for this work has been constructed, but
at the time of writing not enough work has been done to give
sufficient basis for exact statements. When this work has been
done, it will probably furnish more exact information, and, in
view of this, a lengthy discussion of this problem seems unwise.