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MANAGEMENT OF CAVITIES BY CLASSES. 223
and therefore restore the full normal breadth of the interprox-
imal space. This requires that the teeth be separated sufficiently
to allow the finish to be made without in any degree narrowing
the mesio-distal breadth. Indeed, it is better to widen this just
a little. Careful measurements show that when the average
person has arrived at the age of forty years, he has lost, by
wear of the proximal contacts of his teeth, one centimeter in
length of the arch measured around the labial and buccal sur-
faces of the teeth from the mesial cusp of the right third molar
to the mesial cusp of the left third molar. Some of this loss
should be restored with every proximal surface that it is neces-
sary to fill. When the forms of the teeth have been good, their
restoration reinstates the normal conditions, and cleanliness
and health are readily maintained.
If, on the other hand, the mesio-distal breadth is not
restored, the two teeth will soon be crowded together, narrowing
the interproximal space, and the crowding upon the gum septum
will cause its partial absorption. It will be shortened and will
fail to fill the narrowed interproximal space, affording oppor-
tunity for lodgments in a position difficult to clean. The embra-
sures are also narrowed by reason of the teeth falling together,
which prevents the excursions of food through them in masti-
cation, and increases the area of liability, or carries its borders
farther toward the angles of the teeth, so as to place the mar-
gins of the filling in greater danger of recurrence of decay.
"When the proximal contact is not sufficiently prominent
to restore the mesio-distal breadth of the tooth, it is necessarily
flattened and broadened, and is in that degree less well adapted
to maintain the cleanliness of the space. If it is flattened to
any considerable degree, it will not only fail to be self-cleaning,
but will grasp and hold stringy particles of food. These will
be forced upon the gum septum, causing pain in mastication,
which will be a grave annoyance. Absorption of the gum septum
will occur, forming a pocket that will hold debris, which will
decompose and cause recurrence of decay at the gingival mar-
gin of the filling, or it will cause disease of the peridental mem-
brane, with final loss of the tooth. It will also endanger the
neighboring teeth. The failure to obtain correct forms of inter-
proximal surfaces caused widespread loss of fillings from recur-
rence of decay at the gingival border, when dentists first began
making contour fillings with cohesive gold.
In practice, cases are frequently presented of teeth that
have been neglected, in which the contact points have been lost