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CHAPTER XVII.
MANAGEMENT OF ABRADED SURFACES. OCCLUSAL AND
INCISAL. (CLASS SIX.)

Definition. Class six includes the group of cavities necessary
for the repair of injuries to the teeth through the loss of a portion
of their articulating surfaces, as the result of wear. The condition
is abnormal and the extent of the destruction of tooth substance
is by no means in proportion to the amount of use to Avhich the
teeth have been subjected. However it will be noticed in mouths
Avith teeth of short cusps, and particularly if the incisors occlude
directly upon the incisal edge, that there is an abnormal amount of
lateral motion in the act of articulation, and in such mouths we
find the maximum loss of tooth substance at any given age.
Cause Not Wholly Clear. Yet, that friction is the sole cause for
this lesion, can not be demonstrated, as the surfaces thus affected
do not show the exact impression of^the opposing teeth, neither is
this condition always delaj'ed till advanced years. Cases Avill be
occasionally met Avith in the mouths of people in middle life show-
ing the advanced stages of this trouble.
At the same time locations will be found on the occlusal surfaces
of teeth which at one time must have been in articulation but are
so far lost and seemingly worn aAvay that they could not be
l)rought into occlusion.
It would seem from a study of a great number of cases that
there must l)e some causes predisposing and exciting not yet un-
derstood. It is not improbable that the cause is a fault in tooth
structure, not so much in the constituents of the tooth as in the
lack of strength in their com1)ination. This conclusion would seem
plausible from the fact that teeth similarly situated and of the
same chemical analysis are affected to a different degree by even
slight friction. The bond of union does not seem to be so strong.
The Object in Filling or in making a cavitj'- to fill is to perma-
nently check the loss of tooth substance by entirely covering the
affected surface with a substance that will resist the full force of
mastication.
Occlusal Surfaces. In occlusal surfaces, particularly molars
showing the first stages of general erosion, earlj^ interference is ad-
vised. As soon as a cusp is lost it should be restored and if pos-.
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