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MANAGEMENT OF CAVITIES BY CLASSES. 225
absorption of the gum septum and disease of the peridental
membrane, and, in many cases, decay of the teeth occurs, begin-
ning near the gingival line. These decays are very difficult to
treat. See Figures 124-128, inclusive. Whenever these are
noticed, their treatment should be undertaken as described in
the second volume.
Cavities of the Fifth Class.
Cavities of the fifth class include those occurring in the
buccal and lingual surfaces of the bicuspids and molars — not
pit cavities, and in the labial surfaces of the incisors and cuspids.
They are, therefore, all smooth-surface cavities. They are infre-
quent in lingual surfaces. In order of occurrence, these are
usually later in life than cavities of the other classes, though in
this the greatest variety occurs. Occasionally they occur very
early, even appearing in the deciduous teeth, but this is rare.
Occasionally they occur in old age. In this case they are often
termed ' ' senile decay. ' ' In the molars, cavities of this class must
be sharply distinguished from pit cavities. These are all smooth
surface cavities and occur in the smooth portion of the enamel
to the gingival of the pit, generally in the gingival third of the
surface close to the gum margin. They are somewhat rare before
the age of sisteen or eighteen, and are oftener seen at from eight-
een to twenty-five. When they begin very early, they are diffi-
cult cavities to treat. They are not only difficult in themselves,
but are coincident with cavities of the other classes, marking
very intense susceptibility and complicating the whole case at an
age when the patient is difficult to control. On these accounts, it
is the intention to give the general principles of their manage-
ment very fully in this place, repeating much of that which has
been said before under the head of clinical features.
In the buccal surfaces of the bicuspids, and in the labial sur-
faces of the incisors, there are no pits and all the cavities are
of this class. In all of the teeth, including the molars, these
cavities begin close to the gum margin. The distance from the
gingival line will depend upon the length of the free margin of
the gum. When they occur early, the margin of the gum is
long and the beginning is some distance away from the gingival
line, leaving a good margin of enamel, provided the cavities have
not been neglected until they have become so large that it is
undermined by decay of the dentin. Some, in which the decay
of the enamel is slow, will be placed in better position by the
further protrusion of the tooth, or the shortening of the free gum