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they frequently extend beneath the free margin of tlie gum. Thoy are
nearly always elliptical in outline and may consist of simple decalcified
enamel still retaining the usual surface form, or they may possess the
common characteristics of cavities in general.
The opening and j)rcparation of this class of cavities are not attended
with any marked difficulties except that when they extend beneath the
gum care Avill have to be exercised not to wound this tissue, as the
consequent bleeding would obstruct the view and interfere with the
progress of the work. This may be prevented by pressing and holding
the gum away with a suitable instrument held in the left hand while the
cavity is being prepared, Particidar attention should be paid to the care-
ful })reparation of the cervical margin of the cavity and to its terminal
points. The former should be made smooth and even, and the latter
should be extended far enough to include any enamel that shows the
least sign of acid alteration. Slight grooves or enlargements at the
base of the cavity along its upper and lower margins will give it a suf-
ficiently retentive form.
A second locality on the labial surface M'here decay is frequently
found is anywhere between the central portion and the iucisal edge,
in pits and depressions that indicate imperfect development of the
enamel. These pits or grooves extend in a nearly straight line parallel
to the incisal edge, and are frequently the seat of decay.
When quite shallow they may be obliterated by grinding the surface
with a small corundum wheel and polishing, converting the
surface at this point into a distinct concavity. When the
pits are deeper and isolated they may be filled separately,
the result being a lesser degree of conspicuousness ; but
when they are connected by a groove, as they usually are,
thcY will havc to be Converted into a single cavity and
Pitted incisor.
filled. A common type of this defect is shown in Fig. 1 83.
When these pits occur upon the incisal edge or in close proximity
to it the choice lies between an unsightly gold filling, a porcelain tip, or
their removal by grinding and the resultant shortening of the crown.
Class E.—There is usually but one point upon the Ungual surface
of incisors and canines that is liable to decay. It is in the pit at the
junction of the basilar ridge or cingulum with the adjacent tooth
surface. The incipiency of caries at this point presents only as a mi-
nute cavity, the opening and shaping of which is readily accomplished
with a round bur. Although the orifices of these cavities may be
small, the dark spot that marks their direction is often continued quite
a distance toward the pulp chamber. This black point should in all
cases be followed to its termination and obliterated. It will never be
found to reach the pulp or to approach dangerously near it. As the