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MANAGEMENT OF CAVITIES BY CLASSES. 231
flat decay occupying the surface of cementum exposed, some-
times encroaching upon the gingival portion of the enamel, and,
in other cases, sharply limited by the gingival line, as shown in
Figure 169. Often the progress is slow. In a very considerable
proportion of these cases presenting for treatment, the dentist
has the opportunity of treating them before much penetration
has occurred, though in others the penetration of the dentin is
rapid, forming a deep and dangerous cavity. In this latter case,
the only alternative is a mechanical repair by some kind of fill-
ing. The choice of this will depend much upon conditions of
exposure to view. If it be the upper incisors or cuspids and the
lips are very mobile so that the defect is brought prominently
into view in the ordinary movements in conversation and laugh-
ing, a porcelain inlay would seem to be demanded. This may be
made gum color and conceal the recession of gum. If, however,
the conditions are such that the defect does not come into view,
gold may be used.
Fillings of any kind in this position have been unsatisfactory
for the reason that in a considerable proportion of cases the
recession of the gum continues to progress, uncovering more
cementum, and decay again occurs in the part newly uncovered.
The filling fails to protect against recurrence of the decay and
must be repeated at intervals so long as the recession continues.
The filling, whether it be gold or porcelain, does successfully
limit the penetration, however, and in that degree is successful.
When depth of penetration demands it, filling is the best treat-
ment and the only treatment now known that promises long con-
tinued usefulness of the tooth.
On the other hand, those cases that are seen early, before
much penetration of caries has occurred, may be treated with
silver nitrate and penetration of decay prevented for many years
by occasional repetition of the treatment. From the esthetic
point of view, this treatment is more unsightly than the gold fill-
ing, for the surface decayed becomes jet black. Therefore, its
use is limited to those conditions and positions in which this fea-
ture is not a very serious objection. In applying this treatment,
the rubber dam is placed and the Hatch clamp applied, as shown
in Figure 168, so as to give perfect command of the situation.
Then the decayed area is cleaned and dried but is not excavated
in any degree. Instead, the decayed area is to be filled as deeply
as possible with the salts of silver nitrate precipitated by light.
It is well to dry the softened area as deeply as possible with the
warm air blast. Make a saturated solution of silver nitrate bv