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CABLES AS A WHOLE. ITS CLINICAL FEATURES. 93

begun, are unusually large. This has occurred by the breaking
away of the enamel about the pit much earlier in the progress
of the decay than usual. In response to this early widening of
the pit, giving a greater opportunity for washing out acids
formed in the dentin, the penetration of the dentin presents a
much less pointed cone, the penetration is less in proportion to
the breadth than in cases in which there is less breaking of
enamel about the pit. This is seen most distinctly in Figure 106.
In studying these illustrations, one must divide the area of actual
decay from the cloud (hyaline area) stretching away toward the
pulp. In Figure 105 there is really very little decay of dentin.
The triangular (in section) cloud stretching toward the pulp
chamber is not softened dentin. In Figure 106 the area of decay
is more definitely outlined by the distinctly darkened area which
is flattened or rounded rather than in the typical conical form.
This is characteristic of a wide opening through the enamel. The
rate of progress of decay is quite apt to be greater where it is
hidden away under the overlapping enamel than in the central
parts. The tendency, therefore, is to form broad, flat cavities.
Both of these cases, considering each tooth as a whole, are com-
plicated by proximal decays. On account of ease of access and
the absence of the tendency to superficial spreading of decay,
these cavities and pit cavities, wherever they occur, are the
simplest of cavities in the clinical sense. The only thing requir-
ing special attention outside of the area of decay and its full
exposure by trimming away the undermined enamel, is to see
to it that all grooves are cut out to such a point as will give
opportunity for a smooth finish of the filling.
Proximal Surface Decays in Molars.
ILLUSTRATIONS: FIGURES 107-111.
Principal clinical features: (1.) The beginning decays
of this class are hidden from view in the proximal surfaces of
the teeth, making their early discovery difficult. (2.) A tendency
to wide spreading on the surface of the enamel, bucco-lingually,
making extension for prevention necessary in filling operations.
(3.) Tendency to the early undermining of the marginal ridge
by the extension of decay along the dento-enamel junction and
the exposure of the cavity by its breakage. (4.) Wide secondary
spreading gingivally in a considerable number of cases which
is liable to be overlooked in the preparation of cavities. (5.)
Recurrence of decay at the bucco-gingival and linguo-gingival