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CAEIES AS A WHOLE. ITS CLINICAL FEATURES. 109
seen streaking away to the pulp chamber from that as well.
These shadows occur in abrasions the same as in caries, but
usually are not so prominent. Whatever else these zones of
shadow may be, they express a decisive injury to the dentinal
fibrils. A still more extended invasion of dentin is photo-
graphed in Figure 133. This is not an inordinately large cavity,
but one that is easily managed in filling operations. However,
even in this, one is liable to find the labial or lingual enamel
plates considerably undermined by extensions of decay along the
dento-enamel junction. It should be noted particularly that
many of the incisors are thin labio-lingually at the point first
invaded by decay, and a comparatively moderate extension along
the dento-enamel junction may cause such injury to the labial
enamel plate as to make a decisive esthetic blemish. This can be
avoided only by careful watchfulness over these teeth to see
that caries in them receives early attention.
Material for the illustration of this class of decays is exceed-
ingly difficult to obtain and much dependent upon accident. This
is exhibited in Figure 79. In this, decay had practically de-
stroyed the central incisor by exposure of the pulp before the
apex of the root had closed sufficiently to permit of a root filling.
The case exhibits in a striking manner the breadth mesio-distally
of the pulp chamber at this tender age of the child, the proximity
to the pulp of the usual points of the beginning of caries, the
small amount of dentin through which decay must penetrate to
expose the pulp, and strongly suggests the watchfulness that
should be had over such teeth in families highly susceptible to
caries. This is an ugly thing to happen, but it gave an excellent
picture of beginning caries and the form of the penetration of
enamel in the distal surface of the tooth.
Gingival Thied Decays in Labial and Buccal Surfaces.
ILLUSTRATIONS: FIGURES 134-141.
Principal clinical features: (1.) The earliest beginning
of decay is a line of whitening of the enamel running mesio-
distally near the free margin of the gum in the middle third of
the surface mesio-distally. (2.) The spreading of the decay on
the surface of the enamel is usually confined closely to exten-
sions mesially and distally toward the angles of the tooth,
following the curve of the free border of the gum. (3.) In cases
of neglect of cleanliness, and especially in neglect of the use of
the teeth in chewing food, there may be extensions occlusally
and also across the angles of the teeth to connect with proximal