Page 181 - My FlipBook

PHYSICAL PHENOMENA OF DENTAL DECAY. 155

particular tendency to penetrate toward the pulp, nor is there
one which especially avoids the pulp to spread laterally under
the enamel. The causes and the entire process are identical;
in both cases it depends only on the structure of the tooth,
whether the decay presents itself as penetrating or undermining.
In poorly developed teeth, with many interglobular spaces,
the destruction spreads rapidly on all sides under the enamel,
following the course of the interglobular zone, whereas when
the teeth are dense and completely dentinified the decay extends
more rapidly in the direction of the dentinal tubules. It is barely
possible that an infection with small cocci might cause the decay
to spread laterally more rapidly than an infection with large cocci
or bacilli, since the former could advance laterally through the
line branches of the tubules, whereas the latter would be obliged
to keep more to the main track.
"When the softened dentine is strongly saturated with li(|uids,
as is the case in caries acuta, it has been designated as caries
humida. The chronic form of dentine decay, in which the den-
tine is dry and brittle, is sometimes termed caries sicca.

c. Decay of the Cement.
Decay of the cement frequently occurs at the neck of the
tooth. The layer of cement is, however, so thin here that the
characteristic phenomena of cement-caries scarcely become ap-
parent. Caries of the cement of the root occurs only when the
latter is exposed, and is therefore comparatively rare.
The roots of molars which are laid bare by the recession of tlie
gums and destruction of the periosteum show the greatest pref-
erence for decay.
Such roots are often covered with thick wliite or yellowish-
white deposits, consisting of food particles, dead epithelium,
mucus, and fungus masses, and not unfrequently present cases of
typical decay of the cement.
The tirst symptom of cement-decay is an abnormal roughness
or softness of the cement surface, which may be easily penetrated
or scraped off with an excavator.
This phenomenon, which is also nothing but the softening of
the cement, is followed by a loss of the surface-substance ; thus