Page 780 - My FlipBook

790 DENTAL CARIES.
^vhole of the injured tissue will become intensely black. In a number
of instances I have seen the spontaneous cessation of a considerable
number of decays under conditions that showed plainly that the cause
had ceased to act. The fungus was dead.
The fourth class of caries is occasionally seen to become very trou-
blesome after the other classes have ceased altogether. It is the class of
decay that is most likely to give trouble in old age. Its beginnings are
determined almost entirely by irritations of the gingivae, giving rise to
absorptions about the necks of the teeth, which, becoming exposed
through the recession of the gums, become the seat of caries. They are
usually broad cavities that are shielded partially from the free entrance
of the fluids of the mouth, either by debris or by adjoining teeth or by
an overhanging gum. The teeth are attacked one or two at a time,
probably at considerable intervals or very irregularly as to time.
Occasionally the teeth in a certain part of the mouth may be attacked
together. Caries of this character is sometimes very destructive—more
for the reason that the position is such that the pulp of th(^ tooth
is exposed with but little destruction of tissue than on account of
the decay. The beginnings are usually in the cementum near its
junction with the enamel, and in the molars, especially, the pulp-
canals are often in close proximity. Decays very much resembling
these are often seen in younger persons who wear partial plates abut-
ting against the remaining teeth.