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the bony structure and enamel, its progress towards the lin-
ing membrane, is at this time somewhat retarded by the free
evaporation of the putrid vapour, and the partial discharge
and separation of the dead matter ; it is however soon after-
wards exasperated by other exciting causes, viz. the addi-
tional external chemical and mechanical influences.
The caries now proceeds towards the cavity, more or less
speedily according to the constitutional strength of the tooth,
and violence of the general and local causes ; until, at last,
the disease penetrates through the whole bony structure,
and produces considerable irritation upon the lining mem-
brane, so as to involve that important and exquisitely sensible
structure in idiopathic inflammation. At this period the dis-
ease may properly be called complicated caries.
The degree of rapidity of the destructive progress of deep-
seated caries, depends upon the constitutional strength of
the affected tooth, and on the degree of violence of the gen-
eral and local exciting causes, which act simultaneously in
aggravating the disease.
Internal caries, however, proceeds much more rapidly
than external ; and it may be said to be generally from one
to five years from the commencement of its corroding pro-
cess, to penetrate through the whole bony structure, and from
three to twenty-four months afterwards, before the destruc-
tion of the vitality of the lining membrane of the tooth is
totally affected ; putrefaction and absorption however may
still require from seven to fifteen years, to complete the en-
tire destruction and removal of the dead parts.
Simple caries, in each of its forms, differs in its effect on
the temporary teeth, from that on the permanent set, only in
proportion to their less dense and less durable construction,
and requires no separate consideration, except in the surgical
treatment.