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90 Diseases of the Teeth.
much sooner in some mouths than in others, and that this
happens in persons of a weakly constitution, or of a febrile
system, or who neglect to keep their teeth free of foreign mat-
That a vitiated state of the saliva, assisted by other
ter.
causes, may be, and is a principal cause of external caries, we
apprehend cannot be doubted, from what has been said onrtie
chemical action of the causes of external decay. (See page 76.)
The saliva will probably be vitiated by these circumstances.
In healthy persons, by neglect, tartar and putrefactive agents,
decaying teeth and dead stumps, and decomposing artificial
teeth, all indicated by an offensive breath. In sickly persons,
to the above may be added a febrile state of the system,
derangement of the digestive organs, mercurial and oiher
medicines.
CHEMICAL AGENTS.
Though all the exciting causes of external caries, except
the mechanical, act chemically on the teeth ; this term may
be properly applied to the mineral acids and some of their
salts.
seen from its effects oh the teeth especially on artificial teeth which are
sometimes decomposed with wonderful rapidity. The cause of this acid
quality of the saliva is probably muriatic acid : this is the more probable
as the muriatic acid is the principal active agent in the gastric juice,
with which the saliva i.-? somewhat analogous in composition. We have
often tested the saliva of persons under the circumstances we are treat-
ing of, with a solution of the nitrate of silver, but not with satisfactory
results, though we think we have occasionally perceived very slight in-
dications of muriatic acid. Persons who value their teeth, under sueh
circumstances should take great care of ihem. The frequent nncing of
the mouth with an alkaline solution would probably prove of advantage,
as it is evident that some acid is generated, which the alkali will neu-
In healthy persons who neglect the mouth, and allow the food lodged
between the teeth to undergo decomposition, an acid also is generated ;
for the enamel which is principally composed of phosphoric acid and
lime, could not discolor and decompose, unless an acid having a.
acetic. A
powerful affinity for lime be present ; and this acid is the
variety of combinations take place under such circumstances, water and
ammonia are probably generated, also carbonic acid, phosphuretted and
sulphuretted hydrogen gasses, as are indicated by the offensive breath.