Page 52 - My FlipBook

48 CARIES OF THE TEETH.

question, then, is, whether there is any property in
the decayed dentine of one tooth, capable of producing
the same condition in the healthy dentine of another.
The residue of abnormal dentine in the soft decay,

consists of the animal elements and a small portion of
earthy material; and in decay in which the gelatinous
constituent is abstracted, the remainder is chalk-like,
consisting mainly of phosphate of lime. In neither of
these is there anything that can possibly operate on
the healthy dentine. There is one thing here, how-
ever, that is worthy of remark, and that has perhaps
led to the mistaken notion that caries is contagious:
decayed dentine will absorb and retain fluids that
injuriously affect sound dentine; and when the decay

is on the proximal portion, two teeth are subject to
the same exciting cause. But it is seldom that two
teeth thus situated are both in the same stage of decay;
a fact principally attributable to the difference in their
constitution. The decay of the teeth in pairs has also
been adduced as evidence of the contagious character
of the disease. This, however, results from the fact
that the pairs are formed at the same time; are subject
to the same influences in their formation, and hence
are constituted alike ; and if one of the pair is defec-
tive, the other will be in a like condition. When there

is a vitiation of the saliva or mucus, they will be
similarly affected. In no common acceptation of the