Page 181 - My FlipBook

dence is against you. Notwithstanding- this, caries is the
direct effect of an acid, but not the effect of an acid that is
dissolved in the general fluids of the mouth. The general
fluids of the mouth are never sufficiently acid to produce
caries; if they were the teeth would decay all over, not in
isolated spots. Now, this was pointed out clearly and forci-
bly as long ago as 1825 by Robertson, and by various others.
If caries is caused by acidity of the fluids of the mouth they
should decay all over, because all surfaces of the teeth are
exposed almost continuously to the fluids of the mouth.
Robertson also pointed out, as early as 1825, the fact that
for acids to produce caries of the teeth they must be formed
at the immediate spot where caries is produced and act in
the nascent state. Robertson was right, and the expressions
which he gave then, although he knew nothing about micro-
organisms, and seems not to have been very well posted in
the fermentations as they were understood in his day, the
facts that he pointed out are as true to-day as when he stated
them. We do not find that observed facts change with the
progress of time ; our notions about them or our explana-
tion of them may change, but the observed facts that are
gathered from year to year, from decade to decade, or from
century to century, generally remain with us, and we build
upon them, from time to time adding new facts, dispelling
gradually our notions derived from faulty observations, and
we must continue to do that in the future, because the best
of us have many faulty notions vet that must be dispelled
gradually by new facts that will be developed which will

point the way to a more complete understanding of the truth.
Now, these things are to be studied from mouth to
mouth in the future of your practice, the beginnings of de-
cay, particularly, and the factors necessary to the beginnings
of decay. I have told you what they are—the necessity that
there be secluded points, that microbic plaques form that
will prevent the solution of the acids formed by the micro-
organisms in the fluids of the mouth, and apply them di-
rectly to the teeth in these sheltered places, and these pro-
duce certain results ; the enamel begins to be affected, be-
gins to be whitened ; nothing that you will see, perhaps, un-
less you clean the surface and let it dry, and then you will
notice a whitening and an opacity of the immediate surface

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