Page 762 - My FlipBook

772 DENTAL CARIES.
This is occasionally so complete that a portion of the dentine is left
uncovered or with but a slight thickness of very imperfect enamel.
This is not always enamel in the true sense, in that it is devoid of
enamel-rods. It is probably composed of the same matter as the con-
necting substance between the enamel-rods, which, as we have found, is
easier of solution than the substance of the rods themselves. This ease
of solution, however, is not the principal condition predisposing to
caries. The predisposition is found principally in the form—a pit or
groove, giving opportunity for caries by serving as a point for the
retention of particles of food, etc., until the process of fermentation has
created an acid which will act on the tissue. When it is once implanted
in them, these pits protect the fungus from dislodgment, thus favoring
its development, and little by little the enamel is dissolved out and
admission to the dentine gained.
The manner of contact of the proximal surfaces has much significance
in predisposing the teeth to decay. Those in which there is the great-
est amount of surface not self-cleansing are, other things being equal,
most liable to caries. Hence, teeth so formed that the proximal surfaces
are at all points very nearly in contact, yet without actually touching, are
rendered more liable to caries, provided the festoon of the gum does not
fill the space. When I analyze the conditions under Avhich caries is
most liable to occur, I am convinced that this is of great imjiortance,
and that caries generally does not occur while this space is filled by the
gum to the point of contact of the adjacent teeth. Two reasons may
be given for this : First, the festoon of the gum fills the space and
tends to prevent lodgments from occurring ; second, the secretion given
out by the healthy gum, especially that coming from the gingival space,
is antiseptic to a sufficient degree to prevent fermentation of very slight
amounts of matter in immediate contact with it. Therefore, so long as
the gum remains healthy, decay does not begin in immediate contact
with its border. The breaking down of this septum of the gum by
the repeated forcing of food between the teeth or from other causes
becomes a predisposing cause of decay. I may add also that, without
becoming distinctly unhealthy, the gum sometimes recedes slightly from
between the teeth, and in this way predisposes the teeth to caries by
giving opportunity for its beginnings, in that a receptacle is formed for
the lodgment of particles whicli undergo fermentation in contact with
the t^eth. Malpositions of the teeth, when of such character as to favor
such lodgments, also predispose to the beginning of caries ; and in these
cases it is often shown that what is supposed to be the strongest enamel
will be penetrated if placed in such position that lodgments occur
against it.
Hereditary injlvences are very powerful predisjwsing causes of decay
of the teeth. Tliis has been recognized by all who have examined the
subject. Indeed, this influence is too manifest to be overlooked by any
one who has given the subject close attention. It seems to me, however,
that it has in tlic ])ast been by many much overrated, though it must
as well. It seems evident that the ameloblasts will allow of some spreading without
division one from the other, but this tolerance is limited, and in the later stages of cal-
cification tlie power of proliferation is reduced to the lowest point.