Page 182 - My FlipBook

156 THE MICRO-ORQANISMS OF THE HUMAN MOUTH.

a cavity is produced, or rather a depression, since it has little
similarity with the cavities of the crown. Deep bulb-shaped
cavities are hardly ever formed ; they are for the most part shal-
low, widely extended excavations, without a distinct margin.
This is due to the fact that there are no circumscribed points
of retention or foci of decay on the roots, from which alone the
destruction could proceed. It therefore seldom happens that
decay beginning at the root spreads from the cement to the den-
tine and destroys the latter to such an extent that the root-pulp
is exposed.
A natural retention-center is formed at the point of bifurcation of
the molar roots where it has been exposed by recession of the gums,
and penetrating decay is consequently not seldom found here.
Discoloration has been erroneously regarded as the first stage
of cement-decay also. Exposed roots almost invariably become
more or less discolored in time, whether they are decayed or not,
especially when they are not kept clean.
d. Decay of the Enamel-Cuticle.
It is impossible to follow the process of decay in the delicate
membrane covering the crown of the tooth without the aid of
the microscope. All we can see with the naked eye is a more
or less pronounced discoloration surrounding the carious part of
the membrane which has been detached by strong acids. Fre-
quently a thickening and cloudiness are also detectable.
In pulpless and dead human teeth, even in artificial teeth
carved from walrus-teeth, decay exhibits the same physical phe-
nomena as in living teeth.
ACCOMPANYING PHENOMENA OF DENTAL DECAY.
As concomitant phenomena of dental decay I designate cer-
tain processes which manifest themselves cither immediateh' or
some time after the appearance of decay, and which, in my opin-
ion, have been erroneously denominated as characteristics of it.
Those processes are : (1) transparency, (2) the pigmentation or
discoloration of the decayed tissue.
" Coincident with the development of the opacity and the
pigmental degeneration in the commencement of the carious
affection of the dentine, an increased translucency is observed,