Page 178 - My FlipBook

152 THE MICRO-ORGANISMS OF THE HUMAN MOUTH.

formed. The form of the cavity depends upon various circum-
stances, among others upon the breadth of the surface of contact
with the adjacent tooth, also in a high degree upon the structure
of the enamel ; it is sometimes flat and broad with scarcely dis-
tinguishable margins, sometimes narrow and deep with sharp
ragged margins. Soon after the commencement of decay, a more
or less pronounced discoloration sets in. In my opinion the
view held by some that this discoloration is to be regarded as the
first sign of decay is based on an error which is to be explained
only on the supposition that the advocates of this view have not
examined decay in its earliest stages.
A discoloration of intact smooth enamel does not occur;
some change or other must have taken place in the enamel before
a discoloration can take place, and this change is nothing else
than a softening or decalcification of it.
This discoloration appears in very dififerent grades ; when the
decay proceeds very rapidly (caries acutissima), it is slight or
wholly wanting (white decay). In other cases, only the margin
of the enamel is colored brown to l)lack while the center of the
cavity remains white. When the decay proceeds very slowly,
that is, when it is of long standing (caries chronica), the greater
part of the aftected tissue is deep brown or black. This is also
the case where the progress of the decay has been interrupted,
as is often observed on the approximal surfaces of teeth which
have been exposed by extraction of the adjacent tooth. Such
cases are usually designated as caries nigra (black decay). This
badly-chosen term must, however, not mislead us to suppose that
we have to do here with an especial form of deca}'. As a matter
of fact, we are scarcely entitled to speak of such places as decay
at all, any more than we arc to say that a man with a pock-
marked face has got the smallpox, because they do not indicate
that the process of decay is going on at the time being. They
are simply degenerated tissue which in the course of time has
l)eeonie discolored by oxidation, precipitation, or other processes
of tliis,n.ituro. Decay-niarks would be a much better name for
such s})ots.