Page 270 - My FlipBook

the patfent presents for treatment the several classes of
cavities may be present at the same time. These must be
sharply distinguished from cases in which the different classes
of cavities begin very nearly together in persons of fifteen
years or younger. In the first the intensity of susceptibility
has been sufhcient to start many areas of decay, but the early
tendency toward immunity has checked the progress, and
the case is readily manageable, while in the treatment of the
second we have to deal with the full intensity of the suscep-
tibility.
Cavities of the first class, in the large majority of cases
met with in practice, are first to appear. These include
pit and fissure cavities in the molars, bicuspids, lateral in-
cisors, and more rarely in the central incisors also. In a
large proportion of persons the first of these are in the
molar teeth, and in many the only cavities of this class,
the incisors being free from pits and fissures, and decay not
occurring in the pits of the bicuspids. Under equal condi-
tions of susceptibility and local conditions among the differ-
ent teeth, decay in pits and fissures would occur within about
a certain time after the teeth take their places in the arch. In
highly susceptible persons this will be within from one to
three years, and at a later time as the susceptibility is less.
Therefore, while this class is first to appear in individual teeth
liable, they are scattered over a considerable period in the in-
dividual, and as both the susceptibility and local conditions
vary greatly in different persons, we meet with this class
of cavities at various ages of persons. It is only through the
careful observation of many persons that general rules are
made out.
The local conditions relate almost solely to the form and
depth of pits and fissures. Well-closed pits rarely decay.
In very susceptible persons decay begins early in open pits
and in fissures. In immune persons decay may not occur
at all in these.
The First Molars.—The lower first molars are usually
the first of the permanent teeth to be attacked and the decay
is almost always in the central pit of the occlusal surface, but
occasionally in the buccal pit also. Cavities in a similar posi-
tion in the upper first molars begin soon afterward. This is
so common, and the effects of this early beginning of decay

258