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FILLING TEETH 143

former case, the filling either never goes fully up
to the cervical margin, or else it arrives there in
a crumbly condition. In the latter case, it prob-
ably sticks sufficiently to the plugger to be drawn
away from the wall. It has, however, been stated
that cervical failure is the rule with some makes
of cement, and the exception with others. This
probably accounts for the differences of opinion
that exist on this point. Oxyphosphate fillings
possess the inestimable advantage of adhering some-
what to the dentine (providing it is dry), and con-
sequently in sensitive teeth there is often no
necessity to cut retainage in the sound tooth
structure. The decay, if possible, should always
be removed ; and it should not be forgotten that
there are extremely shallow and extremely saucer-
like cavities in which even cement will not stay.
The modern use of porcelain inlays reduces the
number of cavities it was formerly necessary to fill
with cement alone, and at the present time cement
as a filling material is principally of value as a
preparatory filling, or preliminary treatment of
certain cavities before using—or in the hope of
subsequently using— a more permanent material.
It has an average duration of from one to two
years, and can be often successfully used to " tide
over " a bad time as regards either a period of