Page 278 - My FlipBook

they are in more danger from thermal sensitiveness in propor-
tion to their area than other cavities. In proximate cavities
much of the area of the filHngs is shielded by the proximating
tooth. In buccal cavities the fillings are not so directly ex-
posed to thermal changes, therefore especial care should be
had to shield the pulp from thermal changes in very deep
cavities. This is best done by covering the pulpal wall with
a thick layer of oxyphosphate of zinc, and making the filling
over this after it has become fully hard. Theoretically, gutta-
percha is the best non-conductor, but, practically, it is too soft
to serve as the support of a permanent filling and should
never be used.
Filling over softened dentiv.—There is a practice among
many in the profession of leaving a portion of softened den-
tin in the deep occlusal cavities and filling over it, claiming
that when securely covered in, especially if saturated with
an aintiseptic, no more decay will occur. This procedure is
very tempting in handling deep occlusal cavities. So far
as continuance of the decay is concerned, this is correct,
jbut this carious mass contains a poisonous substance elab-
orated during the carious process, which, when shut up in
this way, especially endangers the vitality of the pulp by
its absorption. This is the principal reason why we find
so many dead pulps under such fillings. It is always safer
to remove the decay completely and use oxyphosphate of
zinc when it is very deep. I am persuaded that much of the
bad reputation of oxyphosphate of zinc as a pulp-capping and
as a protection against thermal sensitiveness in deep cavities
is due to its use over a more or less thick mass of carious den-
tin, and especially over pulps already infected and inflamed
from exposure to carious dentin. Pulps thus exposed must
be regarded as inflamed pulps and not proper subjects for
pulp-capping. Only those pulps that become exposed in the
removal of the very last particles of softened material, or in
cutting beyond, are suitable subjects for actual capping. The
principal use for oxychloride of zinc is for the protection of
pulps nearly, but not actually, exposed. Also in deep cavi-
ties, the actual condition is not discovered until the last of the
softened dentin is removed. Not infrequently teeth are filled
when the pulp is fully exposed to the softened material and its
death follows speedily. Under all conditions every particle

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