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94 GENERAL REMARKS ON FILLING.

to subserve the purposes of temporary fillings. It
possesses great adaptability by simply being warmed
:
over a spirit-lamp or in boiling water, it becomes plas-
tic, and is with great facility introduced and con-
formed to the cavity. It may be applied also in solu-
tion, being dissolved in chloroform till it approaches a
pasty consistence, then absorbed in a pledget of cotton,
and introduced into the cavity ; where the chloroform,
evaporating, leaves the gutta-percha as a filling. The
only objection to this method is, the contraction con-
sequent on the evaporation of the chloroform. Another
property that renders this substance highly valuable,
is, its non-conduction of heat, it being in this respect
as nearly perfect as any other material employed.

A preparation of gutta-percha with mineral sub-
stances, known as Hill's stopping, has for some years,
been extensively used for temporary fillings ; indeed,
it has superseded simple gutta-percha almost entirely.
The aim of this preparation was to obviate two or
three objections to pure gutta-percha; as, its contrac-
tibility in the cavity, its softness, and its color. The
composition of Rill's stopping is as follows : With pure
gutta-percha in a plastic state, are mixed quicklime
two parts, and quartz and feldspar one part each,
which latter are reduced to an impalpable powder, and
kneaded into the mass as long as it will receive them

without becoming brittle. Such is the formula given