Page 165 - My FlipBook

FILLING TEETH 149
gutta - percha the preparation is as a rule rapidly
effected.
Gutta-percha shrinks slightly, and in some mouths
becomes dark on the surface. This change of colour
is often accompanied by a softening and porosity of
the surface. It is stated that varnishing the cavity
with either copal ether varnish or resin dissolved in
chloroform prevents the shrinkage of gutta-percha.
Whatever may be the value of this varnishing, the
fact remains that the majority of gutta-percha
fillings, notwithstanding their leakage, save teeth
remarkably well, as long as the tilling remains
fairly intact. Leaky gold fillings have little effect
in saving teeth ; why leaky gutta-percha fillings
should not be open to this objection to the same
extent is not satisfactorily explained. It is true
that an explanation is to be found in the electro-
chemical theory ; but the teachings of the late
Dr. S. Palmer in this respect have not been accepted
by the profession at large.
For filling cavities (not too much exposed to
mastication) where a clasp, or band, or part of a
plate will be in contact with the filling and tooth,
gutta-percha seems usually to answer better than
anything else.
In manipulating gutta-percha, care has to be
taken not to overheat and so spoil its durability. A