Page 65 - My FlipBook

OXYCHLORIDE OF ZINC.
51
periodically than to risk death to the pulp by using a metal. Gutta-
percha is not a non-conductor, but it is a poorer conductor than the
metals, and what is more important, all the tissues of the mouth,
whether hard or soft, are a
singularly tolerant of it. Occasionally
patient will present with a deep cavity in a most inaccessible approxi-
mal surface. Excavation makes it doubtful whether the
pulp is nearly
approached, or whether hypersensitive dentine alone is the cause of the
pain. A very wise course is to temporize by inserting gutta-percha.
Too much examination may expose a pulp in a small cavity, thus ne-
cessitating a tremendous sacrifice of tooth-substance for its proper
removal, whereas under a gutta-percha filling this class of teeth is
frequently troublesome no longer.
Gutta-percha is often used as a capping over pulps which are nearly
approached. Where this is done, and the filling completed with gold,
common sense will indicate the advisability of covering the gutta-percha
before
with a resistant body of oxyphosphate attempting to pack gold
upon it. Many, however, would not think this essential where amalgam
is to be the final It must be remembered that
filling. gutta-percha is
FIG. 63. FIG. 64.

elastic. Therefore where it underlies or other metallic
slightly amalgam
it must not be so that the rests
filling placed superincumbent filling
wholly upon it. In Fig. 63 is shown a cavity filled improperly. The
amalgam, a, rests upon the gutta-percha, b, in such a manner that
pressure during mastication has a tendency to compress the latter, al-
lowing the amalgam to be driven downward away from the walls, thus
producing leakage. In Fig. 64 the arrangement is better, for the
amalgam, a, is now supported by the walls at the points c, c, so that
movement under pressure is rendered impossible. Thus it becomes
not to insert too much under another
important gutta-percha filling
in the vain of obtaining better insulation.
hope
A solution of gutta-percha in chloroform, commonly known as
chloro-percha, is useful for lining cavities before inserting a filling of
oxychloride, thus preventing the pain from irritation by the chloride
of zinc. It is also valuable, and should always be used as a coating
for oxychloride or oxyphosphate fillings where the latter are meant to
serve permanently.
is much less used than it was
Oxychloride of zinc, as a filling-material,
before the introduction of the oxyphosphates. As a permanent filling