Page 359 - My FlipBook

AMALGA3I AND GOLD. 357

the gold with mercury if rubbed against it, Fig. 339.
therefore they must be disposed of or an
unsatisfactory filling will be the result.
The proper amount of amalgam having
been packed in the cavity, medium-sized
pieces of some of the plastic golds before
referred to are immediately added. The
instruments used first on the gold should be as large as
cavity will accommodate, as they will break it up less and
more readily carry the piece where it is wanted, after which
each piece of gold should be thoroughly condensed with
smaller instruments.
As soon as the gold touches the amalgam it will absorb
mercury, and sometimes several pieces of the gold will be
entirelv amalg-amated. The surface of the fillino; will be-
come very granular, and " chop up " to a certain degree as
the first pieces of gold are used, and the instrument will
cause a peculiar squeaky sound as it is pressed against the
filling. The condensation must be very thorough at this
point of the work, or the filling will be porous and the union
between the amalgam and gold unsatisfactory. If the work
is thoroughly done, however, the filling will be just as strong
at this point as any other. As piece after piece of the plastic
gold is added, the mercury will soon cease to penetrate it,
and the surface become entirely gold. As soon as this stage
is reached, and no more mercury is visible, any kind of cohe-
sive gold can be used for the remaining portion of the filling.
Fig. 339 presents some instruments that have been found
especially useful in this work. Tlie gold may be packed
with hand or mallet pressure, or both.
After the gold is all packed the matrix is removed, and
the filling finished with sandpaper disks, strips, burs, and
stones, in the ordinary manner. For finishing the amalgam
portion of the filling only fine disks or strips should be used.
The amalgam being yet in a granular condition, and not
thoroughly hard, will be dragged from the edges somewhat
and made slightly imperfect if a coarse grade of sand or
emery paper be used.
The gold will not break away from a filling made in
this manner, even if there be no undercut in the tooth for
Gold-pnck-
holding it ; the union with the amalgam will be quite suf-
ing instru-
ficient to retain it. The cavity must have the proper shape, ments.