Page 92 - My FlipBook

8o MECHANICAL DENTISTRY AND METALLURGY.

model, so as to form a thick edge of sand for the more per-
fect parting of the flask. Very finely pulverized charcoal
should now be sifted over the exposed surface of the sand,
to prevent the next portion contained in the upper section
from adhering. The plain ring (Fig. 44) is then placed in
position and filled with sand, which should be well packed
over the face of the cast.
The upper ring is now carefully lifted from the lower one,
which may then be parted by removing the long pin, when
the cast should be taken away. The ring may be again

Fig. 46.

closed and fastened by replacing the pin ; the upper section
is then readjusted, and the entire flask inverted, when, if
the process has been accurately conducted, the mold will be
found perfect.
Forming Pattern for Plate.—Having determined upon
the proper form and dimensions of the plate for any given
case, its outlines should first be traced upon the model with a
pencil ; from this an exact pattern in lead- or tin-foil may be
obtained ; in partial cases the pattern may be sufficiently
ample to partially overlap the cut extremities of the teeth.