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ARTIFICIAL DENTURES. 89
tliinncr than is generally employed, or than is consistent
with the required strength, it will fail to he forced perfectly
into the gToove around the chamber by the process of swag-
ing alone; a more definite border, however, may be formed
by forcing the plate in at this place wnth a small, smooth-
faced stamp or tracer, shaped to the angle of the groove,
passing it round the chamber and with a small hammer care-
fully forcing the plate in until a somewdiat sharp and abrupt
angle is obtained to the palatal edge of the chamber. After
the chamber is as perfectly formed as possible in this way,
the plate should be well annealed and again swaged to cor-
rect any partial deformity occasioned by stamping the
chamber.
The Soldered "Air Chamber."—A still more perfectly
defined angle may be gi\'en to the borders of the chamber
in the following manner : After swaging the plate suffi-
ciently to indicate the exact position and form of the cham-
ber, the portion forming the latter should be separated from
the main plate by completely dividing it with a saw, or other
instrument, cutting on a line v/ith the groove around the
chamber until the latter is entirely separated. The cut por-
tion of the main plate is then trimmed evenly with a file
and stones, being careful not to enlarge the opening more
than is required to remove the irregularities of the edge
formed in cutting. The plate, with its central portion
removed, is then placed upon the die, wdien a separate piece
of gold cut to the general form of a chamber, but somewhat
larger than the opening in the main plate, is adjusted over
the chamber, and struck up with the plate until the over-
lapping portions of the central piece are forced down upon
the plate around the margins of the chamber. It is not,
however, always necessary to employ a separate piece of
gold for the chamber, as the central portion cut from the
plate in the first instance may be sufficiently enlarged for
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