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AMALGAM 1 57

5. Insert several cement fillings, with and without
matrices.

AMALGAM
—
Definition. An alloy or union of mercury with one or
more other metals. Most dental amalgams consist of a com-
bination of mercury with silver, tin, copper or zinc. To these
are also sometimes added gold, platinum and other metals.
—
Alloy. A union of two or more metals by means of heat.
The metals are usually melted in a closed electric crucible
in an atmosphere of hydrogen. After cooling and hardening,
the resultant mass is known as an Ingot. The ingot is either
filed into small granules or pared into fine shavings, when,

after being annealed and carried through certain other proc-
esses it is dispensed as alloy for dental use.

Properties of Amalgam

All dental alloys, when mixed with mercury, possess one

or more of the following properties, which are imparted to the
mass by qualities inherent in the constituents, viz.,
1. Spheroiding.

2. Flow.
3. Shrinkage.
4. Expansion.
Spheroiding.—The tendency to become round imparted to
the mass by the mercury. It only occurs while the amalgam
is hardening or setting, and depends on the amount of mercury

left in the mass, the greater the excess of mercury present, the
more marked the spheroiding.
Flow.—Many metals, when subjected to constant stress,

as from the stress of mastication, possess the tendency to
slowly move from under the stress, thus gradually changing