Page 130 - My FlipBook

114 THE TREATMENT OF TEETH
palladium. For some reason palladium is now
rarely if ever used, and will not be further
alluded to.
The amalgams that are now generally used, are
made by melting together several metals, and pour-
ing them into an ingot mould. The ingot is then
reduced to fine filings, or shavings, and mixed with
the mercury. Of the various metals that have
been used for making these alloys, tin, silver, gold,
copper, and zinc, are the ones that are most em-
ployed. Platinum is used in some alloys, but is
thought of little or no value in this connection.
One of the main points that careful investigation
has brought out is, that silver is the metal that
must be used in the largest proportion in making
an alloy, and that at least 60 per cent, of silver is
necessary. Tin is necessary in order to enable an
alloy to be satisfactorily mixed with mercury, and
it has been termed a flux for this reason. Its pro-
portion comes next to silver. A good amalgam
alloy can be made with tin and silver alone, and in
this case the proportion of silver should be from
65 to 74 per cent., depending on whether the alloy
is used fresh cut or annealed. Dr. Black finds that
the best formula for a silver- tin alloy pure and
simple (fully annealed) Avill be close to 73 silver
and 27 tin.