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128 THE TREATMENT OF TEETH

mercury is evidently loaded with the alloy.
Whether the squeezing out of much or little of
the alloy makes any difterence to the value of the
filling ; and whether the absence or presence of a
good deal of alloy in the squeezed out mercury
is advantageous, detrimental, or immaterial, prob-
ably depends on the composition of the alloy, but
the subject has not yet been investigated. It seems,
however, to be rather absurd to use an alloy in the
production of which great care has been taken to
secure exact proportions, and then to destroy these
proportions by squeezing an indefinite quantity of
each ingredient out with the mercury. The alloy
should therefore be mixed with the mercury in such
definite proportions as will secure the best mix ; and
then, if wafering is necessary or advisable, to
squeeze out the mercury in such a manner that it
carries out with it little or none of the alloy.
The maintenance of colour in an amalgam filling is
very uncertain, and just in proportion to mainten-
ance of colour, so are the tooth-saving properties of
the filling reduced. This is to say, that although
an amalgam that maintains its colour may save
certain teeth remarkably well, there are other
teeth in which a filling that readily oxidises and
becomes more or less black, is more advantageous.
It is diflicult to account for this, but that certain