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RELATIVE VALUES OP AMALGAMS. 55

it is preferable to place a portion of the metallic filling while the
oxyphosphate is still plastic, for thus the upper filling is practically
cemented into place. This process will be described later.
As a permanent filling oxyphosphate may be used in cavities where
the more conductive properties of metal would prove injurious. It
also should be employed in conspicuous positions, as, for example, large
corners or labial festoon cavities in the incisor in the mouths
region,
of actors and actresses, ministers, singers, lecturers, and public speakers
generally.
RELATIVE VALUES OF AMALGAMS.

Amalg'atn is one of the most valuable filling-materials at our dis-
At the same time it is the most abused. It is more
posal. frequently
chosen because of its cheapness than because of its special adaptation
to a case. The result is that it is not
given properly manipulated,
and is too often allowed to remain without special polishing. Much
of the disrepute attached to amalgam is probably due to faulty filling
methods, rather than to any bad quality inherent in the material itself.
One of the charges against amalgam is that it shrinks, thus pro-
ducing imperfect borders, which invite decay. How much this may
be due to using the material mixed of an improper consistency,
is worth considering. I believe that the shrinkage of amalgam is
reduced to a minimum by proper mixing. Another thing worthy of
note seems to be the curious fact that this
shrinkage does not appear
to involve the entire mass, for if it did would not the become
filling
loosened within the cavity? This I have never seen. The discrep-
ancy occurs at the surface, so that it would appear that all we need is
a method of which will overcome this
manipulation tendency to
shrink along the border.
necessary gold, it is
If it is to use the dam for the insertion of
equally needful where amalgam has been decided upon. I do not
mean that the dam must always be employed, for I have explained
that it is not always a necessity even with gold, for which it is more
often used than with other materials. It is more exact, then, to say
that the cavity must be kept as dry as possible, whether by using the
dam, or by dependence upon the napkin. I think that amalgam in-
serted without to moisture is more likely to become blackened
regard
than when caution is used to prevent the wetting of the material during
its insertion.
In mixing the alloy with the mercury I prefer adding the mercury, a
little at a time, until a mass is produced, rather than to use too
plastic
a at the outset, and then ex-
great quantity of mercury depend upon
pressing it. If mercury, squeezed from amalgam mixings, be pre-
served in a bottle, and then examined, it will be found that it contains