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METHODS OF FILLING TEETH.
56
a considerable proportion of metals which it has absorbed from the
Thus it would seem that it has with it a
alloy. brought away por-
tion of that metal contained in the alloy for which it has the greatest
The result must be an alteration in the of metals
affinity. proportion
contained in the alloy. Thus, if a given alloy is used for making an
amalgam, and one mixing is made with just the proper quantity of
mercury, while a second is prepared with an excess which is removed
by pressure, it would seem natural to expect that the two would not act
even in the same mouth. This would the
similarly explain, perhaps,
of an where it will fail in a tooth
oft-claimed unreliability amalgam,
upon one side of a mouth, and succeed admirably upon the other.
It is not the amalgam that is unreliable, but the dentist, who has not a
definite method.
As it would be a tedious process to weigh out the alloy and mercury
for each mixing, we may resort to some less accurate way, provided
that it accomplishes the result with reasonable reliability. If the
be made to mix with it will
attempt alloys mercury in the hand,
result in an excess of the latter. We
usually may better depend upon
the pestle and mortar, preferably of small size. Place in the mortar
the amount of alloy desired, and add a little mercury ; stir vigor-
ously, and the mercury will take up all the alloy with which it can
between each addition, until the
unite. Add more, and more, stirring
mass is soaked with but If it now be
mercury, perhaps granular.
turned into the palm of the hand and manipulated vigorously, the
friction will aid in the and a mass
produced amalgamation, quite plastic
can be produced. This plasticity is not the result of an excess of
mercury, for we have seen that while cold, in the mortar, it did not
reach such a consistency ; it has been attained by heat rather, and
there is no need to squeeze out any mercury, though, in order to be
sure that there is no excess, it is as well to squeeze with the finger and
thumb. That amount of pressure will not force out any mercury if
too much has not been used, and if this method of be followed
mixing
it will rarely occur that any excess will be found.
The amalgam is now ready for use. To place within a cavity as
large a mass as can be crowded in, would be as incorrect as to follow
the same rule when using gold. Choose a piece which can be dropped
into the and which under will become packed
cavity easily, pressure
without The is thus With a bit
fracturing : homogeneity preserved.
of bibulous paper rolled into a small ball and held in the foil-carriers,
the amalgam is next pressed, and smeared into all the crooks and
corners of the cavity. Usually this first portion of amalgam may be
treated so that it will form a veneer covering all the walls. This
insures adaptation. Piece after piece is to be placed in this way, and
if the mass was
properly mixed no excess will come to the surface.