Page 132 - My FlipBook

128 THE TECHNICAL PROCEDURES IN FILLING TEETH.

the cavity should be made to see that the matrix is close at that
point, and if it is not, it should be brought close, by inserting a
small, soft wood wedge from the lingual side with just suffi-
cient force to bring the matrix close. This is most likely to be
needed in molars that have broad, flat, proximate surfaces.
Preparing the Amalgam.

It is of great importance to obtain in the beginning the right
proportions of alloy and mercury. This proportion will vary
with the alloy used. Of the higher grades of alloy we are
at present using, this proportion is very nearly equal parts by
weight, but generally a slightly greater proportion of mercury is
required ; or about 52 per cent. This proportion should be
carefully determined for the alloy used, and the proportions
weighed for each mix. We think this of such importance in our
infirmary work that we have this weighing done, and the prop-
portions put in separate capsules. I have also found that to
undertake to knead the alloy with too much mercury results in
very imperfect kneading and makes a weak amalgam, while to
knead with too little mercury also makes a very weak amalgam,
and a mass that is too granular and stiff to work well.

Kneading.

The first of the kneading is done best in a wedgewood or
ground-glass mortar. This should be continued until all of the
fillings are incorporated with the mercury, when it should be
turned into the palm of the hand and vigorously kneaded with
the fingers. For this work the hand should be as dry as possi-
ble. This kneading should be continued until the mass is per-
fectly soft, plastic and free from granulation. If in the kneading
the mass becomes too very soft there is too much mercury in the
mix, and so soon as that is determined a portion of the mercury
should be removed by squeezing the mass between the fingers
and the kneading immediately continued, for if -the mass is
allowed to stand for even a few moments in this condition it is
likely to become too stiff for rekneading. When sufficiently
kneaded, the mass should not very readily break when rolled into
a long roll in the palm of the hand. Everything should be in
exact readiness to insert the filling and the packing immediately