Page 146 - My FlipBook

142 OPERATIVE DENTISTRY

matrix in cases where a wall is missing and applies to all Class Two
cavities which reach the occlusal surface.
The matrix should be thoroughly wedged at the gingival, to pre-
vent excess contour at this point, and to secure additional space that
contact point may be made close. It should be made of steel as thin
as one one-thousandth of an inch. It should be made to encircle the
tooth firmly either by ligating or by a retaining appliance, several
of which are on the market. When two proximal fillings are to be
built at the same time and in the same proximal space, two matrices
are necessary, one for each tooth involved.
However, better results are obtained, particularly with reference
to proper contact restoration, by building up and finishing one fill-
ing first, and then building the other filling at a subsequent sitting.
By using a specially prepared matrix band of the proper size for
the second filling, with a hole cut in the matrix to allow the metal
to protrude at the point of contact with the first made filling, an
ideal result may be obtained.
Separation. Preliminary or immediate separation is just as es-
sential in the use of amalgam as gold.
Making the Proper Proportions of Alloy and Mercury. Each
operator should test his favorite alloys and determine the exact
amount of mercury for a given quantity of alloy, and by the use
of a pair of balances be able to always mix in exactly the same pro-
portions. By this means the operator is able to produce the best
product ]jy having the amalgam at its best. By the uniformity he
becomes familiar with the habits of that particular alloy.
This method need not be a time-loser, if the portions of alloy and
mercury are previously put up in separate capsules ready for im-
mediate use. In early practice this can be done by the dentist him-
self at leisure times and in after years by the assistant.
Making the Mix. Upon the thorough incorporation of the mer-
cury with the alloy prior to placing in the cavity depends much of
the good qualities of an amalgam filling. Poorly mixed alloys have
little strength. Amalgamation in an amalgam filling is never entirely
complete, and while this process is going on, there is a certain
amount of molecular action, which tends to change the form of the
filling as a whole. A very great per cent of this union may be in-
duced before placing the filling by a thorough preliminary mixing
and kneading of the mass.
To this end the alloy and mercury should be put into a wedge-
wood mortar and thoroughly groun^ together till the contents seem
to have become one mass. It should then be removed to the palm