Page 66 - My FlipBook

There is no particular advantage in annealing the matrix several times
(luring the process of construction. The foil should be made pliable pre-
vious to beginning the formation of the matrix, and there is no need of
further annealing unless the foil loses its pliability during the construction
of the matrix.
There are three general methods of construct-
„ .. . ing matrices for cavities.
methods *=
of Constructing (i) Burnishing directly into the cavity.
matrices.
^2) Swaging into a model of the cavity.
(3) Swaging over an impression of the cavity.
The method of burnishing the foil directly into the cavity seems to be
the most popular, and the author believes it to be the best for the con-
struction of matrices for simple approximal and most approximo-incisal
cavities. If the foil is burnished directly into the cavity, it gives a sharper
matrix than can be made by swaging directly into the models of many
cavities. Matrices can be removed from simple approximal cavities where
there is a moderate amount of space, with no danger of distortion, while
an impression of the cavity could not be removed without additional
space or sacrifice of tooth structure. A matrix burnished into a cavity
usually covers more of the surface of the tooth than one swaged into a
model, thereby aiding the operator when applying the porcelain, to obtain
better representation of tooth contour.
There have been a number of special instruments for burnishing
matrices placed on the market. It has been the author's experience, how-
ever, that many of them are useless and that a large supply of burnishers
is more of a hindrance than a help in this work. He has found that a
pair of special inlay matrix pliers (Fig. 65), four ball burnishers (Fig.
66), one blade burnisher (Fig. 67), one special marginal burnisher (Fig.
68), and two gingival marginal burnishers (Fig. 69) meet the require-
ments in a satisfactory manner. The efficiency of the gingival marginal
burnishers is increased by grinding the lip of the instrument iintil it is
about one-third its original length.
The technique of burnishing matrices is de-
pendent upon the material used and the thickness
Ccchniouc
Of Burnishing of this material. If thin gold is used for simple ap-
matrices. proximal and approximo-incisal cavities, the metal
should be surrounded by goldbeater's skin or china
silk, and forced into the cavity with pellets of spunk or cotton (Fig. 70).
After the foil has been forced to the seat and to the axial walls of the

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