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to conform to the margins of the cavity at all points. If hard wax is
used in place of camphor it should be made slightly plastic, then im-
mersed in cold water to destroy its adhesiveness. It should be manipu-
lated between the thumb and fingers, which should have been previously
immersed in cold water. A small ball of wax is then placed into the
matrix and forced into place with a blade burnisher. The tape should
be moistened before placing it over the .wax for the final swaging. The
wax has an advantage over camphor in that it will adhere better to the
walls of the matrix, thereby assisting in tlie removal of many matrices.
Either camphor or wax may be burned from the matrix, leaving no
residue.

Fig. 78.

The following additional details in the technique of forming matrices
for larger approximo-incisal cavities with irregular marginal outlines
should be considered. In case the margins present one or more reverse
curves, the matrix should be burnished differently from the method used
in those cavities in which the marginal outlines form a straight line.
After the foil is irregularly burnished to the cavity it chould be conformed
to the margins of the step with the shank of a small ball burnisher (Fig.
The matrix is then filled with hard wax and the foil turned over
TJ^.
the margins of the cavity in the tooth with rubber dam. The force should
be directed in such manner that uniform pressure is made on the foil to
prevent its overlapping at the margins. The foil should then be forced
into the reverse curves with the marginal burnisher. The matrix should
now be trimmed so that its edges will rest uniformly on a flat surface.
It is then annealed and adjusted to the cavity for final swaging. This is
done by filling the matrix flush to the margins with hard wax (Fig. 78)
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