Page 353 - My FlipBook

CEMENT AND AMALGAM. 351

the tooth, the ends nearly joining against the sound remaining wall (see
Fig. 328). In such cases it may be desirable to slit it one or more
times, in order that it may be made to take the form of
the tooth more easily (Fig. 329).
After the tying is completed, a suitably shaped bur-
nisher is used to form the matrix, by pressing it outward,
to a proper contour.
One of the desirable features of the matrix here de-
scribed is the ease with which it is made to giye just the
right shape and contour to the filling. When used for
gold fillings it yields enough so that with a little care in
packing the gold can be forced beyond the margin of the cayity suf-
ficiently to insure a flush filling when burnished, after remoying the
matrix.
A matrix put on as described will haye sufficient resistance for a gold
filling ; for amalgam, cement, or gutta-percha it
Fig, 329.
may not be necessary to tie it quite so securely.
For compound fillings of cement and amalgam
two methods, A and B, are here giyen.
Matrix with marginal slits.
A. Those cavities whicli, although large and
inyolving much of the tooth, may haye but small or comparatiyely small
openings, especially if a matrix be used—and there are but few cases
where the matrix is not advisable. If, after putting on the matrix, in
this class of cavities, cement is introduced, and pieces of amalgam
thrust into it, the cement will most likely be carried to the margin of
the cavity at the cervical wall, and it will be found, after removing the
matrix and finishing the filling, that a part of the external portion is
of cement, and not being protected by the amalgam, Avould be washed out.
To avoid this, a portion of the filling is made before the
matrix is put o)t. Cement is put in, followed immediately
"
by the amalgam as described for " occlusal cavities
with the added complication of the missing approximal
wall. After sufficient amalgam has been put into the
cement the portion of the latter which may have oozed
out must be carefully cut away, so as to expose the entire
^^™^"* \"""^ -'^"'^
outer edge of the cavity, includino- the cervical wall fsee
° " ' ^ ^~ amalgam.
Fig. 330).
After this has been done, the matrix may be tied on and the filling
completed as though it were but a simple cavity. Sometimes it is well
If this be
to leave the matrix in place until the amalgam is fully set.
done, care must be taken that no sharp edge or corner of it be left to
wound the tongue or cheek.