Page 131 - My FlipBook

FILLING WITH AMALGAM. 127
Amalgam is admissible only in the bicuspids and
molars.
All cavities filled with amalgam must have continu-
ous surrounding walls during the building of the filling.
We can not build up a corner of a tooth with amalgam and
expect good adaptation to the walls, for the material is plastic,
and, when pressed upon, the whole body of the filling is liable
to movement. To prevent this, complete surrounding walls are
a necessity. Therefore, whenever a cavity presents that
has not four surrounding w^alls, the missing w^alls must
iDe supplied by artificial walls. This is done by the applica-
tion of the matrix. It is to be used in filling all proximate cavi-
ties, and in any others in which one wall is broken down.
Placing the matrix.—When a proximate cavity is other-
wise ready for filling with amalgam, a slip of thin metal plate
(copper, brass, German silver or steel) is cut of sufficient width
to extend from the occlusal surface of the tooth to near the gin-
gival line, or far enough to fully cover the gingival margin of the
cavity, and long enough to encircle about half the tooth. The
rubber dam having been applied before the excavation of the
cavity was completed, this slip is passed between the teeth and
roughly fitted to see that the width and length are right. Then
at the corners to the gingival a little ear is turned with the pliers
that will prevent a ligature from slipping off to the gingival, when
it is drawn tightly around the tooth. Also the cut ends of
the metal should be so bent that the sharp angles will
not cut the ligature. This is now passed between the teeth so
as to cover the proximate portion of the cavity. Then a ligature
is thrown two or three times around the tooth, including the
matrix, tightly drawn and tied. This is often a difficult operation
for the beginner, but after a little experience the manipulation
comes easy enough in most cases. A few cases occur where the
conditions arc unfavorable and try one's wits, but these can be
successfully done by a little effort. When this has been done the
Perry separator is applied over the matrix, or in many cases the
matrix may be held with the separator without the ligature. It
is just as important to separate the teeth for amalgam
fillings as for gold fillings, and on no account should this be
neglected in cases requiring it. After the preparation is other-
-wise complete, a careful examination of the gingival margin of