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FILLING CAVITIES WITH GOLD, BY CLASSES. 275

ing with cohesive gold is the same in every respect as if the non-
cohesive gold had not been used, except that it will be necessary
to continue the use of the assistant plugger for a longer time
before the mass is perfectly secure in its position.
The flat cylinder or mat is made by first folding a sheet of
foil, or such part of a sheet as may be reriuired, to the right
width, and then rolling the ribbon formed upon a flat steel instru-
ment of suitable width. The length of the cylinder is controlled
by the width of the ribbon, and the breadth is controlled by the
width of the flat instrument. The length should be such that when
placed flat upon the gingival wall with one end against the axial
wall, the other end protrudes over the gingival cavo-sui'face angle
of the cavity. The breadth should be such that it will extend
fully from the buccal wall to the lingual wall and require some
crowding to make it lay flat. Simply lay this in position, as
shown in Figure 356, press it lightly to the cavity wall and into
the convenience points, as shown in Figure 357, and begin build-
ing upon it practically as has been described for beginning with
all cohesive gold.
Instead of this flat cylinder or mat, ordinary round cylinders
may be used by laying the first in the linguo-gingival angle, a
second in the bucco-gingival angle, and crowding a third between
the two, as in Figures 358, 359. Or, two cylinders may be used
that have breadth enough to fill the space from buccal to lingual.
Do not condense the non-cohesive gold before beginning with the
cohesive. Merely adjust it in position with gentle pressure, as
in Figure 360, and condense it by building cohesive gold upon it.
Then proceed as in all cohesive gold work, except that, after the
filling is otherwise finished, the gingival portion should receive
very thorough after condensation.
The reason that non-cohesive gold is safer in this position
is that there is less disposition to curl from the margin, and if
the margin is not absolutely close, it is easier to make it tight
by the after condensation, because, if not tight, it moves readily
under the blows of the mallet, while cohesive gold does not. Gen-
erally a considerable quantity of non-cohesive gold may be used
in this way and greatly reduce the labor of making the filling.
Yet, caution should be carefully exercised in the amoimt of non-
cohesive gold used. If the gingival wall is broad, as in a deep
proximal cavity, and the step in the occlusal surface is very good
and reliable, much more non-cohesive gold may be used — a
greater thickness — than in a case in which the proximal cavity
is shallow and the gingival wall narrow. Also when a thick mass