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170 FILLING MATERIALS

packed more or less after a process of wedging, but the wedg-
ing principle is carried to its fullest extent with non-cohesive
gold and tin. Owing to the fact that neither of these possesses
the property of cohesion, as the other filling materials do,
they are mechanically wedged into the cavity with great
force, so that each lamina or layer is dependent on the other

to retain it in place. The packing is done with hand pressure,
by means of serrated, wedge-shaped pluggers, the final
condensation being accomplished by means of mallet force.
Owing to the strength of the thrust required for working tin

Fig. 185.—Working gold or tin cylinders (non-cohesive).

and gold by the non-cohesive method, larger handles than
those usually employed are necessary (Fig. 184.)
Two methods are employed, depending on the size of the
cavity and the individual preference of the operator.
1. The Cylinder or Cushion Method.

2. The Ribbon, Roll, or Rope Method.
I. The Cylinder Method.—The cyhnder method is the
more rapid when the size of the cavity will admit of its adop-
tion. The cylinders should be of such length that one end will

protrude above the orifice of the cavity, while the other rests
on the floor or seat. (Fig. 185.)
(i) Place enough cylinders against the wall farthest away