Page 637 - My FlipBook

Fig. 401,

Fig. 4U3.

Fig. 401. A tube with an amalgam test filling. The metal in the center of the filling is a slip
of steel plate, one-hundredth of an inch thick, upon which the touch point makes contact in taking
measurements. This steel is forced into the amalgam filling when finishing the packing.
Fig. 402. One of the steel tubes used for trial fillings. The cavity is eight millimeters in diam-
eter. The tubes are made of tool steel as accurately as possible and a groove cut around the bottom
inside the cavity. They are then hardened and the walls of the cavity and the face of the tube ground
and polished.
Fig. 403. A photograph nf a segment of the margin of an amalgam filling in a steel tube, with
an iimplification of fifty-four diameters. a. The amalgam. n. The steel tube. Tliis amalgam nhowg
no movement whatever.
410