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FILLING TEETH 127

trim and smootli a roiigli amalgam tilling when it is
completely set, especially on the approximal sides of
bicuspids and molars ; and in these positions it is
usually a painful process for the patient, owing to
the free use of trimming and polishing tapes below
the gum, necessitated by maintenance of contour.
All that should be done when the filling is set, is to
perfect the surface with the finest polishing strips,
pumice-stone applied with wet linen or silk tapes,
followed, if thought necessary, by tapes charged
with chalk or Avhiting. The occlusal and other
equally exposed surfaces can, of course, be easily
ground smooth with stones in the engine, and
polished with wooden points or leather buffs, and
a suitable powder ; although the necessity for any
grinding is done away with by careful scraping and
smoothing at the time the filling is made.
Dr. Flagg has pointed out that whenever amalgam
is squeezed in chamois leather, the mercury appears
to come away clean ; while, if the unenveloped
amalgam is squeezed in the fingers, the consistence
of the expelled mercury shows that it is carrying
away with it some of the alloy in solution. This,
however, varies very much, according to the amalgam

used. With some amalgams squeezed in the fingers,
there seems to be little if any thickening of the
mercury, while with others, the squeezed out