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FINISHING FILLINGS. 125

trimmed to form, and the contact which has been left flat with
the saw must be rounded. This part of the work is best done
with the file-cut finishing files.
The blades of these files must be sharp to do this work
well. When they have become dulled they are easily sharpened
with slips of Arkansas stone, made for this purpose. Each blade
is to be carefully ground sharp by drawing the stone back and
forth against it. Generally, oil should be used on the stone.
When the edge of the stone has become dulled or gaped it may
be sharpened by whetting on fine emery paper laid flat on a table.
Generally these files may be used with the thumb and palm
grasp, and the flat sides applied to the gold, and with short,
strong strokes almost parallel with the long axis of the tooth,
the excess of gold is quickly removed. As the margins of the
blades of these files are thin and sharp, they can pass well into
the embrasure toward the contact point, rounding the surface
just up to that point without cutting over it. This is done first
on the buccal and then upon the lingual, and the contact point
sharply rounded, and the embrasures, lingual and buccal, rounded
to the proper form.
Obtaining this marble-like roundness of the contact
points is the critical requirement in finishing proximate
fillings. If the surface is cut flat, the contact will grasp and hold
food between the teeth and cause annoyance and pain, and cause
injury to the gum septum by forcing the confined food against it.
Neglect of this precaution has caused the loss of thousands of
otherwise good fillings, and the teeth themselves, either by
causing a recurrence of decay or by inducing disease of the
peridental membrane.
The occlusal surface, if the case be a molar or bicuspid, is to
be trimmed and finished as described for occlusal fillings, after
which corrections are made in the occlusal third of the proximate
surface, and the whole filling polished.
Polishing of proximate surface fillings should be done
partly with tape and partly with disks in the engine. Tapes
should be used for polishing the gingival two-thirds of the sur-
face, or all of that portion of the filling to the gingival of the
contact point, having especial care not to cut away the contact
point. Narrow strips should be used. The embrasures, buccal
and lingual, should be polished with disks, usually not more