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292 THE TECHNICAL PEOCEDUEES IN FILLING TEETH.

same instrument. This plan of finisliing fillings and the instru-
ments for it was a legacy left to us by the older operators.
After the discovery of the cohesive property of gold, the
use of non-cohesive gold was rapidly abandoned for the cohe-
sive. Although the change of plugger points to correct forms
for packing cohesive gold was made rapidly, the old instru-
ments for finishing fillings were retained. Almost immediately
the effort to build fillings to restore the original contour of the
tooth was begun. There had not, however, been that close study
of tooth forms that enabled dentists to do this successfully;
neither did they have suitable instruments with which to accom-
plish good results. With these conditions most dentists con-
tinued to file the proximal surface fillings flat with the separating
file, as before, but, by using thinner files, left the spaces between
the teeth much narrower than before. The result was much
disaster caused by lodgment of food between these flat sur-
faces. This food material was crowded onto the gum septum
and was held there as a breeding place for microorganisms,
whicli caused acid fermentation and brought about rapid recur-
rence of decay at the gingival margin of the fillings. It has been
a labor of many years to correct these customs and the resulting
conditions, and it is yet one of the acknowledged difficult points
in filling teeth. Many dentists spend more time in the endeavor
to finish proximal fillings to form than in placing the fillings.
In order to present the instruments now thought best for
this work, the uses of each and the fonn of the finished filling,
the same illustration of a molar tooth with a broad mesial cav-
ity, used to illustrate the placing of proximo-occlusal fillings,
will be the basis of a series of twenty-four illustrations, Figui'es
375-398. Figure 354 shows the filling when the packing of gold
has been completed. It is sliown divested of the rubber dam
and separator that the form of the tooth and filling in all parts,
and the instruments to be applied, may be better seen. But in
all of the illustrations, positions of instruments that may be
obtained with these appliances in place have been used, or the
exceptions will be carefully noted.
Separation. When the cavity, such as illustrated, is filled,
the i^roximating tooth is in position to make contact with the
filling, and, although the separator is in place and the teeth sep-
ai'ated to make room for finisliing, the filling is carried out firmly
against the proximating tooth in building out the part that shall
serve as the contact point. This excess may be cut away as the
first sto]) in the finisliing. Or, in some cases the teeth may be