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PROXIMAL CAVITIES IN INCISORS AND CUSPIDS 73
lure will pass from the incisal to the gingival line. Where time
Avill permit the case should be packed for preliminary separation
as described in Chapter IV. If immediate separation and filling is
to be practiced the rubber dam should be adjusted and the me-
chanical separator placed and tightened to a snug pressure. The
separator should be tightened from time to time until the required
separation is obtained. The approximate space required is from
one-half to one millimeter M'here only one cavity exists in the prox-
imal, and a full millimeter in cases Avhere two cavities exist.
Outline Form. As these cavities are located in the most exposed
portion of the mouth esthetic reasons demand as little cutting as
possible consistent -with the demands for permanency. HoAvever,

ABC

Fig. 33.—Class Three cavities filled so that the entire cavity outline, excepting that por-
tion covered by gum tissue, is in full view of the operator. The gingival portion of {B) has
been cut sufficiently low to be covered by gum tissue.

it is a good rule, in outlining cavities of Class Three, to extend in
all directions until when the filling is completed, the entire cavity
outline not covered with gum tissue, is in full view of the operator.
(Fig. 33.) As stated before, excessive cutting to obtain this con-
dition may be obviated by proper separation.
The Gingival Outline should be carried midway between con-
tact and gum line, and farther extended to go under the gum when
it approaches to Avithin one millimeter of the gum. Great care
should be exercised to square out both labial and lingual axio-
gingival angles, carrying them sufficiently into these embrasures