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172 THE TECHNICAL, PROCEDURES IN FILLING TEETH.

gutta-percha more and more against the second molar. The
intermittent use of the separator, in conjunction with the gutta-
percha, as will be described later, may be employed.
When the teeth are sufficiently separated, the cavity may
be again oiJened and the excavation finished (with rubber dam
on) by cutting down the weakened lingual wall to the disto-
lingual groove on the lingual surface and enough past it to make
a good finish, as shown in Figures 218, 219. Then the walls are
to be corrected for convenience form and the surfaces finished,
the toilet of the cavity made, and it is ready for filling. In this
case, the filling, as shown in Figure 220, has been built out to a
prominent contact, increasing slightly mesio-distal breadth of
the tooth to promote the excursions of food over the line of its
buccal margin and to protect the as yet undeeayed, broad, flat
proximal surface of the second molar. The movement actually
made in separating in this case was one millimeter. By taking
time for the occlusion to slowly adjust itself to the changed rela-
tions of the teeth, as much as three, or even four millimeters
separation, may be made in teeth, the necks of which have been
allowed to drop together by loss of portions of their proximal
surfaces.
This case is further illustrated in Figures 221, 222, 223, in
disto-linguo-occlusal views of the first molar with its cavity and
with two i^ictures giving differences in the cutting of the lingual
surfaces. In Figures 224, 225, 226, linguo-occlusal views are
given of the same case. These illustrate more clearly the cutting
of the lingual wall.
The cavity as here shown is suitable to receive either a gold
or an amalgam filling. For a gold inlay, it should be modified
in such form only as might be found necessary to gain condi-
tions to allow an impression to be drawn from it without dis-
tortion.
Undermining of angles op bicuspids. In the upper bicus-
pids, the buccal angles are most likely to be undermined first
because of the contact point being well toward the buccal, and
the first beginning of decay occurring just to the gingival of it.
When the angle, either mesial or distal, is so undermined that
the enamel is unsupported by dentin, it should be cut away
to the mesio-buccal or disto-buccal groove respectively. This
groove, though generally so well closed on the buccal surfaces
of the bicuspids as not to be very ai)parent, is still a weak line
in the enamel, at which it is more than usually liable to break.
This undermining is most often seen in the mesio-buccal