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144 THE techiticaij pkocedtjees in filling teeth.

tooth is to be absent permanently and the decay in the mesial
surface is well to the gingival, and the marginal ridge well sup-
ported by dentin, a simple proximal filling may be justified. Also
in a few cases of decay beginning near the gingival line in old
people (so-called senile decay) this may be done to avoid the
great amount of cutting that would be required. Cases for this
plan of procedure should be confined to those of the most urgent
necessity of shielding the patient from prolonged discomfort in
the chair in cases that can be most easily approached from the
buccal surfaces in such a way as to make the operation reason-
ably good.
Extension limited by sepaeation of teeth. Figures 161,
162, 163, illustrate the opposite condition to that given in Figures
155-160. In these, flat surfaces of the second bicuspid and first
molar are lying together, as shown in Figure 161. A prepared
cavity so narrow as that shown in Figure 157 will not do, but
by separating the teeth and building out a prominent contact as
shown in Figure 162 or 163, the case is, without excessive cutting,
brought into good form for the perfect cleaning of the marginal
lines of the filling by the excursions of food. The result is
brought about principally by wedging the teeth apart, or separat-
ing them sufiiciently to build out a prominent contact point. This
plan not only protects the margins of the filling in the bicuspid
but also places the, as yet undecayed, mesial surface of the first
molar in much better condition to escape decay. In Figure 163
the case is made much safer by just a little further extension of
the buccal wall of the cavity, showing what just a little bit of
cutting will do at a point where the two proximal surfaces are
rounding away from each other.
In Figures 217-220, classed under "Management of Frail
Walls," the same plan has been used, and may be used to advan-
tage in a large number of cases in practice. In many cases, par-
ticularly where the susceptibility to dental caries is very great,
wide cutting to bring the margins of the cavity into the cleanest
area of the angles of the tooth, which will be illustrated as we
proceed, becomes necessary to the highest degree of success. But
under no circumstances should extension be carried around the
angles of the tooth onto a buccal, labial or lingual surface with
the idea of extension for prevention of recurrence of caries, for
the reason that the angle of the tooth is the safer place under all
ordinary conditions. In cases of rotated teeth, or teeth in abnor-
mal positions in the arch, lines corresponding to the changed rela-
tions must be chosen.