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288 THE OPERATION OF FILLING CAVITIES.

cavity, and because also of the danger of displacing the gold in the
approxiinal cavity when filling the channel connecting the two fillings.
Every possible (uire should be exercised in ])ncking the gold
Fio. 246. in cavities of this description. 1'he gold should be made
thoroughly cohesive by recent annealing, and be used in pieces
sutficiently small to prevent cjlogging. Such operations are
more or less exposed to view, and the greatest degree of
artistic skill should be bestowed upon them to render tlunu
as pleasing as possible to the eye. The original outline of
the tooth should be restored with the gold, because it pre-
sents a better appearance than a space between it and the adjoining
tooth (Fig. 246).
Classes K and L.—Cavities upon the mesio-livgual or disto-Ungiial
surfaces of the teeth are filled in precisely the same way as those
described under classes / and /. If the cavity be of con-
siderable depth, non-cohesive gold may be used as part of Fig. 247.
the filling, but in any event the bulk of the filling should
be made of cohesive foil (Fig. 247).
Classes 31 and N.— Mesio-incisal ; Disto-'mcisaL—Cav-
ities situated upon the approximal surfaces of the incisors
and becoming confluent with one on the incisal edge require
great care in the matter of packing gold. It is often an
advantage to have the cavity on the approximal surface unite with
a natural or an artificially made one upon the incisal edge, because
much better anchorage can be obtained in such cavities. Cohesive
gold prepared in the form of ribbon or in pellets or cohesive cylin-
ders, if loosely rolled, may be used. The better method is to fill
the undercut at the cervical border of the cavity first, and then bring
the gold toward the incisal edge as squarely as possible, keeping the
mass on a line with the labial and palatal \valls. The
Fig. 248.
operator feels a sense of security when he is able to an-
chor such fillings in an undercut or retaining pit on the
incisal edge. In teeth with broad incisal edges there is
ample opportunity to make a strong retaining hold, but
Mesio-ineisal
where the edge is narrow a lateral cut into the palatal
filling.
wall one-third back from the incisal edge affords a strong
and secure hold for that ])ortion of the filling. Operations of this class
require great thoroughness in the packing of the gold. It should be
very cohesive and when possible condensed with some form of mallet
(Fig. 248).
Class 0.— lleslo-disto-incisal.—Where both approximal surfaces
and the incisal edge are united in one cavity, the better plan is to begin
the filling at the undercut near the cervical border of the distal cavity,