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G6 OPERATIVE DENTISTRY

is broken away to give access form for the free passage of the dam
and ligature, which should now be placed and the cavity super-
ficially sterilized.
Occlusal Outline. When the cavity has been rendered dry the
occlusal outline should be proceeded with. This is carried out as
previously given in the forming of the step portion, and the full
satisfaction of the rules given in Outline Form, Chapter V.
Removal of Remaining Decay. This is an instance where the
sixth step in cavity preparation comes in third and should now
be cautiously proceeded with.
Technic. Large spoons should be used. The softened and dis-
colored dentine should be lifted from its position with as little pres-
sure pulp-wise as possible. If exposure exists upon its removal, pulp
treatment for devitalization and removal is the immediate pro-
cedure. If exposure does not exist and the operator has reason
to believe that that organ is healthy the pulpal and axial walls
should be lightly scraped with large spoon excavators, the walls
disinfected with the favorite drug, then dried, phenolized and dried
again, the latter precaution to prevent thermal shock to the pulp
during the remaining portion of cavity preparation, the impera-
tive necessity for which is shown when pain is induced by a blast
of air from the chip blower.
Resistance and Retention Forms. "When the central portion of
the decay is fovuid to be deep and no exposure exists, the pulpal
and axial walls should be left in their central portions much as de-
cay has left them, no attempt being made to flatten these walls on
a plane of their greatest depth as pulp exposure may result. The
line angles surrounding these two Avails should be established on
higher levels.
The Gingival Wall should be made flat in every direction. This
is accomplished by lowering the point angles root-wise to the level
of the central portion.
Convenience Form. Every part of the cavity should be exam-
ined to see that it is accessible to direct force in the packing of
the filling and a convenience point cut in each of the gingivo-axio-
lingual and gingivo-axio-buccal point angles.
Pulp Protection. The cavity should be flooded with an efficient
non-irritating disinfectant, dried, phenolized and again dried. If
the pulp is in danger it should be protected as described in Chap-
ter XXXIV.