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122 PREPARATION OF CAVITIES

(2) On the Technic Block.— (a) With a pencil draw the

outHne form, (b) With chisels and excavators remove enough
of the tooth substance to establish a definite cavity.

MESIAL
BUCCAL

UNGUAL
BUCCAL
DISTAL
MESIAL

DISTAL LINGUAL
Fig. 129.—Outline form. Occlusal cavi- Fig. 130.—Outline form. Occlusal
ties in upper molar. cavity in upper molar involving central
and distal fossae and lingual groove.

(3) 07t Extracted Teeth.— (a) With a pencil draw the
outline form, (b) With the chisel cut away the overhanging
and unsupported enamel, (c) If necessary to extend further,

first remove the underlying dentin with excavators (hoes,

BUCCAL

DISTAL
MESIAL
DisrAL
MESIAL

LINGUAL LINGUAL
Fig. 131.—Outline form. Occlusal Fig. 132.—Outline form. Occlusal cav-
cavity in an upper third molar with ity in the lower first molar,
three cusps.

hatchets and spoons) and then chisel the enamel the desired
distance.
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The Technic for obtaining outline form when operating
in the mouth is herewith given.