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304 OPERATIVE DENTISTRY

the remaining cavity "will be found with an objectionable under-
cut hard to manage.
Restoration of a Portion of the Incisal Edge. The general out-
line in this class of cavities when they are simply a notch in the
body of the tooth, is that of the half moon when viewed either from
the labial or the lingual. However the lingual enamel should be
removed for a greater distance root-wise resulting in a lingual
step to provide against the tipping strain. The pulpal wall should
have a groove mesio-distally in its central portion and extend well

Fig. 168.—Incisal cavity for porcelain inlay.

up along both mesial and distal walls, and with the larger cavities
coming out to the cavo-surface angle.
Restoration of the Entire Incisal Edge— Outline Form. The en-
amel is chiseled root-wise till it is firm and will result in a thick-
ness of porcelain at all points equal to at least two millimeters.
Retention is accomplished by the addition of pins, or a generous
lingual step, or both.
In vital cases where pin retention is to be used there should be
cut a V-shaped groove mesio-distally, the spreading angles of