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FILLING TEETH jj

pit at this part out of the question, a mere cutting
of this wall at right angles to the floor is all that
can be done. In many cases, where, owing to
breaking down, or frailty, of the lateral walls, the
retainage is rendered doubtful, the cervical cutting
may be supplemented by extending the cavity well
across the lingual surface, and slightly undercutting
the dentine at this part. By this extension a frail
or shallow lingual wall may be converted into a
strong and most useful one. Care must be taken
in doing this, and the extension had better be broad
and shallow, rather than narrow and deep, so as to
avoid cutting too near the pulp.
Dr. Black's method in these cavities, is to cut the
cervical wall flat at right angles to the floor, and to
extend it in the region of the cervico-labial and
cervico-lingual angles as far as practicable. The
cutting edge of the cavity is made at right angles
to the floor, and the labial wall is also cut at right
angles to the floor. The lingual wall is squared out
in the same way, wherever its thickness will admit of
this being done. This generally means a squaring
out at the cervical portion of this wall, and, if prac-
ticable, a little squaring out near the cutting edge.
When the cavity involves the cutting edge of the
tooth, or approaches it so closely that a break may