Page 76 - My FlipBook

CHAPTER XIV.

MANAGEMENT OF PROXIMAL CAVITIES IN INCISORS AND
CUSPIDS NOT INVOLVING THE ANGLE. (CLASS
THREE.)

Definition. Class Three cavities are those in the proximal of
incisors and cuspids where it is not necessary to restore the incisal
angle. The angle may be allowed to remain when the enamel at
the angle is supported by sound dentine to an extent which will
give it sufficient resistance to prevent fracture under stress of
mastication.
General Form of Class Three. Cavities in incisor proximal sur-
faces differ from all others in that they are in the surface of teeth
of a triangular form and the cavities of necessity must be of this
form, rather than the typical box shape in the other classes of
cavities.
Location of Primary Decay. The location of primary decay, as
with all contact decay, is just gingivally from contact point. This
will result, as a rule, in the seat of initial decay being about mid-
way from the incisal edge to the gingival outline. As the plates
of enamel, l)oth labial and lingual, are quite heavy and usually
removed from direct stress, there will generally be considerable
loss of dentine while the enamel walls are yet intact. The decay
may be apparently small, yet reflected light by the use of mouth
mirror will shoAv a discoloration of a well defined area. The
curved tine of an explorer may or may not enter from either the
labial or lingual embrasure.
Opening the Cavity. Bathe the surfaces of all the anterior teeth
in that jaw Avith water to free them of micro-organisms and gummy
material, particularly the gingival border, and apply the mechan-
ical separator.
Gaining Access. With a small straight chisel of about one milli-
meter in width cut away the enamel edge, throwing the chips into
the cavity. Adequate finger rest must be secured before applying
the chisel and only small portions of enamel engaged at each ap-
plication, as a failure in either respect may result in checking the
enamel to a greater extent than desired. When sufficient entrance
has been made to the cavity to admit the instrument, the remain-
ing enamel margins may be planed from this direction until a liga-
72