Page 44 - My FlipBook

After the frail walls of enamel have been re-
moved with a chisel, a knife-edged carborundum
Ccchniquc of
Step and Gaulty should be used to remove the remaining enamel of
Preparation. the labial wall. A small narrow stone should then be
used to grind the enamel on the lingual surface from
the gingival wall to incisal edges. After the enamel has been partially

Fig. 28 C. Fig. 29.

removed from the lingual surface, flat faced fissure and diamond burs
in the right angle should be used to cut the enamel so that it will have
proper marginal form and to remove enough of the dentine to give the
step proper depth (Fig. 26). With a fissure bur in the straight handpiece
the labial and pulpal walls should be so prepared that they will unite in
the form of an obtuse angle. A shallow groove should run along the
gingival wall. Another groove should be made at the union of the axial
and pulpal walls of the step from the gingival wall to the incisal edge
(Fig. 26 A).
Or a step may be prepared involving the middle and gingival thirds
(Fig. 27). It should extend laterally far enough to give sufificient reten-
tive resistance. The gingival and incisal walls which should unite with the
axial wall in curves should converge slightly toward the a.xial wall of the
step. The pulpal wall of the step should be flat and should be so pre-

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