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RESISTANCE EORM 129
stress of mastication is not great, use the simple mortise form.
(Figs. 154, 155, 156 and 157.)
Rule 5.—In proximo-incisal cavities, when the involvement
of the incisal edge is extensive, use the double, compound or
Fig. 149. Fig. 150.
Fig. 149.—Step form in a mesio-occlusal cavity on an upper molar.
Fig. 150.—Proximo-occlusal cavity on an upper jnolar. The step form.
Fig. 151. Fig. 152. Fig. 153.
Fig. 151.—Proximo-occlusal cavity involving the mesial and distal fossae on an
upper molar.
Fig. 152.—Cavity running full length of the lingual groove on an upper molar.
Fig. 153.—Cavity involving the central and distal fossae and lingual groove on an
upper molar.
auxiliary mortise form, either in the shape of an incisal step
or a lingual step form (see Figs. 158, 159, 160 and 161).
Technic for Obtaining Resistance Form.
Use inverted cone burs, hatchet and hoe excavators and
straight-edged chisels. All of these cut plane surfaces
stress of mastication is not great, use the simple mortise form.
(Figs. 154, 155, 156 and 157.)
Rule 5.—In proximo-incisal cavities, when the involvement
of the incisal edge is extensive, use the double, compound or
Fig. 149. Fig. 150.
Fig. 149.—Step form in a mesio-occlusal cavity on an upper molar.
Fig. 150.—Proximo-occlusal cavity on an upper jnolar. The step form.
Fig. 151. Fig. 152. Fig. 153.
Fig. 151.—Proximo-occlusal cavity involving the mesial and distal fossae on an
upper molar.
Fig. 152.—Cavity running full length of the lingual groove on an upper molar.
Fig. 153.—Cavity involving the central and distal fossae and lingual groove on an
upper molar.
auxiliary mortise form, either in the shape of an incisal step
or a lingual step form (see Figs. 158, 159, 160 and 161).
Technic for Obtaining Resistance Form.
Use inverted cone burs, hatchet and hoe excavators and
straight-edged chisels. All of these cut plane surfaces
