Page 304 - My FlipBook

300 OPERATIVE DENTISTRY

in a cavity retentive in all directions except to the labial Avhich
gives it "draw" in this direction.
Lingual Approach. The whole general plan is reversed result-
ing in the retention of all or a good portion of the labial wall and
an entire absence of the lingual wall resulting in the draw being
to the lingual.
To Resist the Tipping Strain the lingual step may be added.
This is done by cutting away a sufficient amount of the lingual en-
amel resulting in two axial walls. One will face the proximal and

Fis 163.—A Class Four cavity incisal Fig. 164.—A Class Four, plan one, inciso-
approach for porcelain inlay. proximal approach for porcelain inlay.

the other the lingual. This creates a line angle where the two
walls unite, the axio-axial line angle which should be a rounded
angle. Just before setting the inlay the axial wall should be slight-
ly grooved next to the surrounding walls, except in the region of
the incisal point angle.
Cavities in Proximal of Incisors and Cuspids Involving the Angle.
Class Four, Plan One. This plan of angle restoration may be suc-
cessfully accomplished with porcelain when the conditions of
stress would permit of this plan being used with any other ma-