a. 90 degree b. 150 degree
c.<90 d. 180
The angle at the junction of the walls of the cavity preparation and the external surface of the tooth.
It is of two types
[Ref Sturdevant 4th ed. Pg 300]
Lap / Slip joint
90o cavosurface angle
Advocated in amalgam restorations because amalgam is a brittle material and has low edge strength
Butt joint produces maximal strength for both tooth and amalgam.
It is also advocated in silicate and porcelain restorations
> 90 degree cavosurface angle.
Advocated in cast and composite restorations
30 – 40o marginal metal and 140 – 150o cavosurface angle.
Beveling enables superior adaptation and burnishability of marginal metal
FOR MORE IN DENTISTRY: VISIT