Cavosurface margin angulation in chamfer finish line is:

 # Cavosurface margin angulation in chamfer finish line is:

A. Always 90 degree

B. 90 degree or less than 90 degree

C. 90 degree or more than 90 degree

D. 120 degree

The correct answer is C. 90 degree or more than 90 degree.

Chamfer is an obtuse-angled finish line. Indicated where metal forms the margin of a restoration, e.g. complete metal crown. Should not be given for porcelain restorations as the obtuse angle produces shearing forces which is not well tolerated by porcelain. It is prepared using a round-end tapering diamond. This is produced by sinking in half the diamond into the tooth. The tip produces the chamfer while the sides give the necessary taper to the axial surface. 

Cavosurface angle of less than 90 degree produces a lip of unsupported enamel which fractures easily.

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