Violation
A preparation for a porcelain fused to metal crown with a porcelain butt joint margin should have a 1. 90o cavosurface margin. 2. subgingival finish line. 3. 1.2mm shoulder. 4. 90o axiogingival angle.
(2) and (4)
(1) and (3)
(1) (2) (3)
All of the above.
(4) only