The MOST appropriate occlusal finish line design for all-ceramic crowns (ACCs) is:

Correct answer: B. Shoulder (butt joint) or chamfer margins

• A. A knife edge margin is the same as feather edge — contraindicated for ceramics.
• B. Correct. All-ceramic crowns require a SHOULDER or CHAMFER margin. The shoulder (90° finish line) provides bulk of ceramic at the margin for strength and reduces stress concentration. The chamfer provides a curved finish line that allows adequate ceramic thickness. Both are acceptable for ACCs.
• C. A bevel creates a thin, acute ceramic margin that is prone to fracture — not appropriate for full-coverage ceramic crowns.
• D. A feather edge (knife edge) provides inadequate bulk of ceramic at the margin and creates a very thin, fragile edge that is prone to chipping or fracture — contraindicated for all-ceramic restorations.