During preparation for a ceramic ONLAY you note sharp internal line and point angles. What should you do?

Correct answer: C. Round the internal line and point angles

• A. Sharp internal angles do not add meaningful retention to a bonded ceramic restoration, which is retained by adhesive cementation and by its taper — and they materially increase the fracture risk.
• B. Deliberately sharpening internal angles maximises the stress concentration and is the opposite of correct technique.
• C. CORRECT. Sharp internal angles concentrate STRESS. Ceramic is brittle and fails by crack propagation originating at points of tensile stress concentration, so a sharp internal angle becomes the origin of fracture in the restoration. Sharp angles also prevent complete seating of the restoration, trap air in the impression and the cement, and create voids. All internal line and point angles in a ceramic preparation are therefore ROUNDED, while the external outline stays smooth and flowing.
• D. There is no need to escalate to a full crown. The preparation is correctable by rounding the angles with a suitable rotary instrument; unnecessary removal of sound tooth structure violates minimally invasive principles.

Note: Contrast with AMALGAM, which is retained mechanically and requires defined internal form with sharp, well-defined cavosurface margins at 90 degrees. Bonded ceramics need the reverse: rounded internal angles, smooth flowing outline, and no unsupported enamel.