Restorative & Materials · single question
To prevent fracture of an all-ceramic (lithium disilicate) crown, the preparation should have:
Show answer and explanation
Correct answer: C. Rounded internal line angles
- A. Incorrect – sharp angles concentrate stress and promote fracture.
- B. Incorrect – undercuts prevent seating and create stress risers.
- C. Correct – rounded internal angles distribute stress and avoid the stress concentrations that propagate cracks in ceramics. (A shoulder/chamfer margin is also recommended for all-ceramics.)
- D. Incorrect – feather edges give thin, fracture-prone ceramic margins; a defined shoulder/chamfer is preferred.
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