Restorative & Materials · single question
When preparing for an onlay, you notice sharp internal line angles in the preparation. What should you do?
Show answer and explanation
Correct answer: A. Round all internal line angles
A) Round the internal line angles — CORRECT.
For ceramic/porcelain restorations (onlays, inlays, crowns), INTERNAL line angles must be ROUNDED. Sharp internal line angles create stress concentration points in ceramic materials, leading to fracture of the restoration. Principles of ceramic preparation: rounded internal angles, adequate reduction for porcelain thickness, butt-joint or shoulder margins (not chamfer for ceramic).
B) Discard the preparation: Not necessary — the preparation can be corrected by rounding the angles.
C) Proceeding is incorrect — sharp angles will cause ceramic fracture.
D) Liner: Does not substitute for proper preparation geometry.
For ceramic/porcelain restorations (onlays, inlays, crowns), INTERNAL line angles must be ROUNDED. Sharp internal line angles create stress concentration points in ceramic materials, leading to fracture of the restoration. Principles of ceramic preparation: rounded internal angles, adequate reduction for porcelain thickness, butt-joint or shoulder margins (not chamfer for ceramic).
B) Discard the preparation: Not necessary — the preparation can be corrected by rounding the angles.
C) Proceeding is incorrect — sharp angles will cause ceramic fracture.
D) Liner: Does not substitute for proper preparation geometry.
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