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Restorative & Materials · single question

A porcelain veneer on tooth #9 debonded. Given that the preparation had excessive axial taper, what is the most likely cause of failure?

  1. Excessive taper of the preparation reduced resistance and retention form, predisposing the veneer to debonding
  2. Occlusal trauma alone, unrelated to the preparation design
  3. The choice of luting cement alone
  4. Patient noncompliance alone
Show answer and explanation

Correct answer: A. Excessive taper of the preparation reduced resistance and retention form, predisposing the veneer to debonding

Adequate resistance/retention form depends on appropriate preparation geometry. Excessive axial taper reduces the surface area and frictional/mechanical retention available for bonding, making the restoration more dependent on adhesive bond strength alone and more prone to debonding under function.

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