Prosthodontics & Occlusion · single question
What type of margin preparation is used for a VENEER on a tooth with incisal WEAR (window preparation)?
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Correct answer: D. Shoulder margin
For porcelain veneers with an INCISAL REDUCTION (window/wrap preparation involving the incisal edge): a SHOULDER (butt joint) margin is used at the incisal edge to provide adequate bulk of porcelain and proper support. For veneers with NO incisal reduction (traditional preparation), a chamfer margin is used. When the incisal edge is included in the preparation (as with wear cases), a shoulder provides the structural support needed for the ceramic.
- A. Incorrect. A chamfer margin is used for veneers WITHOUT incisal reduction and for all-ceramic crowns. For incisal wear veneers, shoulder is needed for structural support.
- B. CORRECT. A shoulder (butt-joint) margin is used when the veneer preparation includes the incisal edge (as in cases with incisal wear) — it provides maximum porcelain thickness and support.
- C. Incorrect. Featheredge/knife-edge margins are used for full-coverage metal crowns — they provide insufficient support for ceramic veneers.
- D. Incorrect. Bevel margins are used to expose enamel rods for bonding in some preparations — not standard for the incisal portion of a veneer.
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