Prosthodontics & Occlusion · single question
A tooth has only 0.4mm of supragingival circumferential structure remaining. Which of the following is MOST important to consider?
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Correct answer: D. Ferrule effect
The FERRULE EFFECT is critical when minimal supragingival structure exists. The ferrule is the 360° band of tooth structure above the crown margin encompassed by the crown. Minimum ferrule needed: 1.5-2.0mm. With only 0.4mm, there is inadequate ferrule — the tooth is at high risk for fracture. Crown lengthening surgery may be needed to expose more tooth structure.
- A. Incorrect. Esthetics is secondary — a crown with inadequate ferrule will fracture regardless of appearance.
- B. CORRECT. Ferrule effect is paramount — 0.4mm is far below the 1.5-2.0mm minimum, risking catastrophic crown-root fracture.
- C. Incorrect. Occlusal clearance is important but not the primary concern when minimal tooth structure exists.
- D. Incorrect. Margin placement is relevant but secondary to ferrule considerations.
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