Prosthodontics & Occlusion · single question
During a crown try-in, the crown doesn't seat and has open margins on the distal. What is the most likely cause?
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Correct answer: A. Distal contact is too tight
When a crown doesn't fully seat and shows open margins, the most common and first cause to evaluate is TIGHT PROXIMAL CONTACT. A tight distal contact prevents the crown from seating completely, creating an apparent gap at the margins. This is the most common reason for a crown not seating in clinical practice. Check proximal contacts with floss and adjust accordingly before diagnosing other causes.
- A. CORRECT. A tight DISTAL CONTACT is the most common reason a crown fails to seat fully. The crown is prevented from descending to its proper position by the adjacent tooth, creating the appearance of open margins.
- B. INCORRECT. Occlusal interference would prevent the crown from closing in maximum intercuspation but may not always cause open margins on the distal — tight contact is more directly causative.
- C. INCORRECT. A bad impression could cause poor crown fit, but this is a less immediate diagnosis — checking and relieving the proximal contact is the first clinical step.
- D. INCORRECT. A wrong patient's crown would likely show poor fit in multiple areas, not just the distal, and would be obvious on initial placement.
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