During crown delivery (try-in), the crown does NOT seat completely despite seeming to fit. The MOST LIKELY cause is:

Correct answer: C. Tight interproximal contacts (the crown is binding against adjacent teeth before reaching the preparation)

• A. Insufficient occlusal reduction would cause the crown to seat but be too high in occlusion — the crown would seat but hit early.
• B. Incorrect shade affects esthetics only — not crown seating.
• C. Correct. The most common reason a crown DOES NOT FULLY SEAT at try-in is TIGHT INTERPROXIMAL CONTACTS. The crown catches on the adjacent tooth before it can fully seat on the preparation. Test: try the crown without adjacent teeth's influence by flossing around it and applying gentle pressure. Fix: careful adjustment of the proximal contact areas with finishing burs.
• D. Open margins result from poor fit of the crown to the margin — but would allow the crown to seat fully.