Where should the finish line of a crown preparation ideally be placed?

Correct answer: D. Supragingival

• A. Encroaching on the junctional epithelium violates the biologic width (roughly 2 mm of connective tissue plus junctional epithelium), producing chronic inflammation, bone loss, or recession.
• B. Subgingival margins are associated with greater plaque accumulation, gingival inflammation, and difficulty in impression-making. Use them only when necessary — and never violate the biologic width.
• C. Placing the margin exactly at the free gingival margin is unstable, since gingival levels change with inflammation and recession.
• D. CORRECT. SUPRAGINGIVAL margins are the biologic ideal. They are easier to prepare accurately, easier to record in an impression, easier to finish and clean, produce less gingival inflammation, and permit direct clinical detection of recurrent caries. Subgingival placement is a compromise made only when esthetics demands it, when caries or a prior restoration extends subgingivally, or when additional retention or ferrule is required.

Note: Biologic width rule: keep at least 3 mm from the margin to the bone crest (2 mm attachment + 1 mm sulcus). If you cannot, do crown lengthening.