You receive the die shown. The trimming cuts extend ONTO the finish line at the proximal margin, and the margin cannot be clearly identified. What should you do?

Correct answer: C. Reject the die — a crown cannot be fabricated on it

• A. Cement is not a substitute for marginal fit. A wide cement line dissolves over time and leaves a plaque-retentive gap at the most caries-prone location on the tooth.
• B. Further trimming compounds the error. The finish line has already been cut away; removing more stone cannot recreate it.
• C. CORRECT. Once the die has been OVER-TRIMMED into the finish line, the margin no longer exists as a reproducible reference. Any crown waxed to that die will be built to a fictitious margin, producing an overhang or a short, open margin — both of which guarantee plaque retention, recurrent caries and periodontal inflammation. A die whose finish line has been damaged must be discarded and the impression re-poured; if the impression itself is defective, it must be retaken.
• D. Margin discrepancies cannot be meaningfully corrected chairside on a cast restoration. Adjusting a fitting surface at try-in destroys the marginal seal rather than restoring it.

Note: Die trimming is done to just BELOW the finish line, leaving the margin intact and clearly visible with a smooth, uninterrupted profile. A ditched die exposes the margin without cutting into it.