A die is returned from the laboratory with the margin abraded and no longer clearly defined. What is the correct conclusion?

Correct answer: B. The die cannot be used, because a crown made on it will have an inaccurate margin

• A. Trimming further removes still more of the reference and compounds the error.
• B. CORRECT. The die is the exact positive replica of the preparation, and the finish line on the die IS the finish line the crown will be waxed to. Once that margin has been abraded, ditched too deeply or otherwise destroyed, all reference to the true preparation margin is lost. A crown fabricated on it will be over- or under-contoured at the margin, producing an open or overhanging margin and a plaque trap. The die must be remade — which in practice means a new impression.
• C. The margin is developed and read ON THE DIE, not elsewhere on the cast.
• D. Cement lute space is 25–40 µm. It cannot compensate for a lost margin; an open margin is the leading cause of recurrent caries under a crown.

Note: Acceptable marginal discrepancy is generally cited as under 50–120 µm. Ditching the die means relieving the stone just APICAL to the finish line so the margin can be seen — not removing the margin itself. If the margin is unclear on the die, it was probably unclear in the impression, and the honest remedy is a new impression.