Which gypsum product is most appropriate for creating a durable, highly accurate die for crown and bridge fabrication?

• A. Plaster
• B. Dental Stone Type III
• C. Dental Stone Type IV
• D. Dental Stone Type II

Answer: (C)

When making a die for crown and bridge work, you want a gypsum product that stays true in size after it sets and stands up to carving and handling. That means high compressive strength and very low setting expansion, along with good detail reproduction and wear resistance. Dental Stone Type IV is designed for dies exactly for this reason. It has fine fillers that increase strength and greatly reduce setting expansion, so margins remain accurate and the die resists chipping as you trim and inspect the crown prep.

Plaster and the lower-strength dental stones either expand more as they set or wear more quickly, which can blur margins and compromise fit. Type III is stronger than plaster but does not offer the same level of dimensional stability or surface hardness as Type IV. So, for a durable, highly accurate die, the best choice is Dental Stone Type IV.