Gypsum product having least expansion:: (A) Impression plaster, (B) Model plaster, (C) Stone plaster, (D) Die stone
Answer is D. DENTAL STONE, HIGH STRENGTH (TYPE IV)
The principal requisites for a die material are strength, hardness, and minimal setting expansion. To obtain these properties, modified α-hemihydrate is used. The cube-shaped particles and the reduced surface area produce such properties without undue thickening of the mix. This material is also called die stone.