A specially calcined gypsum derivative similar to plaster of Paris manufactured to provide improved properties of strength and hardness. It is frequently coloured yellow. Dental stone is produced by heating gypsum under steam pressure in an autoclave at 120–150°C (248–302°F). Because of its small particle size and low porosity it requires less water to form a mix than plaster of Paris. Dental stones are classified by the American Dental Association (ADA specification no. 25) according to their properties.High-expansion dental stone compensates for the very high shrinkage of some metal alloys.
Contemporary dental materials, ed. V. B. Dhuru, 199–200. Oxford University Press, 2004.
The American Dental Association classification of dental stone
Impression plaster (plaster of Paris)
Impressions, occlusal registration
Model plaster (β-calcium sulphate hemihydrate)
Study models, denture flask investment
Dental stone (Hydrocal) (α-calcium sulphate hemihydrate)
Dental stone, high strength (Densite) (α-calcium sulphate hemihydrate)
Wax pattern dies
Dental stone, high strength, high-setting expansion
Wax pattern dies for high-shrinkage alloys