Calcium Sulfate Hemihydrate Lab Report

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INTRODUCTION
Gypsum is scientifically named calcium sulfate dehydrate with the formula (CaSO4.2H2O). It is known to be a white powdery substance that is a naturally occurring mineral. The main form of calcium sulfate dehydrate used in dentistry is named calcium sulfate hemihydrate with the formula (CaSO4)2.H2O. Gypsum is mainly used for dental restorations and applications to replicate the patients’ oral cavity. Dies and models are created using the 5 gypsum products; impression plaster (Type 1), model plaster (Type 2), dental stone (Type 3), dental stone with high strength and low expansion (Type 4) and dental stone with high strength and high expansion (Type 5). In dentistry the gypsum products that are being used are chemically similar
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However it is porous and also it has got irregular shape. Dental Stone (Type III)
Dehydration of gypsum under pressure in 125 degrees Celsius produces dental stone. This form of hemihydrate is called α-calcium sulfate. The powder particles of stone are much more regular (uniformed) in shape and it has higher density compared to model plaster. Dental Stone with High Strength and Low Expansion (Type IV)
After accomplishment of dehydration, another chemical such as 30% calcium chloride or magnesium chloride is added whilst boiling of gypsum product. The chlorides are later washed with hot water and since the solubilities of the hemihydrate and water are the same, it does not go into forming calcium sulfate dihydrate in presence of hot water. Furthermore, the powder that has been given out is the densest of all the gypsum types. Dental Stone with High Strength and High Expansion (Type V)
The production of dental stone with high strength and high expansion is the same as type IV production. However they do differ in the way that type IV contains extra salts and therefore has reduced expansion during

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