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What retards gypsum materials?
Borax and Sodium citrate
Hydrofluoric acid
Potassium sulfate
Sodium chloride
The correct answer is: Borax and Sodium citrate
Borax and sodium citrate work as retarders for gypsum materials. These additives slow down the setting reaction of gypsum, which is crucial in dental applications where working time and setting time need to be controlled. Borax and sodium citrate help to extend the working time of gypsum products, allowing dental professionals to pour models accurately without the material setting too quickly. This is in contrast to the other options provided: - Hydrofluoric acid is a corrosive liquid and is not used as a retarder for gypsum. - Potassium sulfate is not typically used as a retarder for gypsum materials. - Sodium chloride (table salt) does not retard gypsum materials; in fact, it can actually speed up the setting reaction if added in large quantities.