Which of the following is a type of gypsum used in dental applications?

Calcium sulfate hemihydrate is widely recognized as a type of gypsum used in dental applications. It is a key material in dentistry for creating dental casts, molds, and other forms due to its ability to set and harden quickly when mixed with water. This form of gypsum, commonly referred to as dental plaster or stone, has a favorable property profile, making it suitable for producing accurate and detailed reproductions of dental impressions.

Gypsum itself is derived from the mineral gypsum, which consists primarily of calcium sulfate dihydrate. When the dihydrate form is heated to remove water, it transforms into the hemihydrate, which is the active form used in most dental applications. The other substances listed, such as calcium carbonate and calcium chloride, do not possess the same properties that make calcium sulfate hemihydrate ideal for use in dentistry. Calcium carbonate is primarily used in other contexts, and calcium chloride has applications in different chemical processes, but neither is suitable for the precise needs of dental mold and model fabrication.