Which material is commonly used by dental teams to take impressions for study models?

Impressions for study models in dentistry are primarily taken using alginate, a material that is derived from seaweed. The process involves mixing alginate powder with water to create a viscous paste that is capable of capturing detailed impressions of the teeth and surrounding oral structures.

Alginate sets by undergoing a chemical reaction that involves calcium ions, resulting in a gel-like consistency that maintains the shape of the impression once it hardens. This material is favored due to its ease of use, relatively quick setting time, and ability to accurately reproduce fine details in the mouth. Additionally, alginate impressions are generally used for diagnostic purposes, treatment planning, and the creation of study models, which provide valuable insight for dental professionals.

The other options listed (calcium sulphate, hardened calcium sulphate, and ethyl chloride) do not serve the same purpose in taking impressions for study models. Calcium sulphate is primarily used in dental procedures as gypsum for casting models, while ethyl chloride is a chemical often used as a refrigerant or anesthetic, not for taking impressions. Thus, the selected answer accurately reflects the material commonly employed by dental teams for this specific application in practice.