What material is used to create diagnostic casts when strength and accuracy of the model are not critical?

The material typically used to create diagnostic casts when strength and accuracy are not critical is alginate. Alginate is a hydrocolloid impression material that is known for its ability to capture fine details, but its primary applications are in situations where a quick and easy impression is needed, rather than one that requires high strength and durability. It sets relatively quickly and is easy to manipulate, making it ideal for preliminary impressions, study models, and diagnostic casts in a variety of dental settings.

While gypsum is indeed used for diagnostic casts, it is more appropriate in scenarios where durability and precise details are necessary, as it cures to form a strong and stable model. Therefore, it's not the first choice when the primary need is rapid and simple diagnostic information. Resin materials, on the other hand, are typically used for specific applications that demand high strength and detail, such as custom trays or definitive casts. Polysulfide, known for its strong and flexible qualities, is mainly utilized for final impressions in fields where accuracy and mechanical properties are vital, such as in crown and bridge work.

In summary, alginate's characteristics make it the best choice for creating diagnostic casts in situations where strength and precision are not the primary concerns.