Why is it necessary to keep the preliminary alginate impression moist?

Keeping the preliminary alginate impression moist is essential primarily to prevent distortion. Alginate is a hydrophilic material, and if it dries out, it can cause the impression to lose its shape and detail. The alginate relies on the moisture to maintain its structure; as it dehydrates, it can shrink or warp, leading to inaccuracies in the final cast or model created from the impression.

While there may be aspects of shape retention and detail enhancement associated with moisture, the critical factor is that moisture ensures the integrity of the alginate. Without proper moisture, the impression can be compromised, affecting the quality of the dental work that follows. Keeping the impression moist allows for better reproduction of oral structures, contributing to more accurate diagnostics and treatment planning.