Characterization of an anti-foaming and fast-setting gypsum for dental stone.

Objective: An anti-foaming and fast-setting gypsum for dental stone recently became available on the market. Interestingly, this product can be mixed by the cocktail shaking method, providing a more convenient way to obtain high reproducibility when fabricating error-free study models for digital dentistry. The aim of this study is to investigate setting time, surface bubble formation, and other gypsum characteristics of three dental stone products with different mixing methods.

Methods: Shake mix stone (SM), new plastone 2 white (NP), and Hi-Koseton (HK) were chosen. Using different mixing methods (cocktail shaking, hand mixing, hand mixing+vibrating, and hand mixing+vacuum process), the characteristics of dental stone were investigated according to ISO 6873. Powder size, morphology, and thermo/chemical analyses were performed.

Results: Regardless of the method of mixing, SM exhibited the fastest setting time (3-4min) and the smallest number (˜10% versus HK) and area (˜30% versus HK) of surface bubbles among the investigated products, while setting expansion, mechanical properties such as compressive/impact strength and microhardness and detail reproduction before and after digital scanning were similar. A smaller size (˜1.5μm) and unidentified additives were revealed as possible reasons for the above anti-foaming and fast-setting characteristics.

Significance: Anti-foaming and fast-setting characteristics of a developed gypsum for dental stone were confirmed even with shaking.