Abstract
The influence of boiling water treatment on the surface roughness and surface microstructure of set gypsums was investigated. Typical surfaces before and after immersion in boiling water were compared by means of SEM observation, the Knoop hardness test, and a surface roughness test. The surfaces of set gypsums were rougher than that of an acrylic resin plate, and after immersion in boiling water, highly roughened surfaces and thinner crystal bodies were observed on each specimen under SEM. The knoop hardness of set gypsums was considerably lowered after boiling water immersion. That of die stones was the same or lower than set dental stones. The results showed that even brief immersion in boiling water had profound effects on the dental stone cast, resulting in rougher surfaces and lower hardnesses of set gypsums.
