2022 Volume 41 Issue 2 Pages 162-172
This study aimed to examine setting expansion pressure (SEP) changes of dental α and β-calcium sulfate hemihydrates and analyze the effects of their water-powder ratio (W/P), water temperature, mixing time, and type of α-calcium sulfate hemihydrate on the maximum SEP using a universal testing machine. After mixing, SEP remained at zero for approximately 10 minutes. Subsequently, it dropped below zero, but quickly returned to a positive value, and continued to increase. Approximately 80 to 120 minutes later, it reached the maximum pressure level, and then remained constant. Specifically, this study detected either a fine and stepwise pressure increase or decrease while SEP of both α and β-calcium sulfate hemihydrates increased. Additionally, the larger W/P of both hemihydrates, the lower their SEP. However, the water temperature and mixing time did not have any effects on it. In contrast, the type of α-calcium sulfate hemihydrate had a marked impact on the maximum SEP, indicating that additive agents to suppress setting expansion reduced the maximum SEP. Taken together, the measurement used in this study has potential to be a novel tool to investigate setting phenomena associated with the hydration reaction of calcium sulfate hemihydrates.
