Comparison of Tap Water, Distilled Water and Slurry Water on Surface Hardness of Gypsum Die

The aim of this in vitro study was to evaluate the effect of three liquid types including tap water, distilled water and slurry water on surface hardness of type IV gypsum (GC Fuji Rock, Japan). For each studied groups, 10 dies were produced according to the manufacturer`s instructions whereby gypsum powder were mixed with three different liquids. Twenty four hours after producing the dies, hardness measurement test was carried out by way of microvickers and using the set (MATSUZAVA, MHT2, Japan) and penetration time of 5 sec and power of 25 g. The test was carried out on three points of each die`s surface and averages of hardness of dies were measured. The obtained data were evaluated by using of one-way ANOVA test as well as Tukey test using SPSS program. Results showed that the average of surface hardness between the three studied groups, have significant statistical differences with each other (p< 0.001). In the range of this study, it was shown that distilled water and slurry water produced the most and the least surface hardness when they mixed with gypsum type IV respectively.