Comparison of Some Properties between Commercially Available Gypsum Products

Gypsum models are often used in dental healthcare, and there is an increased need for manipulation of master casts in extensive reconstructions requi ring a material that is not easily abraded or damaged with dimensional accuracy, accurate reproduction of details, and the use of a voids free surface master model. This study was conducted to compare between commercially available type III and type IV dental stones in some of their properties. Four groups were compared: Zhermack and Geastone of Type III dental stone, and Zhermack and Bluejey of Type IV improved dental stone. Ten specimens were fabricated for each material from a rubber ring w ith dimensions of 20mm height and 30mm diameter. Dimensional stability, reproduction of details, surface porosity, and surface hardness were evaluated for the different gypsum products. Results of this study show that for the dimensional stability there was an increase in dimension more than that of the test block and was only highly significant for groups Z3 and Z4. The surface hardness for groups Z3 and Z4 was significant higher than groups G3 and B4 in all of time intervals except after 24h for groups Z4 and B4 this was insignificant. Surface porosity test and reproduction of details test, both revealed no significant difference between the test groups. As conclusion the Zhermack dental stone products, type III & IV, showed higher surface hardness than Zeus dental stone products, type III & IV (Geastone and Bluejey). On the other hand we found that Zeus dental stone products showed good dimensional stability than the Zhermack dental stone products. All stone products provided similar scores for details reproduction, and were similar in relation to surface porosity.