环境湿度和温度对石膏材料的固化膨胀、压缩强度及表面硬度的影响

The effects of relative humidity and temperature on the setting expansion,compressive strength and surface hardness of dental gypsum

目的:探讨环境湿度和温度对普通石膏P、混合石膏H、硬质石膏Y和超硬石膏C的固化膨胀、压缩强度及表面硬度的影响。方法:按湿度10%～90%和温度5℃-35%分成8组,每组制取4种石膏材料的试样,测量其固化膨胀、压缩强度及表面硬度。结果:普通石膏的表面硬度和压缩强度、硬质石膏的固化膨胀不受温度的影响(P>0.05),普通石膏的表面硬度也不受环境湿度的影响(P>0.05)。环境温度和湿度对于4种石膏的固化膨胀均有影响;4种石膏在25℃以上、湿度30%以下和90%以上环境中均会发生收缩(P<0.05),压缩强度和表面硬度也受到温度和湿度影响(P<0.05),在上述环境下均表现以下规律:普通石膏<混合石膏<硬质石膏<超硬石膏。结论:为保证较高的表面硬度和压缩强度,应尽量避免模型暴露于高温(25℃以上)、高湿或低湿(高于90%或低于30%)环境中。

Objective： To study the effects of relative humidity（ RH） and temperature（ Temp） on the setting expansion,compressive strength and surface hardness of dental gypsum（ common gypsum P,mixed gypsum H,artificial stone Y and die stone C）. Methods：Specimens of 4 types of dental gypsum were made in 8 different conditions,which differ in RH 10% ～ 90% and Temp 5 ℃ ～ 35%.Then relevant specimens were used for the test of setting expansion,compressive strength and surface hardness respectively. Results：RH and Temp significantly affected the setting expansion,compressive strength and surface hardness of all 4 types of dental gypsum（ P 〈0. 05）. All 4 types of dental gypsum demonstrated contraction in the conditions of high temperature（ above 25 ℃）,low RH（ under 30%）and high RH（ above 90%）. In general,it was constantly observed that common gypsum showed smallest value for compressive strength and surface hardness,followed by H,Y and C. Conclusion： To get higher compressive strength and surface hardness,it is advised to avoid storing plaster model in the conditions with hign temperature（ above 25 ℃） and high or low RH（ above 90% or under 30%）.