Abstract
The purpose of this study was to investigate the effects of testing temperature(5〜50℃), absorbed water and thermal cycling on composite restorative materials. Three composite resins with different compositions (Isopast, Silar Clearfil-F) and two unfilled PMMA resins (Uni-Fast, Sevriton) which were used as controls, were chosen in order to examine their compression properties, and stress relaxation and surface characteristics. The resistance to compression of all materials tested decreased proportionately with an increase in the testing temperature. A high resistance was observed for two composite materials, Silar and Clearfil-F. Isopast, consisting of an MFR composite, had a resistance value which was lower than that of the unfilled resins. The effect of absorved water on the compression properties was less than that of temperature. However, a relatively larger absorbed water effect was observed for Isopast and Sevriton compared with the other materials. Although the rate of stress relaxation was hardly changed at temperatures below 37℃, it was greatly increased at temperatures above 37℃ in all materials except Silar. Thermal cycling (within 2, 000 times) had little affect on the compression properties, the rate of stress relaxation and the surface characteristics of the cured composite resins.
