AN EXPERIMENTAL STUDY ON HARDNESS IN COMPOSITE RESINS

수종복합레진의 경도측정에 관한 실험적 연구

The purpose of this study was to measure micro-knoop hardness and coefficient of thermal expansion on composite resins (Epolite, Adaptic, Hipol and Compo T.) Four different type of composite resins were measured at the varying depth of 30, 60, 90, 150, 200, 400, 700 and 1000 micron from the surface to deep portion. The specimens were stored both in the air room temperature for 2 days, 30 days and in water at $37^{\circ}C$ for 30 days. Thermal expansions of specimens(4mm in diameter and 50mm in height) were measured in quartz tube dilatometer from $20^{\circ}$ to $70^{\circ}C$ The following results were obtained. 1. The hardness of superficial portion were lower than inner portion of resin. 2. The value of hardness obtained from the specimen stored in room temperature in the water at $37^{\circ}C$ for 30 days were lower than above described Cases. 3. The coefficient of thermal expansion of Adaptic had $29.75{\times}10^{-6}/^{\circ}C$, Hipol had $30{\times}10^{-6}/^{\circ}C$, Epolite had $39.85{\times}10^{-6}/^{\circ}C$ and Compo T had $36.95{\times}10^{-6}/^{\circ}C$.