Compressive creep of posterior and anterior composite resins in water

The compressive creep and the recovery of commercially available composites, 2 kinds for posterior and 2 kinds for anterior use, in water were examined. In posterior composites, creep strain after 500h at a stress level of 8.3 kgf/mm2 was significantly small (within 1%). The results of the compressive creep test showed that posterior composites would be resistant to occlusal stress. Creep strain was higher in anterior composites than that in posterior composites because of their lower inorganic filler content. The rate of recovery of composites was rapid immediately after the creep test. The water sorption of composites after 500h test was almost constant at some reduced stress levels, especially in posterior composites.