[Creep characteristics of Bis.GMA-Tri.EDMA based composite resins].

The creep of chemical activated and visible light activated composite resins was studied using a transverse testing instrument. In addition, the water absorption of their materials was measured, and the effect of the moisture on creep behavior was discussed. The water absorption properties of chemically activated composite resin were smaller than those of light activated composites. However, the former's creep strain increased markedly, in comparison with that of light activated resins. This result indicates that the phenomenon may derive from differences in the reaction accelerators of the composites. Increases in filler content reduced creep strain. Furthermore, the setting reaction of both types of resins was seen proceeding over a fairly long period.