Cyclic fatigue of composite restorative materials*

The purpose of this project was to investigate and evaluate dental composite restorative materials classified according to filler particle size (microfill, small particle, hybrid) regarding fracture characteristics and susceptibility to stress corrosion. The composite materials were tested by cyclic fatigue in distilled water at 37 degrees C. No trend was observed between the number of cycles to fracture and the cycling load as a percentage of the modulus of rupture. Linear regression analysis correlation was weak for most of the composites used to determine the stress corrosion resistance constant, which ranged from 0.80 to 12.05. Observation of the fracture interface revealed inter- and intraparticle fracture for the small particle and hybrid composites. The microfills fractured between and through the prepolymerized particles.