In vitro flexural fatigue limits of dental composites

The flexural fatigue test equipment developed was used to study the fatigue behavior of dental restorative composites, using a "staircase" approach. Three commercial composites were tested after dry and wet storage conditions. The findings indicate that the method is accurate and reliable, and that changes due to water sorption are clearly reflected: The flexural fatigue limit decreases after water sorption. From the present results it seems that under environmentally controlled conditions, the fatigue behavior is characterized by a well-defined fatigue stress level above which the composites tested fail rapidly, and below which they survive.