SUBSURFACE COMPRESSION FATIGUE IN 7 DENTAL COMPOSITES

Objectives. The purpose of this study was to evaluate subsurface fatigue in seven dental composites. Methods. Cylindrical test pieces were subjected to 2000 compression cycles with a load of 120 N. The area of stained subsurface was measured, and subsequently, the specimens were examined by scanning electron microscopy. Results. The greatest staining occurred in the composites with large quartz fillers, whereas there was little staining in the microfilled materials. Electron microscopy demonstrated very little evidence of cracks, suggesting that silver nitrate stained a network of crazes and microcracks in the subsurface. The pattern of staining indicated that the microcracks formed within the depth of the subsurface rather than by direct nucleation from the indenter. Significance. The different patterns of subsurface damage occurring as a result of compression should be considered when studying the wear and degradation of these materials.