SUBSURFACE COMPRESSION FATIGUE IN 7 DENTAL COMPOSITES

Objectives. The purpose of this study was to evaluate subsurface fatig ue in seven dental composites. Methods. Cylindrical test pieces were s ubjected 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 staini ng 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 n itrate stained a network of crazes and microcracks in the subsurface. The pattern of staining indicated that the microcracks formed within t he depth of the subsurface rather than by direct nucleation from the i ndenter. Significance. The different patterns of subsurface damage occ urring as a result of compression should be considered when studying t he wear and degradation of these materials.