title: Fatigue resistance of composite restorations: effect of filler content.
abstract: OBJECTIVE
  The purpose of this study was to evaluate the effects of filler level on the fatigue impact resistance of resin composite.
  
  
  METHODS
  A series of experimental composite materials was prepared by incorporating a silanized quartz filler (3-5 microns in size) into a light-cured resin matrix of Bis-GMA/TEGDMA. The filler contents in the experimental composites varied from 40 to 85 wt%. The composites were placed in standardized Class I cavities prepared in bovine teeth. The specimens were stressed with a repetitive impact load (1.6 x 10(2) joule) with loading cycles ranging from 50,000 to 150,000 times. The cracks induced by cyclic loading were observed on the sectioned surfaces of the tested specimens.
  
  
  RESULTS
  The composites with considerably low or high filler content (< 60% or > 80% by weight) were significantly low in fatigue resistance. The results revealed that an inverse linear relationship tended to exist between filler level and fatigue resistance of the composite materials beyond a certain level of filler content.
  
  
  CONCLUSIONS
  Increased filler level does not necessarily improve the fatigue resistance of a resin composite as determined by applying a repetitive impact load.
mesh_terms: D000818:Animals; D017438:Bisphenol A-Glycidyl Methacrylate / Q000737:chemistry; D002417:Cattle; D016009:Chi-Square Distribution; D003188:Composite Resins / Q000737:chemistry*; D001840:Dental Bonding; D003793:Dental Restoration, Permanent / Q000379:methods*; D003799:Dental Stress Analysis; D004548:Elasticity; D016014:Linear Models; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D011092:Polyethylene Glycols / Q000737:chemistry; D011109:Polymethacrylic Acids / Q000737:chemistry; D011791:Quartz / Q000737:chemistry; D012821:Silanes / Q000737:chemistry; D013718:Tensile Strength
chemical_list: D003188:Composite Resins; D011109:Polymethacrylic Acids; D012821:Silanes; C092420:Clearfil Photo Posterior; D011791:Quartz; C020946:triethylene glycol dimethacrylate; D011092:Polyethylene Glycols; D017438:Bisphenol A-Glycidyl Methacrylate