Although fortunately rare, fracture of implants causes significant problems for both clinicians and patients. The major cause of a fractured implant may be corrosion fatigue fracture. To investigate how to increase the fatigue life and corrosion resistance of dental implants, the surface morphology of six Steri-Oss fractured implants was analyzed. The period of implantation after loading in patient jaws varied between 23 months and 37 months. The topography and surface chemical composition were studied with electron probe micro-analysis (point mapping, energy dispersive x-ray spectroscopy) and field emission scanning electron microscopy. All samples were fractured at the screw root and the crest formed a keen-edged shape. The five samples were fractured at the first thread of the fixture and one sample at the third thread of fixture. The fatigue cracks were mainly nucleated and grown at scratches occurring for the screw root and crest formation and the cervix portion of the implant having a small curvature. The pits were nucleated in the vicinity of inclusions such as SiO2 and corrosion fatigue cracking was predominantly propagated. Corrosion products were found on the opposite side of the starting point of corrosion fatigue crack. From observations of fatigue striations, it is possible to predict the life time of fractured implants and estimate the cleavage fracture and dimple fracture of implants. In this study, analysis of fractured surfaces revealed the characteristics of the implant materials, problems of design, fatigue life, and manufacturing process. In order to protect against corrosion fatigue fractures and prolong the fatigue life of dental implants, we must consider the implant design, implant manufacturing, and surface treatment of the implant materials. [ABSTRACT FROM AUTHOR]