The interface between implant and bone were observed with scanning electron microscope (SEM) and X ray energy spectrum analysis (EDAX).

METHODS The powder X ray diffraction analysis was used by spectrum X ray diffraction analysis. The characteristic marked peaks of talcum was found for identification.

By using visual examination, scanning electronic microscope, X-ray energy spectrum and metallurgy and chemical analysis, the cause of crack occurred in bellow expansion joint was analyzed.