The aim of this study was to evaluate the surface topographical changes and bending properties of AlphaKite and Revo-S rotary endodontic instruments after instrumentation, irrigation and sterilization.Methodology: Ninety unused nickel titanium rotary endodontic files were selected from two brands to be evaluated in the present study, including 45 #25 (0.04 taper) AlphaKite files and 45 #25 (0.04 taper) Revo-S files and were divided into 6 groups , Two control groups of new files of each file (n=10 ) . Two groups , ( no=40 ) , twenty file for each brand that were used to prepare 3 root canals using 5.25% NaOCl as an irrigant and were sterilized by autoclave one cycle at 121°C at 15 psi for 30 minutes. Two last groups , ( no=40 ) , twenty file for each brand that were used to prepare 9 root canals using 5.25% NaOCl and were sterilized by autoclave for three cycles ( one cycle after 3 root canals ) at 121°C at 15 psi for 30 minutes. All files were examined under environmental scanning electron microscopy by two observers.Results:The defects increased dramatically along the surface area of the file with the increase number of use. Defects were more distributed along the AlphaKite files more than the Revo-S files throughout the different groups. The bending decreased dramatically within the different files with the increase number of use. Conclusion:1.Multiple use of endodontic files results in different surface defects.2.Surface treatment by electropolishing adopted by manufacturer to improve files performance was more efficient than physical vapor deposition.3.The Revo-S files showed more flexibility than the AlphaKite file system.