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This study investigated the effect of electropolishing ProFile nickel titanium rotary instruments on torque resistance, fatigue resistance, and cutting efficiency. Size 25/.04 ProFile files (Dentsply Maillefer, Switzerland) that were nonpolished for the control group (n = 15) and electropolished for the experimental group (n = 15) were used for each experiment. Cyclical fatigue was determined by counting rotations until breakage with an applied 30°, 45°, and 60° curve with a 5-mm radius. Torque and angle at failure were measured by rotating clamped files at 2 rpm until breakage. Cutting efficiency was determined by measuring the velocity of file advancement into plastic blocks with 100-g constant force for 5 seconds. Data were analyzed by either an unpaired t test or analysis of variance followed by a Fisher probable least-square difference test. Electropolishing significantly reduced resistance to cyclic fatigue but did not …