Objective: To evaluate the resistance to cyclic fatigue of a replica rotary system in comparison with its original system. Method: F2 rotary instruments (n=19 per group) from the original brand ProTaper Gold system (Dentsply Maillefer, Ballaigues, Switzerland) were compared with a Super File III instrument (n=19 per group) from a Denco replica system (Medical Co., Shenzhen, China) regarding cyclic fatigue strength. The instruments were randomly distributed into two groups, according to the file brand. Subsequently, the fatigue cycle was measured; for which, they were activated using the E-mate Pro motor of the Denco brand (Medical Co., Shenzhen, China) at continuous rotation 300 rpm and a torque of 2.5 Ncm. Results: The fracture resistance time was recorded and statistically compared between both groups according to the type of instrument (original system/replica system) using the ...