Background: Nickel–titanium (NiTi) endodontic files have increased flexibility and strength compared with stainless steel instruments. The present study was conducted to determine cyclic fatigue resistance of two rotary file systems. Materials & Methods: This in vitro study was conducted in the department of Endodontics. It consisted of 2 file system ie. One Shape files (OS) (Group I) and One Curve endodontic files (Group II). All files were rotated until fracture; the time to failure was recorded and the number of cycles to fracture (NCF) calculated. The length of the fractured fragments was measured too. Results: The mean time to failure (TtF) in group I was 52.6 seconds and in group II was 126.8 seconds. The difference was significant (P< 0.05). The number of cycles to failure (NCF) in group I was 314.2 and in group II was 724.8. The mean fragment length in group I was 4.25 mm and in group II was 4.13 mm. The difference was significant (P< 0.05). Conclusion: Authors found that cyclic fatigue resistance of OC endodontic instruments was greater as compared to OS.
Key words: Nickel–titanium, One Curve, One Shape files.