All the instruments were inspected for any defect or irregularity using stereomicroscope (Olympus BX43, Olympus Co., Tokyo, Japan) under ×20 magnification. RPC R25 (size 25/0.08), WOG Primary (size 25/0.07), and TE (size 30/0.04) instruments were included in this study ( n = 20). The null hypothesis of this study was that there would be no difference between the fatigue life of RPC, WOG, and TE files. The aim of this study was to compare the fatigue life of RPC, WOG, and TE files, which are among the file systems working based on the reciprocation movement, under a static model via artificial canals with different angles of curvature (45°, 60°, and 90°). 14ĭuring our comprehensive literature research, no study on the TE files' cyclic fatigue life was found. The company also states that the file's cyclic fatigue resistance was also improved in this design. The manufacturer claims that the cutting efficiency of this file has been improved under favor of 2-patented vertical blades and it is allowed to move until the apex with minimum resistance. Different from the other file systems employing the reciprocation movement, it does not finalize a complete cycle. Hackensack, NJ, USA) rotary file system consisting of 2 files (sizes 30/0.02 and 30/0.04) made of conventional NiTi alloy has its unique reciprocation movement using a handpiece, which is specific to this system. Newly-introduced Tango-Endo (TE, EDS Dental, S. 13 Moreover, Reciproc file is made of M-Wire alloy and employs S-shaped cross-section having 2 cutting edges, while WaveOne GOLD has parallelogram cross-section with 2 cutting edges at apical end and is made of GOLD alloy. Reciproc works at 300 rpm speed in 150° CCW and 30° CW direction, while WaveOne GOLD operates at 350 rpm speed in 170° CCW and 50° CW direction and completes 360° in 3 cycles. The commercially available Reciproc (RPC, VDW, Munich, Germany) and WaveOne GOLD (WOG, Dentsply Maillefer, Ballaigues, Switzerland) single file systems work based on the reciprocation movement at different speeds and angles. 10 The reciprocation movement is called oscillation movement, and the files performing reciprocation movement decrease the stress on file by rotating in counterclockwise (CCW) direction before completing the cycle in clockwise direction they have been reported to improve the files' fatigue life. 7 When compared to the systems performing continuous rotation, the reciprocation systems, which have been developed by purposefully changing the working principles of traditional NiTi rotary files, have been designed in order to decrease the stress on the file and to prevent the failures originating from the cyclic fatigue. The variables such as NiTi files' speed, movement kinematic, metallurgic properties, and finishing procedures play roles in cyclic fatigue resistance. 8 Because the files may fail due to the cyclic fatigue without any prior sign, the cyclic fatigue resistance is measured by the time to failure under a specific load. 7 The fractures originating from cyclic fatigue are observed in files' continuous rotation within the curved root canals the files are exposed to elastic deformation due to the changing compression and stress forces in these media. 5, 6 Among many factors playing roles in NiTi files' fracture, two of the most important factors are the cyclic and torsional fatigues. 2, 3, 4 But, even these features cannot prevent the undesired fractures of files. 1 NiTi files are designed for shaping the curved canals without damaging the anatomical structure for this purpose, their elasticity was improved. Nickel titanium (NiTi) rotary file systems offer easier and faster root canal shaping procedures than manual hand files.
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