LAUSR

Introduction: The purpose of this study was to compare the cyclic fatigue of Reciproc (REC; VDW, Munich, Germany) and Reciproc blue (REB, VDW) with different angles of file access. Methods: The cyclic fatigue resistance of 120 new REC R25 and REB R25 (REB) files was tested. Instruments were divided into 8 groups on the basis of the access angle inside the artificial canal tested (n = 15): groups 1, 2, 3, and 4 included REC tested at 0°, 10°, 20°, and 30°, respectively, and groups 5, 6, 7, and 8 consisted of REB tested at 0°, 10°, 20°, and 30°, respectively. Resistance to cyclic fatigue was determined by recording the time to fracture in a stainless steel artificial canal with a 60° curvature and a 5‐mm radius using a customized testing device. Data were analyzed using 2‐way analysis of variance followed by the post hoc Tukey test with a significance level of 5%. The fracture surface of fragments was examined with a scanning electron microscope. Results: The cyclic fatigue of REC was reduced from each angle of insertion, whereas REB reduced its fatigue resistance when 20° or 30°access inclination was tested. REB exhibited higher cyclic fatigue than REC when the angle of file access was 0° and 10° (P < .05), whereas there was no difference between the instruments tested at 20°. REC had higher cyclic fatigue resistance than REB at 30° (P < .05). Conclusions: REB files exhibited higher cyclic fatigue resistance than REC when the access to the canal was straight or with a limited inclination. HighlightsCyclic fatigue of NiTi files with different access angles was evaluated.Reciproc blue had higher cyclic fatigue resistance than Reciproc at 0° and 10°.No difference was observed between Reciproc and Reciproc blue at 20°.All tested files exhibited a decreased cyclic fatigue at a 30° access angle.High file inclination reduces the cyclic fatigue resistance of Reciproc blue.