Influence of Different Angles of File Access on Cyclic Fatigue Resistance of Reciproc and Reciproc Blue Instruments

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 degrees, 10 degrees, 20 degrees, and 30 degrees, respectively, and groups 5, 6, 7, and 8 consisted of REB tested at 0 degrees, 10 degrees, 20 degrees, and 30 degrees, respectively. Resistance to cyclic fatigue was determined by recording the time to fracture in a stainless steel artificial canal with a 60 degrees 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 degrees or 30 degrees access inclination was tested. REB exhibited higher cyclic fatigue than REC when the angle of file access was 0 degrees and 10 degrees (P < .05), whereas there was no difference between the instruments tested at 20 degrees. REC had higher cyclic fatigue resistance than REB at 30 degrees (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.