Isik, VasfiyeKwak, Sang WonAbu-Tahun, Ibrahim H.Ha, Jung-HongKayahan, Mehmet BayboraKim, Hyeon-Cheol2024-05-252024-05-25202040099-23991878-355410.1016/j.joen.2019.10.0192-s2.0-85076247551https://doi.org/10.1016/j.joen.2019.10.019https://hdl.handle.net/20.500.14517/1398Kim, Hyeon Cheol/0000-0001-8032-1194; Isik, Vasfiye/0000-0003-1622-2698Introduction: This study was conducted to evaluate the effect of file length on the torsional resistance of nickel-titanium rotary files. Methods: Forty-five new files with a #25 tip size and variable taper for ProTaper Next (PTN; Dentsply Sirona, York PA), ProTaper Gold (PTG, Dentsply Sirona), and HyFlex CM (HCM; Coltene-Whaledent, Allstetten, Switzerland) were divided into 3 subgroups (n = 15) according to the file length (21, 25, and 31 mm). Torsional tests were performed using a custom-made device (AEndoS; DMJ System, Busan, Korea). The maximum torsional load and distortion angle were measured until file fracture occurred. The toughness was calculated using these data. All data were statistically analyzed using 2-way analysis of variance at a confidence level of 95%. One-way analysis of variance and Duncan post hoc comparison were also conducted to assess the difference among the independent variables, shaft length, and file system. Results: A statistically significant interaction was observed between the file system and instrument length with respect to the maximum torsional load (P < .05). The 31-mm shaft length of HCM showed higher maximum torsional load than that of the 25- and 21-mm shaft length in the HCM groups (P < .05). Among the instrument systems, PTG showed the significantly highest maximum torsional load followed by PTN and HCM (P < .05). The 31-mm shaft length of PTG showed significantly higher toughness than that of the 21- and 25-mm shaft lengths (P < .05), whereas PTN and HCM did not show any difference in relation to the shaft length. Conclusions: Within the limitations of this study, the instrument with a longer shaft may have higher maximum torsional load or toughness than that with a shorter shaft.eninfo:eu-repo/semantics/closedAccessFile fractureinstrument lengthnickel-titanium fileshaft lengthtorsional resistanceArticleQ1Q1462295300WOS:00051221700002331812358