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BioMed Research International
Volume 2019, Article ID 6368958, 8 pages
https://doi.org/10.1155/2019/6368958
Research Article

Torsional and Bending Properties of V Taper 2H, ProTaper NEXT, NRT, and One Shape

1Department of Conservative Dentistry, KyungHee University Dental Hospital, 23 Kyungheedaero, Dongdaemun-gu, Seoul 02447, Republic of Korea
2Department of Conservative Dentistry, Dental Research Institute, Seoul National University Dental Hospital, School of Dentistry, Seoul National University, 101 Daehak-ro, Jongno-gu, Seoul 03080, Republic of Korea
3The First Dental Clinic, 14 Siga-ro, Deoksan-eup, Jincheon-gun, Chungcheongbuk-do 27875, Republic of Korea
4Department of Conservative Dentistry, Graduate School, Kyung Hee University School of Dentistry, 23 Kyungheedaero, Dongdaemun-gu, Seoul 02447, Republic of Korea
5Department of Conservative Dentistry, Kyung Hee University School of Dentistry, 23 Kyungheedaero, Dongdaemun-gu, Seoul 02447, Republic of Korea
6Schulich School of Medicine & Dentistry, University of Western Ontario, 1151 Richmond Street, London ON N6A3K7, Canada
7Department of Conservative Dentistry, College of Dentistry, Gangneung-Wonju National University, 7 Jukheon-Gil, Gangneung, Kangwon-do 25457, Republic of Korea

Correspondence should be addressed to Seok Woo Chang; rk.ca.uhk@cms7002cws

Received 13 August 2019; Accepted 17 October 2019; Published 7 November 2019

Academic Editor: Radovan Zdero

Copyright © 2019 Soram Oh et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Nickel-titanium (NiTi) rotary files have enabled efficient root canal preparations that maintain the canal center with fewer aberrations compared to hand files. However, NiTi rotary files are susceptible to fracture, which can thereby compromise root canal treatment. Therefore, NiTi files have been developed to enhance fracture resistance by modifying design and thermal treatment. The objective of this study was to compare the torsional fatigue resistance and bending resistance of NiTi files manufactured from different alloys and treatments. ProTaper NEXT X2 (PTN; M-wire), V taper 2H (V2H; controlled memory wire), NRT (heat-treated), and One Shape (OS; conventional alloy) instruments of tip size #25 were compared. Torsional fatigue was evaluated by embedding the 3 mm tip of each instrument (N = 10/brand) in resin and the repetitive application of torsional stress (300 rpm, 1.0 N·cm) by an endodontic motor with autostop when the file fractured. The number of loading cycles to fracture was recorded and analyzed by Kruskal–Wallis and Mann–Whitney U tests with Bonferroni’s correction. Bending resistance of the instruments was tested using a cantilever bending test to the 3 mm point from the tip (N = 10/brand). The stress was measured when deflection of 3 mm was subjected and statistically analyzed with a one-way analysis of variance and Tukey’s honest significance difference test (α = 0.05). V2H withstood the highest number of load applications during torsional fatigue testing (), followed by NRT, PTN, and OS, where the differences between NRT and PTN () and between PTN and OS () were not statistically significant. V2H showed the lowest bending stiffness, followed by NRT, PTN, and OS (). Thermal treatment of NiTi wire resulted in improved mechanical properties, and controlled memory wire provided improved flexibility and torsional fatigue resistance.