title: Cyclic fatigue resistance, torsional resistance, and metallurgical characteristics of V taper 2 and V taper 2H rotary NiTi files.
abstract: The aim of this study was to compare the cyclic fatigue resistance, torsional resistance, and metallurgical characteristics of conventional NiTi wire (V taper 2, V2) and CM wire (V taper 2H, V2H)-based files. Cyclic fatigue and torsional resistance of V2 and V2H were investigated by measuring the number of cycles to fracture, maximum torque at fracture, and maximum angle at fracture. The typical patterns of fatigue and torsional fractures were investigated using a scanning electron microscope (SEM). The metallurgical characteristics were investigated by differential scanning calorimetry (DSC) from -100 °C to 100 °C. The austenite finishing temperature (Af) of each instrument was also measured. The microstructures of the instruments were investigated by a transmission electron microscope (TEM) along with selected area diffraction pattern analysis. The results were statistically analyzed by Mann-Whitney U-test (p = 0.05). V2H showed significantly higher cyclic fatigue resistance and torsional resistance than V2. SEM images of the fractured surfaces showed typical patterns of fatigue and torsional fracture. The DSC analysis of V2 showed one small peak in both the heating and cooling curves. The Af of V2 was -0.32 °C. V2H showed two remarkable peaks in the heating curve and one remarkable peak in the cooling curve. The Af of V2H was 33.25 °C. The TEM analysis showed that both V2 and V2H are mainly composed of austenite. In conclusion, V2H showed higher cyclic fatigue resistance and torsional resistance than V2. The superior properties of V2H could be attributed to the annealing effect and possibly the martensite phase. SCANNING 38:564-570, 2016. © 2016 Wiley Periodicals, Inc.
authors.affiliation: Department of Conservative Dentistry, School of Dentistry, Kyung Hee University, Seoul, Korea.
authors.forename: S W
authors.initials: SW
authors.lastname: Chang
authors.affiliation: Department of Conservative Dentistry, School of Dentistry, Kyung Hee University, Seoul, Korea.
authors.forename: K S
authors.initials: KS
authors.lastname: Shim
authors.affiliation: Biomedical Research Institute, Korea Institute of Science and Technology, Seoul, Korea.
authors.forename: Y C
authors.initials: YC
authors.lastname: Kim
authors.affiliation: Future Convergence Research Division, Korea Institute of Science and Technology, Seoul, Korea.
authors.forename: K K
authors.initials: KK
authors.lastname: Jee
authors.affiliation: Division of Endodontology, Department of Oral Health and Diagnostic Sciences, School of Dental Medicine, University of Connecticut Health Center, Farmington, Connecticut.
authors.forename: Q
authors.initials: Q
authors.lastname: Zhu
authors.affiliation: Schulich School of Medicine and Dentistry, University of Western Ontario, London, Canada.
authors.forename: H
authors.initials: H
authors.lastname: Perinpanayagam
authors.affiliation: Department of Conservative Dentistry, Dental Research Institute and BK21 Program, Seoul National University Dental Hospital, Seoul National, University School of Dentistry, Seoul, Korea.
authors.forename: K Y
authors.initials: KY
authors.lastname: Kum
keywords: V taper; V taper 2H; cyclic fatigue resistance; thermal characteristics; torsional fracture resistance