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UBC Theses and Dissertations

Low-cycle cyclic fatigue properties of novel nickel-titanium rotary endodontic instruments in the single- and double-curvatures. Duke, Frédéric


Introduction: This in vitro study aimed to evaluate and compare the fatigue resistance of ProFile Vortex® (VX) and Vortex Blue® (VB) files in two different artificial double curvature canals (DC1 and DC2) and in an artificial single curvature canal (SC). The bending moment of VX and VB was assessed. Methods: The bending moment (g·cm) was used to measure flexibility of VX and VB (size 25/.04, length: 25mm) according to ISO 3630-1 specifications. Both files types were tested for cyclic fatigue failure inside canals containing: a single curvature (SC: 60⁰ curvature, 5 mm radius) and two canals with different double curvature (DC); [DC1: coronal curvature of 60⁰ and 5 mm radius, and apical curvature of 30⁰ and 2 mm radius; DC2: coronal curvature of 60⁰ and 5 mm radius, and apical curvature of 60⁰ and 2 mm radius]. The number of cycles to failure (NCF) was recorded and the fracture surface of all fragments was examined with a scanning electron microscope (SEM) to confirm cyclic fatigue failure and for qualitative analysis of pattern of fracture. Results: VX and VB followed slightly different trajectories in the identical canals, especially in double curvature canals. The mean bending moment value was significantly lower for VB than for VX (p < .001). NCF for the two files were significantly higher in the single curvature canal (SC) compared to the two double curvature canals (DC1 and DC2) (p < .001). Of the double curvature canals, the NCF was significant higher in DC1 than in DC2 for VB (p < .05) but not for VX (p > .05). In the SC group, VB had NCF superior to VX (p < .05). In DC1 and DC2 groups, NCF of VX and VB was not statistically different from each other (p > .05). Multiple crack origins were observed for the majority of files fractured in DC1 and DC2 canals. Conclusions: DC1 and DC2 canals demonstrated a more stressful and challenging anatomy than the SC canal for VX and VB. In double curvature canals, degree of curvature and radius, and the file’s flexibility may affect the mean NCF.

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