Basic ResearchExperimental Evaluation on the Influence of Autoclave Sterilization on the Cyclic Fatigue of New Nickel-Titanium Rotary Instruments
Section snippets
Materials and Methods
Four NiTi rotary endodontic instruments of the same size (tip diameter 0.40 mm and constant .04 taper) were selected: K3 (SybronEndo, Orange, CA), NiTi traditional alloy; Mtwo (VDW, Munich, Germany), NiTi traditional alloy; Vortex (Dentsply-Tulsa, Tulsa, OK), M-wire alloy; and K3 XF prototypes (SybronEndo), made of the same heat-treated NiTi of the Twisted Files. Each group of 24 instruments was then divided into 2 subgroups (n = 12), unsterilized instruments and sterilized instruments. The
Results
Mean values ± standard deviation expressed as NCF are displayed in Table 1. A higher value of NCF is related to greater resistance to cyclic fatigue fracture of the instruments tested. The one-way analysis of variance indicated that there was a significant difference between groups (P = .000).
Comparing the results between unsterilized and sterilized files for each type of instrument, the t test of Student-Newman-Keuls for multiple comparisons showed that differences were statistically
Discussion
The cyclic fatigue resistance of NiTi rotary instruments has been a subject of great interest in the endodontic literature. The impact of torsional fracture, metal fatigue, or fracture of NiTi rotary instruments caused by a combination of torsional stress and accumulation of fatigue is still debated (16). Material fatigue appears to be an important reason for the separation of rotary instruments during clinical use. Peng et al (17) classified most of the fractured instrument analyzed as
Acknowledgments
The authors deny any conflicts of interest related to this study.
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