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A comparison of cyclic fatigue failure of two nickel titanium rotary endodontic file systems that use different manufacturing methods: a ground file (RaCe™) and a new innovative controlled memory file (HyFlex CM™) in a simulated root canal
du Preez, Henk J.
du Preez, Henk J.
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2014-03
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dissertation
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Research Question - Do controlled memory nickel titanium rotary endodontic files have greater resistance to cyclic fatigue than ground nickel titanium files , in vitro, at test temperatures near those encountered clinically? Context and previous research - Controlled memory rotary files became available in 2010. Two in vitro research papers testing their resistance to cyclic fatigue against ground files have been published to date. These studies conducted their research at room temperature using a three pin bending device to rotate the files around a curvature. They both had sample sizes of twelve files per group. Controlled memory files performed significantly (p < 0.05) better than ground files.
Sample and setting - Forty seven HyFlexCM™ and forty eight RaCe™ files, both with a tip size of .25mm and constant taper of 6% were randomly acquired for comparison. The HyFlexCM™ files were sponsored by the manufacturer, the RaCe™ files were purchased from a U.K supplier. Both groups were run to failure at 500 revolutions per minute in an oil lubricated artificial canal constructed from hardened steel using electrical discharge sinking. The artificial canal tapered at 6%, from .35mm to 1.37mm with a 5mm radius of curvature and 90° bend in one plane. The test temperature was 35 ± 1 °C. Data collection and Analysis - Raw data, in seconds to failure, was recorded by the author and converted to number of rotations to failure. Significance level was set at .05. Statistical analysis was performed with
SPSS™ statistical software. The Cox survival model was used to determine if there was a significant difference in the number of rotations to failure for each group. Findings - There was no statistically significant difference between the two groups. Conclusion - Controlled memory rotary endodontic files may be more likely to fail through cyclic fatigue when tested at clinically relevant temperatures rather than at room temperature as in previous studies.
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University of Chester
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Thesis or dissertation
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en