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UBC Theses and Dissertations

A novel model to evaluate the fatigue resistance of NiTi instruments : rotational and axial movement at body temperature Baird, Evan


Objective: The aim of the study was to develop a model of testing cyclic fatigue resistance of TruNatomy instruments of undergoing rotational and axial movement at body temperature, taking into consideration the size of the canal and location of the curvature. Methods: Prime and Medium files were subjected to cyclic fatigue testing in simulated canals (at 37°C) using a model with either rotational movement only or rotational and axial movement simultaneously. Prime files were tested in 30/.04 and 30/.06 sized canals and Medium files were tested in 38/.04 and 40/.06 sized canals. The location of the curvature was unique for each canal, either in the apical, middle or coronal aspect of the canal. Results: Files tested in the rotation and axial movement groups had a higher number of cycles to failure (NCF) compared to the rotation only group. Prime files had a higher NCF than Medium files. Files tested in apical curvatures had a higher NCF than files tested in middle and coronal curvatures. Conclusion: Since rotational and axial movement of files led to greater fatigue resistance compared to rotational movement alone, future studies on fatigue resistance should implement a model with rotational and axial movement, as it is more comparable to a clinical scenario. Since Prime files had a higher NCF than Medium files, it is important to properly select the file for a particular canal. Apical curvatures led to greater fatigue resistance than curvatures in the coronal and middle third. Therefore, it is important that even when using a very flexible and fatigue resistant file, a proper glide path is developed and a suitable file size is selected when navigating these more coronal curvatures.

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