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http://dx.doi.org/10.5395/JKACD.2004.29.3.267

EFFECT OF SURFACE DEFECTS AND CROSS-SECTIONAL CONFIGURATION ON THE FATIGUE FRACTURE OF NITI ROTARY FILES UNDER CYCLIC LOADING  

Shin, Yu-Mi (Department of Conservative Dentistry, Yonsei University)
Kim, Eui-Sung (Department of Conservative Dentistry, Yonsei University)
Kim, Kwang-Man (Dental Materials, Yonsei University)
Kum, Kee-Yeon (Department of Conservative Dentistry, Yonsei University)
Publication Information
Restorative Dentistry and Endodontics / v.29, no.3, 2004 , pp. 267-272 More about this Journal
Abstract
The purpose of this in vitro study was to evaluate the effect of surface defects and cross-sectional configuration of NiTi rotary files on the fatigue life under cyclic loading. Three NiTi rotary files ($K3^{TM},{\;}ProFile^{\circledR},{\;}and{\;}HERO{\;}642^{\circledR}$) with ＃30/.04 taper were evaluated. Each rotary file was divided into 2 subgroups : control (no surface defects) and experimental group (artificial surface defects), A total of six groups of each 10 were tested. The NiTi rotary files were rotated at 300rpm using the apparatus which simulated curved canal (40 degree of curvature) until they fracture. The number of cycles to fracture was calculated and the fractured surfaces were observed with a scanning electron microscope. The data were analyzed statistically. The results showed that experimental groups with surface defects had lower number of cycles to fracture than control group but there was only a statistical significance between control and experimental group in the $K3^{TM}$ (p<0.05), There was no strong correlation between the cross-sectional configuration area and fracture resistance under experimental conditions. Several of fractured files demonstrated characteristic patterns of brittle fracture consistent with the propagation of pre-existing cracks. This data indicate that surface defects of NiTi rotary files may significantly decrease fatigue life and it may be one possible factor for early fracture of NiTi rotary files in clinical practice.
Keywords
Surface defect; Cross-sectional configuration; Cyclic fatigue; Brittle fracture; Ductile fracture; NiTi rotary files;
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