Restorative Dentistry and Endodontics

The Korean Academy of Conservative Dentistry (대한치과보존학회)
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Effect of internal stress on cyclic fatigue failure in K3

K3에 축적된 내부 응력이 피로 파절에 미치는 영향

  • Kim, Jun-Young (Department of Conservative Dentistry, Gangneung-Wonju National University School of Dentistry) ;
  • Kim, Jin-Woo (Department of Conservative Dentistry, Gangneung-Wonju National University School of Dentistry) ;
  • Cho, Kyung-Mo (Department of Conservative Dentistry, Gangneung-Wonju National University School of Dentistry) ;
  • Park, Se-Hee (Department of Conservative Dentistry, Gangneung-Wonju National University School of Dentistry)
  • 김준영 (강릉원주대학교 치과대학 치과보존학교실) ;
  • 김진우 (강릉원주대학교 치과대학 치과보존학교실) ;
  • 조경모 (강릉원주대학교 치과대학 치과보존학교실) ;
  • 박세희 (강릉원주대학교 치과대학 치과보존학교실)
  • Received : 2011.12.22
  • Accepted : 2012.02.12
  • Published : 2012.06.01
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Abstract

Objectives: This study aimed to evaluate the relationship between the cyclic fatigue of a K3 file and internal stress intentionally induced until the activation of the autostop function of the torque-controlled motor. Materials and Methods: K3 (Sybron Endo) .04 and .06 taper, size 25, 30, 35, 40 and 45 were used in this study. To give the internal stress, the K3 files were put into the .02 taper Endo-Training-Bloc (Dentsply Maillefer) until the activation of the auto-stop function of the torque-controlled motor. The rotation speed was 300 rpm and torque value was 1.0 $N{\cdot}cm$. K3 were grouped by the number of induced internal stress and randomly distributed to 4 experimental groups (n = 10, Stress 0 [control], Stress 1, Stress 2 and Stress 3). For measuring the cyclic fatigue failure, the K3 files were worked against a sloped glass block and time for file separation was recorded. Data was statistically analyzed Statistical analyses were performed using two-way ANOVA and Duncan post-hoc test at p < 0.05 level. Results: Except .04 taper size 30 in Stress 1 group, there were statistically significant differences in time for file separation between control and all experimental groups. K3 with .04 taper showed higher cyclic fatigue resistance than those of .06 taper. Conclusion: In the limitation of this study, the cyclic fatigue of the K3 file was influenced by the accumulated internal stress from use until the auto-stop function was activated by the torque-controlled motor. Therefore, clinicians should avoid the reuse of the K3 file that has undergone auto-stops.

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References

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