- 作者：Yoshitsugu Terauchi ; DDS ; PhD&lowast ; ; yterauchi@intellident.or.jp" class="auth_mail" title="E-mail the corresponding author ; Le O'Leary ; DDS&dagger ; ; Takatomo Yoshioka ; DDS ; PhD&lowast ; ; Hideaki Suda ; DDS ; PhD&lowast ;
- 关键词：Cyclic fatigue ; nickel titanium file ; secondary fracture ; separated file ; ultrasonics
- 刊名：Journal of Endodontics
- 出版年：2013
- 出版时间：October 2013
- 年：2013
- 卷：39
- 期：10
- 页码：1300-1305
- 全文大小：1078 K
Methods
Fifty nickel-titanium file fragments were divided into 5 groups. An ultrasonic tip was activated on a file fragment positioned between dentin blocks simulating several canal conditions: Group 1 consisted of the fragment protruding from a pair of straight dentin blocks. For group 2, the fragment was also positioned between 2 straight dentin blocks except one block was positioned 1 mm more apically than the other block, simulating a troughed area that is often created during file removal attempts. For groups 3–5, the fragment was positioned similarly as group 2 but between blocks with 30°, 45°, and 60° curvatures, respectively. The time it took for secondary fracture to occur was recorded, and the data were statistically analyzed.
Results
Fragments with dentin wall supporting on the opposite side of ultrasonic activation site resisted fracture significantly longer than those without it. Fragments in 30° and 45° curved blocks took significantly longer to fracture than the other groups (Fisher protected least significant difference, P < .05).
Conclusions
Secondary fracture of separated files appeared to be reduced when the ultrasonic tip was applied to the inner curvature of the canal.