Shen Ya, Cheung Gary Shun-Pan, Peng Bin, Haapasalo Markus
Department of Oral Biological & Medical Sciences, Division of Endodontics, Faculty of Dentistry, University of British Columbia, Vancouver, Canada.
J Endod. 2009 Jan;35(1):133-6. doi: 10.1016/j.joen.2008.10.013.
The purpose of this study was to investigate the mode of failure of three brands of nickel-titanium (NiTi) instruments (ProTaper [Dentsply Maillefer, Ballaigues, Switzerland], ProTaper for Hand Use [Dentsply Maillefer], and K3 [SybronEndo, Orange, CA]) that separated during clinical use. A total of 79 fractured instruments were collected from three endodontic clinics over 16 months. The fracture surface of each fragment was examined by scanning electron microscope. Most of the rotary instruments (78% of K3 and 66% of ProTaper) failed because of fatigue fracture, whereas 91% of NiTi hand instruments failed as a result of shear (p < 0.01). The fracture mode of shaping files in rotary ProTaper was different between two different clinics (p < 0.05). All surfaces with fatigue fracture (n = 47) revealed the presence of either one or two crack origins. The vast majority (86%) of K3 fatigue failure had two crack origins that could be found not only at the cutting edge but also at various places along the flute compared with only 28% of ProTaper showing multiple crack origins (p < 0.01). The latter showed one crack origin in 81% of the fatigued shaping files but only 37% for finishing files (p < 0.01). The results of this study indicated that the failure mode of NiTi instruments is related to preparation technique.
本研究的目的是调查临床使用过程中分离的三种品牌镍钛（NiTi）器械（ProTaper [登士柏迈弗，瑞士巴拉格]、手动用ProTaper [登士柏迈弗]和K3 [赛邦恩多，加利福尼亚州奥兰治]）的折断模式。在16个月内从三家牙髓病诊所收集了总共79件折断器械。通过扫描电子显微镜检查每个碎片的折断表面。大多数旋转器械（78%的K3和66%的ProTaper）因疲劳折断而失效，而91%的NiTi手动器械因剪切而失效（p<0.01）。旋转ProTaper中成形锉的折断模式在两家不同诊所之间存在差异（p<0.05）。所有疲劳折断的表面（n = 47）均显示存在一个或两个裂纹源。与仅28%的ProTaper显示多个裂纹源相比，绝大多数（86%）的K3疲劳失效有两个裂纹源，不仅可以在切削刃处发现，还可以在沿凹槽的不同位置发现（p<0.01）。后者在81%的疲劳成形锉中显示一个裂纹源，但在修整锉中仅为37%（p<0.01）。本研究结果表明，NiTi器械的失效模式与预备技术有关。
