Basic Study for Preventing Endodontic Instrument from fatigue breadking

在根管治疗中，根管器械因金属疲劳而意外折断是一个严重的问题。为探讨防止根管器械意外制动的方法，自制了疲劳断裂试验机，测定了三种不锈钢扩髓器和一种镍钛锉的断裂扭矩、断裂角位移，并与ISO标准（3630-1：1992）进行了比较。采用扫描电镜观察断口形貌，用电子探针X射线显微分析仪进行成分分析。疲劳断裂试验机完全符合ISO标准。本机有铝夹头，不会使根管器械断裂和变形.镍钛锉的成分为49.7原子%镍和50.3原子%钛合金镍钛锉的硬度、弯曲扭矩和断裂扭矩均低于不锈钢锉，这些结果于1994年报告给岩手医科大学牙科学会和日本根管学会，1995年，国际牙科研究协会和日本保守牙科学会联合发表了《根管器械疲劳断裂机理及预防》的研究报告不小心打破了。

In endodontic treatment, it is a serious problem that accidentally breaking often results from metal fatigue of the endodontic instrument. The purpose of this study was to investigate the preventing endodontic instrument from accidentally braking.The fatigue breaking test machine was made and determined breaking torque, breaking angular deflection of three stainless steel reamers and a nickel-titanium file in conformity with the ISO standars (3630-1 : 1992). Fractographic observation was used the scanning electron microscope and the composition was analyzed with the electron probe X-ray microanalyzer.The results of the study are as follows :1. Fatigue breaking test machine worked fully for ISO standards. This machine had the aluminum chuck did not make the fracture and the transformation of endodontic instrument.2. The composition of nickel-titanium file was 49.7 atom.% nickel and 50.3atom.% titanium. The nickel-titanium file had lower hardness, bending torque and breaking torque than the stainless steel reamers.These results were reported to the dental society of iwate medical university in 1994 and the japan endodontic association, the international asscoiation for dental research and the japanese society of conservative dentistry in 1995.We would go on studying for the mechanism of fatigue breaking and preventing endodontic instrument from accidentally breaking.