手用ProTaper镍钛锉临床折断原因的初步分析

目的通过记录手用ProTaper镍钛锉临床折断前使用次数,观察其断口形貌的改变,分析折断原因。方法收集临床中记录的废弃手用ProTaper镍钛锉21套(S1-F2)共105支和一套未经使用的手用ProTaper镍钛锉对比,通过肉眼和扫描电镜对其外观和断口形貌进行观察,比较不同使用次数器械受损情况。结果所有根管锉的切割刃肉眼观察无缺陷。SEM观测根管锉的侧面形貌显示在使用过的根管锉靠近断口区,有许多裂纹,呈锐利Ⅰ型平面断口,应属于弯曲疲劳折断,而未使用过的新根管锉表面未见裂纹。F2折断机会多,折断前使用次数最少,一般在使用45～50次左右易断;S1在55～60次易断,其次为F1,最不易折断的为S2。结论在熟练掌握正确的使用技术后,手用ProTaper镍钛锉在使用40～50个根管后容易发生断针。

Clinical analysis of reasons for breaking of Hand ProTaper Nickel-titanium files during root canal therapy

Objective To analyze the reasons of the breaking of the Hand ProTaper Nickel-Titanium files by recording the times of application and observing the morphological characteristics of the fracture surface of the instrument.Methods We collected 21 sets of the abandoned Hand ProTaper Nickel-titanium files（S1-F2,totally 105 files） and one new set file（S1-F2）,then compared the profile damage from the appearance and the fracture surface of the files by naked eyes and scanning electron microscope （SEM）.Results All the root canal files of cutting edge had no flaws by naked eyes. The observation of the side shape appearance of the files by SEM showed the used files cutting edge near the fracture section area had a lot of cracks, showing sharply I type flat fracture surface, and it should be classified as to the weary curved wreckage. But the new one had nothing. F2 file was the easiest broken among all the instruments, about 45-50 times before it was broken. The next one is S1 ,and the application time was about 55-60 times. The third was F1. The S2 was the last one. Conclusions Even the skillful operators should abandon the hand ProTaper for preventing file from breaking before it has been used for 45-50 root canal preparations.