Abstract:

Objective　To test the effect of the cyclic fatigue fracture resistance of Nickel-Titanium（NiTi） files after the magnetron sputtering TiN coating，and to provide basis for clinical application. Methods　The KV4 rotary NiTi files of type 20 and 30（0.04 tapers，25 mm）were selected，40 of each type. The files of type 20 were randomly divided into group A1 and group B1，and the files of type 30 were randomly divided into group A2 and group B2，each group having 20 files. The group A1 and A2 were collectively called coated group，and group B1 and B2 were collectively called uncoated group. A homogeneous layer of 0.6 μm was deposited on the surface of coated group but uncoated group did not underwent any processing. Scanning electron microscopes（SEM）were used to examine surface morphology of NiTi instruments with and without coating. All files were tested for resistance to cyclic fatigue failure inside copper artificial canal. Record the time to fracture from the start of the test until the moment of file breakage and the length of the fractured tip for each file. The number of cycles to fracture（NCF）was calculated according to the rotating speed and fracture time. SEM was used to observe the sectional morphology of each instrument after test. Results　（1）NCF of NiTi instruments with TiN coating was significantly higher than NiTi instruments without TiN coating. The difference was statistically significant（P < 0.05）. There was no statistical significance（P > 0.05）in the length of the fractured tip of each group.（2）The surface morphology of coated group and uncoated group were observed under low and high power SEM before the treatment，and the surface of the coated instruments was more smooth，without obvious cutting marks，than the surface of uncoated instruments. After the cyclic fatigue test，in addition to the main fatigue striations，there were relatively more fatigue lines on the surface of the uncoated instrument than coated instrument. Conclusion　The cycle fatigue resistance of KV4 rotary NiTi endodontic instruments has been improved remarkably after the magnetron sputtering TiN coating.

Key words: magnetron sputtering, titanium nitride, cyclic fatigue fracture resistance, nickel-titanium instrument

摘要：

目的　探讨磁控溅射氮化钛（TiN）镀膜对镍钛锉抗循环疲劳折断性能的影响，为临床应用提供依据。方法　选取20号和30号的KV4型机用镍钛锉（均为0.04锥度、25 mm长）各40支。将20号锉随机分为A1组和B1组，30号锉随机分为A2组和B2组，每组均为20支。A1组和A2组镍钛器械表面进行TiN镀膜处理（统称为镀膜组），B1组和B2组镍钛器械表面不做任何处理（统称为未镀膜组）。实验前扫描电镜（scanning electron microscopes，SEM）观察各组镍钛器械表面形貌。将各组镍钛锉置于铜质弯曲根管模型中进行循环疲劳实验，记录每支锉的断裂时间，并结合其转速计算出该锉断裂时旋转的总圈数（NCF），同时测量其尖端断裂长度。实验后SEM观察各组镍钛器械断面形貌。结果　（1）镀膜组镍钛器械循环疲劳实验中NCF明显大于未镀膜组，差异有统计学意义（P < 0.05）；各组镍钛锉尖端断裂长度差异无统计学意义（P > 0.05）。（2）实验前在低倍及高倍SEM下观察各组镍钛器械表面形貌，发现镀膜组较未镀膜组表面光滑，未见明显加工切割痕迹；实验后发现，除主要疲劳裂纹起源区外，未镀膜组镍钛器械表面的其他位置裂纹相对较多。结论　KV4型机用镍钛锉采用磁控溅射技术进行TiN镀膜后，其抗循环疲劳折断性能显著提高。

关键词: 磁控溅射, 氮化钛, 抗循环疲劳折断性能, 镍钛器械