엔진구동형 Ni-Ti파일의 피로파절거동과 표면코팅효과

Abstract

The purpose of this study was to investigate the fatigue fracture behavior and surface coating effects of rotary Ni-Ti files. ProTaper(Maillfer, Dentsply, Ballaigues, Switzerland) were used, respectively, for experiment. In order to observe the fatigue surface of clinically used file, the fractured files were classified into three groups: fractured files at the upper, middle and lower part after clinical use. The fractured surface and chemical composition were studied with energy dispersive x-ray spectroscopy(EDS) and field emission scanning electron microscope(FE-SEM) to analyze element on the surface of fractured file. In order to decrease the defects, TiN film coating was carried out on the Ni-Ti file surface using pure Ti target materials with nitrogen gas. TiN coated surface of Ni-Ti file was observed with FE-SEM, EDS, atomic force microscopy(AFM), vickers hardness tester, and scratch tester. The results were as follows: 1. Fatigue fracture crack of Ni-Ti file was initiated and propagated at defects such as scratch formed by machine under repeated load. 2. Fractured surface of Ni-Ti file showed the brittle fracture behavior at the exterior and ductile fracture behavior at the interior. The ductile fracture behavior appeared predominantly at the lower part of Ni-Ti file compared with at the upper part of Ni-Ti file. 3. The surface roughness of TiN coated Ni-Ti file was lower than that of non coated Ni-Ti file. The surface roughness increased as coating temperature increased from 25℃ to 300℃. Therefore, TiN coated surface showed decrease of defects such as scratch. 4. The surface hardness of TiN coated Ni-Ti file was higher than that of non coated Ni-Ti file. The surface hardness of TiN coated Ni-Ti file at 40℃showed higher than that of TiN coated Ni-Ti file at 25℃ and 300℃. It is considered that the TiN coated film which would prevent Ni-Ti files from fatigue failure can be applicable to root canal instrument system and confirmed that TiN film coated at temperature region of super- elasticity act as inhibitor against crack initiation on Ni-Ti file surface due to decrease of mechanical defects.