질화 티타늄 코팅된 치과용 니켈-티타늄 파일의 표면안정성 개선효과

Abstract

Ni-Ti file demands on instruments used to clean and shape root canals. The clinical Ni-Ti file is required the longest fatigue fracture life and wear resistance with small metallic ion dissolution in root canal space. Ni-Ti files has been shown to be exceptionally elastic, having a lower bending movement and lower permanent set after torsion, lower fatigue resistance, compared with stainless steel file. The purpose of this study was to investigate the surface stability improvement effects of titanium nitride coated dental Ni-Ti files , ProTaperⓡ(Maillfer, Dentsply, Ballaigues, Switzerland) were used, respectively, for experiment. In order to observe the surface defects of Ni-Ti file before coating, surfaces of specimens were observed by field emission scanning electron microscope (FE-SEM) at the upper, middle and lower part of Ni-Ti 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 at 25℃, 40℃ and 300℃. TiN coated surface of Ni-Ti file was observed with FE-SEM. The metallic ion dissolution of TiN coated Ni-Ti file surface was investigated by using potentiodynamic, cyclic potentiodynamic polarization test and AC impedance test in 0.9% NaCl solution at 36.5 ±} 1℃. The results were as follows: 1.The surface of Ni-Ti file showed the mechanical defects like a scratch formed by manufacture machine, whileas TiN coated surface showed decrease of mechanical defects. 2.From the results of anodic polarization and cyclic potentiodynamic polarization behavior of TiN coated Ni-Ti file, it was found that the corrosion potential of coated specimen was increased and current density was decreased with TiN coating temperature. Also pitting corrosion resistance of TiN coated Ni-Ti file was higher than that of non coated Ni-Ti file. 3.Polarization resistance(R_(p)) values of non-coated and TiN coated Ni-Ti file at 300℃ showed 1.40×10^(6) Ωcm² and 6.44×106 Ωcm² respectively. R_(p) of TiN coated Ni-Ti file was higher than that of non-coated Ni-Ti file. 4.TiN coated Ni-Ti file showed morphology of non metallic dissolution, but non-coated file was severely attacked by Cl- ion. It is considered that the dissolution of metallic ion of Ni-Ti file depended on TiN coating or not, and confirmed that maximum condition of TiN coating such as substrate temperature can be improved the bio-stability, wear resistance and fatigue fracture resistance of Ni-Ti file.