Research Of Properties Of TiN,ZrN Films Coated On Niti Root Canal Files

NiTi root canal file has been widely applied to clinical medicine because of shape memory effect and superelasticity.However,in the process of preparing the root canal,nickel ions separation from the surface of NiTi root canal file,the separation of the instrument and low cutting efficiency are easily to happen.More and more attention has been paid to the surface modification of NiTi root canal file to improve its cutting efficiency,corrosion resistance and cyclic fatigue fracture resistance.In this study,TiN,ZrN films are deposited on the surface of NiTi root canal file by magnetron sputtering technique to investigate the effect of deposition process on the performance of coated NiTi root canal file.Furthermore,two kinds of films are compared and analyzed to find a more suitable film for NiTi root canal file.The surface morphology and composition of the coated NiTi root canal files are detected and analyzed.Analysis of the phase structure and preferred growth orientation of TiN,ZrN films is carried out in X-ray diffractometer.The hardness of TiN,ZrN thin films is tested by Vickers hardness tester.The cutting efficiency of NiTi root canal files is tested by using simulated resin root canals,which have similar hardness and structure with human teeth.The cyclic fatigue fracture resistance of NiTi root canal files is tested by using specially made curved copper canals simulating the root canals of human teeth.The corrosion resistance of NiTi root canal files is tested with electrochemical corrosion method.All property tests are to investigate the change of cutting efficiency,cyclic fatigue fracture resistance and corrosion resistance of uncoated and coated NiTi root canal files.The TiN,ZrN films coated on the NiTi root canal file are both face centered cubic phase with preferred growth orientation(111)and structure characteristic of columnar crystal.The substrate bias and duty cycle have little effect on deposition rate,and the thickness of the film is mainly determined by deposition time.The maximum cutting efficiencies of TiN,ZrN-coated NiTi root canal files are increased respectively by 21% and 72%,comparing with the uncoated NiTi root canal files.The cutting efficiency of ZrN-coated NiTi root canal files is higher than TiN-coated NiTi root canal files.The optimal cyclic fatigue fracture resistance of TiN,ZrN-coated NiTi root canal files are increased by about 96% and 64% respectively,comparing with the uncoated NiTi root canal files.Moreover,the cyclic fatigue fracture resistance of TiN-coated NiTi root canal files is higher than ZrN-coated NiTi root canal files.The corrosion resistance of TiN,ZrN-coated NiTi root canal files is higher than uncoated NiTi root canal files in sodium hypochlorite solution.Moreover,the corrosion resistance of ZrN-coated NiTi root canal files is better than TiN-coated NiTi root canal files.The comprehensive analysis shows that TiN film and ZrN film prepared by magnetron sputtering both can be used to coat on the surface of NiTi root canal file.And ZrN film has better comprehensive performance than TiN film.