The Study Of Electrochemical Corrosion Resistance Of Laser Welding Composite Arch Wire Between NiTi Alloy And Stainless Steel

Background：The clinical application of the orthodontic archwire mostly followthe size and stiffness ascending order, which usually starts from the first use ofnickel-titanium arch wire, and then gradually transforms to the use of stainless steelarch wire. There are many shortcomings of using nickel-titanium or stainless steelarch wire alone. Composite archwire (CAW) is formed by solder connection ofnickel-titanium and stainless steel arch wire.Composite archwire (CAW) is formed bysolder connection of nickel-titanium and stainless steel arch wire. there will be someproblems of lacking of anchorage when using nickel-titanium arch wireindependently.And the stainless steel arch wires also have elastic deficiencies. In2000,college of stomatology of Jilin University and college of materials using liquid silverbased solder melting of the two alloy metal binding, initially realized the goodconnection of nickel titanium wires and stainless steel wires.And then CompositeArch wire was created. In2011, Jilin University Institute of materials using a newmethod that laser welding with copper interlayer, composite arch wire formed byseries of more excellent performance. In the face of composite archwire of newconnections and new problems in materials science research.Whether the precipitationof copper ions in oral after welding is within the scope of biosafety studies is urgentlyneeded to be tested, and the biocompatibility, corrosion resistance, the precipitation ofnickel ion and copper ion of CAW in a simulated oral environment also need furtherexperimental exploration.Objective：The corrosion resistance parameters in simulated oral environment wereobtained by combining the results of electrochemical assay, SEM and EDS analysis.Throe corsion resistance and bio-security of CAW was predicted not only to determine and lay the foundation the clinical application of CAW in the process ofclinical application, but also to provide experimental and theoretical basis for itsfurther improvement.Methods：The electrochemical corrosion resistance of laser welding compositearch wire and two base metals were studied and compared in this study. Theelectrochemical corrosion resistance parameters were obtained and the results wouldprovide evidence for its further improvement and clinical application of experimentaland theoretical basis.Results：The main conclusions are as follows:The experimental results showedthat the open circuit potential values of three kinds of arch wires are concentrated at0V or so. In unidirectional polarization process, the corrosion potential of the stainlesssteel arch wire is higher than the nickel-titanium arch wires. The corrosion potentialof composite arch wire is lower than the two base metals. In the anode polarizationcurve section, the pitting potential of composite arch wire is higher than the stainlesssteel arch wire, while pitting potential of nickel-titanium arch wire is not obvious. Thecorrosion current value of composite arch wire is significantly higher than thestainless steel and nickel-titanium base metals. In cyclic polarization process, thethree arch wire materials did not appear obvious hysteresis loops, but the protectionpotential of three materials are higher than the corrosion potential, meaning theability of re-passivation were limited. The gap of nickel-titanium arch wires betweenprotection and corrosion potential was the biggest, the gap of the stainless steel archwire was the smallest.The scanning electron microscopy showed that the three arch wires after polarizedscanning have shown a rough corrosion morphology. The surface of nickel-titaniumarch wires and the stainless steel arch wire after electrochemical corrosion wererelatively smooth, but there are also a small number of cracks generated. Thecorrosion morphology of CAW after electrochemical etching was rougher than thetwo base materials with larger fissures, indicating corrosion resistance of copperinterlayer composite arch wire was not as good as the two base materials. But thesurface of CAW was intact without significant degradation and crack occurs. The main elements composition of interlayer contains oxygen and phosphorus accordingto the energy spectrum analysis, which may be related with the hinder calcium andphosphate ions in the artificial saliva.Conclusion： According to the electrochemical experimental parameters, themorphology depiction of SEM and EDS analysis, the results of this study indicatedthat the composite arch wire after laser welding exhibit good resistance toelectrochemical corrosion process in simulated oral environment. The test methodsand results in this study could provide the appropriate theoretical basis for furtherdevelopment and improvement of dental metallic materials.Integrated electrochemicalexperimental parameters and scanning electron microscopy of the material corrosioninterface morphology depiction of the experimental results showed that welding wirethrough the middle layer composite arch wire exhibit electrochemical corrosionprocess in simulated oral environment good resistance to electrochemical corrosion,Although the corrosion resistance of CAW decreased slightly compared with stainlesssteel and nickel-titanium base metals, but it still be able to meet the needs of clinicaluse. The test methods and results in this study could provide the appropriatetheoretical basis for further development and improvement of dental metallicmaterials.