The Cytotoxicitic Detection Of Laser Welding Between NiTi Shape Memory Alloy And Stainless Steel

The laser welding methods of dissimilar materials between NiTi shape memory alloyand stainless steel have constantly varied and now the laser welding carried out byusing pure nickel,cobalt and copper is wide popular.Compared with the others,laserwelding NiTi shape memory alloy and stainless steel with pure copper interlayerpossesses the benefits of smooth laser joint appearance,high joint tensile strength andbending angles,as well as better shape recovery ratio of NiTi alloy lateral.Thisinvention has been applied for national patent.While regarding to its biosecurity hasnot been reported since now.In this article I will firstly examine its cytotoxicity invitro.Objective:In this, the cytotoxicity of the new type of composite arch wire oflased-welded nickel titanium archwire and stainless steel archwire with pure copperinterlayer(CoAW) was studied with MTT test in vitro and meanwhile was comparedwith stainless steel archwire(SS) and nickel titanium archwire(NiTi) to explore itscell security.Methods:Test1： The CoAW, which was dealed with95%alcohol,ultrasonicirrigation,deionized water rinsing,stoving and heat sterilization, was immersed intohigh sugar nutrient solution(Dulbecco’s modified Eagle’s medium，DMEM) for42hours.Then the immersion solution was diluted to50%,40%,30%,20%,10%fivegrads(n=6). The cytotoxity in vitro of these agents was assayed on murine fibroblastcell L-929line with MTT test at24hours and48hours which was used to find therelation between concentration and time. Test2: The immersed solution of CoAW,Nickel Titanium(Niti) archwires and stainless steel(SS) archwires(the same dealingway to CoAW) were diluted to100%,75%,50%,25%four grads(n=6). Thecytotoxity of three materials was compared with the same method at48hours whichwas used to compare their cytotoxicity.Results:The results of all samples revealed level0-1cytotoxicity.In test1, the opticaldensity of immersed solutiong statistically incresed with the concentrates decliningfrom50%to10%;the same grade solution optical density (except20%) of24hoursrevealed statistically lower than48hours.The results of test2presented the opticaldensity of CoAW solution in terms of100%,75%,50%and25%（1.964±0.122、2.084±0.056、2.056±0.071、2.096±0.050)revealed statistically lower than the same grade solution of SS（2.168±0.091、2.227±0.160、2.302±0.052、2.301±0.060) and NiTi（2.138±0.105、2.262±0.050、2.271±0.082、2.294±0.056）（P<0.05). However,therewere statistic differences between stainless steel samples and NiTi shape memoryalloy with same solution grade.Conclusions:The MTT test of CoAW in vitro showed that cytotoxicity declinded withsolution concentrate decreasing;the cytotoxicity revealed a little higher as timeextending;the cytotoxicity was more serious than SS and NiTi. But the CoAW hadlower cytotoxity and belonged to secure rang of material toxicity reaction.