The Study Of Four Brands Of Mechanical Properties Of Ni-Ti Wires In Two Different Imitative Oral Environments

Objective The purpose of this paper is to provide some references for the selections of nickel-titanium-based(Ni-Ti) orthodontic wires and the application of fluoride in clinical practice,making the comparion of the fatigue properties differences of round Ni-Ti wires of four different brands in artificial saliva and fluoride artificial saliva, and the analysis of the effect of fluoride on the fatigue properties of the four-different-brands of Ni-Ti orthodontic wires.Materials and methods The 2cm extremities of four-different-brands Ni-Ti archwires,including Nitinol SuperElastic(3M),Ni-Ti Memory Wire(AO),Chinese Ni-Ti archwires,Kleen Pak^TM System NiTi(Ormco),were selected for the study.For each brand,sixteen specimens were chosen,half of which was immersed into artificial saliva while the others into the fluoride artificial saliva.After a week,the dynamic mechanics analysis was carried out until the wire fracture.The experiment time and the storage modulus of the orthodontic wires were recorded.Scanning electron microscopy was used to scan the surfaces and the fracture surfaces of the Ni-Ti orthodontic wires before and after the experiment.Results1 There're no significant differences in fatigue lives of the same Ni-Ti orthodontic immersing into artificial saliva and fluoride artificial saliva(P＞0.05).There're significant differences in fatigue lives between Ni-Ti orthodontic wires of the different brands immersing into the same solution(P＜0.05).For the fluoride artificial saliva group,the 3M and AO Ni-Ti orthodontic wires showed the longer fatigue live than the other two Ni-Ti wires,while the Chinese Ni-Ti wire showed the shortest one. For the artificial saliva group,3M,AO and Ormco Ni-Ti wires showed longer fatigue lives than the Chinese Ni-Ti wire. 2 There're no significant differences in storage modules of the same Ni-Ti orthodontic immersing into artificial saliva and fluoride artificial saliva(P＞0.05).Every Ni-Ti orthodontic wires showed stable storage modules before fracture.There're significant differences in storage modules between Ni-Ti orthodontic wires of different brands immersing into the same solution(P＜0.05).Among the fluoride artificial saliva group, 3M Ni-Ti orthodontic wire had the minimum storage module in the fluoride artificial saliva.However,there're no significant differences in storage modules among Ni-Ti orthodontic wires of the other three brands.For the artificial saliva group,the 3M Ni-Ti orthodontic wire showed the minimum storage module while the Ormco Ni-Ti wire showed the maximum one.3 The scanning electron micrographs showed that the fracture surfaces of 3M and AO Ni-Ti wires were porous structure while the Chinese one was smoother.The fracture surface of the Ormco Ni-Ti orthodontic wire presented strip structure.There're many shell dermal ridges on the fracture surfaces of the 3M,AO and Ormco Ni-Ti orthodontic wires.However,when it came to the Chinese Ni-Ti orthodontic wire,they were rare.Spot corrosion was observed on the surfaces of Ni-Ti orthodontic wires of four brands immersing into both solutions.Conclusion1 Among these four orthodontic wires,the fatigue lives of 3M and AO Ni-Ti orthodontic wires were longer than Ormco and Chinese Ni-Ti orthodontic wires,the Chinese Ni-Ti orthodontic wire has the shortest fatigue lives.2 The Ni-Ti orthodontic wires of all brands in this study have stable mechanical properties.Among which,the 3M Ni-Ti orthodontic wire has the strongest toughness while the Ormco Ni-Ti orthodontic wire has the weakest one.3 There is no effect of fluoride on the fatigue properties and mechanical properties of the Ni-Ti orthodontic wires in this study.