关键词: 类金刚石涂层, 镍钛弓丝, 人工唾液, 电化学腐蚀

Abstract:

Objective: To compare the corrosion resistance abilities between diamond-like carbon (DLC)coated nickel-titanium arch(NiTi) wires and uncoated NiTi wires in the artificial saliva with different pH values and fluoride(F^-)concentrations, and to provide the basis for the application of DLC in the orthodontics treatment. Methods: The DLC coated NiTi wires were prepared by radio-frequency magnetron sputtering technique. Raman spectrum was used to characterizate the NiTi wires. The DLC coated wires were taken as experiment group, and the uncoated NiTi wires were taken as control group, and the NiTi wires in two groups were exposed to four kinds of artificial saliva as four groups, pH7＋0%F^- group: pH 7+0.2% F^- group,pH7+0.5% F^- group,and pH5+0.5% F^- group.The potentiodynamic polarization (Tafel)curves of NiTi wires in two groups were measured by the classic three electrode system of electrochemical workstation,and the corrosion potential (Ecorr) and the corrosion current density (Icorr)of the NiTi wires in two groups were detected; scanning electron microscope(SEM) was used to observe the morphology of the NiTi wires in two groups before and after corrosion with artificial saliva. Results: The Raman spectra results showed the typical D peak and G peak,which indicated that the NiTi wires had been coated by DLC. The electrochemical corrosion test showed that compared with pH7+0% F^- group,the Ecorr of DLC coated NiTi wires in pH7+0.2% F^- group was decreased(P<0.05)and the Icorr was increased(P<0.05);the Ecorr of uncoated NiTi wires was decreased(P<0.05),and the Icorr was increased,but there was no significant difference(P>0.05).Compared with pH7+0.5% F^- group, the Ecorr of DLC coated NiTi wires and uncoated NiTi wires in pH5+0.5% F^-group were decreased(P<0.05)and the Icorr were increased(P<0.05). Meanwhile,in the same group of artificial saliva,the Ecorr of NiTi wires in expiment group was apparently higher than that in control group(P<0.05)and the Icorr was lower than that in control group(P<0.05). The Tafel curves of NiTi wires in two groups were moved to the left with the increasing of F^- concentration and the decreasing of pH value,which indicated that the corrosion resistance ability was decreased. Under scanning electron microscope, much pitting corrosion was observed on the surface of NiTi wires in control group than experiment group. Conclusion: The corrosion resistance ability of DLC coated NiTi wires is higher than that of uncoated NiTi wires,but the increasing of F^- concentration and the decreasing of pH value can decrease the corrosion resistance ability of NiTi wires.

Key words: diamond-like carbon, Nickel-titanium arch wires, artificial saliva, electrochemical corrosion