氟离子和酸对3M镍钛弓丝和Damon铜镍钛弓丝耐腐蚀性的影响

Corrosion resistance of 3M nickel-titanium arch wires and Damon copper-nickel-titanium arch wires in different artificial saliva with different fluoride and pH

背景:在含氟的酸性环境中,Damon铜镍钛弓丝能否具有与传统镍钛弓丝相当的耐腐蚀性能,铜离子的加入会不会影响其耐腐蚀性?目的:观察氟离子和酸对3M镍钛弓丝和Damon铜镍钛弓丝耐腐蚀性的影响。方法:采用动电位极化曲线法测得3M镍钛弓丝和Damon铜镍钛弓丝分别在4种(pH=7、不含氟离子;pH=7、含氟离子浓度0.2%;pH=7、含氟离子浓度0.5%;pH=5、含氟离子浓度0.5%)不同人工唾液中的动电位极化曲线,得到自腐蚀电位、自腐蚀电流密度和极化电阻,并用扫描电镜观察其腐蚀后的形态。结果与结论:在中性(pH=7)人工唾液中加入0.2%氟离子,Damon铜镍钛弓丝试件极化曲线上移,自腐蚀电流密度增大,极化电阻减小(P<0.05),扫描电镜显示试件表面出现腐蚀;3M镍钛弓丝试件极化曲线没有偏移,自腐蚀电流密度、极化电阻基本不变(P>0.05),腐蚀不明显;当氟离子浓度增大到0.5%时,两种试件极化曲线均上移,自腐蚀电流密度增大,极化电阻减小(P<0.05),试件表面均出现明显腐蚀;当加入酸之后(pH=5),腐蚀更加明显。提示低浓度氟不会影响3M镍钛弓丝的耐腐蚀性,但会降低Damon铜镍钛弓丝的耐腐蚀性;高浓度氟和酸均会降低他们的耐腐蚀性,Damon铜镍钛弓丝的耐腐蚀性不及3M镍钛弓丝。

BACKGROUND：In the fluorine-containing acidic environment, it is unclear whether Damon copper- nickel-titanium arch wire can have a corrosion resistance similar to conventional nickel-titanium arch wire and whether copper ion wil affect its corrosion resistance. OBJECTIVE： To evaluate the corrosion resistance of 3M nickel-titanium arch wires and Damon copper-nickel-titanium arch wires in artificial saliva with different fluoride and pH. METHODS：Potentiodynamic polarization curves of 3M nickel-titanium arch wires and Damon copper-nickel-titanium arch wires were measured in four kinds of artificial saliva （pH=7; pH=7, 0.2% fluoride; pH=7, 0.5% fluoride; pH=5, 0.5% fluoride）. Then, the corrosion potential, corrosion current density and polarization resistance were acquired, and scanning electron microscope was used for morphological observation after corrosion. RESULTS AND CONCLUSION： In neutral （pH=7） artificial saliva, 0.2% fluoride ions added could shift up the Damon specimen polarization curve, increase the corrosion cerrent density and reduce the polarization resistance （P 〈 0.05）; under the scanning electron microscope, corrosion was observable on the specimen surface. But 3M specimen polarization curve did not move, corrosion current density and polarization resistance substantialy unchanged （P 〉 0.05）, and no significant corrosion was produced. When fluoride concentration was increased to 0.5%, the polarization curves of two kinds of the specimens moved, the corrosion cerrent density increased, the polarization resistance decreased （P 〈 0.05）, and there was significant presence of corrosion on the specimen surface. When pH=5, corrosion phenomenon was more pronounced. These findings suggest that low concentrations fluoride cannot affect corrosion resistance of 3M arch wire, but can reduce the corrosion resistance of Damon arch wire; high concentrations of fluoride and acid can both reduce their corrosion resistance. In addition, the corrosion resistance of 3M arch is stronger than that of Damon arch wire.