| The fine retention of oral and maxillofacial prostheses is a successful base. So applying magnetic attachments to solve the retention of prostheses is an important developing trend of prosthodontics. With the development of oral science, various dental alloys are applied to clinical therapy, which inevitably causes more galvanic corrosion among different alloys in oral environment, consequently cuts down the use longevity of the prostheses. Therefore it is necessary to investigate the problem of galvanic corrosion between soft magnetic alloy and dental alloys in common use. An electrochemical test and an immersion test in simulated oral environment were used in qualitative and quantitative measurement of galvanic corrosion between Fe-16Cr-2Mo soft magnetic alloy and dental alloys in common use. Meanwhile, in order to provide theory for clinic, we evaluated the property of galvanic corrosion and analyzed the anticorrosive property of four galvanic couples. The following results was indicated:1. The Ecorr values of five kinds of alloys indicated that corrosion of Fe-16Cr-2Mo soft magnetic alloy was accelerated as anode by coupling with Ti75, TA2, Co-Cr alloys, and was protected as cathode in Ni-Cr galvanic couple.2. Potential dynamic polarization curves revealed that Ti75, TAa, Co-Cr alloys were not corroded when voltage was 1200mV, and Ni-Cr, Fe-16Cr-2Mo were corroded when voltage was 700mV and 800mV. But voltage generally didn't exceed3300mV in oral cavity, so all kinds of alloys in this study could meet the need of prosthodontics.3. Values of galvanic current density indicated that whether being anode or cathode, all values of galvanic current density of Fe-16Cr-2Mo soft magnetic alloy were at nA (10-9A/cm2) level and extremely small, so the chances of galvanic corrosion couldn't be taken into account.4. The results of immersion test revealed that after four galvanic couples between soft magnetic alloy and four kinds of dental alloys were immersed in artificial saliva for six months, ions released from four galvanic couples into artificial saliva were determined by means of ICP, and the ICP results revealed that experimental and contrasting groups were not significantly different. The galvanic corrosion seemed not to take place.5. The LM and SEM results revealed that after potential dynamic polarization, intergranular corrosion took place between Fe-16Cr-2Mo soft magnetic alloy and Ni-Cr alloy, and other alloys didn't corrode. There was no corrosion after galvanic current density test and immersion test.6. The optimum alloy that best matched Fe-16Cr-2Mo soft magnetic alloy in prosthodontics was Ni-Cr, Ti75, TA2 and Co-Cr alloy by turns. Fe-16Cr-2Mo soft magnetic alloy wouldn't be corroded by coupling with dental alloys in common use in oral environment, and possessed fine anticorrosive properties. |
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