The purpose of this study was to evaluate the compare the endurance of the commonly used dental magnetic attachments using potentiodynamic polarization method. For this study, 2 kinds of Sm-Co based; Magfit 600 and Magfit 400(G.C.) and 4 kinds of Nd-Fe-B based dental magnetic attachments; Hicolex Super J(Morita Co.), Magfit EX 600(G.C.), Magfit EX 400(G.C.) and Neomagnet(Preat Corp.) were chosen as a specimen and performed electrochemical corrosion test in 4 electrolyte solutions; 0.9% MCI, 1% lactic acid, 0.05% HCl, modified Fusayama´s artificial saliva solution. In 4 kinds of electrolyte solutions, the potential scanning was performed starting from -1000mV(SCE) to 1300mV and scan rate was 1.25mVlsec. From this study, we calculated the values of corrosion potential(Ecoxr), corrosion rate, pitting potential(Epit), and passivation current density resulted from anodic polarization curves and then obtained physical properties such as changing rate of magnetic flux density, amount of metal ion released, mean average surface roughness values, the changing of surface microhardness values, weight loss of dental magnetic attachments and observed surface of dental magnetic attachments using metallurgical microscope after electrochemical corrosion test.
The obtained results were as follows:
1. In Potentiodynamic polarization curves, SNM showed the lowest values of pitting potential and the most fast corrosion rate.
2. The amount of released metal was reduced in the order of ME6, SNM, MG4, MG6, ME4 and HSJ and was the greatest in applying the 0.9% NaCl solution and was the least in applying the the modified Fusayama´s artificial saliva.
3. The order of magnetic flux density was HSJ, MG6, ME6, MG4, ME4, and SNM before corrosion. The decreasing rate of magnetic flux density was the least in case of MG4 and was the greatest in case of SNM after first and second corrosion. The decreasing rate of magnetic flux density of 6 kinds of all magnetic attachments was the least in applying the 1% lactic acid solution.
4. The order of average surface roughness values(Ra) was SNM, MG6, MG4, ME4, ME6 and HSJ before corrosion. Average surface roughness values(Ra) was the greatest in case of SNM and was the least in case of HSJ after first corrosion. ME6 and ME4 showed the greatest increasing rate of average surface roughness values(Ra).
5. The order of average surface microhardness values(V.H.N.) was SNM, ME6, ME4, MG4, MG6, HSJ before corrosion. Decreasing rate of average surface microhardness values(V.H.N.) was the least in case of HSJ and was the greatest in case of SNM after first and second corrosion. The decreasing rate of average surface microhardness values of 6 kinds of all magnetic attachments was the least in applying the 1% lactic acid solution.
6. The decreasing rate of weight loss was reduced in the order of ME6, SNM and ME4 after first corrosion and was reduced in the order of ME4, SNM, ME6 after second corrosion. The decreasing rate of weight change showed the greatest in applying the 0.9% NaCl solution and the least in applying the 1% lactic acid after second corrosion.
In conclusion, all 6 kinds of dental magnetic attachments showed great decreasing of endurance and much more corrosion resulted in increased the amount of metal ion released, decreased the magnetic flux density, increased the surface roughness values, and highly decreased surface microhardness values and increased the weight loss of dental magnetic attachments. it should be considered that the choice of the commercial dental magnetic attachments was needed properly because their endurance showed differences among each kind of products..
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