| ObjectivesTo study cobalt-chromium alloy, pure titanium and high-cobalt chromium molybdenum alloy's electrochemical corrosion behavior and the changes of surface morphology immersed in artificial saliva with different concentrations of fluoride, and to analyze the resistence to corrosion of dental casting alloy.MethodsCobalt-chromium alloy, pure titanium and high-cobalt chromium molybdenum alloy were respectively processed into the size of 10mm*10mm*1mm in tablets.The three kinds of metal were polished according to the clinical standard. The metal specimens were divided into 2 groups, dealt with 36 treatments,every kind of alloy were12 treatments.Then the specimens were measured with electrochemical corrosion test and immersion corrosion test in artificial saliva with different concentrations of fluoride (0%,0.05%,0.2%).Electrochemical corrosion test three alloy's electric potential of corrosion,current density of corrosion and polarization resistance.Immersion corrosion test specimens were immersed for 3 weeks.Metal surface roughness before and after immersion were measured and analyzed by scanning electron microscope.Analysed the results with SPSS 16.0 software package,the results were carried out by LSD-1 test.Results 1.Electrochemical corrosion test:1) Pure titanium and cobalt-chromium alloy's current density of corrosion increased and polarization resistance decreased with the concentration of fluorides increasing.2)There were significant differences for Co-Cr's electric potential of corrosion at the fluoride concentration of 0% and 0.05%(P<0.05), polarization resistance at the fluoride concentration of 0% and 0.2%(P<0.05). Others had no significant difference (P>0.05). There were significant differences for pure Ti's current density of corrosion and polarization resistance in different concentrations of fluoride artificial saliva(P<0.05). There was no significant difference for Vitallium alloy's electric potential of corrosion at the fluoride concentration of 0.05% and 0.2%(P>0.05), current density of corrosion at the fluoride concentration of 0% and 0.2%(P>0.05), polarization resistance at the fluoride concentration of 0% and 0.05%(P>0.05).Others had a significant difference (P<0.05)2.Immersion corrosion test:1) Metal surface roughness increased with the concentration of fluoride changing. At the fluoride concentration of 0%, the surface roughness of the three alloys had no statistically significant differences (P>0.05).The surface roughness of the Co-Cr group and the Ti group had statistically significant differences between before and after immersion (P<0.05) at the fluoride concentration of 0.05%, group Vitallium alloy had no statistically significant difference(P>0.05). The differences of the three groups before and after immersion were statistically significant difference (P<0.05) at the fluoride concentration of 0.2%.2) After immersion test between the three alloys, at the fluoride concentration of 0%, the surface roughness between group Co-Cr and group Ti, group Ti and group Vitallium had no statistically significant difference(P>0.05); Group Co-Cr and group Vitallium had statistically significant differences(P<0.05);. Group Co-Cr and group Ti had no statistically significant difference(P>0.05), and the differences between group Co-Cr and group vitallium, group Ti and group vitallium were statistically significant (P<0.05)at the fluoride concentration of 0.05%; At the fluoride concentration of 0.2%, the differences among three groups were statistically significant(P<0.05). Conclusions1) The presence of fluorides influence the corrosion resistance of cobalt-chromium, titanium and high-cobalt chromium molybdenum alloy.2) The sensitivity to fluoride of three dental casting alloys is Titanium> cobalt-chromium alloy> Vitallium alloy.3) Patients who frequently use fluoride products should not use pure titanium or cobalt-chromium alloy. Patients with prostheses of these three metal are not advised to use high concentration fluoride products long. |
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