The Electrochemical Research Of Heat Treatment In The Corrosion Behavior For Dental Co-Cr Alloys

There are casting crown,onlay,fixed bridge and metal remove denture in prosthodontia since the casting is used in oral medicine. Metal materials are applied in prosthodontics and improve it. But there is segregation in alloys when it is in hard set after casting, it will come into being micro-battery because there are difference between the center and the border in ingredient. So it reduce the corrosion resistant of alloy. There is a special environment with saliva in mouth, restoration with metal material is easy happening electrochemical corrosion by electric difference in mouth, metal material separate out the metal ions and ramification, it will damage body if this kind of metallic ions have no biocompatibility, such as allergy, carcinogenesis, cytotoxicity, genotoxicity, tissue damage et al, on the other hand, restoration would break because the asymmetry of alloy by casting, such as clasp, rest, palatal bar et al, it would not only affect beauty but also reduce its useful time. Therefore,other than the excellent mechanical characteristics, the corrosion resistance should be treated as the important criteria about testing quality of dental alloys material as well.Heat treatment is wildly use in industry, it would improve material's property through change microstructure or surface components. Hereby, we deal with Co-Cr alloy by different heat treatment methods and analyse its metallographic. Then, we should do experiment research about corrosion resistance by electrochemical method.Objective:Through testing electrochemical parameters of heat treatment group and control group, it will useful for comprehensive measure or corrosion properties in heat treatment group and control group, and references and basis for change properties of Co-Cr alloy in the clinic. Methods:Dealing with Co-Cr alloy with three different heat treatment methods: 1000℃+water cooling,1000℃+air cooling,1000℃+furnace cooling. Then, scanning the three groups and control group with metallographic microscope, finally, in artificial saliva which PH was 7.0, the corrosion potential, polarization resistance and corrosion current density of heat treatment group and control group, were tested by the classic three electrodes system of electrochemical method.Results:1.from metallographic microscope: Co-Cr alloy's metallographic structure are made up of austenite +carbide. In comparison, the quantity of carbide in alloy, the furnace cooling group is the most, and the water cooling group is the less,there are tiny impurity in alloy and pore by casting disfigurement.2.in the artificial saliva, the sequence of corrosion potential of four group was water cooling>air cooling>control group>furnace cooling; the sequence of polarization resistance was water cooling>air cooling>control group>furnace cooling; the sequence of corrosion current density was furnace cooling>control group>air cooling>water cooling; the statistic results of water cooling and control group had significant difference(P<0.01); the other heat treatment groups had no significant difference with the control group(P>0.01)。conclusions:1. heat treatment can improve the segregation of alloys in casting by asymmetric ingredient, improved the corrosion resistant of alloys.2. we could improved the casting fault of alloys by heat treatment+water cooling.