|Budget Amount *help
¥23,600,000 (Direct Cost: ¥23,600,000)
Fiscal Year 1989: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 1988: ¥1,000,000 (Direct Cost: ¥1,000,000)
Fiscal Year 1987: ¥1,000,000 (Direct Cost: ¥1,000,000)
Fiscal Year 1986: ¥21,100,000 (Direct Cost: ¥21,100,000)
For the basic testing method in the evaluation of dental alloys, there are immersion tests using solutions such as hydrochloric acid, lactic acid and sodium chloride, or quantitative tests to measure the amount of dissolution electrically. However, these testing methods are not based on the corrosive changes of alloys within an oral environment. Oral cavity, especially the interdental areas between two adjacent teeth, seems to be a complicated environment for corrosion. Thus, observation of corrosion phenomena in these areas is necessary, since the evaluation method must be based on these findings.
We have observed the surface of metallic restorations and analyzed their component elements with energy dispersive type of X-ray microanalyzer (EPMA). Prior to the analysis, analytical accuracy and detection limit of the EPMA, effect of roughness or inclination of the sample surface were studied, and then the change in the composition of component elements due to corrosion was observed on the surface of the interdental area from metal restorations, such as crowns or inlays, which had been placed in the oral environment for a long period of time. Also, in order to find out the early changes of the alloys within the oral environment, standardized inlays or crowns were fabricated with gold alloys, gold-palladium-silver alloy, silver alloy arid nickel-chromium alloys, which were observed and analyzed by the method described above, and then, temporarily cemented to the abutment teeth. These restorations were removed after one week to analyze the same areas, cemented again to the abutment teeth and the same procedures were repeated after two and four weeks.
From these results, a basic testing method for alloys was studied.