| Budget Amount *help |
¥1,900,000 (Direct Cost: ¥1,900,000)
Fiscal Year 1988: ¥300,000 (Direct Cost: ¥300,000)
Fiscal Year 1987: ¥1,600,000 (Direct Cost: ¥1,600,000)
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| Research Abstract |
The outstanding hard magnetic properties of rare earth magnets are well known and the physical origin is currently the subject of many investigations, but the study of application to dentistry is only in an early stage. In the present study, we will try to develop an apparatus for prosthetic appliance ,based on a new mechanism that has the feasibility in both of a castable forming and a convenient treatment. For the aim, the fine powder is dispersed homogeneously into the castable glass ceramics, by which the method the material will be made composite; in the first place, we prepared the glass ceramics which may be melted comparatively at low temperature, followed by the treatment of cast and crystallization. The mechanical strength of glass may be enhanced by the crystallization. Finally, the composite is magnetized after it is formed to cast using lostwax method and crystallized. The test and measurement were carried out, in order to produce an apparatus with a satisfactory corrosion
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resistance and a mechanical strength. Results obtained are summarized as follows. (1) The thermal behavior has been studied in the borophosphate glass system with several compositions,i.e.,P_2O_5-Al_2O_3-Li_2O-ZnO. The glass transition and the softening temperature are 340 ゜C and 400 ゜C, respectively. The thermal expansion ratio is 11x10^<-6>/deg,which is of the same order of that of enamel. (2) The optimum condition of cast has been examined. As a result, it is found that the precision cast may be achieved by using the phosphate investment material after the boron nitride was coated on the wax pattern to prevent burning. (3) The bending strength of crystalline borophosphate glass after the 72 hour test of water resistance is 1750 Kgf/cm^2 at 80゜C. The brush abrasion is satisfactory. The practical application, however, waits for a further exmaination. (4) Fine powder preparation method on Nd-Fe-B magnet is discussed. Crushing in the atmosphere of argon is now found to yield a desirable powder. In a present stage, it is being examined how to obtain more sophisticated glass complexed with the powder. Less
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