Development of Ceramic Mold for Precision Casting of High Temperature Melting Metals as Biomaterial

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Results in the research project were sumarized as follows;(1) Modl for dental precision casting of pure Ti as a biometal was developed. Excellent pure Ti dental restoratives which have good surface properties, several promissing mechanical characteristics and precise-controlled dimension were succesfully cast by utilizing high refractorious MgO and ZrO_2 as aggregate particles, and by controlling the amount of following additives, NaHCO_3 as setting chemicals for MgO or vinyle acetate zirconia sol for zrO_2, and fine metal Zr powder as dimensional controlling agent. Moreover, coating technique which made the cost reduction of mold was achieved by using above new mold powder batch as a coating material and commercial phosphate bonding silica investment as a second investment materials. And the thermal expansion controlling mechanism was alos elucidated from the consideration on the basis of particle packing structures on the mold.(2) The reduction of internal casting defects in pure Ti … More castings was effectively attained by control- ling the permeability of mold and by the new technique which enable cast the molten Ti into mold under ghigher suctioning condition with using metal diaphragm seal to the mold inlet.(3) The excellent biocompatibility of pure Ti dental restoratives was proved by consective obserbation of actually adopted in a human's mouth for long terms. and even after a few years there was no changes observed on the surface of the restoratives.(4) In order to search for usefull ceramic materials of crucible for dental pure Ti casting, wettabli- ities at high temperature between molten Ti and several ceramic substrates were fundamentally tested by Sessile-drop method. As the result of experiment, it was found that CaO is one of hopeful materials for present inverstigqting purpose. By using a commercial argon gas casting machine with CaO crucible which was triallyh made, the cast pure Ti restoratives showed excellent surface properties and some mechanical characteristics in comparison with the current another type of casting machine which use the copper crucible and arc-smelting in argon atmosphere.These fruitful results obtained in this research grant will surelyh contribute to the realization of pure Ti to the dental field. Less