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

主要研究成果如下：（1）研制了牙科用生物纯钛精密铸造模具。以高熔点的MgO和ZrO_2为骨料，以NaHCO_3为MgO的固化剂，以醋酸乙烯酯锆溶胶为ZrO_2的固化剂，以金属锆微粉为尺寸控制剂，通过控制添加剂的用量，成功地铸造出表面性能良好、力学性能优良、尺寸精确可控的纯钛牙科用陶瓷。此外，采用上述新型保护渣配合料作为涂料，以市售磷酸盐结合二氧化硅包埋料作为第二包埋料，实现了降低铸型成本的涂料技术。并从颗粒在铸型上堆积结构的角度阐述了热膨胀控制机理。(2)纯钛内部铸造缺陷的减少 ...更多信息 通过控制结晶器透气性，采用金属隔膜密封铸型入口，使钛液在较高的吸铸条件下进入结晶器，有效地获得了铸件。(3)经口腔内长期实际应用的连续观察，证明纯钛牙科充填材料具有良好的生物相容性。甚至在几年之后，在澄清剂的表面上也没有观察到变化。(4)为了寻找牙科纯钛铸造坩埚的有用陶瓷材料，采用座滴法对熔融钛与几种陶瓷基体之间的高温润湿性进行了初步测试。实验结果表明，CaO是目前最有希望的研究对象之一。用试制的CaO坩埚氩气浇铸机，与现有的铜坩埚氩气熔炼浇铸机相比，所浇铸的纯钛材料具有优良的表面性能和某些力学性能，这些研究成果将有助于实现纯钛在牙科领域的应用。少

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