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

本课题的研究成果总结如下：(1)建立了纯钛生物金属牙科精密铸造模型。以高耐火MgO和ZrO_2为聚合体，通过控制以下添加剂的用量，即NaHCO_3作为MgO的凝结剂或醋酸乙烯二氧化锆溶胶作为ZrO_2的凝结剂，细金属Zr粉作为尺寸控制剂，成功地铸造出了具有良好表面性能、良好力学性能和精确尺寸控制的纯钛牙科修复体。此外，采用上述新型模具粉料为涂层材料，以商业磷合硅料为二次投资材料，实现了降低模具成本的涂层技术。并从模具颗粒堆积结构的角度出发，阐述了热膨胀控制机理。(2)通过控制模具的渗透性和采用金属隔膜密封的新工艺，使熔融钛在较高的吸力条件下进入模具，有效地减少了纯钛的铸件内部缺陷。(3)纯钛口腔修复材料具有良好的生物相容性，并通过连续观察和长期在口腔内实际采用得到了证实。即使在几年后，修复剂的表面也没有观察到任何变化。(4)为了寻找牙用纯钛铸造坩埚用的陶瓷材料，采用Sessile-drop法对熔融钛与几种陶瓷基体在高温下的润湿性进行了基本测试。实验结果表明，CaO是目前研究的有希望的材料之一。在试制的含CaO坩埚的商用氩气铸造机上，与目前另一种含铜坩埚的氩气电弧熔炼铸造机相比，铸出的纯钛恢复体具有优良的表面性能和一定的力学特性。本研究经费所取得的丰硕成果，必将为纯钛在牙科领域的实现作出贡献。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