|Budget Amount *help
¥6,300,000 (Direct Cost : ¥6,300,000)
Fiscal Year 1992 : ¥1,300,000 (Direct Cost : ¥1,300,000)
Fiscal Year 1991 : ¥1,300,000 (Direct Cost : ¥1,300,000)
Fiscal Year 1990 : ¥3,700,000 (Direct Cost : ¥3,700,000)
Since titanium alloys show excellent corrosion resistance and good biocompatibility, they are expected to be applied in the medical and dental fields. Precision and complication are required in dental materials, therefore, precise casting is an indispensable technique for dental alloys. However, dental casting of titanium, a very active metal, involves some problems to be solved, e.g., oxidation at high temperatures, absorption of atmospheric elements, and reaction with mold materials. Many researches for dental casting of titanium have been performed, mainly from the aspect of mold materials. While high melting point of titanium, about 1670 ﾟC, is one of the main factors of casting defects. To solve this problem, the improvement in alloying is thought to play an important role. Alloying is effective not only to lower the melting temperature but also to improve the mechanical properties. The purpose of this study was to develop the titanium alloys showing good mechanical properties as
well as suitable for dental casting.
The first problem in developing new titanium alloys for dental casting was the large scatter in mechanical properties caused by titanium materials. Therefore, the factors influencing the mechanical properties of pure titanium castings were investigated. The factors were the kinds of titanium ingots, the atmosphere in melting, and the impurities in the castings. As a result, basic data on the influential factors - required vacuum degree, titanium grade, amounts of impurity elements - were attained. Based on the findings, researches on Ti-Zr and Ni-Ti alloys were performed. Ti-Zr alloys also show good biocompatibility; the compositional change of Ti-Zr alloy surface in an artificial bioliquid was somewhat different from titanium surface. Dental casting of Ni-Ti alloy was easier than titanium; it could be cast without losing the special properties of shape memory effect and superelasticity by a conventional method because the melting point of Ni-Ti alloy were about 1300 ﾟC, nearly 400 ﾟC lower than titanium. Less