| 3124 Attempt of Titanium Cast by Experimental Gypsum-bonded Investment | ||
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Y. TAMAKI, Z. ZHANG, Y. HOTTA, and T. MIYAZAKI, Showa University, Tokyo, Japan Objectives: Titanium is one of the outstanding prosthetic materials with excellent biocompatibility in dentistry. However, there are various restrictions by the casting processing method. The purpose of this study was to investigate the application of gypsum-bonded investments for titanium cast. Methods: MgO (#330, Tateho Chemical Co.,Ltd., Japan), that is one of stable refractory for titanium cast, and commercial dental gypsum(New Fuji Rock, GC Co.,Ltd., Japan) were prepared to design three kinds of experimental gypsum-bonded MgO investments according to the quantity of gypsum(5,10,15wt%). Each investment was mixed with water at a ratio of 0.2 for 30 seconds by hand and then automatically for 30 seconds under a vacuum using a mixing machine and five cylindrical specimens(diameter:20mm, height:10mm) were made for compressive test after heating until 700°C. Furthermore acrylic plates (10x10x1mm) were prepared as cast specimen. According to instruction, commercial pure titanium (KS-50, Selec, Japan) were cast into the heated mold by argon arc melting and centrifugal casting apparatus (Tycast super R, Selec, Japan). The mold was cooled down to 200°C prior to cast. Results: Hardening time changed according to the amount of gypsum. MgO-15gypsum set early, and it was approximately two hours. MgO-15gypsum was hardest after heating. There were significant differences on fired compressive strength among experimental investments by one-way ANOVA (p<0.05). These values were 3.40±0.31, 4.66±0.60 and 6.20±0.63MPa, respectively. All castings were covered by mold materials, but surface texture was not so bad. External defects for castings were not observed. Conclusions: Within the limited study, the experimental gypsum-bonded MgO investments were possible to cast titanium. In the future, it is necessary to also examine the castability for complicated form or dimensional accuracy of castings. | ||
| Seq #338 - Special Topics 2:00 PM-4:00 PM, Saturday, 12 March 2005 Baltimore Convention Center Exhibit Hall E-F | ||
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