| Budget Amount *help |
¥3,600,000 (Direct Cost: ¥3,600,000)
Fiscal Year 2001: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 2000: ¥3,100,000 (Direct Cost: ¥3,100,000)
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| Research Abstract |
Three different chemical substances were added to a liquid component of a self-curing acrylic resin (Pattern Resin, GC).
OXO (surfactant), ACMO (monomer) and ESCOURON (coumarone-indene resin) were selected as substances. The addition of 2 wt%-OXO to liquid reduces linear shrinkage to 0.04 %, about 1/3 of the shrinkage of the basic resin.
The effect of the addition of various metallic compounds on thermal expansion of an investment (Selevest D) was examined. Then, ZrC and ZrN were selected as additives to the investment. Investments added 3.0, 3.5, 4.0 and 5.0 wt% of ZrC and 5.0, 5.5, 6.0 and 7.0 wt% of ZrN were prepared. All investments showed setting shrinkage of about 0.5%. The thermal expansion of investments increased with the amount of Zr compounds and heating temperature, and remained after cooling at room temperature. The compressive strength of investments decreased with the amount of Zr compounds and firing temperature.
Then, pure titanium was cast into these investment-molds, which were fired and cooled down to room temperature.
The surface condition of castings into higher firing temperature was better than that into lower firing temperature. The surface roughness increased with the amount of Zr compounds. The casting accuracy of crowns were 0.21% in 3.5wt%ZrC-700℃ (firing temperature), 0.25% in 5.5wt%ZrN-700℃ and 0. 14% in 5.0wt%ZrN-900℃. In 5.0wt%ZrC, titanium cast crowns had fins which was formed as a result of cracks in the investment.
The casting accuracy could be controlled by the addition content of Zr compounds. The development of new thermal expansion typed investment for titanium was suggested to be possible.
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