| Summary: | 博士 === 高雄醫學大學 === 牙醫學研究所 === 100 === Titanium (Ti) has many advantages and has been used extensively in dentistry for recent years. When compared with traditional dental investment, producing high success rate of casting is easily to manipulate by using MgO-based investment. However, MgO-based investment still faces the problem about the thicker layer of oxidation which influences of properties on the bond between titanium and porcelain. In this study, pure titanium casting using MgO-based investment at different casting temperature was first examed. Then, the 0.1~0.5 wt% CaO amount was added in Ti powder modified MgO-based investment and the characteristics were investigated. Finally, the titanium recasting procedures were investigated though using 5 wt% ZrO2 additive MgO-based investment could further reduce waste. Experimental results showed that pure Ti should be cast at 800 ℃ to achieve the high accuracy of the marginal gap and less porosity. But the cast sample had more severe surface reaction when the cast process was operated at 800℃. However, the newly developed composition of Ti modified-MgO based investment with 0.5 wt% CaO additive would further reduced the thickness of oxide layer at 800 ℃. This newly developed Ti modified MgO-based investment with 0.1~0.5 wt% CaO additives had shown an acceptable marginal accuracy for the Ti casting and the marginal gap was less than 50 μm; among which, the 0.4 wt% CaO additive gave the best accuracy. As a conclusion, the marginal accuracy of the marginal gap and the thickness of the oxide layer were not affected by the use of the Ti recasting procedures. Nevertheless, based on microhardness and surface roughness analysis in a reuse procedure, the mechanical property was significant decreased by adding 5 wt% amount of ZrO2.
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