以氧化鎂為基底包埋材對純鈦金屬鑄造影響之探討

Application of MgO-based investments in the role of pure titanium casting

賴珮翎(Pei-Ling Lai)

指導教授 ： 洪純正

高雄醫學大學/口腔醫學院/牙醫學研究所/博士(2012年)

摘要

純鈦金屬擁有許多相當優良的性質，包含密度低、理想的機械性質與優良生物相容性等，近年廣泛的應用在牙醫學領域。與傳統牙科用包埋材相比較，目前認為氧化鎂系包埋材可有效提高鑄造成功率，而且操作方便性佳。但是氧化鎂包埋材仍使鑄造物有較厚氧化層，所以還須改善鑄造環境與包埋材條件，才能獲得理想鑄造物。本研究以氧化鎂包埋材做基礎，試圖找出最適合純鈦鑄造條件，並改進原氧化鎂包埋材高溫穩定性不足的缺點，以提高純鈦鑄造物性質，最後探討純鈦反覆鑄造的可能性，全面提升純鈦鑄造物臨床使用度。本研究採用氧化鎂包埋材在不同溫度下800℃、600℃、400℃、200℃與25℃進行純鈦鑄造以決定最佳鑄造溫度。由於當8 wt% 鈦/氧化鎂添加氧化鈣後，可進一步增加包埋材熱膨脹，在決定最佳鑄造溫度後，添加0.1~0.5 wt %氧化鈣進行純鈦鑄造，了解最佳添加濃度。最後配合添加5 wt%氧化鋯，進行純鈦反覆鑄造研究。研究發現在鑄造溫度800 ℃時，純鈦鑄造物擁有最佳精密度與最少量氣泡生成；然而表面硬度與粗糙度仍偏高。當添加0.4 wt%氧化鈣組鑄造物可擁有最佳精密度。添加0.5 wt% 氧化鈣組鑄造物表面的硬度值最小與氧化層最薄。在添加氧化鋯下，5 wt%氧化鋯/二次鑄造世代仍擁有高鑄造成功率與臨床上可接受的精密度，在氧化層厚度亦未有顯著增加。然而重覆鑄造對純鈦金屬鑄造物內層320~520 μm硬度會有顯著改變。由以上研究可知高溫鑄造仍是提高鑄造物精密度的關鍵，當添加氧化鈣讓純鈦在高溫鑄造下仍可擁有表面低反應性。而配合氧化鋯的添加使純鈦可進行重複鑄造，不影響純鈦金屬的精密度與機械性質。

關鍵字

鈦金屬 ； 鑄造溫度 ； 氧化鎂 ； 氧化鈣 ； 重複鑄造 ； 氧化鋯

並列摘要

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.

並列關鍵字

Pure titanium ； Casting temperature ； Calcia investment ； Magnesia investment, Recasting ； Zirconia investment

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