新型氧化鎂包埋材及氬氣真空鑄造機對傳統牙科用合金鑄造之影響

牙科補綴物用金屬、鑄造方式與包埋材料隨著對純鈦鑄造的重視而蓬勃發展。新型氬氣真空純鈦鑄造機可降低金屬氧化現象，針對耐高溫所發展出來的耐火材可以減少與高溫熔融純鈦撞擊後產生的劇烈氧化反應。本實驗之目的是希望能將這些研發出來的先進材料與設備，來鑄造傳統牙科使用的金屬，期待能有不錯的結果。本實驗以氧化鎂系包埋材與傳統石膏結合包埋材兩種不同的包埋材，並搭配新型氬氣真空-加壓鑄造機與傳統離心鑄造機這兩種不同鑄造方式，來探討對傳統牙科用合金鑄造的影響。以熱膨脹測試機測量石膏結合包埋材之凝結膨脹量與熱膨脹量，找出最佳鑄造時機。再以2種鑄造機搭配2種包埋材，並進行金屬的重複鑄造3次，共分12組，每組鑄造3個試片，進行測試。其結果如下：石膏結合包埋材之總膨脹量約只有1.23%。而氧化鎂添加5%氧化鋯包埋材可以提供1.52%之膨脹量，比傳統包埋材更佳。完整鑄造比率在12組之中皆達到100%，顯示新型鑄造機與新型包埋材已可以達到十分穩定的鑄造成功率。邊緣密合度與金屬的重複鑄造次數之間沒有顯著性差異；邊緣密合度與新型、傳統鑄造機之間也沒有顯著性差異，因此新型鑄造機應有取代使用已久傳統鑄造機的能力。邊緣縫隙的大小與包埋材的不同則有顯著性差異（P<0.05），使用新型氧化鎂系包埋材優於使用石膏結合包埋材。如將鑄造體依照兩種鑄造機與兩種包埋材來分為4組發現彼此有顯著性差異，再做事後檢定分析發現一個共同的特點，氧化鎂包埋材的邊緣縫隙都小於石膏結合包埋材。表面粗糙值與金屬的重複鑄造次數之間沒有明顯差異。鑄造體的表面粗糙值與鑄造機的不同有顯著性差異，以新型鑄造機較佳。與包埋材的不同有顯著性差異（P<0.05），以傳統石膏結合包埋材為優。EPMA分析下，不同鑄造機下所有的金屬元素成分都無顯著性差異。邊緣縫隙的大小與金（Au）為負相關，金含量越高邊緣密合度越好。各個元素成分重量百分比與表面粗糙度則並無相關。金屬重複鑄造次數與包埋材的不同會影響表面硬度值。新型、傳統鑄造機對表面硬度影響不大。使用氬氣真空-加壓鑄造機所鑄造出來的鑄造體表面氧化層都明顯的比使用傳統離心鑄造機來的薄。由上述理由可以知道使用新型氬氣真空-加壓鑄造機與新型氧化鎂添加氧化鋯包埋材取代傳統材料與技術會有相當不錯的表現。

關鍵字

包埋材；牙科用合金；鑄造機；鑄造

並列摘要

The dental alloys, casting machines and investments have much improvement in these recent years, especially for casting of pure titanium. New type casting machine designed for pure titanium casting can reduce the oxidation layer when casting. Either entirely new systems or modification of the investments have been needed for the casting of pure titanium. We have been confirmed that MgO with 5% ZrO2 can increase the thermal expansion value and fitness of titanium casting. When using these new investments, the oxidation between molten titanium and investments can be reduced. The purposes of this investigation would want to improve the casting properties by replacement of the traditional casting technique and material by using new casting machine and new investment. In this investigation, we used 2 investments and 2 casting machines and repeated casting 3 generations, totally 12 groups. Each group has 3 samples. The results were described as follows: The total expansion of cristobalite base investment was 1.23%. The expansion value of cristobalite base investment was less than that of MgO base investment 1.62%. The castability was up to 100% in all groups. It means that, new type casting machine and new type MgO investment were suitable for conventional dental alloy casting. The repeated casting and casting machines show no significant difference between marginal gap. It shows a significant difference between marginal gap and investments. (P<0.05) The marginal gaps of MgO base investment were better than cristobalite investment. It means that, new type casting machine has ability to replace traditional casting machine. There is no significant different between surface roughness and repeated casting. Casting machines and investments show significant differences between surface roughness. (p<0.05) New type casting and cristobalite investment can provide batter surface roughness. The composition of alloy measuring by EPMA shows no significant difference with casting machines. The weigh percentage of Au shows negative correlation with marginal gap. The more of Au, the less of marginal gap. The oxidation layers of casting casted by argon vacuum-pressure casting machine were thinner than that casted by traditional centrifugal casting machine. The hardness of casting show significant difference with two investments, the VHN of cristobalite is higher than MgO investment. The hardness of castings are also show significant difference with each generations of repeat casting. The VHN of 100 % as-received alloy are significant higher than other groups. Hence, we concluded the casting machines and investments can affect the outcome of marginal gap and surface roughness of casting. The new type of casting machine and new investment can improve the marginal fitness and surface roughness of casting by traditional dental alloy.

並列關鍵字

investment ； dental alloy ； casting machine ； casting

參考文獻

1.Henning G. : The casting of precious metal alloys in dentistry. Brit. Dent. J. 133: 428-35, 1972

Google Scholar

2.Hideo Ogura, Constantin N. Raptis, Kamal Asgar : Inner surface roughness of complete cast crowns made by centrifugal casting machines. J Prosthet Dent 45:529-35, 1981

Google Scholar

3.Anthony H. L. Tjan, Tao Li, G. Irving Logan, Loyd Baum : Marginal accuracy of complete crowns made from alternative casting alloys. J Prosthet Dent 66:157-64, 1991

Google Scholar

4.James J. : A comparative study of the centrifugal and vacuum-pressure techniques of casting removable partial denture frameworks. J Prosthet Dent 45:18-23, 1981