Earnshaw R, Morey E F
Department of Prosthetic Dentistry, University of Sydney, Surry Hills, NSW, Australia.
J Dent Res. 1992 Dec;71(12):1865-70. doi: 10.1177/00220345920710120201.
Measurements were made of the fit of gold-alloy full-crown castings produced with dry ceramic ring liners. When used with vacuum investing, these liners absorb relatively large amounts of water from the investment mix (thereby reducing its original W/P ratio) and then function as wet liners, thus increasing the investment's potential expansion and giving castings which are consistently larger than when air investing is used. With four of the five liners tested, investing in air produced many castings which were unacceptably undersized (inaccuracy worse than -0.2%). The fifth liner, an industrial material 2 mm thick, gave only one casting out of 12 which was outside this limit, although all castings were undersized to a lesser extent. Vacuum investing gave improved casting accuracy; with four of the five liners, the improvement was highly significant (p < 0.001), and with the fifth, probably significant (p < 0.05). Even with vacuum investing, however, with only two of the liners did all castings show inaccuracies within +/- 0.2%. With the other three liners, some castings (ranging from 2/10 to 7/9) had inaccuracies worse than -0.2%. With both air and vacuum investing, changing from one liner to another caused changes in relative casting accuracy which were often significant (p < 0.01) or highly significant (p < 0.001). In casting techniques where a ceramic ring liner is used, the choice of specific lining material and the choice between investing in air or under vacuum are important factors which can have a major effect on the fit of castings.
对使用干式陶瓷环衬里制作的金合金全冠铸件的适配性进行了测量。当与真空包埋法一起使用时，这些衬里会从包埋混合料中吸收相对大量的水分（从而降低其原始水/粉比），然后起到湿衬里的作用，进而增加包埋料的潜在膨胀，并使铸件尺寸始终大于采用空气包埋法时的尺寸。在测试的五种衬里中，有四种采用空气包埋法制作出的许多铸件尺寸过小，无法接受（误差超过-0.2%）。第五种衬里是一种2毫米厚的工业材料，在12个铸件中只有1个超出此极限，不过所有铸件尺寸缩小的程度较小。真空包埋法提高了铸件精度；对于五种衬里中的四种，这种提高非常显著（p<0.001），对于第五种，可能也显著（p<0.05）。然而，即使采用真空包埋法，也只有两种衬里制作的所有铸件误差在±0.2%以内。对于其他三种衬里，一些铸件（从2/10到7/9不等）的误差超过-0.2%。无论是空气包埋法还是真空包埋法，从一种衬里更换为另一种衬里都会导致相对铸件精度发生变化，这种变化通常显著（p<0.01）或非常显著（p<0.001）。在使用陶瓷环衬里的铸造技术中，特定衬里材料的选择以及空气包埋法或真空包埋法的选择是重要因素，会对铸件的适配性产生重大影响。
