目的 测定IPS E.max A色系牙本质瓷无限光学厚度.方法 制作直径为13.0mm,厚度为1.0、1.5、2.0、2.5、3.0、3.5、4.0、4.5、5.0 mm的IPS E.max A1、A2、A3、A3.5、A4色号的盘状牙本质瓷,应用美能达CM-5分光测色计测试E.max牙本质瓷在标准黑、白背景条件下的色差值(△E),利用拟合回归方程计算出△E分别等于1.0和1.5时各色号牙本质瓷的厚度值.结果 E.max A色系牙本质瓷的无限光学厚度值分别为2.341～3.333 mm(△E=1.0)和2.064～2.904 mm(△E=1.5);随着色号或者厚度增加,背景色的影响逐渐减小,试样也越来越趋近其本质颜色.结论 在制作牙本质瓷背景试样时,必须要等于或超过其无限光学厚度才能表现为该色号的本质颜色,从而避免试样受其他颜色的影响.%Objective To determine the infinite optical thickness of dentine porcelain of IPS E.max A color series. Methods Cylindrical dentine porcelain specimens of the IPS E.max A color series were prepared with a diameter of 13 mm and thickness of 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, and 5.0 mm. The chromatic value of all the specimens was determined with CM-5 spectrometer against standard black and white background. The chromatic aberration (AE) was calculated by regression equation. Results The infinite optical thickness of dentine porcelain of the IPS E.max A color series ranged from 2.341 to 3.333 mm for a AE of 1.0, and from 2.064 to 2.904 mm for a AE of 1.5. As the chromaticity or thickness increased, the influence by the background color decreased, and the color of specimens became gradually close to the intrinsic color. Conclusion The thickness of the background dentine porcelain specimens must exceed its infinite optical thickness to represent the intrinsic color and avoid the influence by the extrinsic color.
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