Transparency and levels of translucency and opacity can be precisely manipulated. Typically, nuchal translucency alone is not sufficient as a screening test for chromosomal abnormalities. How to define a normal or abnormal nuchal translucency measurement can be difficult. Furthermore, the triple test may be combined with an ultrasound measurement of nuchal translucency. The opposite property of translucency is opacity. Tooth discoloration is abnormal tooth color, hue or translucency. Full-porcelain restorations are particularly desirable because their color and translucency mimic natural tooth enamel. The degree of the foreground color's translucency may range from completely transparent to completely opaque. On exposure to UV light some of the translucency and brilliancy is lost. Other stones are classified by their color, translucency and hardness. Other changes include thinner fonts and blurred translucency effects. Affected enamel has a different translucency than the rest of the tooth. Alumina cores have better translucency than zirconia, but worse than lithium disilicate. Preferable qualities of the bisque include a slight translucency without spots or holes. His work is praised for the translucency of the white porcelain on a colored background.