Opacity of glass-ionomer cements.

The translucency of the first generation of glass-ionomer cements to appear on the market was too low to be cosmetically satisfactory. In the present study the opacity of newer editions of glass-ionomer cements was evaluated and compared with that of a well-known composite resin. Disc-shaped specimens were placed on black and on white backings, the luminous reflectances measured and corrected to a specimen thickness of exactly 1 mm, whereafter the contrast ratio was calculated. The newer glass-ionomer cements were found to be more translucent than the first generation of glass-ionomer cements on the market. However, the opacity still needs to be reduced to reach the level of a composite resin. It was further established that early water contact results in a considerable increase in opacity.