UV-radiation aging test on composite materials for dental restorations.

Seven composite materials for dental restorations were examined in order to investigate their color stability. Five of these materials are available for anterior and two for posterior teeth. The change in color was achieved by an accelerated aging test with ultraviolet rays and evaluated, for each material, with the measurement of reflectance. Such measurement was obtained by means of a video display computer working as a computerized photometer. The results show two different types of behavior: some materials turn slightly to yellow, while others bleach. The test was completed with a scanning electron microscope morphologic examination of the surfaces.