Color changes of composites on exposure to various energy sources

Abstract

The color stability of composites, on exposure to irradiation (1) by a 150 klux xenon lamp, (2) a standard RS light source and (3) at elevated temperature at 60°C, in air or water and under different experimental conditions was determined for various times. Composites studied included chemically and light cured hybrid and microfilled resins and a material copolymerized by light and chemical aftercure. Color changes of composites intensified on increasing the irradiation time. Exposure to the 2 light sources under similar conditions gave comparable results. Visible light cured materials studied were more color stable than 2 common chemically cured composites. Light shades yielded more visible color changes than dark shades of the same brand. There was a significantly more severe discoloration of composites kept in water at 60°C than for those stored in air. Comparison with results in 2 clinical studies of color changes, using 2 of the chemically cured composites investigated here, indicates that these 2 restoratives, which pass the ANSI/ADA or ISO specification tests, discolor in clinical use after 2–3 years.