Color Stability of Dental Composites after Thermocycling and Photoaging

The long term esthetic success of composites depends on their color stability which can be affected by sun radiation and the thermal changes within the oral environment. Objectives: The aim of this study is to determine the colour stability of three commercial dental composites, after thermocycling and photoaging. Methods: Three commercial hybridic dental composites of the same hue (A2) were selected, namely Tetric EvoCeram, Estelite Σ and Filtek Supreme. The unpolymerised, the polymerised and the photo-aged material was analysed in a FTIR equipment to determine the unreacted groups. Six discs of each material, 8, 67 mm in diameter and 1, 23 mm in thickness, were fabricated. They were polymerised after the exposure to a halogen lamp's radiation for 40s, in 850mV/cm2. Immediately after polymerisation colour was measured with a colorimetric device (DRLANGE MICROCOLOR). For each specimen 5 measurements were made. Then, all specimens were subjected to 1000 thermal cycles(5-55°C) and photoaging (SUNTEST CPS plus). Colour measurements were repeated. M and SD were statistically assesed. All colour measurements were made in CIE L*a*b* system. The colour change before and after the processing is given by the factor of ΔE* (ΔE*= {(ΔL)2+(Δa)2+(Δb)2}1/2). Results: For the materials Tetric EvoCeram (ΔE*=2,79) , Estelite Σ (ΔE*=2,96) and Filtek Supreme(ΔE*=2,09) a visually acceptable change of color has been observed. after photo curing was 53, 89% for Tetric EvoCeram, 55,8% for Estelite Σ and 44,4% for Filtek Supreme. After photo aging the degree of conversion was 12,61% for Tetric EvoCeram, 34,4% for Estelite " and 39,6%for Filtek Supreme Conclusions:Although the colour change was remarkable for all the three tested materials it was within the acceptable limits (ΔE*<3,3).The degree of conversion was reduced for all the materials with the highest reduction in Tetric EvoCeram.