Influence of color coordinates on the color changes after polymerization and thermocycling of dental resin composites

Color changes after polymerization and aging of dental resin composites are perceptible. If these color changes can be predicted by the shade of material before polymerization or clinical use, color matching of composites with teeth would be improved. The objectives were to measure the correlations among the color coordinates (CIE L∗, a∗ and b∗) of dental resin composites and the changes in color (Δ E∗ab) and color parameters (Δ L∗, Δ C∗ab, and Δ H∗ab) after polymerization (PO) and thermocycling (TC), and to determine whether the range of color coordinates influenced these correlations. Color of two resin composites (26 shades) was measured before and after PO, and after TC with a reflection spectrophotometer. Regression analyses were performed among the color coordinates and the changes in color and color parameters after PO and TC. After PO, Δ E∗ab was correlated with CIE L∗ value measured after PO, and CIE a∗ and b∗ values measured before PO (p < 0.01). After TC, Δ E∗ab was correlated with CIE b∗, a∗, and L∗ measured after PO (p < 0.01). Correlations among the color coordinates and the changes in color parameters after PO or TC varied, but were generally significant (p < 0.01). Multiple regression analyses showed that Δ E∗ab values after PO and TC were mainly influenced by CIE L∗ after PO (multiple r = 0.87 after PO and 0.58 after TC). Correlations were also influenced by the range of color coordinates. Within the limit of this study, shade of resin composites significantly influenced the changes in color and color coordinates after PO and TC. Light shades (high CIE L∗ shades measured after polymerization) showed small color changes after polymerization and thermocycling.