Light polymerization-dependent changes in color and translucency of resin composites.

PURPOSE: To determine the influence of type of polymerization light on changes in color and translucency of resin composites. METHODS: 16 shades of commercial composites were analyzed. Specimens were polymerized with quartz-tungsten-halogen (QTH) and light-emitting diode (LED) polymerization light. Color of non-polymerized and polymerized composites was measured against white and black backgrounds using a spectroradiometer. Changes in color (deltaE'), translucency (deltaTP') and color parameters (deltaL', deltaC' and deltah') were calculated for each polymerization light. The differences among deltaE' values and among deltaTP' values obtained for each device were analyzed by two-way ANOVA. Multiple regression analysis was used to determine the influence of color parameters on deltaE' and deltaTP'. RESULTS: The results indicated that there was significant difference among the deltaE' and deltaTP' values obtained using QTH and LED light polymerization (P< 0.05). The prediction equations for deltaE' and deltaTP' based on the multiple regression analyses indicated that deltaE' was mainly caused by deltaC' for both lights. However deltaTP' was mainly caused by deltah' for LED light and by the deltaC' for QTH light. Changes in translucency significantly influenced the overall color changes after polymerization.

Study of the variation between CIELAB delta E* and CIEDE2000 color-differences of resin composites.

This study sought to assess the significance of the corrections introduced in the new CIEDE2000 color difference formula with respect to deltaE*ab. The purpose of which was to provide sounder knowledge, and hence more informed decision-making, about applying this new formula to dental resin composites. With two different hybrid composites, color differences were calculated between unpolymerized and polymerized resin composites, between polymerized resin composites of different thicknesses (1 and 2 mm), and between polymerized resin composites cured with halogen and LED light curing units (LCUs). The two formulas differed significantly, with VAB(E) (equal size) values higher than the inter-observer variability (VAB (E)=11%) and VAB(O) (original size) values greater than 25% for each of the data sets analyzed. Results obtained in this study agreed with and thus supported the recent recommendation of the Commission Internationale de l'Eclairage (CIE), whereby the new CIEDE2000 formula should be used to evaluate color differences of resin composites.