Effect of exponential polymerization on color stability of resin-based filling materials

PurposeTo investigate the influence of a halogen light curing device used with constant or exponential polymerization mode on the color stability of contemporary resin-based filling materials.Materials and methodsEight samples of Charisma (CH), Durafill (DU), Definite (DE), and Dyract AP (DY) each were light-cured with constant power or with soft-start mode (Translux Energy) for 20, 40 or 60 s. The CIE-Lab-values (L*, a*, b*) were measured prior to and after performing dry aging, water aging or a Suntest (EN ISO 7491) and ΔL-, Δa-, Δb-, and ΔE-values were calculated.ResultsStatistical analysis (GLM and repetition of measures) showed significant changes (p < 0.05) of the color values for each material's curing mode and time after each of the aging processes. Four-way ANOVA revealed significant differences (p < 0.05) between ΔL-, Δa-, Δb-, and ΔE of the materials in dependence on the curing time and mode and aging condition. Exponentially-cured DU was the most color-unstable material after aging in water followed by the 20 s exponentially cured DE and CH samples. After the Suntest, DY showed significant bleaching (negative Δb) and the largest ΔE for all curing times and modes followed by the DE samples. DU and CH were the most color-stable materials in this test.SignificanceThe extent of discoloration depends on the (a) curing time, (b) curing mode, (c) aging condition, and (d) material. For the constant curing mode, 40 s curing time for the exponential 60 s seems to be appropriate.