Effect of different in vitro aging methods on color stability of a dental resin-based composite using CIELAB and CIEDE2000 color-difference formulas

Purpose To evaluate the effect of different in vitro aging methods on color change (CC) of an experimental dental resin-based composite using CIELAB (ΔE_ab) and CIEDE2000 (ΔE₀₀) color-difference formulas. Materials and Methods The CC was evaluated with a spectrophotometer (CM700d, Konica Minolta, Tokyo, Japan) according to the CIE chromatic space. Disk-shaped specimens (Φ=5×1mm thick) (N=10) were submitted to different in vitro aging methods: 30 days of water aging (WA); 120 hours of ultraviolet light aging (UVA); or 300 hours of an accelerated artificial aging (AAA) method with cycles of 4 hours of UV-B light exposure and 4 hours of moisture condensation to induce CC. The temperature was standardized at 37°C for all aging methods. CC was evaluated with ΔE_ab and ΔE₀₀ formulas. Differences in individual Lab coordinates were also calculated. Data for the individual color parameters were submitted to one-way analysis of variance and Tukey's test for multiple comparisons (α=0.05). Results All in vitro aging methods tested induced CC, in the following order: WA: ΔE_ab= 0.83 (0.1); ΔE₀₀=1.15 (0.1)<AAA: ΔE_ab=5.64 (0.2); ΔE₀₀=5.01 (0.1)<UVA: ΔE_ab=6.74 (0.2); ΔE₀₀=6.03 (0.4). No changes in L∗ or a∗ coordinates were ≥1; the methods with UV aging showed a yellowing effect due a large positive change in b∗. Conclusions All in vitro aging methods tested induced a CC, but to different extents. Changes in color followed similar trends, but with different absolute values when calculated with the CIELAB and the CIEDE2000 formulas. Clinical Significance Establishing the efficacy of different artificial aging methods and differences between color change using CIELAB and CIEDE2000 formulas are important to standardize color stability evaluations and facilitate the comparison of outcomes from different studies in the literature.