Masking ability of gingiva-colored resin-based composites over different tooth-colored substrates

The purpose of the study was to investigate the influence of different tooth-colored substrates and restoration thicknesses on the final color of gingiva-colored resin-based composites (GCRBCs). Five different shades of GCRBCs [light pink (LP), dark pink (DP), orange (Or), brown (Br), and purple (P)] were used to prepare disc-shaped specimens with 2 different thicknesses: 1.0 mm, and 2.0 mm. GCRBC discs (n = 5) were placed over 3 different tooth-colored substrates (ND1, ND5, and ND9) and color parameters were assessed using a spectroradiometer. Color differences (∆E*_ab and ∆E₀₀) were calculated using CIELab and CIEDE2000 formulas and compared to 50:50% perceptibility (PT: ∆E*_ab = 1.7, ΔE₀₀ = 1.1) and acceptability (AT: ∆E*_ab = 3.7, ΔE₀₀ = 2.8) visual thresholds. Color variation data were statistically analyzed using two-way ANOVAs followed by Bonferroni's post hoc tests (a = 05). The ∆E*_ab and ΔE₀₀ values of GCRBCs placed over ND9 substrates were significantly higher in the LP-1.0 mm and Or-1.0 mm groups that presented values above AT (p< .001).Regardless of the substrate color and GCRBC thickness applied, ∆E*_ab and ΔE₀₀ values below AT were recorded in the gingival color groups of P. Substrate color significantly affected the color differences in the gingival color groups of LP, DP, and Or with a restoration thickness of 1.0 mm (p < .05). Gingival color, restoration thickness, and substrate color influenced the color differences of GCRBCs. When the gingival color was a lighter gingival color, rather than dark purple, the masking ability was decreased, especially with a restoration thickness of 1.0 mm.