Food dye staining of dental composites: material variability and mouthwash-induced staining reversibility

Food dyes, widely used in consumables, may interact with polymeric materials, yet their staining effects on resin based dental composites remain underexplored. This in vitro study investigates the staining potential of five common water-soluble food dyes on contemporary dental composites and evaluates the efficacy of Listerine Advanced White mouthwash in reversing discolouration, using both colour difference and whiteness-based analyses.

Five synthetic dyes - Tartrazine, Sunset Yellow, Ponceau 4R, Carmoisine, and Brilliant Blue - were tested on six resin composites: Charisma Smart, Estelite ∑ Quick, Filtek One Bulkfill, RubyFlow, Spectra SphereTEC High Viscosity (STHV), and Filtek Ultimate. Sixty disk-shaped samples (7 mm × 2 mm) per composite (N = 360) were immersed in dye solutions (50 mg/L) or distilled water (control) for 7 days. Colour changes were evaluated using the CIEDE2000 colour difference formula (ΔE₀₀) and the dental whiteness index (WI_D), calculated from Commission Internationale de l'Eclairage L*a*b* color space (CIELAB) coordinates obtained with a spectrophotometer.

Brilliant Blue exhibited the highest staining potential, producing ΔE₀₀ values exceeding the clinically unacceptable threshold (1.8) in all composites except Spectra STHV, and was also associated with the greatest changes in WI_D values. Other dyes caused variable and generally less pronounced changes in both ΔE₀₀ and WI_D. The whitening mouthwash partially reversed discolouration, reflected by significant increases in WI_D and reductions in ΔE₀₀, with significant recovery observed in Estelite, RubyFlow, and Filtek One (p < 0.05). Analysis of variance revealed significant effects of dye type, composite material, and treatment on both ΔE₀₀ and WI_D outcomes (p < 0.001).

The colour stability and whiteness of dental resin composites are affected by synthetic food dyes in a material- and dye-dependent manner. Whitening mouthwash can partially restore both colour difference and whiteness; however, complete recovery to baseline values is generally not achieved.