Impact of polyphenol-rich beverages on color stability, translucency and elemental surface composition of composite resins: correlation analysis after staining

The aim of this study was to conduct a multi-parametric assessment of optical degradation and surface chemical changes in composite resins following exposure to polyphenol-rich beverages, by integrating spectrophotometric measurements with SEM–EDS analysis to evaluate potential associations between elemental alterations and esthetic outcomes. 128 disc-shaped (2 mm × 8 mm) composite resin specimens divided into two main groups according to the composite resin used: Supra nano hybrid composite resin (Estelite Palfique Paste) and Microhybrid composite resin (Estelite Posterior). After four-step polishing with Sof-Lex discs, the specimens were weighed, their colors were recorded using a spectrophotometer according to the CIEDE2000 system. Specimens were then immersed for 14 days in black, rooibos, or peppermint teas for 2 h/day to simulate clinically relevant daily tea consumption habits. During the remaining time, specimens were stored in distilled water at 37 °C in an incubator. The tea solutions were prepared using commercial tea bags. Each tea bag (approximately 2 g) was immersed in 200 mL of freshly boiled distilled water and allowed to steep for 5 min. After removal of the tea bags, the solutions were cooled to a drinkable temperature (60 ± 2 °C) and used for the immersion procedures. Total polyphenol content (TPC) of the teas was determined using the Folin–Ciocalteu method. Color change (ΔE 00 ), translucency parameter (TP 00 ), and weight loss were measured at baseline and after post-staining ( n = 10). SEM–EDS analysis ( n = 3) was performed to assess surface morphology and elemental composition. Normality was assessed using Shapiro–Wilk, and parametric or non-parametric tests were applied accordingly. Both parametric (ANOVA) and non-parametric (Kruskal–Wallis) tests were used according to data distribution. Correlations were performed using Spearman’s rank correlation coefficient. The level of statistical significance was set at p < 0.05. TPC differed significantly among teas ( p < 0.05). Black tea caused the greatest ΔE 00 and ΔP 00 change in both composite resins ( p < 0.05). SEM–EDS analysis revealed tea-associated changes in surface elemental signals, including increased carbon and reduced silicon levels. ΔE 00 was positively correlated with total polyphenol content ( ρ = 0.614) and surface carbon percentage ( ρ = 0.660), and negatively correlated with silicon percentage ( ρ = − 0.503) (all p < 0.001). ΔP 00 was positively correlated with silicon and negatively correlated with carbon percentage ( p < 0.001). Composite resins showed different susceptibility to extrinsic staining depending on tea type, with black tea causing the greatest changes in color and translucency properties. Optical degradation was accompanied by alterations in surface elemental composition, particularly involving carbon and silicon.