Non-peroxide eggshell-based experimental material: Effects on the color and composition of human dental enamel

Alternative calcium phosphates are strong candidates as tooth-whitening to mitigate the adverse effects of hydrogen peroxide (HP). This study examines changes in the color and chemical structure of human enamel induced by a biomimetic calcium phosphate-based bleaching ceramic derived from chicken eggshell, known as the experimental remineralizing Substance (ERS). Forty human molars were assigned to four groups: G1: storage group; G2: treated with 35% HP; G3: treated with ERSs; and G4: treated with HP followed by ers. CIE color coordinates (L*, a*, b*) were recorded before and after treatment using a dental spectrophotometer to calculate color differences (ΔE*_ab, ΔE₀₀) and the whiteness index$\left(W{I}_D\right)$ which were later compared with previously established perceptibility (PT) and acceptability (AT) thresholds. After each treatment, enamel surface powders from each specimen were analyzed using attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) and X-ray diffraction (XRD). Statistical analyses included one-way ANOVA and simple linear regression for color measurements, as well as one-way ANOVA, Shapiro-Wilk, Kruskal-Wallis, and Holm-Bonferroni tests for chemical composition. The results indicated a significant decrease in L* (p = 0.01) and b* (p = 0.03) values in G3. The highest mean values of ∆E*_ab and ΔE₀₀ (p ⩽ 0.05) exceeded PT and AT indicating good effectiveness. ATR-FTIR analysis revealed that certain phosphate bands in G3 remained unchanged compared to G1 and G2. Additionally, carbonate substitution at the A and B-positions was reduced, and the degree of mineralization increased compared to G2. XRD patterns showed diffraction peaks linked to hydroxyapatite crystals in all experimental groups. All treatments reduced crystallite size, and this effect was not reversed in G3. Thus, this study demonstrates that ERS achieved a superior whitening effect compared to HP, without altering the chemical composition or crystalline structure of human enamel. These findings suggest the potential of using ERS as a safer alternative to conventional peroxide-based whitening agents.