Evaluation of chlorogenic acids and melanoidin interactions with salivary proteins and their effect on tooth discoloration.

Background: Tooth discoloration is a multifactorial process that is significantly influenced by the interaction between dietary polyphenols and salivary proteins. This study investigates coffee-induced discoloration using in vitro staining models and in silico simulations. Materials and methods: For 14 days, human premolar teeth were soaked in coffee solution (27 g/450 mL) with daily replacement. Lab and ΔE measurements were used to quantify color changes before and after immersion using ultraviolet-visible spectroscopy. Melanoidin compounds docked with salivary proteins (statherin, histatin, and proline-rich protein [PRP]). Hex 8.0 was used for molecular docking, whereas Discovery Studio Visualizer and UCSF Chimera were used for molecular dynamics analysis. Results: Molecular docking revealed the strong binding affinity of chlorogenic acid with PRP (-251.66 kJ/mol), histatin (-245.4 kJ/mol), and statherin (-240.5 kJ/mol), stabilized by hydrogen bonds with glycine/arginine/tyrosine residues. The molecular dynamics simulations confirmed complex stability with statherin (RMSD 4.2-4.6 Å) and histatin (RMSD 4.4-4.6 Å). Chromameter analysis showed significant color changes after coffee exposure (ΔEab = 12.286 ± 3.645), with a decrease in lightness (L: 83.569 → 71.873) and an increase in redness (a*: 1.375 → 2.992) and yellowness (b*: 15.848 → 18.585). Paired samples correlation analysis revealed statistically significant changes in the a* and b* values (p < 0.001), while the L* value showed no significant change (p = 0.257). Conclusion: Chlorogenic acid drives discoloration through stable protein interactions and measurable color shifts, suggesting that targeted inhibition of these molecular pathways could prevent coffee-induced discoloration.