Chemical Effects of Over-the-Counter Bleaching Agents on Exposed Dentin

Objectives: Over-the-counter bleaching products have become increasingly popular and are often used without professional supervision. In these cases, exposed dentin may inadvertently come into contact with peroxide-based products without patient’s awareness. This study evaluated the effects of over-the-counter whitening products on the organic and inorganic content of dentin.
Methods: Cylindrical dentin specimens (3 × 1 mm) were prepared from sound bovine incisors, polished and randomly allocated to five groups (n = 8): (1) hydrogen peroxide (HP) strips (Whitening Strips, Crest – 1 h/day); (2) 6% HP gel (Opal, Ultradent – 1h/day); (3) 2.5% HP mouthwash (Listerine Whitening Extreme, J&J – 1 min, 2x/day); (4) 10% carbamide peroxide gel (Opalescence, Ultradent – 8h/day, positive control); and (5) ultrapure water (negative control). Treatments were performed for 7 days, with specimens stored in artificial saliva between applications. Chemical composition was analyzed using Fourier-transform infrared spectroscopy with attenuated total reflection (FTIR-ATR). Thirty-two spectra per specimen were collected (1800–650 cm^-1), baseline-corrected, and normalized using the v3PO4 absorbance band. Mineral (PO4^3-/CO3^2-) and organic/inorganic (PO4^3-/Amide I) ratios were calculated before (T0) and after treatments (T1). Statistical analysis was performed using ANOVA and Tukey’s test (α = 0.05).
Results: No significant differences in the mineral ratio (PO4^3-/CO3^2-) were observed between groups or treatments (p > 0.05). For the organic/inorganic ratio (PO4^3-/Amide I), only the mouthwash group showed statistically significant increase compared to its baseline (T0: 13.51 ± 2.2; T1: 25.75 ± 17.7; p < 0.05), indicating increased mineral content.
Conclusions: The bleaching products tested did not significantly alter the organic or inorganic composition of dentin and the whitening mouthwash demonstrated a potential remineralizing effect.