Effect of desensitizing and anti-erosive toothpastes on dentin chemical composition and morphology

This study evaluated the effects of brushing with desensitizing and anti-erosive toothpastes on the chemical composition and morphology of eroded dentin. Four groups were tested: Colgate Sensitive Pro-Relief® (ARG), Sensodyne Repair and Protect® (CSPS), Regenerate Enamel Sci-ence® (REG) and a control (Colgate Total®). Particle size, zeta potential, dentin surface charge, chemical composition, and tubule occlusion were assessed using dynamic light scattering (DLS), ATR-FTIR, and SEM-EDS measurements. All toothpastes contained nanosized particles with diameters ranging from 86 to 597 nm and exhibited negative zeta potentials from -25.3 to −45.0 mV. Eroded dentin initially exhibited a higher Ca/P molar ratio than hydroxyapatite, indicating Ca2+ deficiency, which was restored to near-stoichiometric values (1.67) after brushing. Brushing preserved the chemical composition of dentin, as confirmed by infrared spectroscopy, which exhibited bands assigned to phosphate, carbonate, and collagen. Morphologically, all tested toothpastes significantly reduced dentinal tubule diameter compared with the unbrushed control (3.44 ± 0.57 μm). The CSPS group exhibited the most effective occlusion with a final tubule di-ameter of 1.00 ± 0.24 μm and deposit penetration of 22.6 μm, maintaining significant occlusion and penetration even after acid exposure (1.10 ± 0.28 μm and 20.8 μm, respectively). The REG group showed good initial occlusion with a tubule diameter of 1.21 ± 0.33 μm and the deepest penetration (25.0 μm). Still, it exhibited lower acid resistance, characterized by an increased tubule diameter (1.61 ± 0.40 μm) and a reduced penetration depth (10.0 μm). ARG presented intermediate occlusion with a tubule diameter of 1.49 ± 0.48 μm and penetration depth of 13.7 μm, along with good acid resistance (1.78 ± 0.57 μm diameter; 11.5 μm depth). The dentin brushed with the control group also maintained tubule occlusion before and after acid exposure (1.55 ± 0.50 μm and 1.55 ± 0.48 μm, respectively), showing high initial penetration (26.2 μm), but the lowest post-acid penetration depth (5.26 μm). In conclusion, a nanometric particle size and a slight negative charge are critical for coating deposition and tubule penetration. The for-mation of mineral coatings preserves the chemical composition of dentin and may offer a protective barrier against acidic challenges. Sensodyne Repair and Protect® exhibits the most consistent tubule occlusion after acid exposure, suggesting a potential for enhanced acid resistance. Among the tested formulations, CSPS exhibited the most consistent tubule occlusion after acid exposure, suggesting a potential for enhanced acid resistance.