Ultramorphological and chemical characterization of dentin surfaces after application of two desensitizing toothpastes

Abstract

Objectives: To evaluate dentin tubule obliteration after application of two different desensitizing toothpastes using scanning electron microscopy (SEM) for ultramorphological analysis and energy dispersive X-ray spectroscopy (EDX) for chemical evaluation. Methods: Five dentin discs were sectioned into four quarters; surfaces were etched with 6% citric acid for 2 minutes and equally distributed into four groups. In G1 (control) no treatment was performed; dentin surfaces were brushed twice-daily during 14 days with artificial saliva (G2), a combined stabilized stannous fluoride, sodium hexametaphosphate and silica (SFSH) toothpaste (G3) and a calcium sodium phosphosilicate (CSFS) toothpaste (G4), under a standardized protocol. All specimens were analyzed by SEM and EDX and tubule occlusion was scored. Statistical analysis was performed using Kruskal-Wallis (p < 0 . 05). Results: Score distribution across groups consistently increased from G1 to G4, being the last the most consistent group. Statistical between-treatment comparisons for 750-fold and 2000-fold magnification revealed significant differences between groups (p=0.009 and p=0.002, respectively). For both magnifications, post-hoc analysis adjusted for multiple comparisons only indicated statistically significant differences between G1 and G4 (p=0.012 and p=0.001, respectively). Chemical analysis revealed high levels of carbon, oxygen and nitrogen for G1. For G2 an increase of the levels of the phosphorous and calcium elements and a drop of oxygen and carbon levels was registered. G3 and G4 showed a surface layer mainly composed of calcium and phosphorous. Conclusions: Both desensitizing toothpastes induced high levels of tubule occlusion with consistent phosphorus and calcium deposition over dentin surface.