In Vitro Anti-Erosion Efficacy of Two NaF/KNO3 Silica Toothpastes

Objective: A comparison of the restorative and/or preventative properties of two dentifrices in reducing acid propagated surface mineral loss (erosion). Methods: Permanent bovine incisors were sectioned and polished to an optical flat. The distal ends of the enamel specimens were covered with adhesive tape to protect the profilometry reference areas. The exposed enamel was then etched with 5% citric acid at room temperature for 10 sec, treated with a 1:1 slurry of paste at 37 ºC for 5 min and subsequently exposed to surrogate orange juice (SOJ) (1% citric acid, pH 3.9, 2 min). Two toothpastes were evaluated during the treatment step: A, an 1450ppm NaF/KNO3 silica toothpaste (Sensodyne ProNamel) and B, an 1450ppm NaF/KNO3 silica toothpaste. Triplicate profilometry scans were conducted after the initial acid etch, the dentifrice treatment and after exposure to SOJ. Results: Analysis of enamel mineral loss (WeAr) using surface profilometry measurements (N=8/product) indicated that no statistically significant differences (p=0.313) were observed following treatment of acid softened enamel with either toothpaste A or B. Reduction in WeAr was 10.0±2.7µm2 and 13.6±9.0µm2, respectively. It was further observed that there was no statistically significant difference (p=0.389) between both products in preventing enamel mineral loss following subsequent acid challenge - product A (WeAr=18.4±12.6µm2) and product B (WeAr=12.2±15.4µm2). These results were consistent with the enamel solubility studies and enamel fluoride uptake studies wherein both fluoride-based toothpastes provided a protective function for the enamel during acid challenge. Low compositional abrasivity in both product A (RDA=66) and B (RDA=53), favorably reduced the propensity to mechanically abrade acid softened enamel. Conclusion: Results showed that toothpastes A and B provide statistically similar restorative activity to an acid-eroded enamel surface.