In vitro safety evaluation of a hydrogen peroxide whitening emulsion technology on human enamel and dentin

Purpose: To assess effects of a novel hydrogen peroxide leave-on whitening emulsion on surface hardness, fracture susceptibility, surface erosion, and surface morphology of enamel and dentin. Methods: Human enamel and root dentin sections embedded in resin were leveled and polished for uniformity. A cycling treatment simulating overuse conditions (60 hours over 10 days), coupled with incubation in pooled human saliva at 37 degrees C and two daily toothpaste treatments were used to evaluate the safety of a 3% hydrogen peroxide whitening emulsion treatment (Crest Whitening Emulsions). Controls included a no treatment group, three erosion controls (water, 0.25% citric acid pH 3.6, 1% citric acid pH 3.6), and a bleaching control (8.25% sodium hypochlorite). Color measurements (b*) were taken on select post-treated specimens to confirm bleaching activity. Effects on enamel and dentin physical properties were determined by surface microhardness, fracture toughness, erosion depth, and surface morphology by light and scanning electron microscopy. Results: The hydrogen peroxide emulsion b* value was significantly different versus water control (P< 0.05), confirming bleaching activity. Microhardness and fracture toughness results for hydrogen peroxide emulsions were not significantly different versus baseline (P> 0.2) and no treatment (P= 1.0), respectively. Erosion loss for the hydrogen peroxide emulsion was not observed on enamel (comparable to water) and significantly less than 0.25% citric acid (P< 0.05) on dentin which was verified by microscopic visualization. CLINICAL SIGNIFICANCE: The hydrogen peroxide emulsion had no significant negative effects on enamel and dentin properties after 60 hours of bleaching over 10 days, confirming safety under simulated overuse conditions.