Effect of hydrogen peroxide topical applications on enamel and composite resin surfaces

Objectives: The objectives of the present study were to analyze the morphology and the superficial roughness of enamel and composite resin restorations after three different bleaching regimens. Materials and methods: Enamel specimens were obtained from buccal surfaces of 21 human incisors. Two specimens were obtained for each tooth. Half part of each tooth was maintained in distilled water and served as control; the other part was treated with one of three professional bleaching agents: 38% hydrogen peroxide (Opalescence Boost; Ultradent Products, Inc.), 35% hydrogen peroxide (Whiteness HP Maxx; FGM Produtos Odontol\uf3gicos Ltda), light-activated 25% hydrogen peroxide (Zoom 2; Discus Dental Inc.). The same bleaching protocols were applied on standardized composite resin (CeramX mono; Dentsply De Trey) surfaces. Composite specimens were divided in four subgroups (n = 7), according to surface treatment (distilled water was used for control group). Two enamel and composite specimens for each group were submitted to a qualitative scanning electron microscopy (SEM) analysis. Remaining specimens were measured for roughness using a 3D optical profilometer (Talysurf CLI 1000; Taylor Hobson). Data were statistically analyzed. Results: A preliminary profilometric analysis of the enamel and composite surfaces after bleaching protocols showed no significant differences in surface roughness parameters (p > 0.05) compared with those at baseline. Results of the correlated SEM analysis showed no relevant alteration on the enamel surfaces. However, some significant changes of composite surface morphology were SEM observed at high resolution ( 71000 and 73000) after conditioning treatments, suggesting a predominance of depressions after each of the three bleaching procedures. Conclusions: Although SEM analysis seems to suggest that professional bleaching procedures may adversely affect the microscopic surface texture of composites, the profilometric results showed that the tested bleaching regimens do not alter enamel and composite surface roughness