Topographical changes of enamel and root dentin following bleaching

Objectives: The present knowledge of possible adverse effect of carbamide peroxide-containing bleaching agents on dental hard tissues, especially when applying high concentrated products, is still controversial. Thus, this study was devised to gain further insight into the topographical changes of enamel and root dentin after application of carbamide peroxide products having different concentrations. Methods: Sixty bovine incisors were cut at the cemento-enamel junction and rectangular enamel and dentin slabs (6x3x2 mm) were obtained from the coronal and root portions of the teeth, respectively. After sectioned pieces had been minimally ground and metallografically polished, specimens were randomly assigned to 15 experimental blocks. Surface roughness was recorded with a contacting profilometer, whereby each specimen was scanned three times across the surface. Specimens were then exposed to a 10, 15 or 22% carbamide peroxide product (Rembrandt, n=15). The bleaching agents were applied at treatment intervals of 2 hours per day, while covered with an individual flexible tray, over 21 days. The control groups were mock-treated using artificial saliva. In between treatments, specimens were soaked in artificial saliva. At the completion of the bleaching period, surface roughness measurements were carried out following the same protocol as for the pre-testing records. The differences between the post- and pre-bleaching surface roughness were considered for statistical analysis. Results: One-way ANOVA did not reveal significant difference among the bleaching agents applied to either enamel (p=0.2832) or root dentin (p=0.2194). Conclusion: In comparison with the sound substrates, bleaching with carbamide peroxide-containing agents concentrated between 10 and 22% was not detrimental to the surface texture of enamel, nor to that of root dentin. (Supported by FAPESP, grant #03/02150-8).