Placebo-controlled In Situ Study of Enamel Permeability after Bleaching

Objectives: This double-blind, placebo-controlled, 2x2 crossover in situ study assessed whether bleaching with 10% carbamide peroxide agent (CP-Whiteness Perfect 10%) would render enamel more permeable. Methods: After a 7-day lead-in period, a flattened, polished bovine enamel slab was bonded to the buccal surface of each one of 16 subject's upper second premolars. Then, 8 volunteers bleached their maxillary arch with the CP gel for a two-week period, while the remainders used a placebo agent. After a 1-week washout period, a new set o enamel slabs were bonded to the premolars and volunteers were crossed over to the alternate agent for 14 days. Specimens were then submitted to a histochemical coloring method with cooper sulfate and dithiooxamide solutions. Three sections of each sample were imaged in an optical microscope. Permeability was measured in the digitized images as the percentage of cooper ions penetration over the total enamel thickness. Results: The use of the active bleaching agent (CP) made enamel more permeable than the placebo gel, as shown by Friedman's test (a=0.05). Conclusion: Bleaching with 10% carbamide peroxide agent adversely affects enamel permeability. Supported by FAPESP (grant # 04/15795-0) and CNPq (grant # 477419/2004-6).