Abstract
This in vitro study evaluated the surface microhardness of human enamel submitted to bleaching with 10% carbamide peroxide (CP) containing calcium or fluoride. Ninety-eight dental blocks (5 x 5 mm2) with polished enamel surfaces were randomly assigned to 7 treatment groups (n=14), as follows: without bleaching and storage in artificial saliva (control); 10% CP; 10% CP + 0.05% calcium; 10% CP + 0.1% calcium; 10% CP + 0.2% calcium; 10% CP + 0.2% fluoride; and 10% CP + 0.5% fluoride. During 14 days, enamel surfaces were daily exposed to a 6-h bleaching regimen followed by storage in artificial saliva. Surface microhardness was measured before (baseline), during (7th day), immediately after bleaching (14th day) and 1 week post bleaching. Data were analyzed by two-way ANOVA and Tukey's test (p<0.05). All treatments reduced SM significantly during the bleaching cycle (7th day), immediately after bleaching (14th day) and 1 week post bleaching, compared to baseline and to the unbleached control group. In conclusion, in spite of the addition of calcium and fluoride, all bleaching treatments affected the enamel surface microhardness.
Highlights
The use of self-administered carbamide peroxide (CP)-containing bleaching gels at home has become increasingly popular for whitening of stained and discolored teeth, since their introduction by Haywood and Heymann [1]
It has been reported that 10% carbamide peroxide bleaching may decrease calcium and phosphate enamel content, as well as its fluoride concentration [6]
It is generally accepted that the major effects of fluoride ions in enhancing crystal growth and retarding dissolution of dental enamel minerals are derived from their role in the solution phase, increasing supersaturation or decreasing undersaturation [7]
Summary
The use of self-administered carbamide peroxide (CP)-containing bleaching gels at home has become increasingly popular for whitening of stained and discolored teeth, since their introduction by Haywood and Heymann [1]. It has been reported that 10% carbamide peroxide bleaching may decrease calcium and phosphate enamel content, as well as its fluoride concentration [6]. These effects may possibly be overcome by addition of calcium and fluoride to bleaching agents’ compositions. Fluoride and calcium ions would increase the bleaching gel saturation and decrease mineral loss during bleaching action and exchange of ions. It is generally accepted that the major effects of fluoride ions in enhancing crystal growth and retarding dissolution of dental enamel minerals are derived from their role in the solution phase, increasing supersaturation or decreasing undersaturation [7]
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