Effect of a carbamide peroxide bleaching gel containing calcium or fluoride on human enamel surface microhardness

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.

Chemical Analysis of Enamel and Dentin Following the Application of Three Different At-home Bleaching Systems

“…However, controversial results exist on the topic since no supporting evidence regarding the influence of fluoride-containing bleaching gels on the remineralization has been documented. An in vitro study 21 reported that CP combined with F or Ca did not prevent the reduction in the surface microhardness of enamel. Contrarily, an X-ray photoelectron spectroscopy study 22 revealed that the additional sodium fluoride in HP bleaching agents generates fluoridated HAP and calcium fluoride crystals on enamel surfaces.…”

Effect of Different Fluoridation Regimes on the Microhardness of Bleached Enamel

“…This finding is in accordance with a number of previous studies that also showed a decrease in microhardness during bleaching treatment. 7,9,13,[19][20] However, other studies reported that 10% carbamide peroxide gel did not affect enamel surface hardness. [21][22][23] These contradictory findings among different studies might be due to differences in method, such as frequency and time of bleaching treatment, storage media or the use of human or bovine teeth.…”

Influence of Remineralizing Gels on Bleached Enamel Microhardness In Different Time Intervals

“…1 In fact, the effect of bleaching procedures on enamel is still controversial and needs to be elucidated. 3 Although a reduction in enamel microhardness has been reported, 4-7 it must be assumed that this alteration reflects not only the bleaching procedure but also the pH of the formulation used. 1 In fact, some studies have found no significant differences in enamel microhardness after bleaching with hydrogen peroxide in high concentrations.…”