Abstract
High concentrations of hydrogen peroxide can cause adverse effects on composition and structure of teeth. However, the addition of calcium and fluoride in bleaching agents may reduce enamel demineralization.Objective:To evaluate chemical changes of sound and demineralized enamels submitted to high concentrations of hydrogen peroxide containing fluoride (F) or calcium (Ca).Material and Methods:Enamel blocks of bovine incisors with standard dimensions were obtained and half of them were submitted to pH-cycling to promote initial enamel caries lesions. Sound and demineralized enamel samples were divided into (n=10): (C) Control (no whitening treatment); (HP) 35% hydrogen peroxide; and two experimental groups: (HPF) 35% HP+0.2% F and (HPC) 35% HP+0.2% Ca. Experimental groups were submitted to two in-office bleaching sessions and agents were applied 3 times for 15 min to each session. The control group was kept in remineralizing solution at 37°C during the bleaching treatment. The surface mineral content of sound and demineralized enamels was determined through Fourier Transform Raman spectroscopy (FT-Raman), Energy dispersive Micro X-ray fluorescence spectroscopy (μ-EDXRF); and the subsurface, through cross-sectional microhardness (CSMH). In addition, polarized light microscopy (PLM) images of enamel subsurface were observed.Results:According to three-way (FT-Raman and μ-EDXRF analyses) or two-way analysis of variance (ANOVA) (CSMH) and Tukey test (α=5%), the calcium or fluoride added to high-concentrated bleaching agents increased phosphate and carbonate concentrations on sound and demineralized enamels (p<0.05). However, HPC and HPF were unable to completely reverse the subsurface mineral loss promoted by bleaching on sound and demineralized enamels. The calcium/ phosphate (Ca/P) ratio of sound enamel decreased after HP treatment (p<0.001).Conclusion:Even though experimental bleaching agents with Ca or F reduced mineral loss for both sound and demineralized enamel surfaces, these agents were unable to reverse the enamel subsurface demineralization.
Highlights
In-office bleaching has been extensively performed clinically due to the fast whitening promoted by the higher concentrations of hydrogen peroxide (HP) in one single application.1 low and high concentrations of HP can uphold adverse effects on enamel composition and structure.2,3 Among these alterations, the decrease of enamel inorganic content and enamel cohesive strength4 was observed
The surface mineral content of sound and demineralized enamels was determined through Fourier Transform Raman spectroscopy (FT-Raman), Energy dispersive Micro X-ray fluorescence spectroscopy (μ-EDXRF); and the subsurface, through cross-sectional microhardness (CSMH)
According to three-way (FT-Raman and μ-EDXRF analyses) or two-way analysis of variance (ANOVA) (CSMH) and Tukey test (a=5%), the calcium or fluoride added to high-concentrated bleaching agents increased phosphate and carbonate concentrations on sound and demineralized enamels (p
Summary
In-office bleaching has been extensively performed clinically due to the fast whitening promoted by the higher concentrations of hydrogen peroxide (HP) in one single application. low and high concentrations of HP can uphold adverse effects on enamel composition and structure. Among these alterations, the decrease of enamel inorganic content and enamel cohesive strength was observed. In-office bleaching has been extensively performed clinically due to the fast whitening promoted by the higher concentrations of hydrogen peroxide (HP) in one single application.. Low and high concentrations of HP can uphold adverse effects on enamel composition and structure.. Low and high concentrations of HP can uphold adverse effects on enamel composition and structure.2,3 Among these alterations, the decrease of enamel inorganic content and enamel cohesive strength was observed. High concentrations of HP can modify calcium/ phosphate (Ca/P) ratio and the loss of mineral content decreases microhardness, which might increase enamel susceptibility to demineralization.. High concentrations of HP can modify calcium/ phosphate (Ca/P) ratio and the loss of mineral content decreases microhardness, which might increase enamel susceptibility to demineralization.8 Such considerations are concerning since bleaching could interfere in the development of early caries lesions that are not properly detected. High concentrations of HP can modify calcium/ phosphate (Ca/P) ratio and the loss of mineral content decreases microhardness, which might increase enamel susceptibility to demineralization. Such considerations are concerning since bleaching could interfere in the development of early caries lesions that are not properly detected.
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