Contemporary tooth bleaching agents are mainly based on hydrogen peroxide or carbamide peroxide, and the mechanism of action of bleaching agents is based on the oxidation of large chomophore molecules responsible for enamel and dentin discoloration. Numerous studies suggest that bleaching leads to changes in the structure of the enamel surface and these in turn alter the biomechanical properties of the enamel. Therefore, this study compared the effects of professional tooth whitening agents containing highly concentrated hydrogen peroxide (with and without laser activation), on the enamel surface; and the potential of four different toothpastes to remineralize any alterations.
The study was performed on 50 human molars, half of which were treated with a bleaching agent only, whereas the other half was bleached with a bleaching agent activated by a diode laser. Furthermore, the possibility of remineralization was examined by treating of the samples by different remineralization toothpastes containing: aminfluoride, casein phosphopeptide–amorphous calcium phosphate, bioactive glass or hydroxyapatite. The samples were analysed by SEM/3D‐SEM‐micrographs, SEM/EDX‐qualitative analysis and SEM/EDX‐semiquantitative analysis.
The microphotographs show that both types of bleaching cause alterations of the enamel surface: emphasized perikymata, erosions, loss of interprizmatic substance; the laser treatment is more aggressive and loss of integrity of the enamel is determined by shearing off the enamel rods. In all samples undergoing remineralization deposits were observed, those of toothpastes based on calcium phosphate technologies seem to merge with each other and cover almost the entire surface of the enamel. Loss of integrity and minerals were detected only in the line‐scans of the sample remineralized with GC Tooth Mousse™. The semiquantitative EDX analysis of individual elements in the surface layer of the enamel indicates that during tooth‐bleaching with HP statistically significant loss of Na and Mg occurs, whereas the bleaching in combination with a laser leads to statistically significant loss of Ca and P.
The results undoubtedly confirm that teeth whitening procedures lead to enamel alterations. In this context, it must be noted that laser bleaching is more aggressive for dental substances. However, these changes are reversible and can be repaired by application of remineralization toothpastes.