Fluoride-Activated Via Er:YAG, Diode, and Femtosecond Lasers for Reversing Bleached Enamel for Improved Orthodontic Bonding.

Abstract

Aim: This investigation aimed to assess the efficacy of reversal methods on bleached enamel via fluoride-activated Er:YAG, diode, femtosecond laser, focusing on Vickers hardness (VH), shear bond strength (SBS), calcium (Ca⁺⁺)/phosphorus (P) ratio, and the interface between brackets and enamel. Materials and Methods: A total of 112 human maxillary premolars with intact enamel, which had been extracted, were included. About 96 specimens underwent bleaching using a 40% hydrogen peroxide (HP) Office bleaching agent. The remaining 16 samples were taken as control. The enamel samples were divided into six groups (2-7) based on the bleaching reversal technique (n = 16). Samples in Group 1 contained unbleached samples of sound enamel (n = 10). Group 1: Samples did not undergo bleaching; Group 2: bleached samples with no reversal; Group 3: bleached enamel reversal via fluoride activated by Er:YAG laser; Group 4: bleached enamel reversal via fluoride activated by diode laser; Group 5: bleached enamel reversal via fluoride activated by femtosecond laser; Group 6: bleached enamel reversal via Na-Ascorbate; and Group 7: bleached enamel reversal with fluoride. From controls and interventional groups, two pairs of samples were assessed for VH and one pair of samples for EDX to assess Ca/P. All samples were bonded with brackets for SBS assessment and bracket-enamel interface. Analysis of variance, followed by post hoc multiple comparison tests, was used to tabulate results for SBS, VH, and the Ca/P ratio. Results: Ca/P ratio, VH, and SBS in bleached enamel reversed via Er:YAG laser + fluoride and femtosecond laser + fluoride demonstrated the efficacy of reversal similar to bleached enamel reversed by a conventional method, Na-Ascorbate, and control. Conclusions: Fluoride-treated bleached enamel, activated via Er, YAG, or femtosecond lasers, was effective in reversing the undesirable effects of bleaching, improving SBS of orthodontic brackets, Ca/P ratio, and enamel hardness.