Evaluation of the effect of the application of <i>Quercus cerris</i> extract and the use of fluoride bonding material on the bonding strength of orthodontic brackets after tooth bleaching with hydrogen peroxide

The aim of this study was to evaluate the effect of natural antioxidant activity obtained from <i>Q. cerris</i> (<i>Quercus cerris</i>) extract and fluoride-releasing sealant on the shear bond strength (SBS) of orthodontic brackets in teeth after bleaching with hydrogen peroxide (HP). In this research, 200 teeth were divided into two groups, the TT (<i>n</i> = 100) and the OT (<i>n</i> = 100). Each group was further divided into five subgroups (<i>n</i> = 20): TT1 and OT1 = no bleaching; TT2 and OT2 = bleaching; TT3 and OT3 = bleaching+two weeks delayed bonding; TT4 and OT4 = bleaching+10% sodium ascorbate (SA) TT5 and OT5 = bleaching+10% <i>Q. cerris</i> extract. The TT groups were bonded with Transbond sealent + Transbond XT (TT; 3M/Unitek), and the OT groups were bonded with Opal Seal primer (Reliance Orthodontic Products Itasca, IL, USA)+ Transbond XT. Samples were assessed by SBS testing and adhesive remnant index (ARI) scoring. Two-way ANOVA variance analysis, Tukey multiple comparison test and the Chi-square test were used for statistical evaluation. The highest SBS values were obtained in the TT1 (3.17 ± 1.1 MPa) and OT1 (12.58 ± 1.47 MPa) groups, and the lowest SBS values were obtained in the TT2 (4.40 ± 1.11 MPa) and OT2 groups (4.19 ± 1.02 MPa) (<i>p</i> = 0.0001). The mean value of SBS of TT5 was statistically significantly lower than the mean SBS value of TT3 and TT4 (<i>p</i> = 0.042, <i>p</i> = 0.047). No statistically significant difference was observed in the ARI score distribution in the OT groups (<i>p</i> = 0.062), while a significant difference was noticed in the TT groups (<i>p</i> = 0.006). The results indicated that <i>Q. cerris</i> can be safely used to enhance SBS in bleached teeth, based on the dose, duration, and application procedure parameters utilized in this study. In addition, the fluoride-releasing sealant provides clinically sufficient SBS.