## 4 Discussion  
The results of this investigation show that both fluoride and non-fluoride desensitizing agents increase the shear bond strength of ceramic brackets with composite resin cementation, implying that the null hypothesis was accepted. The highest SBS was found in the fluoride group, while the lowest SBS was found in the control group. The process of bleaching works by causing hydrogen peroxide to form free radicals that interact with chromogen macromolecules that stain the teeth and break them down into smaller molecules [21]. The reduction in post-bleaching shear strength is primarily attributable to changes in the enamel surface, such as enamel roughness and loss of prismatic formations, changes in the composition of the organic content of enamel, loss of calcium, and reductions in microhardness [22; 23]. Remaining free radicals on the enamel may prevent the resin's penetration and polymerization, which would reduce the shear bond strength [20]. In this study, there was no time gap between bleaching and the bracket-bonding procedure. When the action was carried out, the possibility of residual free radicals was still high. High levels of free radicals persisting in the control group inhibited the infiltration and polymerization of the composite resin, resulting in the lowest shear bond strength compared to the other groups. The results of this study were supported by scanning electron microscope examination, which revealed substantial demineralization following bleaching in the control group, as evidenced by many porosity characteristics and irregular enamel prism structures. Demineralization is caused by residual free radicals that interact with organic components of the enamel, making the surface of the enamel rough. Hydrogen peroxide that is in contact for a long time can damage the organic matrix, which results in a decrease in the mechanical properties of the teeth [24]. An increase in shear bond strength occurred in both the fluoride and non-fluoride group because desensitization can cause remineralization on post-bleaching enamel, resulting in an improvement in the enamel structure, which results in better attachment of the mechanical bond between the bracket and the enamel [25]. The SEM images of the fluoride and non-fluoride groups support the results of this study by showing remineralization in both groups, marked by a less porous appearance than the control group. The depth of the pores in the fluoride and non-fluoride groups was also shallower than the pores in the control group, which looked deeper and darker in color. The structures around the porous in the fluoride and non-fluoride groups looked more uniformly white than that in the control group, which was surrounded by structures that tended to be thin and irregular. The shear bond strength was lowest in the control group (bleaching without the administration of desensitizing agent). The findings of this investigation are consistent with the findings of prior investigations. [PERSON] et al. 's research using the intracoronal bleaching method with three different types of bleaching materials revealed that the control group with no bleaching application had the highest shear-bond-strength value of the ceramic bracket when compared to other groups that were given bleaching action [9]. [PERSON] et al. 's research also revealed a decrease in the SBS of the ceramic bracket after in-office bleaching, whereas home bleaching had no significant effect on the SBS of the bracket, so the bracket-bonding process was recommended 24 h after bleaching [8]. In accordance with this investigation, [PERSON] et al., found that bleaching drastically lowered the SBS of the brackets [4]. The findings of this study contradict those of [PERSON] and [PERSON], who found no difference in the shear strength of ceramic brackets after intracoronal bleaching. This