## 4 Discussion
Monomer formulations containing an increased triethyleneglycol dimethacrylate (TEGDMA), such as ICON, exhibit a high penetration capability [32] and cause the creation of a thick oxygen-inhibited layer [32] and presumably, this leads to the chemical connection of the resin infiltrant to the monomers of the primer [31]. It has been demonstrated that demineralized enamel that had been exposed to a resin infiltrant showed significantly higher debonding forces than an untreated demineralized surface [33]. It is recommended that the bonding of orthodontic elements should be carried out briefly after the resin infiltration [34]. The Transbond XT primer--used in Group 1 and 2--is considered as one of the standard adhesives in orthodontic bonding and has been part of the many studies [12; 33; 34; 35]. Recent studies have found that the resin infiltrant did not undermine the SBS to demineralized enamel when Transbond XT was used [25; 35]. Further, previous studies have shown that the resin infiltrant did not undermine the bonding to sound and demineralized enamel [36] and that it increased the adhesion of the self-etching agent [24]. However, [PERSON] et al. [12] demonstrated that the SBS was found to be significantly reduced on demineralized enamel that had been pretreated with resin infiltrant in comparison to sound enamel, which is opposite to present results. In addition, their results reveal higher values than SBS from our study. The explanation of these differences can be in the different methods of the studies as in our study thermocycling was performed in contrary to the above-mentioned study. The regimen used in this report is representing a one year interval [37]. As far as we know, no prior studies have considered the co-application of the Scotchbond and Assure PLUS adhesives to a demineralized resin-infiltrated enamel surface. The MDP monomer (10-Methacryloyloxydelyl dihydrogen phosphate), present in the composition of both Assure PLUS and Scotchbond, enables chemical bonding to the tooth tissues via iconic bonding to the calcium in hydroxyapatite [38]. Moreover, the presence of ethanol enhances the bond to dentin [39]. In the current report, the adherent was a resin base (ICON), meaning that the presence of MDP and ethanol is not considered to be an advantage of Assure PLUS and Scotchbond when compared to Transbond XT, which is reflected in the results showing no significant differences between Groups I, II and III. However, Assure PLUS showed significantly higher SBS values. HEMA (2-Hydroxy methyl methacrylate), the most often used hydrophilic monofunctional monomer, is present in the composition of Scotchbond. HEMAhas high water sorption leading to a reduction of the mechanical properties and the disintegration of the matrix [40]. Considering thermocycling was preformed Scotchbond's composition can be an explanation for the lowest SBS results in all four groups. Assure PLUS was previously used in a study that compared the SBS to the surface of fluorosed and nonfluorosed teeth and found that, in both groups, significantly higher SBSs were measured when Assure PLUS was used than when Transbond XT was used [23]. These results are in accordance with those recorded in this report. Additionally, [PERSON] et al. [41] demonstrated that Assure PLUS achieved significantly higher SBS values than Transbond XT in blood-contaminated conditions. The degree of conversion of adhesive could have also affected SBS of the tubes, as it has a direct effect on the chemical, physical and mechanical features of the resin material [42]. A recent study comparing different adhesives used in orthodontics showed no significant difference in the degree of conversion between Scotchbond and Transbond XT [43]. Unfortunately, we found no research investigating the degree of conversion of Assure PLUS, encouraging further investigations in this direction. Further, we found a study that demonstrated that the SBS may not be dependent on the degree of conversion [44].