## 4 Discussions
In the molecular structure of TSEP, there is a combination between a phosphoric acid and a methacrylate group. These two groups form a methacrylate phosphoric acid ester. When TSEP is applied on the hard dental structures, the phosphate group dissolves calcium and removes it. The phosphate group and calcium form a complex that is incorporated into the adhesive network during polymerization. By this mechanism, the acid etching of the enamel and the penetration of the monomer into the created microretentions are synchronized. So, the depth at which the enamel is etched coincides with the depth of penetration of the primer [5]. As a chemical composition, TSEP also has water as a solvent [9]; this could give the primer tolerance to wet conditions. TSEP's performance in such conditions could be explained by the self-etching primer's chemical composition of hydrophilic monomers. Transbond Plus Color Change may owe its tolerance to humid conditions to the polyethylene glycol dimethacrylate (PEGDMA) and the low concentration of hydrophobic bisphenol A diglycidyl ether dimethacrylate (bis-GMA) in its composition; polyethylene glycol dimethacrylate (PEGDMA) favors the infiltration of bis-GMA adhesives into the wet enamel [9] and bonding with TSEP even in humid conditions. Saliva is an oral fluid composed of a variety of minerals and electrolytes such as calcium, sodium, magnesium, potassium, bicarbonate and phosphates. The existence of salivary ions probably multiplies the chemical bonds between TSEP and TPCC and increases the bonding strength [24]. Fuji Ortho LC can be applied on the enamel surface with or without an etching technique [18]. Because this bonding material is basically a glass ionomer luting cement with a high capacity to slowly release fluoride, it prevents the decalcification of the tooth enamel and the appearance of \"white spots\" after debonding brackets. Researchers have demonstrated by many studies that the use of phosphoric acid for slight demineralization of the enamel before bonding with glass ionomers improves the bond strength without affecting the mineralization of the tooth because of their ability to gradually release mineral ions [11; 16]. The superior adhesion of Fuji Ortho LC in the case of acid pretreatment of the enamel with 37% phosphoric acid was even better than that created by using a self-etching adhesive system [25]. Among the groups in which we used Fuji Ortho LC, we found the highest adhesion strength when the teeth were not contaminated with anything after etching and the lowest adhesion strength when the teeth were moistened with saliva after etching. The difference was statistically significant between the dry and saliva-moistened groups and without statistical significance between the dry and water-moistened groups and water-moistened and saliva-moistened groups. In our opinion, it would be desirable to add chemical components to the composition of this material to increase its adhesion in case of salivary contamination. [PERSON] et al. [26] obtained a result similar to that of our study by finding no statistically significant differences between two experimental groups of teeth, one bonded with Fuji Ortho LC with the enamel etched and moistened with water before bonding and another bonded with Fuji Ortho LC with the enamel etched and moistened with saliva before bonding [26]. [PERSON] et al. [18] conducted a study partially similar to ours by applying Fuji Ortho LC after etching on dry enamel, enamel moistened with distilled water and enamel moistened with saliva. They found results similar to those of our study. The bonding strength was maximum in the dry enamel group; they found a statistically significant difference between this group and the group of teeth moistened with saliva, which proved to have the lowest bonding strength value among etched groups [18]. They also found a significant difference between the group of teeth moistened with distilled water and that moistened with saliva.