Tehran University of Medical Sciences Frontiers in Dentistry 2676-296X 17 0 2020 12 15 3201 3201 Mohammad Ali Mohammadi Torkani Department of Restorative Dentistry, Faculty of Dentistry, Urmia University of Medical Sciences, Urmia, Iran Sepideh Mesbahi Dentistry student, Student Research Committee, Urmia University of Medical Sciences, Urmia, Iran Amir Ardalan Abdollahi Department of Endodontics, School of Dentistry, Urmia University of Medical Sciences, Urmia, Iran 2019 06 26 2020 10 12 Objectives: This study aimed to assess the effect of casein phosphopeptide amorphous calcium phosphate (CPP-ACP) on microtensile bond strength of three adhesive systems to deep dentin. Materials and Methods: In this in vitro study, the occlusal surface of 30 sound human third molars was sectioned at 2 mm below and above the cementoenamel junction. The samples were randomly divided into three groups of OptiBond Solo Plus, G-Bond, and Clearfil SE Bond. Before composite resin bonding, each group was divided into two subgroups with and without dentin preparation with CPP-ACP. The teeth were then sectioned into 1 mm rods (n=15), and their microtensile bond strength was measured at a crosshead speed of 0.5 mm/min. Data were analyzed using two-way ANOVA and post-hoc Bonferroni test. Results: There was no significant difference in bond strength of OptiBond Solo Plus (P=0.44) and Clearfil SE Bond (P=0.67) with/without CPP-ACP. A significant difference was found between the two subgroups of G-Bond in this respect (P<0.001). The differences in microtensile bond strength among all subgroups were significant (P<0.05). Conclusion: The microtensile bond strength in use of G-Bond is significantly higher following dentin treatment with CPP-ACP compared with no use of CPP-ACP. https://fid.tums.ac.ir/index.php/fid/article/view/3201 https://fid.tums.ac.ir/index.php/fid/article/download/3201/1830