Background: The effects of fluoride and CPP-ACP before bracket bonding on the shear bond strength of\northodontic brackets have been reported with contradicting results. The objective of this in vitro study was to\nevaluate the effect of different preventive agents namely; casein phosphopeptide-amorphous-calcium-phosphate\n(CPP-ACP), fluoride-containing-CPP-ACP (CPP-ACPF) and 5% sodium fluoride (5% NaF), on the enamel-bracket shear\nbond strength (SBS) and to compare their effects when applied before or after acid-etching.\nMethods: Human premolar teeth were randomly divided into seven groups (16 teeth per group) as follows: the\ncontrol group, where no preventive agent was applied on the enamel and 6 experimental groups. Teeth in groups 1a,\n2a, and 3a were treated with CPP-ACP paste, CPP-ACPF paste, and 5% NaF, respectively before acid-etching. Teeth in\ngroups 1b, 2b and 3b were treated using the same preventive agents after acid-etching. The brackets were then\nbonded and the teeth were thermocycled. The brackets'' SBS was measured and the adhesive remnant was assessed\nusing adhesive remnant index (ARI). Analysis of variance (ANOVA) and Tukey test were performed to compare the SBS\namong different groups. Chi-square test was used to evaluate differences in ARI scores between the groups.\nResults: Enamel surface treatment with CPP-ACPF after acid-etching significantly increased SBS compared to the\ncontrol and to its application before acid-etching (P < 0.05). Higher ARI index was recorded when the preventive agents\nwere applied after acid-etching.\nConclusion: Brackets'' SBS significantly increased when fluoride-containing-CPP-ACP was applied after acid-etching.
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