The effect on the bonding strength of orthodontic brackets of fluoride application after etching

Etching of the enamel surface in preparation for bonding orthodontic brackets is an essential part of the bonding procedure. In an attempt to alleviate concerns regarding the decalcified enamel, it has been suggested that a fluoride solution be applied to the etched surface before placing the bonding material. The purpose of this study is to test the tensile bonding strength of the composite to fluoride-treated enamel. Four groups of 10 teeth each were compared. Group I received a solution of 2% NaF in 0.1 M H3PO4 after etching; groups II and III received a solution of 4% NaF in 0.1 M H3PO4 after etching; and group IV served as the control--that is, no fluoride solution was applied to the enamel after etching. The orthodontic brackets were bonded to the teeth in the four groups with the same procedure. The 40 teeth were then placed in synthetic saliva. Groups I, II, and IV were debonded after 24 hours; group III was debonded after 7 days. The Instron Universal testing machine was used to determine the tensile bonding strength of the adhesive to the teeth. The basic statistics for the tensile strength were calculated and the analysis of variance, general linear models procedure, was used to determine whether significant differences were present among the groups. The findings indicate that the application of either 2% or 4% NaF in a 0.1 M H3PO4 solution does not significantly influence the tensile bonding strength of the adhesive material to the enamel surface.