In vitro Effects of a Neutral Fluoride Agent on Shear Bond Strength and Microleakage of Orthodontic Brackets

This study aimed to evaluate the effect of pretreatment with a neutral fluoride agent on shear bond strength (SBS) and microleakage of orthodontic brackets, and to investigate any significant relationship between SBS and microleakage. Forty intact premolars were selected and randomly divided into 2 groups. Group 1 served as the control, while group 2 underwent treatment with a 2% sodium fluoride (NaF) gel, which was applied on the enamel surface for 4 minutes before etching. After bonding orthodontic brackets, the teeth were immersed for 12 hours in methylen blue dye, followed by mounting in acrylic resin. Shear bond strength was determined using an Instron Universal Testing Machine and the amount of microleakage and the adhesive remnant index (ARI) were assessed under a stereomicroscope. The mean SBS and microleakage beneath metal brackets were not significantly different among the control and NaF-treated groups (P>0.05). Furthermore, no significant correlation was found between SBS and microleakage (r=-0.04, P=0.796). The ARI scores revealed that in both groups, most of the adhesive remained on the enamel surface after debonding. It may be concluded that pretreatment of enamel with 2% NaF prior to the bonding procedure does not significantly affect microleakage and SBS of orthodontic brackets and thus, it can be recommended as a suitable approach to reduce the incidence of white spot lesions in orthodontically treated patients, especially those at high risk of caries formation.