Effects of Fluoride Varnish on Bond Strength of Orthodontic Brackets

Methods: The study consisted of 105 extracted human premolars; 70 were used for the SBS test, and 45 for the adhesive remnant index (ARI) test. For each test, the teeth were divided into a control group and 6 test groups: 3M ESPE Vanish^TM 5% NaFl varnish 1 Day, 8 Days, and 15 Days; and ClearShield 5% NaFl varnish 1 day, 8 Days, and 15 Days. The test groups were coated with their respective topical fluoride and stored in synthetic saliva at 37°C until bonding time. Brackets were bonded to specimens using conventional bonding methods and were then subjected to a shear force in a universal testing machine until failure. Data were analyzed using ANOVA design to assess for differences in the shear bond strength with regards to fluoride varnish and post-fluoride application time.

Results: At all time intervals, there were no differences in bond strength between the control group and the 3M ESPE Vanish^TM groups; however, the SBS of the ClearShield groups were significantly larger than that of the control and 3M ESPE VanishTM groups.  For the same material, there were no significant differences in mean SBS over different time slots. Furthermore, one-way ANOVA analysis determined that adhesive remnant index scores were not statistically different. The groups’ mean scores ranged from 0.6 to 1.8, which signifies that most of the bonding failure occurred at the adhesive-bracket interface.

Conclusion: The application of single-dose fluoride varnish, irrespective of the length of time between the fluoride treatment and bonding procedure, does not reduce the bond strength of orthodontic brackets to enamel.