Effects of fluoride varnish application and phosphate buffered saline solution with or without demineralizing conditions prior to bracket bonding on subsequent enamel-bracket shear bond strength

Abstract

This study examined the effect of sodium fluoride varnish (V) and phosphate buffered saline (PBS) solution with or without demineralization (DM) prior to bracket bonding on subsequent enamel-bracket shear bond strength (SBS). Sixty maxillary third molars were used for the testing procedures after the roots were embedded in acrylic resin. Specimen were randomly assigned to the following four groups: 1) fluoride varnish-PBS only; 2) fluoride varnish-PBS with demineralization; 3) no fluoride varnish-PBS only; 4) no fluoride varnish-PBS with demineralization. Immediately after varnish or no varnish application, all teeth were placed in PBS for four hours to simulate a time of no food or beverage consumption according to the manufacturer’s protocols. All teeth were then brushed to simulate natural brushing removal. Teeth were then placed in their respective solutions of PBS only or PBS+DM for 7 days, and stored in an incubator at 37C and subjected to a shaker set at 15 rpm to simulate oral circulation. A universal ten Cate demineralization solution was used. PBS was changed every day and DM three times daily. After 7 days, metal maxillary premolar brackets were bonded using a primer and resin adhesive to the mesial buccal surface of the molars. Following a 24-hour dark cure, SBS was determined with a universal mechanical tester, and adhesive remnant index (ARI) values were then assigned. There was a significantly (p=0.001) greater SBS with varnish application as compared to no varnish with bracketed teeth stored in the PBS+DM. An effect size of 0.372 indicates that approximately 37% of the SBS difference in the PBS+DM group can be attributed to varnish application. There were no significant differences in ARI results based on varnish application or storage medium. Overall results suggest that metal brackets bonded to teeth treated with fluoride varnish and stored in a medium of PBS+DM exhibited a statistically higher SBS, as compared to teeth with no fluoride varnish application.