Effect of fluoride varnish on demineralization adjacent to brackets bonded with RMGI cement

Far too often a less-than-optimal esthetic result occurs after orthodontic treatment due to demineralization of enamel adjacent to fixed orthodontic appliances in patients with inadequate oral hygiene. In vitro studies have shown that a resin-modified glass ionomer (RMGI) cement and a fluoride varnish might help clinicians combat this problem. The purpose of this study was to evaluate, in vitro, the effect of a fluoride-releasing cavity varnish on inhibition of enamel demineralization adjacent to orthodontic brackets bonded with RMGI and composite resin cements. Brackets were bonded to 48 extracted human third molars. Half were bonded with a composite resin (Transbond, 3M Unitek, Monrovia, Calif) and half with an RMGI (Fuji Ortho LC, GC America, Alsip, III). Each group was further divided into 2, with half receiving an application of fluoride-releasing varnish (Duraflor, Pharmascience, Montreal, Quebec, Canada). The samples were cycled in an artificial caries solution for an hour twice daily for 31 days. After each caries challenge, the teeth were brushed with a soft toothbrush to simulate normal mechanical wear of the varnish. The loss of fluoride varnish was timed. Teeth were sectioned longitudinally and photographed under polarized light microscopy. Mean lesion depth was measured, and analysis of variance (ANOVA) (P less than or equal to .0001) and the Duncan multiple range test (P less than or equal to .05) indicated significant differences among the groups. Teeth bonded with composite resin showed a 35% reduction in mean lesion depth when fluoride varnish was applied. Teeth bonded with RMGI cement showed no significant differences in lesion depth between varnish and nonvarnish groups. Both RMGI groups had 50% smaller mean lesion depths when compared with the composite resin group without fluoride varnish. Samples bonded with RMGI cement illustrated a wedge effect, with lesion depth shallower near the bracket. A chi-square test showed that the fluoride varnish was lost significantly faster in samples bonded with Fuji Ortho LC (P = .013). Although the fluoride varnish could not prevent demineralization, it appears to be beneficial in reducing lesion formation. Clinicians should consider applying fluoride varnish on areas of enamel that exhibit demineralization or are at risk of demineralization in patients with poor oral hygiene.