Effect of topical fluoride application on toothbrushing abrasion of resin composites

Objectives This in vitro study assesses toothbrushing abrasion of a microfill (Heliomolar Radioopaque) and a hybrid composite (Herculite XRV) after application of two acidic fluoride agents. Methods Thirty-six specimens of each resin composite were fabricated, ground flat and polished. Subsequently the 36 samples of each material were evenly assigned to three groups. In the first group, samples were treated with the fluoride varnish Bifluorid 12 (5.5% F, pH 5.6), in the second group with Elmex Fluid (1.25% F, pH 4.3). In the third group, specimens remained unfluoridated (controls). After 8h, the samples were subjected to toothbrushing abrasion (2000 brushing strokes, load: 250 g) in an abrasive slurry. Fluoridation and brushing abrasion were repeated twice. Afterwards, abrasion of the materials was quantitatively determined with a laser profilometer and statistically analyzed (ANOVA). Results and significance With Herculite both, Bifluorid 12 (P = 0.0001) and Elmex Fluid (P = 0.0001) led to a significant increase of brushing abrasion compared to the non-fluoridated group. However, no significant difference was observed between the two fluoridation regimes. Heliomolar showed a tendency towards higher abrasion after treatment with Elmex Fluid compared to Bifluorid 12 (P = 0.0496) and the non-fluoridated group (P = 0.0496), whereas treatment with Bifluorid 12 yielded no significant difference compared to the non-fluoridated Heliomolar specimens. Fluoridation of Herculite resulted in a 106-121% increase of abrasion, whereas Heliomolar only showed an increase by 5-30%. Application of the acidic fluoride products used led to an increase in toothbrushing abrasion of the tested composite restorative materials. However, clinical long-term studies are needed to determine the effect of topical fluoride regimes on resin composite materials.