Protective Effect of Fluoride Varnishes on Enamel After Demineralization/Toothbrush Abrasion

Objectives: To evaluate the protective effects of fluoride varnishes on enamel subjected to pH cycling and toothbrush abrasion via monitoring changes in enamel microhardness.
Methods: One hundred and forty samples were prepared from thirty-five molar and seventy anterior human teeth. Specimens were divided into six varnish groups (Fluor Protector S^â, Vanish^â, NUPRO^âWhite, ProFluorid^â, Duraphat^â, and PreviDent^â), and one no-varnish Control group (n=20). They were applied according to manufacturers’ instructions. Specimens were subjected to an 8-day pH cycling, then exposed to 1,500 cycles of toothbrush abrasion to simulate three months of brushing. Vickers surface microhardness (SMH) testing was conducted at baseline, after pH cycling, and after brushing for all groups.
Results: After pH cycling, the Fluor Protector S group showed significantly higher SMH (104.26±9.15)than NUPRO White (55.92±8.13)(p<0.001), ProFluorid (48.71±11.74)(p<0.001), Vanish (34.41±5.33)(p<0.001), and Control groups (12.31±4.84)(p<0.001). Although no significant difference was observed between Fluor Protector S, Duraphat (97.24±10.18), and PreviDent (77.29±10.31), Fluor Protector S displayed the highest average SMH. Between all varnish groups, Vanish showed significantly lower SMH than all groups. The Control group showed significantly lower SMH when compared with all varnish groups (p<0.001) except for Vanish group (p=0.269).
After brushing abrasion, Fluor Protector S displayed significantly higher SMH (331.16±34.11)when compared to all other groups (p<0.001). No significant differences were detected between the other groups.
Conclusions: Within the limitations of this study, fluoride varnishes demonstrated a significant protective effect on the enamel surfaces. However, not all fluoride varnishes performed equally, despite most of them sharing the same active ingredient.Unprotected enamel is prone to wear as a result of demineralization and toothbrushing, and the application of varnish appears to reduce the amount of demineralization, although results vary by varnish.