Fluoride varnish is a highly concentrated fluoride treatment applied to the surface of the teeth by dental professionals using a brush, cotton tip, or syringe-like applicator, typically 2 to 4 times per year in individuals who are at high risk of caries (dental cavities).[1][2]
Fluoride varnishes form a temporary coating on the teeth that allows fluoride to be slowly released and absorbed into the enamel over time. This process helps reduce enamel demineralization (mineral loss) and promotes remineralization, repairing early tooth damage.[2] More specifically, during an acid attack (in which bacteria in plaque produce acids from sugars), fluoride moves with the acid from plaque into the tooth enamel, where it reduces mineral loss by decreasing the solubility of the enamel, increasing calcium and phosphate availability, and inhibiting the diffusion of acid into the enamel. As the pH normalizes after the acid attack, fluoride combines with calcium and phosphate in the saliva to rebuild and strengthen the enamel by forming fluorapatite, a mineral that is more resistant to future acid damage.[3] This dual action — reducing mineral loss and enhancing mineral gain — makes fluoride a powerful tool for preventing dental caries.