Fluoride varnish works by increasing the concentration of fluoride in the outer surface of teeth, thereby enhancing fluoride uptake during the early stages of demineralization. The varnish hardens on the tooth as soon as it contacts saliva, allowing the high concentration of fluoride to be in contact with tooth enamel for an extended period of time. (About 1-7 days).

Inadvertent ingestion of a high dose of fluoride with varnish application is less likely than with other highly concentrated fluoride products. This is important in younger patients. Fluoride varnish is quickly and easily applied which is especially helpful for treating infants and toddlers who may have difficulty tolerating the tray technique due to their gag reflexes.