When should fluoride varnish be started according to USPSTF guidelines for preventing dental caries in children under 5?

• A. Starting at age 6 years.
• B. Only after the first birthday.
• C. Starting at the age of primary tooth eruption.
• D. Starting at birth.

Answer: (C)

Timing matters because fluoride varnish is most protective when teeth are erupting and enamel is newly exposed to the oral environment. Starting at the age when the first primary teeth emerge allows the fluoride to act on vulnerable enamel early, helping to remineralize surfaces and reduce the risk of early childhood caries as the dentition develops. In practice, primary teeth begin to erupt around the first half of the first year of life, so initiating fluoride varnish at eruption provides protection during the window covered by USPSTF guidelines for children under 5. Starting before teeth appear isn’t beneficial, waiting until after the first birthday can miss early eruption in some children, and waiting until age 6 is outside the recommended preventive period.