Fluoride varnish is a sticky coating a dentist or health worker paints onto teeth. It sets on contact with saliva and releases fluoride over several hours.
How strong is it?
The most commonly used product in Australia, Duraphat, is 5% sodium fluoride, or 22,600 ppm fluoride. That's about 20,000 times the concentration of fluoridated tap water, but it's applied in tiny amounts: national guidance caps a single application at 0.25 mL for baby teeth, 0.4 mL for mixed teeth and 0.75 mL for adult teeth.
What the Australian guidelines say
- The national Guidelines for use of fluorides in Australia (2019 update) recommend varnish for people at moderate to high risk of tooth decay, applied up to four times a year.
- It is not recommended for people at low risk.
- Several states run child varnish programs through schools and community health.
Is it safe?
Reviews conclude the risk of dental fluorosis from varnish is negligible, partly because so little is applied and most is not swallowed. A Cochrane review supports regular varnish to prevent decay in children.
Can you say no?
Yes. Varnish is a treatment, and you can ask for it to be left out or ask about alternatives. Unlike water fluoridation, it's an individual choice made with your dentist, which is one reason some fluoride critics prefer it.