How long to leave fluoride varnish on teeth?

Fluoride varnish is a topical fluoride treatment that is applied on teeth to prevent tooth decay. It is a simple, 3 to 4 minute procedure that is performed in the dentist’s office immediately if your child is a good candidate.

Depending on the specific brand and product instructions, fluoride varnish is typically left on for 4 to 6 hours, and patients are advised to avoid eating or drinking for at least 30 minutes to 1 hour to allow the varnish to fully adhere to the teeth.

After that, patients (children or adults) can use a soft diet or cold drinks if necessary, but they have to wait 6 hours or so to resume their normal diet and oral hygiene routine.

What to expect during fluoride varnish application

Fluoride varnish is a simple and easy way to protect primary teeth from cavities for children between the ages of 3 and 14 years, when they’re most prone to tooth decay and cavities.

There is some debate about whether teeth need to be cleaned before applying the varnish. Some products usage instructions claim that a professional cleaning isn’t necessary, and patients can clean their teeth normally before treatment. However, some manufacturers still recommend a professional cleaning. So, this depends on the specific product your dental professional will be using. 

 Here are the steps followed during varnish application:

  1. Prophylaxis – through either professional cleaning or using a toothbrush – though it’s not always necessary
  2. Removing excess saliva or plaque on the teeth using a small piece of gauze – depends on whether it’s a requirement for the product used – since some varnishes cannot set in the presence of moisture.
  3. Several teeth in the quadrant receiving treatment are isolated using cotton rolls
  4. The varnish is applied with a brush or cotton applicator as per manufacturer’s instructions – Usually 0.5 to 1 ml is sufficient for one session
  5. The entire surface of the tooth is painted with varnish, the front, back, top, in a thin layer, while carefully avoiding getting varnish on the gums and other soft tissues
  6. The varnish sets in a few seconds and creates a fluoride-rich layer on the surface of the teeth.
  7. The entire process takes less than 5 minutes

Some types of varnish can temporarily change the color of teeth, but this is normal and goes away after brushing.

Post-treatment instructions for fluoride varnish

Optimal results from fluoride varnish treatment can only be achieved if the coat is allowed to sit on your teeth for the recommended period of time. So consuming the wrong items too soon can affect the efficacy of the treatment.

After the varnish is applied, patients should avoid brushing their teeth or eating for about 4 to 6 hours for the Fluoride varnish to adhere properly on the teeth.

During that time, you should follow these guidelines to ensure successful treatment:

  • Avoid hard or crunchy foods
  • Avoid hot beverages
  • Do not brush or floss
  • Avoid any fluoride-dental products, including toothpastes, rinses, and gels
  • Avoid any alcohol or tobacco products

These activities can be resumed after 6 hours following treatment. Please note that brushing and flossing your teeth will wash off the remaining traces of fluoride varnish and any temporary discoloration caused.

Here are some additional post-care tips:

  • You should not use any prescription fluoride medications for at least three days post-treatment.
  • Depending on the product used, you can consume soft foods and cold drinks in as little as 30 minutes to 2 hours after the procedure.

How often should varnish treatment be administered?

Once you brush your teeth, the varnish will begin to wear away, and will be completely gone in a few days. But by then, the fluoride will have penetrated your tooth enamel and should protect the teeth for the next several months.

For fluoride varnishes to be effective, reapplication is necessary. How often this is done depends on the individual’s risk of cavities, though the most common regimen is a semi-annual application during routine dental visits and cleaning that are carried out every six months.

For patients at higher risk of cavities, your dental professional may recommend more frequent dental checkups, so the varnish treatment may also coincide with these visits.

So the typical schedule may involve:

  • One application every 6 months
  • One application 4 times a year
  • 3 applications over a period of one week

Is there a risk of excess fluoride toxicity?

Fluoride vanishes have a very high concentration of fluoride content, like 22.6 mg/ml (22,600 ppm of fluoride), which is about 22 times what an adult would use when brushing your teeth normally. This significantly increases the risk of excess fluoride ingestion and toxicity.

But the potential toxic dose for fluoride is 5mg per kg of body weight. So for a child weighing 20kg, he or she would have to swallow 100 mg of fluoride for it to become a concern. But based on the procedure discussed above, treatment requires only 0.5 to 1 ml of varnish (11.3 to 22.6 mg/ml), which is well below the toxic dose if properly applied and carefully monitored.  

As such, most states limit the use of varnish treatments to dental professionals, though some pediatricians and nurse practitioners in other states prescribe it. In such cases, users should be careful to use the recommended amount on tooth surface to avoid toxicity.

What are the benefits of fluoride varnish?

Dental health is a vital part of a child’s total health, and applying fluoride varnish on the teeth can help to reduce the risk of tooth decay, cavities, early tooth loss, and any orthodontic issues that may arise due to early tooth loss, such as teeth shifting and misaligned bite.

When if fluoride varnish not used?

Despite the many benefits, dental professionals might delay or avoid fluoride varnish treatment if there are noticeable sores in your child’s mouth or gums. It is also not recommended if your child is allergic to any of the ingredients in the varnish or to pine nuts. Alternative dental caries prevention tactics may be provided.


  • Editorial team

    A team comprising oral health care professionals, researchers, and professional Writers, striving to impart you with the knowledge to improve your oral health, and that of your loved ones. 

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