Updated on February 29, 2024
6 min read

Fluoride Varnish – Safety and Effectiveness

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What is Fluoride Varnish?

Tooth enamel is the outermost layer of the tooth and is the hardest substance in the body. However, it can become porous and weak when attacked by substances such as plaque, the culprit for cavities.

Animation or illustration of a tooth with labels on tooth anatomy including enamel and dentin

How Does Fluoride Varnish Work?

Professionally applied fluoride varnish is a topical treatment used to prevent tooth decay. It is a clear, sticky gel applied to the teeth with a brush. 

Although fluoride varnish is typically used for children since their teeth are developing, it can be used on anyone who a dentist thinks may benefit from it. For example, adults with dry mouth or a history of radiation in the head and neck area are at a higher risk for cavities. For this reason, many of them benefit from fluoride varnishes. 

Fluoride varnish increases the resistance of enamel to acid attacks. It also enhances remineralization of the tooth surface.1

Fluoride varnish is effective in many ways. For example, it can:

  • Strengthen tooth enamel
  • Reduce risk of cavities
  • Reduce tooth sensitivity

Applying a thin layer of fluoride varnish to the enamel forms a temporary protective barrier. This prevents acid from reaching the tooth surface. It also helps saliva neutralize plaque or bacteria left on the tooth.

Is Fluoride Varnish Safe?

According to resident expert Dr. Khushbu Aggarwal, fluoride, and therefore fluoride varnishes, are considered safe when used appropriately.

Fluoride varnish is considered a low-risk treatment. Only a small amount is used during application, so you will hardly swallow fluoride.

Speak to a dental professional if you or your child receives fluoride in other forms, such as:

  • Drops
  • Tablets
  • Toothpaste

They may advise stopping the additional fluoride for a few days before and after treatment. Alternatively, they may determine fluoride varnish is unsuitable for your situation.


According to the Centers for Disease Control and Prevention (CDC), approximately one in five children have untreated tooth decay by age 19.5 The CDC also states that over half of children between the ages of 6 and 8 have had a cavity in at least one of their baby teeth.

Additionally, over half of all adolescents aged 12 to 19 have had a cavity in at least one of their permanent teeth. Further research shows that 40% of all children experience tooth decay by the time they reach kindergarten.6

So, it’s no wonder dental professionals recommend using treatments such as fluoride varnish when it comes to preventing tooth decay.

A 2013 review evaluated the effectiveness of fluoride varnish in preventing caries in children and adolescents compared to a placebo or no treatment at all.7 There was a significant reduction in cavities in those treated with fluoride varnish.

The evidence suggests a 43% reduction in decayed, missing, and filled tooth surfaces in children and adolescents who received fluoride treatment for their permanent teeth. 

Additionally, the review looked at trials investigating the effect of fluoride varnish on baby teeth. It found a 37% reduction in decayed, missing, and filled tooth surfaces for children in that group.7


Many studies have found that fluoride can help prevent cavities in both children and adults. Additional benefits include:8

  • Varnishes are adhesive, so they make contact with the teeth instantly
  • They are easy and quick to apply, even in children that are otherwise difficult to treat
  • Unlike other methods of professional fluoride application, varnishes are relatively inexpensive 

Fluoride varnish can be applied up to 4 times per year or every 3 months.9 Studies show that children who get fluoride varnish every 3 months have fewer cavities than those who get it less often or not at all.10

Risks and Potential Side Effects 

Fluoride varnishes can leave the teeth temporarily discolored, although this will go away after the varnish has been brushed off the next day. 

Because varnishes can be very sticky, Dr. Aggarwal advises using a “throwaway toothbrush” to brush your teeth 24 hours after application. Also, hold off wearing dental appliances until you have brushed the fluoride off your teeth the next day.11 

Fluoride is a chemical compound that has been debated for its use in dental care.8 Some believe fluoride is toxic and should not be used in any products. Others believe it’s a safe, effective additive to include in toothpaste and water.

In excessive amounts, fluoride has been shown to cause spots on teeth and/or stomach upset. 

How to Apply Fluoride Varnish

Fluoride varnish is a topical treatment dental professionals apply to the teeth. It contains fluoride, which helps prevent tooth decay and can sometimes treat dental caries.

Before application, the dental professional will dry the teeth with gauze. Then, they will paint the fluoride varnish onto all the teeth. 

Dental flouride varnish being applied to a great set of teeth

Fluoride varnish is sticky, so it adheres well to the teeth. When it comes into contact with saliva, it hardens onto the teeth, allowing it to stay in place.2 

While it is on the teeth, the varnish maintains a high concentration of fluoride on the teeth for several hours. According to the American Dental Association (ADA), this allows fluoride to remineralize the teeth.3

Dental professionals usually recommend a fluoride varnish application every 3 to 12 months. 

Some pediatricians are even trained to apply fluoride varnish. This ensures treatment accessibility for people who don’t have access to dental care.4

How Long to Leave Fluoride Varnish on Teeth

Typically, people should leave fluoride varnish on their teeth for at least 6 hours. Some brands require the varnish to stay on teeth for 24 hours. Other brands recommend leaving the fluoride on teeth overnight and brushing it off in the morning.12

When Can You Eat After Applying Fluoride Varnish?

According to Dr. Aggarwal, the type of fluoride you receive determines when you can eat and drink afterward.13 

For example, after application of a 3M fluoride varnish, you should avoid the following for 4 to 24 hours to maximize the effects:

  • Hard foods
  • Hot drinks
  • Alcohol (including mouthwashes with alcohol)
  • Brushing
  • Flossing 

You can eat soft foods or drink cold drinks right away.12

How Much Does Fluoride Treatment Cost?

Some insurance providers will cover the cost of fluoride varnish treatments. This is because it is considered a preventative measure that can promote good oral health. It can also mean saving money in the long run.

For example, a filling costs anywhere from $50 to $300 per tooth. Because fluoride varnish reduces the need for fillings, it makes sense to receive the treatment if possible.  


Fluoride varnish is a topical treatment that contains fluoride ions. A dental professional applies it to the teeth to seal the enamel and increase its resistance to acid attacks. 

Fluoride varnish treatments are used primarily to prevent tooth decay in children and adolescents whose permanent teeth have erupted but have not yet finished developing.

Last updated on February 29, 2024
14 Sources Cited
Last updated on February 29, 2024
All NewMouth content is medically reviewed and fact-checked by a licensed dentist or orthodontist to ensure the information is factual, current, and relevant.

We have strict sourcing guidelines and only cite from current scientific research, such as scholarly articles, dentistry textbooks, government agencies, and medical journals. This also includes information provided by the American Dental Association (ADA), the American Association of Orthodontics (AAO), and the American Academy of Pediatrics (AAP).
  1. Baik, A. et alFluoride Varnishes for Preventing Occlusal Dental Caries: A Review” Dent J (Basel)., Jun. 2021
  2. Fluoride Varnish” County of Sonoma Department of Health Services, n.d.
  3. Fluoride: Topical and Systemic Supplements” American Dental Association, 15 Jul. 2021
  4. Fluoride Varnish: What Parents Need to Know” American Academy of Pediatrics, 15, May 2015
  5. Griffin, S. O. et al Vital Signs: Dental Sealant Use and Untreated Tooth Decay Among U.S. School-Aged Children” MMWR Morb Mortal Wkly Rep., 21 Oct. 2016
  6. Improving the Oral Health of Young Children: Fluoride Varnish Training Materials and Oral Health Information for Child Health Care Providers” New York State Department of Health, Aug. 2020
  7. Marinho, V. C. C. et alFluoride varnishes for preventing dental caries in children and adolescents” Oral Health Group, 11 Jul. 2013
  8. de Sousa F. S. O.  et alFluoride Varnish and Dental Caries in Preschoolers: A Systematic Review and Meta-Analysis” Caries Research, Aug. 2019
  9. Information For Consumers: Fluoride Varnish – Frequently Asked Questions” New York State Department of Health, n.d.
  10. Fluoride Varnish Guide” State of Tennessee Department of Health Division of Community Health Services Oral Health Services, 7 Aug. 2016
  11. Auon, A. et alThe Fluoride Debate: The Pros and Cons of Fluoridation” Prev Nutr Food Sci., Sep. 2018
  12. Directions for Care After Treatment” 3M Science. Applied to LifeTM., 2017.
  13. Fluoride Varnish: A Post-Care Guide to Eating and Drinking” Young Dental, 232 Sep. 2019
  14. New study questions value of fluoride varnish” University of Washington School of Dentistry, 12 Sep. 2019
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