The Safety and Effectiveness of Flouride Varnish

Flouride varnish is used to prevent tooth decay

Fluoride varnish is a solution that the dentist (dental hygienist, or physician) applies to the surface of the teeth to protect the enamel from decay. It hardens over the teeth to offer a layer of protection from decay, as well as repair and reduce decay that has already begun.

Preschool aged girl having her teeth examined by a dentist
Howard Shooter / Getty Images 

How a Fluoride Varnish Is Applied

The dentist (dental hygienist, or another healthcare provider) uses a piece of gauze to clean and dry the teeth. A small brush is dipped into the fluoride varnish solution and used to apply the solution to clean dry teeth. The solution is painted on, starting from the front to the back, and from the top to the bottom of the teeth.

Unlike a simple fluoride rinse, fluoride varnish becomes sticky and, when it encounters saliva, hardens to protect the teeth. The entire process only takes a few minutes. Fluoride varnish can be re-applied as often as every three months.

According to the New York State Department of Health, children who have fluoride varnish applied four times per year get fewer cavities than those who do not receive the varnish regularly.

Sometimes a pediatrician or other healthcare provider will prescribe and apply the fluoride varnish for children who are too young to start seeing the dentist regularly.

How It Works

The fluoride varnish flows into the small cracks and crevices in the enamel of the teeth, making the tooth harder. Its primary action is to prevent tooth decay from forming while slowing down the progression of any decay that has already begun.

Fluoride varnish repairs the tooth without the traditional process of tooth restoration (drilling, filling, or capping teeth). Of course, if a cavity is large, the varnish treatment alone will not be enough to repair the damage, and traditional restoration will be required.

Aftercare Instructions

After the fluoride varnish procedure is complete, avoid brushing until the following day and avoid alcohol, hot liquids, and sticky, chewy food for four to six hours after the procedure. The actual varnish box will have specific instructions. Colgate PreviDent Varnish (a commonly used varnish), for example, suggests eating only soft food for two hours after application.

When small children have the fluoride varnish procedure, it may be best to schedule a late afternoon appointment, to minimize the amount of time that the child must be without nourishment.

Does Fluoride Varnish Discolor the Teeth?

Initially, some brands of fluoride varnish will discolor the teeth slightly. The next day, after the teeth are brushed, they will return to their original color. This is because the varnish stays on overnight and in the morning, the outer coating is removed. A layer of varnish remains on the enamel to protect the teeth.

Potential Side Effects

There are no known major side effects of fluoride varnish; it’s considered safe because of the minimal amount of fluoride that is swallowed. Some dentists and doctors even recommend fluoride varnish treatments for very small children and for babies from the time they begin to get teeth.

However, even though the procedure is relatively safe, it is up to the dentist (or the physician) to decide if fluoride varnish is needed. Some children use prescription fluoride rinse or vitamins with fluoride. The dentist may still deem that fluoride varnish could be beneficial, particularly for kids who are prone to getting cavities.


A contraindication is a factor, or condition in which a specific medical treatment (or drug) could harm a person. Fluoride varnish is contraindicated when there are visible sores in the mouth. In some cases, people may have allergies to components of a specific varnish, so it's important to ask your dentist what is in the varnish being used.

Sealants Versus Fluoride Varnish

Many people wonder what the difference is between fluoride varnish and dental sealants. While fluoride varnish is a sticky paste that is professionally applied to the entire surface of the teeth (to help protect the teeth from cavities), dental sealants are a resin-based material applied over the pits and grooves of the biting surfaces of the back teeth.

Interestingly, a study showed that when children received both dental sealants and fluoride varnish, the incidence of tooth decay was lower than when only one type of preventative treatment was given.

A Cochran Database systematic review study revealed:

  • Resin-based sealants reduced tooth decay by 3.7% (over a two-year period) in children’s permanent teeth.
  • Applying resin-based sealants together with fluoride varnish reduced the incidence of tooth decay by 14.4% (over a two-year period) compared to just fluoride varnish alone.

In several systematic review studies involving children ages 5 to 9, in the U.S., the United Kingdom, Hong Kong, Denmark, and several other countries, the study authors concluded that an application of 2.26% fluoride varnish at least twice each year prevented dental cavities.

What is Remineralization?

Teeth are not, by any means, indestructible. Although the enamel (the outermost layer of the tooth) is one of the hardest parts of the body, it is vulnerable to breakdown.

The tooth is hard because it is mineralized with calcium and phosphate. Bacteria in the mouth creates a type of acid that attacks the enamel of the teeth, resulting in a process called demineralization.

When enamel begins to break down, the body has a natural process of strengthening the tooth. This process is referred to as re-mineralization.

Enamel is not comprised of living cells (like bones). Unfortunately, once it breaks down, it cannot regenerate itself. This is the reason remineralization takes place, to help repair the enamel before cavities can occur.   

A 2016 review of several studies revealed that fluoride varnish was effective in remineralization of early childhood dental caries (tooth decay). In fact, the overall incidence of remineralization that occurred as a result of fluoride varnish treatment was 65% higher than in those who did not receive fluoride varnish.

A Word From Verywell

Fluoride varnish treatment to prevent cavities is considered safe and effective for kids of all ages. The treatment can be started as soon as a baby begins to get teeth. Parents of those kids (and babies) who are prone to cavities (particularly for those who do not have fluoridated water), may want to discuss the use of fluoride varnish for prevention of dental caries, and for long-term oral health.

4 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. New York State Department of Health. Information for Consumers: Fluoride Varnish - Frequently Asked Questions. Health.NY.Gov

  2. New York State Department of Health. Information for Consumers: Fluoride Varnish - Frequently Asked Questions.

  3. Ahovuo-saloranta A, Forss H, Hiiri A, Nordblad A, Mäkelä M. Pit and fissure sealants versus fluoride varnishes for preventing dental decay in the permanent teeth of children and adolescents. Cochrane Database Syst Rev. 2016;(1). doi:10.1002/14651858.CD003067

  4. Abou neel EA, Aljabo A, Strange A, et al. Demineralization-remineralization dynamics in teeth and bone. Int J Nanomedicine. 2016;11:4743-4763. doi:10.2147/IJN.S107624

Additional Reading

By Sherry Christiansen
Sherry Christiansen is a medical writer with a healthcare background. She has worked in the hospital setting and collaborated on Alzheimer's research.