How does fluoride prevent cavities? -

Fluoride offers protection against decay via: 1) Aiding tooth remineralization  2) "Hardening" tooth enamel. | How effective is fluoride in reducing cavities? | How much fluoride exposure is needed?

How important is fluoride protection?

Having exposure to fluoride (like that delivered by your toothpaste or your city's tap water) is likely the most effective cavity-prevention measure available today. As proof, consider these statistics.

  • The introduction of fluoride into a city's drinking water supply (check your town) can lower its citizens' rate of tooth decay on the order of 50% (both adults and children). (Dean)
  • Initiating the use of fluoridated toothpaste can reduce cavities by 24% (Marinho). Using a fluoride toothpaste twice-a-day, as opposed to just once, increases its effectiveness 14% (Dean).

Section references - Marinho, Dean

How does fluoride prevent tooth decay?

Protection #1 - Fluoride promotes tooth remineralization.

You may never have heard of it but there's a process called "remineralization" that plays a giant role in helping to slow down the rate of cavity formation. It's a bit like tooth decay in reverse.

What takes place is that instead of the situation where some of the mineral content is leached from a tooth (a process that's called demineralization), minerals are deposited back onto tooth areas where it has been lost (the damaged area is "healed" by remineralization).

(Use the links above for more details about both processes.)

Why you need to know this.

If you want to have fewer cavities, your goal needs to be one of creating conditions in your mouth that promote tooth remineralization. And one way of helping to do this is by having an appropriate oral exposure to fluoride.

How fluoride assists tooth remineralization.

Research has shown that when fluoride is present in a person's oral environment it acts to enhance the remineralization process, and therefore ultimately helps to limit the amount of mineral loss that occurs during demineralization.

cavities using:

  • When fluoride is not present, low pH conditions (approximately pH 5.5 and below) trigger tooth demineralization. (The loss of the mineral hydroxyapatite from the tooth.)

    Then, when conditions return back above this point, the process of remineralization can occur. (The redeposit of mineral back onto the tooth.)

  • When fluoride is present, the demineralization of hydroxyapatite still occurs as above. But during the remineralization process, fluorohydroxyapatite that has formed is one of the minerals that is deposited back onto the tooth.

    What's different is that remineralization with this molecule can occur at a lower pH than hydroxyapatite. And that means that the remineralization process can begin to start even before the oral environment has fully returned to more neutral pH conditions (like those required for hydroxyapatite). As a result, less overall mineral content is lost from the tooth.

Section references - Abou Neel, Fejerskov

Picture of teeth with extensive tooth decay.

Extensive tooth decay.

Protection #2 - Fluoride helps to make teeth more decay-resistant.

A new type of tooth mineral is created.
Up above we mentioned that when remineralization occurs in the presence of fluoride that a new type of tooth mineral called fluorohydroxyapatite (fluoroapatite, fluorhydroxyapatite) becomes available for the process.

What we didn't mention is that this replacement compound is actually "harder" (more resistant to demineralization) than the type of mineral that was present was originally. And that's an astoundingly important factor in the prevention of cavities.

Here are some details:
  • Most of a tooth's mineral content takes the form of hydroxyapatite and carbonated hydroxyapatite.
  • The type of tooth mineral that's created during the remineralization process when fluoride is present is fluorohydroxyapatite.
  • Fluorohydroxyapatite is "harder" than the other forms, in the sense that it is more resistant to damage caused by bacterial acids (the agents of tooth demineralization).

    Specifically, fluorohydroxyapatite is able to withstand a more acidic environment (pH 4.5 vs. 5.5 for hydroxyapatite [approximate values, depending on mouth conditions]) before it begins to dissolve away.


Let's recap.
Astoundingly ...
  • Not only does fluoride promote tooth remineralization ...
  • But it also helps to create a tooth surface that's even more resistant to decay formation than it was originally.


Those details are so amazing that you'd almost have to think that they're made up.

Of course, they're not. And in fact, they make the addition of fluoride to municipal water supplies one of the most effective, and cost-effective, public health measures possible.

The US Centers for Disease Control and Prevention (CDC) concurs. In 1999 they declared drinking water fluoridation as one of the 10 most important public health measures of the 20th century.

Is your tap water fluoridated?

Are you curious if your city or water district's supply is adjusted so it has the proper amount of fluoride for optimal cavity prevention? If so, it's easy enough to check.

Click here to visit (the website of the US Centers for Disease Control and Prevention) where you can retrieve information about your local area.

(Our Fluoridation USA infographic gives general facts about drinking water fluoridation.)


Tips for preventing tooth decay -

Fact #1 - Tooth remineralization, a process that can help to repair the damage caused by tooth decay, is enhanced by the presence of fluoride.

Cavity prevention suggestions :

  • Drinking fluoridated tap water throughout the day makes a better choice than unfluoridated bottled water.
Picture of the 'ADA Seal of Acceptance.'

The ADA Seal.

  • Make sure your toothpaste contains fluoride, so you get an extra exposure of it every time you brush.
  • Use a toothpaste that has the American Dental Association's (ADA) "Seal of Approval." This seal indicates that the ADA has reviewed details about the product and found its fluoride content to be appropriate.
  • Don't rinse out immediately or vigorously after brushing your teeth with fluoridated toothpaste. You'll get more of an effect if you let it linger in your mouth.
  • If you're having trouble with cavities, ask your dentist if the use of a prescription fluoride toothpaste is warranted.


Does fluoride have antibacterial properties?

While still mentioned in some textbooks and publications, the historic notion that fluoride helped to prevent cavities by way of its effect on oral bacteria/biofilms (dental plaque) appears to lie in question.

  • Fejerskov's textbook on tooth decay states that fluoride does not affect biofilm formation and bacterial sugar metabolism at concentrations found in saliva.
  • A review of historic and current research into this subject by Oh (up to the year 2015) states that "the effects of fluoride on dental cariogenic (cavity-causing) plaque and plaque bacteria in a clinical situation have not yet been well defined."

Section references - Fejerskov, Oh

How much fluoride do you need to get its benefits?

The average person usually gets enough fluoride exposure from just routine sources to get all of the anticavity protection that they need. This includes sources such as:

  • Fluoridated tap water - About 75% of the US population is served by public water supplies that are adjusted to have an optimal level of fluoride (0.7 ppm). (Use the link above to check if where you live has fluoridated tap water.)

    This tiny but regular source is important in two ways:
    1) It introduces fluoride directly into your mouth.
    2) Some swallowed fluoride ends up being incorporated into the saliva you produce.

    In some countries, table salt or foods (like milk) are fluoridated and used as the mechanism to create a population's fluoride exposure.


  • Toothpaste - Using a fluoridated toothpaste is an extremely valuable source of oral fluoride, and using one is such a simple step to take. Here are details about how to pick a good one.
  • Foods and beverages - While the exposure they create is difficult to gauge, many of the foods and drinks we consume contain fluoride, either naturally occurring or else coming from fluoridated water that's been used to manufacture them.
  • Additional sources - For people who don't receive an adequate exposure, or are at high-risk for cavities and therefore need a greater one, other possible fluoride sources exist. They include:

    1) Fluoridated products: Rinses (OTC or prescription), high-concentration prescription toothpaste.
    2) Dentist administered applications: Tooth varnish, in-office fluoride gel treatments, oral fluoride supplements.


Fluoride precautions and side effects.

As wonderfully beneficial as fluoride can be, it must be used judiciously.

Precautions with children.

One prime concern is the ingestion (swallowing) of products that contain fluoride by children during that time frame when their teeth are forming. Doing so can result in a type of permanent tooth staining termed fluorosis. (Use link for details and pictures.)

Are in-office treatments from your dentist necessary?

Low-risk patients.

People who are at low risk for cavities don't substantially benefit from in-office fluoride treatments.

Multiple daily exposures to low concentrations of fluoride (like that you get from toothpaste and drinking water) are more effective in preventing cavities than the high concentration but infrequent (annual or semiannual) exposures given at your dentist's office.

Guidelines: Low caries risk patients.
  • No cavities found during the patient's current dental examination.
  • No new cavities found over the last 3 years.
  • The patient uses fluoridated toothpaste and consumes fluoridated drinking water.
  • The dentist is unaware of any conditions or factors that place the person at increased risk for tooth decay.

Section references - Krachner

High-risk patients.

In the case where a person is considered to be at high risk, periodic at-home use of a prescription (high-concentration) fluoride toothpaste is likely to be more effective than once or twice-a-year in-office applications.


 Page references sources: 

Abou Neel EA, et al. Demineralization–remineralization dynamics in teeth and bone.

Dean JA, et al. McDonald and Avery's Dentistry for the Child and Adolescent.

Fejerskov O, et al. Dental Caries The Disease and Its Clinical Management. Chapter: Biofilms in caries development.

Krachner CM. Current Concepts in Preventive Dentistry.

Marinho VCC, et al. Fluoride toothpastes for preventing dental caries in children and adolescents.

Oh HJ, et al. Chronologic Trends in Studies on Fluoride Mechanisms of Action.

All reference sources for topic Tooth Decay.