How does fluoride prevent cavities? -

Fluoride offers 3 methods of protection against decay: 1) Aiding tooth remineralization  2) Hardening teeth  3) Antibacterial action. | How effective is fluoride in reducing cavities? | How much fluoride exposure is needed?

How important is fluoride protection?

Having an 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%. (Hovius 2014)
  • Initiating the use of a fluoridated toothpaste can reduce cavities by 24%. (Marinho 2003)

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How does fluoride prevent tooth decay?

Fluoride plays a role in preventing cavities in three separate ways:

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 mineral content is leached from a tooth (that's called demineralization and it's the action that actually causes cavities), minerals are deposited back onto tooth areas where mineral content 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.

cavities using:

How fluoride assists tooth remineralization.

Research has shown that when fluoride is present in a person's oral environment, it assists the remineralization process. Here's how:

  • Fluoride ions in a person's mouth (like from fluoridated drinking water, toothpaste or rinses) gets adsorbed (deposited as a thin layer) onto the surface of teeth in areas where demineralization (decay formation) has occurred.

    That step alone is a positive thing. Remineralization (replacement of lost mineral content) is occurring. But note, some of the component being deposited is fluoride as opposed to the types of mineral originally lost (like calcium).

  • Once fluoride has been deposited onto the tooth's surface, it actually attracts other minerals (like calcium) to the damaged area.

    This attraction provides two benefits. It speeds up the rate of remineralization (reformation and repair of tooth mineral) and it also raises the degree to which this process takes place (it helps to create a higher level of repair).

That's all pretty amazing.

Not only does fluoride help to make the repair but it also speeds up the repair process and aids in taking it to a higher level of completion.

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 some of the fluoride itself replaces the kinds of minerals that were originally lost during the demineralization process (such as calcium).

What we didn't mention is that this replacement process results in the formation of a new type of tooth mineral that's actually "harder" (more resistant to demineralization) than the tooth 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 fluorapatite.
  • Fluorapatite 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, fluorapatite is able to withstand a more acidic environment (pH 4.5 vs. 5.5 for hydroxyapatite) before it begins to dissolve away.

Let's recap.

Astoundingly ...

  • Not only does fluoride promote tooth remineralization (participates in it, speeds it up, takes it to a higher degree of completion) ...
  • 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.)

Protection #3 - Fluoride has antibacterial properties.

You're just about to learn that the news about using fluoride to prevent cavities keeps on getting better and better. Beyond just helping to repair teeth, it also helps to combat the bacteria that cause tooth decay in the first place.

a) Fluoride from regular over-the-counter products.

Research has shown that when dental biofilms (deposits of dental plaque) contain just 1 to 5 ppm of fluoride (a level that can be reached by using an OTC fluoridated toothpaste) it inhibits the metabolism, growth, multiplication and adhesion of the kinds of bacteria that cause cavities. (Hovius 2014)

This effect has to do with fluoride's ability to inhibit bacterial enzymes that are necessary for the uptake of sugars (the source of nutrition for bacteria).

b) Fluoride from prescription products.

Fluoride levels in the range of 10 to 100 ppm (a range that can be produced by the use of prescription fluoride dentifrices) have been shown to also inhibit the amount of cavity-causing acids produced by oral bacteria. (Hovius 2014)

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.

Fact #2 - Fluoride has an inhibitory effect on the kinds of bacteria that cause cavities.

But to receive either benefit, it must be present in your mouth.

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.

How much fluoride do you need to get these 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's 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.)

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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.

(Kracher 2016)

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.



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