How does fluoride prevent cavities? -

Effectiveness. / How it aids the tooth remineralization process. / Fluoride side effects- Dental fluorosis.

A) How important is fluoride as a cavity preventer?

An exposure to fluoride (like that contained in toothpaste or possibly your city's tap water) is probably the most effective cavity-prevention measure available today.

For example, studies have shown that introducing fluoride into a previously unfluoridated city's drinking water supply can lower its citizens' rate of tooth decay between 40 and 70 percent. Those are giant numbers.

FYI: Is your tap water fluoridated?

Are you curious if your city's water 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, and look for information about your state and town.

Just want a quick overview about municipal fluoridation? Take a look at our Fluoridation USA infographic!

B) Fluoride precautions.

As beneficial as it can be, fluoride must be used judiciously. For example, if young children swallow too much during that time frame when their teeth are developing, a type of tooth staining termed dental fluorosis can result.

A bottle of fluoride oral rinse.

How does fluoride help to prevent tooth decay?

It plays a role in three separate anti-cavity effects:

1) Fluoride promotes tooth remineralization.

Researchers have discovered that fluoride enhances the all-important tooth remineralization process.

(Remineralization is a little bit like "tooth decay in reverse." If you're not already familiar with this phenomenon you really should use the link above to learn more about it.)

Here's how it assists.
  • Fluoride available in a person's mouth (like that from drinking fluoridated tap water or the use of products such as fluoride toothpaste or rinses) is adsorbed onto the surface of teeth where damage from demineralization (tooth decay formation) has occurred.
  • Once it has, its presence attracts other minerals (such as calcium) to the damaged area. This helps to speed up the rate remineralization (reformation and repair of tooth mineral) and raise the degree to which this process will occur.

2) Fluoride helps to make a tooth more decay resistant.

Amazingly, the new tooth structure that's created during remineralization when fluoride is present (the process we just mentioned) is actually "harder" than the tooth was originally.

  • Most of a tooth's mineral content is in 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 tooth demineralization process).

    Specifically, fluorapatite is able to withstand a more acidic environment (pH 4.5 vs. 5.5 for hydroxyapatite) before it begins to dissolve away.

cavities using:

So, astoundingly, not only does fluoride promote tooth remineralization but it also helps to create a tooth surface that's even more resistant to the formation of tooth decay than it was originally.

3) Fluoride helps to reduce bacterial acid production.

Research has also shown that fluoride tends to inhibit the rate at which bacteria living in dental plaque are able to produce acidic waste products (the chemical compounds that actually cause tooth demineralization).

This effect is due to the fact that fluoride disrupts the bacteria's ability to metabolize sugars. And the fewer sugar molecules that the bacteria are able to consume, the fewer tooth-damaging waste products they will end up creating.

Tips for preventing tooth decay -

Fact - Tooth remineralization, a process that can help to repair the damage caused by tooth decay, is aided by the presence of fluoride. To receive this benefit, however, it must be present in your mouth (saliva).

Cavity prevention suggestions :

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

The ADA Seal.

  • Make sure your toothpaste contains fluoride, so you get an extra exposure every time you brush.
  • Look for toothpastes that have the American Dental Association's (ADA) "Seal of Approval." This seal indicates that the ADA has reviewed evidence about the product and found its fluoride content to be appropriate.

    (More about how to pick out a good fluoride toothpaste.)

Fluoride side effects - Dental fluorosis.

Dental fluorosis is a type of developmental tooth staining caused by a high systemic exposure of fluoride during the time period when a child's tooth enamel is forming.

Due to the presence of the fluoride, the tooth's development is disturbed. The result is areas of decreased enamel mineral content and increased porosity, which alters its appearance in these regions. (AlShehri 2016)

Teeth showing bands of fluorosis stains.

Mild-dental fluorosis. Sometimes called "snow capping."

a) Types of fluorosis. / Appearance.

  • The vast majority of cases that occur in the United States involves a mild form characterized by the appearance of chalky-white lines, or opaque white patches, in a tooth's enamel.
  • More severe forms can occur. In extreme cases, the affected areas have a yellow or brown discoloration. They may also have tooth surface pitting.
  • It may be that the fluorosis first presents itself as a white area that then due to its low mineral content and porosity picks up brown staining over time.
Bilateral symmetry is common.

It's typical that the staining pattern of the fluorosis is at least somewhat bilaterally symmetrical (has affected the same teeth, and even same tooth locations, on both the left and right sides). That's because these teeth and areas were at the same point in tooth enamel development when the exposure to the fluoride took place.

[Here's an digital smile makeover that illustrates and discusses the treatment of severe fluorosis.]

b) It's young children who are at risk.

Dental fluorosis only occurs if excessive amounts of fluoride are ingested (swallowed) during that time period when a child's tooth enamel is forming.

  • That means the most critical years for the risk of fluorosis lie between birth and age 6 or 7.

But because the staining forms while the teeth are developing (and therefore still lie in the jawbone), it's not visible until the affected teeth have come in, which is typically between the years 6 through 12.

Streaks of fluorosis like these would have all form during the same general time frame.

Teeth showing bands of fluorosis stains.

They show at different levels because the teeth were at different stages of development at the time of the exposure.

c) Swallowing toothpaste is frequently the cause.

The problem.

Small children, especially those younger than age 6, may not be able to reliably spit out when brushing.

As a result they may end up swallowing a large quantity of the toothpaste that's been placed on their brush. If it contains fluoride, over time enough may be ingested that fluorosis forms.

  • 1 to 3 year olds may get up to 80% of their daily intake of fluoride from toothpaste. (Almeida 2007)
  • It's estimated that 2 to 3 year olds ingest 48% of the amount of toothpaste dispensed, 4 year olds 42%, 5 year olds 34% and 25% in 6 year olds. The estimate for children between 8 and 12 years is around 10%. For adults it's 10% or less. (SCHER 2011).

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The following suggestions can help to minimize a child's risk for fluorosis.

  • Children should be given instructions about how to properly brush and rinse. So to help them avoid swallowing toothpaste, they should be supervised when brushing.
  • In most cases it's the amount of product that's used rather than the concentration of its fluoride that poses the greatest risk (Davies 2003). Fluoridated toothpaste should always be dispensed by an adult, not the child.

    Read your toothpaste's instructions, generally only a small amount of toothpaste is needed. A common measurement for children is a dab the size of a green pea (0.25 g). For those younger than 3 years, just a smear. Dispensing toothpaste the full length of a child's toothbrush can correlate with an amount that's times (0.75 g) the proper amount.

  • As a general rule, unfluoridated tooth cleanser should be used with children 2 years and under. Ask your dentist for their specific recommendation.
Teeth that have fluorosis staining.

Severe dental fluorosis.

  • Store fluoridated toothpaste out of the reach of children (some kids like the way it tastes and eat it).
  • When purchasing fluoride toothpaste, look for one that has the American Dental Association's (ADA) "Seal of Approval." These products have been shown to be both safe and effective.

d) Fruit drinks can be the culprit too.

Bottled juices and juice-flavored drinks manufactured with water can have fluoride levels that significantly exceed the 0.7 to 1.2 ppm (parts per million) that are considered appropriate and optimal.

Solutions for fluorosis.

With just mild cases of fluorosis, no treatment is required if the person considers the appearance of their tooth acceptable. If not, or in cases where some type of significant surface pitting or dark staining is involved, a repair can be made (filling, veneer or crown placement, depending on the conditions and severity of the case).

Minimally invasive solutions.

In situations where only a relatively minor esthetic improvement is needed, a patient might have several "minimally invasive" options to choose from. They include:

  • Teeth whitening treatments - Treatments are used to lighten the overall color of the affected teeth, which helps to mask the appearance of their fluorosis staining. (View an example case that illustrates this technique.)
  • Microabrasion - When fluorosis staining is confined to the surface layer of a tooth's enamel, this process can be used to remove it.
  • Resin infiltration - This is a relatively new procedure that may offer a minimally invasive solution for mild to moderate fluorosis cases.


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