The fluoride debate

Is fluoride good for your teeth, or a slow poison? We look at the most recent evidence.
 
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  • Updated:23 Feb 2007
 

01 .Introduction

Toothbrush and toothpaste

In brief

  • There’s now solid scientific evidence that fluoride added to drinking water helps to protect your teeth from decay.
  • The claims of those who oppose fluoridation are often based on outdated information, questionable research and selectively picking studies that support their case.
  • There’s no convincing evidence for harmful effects from fluoride at the levels used in our water supply.

Please note: this information was current as of February 2007 but is still a useful guide today.


Fluoride in drinking water

Beaconsfield, Tasmania, is famous for more than a mine rescue - in 1953 it was the first town in Australia to add fluoride to its water supply. Now every capital city has water fluoridation and, on average, Australians have much healthier teeth than 50 years ago.

To what extent is the improvement in Australians' dental health due to fluoride?

Health authorities are convinced of the dental health benefits of fluoride. A number of studies show that people exposed to fluoridated water are less likely to have decayed, filled or missing teeth than those who aren't (see The case for fluoridation).
Opponents continue to maintain that fluoride in the water supply does nothing to prevent tooth decay. And you’ve probably seen claims that it may in fact damage teeth by causing dental fluorosis, often with concerns that it may be adversely affecting our health in other ways (see Fluoride’s downside).

While still a controversial topic that can arouse strong passions, it’s now clear that the dental health benefits claimed for fluoridation are well supported by scientific evidence — and that the risks have been greatly exaggerated.

How does fluoride work?

Tooth decay (dental caries) begins when some of the enamel, the outer surface of the tooth, is destroyed by acid. The acid is produced by bacteria that can grow on the surfaces of teeth in a layer called plaque. When your teeth are exposed to foods or drinks containing sugars, the bacteria rapidly convert some of the sugars into acid. The plaque can hold the acid in contact with the tooth surface for up to two hours before it’s neutralised by saliva.

All the time that the enamel is exposed to acid it loses calcium and phosphate minerals into the plaque. Once the plaque acids have been neutralised the minerals can return to the enamel — a process called remineralisation. But the capacity for remineralisation is limited, so if you eat a series of sugary snacks through the day your natural defences don’t get enough time to do their stuff before the next assault on your tooth enamel. Fluoride helps to protect your teeth in at least three ways:

  • It promotes repair of early damage to the enamel.
  • It improves the chemical structure of the enamel, making it more resistant to acid attack.
  • It reduces the ability of the bacteria on your teeth to produce acid.

The verdict

Many people are less dependent on getting fluoride from water than in the past. Most people now use toothpaste that contains fluoride, and everyone’s exposed to fluoride in foods and drinks manufactured in fluoridated areas, the so-called ‘halo effect’.

But even though improvements in dental health from fluoridated water are now smaller, over the population as a whole they still represent a lot of teeth saved from decay.

Another plus from widely available fluoridated water is that it helps kids from lower socio-economic groups, who are at the greatest risk of tooth decay. They’re less likely to be regularly brushing their teeth, and even less likely to see a dentist.

What about bottled water?

Recent surveys have shown that tooth decay in Australian children is on the increase again. Experts are suggesting this coincides with the rise in popularity of bottled water and sports drinks that don’t contain fluoride (sugary juices and soft drinks are also likely culprits).

CHOICE and dental experts would like manufacturers to offer people the option of bottled water containing about 1 ppm of fluoride (the same as tap water in fluoridated areas).

 
 

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02.The case for fluoridation

 

Most water supplies contain some fluoride naturally (it’s the thirteenth most abundant element in the earth’s crust). Fluoridation is the process of topping up the natural fluoride content of the public water supply to a level high enough to improve dental health. It’s been done, here and overseas, for more than 50 years — long enough to provide reliable information about the benefits (and the risks).

Evidence from the UK

In 2000, a group of 10 experts (commissioned by the UK National Health Service) conducted a systematic review of the entire body of scientific evidence on public water fluoridation available at the time. Though they found much of the research lacked rigour, they found the evidence strong enough to conclude that:

  • Fluoridation of drinking water really does reduce the prevalence of decayed teeth, increasing the percentage of children totally free from tooth decay by about 15%.
  • Fluoride in drinking water provides an additional benefit over and above that derived from fluoride in toothpaste and topical applications provided by dentists.

Further investigation by the UK Department of Health confirmed these findings, examined additional research and highlighted the benefits of fluoridation for adults as well as children. This second report (published in 2002) found evidence that:

  • In general, more adults are keeping more of their own teeth into old age, and having less trouble with them, where there’s fluoride in the drinking water.
  • Fluoridation also confers additional benefits such as reductions in the number of people suffering from toothache or requiring general anaesthesia for dental treatment.

Australian research

Many Australian cities have added fluoride to the water since the 1970s, so millions of people have now been supplied with drinking water containing fluoride at the recommended levels for long enough for the benefits to be clearly evaluated from health statistics.

The National Health and Medical Research Council (NHMRC) reviewed the evidence in 1999 and concluded that, “Water fluoridation at optimal levels, varying from 0.6 ppm in subtropical regions to 1.1 in temperate climates, continues to provide significant benefits in the prevention of dental caries for both deciduous [baby] and permanent teeth. The evidence for a protective effect on dental health is strongest in childhood but can also be demonstrated in adults.” (‘ppm’ means parts per million — 1 ppm would be equivalent to 2 kg of fluoride in an Olympic pool containing two million litres of water.)
These conclusions are supported by more recent research:

In NSW, a major 2005 study that examined the dental records of nearly a quarter of a million schoolchildren aged 3–15 found that those living in areas with fluoridated water were significantly less likely to have decayed, missing or filled teeth than children living in areas without added fluoride in the drinking water.

Another 2005 study of 973 Australian army recruits showed that those with no exposure to water fluoridation had 40% more filled, missing or decayed teeth than recruits who had grown up with fluoridation.

What about toothpaste?

Most toothpaste contains fluoride. Clinical trials have shown that while fluoride toothpaste definitely helps prevent tooth decay, it isn’t as effective a public health program as fluoridated drinking water, which provides significant benefits for children and adults over and above those from fluoride toothpaste.

And fluoride toothpaste isn’t suitable for small children because there’s a risk that they’ll swallow too much of it and develop dental fluorosis (see Fluoride’s downside). Experts recommend that:

  • You don’t use any toothpaste when cleaning very small children’s teeth (up to the age of about 18 months).
  • Children aged between 18 months and five years should use low-fluoride toothpaste (0.04–0.05% fluoride). They should clean their teeth twice a day with adult supervision, use only a pea-sized amount of toothpaste and be taught to spit it out and not swallow.
  • Kids aged six or more should clean their teeth with standard fluoride toothpaste at least twice a day, and not swallow.

If you live in an area without fluoridated water your kids might need to start using fluoride toothpaste earlier — check with your dentist.

03.Fluoride's downside

 

Fluoride’s definitely poisonous if you’re exposed to too much of it. A dose of less than a gram of sodium fluoride can cause nausea and vomiting; 5–10 g can be lethal. Not surprisingly, a major criticism of the public fluoridated water program is that it can provide too much fluoride.

Too much fluoride can cause dental fluorosis, a condition where the enamel surface of the teeth becomes mottled in appearance. Most dental fluorosis is very mild and doesn’t damage teeth, and it occurs only during tooth development in early childhood, so older children and adults aren’t at risk. Although it’s more common in fluoridated areas, it can occur in other areas as well.

Most fluorosis seems to be associated with kids swallowing too much fluoride toothpaste, or parents giving them fluoride supplements. Fluorosis levels have halved since the early 1990s with the wider use of special low-fluoride children’s toothpastes and recommendations that children use only very small amounts of toothpaste. But it’s an area that health authorities continue to monitor.

It’s known that high amounts of fluoride can also cause fluorosis of the bones, increasing your risk of fracture. It occurs most commonly in countries such as India and Pakistan where the natural concentration of fluoride in the water can be as high as 18 ppm.

A number of studies have looked for a relationship between exposure to fluoride at about 1 ppm and the risk of bone fracture. The results have varied, but when both of the UK expert reports looked at the results overall they concluded that there’s no proven additional risk of bone fracture associated with water fluoridation.

An Australian review in 2001 looked at 33 individual studies and concluded that fluoride to 1 ppm doesn’t have an adverse effect on bone strength, mineral density or evidence of fractures.

There have been claims that long-term exposure to levels of fluoride even as low as those found in Australian water may cause bone cancer or birth defects. The two expert reports from the UK found no association between bone cancer and fluoridation. The Australian NHMRC report considered three controlled studies and came to the same conclusion. And there’s no sound evidence at all that fluoride causes birth defects. Studies haven’t found any increase in their prevalence, even in those areas of India and Africa that have very high levels of fluoride in the water.

Is this the end of the story?

There’s a continuing need for high-quality research to track any potential harmful effects of fluoridation. But at present the evidence is very strong that it’s a safe and effective public health measure.

Q. I’ve heard that where some cities overseas have abandoned fluoridation, their rates of dental decay have continued to decline. Doesn’t this prove that fluoridation doesn’t work?

Although this is often claimed, the 2000 UK review found that out of 16 studies reporting on what happens if fluoridation is stopped, 12 found that the rate of tooth decay increased again.

Q. Hasn’t fluoridation been banned in Europe?

No, fluoridation is permitted under European Union regulations. In some countries water fluoridation isn’t practical because of very complex water systems without a central point to add fluoride. As a substitute for fluoride in water, many countries add fluoride to salt, which is then used in products like bread that most people eat, while others add fluoride to milk.

Q. I’ve seen claims that proponents of fluoridation are suppressing scientific evidence.

The UK experts considered this claim from a statistical point of view. They concluded that any missed (or concealed) study would have to be very large and very different from those that they analysed to overturn the overall beneficial result for water fluoridation. In any case, in the internet age any credible research can be brought into the public domain for review and debate.

Q. Isn’t fluoridation unethical? Some people consider it mass medication.

It’s more equivalent to fortifying breakfast cereals with vitamins and minerals to help prevent shortages than medication to cure a disease.