Fluoride is a naturally occurring mineral found in water in varying amounts, depending on which area of the UK you live in.
It's also found in certain foods, including tea and fish.
Fluoride’s main benefit is in helping reduce the risk of tooth decay, which is why it's added to many brands of toothpaste and, in some areas, to the water supply through a process called fluoridation (see below).
Tooth decay, also known as dental decay or dental caries, is a major health concern worldwide and it's still a big problem in the UK.
For example, tooth decay is one of the most common causes of hospital admission in children. While levels of decay have fallen in recent years, significant inequalities between communities remain.
Tooth decay occurs when acid in your mouth attacks the outer layers of your teeth. The acid is produced by bacteria that form a layer called plaque on the surface of your teeth. Eating and drinking sugary food and drink is the main cause of acid formation in plaque.
If you're at risk of tooth decay a cavity (hole) may develop in your tooth. If the decay spreads further into the tooth, the tooth can become infected, which can be painful. A dental abscess (a collection of pus that forms in the teeth or gums) may also develop.
How does fluoride protect teeth?
Fluoride disrupts the process of tooth decay by:
changing the structure of developing enamel, making it more resistant to acid attack – these structural changes occur if a child consumes fluoride during the period when enamel develops (mainly up to seven years of age)
encouraging better quality enamel to form that's more resistant to acid attack
reducing plaque bacteria’s ability to produce acid, which is the cause of tooth decay
Most water supplies contain some fluoride and around half a million people in the UK receive naturally fluoridated water.
Another 5.5 million people receive water that has had the fluoride concentration raised to around one part per million (1ppm). This level of fluoridation has been shown to have the most benefit for reducing decay levels.
The maximum amount of fluoride permitted in drinking water is 1.5 mg/l (milligrammes per litre).
The West Midlands has the biggest water fluoridation scheme in the UK, which serves over three-quarters of the local population. There are also smaller schemes in operation in other parts of the country, including the North East, the East Midlands, Eastern England, the North West and Yorkshire and Humber.
In the early 20th century, levels of tooth decay were found to be associated with fluoride levels in drinking water. This led to the introduction of water fluoridation schemes to add fluoride to water supplies where the level was low.
The first fluoridation scheme was introduced in the US in 1945, in the city of Grand Rapids, Michigan. Following pilot schemes, the first substantive UK scheme was in Birmingham in 1964. There are extensive schemes in Australia, Ireland and the US.
Over the past 50 years, there have been several reviews of the safety and effectiveness of water fluoridation schemes. Recent reviews have been carried out by the:
A Systematic Review of Water Fluoridation (PDF, 6.21Mb) – at the University of York in 2000
Centers for Disease Control and Prevention (US): Recommendations on Selected Interventions to Prevent Dental Caries, Oral and Pharyngeal Cancers and Sports-Related Craniofacial Injuries (PDF, 69kb) – in 2002
National Health and Medical Research Council (Australian Government): Efficacy and Safety of Fluoridation – in 2007
Overall, the reviews have found that water fluoridation contributes to reduced decay levels in populations, although the amount of reduction varies depending on the measures used.
Your local water supplier should be able to tell you how much fluoride is present in your water supply and whether fluoride is being added.
Dentists recommend that children and adults should brush their teeth using toothpaste that contains fluoride. For those who are particularly prone to tooth decay, mouthwash, gels, tablets or toothpastes containing higher concentrations of fluoride are also available. Ask your dentist for advice before using these treatments.
Fluoride varnish is another treatment that can be used to help protect against tooth decay. The varnish contains high levels of fluoride and is painted onto the surface of both baby and adult teeth. It works by strengthening the tooth enamel, making it more resistant to decay.
Safety and risks
There have been some concerns that fluoride may be linked to a variety of health conditions. Reviews of the risks have found no evidence to support these concerns and the general consensus is that water containing the correct amount of fluoride and fluoride toothpaste have a significant benefit in reducing tooth decay.
However, a condition called dental fluorosis can occur, particularly if a child’s teeth are exposed to too much fluoride when they're developing.
Mild dental fluorosis can be seen as very fine pearly white lines or flecking on the surface of the teeth. It can often only be diagnosed by a dental expert because other conditions may give a similar appearance. Severe fluorosis can cause the tooth’s enamel to become pitted or discoloured.
Fluorosis that might be of concern from an aesthetic perspective is rare in the UK because levels of fluoride in water, both natural and added, are carefully monitored and if necessary adjusted.
Because fluorosis can be difficult to spot and record consistently, new research methods are being used to photograph children’s teeth in studies looking at levels of fluorosis in populations.
The Drinking Water Inspectorate (DWI) is an independent organisation that checks that the water companies in England and Wales supply safe drinking water that meets legal standards.