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Fluoridation is the addition of small amounts of fluoride to drinking water to prevent tooth decay. This is done in some areas of the UK.

Tooth decay occurs when the enamel on the outer surface of teeth reacts with acid and dissolves. The acid can be naturally present in food or can be made by bacteria living in our mouths from the sugar we eat (plaque acid). The dissolving of the enamel is known as demineralisation. When the acids are neutralised by saliva or other means, the minerals re-enter the enamel – remineralisation.

Fluoride helps prevent tooth decay in the following ways.

• It alters the structure of the developing enamel of young children so that it is resistant to reacting with acid.
• Low levels of fluoride increase the rate of remineralisation.
• It reduces the ability of plaque bacteria to form acid.

The benefits of fluoride are widely accepted but there are some reasons why people think it should not be added to our water.

• High fluoride levels can cause dental fluorosis, a condition that causes white patches to form on the surface of enamel. High fluoride intake can also cause health problems such as stomach cancer and infertility.
• Around 90 per cent of toothpastes and mouthwashes already contain high concentrations of fluoride and so some people say that fluoridated water is not needed. However, evidence shows that water fluoridation still decreases levels of tooth decay in children, although the reason for this has not been established.
• Some people believe that fluoride should not be added to water as they see it as a form of mass medication that is being given without our consent. However, chlorine is universally accepted as a necessary addition to our water for public safety.

Note that you need to consider the information displayed on the graph very carefully, as sometimes the information may be insufficient to draw a strong conclusion. Possible reasons for this include the following.

• The information may be focused on one specific group of people (ie a certain age group, gender, ethnicity).
• The information may be focused on a small group of people (ie people from only one or two cities instead of the entire country).

During the 1980s, a fluoridation of drinking water trial was carried out across various areas in the UK. In 1989, the fluoridation of drinking water in Anglesey was stopped. A comparison of tooth decay amongst five-year-olds from Anglesey and five-year-olds from mainland Gwynedd during the period of 1987-1993 can be seen in the bar graph.