Tooth Decay

Authored by Dr Ben Williams, 19 May 2017

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The Information Standard

Reviewed by:
Dr Hayley Willacy, 19 May 2017

Tooth decay (dental caries) is the destruction of tooth tissue by the action of cariogenic, or caries causing, germs (bacteria).

Almost as soon as teeth erupt through the gums, germs (bacteria) from the mouth will attach to them and multiply. If left undisturbed they will soon form a sticky white layer of bacteria, called dental plaque, on the tooth surface.

The bacteria in dental plaque thrive on sugars in our diet. Whenever we eat or drink sugary things, the bacteria consume the sugars and release acid as a waste product which weakens enamel by dissolving mineral from its surface. Over time (usually several years), if left unchecked, the acid will dissolve a hole through the enamel and allow bacteria to enter the softer dentine layer, resulting in tooth decay (dental caries). The body’s main natural defence against early tooth decay is SALIVA. It contains compounds which neutralise the bacterial acids and also has minerals which can repair and strengthen enamel.    

Tooth decay will develop more frequently in areas where plaque is left undisturbed. These tend to include the rough biting surfaces of the back teeth and the surfaces in between your teeth because they are the hardest ones to clean effectively. Appropriate tooth brushing techniques and interdental cleaning will significantly lower the risk of dental decay at these sites. 

Tooth surfaces which are repeatedly exposed to sugars are also at a higher risk for developing decay. An example of this is 'baby bottle caries' that occurs when babies and toddlers are fed sugar-containing drinks such as formula and fruit juice, from a bottle during the day and at night for several years. The bottle teat concentrates the sugary liquids around the front teeth which can develop painful and unsightly cavities. To prevent this condition from developing or getting worse, children should be given only milk and water to drink and be encouraged to use a free-flow cup as early as possible, ideally by the age of 1 year. Their teeth should be brushed twice daily as soon as they erupt and they should only be given water to drink at night after tooth brushing.

Read more about causes of tooth decay.

Tooth decay (dental caries) is the most common oral disease in the world. Although it is a mostly preventable disease, almost nine out of ten adults and more than five out of ten children under the age of 16 years will have some experience of caries in the form of a filling, extraction or toothache. This is usually due to the high amount of simple sugars, or refined carbohydrates, in the human diet coupled with poor oral hygiene.

Although the consequences of tooth decay are rarely life-threatening, the effect it can have on normal life can be profound as anyone who has experienced toothache or has too few remaining teeth to chew properly will confirm.

Early on you may have no symptoms. However, as the tooth decay (dental caries) progresses, you may notice a cavity in the middle of the tooth. The first thing you notice will be the sharp edge to it, which your tongue feels. Later still you may start to feel pain, or toothache.

Learn more about symptoms of tooth decay.

Your dentist will be able to see signs of tooth decay (dental caries) during your check-up. If necessary they may also request an X-ray. This can identify areas of your teeth at risk of decay.

Discover more about how tooth decay is diagnosed.

Three things are necessary for tooth decay (dental caries) to develop:

  1. Sugars present in food and drink: without sugar to consume, the plaque germs (bacteria) would not release acid.
  2. Cariogenic bacteria: without bacteria to convert sugar to acid, there would be no tooth decay.
  3. Time: this relates to the amount of time the bacteria are left on the tooth surface and also the number of times that they are supplied with sugary foods during the day and night.

The aim of caries prevention advice is to reduce or disrupt these three factors and prevent or delay the development of dental decay.

Read more about how to treat and prevent tooth decay.

An important concept to understand about caries prevention is that the frequency with which sugar is consumed is more significant than the amount consumed (although lowering overall daily sugar intake is a very important element in one's general health).

For example, drinking a glass of orange juice in less than a minute is much better for your teeth than sipping it slowly for half an hour. The faster all the sugar is past your teeth, the better. This is because your saliva can then wash away the sugar and neutralise the acid. To help you regulate the risk to your teeth from sugary things it is recommended that you only have water or sugar-free drinks and snacks between mealtimes and try to restrict things containing sugar to mealtimes.

Clinical Editor's Comment (September 2017)
Dr Hayley Willacy recent read a large, UK-based trial looking at two interventions to prevent tooth decay: see below. It supports NICE recommendations to apply fluoride varnish to children’s teeth in a school-based dental programme in areas of high need with children at risk. The options were a fluoride varnish - applied six times every six months at school, or a protective polymer coating, applied once and replaced if needed. Children’s permanent back teeth are particularly vulnerable to decay when they first come through. The pitted biting surface can make these teeth difficult to keep clean to prevent decay.

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