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Tooth decay: Overview

Last Update: February 27, 2020; Next update: 2023.


Tooth decay (also called cavities or caries) is caused by bacteria in the plaque on your teeth, sweet foods and drinks, and a lack of oral hygiene.

It can harm your teeth and cause a lot of pain, and may even result in tooth loss.

Tooth decay is much less common than it was just a few decades ago. That’s mostly due to better oral hygiene and more people using fluoride toothpaste. This goes to show that there are a number of things you can do to improve the health of your teeth and prevent cavities.


White or brown spots on your teeth are the first sign of tooth decay. If it gets worse, holes (cavities) develop on the surface of the teeth. If the deeper layers of the teeth are affected, tooth decay can also harm the nerves in the teeth and the roots. Then the teeth become sensitive and hurt – especially whenever you eat or drink anything cold or sweet. Tooth decay can damage the teeth so much that they need to be replaced, for example with a bridge.

Causes and risk factors

Tooth decay is often the result of a combination of three things: plaque, poor oral hygiene and eating a lot of sugar. Plaque covers your teeth like a film and may feel a bit “fuzzy” when you touch it with your tongue. It is made up of bacteria, saliva and food particles. When bacteria break down the food particles and the sugar in them, acid forms on the surface of your teeth. If the teeth aren’t cleaned or treated, this acid attacks the enamel coating the teeth and slowly destroys them. Bacteria that cause tooth decay can be spread through saliva.

Children are especially likely to have tooth decay because the enamel on baby teeth (milk teeth) is more sensitive than the enamel on permanent teeth. Too many sweet foods and drinks can harm baby teeth. Oral hygiene can be a challenge too, especially for younger children. Toddlers who very often drink sugary tea or juice from a baby bottle are also at higher risk of tooth decay.

Permanent teeth are quite sensitive at first too: When they break through, their enamel hasn’t yet fully hardened, making it susceptible to decay.


Permanent teeth stay healthy in many children and teenagers: About 8 out of 10 twelve-year-old children in Germany don't have any tooth decay. The other children in this age group have one or more teeth that are affected by tooth decay.

In children who are six or seven and still have baby teeth, about half have already had tooth decay.

Tooth decay is more common in adults: The average adult between the ages of 35 and 44 has eleven teeth that are affected by tooth decay, have a filling or a crown, or have fallen out.


All a dentist needs to do to diagnose tooth decay is to take a close look at your teeth. X-rays can also be used to tell how much the teeth have decayed – and whether the spaces between your teeth or under any fillings are affected.


Both children and adults can lower their risk of tooth decay by regularly brushing their teeth with fluoride toothpaste. The fluoride helps to make the enamel stronger, protecting the teeth from decay. Brushing the teeth removes plaque containing harmful bacteria and acid. It is generally recommended that you brush your teeth at least twice a day after meals.

Dentists suggest using fluoride toothpaste as soon as a child's first baby teeth come in. Pediatricians often say that it's better to give toddlers fluoride tablets or drops at first, and brush their teeth with small amounts of non-fluoride toothpaste. But children shouldn’t have too much fluoride because it can have side effects.

What you eat also plays an important role: limiting your sugar intake lowers your risk of tooth decay. Soft drinks and candy contain a lot of sugar, as do fruit juices and ketchup.

Regular check-ups at the dentist can also protect your teeth because any tooth decay can be detected early and then treated. Your dentist can give you advice on oral hygiene and apply fluoride varnish or gel to your teeth. The pits and grooves on your larger back teeth (molars) can also be sealed using special plastic materials known as dental sealants.


In early stages of tooth decay (when white or brown spots appear on the teeth) it might be enough just to brush your teeth regularly with fluoride toothpaste and have a fluoride treatment at the dentist’s.

If you have a hole in your tooth, known as a cavity, you will be given a filling. Here the dentist will use a drill to remove decayed material, and then fill the cavity with synthetic resins (composite resins), amalgam, ceramic material or a precious metal. If the tooth damage is more severe, a partial or full crown may be needed for the tooth. If nerves are also affected, root canal treatment is usually recommended. Sometimes the tooth may need to be pulled (extracted). It can then be replaced by a bridge or fixed dentures supported by an implant.

Besides the conventional ways of treating tooth decay, there are a number of newer procedures, some of which no longer use a drill. These include a technique called “caries infiltration” to treat tooth decay in its early stages, which involves using plastic to harden the tooth.

Further information

As well as going to the dentist because of a toothache, many people also go for regular check-ups. Read about how to find the right dentist, how to prepare for the appointment and what to remember.


© IQWiG (Institute for Quality and Efficiency in Health Care)
Bookshelf ID: NBK279514


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