Tooth decay

At a glance

  • Tooth decay (also called cavities or caries) is caused by bacteria in the plaque on your teeth. The acid that the bacteria produce when they break down sugar from food particles damages the surface of the teeth.
  • This causes holes (cavities) to form in your teeth, which may hurt.
  • Too much sweet foods and drinks, and a lack of oral hygiene, can increase your risk of tooth decay.
  • Children are especially at risk.
  • There are effective ways to prevent tooth decay, such as by regularly brushing your teeth with toothpaste that has fluoride.


Photo of a young boy at a visit to the dentist

Tooth decay (also called cavities or caries) is caused by 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 toothpaste. So there are a number of things you can do to 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 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. If your child eats or drinks a lot of sweet things, they have a high risk of tooth decay. This is also true of toddlers, who often drink sugary tea or juice from a baby bottle. And it can be especially difficult to make sure that young children follow good oral hygiene.

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 about 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 toothpaste. The helps to make the enamel stronger, protecting the teeth from decay. Brushing the teeth removes plaque containing harmful and acid. It is generally recommended that you brush your teeth at least twice a day after meals.

Up to the age of twelve months children should either take tablets or have their teeth brushed with toothpaste. Children shouldn’t have too much 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 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 toothpaste and have a 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 methods, 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.

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Deutsche Gesellschaft für Präventivzahnmedizin (DGPZM). Empfehlungen für Kinderzahnpasten mit Fluorid. 2021.

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Kashbour W, Gupta P, Worthington HV et al. Pit and fissure sealants versus fluoride varnishes for preventing dental decay in the permanent teeth of children and adolescents. Cochrane Database Syst Rev 2020; (11): CD003067.

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Schwendicke F, Walsh T, Lamont T et al. Interventions for treating cavitated or dentine carious lesions. Cochrane Database Syst Rev 2021; (7): CD013039.

Worthington HV, MacDonald L, Poklepovic PT et al. Home use of interdental cleaning devices, in addition to toothbrushing, for preventing and controlling periodontal diseases and dental caries. Cochrane Database Syst Rev 2019; (4): CD012018.

IQWiG health information is written with the aim of helping people understand the advantages and disadvantages of the main treatment options and health care services.

Because IQWiG is a German institute, some of the information provided here is specific to the German health care system. The suitability of any of the described options in an individual case can be determined by talking to a doctor. can provide support for talks with doctors and other medical professionals, but cannot replace them. We do not offer individual consultations.

Our information is based on the results of good-quality studies. It is written by a team of health care professionals, scientists and editors, and reviewed by external experts. You can find a detailed description of how our health information is produced and updated in our methods.

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Updated on September 5, 2023

Next planned update: 2026


Institute for Quality and Efficiency in Health Care (IQWiG, Germany)

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