Medical Encyclopaedia › Caries (short definition)
In brief: Tooth decay (caries) is a disease of the hard tooth tissue in which acids from bacterial plaque demineralise the enamel and later the dentine. It develops slowly, can still be stopped in early stages and can largely be prevented through oral hygiene, fluoride and a low-sugar diet.
How does tooth decay develop?
Bacteria in dental plaque (biofilm) metabolise sugar and other fermentable carbohydrates into acids. These dissolve minerals from the tooth enamel. Saliva and fluoride can partially compensate for the loss (remineralisation). If the acid phase predominates over a longer period, for example due to frequent snacks, sweet drinks or little saliva, a defect forms. What matters is less the amount of sugar than how often sugar is consumed.
Stages and signs
- Initial caries: chalky white or brownish spots in the enamel, the surface is still intact; no symptoms.
- Enamel and dentine caries: a cavity forms; in the dentine, caries progresses more quickly. Sensitivity to sweet, cold or hot may occur.
- Deep caries: approaches the dental nerve; inflammation of the pulp (pulpitis) and pain threaten.
Caries on contact surfaces between the teeth is often not visible from the outside; X-rays help to detect it. In older people, caries on exposed tooth necks and roots (root caries) is common.
Treatment
Early enamel lesions can be arrested with fluoride varnish, good oral hygiene and a change in diet. For incipient caries between the teeth, resin infiltration with a low-viscosity resin without drilling is sometimes possible. Once a cavity has formed, the carious tissue is removed as gently as possible and the tooth is restored with a filling. In very deep caries, nowadays often only as much is removed as is possible without exposing the dental nerve (selective caries removal). If the nerve is already inflamed or dead, root canal treatment may be necessary.
Filling materials and costs
Composites (tooth-coloured resins), glass ionomer cements and, for large defects, inlays made of ceramic or gold are used. Since the beginning of 2025, amalgam may only be used in the EU in medically justified exceptional cases. German statutory health insurers cover an adequate and appropriate filling; more elaborate restorations may involve additional payments. It is worth asking about the costs in advance.
Prevention
- brush teeth twice a day with fluoride toothpaste and clean between the teeth
- have sweet and acidic foods and drinks rarely and preferably with main meals
- sugar-free chewing gum, for example with xylitol, stimulates saliva flow
- regular dental check-ups; for children, fissure sealing of the permanent molars and early detection examinations, which German statutory insurers cover
- at increased risk, for example due to dry mouth, braces or exposed tooth necks, additional fluoride applications by arrangement
For babies and toddlers, there are agreed recommendations on fluoride toothpaste from the first tooth; the amount depends on age.
Related terms in the encyclopaedia
Caries, Tooth enamel, Dentine, Enamel caries, Cervical caries, Fluoride, Fluoride varnish, Resin infiltration, Fissure sealing, Dental filling, Pulpitis, Xylitol
Sources
- AWMF-S2k-Leitlinie „Kariesprophylaxe bei bleibenden Zähnen – grundlegende Empfehlungen“ (Deutsche Gesellschaft für Zahnerhaltung, DGZMK)
- AWMF-S2k-Leitlinie „Fluoridierungsmaßnahmen zur Kariesprophylaxe“ (DGZMK)
- Netzwerk Gesund ins Leben: Handlungsempfehlungen Kariesprävention im Säuglings- und frühen Kindesalter (2021)
- Verordnung (EU) 2024/1849 zur Änderung der Quecksilberverordnung (EU) 2017/852 (Dentalamalgam)
- Institut für Qualität und Wirtschaftlichkeit im Gesundheitswesen (IQWiG): gesundheitsinformation.de – Karies
Note: This article is for general information and does not replace advice, diagnosis or treatment from a doctor, dentist or pharmacist. Last updated: October 2026.