Medical Encyclopaedia › Bleaching (short definition)
In brief: In bleaching, discoloured teeth are whitened with oxygen-releasing agents, usually based on hydrogen peroxide or carbamide peroxide. It is particularly suitable for natural teeth with age-related discoloration or discoloration caused by food, drink and tobacco. It does not whiten fillings, crowns or veneers.
How does bleaching work?
Tooth discoloration arises externally from plaque and pigments from coffee, tea, red wine or tobacco, or internally in the tooth, for example due to ageing, dead nerves, injuries, certain medicines in childhood or too much fluoride during tooth development. Superficial deposits can often be removed by professional tooth cleaning alone. In bleaching, peroxide penetrates the enamel and dentine and breaks down pigment molecules so that they absorb less light. The result depends on the type of discoloration: yellowish tones usually respond well, grey or patchy discolorations less well.
Methods
- In-office bleaching: a more highly concentrated gel is applied in the dental practice, with the gums covered beforehand. According to current data, lamps or light provide no clear additional benefit.
- Home bleaching: with individually made plastic trays and lower-dose gel at home over several days to weeks, under dental supervision.
- Internal bleaching: for a single root-treated tooth that has darkened, the bleaching agent is placed inside the tooth.
- Over-the-counter products such as strips or toothpastes contain only small amounts of peroxide and have a correspondingly limited effect; “whitening” toothpastes mainly remove surface stains.
Legal framework
Under EU cosmetics law, tooth whitening products containing more than 0.1% and up to a maximum of 6% hydrogen peroxide (free or released from carbamide peroxide) may only be supplied to dentists. The first application must take place in the practice or under direct dental supervision; treatment can then be continued at home. Such products are not intended for people under 18. Bleaching offers in beauty salons with higher concentrations are therefore not compatible with this.
Side effects and risks
- temporary sensitivity of the teeth to cold or heat, common and usually subsiding after a few days
- irritation or whitish chemical burns of the gums if gel gets onto them
- visible colour differences from fillings or crowns, which may then have to be replaced
- with internal bleaching, rarely resorption processes at the tooth root (external resorption)
Before bleaching, caries, leaky fillings and gum inflammation should be treated. Exposed tooth necks and cracks in the enamel increase sensitivity. Restraint is advised during pregnancy and breastfeeding.
Durability, alternatives and costs
The whitening usually lasts months to a few years and fades due to food, drink and tobacco; touch-ups are possible but should not be overdone. For discolorations that cannot be bleached, or when shape corrections are also needed, composite build-ups, veneers or crowns may be considered, although these can cost tooth substance. Bleaching is a purely aesthetic service that German statutory health insurers do not cover. A consultation about realistic results and a prior examination are advisable.
Related terms in the encyclopaedia
Hydrogen peroxide, Tooth discoloration, Tooth enamel, Dentine, Dentine hypersensitivity, Professional tooth cleaning, Veneers, Dental crown, Root canal treatment
Sources
- Richtlinie 2011/84/EU des Rates zur Änderung der Kosmetikrichtlinie (Zahnaufhellungsprodukte); Verordnung (EG) Nr. 1223/2009 über kosmetische Mittel, Anhang III
- Deutsche Gesellschaft für Zahnerhaltung (DGZ): Patienteninformationen zur Zahnaufhellung
- Scientific Committee on Consumer Products (SCCP): Opinion on hydrogen peroxide, in its free form or when released, in oral hygiene products and tooth whitening products (2007)
- Bundeszahnärztekammer (BZÄK): Patienteninformation Zahnaufhellung
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.