Medical Encyclopaedia › Aligner (short definition)
In brief: Aligners are removable, transparent plastic trays with which tooth misalignments are corrected step by step. Each tray in the series is shaped slightly differently and moves the teeth a little further. Aligners are barely visible in everyday life but only work if worn consistently and are not suitable for every misalignment.
How do aligners work?
The basis is a digital scan or an impression of the teeth. From this, the planned tooth movement is calculated on the computer in many small steps, and a tray is made for each step. Each tray is usually worn for one to two weeks before the next follows. To help the trays transmit certain movements better, small tooth-coloured resin bumps (attachments) are often bonded to the teeth. To create space, a minimal amount of enamel can be removed between the teeth. Depending on the starting situation, treatment takes a few months to more than two years; interim corrections with additional trays are common.
Who are aligners suitable for?
Mild to moderate crowding, smaller gaps and relapses after previous braces can be treated particularly well. With growing experience and additional elements, more complex cases are also being tackled. More difficult are larger tipping and rotation of round teeth, extruding individual teeth from the jaw, pronounced bite discrepancies and cases requiring tooth extraction. Studies show that the actual tooth movement often lags behind the computer plan. In children and adolescents with jaw growth or with skeletal misalignments, fixed braces or combined procedures are often preferable. Caries and gum inflammation must be treated before starting.
Procedure and everyday life
The process begins with an orthodontic examination with findings, usually X-rays, and a treatment plan. The trays generally have to be worn for about 20 to 22 hours a day and are only removed for eating and brushing teeth. Drinks other than water should not be consumed with the trays in, because sugar and acids collect underneath. Teeth and trays should be cleaned after every meal. A feeling of pressure in the first days after each tray change is normal. Regular check-ups are important to see whether the teeth are following the plan.
Risks and side effects
- caries and gum inflammation with inadequate oral hygiene
- shortening of the tooth roots (root resorption), possible as with other orthodontic procedures
- gum recession, especially with thin gums or movements beyond the bone
- treatment goals not achieved, changes in bite
- temporary speech changes and pressure points
- relapse after the end of treatment without consistent retention
Orthodontic professional bodies view offers in which trays are sent without a personal dental examination, based on photos or self-taken impressions, critically, because diseases of the teeth, gums and jaw joint can be overlooked.
After treatment
Teeth tend to move back to their old position. The result is therefore secured with a retainer: a thin wire bonded to the inside of the front teeth or a removable retention tray, which is often worn at night long-term. Without retention, relapse is likely.
Costs and health insurance
German statutory health insurance generally only covers orthodontic treatment up to the 18th birthday and only for pronounced misalignments classified according to the orthodontic indication groups (KIG); in adults only for severe jaw anomalies requiring combined orthodontic and surgical treatment. Aligners are not part of standard care and usually incur additional private costs. Purely aesthetic corrections are private services. A written treatment and cost plan, detailed information about alternatives such as fixed braces, and time to reflect are advisable.
Related terms in the encyclopaedia
Orthodontics, Retainer, Dental crowding, Crossbite, Tooth resorption, Gum recession, Bruxism, Veneers, Professional tooth cleaning
Sources
- Deutsche Gesellschaft für Kieferorthopädie (DGKFO): Stellungnahmen und Patienteninformationen zur Behandlung mit Alignern
- Gemeinsamer Bundesausschuss (G-BA): Richtlinien für die kieferorthopädische Behandlung (KFO-Richtlinien)
- Sozialgesetzbuch Fünftes Buch (SGB V), § 29 Kieferorthopädische Behandlung
- Rossini G et al.: Efficacy of clear aligners in controlling orthodontic tooth movement: a systematic review. Angle Orthod 2015
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.