How does teeth whitening work?
Whitening gels contain hydrogen peroxide or carbamide peroxide. These pass through the enamel and break down the colour molecules in the tooth structure, making the tooth look lighter. Whitening does not wear away the tooth surface, but it is important that the right concentration and duration are set by the dentist.
Methods
In-office (clinic) whitening
After the gums are covered with a protective barrier, a higher-concentration whitening gel is applied to the teeth. The gel is renewed at set intervals. The procedure is usually completed in one session; it can be repeated if needed.
At-home whitening
A low-concentration gel is placed in thin, clear trays made from impressions of your mouth and worn at home for the time recommended by the dentist. The result appears gradually over a few weeks.
Combined method
In-office whitening followed by at-home whitening. It can help the colour lighten more evenly and help maintain the result.
| Feature | In-office | At-home |
|---|---|---|
| Where it is done | Clinic | Home |
| Gel concentration | Higher | Lower |
| When results show | Faster | Within a few weeks |
| Supervision | By the dentist | Depends on regular use by the patient |
Assessment before whitening
- Any cavities, open filling margins and gum disease are treated first.
- The teeth are cleaned of tartar.
- The cause of the discolouration is identified; some internal discolouration responds only partly to whitening.
- Patients are reminded that the colour of fillings, crowns and veneers on the front teeth will not change.
Who may it not be suitable for?
- People who are pregnant or breastfeeding
- People with untreated cavities or gum disease
- People with marked tooth sensitivity, wear or enamel cracks
- People with large fillings or crowns on the front teeth (colour mismatch may occur)
- Children and young people in early adolescence
After whitening
Temporary sensitivity may occur in the first few days after the procedure; it usually settles on its own. It is advisable to avoid staining substances such as coffee, tea, cola, red wine and cigarettes for the first 48 hours. How long the result lasts depends on eating and drinking habits; some colour may return slightly over time.
Whitening after orthodontics
If whitening is planned after orthodontic treatment, it should ideally be done once the brackets or attachments have been removed and the tooth surfaces cleaned. For details, see the page on whitening during clear aligner treatment.