Tooth whitening is a cosmetic dental procedure that lightens the natural colour of your teeth. It does not remove the tooth surface — it changes the colour of the enamel and dentine using a bleaching agent.
In the UK, tooth whitening must be carried out by a registered dentist, dental hygienist, or dental therapist working under the prescription of a dentist. It is illegal for beauty salons or non-dental businesses to carry out tooth whitening. Under UK law (the Dental Products Directive and MHRA regulations), whitening products containing more than 0.1% hydrogen peroxide may only be supplied to and used by registered dental professionals. Products prescribed for at-home use by a dentist may contain up to 6% hydrogen peroxide (or up to 16% carbamide peroxide, which releases an equivalent amount of hydrogen peroxide). Using illegal or unregulated whitening products — which may contain far higher concentrations — can cause serious and permanent harm to your teeth and gums.
Types of professional whitening
Your dentist may offer one or more of the following options:
Home whitening (tray-based) — custom-made trays are fitted to your teeth. You fill them with a whitening gel prescribed by your dentist and wear them at home, typically for 30–60 minutes per day over 2–4 weeks. This is the most commonly recommended approach and produces reliable, lasting results.
In-surgery whitening — a stronger bleaching gel is applied in the practice and may be activated with a light or laser. Results are faster but may require a top-up at home. Sensitivity during and after is common.
Combined approach — in-surgery whitening followed by home whitening trays for maintenance.
Who is suitable for tooth whitening?
Most people with healthy teeth and gums are suitable candidates. However, whitening is not suitable for everyone:
Whitening does not work on crowns, veneers, or tooth-coloured fillings — these will remain their original shade, which may create a mismatch
Teeth with internal discolouration (from trauma, tetracycline antibiotics, or fluorosis) may not respond as well to standard whitening
Whitening is not recommended during pregnancy or breastfeeding
It is not legally available to people under 18 years of age — EU and UK regulations prohibit the supply or application of whitening products above 0.1% hydrogen peroxide to under-18s, regardless of the reason
Active gum disease or tooth decay should be treated before whitening begins
What results can I expect?
Tooth whitening can produce significant improvements in tooth colour, but the results vary from person to person. It is important to have realistic expectations:
Most people notice an improvement of several shades
Yellow-toned teeth respond better than grey-toned teeth
Results are not permanent — teeth naturally yellow again over time, and regular top-ups are needed to maintain whiteness
Smoking, coffee, tea, red wine, and some foods stain teeth and reduce the longevity of whitening results
Risks and possible side effects
Common (affect more than 1 in 10 people):
Tooth sensitivity — increased sensitivity to hot, cold, and sweet is very common during whitening and for a short time afterwards. It usually resolves within a few days of stopping the gel. Sensitivity toothpaste can help.
Gum irritation if the gel comes into contact with the gums — custom trays reduce this risk significantly
Uncommon:
Uneven results — some areas may whiten more than others
Prolonged sensitivity lasting more than a week after treatment
Rare:
Significant gum damage from poorly fitting trays or overuse of gel
Whitening gels available from UK dentists contain hydrogen peroxide at safe, regulated concentrations. Products sold illegally online or in non-dental settings may contain dangerous concentrations of bleach that can cause permanent tooth and gum damage.
Making your results last
Avoid staining food and drink (coffee, tea, red wine, berries, tomato sauce) for at least 48 hours after whitening — this is when the teeth are most porous
Drink staining beverages through a straw where possible
Brush with a good whitening toothpaste for maintenance
Keep your custom trays — top-up whitening at home is much cheaper if you already have the trays
Top-up treatment is typically needed every 6–12 months to maintain results
Do not smoke — smoking is one of the fastest ways to re-stain teeth
Questions to ask your dentist
Are my teeth and gums healthy enough for whitening?
Will my existing fillings or crowns match after whitening?
Which whitening option do you recommend for me?
How many shades of improvement is realistic in my case?
How long will my results last, and how do I top up?
This leaflet is for general information only and does not replace professional dental advice. It is intended to support — not replace — the discussion with your dentist about your individual options, risks, and treatment plan. Treatment outcomes vary between patients depending on individual circumstances. Your dentist will confirm exact fees and what is suitable for your specific circumstances before you agree to any treatment.
References
Aligned with guidance from: SDCEP, FGDP(UK), MHRA.