There is more than one way to whiten teeth. This guide describes each, how it works and what to consider before you choose.
Key points
- Whitening uses a peroxide gel, a bleach that works on the natural tooth, so it only lightens natural teeth.
- The main types are dentist-supervised home trays, in-clinic whitening, light or laser-assisted whitening, over-the-counter and salon products, and internal whitening for a darkened root-treated tooth.
- Adding light or a laser gave no clear extra benefit in a meta-analysis of 21 trials.
- The NHS says products from a pharmacy, online or a salon do not work as well and may harm teeth and gums.1
- People aged 17 or younger, people with unhealthy teeth or gums, and some other groups should not have whitening.1
Whitening changes the colour of natural teeth. The methods differ in where you do them, how strong the gel is and how much a professional is involved. Understanding the types helps you ask the right questions.
How whitening works
The gel is a peroxide bleach that works on the natural tooth, so it only lightens natural teeth: crowns, dentures and implants stay the same colour.1 The peroxide releases oxygen, which breaks down the stain molecules inside the enamel and dentine. It can help with staining from age, frequent coffee, tea or red wine, or smoking.1
Type 1: dentist-supervised home whitening
Whitening gel and trays made to fit your teeth are worn at home, usually for around 2 to 6 weeks.1 The dentist takes impressions or scans, the lab makes the trays, and you wear them with the gel for a set time each day. This is gradual and flexible. The trays fit your teeth, so the gel stays on the teeth and away from the gums.
Type 2: in-clinic whitening
The gel is applied in the clinic, with a shield or paste protecting the gums, in about one appointment of 1 to 2 hours.1 The gel is often stronger. A meta-analysis of randomised trials found no difference in sensitivity or in whitening effect between at-home and in-office bleaching,2 so the choice is mostly about time and convenience.
Type 3: light or laser-assisted whitening
A special light or laser is added to the in-clinic gel. A meta-analysis of 21 trials found that adding light to in-office bleaching gave no improvement in colour change and did not change sensitivity.3 See our comparison of conventional and laser whitening.
Type 4: over-the-counter and salon products
Whitening strips, pens, toothpastes, and kits from pharmacies, online and salons are widely sold. The NHS says these do not work as well and may harm your teeth and gums, and that strong whitening chemicals should only be used or sold by dental professionals.1 Whitening toothpastes mostly remove surface stains and do not bleach.
Type 5: internal (non-vital) whitening
A tooth that has had root canal treatment can darken from inside. The dentist places a whitening agent inside the tooth, seals it and repeats if needed. It treats one tooth at a time, and it is different from the other types because it works from the inside.
Beyond whitening
When colour is not enough, other cosmetic options include bonding and veneers. See our pages on dental bonding and dental veneers.
Choosing a type
| If you want | Consider |
|---|---|
| Gradual change on your own schedule | Dentist-supplied home trays |
| One visit | In-clinic whitening |
| A tooth that went dark after root canal | Internal whitening |
| A temporary lift for surface stains | A professional clean, or whitening toothpaste |
| A big change in shape and colour | Veneers or bonding |
Strength of the gel
A review of 14 studies with 649 patients found that 35 percent hydrogen peroxide caused more sensitivity than 6 to 20 percent gels, and that the lower strengths changed the colour more on instrumental measures.4 Higher strength raised sensitivity without a clear gain in the shade patients saw.4 So stronger is not always better.
Who should not have whitening
The NHS lists people aged 17 or younger, people with unhealthy teeth or gums, people who are pregnant or breastfeeding, and people with crowns, dentures or implants, for whom it does not change the colour.1 Teeth should be examined first, and decay and gum disease treated.
Side effects
Sensitivity to cold or sweet food and drink is a known side effect, and so are sore gums or throat and white patches on the gums.1 A meta-analysis found no difference in the risk or intensity of sensitivity between at-home and in-office bleaching.2 See our page on sensitive teeth.
Restorations
Whitening does not change fillings, crowns or veneers. In laboratory studies, bleaching can affect restorative materials, although no clinical report was found of a restoration that had to be renewed because of it.5
How long the result lasts
With your dentist's advice, it may last around three years.1 See our guide to how long whitening lasts.
Expectations
The research on cosmetic dentistry raises concerns about expectations, and whitening can lighten teeth only so far.6 Ask your dentist to show you the likely shade range before you start.
Over-the-counter and salon products: what to watch for
Strips, pens, kits and salon treatments are easy to buy, and some are advertised as just as good as a dentist's. The NHS says they do not work as well and may harm teeth and gums.1 Common problems include gel that leaks onto the gums, trays that do not fit, unclear strength and no examination first. Salons may not be able to treat gum disease or decay that makes whitening uncomfortable, and they cannot advise on your restorations.
Charcoal products, lemon juice, baking soda and other home remedies need extra caution. Some are abrasive and can wear enamel, and some are acidic. If you are tempted, speak to a dentist first.
Whitening for children and teenagers
The NHS lists people aged 17 or younger among those who should not have whitening.1 Teeth that are still developing, with larger pulps and thinner enamel, are more likely to be sensitive. If a young person is unhappy with the colour of their teeth, a dentist can look for the cause. Sometimes the answer is better cleaning or treatment of a specific problem, such as a stain or a mark, and not whitening.
Parents should be cautious about kits marketed to teenagers and about peer pressure. A dental check is a good first step.
A checklist before you whiten
- Have a dental examination, and treat decay and gum disease first.
- Ask which type suits your teeth and your timetable.
- Ask about gel strength and how your gums will be protected.
- Mention any sensitive teeth, cracks or exposed roots.
- Remind your dentist of visible fillings, crowns and veneers.
- Plan around events, so sensitivity has time to settle.
- Know whom to call if your teeth become very sensitive.
Whitening is better treated as a medical-style decision, not an impulse purchase, because the right method and the right timing protect your teeth and your gums.
What to do if the result is uneven
Uneven results can happen. Teeth have different thicknesses and stains, so some areas lighten faster than others, and white spots or bands can show up as the teeth dry. Tell your dentist, who can look at the cause and suggest a plan, such as a further short course, a gentler approach or another cosmetic option for the teeth that did not respond. Do not keep repeating treatment on your own, since that may cause sensitivity without fixing the problem. In most cases, differences settle as the teeth rehydrate.1
Myths and facts
Myth: all whitening products are the same. The strength, supervision and method differ.
Myth: charcoal and home remedies whiten teeth. Be cautious. Abrasive remedies can wear enamel, and they are not a substitute for professional advice.
Fact: a professional examination comes first.
Questions to ask your dentist
- Which type suits my teeth and my timetable?
- What strength of gel will be used?
- How will my gums be protected?
- What will happen to my fillings, crowns or veneers?
- What should I do if my teeth become sensitive?
- How long should the result last, and what can I do to keep it?
Frequently asked questions
Which type works well for stained teeth?
Dentist-supervised methods are the most reliable, and a meta-analysis found no difference between home and in-office.2
Can children whiten their teeth?
The NHS lists people aged 17 or younger among those who should not.1
Does whitening harm enamel?
Sensitivity and sore gums are known side effects, which usually settle.1 Ask your dentist about your own teeth.
Does whitening toothpaste work?
It can remove surface stains, but it does not bleach.
Can I whiten at home without a dentist?
The NHS says over-the-counter and salon products do not work as well and may harm your teeth and gums.1
Does whitening hurt?
It should not, but sensitivity is a known side effect.1
Is whitening toothpaste enough?
Whitening toothpaste can remove surface stain, but it does not bleach the tooth, so the change is small. A dentist can advise whether you need a stronger approach.
What if my tooth has darkened after a knock?
A tooth that has darkened from inside may respond to internal whitening, a veneer or a crown, depending on the cause. See your dentist, since a darkened tooth can also have a dead nerve.
Why do some teeth whiten less than others?
Teeth differ in thickness, colour and the cause of the stain, and stain from inside the tooth responds differently to stain on the surface. A dentist can explain what to expect for each tooth.
About the author
Dr Anupam Sinha, BDS, MDS – Orthodontics. BDS (2002), KLE Vishwanath Katti Institute of Dental Sciences, Belgaum. MDS in Orthodontics (2006), SDM College of Dental Sciences, Dharwad. His thesis work won a national research award in 2005, and he holds a certification in aesthetic dentistry. He sees patients at Orion Dental Clinic in Greater Kailash 1, South Delhi. Read the full profile of Dr Anupam Sinha.
Sources
- NHS website. Teeth whitening (patient information). Page review date 19 August 2025. https://www.nhs.uk/conditions/teeth-whitening/
- de Geus JL, Wambier LM, Kossatz S, Loguercio AD, Reis A. At-home vs in-office bleaching: a systematic review and meta-analysis. Operative Dentistry, 2016;41(4):341-356. https://pubmed.ncbi.nlm.nih.gov/27045285/
- Maran BM, Burey A, de Paris Matos T, Loguercio AD, Reis A. In-office dental bleaching with light vs. without light: a systematic review and meta-analysis. Journal of Dentistry, 2018;70:1-13. https://pubmed.ncbi.nlm.nih.gov/29289725/
- Pontes M, Gomes J, Lemos C, Leao RS, Moraes S, Vasconcelos B. Effect of bleaching gel concentration on tooth color and sensitivity: a systematic review and meta-analysis. Operative Dentistry, 2020;45(3):265-275. https://pubmed.ncbi.nlm.nih.gov/32396502/
- Attin T, Hannig C, Wiegand A, Attin R. Effect of bleaching on restorative materials and restorations: a systematic review. Dental Materials, 2004;20(9):852-861. https://pubmed.ncbi.nlm.nih.gov/15451241/
- Doughty J, Lala R, Marshman Z. The dental public health implications of cosmetic dentistry: a scoping review of the literature. Community Dental Health, 2016;33(3):218-224. https://pubmed.ncbi.nlm.nih.gov/28509518/
Medically reviewed by Dr Anupam Sinha, BDS, MDS – Orthodontics, on . General information for patients from Orion Dental Clinic, last updated 23 October 2026. It is not advice for one person, so ask a dentist what suits you. To report an error, contact us.