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Teeth whitening

Key points

  • Teeth whitening techniques use bleaching methods to lighten the colour of your teeth.
  • Your teeth can become stained as a result of smoking, tooth decay or strong-coloured foods and drinks.
  • You can buy over-the-counter kits to whiten your teeth or your dentist can do it.

Teeth whitening is a way of lightening the natural colour of your teeth using bleaching methods.

You will meet the dentist carrying out your procedure to discuss your care. It may differ from what is described here as it will be designed to meet your individual needs.

About teeth whitening

As you get older, your teeth naturally become darker. Sometimes if you drink a lot of tea, coffee, red wine or have other foods and drinks with strong colourings, your teeth may become discoloured earlier in your life. Another major cause of discolouration is smoking, which can make your teeth appear yellow. Tooth decay, fillings and tartar (plaque that has built up and hardened on your teeth over time) can also contribute to discolouration.

Teeth whitening products can help to lighten your teeth. They usually contain either hydrogen peroxide or carbamide peroxide. When these chemicals break down, oxygen gets into the hard outer surface (enamel) of your teeth, which whitens them. How long the whitening effects last will be different for everyone and can range from a few months up to three years. See our frequently asked questions for more information.

There are several different ways you can whiten your teeth. You can buy bleaching kits to use at home or your dentist can whiten your teeth for you. Bleaching won't work on false teeth, veneers, crowns or fillings (including tooth-coloured fillings) but your dentist may be able to replace these with lighter ones. If you have had root canal treatment on any teeth, they can become discoloured. It may be possible to lighten these teeth by applying the product to the inside of your tooth.

Talk to your dentist about the different bleaching methods and which will be the most effective for you.

If you have tooth decay or gum disease, this will need to be treated before you have any whitening treatments. There are some instances when your dentist may recommend that you don't have your teeth whitened. For example, bleaching isn't usually recommended for pregnant or breastfeeding women. If you’re under 18, it’s illegal for you to be treated with a product that contains more than 0.1 percent hydrogen peroxide.

What are the alternatives to teeth whitening?

Simple ways that you can help to improve the appearance of discoloured teeth include:

  • brushing regularly with a fluoride toothpaste
  • stopping smoking
  • cutting down on food and drinks that can stain your teeth, such as tea, coffee and red wine
  • visiting your dentist regularly – he or she can scale and polish your teeth to remove any tartar that has built up

Experts are currently reviewing how effective whitening toothpastes are.

Home teeth whitening products

You can buy a range of teeth whitening products over the counter in most pharmacies in the UK. Some of these are explained here.

  • Whitening toothpastes are slightly abrasive, which may help to remove surface staining, but they won't change the natural shade of your teeth.
  • Tray kits – these contain rubber mouth trays (moulds that are approximately the same shape as your teeth) and tubes of bleaching gel. After squeezing some of the gel into the mouth trays, you place them over your teeth, usually for about 30 minutes at a time.
  • Whitening strips are coated with a gel that contains hydrogen peroxide. You usually wear them twice a day for a couple of weeks.
  • Mouth rinses – these are less likely to be effective as you only keep them in your mouth for a very short time compared with other methods.

The bleaching ingredient in the product is usually hydrogen peroxide. Legally, any teeth whitening product that you can buy over the counter can’t contain more than 0.1 percent hydrogen peroxide.

There is some evidence to suggest that you need to use a product with at least 3.6 percent hydrogen peroxide to see a noticeable improvement in the colour of your teeth. Therefore, these kits are likely to be less effective than the stronger products that your dentist can offer. It’s possible to get stronger kits over the internet but you’re advised not to buy these as the product may not be safe and could damage your teeth and mouth.

Always speak to your dentist before using over-the-counter teeth whitening kits – he or she may be able to recommend which ones to use. If you decide to use a home method of tooth whitening, make sure you read the instructions carefully and follow them exactly as described.

Professional teeth whitening

Professional bleaching can only be carried out by a qualified dental professional. It’s illegal for anyone else, for example a beautician or hairdresser, to offer the procedure.

Whitening can be external or internal. If you have external bleaching, the gel is placed on the outer surfaces of your teeth. Internal bleaching involves putting the bleaching product inside your tooth. External bleaching is more common, as internal bleaching can only be used if you have had root canal treatment, allowing access to the inside of your tooth.

External bleaching

If you have external bleaching, your dentist will make rubber mouth trays that fit your teeth exactly. He or she will protect your gums with a rubber shield before applying a whitening gel. This will be stronger and therefore more effective than products you can buy to use at home.

Your dentist will give you tubes of bleaching gel and instructions on how to use it in the mouth trays so you can continue whitening your teeth at home. He or she will tell you how often you need to apply the gel and for how long. This will depend on the product and can vary from 30 minutes at a time to wearing it overnight. Depending on which product you’re using, you may start to see results after one to four weeks.

Your dentist may also offer laser or ‘power’ bleaching. After he or she has applied the bleaching gel to your teeth, a laser (very bright light) is used to speed up the whitening process by reacting with the product. Although many providers claim that this treatment is more effective at changing the colour of your teeth more quickly, there is very little scientific evidence to show that it works. It’s also possible that the laser may damage your teeth.

Internal bleaching

You will only be able to have internal bleaching if you have had root canal treatment. This means that the blood vessels and nerves inside your tooth have been replaced with a rubber filling.

If you have internal bleaching, your dentist will drill a hole in your tooth and put the bleaching product into the hole. He or she will use the hole that was previously made for your root treatment, although it may need to be made slightly larger. Your dentist will seal the hole with a temporary filling, leaving the bleach inside your tooth.

You will need to go back to your dentist about a week later to have the temporary filling and bleach taken out. He or she will fill the hole with a tooth-coloured filling.

What are the risks?

As with every procedure, there are some risks associated with teeth whitening. We have not included the chance of these happening as they are specific to you and differ for every person. Ask your dentist to explain how these risks apply to you.

Provided it’s done by a qualified dental professional, teeth whitening is safe. It's important to be aware that products that are available on the internet may damage your teeth, gums or lips, or they may not work well.


Side-effects are the unwanted, but mostly temporary effects you may get after the procedure.

Side-effects of teeth whitening include temporary sensitivity of your teeth to hot and cold, a sore throat, tender gums and white patches on your gums. These side-effects should disappear after a few days but contact your dentist if they don’t.

It’s important that you have realistic expectations of how much your teeth can be whitened. Talk to your dentist about this before you begin the procedure. See our frequently asked questions for more information. You can increase how long the effects of teeth whitening last by:

  • brushing your teeth twice a day
  • stopping smoking
  • reducing how much you have of foods and drinks that can stain your teeth
  • having regular check-ups with your dentist


Produced by Polly Kerr, Bupa Health Information Team, June 2013.

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For answers to frequently asked questions on this topic, see FAQs.

For sources and links to further information, see Resources.

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  • This information was published by Bupa's Health Information Team and is based on reputable sources of medical evidence. It has been reviewed by appropriate medical or clinical professionals. Photos are only for illustrative purposes and do not reflect every presentation of a condition. The content is intended only for general information and does not replace the need for personal advice from a qualified health professional. For more details on how we produce our content and its sources, visit the about our health information page.

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