Here is what the British Dental Health Foundation have to say about tooth whitneing, which can be found at http://www.dentalhealth.org/tell-me-about/topic/cosmetic-dentistry/tooth-whitening:
What is tooth whitening?
Tooth whitening can be a very effective way of lightening the natural colour of your teeth without removing any of the tooth surface or damaging it. Usually the original shade of the tooth is whitened to a lighter colour, rather than being turned completely white.
Why would I need my teeth whitened?
As we get older our teeth get darker. This is partly due to our getting older, but it is also caused by the foods we eat and drink, and by other habits such as smoking. Tea, coffee, blackcurrant juice, red wine and other foods that have strong colours can have an effect on the overall colour of our teeth. Teeth may also darken as a result of some antibiotics.
Some people naturally have a more grey shade of teeth. Other people have white spots on their teeth. This can be caused by early tooth decay, or illness when the tooth was forming.
There are a number of reasons why you might get your teeth whitened. Everyone is different; and just as our hair and skin colour vary, so do our teeth. Very few people have brilliant-white teeth.
‘Calculus' or tartar can also affect the colour of your teeth. Some people may have staining under the enamel surface or tiny cracks can appear in the teeth which take up stains.
What does tooth whitening involve?
Professional bleaching is the most usual method of tooth whitening. Your dentist will assess you first to see whether tooth whitening is suitable for you. They will tell you about the options you have for tooth whitening and which will be the most suitable for you.
The most common type of whitening is called ‘dentist-supervised home whitening'. You will have trays made specially to fit into your mouth like gum-shields. The whitening gel is then put in the trays and you will be given a routine to follow at home.
Another option is called ‘chair-side whitening'. You will be told if you are suitable for the treatment, and your dentist will supervise it. First the dentist, hygienist or therapist will put a rubber shield or a gel on your gums to protect them. They will then apply the whitening product to your teeth, again using a specially made tray.
The ‘active ingredient' in the whitening product is usually hydrogen peroxide or carbamide peroxide. As the active ingredient is broken down, oxygen gets into the enamel and dentine of the teeth and the tooth colour is made lighter.
How long does home whitening take?
The total length of the home bleaching treatment can vary depending on how discoloured your teeth are and the shade you want to get to. It can usually be finished within two to four weeks. First, you will need up to four visits to the dentist. Your dentist will need to make a thin mouthguard and will take impressions for this at the first appointment. Once your dentist has started the treatment, you will need to continue the treatment at home. This means regularly applying the whitening product over two to four weeks, for 30 minutes to one hour at a time. The dentist will discuss with you exactly how long you should keep the tray in your mouth. It is important to follow the instructions that you are given to get the best result.
There are some products which can be applied for up to eight hours at a time. This means you can get a satisfactory result in as little as two weeks.
What other procedures are there?
There is also chair-side ‘power whitening'. Although this is often called ‘laser whitening', it is not a laser that is used. Gel is painted onto your teeth and then a light is shone onto the gel to speed up the whitening reaction. During this procedure, a soft material is placed over your gums to protect them.
How long does chair-side power whitening take?
Your dentist will need to assess your teeth to make sure that you are suitable for the treatment. Once it has been agreed, this procedure usually takes about one to two hours.
How much does tooth whitening cost?
Private charges will vary from practice to practice and region to region. Chair-side whitening will be more expensive than professionally supervised home bleaching. We recommend you get a written estimate of the cost before you start any treatment.
How long will my teeth stay whiter?
The effects of whitening are thought to last up to three years. However, this will vary from person to person. The effect is less likely to last as long if you smoke, or eat or drink products that can stain your teeth. Ask your dentist for their opinion before you start the treatment.
What are the side effects?
Some people may find that their teeth become sensitive to cold during or after the treatment. Others may have discomfort in the gums, a sore throat or white patches on the gum line. These symptoms are usually temporary and should disappear within a few days of the treatment finishing.
If any of these side effects continue you should go to your dentist.
What about over-the-counter home kits?
Home kits are cheaper but they are not always assessed for safety and tend to be more acidic. So there is a chance that these products could damage your teeth and gums. Because tooth whitening is a complicated procedure we advise that you always talk to your dentist before starting the treatment.
Regulations covering home kits vary from country to country. Kits sold in Europe cannot legally contain more than 0.1% peroxide and this is too little to be effective. In other countries where stronger peroxide is allowed, home whitening is more common. But you need to be careful as some kits sold over the internet may contain mild acids and abrasives.
How safe are beauty kiosks and beauticians?
In Europe and in some other countries whitening can only legally be carried out by a dentist. So tooth whitening by beauticians and in whitening kiosks is illegal. In Europe, it is illegal to supply bleaching material containing more than 0.1% peroxide (or the equivalent in carbamide peroxide) to anyone other than a dentist, or direct to the public.
These regulations are to protect the public. They make sure that anyone carrying out whitening is properly trained and has the right skills and knowledge to carry out the procedure without risking permanent damage to the teeth or gums.
What about whitening toothpastes?
There are several whitening toothpastes on the market. Although they do not affect the natural colour of your teeth they may be effective at removing staining, helping to restore the natural colour of your teeth. Therefore, they may improve the overall appearance of your teeth. Whitening toothpaste may also help the effect to last after your teeth have been professionally whitened.
We recommend that you look for our approved logo on the packaging of oral-care products. This is a guarantee that the claims made about the product have been scientifically and clinically checked by an independent panel of experts.
Can a single tooth which has been root-filled be whitened?
Sometimes. Many dead teeth become discoloured after a root filling. If the tooth has been root-treated, the canal (which contained the nerve) may be reopened. The whitening product is applied from the inside to whiten the tooth.
When might tooth whitening not work?
Tooth whitening can only lighten your existing tooth colour. Also it only works on natural teeth. It will not work on any types of ‘false' teeth such as dentures, crowns and veneers.
If your dentures are stained or discoloured visit your dentist and ask for them to be cleaned.
How can I look after my teeth once they have been whitened?
Many people find that their teeth and gums feel cleaner after they have been whitened. The whitening treatment was first used as a treatment to help heal gums, so this is an added benefit.
You can help to keep your teeth white by cutting down on the amount of food and drink you have that can stain your teeth. Don't forget, stopping smoking can also help prevent discolouration and staining.
We recommend the following tips to care for your teeth:
- brush your teeth for two minutes, twice a day with a fluoride toothpaste.
- cut down on how often you have sugary foods and drinks.
- visit your dentist regularly, as often as they recommend.
‘Incidence of tooth sensitivity after home tooth whitening' by Jorgensen and Carroll Published in JADA p 1076 - 1082 (August 2002).