What is teeth whitening?

Teeth whitening, or bleaching, is a common procedure that may involve professional or home dental care methods. However, not every method is suitable, or effective, for everyone. There are also several very different causes for discoloured teeth.

Reasons for whitening teeth

As you get older, your teeth darken as a result of what you eat and drink, or from lifestyle factors such as smoking. Tea, coffee and red wine can all affect the colour of your teeth, as can genetics and some types of antibiotics. Discoloured teeth can affect a person's appearance and self-esteem. 

Depending on the cause of your discoloured teeth, there may be other methods apart from whitening that your dentist can recommend. Professional cleaning, for example, can effectively remove surface staining from the teeth, if this is the cause of your discolouration.

When not to whiten

Teeth whitening is generally not recommended for children. It is also not recommended if you are pregnant or breastfeeding because the active ingredients are known to cross the placenta into the developing baby's bloodstream and to enter the mother's breastmilk. The effects of these products on fetuses and infants is unknown and therefore their use is best avoided by pregnant or breastfeeding women.

Whitening only works on natural teeth. It does not work on false teeth such as dentures, veneers or crowns. If you have stained dentures, you will need to visit your dentist to get them cleaned.

It is also a good idea to see your dentist before going ahead and whitening your teeth on your own. This is because your teeth may not be suitable for whitening and you may be at risk of side effects associated with whitening products that your dentist can explain to you. You may be able to whiten your teeth with a professional clean if staining is a problem.

Crowns

Also commonly called a cap. This is an artificial shell of porcelain, or metal, or both that is made in a laboratory designed to fit over all or part of the surface of a tooth. It restores the tooth’s form, function and desired colour and is permanently cemented to the underlying prepared tooth.

Placenta

The organ that forms within the uterus of a pregnant woman to provide the fetus with nourishment from the blood supply of the mother.

Veneers

A layer of tooth-coloured material, either porcelain or acrylic, that is directly attached to an original tooth.

Whitening methods

Depending on your age, previous dental treatment, diet, habits and health, some whitening methods may be more effective than others. Whitening methods include:

In-office whitening

This procedure is done in the dental surgery over one or more appointments. After an initial consultation to assess your suitability and examine your teeth, an appointment is made for the in-office whitening. A whitening gel, usually containing between 15-35% hydrogen peroxide, is painted on the teeth by the dentist and a protective coating is placed on the gums to shield them from the effects of the gel. The whitening gel is then activated, or accelerated, with an external light or heat source.

The procedure can take about 1-2 hours. Up to three or four visits may be needed to achieve good results, particularly if your teeth are significantly discoloured.

Over-the-counter products

Over-the-counter whitening products such as whitening strips, toothpastes and gum, or gels administered with mouth trays or painted on are typically safe, but regulations vary from country to country. As there is no assessment of your individual teeth by a dentist, there is a risk that undiagnosed problems such as tooth decay or gum disease can be made worse, or more painful, by the bleaching product. It is a good idea to check with your dentist that over-the-counter whitening products are safe for you before using them.

Any fillings, crowns or veneers that you already have will not change colour with the bleaching treatment. These will then look darker than your natural teeth after whitening and will need to be replaced to match.

Bleaching strips

Bleaching strips are made up of a plastic film coated in a whitening gel, which is placed over the upper and lower front teeth. They typically contain 10% hydrogen peroxide and are worn for 30 minutes at a time. However, because the strips are not custom-fitted, they allow saliva to seep underneath, which quickly inactivates the gel.

Selective bleaching of certain darker teeth is not possible with these products and results are variable. They may be of use to people who cannot tolerate custom-made whitening.

Teeth whitening before and after.Bleaching strips can be used to whiten teeth. 

Paint-on gels

Paint-on gels are typically made up of a variable concentration of whitening gel that is painted directly onto the teeth. However, the gel is rapidly inactivated by saliva and the effects have been shown to be unremarkable.

Whitening toothpastes

Toothpastes can remove surface stains on teeth by way of abrasion and help prevent stain accumulation. However, toothpastes contain less than 0.1% of hydrogen peroxide, so are generally ineffective at whitening natural teeth, despite the manufacturers' claims. In any case, toothpaste is in contact with teeth for a very short time and mixes with saliva immediately, which inactivates the hydrogen peroxide.

Crowns

Also commonly called a cap. This is an artificial shell of porcelain, or metal, or both that is made in a laboratory designed to fit over all or part of the surface of a tooth. It restores the tooth’s form, function and desired colour and is permanently cemented to the underlying prepared tooth.

Gum disease

A chronic, progressive disease of the gums caused mainly by bacteria and poor oral hygiene. Early stages are generally asymptomatic, with the advanced stages characterised by loss of gum tissue, supporting bone and eventual loss of teeth.

Tooth decay

The process of destruction of the tooth’s surface due to the accumulation of bacterial plaque, which produces acids that break down the tooth structure. The decay forms dark patches on the teeth, which grow into holes or cavities and can become painful if left untreated.

Veneers

A layer of tooth-coloured material, either porcelain or acrylic, that is directly attached to an original tooth.

Hydrogen peroxide

A liquid chemical that can be used as a bleach and an antiseptic.

Risks

Risks involved with teeth whitening include:

  • Tooth sensitivity - if your teeth already have a tendency to be sensitive, in-office whitening may not be suitable for you. A home whitening kit, using a much weaker concentration of whitening gel, would be more suitable, although the process will take longer;
  • Chemical burns to the gums - this occurs when strong whitening gel comes into contact with the gums. The gums will appear white and tender after the procedure;
  • Potential harm to your baby - if you are pregnant or breastfeeding, teeth whitening is best avoided, and;
  • If you have tooth decay, whitening gel can seep into a cavity and cause toothache. It is important to have your teeth checked by a dentist before beginning any type of whitening.

Tooth decay

The process of destruction of the tooth’s surface due to the accumulation of bacterial plaque, which produces acids that break down the tooth structure. The decay forms dark patches on the teeth, which grow into holes or cavities and can become painful if left untreated.

After teeth whitening

After whitening your teeth, avoiding food and drink that can stain them, may help to maintain the result. Multiple whitening sessions may be needed, depending on the type of whitening methods you have used. In-office whitening with your dentist usually achieves quicker results than home-whitening products supplied by a dentist, although the effect does not last as long.