Introduction
Tooth whiteners are chemical treatments contained in pastes or gels which can alter the colour of stained pigments on the tooth surface or within the tooth, to improve the overall colour.

About

The normal colour of teeth varies during life. Baby (deciduous) teeth are white, while permanent teeth are a combination of colours with varying degrees of yellow, grey, and red. Teeth tend to darken with advancing years because the outer enamel becomes thinner due to wear, and the inner dentine becomes more mineral-like. There are many lifestyle factors which can cause a tooth to darken. Staining of the outer surfaces of teeth can occur from smoking, coffee, red wine, and other coloured foods, as well as from some mouthwashes. Staining of the internal parts of a tooth can occur following trauma to the tooth or decay, when there may be bleeding within the dental pulp.

Lightening the shade of teeth is a common cosmetic procedure in dentistry. There are many ways to achieve it, and some techniques provide only relatively short-term improvements in tooth colour, whilst others are permanent. Some techniques also involve the destruction of significant amounts of the tooth surface, so there is a limit to how often they can be repeated. Chemical treatments are often combined with physical treatments, such as abrading the tooth surface, to achieve the most stable long term result.

The simplest tooth whitening strategy involves avoiding lifestyle factors which discolour teeth, and keeping the teeth as clean as possible. A professional cleaning and polishing will help remove any calculus, stain or other material from the tooth surface, without physically damaging the teeth. Some toothpastes contain whitening chemicals which release oxygen, which will lighten any stained material on the teeth but will not remove it. Because of this, further staining is likely to occur as the surface is microscopically rough.

Dentists can undertake a micro-abrasion of the tooth surface by etching and then abrading it. The enamel surface will then regenerate and the fresh new surface will often have a very smooth quality which makes staining less likely to recur. This is very effective if small flecks of dense white or yellow have occurred as the enamel formed in childhood because of the deliberate eating of toothpaste. If there are mild surface craters, these can be filled at the same time with a clear or tooth coloured composite resin filling material. The procedure is quick and anaesthetic is generally not necessary.

For stains within the sub-surface and deeper into the tooth, a bleaching agent which can penetrate into the tooth is generally used. A gel containing carbamide peroxide, which breaks down to release hydrogen peroxide, is the most common approach used. The effectiveness of reducing staining using these gels depends on the exposure time to the gel and its temperature. Dentists may heat the gel or activate it with a very bright visible light or laser to accelerate the bleaching process. The gel may also be worn at home for limited periods of time in a mouthguard-type tray which holds the gel in contact with the teeth.

Your dentist will usually want too see you regularly to check the whitening effect, and monitor the health of the gingival (gum) tissues which come in contact with the gel. It is common with many types of bleaching gel to experience sensitive teeth or gums for a few days, depending on how mow long the gel is in contact with the teeth. If the teeth or gums become very sore, it may be necessary to discontinue treatment.

When there has been bleeding inside a tooth (from trauma or infection), the area of the dentine containing the blood pigments becomes darker much like a bruise on the skin, and may eventually become black. When a tooth has been black for a long period of time, the chance of removing all traces of discolouration are very low, and it is often necessary to cut away the stained tooth structure and cover the tooth with a porcelain facing or crown. If bleaching chemicals, such as hydrogen peroxide, are placed inside the tooth, there is a possibility that some may leak out through microscopic cracks in the tooth crown. If this happens, irritation of the gums or surrounding supporting bone of the tooth may develop.

While most bleaching procedures result in a significant improvement in tooth colour, it is likely that the procedure may have to be repeated at some stage in the future to sustain the improvement.

Health care

If you have discoloured teeth, your dentist will be able to identify the factors responsible and suggest the options for treatment. If you are wearing a home appliance with bleaching gel, you should follow the dentist's advice exactly to reduce the chance of developing irritation or sensitivity. If you use a whitening gel for longer than advised, in the hope of getting a better result, problems are more likely to occur. Stains rarely disappear instantly, and most whitening effects improve the tooth colour steadily, so patience is necessary. As with all dental conditions your Dentist should be consulted as to the best approach for your particular problem.