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Tooth bleaching, also known as tooth whitening, is a common procedure in general dentistry but most especially in the field of cosmetic dentistry. Many people consider white teeth to be an attractive feature of a smile. A child's deciduous teeth are generally whiter than the adult teeth that follow. As a person ages the adult teeth often become darker. This darkening is due to changes in the mineral structure of the tooth, as the enamel becomes less porous. Teeth can also become stained by bacterial pigments, foodstuffs and tobacco.
As white teeth are subconsciously associated with youth, they have become desirable. This has been made more apparent with the spread of American culture worldwide, where an especially white smile is coined a "Hollywood smile". The procedure to bleach teeth uses oxidising agents such as hydrogen peroxide or carbamide peroxide to lighten the shade of the tooth. The oxidising agent penetrates the porosities in the rod-like crystal structure of enamel and oxidises interprismatic stain deposits; over a period of time, the dentin layer, lying underneath the enamel, is also bleached. Tooth bleaching will generally last from 5 to 7 years, with variations from factors such as cigarette smoking, and tea and coffee consumption. 
Additional recommended knowledge
There are two main methods of bleaching. The first involves visiting a dentists office where by applying a high concentration of oxidising agent for a short period of time. This produces quick results but risks chemical burns to the soft tissues. Therefore, most in-office bleaching procedures use a light-cured protective layer that is carefully painted on the gums and papilla (the tips of the gums between the teeth). The bleaching agent is either carbamide peroxide, which breaks down in the mouth to form hydrogen peroxide, or hydrogen peroxide itself. The bleaching gel typically contains up to 35% hydrogen peroxide equivalent.
The alternative method or at home whitening involves either purchasing a thin mouthguard or strip at the store to hold a low concentration of oxidising agent next to the teeth for as long as several hours a day for a period of 5 to 14 days. This is known as take-home or over-the-counter bleaching. This is a slower process and the results are usually not as good as can be achieved at a dentist because the strip or mouth-guard does not follow completely the shapes of your teeth. The bleaching agent is typically less than 10% hydrogen peroxide equivalent so irritation to the soft tissue around your teeth is minimized. Dentists as well as some dental laboratories can fabricate custom fitted whitening trays that will greatly improve the results you can achieve with an "at home" whitening method. see
A typical course of bleaching can produce dramatic improvements in the cosmetic appearance of most stained teeth; however, some stains do not respond to bleaching. Tetracycline staining may require prolonged bleaching, as it takes longer for the bleach to reach the dentine layer. White-spot decalcifications may also be highlighted and become more noticeable. Bleaching is least effective if teeth have white spots, decay or infected gums. It is also least effective when the original tooth color is grayish. Bleaching is most effective with yellow discolored teeth.
Recently, efforts have been made to accelerate the bleaching process by the use of light. Studies have shown varying results as to the efficacy of light-activated bleaching.
Side effects of tooth bleaching include: chemical burns (if a high-concentration oxidising agent contacts unprotected tissues, which may bleach or discolor mucous membranes), sensitive teeth, and overbleaching (known in the profession as "over white teeth"). Rebound, or teeth losing the bleached effect and darkening, is also an issue, with some studies showing the rebound effect over 30 days. A recent study by Kugel et al has shown that as much as 4 shades of lightness can be lost over 30 days with light-activated/office bleaching.
The two side effects that occur most often are a temporary increase in tooth sensitivity and mild irritation of the soft tissues of the mouth, particularly the gums. Tooth sensitivity often occurs during early stages of the bleaching treatment. Tissue irritation most commonly results from an ill-fitting mouthpiece tray rather than the tooth-bleaching agent. Both of these conditions usually are temporary and disappear within 1 to 3 days of stopping or completing treatment.
Individuals with sensitive teeth and gums, receding gums and/or defective restorations should consult with their dentist prior to using a tooth whitening system. Anyone allergic to peroxide (the whitening agent) should not use a bleaching product. Also, prolonged exposure to bleaching agents may damage tooth enamel. This is especially the case with home remedy whitening products that contain fruit acids.
Bleaching is not recommended in children under the age of 16. This is because the pulp chamber, or nerve of the tooth, is enlarged until this age. Teeth whitening under this condition could irritate the pulp or cause it to become sensitive. Teeth whitening is also not recommended in pregnant or lactating women.
Tooth whitening does not usually change the colour of fillings and other restorative materials. It does not affect porcelain, other ceramics, or dental gold. However, it can slightly affect restorations made with composite materials, cements and dental amalgams.
Hydrogen peroxide can be a weak cancer promoter, meaning it can slightly stimulate the growth or multiplication of cancer cells. Tobacco use, alcohol abuse, and specific genetic predispositions increase the risk of oral cancer. Hydrogen peroxide may therefore further increase this risk, especially when the treatment is repeated. This may be of concern as smokers are likely candidates for tooth whitening. The risk of harmful effects may be greater for people who have pre-existing oral diseases.
Internal bleaching procedures are performed on devitalized teeth that have undergone endodontic therapy but are unesthetic due to internal staining of the tooth structure by blood and other fluids that leached in.
Generally, consumer organizations and health sector professionals recommend that bleaching products should only be used after consultation with a dentist, while the cosmetic industry and its organizations argue that, since bleaching products are basically safe, they should be freely available over the counter.
Also, regulations concerning bleaching products' availability and concentration in peroxide are more restrictive in the European Union than in the USA.
|This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Tooth_bleaching". A list of authors is available in Wikipedia.|