Tooth bleaching
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2008-07-07T00:08:42Z
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[[Image:Tooth whitener.jpg|thumb|right|300px|Tooth Whitener for Home Use (Brush for Application)]]
'''Tooth bleaching''', also known as '''tooth whitening''', is a common procedure in [[dentistry|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 due to changes in the [[Crystal structure|mineral structure]] of the tooth, as the [[tooth enamel|enamel]] becomes less porous. Teeth can also become stained by bacterial pigments, foodstuffs and tobacco.
The procedure to bleach teeth uses oxidizing agents such as [[hydrogen peroxide]] or [[carbamide peroxide]] to lighten the shade of the tooth. The [[oxidizing agent]] penetrates the porosities in the rod-like crystal structure of [[Tooth enamel|enamel]] and oxidizes interprismatic stain deposits; over a period of time, the [[dentin]] layer, lying underneath the enamel, is also bleached. The effects of bleaching can last for several months, but may be shortened by cigarette smoking, and tea and coffee consumption.
==Methods==
There are two main methods of bleaching--one performed by a dentist and one self-performed. A dentist applies a high concentration of oxidizing agent for a short period of time, which produces quick results. In order to reduce the risk of chemical burns to the [[soft tissue]]s, 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 [[Bleach|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% carbamide peroxide which is roughly equivalent to a 12% hydrogen peroxide concentration.
At-home whitening involves purchasing a thin [[mouthguard]] or strip that holds a relatively low concentration of oxidizing 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 drug|over-the-counter]] bleaching. Results can vary, depending on which application is chosen, with some people achieving whiter teeth in a few days, and others seeing very little results or no results at all. Whitening is potentially better at a dentist because the strip or mouth-guard does not completely conform to the shape of the teeth, sometimes leaving the tips of the teeth (near the gumline) unbleached. The bleaching agent is typically less than 10% hydrogen peroxide equivalent so irritation to the soft tissue around 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.
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.
==Risks==
[[Adverse effect (medicine)|Side effects]] of tooth bleaching include: chemical burns (if a high-concentration oxidizing agent contacts unprotected tissues, which may bleach or discolor [[mucous membrane]]s), 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.<ref>{{cite news |first=Charlie |last=Brooker |authorlink=Charlie Brooker |title=Thinking of getting your teeth whitened? Well don't. Keep them brown |url=http://www.guardian.co.uk/commentisfree/story/0,,1946559,00.html |work=The Guardian |date=November 13, 2006 |accessdate=2007-07-12 }}</ref> 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 [[Dental fillings|fillings]] and other restorative materials. It does not affect [[porcelain]], other [[Ceramic|ceramics]], or dental gold. However, it can slightly affect restorations made with composite materials, cements and [[Amalgam (dentistry)|dental amalgams]]. Tooth whitening can restore colour of [[Dental fillings|fillings]], [[porcelain]], and other [[Ceramic|ceramics]] when they become stained by foods, drinks, and smoking, amongst other activities. {{Fact|date=April 2008}}
==Internal bleaching==
Internal bleaching procedures are performed on devitalized teeth that have undergone [[endodontic therapy]] but are discoloured due to internal staining of the tooth structure by blood and other fluids that leached in. In this variation of whitening the peroxide is sealed within the tooth over a period of some days and replaced as needed, the so called "walking bleach" technique.{{Fact|date=April 2008}}
==Agents==
Various chemical and physical agents can be used to whiten teeth. [[Toothpaste]] typically has small particles of [[silica]], [[aluminum oxide]], [[calcium carbonate]], or [[calcium phosphate]] to grind off stains formed by colored molecules that have lodged onto the teeth from food. Unlike bleaches, whitening toothpaste does not alter the intrinsic color of teeth.
Bleaching solutions contain [[peroxide]] which bleaches the [[tooth enamel]] to change its color.<ref>{{cite web | url = http://copublications.greenfacts.org/en/tooth-whiteners/index.htm | title = Tooth Whiteners containing hydrogen peroxide] summary by GreenFacts of the European Commission SCCP assessment | publisher = [[GreenFacts]] | accessdate = 2008-05-04}}</ref> Off-the-shelf products typically rely on a [[carbamide peroxide]] solution varying in concentration from 10% to 22%. Bleaching solutions may be applied directly to the teeth, embedded in a plastic strip that is placed on the teeth or use a gel held in place by a [[mouthguard]]. Because the concentration is typically low to avoid toxicity, whitening often takes several weeks. A tooth whitening agent that also remineralizes teeth is under development.<ref>{{cite web | url = http://www.ada.org/public/media/releases/0506_release01.asp | title = New tooth whitener could help heal teeth | accessdate = 2008-05-04 | publisher = [[American Dental Association]]}}</ref>
Whitening treatments used by dentists are much more concentrated, containing substances with more than 30% [[hydrogen peroxide]], and require protection of the soft tissues.
Whitening teeth for aesthetic purposes has been dated back to the Ancient Egyptians, where a mixture of ground pumice and wine vinegar was brushed on the teeth with a rudimentary toothbrush. The ancient Romans used human [[urine]] by the belief that it kept the teeth white and firmly in place, a practice that continued into the eighteenth century{{Fact|date=May 2008}}. Whitening in the medieval ages was done by barbers, where the teeth would be filed down and [[nitric acid]] applied to the teeth. This was a dangerous procedure, considering the massive tooth damage this practice caused.
==Controversy==
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 [[North America]].{{Fact|date=May 2008}}
==References==
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[[Category:Dentistry procedures]]
[[de:Zahnaufhellung]]
[[fr:Blanchiment dentaire]]
[[nl:Bleken (tanden)]]
[[pt:Clareamento dental]]