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11. Tooth Whitening - Facts and Fallacies Associate

Contributed by:

Professor Dr. Abdul Aziz Abdul Razak

Dept. of Conservative Dentistry, Faculty of Dentistry University of Malaya

This modern era is characterised by longevity and improved quality of life. There is also greater emphasis placed on feeling and looking better. People are demanding better smiles and whiter teeth. The cultural environment encouraged by toothpaste advertisements and local and Hollywood film stars, including the personal need to appear healthy and young, makes it seem that discoloured or dark teeth are no longer socially acceptable.

Fortunately, as the demand on aesthetic dentistry have escalated, the techniques and working properties of our dental materials have continued to improve. Extensive tooth preparation and destruction have given way to a concern for the preservation of tooth structure.

Even during the 14th century, a surgeon by the name of Guy de Chauliac commented extensively on dental conditions and produced a set of rules for oral hygiene which include the following tooth whitening procedure: " Clean the teeth gently with a mixture of honey and burnt salt to which some vinegar has been added." Over the last couple of decades, bleaching of teeth in order to whiten them has regained popularity and provided people with an excellent method to improve their self-esteem and confidence. Manufacturers have therefore complied with the demand by providing with professional in-office bleaching and home bleaching.

Bleaching of teeth has been done as early as 1877 using oxalic acid. Shortly after, calcium hypochlorite was used as an effective whitening solution. The most effective bleaching agent was found to be hydrogen peroxide which was developed in 1884. Presently, most bleaching products contain some 30 - 35% hydrogen peroxide or 10% carbamide peroxide as the active ingredient. Carbamide peroxide will break down to form urea and hydrogen peroxide which then break down to give free oxygen molecules which are actually the active bleaching component.

There are some negative side effects in bleaching apparent in a small number of patient, such as sensitive teeth, irritated gingival, sore throat, occlusal or temporomandibular joint problems associated with wearing of tray. These problems are considered negligible when compared to the benefits of the home bleaching technique. In general, it seems to be safe and non damaging.

Knowledge as to the cause of dental staining is important as it allows the dentist to plan the technique to be used in the whitening procedure. Staining and and discolouration of teeth are caused by many factors and traditionally can be divided into extrinsic and intrinsic stains.

Extrinsic stains such as food from vegetables, from tea or coffee, smoking or from some medications can occur on the exposed surfaces of teeth. Those that are accessible by toothbrush can be easily removed. While those stains that occur along the gingival margins and interproximal areas are difficult to clean by a toothbrush. These stains can be removed by means of scaling and polishing by a dentist, or by tooth bleaching which can produce dramatic results. Currently, there are also specially formulated toothpastes available in the market to remove such stains from the teeth.

Intrinsic stains which are the result of colour changes of internal structures of the teeth caused by systemic or local factors, are more difficult to remove. Examples are hereditary factors, fluorosis, trauma to teeth, systemic conditions caused by childhood illness, stains caused by antibiotics such as tetracycline during pregnancy and early childhood or stain from dental materials. Of course, the present tooth whitening procedures can remove most intrinsic stains. Teeth that stain with age seem to disappear very quickly when bleached. However those that cannot be removed by bleaching, can be improved by use of porcelain veneers, porcelain crowns or composites.

Here are some questions commonly asked in relation to tooth whitening :

HOW MAY VITAL TEETH BE LIGHTENED?

The most conservative approach is bleaching, done either in-clinic or by patient at home. In-clinic systems are generally faster and uses for example a light-activated solution of 30-35% by hydrogen peroxide or 10% carbamide peroxide in 4 - 10 minutes cycles. Home bleaching with custom trays incorporating spacers at each tooth usually use a 10% carbamide peroxide solution in gel medium, 1-2 hours a day over a period of 2-3 weeks.

Direct composites or laboratory-made porcelain veneers (facings) would be the next most conservative approach especially in cases of tetracycline staining which do not respond well to bleaching. Veneers are also useful when size, shape and arrangement of teeth are not acceptable aesthetically. The other alternative would be full-coverage crowns (all -ceramic or porcelain fused to gold) but are very invasive having to cut more tooth tissues and can be more costly.

HOW LONG WILL BLEACHED TEETH REMAIN LIGHT?

It is difficult to to evaluate long term stability of any procedure. Variables such as drinking tea or coffee, smoking habits and other oral hygiene habits can effect its longevity. The procedure is cosmetic as in the colouring of hair and therefore requires maintenance. Rebleaching is simple and cases have remained stable for at least 2 years with very little colour relapse noted.

ARE THERE ANY SIDE-EFFECTS TO BLEACHING?

Those are clinically supervised (by dentist) are safest. Soft tissue irritation, nausea or vomiting have been reported but occurs very rarely.

WHAT FACTORS MAY AFFECT VITAL BLEACHING RESULTS?

Intensity and type of stain, duration of contact with bleach and concentration of active reagent.

WHAT TYPE OF TOOTH STAIN RESPOND BEST TO VITAL BLEACHING?

Extrinsic stains respond best while intrinsic stains or discolouration may not show any change. Generally, yellow stains are easier to remove than orange/brown stains which in turn are easier to correct than grey stains. Intrinsic stains caused by tetracycline will be difficult to remove as the dentine is dark in colour. Fluorosis and some enamel defects may change but are not predictable.

Finally, if you think that bleaching will help you obtain whiter and better-looking teeth, you must consult your dentist as he will be able to diagnose your condition and recommended you the suitable type of bleaching necessary for you.

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