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Harmed to the teeth
Placed by : Looking for Dental 10-07-2007
IT'S enough to wipe the smile off Catherine Zeta-Jones's face. An Australian dental expert says chemicals in some teeth whiteners are no laughing matter.
Britain's Trading Standards Institute has ordered that most home teeth-whitening kits available in Britain be withdrawn from sale because they contain illegally high levels of hydrogen peroxide.
Last month, manufacturers and suppliers of whitening kits which do not meet the European Union's legal limit of hydrogen peroxide have been advised to withdraw them for sale because of the danger the products present to teeth and gums.
But the concentration level of hydrogen peroxide prescribed by the European Union of 0.1 per cent is commonly breached by mouthwashes, whitening toothpastes and whitening kits freely available on supermarket and pharmacy shelves in Australia.
While dentists in Britain technically face prosecution for using bleaching products above the legal limit, the Australian expert on the issue, Professor Laurie Walsh, professor of dental science at University of Queensland's school of dentistry, says the EU recommended levels are ludicrously low.
"The EU's position is ridiculous," Walsh says. "We have more than that amount of peroxide in toothpaste in Australia and in Canada and the US."
British dentists – like their counterparts in Australia – often use concentrated levels of hydrogen peroxide (30 to 35 per cent) in the so-called "power bleaching" systems.
Kits given by dentists to their patients for at-home treatment use about 6 per cent concentration.
Over-the-counter teeth-whitening gels such as Colgate Simply White and Colgate Simply White Advanced whitening gel in Australia typically contain either hydrogen peroxide (6 per cent) or carbamide peroxide.
Carbamide peroxide is the most common ingredient in whitening systems. When present at a concentration of 10 per cent, it releases 3.5 per cent hydrogen peroxide.
In a major review on the safety of teeth-whitening systems published in the Australian Dental Journal, Walsh points out that hydrogen peroxide is a highly reactive substance which can damage oral soft tissues and hard tissues when present in high concentrations, if precautions are not taken to contain the material on the teeth with isolation systems.
In lower concentrations, such as the 6 per cent strength of some home teeth-whitening systems, care must be taken that the product is not overused because of the risk of breaking down the protein present in tooth enamel, leading to the formation of opaque white areas on the teeth.
Walsh says problems can arise when people have unrealistic expectations of teeth-whitening systems.
Overuse of in-tray bleaching systems provided by dentists using a concentration of 5 per cent hydrogen peroxide or 10 per cent carbamide peroxide can lead to problems.
"A problem only occurs with the overuse of a product," he says.
"Some people want teeth the colour of an enamel fridge door. Instead of inserting the trays for a number of hours a day for 14 days, they think 'what if I keep it in all night for three weeks?'
"In cases like this, there is a small chance they can over bleach teeth which can give teeth a patchy appearance.
"Once the stained molecules have been broken down, the proteins are left and these degrade with excessive exposure to peroxide."
When this happens, the enamel proteins are replaced by water, leaving an opaque appearance, rather than the usual translucency of enamel.
"That's why dentists like in-office bleaching because they can control it," Walsh says.
"At a concentration of 35 per cent, hydrogen peroxide can burn skin. That's why we train practitioners in how to use it safely."
He says finding the cause of tooth discolouration is one of the most important considerations before any at-home treatments are used as over-the-counter products may not be effective against some discolouration.
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