Tooth whitening is a popular cosmetic procedure but take care choosing the method, writes Susan Edmunds.

Ten years ago, summer beauty routines might have stretched as far as a fake tan and a new hairstyle. But in increasing numbers, New Zealanders are turning their attention to their teeth and applying bleach and whitening treatments to get sparkling summer smiles.

There are three main methods of tooth whitening: Dentist-administered laser treatment, done in the dentist's chair which can cost about $1000, tray gel systems designed and fitted by a dentist, costing about $500, and over-the counter treatments, starting from about $20. Beauty therapists in greater numbers are also offering tooth whitening procedures.

But whitening can cause problems, especially when it is not being administered by professionals. Dentists have reported adverse reactions ranging from teeth with holes and teeth being killed by home peroxide treatments, through to allergic reactions in mouth tissue.

Dr Adrian Tan of Dental Associates says his main concern with at-home treatments is anecdotal evidence that some of the cheaper products do not contain the right biological preservatives, and could cause allergic reactions. "I can't even buy my products at wholesale for the same price these are sold at retail." He said it was possible over-the-counter products were not held to the same standard as those used by dentists.


Regulations were approved this year governing the level of hydrogen peroxide that is allowed to be in at-home and beauty-therapist-administered tooth whitening treatments. Hydrogen peroxide can irritate gums and cause tooth sensitivity. All whiteners containing it now have to carry a warning telling consumers to stop using them if they experienced discomfort, and an advisory that they should not be used on anyone under 16.

Restrictions are to be enforced on products containing between 7 and 12 per cent hydrogen peroxide. They will be sold by only by a dentist or registered oral health practitioner. Products with more than 12 per cent hydrogen peroxide will be more tightly controlled - they will have to be administered under the supervision of a dentist.

Tan says: "My understanding is that beauty therapists and non-dentally-trained people are allowed to apply bleaching products with less than 7 per cent hydrogen peroxide. That's very different from a dentist. We'll use hydrogen peroxide as concentrated as 45 per cent."

He says the main difference is the speed of colour change. "Lower concentrations replenished constantly would achieve the same level of lightness but would require nine to 10 hours. There's more of the 'wow' effect if you go to the dentist."

Tan says people thinking about getting their teeth whitened should find out what product is being used. "If it sounds too good to be true, it probably is. If someone is offering the same results, as good as all the other stuff, for $45, well maybe, but I'd like to see the evidence."

Dr Graham Symes, of the New Zealand Dental Association, says: "They should see their dentist for a complete examination and X-rays to make sure there is no disease process that may be made worse from the bleaching process. They should have their teeth professionally cleaned as often this will improve the whiteness by itself. They need to be made aware of the possible complications of the bleaching process applicable to their individual situation and there needs to be a discussion as to how long the effect will last. In my opinion, the bleaching effect rarely lasts for more than a year."

The main problem with over-the-counter bleaching products is that teeth are not examined beforehand. Symes says the kind of teeth that suit whitening are those that do not have any decay, enamel defects or congenital reasons for discolouration. There can be underlying issues causing discolouration, or problems with teeth, such as exposed roots, that can make whitening difficult or not advisable.

Whether to go for tray whitening or laser whitening depends on the individual's patience to get an improvement in colour.


Tan says: "You get the same results with laser whitening and trays, the only difference is the duration. If you don't mind wearing a tray every night for eight weeks, it's the same result."

He says the best results are often a laser whitening session followed up with a tray.

Consumer magazine did a study on teeth whitening recently and found that though whitening toothpastes offered no better result than brushing for longer with ordinary toothpaste, dentists, with their higher concentrations of bleach, could make a significant difference to the appearance of teeth.

Whitening was found to be most effective when the discolouration was light or evenly distributed. The most common side effect is sensitivity, mainly caused by dehydration.