Q. I'm considering getting my teeth whitened professionally, but I've heard from a friend that having this done could increase the risk of cancer. Is there any truth in this?-J.M., via e-mail
A. Teeth-whitening has grown immensely in popularity
in recent years. An array of dentist-supervised and over-the-counter (OTC) products are now available to solve tooth discolora-tion problems and achieve that much-lauded 'Hollywood smile'. While whitening toothpastes remove surface stains only, hydrogen-peroxide-con-taining gels, strips and pastes can change the natural colour of your teeth by bleaching, although this form of teeth whitening has been met with some controversy. While there is little dispute that it works, concerns have been raised over the safety of teeth-bleaching agents and, as your friend says, whether or not they cause cancer (Compend Contin Educ Dent, 1998; 19: 783-6, 788, 790).
A number of scientific reviews have come to the conclusion that teeth-bleaching products are safe and, when used properly, pose no increased risk of cancer-not even in high-risk individuals such as smokers or drinkers (Food Chem Toxicol, 2006; 44: 301-15; Regul Toxicol Pharmacol, 2006; 44: 75-82). Although a few animal studies have shown that hydrogen peroxide can promote cancerous tumours in the cheeks of rodents and cause gastrointestinal cancer when ingested (J Can Dent Assoc, 1999; 65: 453-5), there is no evidence of such effects in humans. However, it's been suggested that peroxide can leak from the dental trays that hold the whitening agent into other parts of the mouth, which might trigger the release of cancer-causing free radicals. This is most likely to happen with OTC products, as the trays are not custom-made to fit your mouth.
Nevertheless, according to Dr Laura Tam, associate professor of dentistry at the University of Toronto, even if this were to happen, the human body is well-equipped to deal with hydrogen peroxide, eventually breaking it down into water and oxygen (J Can Dent Assoc, 1999; 65: 453-5).
Indeed, a number of studies report that the effects seen in animals are not relevant to human teeth-bleach-ing in real life (Food Chem Toxicol, 2006; 44: 301-15; Food Chem Toxicol, 2000; 38: 1021-41). However, there is some evidence that suggests otherwise.
A study presented at the 6th International Conference on Head and Neck Cancer in 2004 looked at patients with oral cancer diagnosed at Georgetown University Medical Center in Washington, DC, between 1997 and 2003. Of 19 participants, they found that three had a history of using tooth whiteners, and two of them had used peroxide-containing products (see http://ec.europa.eu/ health/ph_risk/committees/04_ sccp/docs/sccp_o_022.pdf for more details). These results don't prove cause, but they should raise a note of caution until further research is carried out.
Cancer risks aside, there are a number of other more likely side-effects with tooth-bleaching that you may wish to consider. One of the most common is tooth sensitivity, affecting up to 78 per cent of users (Crit Rev Oral Biol Med, 2003; 14: 292-304). It doesn't usually last very long, but it can be painful, and it's more likely to occur
if you opt for in-clinic techniques that use chemical- or light-activated whitening methods (Minerva Stomatol, 2009; 58: 181-5).
Gum irritation is another problem, especially with OTC tray systems that don't fit properly (Compend Contin Educ Dent, 2003; 24: 376-82). In fact, those with diseased or damaged gums should avoid any type of peroxide-containing tooth-whitening products (Br Dent J, 2006; 200: 371-6).
Far more serious is the fact that tooth-bleaching can cause changes to tooth enamel. In a study of tray and strip (sticking a peroxide-coated plastic strip across the teeth) home-bleaching systems, both led to a significant reduction in the hardness and stiffness ('elasticity') of tooth enamel (J Dent, 2009; 37: 185-90).
Yet another concern is that bleaching can interact with the dental materials already in your mouth. Carbamide peroxide-a precursor to hydrogen peroxide also used to whiten teeth-can increase the release of mercury from dental amalgam (Am J Dent, 1993; 6: 305-9).
Clearly, a number of factors need to be considered when deciding whether teeth-bleaching is right for you. If you do choose to go ahead with the procedure, make sure you do so under the supervision of an experienced dentist and only after a full oral examination has been done.
Alternatively, you could try teeth-whitening methods that don't involve bleaching, such as whitening tooth-pastes. These products use abrasives such as silica to remove surface stains and can improve the overall look of your teeth. However, the results won't be as dramatic, and silica can collect under the gums to form granulomas (small nodules of inflamed tissue) (Dermatology, 2001; 203: 177-9).
Most toothpastes, though, contain potentially harmful chemicals and additives, so you could try making your own stain-removing toothpaste. Just mix 1 cup of baking soda (a mild abrasive and antibacterial) with 1/3 cup of salt, and add 3 tsp of glycerine (sold at supermarkets and pharmacies) and water to make a thick paste. You could also add peppermint oil for flavour.
Keeping Your Teeth White
- Brush at least twice a day (morning and night)
- Avoid stain-causing beverages such as tea and coffee, or drink through a straw to avoid contact with your teeth
- Rinse your mouth with water after eating stain-causing foods such as curry and soy sauce
- Visit your dentist regularly for professional cleaning and oral examination.
Vol. 20 04 July 2009