Tooth whitening: Do at-home bleaching systems work, and what adverse effects could they have?

Tooth whitening systems based on bleaching agents can make your teeth visibly whiter, but it is not known yet how long this lasts. Tooth bleaching kits often cause temporary tooth sensitivity and gum irritation. The long term safety of using high doses of bleach frequently is not yet known.

Many people want to have whiter teeth. Our teeth can get darker as we get older. Stains on the teeth and discolorations can be caused by some drugs, by smoking and by some foods or drink, such as tea or red wine. Discolorations can also form in very fine cracks in the teeth.

As an alternative to tooth polishing or whitening by a dentist, a range of at-home products are available. They come as gels that are applied with mouth trays, paint-on films or whitening strips that you temporarily stick on the surface of your teeth. The products are used for up to two weeks. How they are applied depends on the type of product and your own preferences. Some are applied overnight, others for half an hour twice a day.

These products almost always include one of the bleaching agents carbamide peroxide or hydrogen peroxide. Many are available for general purchase, but some can only be dispensed by dentists. There are also tooth whitening toothpastes for everyday use.

The European Commission has assessed the safety of tooth whiteners containing hydrogen peroxide, and concluded that products with up to 0.1% hydrogen peroxide are safe for short-term use. Products with more than 0.1% and up to 6% hydrogen peroxide they also recommend as safe if a dentist has approved it for the individual. If you want to be on the safe side when buying a whitening product, you can check whether these limits have been followed, as well as get some advice from your dentist.

The Commission recommends that tooth whiteners not be used by people under the age of 18 or by people who have just had, or about to have, dental treatment. The Commission concluded in 2006 that more research was needed on long-term effects of bleaching agents. The Commission recommends that people who already show signs of oral cancer not use these chemicals, and in general also recommends discussing options for preventing stains with a dentist.

Do tooth-whitening kits for use at home really work as their advertisements promise? Are there differences between the products? What are the risks? Researchers from the Cochrane Collaboration have looked into these questions. They analyzed trials that tested tooth-whitening products that use chemical bleaching agents. Products that use a different mode of action such as toothpastes that use abrasives to whiten teeth are planned to be studied in future. When research results become available we will keep you informed.

The researchers analyzed 25 trials with just about 1,400 people. Six of these trials compared tooth bleaching products with a placebo (products without an active ingredient) or with no treatment. The other 19 trials compared different products and doses with one another. However, all of the trials were sponsored by the companies that manufacture the products. In addition, most of the trials were either too small to be able to provide conclusive answers about the individual products, or they had other problems that made it hard to draw reliable conclusions.

The overall evidence suggest that teeth whitening kits that use bleaching agents can make teeth whiter, but for some products it is unclear whether they are actually able to whiten teeth. The trials did not report about users’ satisfaction with the long-term results. The teeth whiteners used in these trials were gels on mouth trays, paint-on films or whitening strips. The products often caused gum irritation and tooth sensitivity, although the problems usually went away after treatment.

Depending on the dose of bleaching agent in the products, these adverse effects were reported for between 1 and 6 out of every 10 participants (that is, from 10% to 60%). No serious adverse effects occurred in these trials, but they were all too short to be able to assess long-term risks: none of the trials lasted for more than 6 months.

Some other questions remain unanswered. For example, the people who took part in these trials all had natural and relatively healthy teeth. So we do not know anything yet about the effects of bleaching systems in people with dentures or specific dental problems such as the necks of teeth being exposed.

We also do not know whether bleaching kits will work on all types of discolorations or darker teeth (such as those which have become grayish-brown with time). Home bleaching products are not suitable for use by people who have internal tooth stains, stains caused by medications such as tetracyclines (a group of antibiotics) or by congenital factors. So before you use a bleaching agent, ask your dentist if it is suitable for you. You can find more information about what your dentist can do in our fact sheet. Another option for very severely discolored teeth is permanent cosmetic dentistry.

© IQWiG (Institute for Quality and Efficiency in Health Care)