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How Does Peroxide Whiten Teeth?

Although teeth whitening and bleaching has increased in popularity recently, records indicate that these procedures were performed in ancient Egypt and Rome. Thanks to chemistry, the techniques have evolved just a little bit.

Ancient Romans, for example, used urine and goat milk to whiten their teeth. This concoction is not as far-fetched as it might first appear. Urine, contains ammonia which is a cleaning agent found in many household products. But today there’s no need to rinse the mouth with urine, which incidentally is usually sterile. Chemistry has given us more effective products.

The American Dental Association (ADA) monitors the use of these various tooth-whitening products. Despite the diversity, there are two basic mechanisms of action to whiten teeth. The non-bleaching products, such as whitening toothpastes, contain chemical agents, which simply remove surface stains and debris in order to restore the tooth’s surface colour. By contrast, the peroxide-containing bleaching products work by actually changing the colour of the tooth.

The majority of bleaching products contain carbamide peroxide, which breaks down into hydrogen peroxide and urea. The active bleaching agent is hydrogen peroxide, H2O2. Because this compound is a weak acid with strong oxidizing properties, it steals the electrons that hold the atoms together, which in turn cause the staining molecules to fall apart.

As with any intervention there is always the possibility of side effects. Tooth sensitivity has been reported to occur during the early stages of the bleaching treatment. During the later stages, tissue irritation may develop causing minor discomfort. Both of these side effects will subside once the bleaching treatment ceases. Unfortunately, there have been some cases in which irreversible tooth damage has occurred, usually through improper application. The amount of time that a bleaching agent is left on the teeth is critical and can best be judged by a dentist. Whitening strips are safe enough, but not very effective. And if you want really pearly whites, a dentist will be happy to discuss veneers and caps.


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