Charcoal-based toothpastes, which claim to whiten teeth, are a "marketing gimmick" which could increase the risk of tooth decay and staining, says a review in the British Dental Journal.
The charcoal products, which are increasingly popular, often may not contain fluoride to help protect the teeth. And there is no scientific evidence to back up the claims they make, the authors say. Excessive brushing with them can do more harm than good, they add.
They advise people to go to their dentist for advice on bleaching, or whitening, their teeth. And they say it is better to stick to using a regular fluoride-based toothpaste. Charcoal was first used for oral hygiene purposes in ancient Greece, as a way of removing stains from teeth and disguising unpleasant odours from diseased gums.