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 contain no 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.
‘Don’t believe the hype’
“When used too often in people with fillings, it can get into them and become difficult to get out,” Dr Greenwall-Cohen said.
“Charcoal particles can also get caught up in the gums and irritate them.”
He said charcoal toothpastes and powders were more abrasive than regular toothpastes, potentially posing a risk to the enamel and gums.
The charcoal contained in today’s toothpastes is usually a fine powder form of treated charcoal, the review says.
Charcoal can be made from materials including nutshells, coconut husks, bamboo and peat, and possibly wood and coal.
Prof Damien Walmsley, from the British Dental Association, said: “Charcoal-based toothpastes offer no silver bullets for anyone seeking a perfect smile, and come with real risks attached.
“So don’t believe the hype. Anyone concerned about staining or discoloured teeth that can’t be shifted by a change in diet, or improvements to their oral hygiene, should see their dentist.”