People should not just buy new toothbrushes when they go for emergency dentistry or other treatments.
This is the advice of a report carried out by the Sun, which found that old, dirty brushes can harbour bugs such as flu and herpes simplex.
Stephen Dunne, consultant at St Thomas's Dental Institute, told the newspaper that these can live for up to a week and can reinfect the user, or affect other members of the same family if the bristles touch other brushes.
A British Dental Association spokesperson also warned Britons never to share toothbrushes, as this could pass on anything from hepatitis B to cold sores.
It was recommended that people buy new toothbrushes once a month, instead of every six months to a year when they visit the dentist.
Earlier this month, the British Dental Health Foundation recommended Oral-B's oscillating-rotating power toothbrush when it comes to fighting emergency dentistry.