People with missing teeth may be able to grow new ones, say Japanese dentists testing a pioneering drug they hope will offer an alternative to dentures and implants.

Unlike reptiles and fish, which usually replace their fangs on a regular basis, it is widely accepted that humans and most other mammals only grow two sets of teeth.

But hidden underneath our gums are the dormant buds of a third generation, according to Katsu Takahashi, head of oral surgery at the Medical Research Institute Kitano Hospital in Osaka.