Dentistry researchers at Okayama University have come up with what could be the world's first movable tongue prosthesis to help oral cancer patients who have partially lost the ability to speak.

The invention, the product of a team led by Shogo Minagi, a professor of dentistry at the university, is good news for scores of oral cancer victims in Japan with speech problems.

The number of oral cancer patients in the nation has surged to 7,800 in 2015, up from around 2,100 in 1975, according to estimates by the Japan Society of Oral Oncology. The figure does not include those with damaged tongues from traffic accidents and other physical injuries.