"I was eating my hamburger when I felt something hard. I almost choked. I spat it out and it was a crowned tooth complete with its root," Nathalie Dahyot told local newspaper Ouest France.
Her friend, Romuald Brut, bought the hamburgers in his local Carrefour supermarket, where he has been shopping for 15 years.
"Everyone stopped eating them immediately. We threw all the hamburgers in the bin. My 23-month old daughter had had one herself: she'd have choked if she'd swallowed the tooth," he said.
Carrefour apologised and expressed shock at the incident:
“This discovery is impossible as the meat is ground and then passed through a metal detector,” a company spokesman told Ouest France. Carrefour has opened an inquiry into the incident.
To dispel any doubt, Brut told the newspaper he would be happy to have DNA tests done on the whole family to prove the tooth did not come from any of them.