Scientists want to fix tooth decay with stem cells

The human body is a marvellous thing. But like anything built by evolution, it has plenty of flaws. Consider teeth. Whereas sharks grow new teeth throughout their lives, adult humans get one set, which must last 60 years or more.That is tricky. A combination of poverty, sugar-rich and poor hygiene means 2.5bn people around the world suffer from tooth decay, in which acid produced by mouth-dwelling bacteria eats away at the hard enamel that coats the outside of a tooth. That can open the door to painful infections, which cause further damage. Once decay has set in, all a dentist can do is fill the gap with an artificial plug—a filling.