It's the hardest substance in the human body, and it's irreplaceable. Around the world, billions are affected by tooth decay stemming from the loss of tooth enamel, but new research offers fresh hope to end this global problem.

Scientists in China have developed a liquid solution that can effectively grow back the external surface of damaged tooth enamel, using a material that mimics the natural mineralisation process of our teeth's protective outer layer.

Read more at Science Alert.