Scientists at China's Zhejiang University have found a way to 'grow' tooth enamel. Usually, tooth cavities are repaired using fillings, which isn't a permanent solution. Now, scientists have created a gel that helps the enamel repair itself. They tested the gel on damaged human teeth and found that it took 48 hours for the enamel to regrow. Currently, they are testing it on mice but hope to test it on people soon.