For things in your head that are designed to eat stuff, eating stuff seems to be kind of a big deal for teeth. They're always demanding to be brushed and flossed and rinsed and taken to the dentist and whatnot. Japan is having none of this, and scientists there have created tooth armor that can keep you from getting any more cavities.
The enamel on your teeth is mostly made of something called hydroxyapatite, because your mouth is used for both drinking and eating. Just kidding. Hydroxyapatite is a crystalline form of calcium, and while it's very hard and durable, over time it can get worn down and/or eaten by bacteria. Researchers at Kinki University in Japan have managed to create flexible apatite sheets just 0.004 millimeter thick that can be bonded directly to teeth, creating a sort of artificial enamel surface that you can't see or feel but effectively restores your tooth enamel to provide perfect protection.
Making these sheets is tricky and involves both lasers and vacuum chambers, but they're good for both treating tooth decay and for cosmetic procedures, since they can be colored that eye-searing shade of bluish white that seems to be what people are going for these days. The apatite sheets should be ready for humans for cosmetic use within three years, and for dental restoration and treatment within five.