A new, sustainably sourced toothpaste additive may soon transform how we strengthen—and even restore—weakened or lost tooth enamel. Tooth enamel doesn’t replenish itself, and retaining it isn’t easy. “Unlike bones and hair, enamel loss does not regenerate,” King’s College London prosthodontics consultant Sherif Elsharkawy said in a statement. After extracting keratin from sheep’s wool, the team added it into a composite mixture that they then applied to the surfaces of human molars. Once adhered to a tooth, the layer kept attracting phosphate and calcium ions to continue growing a new, protective coating—effectively regenerating lost enamel.