Enamel is the hard, protective outer layer of your teeth, and once it is lost, it cannot be naturally regenerated by the body. Enamel is composed of minerals, primarily hydroxyapatite crystals, and it can be damaged or eroded by acids produced by bacteria, sugary and acidic foods, or aggressive brushing. While the body cannot regrow enamel, there are ways to strengthen and protect the existing enamel to prevent further damage.