Tooth enamel is the hard, outer layer of a tooth that protects it from decay and damage. It is the hardest substance in the human body, primarily composed of minerals, mainly hydroxyapatite. Enamel acts as a barrier against acids and bacteria that can lead to cavities. Although tooth enamel is strong, it can be worn down by factors such as poor dental hygiene, acidic foods, and grinding teeth. Once enamel is lost, it cannot regenerate, making it essential to maintain good oral care practices, including regular brushing and visits to the dentist.