The hardness of teeth is comparable to crystal, and the hardness of tooth enamel reaches 7 Mohs hardness. 1. The outermost layer of tooth enamel is the hardest tissue in the human body, with the Mohs hardness scale can reach 5 to 7 degrees, equivalent to crystal, topaz hardness. 2. The main component of enamel is hydroxyapatite crystals, the crystals cross and fall to form a hierarchical structure, tightly arranged, making the enamel hard. However, tooth enamel lacks biological organic matter, so it cannot be regenerated and should be protected. 3. Attention should be paid to oral hygiene, timely cleaning of food debris in the mouth, to prevent caries and other damage to the enamel. If the outer enamel of the teeth is damaged, you should go to the regular hospital stomatology department in time to determine the cause, according to the severity of the disease and the original disease to follow the doctor’s advice to choose the appropriate treatment program.