Sixth age teeth are not replaced for life. Sixth age teeth are the first permanent molars, and the first permanent molars are used for life and will not be replaced. Human beings have only two tooth rows, i.e., the milk teeth row and the permanent teeth row, and after the permanent teeth have erupted, they will not be replaced. Therefore, the health of permanent teeth, especially the first permanent molar, needs to be carefully maintained. The presence of the first permanent molar is crucial as it erupts during the tooth replacement period, has a relatively stable position on the dental arch, and bears the greatest occlusal force. After the first permanent molar is missing, no new teeth will erupt, and the missing teeth should be repaired in time to perform the function in place of the first permanent molar. If the first permanent molar is diseased, it is recommended to go to the hospital in time.