The replacement of a child’s large teeth, also known as molar teeth, generally begins around the age of 9 and ends around the age of 11, but the first permanent molars begin to come in at the age of 6. In children, the first permanent molar, which is similar in shape to the second molar, grows directly behind the last milk tooth from the age of 6. Replacement of the molar teeth starts at around 9 years old, and the first and second molar teeth are replaced by permanent teeth as they grow older, and the replacement of the molar teeth is completed by the age of about 11 years old. However, the specific replacement time will be affected by genetics and nutritional status, and the time will be advanced or delayed. The specific replacement time should be estimated according to the order of teeth replacement in the mouth, and it can be judged after checking the oral condition in the dental hospital.