Children generally begin teething at 6 months of age, with a more stable row of milk teeth around 6 years of age. At around 6 years of age, the lower front teeth begin to be replaced, usually the front incisors are replaced first followed by the lateral incisors. The permanent teeth erupt on the lingual side of the milk teeth, and after the replacement of the lower 4 incisors, the upper incisors begin to be replaced, usually between 6 and 8 years of age, and then the lateral group of teeth begins to be replaced. The lateral group refers to the cuspids, first molars, and second molars, and the replacement of 12 teeth is completed around 9-12 weeks of age. 12 teeth are symmetrical teeth on the top and bottom, and are usually replaced at the same time. The second molar appears behind the sixth tooth around the age of 12 weeks, and the 28 permanent teeth are basically complete. 16-25 years old onwards, due to individual differences, some people have 2 wisdom teeth and some people have 4, so the permanent teeth are about 28-32.