People generally have 28 to 32 teeth (permanent teeth). Usually people have two sets of teeth, milk teeth and permanent teeth, 20 milk teeth and 28 to 32 permanent teeth. Usually there are 20 milk teeth, 5 on the left side and 5 on the right side of the upper and lower jaw. From the midline to the sides, the names are milk mesial incisors, milk lateral incisors, milk cusps, first molar and second molar. Generally, the first milk tooth begins to erupt 6 to 8 months after birth, and all milk teeth erupt at about 2 ½ years of age. There are usually 28-32 permanent teeth, 7-8 on each side of the upper and lower jaw. From the midline to the sides, the names are mesial incisors, lateral incisors, cuspids, first premolar, second premolar, first molar, second molar, and third molar, and it is normal for some people to have no third molar. Permanent teeth usually erupt or replace milk teeth around the age of 6 and are completed around the age of 12. Patients who have an abnormal number of teeth should actively seek medical attention to identify the cause of the problem and then undergo regular treatment.