Children’s teeth begin forming before birth. As early as 4 months, the first primary (or baby) teeth to erupt through the gums are the lower central incisors, followed closely by the upper central incisors. Although all 20 primary teeth usually appear by age 3, the pace and order of their eruption vary.
Permanent teeth begin appearing around age 6, starting with the first molars and lower central incisors. This process continues until approximately age 21.
Adults have 28 permanent teeth, or up to 32 including the third molars (or wisdom teeth).