A child’s teeth start forming before birth. As early as 4 months of age, the primary (baby) teeth push through the gums—the lower central incisors (front teeth) appear first, then the upper central incisors. The rest of the primary teeth appear by 3 years of age, but the place and order varies.
Permanent (adult) teeth start showing up at about 6 years of age. The molars (the large, flat teeth at the back of the mouth) and lower central incisors appear first. The development of permanent teeth goes on until about 21 years of age.
Adults have 28 permanent teeth—32 including the wisdom teeth.