The emergence of the primary teeth and the permanent teeth as they appear above the gum line. Tooth eruption of the primary teeth generally begins with the bottom central incisors (the front teeth) when an infant is 6 months old and is completed when the second molars come in at the age of about 24 months. The primary teeth typically erupt in a fairly regular sequence from the front of the mouth to the back. They are shed in about the same sequence, with the first teeth to erupt being the first to be shed, usually starting at about the age of 6 or 7 years. At that age, the heavier, larger permanent teeth, which have developed within the gum below the primary teeth, usually begin to erupt. By the time a child is 11-½ or 12 years old, he or she has often shed all the primary teeth and acquired most of the permanent teeth, with the exception of the second and third molars (wisdom teeth).