The first permanent molars (which are not preceded by primary teeth) begin erupting around the age of 6. Extra care should be given to this first set of molars; they have a significant impact on the structure and position of future erupting teeth and, consequently, the shape of your child's lower face in later years.
Throughout your child's formative years (up and through the age of 21), the bones and muscles the face are constantly growing, shifting and changing. Most important (and visible to no one because it happens so gradually) is the fact that a child's jaw expands over a period of time, making way for an increase of 12 additional teeth. By about age 14, your child should have a full set of 28 permanent teeth, plus four additional teeth, called wisdom teeth, that grow behind the permanent teeth in late adolescence.