Most permanent teeth are from eight to ten years old before they are completely developed. During part of this time they are forming in the jawbone itself. Usually all the primary or baby teeth have begun to form while the child is still in the mother's womb. As early as the second or third month of pregnancy, these primary tooth buds begin developing. Six-year molars, which are permanent teeth, start to form between the seventh intrauterine month and birth. From this time until about age three the crown grows to its adult size and is calcified.
Eruption of the tooth into the mouth usually takes place between the ages of six and seven, but the root of the tooth is not completely formed until the age of nine or ten.