When our child jaws develop normally (with a lot of spaces between baby teeth), an adult tooth (Fig.3a: blue) is forming immediately below the root (R) of the baby tooth (black). The crown of any given tooth forms first, followed by the root.  When the root of the adult tooth is forming (blue R in Fig.3b), the adult tooth starts to move upward (arrow) and places a lot of pressure against the root of the baby tooth, causing the latter to be gone (resorbed) partially (shorter than the root in Fig.3a).  As the root of the adult tooth grows more (Fig.3c) and the adult tooth moves up more, the root of the baby tooth is eventually gone.  The baby tooth finally finishes its destiny (falling out, black arrow).  Return to original text

Xin Wei, DDS, PhD, MS 1st edition 11/02/2011, last revision 11/02/2011