alveolar crest group, horizontal group, oblique group, apical group, and interradicular group (not present in single rooted teeth).
increase the load on a bone and osteoclasts are created which break it down in response to the load. Remove the load and osteoblasts are created which create new bony cells. Repeat the process through repetitive motion and eventually the bone density increases.
The PDL acts as messenger between the
teeth and surrounding bony sockets.
Pressure between the PDL and bone causes the bone to create
osteoclasts and breakdown the bone to restore the normal spacing between the teeth and bone.
The corresponding tension on the PDL behind the movement causes the bone to create
osteoblasts, effectively building new bone to fill in the difference and restore the normal spacing between teeth and bone.