The connective tissue that connects teeth to the surrounding alveolar bone.

The periodontal ligament (PDL) is a thin layer of connective tissue between the tooth root and the alveolar bone. It acts as a shock absorber during chewing, allows slight tooth movement, and contains sensory nerves that detect bite pressure. In orthodontic treatment, controlled forces remodel the PDL, allowing teeth to move through bone. The PDL is also the tissue that enables reimplantation of knocked-out teeth if performed quickly.