The periodontal ligament connects teeth to the alveolar bone through connective tissue fibers. It serves several important functions: 1. It supports teeth by transmitting occlusal forces to the underlying bone through its principal fibers, which act like a suspension bridge to absorb forces. This allows the ligament to readily absorb axial forces while resisting rotational and lateral forces less easily. 2. It senses tactile, pressure, and pain sensations through trigeminal pathways. 3. It supplies nutrients to cementum, bone, and gingiva through blood vessels and lymphatics. 4. It has regenerative capacity to form new cementum, bone, and fibroblasts during tooth movement and injury

1. Presented by –
Sanket Agrawal (02)

2. Periodontal ligament
Definition
The periodontal ligament is a connective tissue that
sourrounds the root and connect it to the bone. It is
continuos with the connective tissue of gingiva and
communicates with the marrow spaces through vascular
channels in the bone.
~ Carranza and
Bernard

3. Periodontal ligament serves the following functions.
1) Supportive Functions
~ Establishing strong attachment of teeth to the bone.
~ Maintaining conventional relationship of gingival tissues to the
teeth.
~ Protecting blood vessels and nerves from trauma induced by
mechanical forces.
~ Transmitting occlusal forces to the underlying bone: Th e
principal periodontal ligament fibers are arranged in a similar
fashion to a suspension bridge or hammock.

4. On loading axial forces, the wavy principle oblique fibers of
periodontal ligament spread out in their full length to resist the
major part of the forces and tooth gets depressed in the socket.
Hence, periodontal ligament can readily absorb axial forces
induced on it. However, rotational and lateral forces are absorbed
less easily. On the tension side, periodontal fi bers extend and
bone deposits while on pressure side, fibers get compressed and
bone resorbs.
~ Resisting impact of occlusal forces and thus acts as a shock
absorber. There are three dif ferent theories to explain the
mechanism of tooth support:

5. A) Tensional Theory
This theory assumes that the principal fi bers of periodontal
ligament play major role in tooth support and transmission of
forces to the bone

6. B) Viscoelastic System Theory
According to this theory, the displacement of the tooth is largely
controlled by fl uid movement and fi bers play a secondary role

8. C) Thixotropic Theory
According to this theory, periodontal ligament has the
rheological behavior of a thixotropic gel (i.e. the property of
becoming fl uid when shaken/stirred and then becoming
semisolid again).
2) Sensory Functions
Periodontal ligament is capable of transmitting tactile,
pressure and pain sensations by trigeminal pathways.

9. 3) Nutritive Functions
It supplies nutrients to cementum, bone and gingiva through
blood vessels and lymphatics
4) Formative Functions
Th e tissues have the regenerative capacity in providing the cell
lineage namely osteoblast, cementoblast and fi broblast. Th us, it
helps in the formation and resorption of cementum and bone
during physiologic tooth movement and repair of injuries.

10. 5) Homeostasis
With the presence of both formative and resorptive activity the
periodontal ligament provides a homeostasis in the tissue
environment.