2. The periodontal ligament is the connective tissue
that surrounds the root & connects it to the bone
3. FIBERS
Most important -- principal fibers – collagenous
Wavy course
Terminal portions of the principal fibers that
insert into cementum and bone are termed
“sharpey’s fibers”
5. Collagen is a protein composed of different
aminoacids such as : -- glycine
-- proline
-- hydroxylysine
-- hydroxyproline
Collagen is synthesized by :
-- fibroblasts
-- chondroblasts
-- osteoblasts
-- odontoblasts
7. TRANSEPTAL GROUP
Extend interproximally over the alveolar bone crest
and are embedded in the cementum of adjacent teeth
Reconstructed even after destruction of AL.bone
8. ALVEOLAR CREST GROUP
Extend obliquely from the cementum just
beneath the junctional epithelium to the Al.crest
Prevent the extrusion of the tooth and resist
lateral tooth
movements
9. HORIZANTAL GROUP
Extend at right angles to the long axis of the
tooth from the cementum to the alveolar bone
10. OBLIQUE GROUP
Largest group
Extend from the cementum in a coronal
direction obliquely to the bone
They bear vertical masticatory stresses and
transform them into tension on the alveolar bone
15. EPITHELIAL RESTS OF MALLASSEZ
Considered - remnants of Hertwig’s root sheath
Proliferate when stimulated and participate in the
formation of periapical cysts and lateral root cysts
18. CEMENTICLES
Present in the periodontal ligament which are
adherent to or detached from the root surfaces
Cementicles develop from calcified epithelial
rests; around small spicules of cementum or
alveolar bone traumatically displaced into PDL
20. PHYSICAL
Provision of a soft tissue “casing” to protect the vessels
and nerves from injury by mechanical forces
Transmission of occlusal forces to the bone
Attachment of the teeth to the bone
Maintenance of the gingival tissues in their
proper relationship to the teeth
Resistance to impact of occlusal forces
[shock absorption]
21. RESISTANCE TO IMPACT OF OCCLUSSAL FORCES
[SHOCK ABSORPTION]
TWO THEORIES
TENSIONAL THEORY
VISCO-ELASTIC SYSTEM THEORY
22. THE TENSIONAL THEORY
When a force is applied to the crown the
principal fibers first unfold and straighten and
then transmit forces to the alveolar bone
causing an elastic deformation of bony socket
Finally when the alveolar bone has reached
its limit the load is transmitted to basal bone
23. THE VISCOELASTIC THEORY
Considers the displacement of the tooth to
be largely controlled by fluid movements
The extracellular fluid passes from the PDL
into the marrow spaces of bone through
foramina in the cribriform plate
24. These perforations of the cribriform plate link the
PDL with the cancellous portion of the alveolar bone
After depletion of tissue fluids -- fiber bundles tighten
This leads to blood vessel stenosis
Arterial back pressure causes ballooning of the
vessels, and passage of blood ultra filtrates into
the tissues thereby replenishing the tissue fluids
25. FORMATIVE AND REMODELLING FUNCTION
Cells of the periodontal ligament participate in the
formation and resorption of the cementum and bone
27. SENSORY
The periodontal ligament is abundantly supplied
with sensory nerve fibers capable of transmitting
-- tactile
-- pressure
-- pain sensations by trigeminal pathways
