The periodontal ligament contains different types of collagen fibers that are organized into groups based on their orientation. The principal groups are the gingival fibers that run from cementum to gingiva and the dento-alveolar fibers that run from cementum to the alveolar bone. These fiber groups include dento-gingival fibers, alveo-gingival fibers, circumferential fibers, dento-periosteal fibers, and trans-septal fibers. The periodontal ligament also contains elastic fibers, ground substance, and may contain cementicles.
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Periodontal ligament : accessory fibers
2. Organization of the periodontal
ligament
The principal collagen fibers show different
orientation in different regions of the PDL.
They belong to two groups :
The gingival group
Dento-alveolar group
4. 1. Dento-Gingival Fibers : Most numerous.
Arise from the surface of the cementum in
the cervical region and pass into the lamina
propria of free gingiva.
2. Alveo-Gingival Fibers : Arise from the
alveolar crest and pass into the lamina
propria of attached gingiva.
5. 3. Circumferential or Circular Fibers: These
fibers are continuous around the neck of the
tooth and resist gingival displacement.
4. Dento-periosteal fiber: Runs apically from
cementum over the periosteum of the outer
cortical plates of the alveolar process.
Inserts into the alveolar process, or the
vestibular muscle and floor of the mouth.
6. 5. Trans-septal Fibers : They originate in the
cervical cementum of each tooth and extend
to the similar location on the mesial or
distal surface of the adjacent tooth.
9. Small amounts of
-Type V
-Type VI
Trace amount of Type IV, Type VII
(associated with epithelial cell rests and
blood vessels)
10. Most collagen fibrils in the PDL are
arranged in definite and distinct fiber
bundles.
Each bundle resembles a spliced rope.
11. Elastic fibers
Oxytalan
Immature elastin
They have elastin and type IV collagen
Attached to cementum and rarely to the bone
Function:
Tooth support
Help in fibroblast migration in the PDL
12. Elaunin
A variant of elastic fibers.
May be found within fibers of gingival
ligament
Form a meshwork extending from
cementum to bone sheathing the collagen
fiber bundles.
13. Ground substance
It consists of two main components:
GLYCOSAMINOGLYCANS such as
Hyaluronic acid, Proteoglycans, and
GLYCOPROTEINS: such as Fibronectin
and Laminin
It also has a high water content (70%).
14. Function of ground substance:
Acts as a gel like base in which cells and
fibers are arranged in a organized pattern.
15. CEMENTICLES
The periodontal ligament may contain
calcified masses called cementicles.
May be attached to the cementum surface or
may be located free in periodontal
ligament.