MORPHOLOGY OF PERIODONTIUM
Periodontium is a complex of structures that helps to support the tooth. It consist of four principal components:
- Gingiva
- Periodontal ligament
- Cementum
- Alveolar Bone
These tissues form a specialized fibrous joint and are thought to be of ectomesenchymal origin
PRINCIPLES FIBRES OF PDL
- Fibre bundles that exit the cementum and alveolar bone from the periodontal ligament are called the principal fibres.
- Depending on the location, can be classed as Dentoalveolar fibres or Gingival Fibres
- Periodontal fibres of periodontal ligament are primarily composed of Bundles of Type I Collagen Fibrils
Classified into several groups based on their anatomic locations
- (Dental-)Alveolar Fibre Group
- Alveolar Crest Fibres
- Near the cervical region, extend obliquely from the cementum just beneath the junctional epithelium to the alveolar crest
- Prevent tooth’s extrusion and resist to lateral movements
- Horizontal Fibre Group
- Near the middle part of root, attach to cementum apical to alveolar crest
- Attach to cementum and connect root of tooth to alveolar bone
- Oblique Fibre Group
- Immediately above the apical group. Most numerous fibres in the periodontal ligament, running from cementum in an oblique direction to insert into bone coronally
- Apical Fibre Group
- Near apical area of root, fibres prevent the extrusion of tooth and resist lateral tooth movements
- Radiating from cementum around root’s apex into the bone, forming the base of the socket
- Interradicular Group
- Are only found between the roots of multi-rooted teeth, such as molars. Also attach from the cementum and insert to the nearby alveolar bone
Further classified into two groups, gingival and dentoalveolar group
- Gingival Group
- Cemento-Gingival Group
- Attached to the cementum consists of two types:
- Free Gingival Fibres are fixed at one end to the cement, and the other ends are freely in the neck cementum (cervical region) -> free gingiva (attached to, freely)
- Attached Gingival Fibres are attached to the cementum in the neck of the tooth and ending in the attached gingiva cementum (cervical region) -> attached gingiva
- Alveolar Gingival Fibres
- Attached to alveolar ridge and end freely in the gingiva
- Dento-periosteal fibres§
- Emerge from cervical cement and end in alveolar ridge periosteal -> membrane of bone
- Circular Gingival Fibres surround tooth cervically
- Long fibres that circulate the cervix
- Run along the neck of the tooth and encircle it, found at cervical area
- Transgingival Fibres proximal
- Emerge from proximal root surface, pass to adjacent teeth and merge with other vestibular and orally arranged octoid fibres
- Semicircular Fibres