Periodontal Ligament Flashcards
What is the periodontal ligament?
Specialised dense fibrous tissue which attaches tooth to alveolar bone
Describe the PDL width.
Remarkably constant ~0.2mm
Narrower in middle region (wider at coronal and apical regions)
What is the major cell type in the PDL?
Fibroblasts
Give examples of things found in the PDL. (6)
Fibroblasts
Osteoblasts/cementoblasts
Epithelial cell rests of Malassez
Blood vessels
Nerves
Macrophages, mast cells, etc.
What are epithelial cell rests of Malassez?
Persisting epithelial remnants of Hertwig’s epithelial root sheath (closer to tooth side)
What may cause the cell rests of Malassez to become cystic lesions?
Deep inflammation
What makes up the connective tissue matrix of the PDL?
Collagen I, III, V
Proteoglycans/ground substance
Oxytalan fibres
Describe the PDL ground substance.
Amorphous, dense, hydrophilic gel throughout connective tissue
What are oxytalan fibres?
Elastic fibres specific to PDL which run parallel to the tooth root
What are the types of principal fibres found in the PDL?
Oblique
Apical
Horizontal
Crestal
Where are the horizontal collagen fibres located in the PDL?
Close to alveolar crest
Where are the crestal collagen fibres located in the PDL?
In gingiva and attached to bone
What are Sharpey’s fibres?
Regions of principal collagen fibres embedded into tooth/bone
Partially mineralised
How does the root and PDL develop (briefly)? (3)
HERS maps out root form; induces dentinogenesis
HERS breaks down and induces cementum formation
PDL derived from dental follicle mesenchymal cells
What produces the final orientation of the PDL fibres after development?
Occlusal forces
What type of joint is the PDL?
Gomphosis
What are the functions of the PDL? (4)
Tooth eruption
Tooth retention
Absorption of occlusal forces
Neuromuscular
How does the PDL allow absorption of forces?
Hydroelasticity of PDL matrix (proteoglycans) allows recoil
Forces are transmitted to the jaw bone by fibres and dissipate (bone is slightly elastic)
What are the neuromuscular functions of the PDL?
Pain fibres and mechanoreceptors for proprioception allow masticatory control and salivation
Able to determine size and hardness of objects as PDL moves with tooth
How does the PDL contribute in maintaining occlusion?
Remodelling ensures occlusion after wear
What can change the degree of mobility of teeth? (3)
Occlusal load
Damage to PDL
Thickness of overlying bone
How does the occlusal load affect the PDL daily?
Regulates maintenance of PDL width
Preserves structure of PDL
What is periodontal disease?
Chronic inflammatory condition resulting in destruction of tooth attachment, loose teeth and ultimately tooth loss
How do orthodontics affect the PDL?
Compression of PDL = bone resorption
Pulling of PDL = bone deposition
PDL keeps up with bone remodelling
