Periodontal Ligament Flashcards
What are the 4 connective tissues of the periodontium
- Lamina propria (non-calcified)
- Periodontal ligament (non-calcified)
- Cementum (calcified)
- Alveolar bone (calcified)
What do the connective tissue have in common
All share the same major matrix element: Type I Collagen
What forms the epithelial collar, and what does it surround
- The junctional epithelium forms the epithelial collar
- Surrounds the cervical part of the crown, extending from the base of the gingival crevice to the CEJ
What’s unusual about the junctional epithelium
Has a basal lamina on both surfaces
What’s the importance of the upper surface’s ‘adhesive bond’ of the junctional epithelium
- Bond between the gingiva and enamel
- On its own, it’s not enough to oppose mastication, so has fibres and tissue turgor within the gingival cuff
What is known as the epithelial attachment
The attachment of the junctional epithelium to enamel
What is known as the connective tissue attachment
The attachment between the lamina propria to the tooth
What is the combination of the epithelial attachment and the connective tissue attachment known as
The biologic width
Describe the structure and explain the significance of the lamina propria
- Has insertions into tooth & the alveolar crest
- Fibres run in different directional groups
- Act together with tissue fluid to support free gingiva and hold attached gingiva against the tooth
What type of collagen fibres are mainly prevalent in the lamina propria?
What does this collagen do?
- Type I Collagen
- Support free gingiva
- Binding of attached gingiva to alveolar bone + tooth so theres a linkage of teeth
What properties distinguish the lamina propria from the connective tissue of the periodontal ligament
- Extracellular matrix having less ground substance
- Less Type III Collagen
What are the functions of the periodontal ligament
- Resistance to displacing forces
- Protecting dental tissues from damage caused by excessive occlusal loads
- Cells form, maintain and repair alveolar bone and cementum
- Mechanoreceptors involved in neurological control of mastication
How is the periodontal ligament organised
Organised connective tissue :
- Bundles of collagen fibres insert into cementum and the alveolar bone
If fibres in the periodontal space follow the orientation of the collagen fibre bundles, how do they run?
They will run more vertically towards the periphery of the periodontal space
How does the average width of the periodontal space change over time
It is maintained over time, although it slightly changes with age
What does the PDL consist of
Collagen fibres embedded in a non-collagenous extracellular matrix
Describe the non-fibrous matrix in the PDL
- Ground substance made of fibroblasts
- Consists of Glycosaminoglycans, proteoglycans and glycoproteins
- Responsible for ion water binding and exchange
- Responsiblefor control of collagen synthesis
- Responsible for fibre orientation
Describe fibroblasts in the PDL
- Responsible for synthesis + degradation of collagen & producing all components of the ground substance
- Closely associated with collagen fibrils which form collagen bundles
- Responsible for high rate of protein turnover
- Degrade collagen intracellularly - enables cells to control the degradative process precisely
Describe the hard tissue forming and resorbing cells
- Cementoblasts - form cementum on root surface
- Osteoblasts - bone-forming cells lining the tooth socket + only seen where there’s active bone formation
- Osteoclasts - found where bone is being resorbed
- Odontoclasts - Found on surface of cementum where resorption is occurring
Describe epithelial cells in the PDL
- They’re Hertwig’s epithelial root sheath (HERS), breaking up root dentine formation
- Sections through the PDL show a network of interconnecting strands parallel to the long axis of the root
- Epithelial rests of Malassez are capable of producing matrix molecules, proteins, growth factors and neuropeptides
- Represent a stem cell compartment
Describe collagen fibres in the PDL
- Main types of collagen are types III and I
- PDL is rich in Collagen type III
- Collagen is in bundles, which is then in groups
- Groups run between the root and alveolar bone - known as principal fibres
- Principal fibres are embedded in cementum or bone, and the attachments are more numerous but smaller in cementum than in the alveolar bone
Describe oxytalan fibres in the PDL
- Attached into the cementum in the outer part of the ligament
- Fibres run obliquely down and are more longitudinally orientated
Describe any other fibres in the PDL
- Elaunin - found around blood vessels for the vascular system
- Reticulin (Collagen Type III) - Aid tissue support
Where is the blood supply in the PDL derived from
Superior or inferior alveolar arteries
