Periodontal Ligament and Eruption
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What is the PDL?
Dense fibrous CT which occupies the periodontal space between the cementum and alveolar bone
From where is the PDL derived?
Dental follicle
What causes the periodontal space to be reduced?
Non-functioning teeth or unerupted teeth
What causes the periodontal space to increase?
When teeth are subjected to heavy occlusal stress
Is the PDL narrower in permanent or deciduous teeth?
Permanent
Name 4 functions of the PDL
• Tooth support • Attaining and maintaining functional tooth position • Maintain and repair alveolar bone and cementum • Mechanoreceptors are involved in neurological control of mastication
What are the 5 cell types found in the PDL?
• Fibroblasts • Mesenchymal cells • Epithelial cells • Defence cells • Cementoblasts / Osteoblasts
What is the predominant cell type of the PDL?
Fibroblasts
Why can epithelial cells be found in the PDL?
They are remainders of the development root sheath of Hertwig
What are 3 substances which form the ground substance of the PDL?
• GAGs • Proteoglycans • Glycoproteins
Describe the overall composition of the PDL
Collagen Type I - 80% Collagen Type III - 10% Oxytalan fibres - 10%
What are collagen fibres found in the PDL referred to as?
Sharpey’s fibres
Where do Sharpey’s fibres insert?
Cementum and periosteum of alveolar bone
What are interstitial spaces?
Spaces which exist between the bundle of Sharpey’s fibres in the PDL
What 3 things are contained in the interstitial spaces?
• Blood vessels • Nerves • Oxytalan
What can lead to the development of scurvy?
Lack of vitamin C which can cause abnormal collagen production in PDL
Where is the blood supply to the PDL derived from?
Appropriate superior and inferior alveolar arteries
Where do the arteries supplying the PDL enter?
Series of perforation arteries passing through alveolar bone
What are 2 sensory fibres associated with innervation of the PDL?
• Nociception 2. Mechanoreception
What is the main role of mechanoreceptors.
Masticatory reflexes
What is the definition of tooth eruption?
The process where a tooth moves axially from its developmental position within alveolar crypt of jaw to functional position in oral cavity