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BDS 2: Oral Ecosystems > OE L18 Periodontal Ligament > Flashcards

OE L18 Periodontal Ligament Flashcards

1
Q

Where is the PDL?

A

Between the alveolar bone (lamina dura, bundle bone) and cementum.

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2
Q

What are the functions of PDL cells?

A

Cells of the PDL are involved in bone repair and regeneration, and inflammation and the host immune reponse.

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3
Q

How thick is the PDL, does this change with age?

A

PDL thickness: 0.13mm-0.38mm

Thickness decreases with age, 11-16 = 0.21mm, 51-67 = 0.15mm

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4
Q

What is the function of the PDL?

A

Supportive tissue of the tooth against the strong forces of mastication.

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5
Q

What are Sharpey’s fibres?

A

Terminal portions of principal fibres that insert into the cementum and bone.

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6
Q

What are the 3 groups of PDL fibres?

A
  • Principal fibres
  • Gingival ligament fibres
  • Secondary fibres
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7
Q

Describe principal fibres and the 6 types.

A

Principle fibres are made of collagen.

  1. Transseptal fibre: link to neighbouring teeth
  2. Alveolar crest fibre: link acellular cementum to alveolar bone crest
  3. Horizontal fibre: run horizontally
  4. Oblique fibre: run obliqually
  5. Apical fibre: link cementum near root apices to bone
  6. Interradicular fibre: forms between roots to bone (only for multi-rooted teeth)
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8
Q

When do the horizontal and oblique fibres develop?

A
  • Initial oblique fibres form with initial root formation
  • Horizonral fibres form with root extension
  • Oblique fibres form with eruption
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9
Q

Describe gingival ligament fibres.

A

Fibre groups within the ginigval tissue adjacent to teeth. Firmly attaches gingiva to teeth.

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10
Q

What are the 4 ginigval ligament fibre groups?

A
  1. Circular fibre group
  2. Dentogingival fibre group: fibres extend from cementum to free and attached gingiva
  3. Dentoperiosteal fibre group: connects cementum to periostium and alveolar bone surface
  4. Alveologinigval fibre group: connects alveolar bone to gingival lamina propria
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11
Q

Describe secondary fibres and their function.

A

Fibres which support the cells and blood and nerve supply.

  • Randomly orientated
  • Fibres between nerves and blood vessels
  • Do not attach to cementum or bone
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12
Q

What is the PDL made of?

A
  • Collagen fibres
  • Oxytalan
  • Elastin
  • Elaunin
  • Fibronectin
  • Tenascin
  • Laminin
  • Osteopontin and osteonectin
  • Proteoglycans and GAGs
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13
Q

Describe the collagen component of the PDL.

A
  • 50% type I, 20% type III
  • Thick collagen fibre bundles run between cementum and alveolar bone
  • Gly-X-Y repeat

Also contains small amounts of collagen type V, VI, XII, and XIV

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14
Q

What is the function of elastin, oxytalan and elaunin in the PDL?

A

Act as tissue resilience fibres and support the blood and nerve supply.

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15
Q

What is the function of proteins such as fibronectin, osteonectin, osteopontin and laminin in the PDL?

A

These are fibre adhering proteins.

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16
Q

What is the funtion of proteoglycans (e.g. decorin, biglycan and versican) and glycosaminoglycans in the PDL?

A

Important for tissue hydration and space filling.

17
Q

What does PDL turnover involve?

A

PDL turnover involves changes in ECM structures wihout PDL tissue changes.
There are constant extracellular matrix changes against occlusal forces.

18
Q

What is the ECM turnover rate of the PDL?

A

1 day

19
Q

Why is the PDL ECM turnover rate so high?

A

Because the PDL is placed under a lot of stress from occlusal surfaces, and due to the speed of fibre degradation in the PDL- it is prone to rapid inflammatory destruction.

20
Q

What is PDL turnover controlled by?

A
  • Cellular activity
  • Enzyme activity (MMPs and lysosomes)
  • Growth factors and cytokines (promote matrix synthesis)
21
Q

MMPs degrade ECM components but their expression is very tightly controlled, explain these levels of control.

A
  • Controlled at gene trancription level and at translation level
  • Affected by protein inhibitors (TIMPs)
  • Secreted in a pro-enzyme form and require activation
22
Q

What are the 5 functions of the PDL?

A
  • PDL remodelling required for tooth eruption
  • Secure attchment of tooth root to bone
  • Resilience to be able to contract/compress with forces applied to tooth
  • Maintenance of PDL space for blood/nerve supply (secondary fibre group)
  • Contains cells for tissue repair e.g. cementum and bone repair
23
Q

Name 6 cell types found in the PDL.

A
  • Fibroblasts
  • Cementoblasts
  • Epithelial cells
  • Endothelial cells
  • Immune cells
  • Smooth muscle stem cells
24
Q

Describe the role of fibroblasts in the PDL.

A
  • Most common cell type
  • Syntheise and secrete collagen for ECM turnover and remodelling
  • High ER content
  • Can differentiate into cementoblasts
  • Increase hydrostatic pressure to support tooth eruption
25
Q

Describe the role of cementoblasts in the PDL.

A
  • Found on cementum surface next to PDL
  • Secrete organic matrix (mostly collagen)
  • Large glyocgen granule content
26
Q

Describe the role of epithelial cells in the PDL.

A
  • Cells in the epithelial rests of Malassez
  • Can transdifferentiate into cementoblasts to secrete enamel-like proteins onto root surface
  • Can proliferate in response to inflammation- forms cysts
27
Q

Describe the role of endothelial cells in the PDL.

A
  • Found in microvascular bed
  • Line the inside of BVs
  • Provide hydrostatic pressure for tooth eruption
28
Q

Describe the immune cells in the PDL.

A
  • Include macrophages, mast cells, eosinophils, T/B cells

- Important role in inflammatory repsons in periodontal disease

29
Q

Is the PDL vascularised?

A

Yes, the PDL is a highly vascularised connective tissue.

30
Q

Describe the vascular supply of the PDL.

A

Blood supply from the inferior and superior alveolar arteries.

  • Greater blood supply for posterior teeth compared to anterior teeth
  • Greater blood supply for mandibular teeth compared to maxillary teeth
31
Q

Describe the nerve supply of the PDL.

A

Nerve fibres run throughout the PDL and gingiva. Fibres can also perforate into alveolar bone.

32
Q

What are the 4 types of nerve fibre terminations?

A
  • Free nerve ending
  • Ruffini’s corpuscles
  • Coiled ending
  • Spindle like ending
33
Q

Describe the free nerve endings.

A
  • Unmyelinated nerve fibres
  • Branched appearance
  • Exists along length of the root and extends into cementoblast layer
  • Pain receptor and mechanoreceptor
34
Q

Describe Ruffini’s corpuscles.

A
  • Myelinated nerve fibres
  • Dendritic-like ending
  • Act as mechanoreceptor
35
Q

Describe coiled nerve endings.

A
  • Found in mid-region of PDL

- Unknown function

36
Q

Describe spindle like nerve endings.

A
  • Found near root apices

- Present in low numbers

BDS 2: Oral Ecosystems (42 decks)

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