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1 - IOE - Dental Anatomy > Periodontal Ligament > Flashcards

Periodontal Ligament Flashcards

1
Q

What are the 4 connective tissues of the periodontium

A
  • Lamina propria (non-calcified)
  • Periodontal ligament (non-calcified)
  • Cementum (calcified)
  • Alveolar bone (calcified)
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2
Q

What do the connective tissue have in common

A

All share the same major matrix element: Type I Collagen

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3
Q

What forms the epithelial collar, and what does it surround

A
  • 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
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4
Q

What’s unusual about the junctional epithelium

A

Has a basal lamina on both surfaces

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5
Q

What’s the importance of the upper surface’s ‘adhesive bond’ of the junctional epithelium

A
  • 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
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6
Q

What is known as the epithelial attachment

A

The attachment of the junctional epithelium to enamel

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7
Q

What is known as the connective tissue attachment

A

The attachment between the lamina propria to the tooth

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8
Q

What is the combination of the epithelial attachment and the connective tissue attachment known as

A

The biologic width

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9
Q

Describe the structure and explain the significance of the lamina propria

A
  • 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
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10
Q

What type of collagen fibres are mainly prevalent in the lamina propria?
What does this collagen do?

A
  • Type I Collagen
  • Support free gingiva
  • Binding of attached gingiva to alveolar bone + tooth so theres a linkage of teeth
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11
Q

What properties distinguish the lamina propria from the connective tissue of the periodontal ligament

A
  • Extracellular matrix having less ground substance
  • Less Type III Collagen
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12
Q

What are the functions of the periodontal ligament

A
  • 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
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13
Q

How is the periodontal ligament organised

A

Organised connective tissue :
- Bundles of collagen fibres insert into cementum and the alveolar bone

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14
Q

If fibres in the periodontal space follow the orientation of the collagen fibre bundles, how do they run?

A

They will run more vertically towards the periphery of the periodontal space

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15
Q

How does the average width of the periodontal space change over time

A

It is maintained over time, although it slightly changes with age

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16
Q

What does the PDL consist of

A

Collagen fibres embedded in a non-collagenous extracellular matrix

17
Q

Describe the non-fibrous matrix in the PDL

A
  • 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
18
Q

Describe fibroblasts in the PDL

A
  • 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
19
Q

Describe the hard tissue forming and resorbing cells

A
  • 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
20
Q

Describe epithelial cells in the PDL

A
  • 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
21
Q

Describe collagen fibres in the PDL

A
  • 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
22
Q

Describe oxytalan fibres in the PDL

A
  • Attached into the cementum in the outer part of the ligament
  • Fibres run obliquely down and are more longitudinally orientated
23
Q

Describe any other fibres in the PDL

A
  • Elaunin - found around blood vessels for the vascular system
  • Reticulin (Collagen Type III) - Aid tissue support
24
Q

Where is the blood supply in the PDL derived from

A

Superior or inferior alveolar arteries

25
Q

Where do the capillaries in the PDL originate

A

Intrabony spaces in the alveolar bone

26
Q

Where are the capillaries and arterioles within the PDL situated

A

Towards the socket wall

27
Q

How is the PDL further specialized

A
  • Unusually high capillary volume
  • Capillaries have fenestrations
  • Diffusion + filtration of fenestrated capillaries are significantly increased
28
Q

What are the 2 types of nerves

A

Sensory & autonomic

29
Q

What are the sensory fibres associated with

A

Nociception and mechanoreception

30
Q

Where are nerve fibres entering the PDL derived from

A
  • Nerve bundles enter near the root apex + pass up through the periodontal ligament
  • Enter the middle and cervical portions of the ligament as finer branches through the openings in alveolar bone
31
Q

What is the role of the PDL mechanoreceptors

A
  • Play a role in the transmission of touch and textural information during mastication
  • Provide afferent feedback essential in the control of salivation, mastication and swallowing
32
Q

How is the PDL similar to the foetus

A
  • High rate of turnover of the extracellular matrix
  • High proportion of Collagen Type III
  • High cellularity
  • Presence of oxytalan fibres
33
Q

How does the tooth support mechanism show that collagen fibres, vasculature and ground substance of the PDL are involved in tooth support

A

Ligament resists intrusive loads primarily by compression and fluid flow, which shows this

1 - IOE - Dental Anatomy (13 decks)

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