PDL

Question 1

What are the 4 constituents of the periodontium.
+ which are calcified
+ layout

Answer 1

Non-calcified:
1. Lamina propria
2. PDL
Calcified
1. Cementum
2. Alveolar bone

Question 2

What’s the structure of the lamina propria of the gingive?

Answer 2

• Fibrous connective tissue
• Collagen type I
  
  • form principle fibres
  • bind gingiva to alveolar bone

Question 3

What type of tissue is the PDL?

Answer 3

Non-mineralised connective tissue

Question 4

What’re the functions of the PDL + how they relate to the structure?

Answer 4

Un-mineralised = supports teeth
Allow masticatory forces to be transmitted to alveolar bone
PDL is a continuous connective tissue (from alveolar crest and below pulp) = easily transmitted diseases

Question 5

List the components in the extracellular matrix of the PDL.

Answer 5

Collagen fibres
Elastic fibres
Glycoproteins
Ground substance

Question 6

What’s the importance of the collagen fibres in the PDL?

Answer 6

Tensile strength (collagen type 1)
Sharpey’s fibres
Flexibility
Attachment to cementum and bone

Question 7

What are epithelial cell rests and why are they found in the PDL?

Answer 7

Epithelial cell rests of Malassez
- remnants of HERS
- most of HERS undergoes apoptosis some don’t

Question 8

Name all the cell types in the PDL + their function…

Answer 8

Fibroblasts -> synthesising and maintaining the extracellular matrix

Cementoblasts -> secrete cementum
Odontoclasts -> resorption of cementum

Osteoblasts -> bone forming cells in alveolar bone
Osteoclasts -> resorption of bone

Epithelial Cell Rests of Malassez -> remnants of HERS

Question 9

What’s the role of fibroblasts?

Answer 9

Synthesising and maintaining extracellular matrix

Question 10

What’s the main cell in the PDL?

Answer 10

Fibroblasts

Question 11

What’re the different fibre types within the PDL + their composition + their possible function? (4)

Answer 11

Principle Fibres (Sharpey’s fibres) - anchors tooth cementum to alveolar bone
Oxylatan Fibres - parallel to cementum, aid movement of fibroblasts
Horizontal Fibres - horizontal, maintain alignment
Occlusal Fibres - cementum to alveolar bone, resist forces
Interradicular Fibres - in multi-rooted teeth, stability to root
Apical Fibres - from apex of tooth

Question 12

Describe the arrangement and composition of the principal collagen bundles.

Answer 12

-mainly type I collagen
-Sharpey’s fibres (principle)
-horizontal fibres
-oblique fibres
-oxylatan fibres
-interradicular fibres
-apical fibres

Question 13

What’s the nerve and blood supply of the PDL?

Answer 13

NERVE
-nociceptors (pain receptors)
-mechanoreceptors (pressure receptors)

BLOOD
-superior and inferior alveolar arteries
-enter via root apex
-vessels situations around socket of tooth

Question 14

How do foetal-like characteristics of the PDL aid it?

Answer 14

-fast turnover rate
-high proportion of collagen III
-presented of oxytalan fibres

Question 15

Describe the PDL tooth support mechanism.

Answer 15

Sensory Ligament Hypothesis.
- PDL = suspensory ligament during mastication
- load placed on occlusal surface transferred to alveolar bone through principle fibres
- elastic recoil back to resting position
- socket walls pushed apart at crests

Question 16

Where’s the junctional epithelium and what’s its structure?

Answer 16

Between lamina propria and enamel
- non-keratinised squamous epithelium