Periodontal Ligament

Question 1

What are periodontal tissues?

Answer 1

Tissues that surround the tooth: cementum, gingiva, alveolar bone, periodontal ligament

Question 2

What does the periodontal ligament do?

Answer 2

Connects the tooth to the alveolar bone

Question 3

What is the periodontal ligament?

Answer 3

Connective tissue containing cells, ECM, fibres, nerves, blood vessels

Question 4

What is the periodontal ligament ECM composed of?

Answer 4

Hyaluronate glucosaminoglycans, proteoglycans, glycoproteins

Question 5

What do the side chains of proteoglyans and glycoproteins provide in the matrix of the periodontal ligament?

Answer 5

• The side chains adsorb water
• The molecules become more flexible/jelly-like: wobbles then returns to its original shape
• Property: behaves as a viscous, elastic gel

Question 6

What effect does periodontal disease have on glycoproteins and proteoglycans in the matrix of the periodontal ligament?

Answer 6

• Changes the structure of proteoglycans and glycoproteins
• Bacteria produce enzymes that break down macromolecules
• Changes the behaviour of these components

Question 7

Which cells are present in the periodontal ligament?

Answer 7

Fibroblasts, cemetoblasts, osteoclasts, cementoclasts, epithelial cells, defence cells

Question 8

What is the function of epithelial cells in the periodontal ligament?

Answer 8

Cell rests (or debris) of Malassez (epithelial cells are protective cells, form a barrier). Contain desmosomes

Question 9

Which cells do cysts originate from?

Answer 9

Epithelial cells. Desmosomes create cysts

Question 10

Describe the periodontal ligament nerves

Answer 10

• Sensory: mechanoreceptors, nociceptors

- Autonomic (sympathetic): blood vessel control, vasoconstriction

Question 11

What is the ‘true periodontal ligament’?

Answer 11

Fibres connecting tooth to bone at or apical to alveolar crest

Question 12

What is the ‘gingival ligament’?

Answer 12

Fibres mainly above the alveolar crest, including ‘free gingival’ fibres

Question 13

What are the functions of the periodontal ligament?

Answer 13

• Attaches tooth to jaw

- Transmits biting forces to alveolar bone

Question 14

What is the width of the PDL?

Answer 14

Approx. 0.2mm

Question 15

What type of connective tissue is the periodontal ligament?

Answer 15

Organised (regular) connective tissue

Question 16

In denture-wearers, where is the biting force transmitted?

Answer 16

• To the gingiva

- Gingiva not as strong as bone, forces need to be minimised

Question 17

What type of foods should people with dentures avoid?

Answer 17

• Hard foods - biting forces transmitted to the gingiva

- Patients with dentures don’t have mechanoreceptors - cannot differentiate forces/consistency of food

Question 18

Where are the biting forces transmitted in implants?

Answer 18

To the bone

No mechanoreceptors or nociceptors

Question 19

Why can implants not be placed in teeth above/below one another?

Answer 19

• Because they will break if patient bites down hard (implants made of ceramic materials/porcelain)

Question 20

What are the PDL principal fibre groups?

Answer 20

• Alveolo-dental ligament: alveolar crest, horizontal, oblique, apical, inter-radicular (multi-rooted teeth)
• Interdental ligament: trans-septal fibres

Question 21

What is the function of oblique fibres? (alveolo-dental ligament)

Answer 21

The oblique PDL is to transmit the force from the tooth to the bone

Question 22

What is the function of horizontal fibres? (alveolo-dental ligament)

Answer 22

Lateral and rotational forces

Question 23

What is the function of apical fibres? (alveolo-dental ligament)

Answer 23

Work like coils, reducing the force when it gets close to the bone