Periodontal ligament

Question 1

What are the periodontal tissues

Answer 1

Cementum
Gingiva
Alveolar bone
Periodontal ligament

Question 2

What type of tissue is the periodontal ligament

Answer 2

Connective tissue

Question 3

What does the periodontal ligament contain

Answer 3

Cells (fibroblasts)
Extracellular matrix
Fibres
Nerves
Blood vessels

Question 4

What is the property of the periodontal ligament matrix

Answer 4

Behaves as a viscous elastic gel (alike that of jelly)

Question 5

What does the periodontal ligament matrix consist of

Answer 5

Hyaluronate glycosaminoglycans
Proteoglycans
Glycoproteins

Question 6

What cells are found in the periodontal ligament

Answer 6

Fibroblasts
Cementoblasts
Osteoclasts + cementoclasts
Epithelial cells
- cell rests (or debris) of malassez
Defence cells

Question 7

What nerves are found within the PDL

Answer 7

Sensory
-mechanoreceptors
-nociceptors

Autonomic (sympathetic)
-blood vessels control
-vasoconstriction

Question 8

What is the difference between the periodontal ligament and gingival ligament

Answer 8

Fibres in PDL connect tooth to bone at apical or to alveolar crest

Fibres mainly above the alveolar crest in GL connecting soft tissues to bone or cementum

Question 9

What are the functions of the PDL

Answer 9

Attaches tooth to jaw
Transmits biting forces to alveolar bone (enough to support entire weight)
Approx 0.2mm

Question 10

What are the principal fibre groups within the PDL

Answer 10

Alveolo-dental ligament:​
-Alveolar crest​
-Horizontal​
-Oblique​ (diagonal)
-Apical​ (at tip)
-Inter-radicular (multi-rooted teeth)​

Interdental ligament​
-Trans-septal fibres​

Question 11

Forces are transmitted through the tooth, why?

Answer 11

If the forces were placed on tooth without a way to transmit the force the bone would be deformed

Question 12

How does the PDL keep its form after the force has been applied

Answer 12

Extracellular matrix acts as a cushion for the PDL fibres to allow recovery of PDL to original shape and a smooth direct movement of the force from the tooth to bone

Question 13

How does the PDL act to protect the teeth

Answer 13

When PDL is not present there is much weaker detection of forces being applied onto tooth leading to greater chance of damage to the tooth/bone/gingiva

Question 14

What are the functions of these oblique periodontal ligament fibres

Answer 14

Resist biting force
Suspend the tooth within the socket

Question 15

Recall the types of tissues you observed in the histology classes.
How would you classify the periodontal ligament?

Answer 15

Connective tissue

Question 16

Relative to the tooth and bone, in which direction do the periodontal ligament fibres run?

Answer 16

From the bone to insert more apical into the cementum