periodontal ligament

Question 1

what are sharpey’s fibres

Answer 1

fibres which connect the bone and tooth root cementum

Question 2

draw and label the principle fibres in the periodontal ligament

Answer 2

A. Transseptal fibre

• Links to neighbouring teeth
• Fibre groups can be considered as gingival ligament
• Fibre does not have bone attachment

B. Alveolar Crest fibre

• Links alveolar bone crest to the acellular cementum

C. Horizontal fibre

D. Oblique fibre

E. Apical fibre

• Periodontal ligament fibre bundle connect cellular cementum to alveolar bone sulcate

F. Interradicular fibre

• Only found in multirooted teeth

Question 3

draw and label the gingival ligament fibres

Answer 3

A. Circular fibre group

• Bundle around tooth neck
• Bone and cementum attachment

B. Dentogingival fibre group

• Connect cementum and root to the gingival lamina propria(?)
• they extend from the cementum of the cervix of the tooth into the free gingiva and attached gingiva.

C. Dentoperiosteal fibre group

• Link cementum to periosteum and alveolar bone surface

D. Alveologingival fibre group

• Connect alveolar bone crest to gingival lamina propria

Question 4

draw and label the gingival ligament fibres interproximally

Answer 4

Question 5

what are secondary fibres in the PDL

what is their role and characteristics?

Answer 5

• Support cells, blood supply and nerve supply
• Randomly orientated
• Between nerves and blood vessels
• Do not attach to cementum or bone

Question 6

how do the collagen fibres differ in :

• gingival epithelium
• gingival connective tissue
• periodontal ligament

Answer 6

• Gingival epithelium
  
  • No collagen;
  • Keratinized
• Gingival connective tissue
  
  • Which is lamina propria of connective tissue
  • Type I (60%),
  • type III (trace) collagen, and others
• Periodontal ligament
  
  • Type I (50%) and type III (20%) collagen
  • Thick collagen fibre bundles running between cementum and alveolar bone
  • Types V, VI, XII and XIV collagen also present (3D organisation)
    
    • To support blood and nerve supply
  • small amounts but important

Question 7

what protein components are there in the PDL?

Answer 7

• Oxytalan, Elaunin, Elastin
• Fibronectin, Tenascin, Vitronectin, Thrombospondin, Laminin, Osteopontin and Osteonectin
• Proteoglycans/ Glycosaminoglycan

Question 8

what are the functions of the proteins in the periodontal ligament?

Answer 8

Question 9

why does the periodontal ligament have such as high extracellular matrix turnover rate?

Answer 9

high stresses placed on the tissue (periodontal ligament)

Prone to rapid inflammatory destruction

Question 10

what is the turnover of the ECM of the PDL controlled by?

Answer 10

• Increased cellular activity
• Enzyme activity
  
  • Matrix metalloproteinases/lysosomes
• Growth factors and cytokines
  
  • Production which promotes cell matrix synthesis
• Synthesis of new matrix

Question 11

what biomarkers of PDL destruction are there?

where are they taken from?

Answer 11

Decorin and Proteoglycan

Can be released into GCF

Question 12

what is MMP expression controlled by?

Answer 12

RNA expression level (gene transcription)

Translation level (protein transcribed)

Pro-enzyme form (needs activation)

Inhibitors (TIMPS)

Question 13

what are the functions of the periodontal ligament?

what fibres carry out these functions?

Answer 13

Provide eruptive tooth movement

• Remodelling is a mechanism of eruption force

Secure an attachment of the tooth root and bone

• By fibre inserted into bundle bone and cementum

Resilience to be able to contract/compress with the forces applied to the tooth

• By Principle fibres

Maintenance of the PDL space for blood/nerve supplies

• By Secondary fibres

PDL consists of cells for tissue repair including cementum repair and bone repair

Question 14

what are the cells of the periodontal ligament?

Answer 14

Fibroblast cells

Cementoblasts

Osteoblast cells

Epithelial cells

Endothelial cells

Immune cells

Stem cells

Question 15

role of periodontal fibroblasts

Answer 15

Produce collagen fibres for ECM turnover

Question 16

describe the blood supply to the periodontal ligament

Answer 16

Well vascularised connect tissue

Supply from superior and inferior alveolar arteries

• Called “perforating arteries”

More blood supply in Posterior teeth than anterior teeth

More in mandibular than maxillary teeth

Has clinical important in healing of extraction wounds

Question 17

describe the nerve supply in the pdl

Answer 17

From apical to gingival

Perforation into the alveolar bone

4 types of nerve fibre terminations:

• Free nerve ending
• Ruffini’s corpuscles
• Coiled ending
• Spindle like ending

Question 18

what are free nerve endings in the periodontal ligament?

Answer 18

• Unmyelinated nerve fibre
• Treelike configuration
• Along the length of root
• Extended to cementoblast layer
• Pain receptor
• Mechanoreceptor

Question 19

what are Ruffini’s corpuscles in the periodontal ligament?

Answer 19

Dendritic like

Extended amount the fibre bundles

In Schwann cells

• Nerve fibre is wrapped in schwann cells
• Myelinated

Mechanoreceptor

Question 20

where are the coiled ending nerve fibre terminations in the periodontal ligament found

function?

Answer 20

Found in Mid-region of the PDL

Function was unidentified

Question 21

where are spindle-like nerve fibre terminations found in the periodontal ligament?

Answer 21

Very low frequency

Associated with root apex