periodontal ligament Flashcards
what are sharpey’s fibres
fibres which connect the bone and tooth root cementum
draw and label the principle fibres in the periodontal ligament
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
draw and label the gingival ligament fibres
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
draw and label the gingival ligament fibres interproximally
what are secondary fibres in the PDL
what is their role and characteristics?
- Support cells, blood supply and nerve supply
- Randomly orientated
- Between nerves and blood vessels
- Do not attach to cementum or bone
how do the collagen fibres differ in :
- gingival epithelium
- gingival connective tissue
- periodontal ligament
- 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
what protein components are there in the PDL?
- Oxytalan, Elaunin, Elastin
- Fibronectin, Tenascin, Vitronectin, Thrombospondin, Laminin, Osteopontin and Osteonectin
- Proteoglycans/ Glycosaminoglycan
what are the functions of the proteins in the periodontal ligament?
why does the periodontal ligament have such as high extracellular matrix turnover rate?
high stresses placed on the tissue (periodontal ligament)
Prone to rapid inflammatory destruction
what is the turnover of the ECM of the PDL controlled by?
- Increased cellular activity
- Enzyme activity
- Matrix metalloproteinases/lysosomes
- Growth factors and cytokines
- Production which promotes cell matrix synthesis
- Synthesis of new matrix
what biomarkers of PDL destruction are there?
where are they taken from?
Decorin and Proteoglycan
Can be released into GCF
what is MMP expression controlled by?
RNA expression level (gene transcription)
Translation level (protein transcribed)
Pro-enzyme form (needs activation)
Inhibitors (TIMPS)
what are the functions of the periodontal ligament?
what fibres carry out these functions?
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
what are the cells of the periodontal ligament?
Fibroblast cells
Cementoblasts
Osteoblast cells
Epithelial cells
Endothelial cells
Immune cells
Stem cells
role of periodontal fibroblasts
Produce collagen fibres for ECM turnover
describe the blood supply to the periodontal ligament
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
describe the nerve supply in the pdl
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
what are free nerve endings in the periodontal ligament?
- Unmyelinated nerve fibre
- Treelike configuration
- Along the length of root
- Extended to cementoblast layer
- Pain receptor
- Mechanoreceptor
what are Ruffini’s corpuscles in the periodontal ligament?
Dendritic like
Extended amount the fibre bundles
In Schwann cells
- Nerve fibre is wrapped in schwann cells
- Myelinated
Mechanoreceptor
where are the coiled ending nerve fibre terminations in the periodontal ligament found
function?
Found in Mid-region of the PDL
Function was unidentified
where are spindle-like nerve fibre terminations found in the periodontal ligament?
Very low frequency
Associated with root apex
