Periodontal Tissues in Health & Disease II Flashcards
What is the periodontal ligament?
Soft specialised connective tissue situated between the cementum and the bone socket wall
What is the width of the PDL?
What effect does age have on it?
- Width 100-400 micron
- Thinnest at middle third of root
- Decreases with age
What are the main functions of the PDL? (6)
- Supportive
- Sensory
- Formative
- Protective
- Regeneration
- Nutritive
What is the most predominant cell in the PDL?
Fibroblasts
How are fibroblast in the PDL orientated?
Oriented with their long axis parallel to the direction of collagen fibrils
What is the role of the fibroblasts in the PDL?
Synthesise and shape the proteins of the extracellular matrix, in which collagen fibrils form bundles that insert into cementum and bone as Sharpey’s fibers
What are the Epithelial cell rests of Malassez in the PDL?
They are discrete clusters of residual cells from Hertwig’s epithelial root sheath (HERS) that did not completely disappear
What is the role of the epithelial cell rests of Malassez in the PDL? (3)
- Maintain PDL homeostasis to prevent ankylosis and maintain PDL space
- Prevent root resorption
- Contribute to cementum repair
Name some cells found in the PDL (5)
- Fibroblasts
- Epithelial cell rests of Malassez
- Immune cells
- Nerve cells
- Osteoblasts
Name some fibres found in the extracellular substance of the PDL (5)
- Collagen (Mainly Type I)
- Elastic
- Reticular
- Oxytalan
- Indifferent fiber
plexus
What is the difference in width of the collagen fibres in the PDL?
Wider diameter on the bone side than the cementum side
What are Sharpeys fibres?
A matrix of connective tissue consisting of bundles of strong predominantly type I collagen fibres connecting periosteum to bone
What are the 5 types of principal fibres in the PDL?
- Alveolar crest fibers
- Horizontal fibers
- Oblique fibres
- Apical fibers
- Inter-radical fibers
What forces do Alveolar crest fibres resist? (4)
Resist tilting, intrusive, extrusive and rotational forces
What forces do Horizontal fibers resist? (2)
Resist horizontal and tipping forces
What forces do Oblique fibers resist? (2)
Resist vertical and intrusive forces
What forces do Apical fibers resist? (2)
Resist luxation and tipping
What forces do Inter-radical fibers resist? (3)
Resist tooth tipping, torquing and luxation
What is the alveolar bone?
What does it develop from?
- The specialised bone structure that contains the sockets of the teeth and supports the teeth
- Develops from the dental follicle
What are the two main components of the alveolar bone?
- Alveolar process
- Alveolar bone proper
What are the main functions of the alveolar bone?
- Anchorage
- Protection and support for teeth
- Bone synthesis
- Absorbs and distributes forces
What two types of bone is the alveolar process made of?
- Cortical bone
- Cancellous bone
Describe the location of the alveolar bone proper
- Continuation of the cortical plate, it lines the tooth socket
- Surrounds the root of the teeth and gives attachment to the principal fibers of PDL
Why is alveolar bone proper called bundle bone?
As numerous bundles of Sharpey’s fibers pass into it from the PDL
What cell types are found in the alveolar bone? (4)
- Osteoblasts
- Osteocytes (90%-95%)
- Bone-lining cells
- Osteoclasts
What is the composition of alveolar bone bone matrix?
- 35% organic (collagen and non-collagenous proteins)
- 40% inorganic (HA and impurities)
- 25% water
What is bone modelling?
- Process of bone growth
- Seems to occur without coupling of bone formation
and resorption
What is bone remodelling?
How long does this process take?
- Dynamic process through which the skeleton is continuously renewed
- Bone formation and bone resorption are coupled -(Basic Multicellular Unit)
- Approximately 2-8 months in humans
The majority of the tissue damage in periodontitis derives from the excessive and dysregulated production of a variety of inflammatory mediators, what are these mediators? (3)
- Cytokines
- Prostaglandins
- Matrix Metalloproteinases (MMPs)
Give some features of cytokines (4)
- Soluble proteins
- Act as messenger molecules that transmit signals from one cell to another
- They bind to specific receptors on target cells that initiate intracellular signalling cascade
- Effective in low concentrations
Name some actions of cytokines (2)
- Initiation and maintenance of immune and inflammatory responses
- Regulation of growth and differentiation of cells.
Name an important prostaglandin produced by mainly macrophages and fibroblasts
PGE2
Give some features of PGE2 (3)
- Is a potent vasodilator
- Induce cytokine production by various cells
- Acts on fibroblasts and osteoclasts to induce production of MMPs
What are MMPs?
Family of proteolytic enzymes responsible for remodelling and degradation of the matrix components
