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Dental Pulp (Structural Organisation (Odontoblastic Layer (Provides a…

- - - - Protects pulp from external irritants
  - - - Undifferentiated progenitor cells
    - - Formed when blood vessels entering via apical foramen up through the central root portion branch laterally
  - - - Forms the Plexus of Raschkow
- - - - Consists of regular S shaped tubular dentine formed before tooth eruption
      - Convexity of primary curvature nearest the pulp faces towards the root
    - - Regular circumpulpla tubular dentine formed in continuity with primary dentine but at a slower rate, throughout life
      - Produced by downregulated odontoblasts after completion of root formation or tooth goes into occlusion
      - Greater deposition on roof and floor of pulp chamber
  - - - Stimulus causes inward or outward fluid movement within dentinal tubules that excite the nerve endings, interpreted as pain
    - - myelinated, found at PDJ and has low stimulation threshold
    - - non-myelinated, found throughout pulp, high stimulation threshold
    - - acts as a sensory cell
      - may act as mechano-transducer between dentinal fluid and nerve endings
        
        Shear forces in dentinal fluid stimulates odontoblast cell membrane
      - They have primary cilium that helps to convert mechanical fluid movement into an electrical signal
      - Contain
        
        High conductance Ca- activated K+ channels
        
        Modulate warm/ cold
        
        Stretch-activated TREK-1 K+ channels
        
        N-ty[e Ca2+ channels at the base of cilia
        
        Transient receptor potential (TRP) channels
        
        Activated in response to temperature changes
  - - - Dentinal fluid
        
        Outward flow of dentinal fluid makes it difficult for bacteria to reach the pulp
        
        Contains immunoglobulins
      - Intratubular fibres in dentinal tubules can trap bacteria
      - Inflammatory Response
        
        Immunocompetent cells mount inflammatory response to bacteria attack
        
        Inflammation is compartmentalised to area of pulp corresponding to breach of dentine
        
        Achieved through AVA shunt-- fluid (blood) perfusion increases in those areas
        
        Inflammation spreads apically
        
        Usually fluid capacity is not at maximum.
        
        However, during an inflammation, if fluids entering the pulp is faster than drainage pressure builds up --> causes pain
      - Odontoblasts synthesise tertiary dentine to reduce dentine permeability
        
        Dissolution of dentine matrix protein fossilised in dentine stimulates celllar activity to repair dentine
        
        Odontoblasts are upregulated or destroyed
- - - - Enclosed within rigid structure of dentine and enamel
      - Ability of pulp volume to expand when inflammed is restricted
        
        Leads to pain during inflammation
- - - - Post-mitotic --> cannot divide and will die if subject to injury
      - Coronal odontoblasts are columnar
      - Radicular odontoblasts are cuboidal
    - - Lateral branches link the cell to adjacent odontoblasts and other pulp cells
    - - Highest in region of pulp horns
    - - Tight Junction
        
        Limit permeability and maintain integrity of odontoblast layer
      - Gap Junction
        
        Openings for communication of electrical impulses and small molecules directly between adjacent cells
      - Desmosomes
        
        Responible for mechanical union of cells
    - - Lay down dentine throughout the life of the tooth
        
        Cell body: synthesis and control of the amount of proteins
        
        Cell process: secretion of calcium and dentine phosphoprotein
        
        Rate of dentine formation
        
        Primary: 4µm/ day
        
        Secondary: 0.4µm/ day
  - - - Production of extracellular fibres and ground substance
        
        Note; they do NOT contribute to the production of dentine
      - Can differentiate into odontoblast-like cells as replacement
  - - - initiate primary immune response
        
        migrate with trapped antigen to regional lymph nodes and induce T lymphocyte division and differetiation
      - An immunosurveillance cell
      - Found in dentine border and pulp core
    - - Derived from monocytes from blood
        
        Found in proximity of blood vessels
      - Function
        
        Scavanger cells, phagocytose and lysosomal enzymes destroy dead cells and foreign bodies
        
        Antigen presenting cells
    - - Function
        
        Initate primary immune response
        
        When memory T lymphocytes recognise antigen presented by dendritic or macrophages, T cell activation triggers T cell dependant immunity
        
        B lymphocytes are activated by T helper cells
  - - - Induced Pluripotent stem cells (iPS) has the potential to differentiate into fibroblasts or odontoblasts
      - Produced tertiary dentine
- - - - Type V and Type VI in small amount
      - Fibres are grouped into fibrils thingy and irregularly scattered
    - - Synthesized by odontoblasts and fibroblasts
      - Provides consistency and strength
    - - Synthesised by pulp fibroblasts
      - Provides elasticity
      - Abundant in cell free zone
      - Usually co-distributed with Type I collagen
  - - - Chondroitin sulphate
      - Dermatan sulphate
      - Heparan sulphate
      - Hyaluronic Acid
    - - Allow movement of water and ions
        
        Act as a resevoir for growth factors and bioactive molecules
      - Ground substance acts as a binder, providing anchorage and support to the cels
      - Acts as mechanical barrier against bacteria
- - - - More leeway in cutting tooth tissue before the dental pulp is exposed
      - Harder to locate root canals
  - - - Inherent healing ability of aged pulp is reduced
  - - - Free/ attached/ embedded
- - - - AVA shunt becomes active during inflammation and repair to permit regional control of pulpal blood flow so that the effect is compartmentalized
    - - Enters the apical canal and up the root pulp into coronal area
      - Anastomosis with arterioles of other branches entering from other root canals
      - Gives off side branches to periphery
      - Branches profusely within coronal pulp
      - Capillary loops towards dentine
      - Forms sub-odontoblastic capillary plexus below odontoblast layer
    - - they DO NOT enter the dentinal tubules
  - - - Unmyelinated C fibres
        
        in the core and extend to the cell-free zone
      - Myelinated A fibres
        
        One of the last major structures to appear in developing teeth
        
        mainly in the pulp-dentine border