Pulpal and Periapical Physiology

  1. Dentinogenesis
    This process is the result of serial epithelial-mesenchymal interactions. Cells of the inner and outer enamel epithelium contact one another to form Hertwig’s epithelial root sheath (HERS). HERS activates mesenchymal cells to become odontoblasts and produce root dentin. Following dentin deposition, HERS resorbs (Diamond and Applebaum). The exposure of root dentin signals mesenchymal cells to populate the hard tissue and form cementum. Following cementum formation, the periodontal ligament develops from mesenchymal precursor cells.
  2. Ectodermal Derived Tissues

    Mesenchymal Derived Tissues
    Ectodermal Derived Tissues

    • Enamel
    • HERS

    Mesenchymal Derived Tissues

    • Dentin
    • Cementum
    • Pulp
    • Periodontal Ligament
  3. Pulp Vascularization and Innervation
    Pulp vascularization begins prior to innervation.

    The onset of pulpal innervation is delayed until dentin and enamel formation begins.
  4. Dentin Formation
    Mesenchymal origin

    Produced by odontoblasts

    Odontoblasts secrete dentin in its unmineralized form, which then mineralizes throughout development (Butler and Ritchie). The odontoblastic process secretes both collagen and noncollagenous proteins, including dentin sialophosphoprotein and osteocalcin. These noncollagenous proteins likely serve as the impetus for dentin mineralization.
  5. Dentin Composition
    50% mineral

    30% type I collagen

    20% water

    Kinney et al.
  6. Dentinal Tubules

    Number and Diameter
    The number and diameter of dentinal tubules increases in proximity to the pulp.

    At the DEJ, Garberoglio and Brannstrom counted 20,000 tubules per square millimeter, whereas at the pulp surface, 45,000 tubules per square millimeter were noted.

    Just as tubule numbers increase in proximity to the pulp, so do the number of tubule branches (Holland).
  7. Odontoblastic process extension into dentinal tubules.

    Garberoglio and Brannstrom.
    Byers and Sugaya.
    Yamada.
    Garberoglio and Brannstrom - Demonstrated the extension of odontoblastic processes 0.5mm into dentinal tubules.

    Byers and Sugaya - Found that odontoblastic processes extended to the DEJ early in development only.

    Yamada et al. - Found that processes extended to the DEJ following completion of development.

    Despite the controversy, however, it is clear that the odontoblastic process extends to some degree into dentinal tubules at some point during development.
  8. Types of Dentin

    Primary
    Secondary
    Tertiary
    Primary - Formed prior to eruption.

    Secondary - Formed in response to slightly aggressive affects of normal function.

    Tertiary - Formed in response to severe and intense pulpal irritants.
  9. Primary and Secondary Dentin

    Scott and Weber.
    Scott and Weber - Found an abrupt interface between primary and secondary dentin with a change in tubule direction in addition to a decrease in tubule number.
  10. Reactionary and Reparative Dentin

    Mjor et al.
    Mjor et al. - Categorized secondary and tertiary dentin as reactionary or reparative. Reactionary dentin is formed by an existing odontoblast, whereas reparative dentin is formed by the generation of a new odontoblast from precursor cells.
  11. Rate of Reparative Dentin Formation

    Reeves and Stanley
    Reeves and Stanley found that, following an insult, reparative dentin initially forms rapidly and then slows over time. An average of 1.49 μm of reparative dentin is formed per day.
  12. Contents of Pulpal Tissue
    Contents of Pulpal Tissue

    • Odontoblasts (Ruch)
    • Fibroblasts (Harris and Griffin)
    • Vascular structures (Kuttler)
    • Immune cells
    • Lymphatics (Bernick)
    • Nerves (Byers)
    • Extracellular connective tissue (Linde)
  13. Contents of Pulpal Connective Tissue
    Contents of Pulpal Connective Tissue

    • Type I Collagen
    • Type III Collagen
    • Type V Collagen
    • Dermatan sulfate
    • Chondroitin sulfate
    • Hyaluronate
  14. Primary vs. Permanent Dentition Pulpal Nerve Composition

    Rapp et al.
    Rapp et al. - Include both sensory and autonomic nerve fibers, and the composition is relatively unchanged between the primary and permanent dentition
  15. A delta Fibers
    Myelinated

    Respond to dentinal stimuli
  16. C Fibers
    Unmyelinated

    Respond to pulpal irritants

    Releases neuropeptides
  17. Intrapulpal Nerves

    Are A delta or C fibers more abundant?

    Nair
    Nair - Of all axons entering the pulp, 87% are unmyelinated C fibers.
  18. Symptoms associated with A delta Fibers?
    Dentin hypersensitivity

    Create short bursts of sensation

    Relatively insensitive to inflammatory mediators
  19. Symptoms associated with C Fibers?
    Lingering pulpal pain

    Respond to inflammatory mediators

    May respond directly to bacterial byproducts
  20. Theories of Dentin Sensitivty

    Frank
    Avery
    Brannstrom
    Frank - Conduction

    Avery - Transduction

    Brannstrom - Hydrodynamic
  21. Hydrodynamic Theory of Dentin Sensitivty


    Brannstrom
    Brannstrom - Developed the hydrodynamic theory of dental pain. Through an elegant experiment where paper points were applied to dentin, stimulating outward fluid flow, he demonstrated that fluid flow caused painful sensations in the dental pulp.
Author
ucsfendo
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344363
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Pulpal and Periapical Physiology
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Pulpal and Periapical Physiology
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