Dental Pulp Composition, Structure and Function

• By the end of the session students should be able to describe the composition and structure of the pulp.
• By the end of the session students should be able to describe how the structure of pulp relates to its function.
• By the end of the session students should be able to apply this knowledge to interpret the clinical implications of the pulp in health and disease.
• GDC Learning outcomes: 1.1.5, 1.1.6

Histology of Tissues

• Tissues include: Enamel, Dentine, Pulp, Cementum, Bone (alveolar), Periodontal ligament, and Gingiva

Refresh the memory

• Location of the pulp is found within a tooth
• Developed from the ectomesenchyme of the dental papilla

Pulp

• The dental pulp is similar to the heart of a tooth; without it, a tooth cannot survive except with lengthy and costly treatment.

Structure and composition

• The pulpal anatomy is consistent with the type of tooth
• The pulp is encased in the pulp cavity surrounded by the mineralized tissues
• Coronal pulp is located in the pulp chamber
• Root pulp is located in the root canal

Composition

• Highly vascular, soft connective tissue
• Consists of 75-80% water and 20-25% organic material (by weight)

Cells

• A key part of the pulp composition
• Includes odontoblasts, fibroblasts, undifferentiated cells, and defense cells

Extracellular matrix

• Includes fibres, ground substance, blood vessels, lymph vessels, and nerves
• A key part of the pulp composition

Structural composition

• The structure of the pulp visible under a microscope includes 4 different zones:
  • Odontoblast zone lines the periphery of the pulp
  • Cell-free zone is the space observed between zones with only a few fibres
  • Cell-rich zone contains all the cells except odontoblasts.
  • Pulp core contains the blood vessels, nerves, and some cells

Cells - Odontoblasts

• The most distinct cells of the pulp that line the periphery in the odontogenic zone.
• They have a process extending into dentine with the function to perform dentinogenesis and Sensory transduction

Cells - Fibroblasts

• Most prevalent cells in the pulp in the cell-rich zone
• They Form and maintain the extracellular matrix of collagen and ground substance
• Very active in young pulps, as this reduces over time as the pulp shrinks

Cells - Undifferentiated

• Undifferentiated cells found in the cell-rich zone and pulp core include:
  • Ectomesenchymal cells that can differentiate into odontoblasts and fibroblasts
  • Mesenchymal stem cells (MSC) have shown potential to differentiate into various cells, research is ongoing to understand their regenerative ability.

Cells - Defense

• Numerous defense cells are located in the pulp core
  • Includes: Macrophages, T-lymphocytes, and B lymphocytes (scarce)
• Some leukocytes will increase during infection
• Dendritic cells beneath the odontoblast zone function in immunosurveillance and thus increase in carious teeth.

Extracellular Matrix

• Consists of fibers of collagen, principally type I and III, that increase in content with age
• The apical pulp contains the greatest concentration
• Ground substance, a loose connective tissue, that supports the cells and consists of glycosaminoglycogens, glycoproteins and water

Vascular and Lymph Supply

• Circulate the pulp and are located in the pulp core
• They enter and exit through the apical foramen along with the nerve supply, some through accessory foramina
• The largest vessels consist of arterioles and venules that branch into an extensive capillary network in the coronal portion.

Nerve Supply 1

• The pulp is richly supplied with nerves that enter through the apical foramen along with the vascular and lymph supply following the same course to the pulp core
• Enables the pulp to recognize stimuli, perceived as pain and trigger defense responses.

Nerve Supply 2

• In the coronal portion the nerve plexus of Raschkow can be found just beneath the cell-free zone
• Most nerve bundles end as free nerve endings in the plexus
• Some continue to end between the odontoblasts and into the dentinal tubules

Nerve Supply 3

• There are two types of nerves:
  • Predominantly sensory afferent nerves of the trigeminal nerve which enables perception of pain
  • Sympathetic nerve branches from the superior cervical ganglion help regulate blood flow in the smooth muscles of the vascular vessels
• Nerve bundles can be both myelinated and unmyelinated

Functions of the pulp

• Formative
• Circulation
• Protective
• Vital, healthy tooth

Pulp over the life-course

• Over time, the deposition of secondary dentine reduces the size of the pulp tissue and the diameter of the apical foramen
• Has a number of impacts including Reduced circulation, Reduced innervation, Fewer odontoblasts, and Increased fibres/collagen
• Impacts reduce the pulp's ability to respond and repair

Clinical significance

• In response to stimuli or injury, the pulp experiences either reversible pulpitis or irreversible pulpitis (painful!).
• The ability of the pulp to repair itself is limited to the size of the apical foramen and can lead to necrosis of the pulp.

Structural anomalies - Pulp stones

• Pulp stones are small calcified areas of tissue (similar to dentine) frequently found in pulp tissue
• They are either free or attached to the dentine
• Reduces the cell content in the pulp and pose as a challenge for endodontic treatment

Structural anomalies - Accessory Canals

• Disruptions during development of the root may lead to a break in the continuity of Hertwig's epithelial root sheath
• Leads to a disruption in odontogenesis of the root-forming accessory root canals
• This may have implications for the ingress of bacteria to the pulp if become exposed, leading to periodontal and endodontic problems.

Explore the dental pulp's structure, composition, and function, and its clinical implications in health and disease. The pulp, located within the tooth, is vital for tooth survival and develops from the dental papilla's ectomesenchyme. Pulpal anatomy varies with tooth type and is encased in the pulp cavity surrounded by mineralized tissues.