Dental Pulp: Anatomy, Composition & Function

• The dental pulp's composition, structure, and function, along with its clinical implications in both health and disease, are key aspects of study.

Pulp Location and Origin

• The pulp is located within a tooth.
• The pulp's embryonic origin is the ectomesenchyme of the dental papilla.

Pulp as the Tooth's "Heart"

• The dental pulp's vitality is crucial for tooth survival, treatment is lengthy and costly without it.

Pulp Anatomy

• Pulpal anatomy varies with tooth type, encased in the pulp cavity within mineralized tissues.
• Coronal pulp resides in the pulp chamber, while root pulp is located in the root canal(s).

Pulp Composition

• Pulp is a highly vascular, soft connective tissue composed of 75-80% water and 20-25% organic material.
• Cellular components include odontoblasts, fibroblasts, undifferentiated cells, and defense cells.
• The extracellular matrix consists of fibers, ground substance, blood vessels, lymph vessels, and nerves.

Pulp's Structural Zones

• The pulp has four zones, identified under a microscope.
• The odontoblast zone lines the periphery.
• The cell-free zone has only a few fibers.
• The cell-rich zone contains all cells except odontoblasts.
• The pulp core contains blood vessels, nerves, and some cells.

Odontoblasts

• Odontoblasts, the pulp's most distinct cells, line the periphery in the odontogenic zone.
• They extend a process into the dentine.
• They perform dentinogenesis.
• These cells are responsible sensory transduction.

Fibroblasts

• Fibroblasts are the most prevalent cells in the pulp's cell-rich zone.
• They form and maintain the extracellular matrix of collagen and ground substance.
• Fibroblasts are active in young pulps, but their activity reduces as the pulp shrinks with age.

Undifferentiated Cells

• Found in the cell-rich zone and pulp core, they include ectomesenchymal cells, which differentiate into odontoblasts and fibroblasts.
• Mesenchymal stem cells (MSC) show potential to differentiate into various cells, under ongoing research to understand their regenerative ability.

Defense Cells

• Defense cells, including macrophages and T-lymphocytes, are located in the pulp core.
• B lymphocytes are scarce.
• Some leukocytes increase during infections.
• Dendritic cells beneath the odontoblast zone function in immunosurveillance and increase in carious teeth.

Extracellular Matrix

• Includes collagen fibers, mainly types I and III, increasing with age, concentrated in the apical pulp.
• Ground substance is a loose connective tissue that supports cells and consists of glycosaminoglycogens, glycoproteins, and water.

Vascular and Lymph Supply

• Vascular and lymph vessels supply circulation, found in the pulp core.
• Vessels enter and exit through the apical foramen with the nerve supply, and some through accessory foramina.
• Arterioles and venules are the largest vessels, branching into a capillary network in the coronal portion.

Nerve Supply

• The pulp is richly supplied with the nerves, entering through the apical foramen with vascular and lymph supply.
• The nerve supply enables stimulus recognition, pain perception, and defense response triggering.
• The Nerve Plexus of Raschkow is in the coronal portion, beneath the cell-free zone.
• Most nerve bundles end in the plexus as free nerve endings; some end between odontoblasts and in dentinal tubules.
• Two nerve types are present: sensory afferent nerves from the trigeminal nerve and sympathetic nerve branches from the superior cervical ganglion.
• Sympathetic nerves regulate blood flow in vascular vessel smooth muscles.
• The nerve bundles are both myelinated and unmyelinated.

Functions

• Formative
• Circulation
• Protective

Pulp's Life-Course Changes

• Secondary dentine deposition reduces the pulp size and apical foramen diameter over time.
• Impacts include reduced circulation and innervation, fewer odontoblasts, and increased fibers and collagen.
• Resulting in a reduced ability to respond and repair.

Clinical Significance

• In response to stimuli or injury, the pulp experiences reversible or irreversible (painful) pulpitis.
• Although the pulp can repair itself, the response is limited by the size of the apical foramen, which can lead to necrosis.

Structural Anomalies: Pulp Stones

• Pulp stones are small calcified tissue areas, similar to dentine, found in pulp tissue.
• They can be free or attached to the dentine.
• Clinical significance is, they reduce cell content and pose a challenge for endodontic treatment.

Structural Anomalies: Accessory Canals

• Disruptions during root development can cause a break in Hertwig’s epithelial root sheath continuity, leading to disrupted odontogenesis of accessory root canals.
• Ingress of bacteria to the pulp can lead to periodontal and endodontic problems.