Preclinics of Conservative Dental Medicine · MU Sofia

50. Morphology, blood supply and innervation of the pulp; physiology of the pulp.

Covers the four zones of the dental pulp from the odontoblastic layer inwards, along with its cell types, extracellular matrix and age-related changes such as pulp stones. It then describes arterial, venous and lymphatic supply, the low-compliance pressure problem in inflammation, and trigeminal innervation. A table compares A-delta and C nerve fibres, and the hydrodynamic theory of dentine pain is explained. It ends with the pulp's formative, nutritive, sensory and defensive functions, including reactionary and reparative dentine.

Inside: 6 sections · 1 labelled picture · 1 table · 17 flashcards · 7 min

Topic 50 of 53 in the MU Sofia syllabus for Preclinics of Conservative Dental Medicine (Dental Medicine, Year 3). The free AceMed note covers it in 6 sections, about 887 words (7 min of reading), with 17 flashcards.

In this note

  1. Introduction
  2. Morphology: zones and cells
  3. Blood supply and lymphatics
  4. Innervation and dentin sensitivity
  5. Physiology: functions of the pulp
  6. Key points

Introduction

The dental pulp is the loose connective tissue in the pulp chamber and root canals; with dentin it forms the pulp–dentin complex. Its structure explains pulp testing, dentin hypersensitivity, the response to caries and cavity preparation, and why an inflamed pulp dies so easily.

Morphology: zones and cells

The pulp is of ectomesenchymal (neural crest) origin and about 75% water. The coronal pulp fills the chamber, with a horn under each cusp; the radicular pulp fills the canals (topic 34) and meets the periodontium at the apical foramen and accessory canals. Four zones lie from the periphery inwards:

  1. Odontoblastic layer – a palisade of odontoblasts lining the predentin (columnar in the crown, flatter in the root). Each sends an odontoblast process into a dentinal tubule, at least through its inner third.
  2. Cell-free zone of Weil – about 40 µm wide, clearest in the crown; contains the subodontoblastic capillary plexus and nerve fibres from the plexus of Raschkow.
  3. Cell-rich zone – densely packed fibroblasts and undifferentiated mesenchymal cells, the reserve that replaces lost odontoblasts.
  4. Pulp core (pulp proper) – the central tissue with the larger arterioles, venules and nerve bundles.

Cells and matrix

  • Odontoblasts – post-mitotic cells that form and maintain dentin; lost ones are replaced only by new odontoblast-like cells.
  • Fibroblasts – the most numerous cells; produce and remodel collagen and ground substance.
  • Undifferentiated mesenchymal cells (dental pulp stem cells) – in the cell-rich zone and around vessels; differentiate into odontoblast-like cells after injury.
  • Immune cells – macrophages, dendritic cells (near the odontoblasts) and T lymphocytes.
  • Extracellular matrix – collagen types I and III in a gel of proteoglycans (hyaluronic acid, chondroitin sulphate), fibronectin and water.

Age changes

Secondary dentin narrows the chamber and canals throughout life (in molars mainly from the roof and floor). Cells, vessels and nerves decrease and collagen increases (fibrosis). Calcifications appear: diffuse (linear) ones along radicular vessels and nerves, and pulp stones (denticles) – true (with tubules, rare) or false (concentric layers, common), free, attached or embedded. Old pulps respond less to tests and heal more slowly, and stones and narrow canals hinder access and canal location.

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