5. Pulp Biology

Question 1

Where does the pulp originate from in the formative stage?

Answer 1

It develops from the dental papilla / ectomesenchymal cells. The differentiation to odontoblasts occurs due to mesenchymal-epithelial interactions.

Question 2

What are the 3 components of the dental pulp that works together for defense?

Answer 2

1. Cells
2. Proteins and ground subtance
3. The neurovascular system

Question 3

Which cells are involved in the defense of the dental pulp? Briefly describe their role.

Answer 3

Odontoblasts, fibroblasts, stem cells, immune system cells (macrophages, T-lymphocytes and dendritic cells)

• Odontoblasts synthesize dentine matrix and control dentine mineralization. They are also antigen-presenting cells and they secrete immunoactive peptides and vasoactive mediators
• Fibroblasts are the most common cells throughout pulp, they produce collagen and ground substance. They also eliminate collagen in remodelling process
• Stem cells are precursor cells that act as a cell pool from which connective tissue cells are derived. They differentiate into fibroblasts / odontoblast-like cells depending on stimulus
• Macrophages, T-lymphocytes and dendritic cells carry our surveillance and the initial response mechanism. They present and eliminate antigens like dead cells and foreign bodies

Question 4

How does ground substance contribute to the defense of the dental pulp?

Answer 4

Ground substance is made of proteins and carbohydrate complexes that form a sol-gel milieu. This supports the cells and serves as a medium for transport of nutrients and metabolites.

Question 5

How does the neurovascular system contribute to the defense of the dental pulp?

Answer 5

The nerves in the pulp are the sensory nerve fibres and the sympathetic nerve fibres. There is nervous regulation of vascular physiology:

• The volume of the vascular bed of the pulp is greater than the volume of the blood flowing through it. This allows for the local increase in blood flow in response to injury
• This blood supply regulation is carried out by the sympathetic innervation (Autonomic Control) and neuropeptides and CGRP (Local Control)

Question 6

Why does a coronal dentine exposure hurt more than a root dentine exposure?

Answer 6

The density of nerve bundles is greater at the coronal portions of the tooth compared to the root.

Question 7

What happens during tooth sensitivity? Briefly describe the mechanism behind this sensitivity.

Answer 7

A tooth can feel sensitive when its dentine is exposed to external stimuli

In the hydrodynamic mechanism, the displacement of dentinal fluids due to outward flow (by expansion) and inward flow (by contraction) stimulates the myelinated A-Delta fibres. This stimulation results in a fast, short and sharp pain.

Question 8

Describe pulpal pain and highlight the differences with dentine sensitivity.

Answer 8

Pulpal pain occurs due to an inflammatory process in the pulp. It involves unmyelinated C-alpha fibres that cause a delayed, lingering dull ache. There is an increase in pulpal pain in the evening due to increased arterial pressure associated with that time of day.

This is unlike the fast, short and sharp pain produced by the A-delta fibres in dentine sensitivity.

Question 9

How does the dental pulp change as a person ages?

Answer 9

• Reduced pulp volume and cell number
• Reduced nerves and blood vessels
• Decreased dentine permeability
• Decreased ability for repair