what is the dental pulp
the connective tissue ‘core’ of the tooth
what does the dental pulp contain
cells extracellular components nerves blood vessels lymphatics
what are the cells in the dental pulp
odontoblasts
fibroblasts
defence cells
what are the extracellular components of pulp
fibres (collagen, oxytalan)
matrix (proteoglycans, chondroitin SO4, dermatan SO4)
what are the nerves of the pulp
sensory autonomic (sympathetic)
what are the functions of the dental pulp
nutritive (blood vessels) dentine growth dentine repair defence neural
what is the function of the neural function of the dental pulp
sensory - pain - everything is felt as pain
control of dentinogenesis
what are the 3 types of links between dentine and pulp
developmental
structural
functional
what is the developmental link between dentine and pulp
they both develop from the dental papilla
what is the structural link between dentine and pulp
some plural elements extend into dentine
what pulpal elements extend into dentine
- Odontoblast processes
- Nerve terminals
- Immune cells (dendritic cells)
- Dentinal fluid
what are the functional links between dentine and pulp
formation of secondary dentine
formation of tertiary dentine in response to tooth wear (reactionary and reparative dentine)
regulate exchange of material between dentine and pulp
describe the hemodynamics and hydrodynamics of the pulp
fluid leaks from pulp capillaries into interstitial space due to pressure
fluid passes along dentinal tubules resulting in dentinal fluid
flow of dentinal fluid is proportional to pulp pressure
believed to have defence role
what are the different ways tooth wear can happen
o Mastication (abrasion) o Bruxism (attrition) o Abfraction (occlusal overload leads to fractures and cervical lesions) o Diet (erosion) o Caries – pathological o Operative procedures
how can operative procedures result in tooth wear
Occlusal equilibrium (used to cut teeth to give individuals a better occlusal arrangement)
Cavity cutting; crown preparation etc – if this reaches dentine then this can cause a reaction
when is tertiary dentine formed
When you expose the dentine you may create a reaction of the dentine-pulp complex to produce dentine, this dentine is referred to as tertiary dentine
what is reactionary dentine
It is in response to mild stimulus
The response is mild and the dentine is laid down by primary odontoblasts
what is reparative dentine
It is in response to intense stimulus that has destroyed the primary odontoblasts
It is laid down by secondary odontoblasts (stem cells)
what can the odontoblast layer be considered as
a permeability barrier
separates the pulp and tubular space
regulates movement of material between the 2 - movement may be in either direction
what materials move from the pulp to the dentine
nutrients, to sustain cells
formation of secondary and tertiary dentine
potassium needed for function of tubular nerves
what materials move from dentine to pulp
medicaments applied to dentine
diffusion of toxins from bacteria, components of filling materials
what nerves supply the pulp
alveolar nerve
describe the anatomy of the pulp nerves
Neurovascular bundles enter pulp via the apical foramen and pass along the root canal in the center of pulp towards the coronal pulp chamber
The branches fan out in the sub-odontoblastic layer to form plexus of Raschkow
Terminal branches enter the odontoblast layer, some nerves enter the dentinal tubules
what % of tubules under cusps contain nerves
40%
why do more cusp tubules have nerves
cusp tubules have more as they have a sensorial function, a monitory system inside the tooth to generate a response if there is more tooth wear, stimulating the pulp to form tertiary dentine
how far do axons extend in the cusp tubules
100-200 nanometres
what is the % of tubular innervation in coronal dentine
15
what is the % of tubular innervation in root dentine
4
what is name of the mechanism for activating interdental sensory nerves
hydrodynamic mechanism
where do most axons end in coronal and root dentine
pulp-predentine region
what is the hydrodynamic mechanism
- Stimulus (thermal, mechanical, evaporative, chemical) acts on exposed dentine (open tubules)
- This increases the rate of dentinal fluid flow
- This causes the generation of action potentials in intra dental nerves
- These action potentials pass to the brain to cause pain
what are the two directions of dentinal fluid flow
outward
inward
what causes outward fluid flow
cooling, drying, evaporation, hypertonic solutions, decreased hydrostatic pressure
what causes inward fluid flow
heating, mechanical, increased hydrostatic pressure
what type of fluid flow is more effective at activating intradentall nerves and why
outward
outward movement stretches the axons causing generation of an action potential
what stimuli bypass the hydrodynamic mechanism and act directly on the interdental nerves
intense heating
intense cooling
electrical current
pain-producing chemicals
how can high fillings cause dentinal pain
force distorts the dentine and alters tubular flow
what do Abeta and Adelta fibres do
activated by hydrodynamic stimuli applied to dentine
probably mediate normal dentinal sensitivity
what do c fibres do
o Probably activated directly by stimuli, rather than hydrodynamic mechanism
o They respond to most forms of intense stimuli
o Probably mediate pain associated with pulp inflammation (e.g caries)
what is the blood supply to teeth
branches of the maxillary artery
what is pulp blood flow controlled by
local factors
nerves
circulating hormones
drugs
what can use of an uncooled bur with high speed motor cause
irreversible damage to the pulp as it can dramatically reduce blood flow and so benefits of the circulation will be eliminated which starves the pulp causing it to inflame
what does pulp infammation result in
causes an increase in pressure due to swelling but there is no room to expand unlike normal tissue where there is expansion.
The pulp cannot swell due to constraint and so the ability of exchange of nutrients will be effected ultimately causing necrosis
what are the function of the pulp nerves
sensory control of pulp blood vessels promote neurogenic inflammation promote dentine formation facilitate immune response
what is the immediate dentine pulp response to injury
Nociceptor activation – pain
what is the response to injury after 1 minute
Early inflammatory response
Vasodilation
what is the response to injury after 10 minutes
Nociceptor sensitization
Extravasation of fluid, oedema
Polymorph migration
what is the response to injury after 100 minutes
Enzyme activation
Monocyte presence
what is the response to injury after 1 day
Nerve sprouting (NGF)
Increased axonal transport
Altered excitability of CNS synapses
what is the response to injury after a week
Repair; tertiary dentine formation
describe pulpitis
acute inflammation in the dental pulp is similar to that in other tissues except that the pulp cannot swell as it is confined to the pulp chamber
oedema causes an increase in pulp pressure
this can have variable effects on blood flow and on nerve excitability
