D11 - Sensations from teeth Flashcards by Emma Williams

What is the site of receptors for the sensation of touch for teeth?

periodontal ligament

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What is the site of receptors for the sensation of pain for teeth?

dentine/pulp, periodontal ligament

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What is the site of receptors for the sensation of cold for teeth?

gingiva, dentine/pulp

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what are the pain receptors?

nociceptors

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what stimulus causes in pain in all enamel , dentine and pulp?

electric current and heating/cooling

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what stimulus have a no pain effect on enamel but cause pain in dentine and pulp?

mechanical
drying
hypertonic solution
hydrostatic pressure

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what effect does alogenic chemicals have on enamel , dentine and pulp?

No pain- enamel and dentine

Pain - pulp

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Describe pain in enamel.

short, sharp pain in a healthy tooth (delta fibres)

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Describe pain in dentine.

short, sharp pain in a healthy tooth (delta fibres)

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Describe pain in pulp.

Long, dull ache ( more likely to be c fibres )

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What percent of pulpal innervation are non-myelinated?

70-80%

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what makes up the other 20-30% of myelinated fibres?

– 90% Ad (1-6m diameter)

– 10% are AB (6-12m diameter)

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where is the plexus of raschkow found?

Cell free zone

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where is the marginal plexus found?

around odontoblast and into dentine

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what is the key clinical relevance of pulpal innervation?

Nerves branch to supply >1 tooth pulp – difficult to localise dentinal/pulpal pain
(1 axon will branch - patient cant distinguish where source of pain is. pain from dentine and pulpal origin is very difficult to find where cause is)

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Describe the innervation of the pulp.

Dense innervation, extensive branching of axons:
– Myelinated: Aβ and Aδ
– Unmyelinated: c – including sympathetic vasomotor

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Describe the innervation of the dentine.

 Nerves extend 100μm into some tubules (don’t go into tubule v far)
 Mainly over pulp horns
 <0.2μm diameter
 Probably unmyelinated terminals of myelinated axons  -functional contacts with Odontoblasts

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Describe pulpal pain.

- Neurones activated + sensitised by inflammatory mediators
- Substance P:
> axon reflex
> 100x increase in SP in inflamed teeth
> 1000x increase in SP in irreversible pulpitis
> Enhances activity of TRP1 and P2X3 nociceptors
- C-fibres

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What are the 3 theories of dentinal sensitivity?

Dentine is innervated - nerves activate the dentine directly
Odontoblast receptor theory - odontoblast act as receptor cell
Hydrodynamic theory - fluid movement

what is the percentage of tubules containing nerves in the pulp horn?

pre-dentine - 27-85%
Inner 1/3 - 10%
Outer 2/3 - 0%

what is the percentage of tubules containing nerves in the cervical margin?

pre-dentine - 7%
Inner 1/3 - 2%
Outer 2/3 - 0%

what is the percentage of tubules containing nerves in the root?

pre-dentine - <7%
Inner 1/3 - 0%
Outer 2/3 - 0%

Describe the tubules at the ameldodentinal junction.

Tubules per mm2 - 15000-20000
tubule diameter (microns)-0.5-1.0
Tubule separation (microns)- 15.0
% of surface occupied by tubules - 4%

Describe the tubules at the predentine.

Tubules per mm2 - 45000-65000
tubule diameter (microns)-2.0-3.0
Tubule separation (microns)- 6.0
% of surface occupied by tubules - 28%

Comment on the innervation of dentine.

Dentine is highly innervated but the nerve just don't go very far into dentine

Describe the odontoblast receptor theory.

- Stimulus transduction via the odontoblast process | - communication between odontoblast and primary afferents

What is the problem with the odontoblast receptor theory.

– No evidence of electrical, communication chemical synapses between odontoblast and nerve – Odontoblast process likely only extends 1/3 into dentine

what do human odontoblasts express?

-Human odontoblasts express functional thermo- | sensitive TRP channels: implications for dentin sensitivity

what TRP channels are foundi in odontoblasts.

- TRPV1 - TRPA1 - TRPM8

what do TRPVs seen in nerves respond to?

hot and cold -thermal stimulus

Hydrodynamic theory ; what effect do stimuli that cause pain when applied to dentine have?

– Increase fluid flow in dentine in vitro – Generate action potentials in intradental nerves in vivo – Action potential rate linked to fluid flow

Describe the outflow of hydrodynamic theory.

- cooling - drying - evaporation - hypertonic solutions - decreased hydrostatic pressure

why are nerve more sensitive to outwards fluid flow?

Nerves may contain stretch sensitive ion channels

what happens when nerves become stretched with outward flow?

causing increase ion channels leaving them susceptible

Describe the inward flow of hydrodynamic theory.

- heating - mechanical - increased hydrostatic pressure

what happens when nerve cells are compressed?

distorting cells and causing pain

what is the result of open dentinal tubules by acid etch?

- increased cold sensitivity but | - decreased outward fluid flow on cooling

what is the result of occlusion of tubules with oxalate salts?

- decreased cold sensitivity but | - increased outward fluid flow on cooling

what may cold sensitivity not be mediated by?

hydrodynamic mechanism

what nerves are involved in the hydrodynamic theory?

– Unmylelinated endings of Ad and AB fibres | – (C-fibres for pulpal pain)

How does fluid flow result in action potentials in pulpo-dentinal nerves?

– Stretch sensitive ion channels in nerve endings • ASIC3 Channels – ATP released from odontoblasts • P2X3 ATP receptors

what happens if odontoblasts are stretched?

release ATP

Give examples of pain from high restorations.

- -High intra-coronal restoration e.g filling | - High cusp coverage intra-coronal restoration

Give an example of a restoration that causes no pain on biting.

-High cuspal coverage restoration :no pain on biting

where is pain likely to come from?

dentine and not PDL

What is the Dahl effect?

back teeth over erupt and regain occlusion but with space between front teeth - allows restorations to be done that are high