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Oral biology > D11 - Sensations from teeth > Flashcards

D11 - Sensations from teeth Flashcards

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1
Q

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

A

periodontal ligament

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2
Q

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

A

dentine/pulp, periodontal ligament

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3
Q

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

A

gingiva, dentine/pulp

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4
Q

what are the pain receptors?

A

nociceptors

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5
Q

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

A

electric current and heating/cooling

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6
Q

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

A
  • mechanical
  • drying
  • hypertonic solution
  • hydrostatic pressure
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7
Q

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

A

No pain- enamel and dentine

Pain - pulp

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8
Q

Describe pain in enamel.

A

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

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9
Q

Describe pain in dentine.

A

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

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10
Q

Describe pain in pulp.

A

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

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11
Q

What percent of pulpal innervation are non-myelinated?

A

70-80%

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12
Q

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

A

– 90% Ad (1-6m diameter)

– 10% are AB (6-12m diameter)

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13
Q

where is the plexus of raschkow found?

A

Cell free zone

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14
Q

where is the marginal plexus found?

A

around odontoblast and into dentine

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15
Q

what is the key clinical relevance of pulpal innervation?

A

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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16
Q

Describe the innervation of the pulp.

A

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

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17
Q

Describe the innervation of the dentine.

A
  •  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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18
Q

Describe pulpal pain.

A

- 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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19
Q

What are the 3 theories of dentinal sensitivity?

A
  • Dentine is innervated - nerves activate the dentine directly
  • Odontoblast receptor theory - odontoblast act as receptor cell
  • Hydrodynamic theory - fluid movement
20
Q

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

A

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

21
Q

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

A

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

22
Q

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

A

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

23
Q

Describe the tubules at the ameldodentinal junction.

A

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

24
Q

Describe the tubules at the predentine.

A

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

25
Q

Comment on the innervation of dentine.

A

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

26
Q

Describe the odontoblast receptor theory.

A
  • Stimulus transduction via the odontoblast process

- communication between odontoblast and primary afferents

27
Q

What is the problem with the odontoblast receptor theory.

A

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

28
Q

what do human odontoblasts express?

A

-Human odontoblasts express functional thermo-

sensitive TRP channels: implications for dentin sensitivity

29
Q

what TRP channels are foundi in odontoblasts.

A
  • TRPV1
  • TRPA1
  • TRPM8
30
Q

what do TRPVs seen in nerves respond to?

A

hot and cold -thermal stimulus

31
Q

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

A

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

32
Q

Describe the outflow of hydrodynamic theory.

A
  • cooling
  • drying
  • evaporation
  • hypertonic solutions
  • decreased hydrostatic pressure
33
Q

why are nerve more sensitive to outwards fluid flow?

A

Nerves may contain stretch sensitive ion channels

34
Q

what happens when nerves become stretched with outward flow?

A

causing increase ion channels leaving them susceptible

35
Q

Describe the inward flow of hydrodynamic theory.

A
  • heating
  • mechanical
  • increased hydrostatic pressure
36
Q

what happens when nerve cells are compressed?

A

distorting cells and causing pain

37
Q

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

A
  • increased cold sensitivity but

- decreased outward fluid flow on cooling

38
Q

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

A
  • decreased cold sensitivity but

- increased outward fluid flow on cooling

39
Q

what may cold sensitivity not be mediated by?

A

hydrodynamic mechanism

40
Q

what nerves are involved in the hydrodynamic theory?

A

– Unmylelinated endings of Ad and AB fibres

– (C-fibres for pulpal pain)

41
Q

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

A

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

42
Q

what happens if odontoblasts are stretched?

A

release ATP

43
Q

Give examples of pain from high restorations.

A
  • -High intra-coronal restoration e.g filling

- High cusp coverage intra-coronal restoration

44
Q

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

A

-High cuspal coverage restoration :no pain on biting

45
Q

where is pain likely to come from?

A

dentine and not PDL

46
Q

What is the Dahl effect?

A

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

Oral biology (29 decks)

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