dentine sensivity physiology and pathology

Question 1

pain producing stimli intact tooth

Answer 1

Heating
- above 45 degrees
Cooling
- below 27 degrees

Question 2

pain producing stimuli with enamel removed

Answer 2

1) Mechanical stimuli eg using a probe
2) drying
- air
- responds to dry but not moist absorbent paper
3) hydrostatic pressure
4) thermal stimuli
5) Chemical stimuli
- algesic substances (no pain, compared to skin which will produce pain)
- concentrated sugar solutions (pain caused, related to osmotic pressure)
- topical application of local anaesthetic (no effect on dentine sensitivity, topical application of local anaesthetic)

Question 3

nerves in the inner dentine and outer dentine

Answer 3

odontoblast cell processes
outer
- odontoblast cell processes 
extend through dentinal tubules from pulp to ADJ
not very innervated or sensitive

Question 4

classes of interdental afferent neurones

Answer 4

cold sensitive neurones

heat sensitivie neurones

Question 5

effect of smearlayer and what removes it

Answer 5

layer produced when dentine is cut
smear layer covers tubules blocking them
can cover dentine surface
acid etching removes the smear layer

Question 6

aetiology for dentine hypersensitivt

Answer 6

1) enamel erosion
2) recession
- exposing tubules in the dentine
3) viability of cementum
- i.e. exposed tubules

Question 7

treatment of dentine sensivity aims

Answer 7

1) Reducing dentine permeability
- i.e. reduce how many tubules are exposed
- and reduce diameter of tubules to less than a micro
2) Altering the ionic environment in the tubules
- stop fluid being displaced to prevent nerve activation
- i.e. diminish neurotransmision

Question 8

ways to treat dentine sensitivity

Answer 8

1) Management
- reduction of erosion dietary intake
- gentle brushing
2) Desentisity toothpastes
- arginine
- strontium chloride
- stannous fluoride
- Ca Na phosphsilicate
3) Others (insufficient evidence)
- calcium oxalate
- casein derivatives
- Potassium chloride, citrate, nitrate (depolarised nerve fibres and stops repolarising)
4) Professionally applied agents
- resins (seal surface), varnishes, lasers (fuse tubules by coagulating proteins)

Question 9

types of pulpal damage

Answer 9

mechanical

chemical

Question 10

what happens after severe pulpal injury

Answer 10

Nerve fibres proliferate

• odontoblasts distorted, nerve stretched and stimulated (no correlation with pain and nerve density)
• Odontoblast release NGF on stimulation (6hrs after cavity preparation)
• nerves have other functions under pathological conditions than pain in tooth pulp: role in pulpal healing, chemotactant, protective

Question 11

different injuries to the tooth pulp and what occurs after them

Answer 11

Coronal injury
- aspiration of odontoblast
- nerves survive operative procedures and placement of materials
Cervical injury
- calcitonin gene related peptide (CGRP) fibres proliferate after cervical injury
- Relates to developing sensitivity after injury
Local pulpitis
- large areas of SP and CGRP containing fibres sprout near injury site
- tertiary dentine forms
Irreversible pulpitis (necrosis)
- CGRP and sprouting at interface between vital and non vital tissue