methods of determining pulp vitality

Question 1

vitality

Answer 1

• relating to, accompanying or characteristic of life inherent or exhibited by living things or organic bodies

Question 2

ideal characteristics of pulp tester

Answer 2

1) Must be effective on both anterior/posterior teeth (single/multirooted)
2) Must be effective if the tooth is carious or if it has been restored
3) must be effective when secondary dentine has been deposited
4) Must be effective in unusual circumstances (reimplanted/transplanted teeth)

Question 3

current methods of vitality testing

Answer 3

1) Test if integrity of innervation
- electrical stimuli
- thermal stimuli (cold ethyl chloride, hot utta percha)
2) Tests of integrity of blood flow
- Uv light photograpjy
- oximetry/photoplethysmography
- laser-doppler flowmetry

Question 4

difficulties in pulp testing

Answer 4

1) Pulp is in an enclosed chamber making access difficult
2) pulp chamber is practically opaque (n.b dentinal tubules)
3) electrical resistance (impedance) varies widely
4) Pulp size diminished due to secodnayr dentine

Question 5

false positive

Answer 5

• when pulp testing indicated that the tooth is vital, when it is not
  False negative

Question 6

false negative

Answer 6

• when pulp testing indicated the tooth is non vital when it is vital

Question 7

how do electrical pulp testers work

Answer 7

Electrical pulp testers directly activate pulpal nerve fibre (bypass receptors)

• pulp testers achive this by deplorasing pulpal nerve fibre, so that they generative action potentials
• For a nerve fibre to be depolirsed electrical current ahs to flow into it
• But most pulp testers generate voltage pulses, not current pulses
• therefore the electrical resistance of the tooth (impendace) is important

Question 8

thermal testing examples

Answer 8

Heat
- hot gutta percha
- sticks to teeth when surface dry – use Vaseline
- difficult to control temperature
Cold
- Ethyl chloride spray (evaporative cooling)
- Apply with cotton wool pledget to single tooth
- avoid soft tissues
- better than electrical

Question 9

how do laser doppler flow meters work

Answer 9

• Opitcal fibre directs infra red light to the tissue to be studies
• light scattered by moving cells undergoes a 4kHz change in frequency (doppler shift)
• light that is scattered by moving objects (blood cells) mixes with light that has been scattered by stationary objects, resulting in beating
• greater no of moving cells greater intensity of beating
• a second fibre collects the light which is analysed by a photodetector to produce an estimate of blood flow

Question 10

problems with laser doppler methods

Answer 10

• Signal produced is not in absolute units, it is the product of the number of cells scattering the light an their velocity
• the flux signal is only linear if the volume fraction of red cells in the tissue is less than 1%
• in humans there is considerable gingival and periodontal contamintion of blood flow signal recorded from a tooth
• cost is 10k upwards