The following nerve fibers are responsible for pain of pulpal origin:
A Delta Fibers:
- Largest diameter 3 to 20 mm
- Faster conducting up to 100 m/s
- Responsible for localized, sharp dentinal pain
Electric pulp tester stimulates A delta fibres first because of their lower threshold.
- Smallest diameter 0.5 to 1 mm
- Slow conducting 0.5 to 2 m/s
- Responsible for dull and throbbing pain
Thermal, chemical or mechanical stimuli stimulate “C” fibers resulting in dull, poorly, localized and throbbing pain.
NOTE: As the intensity of stimulus is increased along with A delta fibres , some of the C fibres also get stimulated resulting in strong unpleasant sensation.