Dull, aching, poorly localised pain is transmitted by which fibres?

Correct answer: B. Unmyelinated C fibres

• A. A-beta fibres carry touch, pressure and vibration, not pain.
• B. Correct. C fibres are small and unmyelinated, so they conduct slowly. They carry the second wave of pain — dull, burning, throbbing and hard to localise, characteristic of pulpal inflammation.
• C. A-alpha fibres are the largest, serving proprioception and motor function to skeletal muscle.
• D. A-delta fibres are thinly myelinated and fast. They carry sharp, well-localised first pain, including the response to cold testing.

Note: Clinically useful: sharp pain that stops when the stimulus is removed suggests A-delta and reversible pulpitis, while lingering dull pain suggests C-fibre involvement and irreversible pulpitis.