Dental pulp neurophysiology: part 1. Clinical and diagnostic implications

Diagnosis in endodontics requires an understanding of pulpal histology, neurology and physiology, and their relationship to the various diagnostic tests commonly used in dental practice. Thermal changes in the oral environment cause rapid displacement of dentinal tubular contents, resulting in pain. This effect, known as the hydrodynamic effect, is the regulator of pain sensation in thermal-pulp testing. Hundreds of axons enter the tooth from the apical foramen to provide it with its sensory supply. The nerve supply of the dentin-pulp complex is mainly made up of A fibres (both delta and beta) and C fibres. They are classified according to their diameter and their conduction velocity. The A fibres are mainly stimulated by an application of cold, producing sharp pain, whereas stimulation of the C fibres produces a dull aching pain. Because of their location and arrangement, the C fibres are responsible for referred pain. This first part of a 2-part review examines the relation between clinical sensations during the diagnostic visit and the neurophysiology of the dental pulp to explore the connection between the art (clinical diagnosis) and the science (neurophysiology) of endodontics.