Spatial summation of pre-pain and pain in human teeth.
The purpose of this work was to investigate the relation between the sensations of pain and 'pre-pain' evoked by stimulation of teeth in human subjects. Electrical pulses of progressively increasing amplitude, generated by a computer-controlled stimulator, were applied to 1 or 2 teeth, and the subjects responded by indicating the nature of the resulting sensation. Pre-pain and pain could be readily and rapidly distinguished by all 11 subjects (response latency about 0.4 sec). Both sensations had stable thresholds with relatively small variance (S.D. 10-15% of threshold value) for a given subject. Subjects characterized the stimuli as indifferent or unpleasant, localized, and brief. By using special stimulation strategies (termed 'optimal trajectories') for exciting 2 teeth simultaneously, spatial summation for pre-pain was demonstrated in most subjects and for pain in almost all subjects. Spatial summation of pre-pain resulted in pain rather than in more intense pre-pain. These results are consistent with both the dual modality (separate afferent fibers for pre-pain and pain) and the single modality hypotheses (single type of afferent fibers) of tooth pulp sensibility, but favor single modality innervation.
D000328:Adult; D000344:Afferent Pathways; D001339:Autonomic Fibers, Preganglionic / Q000502:physiology; D004558:Electric Stimulation; D005260:Female; D006801:Humans; D008297:Male; D009412:Nerve Fibers / Q000502:physiology; D010146:Pain / Q000503:physiopathology*; D012677:Sensation; D012684:Sensory Thresholds; D014070:Tooth / Q000294:innervation / Q000502:physiology*