Inflammation and dental pain in man

In the present article special interest has been focused on indicators of latent and manifest pulpal inflammation studied by psychophysical and electrophysiological techniques. Intradental A-delta nerve activity was recorded from two electrodes placed in the dentin on the labial tooth surface. The psychophysical measures were obtained by means of direct scaling methods in combination with sensory verbal descriptors. For stimulation cooling (ethyl chloride) and heating (hot guttapercha) of the tooth surface were employed. In addition, potentially algogenic substances, bradykinin and histamine, were administered on partly exposed pulps. Hot guttapercha induced a more complex neural response pattern than ethyl chloride. In all the recordings the responses evoked by heat showed a characteristic pattern consisting of three phases: an initial phase of short duration (i) followed by a depression in activity relative to the baseline (ii) and a slow spontaneously emerging activity in the absence of a physical stimulus (iii). The latter neutral event (iii) passed unnoticed by all the subjects. In the light of earlier experiments on feline pulp it was hypothesized that this third phase of the neural response was an indication of hyperexcitability in dental pulps and thus inflammation. Those subjects who experienced pulsating, dull, lingering pain (clinically diagnosed as pulpitis) showed a poor correlation between magnitude estimates of their mixed pain percepts and the total flux of A-delta nerve activity. Bradykinin and histamine evoked dull pain in the majority of cases probably caused by excitation of pulpal C fibers. In one experiment A-delta neural discharge of short duration could also be triggered by histamine.(ABSTRACT TRUNCATED AT 250 WORDS)