Changes in tooth pulpal detection and pain thresholds in relation to jaw movement in man

The effect of jaw movements on pulpal sensory thresholds to electrical stim ulation was studied in healthy humans. The movements consisted of repeated jaw opening and closing at two different frequencies (1 and 3 s(-1)). The d etection/perception and pain thresholds of an upper or lower central inciso r were determined by stimulation with monopolar constant current pulses at two different durations (0.5 and 5.0 ms). In the absence of jaw movement, t he control (baseline) pain threshold was significantly higher than the dete ction threshold, and both thresholds were significantly decreased with an i ncrease of the stimulus pulse duration. During jaw movement, pulpal detecti on and pain thresholds were significantly elevated, independent of the dura tion of the stimulus pulse. The jaw movement-related increase in detection thresholds was significantly dependent on the rate of cyclical jaw movement s and on the site of stimulation. An increase in pulpal sensory thresholds was observed with stimulation of the lower incisor only; there was no chang e in thresholds for the upper incisor. Pulpal detection thresholds were sig nificantly more elevated during jaw movement than pulpal pain thresholds. T he results indicate that the reduction in pulpal sensitivity is related to the jaw movements. The effect of jaw movement on pulpal detection threshold s was segmentally restricted. In contrast, modulation of the pulpal pain th resholds was considerably weaker. The jaw movement-related suppression of p ulpal sensitivity may be explained by activation of segmental afferent-indu ced inhibition, corollary efferent barrage from motor to sensory areas, or a combination of both. (C) 2000 Elsevier Science Ltd. All rights reserved.