Electrophysiological study on tooth-grinding during sleep

Abstract In order to gain an insight into the central mechanism of tooth-grinding (TG) during sleep, polygraphic recordings were performed on fifteen tooth-grinders. Two hundred and ninety-one episodes of spontaneous TG and 34 episodes of artificially induced TG were observed. The TG commenced at any stage of sleep, but mainly during light sleep. It seldom occurred during deep slow wave sleep, and never during rapid eye movement (REM) bursts of REM sleep. It sometimes occurred on the background of recurring α-waves in drowsy subjects. The termination of TG was usually followed by a sleep stage lighter than that before the episode, and never by a deeper sleep. The episodes of TG were frequently preceded by a K-complex and followed by α-waves. Vasoconstriction of the finger tip and tachycardia were the invariable concomitants of TG. Skin potential changes on the forearm and, less frequently, on the palm were often associated with TG. These changes in the sympathetic activity preceded, in general, the onset of TG. The H-wave was strikingly depressed in amplitude or completely abolished during TG as well as during gross body movements unassociated with TG. Signs of lightening of sleep without gross muscular activities were, in contrast, associated with an increase in the H-wave amplitude. The episodes of TG which could be induced by giving arousing stimuli to sleeping subjects were identical in all their features to the spontaneous episodes. It was concluded that the TG is triggered by an abrupt lightening of sleep and manifests itself during transition from sleep to wakefulness; that is, it appears as an arousal reaction. The hypothetical neuronal mechanisms underlying TG were discussed.