Changes in cortical negative potential associated with local anesthetization of apex of tooth root

Abstract

To determine whether cortical negative potential (hereafter referred to as CNP), which was recorded from the scalp (sites: T3, CZ and T4), preceding the right-side chewing is affected by input from the periodontal membrane, the CNP and pattern of the appearance of masseter electric discharge before the anesthetization of the apex of the tooth root and those after the anesthetization were compared. 1) CNP preceding the right-side chewing appeared at T4 early both before and after the anesthetization and showed a maximum amplitude immediately before masseter electric discharge. CNP duration and amplitude increased after the anesthetization as compared with those before the anesthetization.2) The initial increase in electromyogram associated with chewing became sharper after the anesthetization than before the anesthetization. From these findings, that the cerebral cortex is in a preparatory state at an early stage when the sensation in the periodontal membrane on the chewing side is blocked, and that, as a consequence, strong chewing is produced.recorded from an outside lateral area corresponding to hand motor function. However, they observed CNP only in one hemisphere, and did not investigate the distribution of CNP appearance in the entire brain in detail.Nakajima et al. 1,2) compared the distributions of CNP appearance ipsilateral and contralateral to the chewing side and reported that the ipsilateral distribution of CNP appearance is predominant. Tanaka et al. 3) recorded the topography of CNP from electrodes placed at 12 sites of the scalp and reported that CNP for the chewing motion is localized to the temporal area ipsilateral to the chewing side 50 to 70 ms before the start of masseter electric discharge.On the other hand, the chewing motion functions to crush food voluntarily 18) . It is easily conceivable therefore that one's sensation of the periodontal membrane has a great effect on one's occlusion force and chewing force depending on one's dental