Characteristics and clinical application of a surface array electrode for recording masticatory muscle motor unit action potentials

To date, a number of needle electrodes have been used to measure motor unit action potentials (MUAPs) during masticatory muscle activity. On the other hand, surface electrodes are non-invasive and simple to use, but it is necessary to analyze recorded composite wave data to determine MUAPs. Herein, we describe an improved non-invasive surface electrode with improved capability for capturing masticatory muscle MUAP. We investigated the characteristics and clinical application of this electrode. Surface array electrodes comprised silver–silver chloride electrode poles (1 mm in diameter and 5 mm in length) fixed by silicon, which were smaller than previous surface array electrodes. The electrode potential and the impedance measured in physiological saline at 25 °C were 69 mV (stable over time) and 415 Ω, respectively. The MUAP was measured in a human masseter muscle using this electrode, and was found to be fairly constant over time. Thus, the electrode fulfilled the criteria necessary for measuring MUAPs.