Surface Electromyographic Evaluation of the Asymptomatic Human Masseter Muscle with Turns and Amplitude Analysis

ABSTRACT

Electromyographic turns, or reversals of direction, per second (TS) and mean amplitude per turn (AT) are variables that have been widely used to assist and support an electrodiagnosis in neuromuscular disorders. The purpose of this study was to explore the feasibility of utilizing the TS and AT in conjunction with surface electrodes as a method for assessing masticatory muscle function. Ten normal subjects were instructed to exert brief isometric contractions at various levels, and the TS and AT were calculated from the surface electromyographic signals of the masseter muscle. Our results showed that the AT increased with contraction at all contraction levels, demonstrating a linear relationship, while the TS showed a nonlinear increase characterized by an initial steep rise followed by a plateau, which was simulated with a third polynomial function. It is considered that the TS and AT may provide valuable physiological information about the underlying mechanisms of recruitment and the firing of motor units.

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Notes on contributors

Koji Kashima

Dr. Koji Kashima received his D.D.S. degree from Kyushu University Faculty of Dentistry in 1987 and Ph.D. degree from Miyazaki Medical College in 1998. He is now an assistant professor at the Department of Oral and Maxillofacial Surgery, Miyazaki Medical College, Miyazaki, Japan.

Omar Ibna Faizur Rahman

Dr. Omar Ibna Faizur Rahman received his B.D.S. degree from Dhaka Dental College in Bangladesh in 1989 and Ph.D. degree from Miyazaki Medical College in 1999. He is now a visiting researcher at the Department of Oral and Maxillofacial Surgery, Miyazaki Medical College, Miyazaki, Japan.

Sumio Sakoda

Dr. Sumio Sakoda received his D.D.S. degree from Kyushu Dental College in 1972, and Ph.D. degree from the same school in 1976. He is currently an associate professor at the Department of Oral and Maxillofacial Surgery, Miyazaki Medical College.

Ryosuke Shiba

Dr. Ryosuke Shiba received his D.D.S. degree from Osaka University Faculty of Dentistry in Osaka, Japan, in 1963, and Ph.D. degree from the same university in 1967. He is currently a professor and a chairman of the Department of Oral and Maxillofacial Surgery, Miyazaki Medical College.