A quantitative electromyographic analysis of masticatory muscle activity in usual daily life.
OBJECTIVE
This study was designed to investigate whether a quantitative electromyographic (EMG) analysis with a special reference to the EMG amplitude at 98N bite force could reduce the influence of electrode relocation and to examine the reproducibility of masticatory muscle activity in usual daily life within individuals.


METHODS
In the first experiment, two sessions of surface EMG recording for masseter and anterior temporal muscles during tapping, and chewing gum and marshmallow were performed for 10 subjects with an interval of at least 1 week with electrode relocation. In the second experiment, two sessions of EMG recording during daytime (142 min, including mealtime) and sleep (142 min) were carried out for 10 subjects with an interval of at least 1 week. The average rectified EMG values were normalised with a special reference to the EMG amplitude induced by a 98N bite force.


RESULTS
In the first experiment, high correlation coefficients and no significant differences in the mean normalised values of muscle activity were found between two sessions. Although the average rectified values showed high correlation coefficients, the mean masseter muscle activity while chewing gum was significantly different between two sessions. In addition, the variation in temporal muscle activity between two sessions while chewing gum was significantly smaller in the normalised values than in the average rectified ones. In the second experiment, less intra-individual variation in the normalised values of masticatory muscle activity between two sessions indicated the reproducibility. Normalised masticatory muscle activity showed less variation during mealtimes than during usual daytime and sleep.


CONCLUSIONS
This quantitative EMG analysis could estimate the masticatory muscle activity by reducing the influences of electrode relocation, demonstrating an availability of this analysis for the evaluation of masticatory muscle activity in usual daily life.
Saifuddin
M
M
Department of Orthodontics, Hiroshima University Faculty of Dentistry, 1-2-3 Kasumi, Minami-ku, Hiroshima 734-8553, Japan. milm@hiroshima-u.ac.jp
Miyamoto
K
K
Ueda
H M
HM
Shikata
N
N
Tanne
K
K
D000203:Activities of Daily Living; D000328:Adult; D000704:Analysis of Variance; D001732:Bite Force; D002182:Candy; D002638:Chewing Gum; D002940:Circadian Rhythm; D004435:Eating / Q000502:physiology; D004576:Electromyography; D005260:Female; D006801:Humans; D008297:Male; D008406:Masseter Muscle / Q000502:physiology; D008409:Mastication / Q000502:physiology; D008410:Masticatory Muscles / Q000502:physiology*; D010474:Percussion; D015203:Reproducibility of Results; D012815:Signal Processing, Computer-Assisted; D012890:Sleep / Q000502:physiology; D013223:Statistics as Topic; D013703:Temporal Muscle / Q000502:physiology
D002638:Chewing Gum