title: Contribution of each masticatory muscle to the bite force determined by MRI using a novel metal-free bite force gauge and an index of total muscle activity.
abstract: To develop a metal-free bite force gauge that can monitor the bite force in a strong magnetic field and to analyze the correlations between bite-force and total T2 shift of the mastication muscles.
  
  
  
  The gauge used a micro-pressure sensor made of optical fiber. Ten subjects performed a 60-s isometric bite task at 40% of maximum clenching in various occlusal support conditions (intact dentition, right molar loss, or left molar loss). Spin-echo images were taken with a 1.5 Tesla scanner before and immediately after the task to correlate the bite force with the mean voxel count, mean shift in transverse relaxation time (ΔT2), and total T2 shift of each masticatory muscle.
  
  
  
  Measurements of total T2 shift identified significant correlations between the bite force and activities of the superficial layer of the bilateral masseter muscle, regardless of the occlusion condition (intact dentition: left, P = 0.007 and right, P < 0.001; right molar loss: left, P = 0.02 and right, P = 0.021; and left molar loss: left, P = 0.022 and right, P = 0.049). In contrast, significant correlations were not detected between the bite force and mean ΔT2 (intact dentition: left, P = 0.102 and right, P = 0.053; right molar loss: left, P = 0.393 and right, P = 0.868; and left molar loss: left, P = 0.531 and right, P = 0.92).
  
  
  
  Measurement of total T2 shift using a metal-free bite force gauge is a more sensitive index of individual muscle activity than mean ΔT2 during a bite task. J. MAGN. RESON. IMAGING 2016;44:804-813.
authors.affiliation: Division of Aging and Geriatric Dentistry, Tohoku University Graduate School of Dentistry, Sendai, Japan.
authors.forename: Minoru
authors.initials: M
authors.lastname: Takahashi
authors.affiliation: Division of Aging and Geriatric Dentistry, Tohoku University Graduate School of Dentistry, Sendai, Japan. s-yamaguchi@m.tohoku.ac.jp.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Yamaguchi
authors.affiliation: Division of Aging and Geriatric Dentistry, Tohoku University Graduate School of Dentistry, Sendai, Japan.
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Fujii
authors.affiliation: Division of Aging and Geriatric Dentistry, Tohoku University Graduate School of Dentistry, Sendai, Japan.|Kansei Fukushi Research Center, Tohoku Fukushi University, Sendai, Japan.
authors.forename: Makoto
authors.initials: M
authors.lastname: Watanabe
authors.affiliation: Division of Aging and Geriatric Dentistry, Tohoku University Graduate School of Dentistry, Sendai, Japan.
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Hattori
mesh_terms: D000328:Adult; D001732:Bite Force; D004867:Equipment Design; D019544:Equipment Failure Analysis; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000295:instrumentation* / Q000379:methods; D008297:Male; D008410:Masticatory Muscles / Q000502:physiology*; D055617:Micro-Electrical-Mechanical Systems / Q000295:instrumentation*; D009119:Muscle Contraction / Q000502:physiology*; D053580:Muscle Strength / Q000502:physiology*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013314:Stress, Mechanical
keywords: T2; bite force; masticatory muscles; muscle activity