Estimation of temporomandibular joint loading by use of measured values of occlusal force and time-integrated electromyogram

DOI 5 Citations 24 References
  • HOSOI Eiji
    Department of Oral and Maxillofacial Surgery, Nara Medical University
  • SHOHARA Etsuo
    Department of Oral and Maxillofacial Surgery, Nara Medical University
  • KAWAKAMI Tetsuji
    Department of Oral and Maxillofacial Surgery, Nara Medical University
  • TSUZUKI Masashi
    Department of Oral and Maxillofacial Surgery, Nara Medical University
  • MORIMOTO Yoshinari
    Department of Oral and Maxillofacial Surgery, Nara Medical University
  • TAKAYAMA Ken-ichi
    Department of Oral and Maxillofacial Surgery, Nara Medical University
  • SUGIMURA Masahito
    Department of Oral and Maxillofacial Surgery, Nara Medical University

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  • こう合力と積分筋電位の実測値を用い静力学的平衡式により試みた顎関節負荷算出法

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Abstract

Pathogenesis of the internal derangement or degenerative arthrosis of the temporomandibular joint (TMJ) is considered to be due to the TMJ loading condition. This report deals with the biomechanical method using pressure sensitive film (Prescale TM) to estimate TMJ loading which varies with jaw dimension, occlusion, muscular insertion, and chewing force of differnt individuals.<br>During biting, muscle force is in equilibrium with occlusal force and TMJ loading, where three eqilibrium equations can be given by considering the force balance in the direction vertical to the occlusal plane -(1), and the balance of moment around the axis passing the bilateral condylar heads -(2) and around the axis of the median line parallel to the occlusal plane. Since muscle force is assumed to be proportional to its time-integrated electromyogram (i-EMG) in the isometric contraction and the maximum muscle force is to be proportional to its cross section, the terms containing muscle force in the above equations can be replaced by the i-EMG readings multiplied by a constant ratio. By giving real EMG readings, moment of the occlusal points computed from Prescale recordings and anatomical data from the cephalogram, solving the equation (2) can determine the ratios which are constant for the muscle type. Muscle force by multiplying i-EMG heights by the obtained ratio, force and moment of the occlusal contact points recorded on a Prescale sheet and anatomical data further afford to give the value of TMJ loading of different biting at the centric occlusion by solving the simultaneous equations consisting of (1) and (3).<br>Estimation of TMJ loading in this report has also shown that the TMJ bears more loading on the side where greater muscle force is exerted.

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