Relationships between functional properties of masseter motor units and 3-D bite force

T. Ogawa, T. Kawata, A. Tsuboi, Y. Hattori, M. Watanabe, K. Sasaki

Research output: Contribution to journalReview articlepeer-review

Abstract

Objective: The human masseter muscle consists of several separate portions having different fiber directions. The aim of this study was to reveal the functional properties of the masseter motor units (MUs) related to 3-dimensional (3D) bite force and to clarify the hypothesis that contribution of human masseter MUs to bite force production is not uniform within the muscle. Methods: Subjects were 4 healthy men. MU activity of the right masseter was recorded using a Teflon-coated monopolar needle electrode in combination with a surface reference electrode. The location of the needle electrode was estimated stereo-tactically with the aid of MR images from the masseter with a reference plate. Magnitude and direction of the bite force was recorded with a custom-made 3-D bite force transducer. The recorded bite force was displayed on the signal processor, which enabled a subject to exert bite force in an arbitrary direction and magnitude. Results: Activities of 65 masseter MUs were investigated. Each MU fired in an individual range of the bite force direction (firing range: FR). The firing threshold varied depending on the direction. A specific direction in which an MU fired with a minimum firing threshold (MFT) was observed. There are functional differences in MU's properties between superficial and deep masseter and, furthermore, between superficial layer and deep layer in the superficial masseter. Conclusion: These findings indicate that contribution of human masseter MUs to bite force production is heterogeneous within the muscle.

Original languageEnglish
Pages (from-to)43-48
Number of pages6
JournalInternational Congress Series
Volume1284
DOIs
Publication statusPublished - 2005 Sep

Keywords

  • Bite force
  • Human masseter
  • Motor unit

ASJC Scopus subject areas

  • Medicine(all)

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