Development of a new mouth opening force test using an indirect cervical traction device

Yuji Koyama, Shin Ichi Izumi, Kazuo Sakaizumi, Minoru Toyokura, Akira Ishida

Research output: Contribution to journalArticlepeer-review

3 Citations (Scopus)


Background and Aims: There have been few reports of objective jaw opening tests, and such studies have involved devices specifically designed for research. In the present study, in order to conveniently and objectively assess mouth opening movements, we replaced the manual resistance used in Daniels and Worthingham's muscle test (DMT) with an indirect cervical traction device. We examined whether the maximum mouth opening force (MOF) could be reliably quantified using this device. Methods: The subjects were 12 healthy individuals with a mean age of 28.8 years. The MOF measurement procedure was as follows: 1) the subject sat in the chair, and a head belt was placed under the chin so that a traction force was applied almost parallel to the body axis; 2) the researcher instructed the subject to maintain the maximum mouth opening; 3) as maximum resistance was approached, the rate of increase in the traction force decreased. Maximum opening force was recorded; 4) one measurement was taken per session, for a total of two measurements per subject. Pearson's correlation coefficients were used to assess the reproducibility of MOF values. Results: The average MOF (mean ± SD) in the first and second tests was 24.2 ± 1.9 and 24.5 ± 2.0 kg. There was an extremely high correlation between first and second measurements (r = 0.969). Conclusions: The presently described indirect cervical traction device can be used to reliably quantify MOF.

Original languageEnglish
Pages (from-to)7-10
Number of pages4
JournalTokai Journal of Experimental and Clinical Medicine
Issue number1
Publication statusPublished - 2005 Apr


  • Daniels and Worthingham's muscle testing
  • Indirect cervical traction device
  • Jaw opening force
  • Mouth opening force

ASJC Scopus subject areas

  • Medicine(all)


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