Study on Active Jaw-Opening Forces in Man

• Published in: Nihon Hotetsu Shika Gakkai Zasshi Vol. 29; no. 2; pp. 235 - 240
• Main Authors: Fujii, Tetsunori, Nakamura, Tsukasa, Sato, Hironobu, Fujii, Hiroyuki
• Format: Journal Article
• Language: Japanese
• Published: Japan Prosthodontic Society 01.04.1985
• ISSN: 0389-5386; 1883-177X
• DOI: 10.2186/jjps.29.235

In 10 healthy subjects, isometric jaw-opening force and relations between the force and EMGs from the masseter and the anterior venter of the digastric muscles were studied. The opening force was actively exerted at various jaw positions; i. e. 0 mm (an intercuspal position), 10, 20, 30 and 40 mm opening position of the jaw. In each positions, successive five trials were repeated. Next results were obtained. (1) Mean value of Maximum opening forces was 2.55± 0.35 kg. (2) Jaw position had significant effect on the force (P<0.05); in 10 mm opening position the most forceful value of 3.19 kg and in 40 mm opening position the minimum of 1.07 kg were obtained on an average. An intertrial variation of opening force in the former position was smaller than that of the latter (P<0.05). (3) In terms of time relationships between onsets or offsets of the opening force and EMGs, highly interindividual difference was found (P<0.0003). (4) During isometric jaw opening, electromyographic activity of the masseter muscle was facilitated in 9 out of 10 subjects, although it differed with trials and/or jaw position.