A mathematical model of the human jaw system simulating static biting and
movements after unloading.
G.E.C. Slager, E. Otten, T.M.G.J. van Eijden and J.D. van Willigen.
Dept. Medical Physiology, University of Groningen, Groningen, The
Netherlands. Dept. Functional Anatomy, Academic Center for Dentistry
Amsterdam, Amsterdam, The Netherlands.
APStracts 4:176N, 1997.
ABSTRACT
When the resistance to a forceful isometric bite is suddenly removed in
unloading experiments, the bite force drops to zero and the mandible reaches a
constant velocity. This occurs at an initial bite force of 100 N after about
12 msec when the incisors have moved 4.5 mm. Reflex activity is far too slow
to limit the velocity at impact. To explore the influence of other factors
(co-contraction, force-length properties and force-velocity properties of the
muscles) on the velocity at impact, a numerical forward dynamic model of the
jaw system is formulated. Unloading experiments in different experimental
conditions were simulated with the model. Most parameter values of the model
are based on physiological data, both from literature and a data basis from a
human cadaver study. Other parameter values were found by optimally fitting
the model results to data from the unloading experiments.
The model analysis shows that the limitation of the jaw velocity may be mainly
due to the force-velocity properties of the jaw closing muscles. Force-length
properties of the jaw muscles hardly contribute to the impact velocity. The
compliance of tendinous sheets in the jaw muscles is unfavourable for the
reduction in impact velocity, while co-contraction of jaw opening and closing
muscles helps to limit impact velocity. The force-velocity properties of the
muscles provide a quick mechanism for dealing with unexpected closing
movements, and so avoid damage to the dental elements.
Received 15 April 1997; accepted in final form 31 July 1997.
APS Manuscript Number J306-7.
Article publication pending J. Neurophysiol.
ISSN 1080-4757 Copyright 1997 The American Physiological Society.
Published in APStracts on 28 August 1997