The control of bite-force in relation to jaw position and load in man

Whether bite-force is controlled independently of mouth opening, and jaw position is controlled independently of the imposed load of the mandible, was examined. Subjects were asked to match, at 15 and 30 mm inter-incisor distance, reference forces of 2, 10 and 50 N exerted at 15 and 30 mm mouth opening. They were able to grade bite-force, as matches made of the different forces hardly overlapped. However, at a 5 per cent level of significance in 90 per cent of the cases, the matches were dependent on jaw position. The imprecision of the 2 N matches was about 40 per cent of the reference force; those of the 10 and 50 N matches were about 25 per cent. Thus a mechanism controlling bite-force with any degree of precision is absent in the jaw system.