Forces acting on the mandible during bilateral static bite at different bite force levels.

Abstract

Abstract A mathematical model based on an assumed linear relationship between the forces exerted by a muscle and its integrated electromyogram is presented for calculating muscle forces and joint forces acting on the human mandible during static bite situations. Full data from one of 7 male subjects are included as an example of the approach and to illustrate the relevance of the mechanical model for calculating these forces. Under the assumption that the maximum muscle tension (Γ), expressed in N/m2 (kg/cm2) is equal for all muscles, a value of this quantity can be calculated for any bite in any of three bite positions. It appears to be dependent upon the test person only. Alinearity between EMGI and bite force is caused by alinear behavior of muscle force and bite force and is not due to alinearity between EMGI and muscle force. The ratios between muscle force values are dependent on the location of the bite force. Forces in the lateral pterygoid muscles and in the temporomandibular joints increase nearly linearly with increasing bite forces. Reduced data on bite forces, forces in jaw muscles and in temporomandibular joints found from all subjects are presented. Data on maximum bite forces are higher than those found in the literature. Highest bite forces and muscle forces are exerted most often when biting takes place in the region of the first molar. The loading of the temporomandibular joints is highest when biting in the region of the first premolar. Muscle activity may be inhibited in this situation. Forces in all muscles are dependent on the location of the bite force, most clearly demonstrated in the temporal muscles. Joint forces are higher when the bite force is applied more ventrally and may initiate an inhibition when biting in position P1. In position M2 all forces are considerably lower than expected on the basis of the mechanical model only.