Some biomechanical correlates of jaw movements

The relative contributions of jaw mass and supporting muscle system stiffness to jaw movements were studied to a first approximation. The amplitude‐frequency characteristics of jaw movements were measured in both the normal state and under conditions of increased mass (externally applied weights) and stiffness (spring loading). Vertical jaw movements were produced and controlled by muscle stimulation through wire electrodes implanted directly into the masseter muscle of a single subject. The stimulation signal (2‐ms pulse width, 200 pps) was modulated through a function generator to produce oscillatory jaw movements varying from 1 to 15 Hz. Jaw movement was tracked in the vertical dimension using a photoelectric sensing device. It was found that increases in both load and stiffness reduced the amplitude‐frequency characteristics of the jaw and that the bandwidth of the amplitude‐frequency characteristics of the jaw corresponded to the calculated Eigen frequency of the jaw. These findings suggest that the ...