Three-dimensional unilateral method for the bilateral measurement of condylar movements

Using a unilateral optoelectronic tracking system (JAWS-3D), a method was developed for the simultaneous measurement of the three-dimensional kinematics of both ipsilateral and contralateral human condyles, the latter being represented by virtual points bcyond the field of vision of the camera system during the actual recording. The method leaves the subjectʹs head unrestrained while measuring the movements of two sets of three light-emitting diodes rigidly attached to the upper and lower tech. The Tait-Bryan angles method was employed for calculating the jaw rotations in three dimensions. Movements were referenced to both a skeletal and a dental coordinate system. The worst-case static measurement errors were 0.24 mm for a 20 mm translation and 0.71° for a 35° rotation. The mean dynamic measurement errors were 9.73 μm s−1 at a constant linear velocity of 200 μm s−1 and 0.73° s−1 at a constant angular velocity of 149° s−1. The utility of the method was demonstrated in a subject who was asked to open and close the mouth in a cyclic fashion.