Wireless Intraoral Jaw Motion Tracker Performance Evaluation and Demonstration of Operation In Vitro and In Vivo

This work is focused on presenting and evaluating a minimally restricting wireless intraoral sensor, which can continuously track jaw motion during usual daily activities. The article presents the results of a full working range accuracy evaluation of the system, as well as in vitro and in vivo demonstration of operation. Ambient magnetic field–resistant magnetic localization of a permanent magnet is achieved using two adjacent tri-axial magnetometers and utilizing a least squares (LSs) optimization for solving a nonlinear equation system based on first-order magnetic dipole approximation. Such approach with only two magnetometers was not reported to be done before. The method allows 3 degrees of freedom (DOF) localization, when the device and the sensor do not change orientation and moves in parallel to each other in any direction. Only the restricted and predictable kinematics of the human masticatory system enables the use of proposed system for human jaw tracking. The 5 DOF jaw motion tracking is achieved by introducing a system of trigonometric equations describing the relationship between translation and rotation of the jaw. Also, a software environment was created for the recorded magnetic data conversion to Cartesian coordinates in a user-friendly way and for the review of the temporomandibular activity of the patient in video-like fashion. Extensive datasets of continuous jaw motion data could significantly improve jaw parafunction diagnostics, including acquisition of jaw movement trajectories, estimation of parafunction episode frequency and intensity, determination of parafunction type and subtype, and extraction of any other needed parameters, for example, the number of teeth contacts.