Accuracy and Linearity of the JT-3D Jaw tracker

Objectives:  This study evaluated the accuracy and linearity of the JT-3D Magnetic Jaw Tracker. 

Methods:  This experiment was a bench test.  The calibration of the instrument was tested first with a fixture of known positions for the magnet.  A dial caliber was used in moving a magnet in known increments of 5mm along the median axis in each of the 3 dimensions:  vertical, A/P, and lateral.  This testing was repeated 3 times in each dimension. 

Results:  The linearity was analyzed by calculating an r-squared value for each trial.  The average r² for the three trials for vertical was 0.9996.  The average r² for three trials for anterior-posterior was 0.9999.  The average r² for the three trials for lateral was 0.9999.  The results are displayed graphically below.

Conclusions:  This bench study shows that the JT-3D Jaw Tracker measures accurately in 3 dimensions and with a high degree of linearity over the usual range of human jaw motion.  Many earlier jaw tracking models were less linear and provided less accurate measurements except near centric occlusion.