Studies evaluating measurement accuracy of CMS-JAW, a jaw motion tracking device with six degrees of freedom using an ultrasonic recording system

Abstract

PURPOSE: For diagnoses of temporomandibular dysfunction, reports indicate the importance of analyzing jaw movements using a jaw motion tracking device with six degrees of freedom. However, such devices are not widely applied in clinical practice, due to difficulty of use. To determine whether CMS-JAW (a newly developed six degrees of freedom jaw motion tracking device that features easy analysis of jaw movements) offers the measurement accuracy required for clinical use, we evaluated the device by measuring condyle translation and rotation during jaw movement. METHODS: In this study, we evaluated measurement accuracy by comparing measurements of condyle movements obtained from the Win Jaw System, a comparable jaw motion tracking device with six degrees of freedom based on an ultrasonic recording system; the Gnathohexagraph II, a device based on a different measurement principle; and the CMS-JAW. In the experiment, we confirmed the condyle translations and rotations obtained by each device by measuring distances and angles, respectively, with a micro slider for three-dimensional measurements (to an accuracy of 0.01 mm and 0.02 mm) and a digital protractor (to an accuracy of 0.1 degrees). RESULTS: No significant distortions were observed in the space replicated based on the range of condyle translations obtained with CMS-JAW. Deviations from theoretical values were greatest along the z-axis, with a maximum error of 0.20 mm and root mean square (RMS) error of 0.10 mm. The maximum error for angles of condyle rotation was 0.50 degrees; RMS errors ranged from 0.05 to 0.30 degrees. CONCLUSION: Our analysis of condyle movement demonstrates that the CMS-JAW provides acceptable measurement accuracy for clinical applications.