A Comparison of Methods for Decoupling Tongue and Lower Lip From Jaw Movements in 3D Articulography

Purpose: One popular method to study the motion of oral articulators is 3D electromagnetic articulography. For many studies, it is important to use an algorithm to decouple the motion of the tongue and the lower lip from the motion of the mandible. In this article, the authors describe and compare 4 methods for decoupling jaw motion by using 3D tongue and lower lip data. Method: A 3D position estimation method (3DPE), an adapted version of the estimated rotation method (ERM) proposed by Westbury, Lindstrom, and McClean (2002) for 3D recordings, a linear subtraction method, and a new method called Jaw and Oral Analysis (JOANA) were evaluated with data recorded from sensors attached to the lower molars, lower lip, and tongue. Results: The 3DPE method showed the fewest errors. However, unlike the other methods, it requires more than one sensor attached to the lower jaw. Among the single-sensor methods, JOANA was found to be the most comparable to 3DPE. Conclusion: The findings suggest that JOANA is efficient in decoupling tongue and lower lip motion from jaw motion, whereas ERM, with its less complicated procedure for attaching the lower jaw incisor sensor, can be considered a viable alternative.