An Accurate Kinematic Analysis with Clinical Convenience for Decomposing Mandibular Movement into Translational and Rotational Components: A Preliminary Proof-of-Concept Study

Motion dysfunction constitutes a critical clinical manifestation of temporomandibular joint disorder (TMD). Notably, prior research predominantly consists of qualitative clinical descriptions. To better understand the mandibular movement by quantitative analysis, our study proposes a mathematical approach for extracting kinematic parameters and preliminarily illustrates the feasibility and technical advantages through a comparative kinematic parameters analysis of a volunteer opening–closing movement performed in maximum intercuspal position (MIP) and therapeutic position (TP). By decomposing the translational and rotational components of opening–closing movement, the symmetry of the mandibular movement was improved and the maximum mouth opening was increased after wearing a bite-guiding splint. Furthermore, changes in the spatial position of the finite helical axis (FHA) indicated that the FHA position became more stable after wearing the splint, suggesting that this metric has potential kinematic assessment value. Finally, a cushioning effect was observed at the maximum mouth opening when the bite-guiding splint was worn. This approach is expected to provide clinical practice with a high-precision digital assessment tool and a valuable reference for the quantitative evaluation of personalized temporomandibular joint (TMJ) functional rehabilitation. The method could not only conveniently extract the key kinematic parameters of mandible movement but also efficiently evaluate the therapeutic outcomes of clinical intervention.