A Dynamic Study of Mandibular Movement Trajectories in Patients With Disc Displacement Without Reduction

Introduction and aims: Mandibular movement is a complex physiological process essential for orofacial function. Patients with disc displacement without reduction (DDWoR) exhibit significant kinematic impairments, which are thought to arise from structural joint damage and neuromuscular dysregulation. This study characterised mandibular movement in DDWoR using the Jaw Motion Analyzer. Through quantitative trajectory analysis and principal component analysis, we identified the primary variation patterns in mandibular kinematics. Furthermore, receiver operating characteristic (ROC) curve analysis was performed to evaluate the diagnostic efficacy of key movement parameters. This work provides a basis for functional movement-based assessment and objective diagnosis of temporomandibular disorders. Methods: This case-control study enrolled 40 DDWoR patients and 20 matched healthy controls. Mandibular movement trajectories were recorded using the Zebris Jaw Motion Analyzer system during standardised tasks. Trajectory symmetry was analysed via mathematical programming. Statistical analyses included group comparisons, principal component analysis and ROC curve evaluation to identify diagnostic kinematic indicators. Results: DDWoR patients exhibited significant kinematic alterations compared to healthy controls. Bilateral DDWoR patients showed reduced protrusive and opening movement ranges. In contrast, unilateral DDWoR patients demonstrated relatively asymmetrical patterns characterised by asymmetric condylar trajectories with increased lateral excursion ranges. Principal component analysis between the bilateral DDWoR group and the healthy group revealed 2 dominant variation patterns explaining 53.69% of total variance. ROC analysis identified excellent diagnostic value for sagittal opening symmetry (AUC = 0.901) and good value for incisal point inclination (AUC = 0.813). Conclusion: Our findings confirm distinctive and heterogeneous mandibular movement patterns in DDWoR, revealing several parameters with diagnostic potential to inform functional assessment and personalised treatment strategies for temporomandibular disorder. Clinical relevance: This study identifies specific mandibular movement signatures in DDWoR patients, providing objective kinematic parameters for functional assessment. These findings facilitate early diagnosis, enable real-time treatment monitoring and support the development of personalised rehabilitation strategies for temporomandibular disorders.