Modjaw-Derived Mandibular Kinematics in Unilateral and Bilateral MRI-Defined Disc Displacement: Associations with CBCT Measurements in a Pilot Clinical Cross-Sectional Study

Background/Objectives: Digital mandibular tracking enables non-invasive assessment of mandibular kinematics, but the relationship between tracking-derived functional parameters and structural temporomandibular joint alterations remains insufficiently understood. This pilot clinical cross-sectional study aimed to evaluate associations between Modjaw®-derived sagittal condylar inclination and Bennett angle, CBCT-derived structural measurements, and MRI-defined disc displacement. Methods: Thirty participants were included: 15 patients with clinical signs and/or symptoms suggestive of temporomandibular disorder and MRI-confirmed disc displacement, and 15 clinically asymptomatic control participants. MRI was performed in the TMD group to classify disc position, while CBCT and digital mandibular tracking using the Modjaw® system were performed in all participants. Sagittal condylar inclination and Bennett angle were analyzed together with CBCT-derived structural measurements. Results: CBCT measurements demonstrated good-to-excellent inter-observer agreement, and Modjaw®-derived sagittal condylar inclination and Bennett angle showed high intra-session repeatability. Linear mixed-effects models, accounting for bilateral joint interdependence (ICC: 50.2–66.9%), revealed that static anatomical joint spaces and local asymmetries were generally weak isolated predictors of mandibular kinematics. Functional kinematic parameters varied across MRI-defined dyadic disc-displacement categories. MRI-normal contralateral TMJs in participants with unilateral disc displacement showed increased transverse condylar inclination values, corresponding to Bennett angles. Unilateral disc-displacement TMJs were associated with higher sagittal condylar inclination values, whereas bilateral disc-displacement TMJs were associated with lower sagittal condylar inclination values. Conclusions: Modjaw®-derived sagittal condylar inclination and Bennett angle showed different patterns across MRI-defined dyadic disc-displacement categories. Unilateral disc displacement was associated with increased sagittal condylar inclination in affected joints and increased Bennett angles in MRI-normal contralateral joints, whereas bilateral disc displacement was associated with lower sagittal condylar inclination values. CBCT-derived structural measurements provided complementary information regarding temporomandibular joint morphology and joint–space relationships, while digital mandibular tracking characterized mandibular kinematic patterns. Digital mandibular tracking may provide complementary functional information alongside standardized clinical examination and appropriately indicated imaging, although its additional clinical value requires further evaluation.