## 2 Materials and Methods  
This study was conducted at the Medical University of Gdansk (Gdansk, Poland). Thirty healthy individuals (aged 20-24 years) without a history of temporomandibular disorders (TMD), orthodontic treatment, or craniofacial trauma were recruited from among university volunteers. Subjects were screened via a questionnaire and the Research Diagnostic Criteria/Temporomandibular Disorders (RDC/TMD) [25] protocol. Flow chart Figure 2 detailing study design process. Examinations were performed using the Modjaw device (MODJAW, Lyon, France) to capture real-time mandibular movement and cone beam computed tomogram (CBCT) imaging (Carestream 9300) to measure glenoid fossa height/anatomy. Mandibular movement recordings included the following (Figure 3):  
Repetitive mouth opening and closing;  
Protrusive movements from maximum intercuspation (MIP);  
Full mouth opening from MIP. The Modjaw system (MODJAW, Lyon, France) optically tracked mandibular motion in real time. Each subject performed multiple cycles of the above movements. The Frankfort Horizontal Plane (FHP) was used as the reference, constructed by connecting the left Orbitale and Porion landmarks bilaterally (Figure 4) [26]. In the sagittal view, a cross-sectional plane perpendicular to a line passing through the innermost and outermost points of the condyle in the transverse section was selected individually for each TMJ, ensuring consistent orientation for measurements (Figure 5). CBCT imaging was performed by a skilled radiology technician using the Carestream 9300 system (Carestream Dental, Atlanta, GA, USA) under standardized settings: 120 kV, 3.20 mA, 40 s exposure, and a delivered dose of 1698.19 mGy/cm\({}^{2}\). Each patient was positioned in a standing posture with the mandible in maximum intercuspation position (MIP) to ensure consistency. Image analysis was conducted using CS Imaging 8.0.5 software to measure the vertical dimension of the  
Figure 1: Aiding visualization of the TCI and CGA. glenoid fossa. For each movement, Modjaw TWIM version software was used to calculate the sagittal condylar guidance angle (SCI, in degrees) for the right and left TMJs. The temporomandibular joint (TMJ) space was evaluated by identifying the antero-superior space (ASS) and superior space (SS). The ASS corresponds to the thickness of the intermediate disc band, while the SS reflects the thickness of the posterior disc band. In addition, the vertical height of the fossa (H) was measured (Figure 6). All measurements from the CBCT images were performed by two independent examiners; the vertical fossa height values obtained showed negligible differences (inter-observer variation \(<\) 0.2 mm, indicating high consistency). Figure 3: Illustrates recordings obtained using the Modjaw device, providing a detailed comparison between mandibular protrusion and mouth opening movements in sagittal views. The tracings clearly depict the trajectories of each movement and the calculation of CGA. Figure 2: Flowchart detailing the study design process. Figure 4: FHP connecting the left Orbitale and Porion landmarks. Figure 5: Transverse view highlighting FHP. Figure 6: Vertical height of the fossa and the corresponding measurements of the joint space. The research protocol was approved by the Independent Bioethics Committee for Scientific Research at the Medical University of Gdansk (approval number: NKBBN/1043/2021-2022) and retrospectively registered at ClinicalTrials.gov (NCT05637372). All participants were provided with oral and written information about the study and gave informed consent to participate. Statistical Analysis: All calculations were performed using Microsoft Excel 2019 and STATISTICA 13.6 (TIBCO Software Inc., Palo Alto, CA, USA; 2020) Data Science Workbench, version 14. Descriptive statistics (mean, median, standard deviation, and range) were calculated for all quantitative variables. The Shapiro-Wilk test was used to assess the normality of distributions.