Three-dimensional assessment of pharyngeal airway hyoid bone and craniocervical changes after stabilization splint treatment in temporomandibular disorder patients

Stabilization splint (SS) therapy is commonly used to treat temporomandibular disorders (TMD), but its three-dimensional (3D) effects on pharyngeal airway (PA) dimensions, hyoid bone (HB) position, and craniocervical (CC) posture remain unclear. This study primarily aimed to evaluate the 3D changes in the PA, with a secondary focus on the HB and CC posture, in adult TMD patients after SS therapy. This retrospective study analyzed 80 adult TMD patients (mean age: 23.88 ± 5.8 years) treated with SS for 6-12 months. Pre- and post-treatment cone-beam computed tomography (CBCT) scans were used to measure 3D changes in PA (naso-, oro-, hypo-, and total pharyngeal spaces), HB position, and CC posture using InVivo and Dolphin software. Statistical analysis included paired t-tests and Wilcoxon signed-rank test (P < 0.05). Significant reductions occurred in oropharyngeal surface area and sagittal width (P = 0.021; P = 0.017, respectively) and hypopharyngeal parameters (surface area, volume, minimal constriction area, sagittal width; P < 0.05). HB measurements showed significant decrease in hyoid-mandibular plane (H-MP), hyoid-retrognathia distances (H-RGN) and hyoid triangle height measurements (P = 0.002, P = 0.014 and P = 0.029, respectively), with a significant increase in retrognathia-sella distance (RGN-S, P = 0.003). CC posture showed significant decreases in the Sella-Nasion to odontoid process tangent angle (SNL-OPT) and to the cervical vertebra tangent angle (SNL-CVT) (P = 0.005, P = 0.003, respectively). SS therapy significantly reduced oropharyngeal and hypopharyngeal airway dimensions, changed HB position, and improved CC posture post-treatment. These results highlight the multidimensional impact of SS therapy and support incorporating airway and CC posture assessments into TMD management which enhances diagnosis and therapeutic outcomes.