Changes in temporomandibular joint morphology, condylar position, and mandibular functional movement induced by orthodontic treatment in class ii malocclusion: a retrospective study based on CBCT and electronic articulator technology.

OBJECTIVE: This study aimed to evaluate the morphological and positional changes in the temporomandibular joint (TMJ), as well as alterations in mandibular functional movement, before and after orthodontic treatment in patients with Class II malocclusion using cone-beam computed tomography (CBCT) and electronic articulator technology. METHODS: A total of 82 adult patients (43 females, 39 males; aged 18-35 years) were retrospectively enrolled, including 54 with Class II Division 1 and 28 with Class II Division 2 malocclusion. Sample size adequacy was evaluated before data analysis, and the final sample size met the minimum requirement for the primary subtype-specific pre-treatment and post-treatment comparisons. All participants underwent comprehensive orthodontic treatment. Among Class II Division 1 patients, 20 were treated without extraction, 13 underwent single-arch extraction, and 21 underwent double-arch extraction; all Class II Division 2 patients were treated without extraction. CBCT was performed before and after treatment to evaluate TMJ morphology and condylar position, including coronal and sagittal joint spaces, axial condylar angle, condylar height, condylar length, condylar sagittal inclination, and glenoid fossa morphology. Mandibular functional movements were assessed using an electronic articulator, including incisal protrusive movement, lateral excursion, mouth opening-closing movement, condylar movement trajectory, and protrusive condylar inclination. The main comparisons were conducted before and after treatment within Class II Division 1 and Class II Division 2 patients. In Class II Division 1 patients, additional analyses according to extraction pattern were performed only as exploratory subgroup analyses because of the limited sample size in each subgroup. RESULTS: In patients with Class II Division 1 malocclusion, no significant overall changes were observed in condylar size, sagittal inclination, joint space, or fossa morphology after treatment (P > 0.05), whereas the incisal protrusive movement distance significantly decreased (P = 0.020). Exploratory extraction-pattern subgroup analyses suggested mild changes in condylar length, condylar height, sagittal inclination, anterior joint space, and incisal protrusive range; however, these findings should be interpreted cautiously because of the small number of patients in each subgroup. In patients with Class II Division 2 malocclusion, bilateral condylar length, height, and sagittal inclination increased significantly following treatment. The left anterior, right anterior, and left superior joint spaces decreased, whereas the posterior joint spaces increased bilaterally. The right posterior slope angle decreased, while the condylar protrusive trajectory angle decreased bilaterally. No significant changes were observed in incisal protrusion, lateral excursion, or mouth opening and closing distances. CONCLUSIONS: Orthodontic treatment was associated with adaptive TMJ remodeling in adult patients with Class II malocclusion. Patients with Class II Division 1 malocclusion showed overall structural stability with limited functional changes, although exploratory analyses suggested modest remodeling patterns across different extraction subgroups. In contrast, patients with Class II Division 2 malocclusion exhibited more pronounced changes in condylar dimensions, sagittal inclination, joint spaces, and protrusive condylar trajectory. Overall, changes in mandibular functional movements were limited. Because extraction-pattern subgroup analyses were exploratory and based on relatively small samples, these results should not be overinterpreted as definitive evidence of extraction-related TMJ remodeling.