Structural Alterations of the Temporomandibular Joint in Rheumatoid Arthritis: A Cone-Beam Computed Tomography Study

Background and Objectives: Rheumatoid arthritis (RA) may involve the temporomandibular joint (TMJ), but structural features distinguishing RA-related involvement from non-RA temporomandibular disorders (TMDs) remain incompletely defined. This study compared quantitative and qualitative cone-beam computed tomography (CBCT) findings between patients with RA and a symptomatic non-RA TMD comparison group and explored bilateral asymmetry and associations with RA-related characteristics. Materials and Methods: This single-center retrospective cross-sectional study included 84 adults (42 RA and 42 non-RA TMD). All participants had TMJ-related symptoms or signs and clinically indicated CBCT examinations available. Bilateral CBCT assessment included condylar and mandibular fossa morphometry, joint-space measurements, condylar position, and qualitative osseous abnormalities. Linear mixed-effects models and generalized estimating equations accounted for bilateral observations, with Holm correction for multiple testing. Exploratory clinical associations and intraobserver reliability were also evaluated. Results: Clinical TMJ manifestations did not differ significantly between groups. The inferential analyses showed lower condylar height and anterior joint space and greater condylar length, anteroposterior condylar length, and condylar-to-midsagittal distance in RA. The largest quantitative difference involved condylar height (−5.43 mm; adjusted p < 0.001). Cortical erosions (OR = 5.94; 95% CI, 2.57–13.70) and joint-space narrowing (OR = 3.96; 95% CI, 1.66–9.42) were more strongly associated with RA. Absolute bilateral asymmetry did not differ after multiplicity correction, although group-by-side interactions persisted for condylar height and condylar position. Longer disease duration correlated with greater condylar-height asymmetry (ρ = 0.62; adjusted p < 0.001). Intraobserver reliability was high to excellent. Conclusions: RA-related TMJ involvement appears to reflect combined condylar remodeling, vertical structural loss, altered condyle–fossa relationships, and erosive change rather than uniform degeneration. These findings support CBCT as a potentially useful tool for structural characterization, but prospective multimodal validation using observed patient-level data is required.