Sinonasal Anatomic Variations Across Vertical Skeletal Patterns in Skeletal Class I Adults: A Retrospective Cone-Beam Computed Tomography Study

Background/Objectives: Vertical skeletal morphology may influence maxillofacial dimensions, but its relationship with discrete sinonasal anatomic variations remains uncertain. This study compared the prevalence of paranasal sinus and nasal cavity variations among adults with hypodivergent, hyperdivergent, and normodivergent skeletal patterns. Methods: Faculty archives spanning 2016–2025 were screened. Eighty-seven untreated adults with a skeletal Class I relationship were included and categorized according to their vertical skeletal pattern as follows: 27 hypodivergent, 26 hyperdivergent, and 34 normodivergent. All cone-beam computed tomography (CBCT) examinations were acquired using a single NewTom 5G unit with 0.25 mm isotropic voxels. Nasal septal deviation and septal spur were evaluated per participant; 22 additional variants were evaluated bilaterally. Side-level comparisons used binary logistic generalized estimating equations with Benjamini–Hochberg false-discovery-rate correction. Results: Age (p = 0.5072), nasal septal deviation (p = 0.2247), and septal spur (p = 0.9294) did not differ significantly among groups. The paradoxical middle turbinate showed a nominal group effect (Wald χ2 = 6.199, p = 0.0451), but the association was no longer significant after false discovery rate correction (q = 0.4642). No other estimable side-level group or within-group right–left comparison was significant. Conclusions: No statistically significant associations were detected between vertical skeletal pattern and sinonasal anatomical variations in this sample of skeletal Class I adults. However, small-to-moderate associations cannot be excluded, particularly for rare variants. The nominal finding for the paradoxical middle turbinate requires confirmation in larger, prospectively defined cohorts.