Anatomical Proximity Between Posterior Maxillary Tooth Roots and Sinus Floor Independently Predicts Mucosal Thickening: A CBCT Study

Objectives This study aimed to investigate the association between anatomical proximity of posterior maxillary tooth roots to the maxillary sinus floor and both the presence and severity of maxillary sinus mucosal thickening (MT) using cone-beam computed tomography (CBCT). Materials and Methods A retrospective CBCT-based analysis was performed on 300 patients (175 females, 125 males; mean age: 27.55 ± 8.74 years). Root–sinus anatomical relationships were classified into three proximity types based on increasing root–sinus closeness. Maxillary sinus mucosal thickness was measured in millimeters, and mucosal thickening was defined using both a binary threshold (> 2 mm vs. ≤2 mm) and an ordinal severity classification (≤ 2 mm, 2–10 mm, > 10 mm). Multivariable binary logistic regression and ordinal logistic regression analyses were conducted to evaluate the independent association between proximity type and mucosal thickening, after adjustment for age, sex, diabetes, cardiovascular disease, and smoking status. Results Mucosal thickening (> 2 mm) was observed in 34.7% of patients on both sides. Proximity type was significantly associated with mucosal thickening on the right and left sides (p < 0.01). In multivariable binary logistic regression, each one-unit increase in proximity type was associated with a 2.58-fold increase in the odds of mucosal thickening on the right side (OR = 2.58; 95% CI: 1.61–4.12; p < 0.001) and a 1.93-fold increase on the left side (OR = 1.93; 95% CI: 1.23–3.03; p = 0.004). Ordinal logistic regression further demonstrated that proximity type was an independent predictor of greater mucosal thickening severity on both sides (right: OR = 2.43; left: OR = 1.90; both p < 0.01). Age showed a modest independent association, whereas systemic factors, including diabetes, cardiovascular disease, and smoking, were not significantly associated with mucosal thickening. Conclusion Anatomical proximity between posterior maxillary tooth roots and the sinus floor is a strong and independent predictor of both the presence and severity of maxillary sinus mucosal thickening. These findings emphasize the clinical importance of evaluating tooth–sinus anatomical relationships in CBCT-based diagnostic assessment and treatment planning in the posterior maxilla.