BACKGROUND: Due to the close proximity of maxillary molars to the maxillary sinuses, the bacteria at the root tip region of the sinus can quickly access the maxillary sinus. This can result in maxillary sinus mucosal inflammation and thickening of the Schneiderian membrane. OBJECTIVES: The aim of the study was to determine the thickness of the maxillary sinus membrane and to correlate this thickening with the severity of periodontitis using cone beam computed tomography (CBCT) analysis. MATERIAL AND METHODS: The CBCT data of 231 patients, with a mean age of 40.59 years, was assessed to evaluate the mucosal thickness (MT), the remaining height of the alveolar bone (RHAB), the type of periodontitis, the type of defect, and the extent of bone loss. RESULTS: When RHAB was ≤4 mm, mucosal thickening was evident in the majority of the images (128 (89.5%)
p = 0.000). The multivariate logistic regression analysis demonstrated that the probability of MT increase is proportionate to the severity of periodontal disease (odds ratio (OR): 9.179, confidence interval (CI): 2.831-29.761
p = 0.000). First molars were most frequently associated with mucosal thickening (OR: 1.050, CI: 0.311-3.541
p = 0.009). Additionally, mucosal thickening was more evident on the sinus floor in cases where RHAB was less than 4 mm. CONCLUSIONS: The increase in MT is associated with the severity and distribution of periodontal disease, particularly with horizontal defects.