Background/Objectives: Perforation of the maxillary sinus floor by dental implants is a complication that can occur during treatment in posterior sectors; however, its clinical and radiological consequences remain controversial. Therefore, this study aimed to use the diagnostic value of CBCT to determine the possible association between sinus floor-perforating implants and their clinical and/or radiological impact. Methods: A retrospective observational study was conducted on CBCT scans from 21 patients with implants protruding into the maxillary sinus. Morphometric analysis was performed to assess sinus membrane thickening (SMT) patterns, height, surface area and density and the presence of sinonasal symptoms. Statistical analysis was used to explore potential associations between SMT and variables such as implant protrusion length, number of perforating implants, age and gender. Results: SMT was observed in all patients, with a mean area of 11.1 ± 6.4 mm² in panoramic sections. Most cases (85.7%) exhibited a circumferential SMT pattern. No statistically significant correlation was found between SMT and implant protrusion length, age or sex. Additionally, none of the patients reported sinonasal symptoms, and no clinical signs of sinusitis were detected during follow-up. Conclusions: Although sinus floor-perforating implants commonly induce SMT detectable on CBCT, this thickening appears largely asymptomatic and may not compromise patient well-being in the short term. Nevertheless, clinicians should monitor these cases radiographically to detect possible long-term complications.

Background: Rhinosinusitis is an increasingly prevalent condition that compromises patients’ quality of life and imposes a substantial burden on healthcare systems. Odontogenic sinusitis, a predominantly unilateral form of rhinosinusitis, accounts for up to 40% of unilateral maxillary sinusitis cases. This study aimed to characterize the clinical presentation, radiological extension, and quality-of-life impairment associated with odontogenic sinusitis. Methods: Thirty-eight patients with unilateral sinusitis caused by dental pathology/treatment were recruited. OS diagnosis criteria were established according to EPOS-2020 guidelines. The 22-item SNOT-22 questionnaire was used to assess symptom severity and social/emotional impact. In addition, all patients underwent CT imaging and were staged with the Lund–Mackay scale for involvement of the maxillary, anterior and posterior ethmoid, sphenoid and frontal sinuses. Results: Smoking was associated with significantly worse patient-reported quality of life, with higher SNOT-22 scores in current smokers than in non-smokers (59.4 vs. 38.2; p = 0.026). Purulent discharge was associated with greater radiological severity, longer symptom duration, and a markedly higher prevalence of extra-maxillary extension (92.3%; p < 0.001). Extra-maxillary involvement was identified in 71.1% of patients, predominantly affecting the anterior ethmoid sinus. Although Lund–Mackay scores objectively reflected radiological disease extension, their correlation with symptom burden was limited. Conclusions: Odontogenic sinusitis frequently presents with substantial extra-maxillary extension and significant impairment of quality of life. Smoking and purulent discharge were associated with markers of greater disease severity in this exploratory cohort. These associations should be interpreted cautiously and confirmed in larger studies using multivariable analyses.