Introduction. The presence of bone septum in the maxillary sinus is one of the most common anatomical findings. So-called Underwood septa (US) are an atypical bone formation in the maxillary sinuses. Mostly they are quite easily found in CBCT studies and have major importance in sinus lift procedures in dental surgery. Furthermore, the shape, location, and size of the bony septa are important in each maxillary sinus surgery. Material and methods. A retrospective study of 120CBCT scans from the authors' own database was conducted. Results. Approximately 37.5% of each CBCT was associated with the occurrence of US, while just 25% had a full septum, and a total of only 14 patients had a half septa. More females have US, while healthy pneumatized maxillary sinus is most commonly found (82.22%). There is no correlation between the occurrence of silent sinus syndrome (p = 0.174), mucosal thickening (p = 0.325), or retention cyst formation (p = 0.272). Most sinuses are without any opacification in CBCT evaluation (91.11%), while other syndromes are not statistically relevant. Conclusions. It seems that the occurrence of Underwood septa is not statistically related to any clinical, radiological, or pathological condition within the sinus (p > 0.05). Furthermore, a more full or partial appearance of US was found in female patients.
Keywords: Underwood septa; maxillary hypoplasia; maxillary sinus; sinus floor; sinus lift.