Relationship among Schneiderian Membrane, Underwood's Septa, and the Maxillary Sinus Inferior Border


Dr. Binali Çakur, Department of Oral Diagnosis and Radiology, Faculty of Dentistry, Ataturk University, 25240 Erzurum, Turkey; e-mail:


Background: Osseo-integrated implants are increasingly being used to restore functional dentition; however, in the posterior region, implant placement can be problematic because of inadequate bone height. In this condition, maxillary sinus floor elevation surgery has become the treatment of choice. The presence of anatomic variations within the maxillary sinus such as Underwood's septa and thin schneiderian membrane decreases the success of the sinus floor elevation.

Purpose: In this study, we tried to determine the relationship between the anatomic variations of the maxillary sinus: Underwood's septa, schneiderian membrane thickness, and the cortical thickness of the inferior border of the maxillary sinus.

Material and Methods: The left and right maxillary sinus images of 74 patients were obtained by using dental computed tomography (CT). The schneiderian membrane and the cortical thickness of the inferior border of the maxillary sinus were measured on the coronal images of dental CT scans at the deepest portion of the sinus cavity. The presence of Underwood's septa was identified on the axial images. The correlations between these variables were assessed.

Results: We found that there was only a negative correlation between the schneiderian membrane thickness and the presence of Underwood's septa (r = –0.168 p = .042).

Conclusion: It is suggested that Underwood's septa may be the reason for the thinness of the schneiderian membrane. However, future studies among larger groups are necessary for confirming the finding by using well-designed clinical studies.