It is very important to pre-operatively evaluate the thickness of the Schneiderian membrane to plan the surgical procedure in the region that involves the membrane, such as a sinus lift augmentation, which increases the possibility of membrane perforation or other complications.

The present study assumed that the average thickness of the Schneiderian membrane is 1.60 ± 1.20 mm.

There are many studies which estimate the average thickness of the mucosa of the maxillary sinus, some of which have used CBCTs while others have not. These studies are presented in Table 7. These values are not completely different to the results of the present study. From these studies, we can conclude that, clearly, there is variability regarding the thickness of the Schneiderian membrane. This means that a clinician cannot collect information about the thickness of a sinus membrane by patient sex, side, or age.

In this study, it was detected that 27.5% of the measurements made (99 out of 360) were more than 2 mm. However, all X-ray examinations that showed a visually detectable pathology were excluded from our study. For this reason, our study cannot conclude that the limit of 2 mm is an accurate limit to evaluate a sinus membrane as healthy or pathological. The limit of 2 mm as a criterion is used by Shanbhag et al. 2014, Ji-Young Yoo et al. 2011, Janner et al. 2011, and Cagici et al. 2008 [10,11,12,13]. On the contrary, Eggesbo et al. 2006 and Cakur et al. 2011 set the limit of 4 mm as a safe threshold to evaluate a sinus membrane as pathological [9, 14]. Furthermore, Lozano-Carrascal et al. 2017 accept a threshold of 3 mm of membrane thickness for pathology existence [15]. In our study, the membrane thickness of 6.94% of our sample was over 4 mm. For this reason, we can accept a thickness over 4 mm as a safer limit to evaluate if there is a pathology in the sinus or not.