## 4 Discussion  
The present study used CBCT images to evaluate the effect of various factors associated with periapical lesions on the amount of mucosal thickness: conditions such as chronic sinusitis, pseudocysts, retention cysts, and mucocele have all been reported to have a major effect on the basal membrane of the MS [36; 37; 38]. In addition, local and patient-related factors including age, gender, smoking, and periodontal status may also affect the thickness of MS membrane [7; 39; 40]. CBCT imaging can be useful in diagnosing the etiology and extent of an endodontic pathology and the involved sinus [41]. [PERSON] et al. [42] used CBCT scanning to report that odontogenic sinusitis can be identified as localized thickening of the mucous membrane of the MS associated with dental lesions. Recent reports of the relationship between maxillary teeth and the MS [23; 25; 43] differed from our study, in that [PERSON] et al. [23] included only cases with mucosal thickness and excluded other areas. In addition, they did not measure the distance between the root apices and the sinus floor, while [PERSON] [25] only evaluated endodontically treated teeth. Similarly, [PERSON] et al. [43] only included teeth with periapical pathology. Even though mucosal thickening is usually more pronounced in the region of teeth with periapical pathology [44], and the degree of apical periodontitis has been positively correlated with sinus mucosal thickening [6; 7], [PERSON] et al. [21] reported sinus membrane thickening in 46.7% of patients, with an almost equal association with unhealthy and healthy teeth. For our study, we decided to include both treated and non-treated teeth, and the condition of the tooth was not an exclusion criterion. It is clinically \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \
\begin{tabular}{c} **Maxillary** \\ **Sinus** \\ **Proximity** \\ \end{tabular} &
\begin{tabular}{c} **Percent of** \\ **Total** \\ \end{tabular} & \multicolumn{5}{c}{**Mucosal Thickening**} \\ \cline{3-6}  & 60.5\% & 24.6\% & 13.1\% & 10.8\% & 5.8\% & 6.2\% \\ CS & 32.1\% & 7.4\% & 4.9\% & 8.5\% & 5.8\% & 5.5\% \\ IS & 7.4\% & 1\% & 1.5\% & 0.4\% & 0.8\% & 3.7\% \\ \hline \hline \end{tabular}
\end{table} 
Table 4: The anatomical relationship between the sinus floor and the root tips of adjacent teeth, and the maxillary mucosal thickness. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \begin{tabular}{c} **Size of PA Lesion** \\ **(CBCT PAI)** \\ \end{tabular} & \begin{tabular}{c} **Percent of Total** \\ \end{tabular} & \begin{tabular}{c} **0** \\ \end{tabular} & \begin{tabular}{c} **1** \\ \end{tabular} & \begin{tabular}{c} **2** \\ \end{tabular} & \
\begin{tabular}{c} **3** \\ \end{tabular} &
\begin{tabular}{c} **4** \\ \end{tabular} \\ \hline \multirow{3}{*}{0} & 31.5\% & 46/275 & 19/275 & 13/274 & 2/275 & 6/275 \\  & (16.9\%) & (6.9\%) & (4.9\%) & (0.7\%) & (2.1\%) \\  & 27.8\% & 23/275 & 22/275 & 26/275 & 5/275 & 1/275 \\  & (8.3\%) & (8\%) & (9.3\%) & (1.8\%) & (0.4\%) \\  & 9/275 & 6/275 & 12/275 & 5/275 & 13/274 & 13/274 \\  & (3.2\%) & (2.1\%) & (4.4\%) & (1.8\%) & (4.9\%) \\  & 7/275 & 6/275 & 2/275 & 13/274 & 12/275 \\  & (2.5\%) & (2.1\%) & (0.7\%) & (4.9\%) & (4.4\%) \\
4 & 7.6\% & 4/275 & 1/275 & 1/275 & 7/275 & 8/275 \\  & (1.4\%) & (0.4\%) & (0.4\%) & (2.5\%) & 2.9\%( \\
5 & 2.1\% & 2/275 & 0/275 & 0/275 & 2/275 & 2/275 \\  & (0.7\%) & (0\%) & (0\%) & (0.7\%) & (0.7\%) \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Size of periapical lesion and the relationship to mucosal thickness. important that the mucosal changes maybe not resolve following the extraction or treatment of the involved teeth [21; 30]. Patients with systemic diseases were excluded from this study. While, on the one hand, this may be a limitation of this investigation, on the other hand it reduced the variability and helped with the standardization of the study. The percentage of teeth with MS involvement seen in our study was lower than the 38.04-70.52% reported previously [7; 21; 22; 25; 45].