# Effect of the Mandibular Repositioning Appliance (MARA) on Posterior Airway Space (PAS)
## 3 Results
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Group** & **SNB T1** & **SNB T2** & **\(\Delta\)****SNA** & **\(\Delta\)****S****Rel.** \\ \hline
1 & 77.31 \(\pm\) 4.8\({}^{\circ}\) & 77.63 \(\pm\) 4.7\({}^{\circ}\) & 0.32 \(\pm\) 0.23\({}^{\circ}\) & 0.41\% \(p\) = 0.810 \\ \hline
2 & 75.98 \(\pm\) 3.9\({}^{\circ}\) & 76.08 \(\pm\) 4.3\({}^{\circ}\) & 0.10 \(\pm\) 0.07\({}^{\circ}\) & 0.13\% \(p\) = 0.930 \\ \hline
[20] & 74.6 \(\pm\) 4.99\({}^{\circ}\) & 75.89 \(\pm\) 5.12\({}^{\circ}\) & +1.29 \(\pm\) 1.34\({}^{\circ}\) & \(p\) = 0.0008 \\ \hline \hline \end{tabular}
\end{table} 
Table 6: SNB. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Group** & **SNB T1** & **SNB T2** & **\(\Delta\)****SNA** & **\(\Delta\)****Rel.** \\ \hline
1 & 81.98 \(\pm\) 4.3\({}^{\circ}\) & 81.34 \(\pm\) 5.3\({}^{\circ}\) & \(-\)0.64 \(\pm\) 0.45\({}^{\circ}\) & \(-\)0.78\% \(p\) = 0.630 \\ \hline
2 & 80.12 \(\pm\) 4.2\({}^{\circ}\) & 79.56 \(\pm\) 4.4\({}^{\circ}\) & \(-\)0.56 \(\pm\) 0.40\({}^{\circ}\) & \(-\)0.70\% \(p\) = 0.640 \\ \hline
[20] & 80.15 \(\pm\) 4.58\({}^{\circ}\) & 80.47 \(\pm\) 4.17\({}^{\circ}\) & +0.32 \(\pm\) 1.44\({}^{\circ}\) & \(p\) = 0.363 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: SNA. sagittal pharyngeal depth that is mostly significant at the 5% level, while the comparative study, at the P4 level, using the FMA (functional mandibular advancer), found a non-significant decrease, i.e., an anti-proportional relationship at the same pharyngeal level as in the present study. While the changes resulting from MARA treatment were significant at the 5% level, the FMA resulted in a change that was non-significant. Individual factors could have a negative influence on the PAS in spite of any growth happening. These negative factors could theoretically originate in the hard tissues or in the surrounding soft tissues. Soft tissues (muscles, fat, fibrous tissues and lymphatic tissue) are subject to substantial individual differences and also differences occurring in the same individual over time. Weight gain can increase pharyngeal tissue mass, particularly in the area of the root of the tongue, thereby causing the PAS to decrease in diameter [22]. However, we did not record the individual weight changes between T1 and T2, so we cannot make any assumptions here. Allergies and chronic upper respiratory infections cause an increase in lymphatic tissues, thereby negatively affecting PAS lumen and aerodynamic properties. When measuring the sagittal PAS diameter, both general methodological and individual measurement errors are possible. The posterior airway space is a complex elastic three-dimensional structure. In the lateral cephalograms, we are seeing two-dimensional projections of three-dimensional spatial relationships superimposed laterally [23]. A three-dimensional representation of the PAS would require CT or MRI imaging to obtain both sagittal and transverse measurements as well as volume measurements [24]. CTs come with the great disadvantage of ionizing radiation exposure. MRIs do not involve such radiation, but they are associated with the major disadvantage of substantial financial costs both for the imaging procedure and the contrast agent [24]. By using pre-existing lateral cephalograms, we avoided both problems by opting for a procedure that involves little radiation exposure and costs. Lateral cephalograms are routinely taken as part of orthodontic diagnostics. [PERSON] et al. validated the lateral cephalogram as a predictor for intraoral splint therapy in OSAS [25]. They conclude that lateral cephalograms taken in a supine position are a valid, practical point of reference for the PAS while lateral cephalograms taken in an upright position do not represent the PAS situation during sleep.