## 4 Discussion  
This retrospective study in a pediatric population was aimed at reporting changes in cephalometric variables after rapid maxillary expansion orthodontic treatment in subjects affected by OSA and in control healthy children. In both groups, statistically significant increases were observed regarding the parameters relating to the airway dimension, such as width of the pharyngeal spaces. In the study group, before the treatment, the mean cephalometric values for nasopharyngeal, oropharyngeal, and hypopharynxgeal spaces were 11.6 mm (\(\pm\)1.8), 10.6 mm (\(\pm\)1.6), and 11.1 mm (\(\pm\)1.9), respectively. After the treatment, averages of 14.1 mm (\(\pm\)1.5), 13.4 mm (\(\pm\)1.5), and 14.7 mm (5.1) were observed. Therefore, a statistically significant increase in values was recorded (nasopharynx: \(z=-\)4.24, \(p=\) 0.00; oropharynx: \(z=-\)4.24, \(p=\) 0.00; hypopharynx: \(z=-\)4.12, \(p=\) 0.00). In the control healthy group, statistically significant changes were also observed in the nasopharynx and oropharynx; before treatment, the mean cephalometric values for nasopharyngeal and oropharyngeal spaces were 11.55 mm (\(\pm\)1.88) and 9.67 mm (\(\pm\)9.33), respectively, whereas averages of 12.05 mm (\(\pm\)1.54) and 10.04 (\(\pm\)1.17) were observed following orthodontic therapy. Therefore, a statistically significant increase in values was recorded (nasopharynx: \(z=-\)2.95, \(p=\) 0.00; oropharynx: \(z=-\)3.44, \(p=\) 0.00). These results confirm that maxillary expansion induces an increase in the width of the airways. In comparison with the literature, [PERSON] et al. [13] showed no significant changes in the pharyngeal spaces following rapid maxillary expansion, but it is important to mention that the [PERSON] study consisted of a sample of children affected by Marfan syndrome (a total of 30 children, aged 8 to 10 years). Moreover, all their Marfan patients initially presented a skeletal class II (ANB \(>\) 4\({}^{\circ}\)), and the treatment time (active and passive phases) was between 3 and 9 months. We, therefore, attribute the difference between our results and the Taddei results to the difference in sample selection criteria between both studies. \begin{table}
\begin{tabular}{l c c c c} \hline \hline
**Variable** & **T0** & **T1** & **T1 – T0** & \(Z\) (\(p\)) \\ \hline  & **Mean and SD** & **Mean and SD** & **Mean and SD** & **Wilcoxon Test** \\ \hline OVJ & 4.67 (1.91) & 3.72 (0.88) & 0.95 (1.55) & \(-\)2.51 (0.01) \({}^{*}\) \\ \hline
1’MAX & 111.25 (4.25) & 111.7 (3.12) & 1.2 (4.14) & \(-\)0.24 (0.80) \\ \hline
1s-N-FH & 3.95 (2.94) & 3.32 (2.36) & 0.47 (1.14) & \(-\)2.51 (0.01) \({}^{*}\) \\ \hline
1i-N-FH & 1.27 (2.6) & 0.9 (1.8) & 0.37 (1.21) & \(-\)1.47 (0.14) \\ \hline
1i’MAND & 93.27 (5.15) & 92.35 (3.1) & 0.97 (3.04) & \(-\)1.30 (0.19) \\ \hline
1s-A-Po & 2.95 (4.89) & 1.55 (3.79) & 1.45 (1.7) & \(-\)2.83 (0.00) \({}^{**}\) \\ \hline
1i-A-Po & 1.67 (2.54) & 1.1 (2.31) & 0.57 (1.32) & \(-\)1.83 (0.07) \\ \hline
1s’1i & 131.07 (4.64) & 131.57 (3.24) & 0.5 (3.1) & \(-\)0.5 (0.61) \\ \hline Ul-E-line & 1.05 (1.98) & 2.17 (1.87) & 1.07 (1.09) & \(-\)3.38 (0.00) \({}^{**}\) \\ \hline LI-E-line & 0.22 (1.88) & 1.12 (1.85) & 0.85 (0.85) & \(-\)3.31 (0.00) \({}^{**}\) \\ \hline Upper airway spaces & & & & \\ dimensions & & & & \\ \hline Nasopharynx & 11.55 (1.88) & 12.05 (1.54) & 0.55 (0.62) & \(-\)2.95 (0.00) \({}^{**}\) \\ \hline Oropharynx & 9.67 (1.33) & 10.4 (1.17) & 0.72 (0.59) & \(-\)3.44 (0.00) \({}^{**}\) \\ \hline Hypopharynx & 11.67 (1.56) & 11.67 (1.88) & 0.5 (0.53) & \(-\)0.22 (0.82) \\ \hline PNS-P & 36.47 (3.4) & 36.85 (4.06) & 0.87 (0.68) & \(-\)2.7 (0.00) \({}^{**}\) \\ \hline MP-H & 13.35 (1.25) & 14.2 (1.23) & 0.85 (0.56) & \(-\)3.59 (0.00) \({}^{**}\) \\ \hline PH L & 77 (3.22) & 77.65 (2.83) & 0.65 (0.63) & \(-\)3.21 (0.00) \({}^{**}\) \\ \hline \hline \end{tabular} \({}^{*}\)\(p<\) 0.05; \({}^{**}\)\(p<\) 0.01.  
\end{table} 
Table 5: _Cont._Another study, by [PERSON] et al.