## 3 Results
### Intragroup Comparisons  
After treatment, the RS group showed an improvement in arch width, which was supported by statistical increases in smile width (5.23 mm) and smile index (0.80 ratio),  
\begin{table}
\begin{tabular}{l l l l l l} \hline \hline  & **RS Group** & \multicolumn{3}{c}{**IF Group**} \\ \hline
**Variable** & **Median** & **Mean (SD)** & **Median** & **Mean (SD)** & \(\mathbf{p}\) **Value** \\ \hline Smile width (mm) & 44.12 & 43.75 (4.33) & 44.15 & 44.2 (4.67) & 0.62 \\ \hline Lip symmetry (ratio) & 1.05 & 1.07 (0.02) & 1.09 & 1.07 (0.09) & 1.00 \\ \hline Smile index (ratio) & 5.98 & 5.71 (1.33) & 5.96 & 5.56 (1.61) & 0.39 \\ \hline Smile cant (\({}^{\circ}\)) & 0.99 & 1.18 (0.27) & 1.03 & 1.12 (0.13) & 0.46 \\ \hline Buccal corridor (ratio) & 23.45 & 23.32 (4.22) & 23.07 & 22.86 (4.67) & 0.07 \\ \hline Buccal corridor (mm) & 8.21 & 8.11 (0.56) & 8.56 & 8.48 (0.39) & 0.61 \\ \hline Upper lip thickness (mm) & 6.77 & 6.02 (1.22) & 6.43 & 6.07 (1.94) & 0.73 \\ \hline Lower lip thickness (mm) & 8.93 & 8.12 (1.03) & 8.65 & 8.39 (1.18) & 0.75 \\ \hline Incisor gingival display (mm) & 2.02 & 2.82 (1.0) & 2.89 & 2.67 (0.87) & 0.62 \\ \hline Maximly dental midline (mm) & 0.85 & 0.94 (0.02) & 0.79 & 0.98 (0.19) & 0.89 \\ \hline Canine gingival display (mm) & 1.72 & 1.52 (0.85) & 1.63 & 1.34 (0.66) & 0.34 \\ \hline C angulation (\({}^{\circ}\)) & 77.01 & 76.32 (7.55) & 77.32 & 77.43 (8.97) & 0.47 \\ \hline Maximly incisor position (mm) & 5.54 & 4.62 (2.01) & 5.76 & 4.73 (2.33) & 0.54 \\ \hline Maximly incisor inclination (\({}^{\circ}\)) & 106.91 & 106.23 (8.54) & 106.06 & 105.62 (7.53) & 0.69 \\ \hline IMPA (\({}^{\circ}\)) & 88.09 & 88 (5.45) & 88.01 & 87.23 (4.73) & 0.72 \\ \hline \multicolumn{6}{l}{SD = standard deviation.} \\ \hline \hline \end{tabular}
\end{table}
Table 4: Descriptive statistics and statistical comparison on the starting forms (valuated at T1).  
Figure 4: (**a**) Pre-treatment; (**b**) post-treatment smile outcomes after RME treatment; (**c**) post-treatment smile outcomes after clear aligners treatment.  
and a significant decrease in buccal corridor (\(-\)6.35 ratio, \(-\)3.53 mm). After RME therapy, the RS group subjects also evidenced an extrusion and lingualization of the maxillary incisors, which was supported by statistically significant increases in incisor gingival display (0.80 mm) and OVB (0.51 mm), and significant reductions in maxillary incisor inclination (\(-\)3.33\({}^{\circ}\)) and OVJ (\(-\)1.55 mm) values. In addition to these movements, a worsening in maxillary dental midline (0.21 mm) was also evident after RME treatment.  
No statistical differences in canine gingival display or C angulation parameters were reported at T2.  
In the same intragroup comparisons, at the end of treatment (T2), the CAs group evidenced an effective improvement in arch width, as shown by increases in smile width (3.42 mm) and smile index (0.53 ratio) and a reduction in buccal corridor (3.02 mm, 1.48 ratio). Furthermore, differently to the RS group, after therapy, the CAs subjects evidenced incisor intrusion movement, supported by reductions in incisor gingival display (\(-\)0.45\({}^{\circ}\)), overbite (\(-\)1.54 mm) and canine gingival display (\(-\)0.41 mm) values. At the same time, significant improvements in incisor and canine inclination were achieved, as demonstrated by increases in maxillary incisor inclination (3.70\({}^{\circ}\)) and C angulation (3.57\({}^{\circ}\)) values. A statistical improvement in maxillary dental midline (\(-\)0.62\({}^{\circ}\)) was also evidenced in the CAs group.  
The results for intragroup comparisons are reported in Table 5.