## 4 Discussion  
The study was conducted to measure the effectiveness of ASSD appliances in treating severe Class III malocclusion cases that were indicated for surgical treatment. There were some unique characteristics to this study. First, the sample of the study was collected from 18 secondary schools by a screening of 13,500 students. It was considered a very big number in comparison to similar studies, which collect smaller sample sizes from the outpatient clinic, not by screening of the target population. In addition, many studies were carried out to investigate the effects of using rigid skeletal anchorage, Alt.RAMEC and sutural distraction method for treatment of Class III malocclusion, but as far as we are aware, no study had been performed to investigate the effect of combining these three approaches. Furthermore, we innovated a unique design for the ASSD appliance, which involves a small size maxillary expander that is not presented in any other similar studies making the appliance suitable for any patients who have different palatal shape and height. Next, the effects on the craniofacial skeleton induced by facemask therapy have seldom been investigated in adequate samples, especially in late adolescent subjects, as evident in this study [19]. The result of this study showed that the ASSD was effective in the treatment of Class III malocclusion in late adolescent subjects. Although most of the subjects showed improvement of the Class III malocclusion, the amount of the correction varied greatly among patients, as did their level of cooperation. Assessment of the results demonstrated significant changes in the maxilla as well as in the mandible that favored correction of Class III malocclusion. The maxilla became more forward due to a significant increase in the maxillary position (SNA), increase in maxillary length (CO-A), and forward movement of A point (A-N perp). The skeletal point A forward changes by 3.69 mm revealed that maxillary growth was achieved in the ASSD treatment group and that the ASSD effectively facilitated skeletal growth of the maxilla. In spite of differences between ASSD treatment protocols and the other similar studies, a common trend was observed in similar studies for A-point advancement in the horizontal plane as a result of bone-anchored orthopedic treatment. [PERSON] et al. [20] compared the results of conventional orthopedic appliances with those obtained from recent bone-anchored orthopedics for Class III malocclusion treatment. In those studies, using skeletal anchorage, there was forward movement in the horizontal plane with a mean A-point advancement of 5.2 mm [21; 22; 23]. \begin{table}
\begin{tabular}{l c c c c} \hline \hline
**Variables** & \multicolumn{2}{c}{**Mean (SD)**} & \multicolumn{1}{c}{**Mean Difference (95\% CI)**} & \multicolumn{1}{c}{**t-Statistics (df = 25)**} & \multicolumn{1}{c}{\(p\)**-Value**} \\ \hline  & **T1** & **T2** & & \\ \hline ICW & 35.8 (3.31) & 36.1 (3.38) & 0.35 (\(-\)0.07, 0.76) & 1.74 & 0.095 \\ IPW & 44.1 (3.38) & 44.3 (3.47) & 0.23 (\(-\)0.06, 0.52) & 1.66 & 0.110 \\ IMW & 54.5 (3.10) & 59.9 (3.41) & 5.38 (4.72, 6.05) & 16.63 & \textless{}0.001 * \\ PW & 26.0 (3.35) & 26.9 (2.90) & 0.92 (0.38, 1.47) & 3.48 & 0.002 * \\ \hline \hline \end{tabular}  
* \(p\) < 0.05.  
\end{table} 
Table 7: Difference in pretreatment (T1) and post-treatment (T2) transverse variables in ASSD group (n = 26). In addition, the maxilla became more forward due to an increase in the maxillary position (SNA) by 2.73\({}^{\circ}\), similar to the finding of [PERSON] et al. [24] by 2.4\({}^{\circ}\) as well as [PERSON] et al. [25] by 2\({}^{\circ}\) with more increments. These differences may be attributed to the differences in the subject's characteristics, treatment protocol, and treatment durations (14 months). In addition to that, an increase in maxillary length (Co-A) was significant as well (4.62 mm), and this was in agreement with [6; 24; 25].