## 4 Discussion  
Cleft lip and palate are the most common congenital craniofacial anomaly. One of the common problems is midfacial retrusion owing to maxillary hypoplasia, which needs to be addressed after skeletal maturity. With the mandible in a relative prognathic position, patients have a class III facial profile. Orthognathic surgery serves as a definitive approach to rehabilitate function and esthetics [3, 6]. Traditionally, a single-jaw LeFort I osteotomy with advancement was performed for the skeletal discrepancy, accepting that the mandible was generally in the correct anteroposterior position in order to avoid setting the mandible back [5]. However, orthognathic surgery for patients with cleft is more challenging due to scarring in orofacial tissues, less predictable vascular supply, inadequate tissue quality, and poor dental occlusion [21, 22]. Compared to the cephalometric norms, SNA and A-N perpendicular of the subjects were significantly smaller, indicating prominent maxillary \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Parameters**} & \multicolumn{2}{c}{**One-Jaw**} & \multicolumn{2}{c}{**Two-Jaw**} & \multicolumn{2}{c}{**One-Jaw vs. Two-Jaw**} \\ \cline{2-7}  & **Mean** & **SD** & **Mean** & **SD** & **\(p\) Value** \\ \hline \multicolumn{7}{c}{**Regular advancement (\(t\) = 15)**} \\ SNA & 85.23 & 4.25 & 80.68 & 2.95 & 0.000 ** \\ SNB & 80.83 & 4.86 & 77.73 & 3.67 & 0.000 ** \\ ANB & 4.67 & 3.41 & 3.20 & 3.12 & 0.050 \\ A-N perpendicular & 3.88 & 3.94 & \(-\)0.66 & 2.85 & 0.000 ** \\ Pog-N perpendicular & \(-\)0.13 & 8.42 & \(-\)1.90 & 4.36 & 0.188 \\ \hline \multicolumn{7}{c}{**Regular advancement (\(t\) = 15)**} \\ SNA & 80.41 & 5.77 & 80.99 & 4.82 & 0.316 \\ SNB & 79.91 & 4.64 & 77.73 & 3.21 & 0.007 ** \\ ANB & 0.25 & 4.34 & 3.53 & 4.15 & 0.004 ** \\ A-N perpendicular & 0.05 & 4.13 & 0.67 & 3.38 & 0.236 \\ Pog-N perpendicular & 0.14 & 5.42 & \(-\)1.32 & 4.94 & 0.441 \\ \hline \multicolumn{7}{c}{**\(p\) < 0.01.} \\ \end{tabular}
\end{table} 
Table 4: The 3D cephalometric measurements in the larger (more than 6 mm) and regular (6 mm or less) advancement designs. \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Landmarks**} & \multicolumn{2}{c}{**T0**} & \multicolumn{2}{c}{**One-Jaw**} & \multicolumn{2}{c}{**Two-Jaw**} & \multicolumn{2}{c}{**T0 vs. One-Jaw**} & \multicolumn{2}{c}{**T0 vs. Two-Jaw**} & \multicolumn{2}{c}{**One-Jaw vs. Two-Jaw**} \\ \cline{2-10}  & **Mean** & **SD** & **Mean** & **SD** & **Mean** & **SD** & **\(p\) Value** & **\(p\) Value** & **\(p\) Value** \\ \hline \multicolumn{10}{c}{**Maxilla**} \\ A & 1.58 & 1.19 & 2.27 & 1.60 & 1.75 & 1.19 & 0.010 * & 0.497 & 0.039 * \\ U1 & 3.06 & 1.90 & 2.77 & 2  
retrusion (Table 2). It is expected that the single movement of maxillary advancement could be more difficult. For comparison of one-jaw and two-jaw designs, SNA, SNB, and A-N perpendicular were significantly smaller in the two-jaw design due to simultaneous mandible setback and clockwise pitch rotation of the maxillomandibular complex. The simulation after two-jaw surgery revealed a relatively bimaxillary retusive facial profile as compared to the result with one-jaw surgery. However, Pog-N perpendicular was not significantly different because 31 out of 41 subjects received genioplasty in the two-jaw surgery (Table 3). In this computer-assisted surgical simulation study, the occlusal set-up of one-jaw and two-jaw was identical. The final occlusion of all cases was set up by the same orthodontist in this study cohort. Overjet and overbite were set up at 2 mm with upper and lower dental midline coincidence. To achieve stable postoperative occlusion, the movement of maxilla was restricted by mandible and dental occlusion in the one-jaw surgery. Therefore, the occlusal plane cannot be adjusted without a mandibular osteotomy. Both anterior and posterior occlusal plane cants of the two-jaw design were superior to the one-jaw design.