## 4 Discussion
The results indicated that the two-jaw surgery could more likely achieve facial symmetry and balance, particularly in the lower part of the face [20]. The surgical design of cleft OGS is based on the patient's deformity, surgeon's preference and training background. In the literature review, Table 6 shows that the rate of one-jaw or two-jaw surgery varied among different institutions, ranging from 12% to 100% for two-jaw surgery. From 2017 to 2020, all patients with a unilateral cleft lip and palate received two-jaw orthognathic surgery in our center. An important reason for such a high rate of two-jaw cleft OGS was the application of 3D imaging and virtual surgery planning, which accurately detected bony abnormalities to achieve symmetry in the simulation [33]. Mandibular yaw rotation to avoid ramus bony collision and attain cheek symmetry was conveniently achieved in the two-jaw surgery planning (Figure 4). More than 98% of patients with cleft received two-jaw orthognathic surgery when it was indicated. This paradigm shift was mentioned in our previous publications, with the more reasons than facial symmetry, but also including other facial aesthetic purposes, such as smile arc. It is the center's treatment preference and could be a bias. However, for the discrepancies that remain after the one-jaw surgery, there is the possibility of orthodontic correction with temporary anchorage devices which can correct the occlusal cantus and midline discrepancies for the unoperated maxilla. It is believed that with the right collaboration, some of the cases which were two-jaw surgery at the first glance can be resolved with only one-jaw  
Figure 3: A case in the regular advancement design showed that the jaw relationship was improved by the clockwise rotation of the maxillomandibular complex. (**Left**) Preoperative image showing that ANB was \(-5.26^{\circ}\). (**Middle**) In one-jaw surgical simulation, the maxilla was advanced 4.63 mm following Le Fort I osteotomy. The skeletal class III jaw relationship was not fully corrected with the ANB angle of \(0.11^{\circ}\). (**Right**) A skeletal class I jaw relationship with an ANB angle of \(3.57^{\circ}\) was achieved following two-jaw surgery with the clockwise rotation of the maxillomandibular complex. surgery if temporary anchorage devices are placed. The occlusal plane can also be adjusted by maxillary molar intrusion. Ethnic differences should be considered in designing the cleft OGS. It is noted that Asians have a higher incidence of Angle class III malocclusion and a relatively large mandible compared to maxilla and cranial base [34; 35]. It is, therefore, favorable and popular to include mandibular setback and rotation in the cleft OGS [36; 37; 38]. Possible drawbacks from the addition of mandibular osteotomy should also be concerned. These included longer operative time, infection, blood loss, and chin numbness. With preoperative imaging of the inferior alveolar nerves and careful performance of the ramus split osteotomy, the neurosensory disturbance should be kept to a minimum [39; 40]. Airway decrease by mandibular setback was reported and should be cautioned in patients with  
Figure 4: The same case as in Figure 1 demonstrated roll and yaw rotations of the maxillomandibular complex for asymmetry correction in two-jaw surgical planning. (**A**) Occlusal plane and chin deviation were improved after clockwise rotation in the roll direction. (**B**) Elimination of residual asymmetry of contour and interference between the osteotomized bony segments by counterclockwise rotation of the maxillomandibular complex in the yaw direction. As a result, the advancement in the LeFort I level was 1.50 mm in the right piriform and 5.07 mm in the left piriform. breathing problems [41; 42]. However, the improvement in sleep apnea and snoring without airway-related problems was also described [43; 44]. This is consistent with our clinical experience.