## 4 Discussion  
With the rapid development of digital technology, various innovative surgical aids for more accurate surgery, including surgical guides, patient-specific plates, and surgical navigation, have been developed and applied. Surgical navigation provides a 3D anatomical position through the application of an indicator with a tracking device, and can also track positional changes of anatomical structures in real time during surgery. In the field of maxillofacial surgery, including orthognathic surgery, the movement of bone segment can be tracked during the operation, and it can be confirmed whether the bone segment is located as planned [7; 22; 23; 24; 25]. [PERSON], et al. [25] used intraoperative navigation for the final fixation of the maxilla after intermediary fixation using an intermediate splint. In the study by [PERSON], et al. [24], maxillary repositioning was performed using navigation with 3D printed positioning guides. [PERSON], et al. [23] developed an image-guided orthognathic surgical system for repositioning the maxillomandibular complex. However, stabilization and fixation of the movable bone segment while holding the bone segment in the target position is challenging in navigation assisted orthognathic surgery [7; 26; 27]. Although various temporary support of the mobilized maxillary segment can be used, drilling on an unstable maxillary segment and the unsuitability of the plate bending may influence the repositioning accuracy. To overcome the difficulties in stabilization and fixation of the maxilla, a surgical system that combines the surgical navigation and the robot arm has been proposed [28; 29; 30; 21]. The robot arm can hold the osteotomized maxilla stable for a long time and minor changes of the maxilla can be monitored using the navigation. Since the [PERSON], et al. [31] introduced the first robotic surgical system that was used for orientation of a needle for brain biopsy, the use of robotic assistants is expanding into various surgical fields due to the distinctive advantages, such as magnified visualization, bimanual operation with robot arms, minimal invasiveness, and lack of tremor. In orthognathic surgery, there also have been efforts to introduce robotic technology into the operation field. [PERSON], et al. [28] developed a prototype end-effector for Le Fort I osteotomy and registration methods and presented a system for robot assisted orthognathic surgery. In their system, the preoperative planning of the surgical procedure, such as the acquisition of the initial and target position of the maxilla, was achieved using a mechanical articulator, and then the robotic system acquired the relative transformation between the initial and target positions. After intraoperative registration of the initial position, the maxilla was moved to the target position using the transformation. [PERSON], et al. [29] assessed the stability and usability of light-weight robot to hold the maxillary segment in the target position during the drilling and fastening of the maxilla. In the recent study by [PERSON], et al. [30], a robotic system for orthognathic surgery that consisted of virtual surgery, surgical navigation and a robot-arm was proposed, and its reliability was analyzed according to the preliminary experiments to measure the distance between the fiducial markers after repositioning the maxilla. Despite the fact the several robot-assisted surgical systems for orthognathic surgery has been proposed, the clinical application of the robot-assisted surgical system has not been reported, and this system still remains in an experimental stage [20]. There are several limitations have to overcome for broader application of the robot assistant to orthognathic surgery. One of the limitations of current robotic assistants is a lack of tactile perception and haptic feedback. Thus, the proper resistance is not provided to the surgeon, which can cause undesirable damage when performing the osteotomy or moving bone segments.