## 1 Introduction  
Correct repositioning of the maxilla to the planned position is essential to achieve a successful treatment outcome in orthognathic surgery [1; 2; 3]. To transfer a surgical plan to the operation field, most surgeons use intermediate splints which require several error-prone procedures including making a cast model, transfer of the face bow, model surgery, and fabrication of acrylic splints [4; 5]. In addition, intermediate splints can provide the transverse and sagittal position of the maxilla; however, the vertical position of the maxilla in relation to the basal skull is controlled intraoperatively by the surgeon on the basis of the various intraoral and/or extraoral measurements, including the distance between the reference points and the amount of incisional exposure [6; 7; 8; 9]. In the comparison of model surgery prediction with the actual surgical changes, over- or under-advancement of the maxilla occurred in over 50% of patients, and over- or under-impaction also occurred in over 40% of patients [10]. In another study, the difference between the model surgery and the surgical result ranged from \(-\)7.7 to 6.6 mm, and the absolute mean difference was 2.2 mm [11]. Recently, [PERSON] et al. [12] reported that a repositioning error of the maxilla between 2 and 4 mm was seen in 16.4% and 20.0% for anterior posterior and superior inferior directions, respectively. Recent advances in computer-aided design computer-aided manufacturing (CAD/CAM) technology and three-dimensional (3D) printing techniques have constituted a paradigm shift in orthognathic surgery, which has enabled more accurate treatment planning and surgery [1; 9; 13; 14; 15]. Two-dimensional cephalometric analysis has been replaced by 3D computed tomography (CT) analysis, and postoperative surgical outcome has been predicted using 3D simulation programs in place of paper surgery [16; 17]. Various CAD/CAM-based templates for orthognathic surgery have been developed as an alternative to intermediate splints [1; 3; 6; 9; 18; 19; 20; 21]. These templates include surgical templates and patient-specific implants (PSI). Surgical templates can provide the location and orientation of the osteotomy line, the areas of bone interferences, and the final position of the bony segments [1; 2; 9; 20; 21]. Following repositioning of the bony segments using the template, the mini-plate is bent intraoperatively according to the contours of the bone, which is then applied for fixation. In contrast, PSI can serve not only as a positioning or osteotomy guide but can also be used in osteosynthesis for rigid fixation of the maxillary segment [3; 18; 19; 20]. Currently, such 3D CAD/CAM-based templates have been widely used for various facial skeleton surgeries including Le Fort I osteotomy, bilateral sagittal split ramus osteotomy, genioplasty, or facial contouring surgery [15; 22; 23; 24; 25; 26]. With the increased use of CAD/CAM-based templates, several investigators assessed the surgical accuracy after orthognathic surgery using CAD/CAM-based templates [3; 18; 20; 27]. Although successful surgical outcomes have been reported in most of patients, clinically significant surgical error occurred in some patients. Furthermore, the cases where the CAD/CAM-based template was not usable were also reported. Hence, in addition to the use of CAD/CAM-based templates in orthognathic surgery, several surgeons have also prepared an intermediate splint as an alternative plan [3; 18]. Therefore, to ultimately replace the intermediate splint, researches on the causes of the surgical error or the situations when the template is not usable are necessary. In the previous reports, the positioning accuracy of the template has been suggested as one of the contributing factors to the surgical accuracy [28; 29]. CAD/CAM-based templates can transfer the presurgical plan to the surgical site accurately only when the template is positioned correctly. Nevertheless, to our knowledge, few reports have assessed the positioning accuracy of the template.