Abstract: Objective: To describe the design and manufacture of a novel condylar positioning device with computer-aided design in sagittal split ramus osteotomy,and to verify the accuracy by model test. Methods: The sample included 10 patients with a total 20 condyles. The patients had completed preoperative orthodontic treatments and were undergoing orthognathic surgeries. CT data containing patient's jaw and occlusion information were imported into Mimics 17.0 software. The mandible and midface were reconstructed, and were completed with the virtual SSRO, Lefort I osteotomy and bone movements, to obtain a new upper and lower jaw position. Freeform 12.0 software was used to design the guiding splint and proximal segment positioning guide. They were connected with a cylinder. Integrated condylar positioning device, proximal segment, and distal segment were 3D printed. The condylar positioning devices were used to connect the proximal segment models and distal segment models. The segments were joined together and went through a CT scan. CT data were imported into Mimics 17.0 software, the linear differences and coordinate differences of three condylar landmarks in the virtual group and the model group were measured. Statistical analyses were performed using RMSD. Results: Excellent consistency was proved with largest positional RMSD of 0.738mm and largest postural angular RSMD discrepancy of 1.1°. Conclusion: This condylar positioning device with computer-aided design can accurately locate the condyles in in vitro experiment, which might be used as an alternative method to obtain the correct position of the condyle in orthognathic surgery.

Key words: Condyle position, Guiding splint, Sagittal split, CAD/CAM, Proximal segment