Objective: The purpose of the present study is to evaluate the accuracy of repositioning of the maxilla during orthognathic surgery using Le Fort I osteotomy.

Patients and methods: Forty-two patients with jaw deformity who underwent Le Fort I osteotomy were enrolled in the study. All the osteotomies were performed by the same operator. The patients were divided into 3 groups; backward transference group (16 cases), in whom both molar regions were moved 3 mm in the posterior direction; forward transference group (22 cases), in whom both molar regions were moved 3 mm in the anterior direction; and minor transference group (18 cases), in both molar regions were moved 3 mm. The three-dimensional position of the maxillary central incisor (U1) and both first molars (R6, L6) were measured with presurgical, surgical and post-surgical dental models. The differences between planned (model surgery) and actual movement (within 3 weeks of surgery) were analyzed with Wilcoxon sighed-test.

Result: In the backward transference group, maxilla was moved backward more excessively than the planned, probably because of the preconception that forward movement will occur after the operation due to occlusal force. In the forward transference group, maxilla was located more forword as a consequence of being excessively moved upward. In the horizontal direction at the backward transference group, maxilla was moved to right side. The influence of the operators position and the plate fixation method were thought.

Conclusion: To perform the operation more precisely, additional reference points with a plane factor are needed for repositioning maxilla during Le Fort I osteotomy.

Key words : three dimensional; maxilla; Le Fort I osteotomy