Three-dimensional Assessment of the Accuracy of Maxillary Repositioning by Le Fort I Osteotomy with Emphasis on Maxillary Backward Transference

Objective: To evaluate the accuracy of repositioning of the maxilla by Le Fort I osteotomy with emphasis on maxillary backward transference.Materials and Methods: Thirty patients with jaw deformity who underwent Le Fort I osteotomy were enrolled in the study. The patients were divided into 3 groups: backward transference group, in whom both molar regions were moved >2 mm in the posterior direction; forward transference group, in whom both molar regions were moved >2 mm in the anterior direction; and minor transference group, in whom both molar regions were moved <2 mm. The 3-dimensional position of the maxillary central incisor (U1) and both first molars (R6, L6) were measured on presurgical, surgical, and post-surgical dental models. The difference between planned and actual movements was analysed using Wilcoxon signed-rank test.Results: In the backward transference group, the maxilla was moved backward to excess, probably because of a preconception that forward movement after the operation due to occlusal force will occur. In the forward transference group, the maxilla was located more forward as a consequence of being excessively moved upwards. In the horizontal direction, influence of the operator's position and the plate fixation method were thought to explain the differences between the backward transference group and the forward transference group.Conclusion: To perform the operation more precisely, additional reference points with a plane factor are needed for Le Fort I osteotomy. In the future, the infrared sensor might be useful and effective.