Résumé
Context: There are a lot of disagreements among surgeons over controlling the maxillary position during orthognathic surgery. Aim: To investigate maxillary repositioning according to Frankfort horizontal plane in orthognathic surgery. Materials and Methods: Fourteen patients were selected who were submitted to maxillary or bimaxillary surgery. Maxillary model surgery was performed based on the treatment planning and an intermediate splint was made. The surgical technique in this study was based on maxillary osteotomy according to the findings of the model surgery, in a manner that the osteotomy line was parallel to the Frankfort horizontal plane. Intermediate splint was used for repositioning of the maxilla in the new position and the vertical position of that was determined according to external reference point and fixed on this position. The upper central incisor designed from prediction tracing and post-operative cephalometry on the first tracing. The new position of maxilla was evaluated horizontally and vertically. Statistical Analysis Used: A paired t-test was used to compare the predicted maxillary position and the actual position. Association between these two groups of variables was evaluated with Pearson correlation. Results: The mean difference between the maxillary planned position and post-operative cephalometric radiography varied between 0.3 mm and 0.9 mm vertically (P value = 0.315) and 0.0 mm and 0.9 mm horizontally (P value = 0.034). The averages of horizontally and vertically observed changes were 0.3 mm and 0.17 mm respectively (P < 0.001). Conclusion: Good surgical accuracy in repositioning of the maxilla can be achieved according to Frankfort horizontal plane during the surgery. By eliminating the ramping effect the accuracy of surgery increases.