Cephalometric Evaluation of Maxillary and Mandibular Centers of Rotation Subsequent to Maxillary and Mandibular Surgery

Abstract

Background: Due to significant effect of joint orthodontic and surgical treatment planning on the patients’ facial appearances, precise prediction of surgical outcomes is of great importance. Objectives: The aim of this study was to determine the maxillary and mandibular centers of rotation and its distance to center of condyle (CC) in patients who underwent maxillary impaction surgery concomitant with mandibular advancement or setback surgery and also to determine the correlation between maxillary center of rotation (MxCR) with that of mandible (MnCR) and also the direction of rotation in distal and proximal segments of the mandible. Methods: Preoperative and postoperative lateral cephalograms of 24 adult non-syndromic patients were studied. Using cephalometric tracings MxCR was located as the intersection of ANS-PNS (preoperative) and ANS’-PNS’ (postoperative) lines. MnCR was located using Reuleaux method, where perpendicular bisectors of B-B’ and Go-Go’ lines meet. Using statistical analysis of correlation and comparison, all the points’ coordinates and centers of rotation were compared. Results: The average distance of MnCR to CC was 10.45 cm and the average distance of MxCR to CC was 8.39 cm. MxCR and MnCR had positive correlation in horizontal plane and they had negative correlation in vertical plane but the correlation was insignificant (P > 0.05). In addition, there seemed to be no specific pattern in the direction of mandibular proximal and distal segments’ rotations. Conclusions: The results showed that: (1) The center of rotation calculated for mandible after bimaxillary surgery was not located within the condylar area. But generally whenever MxCR was closer to ANS, MnCR was located more anteriorly. (2) In patients with decreased distance between MxCR and SN line, MnCR would be located more superiorly. Also, whenever MxCR had greater distance from condyle, the MnCR to condyle distance was greater too. (3) The direction of rotation in proximal and distal segments of mandible had no specific pattern.