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Purpose: While regional voxel-based registration (R-VBR) has been shown to have excellent reproducibility and angular accuracy, there are limited data on the linear accuracy of R-VBR for common orthognathic surgery landmarks, or on whether angular accuracy correlates with linear accuracy. The purpose of this study was to estimate the linear accuracy of R-VBR for several skeletal landmarks commonly used in orthognathic surgical planning, and to measure the correlation between angular and linear discrepancies., Materials and Methods: This is a retrospective cross-sectional study of consecutive patients treated at a single center with nonsegmental LeFort I and bilateral sagittal split osteotomy surgery from January 2019 to November 2020. Cone beam computed tomography at the preoperative (T0) and immediate postoperative (T1) stages were analyzed to measure the postoperative positional changes of 11 orthognathic landmarks in 4 regions of interest (ROI) using R-VBR performed twice by two examiners. Pairwise correlation analysis and canonical correlation analysis were performed for the angular discrepancies (primary predictor variable) and the linear discrepancies (primary outcome variable) to measure the correlation between the two., Results: In cone beam computed tomography analysis of 28 eligible subjects (16 males, 12 females; mean age 18.9 years, range 15 to 25), the mean absolute (MA) angular discrepancies ranged from 0.15° to 0.55°, while the corresponding MA linear discrepancies ranged from 0.05 to 0.41 mm. There was a strong correlation between angular and linear discrepancies that was statistically significant (P = .001 to .04, Spearman's rank correlation coefficient 0.38 to 0.87)., Conclusions: For nonsegmental LeFort I osteotomies and bilateral sagittal split osteotomy, R-VBR has excellent linear accuracy within a single voxel size (0.3 mm) for commonly used orthognathic landmarks in the maxillary and distal mandibular ROI. The MA linear discrepancy for the proximal mandibular segment ROI was greater than a single voxel size, with a maximum of 0.41 mm., (Copyright © 2023 American Association of Oral and Maxillofacial Surgeons. Published by Elsevier Inc. All rights reserved.)

Changing the facial appearance with facial contouring surgery is popular, especially in East Asian countries where a square face is a common chief complaint. Mandibular angle reduction, malar reduction, genioplasty, and chin and body contouring surgery can be performed as independent or ancillary procedures during orthognathic surgery. Many techniques have been developed and different osteotomy designs have been proposed to enhance outcomes and minimize complication risks. Here, we review the surgical techniques and considerations for mandibular angle and malar reduction, the two most commonly performed contouring surgeries in East Asia to correct the square face., Competing Interests: Disclosure There are no commercial or financial conflicts of interest or any funding sources for all authors., (Copyright © 2022 Elsevier Inc. All rights reserved.)

Purpose: While the accuracy, cost-effectiveness, and time-efficiency of computer-aided orthognathic surgical planning (CAOP) have been studied, little is known about the influence of logistical factors of outsourced CAOP (OS-CAOP) on patient care. The purpose of this study was to investigate the limitations of OS-CAOP and their effect on treatment planning workflow and surgical outcomes., Methods: A retrospective cross-sectional study was designed involving subjects who had undergone orthognathic surgery using CAOP from 2 academic oral and maxillofacial surgery centers in South Korea (Kyungpook National University, KNU) and the United States (University of Illinois Chicago, UIC) over an 8-year period. The primary predictor variable was use of modifications or alternatives to OS-CAOP. The primary outcome variable was the frequency of planning changes due to reasons that may have affected outcomes. Covariates included age and sex. Descriptive statistics was used, in addition to a chi-square test to analyze differences among categorical variables., Results: Of a total of 642 eligible subjects in both centers, 5.8% used alternatives to OS-CAOP. 78.4% of these were due to reasons that may have affected outcomes (P < .001), representing 4.5% of all cases. The frequency of the need for OS-CAOP alternatives was identical in both centers (5.8%), but the specific reasons varied, with KNU having mostly plan-related changes (38.1% of alternatives), and UIC with more access and education-related reasons (68.8% of alternatives). At KNU, 71.4% of all alternatives were by repeat OS-CAOP, whereas at UIC, all were by in-house CAOP (IH-CAOP)., Conclusions: In 2 major academic oral and maxillofacial surgery centers in South Korea and the United States, a substantial portion of OS-CAOP required pre-surgical modification, or use of alternatives. Most of the changes were for reasons that could potentially impact outcomes, prompting the need to consider establishing a "safety net" plan compatible with individual clinician's practice setting and healthcare system., (Copyright © 2022 American Association of Oral and Maxillofacial Surgeons. Published by Elsevier Inc. All rights reserved.)

Purpose: Despite having excellent reproducibility, the accuracy of regional voxel-based registration (R-VBR) techniques used for postoperative orthognathic surgical analysis has not been validated. The purpose of this study was to validate the accuracy of R-VBR., Methods: Preoperative (T0) and postoperative (T1) cone beam computed tomography (CBCT) of consecutive patients treated at a single center with nonsegmental LeFort I and bilateral sagittal split osteotomy were included. T1 CBCTs were oriented to match that of the standardized T0, and thus were assigned a known rotational transformation matrix in pitch/roll/yaw (P/R/Y), to create T1-prime (T1'). A copy of T1 (cT1) was made and was superimposed to T1' using R-VBR for 4 regions of interest (ROI): maxilla, distal mandible, right proximal mandible, and left proximal mandible, to create cT1'. The transformation matrix for each of the ROI was compared to those of T1' using paired t test and Bland-Altman analysis., Results: Twenty-eight eligible subjects' CBCTs were analyzed. Mean difference between T1' and cT1' ranged from -0.08 to 0.14° (maximum 0.73°), with no statistically significant differences (P = 0.216 to 1). Mean absolute difference ranged from 0.13 to 0.31° (maximum 0.73°). Bland-Altman analysis showed good agreement between T1' and cT1', indicating excellent accuracy., Conclusions: R-VBR using the maxilla, distal mandible, and the bilateral proximal mandibular segments as ROI has excellent accuracy in terms of rotational measurements., (Copyright © 2021 The American Association of Oral and Maxillofacial Surgeons. Published by Elsevier Inc. All rights reserved.)

Purpose: The 3-dimensional (3D) accuracy of computer-assisted planning (CAP) of segmental maxillary osteotomies has seldom been reported with a comprehensive 3D analysis. The aim of the present study was to measure the accuracy of computer-planned segmental maxillary surgery and to identify the factors associated with accuracy., Materials and Methods: The present retrospective, cross-sectional study investigated cone-beam computed tomography (CBCT) scans of patients who had undergone segmental maxillary osteotomy with CAP at a single center from January 2013 to October 2019. The predictor variables were age, gender, diagnosis, CAP method, type of maxillary segmentalization, surgeon, surgical sequence, and magnitude of planned and actual movements. The primary outcome variable was surgical discrepancy (linear differences between the actual and planned maxillary movements using CAP in the x, y, and z coordinates) at various 3D landmarks. The mean difference and absolute mean difference (AMD) were computed to estimate the direction and magnitude of the discrepancies. In addition, a 2.0-mm threshold of surgical discrepancy was used to determine clinically acceptable accuracy. The association between the predictor and outcome variables were analyzed statistically using correlation and regression analyses., Results: The sample included 63 patients (mean age, 20.1 years; 42.9% male). The surgical discrepancy was similar for 2- and 3-piece segmental maxillary osteotomies. Overall, the AMD for all patients was 0.96 ± 0.69 mm transversely, 1.23 ± 0.83 mm vertically, and 1.16 ± 0.80 mm anteroposteriorly (P < .01 for all). The discrepancy between the actual and planned movements was within 2.0 mm for more than 80% of cases. The major predictor variable that affected surgical discrepancy was the magnitude of the actual surgical movements (P < .01)., Conclusions: 3D CAP showed clinically acceptable accuracy for segmental maxillary osteotomies comparable to that of nonsegmental cases. Although the magnitude of actual surgical movements was shown to affect surgical accuracy, the sources of surgical discrepancies requires further investigation., (Copyright © 2020 American Association of Oral and Maxillofacial Surgeons. Published by Elsevier Inc. All rights reserved.)

Purpose: Lip asymmetry greatly influences patient satisfaction after 2-jaw surgery. The purpose of the present study was to identify the influence of skeletal changes on lip cant correction in 2-jaw surgery for mandibular prognathism with asymmetry., Material and Methods: The present retrospective cohort study included consecutive skeletal Class III patients who had undergone Le Fort I and sagittal split ramus osteotomy with preoperative and 6-month postoperative cone-beam tomography scans available. The primary predictor variables were the postoperative hard tissue changes (canine cant, first molar cant, transverse change at menton [Me] after surgery, and changes postoperatively from preoperatively). The primary outcome variable was the change in the soft tissue lip cant. The secondary outcome variables were the changes in various landmarks representing perioral asymmetry, including center of cupid's bow, lower lip vermilion, and subnasale. Other variables included subject age and gender. Descriptive statistics and regression and correlation analyses were used to investigate the important predictors influencing lip cant change., Results: A total of 58 patients (33 males; average age, 21.7 years) were included in the present study. The demographic variables of the asymmetry group (Me deviation >4 mm) were not different from those of the control group. Postoperative changes in Me deviation correlated significantly with the changes in the transverse position of the subnasale, upper lip, and horizontal and vertical differences in the mouth corner position (P < .01 for all) but not with the maxillary occlusal cant change. Linear regression analysis showed lip cant correction was associated with changes in Me deviation (P < .001) and molar cant change (P = .032), but not with canine cant change., Conclusions: Maxillary occlusal cant correction itself cannot fully account for changes in lip cant. The transverse Me change-rather than maxillary cant correction-had the greatest influence on lip cant. These results suggest that correction of chin deviation must be addressed in lip cant correction for facial asymmetry., (Copyright © 2020 American Association of Oral and Maxillofacial Surgeons. Published by Elsevier Inc. All rights reserved.)

Purpose: Surgical simulation should reflect the 3D movement of dentition and the resultant movement of the osteotomized segments, which can influence surgical outcome. The present study was aimed at developing a new simulation system that enables virtual osteotomy of a given surgical situation and evaluation of the bony interference between the osteotomized segments of the mandible., Subjects and Methods: The data of 3D computer tomography (CT) for maxillomandibular dental casts were integrated into the standard coordinates of a 3D cephalogram. To evaluate the accuracy of the system, measurement errors of the 3D CT virtual model from a dry skull were compared with the computer simulation system and a contact-type 3D digitizer. To examine the clinical accessibility, 15 mandibular prognathism patients with mild to severe asymmetry were evaluated with the simulation program., Results: The average error of measurement in all directions was 1.31 mm. It was possible to simulate various osteotomy procedures by conversion of the 3D coordinates of the dental cast and CT data into the standard coordinate system of a 3D cephalogram. Using this simulation system, it was possible to prevent condylar torque or segment malpositioning by removing the bony interference visualized by a 3D virtual model., Conclusion: A new system, which enables the precise visualization of osteotomized segments and calculation of bony interference, was proposed in the present study. This new system provides an acceptable precision of treatment planning of orthognathic surgery, especially for facial asymmetry.

Introduction: To increase stability and mandibular setback movement, surgical maxillary impaction is normally performed with mandibular setback surgery in treating adult skeletal Class III patients. This article demonstrates the use of microimplants for anchorage to intrude molars and the resultant rotation of the maxillary occlusal plane clockwise to increase the surgical mandibular setback and reduce the posterior vertical dimension instead of maxillary surgical impaction., Methods and Results: A 21-year-old man with mandibular prognathism was treated with mandibular setback surgery that included orthodontic treatment for decompensation. Microimplants placed into the palatal alveolar bone between the maxillary first and second molars were used to intrude the maxillary posterior teeth and change the occlusal plane clockwise. This produced 4 mm more of distal movement of the chin during mandibular setback surgery compared with the surgical prediction with no change in the occlusal plane. These results were similar to those of 2-jaw surgery with maxillary posterior impaction., Conclusions: The intrusion of the maxillary posterior teeth with microimplants might prevent the need for maxillary surgery in adult skeletal Class III patients., (Copyright © 2010 American Association of Orthodontists. Published by Mosby, Inc. All rights reserved.)