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This study aimed to enhance the evaluation of facial symmetry crucial for planning and assessing outcomes of orthognathic surgery (OGS). An innovative approach combining three-dimensional (3D) facial contour lines with hyperdimensional (HD) computing was developed for this purpose. Data were collected using 3D cone beam computed tomography (CBCT) at Chang Gung Memorial Hospital from 2016 to 2021. A comprehensive dataset was compiled, including images from 150 normal individuals and 2500 patients, totaling 5150 preoperative and postoperative facial images. A machine learning model was trained to analyze these images, and 3D contour data were used to create a facial symmetry quantification system with HD computing. Additionally, 3D CBCT data from 200 patients before and after OGS were retrospectively reviewed for clinical application. The developed facial symmetry algorithm demonstrated an overall accuracy of 84.1 %. Postoperative facial symmetry scores improved significantly, with a mean score increase of 53 %, from 2.40 to 3.63. The study culminated in the creation of a web-based system that leverages HD computing and 3D contour mapping to automate facial symmetry assessment. This system offers a user-friendly interface for rapid and accurate evaluations, facilitating better communication between clinicians and patients., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Three-dimensional (3D) imaging technologies are increasingly used in craniomaxillofacial (CMF) surgery, especially to enable clinicians to get an effective approach and obtain better treatment results during different preoperative and postoperative phases, namely during image acquisition and diagnosis, virtual surgical planning (VSP), actual surgery, and treatment outcome assessment. The article presents an overview of 3D imaging technologies used in the aforementioned phases of the most common CMF surgery. We searched for relevant studies on 3D imaging applications in CMF surgery published over the past 10 years in the PubMed, ProQuest (Medline), Web of Science, Science Direct, Clinical Key, and Embase databases. A total of 2094 articles were found, of which 712 were relevant. An additional 26 manually searched articles were included in the analysis. The findings of the review demonstrated that 3D imaging technology is becoming increasingly popular in clinical practice and an essential tool for plastic surgeons. This review provides information that will help researchers and clinicians consider the use of 3D imaging techniques in CMF surgery to improve the quality of surgical procedures and achieve satisfactory treatment outcomes., Competing Interests: Conflicts of interest The authors have no financial conflicts of interest., (Copyright © 2023 The Authors. Published by Elsevier B.V. All rights reserved.)

Background: No consensus exists about the safest position for performing the osseous genioplasty, with 5 to 6 mm below the mental foramen being the most frequently recommended position. This study intends to generate a safe distance guide to minimize the risk of inferior alveolar nerve injury during osteotomy., Methods: Pretreatment cone-beam computed tomography-derived three-dimensional models from adult patients with skeletal class I to III patterns and cleft lip/palate deformity who underwent orthodontic-surgical interventions (n = 317) were analyzed. A three-dimensional vertical distance between the inferior margin of the mental foramen and the lowest point of the inferior alveolar nerve canal was measured in each three-dimensional hemimandible (n = 634). Statistical analysis was performed to generate the safe distance guide in a stepwise fashion at 95, 99, and 99.99 percent confidence levels., Results: Class III (4.35 ± 1.42 mm) and cleft lip/palate (4.42 ± 1.53 mm) groups presented significantly (p < 0.001) larger three-dimensional distances than class I (3.44 ± 1.54 mm) and class II (3.66 ± 1.51 mm) groups. By considering the 5- to 6-mm safe distance parameter, 6.4, 5.0, 10.6, 16, and 9.9 percent of hemimandibles were at risk of osteotomy-induced nerve injury in the class I, class II, class III, cleft lip/palate, and overall cohorts, respectively. Overall, the safe distance zone to perform the osteotomy was set at 7.06, 8.01, and 9.12 mm below the mental foramen, with risk probabilities of 2.5, 0.5, and 0.0005 percent, respectively., Conclusion: This study contributes to patient safety and surgeon practice by proving a safe distance guide for genioplasty.

Computer-assisted 3D planning has overcome the limitations of conventional 2D planning-guided orthognathic surgery (OGS), but difference for facial contour asymmetry outcome has not been verified to date. This comparative study assessed the facial contour asymmetry outcome of consecutive patients with unilateral cleft lip and palate who underwent 2D planning (n = 37)- or 3D simulation (n = 38)-guided OGS treatment for correction of maxillary hypoplasia and skeletal Class III malocclusion between 2010 and 2018. Normal age-, gender-, and ethnicity-matched individuals (n = 60) were enrolled for comparative analyses. 2D (n = 60, with 30 images for each group) and 3D (n = 43, with 18 and 25 images for 2D planning and 3D simulation groups, respectively) photogrammetric-based facial contour asymmetry-related measurements were collected from patients and normal individuals. The facial asymmetry was further verified by using subjective perception of a panel composed of 6 blinded raters. On average, the facial contour asymmetry was significantly (all p < 0.05) reduced after 3D virtual surgery planning for all tested parameters, with no significant differences between post-OGS 3D simulation-related values and normal individuals. No significant differences were observed for pre- and post-OGS values in conventional 2D planning-based treatment, with significant (all p < 0.05) differences for all normal individuals-related comparisons. This study suggests that 3D planning presents superior facial contour asymmetry outcome than 2D planning.

Background/purpose: The objective of this study was to create a normative database of 3D cephalometric measurements for adult Chinese in Taiwan to understand the specific features, as well as to provide information for 3-dimensional (3D) orthognathic surgery planning for patients with maxillofacial deformity., Methods: A cross-sectional study was conducted on 30 male and 30 female adults with normal and balanced facial appearance, skeletal Class I pattern, and proper interincisal relationship with normal occlusion. Cone-beam computed tomography was performed. After standard orientation of the 3D image models, 51 landmarks were digitized and 3D cephalometric measurements of overall facial features, midface, maxilla, mandible, dentoalveolus, and soft tissue were performed and analyzed., Results: Reliability and reproducibility of the 3D measurement were achieved. The data showed significant differences between males and females in facial height ratio, midface prominence, midface and maxilla width, mandible width and length for the skeleton, lower incisal inclination and interincisal angle for the dentoalveolus, and lip height, facial height and chin throat angle for the soft tissue. These dataset presented specific facial characteristics of the Chinese face as compared with other populations., Conclusion: The normative data helps to serve as a guide for maxillofacial treatment for globally ethnic Chinese, particularly useful for orthodontic treatment, 3D planning of orthognathic surgery and outcome assessment. Gender and ethnic differences need to be taken into consideration., (Copyright © 2019. Published by Elsevier B.V.)

The mandibular proximal ramus segments should be moved and rotated during orthognathic surgery-based skeletofacial reconstruction for the correction of challenging patients with facial asymmetry and malocclusion, but quantitative data regarding this rotation were not sufficient to date. This 3D computer-assisted study measured the proximal ramus segment rotation after 3D simulation-guided two-jaw surgery in patients with facial asymmetric deformity and class III malocclusion (n = 31). Using 3D mandible models and a reliable proximal ramus segment-related plane, angular changes in pitch, roll and yaw directions were measured before and one month after surgery. Significant rotational changes (p < 0.01) were observed in the left and right sides and overall proximal ramus segments after surgery, with absolute differences of 4.1 ± 3.0 (range -7.8 to 6.9), 2.8 ± 2.3 (-8.8 to 5.0), and 2.7 ± 2.4 (-6.6 to 9.9) degrees in pitch, roll, and yaw rotations, respectively. Numbness and mouth opening limiting occurred within the first 6 months after surgery but the patients had an unremarkable long-term postoperative course, with no revisionary surgery required. This study contributes to the multidisciplinary-related literature by revealing that proximal ramus segment rotation and rigid fixation with no postoperative intermaxillary immobilization was practicable in skeletofacial surgery for the successful treatment of asymmetric deformity and class III malocclusion.

Background: Three-dimensional surgical planning for orthognathic surgery is becoming prevalent, with improving outcomes. However, conventional dental casts are still used for evaluations, digital image conversion, surgical planning, and occlusal splint production. This study used intraoral scanning for the three-dimensional planning of the final digital occlusion and compared this method with the conventional dental cast approach., Methods: Thirty consecutive patients who underwent two-jaw orthognathic surgery to treat mandibular prognathism and asymmetry were included. Dental casts (control group) and intraoral scans (study group) were collected simultaneously for designing the final dental occlusion. A step-by-step setup of the final digital occlusion was established for the study group. To validate results, the intraoral scanning-based virtual occlusion was superimposed over the dental model-based final digital occlusion for comparison. Intraobserver and interobserver variability were assessed for setting up the final digital occlusion. The fitness of splints fabricated using the conventional and virtual occlusion methods were compared., Results: The steps for setting up the final digital occlusion were applicable in all cases. The average root-mean-square difference of final occlusion images between the two groups was 0.45 mm, indicating a comparable occlusal relationship. The intraobserver reproducibility and interobserver reliability for setting up the virtual occlusion were satisfactory. Moreover, no significant difference existed in the splint fitness test between the groups., Conclusions: The proposed intraoral scan and setup process of the final digital occlusion was reliable and accurate. Thus, the method can replace the dental model approach for the three-dimensional planning of orthognathic surgery., Clinical Question/level of Evidence: Therapeutic, II.

Objective: Compared with conventional two-dimensional (2D) planning, three-dimensional (3D) planning in orthognathic surgery yields more accurate anatomical information and enables the precise positioning of maxillary and mandibular segments, particularly for patients with facial asymmetry. Accordingly, surgical outcomes achieved using 3D planning should be superior. This study determined the differences between the 2D and 3D planning techniques by comparing their surgical outcomes., Materials and Methods: In this retrospective study, patients who underwent surgery following the traditional 2D planning technique were classified into the 2D planning group. Patients in whom the 2D plan was transferred to a 3D system after surgical simulation were classified into the 3D planning group. Surgical outcomes were compared using cephalometric measurements and patient perception of the results., Results: In the 3D planning group, more favorable results were observed in frontal symmetry, change in the angle between the orbital and occlusal lines, frontal ramus inclination, and the distances from the mandibular central incisor and menton to the midsagittal line. No significant differences were observed in the lateral profiles (SNA, SNB, ANB, and angle convexity) of the two groups. Patient satisfaction was favorable in the two groups, but more patients in the 3D planning group reported being very satisfied., Conclusion: The 3D planning technique provided superior overall outcomes. The study findings can be used to augment clinical planning and surgical execution when using a conventional approach., (Copyright © 2017 British Association of Plastic, Reconstructive and Aesthetic Surgeons. Published by Elsevier Ltd. All rights reserved.)

Facial asymmetry and dental occlusal cant have been detected in two-dimensional cephalometry using different horizontal reference lines, but equivalent 3-dimensional (3D) reference planes have not been thoroughly investigated. In this study, 3D cone-beam computed tomography scans of 83 consecutive patients were evaluated using a standardized 3D frame and three horizontal reference planes, Supraorbitale (Sor), Frontozygomatic (Z), and Frankfurt horizontal (FH) for cant detection. Canting was defined as a vertical difference between left and right sides of 2 mm or more, and in at least two investigated planes. Concordance for negative canting was found in 38 patients, and for positive canting in 22 patients. Discordance in cant detection was found in 23 patients (28%). 29 patients were found to have canting in at least 2 planes. The FH plane was discordant to the other two planes in 4 patients, the Sor plane in 7 patients and the Z plane in 12 patients. Youden's index showed the highest performance for FH (0.878), followed by Sor (0.823) and Z plane (0.762). This study revealed that the FH plane was the best method for cant detection in 3D imaging. The FH plane and Sor plane can be combined if orbital asymmetry is suspected.

Objective: This study reported an intraoperative navigation system for single-splint two-jaw orthognathic surgery, and assessed the accuracy of transferring the computer assisted surgical simulation., Methods: A skull model was used for validation, and twenty patients receiving such procedure were enrolled. The procedure contained five phases, including virtual surgery on three-dimensional images, fabrication of surgical positioning guides, preparation of registration and validation landmarks, confirmation of bony position during surgery, and postoperative assessment. Target registration error (TRE) and differences between simulation (T0) and postoperative images (T1) were measured from landmarks to Frankfort horizontal plane (FHP), mid-sagittal plane (MSP), and coronal plane (COP)., Results: For the model experiment, mean TRE was lowest using the hard tissue landmarks (0.60 ± 0.27 mm), and the mean difference (T1-T0) was less than 1 mm to all three planes. For the patients, mean TRE was 1.07 ± 0.18 mm from the hard tissue landmarks. The mean difference was 0.96. ± 0.60 mm from MSP, 1.39 ± 1.11 mm from FHP, and 2.12 ± 1.82 mm from COP. The differences were not significant. Both surgeons and patients were satisfied with the surgical outcome., Conclusion: This study showed that the navigation system had acceptable accuracy and was useful for the two-jaw orthognathic surgery using single-splint method., (Copyright © 2015 European Association for Cranio-Maxillo-Facial Surgery. Published by Elsevier Ltd. All rights reserved.)

Purpose: Three-dimensional computer-assisted orthognathic surgery has been applied to improve planning and outcome. This study presents our experience with this promising modality for simulation of surgery, prefabrication of positioning guides, and navigation of the surgery., Methods: Thirty-seven patients who received surgical simulation and intraoperative navigation for 2-jaw orthognathic surgery were recruited. Preoperative 3-dimensional cone-beam computed tomographic images were used for surgical simulation and design of intraoperative guidance. An initial surgical plan was developed and transferred for 3-dimensional virtual surgery. Modification of the surgical plan was made if facial symmetry and skeletal harmony or collision of ramus segments were concerned. The result of virtual surgery was used to design and manufacture positioning guides and perform preoperative navigation planning. During the operation, the positioning guides were used to transfer the virtual planning to actual surgery, and a real-time navigation system was used to confirm the predetermined position of the maxillomandibular complex. For assessment of the computer-assisted surgical system, the simulation image was superimposed to the postoperative image for comparison., Results: The computer-assisted orthognathic surgery was successfully carried out in all patients. The initial surgical plan was modified in 17 patients in whom the position of maxillomandibular complex was changed. The positioning guides were helpful in controlling the spatial position of the maxillomandibular complex. The BrainLabTR navigation system was useful to further confirm the position of the facial bone. Superimposition of the simulation and postoperative images revealed satisfactory result with acceptable errors. The difference ranged from 0.05 to 1.46 mm, with a mean value of 0.66 mm, for patients using the positioning guides; and the difference ranged from 0.07 to 2.30 mm, with a mean value of 1.20 mm, for patients using the navigation system. Overall, patient and doctor satisfaction was high., Conclusion: This computer-assisted orthognathic surgery system helps to improve surgical planning, reduce surgical difficulty, facilitate positioning and fixation of the maxillomandibular complex, and improve outcome.

By incorporating three-dimensional (3D) imaging and computer-aided design and manufacturing techniques, 3D computer-assisted technology has been applied widely to provide accurate guidance for assessment and treatment planning in clinical practice. This technology has recently been used in orthognathic surgery to improve surgical planning and outcome. The modality will gradually become popular. This study reviewed the literature concerning the use of computer-assisted techniques in orthognathic surgery including surgical planning, simulation, intraoperative translation of the virtual surgery, and postoperative evaluation. A Medline, PubMed, ProQuest, and ScienceDirect search was performed to find relevant articles with regard to 3D computer-assisted orthognathic surgery in the past 10 years. A total of 460 articles were revealed, out of which 174 were publications addressed the topic of this study. The purpose of this article is to present an overview of the state-of-art methods for 3D computer-assisted technology in orthognathic surgery. From the review we can conclude that the use of computer-assisted technique in orthognathic surgery provides the benefit of optimal functional and aesthetic results, patient satisfaction, precise translation of the treatment plan, and facilitating intraoperative manipulation., (Copyright © 2015. Published by Elsevier B.V.)