Average Three-Dimensional Skeletofacial Model as a Template for Bone Repositioning during Virtual Orthognathic Surgery.

BACKGROUND: Virtual planning has revolutionized orthognathic surgery. This study presents a computer-assisted method for constructing average three-dimensional skeletofacial models that can be applied as templates for surgical planning for maxillomandibular repositioning. METHODS: The authors used the images of 60 individuals (30 women and 30 men) who had never undergone orthognathic surgery to construct an average three-dimensional skeletofacial model for male participants and one for female participants. The authors validated the accuracy of the newly developed skeletofacial models by comparing their images with 30 surgical simulation images (ie, skulls) that had been created using three-dimensional cephalometric normative data. The comparison was conducted by superimposing surgical simulation images created using the authors' models with the previously created images to analyze their differences, particularly differences in the jawbone position. RESULTS: For all participants, the authors compared the jaw position in the surgical simulation images created using the authors' average three-dimensional skeletofacial models with that in the images created using three-dimensional cephalometric normative data. The results revealed that the planned maxillary and mandibular positions were similar in both images and that the differences between all facial landmarks were less than 1 mm, except for one dental position. Most studies have reported less than 2 mm to be the success criterion for the distance difference between planned and outcome images; thus, the authors' data indicate high consistency between the images in terms of jawbone position. CONCLUSION: The authors' average three-dimensional skeletofacial models provide an innovative template-assisted orthognathic surgery planning modality that can enhance the fully digital workflow for virtual orthognathic surgical planning. CLINICAL QUESTION/LEVEL OF EVIDENCE: Therapeutic, V.

Optimizing Orthognathic Surgery: Leveraging the Average Skull as a Dynamic Template for Surgical Simulation and Planning in 30 Patient Cases.

Virtual planning has revolutionized orthognathic surgery (OGS), marking a significant advancement in the field. This study aims to showcase the practical application of our established 3D average skull template as a guiding framework for surgical planning, and to share valuable insights from our clinical experience. We enrolled 30 consecutive Taiwanese patients (18 females and 12 males) who underwent two-jaw orthognathic surgery with surgical simulation, utilizing the average skull template for planning. Results indicate the method's applicability and precision. By adhering to the surgical plan, post-operative outcomes closely aligned with the average skull template, showing negligible deviations of less than 2 mm. Moreover, patients expressed high satisfaction with post-surgery facial changes, with the chin appearance receiving the highest satisfaction scores, while the lowest scores were attributed to nose appearance. Notably, the substantial change in lower jaw position post-mandibular setback surgery contributed to increased satisfaction with the chin position. In conclusion, this study does not seek to replace established surgical planning methods, but underscores that utilizing an average skull as a surgical design template provides a viable, accurate, and efficient option for OGS patients.

Application of Orthognathic Surgery Principles and Techniques in the Management of Craniomaxillofacial Trauma.

BACKGROUND: Posttraumatic secondary deformities of facial skeleton may occur because of nonmanagement or ill management of primary injuries, whereas some unexpectedly occur even after dedicated management attempts. Orthognathic surgery (OGS) principles and techniques can be used as an efficient tool to correct posttraumatic craniomaxillofacial deformities or skeletal developmental deformities during trauma management. AIM AND OBJECTIVES: The aims of this study were to describe the different types of posttraumatic secondary deformity and address how to use the principles of orthognathic techniques to correct them. MATERIALS AND METHODS: Patients with orthognathic surgical osteotomies during primary or secondary management of facial trauma (referred to as trauma-OGS) during the period of 2010 to 2018 were retrospectively reviewed. Variables pertaining to patients and surgery were collected, including trauma diagnosis, etiology, duration between trauma/primary surgery and secondary presentation, suggested reason for secondary deformity, intervention undertaken to address, and the surgical outcome. RESULTS: Twenty-seven patients were eligible and extensively reviewed. Etiological categorization of trauma-OGS could be done into posttraumatic deformities (18) and developmental deformities (9). The former group was further categorized as OGS done as primary procedure (8) that included immobile Le Fort fractures and delayed initial treatment, and OGS done as secondary procedure (10) that included complex fractures and condylar fractures. The developmental deformity group was categorized into OGS done simultaneously during trauma management (5) or done as a secondary procedure after trauma management (4). CONCLUSIONS: Application of principles and techniques of OGS in indicated primary or secondary management of facial trauma patients should always be considered. The categorization of scenarios presented in this article relating facial trauma and OGS may further help to understand the application.

Outcome of full digital workflow for orthognathic surgery planning in the treatment of asymmetric skeletal class III deformity.

BACKGROUND/PURPOSE: Studies have reported the advantages of digital imaging-assisted orthognathic surgery planning, but there is scarce information about a full digital planning modality. This study evaluated the 3D cephalometric-based and patient-reported outcomes of a full digital workflow for orthognathic surgery planning in the treatment of asymmetric maxillomandibular disharmony. METHODS: A postoperative 3D image dataset of 30 Taiwanese Chinese patients with asymmetric skeletal Class III deformities who underwent full digital planning for two-jaw surgery were retrieved from the authors' database. The 3D cephalometric data (dental, skeletal, and soft tissue evaluations) were compared to the ethnicity-matched 3D cephalometric normative values. Patient-reported outcome measure tools regarding postoperative overall appearance and satisfaction with facial areas (ranging from 0 to 100 and 0 to 10, respectively) were administered. The number of needed or requested revisionary surgery was collected. RESULTS: No difference (all p > 0.05) was observed between the orthognathic-surgery-treated patients and the normative value for most of the tested 3D cephalometric parameters, with the exception (p < 0.05) of three mandible and occlusal-plane-related parameters. Both patient-reported outcome measure tools showed that patients' satisfaction with their postoperative appearance was high for overall face (89.7 ± 4.5) and specific facial regions (nose, 7.1 ± 1.3; lip, 8.3 ± 1.6; upper gum, 8.5 ± 1.2; cheek, 8.8 ± 1.1; chin, 9.2 ± 1.2; and teeth, 9.3 ± 0.8), with no need for revisionary surgery. CONCLUSION: The patients treated with a full 3D digital planning-assisted two-jaw surgery had a similar 3D dental relation, facial convexity, and symmetry compared to healthy ethnicity-matched individuals, and they reported higher satisfaction levels with their postoperative facial appearance results.

Cheek soft tissue prediction in cleft orthognathic surgery: A 3D computer-assisted investigation with comparative analysis.

BACKGROUND: The Le Fort I maxillary advancement and rotational movement have been adopted to treat patients with cleft-related skeletal Class III pattern and anteromedial cheek soft tissue deficiency, but cleft-specific cheek soft tissue prediction data are insufficient. This 3D imaging-based study addressed the issue. METHODS: 3D craniofacial soft tissue and bone models were created from 32 consecutive patients who received computer-aided two-jaw orthognathic surgery for the correction of cleft-related Class III deformity and cheek soft tissue deficiency. Using superimposed 3D models, the cheek volumetric change, the cheek sagittal movement, and the 3D cheek mass position were calculated. 3D data from orthognathic surgery-treated patients with no cleft (noncleft cohort) and individuals with no facial deformity (3D norm value) were retrieved for comparative analysis. RESULTS: Surgical maxillary advancement (p < 0.001) but not maxillary clockwise rotation (p > 0.05) had a significant impact on the cheek soft tissue change, with prediction models showing that maxillary advancement elucidated 77 and 79% of this change on the cleft and noncleft sides, respectively. Cleft cohort (0.46±0.12) had a significantly (p < 0.001) smaller cheek soft-to-hard tissue ratio than that of the noncleft cohort (0.73±0.13). Cleft maxillary advancements >4 mm resulted in a 3D cheek mass position (2.1±1.1 mm) similar (p > 0.05) to the 3D norm value (2.2±1.2 mm), but different (p = 0.037) from the noncleft cohort (2.38±0.7 mm). CONCLUSION: This study showed that maxillary advancement but not the maxillary rotation affects the cheek soft tissue change, and the predictive values and comparative data could assist the orthodontist-surgeon interaction during preoperative planning and patient counseling.

Automatic Assessment of 3-Dimensional Facial Soft Tissue Symmetry Before and After Orthognathic Surgery Using a Machine Learning Model: A Preliminary Experience.

PURPOSE: An objective and quantitative assessment of facial symmetry is essential for the surgical planning and evaluation of treatment outcomes in orthognathic surgery (OGS). This study applied the transfer learning model with a convolutional neural network based on 3-dimensional (3D) contour line features to evaluate the facial symmetry before and after OGS. METHODS: A total of 158 patients were recruited in a retrospective cohort study for the assessment and comparison of facial symmetry before and after OGS from January 2018 to March 2020. Three-dimensional facial photographs were captured by the 3dMD face system in a natural head position, with eyes looking forward, relaxed facial muscles, and habitual dental occlusion before and at least 6 months after surgery. Three-dimensional contour images were extracted from 3D facial images for the subsequent Web-based automatic assessment of facial symmetry by using the transfer learning with a convolutional neural network model. RESULTS: The mean score of postoperative facial symmetry showed significant improvements from 2.74 to 3.52, and the improvement degree of facial symmetry (in percentage) after surgery was 21% using the constructed machine learning model. A Web-based system provided a user-friendly interface and quick assessment results for clinicians and was an effective doctor-patient communication tool. CONCLUSIONS: This work was the first attempt to automatically assess the facial symmetry before and after surgery in an objective and quantitative value by using a machine learning model based on the 3D contour feature map.

Three-Dimensional Computer-Assisted Orthognathic Surgery: Traditional Hybrid Versus Full Digital Planning Models.

PURPOSE: Three-dimensional (3D) computer-aided planning has truly revolutionized orthognathic surgery (OGS) treatment, but no study has compared the traditional hybrid and full 3D digital planning models. This study compared these virtual planning models in the treatment of asymmetric maxillomandibular disharmony. METHODS: Young adult patients with an asymmetric skeletal class III deformity who underwent 3D computer-aided 2-jaw OGS using hybrid (alginate dental impression, 2D cephalometric tracings, manual-guided stone model surgery, occlusion setup, and splint fabrication; n = 30) or full digital (laser-scanned dentition, 3D cephalometric tracings, virtual-based occlusion setup and surgery, and computer-generated surgical splint; n = 30) planning models were consecutively recruited. Preoperative and postoperative 3D cephalometric analyses (dental relation, skeletal assessments based on sagittal and frontal views, and soft tissue evaluations) were adopted for intragroup and intergroup comparisons. Postoperative patient-perceived satisfaction with facial appearance was also recorded. RESULTS: Both hybrid and full digital planning groups had significant (all P < 0.05) improvements after surgery with respect to facial convexity, incisor overjet, and frontal symmetry parameters. The full 3D digital planning-based OGS treatment had similar (all P > 0.05) 3D cephalometric-derived outcomes (preoperative, postoperative, and treatment-induced change data) and patient-perceived outcomes compared with the traditional hybrid 3D planning method. CONCLUSIONS: For the decision-making process in selecting the planning model, multidisciplinary teams could consider additional parameters such as patient comfort, storage needs, convenience for data reuse, overall planning time, availability, and costs.

The Impacts of Orthognathic Surgery on the Facial Appearance and Age Perception of Patients Presenting Skeletal Class III Deformity: An Outcome Study Using the FACE-Q Report and Surgical Professional-Based Panel Assessment.

BACKGROUND: A recent artificial intelligence-based investigation has shown the impacts of orthognathic surgery on the patient's facial appearance and apparent age. However, appearance and age perception as reported by patients and surgical professionals have not been addressed in the same cohort to date. METHODS: FACE-Q facial appraisal (appearance and age) and quality-of-life scale scores obtained before and after orthognathic surgery, in addition to three-dimensional photographs of 70 patients with skeletal class III deformity, were collected for a comparative cross-sectional study. Seven blinded plastic surgeons rated all photographs for apparent facial aesthetic and age scales. The FACE-Q data from 57 matched normal individuals were adopted for the comparative analyses. The correlation between the FACE-Q and the professional-based scales was tested. RESULTS: Pre-orthognathic surgery versus post-orthognathic surgery comparisons showed significant differences (p < 0.001) for all FACE-Q scales and panel assessments, with higher (FACE-Q scales and professional-based aesthetic parameters) and lower (FACE-Q patient-perceived age scale and professional-based age parameter) values for post-orthognathic surgery measurements. Patients had significantly (p < 0.001) higher (patient-perceived age scale) and lower (facial appraisal and quality-of-life scales) FACE-Q values than normal individuals for pre-orthognathic surgery but not for post-orthognathic surgery measurements. The FACE-Q facial appearance overall scale had significant correlations (p < 0.001) with the panel assessment for the parameters "beautiful" and "attractive" but not for the "pleasant" parameter. No significant correlations were observed for facial age scales. CONCLUSION: This study contributes to the orthognathic surgery literature by revealing that orthognathic surgery positively impacts the perception of apparent facial age and improves facial appearance and quality of life. CLINICAL QUESTION/LEVEL OF EVIDENCE: Therapeutic, IV.

Measuring patient-reported outcomes in orthognathic surgery: Linguistic and psychometric validation of the Mandarin Chinese version of FACE-Q instrument.

BACKGROUND: Orthognathic surgery is useful for correction of dental malocclusion and improvement of facial appearance. The FACE-Q is a patient-reported outcome instrument for evaluation of surgical and psychosocial effect. The purposes of this study were to conduct a linguistic validation of all FACE-Q scales to Mandarin Chinese, to test the orthognathic surgery-related scales for reliability and validity, and to evaluate the effect of orthognathic surgery. METHODS: All FACE-Q scales and checklists were translated from English to Mandarin Chinese according to international recommendations: forward translations, backward translation, and cognitive interviews. Psychometric testing of orthognathic surgery-related scales of translated version was administered to patients with facial deformities and history of orthognathic surgery (n = 53; 17 scales) or no history of orthognathic surgery (n = 44; 11 scales), and control subjects (n = 57; 11 scales). RESULTS: All FACE-Q scales and checklists were linguistically validated into Mandarin Chinese. The contents were confirmed valid among Mandarin Chinese-speaking population. The FACE-Q scales had excellent internal consistency (Cronbach's alpha >0.70) and discriminated (p < 0.05) well between patients before and after orthognathic surgeries and normal subjects. CONCLUSIONS: This study discovered significant benefit of orthognathic surgery on improving facial appearance and psychosocial function, as compared with the non-surgical patients and normal controls.

Effect of Le Fort I Maxillary Advancement and Clockwise Rotation on the Anteromedial Cheek Soft Tissue Change in Patients with Skeletal Class III Pattern and Midface Deficiency: A 3D Imaging-Based Prediction Study.

Patients with a skeletal Class III deformity may present with a concave contour of the anteromedial cheek region. Le Fort I maxillary advancement and rotational movements correct the problem but information on the impact on the anteromedial cheek soft tissue change has been insufficient to date. This three-dimensional (3D) imaging-assisted study assessed the effect of surgical maxillary advancement and clockwise rotational movements on the anteromedial cheek soft tissue change. Two-week preoperative and 6-month postoperative cone-beam computed tomography scans were obtained from 48 consecutive patients who received 3D-guided two-jaw orthognathic surgery for the correction of Class III malocclusion associated with a midface deficiency and concave facial profile. Postoperative 3D facial bone and soft tissue models were superimposed on the corresponding preoperative models. The region of interest at the anteromedial cheek area was defined. The 3D cheek volumetric change (mm3; postoperative minus preoperative models) and the preoperative surface area (mm2) were computed to estimate the average sagittal movement (mm). The 3D cheek mass position from orthognathic surgery-treated patients was compared with published 3D normative data. Surgical maxillary advancement (all p < 0.001) and maxillary rotation (all p < 0.006) had a significant effect on the 3D anteromedial cheek soft tissue change. In total, 78.9%, 78.8%, and 78.8% of the variation in the cheek soft tissue sagittal movement was explained by the variation in the maxillary advancement and rotation movements for the right, left, and total cheek regions, respectively. The multiple linear regression models defined ratio values (relationship) between the 3D cheek soft tissue sagittal movement and maxillary bone advancement and rotational movements of 0.627 and 0.070, respectively. Maxillary advancements of 3-4 mm and >4 mm resulted in a 3D cheek mass position (1.91 ± 0.53 mm and 2.36 ± 0.72 mm, respectively) similar (all p > 0.05) to the 3D norm value (2.15 ± 1.2 mm). This study showed that both Le Fort I maxillary advancement and rotational movements affect the anteromedial cheek soft tissue change, with the maxillary advancement movement presenting a larger effect on the cheek soft tissue movement than the maxillary rotational movement. These findings can be applied in future multidisciplinary-based decision-making processes for planning and executing orthognathic surgery.

Three-dimensional cephalometry for orthognathic planning: Normative data and analyses.

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.

Computer-Aided Planning in Orthognathic Surgery: A Comparative Study with the Establishment of Burstone Analysis-Derived 3D Norms.

Three-dimensional (3D) computer-aided simulation has revolutionized orthognathic surgery treatment, but scarce 3D cephalometric norms have been defined to date. The purposes of this study were to (1) establish a normative database of 3D Burstone cephalometric measurements for adult male and female Chinese in Taiwan, (2) compare this 3D norm dataset with the two-dimensional (2D) Burstone norms from Caucasian and Singaporean Chinese populations, and (3) apply these 3D norms to assess the outcome of a computer-aided simulation of orthognathic surgery. Three-dimensional Burstone cephalometric analysis was performed on 3D digital craniofacial image models generated from cone-beam computed tomography datasets of 60 adult Taiwanese Chinese individuals with normal occlusion and balanced facial profile. Three-dimensional Burstone analysis was performed on 3D image datasets from patients with skeletal Class III pattern (n = 30) with prior computer-aided simulation. Three-dimensional Burstone cephalometric measurements showed that Taiwanese Chinese males had significantly (p < 0.05) larger anterior and posterior facial heights, maxillary length, and mandibular ramus height than females, with no significant (p > 0.05) difference for facial soft-tissue parameters. The 3D norm dataset revealed Taiwanese Chinese-specific facial characteristics, with Taiwanese presenting (p < 0.05) a more convex profile, protrusive maxillary apical bases, protruding mandible, protruding upper and lower lips, and a shorter maxillary length and lower facial height than Caucasians. Taiwanese had significantly (p < 0.05) larger maxillary projection, vertical height ratio, lower face throat angle, nasolabial angle, and upper lip protrusion than Singaporean Chinese. No significant (p > 0.05) difference was observed between 3D norms and computer-aided simulation-derived 3D patient images for horizontal skeletal, vertical skeletal, and dental measurements, with the exception of two dental parameters (p < 0.05). This study contributes to literature by providing gender- and ethnic-specific 3D Burstone cephalometric norms, which can assist in the multidisciplinary-based delivery of orthodontic surgical care for Taiwanese Chinese individuals worldwide, including orthodontic management, computer-assisted simulation, and outcome assessment.

Simultaneous Surgical Correction of Skeletal Class III Dentofacial Deformity During Acute Management of Facial Fractures: Patient Selection and Surgical Technique.

BACKGROUND: Mandibular prognathism is a common dentofacial deformity in Asia. Treatment of such condition may vary from orthodontic camouflage to surgical orthodontics with orthognathic surgery depending on the severity of the condition. Because of the prominent position of the mandible, fractures involving different locations of the mandible commonly occur in maxillofacial trauma. Anatomical reduction of maxillofacial fractures and restoration of the pretraumatic occlusion are the primary goals of acute management of facial fractures. In patients with dentofacial deformity, simultaneous surgical correction of their malocclusion and improvement of their facial aesthetics while providing open treatment to the maxillofacial fractures are rarely reported in the literature. PATIENTS AND METHODS: We reported 3 cases with combined open reduction and internal fixation and surgery-first orthognathic surgery principles to correct class III malocclusion with mandibular prognathism during acute management of maxillofacial fractures. Computer-assisted surgical simulation was used in surgical planning and fabrication of surgical splint. RESULTS: Two patients underwent mandibular osteotomies in addition to open reduction and internal fixation of maxillofacial fractures. One patient had both maxillary and mandibular osteotomies during facial fracture repair. Class I occlusion with satisfactory facial profile was achieved in all 3 cases. CONCLUSIONS: Careful patient selection with presurgical planning using computer-assisted surgical simulation is essential in achieving successful outcomes in correcting dentofacial deformities while managing maxillofacial fractures. This combined technique is a viable option in the surgical management of facial fractures in patients with dentofacial deformities.

The outcome of skeletofacial reconstruction with mandibular rotation for management of asymmetric skeletal class III deformity: A three-dimensional computer-assisted investigation.

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.

Facial Appearance and Psychosocial Features in Orthognathic Surgery: A FACE-Q- and 3D Facial Image-Based Comparative Study of Patient-, Clinician-, and Lay-Observer-Reported Outcomes.

Outcome measures reported by patients, clinicians, and lay-observers can help to tailor treatment plans to meet patients' needs. This study evaluated orthognathic surgery (OGS) outcomes using pre- and post-OGS patients' (n = 84) FACE-Q reports, and a three-dimensional facial photograph-based panel assessment of facial appearance and psychosocial parameters, with 96 blinded layperson and orthodontic and surgical professional raters, and verified whether there were correlations between these outcome measurement tools. Post-OGS FACE-Q and panel assessment measurements showed significant (p < 0.001) differences from pre-OGS measurements. Pre-OGS patients' FACE-Q scores were significantly (p < 0.01) lower than normal, age-, gender-, and ethnicity-matched individuals' (n = 54) FACE-Q scores, with no differences in post-OGS comparisons. The FACE-Q overall facial appearance scale had a low, statistically significant (p < 0.001) correlation to the facial-aesthetic-based panel assessment, but no correlation to the FACE-Q lower face and lips scales. No significant correlation was observed between the FACE-Q and panel assessment psychosocial-related scales. This study demonstrates that OGS treatment positively influences the facial appearance and psychosocial-related perceptions of patients, clinicians and lay observers, but that there is only a low, or no, correlation between the FACE-Q and panel assessment tools. Future investigations may consider the inclusion of both tools as OGS treatment endpoints for the improvement of patient-centered care, and guiding the health-system-related decision-making processes of multidisciplinary teams, policymakers, and other stakeholders.

Intraoral Scanning and Setting Up the Digital Final Occlusion in Three-Dimensional Planning of Orthognathic Surgery: Its Comparison with the Dental Model Approach.

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.

Three-dimensional region-based study on the relationship between soft and hard tissue changes after orthognathic surgery in patients with prognathism.

Both deep understanding and reliable prediction of postoperative soft tissue changes are crucial for planning orthognathic surgery. Instead of estimating soft tissue responses by measuring individual landmark changes, this study aimed to investigate the relationship (ratio) between soft and hard tissue movements in different facial regions through three-dimensional cone-beam computed tomography (CBCT). Preoperative and postoperative CBCT images were superimposed using the surface registration method on the basis of the cranial base, and 10 facial regions of interest were defined. Region-based volumetric subtractions between the preoperative and postoperative segments were performed. The volumetric differences and surface of each region were used to estimate the average movement. Correlation and regression analyses were performed to examine the relationships between the corresponding soft and hard tissue movements. An overall pattern of facial soft tissue movement was observed in patients with prognathism who underwent orthognathic surgery. The experiment results have shown that mean ratios for the average soft-to-hard tissue movements in the facial regions varied, which may not exactly be similar to the published reports because of the population biocharacteristics and study methods, but the trend is in agreement with the previous studies. Additionally, the prediction capability of the regression model was significantly high, ranging from 0.786 to 0.857, in upper lip, upper vermilion, and chin regions, thus demonstrating that the skin outline changes in these critical regions could be reliably predicted from the underlying bone movements. These results could likely be applied in future soft tissue simulation in orthognathic surgery.

Postoperative outcomes of two- and three-dimensional planning in orthognathic surgery: A comparative study.

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.

Three-dimensional surgical simulation improves the planning for correction of facial prognathism and asymmetry: A qualitative and quantitative study.

Traditional planning method for orthognathic surgery has limitations of cephalometric analysis, especially for patients with asymmetry. The aim of this study was to assess surgical plan modification after 3-demensional (3D) simulation. The procedures were to perform traditional surgical planning, construction of 3D model for the initial surgical plan (P1), 3D model of altered surgical plan after simulation (P2), comparison between P1 and P2 models, surgical execution, and postoperative validation using superimposition and root-mean-square difference (RMSD) between postoperative 3D image and P2 simulation model. Surgical plan was modified after 3D simulation in 93% of the cases. Absolute linear changes of landmarks in mediolateral direction (x-axis) were significant and between 1.11 to 1.62 mm. The pitch, yaw, and roll rotation as well as ramus inclination correction also showed significant changes after the 3D planning. Yaw rotation of the maxillomandibular complex (1.88 ± 0.32°) and change of ramus inclination (3.37 ± 3.21°) were most frequently performed for correction of the facial asymmetry. Errors between the postsurgical image and 3D simulation were acceptable, with RMSD 0.63 ± 0.25 mm for the maxilla and 0.85 ± 0.41 mm for the mandible. The information from this study could be used to augment the clinical planning and surgical execution when a conventional approach is applied.

Automatic Superimposition of Palatal Fiducial Markers for Accurate Integration of Digital Dental Model and Cone Beam Computed Tomography.

PURPOSE: Obtaining a detailed dentition image is important for 3-dimensional orthognathic surgical simulation. The purpose of the present study was to evaluate the accuracy of a method using automatic superimposition of intraoral fiducial markers for integrating the digital dental model with the cone beam computed tomography (CBCT) scan. PATIENTS AND METHODS: A preliminary test was performed on a plastic skull model for the proper selection of the size and number of the fiducial markers fixed to the palatal plate. Five patients were enrolled in the present study. Plaster dental models were taken and scanned. Integration of the upper dental and occlusion dental image with the CBCT scan was performed by superimposition of the markers. The occlusion dental image was used to connect the lower dental image and the corresponding position of the CBCT mandibular dentition. The root mean square difference (RMSD) was used to evaluate the accuracy of fiducial marker superimposition, and the Euclidean distances were measured between 2 occlusion surfaces to evaluate the registration accuracy. RESULTS: The RMSD was less than 0.13 mm in the superimposition of fiducial markers, and the Euclidean distance was less than 0.28 mm in the occlusal surface deviation. The results showed high accuracy on integration. The patients reported good tolerance to the markers. CONCLUSION: This superimposition method provided high accuracy for the replacement of dentition using CBCT and was patient- and user-friendly for clinical application.