Feasibility of Augmented Reality combine patient-specific implants (PSI) Applied to Navigation in Mandibular genioplasty: A Phantom Experiment.

PURPOSE: Genitoplasty is becoming more and more common, and it is important to improve the accuracy of the procedure and simplify the procedure. This experiment explores the feasibility of using augmented reality (AR) technology combined with PSI titanium plates for navigational assistance in genioplasty performed on models, aiming to study the precision of such surgical interventions. METHODS: Twelve genioplasty procedures were designed and implemented on 3D-printed resin mandibular models by the same surgeon using three different approaches: AR+3DT group (AR+PSI) , 3DT group (patient-specific titanium plate) , and a traditional free-hand group(FH group). Postoperative models were assessed using CBCT to evaluate surgical accuracy. RESULTS: In terms of osteotomy accuracy, the AR group demonstrated a surgical error of 0.9440±0.5441 mm, significantly lower than the control group, which had an error of 1.685±0.8907 mm (P<0.0001). In experiments positioning the distal segment of the chin, the overall centroid shift in the AR group was 0.3661±0.1360 mm, significantly less than the 2.304±0.9629 mm in the 3DT group and 1.562±0.9799 mm in the FH group (P<0.0001). Regarding angular error, the AR+3DT group showed 2.825±1.373°, significantly less than 8.283±3.640° in the 3DT group and 7.234±5.241° in the FH group. CONCLUSION: AR navigation technology combined with PSI titanium plates demonstrates higher surgical accuracy compared to traditional methods and shows feasibility for use. Further validation through clinical trials is necessary.

Factors predicting neurosensory disturbance after bilateral sagittal split ramus osteotomy: a retrospective cohort study.

Neurosensory disturbances (NSD) are the most widely recognized complication of bilateral sagittal split ramus osteotomy (BSSRO), but predictors of NSD remain unclear. The aim of this study was to identify factors predicting NSD following BSSRO. A retrospective cohort study of 129 consecutive patients with dentofacial deformities (median age 24.0 years; 76.0% female), who underwent BSSRO (95 without genioplasty, 34 with genioplasty), was conducted. The presence of NSD was evaluated at 6 months postoperatively and was found in 97 patients (absent in 32 patients). Potential NSD-related factors investigated were age, sex, genioplasty, mandibular canal type, inferior alveolar nerve (IAN) exposure, mandibular movement, and laterality. Multivariate binary logistic regression analysis was conducted to elucidate factors predicting NSD, with calculation of odds ratios (OR) and 95% confidence intervals (CI). The dependent variable was defined as NSD after BSSRO. Independent variables were those with P < 0.100 in the univariate analysis. In the multivariate binary logistic regression analysis, NSD showed a significant association with BSSRO with genioplasty (adjusted OR 3.87, 95% CI 1.21-12.26; P = 0.022) and left IAN exposure (adjusted OR 4.69, 95% CI 1.49-14.73; P = 0.008). The study findings may lead to enhanced clinical outcomes for BSSRO.

Satisfaction Level of Patients with the Outcome of Genioplasty.

Background: We aimed to assess the satisfaction level of patients with the outcome of genioplasty and the influential parameters in this respect. Methods: This retrospective study was conducted on 70 patients between 18 to 59 years, who underwent genioplasty in the Oral and Maxillofacial Surgery Department at Shariati and Sina Hospitals, Tehran, Iran, between 2010 and 2020. Patient records were evaluated and a questionnaire was filled out over the phone to assess the influential parameters on the satisfaction level of patients with the outcome of genioplasty. Data were analyzed by PASS 11 (alpha=0.1). Results: Seventy patients were evaluated including 56 (80%) females and 14 (20%) males. Forty patients (52.6%) had no complaint with regard to the outcome of genioplasty. Postoperative chin deviation (not correcting the initial complaint) (10.52%), postoperative pain in the chin area (10.52%), and lower lip paresthesia (9.21%) were the most common patient complaints. The minimum and maximum satisfaction scores were 22 and 80, respectively. Number of follow-up sessions had a significant effect on satisfaction with the outcome of genioplasty (P=0.076). Patients who underwent advancement genioplasty alone had the highest level of long-term satisfaction with the outcome while those who underwent setback genioplasty alone had the lowest level of long-term satisfaction. Conclusion: Advancement genioplasty had the highest rate of patient satisfaction, and chin asymmetry in the frontal view was the most common patient complaint after genioplasty.

Guided versus non-guided chin repositioning: a retrospective study on accuracy.

Genioplasty is a widely used surgical approach to address chin deformities by performing an osteotomy on the inferior border of the mandible to allow for comprehensive repositioning of the chin. This study aimed to compare the accuracy of freehand chin repositioning with a guided technique that employed specialised surgical guides. For this retrospective study, data from 30 adult patients who underwent orthognathic surgery to correct dentofacial deformities were analysed. All patients underwent virtual planning before surgery, with half of them treated using freehand chin repositioning and the other half using the guided technique. The surgical outcomes were measured and compared with the virtual plan to assess the positional and rotational accuracy of the techniques. In terms of translational assessment, noteworthy values that exceeded clinically acceptable limits were observed only in sagittal movement in the freehand group (0.97 mm, interquartile range (IQR) 0.73-2.29 mm). Regarding rotational accuracy, both groups exhibited an IQR that surpassed acceptable limits for pitch (3.26°, IQR 2.06-5.20 for the guided group and 2.57°, IQR 1.63-4.24° for the freehand group). The Mann-Whitney test indicated no statistical differences between the groups in any translational or rotational assessment. In conclusion, although there was no statistical difference, the guided technique proved effective in achieving clinically acceptable accuracy in all positions and almost all rotations, displaying superior results in sagittal positioning compared with the freehand technique. To fully harness the advantages of guides and to guarantee accuracy in all rotations, we recommend further research involving guides made of more rigid materials, and customised implants.

Digital Surgical Guides in Mandibular Genioplasty: Evaluating Precision Against Conventional Techniques.

BACKGROUND: Mandibular genioplasty, a central procedure in oral and maxillofacial surgery, has traditionally relied on surgeon experience with potential limitations in precision. The advent of digital methods, particularly computer-aided design/computer-aided manufacturing (CAD/CAM), offers a promising alternative. This study aims to evaluate the efficacy of digital surgical guides in improving the precision of mandibular genioplasty. METHODS: A prospective analysis of 50 patients undergoing genioplasty was performed, 30 in the experimental group using digital surgical guides and 20 in the control group using traditional methods. Three-dimensional reconstructions were obtained using cone-beam computed tomography (CBCT) and digital scans. Osteotomy guides were 3D-printed based on group assignment. Postoperatively, accuracy was assessed by measuring distances between landmarks. RESULTS: The experimental group showed significantly reduced horizontal positioning errors in genioplasty advancement, with no significant differences in vertical errors. For genioplasty retraction, the experimental group showed fewer vertical positioning errors, while horizontal errors remained consistent. CONCLUSIONS: The use of digital surgical guides in mandibular genioplasty significantly improves surgical accuracy, resulting in improved outcomes and patient satisfaction. This study highlights the potential of digital methods in refining oral and maxillofacial surgical procedures. LEVEL OF EVIDENCE III: This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266.

Augmentation genioplasty using discarded bone fragments following proximal segment osteotomy of the ramus in intraoral vertical ramus osteotomy (IVRO).

BACKGROUND: Based on a three-dimensional (3D) orthognathic simulation, this technical report introduces a method for augmentation genioplasty using a proximal bone fragment of the mandible, which is typically discarded in intraoral vertical ramus osteotomy (IVRO). RESULTS: A 43-year-old female patient diagnosed with Class III malocclusion, presenting with a protruding mandible and long facial height, underwent surgical treatment. The surgical plan involved mandibular setback position using IVRO and augmentation genioplasty. The 3D orthognathic surgery including augmentation genioplasty simulation was performed. An excessively elongated proximal segment was sectioned following IVRO. The inferior part of the sectioned proximal bone fragment of the mandible was positioned to align with the requirements of advancement genioplasty. After ensuring that the placement of the fragment matched that of the simulated surgery, each bone fragment was fixed. At 1.5 years post-surgery, the grafted bone on the augmentation genioplasty was well maintained, with slight bone resorption. CONCLUSIONS: Augmentation genioplasty using the proximal bone fragment of the mandible, which is typically discarded in IVRO, reduces the surgical complications associated with chin osteotomy. When a secondary genioplasty is required, genioplasty with osteotomy, movement of the cut bone fragments, partial bone-shaving osteotomy, and additional bone grafting are viable options.

Efficacy of photobiomodulation following L-PRF application for recovery of mental nerve neurosensory disturbances caused by genioplasty: A randomized triple-blind clinical trial.

The present study assessed the efficacy of photobiomodulation (PBM) following leukocyte-platelet rich fibrin (L-PRF) application for recovery of mental nerve neurosensory disturbances (NSDs) caused by genioplasty. This randomized triple-blind split-mouth clinical trial was conducted on 20 female patients (40 quadrants) requiring genioplasty. In each patient, one random side of the mandible served as the intervention (laser), and the other side as the control group. After genioplasty and L-PRF application, the intervention side underwent GaAIAs diode laser irradiation (880 nm, 500 mW, 15 J/cm2, 0.5 cm2 spot size, continuous-wave). Each point was laser irradiated for 15 s. Unilateral extraoral PBM was performed at 1, 3, 7, 14, 21, and 28 days, postoperatively. Laser in off mode (sham laser) was used for the control side. A visual analog scale (VAS) was used for general sensitivity, and 2-point discrimination, directional discrimination, pain discrimination, and thermal discrimination tests were used to assess the neurosensory recovery at 2 days, 2 weeks, 4 weeks, and 2 months, postoperatively. Statistical analyses were performed using two-way repeated measures ANOVA, Bonferroni test, and generalized estimating equation (alpha = 0.05). Time had a significant effect on improvement of all sensory variables (P < 0.05). Neurosensory recovery was significantly better in the intervention than the control group at all time points according to the two-point discrimination test (P = 0.0135) and brush test (P = 0.025) results. The interaction effect of time and intervention was not significant on any dependent variable (P > 0.05). Application of L-PRF + PBM resulted in significantly greater sensorineural recovery according to the two-point discrimination and brush test results.

Neurosensory Evaluation Following Genioplasty: A Case Report.

Genioplasty is a common procedure in plastic surgery, with various alloplastic biomaterials utilized for chin augmentation. Despite their advantages, complications such as neuropraxia of the mental nerve can occur, leading to temporary or persistent sensory disturbances. This case report describes a 35-year-old female who sought correction of a small chin. Preoperative evaluation revealed a retrognathic profile, and the patient underwent genioplasty with high-density porous polyethylene implantation. Postoperatively, she experienced mild paresthesia, which improved over time. Neurosensory assessments, including mechanical and light touch tests, showed no abnormalities in A-beta and C fibers but decreased sensitivity in A-delta fibers. This case report emphasizes the importance of evaluating larger nerve fibers during postoperative assessments and the need for standardized testing methodologies to comprehensively assess nerve damage after genioplasty. Further research should explore strategies to standardize neurosensory assessment and optimize therapeutic interventions for nerve damage after genioplasty.

Evaluation of soft tissue profile changes following autogenous fat or onlay PEEK augmentation versus sliding genioplasty for correction of deficient chin: Randomized controlled clinical trial.

AIM: The study was conducted to evaluate soft tissue profile changes using autogenous fat augmentation or onlay PEEK versus sliding genioplasty for correction of deficient chin in patients with retruded chin. MATERIAL AND METHODS: Thirty-three patients with deficient chins were included in the study. The patients were distributed into 3 groups: the fat augmentation group as intervention I, the PEEK augmentation group as intervention II, and the osseous genioplasty group as control group. Preoperative and postoperative CBCT were performed for all patients. With the aid of MIMICS,3-MATIC, and PROPLAN software, diagnosis, virtual planning, and evaluation were performed. The Face-Q questionnaire was used to assess patient satisfaction. RESULTS: There was a statistically significant difference regarding soft tissue relapse in the fat group after 6 months when compared to the control group (mean difference= 0.770), while there was no statistically significant difference regarding soft tissue relapse between PEEK and control group (mean difference= -0.060). Intragroup comparison has shown no statistically significant difference regarding soft tissue relapse within all groups between follow-up periods (P = 0.1389 for the fat group, P = 0.8739 for the peek group, and P = 0.8410 for the control group). All patients showed a statistically significant increase in scores of satisfaction with the chin between follow-up periods (P = 0.0165, P = 0.0150, and P = 0.0293) respectively. CONCLUSIONS: Fat augmentation can be a good intervention choice in mild-moderate deficient cases. PEEK PSI has a stable surgical outcome.

F-Chin/Feminizing the Chin: A Genioplasty Technique with Virtual Planning for Male-to-Female Transgender Patients.

The chin is an essential structure in facial harmony and an important gender marker. Advancing a receding chin is fundamental to improve the facial appearance, particularly in male-to-female transgender patients. However, in patients with microgenia and/or retrognathia, desiring a more feminine appearance, a chin advancement can result in a wider, square shape; an undesirable effect. Genioplasty is a versatile procedure used in facial feminization surgery that allows modifying the natural anatomy of the chin in all three spatial dimensions. The technique herein described proposes a simple genioplasty procedure for feminizing the chin (F-chin genioplasty) in transgender patients where anteroposterior advance is required. Virtual planning was used to establish the landmarks for an anteroposterior advancement with transverse reduction in the chin. A perpendicular line to the Frankfurt plane passing through the incisal edge of the upper central incisor was used to plan the anteroposterior movement, and two vertical lines on the outer wall of the nasal cavity  for the chin transverse measurement. The authors present three case reports with the F-chin genioplasty transgender technique with satisfactory results, ensuring a more feminine facial appearance.Level of Evidence V This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Accuracy of the CAD/CAM technique compared with the conventional technique used for stand-alone genioplasty.

The benefit of the computer-aided design and manufacturing (CAD/CAM) technique for stand-alone genioplasty remains uncertain and was evaluated in this study. Patients who underwent a conventional genioplasty (n = 20) or genioplasty with the CAD/CAM technique (n = 20), and for whom cephalometry and photogrammetry were performed before and 6 months after surgery, were included. Deviations from predictions of the soft tissue pogonion (Pg'), lip inferior point to aesthetic line (Li-Esth), facial convexity angle (FCA), mentolabial angle (MLA), and ratios of soft to hard tissue movements were calculated. No significant deviation was observed for Pg' in either the conventional group (3.85 ± 4.36 mm; 1.91 ± 1.11 mm) or CAD/CAM group (1.28 ± 1.16 mm; 2.81 ± 3.08 mm), for horizontal and vertical movements, respectively. However, for forward movement, deviation from the prediction of Pg´ in the CAD/CAM group was significantly lower than that in the conventional group (P = 0.015). Deviations of Li-Esth, MLA, and FCA did not differ significantly between the groups. No definite preference for the CAD/CAM technique could be established, because deviations from predictions were not significant in either of the technique groups and lay within the clinically acceptable range.

Genioplasty and Hyoid Advancement by Distraction Osteogenesis for the Correction of Obstructive Sleep Apnea in a Pediatric Patient.

Advancement genioplasty is one variation of genioglossus advancement (GA) and GA is a surgical intervention that can be applied for obstructive sleep apnea (OSA) caused by hypopharyngeal collapse. The genioglossus muscle originates from the posterior surface of the midline mandible and inserts into the entire tongue mass and the body of the hyoid bone. Placing horizontal tension on the genioglossus muscle enlarges the posterior airway space. We use a modified GA that applies distraction osteogenesis to increase forward movement of the genioglossus muscle and also connects the bone transport segment to the hyoid bone with a thread to maximize the anterior movement of the hyoid bone. We used this technique on a young patient and obtained good results.

Validation of a fully automatic three-dimensional assessment of orthognathic surgery.

The aim of the present study was to propose and validate FAST3D: a fully automatic three-dimensional (3D) assessment of the surgical accuracy and the long-term skeletal stability of orthognathic surgery. To validate FAST3D, the agreement between FAST3D and a validated state-of-the-art semi-automatic method was calculated by intra-class correlation coefficients (ICC) at a 95 % confidence interval. A one-sided hypothesis test was performed to evaluate whether the absolute discrepancy between the measurements produced by the two methods was statistically significantly below a clinically relevant error margin of 0.5 mm. Ten subjects (six male, four female; mean age 24.4 years), class II and III, who underwent a combined three-piece Le Fort I osteotomy, bilateral sagittal split osteotomy and genioplasty, were included in the validation study. The agreement between the two methods was excellent for all measurements, ICC range (0.85-1.00), and fair for the rotational stability of the chin, ICC = 0.54. The absolute discrepancy for all measurements was statistically significantly lower than the clinical relevant error margin (p < 0.008). Within the limitations of the present validation study, FAST3D demonstrated to be reliable and may be adopted whenever appropriate in order to reduce the work load of the medical staff.

Gender-Affirming Facial Surgery: Lower Third of the Face.

This article is intended to give the reader an overview of facial gender-affirming procedures applicable to the lower face and neck. A review of facial analysis in the context of masculine versus feminine facial features and the contributions of both soft tissue and bone to this anatomy is provided. The use of systematic facial evaluation and patient-driven concerns as a guide for presurgical planning is reviewed. Detailed descriptions of the unique surgical interventions to feminize the soft tissues and the skeletal framework of the lower face and neck are provided.

Esthetic Surgery of the Chin in Cis- and Transgender Patients-Application of T-Genioplasty vs. Single-Piece Segment Lateralization.

Background and Objectives: Correction of lower face asymmetry still remains challenging in maxillofacial surgery. This report describes techniques for the lateral transposition of the symphyseal segment to restore lower face symmetry while maintaining gender-related features in cis- and transgender patients. Materials and Methods: A retrospective review of medical records of 31 patients who attended for esthetic corrective surgery after orthodontic camouflage or orthognathic treatment, or during facial feminization of the lower face between June 2021 and June 2023 was performed. Result: All patients underwent lateralization genioplasty (with or without advancement or setback), either with or without narrowing T-osteotomy supplemented with necessary procedures in order to obtain proper facial balance and desired esthetical effects, such as bichectomy, liposuction, and face and neck lift. The mean asymmetry of the chin was 5.15 mm and was surgically corrected either by single segment lateralization or T-shape narrowing genioplasty depending on the gender and esthetical requirements. No complications were reported. Conclusions: Lateral shift genioplasty serves as a powerful tool in primary and secondary corrective surgery for lower face asymmetry that maintains gender-specific facial features. It may serve either as an additive to orthodontic camouflage or a way to correct previous orthognathic surgery pitfalls. The surgeon performing esthetic genioplasty associated with gender-specific expectations must be trained in facelift and facial liposculpting techniques in order to provide the best results and properly choose the right procedures for the right patients.

What is the angular accuracy of regional voxel-based registration for segmental Le Fort I and genioplasty osteotomies?

Among the accuracy analysis techniques for orthognathic surgery, regional voxel-based registration (R-VBR) has robust data, but remains unvalidated for smaller jaw segments. The purpose of this study was to validate the angular accuracy of R-VBR for segmental Le Fort I (SLFI) and genioplasty osteotomies. Postoperative cone beam computed tomography (CBCT) of consecutive patients with three-piece SLFI or genioplasties was rotated to a known pitch/roll/yaw (P/R/Y). Using R-VBR, a copy of the raw CBCT was superimposed onto the rotated CBCT at four mutual regions of interest (ROI): anterior, right posterior, and left posterior maxilla, and chin. The P/R/Y of each was subtracted from those of the rotated CBCT to calculate the angular error. The predictor and outcome variables were ROI and absolute angular error, respectively. The accuracy threshold was 0.5°. Ten SLFI and 34 genioplasties were analyzed based on the sample size calculation. The one-sample t-test and Wilcoxon signed rank test were applied in the analysis. The mean absolute error was 0.20-0.54° for the maxillary segments (all P ≤ 0.01) and 0.83-2.51° for the genioplasty segments (all P < 0.001). R-VBR has variable angular accuracy for SLFI osteotomies and may be insufficient for genioplasty. The findings may allow the design and interpretation of studies on SLFI and genioplasty with greater rigor, thereby contributing to minimizing the discrepancy between planned and achieved outcomes.

Osseous genioplasty versus chin implants: early complications and patient satisfaction.

Osseous genioplasty and chin augmentation with implants are the two main treatment options for retrognathia. This retrospective cohort study was performed to compare the prevalence of complications and patient satisfaction following osseous genioplasty and chin augmentation by implant. Eighty patients were included: 38 underwent advancement osseous genioplasty and 42 received chin implants (alloplastic, either Medpor or Silastic) intraorally or extraorally. The patients were assessed for complications 12 months after surgery, including neurosensory disturbances, infection or extrusion, wound dehiscence, and the need for reoperation. Patient satisfaction was evaluated using a visual analogue scale. The infection rate was significantly higher in the chin implant group than in the genioplasty group (P = 0.028). Moreover, dehiscence and the need for reoperation appeared to be more common following chin augmentation with implants. However, there was no significant difference in the prevalence of neurosensory disturbances between the two groups (P = 0.137). In the chin implants group, the extraoral approach resulted in a lower dehiscence rate than the intraoral approach. Patients in the genioplasty group had significantly higher satisfaction scores than those in the chin implant group (P = 0.001). Overall, the rates of the complications assessed were lower and patient satisfaction was higher after osseous genioplasty when compared to chin augmentation with implants.

Chin Dysmorphology in the Primary Rhinoplasty Population: Prevalence, Objective Analysis, and Implications.

BACKGROUND: Chin flaws are far more common than recognized. Denial of genioplasty by parents or adult patients can present a surgical planning enigma, especially in patients with microgenia and chin deviation. This study aims to investigate the frequency of chin imperfections on patients seeking rhinoplasty, review the conundrum they generate, and offer management suggestions based on over 40 years of the senior author's experience. METHODS: This review included 108 consecutive patients presenting for primary rhinoplasty. Demographics, soft tissue cephalometrics, and surgical details were obtained. Exclusion criteria included prior orthognathic or isolated chin surgery, mandiblular trauma, or congenital craniofacial deformities. RESULTS: Of the 108 patients, 92 (85.2%) were female. Mean age was 30.8 years (SD±13, range 14-72). Ninety-seven (89.8%) patients exhibited some degree of objective chin dysmorphology. Fifteen (13.9%) had Class I deformities (macrogenia), 63 (58.3%) Class II (microgenia), and 14 (12.9%) Class III (combined macro and microgenia in the horizontal or vertical vectors). Forty-one (38%) patients had Class IV deformities (asymmetry). While all patients were offered the opportunity to correct chin flaws, only 11 (10.1%) underwent such procedures. Five (4.6%) patients had simultaneous osseous genioplasty (mean advancement 7.8mm, range 5-9mm); 7 (6.5%) received fat grafting to the chin (mean volume 4.4cc, range 1-9cc). CONCLUSIONS: A considerable proportion of primary rhinoplasty patients possess quantifiable chin dysmorphology on circumspect examination, high-resolution photographs and cephalometric analysis. Only a small number agree to surgical interventions that pursue full facial harmony. Potential reasons for these findings, patient aversion, and mitigation strategies will be discussed. LEVEL OF EVIDENCE III: This journal requires that authors assign a level of evidence to each article. For a full description of these evidence-based medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Tetris Genioplasty: A New Paradigm for Chin Asymmetries Correction.

The chin plays a crucial role as a fundamental structural component that contributes to the overall aesthetics and harmony of the face. Recognizing its central position, medical science has seen the evolution of numerous surgical techniques over the years, all aimed at correcting the range of structural irregularities that can affect the chin. In this contribution, the authors introduce an innovative osteotomy technique, aimed at cases of chin asymmetry in which the skeletal median diverges from the dental median. This technique, called "Tetris genioplasty", involves performing the classic rectangular osteotomy, but includes an additional vertical osteotomy in order to obtain two distinct segments. Finally, these segments are translocated and repositioned to obtain a realignment between the skeletal median and the dental median. The results were entirely satisfactory for the patients, aligning perfectly with the expected appearance after the operation. Furthermore, no complications were reported, proving the success and safety of the procedure. The Tetris genioplasty aligns itself with this progressive trend by offering a minimally invasive method that nevertheless is able to achieve excellent results with a high impact on the patient's quality of life, presenting a promising path in the pursuit of optimal aesthetic results with minimized patient morbidity and greater overall safety.

Enhanced Precision in Genioplasty: A Novel Intraoperative Spatial Repositioning Using Computer-Aided Design and Manufacturing Technology and a Holographic Mixed Reality Application.

Genioplasty is performed for the orthognathic surgical correction of dentofacial deformities. This article reports a safe and accurate method for genioplasty combining a novel three-dimensional (3D) device with mixed reality (MR)-assisted surgery using a registration marker and a head-mounted display. Four types of devices were designed based on the virtual operation: a surgical splint with a connector; an osteotomy device; a repositioning device; and a registration marker. Microsoft HoloLens 2 and Holoeyes MD were used to project holograms created using computed tomography (CT) data onto the surgical field to improve the accuracy of the computer-aided designed and manufactured (CAD/CAM) surgical guides. After making an incision on the oral vestibule, the splint was fitted on the teeth and the osteotomy device was mounted at the junction site, placed directly on the exposed mandible bone surface. Temporary screws were fixed into the screw hole. An ultrasonic cutting instrument was used for the osteotomy. After separating the bone, a repositioning device was connected to the splint junction and bone segment, and repositioning was performed. At the time of repositioning, the registration marker was connected to the splint junction, and mandible repositioning was confirmed three-dimensionally through HoloLens 2 into the position specified in the virtual surgery. The rate of overlay error between the preoperative virtual operation and one-month postoperative CT data within 2 mm was 100%. CAD/CAM combined with MR enabled accurate genioplasty.