Can electromagnetic-navigated maxillary positioning replace occlusional splints in orthognathic surgery? A clinical pilot study

Accuracy analysis of the digital occlusal relationship reconstruction workflow in patients with maxillofacial fractures: An in vitro retrospective cohort study

OBJECTIVE

To verify the accuracy of a digital workflow for occlusal relationship reduction in patients with maxillofacial fractures via cone beam computed tomograhy/ computerized tomography (CBCT/CT).

METHODS

We collected CBCT/CT data and oral scan data from both general patients and fracture patients and established digital models. The differences between the oral scan model and the CBCT/CT digital model were compared. 3D-printed dental models were made for general patients, and comparisons were made matching the dental model with the original occlusion. Differences among the postoperative CT digital models of fracture patients, the virtual reconstruction models, and the model surgery reconstructed models were compared.

RESULTS

A total of 20 general patients and 27 fracture patients participated in this study. The average error for the segmented CBCT/CT modelling group was 122.90±26.94 μm, whereas the average error for the nonsegmented CBCT/CT modelling group was 84.50±9.21 μm, with a significant difference between the two groups (t = 6.364, P < 0.01). The error in the occlusal relationship between the 3D-printed models and the patient's actual occlusion was 18.35±2.20 μm. The average error for the virtual reconstruction group was 438.89±155.55 μm, whereas it was 857.09±116.55 μm for the model surgery reconstruction group, with a significant difference between the two groups (t = 11.180, P < 0.01).

CONCLUSION

CBCT/CT-based digital dental models can be created with high accuracy. Using 3D-printed models and intercuspal occlusion guidance, the original occlusal relationship can be restored. Compared with model surgery, virtual fracture reconstruction offers superior accuracy.

CLINICAL SIGNIFICANCE

This study demonstrates the feasibility of accurate digital occlusal restoration in fracture patients, providing a new approach for maxillofacial fracture management.

Novel CAD/CAM-splint-based navigation protocol enhances intraoperative maxillary position control in orthognathic surgery: a case control study

BACKGROUND

Virtual surgical planning for orthognathic surgery typically relies on two methods for intraoperative plan transfer: CAD/CAM occlusal splints and patient-specific implants (PSI). While CAD/CAM splints may offer limited accuracy, particularly in the vertical dimension, PSIs are constrained by higher costs and extended preparation times. Surgical navigation has emerged as a potential alternative, but existing protocols often involve invasive registration or lack transparent evaluation. This study introduces a novel protocol for point-based optical navigation using modified CAD/CAM splints for non-invasive registration and transparent intraoperative evaluation, assessing its effectiveness in maxillary positioning.

METHODS

This prospective case-control study included 20 patients undergoing bimaxillary orthognathic surgery. The experimental group employed surgical navigation with modified CAD/CAM splints, while the control group used standard CAD/CAM splints. Surgical accuracy was evaluated by measuring translational and rotational discrepancies between the planned and achieved maxillary positions. A mixed ANOVA was conducted to assess other factors, aside from surgical navigation, that might influence surgical accuracy.

RESULTS

Surgical navigation significantly improved accuracy in translational movements along the x-axis (right-left: -0.81 mm; p = 0.021) and z-axis (down-up: -0.82 mm; p = 0.014), as well as in yaw rotation (-0.45°; p = 0.045). Other movements also showed improved precision in the navigated group, though not statistically significant; y-axis (back-front): -0.60 mm (p = 0.094); pitch rotation: -0.70° (p = 0.071); roll rotation: -0.04° (p = 0.428). Besides the use of surgical navigation, the amount of planned movement significantly impacted surgical accuracy, although no specific factors could be identified to predict which cases would particularly benefit from surgical navigation.

CONCLUSIONS

Surgical navigation with modified CAD/CAM splints enhances surgical accuracy without requiring invasive procedures, offering a straightforward and transparent protocol suitable for routine clinical practice that allows intraoperative evaluation of maxillary positioning. However, the clinical significance and cost-effectiveness compared to PSI need further investigation. These findings suggest new directions for future developments, especially with advancements in mixed reality technologies, which could broaden the application of surgical navigation.

TRIAL REGISTRATION

Retrospectively registered with the German Clinical Trials Register (DRKS00034795).

Personalized Occlusal Guide Guides Panfacial Fracture Repair and Reconstruction

Restoration of the occlusal relationship is the key point in the treatment of maxillofacial fractures. Poor restoration of the occlusal relationship seriously impacts oral function as well as physical and mental health. This study combines virtual surgical technology with model surgery, uses computed tomography data to establish a maxillofacial bone model, and performs a virtual reduction of fractures. The upper and lower dentition models after reconstruction were intercepted and 3-dimensional printed. After the occlusal relationship was reconstructed by the prosthodontist using the model, an occlusal reduction guide was designed and manufactured based on the reconstructed occlusal relationship to accurately reduce the occlusal relationship in patients with maxillofacial fractures. This study proposes an occlusal guide design process for maxillofacial fractures and optimizes the traditional model surgical process to provide a convenient surgical strategy. This study provides new ideas for the design of personalized surgical guides for maxillofacial fractures.

3-Dimensional accuracy of navigation-guided bimaxillary orthognathic surgery: A systematic review and meta-analysis

The transfer of a virtual orthognathic surgical plan to the patient still relies on the use of occlusal splints, which have limitations for vertical positioning of the maxilla. The use of real-time navigation has been proposed to enhance surgical accuracy. This systematic review (PROSPERO CRD42024497588) aimed to investigate if surgical navigation can improve the three-dimensional accuracy of orthognathic surgery. The inclusion criteria were orthognathic surgery, use of intra-operative navigation and quantitative assessment of surgical accuracy. The exclusion criteria were non-bimaxillary orthognathic surgeries, non-clinical studies, studies without post-operative 3D analysis and publications not in the English language. A search of PubMed, Embase and Cochrane Library generated 940 records, of which 12 were found relevant. Risk of bias was assessed done using the Joanna Briggs Institute Critical Appraisal Checklist Tool. Among the included studies, there were nine of observational character and three randomized control studies (RCTs). All studies demonstrated promising outcomes with reported good surgical accuracy within a 2 mm difference between the planned and post-surgical result. Meta-analysis of two RCTs was carried out and results were in favor of surgical navigation with a total odds ratio of 4.44 [2.11, 9.37] and an overall effect outcome of Z = 3.92 (p < 0.0001). Navigation was up to 0.60 mm more accurate than occlusal wafers only (p < 0.001). However, there were variations in the application of surgical navigation and methods of analysis, leading to a heterogenous data set. Future studies should focus on standardized protocols and analysis methods to further validate the use of surgical navigation in orthognathic surgery. Despite some limitations, surgical navigation shows potential as a valuable tool in improving the accuracy of orthognathic surgery.

A hybrid registration method using the mandibular bone surface for electromagnetic navigation in mandibular surgery

PURPOSE

To utilize navigated mandibular (reconstructive) surgery, accurate registration of the preoperative CT scan with the actual patient in the operating room (OR) is required. In this phantom study, the feasibility of a noninvasive hybrid registration method is assessed. This method consists of a point registration with anatomic landmarks for initialization and a surface registration using the bare mandibular bone surface for optimization.

METHODS

Three mandible phantoms with reference notches on two osteotomy planes were 3D printed. An electromagnetic tracking system in combination with 3D Slicer software was used for navigation. Different configurations, i.e., different surface point areas and number and configuration of surface points, were tested with a dentate phantom (A) in a metal-free environment. To simulate the intraoperative environment and different anatomies, the registration procedure was also performed with an OR bed using the dentate phantom and two (partially) edentulous phantoms with atypical anatomy (B and C). The accuracy of the registration was calculated using the notches on the osteotomy planes and was expressed as the target registration error (TRE). TRE values of less than 2.0 mm were considered as clinically acceptable.

RESULTS

In all experiments, the mean TRE was less than 2.0 mm. No differences were found using different surface point areas or number or configurations of surface points. Registration accuracy in the simulated intraoperative setting was-mean (SD)-0.96 (0.22), 0.93 (0.26), and 1.50 (0.28) mm for phantom A, phantom B, and phantom C.

CONCLUSION

Hybrid registration is a noninvasive method that requires only a small area of the bare mandibular bone surface to obtain high accuracy in phantom setting. Future studies should test this method in clinical setting during actual surgery.

Virtual extensions improve perception-based instrument alignment using optical see-through devices

Instrument alignment is a common task in various surgical interventions using navigation. The goal of the task is to position and orient an instrument as it has been planned preoperatively. To this end, surgeons rely on patient-specific data visualized on screens alongside preplanned trajectories. The purpose of this manuscript is to investigate the effect of instrument visualization/non visualization on alignment tasks, and to compare it with virtual extensions approach which augments the realistic representation of the instrument with simple 3D objects. 18 volunteers performed six alignment tasks under each of the following conditions: no visualization on the instrument; realistic visualization of the instrument; realistic visualization extended with virtual elements (Virtual extensions). The first condition represents an egocentric-based alignment while the two other conditions additionally make use of exocentric depth estimation to perform the alignment. The device used was a see-through device (Microsoft HoloLens 2). The positions of the head and the instrument were acquired during the experiment. Additionally, the users were asked to fill NASA-TLX and SUS forms for each condition. The results show that instrument visualization is essential for a good alignment using see-through devices. Moreover, virtual extensions helped achieve the best performance compared to the other conditions with medians of 2 mm and 2° positional and angular error respectively. Furthermore, the virtual extensions decreased the average head velocity while similarly reducing the frustration levels. Therefore, making use of virtual extensions could facilitate alignment tasks in augmented and virtual reality (AR/VR) environments, specifically in AR navigated surgical procedures when using optical see-through devices.

Robot-Assisted Maxillary Positioning in Orthognathic Surgery: A Feasibility and Accuracy Evaluation

Several methods enabling independent repositioning of the maxilla have been introduced to reduce intraoperative errors inherent in the intermediate splint. However, the accuracy is still to be improved and a different approach without time-consuming laboratory process is needed, which can allow perioperative modification of unoptimized maxillary position. The purpose of this study is to assess the feasibility and accuracy of a robot arm combined with intraoperative image-guided navigation in orthognathic surgery. The experiments were performed on 12 full skull phantom models. After Le Fort I osteotomy, the maxillary segment was repositioned to a different target position using a robot arm and image-guided navigation and stabilized. Using the navigation and the postoperative computed tomography (CT) images, the achieved maxillary position was compared with the planned position. Although the maxilla showed mild displacement during the fixation, the mean absolute deviations from the target position were 0.16 mm, 0.18 mm, and 0.20 mm in medio-lateral, antero-posterior, and supero-inferior directions, respectively, in the intraoperative navigation. Compared with the target position using postoperative CT, the achieved maxillary position had a mean absolute deviation of less than 0.5 mm for all dimensions and the mean root mean square deviation was 0.79 mm. The results of this study suggest that the robot arm combined with the intraoperative image-guided navigation may have great potential for surgical plan transfer with the accurate repositioning of the maxilla in the orthognathic surgery.

Robot-assisted mandibular angle osteotomy using electromagnetic navigation

BACKGROUND

To explore the potential of electromagnetic (EM) navigation technology in the field of robot-assisted surgery, we set up a maxillofacial surgical robotic system (MSRS) guided by an EM navigation tool. Mandibular angle osteotomy was used to analyze the feasibility in confined surgical areas.

METHODS

Model and animal experiments were implemented to validate the system precision. Before the experiment, a customized dental splint was made and then fixed with a standard navigation part. An accurate 3D surgical plan was designed based on the preoperative CT scan. During the experiment, the splint was rigidly mounted on teeth for navigation registration, so the robot could position a specially designed template to guide the accurate osteotomy according to the preoperative plan. For the model experiment, a Coordinate Measuring Machine was used to measure the template's position and angle. For the animal experiment, surgeons completed the surgery by moving a saw along the template, while a postoperative CT scan was carried out to calculate the precision.

RESULTS

All procedures were successfully completed, with no complications in any of the experimental animals. In the model experiment, the accuracy of the navigation position and angle was 0.44±0.19 mm and 3.5°±2.1°, respectively. In the animal experiment, the lateral osteotomy line error was 0.83±0.62 mm, the interior error was 1.06±1.03 mm, and the angle between the actual cutting plane and preoperative planning plane was 5.9°±4.7°.

CONCLUSIONS

Robot-assisted surgery with EM navigation resulted feasible in the real operating environment. Moreover, this system's precision could meet clinical needs, while the proposed procedure was safe and easy on animals. Consequently, this approach has the potential to be applied to clinical craniomaxillofacial practice in the near future.

Improving accuracy of the intermediate splint in substantial intermaxillary sagittal discrepancies using an extra anterior anchorage point: technical note

Background

To describe a technical feature that increases the stability of the intermediate splint in patients where bimaxillary surgery with great maxillary/mandibular advancements are planned.

Material and Methods

Prospective evaluation of the intermediate splint dental vertical penetration in patients undergoing bimaxillary surgery where great sagittal discrepancy occur in the anterior sector between the upper and lower jaws when the intermediate splint is placed by adding an extra intermaxillary fixation (IMF) screw (2x9 mm) placed between the central incisors of the maxilla and fixed to the most anterior aspect of the intermediate splint following the direction of the sagittal maxillo-mandibular discrepancy from January to September 2018.

Results

The postoperative evaluation comparing the accuracy of conventional fixation versus fixation with an extra anterior anchorage point through photographic assessment and intraoral digital scanner demonstrated better dental penetration, and therefore improved intermediate splint precision with the latter in all cases

Conclusions

Our results suggest that this is a simple and safe technique that can be easily reproduced and optimizes the outcomes by increasing the accuracy of translation of the planned surgical movements to the operating room.

Key words:Orthognathic surgery, intermediate splint, accuracy, intermaxillary fixation, bone screw.

An electromagnetic tracking implantation navigation system in dentistry with virtual calibration

BACKGROUND

Dental implant placement navigation systems based on optical tracking have been widely used in clinics. However, electromagnetic (EM) navigation method that does not suffer from problems of hidden line-of-light has not yet been described.

METHODS

This work proposes an EM-guided navigation method named TianShu-ESNS with virtual calibration. Model (12 implants) and animal experiments (pig head: six implants) were conducted to evaluate its performance and stability.

RESULT

The mean virtual calibration error was 0.83 ± 0.20 mm. The mean deviations at the entry point, end point and angle in the phantom experiment of TianShu-ESNS were 1.23 ± 0.17 mm, 1.59 ± 0.20 mm and 1.83 ± 0.27°, respectively. In the animal experiment, the same deviations were 1.25 ± 0.07 mm, 1.57 ± 0.35 mm and 1.90 ± 0.60°, respectively.

CONCLUSIONS

The experimental results show that TianShu-ESNS with the virtual calibration method could serve as a promising tool to eliminate the line-of-light hidden problem and simplify operation procedure in dental implant placement.

The use of 3D virtual surgical planning and computer aided design in reconstruction of maxillary surgical defects

PURPOSE OF REVIEW

The present review describes the latest development of 3D virtual surgical planning (VSP) and computer aided design (CAD) for reconstruction of maxillary defects with an aim of fully prosthetic rehabilitation. The purpose is to give an overview of different methods that use CAD in maxillary reconstruction in patients with head and neck cancer.

RECENT FINDINGS

3D VSP enables preoperative planning of resection margins and osteotomies. The current 3D VSP workflow is expanded with multimodal imaging, merging decision supportive information. Development of more personalized implants is possible using CAD, individualized virtual muscle modelling and topology optimization. Meanwhile the translation of the 3D VSP towards surgery is improved by techniques like intraoperative imaging and augmented reality. Recent improvements of preoperative 3D VSP enables surgical reconstruction and/or prosthetic rehabilitation of the surgical defect in one combined procedure.

SUMMARY

With the use of 3D VSP and CAD, ablation surgery, reconstructive surgery, and prosthetic rehabilitation can be planned preoperatively. Many reconstruction possibilities exist and a choice depends on patient characteristics, tumour location and experience of the surgeon. The overall objective in patients with maxillary defects is to follow a prosthetic-driven reconstruction with the aim to restore facial form, oral function, and do so in accordance with the individual needs of the patient.

Three-dimensional virtual surgical planning in the oncologic treatment of the mandible

OBJECTIVES

In case of surgical removal of oral squamous cell carcinomas, a resection of mandibular bone is frequently part of the treatment. Nowadays, such resections frequently include the application of 3D virtual surgical planning (VSP) and guided surgery techniques. In this paper, current methods for 3D VSP leads for optimisation of the workflow, and patient-specific application of guides and implants are reviewed.

RECENT FINDINGS

Current methods for 3D VSP enable multi-modality fusion of images. This fusion of images is not restricted to a specific software package or workflow. New strategies for 3D VSP in Oral and Maxillofacial Surgery include finite element analysis, deep learning and advanced augmented reality techniques. These strategies aim to improve the treatment in terms of accuracy, predictability and safety.

CONCLUSIONS

Application of the discussed novel technologies and strategies will improve the accuracy and safety of mandibular resection and reconstruction planning. Accurate, easy-to-use, safe and efficient three-dimensional VSP can be applied for every patient with malignancies needing resection of the mandible.

Current Orthognathic Practice in India: Do We Need to Change?

The last decade or so has seen paradigm shifts in the various aspects of orthognathic surgery. A lot of these changes are to do with digitalization of the orthodontic-surgical workflow, optimization of surgery-first protocols, virtual surgical planning-based 3D printing solutions and changing patient-health-care dynamics. The aim of this article is to provide evidence-based recommendations that are both practical and economically viable for the current orthognathic practice in India.

Relevance of 3D virtual planning in predicting bony interferences between distal and proximal fragments after sagittal split osteotomy

After sagittal split osteotomy, the mandibular distal and proximal fragments do not always align themselves passively to one another, resulting in bony interferences and subsequent anomalous settlement of the condyles. Predicting these interferences could be an important ancillary procedure for avoiding intra- and postoperative surgical complications, rendering orthognathic surgery more effective and safer. This study evaluated the relevance of virtual surgical planning in assessing the displacement of the proximal segments after virtual distal segment repositioning, for predicting bony interferences between the segments and thus avoiding related intra- and postoperative surgical complications. The presence of interferences between the distal and proximal segments was compared between virtually predicted (computer-assisted simulation surgery, Dolphin software) and real cases in 100 consecutive patients diagnosed with dentofacial deformities who underwent orthognathic surgery with mandibular repositioning (using a short lingual osteotomy (SLO)). The results indicated that clockwise rotation of the mandible was the mandibular movement most prone to segment interference. Furthermore, virtual planning was sensitive (100%) but had low specificity (51.6%) in predicting proximal and distal segment interferences. This low specificity was due to the software-based automated design of the mandibular osteotomy, where the length of the distal segment was longer than the real SLO, and the mandibular ramus sagittal split was located just behind Spix's spine. Thus, more precise simulated osteotomies are needed to further validate the accuracy of virtual planning for this purpose.

Accuracy of mandible-independent maxillary repositioning using pre-bent locking plates: a pilot study

The double splint method is considered the gold standard for maxillary repositioning, but the procedure is lengthy and prone to error. Recent splintless methods have shown high repositioning accuracy; however, high costs and technical demands make them inaccessible to many patients. Therefore, a new cost-effective method of mandible-independent maxillary repositioning using pre-bent locking plates is proposed. Plates are bent on maxillary models in the planned position prior to surgery. The locations of the plate holes are replicated during surgery using osteotomy guides made from thermoplastic resin sheets. Pre-bent plates are subsequently fitted onto the maxilla, and plate holes are properly set to reposition the maxilla. The purpose of this study was to evaluate the accuracy of this method for maxillary repositioning and the reproducibility of the plate holes. Fifteen orthognathic surgery patients were evaluated retrospectively by superimposing preoperative simulations over their postoperative computed tomography models. The median deviations in maxillary repositioning and plate hole positioning between the preoperative plan and postoperative results were 0.43mm (range 0-1.55mm) and 0.33mm (range 0-1.86mm), respectively. There was no significant correlation between these deviations, suggesting that the method presented here allows highly accurate and reliable mandible-independent maxillary repositioning.