Prototype of simulation of orthognathic surgery using a virtual reality haptic device

Haptic devices as an educational approach for oral and maxillofacial surgical procedures

OBJECTIVE

Developing the skills of a proficient surgeon with a deep understanding of force requires extensive training and repetitive practice. Traditionally, dental students and surgical trainees observed and participated in procedures using models, animals, or cadavers under expert supervision before performing the procedures independently. To address these challenges, interactive simulators with visuo-haptic features have been introduced in surgical training, providing visual and tactile feedback that replicates the sense of touch through applied forces, vibrations, or motions.

STUDY DESIGN

Two independent reviewers employed a specific search strategy to explore online databases such as PubMed, Scopus, and Web of Science (WoS). This strategy included keywords such as "haptic device," "education," "oral surgery," "surgery," and "maxillofacial surgery." All types of studies related to maxillofacial surgery, except for case reports, reviews, and eBooks, were considered for inclusion.

RESULTS

A total of 22 articles meeting the screening criteria were identified. The use of haptic devices for training dental students in oral surgery, anesthesia, as well as oral and maxillofacial trainees and surgeons in various surgical procedures, was evaluated.

CONCLUSION

Incorporating tactile devices into the training of residents and maxillofacial surgeons offers numerous advantages, including improved technical skills and enhanced patient safety.

The use of virtual reality and augmented reality in oral and maxillofacial surgery: A narrative review

OBJECTIVE

The purpose of this article is to review the current uses of virtual reality (VR) and augmented reality (AR) in oral and maxillofacial surgery. We discuss the use of VR/AR in educational training, surgical planning, advances in hardware and software, and the implementation of VR/AR in this field.

STUDY DESIGN

A retrospective comprehensive review search of PubMed, Web of Science, Embase, and Cochrane Library was conducted. The search resulted in finding 313 English articles in the last 10 years.

RESULTS

A total of 38 articles were selected after a meticulous review of the aims, objectives, and methodology by 2 independent reviewers.

CONCLUSIONS

Virtual reality/AR technology offers significant potential in various aspects, including student education, resident evaluation, surgical planning, and overall surgical implementation. However, its widespread adoption in practice is hindered by factors such as the need for further research, cost concerns, unfamiliarity among current educators, and the necessity for technological improvement. Furthermore, residency programs hold a unique position to influence the future of oral and maxillofacial surgery. As VR/AR has demonstrated substantial benefits in resident education and other applications, residency programs have much to gain by integrating these emerging technologies into their curricula.

Redefining precision and efficiency in orthognathic surgery through virtual surgical planning and 3D printing: a narrative review

Orthognathic surgery, essential for addressing jaw and facial skeletal irregularities, has historically relied on traditional surgical planning (TSP) involving a series of time-consuming steps including two-dimensional radiographs. The advent of virtual surgical planning (VSP) and 3D printing technologies has revolutionized this field, bringing unprecedented precision and customization to surgical processes. VSP facilitates 3D visualization of the surgical site, allowing for real-time adjustments and improving preoperative stress for patients by reducing planning time. 3D printing dovetails with VSP, offering the creation of anatomical models and surgical guides, enhancing the predictability of surgical outcomes despite higher initial setup and material costs. The integration of VSP and 3D printing promises innovative and effective solutions in orthognathic surgery, surpassing the limitations of traditional methods. Patient-reported outcomes show a positive post-surgery impact on the quality of life, underlining the significant role of these technologies in enhancing self-esteem and reducing anxiety. Economic analyses depict a promising long-term fiscal advantage with these modern technologies, notwithstanding the higher initial costs. The review emphasizes the need for large-scale randomized controlled trials to address existing research gaps and calls for a deeper exploration into the long-term impacts and ethical considerations of these technologies. In conclusion, while standing on the cusp of a technological renaissance in orthognathic surgery, it is incumbent upon the medical fraternity to foster a collaborative approach, balancing innovation with scrutiny to enhance patient care. The narrative review encourages the leveraging of VSP and 3D printing technologies for more efficient and patient-centric orthognathic surgery, urging the community to navigate uncharted territories in pursuit of precision and efficiency in the surgical landscape.

Development of a maxillofacial virtual surgical system based on biomechanical parameters of facial soft tissue

Purpose

Lack of biomechanical force model of soft tissue hinders the development of virtual surgical simulation in maxillofacial surgery. In this study, a physical model of facial soft tissue based on real biomechanical parameters was constructed, and a haptics-enabled virtual surgical system was developed to simulate incision-making process on facial soft tissue and to help maxillofacial surgery training.

Methods

CT data of a 25-year-old female patient were imported into Mimics software to reconstruct 3D models of maxillofacial soft and skeletal tissues. 3dMD stereo-photo of the patient was fused on facial surface to include texture information. Insertion and cutting parameters of facial soft tissue measured on fresh cadavers were integrated, and a maxillofacial biomechanical force model was established. Rapid deformation and force feedback were realized through localized deformation algorithm and axis aligned bounding box (AABB)-based collision detection. The virtual model was validated quantitatively and qualitatively.

Results

A patient-specific physical model composed of skeletal and facial soft tissue was constructed and embedded in the virtual surgical system. Insertion and cutting in different regions of facial soft tissue were simulated using omega 6, and real-time feedback force was recorded. The feedback force was consistent with acquired force data of experiments conducted on tissue specimen. Real-time graphic and haptic feedback were realized. The mean score of the system performance was 3.71 given by surgeons in evaluation questionnaires.

Conclusion

The maxillofacial physical model enabled operators to simulate insertion and cutting on facial soft tissue with realization of realistic deformation and haptic feedback. The combination of localized deformation algorithm and AABB-based collision detection improved computational efficiency. The proposed virtual surgical system demonstrated excellent performance in simulation and training of incision-making process.

Supplementary Information

The online version contains supplementary material available at 10.1007/s11548-022-02657-5.

Computer simulation and virtual reality in undergraduate operative and restorative dental education: A critical review

The primary aim of this review was to synthesize the literature for studies investigating the use of computer simulation (CS) and virtual reality (VR) in undergraduate dental education in operative and restorative dentistry. The secondary aim was to list best practices that maximize the simulation experience in dental education. A literature review of the PubMed and ERIC databases was conducted using the search terms "Dental AND Simulator," "Dental AND Virtual reality," and "Simulation AND Dental education." Studies in English language were categorized into 1 of 5 themes: Manual dexterity and cavity preparation, light curing skills, simulation perception and experience, predictability, and simulation model development. Main practices of simulation education indicated in the McGaghie et al. critical review published in 2010 were used as a reference to identify common practices for dental simulation. Thirty nine of 579 identified abstracts met the inclusion criteria. Skill acquisition and feedback were the two most frequently investigated parameters found in the review. CS was efficient in teaching cavity preparation and light curing skills. Feedback and deliberate practice were among the best practices that should be emphasized in order to enhance the efficiency of the CS and VR simulation exercises. The use of CS is effective in teaching operative skills (such as light curing and cavity preparation) reliably; whereas, the use of VR in undergraduate curricula is debatable. To achieve the maximum benefits of the simulation exercises, emphasis must be given to the timely feedback and deliberate practice approaches.

Assessment of a Novel Standardized Training System for Mandibular Contour Surgeries

Importance

Mandibular contour surgeries (MCS) involving reduction gonioplasty and genioplasty are rewarding for patients with square faces; however, the procedure has inherently difficult clinician learning curves and unpredictable skill acquisitions. To our knowledge, there has been no effective, validated training model that might improve training and surgical outcomes for MCS.

Objective

To establish and evaluate a standardized intraoral MCS training system.

Design, Setting, and Participants

Intraoral MCS training models were constructed by 3-dimensional (3D) skull models covered with elastic head cloths. From April 2016 to April 2018, 90 consecutive MCS patients (30 per group) and 15 craniofacial surgery fellow physicians (5 per group) were enrolled in the prospective observational study. They were randomly divided into intervention groups (A and B) and a control group (C). Intervention groups A and B completed 5 training sessions on the intraoral MCS training models before each clinical case. Group A performed both the model training sessions and clinical surgeries with surgical templates. Control group C had no extra training before clinical surgeries. All groups completed clinical surgery under supervision on 6 patients. The duration of follow-up was at least 3 months postoperatively.

Interventions

Intraoral MCS training models were provided to intervention groups (A and B) before clinical surgeries. Surgical templates were provided to intervention group A both in training sessions and clinical surgeries.

Main Outcomes and Measures

The completion time, surgical accuracy, learning curves, operating confidence, surgical skill, and outcome satisfaction of each procedure were recorded and analyzed with paired t test and 1-way analysis of variance test by blinded observers.

Results

All 90 patients (14 men, 76 women; mean [SD] age, 26 [5] years) were satisfied with their postoperative mandible contours. The intervention groups (A and B), especially the group with surgical templates (A) showed improvements in clinical surgery time (mean [SD], group A 147.2 [24.71] min; group B, 184.47 [16.28] min; group C, 219.3 [35.3] min; P = .001), surgical accuracy (mean [SD], group A, 0.68 [0.22] mm; group B, 1.22 [0.38] mm; group C, 1.88 [0.54] mm; P < .001), learning curves, and operators' confidence and surgical skill.

Conclusions and Relevance

The intraoral MCS training model was effective and practical. The optimal intraoral MCS training system included intraoral MCS training models and surgical templates. The system significantly decreased clinical surgery time, improved surgical accuracy, shortened the learning curve, boosted operators' confidence, and was associated with better acquisition of surgical skills.

Level of Evidence

NA.

Haptic, Physical, and Web-Based Simulators: Are They Underused in Maxillofacial Surgery Training?

PURPOSE

Surgical residencies have increasingly incorporated both digital and mannequin simulation into their training programs. The aim of our review was to identify all digital and mannequin maxillofacial simulators available for education and training, highlight their benefit, and critically assess the evidence in support of these educational resources.

MATERIALS AND METHODS

We performed a comprehensive literature review of all peer-reviewed publications of digital and mannequin simulators that met the inclusion criteria, defined as any simulator used in education or training. All simulators used in surgical planning were excluded. Before the query, it was hypothesized that most studies would be descriptive in nature and supported by low levels of evidence. Literature search strategies included the use of multiple combinations of key search terms, review of titles and abstracts, and precise identification of the use of the simulator described. All statistics were descriptive.

RESULTS

The primary search yielded 259 results, from which 22 total simulators published on from 2001 to 2016 were identified using the inclusion and exclusion criteria: 10 virtual reality haptic-based simulators, 6 physical model simulators, and 6 Web-based simulators used for a variety of procedures such as dental skills, instrument handling, orthognathic surgery (Le Fort I osteotomy, vertical ramus osteotomy, bilateral sagittal split ramus osteotomy), genioplasty, bone grafting, sinus surgery, cleft lip repair, orbital floor repair, and oral biopsy. Only 9 formalized studies were completed; these were classified as low-level evidence-based cohort studies (Levels IV and V). All other simulator reports were descriptive in nature. There were no studies with high levels of evidence completed (Level I to III).

CONCLUSIONS

The results of this review suggest that, although seemingly beneficial to the trainee in maxillofacial surgery, simulation in education in this field is an underused commodity because of the significant lack of scientific and validated study designs reported on in the literature thus far. The maxillofacial and simulation communities would benefit from studies on utility and efficacy with higher levels of evidence.

A review of haptic simulator for oral and maxillofacial surgery based on virtual reality

INTRODUCTION

Traditional medical training in oral and maxillofacial surgery (OMFS) may be limited by its low efficiency and high price due to the shortage of cadaver resources. With the combination of visual rendering and feedback force, surgery simulators become increasingly popular in hospitals and medical schools as an alternative to the traditional training.

AREAS COVERED

The major goal of this review is to provide a comprehensive reference source of current and future developments of haptic OMFS simulators based on virtual reality (VR) for relevant researchers.

EXPERT COMMENTARY

Visual rendering, haptic rendering, tissue deformation, and evaluation are key components of haptic surgery simulator based on VR. Compared with traditional medical training, virtual and tactical fusion of virtual environment in surgery simulator enables considerably vivid sensation, and the operators have more opportunities to practice surgical skills and receive objective evaluation as reference.

Haptic simulation framework for determining virtual dental occlusion

PURPOSE

The surgical treatment of many dentofacial deformities is often complex due to its three-dimensional nature. To determine the dental occlusion in the most stable position is essential for the success of the treatment. Computer-aided virtual planning on individualized patient-specific 3D model can help formulate the surgical plan and predict the surgical change. However, in current computer-aided planning systems, it is not possible to determine the dental occlusion of the digital models in the intuitive way during virtual surgical planning because of absence of haptic feedback. In this paper, a physically based haptic simulation framework is proposed, which can provide surgeons with the intuitive haptic feedback to determine the dental occlusion of the digital models in their most stable position.

METHODS

To provide the physically realistic force feedback when the dental models contact each other during the searching process, the contact model is proposed to describe the dynamic and collision properties of the dental models during the alignment. The simulated impulse/contact-based forces are integrated into the unified simulation framework.

RESULTS

A validation study has been conducted on fifteen sets of virtual dental models chosen at random and covering a wide range of the dental relationships found clinically. The dental occlusions obtained by an expert were employed as a benchmark to compare the virtual occlusion results. The mean translational and angular deviations of the virtual occlusion results from the benchmark were small.

CONCLUSIONS

The experimental results show the validity of our method. The simulated forces can provide valuable insights to determine the virtual dental occlusion. The findings of this work and the validation of proposed concept lead the way for full virtual surgical planning on patient-specific virtual models allowing fully customized treatment plans for the surgical correction of dentofacial deformities.

Accuracy of virtual surgical planning in two-jaw orthognathic surgery: comparison of planned and actual results

OBJECTIVE

This study aims to evaluate the accuracy of virtual surgical planning in two-jaw orthognathic surgery via quantitative comparison of preoperative planned and postoperative actual skull models.

STUDY DESIGN

Thirty consecutive patients who required two-jaw orthognathic surgery were included. A composite skull model was reconstructed by using Digital Imaging and Communications in Medicine (DICOM) data from spiral computed tomography (CT) and STL (stereolithography) data from surface scanning of the dental arch. LeFort I osteotomy of the maxilla and bilateral sagittal split ramus osteotomy (of the mandible were simulated by using Dolphin Imaging 11.7 Premium (Dolphin Imaging and Management Solutions, Chatsworth, CA). Genioplasty was performed, if indicated. The virtual plan was then transferred to the operation room by using three-dimensional (3-D)-printed surgical templates. Linear and angular differences between virtually simulated and postoperative skull models were evaluated.

RESULTS

The virtual surgical planning was successfully transferred to actual surgery with the help of 3-D-printed surgical templates. All patients were satisfied with the postoperative facial profile and occlusion. The overall mean linear difference was 0.81 mm (0.71 mm for the maxilla and 0.91 mm for the mandible); and the overall mean angular difference was 0.95 degrees.

CONCLUSIONS

Virtual surgical planning and 3-D-printed surgical templates facilitated the diagnosis, treatment planning, and accurate repositioning of bony segments in two-jaw orthognathic surgery.

A pilot study to assess the feasibility and accuracy of using haptic technology to occlude digital dental models

OBJECTIVES

The use of haptic technology as an adjunct to clinical teaching is well documented in medicine and dentistry. However its application in clinical patient care is less well documented. The aim of this pilot study was to determine the feasibility and accuracy of using a haptic device to determine the occlusion of virtual dental models.

METHODS

The non-occluded digital models of 20 pre-treatment individuals were chosen from the database of Faculty of Dentistry, The University of Hong Kong. Following minimal training with the haptic device (Geomagic(®) Touch™), the upper model was occluded with the lower model until a stable occlusion was achieved. Seven landmarks were placed on each of the corners of the original and haptically aligned upper model bases. The absolute distance between the landmarks was calculated. Intra- and inter-operator errors were assessed.

RESULTS

The absolute distance between the 7 landmarks for each original and corresponding haptically aligned model was 0.54 ± 0.40 mm in the x-direction (lateral), 0.73 ± 0.63 mm in the y-direction (anterior-posterior) and 0.55 ± 0.48 mm in the z-direction (inferior-superior).

CONCLUSION

Based on initial collision detection to prevent interpenetration of the upper and lower digital model surfaces, and contact form resistance during contact, it is possible to use a haptic device to occlude digital study models.

CLINICAL SIGNIFICANCE

The use of 3D digital study models is routine, but new problems arise, such as the lack of "touch" in a virtual environment. Occluding study models requires the sense of touch. For the first time, using haptic technology, it is possible to occlude digital study models in a virtual environment.

Clinical feasibility and efficacy of using virtual surgical planning in bimaxillary orthognathic surgery without intermediate splint

BACKGROUND

Computer-aided jaw surgery has been extensively studied recently. The purpose of this study was to determine the clinical feasibility of performing bimaxillary orthognathic surgery without intermediate splint using virtual surgical planning and rapid prototyping technology.

METHODS

Twelve consecutive patients who underwent bimaxillary orthognathic surgery were included. The presented treatment plan here mainly consists of 6 procedures: (1) data acquisition from computed tomography (CT) of the skull and laser scanning of the dentition; (2) reconstruction and fusion of a virtual skull model with accurate dentition; (3) virtual surgery simulation including osteotomy and movement and repositioning of bony segments; (4) final surgical splint fabrication (no intermediate splint) using computer-aided design and rapid prototyping technology; (5) transfer of the virtual surgical plan to the operating room; and (6) comparison of the actual surgical outcome to the virtual surgical plan.

RESULTS

All procedures of the treatment were successfully performed on all 12 patients. In quantification of differences between simulated and actual postoperative outcome, we found that the mean linear difference was less than 1.8 mm, and the mean angular difference was less than 2.5 degrees in all evaluated patients.

CONCLUSION

Results from this study suggested that it was feasible to perform bimaxillary orthognathic surgery without intermediate splint. Virtual surgical planning and the guiding splints facilitated the diagnosis, treatment planning, accurate osteotomy, and bony segments repositioning in orthognathic surgery.

Simulation and evaluation of a bone sawing procedure for orthognathic surgery based on an experimental force model

Bone sawing is widely used in orthognathic surgery to correct maxillary deformities. Successful execution of bone sawing requires a high level of dexterity and experience. A virtual reality (VR) surgical simulator can provide a safe, cost-effective, and repeatable training method. In this study, we developed a VR training simulator with haptic functions to simulate bone-sawing force, which was generated by the experimental force model. Ten human skulls were obtained in this study for the determination of surgical bone-sawing force. Using a 5-DOF machining center and a micro-reciprocating saw, bone specimens with different bone density were sawed at different feed rates (20, 40, and 60 mm/min) and spindle speeds (9800, 11,200 and 12,600 cycles per minute). The sawing forces were recorded with a piezoelectric dynamometer and a signal acquisition system. Linear correlation analysis of all experimental data indicates that there were significant positive linear correlations between bone-sawing force and bone density and tool feed rate and a moderate negative linear correlation with tool spindle rate. By performing multiple regression analysis, the prediction models for the bone-sawing procedure were determined. By employing Omega.6 as a haptic device, a medical simulator for the Lefort I osteotomy was developed based on an experimental force model. Comparison of the force-time curve acquired through experiments and the curve computed from the simulator indicate that the obtained forces based on the experimental force model and the acquired data had the same trend for the bone-sawing procedure of orthognathic surgery.

Towards a Virtual Reality Simulator for Orthognathic Basic Skils

Bone sawing skill demands a high level of dexterity from the surgeon that can be achieved only with a lot of training. Sawing is a basic skill required in many procedures, such as: osteotomy, ostectomy, amputation and arthroplasty surgery. Inefficient sawing can lead in orthognathic surgery to nerve lesion, bad split and non-union. Using virtual reality technology this complications can be reduced, by training the students on simulators until they assimilate the skill. This paper presents an early prototype for a bone sawing simulator in orthognathic surgery. A voxel-based mandible model obtained from a Computer Tomography is cut by removing the voxels that are inside the saw blade. The collision detection is based on hierarchical bounding volumes. The removal process is observed both visually and haptically.

Creating a virtual surgical atlas of craniofacial procedures: Part I. Three-dimensional digital models of craniofacial deformities

BACKGROUND

Three-dimensional digital animation can enable surgeons to create anatomically accurate, virtual models of normal and pathologic human anatomy. From these models, surgical procedures can be digitally performed, recorded, and distributed as a teaching tool or as a virtual surgical atlas. The idea of a virtual surgical atlas has recently become a part of contemporary surgical teaching. In the field of craniofacial surgery, no such educational tool exists. Presented is the first part of the creation of a virtual atlas of craniofacial surgical procedures: the three-dimensional digital modeling of pathologic deformities commonly treated by craniofacial surgeons.

METHODS

Three-dimensional craniofacial models were constructed using Maya 8.5. A skeletally "normal" craniofacial skeleton was first produced from a preexisting digital skull using Bolton tracings as a reference. The remaining soft-tissue elements were then added to create an anatomically complete three-dimensional face. The "normal" model was then deformed in Maya to produce specific craniofacial deformities using computed tomographic scans, cephalograms, and photographs as a reference. One of the craniofacial deformity models was created directly from computed tomographic data.

RESULTS

One model of the normal face and eight pathologic models of craniofacial deformities were created: microgenia, micrognathia, prognathia, temporomandibular joint ankylosis, maxillary hypoplasia, Crouzon syndrome with and without the need for cranial vault expansion, and bicoronal craniosynostosis.

CONCLUSIONS

For the first time, anatomically accurate three-dimensional digital models of craniofacial deformities have been created. The models are the first step in the creation of a virtual surgical atlas of craniofacial procedures.

Cost-Effectiveness Analysis for Computer-Aided Surgical Simulation in Complex Cranio-Maxillofacial Surgery

PURPOSE

The purpose of this study is to assess the costs and benefits of computer-aided surgical simulation (CASS) and to compare it with the current surgical planning methods for complex cranio-maxillofacial (CMF) surgery.

MATERIALS AND METHODS

The comparison of methods applies to all CMF surgeries where the patient's condition is severe enough to undergo a computed tomography scan and a stereolithographic model is necessary for the surgical planning process. The costs for each method can be divided into time and other costs. The time was estimated based on the authors' experience as well as on a survey of a small group of 6 experienced CMF surgeons in the United States. The other costs were estimated based on the authors' experience.

RESULTS

CASS has lower costs in terms of surgeon time, patient time, and material costs. Specifically, total surgeon hours spent in planning are 5.25 hours compared with 9.75 for current standard methods. Material and scanning costs are Dollars 1,900 for CASS compared with about Dollars 3,510 for standard methods. Patient time for planning is reduced from 4.75 hours to 2.25 hours with CASS. The reduction in both time and other costs remains when the fixed fee costs of CASS are added to the variable costs. Amortized across the 600 patients per year (1,800 for the assumed 3-year life of the training and software), this adds only a few dollars and a fraction of an hour per surgery. Even in the case of a small clinic when the cost is amortized for 6 patients per year (18 patients for the assumed 3-year life of the training and software), the per surgery costs (9.65 hours and Dollars 2,456) will still favor CASS.

CONCLUSION

Any great new design should consist of at least 2 of the 3 following features: faster, cheaper, and better outcome. This analysis demonstrates that CASS is faster and less costly than the current standard planning methods for complex CMF surgery. Previous studies have also shown that CASS results in better surgical outcomes. Thus, in all regards, CASS appears to be at least as good as the current methods of surgical planning.

Application of virtual reality force feedback haptic device for oral implant surgery

A novel support system for implant surgery was tried out, which involves manipulating a three-dimensional (3-D) computed tomography (CT) image of a jawbone with a virtual reality force feedback haptic device. Through this virtual system, the haptic experience of bone drilling with vibration and the sound of the contra-angle handpiece could be realized. It is expected to be useful for training inexperienced dentists and educating dental students. The simulation of oral implant insertion was also focused on. A simple cylindrical implant model was inserted into a 3-D image of the jawbone by operating the haptic device, with consideration of bone condition. A rectangular solid object that served as a bone-supported surgical template was adopted, and the shapes of the bone and the implant were subtracted from the object. In this manner, the CAD of the surgical template with impressions of the bone and the implant guide holes for insertion was realized. The surgical template was milled with a computer-controlled milling machine (CAM). Surgical template accuracy was examined with an edentulous gypsum bone model having six holes for implant insertion. Simulation of the oral implant insertion and CAD/CAM of the surgical template were conducted. The milled surgical template was fitted on the gypsum bone model, and CT images were taken. Cross-sections of the guide holes in the surgical template were imaged, and misalignment between the guide holes of the surgical template and the drilled holes on the jawbone was measured. The average misalignment is less than 0.2 mm, and it indicates that the present system is potentially applicable to oral implant surgery.

A novel method for the 3-dimensional simulation of orthognathic surgery by using a multimodal image-fusion technique

INTRODUCTION

The aim of this study was to establish a novel method for simulating orthognathic surgery in 3-dimensional (3D) space.

METHODS

This system mainly consists of 6 procedures: (1) reconstruction of a virtual skull model (VS) from presurgical computed tomography scans; (2) reconstruction of virtual dentition models from 3D surface scanning of dental casts occluded at presurgical and postsurgical intercuspal positions (VD1 and VD2, respectively); (3) reconstruction of a preliminary fusion model of VS and VD1 by an initial intermodality registration; (4) reconstruction of another preliminary fusion model of VS, VD1, and VD2 by a second intramodality registration; (5) repositioning of bony segments by a third intramodality registration and reconstruction of final fusion models at presurgery and postsurgery; and (6) 3D analysis of the movement of bony segments. To test this system, 2 patients with severe skeletal deformities, who had undergone presurgical orthodontic treatment, were used as models. Registration accuracy was determined by the root mean squared distance between the corresponding fiducial markers in a set of 2 images.

RESULTS AND CONCLUSIONS

The sum of the root mean squared error of the 3 registration processes was less than 0.4 mm in both patients. This simulation system could be used to precisely realize the presurgical and postsurgical occlusal relationships and craniofacial morphology of a patient with severe skeletal deformities, and to quantitatively describe the movement of a given anatomical point of bony segments. It is assumed that there could be significant benefits in sharing visual and quantitative 3D information from this simulation system among orthodontists and surgeons.

Biomodels of Bone: A Review

In this paper, a definition of a biomodel is presented, based on which different specific types of biomodels are identified, viz., virtual biomodels, computational biomodels, and physical biomodels. The paper then focuses on both physical and virtual biomodels of bone, and presents a review of model generation methodologies, giving examples of typical biomodel applications. The use of macroscale biomodels for such issues as the design and preclinical testing of surgical implants and preoperative planning is discussed. At the microscale, biomodels of trabecular bone are examined and the link with scaffolds for tissue engineering is established. Conclusions are drawn on the state of the art, and the major developments necessary for the continued expansion of the field are identified. Finally, arguments are given on the benefits of integrating the use of the different types of biomodels reviewed in this paper, for the benefit of future research in biomechanics and biomaterials.