Three-dimensional surgical simulation

Utilization of a 3D-Printed Mandibular Jaw for Ridge Reconstruction in Periodontics: A Case Report

Three-dimensional (3D) printing is an emerging manufacturing technology in dentistry with a range of applications. Digital dentistry presented in cone beam CT scan radiographs is a revolution that improved surgical outcomes by optimizing accurate diagnosis and analysis of the surgical sites before surgery. A periodontist can modify the treatment plan, surgical techniques, and incision design based on bone defects seen on cone beam CT scans. Block grafting has been a technique of choice when wound stability is required for guided bone regeneration. There was no significant difference between the different surgical procedures for reconstruction and choice should be given to the simpler and less invasive procedure. A xenograft or allograft block can work as an alternative to the autogenous bone block to reduce the surgery time and patient morbidity. Preparation and shaping of block graft during surgery time to match the defect shape can prolong the operative time, reduce the treatment success, and increase postoperative complications. In this case report, a sterilized 3D-printed mandibular jaw was utilized to visualize the defect size and shape. A bovine xenograft block was then prepared, shaped, and adapted on the 3D-printed jaw 30 minutes before the surgery. The block graft was then transferred and well-fitted on the surgical defect. Handling experience was greater and surgery time and postoperative pain were reduced.

Asymmetry in Class II subdivision malocclusion: Assessment based on 3D surface models

INTRODUCTION

There is currently no consensus in the literature whether the aetiology of a Class II subdivision is dental, skeletal or both. The aim of this study was to identify and quantify skeletal and dental asymmetries in Class II subdivision malocclusions.

METHODS

CBCTs from 33 Class II subdivision malocclusion patients were used to construct 3D volumetric label maps. Eighteen landmarks were identified. The original scan and associated 3D volumetric label map were mirrored. Registration of the original and mirrored images relative to the anterior cranial base, maxilla and mandible were performed. Surface models were generated, and 3D differences were quantified. Statistical analysis was performed.

RESULTS

Anterior cranial base registration showed significant differences for fossa vertical difference, fossa roll, mandibular yaw, mandibular lateral displacement and lower midline displacement. Regional registrations showed significant differences for antero-posterior (A-P) mandibular length, maxillary roll, A-P maxillary first molar position, maxillary first molar yaw and maxillary first molar roll. Class II subdivision patients also show an asymmetric mandibular length as well as an asymmetric gonial angle. Moderate correlations were found between the A-P molar relationship and fossa A-P difference, mandibular first molar A-P difference, maxillary first molar A-P difference and maxillary first molar yaw.

CONCLUSIONS

This study suggests that Class II subdivisions can result from both significant skeletal and dental factors. Skeletal factors include a shorter mandible as well as posterior and higher displacement of the fossa on the Class II side, resulting in mandibular yaw. Dental factors include maxillary and mandibular first molar antero-posterior asymmetry.

Simulation of Velopharyngeal Biomechanics Identifies Differences in Sphincter Pharyngoplasty Outcomes: A Matched Case-Control Study

The purpose of this study was to develop a framework for 3D subject-specific computational models capable of simulating velopharyngeal biomechanics for anatomic changes that occur following pharyngoplasty and to gain insight into biomechanical factors that may lead to different speech/surgical outcomes. Patient-specific models for two, matched participants with differing speech/surgical outcomes were developed: one with a successful pharyngoplasty outcome and one with a failed pharyngoplasty outcome. Surgical scenarios were simulated to model pharyngoplasty location, identify LVP muscle biomechanics, and identify an optimal pharyngoplasty location for each participant. These simulations illustrate the potential for optimizing pharyngoplasties based on patient-specific geometry.

Custom CAD/CAM Peek Implants for Complex Orbitocranial Reconstruction: Our Experience with 15 Patients

Bone defects within the cranio-orbital complex present unique challenges in terms of surgical planning and reconstruction. This article presents a novel approach using PEEK material and advanced surgical technologies to address these challenges. A retrospective analysis of 15 patients who underwent craniofacial reconstruction using patient-specific polyetheretherketone (PEEK) implants between 2016 and 2021 was carried out. Comprehensive preoperative planning was performed, utilizing advanced imaging techniques and specialized software for virtual surgical planning. Patient-specific PEEK PSIs were designed and manufactured based on the preoperative plan. Intraoperative navigation was used to guide the surgical procedure, enabling precise osteotomy and optimal implant placement. This article describes the step-by-step process and the tools utilized in each phase. The etiologies were as follows: meningioma in seven cases, benign lesions in five cases, malignant tumors in two cases, and trauma sequelae in one case. In all cases, 3D-printed PEEK implants were utilized to achieve precise reconstruction. No major complications were described. In one case, an implant replacement was needed with successful outcomes. Our study demonstrates the feasibility and effectiveness of using PEEK patient-specific implants for personalized craniofacial reconstruction. The combination of advanced imaging, virtual planning, and CAD-CAM technology contributes to improved surgical outcomes in terms of oncologic margin control, functional restoration, and aesthetic results.

Soft tissue prediction in orthognathic surgery: Improving accuracy by means of anatomical details

Three-dimensional virtual simulation of orthognathic surgery is now a well-established method in maxillo-facial surgery. The commercial software packages are still burdened by a consistent imprecision on soft tissue predictions. In this study, the authors produced an anatomically detailed patient specific numerical model for simulation of soft tissue changes in orthognathic surgery. Eight patients were prospectively enrolled. Each patient underwent CBCT and planar x-rays prior to surgery and in addition received an MRI scan. Postoperative soft-tissue change was simulated using Finite Element Modeling (FEM) relying on a patient-specific 3D models generated combining data from preoperative CBCT (hard tissue) scans and MRI scans (muscles and skin). An initial simulation was performed assuming that all the muscles and the other soft tissue had the same material properties (Homogeneous Model). This model was compared with the postoperative CBCT 3D simulation for validation purpose. Design of experiments (DoE) was used to assess the effect of the presence of the muscles considered and of their variation in stiffness. The effect of single muscles was evaluated in specific areas of the midface. The quantitative distance error between the homogeneous model and actual patient surfaces for the midface area was 0.55 mm, standard deviation 2.9 mm. In our experience, including muscles in the numerical simulation of orthognathic surgery, brought an improvement in the quality of the simulation obtained.

The untold history of planning in orthognathic surgery: a narrative review from the beginning to virtual surgical simulation

We aimed to produce a narrative review of planning orthognathic surgery, chronologically. Also, to present flaws of methods and the future of orthognathic surgery planning. The search was carried out mainly in PubMed, SCOPUS, Embase, and Cochrane databases. Also was complemented by manual search in reference lists from identified studies and in grey literature. The first orthognathic surgery was reported in 1849, and it took more than a century for the development of the traditional orthognathic 2D planning. Besides the advances, surgeons observed failures and lacks on 2D method in representing with reliability the facial and maxillary tridimensional structure (3D). With technological developments in 90s and 2000s, methodological improvements were granted, and the 3D protocol was created. The CASS and Charlotte protocols were the earliest 3D planning protocols conceived. Since then, some steps were simplified, and new technologies are being developed and added to create a more reliable and precise way of planning orthognathic surgery.

Integrating mechanism-based modeling with biomedical imaging to build practical digital twins for clinical oncology

Digital twins employ mathematical and computational models to virtually represent a physical object (e.g., planes and human organs), predict the behavior of the object, and enable decision-making to optimize the future behavior of the object. While digital twins have been widely used in engineering for decades, their applications to oncology are only just emerging. Due to advances in experimental techniques quantitatively characterizing cancer, as well as advances in the mathematical and computational sciences, the notion of building and applying digital twins to understand tumor dynamics and personalize the care of cancer patients has been increasingly appreciated. In this review, we present the opportunities and challenges of applying digital twins in clinical oncology, with a particular focus on integrating medical imaging with mechanism-based, tissue-scale mathematical modeling. Specifically, we first introduce the general digital twin framework and then illustrate existing applications of image-guided digital twins in healthcare. Next, we detail both the imaging and modeling techniques that provide practical opportunities to build patient-specific digital twins for oncology. We then describe the current challenges and limitations in developing image-guided, mechanism-based digital twins for oncology along with potential solutions. We conclude by outlining five fundamental questions that can serve as a roadmap when designing and building a practical digital twin for oncology and attempt to provide answers for a specific application to brain cancer. We hope that this contribution provides motivation for the imaging science, oncology, and computational communities to develop practical digital twin technologies to improve the care of patients battling cancer.

Accuracy of 3 Soft Tissue Prediction Methods After Double-Jaw Orthognathic Surgery in Class III Patients

PURPOSE

We aimed to evaluate the accuracy and validity of conventional manual prediction method (CM) and 2-dimensional and 3-dimensional (3D) soft tissue prediction methods for Class III bimaxillary orthognathic surgery patients.

METHODS

Twenty skeletal Class III patients were included in this study. Soft tissue prediction was achieved with a traditional manual technique, 2-dimensional software (Dolphin Imaging, version 11.5), and 3-dimensional software (SimPlant Master, version 16.0) on preoperative lateral cephalometric radiographs and cone beam computurized tomography (CBCT) images and then compared with postoperative lateral cephalometric radiographs obtained at least 6 months after surgery (mean, 11.5 ± 6.77 months). Forty-eight measurements were done to determine the reliability of the methods.

RESULTS

All prediction methods have limited postsurgery prediction accuracy for the subnasal upper lip area. Most of the differences were not more than 3 mm for all study groups, except the 3D software, which predicted the upper lip area to be, on average, 3.08 ± 1.38 mm further back (P < 0.001). Although the conventional method predicted 20 of 48 measurements similar to the final results, the poorest predictions were found at the nasal and labiomental areas (P < 0.001). Two-dimensional software predicted 23 of 48 measurements very close to the final results but made significantly different predictions for the nasolabial and labiomental angles, labrale superius point, and the chin area.

CONCLUSIONS

The 3D method predicted, especially the upper lip area, to be significantly and clinically incorrect, and its soft tissue prediction was insufficient compared with the other 2 methods. The 3D software needs to be updated, especially in evaluating soft tissue A point and upper lip changes after surgery.

Soft-Tissue Simulation for Computational Planning of Orthognathic Surgery

Simulation technologies offer interesting opportunities for computer planning of orthognathic surgery. However, the methods used to date require tedious set up of simulation meshes based on patient imaging data, and they rely on complex simulation models that require long computations. In this work, we propose a modeling and simulation methodology that addresses model set up and runtime simulation in a holistic manner. We pay special attention to modeling the coupling of rigid-bone and soft-tissue components of the facial model, such that the resulting model is computationally simple yet accurate. The proposed simulation methodology has been evaluated on a cohort of 10 patients of orthognathic surgery, comparing quantitatively simulation results to post-operative scans. The results suggest that the proposed simulation methods admit the use of coarse simulation meshes, with planning computation times of less than 10 seconds in most cases, and with clinically viable accuracy.

3D-Guided Face Manipulation of 2D Images for the Prediction of Post-Operative Outcome After Cranio-Maxillofacial Surgery

Cranio-maxillofacial surgery often alters the aesthetics of the face which can be a heavy burden for patients to decide whether or not to undergo surgery. Today, physicians can predict the post-operative face using surgery planning tools to support the patient's decision-making. While these planning tools allow a simulation of the post-operative face, the facial texture must usually be captured by another 3D texture scan and subsequently mapped on the simulated face. This approach often results in face predictions that do not appear realistic or lively looking and are therefore ill-suited to guide the patient's decision-making. Instead, we propose a method using a generative adversarial network to modify a facial image according to a 3D soft-tissue estimation of the post-operative face. To circumvent the lack of available data pairs between pre- and post-operative measurements we propose a semi-supervised training strategy using cycle losses that only requires paired open-source data of images and 3D surfaces of the face's shape. After training on "in-the-wild" images we show that our model can realistically manipulate local regions of a face in a 2D image based on a modified 3D shape. We then test our model on four clinical examples where we predict the post-operative face according to a 3D soft-tissue prediction of surgery outcome, which was simulated by a surgery planning tool. As a result, we aim to demonstrate the potential of our approach to predict realistic post-operative images of faces without the need of paired clinical data, physical models, or 3D texture scans.

Reliability of cephalometric landmark identification on three-dimensional computed tomographic images

Our aims were to evaluate the reliability of three-dimensional (3D) cephalometric landmark identification in 3D images, and to propose an improved protocol for determining these landmarks. Computed tomographic (CT) images of 13 landmarks were obtained. One that did not show any artifacts, asymmetry in maxillofacial structures, or bony defects, was selected. Two orthodontic practitioners identified 3D cephalometric landmarks 10 times at one-week intervals. The distances of 26 landmarks were measured on the basis of three reference planes (coronal, horizontal, and sagittal). Ten mean (SD) measurements from each examiner were calculated, and the maximum and minimum values and the difference from the 10 measurements of each one were measured at a 95% confidence interval. Interexaminer differences for the three planes were found in the upper right first molar, point A, both gonions, left orbitale, and both porions. The lower right first molar, foramen magnum, gnathion, nasion, and pogonion showed interexaminer differences in two planes. Menton, basion, posterior nasal spine, upper and lower left first molar, and right mental foramen showed interexaminer differences in only one plane. With reference to intraexaminer differences, poor repeatability was observed for gonion, orbitale, condylion, and porion. Reliable 3D landmarks are the meeting point of sutures, distinct structures at converging planes, landmarks positioned in the midline, distinct anatomical structures such as the mental foramen, and teeth using multiplanar views.

Correction of Severe Facial Asymmetry in Patients With Unilateral Craniofacial Microsomia Using Computer-Aided Design/Computer-Aided Manufacturing Technology: An Evaluation of Postsurgical Results

ABSTRACT

This is a retrospective study to evaluate the postsurgical position of the maxilla and mandible in 5 matured craniofacial patients with unilateral craniofacial microsomia who underwent 2 jaw surgical procedures using computerized surgical planning. The craniofacial surgeon and orthodontist completed the virtual surgical treatment plan with a biomedical engineer's assistance via a web meeting. The treatment plan of each patient included 2 jaw surgery with genioplasty. At the maxillary dental midline, the planned mean advancement was 4 mm; yaw, a rotational correction towards the unaffected side was 4.96 mm; and impaction was 2.74 mm. The mean advancement measured at point B was 10.5 mm, and the rotational correction towards the unaffected side was 6.58 mm. The mean advancement following genioplasty was 8.43 mm, and the mean transverse correction was 6.33 mm towards the midsagittal plane. The intermediate surgical splint, final surgical splint, bone graft templates, and cutting guides were constructed utilizing computer-aided design/computer-aided manufacturing technology. The surgeon executed the treatment plan in the operating room using appropriate computer-generated guides and splints. A postsurgical cone-beam computed tomography scan was obtained and superimposed on the surgical treatment plan using Simplant OMS 10.1 software. The cranial base was used as a reference for superimposition. Three-dimensional color-coded displacement maps were generated to visually and quantitatively assess the surgical outcome. There was a mean error of 0.88 mm (+0.30) for the position of the maxillary anatomical structures from the planned position, and the anterior mandibular anatomical structures were on average 0.96 mm (+0.26) from the planned position.

Total Face Approach (TFA) 3D Cephalometry and Superimposition in Orthognathic Surgery: Evaluation of the Vertical Dimensions in a Consecutive Series

Background: Cephalometry is fundamental in diagnosis, analysis, and planning of orthodontic-surgical treatment as it reveals skeletal relationship between the upper and lower jaw as well as facial aesthetic parameters. Nevertheless, 3D cephalometry has still not become the exam of choice in orthognathic treatment even though today CBCT (Cone Beam Computed Tomography) is routinely used in other branches of dentistry. Methods: In a sample of 13 patients undergoing bimaxillary orthognathic surgery a chin-vertex CBCT exam was prescribed prior to orthodontic treatment (OT) and 12 months after surgery (T1). The DICOM files uploaded to MaterialiseSimplant Ortho software pro 2.1 (Materialise Co., Leuven, Belgium) were analyzed following the multiplane 3D Total Face cephalometry protocol (TFA). Results: Results comparing pre-op and post-op TFA 3D cephalometry, were then evaluated considering reference values reported in literature. The CBCT, carried out pre- and post-surgery, were subsequently analyzed employing the superimposition method using cranial base as reference. The aim of this study is to evaluate the advantages and disadvantages of the two methods in orthognathic surgery. Conclusions: Multiplane 3D TFA allows the clinician to locate where major or minor skeletal discrepancies are found with respect to ideal parameters and is also useful in classifying skeletal intermaxillary relation. The superimposition method is highly intuitive but does not provide information on the quantity and location of osteotomic movement.

Effectiveness Assessment of CAD Simulation in Complex Orthopedic Surgery Practices

This experimental study defines the usage of a computer-aided surgical simulation process that is effective, safe, user-friendly, and low-cost, that achieves a detailed and realistic representation of the anatomical region of interest. The chosen tools for this purpose are state-of-the-art Computer Aided Design (CAD) software for mechanical design, and are the fundamental application dedicated to parametric modeling. These tools support different work environments, each one is for a specific type of modeling, and they allow the simulation of surgery. The result will be a faithful representation of the anatomical part both before and after the surgical procedure, screening all the intermediate phases. The doctor will assess different lines of action according to the results, then he will communicate them to the engineer who, consequently, will correct the antisymmetric issue and regenerate the model. Exact measurements of the mutual positions of the various components, skeletal and synthetic, can be achieved; all the osteosynthesis tools, necessary for the surgeon, can be included in the project according to different types of fracture to perfectly match the morphology of the bone to be treated. The method has been tested on seven clinical cases of different complexity and nature and the results of the simulations have been found to be of great effectiveness in the phase of diagnosis and of preoperative planning for the doctors and surgeons; therefore, allowing a lower risk medical operation with a better outcome. This work delivers experimental results in line with theoretical research findings in detail; moreover, full experimental and/or methodical details are provided, so that outcomes could be obtained.

Clinical Accuracy of 3D-Planned Maxillary Positioning Using CAD/CAM-Generated Splints in Combination With Temporary Mandibular Fixation in Bimaxillary Orthognathic Surgery

Study Design

The aim of this study was to evaluate the accuracy of 3-dimensional (3D)-planned maxillary positioning by using computer-assisted design (CAD)/computer-assisted manufacturing (CAM) splints combined with temporary mandibular fixation in bimaxillary orthognathic surgery. In orthognathic surgery, customized splints work sufficiently well to transfer preoperative planning into the operation site for transverse und sagittal positioning of the maxilla. The vertical positioning is more difficult due to the non-fixed mandibular reference. Therefore, the combined use of CAD/CAM splints and temporary mandibular fixation to the zygomatic region was applied for transferring the 3D-planned maxillary position into the operation site from 2012 until 2015 in our hospital.

Objective

In addition to the general accuracy, the precision should therefore be checked especially in the vertical plane compared to axial and sagittal plane.

Methods

In this retrospective study, we calculated the deviation of 5 occlusal landmarks of the maxilla in 35 consecutive patients by fusing preoperative 3D planning images and postoperative computed tomography scans after bimaxillary surgery.

Results

The overall median deviation of maxillary positioning between plan and surgical result was 0.99 mm. The accuracy of left-right positioning was median 0.96 mm. Anterior-posterior positioning of the maxilla showed a median accuracy of 0.94 mm. Just slightly higher values were determined for the upward-downward positioning (median 1.06 mm).

Conclusions

This demonstrates the predictability of maxillary positioning by using CAD/CAM splints in combination with temporary mandibular fixation in all 3 axes.

Application of Finite Element Analysis in Oral and Maxillofacial Surgery-A Literature Review

In recent years in the field of biomechanics, the intensive development of various experimental methods has been observed. The implementation of virtual studies that for a long time have been successfully used in technical sciences also represents a new trend in dental engineering. Among these methods, finite element analysis (FEA) deserves special attention. FEA is a method used to analyze stresses and strains in complex mechanical systems. It enables the mathematical conversion and analysis of mechanical properties of a geometric object. Since the mechanical properties of the human skeleton cannot be examined in vivo, a discipline in which FEA has found particular application is oral and maxillofacial surgery. In this review we summarize the application of FEA in particular oral and maxillofacial fields such as traumatology, orthognathic surgery, reconstructive surgery and implantology presented in the current literature. Based on the available literature, we discuss the methodology and results of research where FEA has been used to understand the pathomechanism of fractures, identify optimal osteosynthesis methods, plan reconstructive operations and design intraosseous implants or osteosynthesis elements. As well as indicating the benefits of FEA in mechanical parameter analysis, we also point out the assumptions and simplifications that are commonly used. The understanding of FEA's opportunities and advantages as well as its limitations and main flaws is crucial to fully exploit its potential.

Current status of surgery-first approach (part III): the use of 3D technology and the implication in obstructive sleep apnea

Considering psychosocial needs of patients, it is not surprising that surgery-first approach (SFA) is becoming more popular than ever. Although the concept of SFA was introduced a few decades ago, the limitation of analysis method based on two-dimensional images makes surgeons reluctant to choose SFA. Recently, the advancement of three-dimensional technology allows us to perform SFA even without minimal pre-surgical orthodontic treatment, and the prediction of surgical outcome became more accurate, especially in obstructive sleep apnea (OSA) patients to whom the advantages of SFA should be more significant. Here, we describe the current trend of SFA and its implication in OSA patients.

Comparison of the efficacy and characteristics of metallic foreign body extraction by incision surgery and x-ray guided forceps after body-surface projection positioning: A STROBE-compliant article

A foreign body retained in soft tissue may give rise to infection and dysfunction, which may pose a potential threat to patient health. Our study is to compare the efficacy and characteristics of metallic foreign body (MFB) extraction from soft tissue by incision surgery and x-ray-guided forceps after body surface projection positioning.This study enrolled 775 patients who underwent percutaneous MFB extraction between January 2011 and December 2016. A total of 257 cases underwent extraction by incision surgery and 518 cases underwent x-ray-guided forceps extraction after body surface projection positioning.All patients were diagnosed by x-ray and the diagnostic accuracy rate was 100%. In the incision surgery group, MFB extraction was successful in 193 of 257 cases. All cases in the forceps extraction group were successful, and the success rate was significantly higher than that of the incision surgery group (100% vs.75.1%, P < .01). Sixty-four patients in the incision surgery group who failed treatment were subsequently treated with x-ray-guided forceps extraction and all MFBs were extracted. The symptoms in all patients were relieved, wound healing was good, and there were no major bleeding, incision infection, or other complications.Compared with incision surgery, x-ray-guided foreign body forceps extraction after body surface projection positioning is a less invasive, safer, and more effective treatment for MFB extraction.

A review of translational medicine. The future paradigm: how can we connect the orthopedic dots better?

INTRODUCTION

Patients with complex medical and surgical problems often travel great distances to prestigious university medical centers in search of solutions and in some cases for nothing more than a diagnosis of their condition. Translational medicine (TM) is an emerging method and process of facilitating medical advances efficiently from the scientist to the clinician. Most established clinicians and those in training know very little about this new discipline. The purpose of this article is to illustrate TM in varied scientific, medical and surgical fields.

MATERIALS AND METHODS

Anecdotal events in medicine and orthopaedics based upon a practicing orthopaedic surgeon's training and clinical experience are presented.

RESULTS

TM is rapidly assuming a greater presence in the medical community. The National Institute of Health (NIH) recognizes this discipline and has funded TM projects. Numerous institutions in Europe and the USA offer advanced degrees in TM. Finally there is a European Society for Translational Medicine (EUTMS), an International Society for Translational Medicine, and an Academy of Translational Medical Professionals (ATMP).

DISCUSSION

The examples of TM presented in this article support the argument for the formation of more TM networks on the local and regional levels. The need for increased participation of researchers and clinicians requires further study to identify the economic and social impact of TM.

CONCLUSIONS

The examples of TM presented in this article support the argument for the formation of more TM networks on the local and regional levels. Financial constraints for TM can be overcome by pooling government, academic, private, and industry resources in an organized fashion with oversight by a lead TM researcher.

Three-dimensional evaluation of the posterior airway space: differences in computed tomography and cone beam computed tomography

OBJECTIVES

Obstructive sleep apnea syndrome (OSAS) becomes increasingly important. For diagnosis and surgery, computed tomography (CT), and cone beam computed tomography (CB-CT) are used equally, although in most of cases, patient positioning differs between supine positioning (CT) and upright seating positioning (CB-CT). We measured volumetric and anatomical changes in the posterior airway space (PAS) between upright and supine positioning in a three-dimensional set up.

MATERIALS AND METHODS

Coherent CT and CB-CT scans of 55 patients were included in the study. Using Brainlab ENT 3.0, image data was superimposed, and three-dimensional models were segmented. PAS height, cross-sectional area, vertical and horizontal position of the mandible and hyoid, and volumetric analyses of the three-dimensional models were measured.

RESULTS

PAS height and cross-sectional area were significantly higher in CB-CT compared to CT scans (p < 0.001). In the vertical dimension, the mandible and hyoid were localized more caudally in CB-CT in contrast to CT scans (p < 0.04; p < 0.001). Three-dimensional evaluation showed a greater volume of the PAS in CB-CT (p < 0.0001). Pearson correlation coefficient showed a correlation between vertical positioning of the mandible and hyoid compared to the positioning of the patient.

CONCLUSIONS

Patient positioning during CT and CB-CT has an effect on the location of anatomical structures like the mandible and hyoid and changes the dimensions and volume of the posterior airway space significantly.

CLINICAL RELEVANCE

The radiological technique used and the positioning of the patient should be taken into account when considering further surgical therapy.

Concepts, protocol, variations and current trends in surgery first orthognathic approach: a literature review

In the current era of expedited orthodontics, among many clinicians, tertiary care hospitals and patients, surgery first orthognathic approach (SFOA) has gained popularity. The advantages of SFOA (face first approach) are the reduced overall treatment duration and the early improvement in facial esthetics. In SFOA, the absence of a presurgical phase allows surgery to be performed first, followed by comprehensive orthodontic treatment to achieve the desired occlusion. The basic concepts of surgery early, surgery last, SFOA and Sendai SFOA technique along with its variations are reviewed in the present article. The recent advancement in SFOA in the context of preoperative preparation, surgical procedures and post-surgical orthodontics with pertinent literature survey are also discussed.

Removing a metal foreign object successfully from a patient's retroperitoneal space using laparoscopy and a novel navigation system

Trauma with foreign objects retained within the human body has become a common surgical emergency condition. Traditional surgical methods often involve creating large incisions in soft tissue and may lead to additional complications during wound healing. We have developed a new method of removing foreign bodies from patients' abdomens by using laparoscopy with the help of a novel navigation system that provides accurate positioning. This approach is minimally invasive and simple. This is the first combination of both technologies in this field.

Accuracy of orthognathic surgery using 3D computer-assisted surgical simulation

Objective

To evaluate the accuracy of maxilla and mandibular repositioning during two-jaw orthognathic surgery using computerassisted surgical simulation (CASS)

Materials and methods

Fifteen patients who underwent two-jaw orthognathic surgery using CASS (VSP,® Orthognathics by 3D Systems) were evaluated to assess the accuracy of the simulation. Translational and rotational discrepancies of the centroids of the maxilla and mandible and the translational discrepancy of the dental midline between the planned and actual outcomes were reported using the root mean square error (RMSE). The number of cases that exceeded limits set for clinical significance, the direction of the error in relation to the direction of planned movement and the differences between segmental and non-segmental procedures were evaluated as secondary outcomes

Results

The largest translational RMSE was 1.53 mm along the y-axis in the maxilla and 1.34 mm along the y-axis in the mandible. The largest rotational RMSE was 1.9° about the x-axis in the maxilla and 1.16° about the x- and y-axes in the mandible. The largest RMSE for the dental midline was 1.6 mm along the y-axis in the maxilla and 1.34 mm along the y-axis in the mandible. A tendency for insufficient advancement of the maxilla was noted

Conclusions

CASS is an efficient and accurate way to develop the surgical plan and transfer the plan to the patient intraoperatively. While CASS is accurate on a population level, there remains the potential for clinically significant errors to occur on an individual basis

Conclusion

The present case indicated that the timely extraction of palatally-placed maxillary lateral incisors facilitated functional appliance therapy in the management of a skeletal Class II problem. The crowding of the lower anterior teeth was relieved and alignment of the upper arch was achieved with full fixed appliance therapy, resulting in improved aesthetics and a stable occlusion at one year review

Accuracy of 3-Dimensional Virtual Surgical Simulation Combined With Digital Teeth Alignment: A Pilot Study

PURPOSE

To evaluate the accuracy of virtual surgical simulation combined with digital teeth alignment and the applicability of this technique to the diagnosis and establishment of a 3-dimensional (3D) visualized treatment objective for orthognathic surgery by comparing virtual simulation images with actual post-treatment images.

MATERIALS AND METHODS

This retrospective study included patients who underwent computed tomography (CT) before and after treatment. The 3D digital images were constructed from the initial CT images and dental cast scan data, and virtual surgical simulation combined with digital teeth alignment was performed. Accuracy of the virtual simulation was analyzed by comparing the distances of skeletal and dental landmarks in the horizontal, sagittal, and coronal reference planes with those on post-treatment images using the Wilcoxon signed rank test. Intraclass correlation coefficients were calculated to evaluate the degree of concordance between the 2 images.

RESULTS

The study sample included 11 patients (mean age, 18.8 yr). Most landmarks had differences smaller than 2 mm in the 3 reference planes between virtual simulation and post-treatment images; these differences were not statistically significant (P > .05). Most skeletal landmarks, except the A point, B point, and gonion, showed normal to high concordance between the virtual simulation and post-treatment images in the 3 reference planes (P < .05); dental landmarks exhibited a broad range of concordance.

CONCLUSION

The 3D virtual surgical simulation combined with digital teeth alignment using pretreatment CT images yielded results sufficiently accurate to be used for the diagnosis and establishment of visualized treatment objectives for orthognathic surgery.

Improved Virtual Planning for Bimaxillary Orthognathic Surgery

Conventional model surgery planning for bimaxillary orthognathic surgery can be laborious, time-consuming and may contain potential errors; hence three-dimensional (3D) virtual orthognathic planning has been proven to be an efficient, reliable, and cost-effective alternative. In this report, the 3D planning is described for a patient presenting with a Class III incisor relationship on a Skeletal III base with pan facial asymmetry complicated by reverse overjet and anterior open bite. A combined scan data of direct cone beam computer tomography and indirect dental scan were used in the planning. Additionally, a new method of establishing optimum intercuspation by scanning dental casts in final occlusion and positioning it to the composite-scans model was shown. Furthermore, conventional model surgery planning was carried out following in-house protocol. Intermediate and final intermaxillary splints were produced following the conventional method and 3D printing. Three-dimensional planning showed great accuracy and treatment outcome and reduced laboratory time in comparison with the conventional method. Establishing the final dental occlusion on casts and integrating it in final 3D planning enabled us to achieve the best possible intercuspation.

Soft Tissue Changes Measured With Three-Dimensional Software Provides New Insights for Surgical Predictions

PURPOSE

Although computer-aided craniofacial reconstructions allow for simulation of hard tissue changes, the prediction of the final soft tissue facial changes remains a challenge. The purpose of the present study was to evaluate the 3-dimensional (3D) soft tissue changes in patients undergoing 2-jaw orthognathic surgery.

PATIENTS AND METHODS

For the present retrospective cohort study, 40 consecutive patients (11 men and 29 women; mean age 23.5 ± 4.9 years) who had undergone 2-jaw orthognathic surgery were selected. We obtained the medical and dental records from 3 weeks before surgery and 6 months after surgery. We used image processing software to segment, superimpose, and quantify the hard and soft tissue displacements in 3 dimensions before and after surgery at 15 paired locations. The soft tissue and hard tissue changes were determined through quantification of homologous landmark displacements between the preoperative and postoperative computed tomography data. We measured the 3D soft and hard tissue changes and the anteroposterior, inferosuperior, and transverse components of the changes. We quantified the ratios between the soft and hard tissue changes, tested Pearson's correlation between these changes, and developed a predictive regression equation for the observations at each location.

RESULTS

We found that soft tissue movement followed the hard tissue movement, with a correlation nearly equal to 0.9 (range 0.85 to 0.98), suggesting that in general the soft tissues of the maxillary and mandibular landmarks are affected similarly by the skeletal movements. The anteroposterior component of the soft tissue 3D displacements followed the hard tissue movement with a ratio greater than 0.9 and with high correlation (r > 0.9) in the mandible.

CONCLUSION

The results of the present study provide surgeons with a ratio of hard to soft tissue change and the strength of the correlations, which will allow for more accurate 3D predictions for both midline and lateral structures in bimaxillary orthognathic surgical cases. In addition, predictive equations for various landmarks were developed and can be used in computer-based prediction programs to aid in treatment planning of soft tissue changes.

3D segmentation of intervertebral discs: from concept to the fabrication of patient-specific scaffolds

Aim: To develop a methodology for producing patient-specific scaffolds that mimic the annulus fibrosus (AF) of the human intervertebral disc by means of combining MRI and 3D bioprinting. Methods: In order to obtain the AF 3D model from patient's volumetric MRI dataset, the RheumaSCORE segmentation software was used. Polycaprolactone scaffolds with three different internal architectures were fabricated by 3D bioprinting, and characterized by microcomputed tomography. Results: The demonstrated methodology of a geometry reconstruction pipeline enabled us to successfully obtain an accurate AF model and 3D print patient-specific scaffolds with different internal architectures. Conclusion: The results guide us toward patient-specific intervertebral disc tissue engineering as demonstrated by a way of manufacturing personalized scaffolds using patient's MRI data.

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.

A novel navigation system to guide metallic foreign body extraction

PURPOSE

Metallic foreign bodies (MFBs) retained in soft tissue may pose potential threats to patient health. Interventional procedures using conventional navigation systems are associated with high rate of radiation exposure. We postulated that the surgical approach visualization and navigation system would offer precise percutaneous localization and linear guidance with reduced radiation dosage and system complexity.

METHODS

In total, 76 patients underwent percutaneous MFB extraction with the technique, which consists of: (A) displaying the target spot (here the MFB) on the screen; (B) projecting the laser beam onto the skin surface; (C) indicating the optimal direction and angle of the needle; and (D) guiding the surgical approach until the MFB was extracted.

RESULTS

A total of 76 MFBs were successfully extracted with a single operation. No systemic complications were observed. The procedure took between 2 and 11 min, with an average of [Formula: see text] min, demonstrating the characteristics of a normal distribution. The mean size of wound was [Formula: see text] mm. The mean amount of bleeding was [Formula: see text] ml. The number of times the intra-operative fluoroscopy was used ranged from one to four times for a single procedure, with an average of 1.89 ± 0.74.

CONCLUSION

The proposed navigation system which combines the laser positioning and navigation techniques seems to be a novel surgical approach of high accuracy and efficiency.

Soft tissue coverage on the segmentation accuracy of the 3D surface-rendered model from cone-beam CT

OBJECTIVES

The aim of this study is to investigate the effect of soft tissue presence on the segmentation accuracy of the 3D hard tissue models from cone-beam computed tomography (CBCT).

MATERIALS AND METHODS

Seven pairs of CBCT Digital Imaging and Communication in Medicine (DICOM) datasets, containing data of human cadaver heads and their respective dry skulls, were used. The effect of the soft tissue presence on the accuracy of the segmented models was evaluated by performing linear and angular measurements and by superimposition and color mapping of the surface discrepancies after splitting the mandible and maxillo-facial complex in the midsagittal plane.

RESULTS

The linear and angular measurements showed significant differences for the more posterior transversal measurements on the mandible (p < 0.01). By splitting and superimposing the maxillo-facial complex, the mean root-mean-square error (RMSE) as a measurement of inaccuracy decreased insignificantly from 0.936 to 0.922 mm (p > 0.05). The RMSE value for the mandible, however, significantly decreased from 1.240 to 0.981 mm after splitting (p < 0.01).

CONCLUSIONS

The soft tissue presence seems to affect the accuracy of the 3D hard tissue model obtained from a cone-beam CT, below a generally accepted level of clinical significance of 1 mm. However, this level of accuracy may not meet the requirement for applications where high precision is paramount.

CLINICAL RELEVANCE

Accuracy of CBCT-based 3D surface-rendered models, especially of the hard tissues, are crucial in several dental and medical applications, such as implant planning and virtual surgical planning on patients undergoing orthognathic and navigational surgeries. When used in applications where high precision is paramount, the effect of soft tissue presence should be taken into consideration during the segmentation process.

Three-dimensional regional displacement after surgical-orthodontic correction of Class III malocclusion

OBJECTIVES

To investigate how displacements of maxillo-mandibular structures are associated with each other at splint removal and 1 year post-surgery following 1-jaw and 2-jaw surgeries for correction of Class III malocclusion.

SETTING AND SAMPLE POPULATION

Fifty patients who underwent surgical correction with maxillary advancement only (n = 25) or combined with mandibular setback (n = 25) were prospectively enrolled in this study.

METHODS

Cone-beam computed tomographies were taken pre-surgery, at splint removal and at 1 year post-surgery. Three-dimensional cranial base superimpositions and shape correspondence were used to measure the outcomes from pre-surgery to splint removal (surgical changes) and splint removal to 1 year post-surgery (post-surgical adaptations). Pearson's correlation coefficients were used to evaluate the association between the regional displacements.

RESULTS

Both surgery groups presented mandibular clockwise rotation with surgery and post-surgical adaptive counterclockwise rotation. In patients treated with maxillary advancement only, the surgical changes of the maxilla were significantly correlated with chin changes. The amount and direction of chin autorotation were significantly correlated with right and left ramus autorotation. Right and left condylar displacements were significantly correlated. One year post-surgery, adaptive displacements and bone remodeling of both rami were correlated with the chin and condylar changes. For the 2-jaw group, the few correlations between the positional and remodeling changes in the anatomic regions of interest observed due to the surgery were different than those observed after post-surgical adaptations, suggesting that these changes occurred independently.

CONCLUSION

Our results indicate that surgical displacements and post-surgical adaptations are often correlated in one-jaw surgery and are, in general, independent in two-jaw surgery.

Accurate movement of jaw segment in virtual 3D orthognathic surgery

In traditional virtual 3D orthognathic surgery, after repositioning the maxillary segment to the desired position, surgeons usually roughly rotate or adjust the mandibular segment to obtain a relatively good relationship with maxillary dentition to calculate the virtual terminal occlusion splint. However, surgeons are not easy to avoid penetrability, overlap, or an overly large space existing between the maxillary and mandibular dentitions during this process. The present report offered a new method to obtain a suitable virtual terminal occlusal splint that could avoid penetrability, overlap, or an overly large space between the maxillary and mandibular dentitions, and simultaneously accurately moving the maxillary or mandibular segment to the desired position utilizing the planned terminal occlusion plaster models in virtual orthognathic surgery. For double jaw surgery, after aligning the planned plaster models to the 3D maxilla and mandible, we could simultaneously move the maxillary and mandibular segment as a whole that maintain the planned terminal occlusion to the desired position. This present method may enhance the accuracy of 3D virtual orthognathic surgery and save plenty of time spend on virtual surgery simulation, which also offers a useful educational method for training junior surgeons and students.

3D dento-maxillary osteolytic lesion and active contour segmentation pilot study in CBCT: semi-automatic vs manual methods

OBJECTIVES

This study was designed to evaluate the reliability of a semi-automatic segmentation tool for dento-maxillary osteolytic image analysis compared with manually defined segmentation in CBCT scans.

METHODS

Five CBCT scans were selected from patients for whom periapical radiolucency images were available. All images were obtained using a ProMax® 3D Mid Planmeca (Planmeca Oy, Helsinki, Finland) and were acquired with 200-μm voxel size. Two clinicians performed the manual segmentations. Four operators applied three different semi-automatic procedures. The volumes of the lesions were measured. An analysis of dispersion was made for each procedure and each case. An ANOVA was used to evaluate the operator effect. Non-paired t-tests were used to compare semi-automatic procedures with the manual procedure. Statistical significance was set at α = 0.01.

RESULTS

The coefficients of variation for the manual procedure were 2.5-3.5% on average. There was no statistical difference between the two operators. The results of manual procedures can be used as a reference. For the semi-automatic procedures, the dispersion around the mean can be elevated depending on the operator and case. ANOVA revealed significant differences between the operators for the three techniques according to cases.

CONCLUSIONS

Region-based segmentation was only comparable with the manual procedure for delineating a circumscribed osteolytic dento-maxillary lesion. The semi-automatic segmentations tested are interesting but are limited to complex surface structures. A methodology that combines the strengths of both methods could be of interest and should be tested. The improvement in the image analysis that is possible through the segmentation procedure and CBCT image quality could be of value.