Orthognathic positioning system: intraoperative system to transfer virtual surgical plan to operating field during orthognathic surgery

3D Printing-Encompassing the Facets of Dentistry

This narrative review presents an overview on the currently available 3D printing technologies and their utilization in experimental, clinical and educational facets, from the perspective of different specialties of dentistry, including oral and maxillofacial surgery, orthodontics, endodontics, prosthodontics, and periodontics. It covers research and innovation, treatment modalities, education and training, employing the rapidly developing 3D printing process. Research-oriented advancement in 3D printing in dentistry is witnessed by the rising number of publications on this topic. Visualization of treatment outcomes makes it a promising clinical tool. Educational programs utilizing 3D-printed models stimulate training of dental skills in students and trainees. 3D printing has enormous potential to ameliorate oral health care in research, clinical treatment, and education in dentistry.

Real-time augmented model guidance for mandibular proximal segment repositioning in orthognathic surgery, using electromagnetic tracking

It is essential to reposition the mandibular proximal segment (MPS) as close to its original position as possible during orthognathic surgery. Conventional methods cannot pinpoint the exact position of the condyle in the fossa in real time during repositioning. In this study, based on an improved registration method and a separable electromagnetic tracking tool, we developed a real-time, augmented, model-guided method for MPS surgery to reposition the condyle into its original position more accurately. After virtual surgery planning, using a complex maxillomandibular model, the final position of the virtual MPS model was simulated via 3D rotations. The displacements resulting from the MPS simulation were applied to the MPS landmarks to indicate their final postoperative positions. We designed a new registration body with 24 fiducial points for registration, and determined the optimal point group on the registration body through a phantom study. The registration between the patient's CT image and physical spaces was performed preoperatively using the optimal points. We also developed a separable frame for installing the electromagnetic tracking tool on the patient's MPS. During MPS surgery, the electromagnetic tracking tool was repeatedly attached to, and separated from, the MPS using the separable frame. The MPS movement resulting from the surgeon's manipulation was tracked by the electromagnetic tracking system. The augmented condyle model and its landmarks were visualized continuously in real time with respect to the simulated model and landmarks. Our method also provides augmented 3D coronal and sagittal views of the fossa and condyle, to allow the surgeon to examine the 3D condyle-fossa positional relationship more accurately. The root mean square differences between the simulated and intraoperative MPS models, and between the simulated and postoperative CT models, were 1.71 ± 0.63 mm and 1.89 ± 0.22 mm respectively at three condylar landmarks. Thus, the surgeons could perform MPS repositioning conveniently and accurately based on real-time augmented model guidance on the 3D condyle positional relationship with respect to the glenoid fossa, using augmented and simulated models and landmarks.

Advantages of performing mentoplasties with customized guides and plates generated with 3D planning and printing. Results from a series of 23 cases

PURPOSE

To evaluate the benefits of performing mentoplasty using custom guides and plates in a series of 23 patients.

PATIENTS AND METHODS

An 18-month observational study in 23 patients (16 women, 7 men) who underwent procedures for chin augmentation (n = 15), reduction and centering mentoplasty (n = 6), chin asymmetry correction (n = 1) and placement of a custom chin implant to correct esthetics (n = 1) was conducted in the Department of Oral and Maxillofacial Surgery of Hospital Universitario Dexeus (Barcelona, Spain).

RESULTS

A mentoplasty technique using customized surgical guides and plates, performed under local anesthesia and oral sedation, was performed in every case. Surgery times were approximately 45 min. Postoperative recovery was satisfactory in all patients. There were no intraoperative or serious postoperative complications, except for one self-limiting edema and some small hematomas of no clinical significance. Post-operative pain intensity measured by the Visual Analog Scale (VAS) was less than 3 (mild pain) in 80% and 4-7 (moderate pain) in 20% of patients.

CONCLUSION

The results obtained in this study show that using customized surgical guides and plates in performing mentoplasty is an advantage over conventional techniques as they provide greater accuracy and safety in the surgery and more predictable results. This simplifies the procedure.

Surgical guide and CAD/CAM prebent titanium plate for sagittal split ramus osteotomy in the correction of mandibular prognathism

This study was designed to introduce and evaluate the clinical use of a surgical guide and a CAD/CAM prebent titanium plate for sagittal split ramus osteotomy (SSRO) in the correction of mandibular prognathism. We studied 14 patients who had been diagnosed, and treated by bilateral SSRO with the guide, during the period July 2015-January 2016. Surface deviations of distal segments from simulation until the end of the operation were measured on a coloured map. Deviations of position and orientation of the condyle and proximal segment from before to after operation, and those from simulation until the end of the operation, were measured with a 3-dimensional vector. All patients were followed up for at least a year. The coloured map showed that the mean (SD) distances were 0.40 (0.25)mm between the simulated and postoperative distal segments. The 3-dimensional vector showed that the mean values of mediolateral, anteroposterior, and superior-inferior translations of the condyles were less than 1mm (p<0.02) from before the operation until the end, and from simulation to the end of the operation, and the mean value of pitching for proximal segments was less than 1° (p<0.02) from simulation to the end of the operation. At the one year follow-up, the occlusions were stable. Based on accurate diagnosis and simulation, this guide takes the distal segment precisely to its planned position, and the condyle and proximal segment are well-controlled. This is a useful tool, which is comparatively easy to make and operate.

Current status of surgical planning and transfer methods in orthognathic surgery

Since the advent of orthognathic surgery major efforts have been made to render these surgical procedures more reliable, accurate, reproducible, and shorter. Such improvements imply the enhancement of surgical planning (SP) techniques and optimization of SP transfer tools. Most widespread current SP methods are based on physical examination/anthropometric measurements combined with cephalometric analysis. Most surgeons currently use handmade acrylic surgical splints or sometimes freehand surgery as transfer tool. The emergence of virtual surgical planning (VSP) procedures gave birth to several modern transfer tools, such as computer-assisted design and manufactured (CAD/CAM) splints, CAD/CAM splints with extra-oral bone support, customized miniplates, and surgical navigation. This article classifies and describes these emerging transfer tools, therewith underlining their advantages and drawbacks.

Digital Diagnosis and Treatment Program for Maxillofacial Fractures: A Retrospective Analysis of 626 Cases

PURPOSE

The purpose of this study was to evaluate the accuracy of the digital diagnosis and treatment program for maxillofacial fractures.

MATERIALS AND METHODS

The data of 626 patients with maxillofacial fractures were analyzed retrospectively from January 2010 to August 2016. These patients were divided into 2 groups. In the experimental group, preoperative planning was conducted and transferred to patients with guiding templates and navigation according to the digital diagnosis and treatment program for maxillofacial fractures. In the control group, postsurgical planning was performed instead of preoperative planning. To assess the accuracy of the digital diagnosis and treatment program for maxillofacial fractures, preoperative planning and postoperative computed tomographic models were superimposed and imported to dedicated software (Geomagic Studio 13.0, Geomagic, Inc, Research Triangle Park, NC) to calculate the difference between the 2 models in the 2 groups.

RESULTS

Results of the experimental set showed that the mean error between the preoperative planning model and the postoperative model ranged from 0.65 to 0.97 mm (average, 0.89 mm). For the control group, the mean error was 0.78 to 1.45 mm (average, 1.01 mm). Thus, the mean error of the experimental group was statistically lower than that of the control group (P < .0001). Postoperative analysis of the subjective evaluation of occlusion recovery showed that 92.13% of patients achieved good occlusion recovery in the experimental group compared with only 84.91% in the control group. The digital diagnosis and treatment program for maxillofacial fractures was more accurate.

CONCLUSION

Aided by the digital diagnosis and treatment program, the accuracy for maxillofacial fractures was notably improved. To facilitate the application and promotion of digital technology, further modification of the complete digital diagnosis and treatment pathway for maxillofacial fractures is highly desired.

Computer Simulation and Optimization of Cranial Vault Distraction

Objective:

The objective of this study was to validate the proof of concept of a computer-simulated cranial distraction, demonstrating accurate shape and end volume.

Design:

Detailed modeling was performed on pre- and postoperative computed tomographic (CT) scans to generate accurate measurements of intracranial volume. Additionally, digital distraction simulations were performed on the preoperative scan and the resultant intracranial volume and shape were evaluated.

Setting:

Tertiary Children’s Hospital.

Patients, Participants:

Preoperative and postoperative CT images were used from 10 patients having undergone cranial distraction for cephalocranial disproportion.

Interventions:

None; computer simulation.

Main Outcome Measure:

Computer simulation feasibility of cranial vault distraction was demonstrated through creation of digital osteotomies, simulating distraction through translating skull segments, followed by simulated consolidation. Accuracy of the model was evaluated through comparing the intracranial volumes of actual and simulated distracted skulls.

Results:

The developed digital distraction simulation was performed on the CT images of 10 patients. Plotting the relationship between the actual and simulated postdistraction volumes for the 10 patients yielded a slope of 1.0 and a correlation coefficient of 0.99. The average actual resultant volume change from distraction was 77.0 mL, compared to a simulated volume change of 76.9 mL.

Conclusions:

Digital simulation of cranial distraction was demonstrated through manipulation of the CT images and confirmed by comparing the actual to simulated volume change. This process may provide objective data in designing an individual distraction plan to optimize volume expansion and resultant cranial shape as well as patient education.

3D virtual planning in orthognathic surgery and CAD/CAM surgical splints generation in one patient with craniofacial microsomia: a case report

Objective:

In this case report, the feasibility and precision of tridimensional (3D) virtual planning in one patient with craniofacial microsomia is tested using Nemoceph 3D-OS software (Software Nemotec SL, Madrid, Spain) to predict postoperative outcomes on hard tissue and produce CAD/CAM (Computer Aided Design/Computer Aided Manufacturing) surgical splints.

Methods:

The clinical protocol consists of 3D data acquisition of the craniofacial complex by cone-beam computed tomography (CBCT) and surface scanning of the plaster dental casts. The ''virtual patient'' created underwent virtual surgery and a simulation of postoperative results on hard tissues. Surgical splints were manufactured using CAD/CAM technology in order to transfer the virtual surgical plan to the operating room. Intraoperatively, both CAD/CAM and conventional surgical splints are comparable. A second set of 3D images was obtained after surgery to acquire linear measurements and compare them with measurements obtained when predicting postoperative results virtually.

Results:

It was found a high similarity between both types of surgical splints with equal fitting on the dental arches. The linear measurements presented some discrepancies between the actual surgical outcomes and the predicted results from the 3D virtual simulation, but caution must be taken in the analysis of these results due to several variables.

Conclusions:

The reported case confirms the clinical feasibility of the described computer-assisted orthognathic surgical protocol. Further progress in the development of technologies for 3D image acquisition and improvements on software programs to simulate postoperative changes on soft tissue are required.

Three-dimensional Planning and Reconstruction of the Mandible in Children with Craniofacial Microsomia Type III Using Costochondral Grafts

Background:

In craniofacial microsomia (CFM) Type III patients, autogenous costochondral grafts (CCG) are conventionally used for the reconstruction of the ramus and condyle. The aim of this study was to describe the use of CCG in children with CFM in terms of outcomes, growth patterns, and complications.

Materials and Methods:

This is a retrospective study of nine, aged 4–12 years, patients with CFM Type III, who underwent reconstruction of the mandibular ramus condyle unit by CCG. Seven patients had right-sided CFM and two had left-sided CFM. The rationale for this choice was to utilize the potential growth of the CCG, providing length to the ramus, and the joint by acting as a growth center; to control the repositioning of the chin center; and to improve child compliance by undergoing only one operation. The surgical treatment plan was determined preoperatively, based on measurements of mandibular vertical and horizontal deficiency and analysis of the mandibular posterior and anterior angulation. The mandibular planes and axis were defined by a three-dimensional simulation software program to perform a “mock surgery”, by creating a prototype model. Clinical follow-up included measurements of the maximal opening, observation of the facial symmetry, and recording of complications, such as reankylosis.

Results:

There were no serious postoperative complications, infections, or graft rejections. Successful postoperative occlusal cants were noted and measured in five patients and acceptable results were obtained in three patients. In one case, the CCG underwent distraction osteogenesis to improve the facial symmetry. In one patient, the graft continued to grow and the chin started to deviate into the opposite side. Measuring and calculating the ratio of the ramus height on the panoramic X-ray revealed a good relation between the healthy contralateral and the reconstructed ipsilateral ramus. Postoperative mean mouth opening was 34.3 mm, with minimal midline deviation of 2.6 mm in occlusion. Mean follow-up was 51.7 months. The mean postoperative occlusal cant analysis for eight patients was 3.66°.

Conclusion:

CCG is useful in treating CFM Type III. The growth potential of the CCG makes it the ideal choice for children. The advantages of this graft are its biological compatibility, workability, functional adaptability, and minimal additional detriment to the patient. The use of a stereolithographic model preoperatively improved intraoperative precision by clearly displaying detailed anatomy of the patient undergoing craniofacial surgery. The surgeon can plan the length of the CCG before surgery and use the printed template while harvesting without waiting for the exact measurements to be provided by the facial surgical team.

Application of A Novel Three-dimensional Printing Genioplasty Template System and Its Clinical Validation: A Control Study

The purpose of this control study was to assess the accuracy and clinical validation of a novel genioplasty template system. Eighty-eight patients were enrolled and divided into 2 groups: experimental group (using genioplasty templates) and control group (without genioplasty templates). For the experimental group, the templates were designed based on computerized surgical plan and manufactured using three-dimensional printing technique. The template system included a cutting guide and a pair of repositioning guides. For the control group, traditional intraoperative measurements were used without genioplasty templates. The outcome evaluation was completed by comparing planned outcomes with postoperative outcomes. Linear and angular differences for the chin was measured and reported using root mean square deviation (RMSD) and the Bland-Altman method. All surgeries were successfully completed. There was no difficulty to use genioplasty templates. For the experimental group, the largest RMSDs were 1.1 mm in anteroposterior direction and 2.6° in pitch orientation. For the control group without templates, the largest RMSDs were 2.63 mm in superoinferior direction and 7.21° in pitch orientation. Our findings suggest that this genioplasty template system provides greater accuracy in repositioning the chin than traditional intraoperative measurements, and the computerized plan can be transferred accurately to the patient for genioplasty.

3D Boolean operations in virtual surgical planning

PURPOSE

Boolean operations in computer-aided design or computer graphics are a set of operations (e.g. intersection, union, subtraction) between two objects (e.g. a patient model and an implant model) that are important in performing accurate and reproducible virtual surgical planning. This requires accurate and robust techniques that can handle various types of data, such as a surface extracted from volumetric data, synthetic models, and 3D scan data.

METHODS

This article compares the performance of the proposed method (Boolean operations by a robust, exact, and simple method between two colliding shells (BORES)) and an existing method based on the Visualization Toolkit (VTK).

RESULTS

In all tests presented in this article, BORES could handle complex configurations as well as report impossible configurations of the input. In contrast, the VTK implementations were unstable, do not deal with singular edges and coplanar collisions, and have created several defects.

CONCLUSIONS

The proposed method of Boolean operations, BORES, is efficient and appropriate for virtual surgical planning. Moreover, it is simple and easy to implement. In future work, we will extend the proposed method to handle non-colliding components.

A new approach of splint-less orthognathic surgery using a personalized orthognathic surgical guide system: A preliminary study

The purpose of this study was to evaluate a personalized orthognathic surgical guide (POSG) system for bimaxillary surgery without the use of surgical splint. Ten patients with dentofacial deformities were enrolled. Surgeries were planned with the computer-aided surgical simulation method. The POSG system was designed for both maxillary and mandibular surgery. Each consisted of cutting guides and three-dimensionally (3D) printed custom titanium plates to guide the osteotomy and repositioning the bony segments without the use of the surgical splints. Finally, the outcome evaluation was completed by comparing planned outcomes with postoperative outcomes. All operations were successfully completed using the POSG system. The largest root-mean-square deviations were 0.74mm and 1.93° for the maxillary dental arch, 1.10mm and 2.82° for the mandibular arch, 0.83mm and 2.59° for the mandibular body, and 0.98mm and 2.45° for the proximal segments. The results of the study indicated that our POSG system is capable of accurately and effectively transferring the surgical plan without the use of surgical splint. A significant advantage is that the repositioning of the bony segments is independent to the mandibular autorotation, thus eliminates the potential problems associated with the surgical splint.

Design, development and clinical validation of computer-aided surgical simulation system for streamlined orthognathic surgical planning

PURPOSE

There are many proven problems associated with traditional surgical planning methods for orthognathic surgery. To address these problems, we developed a computer-aided surgical simulation (CASS) system, the AnatomicAligner, to plan orthognathic surgery following our streamlined clinical protocol.

METHODS

The system includes six modules: image segmentation and three-dimensional (3D) reconstruction, registration and reorientation of models to neutral head posture, 3D cephalometric analysis, virtual osteotomy, surgical simulation, and surgical splint generation. The accuracy of the system was validated in a stepwise fashion: first to evaluate the accuracy of AnatomicAligner using 30 sets of patient data, then to evaluate the fitting of splints generated by AnatomicAligner using 10 sets of patient data. The industrial gold standard system, Mimics, was used as the reference.

RESULT

When comparing the results of segmentation, virtual osteotomy and transformation achieved with AnatomicAligner to the ones achieved with Mimics, the absolute deviation between the two systems was clinically insignificant. The average surface deviation between the two models after 3D model reconstruction in AnatomicAligner and Mimics was 0.3 mm with a standard deviation (SD) of 0.03 mm. All the average surface deviations between the two models after virtual osteotomy and transformations were smaller than 0.01 mm with a SD of 0.01 mm. In addition, the fitting of splints generated by AnatomicAligner was at least as good as the ones generated by Mimics.

CONCLUSION

We successfully developed a CASS system, the AnatomicAligner, for planning orthognathic surgery following the streamlined planning protocol. The system has been proven accurate. AnatomicAligner will soon be available freely to the boarder clinical and research communities.

Computer assisted positioning of the proximal segment after sagittal split osteotomy of the mandible: Preclinical investigation of a novel electromagnetic navigation system

INTRODUCTION

Modifications of the temporomandibular joint position after mandible osteotomy are reluctantly accepted in orthognathic surgery. To tackle this problem, we developed a new navigation system using miniaturized electromagnetic sensors. Our imageless navigation approach is therefore optimized to avoid complications of previously proposed optical approaches such as the interference with established surgical procedures and the line of sight problem.

MATERIAL AND METHODS

High oblique sagittal split osteotomies were performed on 6 plastic skull mandibles in a laboratory under conditions comparable to the operating theatre. The subsequent condyle reposition was guided by an intuitive user interface and performed by electromagnetic navigation. To prove the suitability and accuracy of this novel approach for condyle navigation, the positions of 3 titanium marker screws placed on each of the proximal segments were compared using pre- and postoperative Cone Beam Computed Tomography (CBCT) imaging.

RESULTS

Guided by the electromagnetic navigation system, positioning of the condyles was highly accurate in all dimensions. Translational discrepancies up to 0,65 mm and rotations up to 0,38° in mean could be measured postoperatively. There were no statistically significant differences between navigation results and CBCT measurements.

CONCLUSION

The intuitive user interface provides a simple way to precisely restore the initial position and orientation of the proximal mandibular segments. Our electromagnetic navigation system therefore yields a promising approach for orthognathic surgery applications.

Surgical Navigation: A Systematic Review of Indications, Treatments, and Outcomes in Oral and Maxillofacial Surgery

PURPOSE

This systematic review investigates the most common indications, treatments, and outcomes of surgical navigation (SN) published from 2010 to 2015. The evolution of SN and its application in oral and maxillofacial surgery have rapidly developed over recent years, and therapeutic indications are discussed.

MATERIALS AND METHODS

A systematic search in relevant electronic databases, journals, and bibliographies of the included articles was carried out. Clinical studies with 5 or more patients published between 2010 and 2015 were included. Traumatology, orthognathic surgery, cancer and reconstruction surgery, skull-base surgery, and foreign body removal were the areas of interests.

RESULTS

The search generated 13 articles dealing with traumatology; 5, 6, 2, and 0 studies were found that dealt with the topics of orthognathic surgery, cancer and reconstruction surgery, skull-base surgery, and foreign body removal, respectively. The average technical system accuracy and intraoperative precision reported were less than 1 mm and 1 to 2 mm, respectively. In general, SN is reported to be a useful tool for surgical planning, execution, evaluation, and research. The largest numbers of studies and patients were identified in the field of traumatology. Treatment of complex orbital fractures was considerably improved by the use of SN compared with traditionally treated control groups.

CONCLUSIONS

SN seems to be a very promising addition to the surgical toolkit. Planning details of the surgical procedure in a 3-dimensional virtual environment and execution with real-time guidance can significantly improve precision. Among factors to be considered are the financial investments necessary and the learning curve.

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.

Virtual skeletal complex model- and landmark-guided orthognathic surgery system

In this study, correction of the maxillofacial deformities was performed by repositioning bone segments to an appropriate location according to the preoperative planning in orthognathic surgery. The surgery was planned using the patient's virtual skeletal models fused with optically scanned three-dimensional dentition. The virtual maxillomandibular complex (MMC) model of the patient's final occlusal relationship was generated by fusion of the maxillary and mandibular models with scanned occlusion. The final position of the MMC was simulated preoperatively by planning and was used as a goal model for guidance. During surgery, the intraoperative registration was finished immediately using only software processing. For accurate repositioning, the intraoperative MMC model was visualized on the monitor with respect to the simulated MMC model, and the intraoperative positions of multiple landmarks were also visualized on the MMC surface model. The deviation errors between the intraoperative and the final positions of each landmark were visualized quantitatively. As a result, the surgeon could easily recognize the three-dimensional deviation of the intraoperative MMC state from the final goal model without manually applying a pointing tool, and could also quickly determine the amount and direction of further MMC movements needed to reach the goal position. The surgeon could also perform various osteotomies and remove bone interference conveniently, as the maxillary tracking tool could be separated from the MMC. The root mean square (RMS) difference between the preoperative planning and the intraoperative guidance was 1.16 ± 0.34 mm immediately after repositioning. After surgery, the RMS differences between the planning and the postoperative computed tomographic model were 1.31 ± 0.28 mm and 1.74 ± 0.73 mm for the maxillary and mandibular landmarks, respectively. Our method provides accurate and flexible guidance for bimaxillary orthognathic surgery based on intraoperative visualization and quantification of deviations for simulated postoperative MMC and landmarks. The guidance using simulated skeletal models and landmarks can complement and improve conventional navigational surgery for bone repositioning in the craniomaxillofacial area.

A new design of CAD/CAM surgical template system for two-piece narrowing genioplasty

The purpose of this study was to develop and validate a new chin template system for a two-piece narrowing genioplasty. Nine patients with wide chin deformities were enrolled. Surgeries were planned with the computer-aided surgical simulation (CASS) planning method. Surgical splints and chin templates were designed in a computer and fabricated using a three-dimensional printing technique. The chin template system included a cutting guide and a repositioning guide for a two-piece narrowing genioplasty. These guides were also designed to avoid the mental foramen area and inferior alveolar nerve loops during the osteotomy, for nerve protection. After surgery, the outcome evaluation was completed by first superimposing the postoperative computed tomography model onto the planned model, and then measuring the differences between the planned and actual outcomes. All surgeries were completed successfully using the chin template system. No inferior alveolar nerve damage was seen in this study. With the use of the chin templates, the largest linear root mean square deviation (RMSD) between the planned and the postoperative chin segments was 0.7mm and the largest angular RMSD was 4.5°. The results showed that the chin template system provides a reliable method of transfer for two-piece osseous narrowing genioplasty planning.

Computer-aided design and computer-aided modeling (CAD/CAM) generated surgical splints, cutting guides and custom-made implants: Which indications in orthognathic surgery?

INTRODUCTION

The purpose of the present report was to describe our indications, results and complications of computer-aided design and computer-aided modeling CAD/CAM surgical splints, cutting guides and custom-made implants in orthognathic surgery.

PATIENTS AND METHODS

We analyzed the clinical and radiological data of ten consecutive patients with dentofacial deformities treated using a CAD/CAM technique. Four patients had surgical splints and cutting guides for correction of maxillomandibular asymmetries, three had surgical cutting guides and customized internal distractors for correction of severe maxillary deficiencies and three had custom-made implants for additional chin contouring and/or mandibular defects following bimaxillary osteotomies and sliding genioplasty. We recorded age, gender, dentofacial deformity, surgical procedure and intra- and postoperative complications.

RESULTS

All of the patients had stable cosmetic results with a high rate of patient satisfaction at the 1-year follow-up examination. No intra- and/or postoperative complications were encountered during any of the different steps of the procedure.

DISCUSSION

This study demonstrated that the application of CAD/CAM patient-specific surgical splints, cutting guides and custom-made implants in orthognathic surgery allows for a successful outcome in the ten patients presented in this series.

Genioplasty using a simple CAD/CAM (computer-aided design and computer-aided manufacturing) surgical guide

BACKGROUND

The present study introduces the design and fabrication of a simple surgical guide with which to perform genioplasty.

METHODS

A three-dimensional reconstruction of the patient's cranio-maxilla region was built, with a dentofacial skeletal model, then derived from CT DICOM data. A surgical simulation was performed on the maxilla and mandible, using three-dimensional cephalometry. We then simulated a full genioplasty, in silico, using the three-dimensional (3D) model of the mandible, according to the final surgical treatment plan. The simulation allowed us to design a surgical guide for genioplasty, which was then computer-rendered and 3D-printed. The manufactured surgical device was ultimately used in an actual genioplasty to guide the osteotomy and to move the cut bone segment to the intended location.

RESULTS

We successfully performed the osteotomy, as planned during a genioplasty, using the computer-aided design and computer-aided manufacturing (CAD/CAM) surgical guide that we initially designed and tested using simulated surgery.

CONCLUSIONS

The surgical guide that we developed proved to be a simple and practical tool with which to assist the surgeon in accurately cutting and removing bone segments, during a genioplasty surgery, as preoperatively planned during 3D surgical simulations.

Accuracy evaluation of CAD/CAM generated splints in orthognathic surgery: a cadaveric study

Introduction

To evaluate the accuracy of CAD/CAM generated splints in orthognathic surgery by comparing planned versus actual post-operative 3D images.

Methods

Specific planning software (SimPlant^® OMS Standalone 14.0) was used to perform a 3D virtual Le Fort I osteotomy in 10 fresh human cadaver heads. Stereolithographic splints were then generated and used during the surgical procedure to reposition the maxilla according to the planned position. Pre-operative planned and postoperative 3D CT scan images were fused and imported to dedicated software (MATLAB^®) 7.11.) for calculating the translational and rotational (pitch, roll and yaw) differences between the two 3D images. Geometrical accuracy was estimated using the Root Mean Square Deviations (RMSD) and lower and upper limits of accuracy were computed using the Bland & Altman method, with 95 % confidence intervals around the limits. The accuracy cutoff was set at +/− 2 mm for translational and ≤ 4° for rotational measurements.

Results

Overall accuracy between the two 3D images was within the accuracy cutoff for all values except for the antero-posterior positioning of the maxilla (2.17 mm). The translational and rotational differences due to the splint were all within the accuracy cutoff. However, the width of the limits of agreement (range between lower and upper limits) showed that rotational differences could be particularly large.

Conclusion

This study demonstrated that maxillary repositioning can be accurately approximated and thus predicted by specific computational planning and CAD/CAM generated splints in orthognathic surgery. Further study should focus on the risk factors for inaccurate prediction.

Correction of facial asymmetry associated with vertical maxillary excess and mandibular prognathism by combined orthognathic surgery and guiding templates and splints fabricated by rapid prototyping technique

The facial asymmetry associated with vertical maxillary excess and mandibular prognathism is one of the more complicated types in the field of oral and maxillofacial surgery. The purpose of this study was to investigate the efficacy of combined orthognathic surgeries, together with guiding templates and splints fabricated by rapid prototyping technique, for the correction of facial asymmetry. Fourteen patients with facial asymmetry associated with vertical maxillary excess and mandibular prognathism were included. A maxillary Le Fort I osteotomy, a sagittal split ramus osteotomy on the shorter side of the face, and an intraoral vertical ramus osteotomy on the longer side of the face were performed with the aid of guiding templates and splints fabricated by rapid prototyping technique. Parameters reflecting maxillary canting, ramal inclination, mandibular deviation, and chin inclination were measured before surgery, 7 days after surgery, and 1 year after surgery, and compared. Significant differences in these parameters were found between the two sides preoperatively, whereas no differences were observed postoperatively. Facial asymmetry was corrected in all patients with satisfactory outcomes. In conclusion, combined orthognathic surgery and guiding templates and splints can offer improvements in accuracy, complexity, and duration over traditional procedures for the correction of facial asymmetry associated with vertical maxillary excess and mandibular prognathism.

Combined maxillary and mandibular distraction osteogenesis in patients with hemifacial microsomia

INTRODUCTION

Hemifacial microsomia is a deformity of variable expressivity with unilateral hypoplasia of the mandible and the ear. In this study, we evaluated skeletal soft tissue changes after bimaxillary unilateral vertical distraction.

METHODS

Eight patients (4 preadolescents 4 adolescents) each with a grade II mandibular deformity underwent a LeFort I osteotomy and an ipsilateral horizontal mandibular ramus osteotomy. A semiburied distraction device was placed over the ramus, and intermaxillary fixation was applied. Anteroposterior cephalometric and frontal photographic analyses were conducted before and after distraction. Statistics were used to analyze the preoperative and postoperative changes.

RESULTS

Cephalometrically, the nasal floor and the occlusal and gonial plane angles decreased. The ratios of affected-unaffected ramus and gonial angle heights improved by 15% and 20%, respectively. The position of menton moved toward the midline. The photographic analysis showed a decrease of the nasal and commissure plane angles, and the chin moved to the unaffected side. The parallelism between the horizontal skeletal and soft tissue planes improved, with an increase in the affected side ramus height and correction of the chin point toward the midline.

CONCLUSIONS

Simultaneous maxillary and mandibular distraction improved facial balance and symmetry. Patients in the permanent dentition with fixed orthodontic appliances and well-aligned dental arches responded well to this intervention.

Intraoperative navigation for single-splint two-jaw orthognathic surgery: From model to actual surgery

OBJECTIVE

This study reported an intraoperative navigation system for single-splint two-jaw orthognathic surgery, and assessed the accuracy of transferring the computer assisted surgical simulation.

METHODS

A skull model was used for validation, and twenty patients receiving such procedure were enrolled. The procedure contained five phases, including virtual surgery on three-dimensional images, fabrication of surgical positioning guides, preparation of registration and validation landmarks, confirmation of bony position during surgery, and postoperative assessment. Target registration error (TRE) and differences between simulation (T0) and postoperative images (T1) were measured from landmarks to Frankfort horizontal plane (FHP), mid-sagittal plane (MSP), and coronal plane (COP).

RESULTS

For the model experiment, mean TRE was lowest using the hard tissue landmarks (0.60 ± 0.27 mm), and the mean difference (T1-T0) was less than 1 mm to all three planes. For the patients, mean TRE was 1.07 ± 0.18 mm from the hard tissue landmarks. The mean difference was 0.96. ± 0.60 mm from MSP, 1.39 ± 1.11 mm from FHP, and 2.12 ± 1.82 mm from COP. The differences were not significant. Both surgeons and patients were satisfied with the surgical outcome.

CONCLUSION

This study showed that the navigation system had acceptable accuracy and was useful for the two-jaw orthognathic surgery using single-splint method.

Development of customized positioning guides using computer-aided design and manufacturing technology for orthognathic surgery

PURPOSE

The purpose of this study was to devise a method for producing customized positioning guides for translating virtual plans to actual orthognathic surgery, and evaluation of the feasibility and validity of the devised method.

METHODS

Patients requiring two-jaw orthognathic surgery were enrolled and consented before operation. Two types of positioning guides were designed and fabricated using computer-aided design and manufacturing technology: One of the guides was used for the LeFort I osteotomy, and the other guide was used for positioning the maxillomandibular complex. The guides were fixed to the medial side of maxilla. For validation, the simulation images and postoperative cone beam computed tomography images were superimposed using surface registration to quantify the difference between the images. The data were presented in root-mean-square difference (RMSD) values.

RESULTS

Both sets of guides were experienced to provide ideal fit and maximal contact to the maxillary surface to facilitate their accurate management in clinical applications. The validation results indicated that RMSD values between the images ranged from 0.18 to 0.33 mm in the maxilla and from 0.99 to 1.56 mm in the mandible. The patients were followed up for 6 months or more, and all of them were satisfied with the results.

CONCLUSION

The proposed customized positioning guides are practical and reliable for translation of virtual plans to actual surgery. Furthermore, these guides improved the efficiency and outcome of surgery. This approach is uncomplicated in design, cost-effective in fabrication, and particularly convenient to use.

Keyhole System: A Computer-Assisted Designed and Computer-Assisted Manufactured Maxillomandibular Complex Repositioner in Orthognathic Surgery

Currently, virtual orthognathic surgery using the CAD/CAM program and three-dimensional printing technology has provided a valuable tool supporting accurate surgical planning and precise surgery. However, despite the advancements in CAD/CAM virtual surgical planning, accurately reproducing surgical planning from a virtual surgery to the operating field is still challenging. Here, we report the Keyhole system as a method that has constantly provided us with consistent results during double-jaw surgery, especially during this age of ever increasing aesthetic demand from patients.

Current Status of Surgical Planning for Orthognathic Surgery: Traditional Methods versus 3D Surgical Planning

Background:

Orthognathic surgery has traditionally been performed using stone model surgery. This involves translating desired clinical movements of the maxilla and mandible into stone models that are then cut and repositioned into class I occlusion from which a splint is generated. Model surgery is an accurate and reproducible method of surgical correction of the dentofacial skeleton in cleft and noncleft patients, albeit considerably time-consuming. With the advent of computed tomography scanning, 3D imaging and virtual surgical planning (VSP) have gained a foothold in orthognathic surgery with VSP rapidly replacing traditional model surgery in many parts of the country and the world. What has yet to be determined is whether the application and feasibility of virtual model surgery is at a point where it will eliminate the need for traditional model surgery in both the private and academic setting.

Methods:

Traditional model surgery was compared with VSP splint fabrication to determine the feasibility of use and accuracy of application in orthognathic surgery within our institution.

Results:

VSP was found to generate acrylic splints of equal quality to model surgery splints in a fraction of the time. Drawbacks of VSP splint fabrication are the increased cost of production and certain limitations as it relates to complex craniofacial patients.

Conclusions:

It is our opinion that virtual model surgery will displace and replace traditional model surgery as it will become cost and time effective in both the private and academic setting for practitioners providing orthognathic surgical care in cleft and noncleft patients.

Three-dimensional computer-assisted surgical simulation and intraoperative navigation in orthognathic surgery: a literature review

By incorporating three-dimensional (3D) imaging and computer-aided design and manufacturing techniques, 3D computer-assisted technology has been applied widely to provide accurate guidance for assessment and treatment planning in clinical practice. This technology has recently been used in orthognathic surgery to improve surgical planning and outcome. The modality will gradually become popular. This study reviewed the literature concerning the use of computer-assisted techniques in orthognathic surgery including surgical planning, simulation, intraoperative translation of the virtual surgery, and postoperative evaluation. A Medline, PubMed, ProQuest, and ScienceDirect search was performed to find relevant articles with regard to 3D computer-assisted orthognathic surgery in the past 10 years. A total of 460 articles were revealed, out of which 174 were publications addressed the topic of this study. The purpose of this article is to present an overview of the state-of-art methods for 3D computer-assisted technology in orthognathic surgery. From the review we can conclude that the use of computer-assisted technique in orthognathic surgery provides the benefit of optimal functional and aesthetic results, patient satisfaction, precise translation of the treatment plan, and facilitating intraoperative manipulation.

Splintless orthognathic surgery: a novel technique using patient-specific implants (PSI)

In the past few years, advances in three-dimensional imaging have conducted to breakthrough in the diagnosis, treatment planning and result assessment in orthognathic surgery. Hereby error-prone and time-consuming planning steps, like model surgery and transfer of the face bow, can be eluded. Numerous positioning devices, in order to transfer the three-dimensional treatment plan to the intraoperative site, have been described. Nevertheless the use of positioning devices and intraoperative splints are failure-prone and time-consuming steps, which have to be performed during the operation and during general anesthesia of the patient. We describe a novel time-sparing and failsafe technique using patient-specific implants (PSI) as positioning guides and concurrently as rigid fixation of the maxilla in the planned position. This technique avoids elaborate positioning and removal of manufactured positioning devices and allows maxillary positioning without the use of occlusal splints.

Customised osteotomy guides and endoprosthetic reconstruction for periacetabular tumours

PURPOSE

We sought to analyse clinical and oncological outcomes of patients after guided resection of periacetabular tumours and endoprosthetic reconstruction of the remaining defect.

METHODS

From 1988 to 2008, we treated 56 consecutive patients (mean age 52.5 years, 41.1 % women). Patients were followed up either until death or February 2011 (mean follow up 5.5 years, range 0.1-22.5, standard deviation ± 5.3). Kaplan-Meier analysis was used to estimate survival rates.

RESULTS

Disease-specific survival was 59.9 % at five years and 49.7 % at ten and 20 years, respectively. Wide resection margins were achieved in 38 patients, whereas 11 patients underwent marginal and seven intralesional resection. Survival was significantly better in patients with wide or marginal resection than in patients with intralesional resection (p = 0.022). Survival for patients with secondary tumours was significantly worse than for patients with primary tumours (p = 0.003). In 29 patients (51.8 %), at least one reoperation was necessary, resulting in a revision-free survival of 50.5 % at five years, 41.1 % at ten years and 30.6 % at 20 years. Implant survival was 77.0 % at five years, 68.6 % at ten years and 51.8 % at 20 years. A total of 35 patients (62.5 %) experienced one or more complications after surgery. Ten of 56 patients (17.9 %) experienced local recurrence after a mean of 8.9 months. The mean postoperative Musculoskeletal Tumor Society (MSTS) score was 18.1 (60.1 %).

CONCLUSION

The surgical approach assessed in this study simplifies the process of tumour resection and prosthesis implantation and leads to acceptable clinical and oncological outcomes.

Computer-aided design and computer-aided manufacturing cutting guides and customized titanium plates are useful in upper maxilla waferless repositioning

PURPOSE

The purpose of the present study was to develop a computer-aided design (CAD) and computer-aided manufacturing (CAM) technique that enabled fabrication of surgical cutting guides and titanium fixation plates that would allow the upper maxilla to be repositioned correctly without a surgical splint in orthognathic patients.

MATERIALS AND METHODS

Ten patients were recruited. A complete CAD-CAM workflow for orthognathic surgery has 3 steps: 1) virtual planning of the surgical treatment, 2) CAD-CAM and 3-dimensional printing of customized surgical devices (surgical cutting guide and titanium fixation plates), and 3) computer-aided surgery. Upper maxilla repositioning was performed in a waferless manner using a CAD-CAM device: the surgical cutting guide was used during surgery to pilot the osteotomy line that had been planned preoperatively at the computer and the custom-made fixation titanium plates allowed desired repositioning of the maxilla.

RESULTS

To evaluate the reproducibility of this CAD-CAM orthognathic surgical method, the virtually planned and actually achieved positions of the upper maxilla were compared. Overlap errors using a threshold value smaller than 2 mm were evaluated, and the frequency of such errors was used as a measurement of accuracy. By this definition, the accuracy was 100% in 7 patients (range in all patients, 62 to 100%; median, 92.7%).

CONCLUSION

These results tend to confirm that the use of CAD-CAM cutting guides and customized titanium plates for upper maxilla repositioning represents a promising method for the accurate reproduction of preoperative virtual planning without the use of surgical splints.

Computer-aided planning in orthognathic surgery-systematic review

The aim of this study was to conduct a systematic review to evaluate the accuracy and benefits of computer-aided planning in orthognathic surgery. The search was performed in PubMed, EMBASE, Cochrane Library, LILACS, and SciELO. The articles identified were assessed independently and in a blinded manner by two authors using selection criteria and eligibility criteria. The database search yielded 375 studies. Following the application of search and eligibility criteria, a final nine studies were included in the systematic review. The level of agreement between the authors in the study selection process was substantial (κ=0.767) and study eligibility was considered excellent (κ=0.863). The accuracy of translation was <1.2mm in the maxilla (vertical) and <1.1mm in the mandible (sagittal), and for rotation was <1.5° in the maxilla (pitch) and <1.8° in the mandible (pitch). Two studies showed a medium potential risk of bias and six studies showed a high potential risk of bias. Computer-aided planning in orthognathic surgery was considered accurate for the studies included in this systematic review. However, the low quality of these studies means that randomized clinical trials are needed to compare computer-aided planning to conventional planning in orthognathic surgery.

Intraoperative condyle positioning by sonographic monitoring in orthognathic surgery verified by MRI

OBJECTIVE

Repositioning of the jaw in orthognathic surgery must produce precise and stable long-term results; an effective and practical method of intraoperative condyle positioning is required to achieve this. Most traditional methods, such as manual positioning or positioning plates do not permit intraoperative monitoring of the temporomandibular joint (TMJ) position. This study evaluates the results of intraoperative, sonographically-monitored joint positioning, comparing preoperative and postoperative MRI scans.

PATIENTS AND METHODS

Of the 97 patients who were originally assessed (53 female, average age 29 ± 10.93; and 44 male, average age 28 ± 9.25), 21 had incomplete data sets and were excluded, leaving 76 evaluable patients. MRIs were performed preoperatively between 2 days and 100 weeks (median 30.5 days), and postoperatively between 12 and 96 weeks (median 150 days). Condyle positioning, intercondylar distance, and disc degeneration and dislocation were compared in preoperative and postoperative MRIs, and differentiated by Angle class on horizontal, axial and sagittal scans. Condyle to fossa distances were measured on parasagittal images from 0° (the vertical sagittal plane), 45° anteriorly and 45° posteriorly. The intercondylar distances between the condylar head midpoints were measured on axial sections. Two-sided t-tests (α < 0.05) were used for comparisons within classes; the interclass correlation was performed using univariate ANOVA and linear correlation for paired sample correlation settings.

RESULTS

In 27 Angle class II cases, the anterior distance of both condyles increased on average 0.3 ± 1.0 mm, the posterior position decreased 0.1 ± 1.2 mm, and the vertical position decreased 0.2 ± 1.1 mm postoperatively. In 47 Angle class III cases the anterior distance of both condyles increased on average 0.3 ± 0.8 mm, the posterior 0.1 ± 0.8 mm and the vertical distance 0.1 ± 0.8 mm postoperatively. All alterations of the condyle-fossa relation were non-significant except for the anterior distance in Angle class ІІІ (p = 0.02). Alterations of the disc position and disc degeneration were non-significant in class II. In class ІІІ, the disc degeneration deteriorated slightly on the left side (p = 0.02). Intercondylar distance increased 1 ± 5.5 mm in class ІІ and decreased by 1 ± 5.5 mm in class ІІІ postoperatively, alterations were non-significant.

CONCLUSION

Sonography is a non-invasive, comfortable, fast, economical and effective intraoperative method of condyle positioning. The results of the present study support this statement because the degree of disc degeneration and luxation remained unaltered and the condyle position did not change significantly. Prospective randomized comparison to manual positioning is in preparation and will be conducted in the near future.