Steve Guofang Shen

A novel method of computer aided orthognathic surgery using individual CAD/CAM templates: a combination of osteotomy and repositioning guides.

The maxilla is usually positioned during orthognathic surgery using surgical splints, which has many limitations. In this preliminary study we present a new computer-aided design and manufacture (CAD/CAM) template to guide the osteotomy and the repositioning, and illustrate its feasibility and validity. Six patients with dental maxillofacial deformities were studied. The design of the templates was based on three-dimensional surgical planning, including the Le Fort osteotomy and the repositioning of the maxilla, and were made using a three-dimensional printing technique. Two parts of the templates, respectively, guided the osteotomy and repositioned the maxilla during operation. The traditional occlusal splint was used to achieve the final occlusion with the mandible in the expected position. Postoperative measurements were made between maxillary hard tissue landmarks, relative to reference planes based on computed tomographic (CT) data. The results of the measurements were analysed and compared with the virtual plan. The preliminary results showed that we achieved clinically acceptable precision for the position of the maxilla (<1.0 mm). Preoperative preparation time was reduced to about 145 min. All patients were satisfied with the aesthetic results. Our CAD/CAM templates provide a reliable method for transfer of maxillary surgical planning, which may be a useful alternative to the intermediate splint technique. Our technique does not require traditional model surgery, scanning of dental casts, or recording of the CAD/CAM splint.

Automated bone segmentation from dental CBCT images using patch-based sparse representation and convex optimization

PURPOSE Cone-beam computed tomography (CBCT) is an increasingly utilized imaging modality for the diagnosis and treatment planning of the patients with craniomaxillofacial (CMF) deformities. Accurate segmentation of CBCT image is an essential step to generate three-dimensional (3D) models for the diagnosis and treatment planning of the patients with CMF deformities. However, due to the poor image quality, including very low signal-to-noise ratio and the widespread image artifacts such as noise, beam hardening, and inhomogeneity, it is challenging to segment the CBCT images. In this paper, the authors present a new automatic segmentation method to address these problems. METHODS To segment CBCT images, the authors propose a new method for fully automated CBCT segmentation by using patch-based sparse representation to (1) segment bony structures from the soft tissues and (2) further separate the mandible from the maxilla. Specifically, a region-specific registration strategy is first proposed to warp all the atlases to the current testing subject and then a sparse-based label propagation strategy is employed to estimate a patient-specific atlas from all aligned atlases. Finally, the patient-specific atlas is integrated into a maximum a posteriori probability-based convex segmentation framework for accurate segmentation. RESULTS The proposed method has been evaluated on a dataset with 15 CBCT images. The effectiveness of the proposed region-specific registration strategy and patient-specific atlas has been validated by comparing with the traditional registration strategy and population-based atlas. The experimental results show that the proposed method achieves the best segmentation accuracy by comparison with other state-of-the-art segmentation methods. CONCLUSIONS The authors have proposed a new CBCT segmentation method by using patch-based sparse representation and convex optimization, which can achieve considerably accurate segmentation results in CBCT segmentation based on 15 patients.

A new method of surgical navigation for orthognathic surgery: optical tracking guided free-hand repositioning of the maxillomandibular complex.

AbstractIn bimaxillary orthognathic surgery, the positioning of the maxilla and the mandible is typically accomplished via 2-splint technique, which may be the sources of several types of inaccuracy. To overcome the limitations of the 2-splint technique, we developed a new navigation method, which guided the surgeon to free-hand reposition the maxillomandibular complex as a whole intraoperatively, without the intermediate splint. In this preliminary study, the feasibility was demonstrated. Five patients with dental maxillofacial deformities were enrolled. Before the surgery, 3-dimensional planning was conducted and imported into a navigation system. During the operation, a tracker was connected to the osteotomized maxillomandibular complex via a splint. The navigation system tracked the movement of the complex and displayed it on the screen in real time to guide the surgeon to reposition the complex. The postoperative result was compared with the plan by analyzing the measured distances between the maxillary landmarks and reference planes, as determined from computed tomography data. The mean absolute errors of the maxillary position were clinically acceptable (<1.0 mm). Preoperative preparation time was reduced to 100 minutes on average. All patients were satisfied with the aesthetic results. This navigation method without intraoperative image registration provided a feasible means of transferring virtual planning to the real orthognathic surgery. The real-time position of the maxillomandibular complex was displayed on a monitor to visually guide the surgeon to reposition the complex. In this method, the traditional model surgery and the intermediate splint were discarded, and the preoperative preparation was simplified.

Navigation-guided lateral gap arthroplasty as the treatment of temporomandibular joint ankylosis.

PURPOSE This article presents a novel method of navigation-guided lateral gap arthroplasty (LGA) in the treatment of temporomandibular joint ankylosis (TMJA). MATERIALS AND METHODS Six patients with unilateral TMJA from 2007 through 2011 were included in this study. Presurgical planning was performed to determine the amount and extent of ankylosed bone to be resected using the simulation platform. Minimum follow-up was 6 months. Patients were monitored for complications and signs of recurrence. Maximum mouth opening (MO) was measured and compared intra- and postoperatively. RESULTS Preoperative planning was performed at the STN or Accu-Navi workstation. The amount and extent of ankylosed bone to be resected was determined. All 6 LGAs were completed successfully using real-time instrument- and pointer-based navigation. Measurements performed intraoperatively showed that the mean for maximum MO was about 35 to 40 mm and remained the same postoperatively. Follow-up evaluation showed remarkable improvement in function and esthetics, with no signs of recurrence. CONCLUSION Navigation-guided LGA can be regarded a viable option for performing this delicate and complicated surgical procedure.

Automated segmentation of CBCT image using spiral CT atlases and convex optimization.

Cone-beam computed tomography (CBCT) is an increasingly utilized imaging modality for the diagnosis and treatment planning of the patients with craniomaxillofacial (CMF) deformities. CBCT scans have relatively low cost and low radiation dose in comparison to conventional spiral CT scans. However, a major limitation of CBCT scans is the widespread image artifacts such as noise, beam hardening and inhomogeneity, causing great difficulties for accurate segmentation of bony structures from soft tissues, as well as separating mandible from maxilla. In this paper, we presented a novel fully automated method for CBCT image segmentation. In this method, we first estimated a patient-specific atlas using a sparse label fusion strategy from predefined spiral CT atlases. This patient-specific atlas was then integrated into a convex segmentation framework based on maximum a posteriori probability for accurate segmentation. Finally, the performance of our method was validated via comparisons with manual ground-truth segmentations.

Image fusion in craniofacial virtual reality modeling based on CT and 3dMD photogrammetry.

Purpose The aim of this study was to demonstrate the feasibility of building a craniofacial virtual reality model by image fusion of 3-dimensional (3D) CT models and 3dMD stereophotogrammetric facial surface. Methods A CT scan and stereophotography were performed. The 3D CT models were reconstructed by Materialise Mimics software, and the stereophotogrammetric facial surface was reconstructed by 3dMD patient software. All 3D CT models were exported as Stereo Lithography file format, and the 3dMD model was exported as Virtual Reality Modeling Language file format. Image registration and fusion were performed in Mimics software. Genetic algorithm was used for precise image fusion alignment with minimum error. The 3D CT models and the 3dMD stereophotogrammetric facial surface were finally merged into a single file and displayed using Deep Exploration software. Errors between the CT soft tissue model and 3dMD facial surface were also analyzed. Results Virtual model based on CT-3dMD image fusion clearly showed the photorealistic face and bone structures. Image registration errors in virtual face are mainly located in bilateral cheeks and eyeballs, and the errors are more than 1.5 mm. However, the image fusion of whole point cloud sets of CT and 3dMD is acceptable with a minimum error that is less than 1 mm. Conclusions The ease of use and high reliability of CT-3dMD image fusion allows the 3D virtual head to be an accurate, realistic, and widespread tool, and has a great benefit to virtual face model.

Osteogenic Differentiation of Human Amniotic Epithelial Cells and Its Application in Alveolar Defect Restoration

The present study investigated the detailed in vitro osteogenic differentiation process and in vivo bone regenerative property of human amniotic epithelial cells (hAECs). The in vitro osteogenic differentiation process of hAECs was evaluated by biochemical staining, real‐time polymerase chain reaction, and immunofluorescence. Next, β‐tricalcium phosphate (β‐TCP) scaffolds alone or loaded with hAECs were implanted into the alveolar defects of rats. Micro‐computed tomography evaluation and histologic studies were conducted. Our results validated the in vitro osteogenic capacity of hAECs by upregulation of Runx2, osterix, alkaline phosphatase, collagen I, and osteopontin, with positive biochemical staining for osteoblasts. An epithelial‐mesenchymal transformation process might be involved in the osteogenic differentiation of hAECs by increased expression of transforming growth factor‐β1. Our data also demonstrated that in vivo implantation of hAECs loaded on β‐TCP scaffolds, not only improved bone regeneration by direct participation, but also reduced the early host immune response to the scaffolds. The presented data indicate that hAECs possess proper osteogenic differentiation potential and a modulatory influence on the early tissue remodeling process, making these cells a potential source of progenitor cells for clinical restoration of the alveolar defect.

Navigation-guided en bloc resection and defect reconstruction of craniomaxillary bony tumours.

The aim of this study was to evaluate the validity of navigation-guided en bloc tumour resection and defect reconstruction in the treatment of craniomaxillary bony tumours. Three patients with ossifying fibroma and two patients with fibrous dysplasia were enrolled in this study. After preoperative planning and three-dimensional simulation, the osteotomy lines for resection were delineated and the normal anatomic structures for defect reconstruction were ascertained. With the guidance of an Accu-Navi navigation system, an en bloc tumour resection and simultaneous defect rehabilitation were performed. The system provided continuously updated information on the position and movement of surgical instruments in the operating field in relation to the preoperative imaging data set. The system error measured by the computer did not exceed 1mm. The osteotomy lines and reconstruction contour were checked by postoperative computed tomography, and good matching with the preoperative planning was achieved. Patients showed no signs of tumour recurrence or prosthesis infection during follow-up (range 12-35 months). Image-guided navigation makes radical bone tumour resection more reliable by implementing preoperative planning, showing the determined safety margins, preserving vital structures and guiding reconstruction.

Distraction Osteogenesis Combined With Tissue-Engineered Cartilage in the Reconstruction of Condylar Osteochondral Defect

PURPOSE Surgical rehabilitation of condylar osteochondral defect remains a challenge for surgeons. The aim of this study was to explore the feasibility of combining distraction osteogenesis with tissue-engineered cartilage in the reconstruction of condylar osteochondral defect. MATERIALS AND METHODS A condylar defect model was established in 18 goats that were randomly divided into 2 groups: the experimental group and the control group. Mandibular ramus osteotomies were performed and distractors were implanted in all animals. The mixture of chondrocytes and Pluronic F-127 (Sigma-Aldrich, St Louis, MO) was injected on the notched surface of a transport disc in the experimental group, whereas a scaffold without cells was transplanted into the control group. After a 5-day latency period, distraction was activated at a rate of 0.5 mm twice per day for 15 days. The goats were killed at the end of the fourth, eighth, or twelfth week in the consolidation period. Specimens were harvested and macroscopic evaluation, as well as Masson trichrome and immunohistochemical staining, were performed to compare the results between the 2 groups. RESULTS Osteogenesis was found in all animals with no evidence of infection. Condyle-like structures were formed at the upper end of the transport segment in all animals. The neocondylar surface was covered with a layer of smooth lustrous fibrocartilage in the experimental group. Collagen was shown in the reparative tissue by Masson trichrome staining. Immunohistochemistry staining indicated that type II collagen was positive, whereas type I collagen was negative on the neocondylar surface in the experimental group. No cartilage-like tissue was seen, but fibrous tissue was identified at the bony surface in the control group. In the experimental group, immunofluorescent semiquantitative analysis showed that the positive rate of type II collagen was 1.62% ± 0.53% after the fourth week of consolidation, and it increased to 12.39% ± 3.27% after the twelfth week. There was a significant difference in the expression of type II collagen between the goats examined after the fourth week, and those examined after the twelfth week. CONCLUSION The combination of distraction osteogenesis with tissue-engineered cartilage is an ideal alternative in the reconstruction of condylar osteochondral defect. By use of this method, the simultaneous rehabilitation and regeneration of condylar bone and cartilage were achieved.

Presurgical motivations, self-esteem, and oral health of orthognathic surgery patients.

PurposeThe aim of this study was to evaluate motivations, self-esteem, and oral health for undergoing orthognathic patients by gender in China before orthognathic surgery. Patients and MethodsUsing a prospective and control study design, 429 subjects in China were collected from December 2010 to May 2011. The patient group consisted of 210 consecutive healthy patients, and 219 young individuals comprised the control group. All the subjects filled out a questionnaire and were assessed by Self-esteem Scale and Oral Health Impact Profile validated for Chinese patients before surgery. To measure the discrepancy, the Student t test was computed. P <0.05 was considered significant. ResultsIn China, major motivations for orthognathic surgery are to improve facial appearance (83.33%), occlusion (50%), and self-confidence (48.1%). Females expect to improve facial appearance (83.87%), self-confidence (43.55%), and occlusion (41.94%). Males are for the improvement of facial appearance (82.56%), occlusion (63.95%), and self-confidence (54.65%). Self-esteem in the patient group is obviously lower (P < 0.01). There is a significant difference of self-esteem in female groups (P < 0.01), but none in male groups. Statistically significant differences were observed on oral health between both sexes. Conclusions(1) Special attention should be paid on patients’ ethnic, economic, cultural, and social aspects. In Chinese orthognathic patients, improving facial appearance is the primary motivation. Self-confidence has been more frequently mentioned, while headache far less than other countries. (2) Female patients have less self-esteem than females in the control group. (3) Patients’ oral health are worse than those in the control group.