Publications (93)213.36 Total impact
- [Show abstract] [Hide abstract] ABSTRACT: Mandibular fractures are amongst the most common facial fractures and are usually treated by open reduction and internal fixation (ORIF). Inferior alveolar nerve (IAN) injuries are seen frequently in mandibular fractures as well as after ORIF of these fractures due to the exposition and the close proximity of the nerve during fracture reduction. Therefore the continuity of the IAN can be disrupted. Permanent injury to the IAN can result in diminished quality of life. This retrospective study was designed to objectively analyse the incidence and the outcome of pre- and postoperative mental nerve hypoesthesia after ORIF of mandibular fractures.
- [Show abstract] [Hide abstract] ABSTRACT: Background Three-dimensional photography of the face is increasingly used to overcome the downsides of conventional photography or anthropometry regarding reliable evaluation. However, the precision of such a system has to be validated before it can be implemented for clinical use. Material and methods Eight people were photographed with the 3dMDface system using lighting from sets of 2 × 4 compact fluorescent lights in a clinical photography room without natural light sources. Two different operators then individually, and without interaction, marked 27 different anatomical landmarks using the 3dMD Patient software. During this process, the operators were fully blinded against each other. The purpose of the study was to determine the repeatability and accuracy of the system when used by different operators and at different times. The 3D differentiation was analyzed using mixed ANOVA with person as the random factor, and operator, repetition, and landmark as the fixed factors. The ANOVA was followed by a Ryan-Einot-Gabriel-Welsch F post-hoc test for landmarks. Results Statistical analysis grouped the landmarks into three subgroups: high precision, medium precision and low precision. Conclusions Virtual 3D models derived from the 3dMDface system not only provide a high level of technical precision but also of intra- and interobserver reliability regarding landmark identification. However, some of the classical landmarks are not reliable when it comes to virtual models; these are generally landmarks that examiners of real patients would tend to identify using palpation of underlying bony structures, such as the soft gonion.
- [Show abstract] [Hide abstract] ABSTRACT: There is an urgent critical need for the development of clinically relevant tissue-engineered large bone substitutes that can promote early vascularization after transplantation. To promote rapid blood vessel growth in the engineered tissue, we preincubated aortic fragments, as well as, co-cultures of aortic fragments and osteoblast-like cells in matrigel-filled PLGA scaffolds before implantation into the dorsal skinfold chambers of balb/c mice. Despite an acceptable and low inflammatory response, preincubated aortic fragments accelerate early angiogenesis of tissue-engineered constructs; the angiogenesis was found to occur faster than that observed in previous studies. Thus, the time-period for achieving a denser microvascular network could be reduced to half. In addition, co-culture with osteoblasts enhances this angiogenic effect significantly (against preincubated aortic fragments alone). During the preincubation period, aortic fragments begin to form a network of vessel-like structures additionally supported by osteoblast-like cells. After transplantation, further development of a dense microvasculature continues rapidly. Therefore, preincubation of aortic fragments, especially in co-culture with osteoblast-like cells, in 3D extracellular matrices supports the rapid vascularization of tissue-engineered constructs. This method is a promising approach to establish a dense microvascular network in these constructs.
- [Show abstract] [Hide abstract] ABSTRACT: The treatment of fractures of the mandibular process remains controversial, although there is a trend towards open reduction and internal fixation. This study compared open and closed treatments and assessed the results with a meta-analysis. A literature search of PubMed found eight studies that met the search criteria and were included in the meta-analysis. The studies increasingly suggest better results for open treatment, in terms of mouth opening, protrusion, laterotrusion, pain, and malocclusion. In the meta-analysis, the outcome was significantly better for laterotrusion and protrusion in patients treated by open reduction and internal fixation. Due to the different study protocols and lack of information on classification, follow-up time, and inclusion criteria, comparison of the studies remains difficult and further prospective, randomized studies should examine these issues. Copyright © 2015 European Association for Cranio-Maxillo-Facial Surgery. Published by Elsevier Ltd. All rights reserved.
- [Show abstract] [Hide abstract] ABSTRACT: PURPOSE: This study evaluated whether intraoperative imaging with computer-assisted virtual reconstruction would be advantageous in reconstructions of orbital floor fractures. The surgeon's intention to revise a reconstructed primary orbital floor fracture by evaluating a postoperative mirrored computed tomographic (CT) scan was analyzed intraoperatively before wound closure, during inpatient hospitalization, and after hospitalization. The inter-rater agreement and the match of intention to revise and actual revision were analyzed.
- [Show abstract] [Hide abstract] ABSTRACT: Rapid blood vessel ingrowth in transplanted tissue engineering constructs is the key factor for successful incorporation, but many potential patients who may use engineered tissues suffer from widespread diseases that limit the capacity of neovascularization (e.g. diabetes). Thus, in vivo vascularization analyses of tissue-engineered constructs in angiogenically affected organisms are required. We therefore investigated the in vivo incorporation of collagen-coated and cell-seeded poly-L-lactide-co-glycolide scaffolds in diabetic B6.BKS(D)-Lepr(db)/J mice using repetitive intravital fluorescence microscopy over a time period of two weeks. For this purpose, scaffolds were seeded with osteoblast-like or bone marrow mesenchymal stem cells and implanted into the dorsal skinfold chambers of diabetic and non-diabetic (C57BL/6) mice. Apart from slightly increased inflammatory parameters, diabetic mice showed significantly reduced capillary densities compared with non-diabetic animals from day 6 onward. In line with previous studies, more densely meshed microvascular networks were demonstrated in cell-seeded than in collagen-coated scaffolds from day 6 onward within the single groups (diabetic and control). A large number of patients who suffer from systemic diseases that affect angiogenesis would profit from tissue engineering. Therefore, the challenge for the clinical introduction of tissue-engineered constructs will be to overcome the decreased angiogenesis in diabetic organisms. Copyright © 2015. Published by Elsevier Inc.
- [Show abstract] [Hide abstract] ABSTRACT: A diagnosis of squamous cell carcinoma of an unknown primary (CUP) is a major burden for patients. Because the location of the primary tumor is unclear, patients remain fearful of recurrence, which aggravates the uncertain prognosis of the disease. This study evaluates factors associated with long-term recurrence-free and overall survival of patients with CUP of the head and neck. Additionally, patient survival rates are compared with those of patients with head and neck squamous cell carcinoma (HNSCC). A total of 293 consecutive patients operated on between January 1999 and December 2009 with at least a 5-year follow-up (survival permitting), were evaluated retrospectively. Twenty-six patients with a CUP of the head and neck were identified. Patients with CUP had a low overall survival rate, comparable with that of patients with pN + HNSCC, and recurrent disease occurred with a similar likelihood as in patients with pN + HNSCC. The median recurrence-free survival in the CUP group was 28.5 months compared with 48 months in the whole of the HNSCC group. The median overall survival of the CUP group was 56 months versus 65 months for the HNSCC group. Extracapsular spread was the only independent prognostic factor for overall survival for CUP patients. Patients diagnosed with CUP syndrome have a poorer prognosis for overall survival compared with other HNSCC patients. Postoperative radiotherapy diminished disease recurrence and improved overall survival. Omission of postoperative radiotherapy resulted in a very high recurrence rate (75%) for CUP patients. Based on these results we suggest postoperative radiotherapy including the oral mucosa for all patients, regardless of histopathological results, possible favorable nodal disease, or favorable lymph node ratios. Copyright © 2015 European Association for Cranio-Maxillo-Facial Surgery. Published by Elsevier Ltd. All rights reserved.
- [Show abstract] [Hide abstract] ABSTRACT: 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. Copyright © 2014 European Association for Cranio-Maxillo-Facial Surgery. Published by Elsevier Ltd. All rights reserved.
- [Show abstract] [Hide abstract] ABSTRACT: Fractures of the orbital wall and floor can be challenging due to the demanding three-dimensional anatomy and limited intraoperative overview. Misfitting implants and inaccurate surgical technique may lead to visual disturbance and unaesthetic results. A new approach using individually manufactured titanium implants (KLS Martin, Group, Germany) for daily routine is presented in the current paper. Preoperative CT-scan data were processed in iPlan 3.0.5 (Brainlab, Feldkirchen, Germany) to generate a 3D-reconstruction of the affected orbit using the mirrored non-affected orbit as template and the extent of the patient specific implant (PSI) was outlined and three landmarks were positioned on the planned implant in order to allow easy control of the implant’s position by intraoperative navigation. Superimposition allowsthe comparison of the postoperative result with the preoperative planning. Neither reoperation was indicated due to malposition of the implant and the ocular bulb nor visual impairments could be assessed. PSI allows precise reconstruction of orbital fractures by using a complete digital workflow and should be consideredsuperior to manually bent titanium mesh implants.
- [Show abstract] [Hide abstract] ABSTRACT: Objectives Clinical success of oral implants is related to primary stability and osseointegration. These parameters are associated with delicate surgical techniques. We herein studied whether template-guided drilling has a significant influence on drillholes diameter and accuracy in an in vitro model. Materials and methods Fresh cadaveric porcine mandibles were used for drilling experiments of four experimental groups. Each group consisted of three operators, comparing guide templates for drilling with free-handed procedure. Operators without surgical knowledge were grouped together, contrasting highly experienced oral surgeons in other groups. A total of 180 drilling actions were performed, and diameters were recorded at multiple depth levels, with a precision measuring instrument. Results Template-guided drilling procedure improved accuracy on a very significant level in comparison with free-handed drilling operation (p ≤ 0.001). Inaccuracy of free-handed drilling became more significant in relation to measurement depth. High homogenic uniformity of template-guided drillholes was significantly stronger than unguided drilling operations by highly experienced oral surgeons (p ≤ 0.001). Conclusion Template-guided drilling procedure leads to significantly enhanced accuracy. Significant results compared to free-handed drilling actions were achieved, irrespective of the clinical experience level of the operator. Clinical relevance Template-guided drilling procedures lead to a more predictable clinical diameter. It shows that any set of instruments has to be carefully chosen to match the specific implant system. The current in vitro study is implicating an improvement of implant bed preparation but needs to be confirmed in clinical studies.
- [Show abstract] [Hide abstract] ABSTRACT: PURPOSE: The placement of self-tapping implants is associated with microfractures and the formation of bone chips along the cutting flutes. This study was conducted to investigate the effect of different cutting edge angles on chip formation during the machining of trabecular and cortical bone using instruments with a rough titanium surface. MATERIALS AND METHODS: Mandibular cortical and trabecular bone specimens were obtained from freshly slaughtered domestic pigs. A predefined thrust force was applied to the specimens. Four specially designed cutting instruments that simulated dental implants and had a rough titanium surface were allowed to complete one full revolution at cutting edge angles of 55, 65, 75, and 85 degrees, respectively. Torque and thrust were measured during the cutting process. Bone chips were measured and weighed under a microscope. RESULTS: Different cutting edge angles did not lead to significant differences in torque. The lowest torque values were measured when the cutting edges were positioned at 65 degrees in trabecular bone and at 85 degrees in cortical bone. Bone chips were significantly larger and heavier at angles of 55 and 65 degrees than at angles of 75 and 85 degrees in trabecular bone. CONCLUSION: Instruments with a rough titanium surface show considerable angle-dependent differences in chip formation. In addition to bone density, the angle of the cutting edges should be taken into consideration during the placement of dental implants. Good results were obtained when the cutting edges were positioned at an angle of 65 degrees. This angle can have positive effects on osseointegration.
- [Show abstract] [Hide abstract] ABSTRACT: INTRODUCTION: Subperiosteal preparation using a periosteal elevator leads to disturbances of local periosteal microcirculation. Soft-tissue damage can usually be considerably reduced using piezoelectric technology. For this reason, we investigated the effects of a novel piezoelectric device on local periosteal microcirculation and compared this approach with the conventional preparation of the periosteum using a periosteal elevator. MATERIAL AND METHODS: A total of 20 Lewis rats were randomly assigned to one of two groups. Subperiosteal preparation was performed using either a piezoelectric device or a periosteal elevator. Intravital microscopy was performed immediately after the procedure as well as three and eight days postoperatively. Statistical analysis of microcirculatory parameters was performed offline using analysis of variance (ANOVA) on ranks (p<0.05). RESULTS: At all time points investigated, intravital microscopy demonstrated significantly higher levels of periosteal perfusion in the group of rats that underwent piezosurgery than in the group of rats that underwent treatment with a periosteal elevator. CONCLUSION: The use of a piezoelectric device for subperiosteal preparation is associated with better periosteal microcirculation than the use of a conventional periosteal elevator. As a result, piezoelectric devices can be expected to have a positive effect on bone metabolism.
- [Show abstract] [Hide abstract] ABSTRACT: In tissue engineering research, generating constructs with an adequate extent of clinical applications remains a major challenge. In this context, rapid blood vessel ingrowth in the transplanted tissue engineering constructs is the key factor for successful incorporation. To accelerate the microvascular development in engineered tissues, we preincubated osteoblast-like cells as well as mesenchymal stem cells or a combination of both cell types in Matrigel-filled PLGA scaffolds before transplantation into the dorsal skinfold chambers of balb/c mice. By the use of preincubated mesenchymal stem cells, a significantly accelerated angiogenesis was achieved. Compared with previous studies that showed a decisive increase of vascularization on day 6 after the implantation, we were able to halve this period and achieve explicitly denser microvascular networks 3 days after transplantation of the tissue engineering constructs. Thereby, the inflammatory host tissue response was acceptable and low, comparable with former investigations. A co-incubation of osteoblast-like cells and stem cells showed no additive effect on the density of the newly formed microvascular network. Preincubation of mesenchymal stem cells in Matrigel is a promising approach to develop rapid microvascular growth into tissue engineering constructs. After the implantation into the host organism, scaffolds comprising stem cells generate microvascular capillary-like structures exceptionally fast. Thereby, transplanted stem cells likely differentiate into vessel-associated cells. For this reason, preincubation of mesenchymal stem cells in nutrient solutions supporting different steps of angiogenesis provides a technique to promote the routine use of tissue engineering in the clinic.
- [Show abstract] [Hide abstract] ABSTRACT: Loosening or fracture of the abutment screw are frequent complications in implant dentistry and are detrimental to the long-term success of the restorations. However, little is known about the factors influencing the stability of the screw-abutment complex. The purpose of this study was to investigate the influence of lubricant action during implant assembly on screw preload and stresses in a dental implant-abutment complex. A dental implant was modeled for finite element stress analysis. Different friction coefficients (μ=0.2 to 0.5) were chosen for the interfaces between implant components to simulate lubricant action or dry conditions. The stress analyses were each divided into 2 load steps. First, the abutment screw was virtually tightened with a torque of 25 Ncm. This was achieved by applying an equivalent preload calculated according to the different friction coefficients chosen. Second, the construction was externally loaded with a force of 200 N inclined by 30 degrees relative to the implant axis. The screw preload increased with the decreasing friction coefficient. In all components, stresses increased with decreasing friction coefficient. Plastic deformation was observed at the implant neck in an area that expanded with decreasing friction coefficient. No plastic deformation occurred in the abutment. The results of this study indicated that screw preload should be included in the finite element analysis of dental implants for a realistic evaluation of stresses in the implant-abutment complex. The friction coefficient significantly influenced the screw preload value and modified the stresses in the implant-abutment complex.
- [Show abstract] [Hide abstract] ABSTRACT: Background As a prerequisite in navigation-assisted surgery, a three-dimensional image data set with registration marker is necessary. Often patients are presented, not being aware of facing a computer-assisted surgical intervention (CAS), with an already performed computed tomography (CT) data set without marker. The aim of this study was to evaluate the accuracy of a new method which allows performing CAS by enhancing the initial markerless data set with a marked subvolume gained by cone beam (CBCT) scan. Methods Therefore four registration markers are inserted and afterwards the patient is strongly limited to the field of interest scanned by CBCT scan (marked data set). Superimposed with the initial data set, a data set with reference markers and with full information is obtained. Registration procedure was performed with group A (25 patients, superimposed marked CBCT scan) and group B (25 patients, initially marked CT scan) using BrainLab (R) navigation by two observers and overall system accuracy was measured using the registration landmarks and additional intraoperative landmarks (tooth cusps). ResultsAdequate image quality assumed, no significant difference between group A and B was detected. Enhancing an initially performed data set with registration marker by using a marked subvolume could improve the workflow for navigation-assisted surgery due to the availability of cone beam scan technology, provide excellent resolution with reduced metal artifacts nearby dental restorations, and reduce radiation dose for the patient. Conclusion Regarding the advantages of the new method which allows performing CAS by enhancing the initial markerless data set with a marked subvolume gained by cone beam (CBCT) scan, this technique will play a major part in navigation-assisted surgery and will address widespread general methodological solutions that are of great interest in multidisciplinary treatment. Copyright (c) 2013 John Wiley & Sons, Ltd.
- [Show abstract] [Hide abstract] ABSTRACT: Bone marrow derived mesenchymal stem cells (bmMSC) are widely used for the generation of tissue engineering constructs, since they can differentiate into different cell types occurring in bone tissues. Until now their use for the generation of tissue engineering constructs is limited. All cells inside a tissue engineering construct die within a short period of time after implantation of the construct because vascularization and establishment of connections to the recipient circulatory system is a time consuming process. We therefore compared the influences of bmMSC, VEGF and a combination of both on the early processes of vascularization, utilizing the mice skinfold chamber model and intravital fluorescence microscopy. Tissue engineering constructs based on collagen coated Poly D,L-lactide-co-glycolide (PLGA) scaffolds, were either functionalized by coating with vascular endothelial growth factor (VEGF) or vitalized with bmMSC. PLGA without cells and growth factor were used as the control group. Functionalized and vitalized tissue engineering constructs showed an accelerated growth of micro vessels compared to controls. Only marginal differences in vascular growth were detected between VEGF containing and bmMSC containing constructs. Constructs containing VEGF and bmMSC showed a further enhanced microvascular growth at day 14. We conclude that bmMSC are well suited for bone tissue engineering applications, since they are a valuable source of angiogenic growth factors and are able to differentiate into the tissue specific cell types of interest. The dynamic process of vascularization triggered by growth factor producing cells can be amplified and stabilized with the addition of accessory growth factors, leading to a persisting angiogenesis, but strategies are needed that enhance the resistance of bmMSC to hypoxia and increase survival of these cells until the tissue engineering construct has build up a functional vascular system.
- [Show abstract] [Hide abstract] ABSTRACT: The aim of orbital wall reconstruction is to reestablish anatomically exact orbital volumes to avoid long-term complications. Navigation could facilitate complex reconstructions. Quality of the orbital reconstruction (n = 94) was measured based on (A) volume changes and (B) on 3D shape deviations compared to the unaffected side. Volume analysis included segmentation of the orbital cavity in the pre- and post-operative 3D data set (VoXim(R), IVS Solutions, Germany), and shape analysis was performed by vector-based 3D tools (Comparison(R), 3Dshape, Germany). Orbital volume of the unaffected side ranged from 26.6 ml +/- 2.8 ml in male and 25.2 ml +/- 2.6 ml in female (CT). Significant orbital enlargement was found in orbital fractures with involvement of the posterior third of the orbital floor and in comminuted fracture pattern. Reconstructed orbital volume ranged from 26.9 +/- 2.7 ml in male and 24.26 +/- 2.5 ml in female (CBCT). 3D Analysis of the color mapping showed minor deviations compared to the mirrored unaffected side. Measurements demonstrate that even in comminuted orbital fractures true-to-original reconstruction is feasible.
Article: Optic Nerve Monitoring[Show abstract] [Hide abstract] ABSTRACT: Orbital and anterior skull base surgery is generally performed close to the prechiasmatic visual pathway, and clear strategies for detecting and handling visual pathway damage are essential. To overcome the common problem of a missed clinical examination because of an uncooperative or unresponsive patient, flash visual evoked potentials and electroretinograms should be used. These electrophysiologic examination techniques can provide evidence of intact, pathologic, or absent conductivity of the visual pathway when clinical assessment is not feasible. Visual evoked potentials and electroretinograms are thus essential diagnostic procedures not only for primary diagnosis but also for intraoperative evaluation. A decision for or against treatment of a visual pathway injury has to be made as fast as possible due to the enormous importance of the time elapsed with such injuries; this can be achieved additionally using multislice spiral computed tomography. The first-line conservative treatment of choice for such injuries is megadose methylprednisolone therapy. Surgery is used to decompress the orbital compartment by exposure of the intracanalicular part of the optic nerve in the case of optic canal compression. Modern craniomaxillofacial surgery requires detailed consideration of the diagnosis and treatment of traumatic visual pathway damage with the ultimate goal of preserving visual acuity.
University Hospital ZürichZürich, Zurich, Switzerland
Hannover Medical School
Hanover, Lower Saxony, Germany
- Clinic for Cranio-Maxillo-Facial Surgery
Universität des Saarlandes
Homburg, Saarland, Germany
- • Institut für Medizinische Mikrobiologie und Hygiene
- • Institut für Klinisch-Experimentelle Chirurgie