Martin Rücker

University Hospital Zürich, Zürich, Zurich, Switzerland

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Publications (133)267.62 Total impact

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    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.
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    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.
    Journal of Cranio-Maxillofacial Surgery 03/2015; 43(4). DOI:10.1016/j.jcms.2015.03.004 · 2.60 Impact Factor
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    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.
    Journal of Cranio-Maxillofacial Surgery 12/2014; 43(3). DOI:10.1016/j.jcms.2014.12.003 · 2.60 Impact Factor
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    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.
    Journal of Cranio-Maxillofacial Surgery 10/2014; DOI:10.1016/j.jcms.2014.10.024 · 2.60 Impact Factor
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    ABSTRACT: 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.
    Clinical Oral Investigations 10/2014; DOI:10.1007/s00784-014-1346-7 · 2.29 Impact Factor
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    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.
    The International journal of oral & maxillofacial implants 07/2014; 29(4):942-948. DOI:10.11607/jomi.3499 · 1.49 Impact Factor
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    ABSTRACT: 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.
    Microvascular Research 06/2014; DOI:10.1016/j.mvr.2014.06.003 · 2.43 Impact Factor
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    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.
    Journal of Biomedical Materials Research Part A 06/2014; 102(6). DOI:10.1002/jbm.a.34826 · 2.83 Impact Factor
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    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.
    The Journal of prosthetic dentistry 02/2014; DOI:10.1016/j.prosdent.2013.10.016 · 1.42 Impact Factor
  • 01/2014; 4(1):22. DOI:10.4103/0974-6781.130949
  • International Journal of Oral and Maxillofacial Surgery 10/2013; 42(10):1255. DOI:10.1016/j.ijom.2013.07.287 · 1.36 Impact Factor
  • International Journal of Oral and Maxillofacial Surgery 10/2013; 42(10):1236. DOI:10.1016/j.ijom.2013.07.227 · 1.36 Impact Factor
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    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.
    International Journal of Medical Robotics and Computer Assisted Surgery 09/2013; 9(3). DOI:10.1002/rcs.1444 · 1.53 Impact Factor
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    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.
    Microvascular Research 07/2013; DOI:10.1016/j.mvr.2013.07.006 · 2.43 Impact Factor
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    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.
    Head & Face Medicine 07/2013; 9(1):18. DOI:10.1186/1746-160X-9-18 · 0.87 Impact Factor
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    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.
    Craniomaxillofacial Trauma and Reconstruction 06/2013; 6(2):75-86. DOI:10.1055/s-0033-1343783
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    ABSTRACT: Since introduction to the clinics in the 1990s, resorbable osteosynthesis systems have undergone extensive improvements in order to establish their use as a standard treatment, especially in craniomaxillofacial surgery. However, the development of osteosynthesis systems made of poly(α-hydroxy acid) polymers has been hindered by the lack of information on the mechanical properties and biocompatibility of these materials. Moreover, magnesium-based degredable osteosynthesis materials have not yet been integrated into clinical practice owing to biocompatibility problems. Osteosynthesis systems made from nonresorbable titanium alloys have shown excellent biocompatibility, stability and individual fitting to the implant bed, so these materials are currently considered the 'gold standard'. The procedure of plate removal has been subjected to intense scrutiny and controversy. Bioresorbable materials are indicated for special conditions, such as osteosynthesis of the growing skull or orbital floor reconstructions. This paper presents an overview of the currently available and investigated resorbable osteosynthesis materials in comparison with the nonresorbable 'gold standard' titanium. The main problem areas such as sterilization, biocompatibility and stability are highlighted and perspectives for further improvements are provided.
    Pathobiology 01/2013; 80(4):211-7. DOI:10.1159/000348328 · 2.32 Impact Factor
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    ABSTRACT: Changes in ambient pressure occur during flying, diving, or hyperbaric oxygen therapy and can cause different types of pathophysiological conditions and pain including toothache (barodontalgia). We report the case of a patient with severe pain in the region of his mandibular left first molar, which had been satisfactorily restored with a conservative restoration. Pain occurred during an airplane flight and persisted after landing. Radiology revealed a periapical radiolucency in the region of the distal root apex. Pain relief was achieved only after endodontic treatment. On the basis of this paper, we investigated the aetiology and management of barodontalgia. Dentists should advise patients to avoid exposure to pressure changes until all necessary surgical, conservative, and prosthetic procedures have been completed. The influence of pressure divergences should be noted at any time. Under changed environment pressures may be the changing perception of pathologies.
    12/2012; 2012:453415. DOI:10.1155/2012/453415
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    ABSTRACT: Ablative surgery of the orbit is often associated with dramatic changes in facial geometry. Surgical intervention is often necessary to correct the functional and esthetic appearance in those patients who are anophthalmic, having an intact eyelid appearance and an orbital prosthesis. The outcome of the surgical correction depends on the shape of the orbital implants and their adequate placement. In the case of comparatively small rearrangements, the effect of implants on soft tissues can be estimated by surgeons on the basis of their experience. However, large deformities in complex cases (including large deformation of soft tissue or asymmetry) can be hardly predicted on the basis of simple empirical considerations. The purpose of the present technical note was to describe a new procedure of inverse design of customized orbital titanium meshes. To demonstrate this procedure, an anophthalmic patient with superior sulcus deformity and enophthalmos was enrolled. The volume and structure of the extraocular muscles, soft tissue, and bony structure of the orbital walls were examined using high-resolution multislice computed tomography. Next, a geometric model of the patient's anatomy was generated from the tomography data. Afterward, the orbital prosthesis was virtually relocated to a new position. Then, the desired correction of the particular soft tissue regions was performed using virtual sculpturing tools. Next, the deformation of the soft tissues and initial prosthesis boundaries were computed from the predefined displacements of the relocated tissue regions with the help of the Finite Element Method. The differential volume between the initial and designated position of the orbital prosthesis yielded the preferred implant shape required to effect the desired correction of soft tissue. During surgery, the preplanned position of the customized titanium meshes was guided using a navigation system. Although the inverse design of custom-tailored titanium meshes for precision treatment of severe enophthalmos in anophthalmic patients appears to be a promising approach, it has rarely been applied in the past because of the technological complexity and additional time required. With the present study, we have launched a series of clinical evaluations of this novel method. To date, scientific evidence and trials showing a predictable simulation using an inverse finite element approach in the correction of severe enophthalmos in anophthalmic patients with computer-assisted fabricated individual titanium meshes for reconstruction of orbital walls have been rare.
    Journal of oral and maxillofacial surgery: official journal of the American Association of Oral and Maxillofacial Surgeons 11/2012; 70(11):e631-8. DOI:10.1016/j.joms.2012.07.028 · 1.28 Impact Factor
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    ABSTRACT: Aim. To measure and validate the permeability of pressure changes in correlation to different root filling techniques. Methods. Eighty extracted single-rooted teeth were randomly assigned to one of eight groups of ten teeth. Following standardized instrumentation and irrigation, root canal fillings were performed using either cold lateral condensation, a warm carrier-based gutta-percha obturation technique, a warm carrier-based Resilon, or warm gutta-percha compaction with the downpack/backfill technique. After insertion of a pressure sensor within the pulp chamber ten teeth of each group then underwent simulated dives with pressure measurement and the other ten a dye penetration test during simulated dives to 5.0 bar. Differences were analyzed statistically (P < 0.05) using one-way analysis of variance (ANOVA). Results. When the warm carrier-based gutta-percha obturation technique and vertical gutta-percha obturation techniques were used, there was significant lower intrapulpal pressure to experimental chamber pressure (P > 0.05). When cold lateral condensation or carrier-based Resilon as used, pressure was sometimes almost completely equalized. Conclusions. Warm gutta-percha obturation techniques provide a largely pressure-tight seal whereas the Resilon obturation technique and cold lateral condensation appear to be unsuitable to pressure changes.
    10/2012; 2012:418609. DOI:10.5402/2012/418609

Publication Stats

1k Citations
267.62 Total Impact Points

Institutions

  • 2014–2015
    • University Hospital Zürich
      Zürich, Zurich, Switzerland
    • University of Zurich
      Zürich, Zurich, Switzerland
  • 2005–2014
    • Hannover Medical School
      • Clinic for Cranio-Maxillo-Facial Surgery
      Hanover, Lower Saxony, Germany
  • 2009–2010
    • Center For Oral & Maxillofacial Surgery
      Georgia, United States
  • 1996–2010
    • Universität des Saarlandes
      • • Institut für Medizinische Mikrobiologie und Hygiene
      • • Institut für Klinisch-Experimentelle Chirurgie
      Saarbrücken, Saarland, Germany
  • 2008
    • Bundeswehrzentralkrankenhaus Koblenz
      Coblenz, Rheinland-Pfalz, Germany
  • 2006
    • University of Rostock
      Rostock, Mecklenburg-Vorpommern, Germany
  • 1998
    • Deutsche Gesellschaft für Mund-, Kiefer- und Gesichtschirurgie e.V.
      Homburg, Saarland, Germany