Biomedical subjects

U Joos

Publications and source records attributed to U Joos.

At least 19 recordsLinked to original sources

PubMed2006

Reconstruction of large defects on the scalp and forehead as an interdisciplinary challenge: experience in the management of 39 cases.

AIMS: To describe options and indications for different surgical reconstruction techniques after resection of large skin tumours on the scalp taking into account an interdisciplinary approach of cranio-maxillofacial surgeon, dermatologist, and neurosurgeon, and to evaluate complications and postoperative outcome. PATIENTS AND METHODS: From a total of 39 patients with large skin tumour resections on the scalp and/or the forehead, treated between January 01, 1995 and June 30, 2005, a number of 42 surgical reconstructions were performed. The medical histories, the surgical treatment, postoperative complications, follow-up and outcome were evaluated. RESULTS: The excision defects measured 146 cm(2) (range: 80.6-546 cm(2)) on average. The most common methods for defect closure were multiple rotation-advancement flaps (n=19). Six patients were treated with split-thickness skin grafts after bone drilling for inducing granulation tissue to grow. Free latissimus dorsi muscle flaps were used in 8 patients and radial forearm flaps in 4 cases. Postoperative complications were rare. An algorithm for the surgical approach to large scalp defects was developed. CONCLUSION: For reconstruction of large defects on the scalp and forehead, various reliable methods may be used with regard to individual patient-specific parameters in cooperation with different medical specialties involved.

Aged↗

PubMed2006

Mineralization at the interface of implants.

Osseointegration of implants is crucial for the long-term success of oral implants. Mineralization of the bone's extracellular matrix as the ultimate step of a mature bone formation is closely related to implant osseointegration. Osteogenesis at oral implants is a complex process, driven by cellular and acellular phenomena. The biological process of the maintenance and emergence of minerals in the vicinity of oral implants is influenced to a great extent by biophysical parameters. Implant-related structural and functional factors, as well as patient-specific factors, govern the features of osteogenesis. To understand the influence of these factors in peri-implant bone mineralization, it is important to consider the basic biological processes. Biological and crystallographic investigations have to be applied to evaluate mineralization at implant surfaces at the different hierarchical levels of analysis. This review gives insight into the complex theme of mineral formation around implants. Special focus is given to new developments in implant design and loading protocols aimed at accelerating osseointegration of dental implants.

Bone and Bones↗

PubMed2006

Technical and clinical assessment of the use of a new material-based splint in orthognathic surgery.

Heat or auto-cured acrylic resins are materials that are commonly used in splint construction. Newly developed light-cured resins hold promise in view of the altered characteristics of the material. The aim of this study was to evaluate how far light-curing resin-based splints can be used in orthognathic surgery. Over a period of 1 year, 141 orthognathic surgeries were planned and performed using randomly chosen light-cured splints versus auto-polymerized splints. The performance of splint fabrication, the model planning and the clinical use were assessed by different measurements. The dental technician, the orthodontist and the surgeon evaluated objective parameters (model damage, fabrication time, accuracy of registration, adjustment time) as well as subjective criteria (handling). This study revealed that the use of light-curing splints significantly improved the accuracy (97.7% versus 81.2% in the case of acrylic materials). Less time was needed for the fabrication and adjustment of the splint. There was concomitantly less model damage to be observed when light-curing resins were used (9.2% versus 83.5%) and subjective measurements revealed significantly better handling of light-curing resin-based splints. Light-curing resin splints used in orthognathic surgery seem to be advantageous.

Acrylic Resins↗

PubMed2006

Surgical reconstruction after subtotal ear resection in malignant melanoma of the ear.

Surgery in malignant melanoma of the external ear often leads to substantial defects where reconstruction poses a difficult challenge. We describe an option of a one-step ear reconstruction after subtotal ear resection in malignant melanoma surgery. In a patient with a high-risk melanoma of the helical rim, a wide local excision was performed. Because of a metastasis-suspect lymph node in the parotid gland, surgery included asservation of the sentinel lymph node, neck dissection and parotidectomy. A complete reconstruction of the ear was achieved using a bilobed flap from the retroauricular and neck region with acceptable cosmetic and functional results by one-step surgery. One micrometastasis was detected in the nuchal region but not in the marked sentinel lymph node. An adequate one-step ear reconstruction as described may also be performed to the benefit of patients with high-risk melanomas, allowing early adjuvant therapy.

Adult↗

PubMed2005

Basic reactions of osteoblasts on structured material surfaces.

In order to assess how bone substitute materials determine bone formation in vivo it is useful to understand the mechanisms of the material surface/tissue interaction on a cellular level. Artificial materials are used in two applications, as biomaterials alone or as a scaffold for osteoblasts in a tissue engineering approach. Recently, many efforts have been undertaken to improve bone regeneration by the use of structured material surfaces. In vitro studies of bone cell responses to artificial materials are the basic tool to determine these interactions. Surface properties of materials surfaces as well as biophysical constraints at the biomaterial surface are of major importance since these features will direct the cell responses. Studies on osteoblastlike cell reactivity towards materials will have to focus on the different steps of protein and cell reactions towards defined surface properties. The introduction of new techniques allows nowadays the fabrication of materials with ordered surface structures. This paper gives a review of present knowledge on the various stages of osteoblast reactions on material surfaces, focused on basic cell events under in vitro conditions. Special emphasis is given to cellular reactions towards ordered nano-sized topographies.

Biocompatible Materials↗

PubMed2005

[Osteoblast reaction on SLA and microgrooved implant surfaces].

The osseointegration process of dental implants depends on the tissue reaction at the tissue-implant interface. Osteoblasts are the main cells responsible for the regulation of osteoinduction. The manner and kinetics of the tissue reaction crucially depend on the interaction between osteoblasts and the morphology of the implant surface. The aim of this study was to investigate osteoblast behaviour on different implant surfaces (smooth, microgrooved, SLA) under standardized conditions. For this in vitro investigation we used primary bovine osteoblasts. Attachment kinetics, proliferation rate and synthesis of bone-associated proteins were used as parameters for cell reaction. The results demonstrate that both attachment and adhesion strength of the primary cell surface interaction was higher on the microgrooved surfaces than on SLA surfaces. The proliferation rate of cells and the synthesis of bone-specific proteins were higher on microgrooved surfaces in contrast to SLA surfaces. Ultrastructural analysis revealed phenotypic osteoblast-like cells on smooth and microgrooved surfaces, whereas cells on SLA surfaces showed a more fibroblastic appearance. This study demonstrates that the morphology of the implant surface determined the subsequent osteoblast reaction. An optimal cell reaction was found at surfaces which are smooth in the microenvironment of osteoblasts.

Animals↗

PubMed2005

[Aggressive fibromatosis in the jaw and facial region with bone involvement. A review].

BACKGROUND: Aggressive fibromatosis (AF) involving bones of the head is rare and surgery is often complicated by a high recurrence rate. Interdisciplinary treatment is of the utmost importance to avoid extensive, mutilating resection. Two cases emphasize the difficulties in the management. CASE REPORTS: A 67-year-old woman was referred to our unit with a blepharochalasis of the left upper palpebra and a palsy of the face on the left side. Her medical history included 12 operations over the previous 4 years for an extensive AF. MATERIAL AND METHODS: Our review includes all case reports of AF involving bones of the head published between 1960 and 2004. Additionally, our two cases are presented. Signs, symptoms and outcome were analyzed in relation to different treatment options. CONCLUSION: According to the literature, surgery is the most common treatment for AF in the head and neck region. Alternative modes of therapy must be considered because of the high recurrence rate and to avoid mutilating operations.

Aged↗

PubMed2005

Catenin expression in T1/2 carcinomas of the floor of the mouth.

Reduction of the expression of catenin is a crucial step in the pathogenesis, progression and prognosis of many epithelial cancers including squamous cell carcinomas (SCCs). Catenin expression in oral carcinomas was evaluated in relation to clinico-pathological features in order to determine its value as a prognostic marker. Eighty-five patients with histologically proven T1/2 squamous cell carcinoma of the oral floor who underwent surgical treatment were eligible for the study. A tissue microarray consisting of multiple representative tissue cores of each carcinoma was composed. The expression levels of alpha, beta and gamma-catenins were determined immunohistologically. Correlation between clinical features and the expression of catenin proteins was evaluated statistically using Kaplan-Meier curves, log-rank tests and chi(2)-tests. Loss of alpha-catenin expression in carcinoma of the floor of the mouth correlated significantly with poor prognosis (P=0.05). Conversely, significantly reduced rates of lymph-node metastases were observed in alpha- and beta-catenin-positive T1 and T2 SCCs. Loss of gamma-catenin expression indicated a reduced survival rate in nodal-negative tumours (P=0.02). Catenin expression in carcinomas of the floor of the mouth seems to be a predictive parameter in the prognosis of T1 and T2 SSCs.

Adult↗

PubMed2005

Score system for elective tracheotomy in major head and neck tumour surgery.

BACKGROUND: This study was designed to evaluate prognostic parameters for respiratory failure after major oropharyngeal resections in head and neck cancer surgery, focusing on a score system to identify patients requiring an elective tracheotomy and to avoid tracheotomy under emergency conditions. METHODS: One hundred and fifty-two out of 928 patients with oropharyngeal cancers, treated between January 1993 and June 2000 at our hospital, fulfilled the inclusion criteria for a retrospective analysis. This collective underwent tumour resection in different regions of the oropharynx combined with bony resection of the mandible and neck dissection without primary tracheotomy. The reconstruction was accomplished using radial forearm flaps (n1 = 59) or local flaps (n2 = 93). These two groups were subdivided into patients treated post-operatively by tracheotomy due to respiratory failure (n1 = 26; n2 = 12) and those without such treatment (n1 = 33; n2 = 81). The database comprising tumour localization and size, staging, general medical condition, smoking and alcohol consumption was evaluated by logistic regression. RESULTS: We developed a score system which predicts the likelihood of post-operative respiratory failure. For indication of tracheotomy, tumour size and localization, multimorbidity, alcohol consumption and pathologic chest X-ray findings were identified as significant parameters with different weightings. The predictive value for tracheotomy (yes/no) using the score system was 96.7% for the total collective. CONCLUSION: The decision on whether or not an elective tracheotomy in major head and neck tumour surgery is necessary can be facilitated using this score system which is based on objective facts. It may reduce post-operative complications and contribute to safer treatment.

Adult↗

PubMed2004

[Peri-implant bone formation around cylindrical and conical implant systems].

BACKGROUND: The treatment of patients with early or immediately loaded dental implants has renewed interest in the behavior of osseointegration at the implant surface. Whereas it is generally accepted that peri-implant tissue formation and mineralization are dependent on the local mechanical environment in the interface zone, controversies exist concerning the impact of implant design on peri-implant bone formation. The aim of the present study was the in vivo evaluation of peri-implant bone formation by two different implant systems: cylindrical (ITI) versus conical (ILI). MATERIAL AND METHOD: A total of 60 implants (30 ITI and 30 ILI) were placed in the cranial and caudal part of the tibia of eight Göttinger minipigs. Half of the minipigs were sacrificed at 7 days and 28 days of osseointegration. Implant-containing bone specimens were prepared for histological and ultrastructural investigations. RESULTS: Histological and scanning electron-microscopic investigations showed a direct contact of bone-like minerals over the whole implant surface from day 7 of implant/bone interaction. Whereas the ILI implant showed direct contact up to the top of the crestal bone, ITI implants demonstrated a crestally located narrow gap without ossification over the whole experimental period. CONCLUSION: Our investigations support the hypothesis of an implant design-inherent emergence and maintenance of crestal bone.

Animals↗

PubMed2004

Ultrastructural characterization of the implant/bone interface of immediately loaded dental implants.

Primary stability and an optimized load transfer are assumed to account for an undisturbed osseointegration process of implants. Immediate loaded newly designed titanium dental implants inserted in the mandible of minipigs were used for the characterization of the interfacial area between the implant surface and the surrounding bone tissue during the early healing phase. Histological and electron microscopical studies were performed from implant containing bone specimens. Two different load regimens were applied to investigate the load related tissue reaction. Histological and electron microscopical analysis revealed a direct bone apposition on the implant surfaces, as well as the attachment of cells and matrix proteins in the early loading phase. A striking finding of the ultrastructural immunocytochemical investigations was the synthesis and deposition of bone related proteins (osteonectin, fibronectin, fibronectin receptor) by osteoblasts from day one of bone/biomaterial interaction. Calcium-phosphate needle-like crystallites were newly synthesized in a time-related manner directly at the titanium surface. No difference in the ultrastructural appearance of the interface was found between the two loading groups. Our experimental data suggest that loading of specially designed implants can be performed immediately after insertion without disturbing the biological osseointegration process.

Animals↗

PubMed2004

Biological and biophysical principles in extracorporal bone tissue engineering. Part II.

The aim of this review is to characterise the biological and biophysical background of in vitro bone tissue engineering. The paper focuses on basic principles in extracorporal engineering of bone-like tissues, considering parameters such as scaffold design, tissue construction, bioreactors, and cell stimulation in vivo and in vitro. Scaffolds have a key function concerning cellular invasion and bone formation. The intra-architectural scaffold geometry, as well as the scaffold material, play an important role in the process of bone regeneration. Various types of bioreactors have been tested for their utility in bone substitute fabrication that is clinically effective and reproducible. Sophisticated bioreactor systems are those that mimic the three-dimensional morphology and the mechanical situation of bones. Mechanical stimulation as well as other biophysical stimuli appear to be critical factors for proliferation and differentiation of bone cells and for bone mineral and structure formation. Furthermore an enhancement of bone regeneration by application of chemical stimulation factors is discussed.

Animals↗

PubMed2004

Biological and biophysical principles in extracorporal bone tissue engineering. Part III.

Over the last decade extracorporal bone tissue engineering has moved from laboratory to clinical application. The restoration of maxillofacial bones from cell harvesting through product manufacture and end-use has benefited from innovations in the fields of biomechanical engineering, product marketing and transplant research. Cell/scaffold bone substitutes face a variety of unique clinical challenges which must be addressed. This overview summarises the recent state of the art and future anticipations in the transplantation of extracorporally fabricated bone tissues.

Animals↗

PubMed2004

Biological and biophysical principles in extracorporal bone tissue engineering. Part I.

Advances in the field of bone tissue engineering have encouraged physicians to introduce these techniques into clinical practice. Bone tissue engineering is the construction, repair or replacement of damaged or missing bone in humans or animals. Engineering of bone can take place within the animal body or extracorporal in a bioreactor for later grafting into the body. Appropriate cell types and non-living substrata are minimal requirements for an extracorporal tissue engineering approach. This review discusses the biological and biophysical background of in vitro bone tissue engineering. Biochemical and biophysical stimuli of cell growth and differentiation are regarded as potent tools to improve bone formation in vitro. The paper focuses on basic principles in extracorporal engineering of bone-like tissues, intended to be implanted in animal experiments and clinical studies. Particular attention is given in this part to the contributions of cell and material science to the development of bone-like tissues. Several approaches are at the level of clinical applicability and it can be expected that widespread use of engineered bone constructs will change the surgeon's work in the near future.

Animals↗

PubMed2004

Combined space management through Delaire/Joos osteotomy and postoperative orthodontic treatment. A retrospective longitudinal study.

The diagnostic records of all patients who had undergone Delaire/Joos osteotomy with mandibular setback at the Muenster University Hospital (period 1995-2000, n=22) were used for space management evaluation in the context of combined surgical-orthodontic treatment.Twenty-eight dental spaces were present prior to the start of treatment and 14 were created by extracting teeth as a pretreatment measure. In two patients, unilateral setback was performed according to Obwegeser/Dal Pont. Thus, 42 tooth-bounded spaces were present at the time of Delaire/Joos osteotomy with mandibular setback, most of them in the first molar region, followed by the second premolar region. A significant space reduction was achieved by the surgical intervention, but not by the subsequent orthodontic treatment. The best results with respect to complete space closure by orthognathic surgery/orthodontic treatment without the need for subsequent prosthetic rehabilitation were recorded in the second premolar region. In the absence of spaces and with a similar long-term prognosis for all potentially extractable teeth and adequate space for the necessary surgical repositioning, the second premolars should therefore be regarded as the 'extraction teeth of choice' for mandibular setback within the context of Delaire/Joos osteotomy.

Adolescent↗

PubMed2003

[Primary implant stability with different bone surgery techniques. An in vitro study of the mandible of the minipig].

The treatment concept of osseointegration is based on a stable embodiment of implants in bone and the maintenance of stability during functional load. A goal of the surgical preparation technique is therefore to obtain a stable and firm implant anchorage. The aim of this study was to evaluate implant stability after different surgical treatment of the bony implantation bed. Thirty cylindrical solid-screw-shaped implants with standard SLA ITI configuration were implanted into the explanted mandibles of five minipigs. The implant sites were prepared either by a conventional burr technique (group A), by burr technique with additional thread cutting (group B), or by the osteotome technique (group C). Primary implant stability was evaluated by resonance frequency analysis and removal torque test. The average value of the resonance frequency analysis (RFA) was 6000+/-469 cycles/s in group A, 5700+/-557 cycles/s in group B, and 5540+/-527 cycles/s in group C. Removal torque values of group A (507+/-57 Nmm) were significantly higher than those of group B (466+/-45 Nmm) and group C (240+/-31 Nmm) (between group A and C p<0.05, group A to B p=0.39, and B to C p<0.05). It can be concluded from this study that the conventional burr technique achieves a statistically significantly better primary bone anchorage than the osteotome technique.

Animals↗

PubMed2003

[Odontogenic foci--possible etiology of urticaria?].

Recent studies have shown that chronic odontogenic infections could pose a risk for myocardial infarction, cerebral ischemia, and arteriosclerosis. However, the correlation between urticaria and dental infections has rarely been examined so far. Therefore, we performed a case-control study using a standardized questionnaire and examination. We investigated 66 patients suffering from an acute or chronic urticaria and 65 age- and sex-matched healthy patients as a control group. Dental status was determined by a so-called total dental index (TDI) which primarily reflects caries, periodontitis, periapical lesions, and nonvital and missing teeth. All 66 patients were referred from the department of dermatology. After their treatment in hospital, all patients received a questionnaire with questions on intensity and localization of the urticaria. The TDI of the urticaria patients was slightly better ( n=66; 2.6+/-1.98) than that of the control group ( n=65, TDI=3.3+/-1.86). Subsequently, it was determined if the urticaria had receded after dental treatment. In conclusion, chronic dental infections do not seem to correlate with an increased risk for urticaria.

Adult↗

PubMed2003

[Experimental and clinical study of the stability of an osteosynthesis plate for the atrophic mandible].

BACKGROUND: The high rate of complications led us to develop a new osteosynthesis plate for the treatment of the fractured atrophied mandible. The development of the new so-called pencil-bone plate is based on the 2.0 mini-plate system manufactured by the Medartis Company. MATERIAL AND METHODS: Finite elements (FE) analysis of the new plate as well as flexibility experiments were undertaken, and 14 patients with 16 fractures of the atrophied mandible were treated with the pencil-bone plate between October 2000 and November 2001. RESULTS: The results clearly show that the pencil-bone plate reacted in both the FE model and the static flexibility experiment in a more stable way than a standard 2.0 plate. In 13 patients, healing proceeded without serious complications; all of the patients showed subjective, nearly unchanged chewing, speaking, and swallowing abilities and no complications occurred when wearing dentures. One patient underwent surgical intervention after a new trauma. CONCLUSION: The clinical outcome of the treated fractures confirmed the experimental results, which proved the high stability of the plate in the area of the fracture site. Due to the mini-plate format the intraoral application of the plate is possible without problems. The intraoral access allows rapid operation followed by a minimum of morbidity. A great advantage of the small dimension system is the unrestricted wearing of dentures after the application.

Aged↗