Biomedical subjects

U Joos

Publications and source records attributed to U Joos.

At least 73 records · Page 4Linked to original sources

PubMed1999

[Regeneration of mouth mucosa in the buccal plane following graft procurement for reconstruction of bulbar urethral stenoses].

The use of free buccal mucosal grafts in the treatment of urethral strictures has become very popular. In 1996 and 1997 we harvested free buccal mucosal grafts up to 7 cm long and 4 cm wide from 12 patients who underwent urologic surgery for urethral strictures. In 2 patients the donor site was closed primarily by sutures. Four patients received Lyodura and another 4 patients received Syspurderm as temporary wound coverage. In 2 patients Ethisorp patches were used. Donor site pain was judged by the patients on a visual analogue scale during the first postoperative week. The 2 patients who received the Ethisorp patches complained of more intense pain, probably caused by the rigidity of the material. In all patients regeneration of the donor site mucosa was good. During the follow-up period of 4-18 months scar formation at the lower vestibulum was noticed as the only complication. Permanent limitation of mouth opening, stenosis of the parotid duct or hypesthesia did not occur.

Adolescent↗

PubMed1999

[Examining patients with facial skull fractures from an etiological and legal perspective].

Maxillofacial traumas are common and often associated with other injuries. From a forensic point of view, it is often necessary to relate the traumatic event to the subsequent injuries. The aim of this study was to explore the etiology of maxillofacial injuries due to objective signs and the anamnestic history of patients. In a prospective study over a 1-year period, all patients presenting with mandibular and midface fractures seeking treatment at the University Medical Center in Münster. Germany, were investigated. Demographic data, patient history, and pattern and etiology of injury were recorded, along with evaluations of the patients' descriptions. Thorough clinical and radiological investigation was performed and photographic records were taken. In our study, 122 patients, with a male to female ratio of 2:1 were included. The mean age was 30.7 +/- 13.4 years. Assault was the most common etiology (40%), followed by traffic accidents (29%) and falls (17%). Alcohol was reported to play a role in 40% of all injuries. There was no difference in the number of patients with mandibular or midface fractures. In 75%, maxillofacial fractures were associated with other injuries. The patients' descriptions of the orofacial traumas seemed to be highly. For age, anatomical location, concomitant injuries, and other signs of trauma, we found no statistical association with the underlying etiology.

Adolescent↗

PubMed1999

Use of a mandibular fracture score to predict the development of complications.

PURPOSE: Mandibular fractures are common facial injuries. Classifications are diverse and sometimes correlated with specific treatment modalities. Osteosynthesis using plate and screws is the standard method of fracture treatment. To evaluate the outcome of such fracture management in our clinic, we developed a numeric scoring system for mandibular fractures and investigated the relationship between the scoring of the fracture being treated and the incidence of complications after surgical treatment. PATIENTS AND METHODS: Seventy-six adult patients treated over a 2-year period were evaluated, and the fractures were classified using the mandibular trauma score. This score was based on clinical and radiologic evaluation of each fracture line and ranks from 0 to 15 points. Osteosynthesis was performed using the AO plate systems. Patients were followed-up postoperatively for the presence of complications. RESULTS: During the 2-year period, 76 patients with 134 fractures underwent plate osteosynthesis. Fracture scoring indicated a homogeneous distribution between uncomplicated and severe fractures. The incidence of complications increased with the fracture severity, assessed by the fracture score index. Severe fractures showed fewer complications when treated with a rigid plate system, whereas low-score fractures showed better results when treated with less rigid systems. CONCLUSIONS: The numeric scoring system for mandibular fractures allows an objective and standardized assessment of the degree of severity of a fracture and may facilitate decisions about the use of specific treatment modalities.

Adult↗

PubMed1999

The effect of magnitude and frequency of interfragmentary strain on the tissue response to distraction osteogenesis.

PURPOSE: Bone regeneration is believed to be partially controlled by the applied local mechanical strain. To test whether the magnitude or frequency of discontinuous traction regulates the tissue response, defined daily strains were applied on mandibular osteotomies using an implanted mechanical distractor. MATERIALS AND METHODS: Unilateral mandibular osteotomies were performed in skeletally immature rabbits (n = 36). and distraction was done by applying 2,000, 20,000, 200,000, or 300,000 microstrains once or 10 times (2,000, 20,000 microstrains) per day, respectively. Sham-operated animals (n = 6), serving as controls, underwent frame application and osteotomy without distraction. At the end of the distraction process, the newly formed tissue was evaluated histomorphometrically by the use of a well-defined scoring system of bone-forming indices. RESULTS: The highest bone-forming indices were detected in the osteotomized, nondistracted group and in samples exposed to a physiologic strain (2,000 microstrains). Application of hyperphysiologic strains (200,000 and 300,000 microstrains) resulted in the formation of fibrous tissue and decreased bone-forming indices. Using Kruskal-Wallis tests, a statistically significant relationship was found between the bone-forming indices and the applied strain magnitudes. Scanning and transmission electron microscopic examinations showed osteoblastic differentiation and early mineral deposition in samples distracted up to 20,000 microstrains, whereas higher strain magnitudes led to the formation of fibroblast-like cells surrounded by collagen fibrils and only slight mineralization. Multiple strain applications (10 cycles/d vs 1 cycle/d) did not alter the histomorphometric indices or ultrastructural morphology significantly but increased the amount of newly formed tissue. CONCLUSIONS: These results suggest that the magnitude and not the frequency of mechanical loading controls the differentiation of bone cells and the subsequent formation of bone tissue.

Analysis of Variance↗

PubMed1999

Rehabilitation with dental implants of oral cancer patients.

The aim of this study was to evaluate the risks and complications of rehabilitation with dental implants after tumour surgery and radiotherapy. After a disease-free survival of 18 months, 29 patients who had undergone oral cancer treatment were rehabilitated with dental implants. The complication rate of implants in irradiated, non-irradiated and grafted bone was analyzed at least 3 years after implant placement. In the healing period, 28.6% of the implants in irradiated bone and 8.4% in non-irradiated bone showed soft tissue complications. Of the implants, 26.7% in the irradiated and 14.7% in the non-irradiated mandibular bone were lost in the first 36 months after placement. Thirty-one point two percent of implants inserted in non-irradiated bone grafts were affected and did not osseointegrate. Of 109 inserted implants, 70 were suitable for prosthetic rehabilitation. There are high complication rates after implant placement in oral cancer patients. Irradiation adversely affects soft tissue healing. Osseointegration is frequently disturbed, especially when implants were placed in non-vascularized bone grafts.

Adult↗

PubMed1999

Decreased expression of osteocalcin and osteonectin in relation to high strains and decreased mineralization in mandibular distraction osteogenesis.

In a rabbit model of mandibular distraction osteogenesis, high strains resulted in a substantial reduction in the expression rate of the two osteogenic marker proteins, osteocalcin and osteonectin. In non-distracted samples and mandibles exposed to 2000 microstrains, staining for osteocalcin in the osteotomized area was detected in osteoblasts and diffusely dispersed in the mineralized matrix of the surrounding bone. However, in osteotomized mandibles distracted at strains above physiological levels (200,000 and 300,000 mustrains, respectively) the majority of osteoblast-like cells failed to express immunodetectable amounts of osteocalcin. Similarly, in the extracellular matrix of the distraction area the expression of osteonectin decreased by applying higher strains. Ultrastructural analyses of mandibular samples exposed to hyperphysiological strains revealed that the reduced expression rate of osteocalcin and osteonectin was paralleled by a significant loss of crystal formation, suggesting a functional role of both proteins related to mechanical loading.

Animals↗

PubMed1999

Reproducible X-ray projection geometry in edentulous patients.

OBJECTIVE: To evaluate a novel fixation system for reproducible radiography in edentulous patients. METHODS: A conventional extra-oral fixation system was modified with a filmholder and adjustable scales. For measuring reproducibility and angulation errors two rods and two balls were fixed on the alveolar crests of the maxilla and the mandible and angular variations were measured. One hundred radiographs of a conventional phantom were taken by one of the authors and by ten dental students. The angular disparity was calculated and intra- and interoperator precision determined. RESULTS: The average time taken to assemble the fixation system was 4 min. The 95% confidence interval for precision of the single operator was less than 2.5 degrees in both the maxilla and mandible. The 95% confidence interval for precision of the ten students was less than 2.2 degrees for the maxilla and 2.7 degrees for the mandible. There was no significant difference (P>0.05) in interoperator precision. CONCLUSION: The novel extra-oral fixation system appears to be a potential means of obtaining reproducible radiographs of edentulous patients.

Humans↗

PubMed1999

Chemosensitivity testing of oral cancer cells treated with a p185neu-specific agent.

The amplification and overexpression of the erbB-2 oncogene and its involvement in tumorigenesis makes this receptor an appropriate target for specific agents directed towards tumor cells. The purpose of this study was to evaluate the in vitro effect of the bacterially produced recombinant immunotoxin scFv(FRP5)-ETA on the protein synthesis and adenosine triphosphate (ATP) reduction in oral squamous cell carcinoma (OSCC) cells. This agent recognizes the erbB-2 receptor and inhibits protein synthesis in receptor-overexpressing cells. OSCC cells were selected for this study, and amplification and expression levels of the erbB-2 receptor were determined. Cell suspensions were cultured for 6 d with various concentrations of scFv(FRP5)-ETA (1-1000 ng/ml). A431 and MDA-MB468 cell lines were used as controls. Chemosensibility of tumor cells was measured by [3H]leucine incorporation assay and by an ATP luminescence assay. In OSCC cells with amplification and overexpression of erbB-2 inhibition, up to 92% of protein synthesis and 90% of ATP reduction was observed when cells were exposed to 1,000 ng/ml immunotoxin. In OSCC cells showing a deletion of erbB-2 and in erbB-2-negative MDA-MB468 cells, protein synthesis was inhibited by 22% and 8%, respectively. These results indicate that the effectiveness of a recombinant immunotoxin targeting erbB-2 receptors in OSCC cells depends on the level of erbB-2 amplification and expression, that it is highly specific for tumor cells expressing these receptors, and that a dose-dependency can be observed.

ADP Ribose Transferases↗

PubMed1999

Immunophenotypic analysis of normal mucosa and squamous cell carcinoma of the oral cavity.

Detection of tumor-associated alterations in peritumoral normal mucosa may give insight into the molecular pathogenesis of oral cancer. In the present study, 100 archival oral squamous cell carcinomaswith adjacent nontumorous mucosa were immunohistochemically investigated with antibodies against p53, Mdm2, Bcl-2, WAF1, MIB1, epidermal growth factor receptor (EGF-R), and various CD44 isoforms. Additionally a standardized argyrophilic nucleolar organizer region (AgNOR)-associated proteins analysis was performed. No correlation was found between p53, Mdm2, Bcl-2, and WAF1 immunophenotypes of the respective tumors and adjacent mucosa. The proliferation-associated markers MIB1 and AgNORs showed a statistically significant sequential increase from normal to dysplastic mucosa to invasive carcinoma. Investigation of various CD44 adhesion molecules revealed a highly variable expression pattern in overt carcinomas with a significantly decreased expression of CD44 v4 and v9 variants and unaltered strong expression of v5 and v6 isoforms compared with normal oral epithelium. We conclude that proliferation markers (MIB1 and AgNORs), as well as selected CD44 isoforms, represent useful markers for the assessment of precancerous lesions. They may be utilized for screening patients at high risk for the development of oral cancer.

Biomarkers, Tumor↗

PubMed1999

An adjustable bone fixation system for sagittal split ramus osteotomy: preliminary report.

After sagittal split osteotomy, osteosynthesis for stabilization of the fragments is usually performed by means of rigid or semirigid fixation to avoid maxillomandibular fixation (MMF). Sometimes, this leads to malpositioning of the fragments with resulting 'immediate relapse' or disturbances of the temporomandibular joints (TMJs) such as progressive idiopathic condylar resorption, which is the worst effect. We have therefore developed a new bone fixation system that allows three-dimensional adjustment even after fixation of the fragments. The special configuration of the system avoids intraoperative dislocation of the mandibular condyle. We have used the method successfully in 40 patients, 27 of whom had mandibular retrognathism and 13 of whom had mandibular prognathism. In particular, there has been no evidence of resorptive changes. There were no postoperative complications.

Adolescent↗

PubMed1999

Aberrations of erbB-1 and erbB-2 oncogenes in non-dysplastic leukoplakias of the oral cavity.

The purpose of this study was to analyse erbB-1 and erbB-2 oncogenes in non-dysplastic oral leukoplakia to see if we could pinpoint the first steps towards dysplasia and possible carcinogenesis. Fresh biopsy specimens of leukoplakia in 13 patients with no history of oral cancer were examined using the competitive-differential polymerase chain reaction. The mean gene copy numbers of erbB-1 and erbB-2 were calculated from the formula to compare the absolute quantities of reference gene and oncogene from 24 patients who did not have leukoplakia. Healthy mucosa was taken as controls. In eight patients with leukoplakias, the results indicated aberrations of the erbB-1 oncogene, and two patients had gene dosage changes of erbB-2. There were no signs of deletions or amplifications in the controls. These results suggest that aberrations of erbB-1 and erbB-2 are additional markers in premalignant oral lesions at the beginning of the carcinogenic process, and that genetic alterations in histologically non-dysplastic premalignant oral lesions are common.

Adult↗

PubMed1999

Strain-related bone remodeling in distraction osteogenesis of the mandible.

Distraction osteogenesis has become a mainstay in craniofacial surgery. However, there are several unresolved problems concerning the biology of bone regeneration. We investigated the biomechanical effects of mandibular lengthening in 32 rabbits on a cellular and histologic level. The mandible was subjected to a corticotomy, held in a neutral position for 4 days, and then lengthened at various strain rates and frequencies for 10 days. Radiographic, histologic, and electron microscopic examinations showed a strain-related bone regeneration. Application of physiologic strain rates (2000 microstrains or 0.2 percent) led to a bridging of the artificial fracture exhibiting woven ossification, whereas at 20,000 microstrains trabecular bone formation was demonstrated. In contrast, hyperphysiologic strain magnitudes (200,000 microstrains and 300,000 microstrains) showed a fibrous tissue formation. Multiple strain applications (10 cycles/day versus 1 cycle/day) increased the width of the distraction gap without changing the stage of bone regeneration. The gradual distraction of bone in physiologic magnitudes at higher frequencies seems to be desirable for a bony differentiation and may help to improve clinical applications.

Animals↗

PubMed1999

Indications for treatment of subcondylar mandibular fractures.

BACKGROUND AND OBJECTIVES: The purpose of this study was to establish a reliable criteria for implementation of either an open surgical or a closed conservative treatment of subcondylar fractures, based on clinical data and analytical mathematical model. METHODS AND MATERIALS: A total of 512 subcondylar fractures were treated during a 3-year period. Of these, 256 were fractures characterized by either displacement or dislocation of the proximal (condylar) segment. Patients were treated with open reduction and internal fixation (ORIF) or closed reduction (CR) techniques. Patients were evaluated pre- and postoperatively by clinical examination, 3-dimensional axiography, radiographic imaging, and ultrasonography. A mathematical model was developed for estimating the loss of vertical ramus height. RESULTS AND/OR CONCLUSIONS: When the displacements were less than 37 degrees from the sagittal axis of the ascending ramus, the ensuing loss of vertical height was negligible when fractures were treated by conservative techniques. When the displacements exceeded 37 degrees, the fractures resulted in a significant decrease of vertical ramus height. Based on these data, 37 degrees appears to be the point for decision of whether to use closed or open treatment.

Adolescent↗

PubMed1998

Surgical management of intraosseous skull base tumors with aid of Operating Arm System.

Invasion of bone and critical neurovascular structures often impedes complete resection of intraosseous skull base neoplasms, and these lesions tend to recur unless all infiltrated bone is removed. Evolving experience with image guidance over the past few years indicates the potential value of neuronavigation in skull base lesions diffusely infiltrating or fixed to bone structures. We report our early experience with the Radionics Operating Arm System (OAS), specifically emphasizing its utility as an adjunct in the treatment of intraosseous skull base tumors, mainly meningiomas. In April 1995 the OAS was introduced into clinical use at the neurosurgical university clinic in Münster, Germany. Since then, the system's utility has been explored in 10 patients out of the total neuronavigation series presenting with intraosseous skull base tumors (nine females and one male, mean age 47 years; nine meningiomas, one chordoma). For navigational planning, both 3-mm computed tomography scans and a set of 3-mm fat-suppression magnetic resonance images were chosen. At least four adhesive skin markers were used for system calibration. The system was technically usable in all cases in this small series. Because of the relative immobility of the bone structures and/or the tumor, no significant deviation from the preoperative registration accuracy was noted at the end of the procedures. The main advantages were easier localization and resection of infiltrated bone, which is often not grossly identifiable, even under the microscope. Our preliminary experience with the OAS suggests that image guidance is helpful in this type of lesion, providing better anatomical orientation during surgery and delineating tumor margins and their relation to critical neurovascular structures. The problem of a possible intracranial tumor and brain shift can be neglected in these lesions. The system facilitates resection by volumetric contour information, allowing more aggressive and complete resection.

Adult↗

PubMed1998

Molecular assessment of p53 abnormalities at the invasive front of oral squamous cell carcinomas.

BACKGROUND: The prognostic significance of the invasive tumor front in squamous cell carcinomas has recently been recognized. The aim of the present study was to investigate possible molecular mechanisms underlying the significance of this area in oral squamous cell carcinomas. METHODS: We used immunohistochemical and molecular genetic techniques to investigate whether p53 alterations at the invasive tumor front could determine the aggressiveness of oral cancers. RESULTS: p53 Overexpression was detected in 52% to 56% (four different p53 antibodies) of 100 carcinomas studied. The concordance rate between results of immunohistochemistry and genetic analysis was 60%. No correlation was found between p53 status of the tumors and clinicopathologic parameters analyzed statistically. CONCLUSIONS: p53 Alterations have no prognostic impact in oral squamous cell carcinomas and apparently do not represent a molecular basis for the biologic significance of the invasive tumor front. The detection of discordant p53 aberrations between primary and second primary carcinomas in some patients provide evidence for their independent origin, with possible impact on prevention and therapy.

Adult↗

PubMed1998

[MRI 3D imaging of the orbits in craniofacial abnormalities and injuries].

Craniofacial malformations and trauma often lead to changes in orbital soft tissues that require operative correction of both hard and soft tissues. CT scan and 3D reconstructions are optimal tools for the evaluation of the bony structures but there is no equivalent for the orbital soft tissues. The aim of this study was to establish a 3D-MRI technique that allows differentiated visualization of the different soft-tissue types of the orbit. A total of eight patients with different pathologic conditions of the orbit were examined. Five of these patients came for secondary correction after trauma and three showed a craniofacial malformation. 3D reconstruction was performed in volume-rendering technique after acquisition of 3 mm axial slices. It was shown that differentiated visualization of the orbital soft tissues is possible. Even though the thin bony structures have a weak signal and therefore the imaging is poor, the globe could be reconstructed reliably by different radiologists because of its circular delimitation from the bone. This technique provides additional support in the planning of orbital operations.

Craniofacial Abnormalities↗

PubMed1998

Sutural mineralization of rat calvaria characterized by atomic-force microscopy and transmission electron microscopy.

The application of transmission electron microscopy (TEM) and atomic-force microscopy (AFM) aid the acquisition of detailed structural information on the process of hard tissue formation. The sutural mineralization of rat calvaria is taken as a model for a collagen-related mineralization system. After cryofixation or chemical fixation an anhydrous tissue preparation technique with no staining procedures is used. The atomic-force microscope and the transmission electron microscope are used for structural analysis of the mineralizing region of the sutural tissue. With the application of AFM the collagen macroperiod is shown to be well represented in the unmineralized sutural tissue. At the mineralization front the collagen fibrils are found to be thickened and to change to a characteristic stacked platelet structure. Using TEM the macroperiod is faintly visible before mineral crystallites have formed and is more prominent after the apatite crystallization has started in the fibrils. In this step a needle-like structure of the newly formed apatitic crystals is visible.

Animals↗

PubMed1998

[Prospective study of the pathology of radiation-induced mucositis].

One of the most severe early side effects of radiation in head and neck cancer patients is mucositis. Inflammation of the oral mucose may lead to an extreme subjective burden, restricting the patients' well-being and even leading to an interruption of radiotherapy. The aim of our prospective study was to investigate the pathological alterations of the oral mucosa during irradiation. Therefore, samples from head and neck cancer patients were taken before radiation and a 30-G and a 60-G radiation dose. Pathogenetic alterations were determined by immunohistochemical staining of various cell surface molecules known to be involved in the pathogenesis of inflammation. Staining was performed with antibodies against ICAM 1, VCAM 1, ELAM, 25F9, 27E10, and RM3-1. Our study demonstrates the expression rates of the various surface molecules during inflammation. Expression of RM3-1 and ICAM 1 showed a steep increase during the time of radiation, whereas expression of ELAM reached a low constant value. Therefore, we conclude that distinct cell surface molecules demonstrate a characteristic time-dependent expression during radiation. Better insight into the pathogenesis of radiation-induced mucositis may help to develop a pathological classification of mucositis and to improve therapeutic strategies.

Aged↗