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Biomedical subjects

Ulrich Joos

Publications and source records attributed to Ulrich Joos.

31 records · Page 2Linked to original sources
PubMed2005

Histologic, histomorphometric and immunohistologic changes of the gingival tissues immediately following mandibular osteodistraction.

OBJECTIVES: Even though osteogenesis after osteodistraction has been investigated in numerous experimental studies, there is limited information focusing on the influence of well-defined mechanical distraction forces on the associated gingival tissues. MATERIAL AND METHODS: In a study including 48 rabbits, mandibular osteodistraction was performed in vertically osteotomized mandibular body, using defined distraction protocols with physiologic, moderate and hyperphysiologic forces. The soft tissues overlying the distraction gap were harvested finally for histologic, immunohistologic and histomorphometric investigations. RESULTS: The control group without distraction showed the typical architecture and thickness of normal gingiva. In groups with distracted mandibles, an accelerating atrophy of gingiva depending on the degree of mechanical loading was obvious, characterized by decreasing thickness of epithelial layer, loss of rete ridges and disorganization of the different cell layers with a high number of apoptotic cells. In lamina propria collagen fibres were reduced and elastic fibres increased. Histomorphometric analysis revealed significant correlation between degree of distraction and atrophy in overlying soft tissues. CONCLUSION: This rabbit model of mandibular lengthening shows an accelerating atrophy in the covering soft tissues following hyperphysiologic distraction. The long-term outcome of these distraction-related soft-tissue alterations remains unclear. The atrophic changes may likely be of temporary nature.

Animals↗
PubMed2005

A clinical phase I/II trial of rhIL-4 applied topically in patients with oral squamous cell carcinomas to assess safety and therapeutic activity.

Besides its immunoregulatory effects, interleukin-4 (IL-4) has growth inhibitory activity on cells from human solid tumors, and IL-4 receptors are present on tumor cells including cells from head and neck squamous cell carcinomas. We have conducted a phase I/II trial in patients with oral squamous cell carcinomas of T(4), N(+) (1 exception) stage to assess safety and therapeutic activity of recombinant human (rh) IL-4 applying the drug intratumorally 3 times a week with dose escalation for a duration of 4 weeks. A total of 7 patients entered the study using doses of 1, 3, and 5 microg/kg. There was no reduction of tumor size with 1 patient showing clear progression of the tumor after 4 weeks of treatment. This, and the observation of limiting toxicity occurring as local pain at the injection site, led to study termination. Therefore, rhIL-4 cannot be recommended as an antitumor drug in this disease using monotherapy with the schedules applied in this trial.

Administration, Topical↗
PubMed2004

Sustained release of doxycycline for the treatment of peri-implantitis: randomised controlled trial.

UNLABELLED: With the increased use of osseointegrated implants and with many implants functioning for a long time, the treatment of peri-implantitis has become important. Animal studies and clinical case reports have shown that the principle of guided bone regeneration can be applied to the surgical treatment of moderate to profound loss of bone around the implant, but we have found no published clinical studies. PATIENTS AND METHODS: Twenty-eight patients whose ages ranged from 25 to 78 years and who had a total of 48 peri-implant defects were examined at baseline (week 0) and after 18 weeks. This included the recording of bleeding on probing, pocket probing depths, and probing attachment levels at six sites for each tooth. For 2-18 weeks before week 0 all patients had been treated for peri-implantitis, including motivation, instruction in oral hygiene, and implant scaling with a hand plastic instrument. They were then randomly allocated to continue with this treatment or to have in addition mechanical debridement and local application of Atridox trade mark which slowly release doxycycline. RESULTS: Patients treated with Atridox trade mark showed a significantly greater gain in mean (S.D.) probing attachment levels than those not treated with Atridox. Only subjects treated with Atridox had a significant gain in mean bleeding on probing (P = 0.001). Application of the biodegradable sustained release device after initial periodontal treatment resulted in a significant gain in mean probing attachment levels in the Atridox trade mark group and a significant reduction in pocket probing depths. There was also a significant difference in mean probing attachment levels (0.6mm).

Adult↗
PubMed2004

Treatment of severe peri-implant bone loss using autogenous bone and a bioabsorbable polymer that delivered doxycycline (Atridox).

With an increase of the number of implants being inserted, it is inevitable that the number of cases of peri-implantitis with loss of bone will rise. We report a case in which an autogenous cancellous bone graft was placed into the peri-implant bone defect and given protection with a bioabsorbable polymer barrier (Atridox) that released doxycycline slowly.

Absorbable Implants↗
PubMed2004

Biomechanical and clinical implications of distraction osteogenesis in craniofacial surgery.

INTRODUCTION: Craniofacial distraction osteogenesis is an established surgical procedure to correct bony malformations. Force transduction through the osteotomized bone fragments elicits defined biological responses in the gap tissue, which determines the clinical success of the distraction treatment. OBJECTIVE: The purpose of this investigation was to evaluate clinically a new distraction protocol based on an analysis of the biological and biomechanical parameters executing direct effects on bone regeneration during distraction. STUDY DESIGN: A multistep distraction protocol was used in 39 patients and the clinical outcome was monitored postoperatively. RESULTS: All the distraction cases were successful with a single exception. Segmental displacements were stable clinically and radiologically. CONCLUSION: In order to improve the clinical success of distraction osteogenesis, individual treatment protocols are recommended.

Adolescent↗
PubMed2004

Influence of titanium surfaces on attachment of osteoblast-like cells in vitro.

Implant surface topography influences osteoblastic proliferation, differentiation and extracellular matrix protein expressions. Studies on preliminary interactions of osteoblast-like cells on implant interface through in vitro systems, can give lucid insights to osseo-integrative efficacies of when in vivo implants. In the present investigation two titanium surfaces of dental implants, a sandblasted and acid-etched surface and an experimental grooved surface were compared through in vitro systems. The titanium implants were seeded with osteoblast-like primary cells and maintained for a period of 1-7 days. Expressions of fibronectin and osteonectin were assessed through immunogold labelling by scanning electron microscopy. The grooved surface, supported better osteoblastic cell adhesion and proliferation than the rough surfaces. Further, osteoblastic cells on the grooved surfaces also displayed a strong labelling for fibronectin at the cytoplasmic extensions coupled with intense osteonectin expression in comparison to the rough surfaced implants. In conclusion, grooved surfaces offered better cell attachment and proliferation than the other rough surfaces studied.

Animals↗
PubMed2002

Public domain computer-aided surgery (CAS) in orthodontic and maxillofacial surgery.

BACKGROUND: Computer-aided virtual three-dimensional (3D) surgical simulation assists the necessary visual understanding of complex pathological situations but has so far been dependent on expensive hardware and software. METHOD: For the first time a non-commercial, user-orientated application for orthognathic and craniofacial surgical simulation has been introduced, based on freeware NIH Image 1.62 provided by the National Institute of Mental Health (NIMH). Use and limitations are demonstrated here by the example of hypertelorism surgery. The osteotomy lines and the amount of resection for outward positioning of the orbits were determined by the surgeon on a workstation using CT data. Possible movement patterns of the osteotomy fragments were rotations, sagittal and transversal movements or combinations of these. The program then allows the calculation of anatomical distances on the screen in a 1:1 relation. Normative values according to age and pathological anatomy determine the degree of displacement. The program calculates the new position of the osteotomy fragments and transfers the data of the segment movement to the original CT data. RESULTS: 3D visualization of bone and soft tissue contours have been produced with an acceptable quality on a workstation for the demonstration and visual understanding of the surgical plan. Evaluation of a postoperative CT showed that the amount of movement and size of bone resection in the simulation was slightly overestimated rather than underestimated. This was also dependent on the complexity of the pathological anatomy and on how experienced the surgeon was. CONCLUSION: The use of 3D simulation programs allows a better understanding of the pathological anatomy in all dimensions, and in many cases enables limitations to be recognized in advance. The public domain program makes a major contribution to the quality of orthognathic and craniofacial surgical planning through cost-free usability, and supports continuous development and exchange of experience.

Cephalometry↗
PubMed2002

TCP is hardly resorbed and not osteoconductive in a non-loading calvarial model.

Tricalciumphosphate (TCP) has been used as a ceramic bone substitute material in the orthopedic field as well as in craniofacial surgery. Some controversies exist concerning the osteoconductive potential of this material in different implantation sites. This study was designed to evaluate the biological response of calvarial bone towards TCP granules under non-loading conditions to assess the potential of TCP as a biodegredable and osteoconductive bone substitue material for the cranial vault. Full-thickness non-critical size defects were made bilaterally in the calvaria of 21 adult Wistar rats. One side was filled by TCP granules, the contralateral side was left empty and used as a control. Animals were sacrified in defined time intervals up to 6 months. Bone regeneration was analyzed with special respect toward the micromorphological and microanalytical features of the material-bone interaction by electron microscopy and electron diffraction analysis. Histologic examination revealed no TCP degradation even after 6 months of implantation. In contrast, a nearly complete bone regeneration of control defects was found after 6 months. At all times TCP was surrounded by a thin fibrous layer without presence of osteoblasts and features of regular mineralization. As far as degradation and substitution are concerned, TCP is a less favourable material tinder conditions of non-loading.

Animals↗
PubMed2002

Optimizing presurgical orthodontic planning by means of the transverse coordinate simulation system (TCSS).

INTRODUCTION: When planning bilateral sagittal split osteotomies according to Obwegeser and Dal Pont, inaccuracies in the presurgical prediction of the transverse osteotomy gaps may occur. This is due to limitations of plaster models when simulating surgery on an articulator. AIM: This paper demonstrates the transverse coordinate simulation system which allows presurgical prediction of the transverse discrepancy between the tooth bearing and the proximal segment after displacement, thus minimizing uncertainty for the surgeon. METHOD: Diagnostic landmarks (taken from lateral and frontal cephalograms) and clinical data describing mandibular dimensions are transferred to a two-dimensional coordinate diagram. A mandibular model is then constructed using the anterior arch form, the temporomandibular joint distance and the prospective incision pattern. RESULT: Movements in the horizontal plane and displacement of the three segments (two condylar and one mandibular arch segment) can be simulated and measured. CONCLUSION: Transverse coordinate simulation system effectively increases the accuracy of presurgical planning without additional CT data or three-dimensional jaw models. This technique may decrease the number of additional surgical manoeuvres resulting from unexpectedly wide transverse discrepancies at the osteotomy site, which often increase surgery time, necessitate additional bone grafting, and entail the risk of healing disturbances and of malrotation or dislocation of the condyle.

Cephalometry↗
PubMed2001

Bone loading pattern around implants in average and atrophic edentulous maxillae: a finite-element analysis.

Introduction: Oral implants placed in the maxilla, especially the posterior region, have a lower success rate than those placed in the mandible. Poor bone quantity and quality have been suggested as a reason for this differential success rate. Objective: The purpose of this study was, therefore, to evaluate stress and strain distributions around loaded implants in the normal and atrophic maxilla by finite-element (FE) analyses. Material: FE models of a solitary implant were generated to determine stresses and strains in the bone adjacent to the implant surface under loading conditions. Study design: Different bony situations and implant lengths were used in a FE model. Static loads were applied axially and the resulting stresses and strains calculated. Results: Bone quality and quantity play a major role in decreasing bone strains adjacent to the implant surface under loading. It was found that stresses were more homogeneously distributed when more spongy bone was present. Decreased bone height was found to have less pronounced effects on strain and stress alterations than poor bone quality. Atrophic bony dimensions in combination with poor bone quality were associated with surface strains exceeding physiological levels (>6000 microstrains). Conclusion: Our investigation indicates that supraphysiological bone strains adjacent to the implant surface should be expected under mechanical loading in the atrophic maxilla. Copyright 2001 European Association for Cranio-Maxillofacial Surgery.

Journal Article↗
PubMed1996

Proliferative (MIB1, mdm2) Versus Anti-Proliferative (p53) Markers in Head and Neck Cancer. An Immunohistochemical Study.

Formalin fixed and paraffin embedded samples from 36 squamous cell carcinomas of the larynx and the oral cavity (pT2N0M0, R0) surrounded by non-tumorous mucosa were studied immunohistochemically using a panel of four different anti-p53 antibodies (CM1, PAb1801, D07, PAb240), a monoclonal anti-mdm2 antibody and MIB1, following wet autoclave antigen retrieval. P53 immunoreactivity was detected in 11/14 laryngeal and in 9/22 oral carcinomas. All p53 positive oral, and all but one laryngeal tumors revealed mdm2 positivity as well, whereas in p53 negative tumors 4/12 and 1/3 mdm2 immunopositive cases were demonstrated, respectively. MIB1 labeling indices of the tumors ranged between 18% - 64% in p53 positive cases, and 10% - 53% in p53 negative ones. The difference was not statistically significant. Close spatial coexpression of p53, mdm2 and MIB1 immunoreactivity was observed at the invasive front of the carcinomas and in the basal and suprabasal layers of the non-tumorous epithelium in all p53 positive cases. However, the MIB1 expression was similarly increased at the invasive margins in carcinomas lacking immunohistochemically detectable p53 alterations. Our results strongly suggest that p53 overexpression does not necessarily correspond to increased rate of proliferation, but rather to mdm2 overexpression and is largely dependent on the anatomical site in case of small and localized squamous cell carcinomas of the head and neck region.

Journal Article↗
PubMedDate not supplied

Early tissue reaction at the interface of immediately loaded dental implants.

PURPOSE: The treatment of patients with early or immediately loaded dental implants has renewed interest in the behavior of osteoblasts at the implant surface under load. A newly designed dental implant indicated for immediate loading was tested in vivo for early stages of osteoblast behavior at the implant surface. MATERIALS AND METHODS: Thirty-two implants were placed in the mandibles of 8 minipigs. Half of the implants (n = 16) were immediately loaded under occlusal contacts, and implants placed in non-occlusal relations served as a control. RESULTS: All implants, except 1 that showed signs of tissue infection, healed uneventfully and were stable throughout the experimental period. Ultrastructural analysis of mandibular specimens revealed an intimate attachment of osteoblasts to the material surface beginning as early as day 1. Application of either occlusal or non-occlusal load did not alter the phenotypic morphology of the attached osteoblasts. Transmission electron microscopy and x-ray diffraction analysis demonstrated a direct contact of bone-like minerals over the whole implant surface with no signs of crestal hard tissue alteration. Electron diffraction analysis showed a slight release of titanium from the implant side. DISCUSSION: These results indicate that immediate loading of specially designed dental implants can be performed without disruption of the titanium/bone interface or disturbance of osteoblast physiology in the early loading phase. CONCLUSION: Immediate loading protocols can be performed without disturbance of normal bone biology.

Animals↗