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  • Munksgaard International Publishers  (4)
  • 2005-2009  (4)
  • 1
    ISSN: 1600-0501
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: The aim of the present study was (1) to test whether or not platelet-rich plasma (PRP) or commercially available fibrin can increase bone regeneration compared with non-treated defects and (2) to test whether or not PRP or fibrin increases bone regeneration when used as a delivery system for recombinant human bone morphogenetic protein-2 (rhBMP-2). In 16 New Zealand White rabbits, four evenly distributed 6 mm diameter defects were drilled into the calvarial bone. The following five treatment modalities were randomly allocated to all 64 defects: (0) untreated control, (1) fibrin alone, (2) PRP alone, (3) fibrin with 15 μg rhBMP-2 and (4) PRP with 15 μg rhBMP-2. For the fibrin gels and the PRP containing rhBMP-2, the 15 μg rhBMP-2 was incorporated by precipitation within the matrices before their gelation. After 4 weeks, the animals were sacrificed and the calvarial bones were removed for histological preparation. The area fraction of newly formed bone was determined in vertical sections from the middle of the defect by applying histomorphometrical analysis. A mean area fraction of newly formed bone was found within the former defect of 23.4% (±13.5%) in the control sites, of 28.4% (±17.4%) in the fibrin sites and of 34.5% (±17.4%) in the PRP sites. The statistical analysis revealed no significant difference in bone formation between the three groups (ANOVA). Addition of 15 μg rhBMP-2 in the fibrin gel (59.9±20.3%) and the PRP gels (63.1±25.3%) increased bone formation significantly. No significant difference was observed between sites, where PRP or fibrin has been used as a delivery system for rhBMP-2 (ANOVA). In conclusion, the application of fibrin gels or PRP gels to bone defects is not superior to leaving the defect untreated. Regarding the amount of bone formation, the application of 15 μg rhBMP-2 in bone defects enhances the healing significantly at 4 weeks. In this animal model, commercially available fibrin and autologous PRP gels are equally effective as delivery systems for rhBMP-2.
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  • 2
    ISSN: 1600-079X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract:  The aim of the present study was to identify the distribution of the second melatonin receptor (MT2) in the human hippocampus of elderly controls and Alzheimer's disease (AD) patients. This is the first report of immunohistochemical MT2 localization in the human hippocampus both in control and AD cases. The specificity of the MT2 antibody was ascertained by fluorescence microscopy using the anti-MT2 antibody in HEK 293 cells expressing recombinant MT2, in immunoblot experiments on membranes from MT2 expressing cells, and, finally, by immunoprecipitation experiments of the native MT2. MT2 immunoreactivity was studied in the hippocampus of 16 elderly control and 16 AD cases. In controls, MT2 was localized in pyramidal neurons of the hippocampal subfields CA1-4 and in some granular neurons of the stratum granulosum. The overall intensity of the MT2 staining was distinctly decreased in AD cases. The results indicate that MT2 may be involved in mediating the effects of melatonin in the human hippocampus, and this mechanism may be heavily impaired in AD.
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  • 3
    ISSN: 1600-0501
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Introduction: Computer-guided navigation has proven a valuable tool in several surgical disciplines. During oral implant placement, its application is intended to accomplish optimal implant localization and to reduce the risk of damage to adjacent structures. The aim of this study was to compare the precision limits of conventional vs. navigated implant insertion in practice.Materials and methods: In cast models of the maxilla, implants were inserted to replace the left central incisor (n=40) and the right canine (n=40); each of those were inserted either conventionally (n=20) or navigated (n=20). Implant position, angulation and insertion depth were calculated from computer tomography scans of the implants that were connected to an index abutment of 40 cm length.Results: The variations of implant positions were reduced for implants that were inserted by navigation (P〈0.05). In both the axial and the transversal plane, the variations of implant angulations were reduced for implants that were inserted by a navigation protocol (P〈0.05). The variations of insertion depth were less (P〈0.05) when the implants were placed by navigation in comparison with conventional insertion procedures.Conclusions: Given the experimental conditions, although they tried to mimic a clinical situation, no final conclusions can be drawn. The in vitro application of a navigation system resulted in an improved precision of insertion surgery regarding the position, angulation and depth of an implant. Clinical studies will have to prove if routine image guidance will result in superior surgical outcome.
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Munksgaard International Publishers
    ISSN: 1600-0501
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract Objectives: The transfer of the osseofasciocutaneus fibula-free flap has become a routine procedure in the reconstruction of comprehensive orofacial defects. Besides its length, major advantages of the fibula-free flap include the trigonal diameter of the fibular bone, which usually allows the placement of dental implants.Patients and methods: In a prospective study, 16 consecutive patients who received free fibula grafts and in total 51 dental implants between 1999 and 2001 were examined. All implants were inserted secondary after bone grafting and loaded after 3 months of submerged healing. The observation period extended 2.5 years on average. The implant success was controlled clinically, radiographically and by resonance frequency analysis.Results: One implant that was located at the interface between the fibula graft and the mandible was lost due to dehiscence and local infection during the healing period. In two other patients, one implant had to remain unexposed as ‘sleeper’ due to an unfavourable soft tissue situation. The success rate calculated by Kaplan–Meier analysis was 96.1% after an observation period of 1400 days. Resonance frequency analysis (ISQ-values) revealed significant differences related to the orientation (vestibulo-oral/mesio-distal; vo/md) of the transducer unit (P〈0.01). In general, a high primary stability for implants placed in free fibula grafts could be achieved (vo/md 66/74.1), which on average increased slightly during the healing period (vo/md 67.4/75.4) and within 12 month of functional loading (vo/md 72.1/79.9). Additional augmentation with iliac bone grafts or reconstructions with a double barred fibula resulted in an improved reconstruction of the alveolar process, thus allowing superior individual implant positions or angulations, but no elevation of the ISQ-values.Conclusion: The fibula-free flap provides a consistent bone graft that allows a reliable and predictable restoration with dental implants.
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