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Aims: To identify the potential pitfalls and indicate procedures to prevent them, during the evaluation of biomaterials for orthopaedic and craniofacial research in the New Zealand White (NZW) rabbit animal model of femoral bone defects. Place and Duration of Study: Laboratory for Research of the Musculoskeletal System, School of Medicine, University of Athens, between June 2014 and July 2015. Materials and Methods: Pre-emptive analgesia (carprofen 2.2 mg/kg sc), chemoprophylaxis (enrofloxacin 10 mg/kg sc) and anaesthesia (ketamine/xylazine 30/5 mg/kg im) were administered to NZW rabbits (body weight 3.3±0.2 kg, mean ± SD) for the aseptic surgical creation of drilled bone defects of 6 mm diameter (“critical size defect”) in the external femoral condyle of the left limb. All rabbits recovered without post-surgical complications from the first postoperative day. Results and Discussion: Although the research group consisted of Veterinarians and Orthopaedic Surgeons with experience in this model, they were challenged with potential pitfalls which were overcome step by step. Among them is the precise localization of the defect to be drilled. Intra-operative palpation of the external femoral condyle assists in determining the site, and post-operative X-ray evaluation confirms it. Additionally the correct width and depth of the bone defect are important to adhere to, which was achieved by using a 5.5 mm diameter bone drill and observing its depth marks. Another challenge is to have the specific amount of biomaterial implanted confined to the defect. Its potential distribution in the femoral shaft, diffusion in the metaphysial trabecular bone or excessive covering of the bone surface, are also pitfalls to be avoided. Conclusions: The increased use of this animal model in the evaluation of biomaterials in orthopaedic and craniofacial research requires knowledge, skills, surgical accuracy and attention to a sequence of steps, in order to achieve homogenous results and high repeatability of the implantation technique. With the fulfillment of these conditions, the extraction of valid scientific results and reduction of the number of animals used are possible.
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Laboratory mice with Middle Cerebral Artery Occlusion (MCAO) represent the main animal models for ischemic stroke research. Appropriate anesthetic protocols are essential, as anesthetic agents might affect the central nervous system (CNS) and therefore interfere with the outcome of pre-clinical ischemic stroke studies. In the present study we sought to investigate whether isoflurane, a widely used inhalational anesthetic, has any effect on MCAO mice pretreated with simvastatin, a well-known neuroprotective compound, compared with the administration of injectable ketamine/xylazine combination. Forty adult C57Bl/6J mice randomly allocated into four groups underwent ischemic injury by permanent coagulation of the Middle Cerebral Artery (MCA): Group A (n=11) animals were anesthetized with ketamine/xylazine, Group B (n=9) with isoflurane, Group C (n=9) with ketamine/xylazine after pretreatment with simvastatin 2h before permanent Middle Cerebral Artery Occlusion (pMCAO) and Group D (n=11) with isoflurane after similar pretreatment with simvastatin. The potential neuroprotective effect of the anesthetics was evaluated in terms of brain infarct volumes and neuron death. No significant differences, both quantitatively and qualitatively, were detected in brain lesions measured up to 7 days after pMCAO when comparing isoflurane inhalational anesthesia to ketamine/xylazine injectable anesthesia. Group C mice (simvastatin-treated ketamine/xylazine) had a significantly reduced brain infarct volume compared to Group A mice (non-simvastatin ketamine/xylazine) (P<.0005). Similarly Group D mice (simvastatin-treated isoflurane) had a significantly reduced brain infarct volume compared to Group B mice (non-simvastatin isoflurane) (P<.0005). No difference between morphology and number of apoptotic neurons was detected due to the two different anesthetic regimens. These results demonstrated the safe use of the established anesthetic agent isoflurane in mice where simvastatin is investigated as a neuroprotective compound.
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Objective: Growth factors have been applied in maxillary sinus augmentation with clinically successful results. The purpose of this article is to evaluate the effectiveness of growth factors in combination with various synthetic scaffolds. Methods and Materials: A systematic review of studies examining the effects of synthetic materials in combination with growth factors were performed. Results: Twelve (1 human and 11 animal) studies were eligible for inclusion. Due to the great heterogeneity of the studies regarding design, materials and outcomes, a meta-analysis was not performed. The majority of the studies show a reduction in healing time and enhancement of bone formation within the subantral environment. Bone Morphogenetic Protein-2 and GDF-5 were the two most common osteoinductive factors studied, showing a significant effect on new bone formation. Moreover, initial outcomes of trials with stem cells genetic transformation, that results in increased production of growth factors, are positive and justify further research. Conclusion: The incorporation of growth factors into the synthetic scaffold may be beneficial regarding the healing process.
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Background: Orthodontic forces may not only influence the dentoalveolar system, but also the adjacent and surrounding cortical bone. Aim: Since there is very limited information on this issue, we aimed to study the possible changes in maxillary cortical bone following the application of heavy orthodontic forces in mature normal and osteoporotic rats. Materials and Methods: Twenty-four 6-month-old female rats were selected and divided into an ovariectomized group and a normal group. In both groups, the rats were subjected to a 60 gr* orthodontic force on the upper right first molar for 14 days. Results: In both groups, histological sections showed that the application of this force caused hypertrophy and fatigue failure of the cortical maxillary bone. The osteogenic reaction to distraction is expressed by the formation of subperiosteal callus on the outer bony side, resembling that seen in distracted bones. Conclusion: From this study we concluded that heavy experimental orthodontic forces in rats affect the maxillary cortical bone. The osteogenic reaction to these forces, expressed histologically by subperiosteal callus formation, is similar to that seen in distraction osteogenesis models.