Early dural reaction to polylactide in cranial defects in rabbits

Restoring the bone integrity to injured calvariae remains a challenge to surgeons. In this study, the dural biocompatibility of biodegradable poly-L/DL-lactide 80/20 and 70/30 defect covers, designed for guided bone regeneration, was assessed. In each of the 16 test rabbits, bilateral (8.3 mm) cranial defects were created. The different covers were applied to one defect each in every rabbit and consisted of three parts: an epicranial cover, a spacer, and a dural cover. All defects had closed after 8 weeks due to new bone formation. A few giant cells were found at the cover-to-dura interface in equal numbers for both covers. Dural bone formation was present in 15 of 16 rabbits and progressed unhindered by the defect cover or its early degradation products

Elastomeric enriched biodegradable polyurethane sponges for critical bone defects: a successful case study reducing donor site morbidity

Bone substitutes have been a critical issue as the natural source can seldom provide enough bone to support full healing. No bone substitute complies with all necessary functions and characteristics that an autograft does. Polyurethane sponges have been used as a surgical alternative to cancellous bone grafts for critical bone defect donor sites. Critical bone defects were created on the tibial tuberosity and iliac crest using an ovine model. In group I (control-untreated), no bone regeneration was observed in any animal. In group II (defects left empty but covered with a microporous polymeric membrane), the new bone bridged the top ends in all animals. In groups III and IV, bone defects were implanted with polyurethane scaffolds modified with biologically active compounds, and bone regeneration was more efficient than in group II. In groups III and IV there were higher values of bone regeneration specific parameters used for evaluation (P\0.05) although the comparison between these groups was not possible. The results obtained in this study suggest that biodegradable polyurethane substitutes modified with biologically active substances may offer an alternative to bone graft, reducing donor site morbidity associated with autogenous cancellous bone harvesting

Influence of copolymer composition of polylactide implants on cranial bone regeneration

Biodegradable polymers have become useful auxiliary materials for the functional and structural restoration of bone deficiencies. Commercial implants from poly(l/dl-lactide) 70:30 are used clinically for fracture fixation in regions of low load. Implants manufactured from poly(l/dl-lactide) 80:20 are currently being investigated experimentally. The higher degree of crystallinity results in a higher chemical strength and loading capacity which promises advantages for long-term implantation. In this study implants from these two copolymers were applied to promote bone regeneration of bilateral, full thickness, circular cranial defects in 16 adult New Zealand white rabbits. The defects were covered with melt extruded and laser cut polylactide burr hole covers epicranially and endocranially in direct contact to the dura. The defect spaces were kept open with a spacer which created a hollow chamber. Both materials were implanted in each animal. Bone seeking fluorochromes were used to assess the pattern of bone growth. After eight weeks bone regeneration in the defects was assessed radiologically, histologically and by fluorescence microscopy. During the eight weeks observation period the application of a hollow chamber design resulted in almost complete cranial defect healing, whereby the copolymer composition had no effect on the amount or the morphology of the regenerate. The dura mater showed no adverse tissue reactions during these early stages of implantation. Eight weeks is only a short period in the lifetime of the tested polymers and complete bone regeneration can only be expected after complete polymer degradation. Long-term studies or accelerated degradation studies are required to confirm the expected advantages of poly(l/dl-lactide) 80:20. textcopyright 2005 Elsevier Ltd. All rights reserved

De que falamos quando falamos de criatividade?

Muitos têm sido os mitos que se geraram em torno do conceito de criatividade, onde se generalizou a ideia de que a criatividade seria algo de transcendente, privilégio a que alguns indivíduos iluminados teriam acesso, o que impediu, durante largo tempo, o seu estudo e aprofundamento científico. A ciência, ao desfazer o halo do divino de que se revestia o conceito, conferiu-lhe uma consistência mais próxima da entidade humana. As propostas da psicologia, através de estudos empíricos, trouxeram-nos a possibilidade de uma melhor compreensão do fenómeno, abrindo caminhos para o conhecimento da sua estrutura, definição, estimulação e reflexão sobre a sua natureza. O estudo da criatividade implicará definir os seus limites, considerar as dimensões definidas para a sua abordagem, concorrendo, deste modo, para um olhar esclarecido sobre este complexo constructo. Guilford (1967) na sua definição da estrutura do intelecto, ao ter desvendado as aptidões cognitivas que integram a criatividade, desvendou, igualmente, que a criatividade não é um bloco uno, monolítico. Foi, pois, a partir deste conhecimento que vários investigadores se dedicaram ao estudo de métodos e técnicas, desenvolvendo um conjunto de procedimentos promotores e facilitadores da estimulação destas aptidões criativas, transversais a todas as áreas do conhecimento.info:eu-repo/semantics/publishedVersio