Fundamentals and Current Strategies for Peripheral Nerve Repair and Regeneration.

A body of evidence indicates that peripheral nerves have an extraordinary yet limited capacity to regenerate after an injury. Peripheral nerve injuries have confounded professionals in this field, from neuroscientists to neurologists, plastic surgeons, and the scientific community. Despite all the efforts, full functional recovery is still seldom. The inadequate results attained with the "gold standard" autograft procedure still encourage a dynamic and energetic research around the world for establishing good performing tissue-engineered alternative grafts. Resourcing to nerve guidance conduits, a variety of methods have been experimentally used to bridge peripheral nerve gaps of limited size, up to 30-40 mm in length, in humans. Herein, we aim to summarize the fundamentals related to peripheral nerve anatomy and overview the challenges and scientific evidences related to peripheral nerve injury and repair mechanisms. The most relevant reports dealing with the use of both synthetic and natural-based biomaterials used in tissue engineering strategies when treatment of nerve injuries is envisioned are also discussed in depth, along with the state-of-the-art approaches in this field.

Enhanced performance of chitosan/keratin membranes with potential application in peripheral nerve repair.

Although surgical management of peripheral nerve injuries (PNIs) has improved over time, autografts are still the current "gold standard" treatment for PNIs, which presents numerous limitations. In an attempt to improve natural biomaterial-based nerve guidance conduits (NGCs), chitosan (CHT), a derivative of the naturally occurring biopolymer chitin, has been explored for peripheral nerve regeneration (PNR). In addition to CHT, keratin has gained enormous attention as a biomaterial and tissue engineering scaffolding. In this study, biomimetic CHT/keratin membranes were produced using a solvent casting technique. These membranes were broadly characterized in terms of their surface topography and physicochemical properties, with techniques such as Fourier Transform Infrared Spectroscopy (FTIR), Differential Scanning Calorimetry (DSC), contact angle, weight loss and water uptake measurements, Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). Biological in vitro assays were also performed, where a preliminary cytotoxicity screening with the L929 fibroblast cell line revealed that the membranes and respective materials are suitable for cell culture. In addition, Schwann cells, fibroblasts and endothelial cells were directly seeded in the membranes. Quantitative and qualitative assays revealed that the addition of keratin enhanced cell viablity and adhesion. Based on the encouraging in vitro results, the in vivo angiogenic/antiangiogenic potential of CHT and CHT/keratin membranes was assessed, using an optimized chick embryo chorioallantoic membrane assay, where higher angiogenic responses were seen in keratin-enriched materials. Overall, the obtained results indicate the higher potential of CHT/keratin membranes for guided tissue regeneration applications in the field of PNR.

Investigation of cell adhesion in chitosan membranes for peripheral nerve regeneration.

Peripheral nerve injuries have produced major concerns in regenerative medicine for several years, as the recovery of normal nerve function continues to be a significant clinical challenge. Chitosan (CHT), because of its good biocompatibility, biodegradability and physicochemical properties, has been widely used as a biomaterial in tissue engineering scaffolding. In this study, CHT membranes were produced with three different Degrees of Acetylation (DA), envisioning its application in peripheral nerve regeneration. The three CHT membranes (DA I: 1%, DA II: 2%, DA III: 5%) were extensively characterized and were found to have a smooth and flat surface, with DA III membrane having slightly higher roughness and surface energy. All the membranes presented suitable mechanical properties and did not show any signs of calcification after SBF test. Biodegradability was similar for all samples, and adequate to physically support neurite outgrowth. The in vitro cell culture results indicate selective cell adhesion. The CHT membranes favoured Schwann cells invasion and proliferation, with a display of appropriate cytoskeletal morphology. At the same time they presented low fibroblast infiltration. This fact may be greatly beneficial for the prevention of fibrotic tissue formation, a common phenomenon impairing peripheral nerve regeneration. The great deal of results obtained during this work permitted to select the formulation with the greatest potential for further biological tests.

[The transformation of the dental services market and the battle over a monopoly in 19th century dental practice]. / A transformação no mercado de serviços odontológicos e as disputas pelo monopólio da prática odontológica no século XIX.

The article analyzes the process by which dentistry acquired the status of a profession. The setting is the mid-nineteenth-century United States, where the West's first professional dental organizations were founded, and the focus is on some aspects of the development of a dental market and on the professional disputes among practitioners of the dental trade, who wanted a monopoly within this field of knowledge. Certain outside factors played a major role in the emergence of the profession, including changes in patterns of sugar consumption (which spread dental caries disease throughout society) as well as the expansion of the dental service market. The subsequent proliferation of distinct groups of dental practitioners--both qualified and unqualified to practice dentistry--and their competition for a place in the dental market reflect the battle waged to establish jurisdiction in this field and the emergence of dentistry as a 'modern profession'.

Acquired antiprothrombin antibodies: an unusual cause of bleeding.

Acquired inhibitors of coagulation causing bleeding manifestations are rare in children. They emerge, normally in the context of autoimmune diseases or drug ingestion, but transient and self-limiting cases can occur after viral infection. We describe, an otherwise healthy, 7-year-old girl who had gingival bleeding after a tooth extraction. The prothrombin time (PT) and the activated partial thromboplastin time (APTT) were both prolonged with evidence of an immediate acting inhibitor (lupic anticoagulant). Further coagulation studies demonstrated prothrombin (FII) deficiency and prothrombin directed (FII) antibodies. The serological tests to detect an underlying autoimmune disease were all negative. The coagulation studies normalised alongside the disappearance of the antibody. This article presents lupus anticoagulant hypoprothrombinaemia syndrome (LAHS) as a rare case of acquired bleeding diathesis in childhood.

A transformacão no mercado de servicos odontológicos e as disputas pelo monopólio da prática odontológica no século XIX / The transformation of the dental services market and the battle over a monopoly in 19th century dental practice

Este artigo analisa o processo de profissionalizacão da odontologia, tendo como cenário os Estados Unidos em meados do século XIX, local e época em que se estabeleceram as primeiras organizacões odontológicas profissionais no Ocidente. Busca revelar aspectos referentes à conformacão de um mercado de servicos odontológicos e as disputas entre os diversos praticantes da arte dentária pelo monopólio desse campo de saber. Fatores externos específicos tiveram um papel fundamental na emergência da profissão, entre eles a transformacão nos padrões de consumo do acúcar, determinando a disseminacão da doenca cárie dentária na sociedade e a expansão do mercado de servicos odontológicos. A conseqüente proliferacão de grupos distintos de praticantes, qualificados e desqualificados na arte dental, competindo pelo mercado de servicos odontológicos evidenciam as disputas travadas em torno do estabelecimento de uma jurisdicão sobre esse campo de trabalho e a emergência da odontologia como 'profissão moderna'.

Dentistas práticos no Brasil: história de exclusão e resistência na profissionalização da odontologia brasileira / Practical dentists in Brazil: exclusion history and resistance in the professionalization of the Brazilian dentistry

O objetivo desta tese é analisar a disputa entre cirurgiões-dentistas e dentistas práticos, como um problema do processo de profissionalização da odontologia no Brasil. A profissão odontológica está regulamentada no país desde a década de 30, com o estabelecimento de um sistema de licenciamento profissional, adquirido por meio de credenciais educacionais. No entanto, observa-se que o exercício da odontologia não tem se restringido ao cirurgião-dentista graduado e licenciado pelos conselhos de odontologia, o que pode ser verificado pela existência de dentistas práticos atuando em vários municípios do país. Com o propósito de analisar as circunstâncias que determinam a inserção dos dentistas práticos no mercado de trabalho, buscamos conhecer o desenvolvimento histórico da regulamentação da odontologia, no contexto da conformação do modelo de regulação profissional no país. Foi realizada uma pesquisa documental com vistas a identificar a evolução da regulamentação da odontologia, com ênfase na análise dos dispositivos legais, estabelecidos a partir da Primeira República. Foram analisadas as legislações e normas aprovadas e sancionadas pelos poderes legislativo e executivo, para regulamentação da profissão odontológica no Brasil, e as demandas apresentadas ao poder legislativo, com vistas à regulamentação da atividade dos dentistas práticos. Realizou-se uma pesquisa empírica com o propósito de conhecer e analisar o exercício ilegal da odontologia pelos dentistas práticos e sua inserção no mercado de trabalho. Os dentistas práticos entrevistados Praticamente todos os entrevistados possuem experiências de notificação ou denúncia pelo exercício ilegal da odontologia, o que não os impediu de seguir praticando a atividade, fato que atribuem, quase sempre, à tolerância das autoridades ligadas à questão. Com base nas informações coletadas, verificou-se que a profissão odontológica é contestada em relação ao monopólio legal que detém sobre o campo de trabalho da odontologia nas três arenas da jurisdição profissional: do espaço do trabalho, onde os dentistas práticos oferecem seus serviços para um segmento do mercado de serviços odontológico; na arena da opinião pública, em que a população consome e, portanto, reconhece os serviços ofertados pelos dentistas práticos e, no sistema legal, no qual os dentistas práticos têm apresentado, de forma sistemática, projetos de lei visando ao reconhecimento e à legalização da sua atividade.