Recebido em 21/9/98; aceito em 10/2/00 BIOCERAMICS: TENDENCIES AND PERSPECTIVES OF AN INTERDISCIPLINARY AREA.The need for new materials to substitute injured or damaged parts of the human body has led scientists of different areas to the investigation of bioceramics since the 70's, when other materials in use started to show implantation problems. Bioceramics show some advantages like being the material that best mimics the bone tissue but also, present low mechanical strength due to its ceramic nature. This paper presents a general view about the topic.Keywords: bioceramics; biomaterials; calcium phosphate. DIVULGAÇÃO INTRODUÇÃOO aumento da expectativa de vida do homem, como conseqüência dos avanços da medicina, da maior preocupação com a alimentação e do conforto gerado pela assim denominada "vida moderna", tem resultado no aumento da população de idosos e, conseqüentemente, das doenças relacionadas à velhice. Dentre os diversos males que afetam a estrutura óssea, a osteoporose e a perda de massa óssea têm sido intensamente estudados devido a seus efeitos devastadores na qualidade de vida das pessoas. Os problemas de estrutura óssea não são apenas "doença de velhos", eles também atingem indivíduos jovens em sua fase mais produtiva, em decorrência de acidentes, notadamente os automobilísticos e os de trabalho.A magnitude destes problemas de saúde junto à população tem levado pesquisadores, principalmente dos países mais desenvolvidos, à procura de materiais que possam substituir de forma apropriada os ossos danificados.Os materiais utilizados na substituição de ossos enquadram-se em uma classe denominada de biomateriais 1,2 e devem apresentar propriedades físicas e biológicas compatíveis com os tecidos vivos hospedeiros, de modo a estimular uma resposta adequada dos mesmos. Tais propriedades caracterizam a biocompatibilidade 2,3 . Os materiais sintéticos utilizados para estes fins podem ser metais, polímeros, compósitos, cerâmicas e vidros.Em geral, biomateriais utilizados na reposição dos chamados tecidos moles são muito diferentes daqueles usados na substituição de tecidos duros (ossos e dentes). Para os tecidos duros, dependendo do esforço mecânico a que são submetidos, alguns materiais podem ser mais apropriados que outros, devido à sua maior resistência. A Tabela 1 relaciona algumas aplicações de biomateriais sintéticos.A diversidade das aplicações dos biomateriais mostrada pela Tabela 1, assim como o amplo espectro de sua composição química e a necessidade de formas e morfologias apropriadas para sua utilização, fazem da pesquisa nesta área do conhecimento um trabalho de característica eminentemente interdisciplinar, envolvendo fatores que definem o sucesso de suas aplicações, tais como: rotas de síntese, processamento em formas variadas, qualidade e esterilidade clínica e resposta do tecido hospedeiro. Desta forma, o desenvolvimento de biocerâmicas e de próteses constituídas destes materiais deve ocorrer sob as mesmas condições de interdisciplinaridade que determinam o desenvolvimento de qualquer outro b...
Porous and dense hydroxyapatite cylinders (PHA and DHA) were implanted into cavities produced in rat femora and the sites of implantation were examined at different times over a period of 24 weeks by microradiologic and histological techniques. Microradiographs showed the presence of a layer of trabecular bone around the implants, which became more radiopaque and thinner along the experimental time. The microradiologic methodology used was suitable for the evaluation of the interface between hydroxyapatite and newly formed bone in nondecalcified materials. Microscopic observations showed that young bone grew over the surface of both types of implants after 1 and 2 weeks of surgery and that bone also grew inside PHA implants. Progressive bone absorption was observed in both types of implants after the fourth week. A layer of fibrous tissue was formed in the interface between new bone and DHA. Mature bone with haversian systems surrounded DHA implants and filled the pores of PHA implants throughout the experimental period. The pores of PHA implants were smaller than those commonly reported, which should have been a disadvantage, although it was observed that the extra cellular fluid induced disintegration of the ceramic granules, allowing the gradual growth of bone tissue into the spaces among them, without the interposition of fibrous tissue.
Autogenous bone grafts have frequently been used in the treatment of bone defects; however, this procedure can cause clinical complications after surgery. Besides, the amount of available bone is sometimes insufficient. Therefore, synthetic biomaterials have been researched as an alternative to autogenous bone graft implants. The objective of this study was to evaluate the repair of bone defects treated with compact autogenous bone graft or porous calcium phosphate ceramics. Three defects 3 mm in diameter were produced in the skull of 21 rats. One the defects was produced in the frontal bone, which remained empty, while the others were produced in the right and left parietal bones, which were filled respectively with ceramics and autogenous bone graft. The animals were sacrificed 1, 2, 4, and 24 weeks after surgery and analyzed by light microscopy and radiography. In the twenty-fourth week, the defects filled with autogenous bone graft and ceramics had similar volumes of newly formed bone tissue. The ceramics offered favorable conditions to bone tissue growth. Thus, we concluded that the calcium phosphate ceramic implant proved to be effective in repairing defects produced in the skull of rats.
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