Resumo O objetivo deste estudo foi analisar o comportamento biológico de microesferas de hidroxiapatita (HA) substituída com magnésio (Mg) durante o reparo de defeito ósseo crítico, tendo em vista que este íon é de grande interesse clínico, pois está intimamente associado à homeostasia e à mineralização óssea. Para tanto, utilizou-se 30 ratos para compor três grupos experimentais: GI - defeito ósseo preenchido com microesferas de HA; GII - defeito ósseo preenchido com microesferas de HA substituída com Mg; GIII (controle) - defeito ósseo vazio; avaliados nos pontos biológicos de 15 e 45 dias. Os resultados histológicos evidenciaram, aos 15 dias, discreto infiltrado inflamatório crônico e neoformação óssea restrita às bordas, em todos os grupos. Nos grupos GI e GII, os biomateriais mantiveram-se íntegros e circundados por tecido conjuntivo frouxo. Aos 45 dias, notou-se resposta inflamatória do tipo crônica granulomatosa discreta nos grupos GI e GII, e no GIII presença escassa de células inflamatórias mononucleares. As microesferas implantadas no GI e GII mantiveram-se, em sua maioria, íntegras e envolvidas por tecido conjuntivo fibroso. Notou-se discreta neoformação óssea próxima às bordas e circunjacente a algumas microesferas. No GIII, a mineralização limitou-se às bordas e a área remanescente foi preenchida por tecido conjuntivo fibroso. Conclui-se que os biomateriais foram biocompatíveis, bioativos, osteocondutores e apresentaram biodegradação lenta, indicando seu grande potencial para em aplicações clínica como biomaterial de preenchimento.

Abstract The aim of this study was to analyze the biological behavior and osteogenic potential of magnesium (Mg) substituted hydroxyapatite (HA) microspheres, implanted in a critical bone defect, considering that this ion is of great clinical interest, since it is closely associated with homeostasis and bone mineralization. For the purpose of this study, 30 rats were used to compose three experimental groups: GI - bone defect filled with HA microspheres; GII - bone defect filled with HA microspheres replaced with Mg; GIII - empty bone defect; evaluated at biological points of 15 and 45 days. The histological results, at 15 days, showed, in all the groups, a discrete chronic inflammatory infiltrate; biomaterials intact and surrounded by connective tissue; and bone neoformation restricted to the borders. At 45 days, in the GI and GII groups, an inflammatory response of discrete granulomatous chronic type was observed, and in the GIII there was a scarce presence of mononuclear inflammatory cells; in GI and GII, the microspheres were seen to be either intact or fragmented, surrounded by fibrous connective tissue rich in blood vessels; and discrete bone neoformation near the edges and surrounding some microspheres. In GIII, the mineralization was limited to the borders and the remaining area was filled by fibrous connective tissue. It was concluded that the biomaterials were biocompatible and osteoconductive, and the percentage of Mg used as replacement ion in the HA did not favor a greater bone neoformation in relation to the HA without the metal.

Resumo Biomateriais compósitos têm ganhado notoriedade nas últimas décadas, devido à capacidade de combinar propriedades desejáveis de cada material. Assim, associar a bioatividade da wollastonita (W) com a biodegradabilidade do fosfato tricálcico (TCP) torna-se promissor para o reparo ósseo. Deste modo, este trabalho investigou, por meio de revisão sistemática e metanálise, estudos in vivo que avaliaram histomorfometricamente o reparo ósseo após implantação de compósitos de W/TCP. As buscas foram realizadas nas bases de dados PubMed/MEDLINE, LILACS/BIREME/Biblioteca Virtual em Saúde (BVS) e Scientific Electronic Library Online (SciELO). Dos 312 estudos encontrados, 6 foram incluídos. Na comparação dos dados considerou-se o percentual de neoformação óssea (NB). Compósitos com maior percentual de W e/ou no formato de arcabouços apresentaram maior NB. Estes resultados sugerem que a associação destes dois materiais bem como o formato de arcabouço poroso foram determinantes na NB, o que tornam estes novos compósitos profícuos para o uso clínico.

Abstract Composite biomaterials have gained notoriety in recent decades due to the ability to combine desirable properties of each material. Thus, associating bioactivity of wollastonite (W) with biodegradability of tricalcium phosphate (TCP) becomes promising for bone repair. Therefore, this study investigated, through systematic review and meta-analysis, in vivo studies that evaluated histomorphometrically the bone repair after implantation of W/TCP composites. The searches were performed in the PubMed/MEDLINE, LILACS/BIREME/Virtual Health Library (VHL), and Scientific Electronic Library Online (SciELO) databases. A total of 312 studies were identified in the databases, of which 6 were included. In data comparison, it was considered the percentage of neoformed bone (NB). Composites with a higher percentage of W and/or in the scaffold format presented higher NB. These results suggested that the association of these two materials, as well as the porous scaffold format, was determinant on NB, which makes these new composites potential for clinical use.

In a previous work of this group, theoretical studies and stability measurements were performed in order to describe the particle coagulation provoked by electrolytes. The work of the current paper concerns the development of mathematical models based on the DLVO theory and on population balance equations (PBE), which involve highly complex integro-differential equations. This model includes particle coagulation, particle nucleation, the polymerization kinetics and monomer partitioning among the many phases of the system. The model ensured a proper description of butyl acrylate/methyl methacrylate emulsion copolymerizations reactions, and related phenomena such as coagulation and particle nucleation in the presence of large seed particles. These latter systems are very important to the multimodal latexes production. Finally, simulation studies were performed in order to test the model ability to follow the competitive growth of polymer particles during semibatch operations.