Scaffolds with a standardized macro-architecture fabricated from several calcium phosphate ceramics using an indirect rapid prototyping technique

Calcium phosphate ceramics, commonly applied as bone graft substitutes, are a natural choice of scaffolding material for bone tissue engineering. Evidence shows that the chemical composition, macroporosity and microporosity of these ceramics influences their behavior as bone graft substitutes and bone tissue engineering scaffolds but little has been done to optimize these parameters. One method of optimization is to place focus on a particular parameter by normalizing the influence, as much as possible, of confounding parameters. This is difficult to accomplish with traditional fabrication techniques. In this study we describe a design based rapid prototyping method of manufacturing scaffolds with virtually identical macroporous architectures from different calcium phosphate ceramic compositions. Beta-tricalcium phosphate, hydroxyapatite (at two sintering temperatures) and biphasic calcium phosphate scaffolds were manufactured. The macro- and micro-architectures of the scaffolds were characterized as well as the influence of the manufacturing method on the chemistries of the calcium phosphate compositions. The structural characteristics of the resulting scaffolds were remarkably similar. The manufacturing process had little influence on the composition of the materials except for the consistent but small addition of, or increase in, a beta-tricalcium phosphate phase. Among other applications, scaffolds produced by the method described provide a means of examining the influence of different calcium phosphate compositions while confidently excluding the influence of the macroporous structure of the scaffolds

Macroporous calcium phosphate ceramic: A prospective study of 106 cases in lumbar spinal fusion

Macroporous biphasic calcium phosphate (MBCP, Triosite(TM)) is well known for its safety absence of allergenicity, and excellent bone-bonding capacity, and it has been widely used as a bone graft substitute in orthopaedic, ENT, and dental surgery. This study investigates the clinical performance of this synthetic porous ceramic in a series of 106 patients, mainly with degenerative spine aetiologies (95/106) and with a minimum follow-up of 2 years. AU patients were treated with posterior correction involving the semi-rigid New Orleans(TM) instrumentation. Spinal fusion was always performed using MBCP granules mixed with autogenous bone chips and bone marrow obtained from the local spine. Fusion of the spine was confirmed for 100 patients, and 6 non-unions were observed (3 resulting from primary spondylolisthesis). This study shows that MBCP provides suitable results in spinal fusion involving a semi-rigid instrumentation. Because the indication of degenerative spine is not very favorable to fusion, this technique appears to be a good alternative to autografts and could decrease patient morbidity resulting from iliac bone grafting

BIODEGRADATION OF SYNTHETIC BIPHASIC CALCIUM-PHOSPHATE AND BIOLOGICAL CALCIFIED SUBSTRATUM BY CELLS OF HEMATOPOIETIC ORIGIN

Different types of osteoclastic cells (authentic osteoclasts from human giant cell tumor and bone marrow of newborn rats; newly-formed osteoclasts from adult rat bone marrow), giant multinucleated cells and macrophages were studied for their effect on synthetic and natural mineralized substrata. Biphasic calcium phosphate ceramic consisted of hydroxyapatite and beta tricalcium phosphate was chosen for in vitro experiments, and dentine served as a positive control for cell-resorbing activity. Our results show the limited capacity of authentic and newly-formed osteoclasts to resorb synthetic ceramic as compared to that of natural substrata. In vitro cell-mediated biodegradation included also modifications of the synthetic substratum surface caused presumably by phagocytosis of the material

Macroporous biphasic calcium phosphate ceramics: influence of macropore diameter and macroporosity percentage on bone ingrowth

A total of 60 cylindrical 6 x 6 mm samples of a macroporous biphasic calcium phosphate (MBCP) ceramic were implanted into a distal femoral site in 30 rabbits. These samples represented six kinds of implants with two different macropore diameters and three different macroporosity percentages. Analysis of backscattered electron images of implant surfaces analysed by a factorial design method showed that implants with 565 mu m pore size provided more abundant newly formed bone both in peripheral and deep pores than those with 300 mu m pore size. No significant differences were found between implants with 40 and 50% macroporosity, suggesting that the influence of macropore size on bone ingrowth was greater than that of macroporosity percentage. MBCP implants with 565 mu m pore diameter and 40% macroporosity represented the optimal association for homogeneous and abundant bone ingrowth. (C) 1998 Published by Elsevier Science Ltd. All rights reserved

Mineral fertilizers: analysis of the dynamics in the agricultural economy of Central-West Region of Brazil

Os fertilizantes minerais apresentam-se como um dos insumos contribuidores para o aumento da produtividade no Brasil desde os anos de 1980, diante da limitada expansão da área agrícola, e são considerados como poupadores de terra. No entanto, por serem provindos de recursos naturais escassos, extraidos viávelmente (econômico e físico) de limitados locais do mundo, e dependerem altamente de energia para a síntese, fazem com que a produção agrícola seja sensível aos impactos de oferta e demanda pelos fertiliznates. A exemplo do ocorrido em 2008/2009, em que a elevação dos preços dos fertilizantes reduziu sua quantidade de consumo e houve alteração no mercado das commodities agrícolas. Diante disso, objetivou analisar a dinâmica econômica entre os fertilizantes minerais com o mercado agrícola da região Centro-Oeste (CO), onde apresenta o maior consumo de fertilizante minerais e concentra a maior produção agrícola do país. Para análise, considerou-se as variáveis como a quantidade consumida de fertilizantes e o poder de compra ponderado à produtividade (poder de compra p.p.) no CO, e o preço do fertilizante específico. Empregou-se a metodologia de séries temporais, mais especificamente o modelo Autorregressivo Vetorial Estrutural (SVAR), para cada macronutriente primário, ou seja, os fertilizantes nitrogenados, fosfatados e potássicos. Tal modelo permitiu estimar as respostas das variáveis endógenas aos impactos positivos tanto das demais variáveis como de si próprio. Os resultados mostram que a quantidade consumida como sendo a variável mais endógena, com a maior participação do poder de compra p.p. do que seus preços, além da própria variação para os três modelos. Diferentemente dos preços que se apresentaram mais exógenos, cuja contribuição própria foi mais de 90%, também para os três modelos. Por conseguinte, nas análises dos impactos determinou-se a maior sensibilidade de variação entre o impacto no poder de compra p.p. sobre a quantidade consumida do fertilizante para os três modelos. Ao serem comparados, obtiveram a ordem decrescente das elasticidades igual a 0,65; 0,58; e 0,48, respectivamente aos fertilizantes N > P205 > K2O, sequência esta conferida pela atuação agronômica dos nutrientes no solo da região e nas culturas. Já a menor sensibilidade de variação ocorreu entre o poder de compra p.p. sobre o choque nos preços dos fertilizantes, resultado esse esperado, devido os fertilizantes serem um dos insumos necessários para o aumento de produtividade. Assim, reconhece-se a relação positiva entre os três tipos de fertilizantes minerais e a produção no Centro-Oeste pelas demandas dos fertilizantes se apresentarem inelásticas à variação dos preços dos fertilizantes.Mineral fertilizers are one of the contributor inputs to increase productivity in Brazil since the 1980s, given the limited expansion of the agricultural area, and are considered land-savers. However, because they are derived from scarce natural resources, viably extracted (economically and structurally) from limited locations of the world, and highly dependent on energy for synthesis, they make agricultural production sensitive to the impacts of supply and demand. As in 2008/2009, when the increase in fertilizer prices reduced its quantity of consumption, there were changes in the agricultural commodities market. The present dissertation aims to analyze the economic dynamics between mineral fertilizers and the agricultural market of the Central-West region, where the highest mineral fertilizer consumption is presented and the largest agricultural production in the country is concentrated. For the analysis, we considered some variables, such as the quantity of fertilizers consumed, and the purchasing power weighted by productivity, as well as the price of the specific fertilizer. The time series methodology, more specifically the Autoregressive Structural Vector Model (SVAR), was used for each primary macronutrient, that is, the nitrogen, phosphate and potassium fertilizers. This model allowed us to estimate the responses of the endogenous variables to the positive impacts of the other variables as well as of themselves. The results found the quantity consumed as being the most endogenous variable, with the greater participation of weighted purchasing power than its prices, besides its own variation for the three models. Differently from the prices that presented more exogenous, whose own contribution was more than 90% also for the three models. Therefore, in the analysis of the impacts, it was determined the greater sensitivity of variation between the amount of fertilizer consumed on the shock in purchasing power for three models. When compared, they obtained the decreasing order of elasticities equal to 0.65; 0.58; and 0,48, respectively, to N> P205 > K2O fertilizers, a sequence that is conferred by the agronomic performance of the nutrients in the soil of the region and in the crops. On the other hand, the lower sensitivity of variation occurred between purchasing power over the shock of fertilizer prices, a result expected, because fertilizers are one of the inputs needed to increase productivity. Thus, the positive relation between the three types of mineral fertilizers and the production in the Central-West by the demands of the fertilizers are inelastic to the variation of the fertilizer prices

Influence of human osteoblasts on hematopoietic stem cells: Analysis in coculture on a synthetic biphasic calcium phosphate ceramic.

24th Annual Meeting of the American-Society-for-Bone-and-Mineral-Research, SAN ANTONIO, TEXAS, SEP 20-24, 200