Carbonate-apatite forming ability of polyphase glass-ceramics in the CaO - MgO - SiO2 system

Several types of glass-ceramics in the CaO - MgO - SiO 2 system are shown to be bioactive, biocompatible and exhibiting various advantages for bone regeneration. A polyphase calcium-magnesium-silicate glass-ceramics is prepared by the sol-gel method including a two-step thermal treatment procedure aiming to investigate the effect of its phase composition on the in-vitro bioactivity observed. The dried gels of a chemical composition 3CaO.MgO.2SiO 2 corresponding to merwinite are thermally treated at 700°C and 1100°C. The structural behavior of the synthesized samples is examined by X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscopy (SEM). Larnite as the main crystalline phase, accompanied by merwinite, akermanite and periclase are detected after heat treatment at 1100°C. The in-vitro bioactivity of the glass-ceramics is detected by investigating the apatite formation ability in Simulated Body Fluid (SBF) for different times of soaking. The changes on the surface of the immersed samples and the formation of Mg- and Si-substituted carbonated apatites are verified by FTIR, SEM and Energy Dispersive Spectroscopy (EDS) techniques. The dissolution behavior of the glass-ceramics in SBF is also carried out by Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES). The results indicate fast degradation in SBF and high reactivity of the polyphase glass-ceramics. The latter might be used as a bioactive implant material

A deficiência de vitamina A em crianças no Brasil e no mundo Vitamin A deficiency among children in Brazil and worldwide

O presente artigo expõe, com base em uma revisão de literatura dos últimos dez anos, aspectos relevantes da Deficiência de Vitamina A (DVA) em crianças no Brasil e no mundo. Apresenta a DVA no contexto da deficiência clínica e subclínica, com ênfase na caracterização desta como problema de saúde pública. A DVA foi diagnosticada em crianças de várias regiões do Brasil, principalmente no Sudeste e Nordeste; entretanto, não foram encontrados estudos relativos a sinais clínicos. Mundialmente, as maiores prevalências de DVA foram registradas em países da África como Mali, Etiópia e Nigéria, sendo que os sinais clínicos estiveram presentes, principalmente, em regiões da Ásia e África. Os estudos apontam a DVA como problema de saúde pública em crianças, principalmente nas regiões mais pobres do globo.<br>Based on a ten-year literature review, this paper describes important aspects of Vitamin A Deficiency (VAD) among children in Brazil and worldwide. It presents VAD within a clinical and sub-clinical deficiency context, emphasizing this as a public health issue. VAD has been diagnosed in children from several parts of Brazil, especially in the Southeast and Northeast. Worldwide, the highest VAD prevalence is found in parts of parts of Africa: Mali, Ethiopia and Nigeria, and clinical indications noted especially in parts of Asia and Africa. However, no studies of clinical indications were located. Studies point to VAD as a public health issue among children, particularly in the poorest parts of the world