Materials Science Forum Vols. 727-728

Abstract: A compound contending silver ion specimens presents biocidal properties with effect proportional to ion concentration. An efficient biocidal material can be developed by incorporating silver ions species in glasses by ionic exchange process. The reactive area and material porosity are factors that influence the ion exchange reaction efficiency. Previous studies show that the acid activation of glasses increases the absorption capacity and can also increase the exchange capacity. This paper presents preliminary results on the biocide potencial optimization of the biocide powder glass. This process was performed using hydrochloric acid. Different pH (1.00, 3.00 and 5.00), treatment time (2.0, 4.0 and 6.0 hours) and temperature (30.0, 60.0 and 90.0°C) were used in the samples development. Microbiological analysis of the samples was made by disk diffusion method in the bacteria species Echerichia coli and Staphylococcus aureus. Samples were still submitted to EDS and Atomic Absorption.

Abstract: The Calcium Phosphate Cement (CFC) has been used as filling material for bone defects because of osteoconductivity properties, bioactivity and biocompatibility. Recent studies, mostly in animals, indicate its use as an adjunct to treatment with osseointegrated implants. Thus this work aims reporting the event in which post-extraction socket was filled with CFC-based α-tricalcium phosphate and calcium sulfate and after four months, the implant was installed through the cement which was not reabsorbed with good primary stability. Upon reopening of the implants after six months, the clinical appearance of peri-implant region was considered normal. Radiographically, there wasnt radiopaque appearance of CFCs in the alveolar region of the test anymore. Histologically, remaining CFC in direct contact with bone without intervening fibrous connective tissue was noticed. Its concluded that the CFC showed osteoconductive behavior. The material tested seems to be an acceptable option for filling the post-extraction socket with the purpose of maintaining bone volume, however, more research is needed to generalize the indication.

Abstract: ZrO₂ ceramics are one of the most important materials used in dental prostheses production, due to their excellent mechanical resistance and chemical inertness in the mouth environment. Nevertheless, the combination of low pHs and fluoride presence is able to reduce the chemical stability of these ceramics. In this work, the resistance of commercial blocks of micrometric and nanometric sized Y₂O₃-stabilized ZrO₂ ceramics (ProtMat Materiais Avançados® and Ivoclar®) was evaluated in Fusayama artificial saliva of different pHs with (and without) the presence of fluoride ions. The study was based on the analysis of the amount of Zr⁴⁺ and Y³⁺ ions dissolved in the artificial saliva after different exposure times using ICP OES technique. The XRD technique was also employed to investigate the phase transformations occurring during the degradation process in artificial saliva. The micrometric sized ZrO₂ ceramics presented higher resistance in the artificial saliva than nanometric sized structures.

Abstract: The rise of human life expectancy results in the increasing of elderly population and consequently the diseases of old age, which are mostly related with bone degenerative diseases. These problems also affect young individuals, commonly due to accidents (automobile and work). This fact has stimulated the research and development of materials that can replace or regenerate the damaged bone. From the engineering view, bone is a composite material consisting of an organic matrix (collagen), reinforced by an inorganic component (hydroxyapatite). The search for a suitable material, with properties tailored to the needs of the bone metabolism, as well as the adequate way of material processing, which ensures the maintenance or improvement of their initial properties, motivated this research. In this work was developed composite materials, based on bioresorbable polymer (PLLA) and phosphocalcic nanoceramic (HA). The composites were characterized by scanning electron microscopy (microstructure) and dynamical mechanical analyses (mechanical behavior). The results indicated these materials as promising for applications in the medical and dental manufacturing devices (plates and screws) by injection molding, and also for scaffolds by rapid manufacturing, in the tissue engineering area.

Abstract: The bovine bone and sintetic hydroxyapatite (HA) bioceramics are reference materials to employment as a bone substitute, however, their slow rate of degradation and its low rate of bioactivity index (Ib) are presented as limiting factors for application as bone graft. In contrast, the bioglass is a resorbable and osteoinductive material. the present work objective the development of composites of dispersed bovine bone or sintetic HA in silicate-phosphate bioglass, seeking to obtain a biomaterial with properties suitable for application as bone grafts. The composites were prepared by mixing between the powder components followed by sintering for 1h. Were used HA and bioglass (45S5) with particle size <240μm. The tested proportions of HA/45S5 were 20/80, 30/70 and 40/60 (wt%). The composites characterization was made employing scanning electron microscopy, Infra-Red Spectrometry and hydrolytic resistance test. The test results indicate the potential use of the materials developed for applications such as bone graft.

Abstract: Extracellular synthesis of silica particles was carried out by Fusarium oxysporum mycelia using rice husk ash (RHA) as raw material. RHA before and after bioprocessing was analyzed by SEM and specific surface area. Dissolved silica was quantified using colorimetry. Incubation of rice husk ash with F. Oxysporum at 28°C and pH 6.8 indicated that 80% silica was dissolved and micrographs of RHA before and after reaction with fungi showed that the morphology of silica particles changed and the average size decreased (~600 to ~5 µm). Moreover, specific volume pore of particles was reduced from 0.026 to 0.013 cm³/g and surface area increased from 115 to 125 m²/g. Dissolved silica corresponds to 177 m²/g. It is concluded that synthesis of oxide materials using fungal biotransformation is a viable process to obtain added value products from agro-industrial waste materials.

Abstract: The crystallization process of lithium disilicate glass-ceramic with SiO₂ from rice husk silica replacing the high-purity SiO₂ starting powder has been investigated in this work. Glasses were developed at the stoichiometric composition of 66%.molSiO₂:33%.molLiO₂ using commercial SiO₂ and the one obtained by thermochemical treatment of rice husk. The influence of rice husk-SiO₂ on crystallization process to different granulometry, microstructure and kinetic behavior was determined and discussed. Investigations were carried out by means of differential thermal analysis (DTA), X-ray fluorescence (XRF), X-ray diffractometry (XRD) and scanning electron microscopy (SEM). Amorphous and transparent glasses were obtained after melting. The lithium disilicate glass-ceramic crystallization peaks (Tp) are between 550 to 660°C to different granulometry (<63μm, 63μm < x < 250μm and 1mm < x < 2mm) and DTA heat rates (5; 10; 15; and 20°C/min) in both glasses from different silica sources, and the formed phase was Li₂Si₂O₅ as the crystalline phase after DTA thermal analysis as XRD confirmation. Improve in mechanical properties were estimated by morphological analysis of the microstructure modification in increasing the heat treatments temperature by SEM. The increase of glass substitution for crystalline phase was also observed with SEM images to both glass-ceramics from different silica sources.

Abstract: Calcium phosphate cements have bioactivity and osteoconductivity and can be molded and replace portions of bone tissue. The aim of this work was to study the obtainment of α-tricalcium phosphate, the main phase of calcium phosphate cement, by wet reaction from calcium nitrate and phosphoric acid. There are no reports about α-tricalcium phosphate obtained by this method. Two routes of chemical precipitation were evaluated and the use of two calcinations temperatures to obtain the phase of cement. The influence of calcination temperature on the mechanical properties of cement was evaluated. Cement samples were characterized by particle size analysis, X-ray diffraction, mechanical strength and scanning electron microscopy. The results demonstrate the strong influence of synthesis route on the crystalline phases of cement and the influence of concentration of reactants on the product of the reaction, as well as, on the mechanical properties of cement.

Abstract: The calcium phosphate cements (CPCs) have attracted great interest for use in orthopedics and dentistry as replacements for damaged parts of the skeletal system,showing good biocompatibility and osseointegration. These characteristics allow its use as a bone graft.Several studies in literature have shown that the addition of polymeric additives has a strong influence on the mechanical properties of cement. The low mechanical strength is the main impediment to a broader use of calcium phosphate bone cement (CPCs) as implant material. The aim of this work was evaluate the strength of a CPC based on α-tricalcium phosphate, with polymeric additions. CPC was synthesized and sodium alginate were added (1%, 2% and 3% by weight) and ammonium polyacrylate (3%; dispersant) in aqueous solution. Specimens were molded and evaluated for density, pH, porosity, in vitro test (Simulated Body Fluid),crystalline phases and mechanical strength. The results show the increase of the mechanical properties of cement when added with sodium alginate and dispersant.

Abstract: A potential approach to achieving the objective of favorably modulating the biological response of implantable biopolymers combined with good mechanical properties is to consider compounding the biopolymer with a bioactive nanocrystalline ceramic biomimetic material with high surface area. In this work, n-HAp (nanohydroxyapatite) and n-α-TCP (nanoα-tricalcium phosphate) powders were modified by silane coupling agent and mixed with poly (dimethyl siloxane) gum so nanocomposites could be achieved. The influence of the introduction of modified and unmodified calcium phosphate particles on the composite thermodynamics parameters of cross-linking, static contact angle and surface energy were investigated. It was found that the dispersion state of modified particles in the silicone matrix was homogeneous. The introduction of fillers into the silicone matrix changed the enthalpy of cross-linking. The addition of unmodified particles led to higher surface energy values, on the other hand, modified particles led to lower surface energy values.