Background Implants or implantable devices should integrate into the host tissue faster than fibrous capsule formation, in which the design of the interface is one of the biggest challenges. Generally, bioactive materials are not viable for load-bearing applications, so inert biomaterials are proposed. However, the surface must be modified through techniques such as coating with bioactive materials, roughness and sized pores. The aim of this research was to validate an approach for the evaluation of the tissue growth on implants of porous alumina coated with bioactive materials. Methods Porous alumina implants were coated with 45S5 Bioglass® (BG) and hydroxyapatite (HA) and implanted in rat tibiae for a period of 28 days. Ex vivo resections were performed to analyze osseointegration, along with histological analysis, Scanning Electron Microscopy with Energy Dispersive X-Ray spectroscopy (SEM-EDX) line scanning, radiography and biomechanical testing. Results Given that the process of implant integration needs with the bone tissue to be accelerated, it was then seen that BG acted to start the rapid integration, and HA acted to sustaining the process. Conclusions Inert materials coated with bioglass and HA present a potential for application as bone substitutes, preferably with pores of diameters between 100 μm and 400 μm and, restrict for smaller than 100 μm, because it prevents pores without organized tissue formation or vacant. Designed as functional gradient material, stand out for applications in bone tissue under load, where, being the porous surface responsible for the osseointegration and the inner material to bear and to transmit the loads.

This study aimed to evaluate the osteointegration and genotoxic potential of a bioactive scaffold, composed of alumina and coated with hydroxyapatite and bioglass, after their implantation in tibias of rats. For this purpose, Wistar rats underwent surgery to induce a tibial bone defect, which was filled with the bioactive scaffolds. Histology analysis (descriptive and morphometry) of the bone tissue and the single-cell gel assay (comet) in multiple organs (blood, liver, and kidney) were used to reach this aim after a period of 30, 60, 90, and 180 days of material implantation. The main findings showed that the incorporation of hydroxyapatite and bioglass in the alumina scaffolds produced a suitable environment for bone ingrowth in the tibial defects and did not demonstrate any genotoxicity in the organs evaluated in all experimental periods. These results clearly indicate that the bioactive scaffolds used in this study present osteogenic potential and still exhibit local and systemic biocompatibility. These findings are promising once they convey important information about the behavior of this novel biomaterial in biological system and highlight its possible clinical application.

The objective of this study was to manufacture porous scaffolds with bioinert and bioactive materials to join mechanical properties and bony integration. Porous alumina ceramic matrices were produced using the slurry technique followed by isostatic pressing, leaching and sintering. Porous alumina samples presented 75.0vol% porosity and 52.27MPa of compressive strength. Bioglass/hydroxyapatite ceramic slurry was used as coating on alumina matrices. The infiltration was performed by dipping the alumina porous samples into bio-glass/hydroxyapatite ceramics slurry under vacuum and followed by sintering. The evaluation of the alumina ceramic scaffolds samples were made using EDX, mechanical and in vitro tests. For the in vitro tests, fibroblastic VERO cell line was employed. The porous alumina ceramic coated acquired a higher strength and more pronounced cell interaction than the non coated alumina scaffolds.

Introduction: The mechanical properties and corrosion resistance of a material are dependent on its microstructure and can be modifi ed by phase transformation. When a phase transformation occurs in a material it usually forms at least one new phase, with physical-chemical characteristics that differ from the original phase. Moreover, most phase transformations do not occur instantly. This paper presents an evaluation of the phase transformation of martensitic stainless steels ASTM 420A and ASTM 440C when submitted to different thermal processes. Methods: Dilatometry tests were performed with several continuous heating and cooling rates in order to obtain the profi les of the continuous heating transformation (CHT) and continuous cooling transformation (CCT) diagrams for these two types of steel. Also, the temperature ranges for the formation of the different phases (ferrite and carbides; ferrite; austenite and carbides; non-homogeneous and homogeneous austenite phases) were identifi ed. Rockwell hardness (HRC) tests were performed on all thermally treated steels. Anodic and cathodic potential dynamic polarization measurements were carried out through immersion in enzymatic detergent as an electrolyte for different samples submitted to the thermal processes in order to select the best routes for the heat treatment and to recommend steels for the manufacture of surgical tools. Results: The martensitic transformation temperature tends to increase with increasing temperature for the initiation of cooling. The 440C steel had a higher hardness value than the 420A steel at the austenitizing temperature of 1100 °C. Above the austenitizing temperature of 1100 °C, the material does not form martensite at the cooling rate used, which explains the sharp decline in the hardness values. Conclusion: The study reported herein achieved its proposed objectives, successfully investigating the issues and indicating solutions to the industrial problems addressed, which are frequently encountered in the manufacture of surgical instruments.

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Ceramic scaffolds, mechanically qualified, highly porous, non biodegradable and with bioactive coating have been manufactured. The aim of this study was evaluated mechanical and in vivo responses of the porous alumina scaffolds with bioactive coating. The bioactive coating was performed under vacuum with bio-glass (45S5®)) and hydroxyapatite (HAp). Alumina ceramics (Al2O3) are used for bone implants in function of the biocompatibility and the high mechanical reliability of this material. Unfavourably alumina is a bioinert material and bone ingrowths are hard to occur and any implant anchorage becomes difficult. To improve this, ceramic scaffold samples were made with porosity concentration around 75vol% and with average pores diameters around 190.0µm. They were mechanically characterized through macro and micro structural analyses and mechanical tests and biologically through cell culture tests with fibroblastic VERO cell line for cytotoxicity and animal experiments on tibiae rats – Rattus norvegiicus albinos – aiming histological and line scan analysis in order to check the scaffold-bone cellular interaction. Current results seem to suggest the promising properties of the bioactive coated alumina ceramic scaffolds tested. The concentration of 75vol% alumina showed to be the great alternative for an economical solution for porous alumina ceramic scaffolds related to the mechanical properties and bone integration.

This research consisted of implementing and evaluating an empirical mathematical model to reproduce analytically the dilatometric behavior of ASTM 420A and ASTM 440C martensitic stainless steels, widely used for manufacturing surgical tools. Martensitic stainless steels can be subdivided into three subgroups: low-carbon, medium-carbon and high-carbon steels. The microstructure of each group is also characteristic as needlelike martensitic; very fine martensitic; and ultra-fine martensitic containing carbides. The proposed method was based on experimental data obtained from the dilatometric testing of the steel samples applying low heating rates. It was possible to determine the formation of phase fields near the equilibrium conditions. The method, being based on empirical data, ensured a greater approximation to the experimental values, verifying that it can be applied as a useful tool in the evaluation of industrial heat treatments for surgical tools.Keywords Dilatometric test, Mathematical modeling, Phase transformation, Martensitic stainless steels, Surgical tools. Modelamento matemático de ensaio dilatométrico em aços inoxidáveis martensíticos 420A e 440C utilizados em ferramental cirúrgico

The formation of grains and their growth based on the elimination of other grains, before thermal cycles are imposed, are essential for the correct conformation of a material and to control the microstructure, texture and orientation relationships between phases. However, when the boundary of a polycrystalline grain intersects the outer surface and the material is exposed to temperatures higher than half of its fusion temperature, a crack or groove appears. This research aims to apply a method to evaluate the energy of the grain boundary (GB) and also to compare the energy values of the faces of the GB, and to investigate commercially-pure grade 2 titanium in relation to the action of forces on the grain boundary of the free surface. The thermal attack under vacuum technique was used to reveal, at high temperatures, the titanium microstructure, which is preserved under a very thin oxide layer even when the sample is brought to room temperature. Thus, at room temperature, it was possible to analyze the Ti surface viewed at high temperature. The thermal cracks or grooves appearing due to the selective vaporization of atoms at the GB were measured geometrically using atomic force microscopy. The energy relationship of the GB was determined from the microstructural appearance at high temperatures and applying the equation g gb = 2·g s ·senj to the thermal crack formed between two grains.The results were compared experimentally with others reported in the literature. With the method applied in this study it was possible to evaluate the energy of the GB and it was verified that this energy was anisotropic for the material under study.Keywords Titanium, Grain boundary energy, Atomic force microscopy, Thermal attack under vacuum. Medida de energia de contorno de grão do titânio comercialmente purograu 2 -em alta temperaturaResumo A formação e o crescimento de grãos a partir de outros existentes, perante ciclos térmicos impostos, são fundamentais para a conformação adequada do material, para controlar a microestrutura, textura e relações de orientação entre as fases. Com o princípio da formação de uma fenda térmica á partir da exposição do material a temperaturas maiores que a metade de sua temperatura de fusão, esta pesquisa visa a comprovação de um método para avaliar a energia de contorno de grão (CG), comparar os valores da energia das faces do CG e investigar a ação das forças na superfície livre dos CGs do titânio comercialmente puro grau 2. A técnica de ataque térmico sob vácuo foi empregada para revelar, em altas temperaturas, a microestrutura do titânio, esta técnica permite a manutenção da estrutura "congelada" sob uma camada de óxido de pequena espessura mesmo quando a amostra é trazida à temperatura ambiente. Com este método foi possível analisar a superfície do Ti em temperatura ambiente, como se estivesse sendo visualizada em altas temperaturas. As trincas ou fendas térmicas provenientes da vaporização seletiva de átomos no CG foram medidas geometricamente utilizando Microscopia de Força Atômica. A energia d...