Given the increased aesthetic demands of patients, along with improvements in the formulation of resin composites, the ability of these materials to bond to tooth structures, and concerns about dental amalgam fillings, the applicability of resin composites in dentistry has become increasingly widespread. As resistance to wear represents an important factor in determining the clinical success of resin composite restoratives, the aim of this article was to define what constitutes wear; the major underlying phenomena involved in this process-adhesion, abrasion, fatigue, and corrosion-being described. Discussions were also focused on factors that contribute both to the magnitude and minimization of resin composite wear. Finally, insights were included on both in vivo and laboratory studies used to determine wear resistance.

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 paper presents the development of an advanced ceramic material for manufacturing aerostatic porous bearing. The results show that there is homogeneous distribution of the pores in the alumina matrix by using different concentrations of the added component (sucrose). The average pore diameter remained around 0.14 µm and respective porosity around 28%, with small standard deviation. The mathematical model of the aerostatic porous bearing is presented, and numerical results indicate that the parameter related to porous medium (G) strongly affects the resultant bearing load capacity and stiffness. Considering the experimental and numerical results, the porous matrix obtained with 40% of sucrose concentration is more suitable for the aerostatic porous bearing application in study. Keywords: porous ceramic materials, aerostatic bearings, permeability identification, bearing modeling. Resumo Este trabalho apresenta o desenvolvimento de materiais cerâmicos porosos, obtidos a partir de cerâmicas estruturais (alumina), para a fabricação de mancais aerostáticos. Os resultados iniciais indicaram que, houve homogeneidade na distribuição dos poros na matriz de alumina, obtida com diferentes concentrações de agente poroso (sacarose). O valor médio dos poros foi de

The new wheelchair pushrim provides a proper fit for the hands due to its ergonomic design and its polyurethane composition, making wheelchair propulsion easier and more comfortable than the conventional wheelchair pushrim. Assistive technology devices should be design based on ergonomic concepts that involve less effort and offer greater comfort for the user. [Box: see text].

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.

The mathematical modeling of aerostatic porous bearings, represented by the Reynolds equation, depends on the assumptions for the flow in the porous medium. One proposes a modified Reynolds equation based on the quadratic Forchheimer assumption, which can be used for both linear and quadratic conditions. Numerical results are compared to those obtained with the linear Darcy model. It is shown that, the non-dimensional parameter Φ, related to non-linear effects, strongly affects the bearing dynamic characteristics, but for values of Φ > 10, the results tend to those obtained with the linear model.

Green and white machining has being extensively employed in compact blanks to obtain a pre-form prior to the sintering of advanced ceramics. Both machining processes involve low-energy consumption and high material removal capacity. Green machining is more sustainable than white machining; however, its use should be more demanding because of the complex binder links between ceramic powders. The goal of this work is to identify the limits of aggressive cutting through measures of machining forces on green specimens and its correlation with the mechanical properties of sintered alumina rods. Rod specimens were obtained from alumina-PVAl granules compacted at 100 and 200 MPa, thermal annealed and green machining employing a head with aerostatic bearings. Gradual introduction of critical defects on the surface due to the action of the wheel was detected. Surface without damage was detected with a material removal rate of 10,000 mm 3 /min and with power consumption of 1700 W. The speed limit that was identified resulted in the rupture of the specimen, depending on the depth of cut, which exceeded the mechanical strength. The correlation between power consumption and rate of removal proved to be critically important processing parameters for the design of machining in green ceramic.

This work presents a numerical study on the effect of permeability on the static characteristics of aerostatic ceramic porous bearings. This study is important in bearing design because of the inherent permeability variation of the porous ceramic samples induced by manufacturing and sintering processes. The mathematical modelling of these bearings is based on the modified Reynolds equation, which depends on the pressure‐flow assumption (Darcy or Forchheimer) and on the static and dynamic permeability coefficients of the porous matrix. In this work, the modified Reynolds equation is numerically solved considering the variations of permeability values, whose distribution was obtained from experimental tests of the ceramic samples. Monte Carlo method is used to introduce variability in the solutions. One focuses on the effects of such variation on the results of predicted bearing loading capacity. Results show that optimum regions of the bearing load capacity do not vary significantly due to static and dynamic permeability variations. Copyright © 2012 John Wiley & Sons, Ltd.