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- Poly(ɛ-caprolactone) and Polyethylene Glycol Diacrylate-based Scaffolds for TMJ Bioengineered Disc ImplantsPublication . Francisco, Luís; Moura, Carla; Viana, Tânia; Ângelo, David; Morouço, Pedro; Alves, NunoThe temporomandibular joint (TMJ), articulation between the mandibular condyle and the temporal bone, is divided into two compartments (superior and inferior) by a fibrocartilaginous disc. The TMJ disc consists on an avascular and non-innervated tissue, with viscoelastic behavior. Mechanically, the TMJ disc experiences tensile, compressive and shear forces. TMJ disc displacement or degeneration could lead to severe intra-articular temporomandibular joint disorders (TMD). Despite the large number of current therapies/treatments, there is limited treatment options for severe intra-articular TMD. A strategy to solve this problem could be the use of an interposal material to substitute the damaged TMJ disc, which will gradually degrade and give rise to new tissue. In this work three options were used and tested, one using a thermoplastic material, poly(ε-caprolactone) (PCL), another using an photopolymerized hydrogel, polyethylene glycol diacrilate (PEGDA) and the third using the combination of the two materials. Obtained results demonstrated that that the combination of different materials could represent a significant advantage in the TMJ disc TE and in the cartilage TE in general.
- EditorialPublication . Bartolo, Paulo; Chua, C. K.
- Biomedical production of implants by additive electro-chemical and physical processesPublication . Bartolo, Paulo; Kruth, Jean-Pierre; Silva, Jorge; Levy, Gideon; Malshe, Ajay; Rajurkar, Kamlakar; Mitsuishi, Mamoru; Ciurana, Joaquim; Leu, MingBiomanufacturing integrates life science and engineering fundamentals to produce biocompatible products enhancing the quality of life. The state-of-the-art of this rapidly evolving manufacturing sector is presented and discussed, in particular the additive electrical, chemical and physical processes currently being applied to produce synthetic and biological parts. This fabrication strategy is strongly materialdependent, so the main classes of biomaterials are detailed. It is explained the potential to process composite materials combining synthetic and biological materials, such as cells, proteins and growth factors, as well the interdependences between materials and processes. The techniques commonly used to increase the bioactivity of clinical implants and improve the interface characteristics between biological tissues and implants are also presented.
- On distributive lattices and weakly Mal’tsev categoriesPublication . Martins-Ferreira, NelsonWe prove that a variety of lattices is weakly Mal’tsev if and only if it is a variety of distributive lattices.
- A study of the mechanical properties of natural fibre reinforced compositesPublication . Ferreira, J. A. M.; Capela, C.; Costa, J. D.This paper presents the results of a current research of the tensile properties: ultimate strength and stiffness modulus in composites using natural reinforcements. Hemp short fibres and pine sawdust were randomly distributed in polypropylene matrices to produce composite plates with 5 mm thickness by injection moulding technique. The specimens were cut from these plates with bone dog shape or plane bars, and tested in tensile and four points bending, respectively. Stiffness modulus and ultimate stresses were obtained for different weight fraction content of reinforcement and discussed taking in account the failure modes. Four series of pine sawdust reinforced specimens were immersed in water in periods up to 20 days. Periodically, the specimens were removed from the water recipient and immediately tested. The damage effect of water immersion time was discussed based in the tensile results and in the water absorption curves.
- On categories with semidirect productsPublication . Martins-Ferreira, Nelson; Sobral, ManuelaNecessary and sufficient conditions for a pointed category to admit semidirect products, in the sense of Bourn and Janelidze (1998) [3], are provided and interpreted in terms of protomodularity and exactness of appropriate split chains.
- Evaluation of in vitro degradation of PCL scaffolds fabricated via BioExtrusion – Part 2: Influence of pore size and geometry: The present study is to accurately investigate the influence of design parameters, such as filament distance (FD) and lay-down pattern, on the degradation behaviour and kinetics of PCL scaffolds, obtained via BioExtrusionPublication . Domingos, Marco; Chiellini, F.; Cometa, S.; Giglio, E. De; Grillo-Fernandes, E.; Bartolo, Paulo; Chiellini, E.The in vivo degradation processes by which scaffolds degrade and are replaced by neo-tissue are complex and may be influenced by many factors, including environmental conditions, material properties, porosity and 3D architecture. The present study is focused on the influence of design parameters, filament distance (FD) and lay-down pattern, on the degradation kinetics of Polycaprolactone (PCL) scaffolds obtained via BioExtrusion. Through the variation of design parameters it was possible to obtain two groups of scaffolds with distinct pore geometry and size. The in vitro degradation was performed in simulated body fluid (SBF) and in phosphate buffer solution (PBS) for six months. Our results highlight a more complex degradation pattern of the scaffolds in SBF than in PBS, probably related to a mineral deposition. Significant statistical differences in weight loss values at month 6, allowed us to conclude that degradation kinetics of PCL scaffolds is strongly influenced by the pore size.
- EditorialPublication . Bartolo, Paulo; Chua, C. K.Welcome to a brand new year of 2010! In this editorial, we bring you the latest update concerning rapid prototyping technologies,which of coursemany of you are aware, include many terminologies such as layer manufacturing and solid freeform fabrication, amongst others. The longstanding need to standardize the terminologies within the rapid prototyping andmanufacturing industry has nowbeenmetwith a new ASTMInternational standard, ASTMF2792, Terminology for Additive Manufacturing Technologies. The new document is the first approved standard under the jurisdiction of ASTM Committee F42 on Additive Manufacturing Technologies, which was formed in 2009.
- Effect of process parameters on the strength of resistance spot welds in 6082-T6 aluminium alloyPublication . Pereira, A. M.; Ferreira, J. M.; Loureiro, A.; Costa, J. D. M.; Bártolo, P. J.In this study the microstructural and mechanical behaviour of resistance spot welds (RSW) done on aluminium alloy 6082-T6 sheets, welded at different welding parameters, is examined. Microstructural examinations and hardness evaluations were carried out in order to determine the influence of welding parameters on the quality of the welds. The welded joints were subjected to static tensile-shear tests in order to determine their strength and failure mode. The increase in weld current and duration increased the nugget size and the weld strength. Beyond a critical nugget diameter the failure mode changed from interfacial to pullout. Taking into consideration the sheet thickness and the mechanical properties of the weld, a simple model is proposed to predict the critical nugget diameter required to produce pull-out failure mode in undermatched welds in heat-treatable aluminium alloys.
- Cork Plastic Composite Optimization for 3D Printing ApplicationsPublication . Brites, F.; Malça, C.; Gaspar, F.; Horta, J. F.; Franco, M. C.; Biscaia, S.; Mateus, A.Among natural fillers, cork has been acknowledged as a suitable alternative of other cellular materials that are widely employed in engineering applications due to their low conductivity to heat, noise and vibration, high abrasion resistance and flexibility, high compressibility ratio, among other characteristics [1]. The eco-friendly features of natural fillers based composites make them a very promising and sustainable solution to large markets mainly if additive manufacturing technologies, such as 3D printing, are used [2]. Through 3D printers, engineers, designers and architects can create design and decor products with a free complexity of geometry. In this research work, plastic matrices of HDPE – obtained from conventional suppliers – were reinforced with different ratios of cork waste and natural cork powders – obtained from cork transformation industries – to find the optimum mixture for 3D printing. The effects of cork powders content in the plastic on the morphological, physical and mechanical properties of the composites were investigated through the density, optical microscopy, wettability, thermal analysis and tensile testing. Cork-based composites were processed by an extrusion system, and the mixture of polymer, adhesive and fillers is discussed. The results show that the addition of pure cork and cork waste can be processed with polymers such as HDPE, having adequate physical and mechanical properties.