José Henriques

Physicochemical characterization of biomaterials commonly used in dentistry as bone substitutes--comparison with human bone

The present work focuses on the physicochemical characterization of selected mineral-based biomaterials that are frequently used in dental applications. The selected materials are commercially available as granules from different biological origins: bovine, porcine, and coralline. Natural and calcined human bone were used for comparison purposes. Besides a classical rationalization of chemical composition and crystallinity, a major emphasis was placed on the measurement of various morphostructural properties such as particle size, porosity, density, and specific surface area. Such properties are crucial to acquiring a full interpretation of the in vivo performance. The studied samples exhibited distinct particle sizes (between 200 and 1000 microm) and shapes. Mercury intrusion revealed not only that the total sample porosity varied considerably (33% for OsteoBiol, 50% for PepGen P-15, and 60% for BioOss) but also that a significant percentage of that porosity corresponded to submicron pores. Biocoral was not analyzed by this technique as it possesses larger pores than those of the porosimeter upper limit. The density values determined for the calcined samples were close to the theoretical values of hydroxyapatite. However, the values for the collagenated samples were lower, in accordance with their lower mineral content. The specific surface areas ranged from less than 1 m(2)/g (Biocoral) up to 60 m(2)/g (BioOss). The chemical and phase composition of most of the samples, the exception being Biocoral (aragonite), were hydroxyapatite based. Nonetheless, the samples exhibited different organic material content as a consequence of the distinct heat treatments that each had received.

Tensile Resistance of Steel-Reinforced Anchorages: Experimental Evaluation

One of the research topics related to composite steel-concrete structures is the connection between steel and concrete members-namely, the design of the anchorages. Because the design of steel-reinforced anchorages using the available methodologies (namely, from the CEB Design Guide, CEN/TS 1992-4, and ACI 318-08) may lead to excessively conservative results, experimental studies were conducted at the Civil Engineering Department of the University of Coimbra dealing with cast-in-place headed anchors. The aim of this study is the evaluation of the effect of hanger reinforcement on the behavior of steel-headed anchors embedded in concrete subjected to tension loads. A total of 40 laboratory tests, divided into two groups, were performed, dealing with plain concrete; hanger and usual grid surface reinforcement; and the variation of the member thickness, embedment depth, and proximity of the concrete member edges. Some conclusions from the tests are analyzed and discussed.

High-strength tower in steel for wind turbines (Histwin) : Final report

Innovative solutions for assembling joints of a tubular tower for wind turbines were studied and the project provides a background for design. This solution is simpler to produce and 80 % less expe ...