No abstract

The developement and regeneration of healthy bone tissue is a complex process that includes the interaction of different cell types and requires a set of coordinated processes. The loss of bone tissue may occur due to various reasons: surgical removal, bone trauma (i.e., fractures) or systemic bone loss (i.e., osteoporosis). When the natural bone tissue is destroyed, the regeneration capacity of the bone is not always satisfactory. The result consists therefore in many functional and structural aberrations. In order to improve and accelerate the healing process, bone substitutes have been developed. Hydroxyapatite has been widely used in bone applications due to its excellent biocompatibility, osteoconductivity and bioactivity [1,2]. The objective of this research is to obtain a new composite biomaterial that can be used as bone substitute. In this study, bovine hydroxyapatite obtained from freshly calcined bovine femur was used. The objective of this research is to obtain a new composite biomaterial that can be used as bone substitute. The experimental composite samples were obtained using bovine hydroxyapatite as matrix and tricalcium phosphate, respectively, magnesium oxide as reinforcement materials. The synthesis process of these new biomaterial composites, the effect of chemical composition, surface structure, chemical and phase composition as well as mechanical features have been investigated.

The dies used for copper/brass hot extrusion made of tool steels failed after a small number of runs. The die must be either refurbished (reconditioned) either discarded or replaced by a new die. These results are not satisfactory for a good production, so we took into account a new alloy to use for confectioning the dies. Before the first die was readily made, an experiment was performed to justify the migration to this new alloy.Heating cycles are performed to observe microstructure evolution in Rene 41. These heating cycles mimic the usage conditions of the die in service, except the stresses during extrusion. The alloy at specific number of cycles is analyzed by optic and electron microscopy (SEM), X-ray diffraction analysis (XRD), Vickers microhardness investigations and dilatometric tests.Minor changes occurred in the microstructure: M23C6 carbides appeared at grain boundary and depleted adjacent regions in alloying elements.

Al-Cu matrix composite materials with 5-20 wt. proportions of SiC hard particles and un-reinforced Al-Cu alloys obtained by powder metallurgy (P/M), in the same homogenization (20 r.p.m., about 7 hours)– pressing (450 MPa for composites) - presintering (300-420oC/30 min/H2) conditions but at different sintering temperatures (520-620oC/60min/H2, furnace cooling) were analyzed in terms of microstructural and physical characteristics. The existence of good bonding between metallic matrix and ceramic particles at interface and the morphology and distribution of pores and carbides in the matrix was evaluated by means of quantitative analysis. Using computer-assisted Optic Quantitative Microscopy on the samples, we determined the pore surface area for the studied materials and the surface area and grain size distribution of the SiC particles of sintered composites by analyzing the captured images in many fields. The hardness were correlated with quantity pore surface area and resulted that the lowest values of porosity were achieved at 620oC and at 10 and 15% silicon carbide in matrix.

Higher-noble dental alloys (Au, Ag, and Pd) are the most desirable for dentistry applications, but they are expensive. Low-noble (Ag, Pd, Cu) dental alloys are alternatives to higher-noble ones due to their lower price. In this regard, the paper supports the price lowering of dental alloy by increasing the Cu content, i.e., a new 58Ag24Pd11Cu2Au2Zn1.5In1.5Sn dental alloy. The increasing addition of the Cu leads to a complex structure consisting of a solid solution that engulfs compounds of micrometric and nanometric sizes. The 58Ag24Pd11Cu2Au2Zn1.5In1.5Sn has demonstrated a much better electrochemical corrosion behavior in artificial saliva compared to the Paliag and Unique White dental alloys. The improved corrosion behavior of the new alloy is supported by the diminishing of the Cu selective diffusion into the electrolyte due to its retaining into compounds and into Ag-Pd solid solution. Also, the synergic effects of Cu, Zn, In, Sn may improve the corrosion resistance, but they have strengthened the 58Ag24Pd11Cu2Au2Zn1.5In1.5Sn matrix. The main finding addressed in the paper consists in a new 58Ag24Pd11Cu2Au2Zn1.5In1.5Sn dental alloy with improved corrosion resistance in artificial saliva.