Cylindrical dental implants made of commercially pure titanium were analysed in four different surface finishes: as-machined, Al2O3 blasted with Al2O3 particles, plasma-sprayed with titanium beads and electrolytically coated with hydroxyapatite. Scanning electron microscopy (SEM) with Energy Dispersive X-ray Analysis (EDX) revealed the topography of the surfaces and provided qualitative results of the chemical composition of the different implants. X-ray Photoelectron Spectroscopy (XPS) was used to perform chemical analysis on the surface of the implants while Laser Scanning Confocal Microscopy (LSM) produced topographic maps of the analysed surfaces. Optical Profilometry was used to quantitatively characterise the level of roughness of the surfaces. The implant that was plasma-sprayed and the hydroxyapatite coated implant showed the roughest surface, followed by the implant blasted with alumina and the as-machined implant. Some remnant contamination from the processes of blasting, coating and cleaning was detected by XPS.

titanium --- dental implants --- surface characterisation

Evaluations of the fracture toughness in metal matrix composites (Duralcan reinforced with 15% of Al(2)0(3) and SiC) are presented in this work. The application of Elastic Plastic Fracture Mechanics is discussed and the obtained values are compared with the ones obtained by means of Linear Elastic Fracture Mechanics. Results show that J IC derived K JC values are higher than the corresponding values obtained by direct application of the linear elastic methodology. The effect of a heat treatment on the material fracture toughness was also evaluated in which the analyzed approaches showed, not only different toughness values, but also opposite tendencies. A second comparison of the J IC and K JC values obtained in this work with toughness values reported in the literature is presented and discussed.

metal matrix composite --- elastic plastic feature mechanics --- feature toughness --- experimental techniques

Medium Density Fiberboard (MDF) is a wood-based composite widely employed in several industrial applications, in addition to its use in structures subjected to dynamic loads. Its fatigue-related aspects, however, have been consistently ignored. This work proposes to study fatigue in MDF, including the following factors: the basic concepts of MDF and fatigue and the statistical design of fatigue experiments in MDF, with the purpose of obtaining accurate information for analysis by means of statistical methods. The results of our tests revealed that the statistical model is suitable to fit the number of cycles in intermediary S and f levels and to determine the levels of the factors that maximize the total number of cycles to failure. It was also found that the proposed design is of great practical interest for fatigue strength in the tension in wood and wood derivatives.

MDF --- fatigue --- fatigue properties in wood composites --- factorial designs

The austenitic stainless steel of orthodontic wires may undergo phase transformation induced by plastic deformation and heat treatment for stress relief. In order to study these changes, arches were made with 0.0215 x 0.027" orthodontic wires and ferromagnetic resonance measurements were performed. The results showed that the best heat treatment for recovery of the austenitic phase seems to be at 450 °C for 3 min.

phase transitions --- ferromagnetic resonance