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Rough surfaces have been shown to promote osseointegration, which is one of the keys for a successful dental implantation. Among the diverse treatments proposed to roughen zirconia, hydrofluoric acid (HF) etching appears to be a good candidate, however little is known about this process. In this work, the effect of HF concentration and etching time on the surface topography and chemistry of yttria-stabilized zirconia was assessed.Besides, to understand the etching mechanism, the reaction products present in solution and on the surface were characterized. The results indicate suitable parameters for a fast and uniform roughening of zirconia. The formation of adhered fluoride precipitates on the surface is reported for the first time and highlights the importance of cleaning after etching. Finally, it is shown that monitoring the time allows controlling the surface roughness, smooth-rough transition and fractal dimension, which should make possible the fabrication of implants with an optimal topography.

Comparisons of 2D fluid simulations with experimental measurements of Ar/Cl 2 plasmas in a low-pressure inductively coupled reactor are reported. Simulations show that the wall recombination coefficient of Cl atom (γ) is a crucial parameter of the model and that neutral densities are very sensitive to its variations. The best agreement between model and experiment is obtained for γ = 0.02, which is much lower than the value predicted for stainless steel walls (γ = 0.6). This is consistent with reactor wall contaminations classically observed in such discharges. The electron density, negative ion fraction and Cl atom density have been investigated under various conditions of chlorine and argon concentrations, gas pressure and applied rf input power. The plasma electronegativity decreases with rf power and increases with chlorine concentration. At high pressure, the power absorption and distribution of charged particles become more localized below the quartz window. Although the experimental trends are well reproduced by the simulations, the calculated charged particle densities are systematically overestimated by a factor of 3-5. The reasons for this discrepancy are discussed in the paper.

An increasing number of dental applications based on yttria-stabilized zirconia (3Y-TZP) have been developed in recent years as a result of the advances and versatility of dry-processing and soft machining at the pre-sintered state. Nonetheless, the long-term surface stability of these materials in humid environment is still a matter of concern and may limit its application. In this work, a simple method to prevent hydrothermal degradation on zirconia surface is studied in detail. This method involves the infiltration of pre-sintered parts with optimized solutions containing Ce salts, leaving unchanged the other processing steps, allowing the diffusion of Ce during conventional sintering. Several pre-sintering conditions, solution concentrations and sintering temperatures were studied and characterized, obtaining working parameters for the production of zirconia parts with mechanical properties similar to standard 3Y-TZP and high resistance to hydrothermal aging. This optimal combination was obtained with the 1150 ºC pre-sintering temperature, 50 wt% solution and sintering at 1450 ºC, leading to a superficial CeO 2 content of about 3 mol%.

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Spark plasma sintered 3Y-TZP has been investigated with respect to hydrothermal ageing and grinding. The sintering was performed between the temperatures of 1,100 and 1,600 °C for a soaking time of 5 minutes and the resulting materials were obtained with grain sizes between 65 to 800 nm and relative densities between 88.5 to 98.8%. Experiments on hydrothermal ageing in water vapour at 131 °C, 2 bars during 60 hours shows that phase stability is retained, elastic modulus and hardness of near surface region measured by nanoindentation does not change in fine grain (<200 nm) materials, in spite of porosity. In ground specimens, very small amount of transformation was found for all grain sizes studied.

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