Abstract Up to now, plasma electrolytic oxidation (PEO) has been either produced direct current or ultra-low frequency (< 1 kHz) pulsed discharge using high concentration alkaline-silicate electrolytic (Na2SiO3 > 8 g.L-1 with presence of KOH). In order to contribute to these studies, the effect of current pulse width and time duration was investigated using diluted silicate electrolytic (Na2SiO3 2 g.L-1) and high pulse frequencies (> 1 kHz). The PEO process was performed on pure aluminum to try to explain how the phases composing the coatings are formed and distributed over the treatment time. For this, was made in situ monitoring using optical emission spectroscopy (OES) coupled with CCD camera. The crystalline phases evolution in the sample surface was investigated using grazing incidence X-ray diffraction (GIXRD). Regarding the evolution of ceramic phases, it is possible to verify that, internally, the predominant phase is rhombohedral α-Al2O3 but, superficially, the predominant phase is cubic γ-Al2O3. It was verified the presence of Si on the borders of the pores or in proximity to cracks, especially in the treatments with higher pulse width. SEM analysis shows a reduction of the superficial porosity and an increase in coating thickness with pulse width and treatment time.

A current goal of dental implant research is the development of titanium (Ti) surfaces to improve osseointegration. Plasma nitriding treatments generate surfaces that favor osteoblast differentiation, a key event to the process of osteogenesis. Based on this, it is possible to hypothesize that plasma-nitrided Ti implants may positively impact osseointegration. Objective The aim of this study was to evaluate the in vivo bone response to Ti surfaces modified by plasma-nitriding treatments. Material and Methods Surface treatments consisted of 20% N2 and 80% H2, 450°C and 1.5 mbar during 1 h for planar and 3 h for hollow cathode. Untreated surface was used as control. Ten implants of each surface were placed into rabbit tibiae and 6 weeks post-implantation they were harvested for histological and histomorphometric analyses. Results Bone formation was observed in contact with all implants without statistically significant differences among the evaluated surfaces in terms of bone-to-implant contact, bone area between threads, and bone area within the mirror area. Conclusion Our results indicate that plasma nitriding treatments generate Ti implants that induce similar bone response to the untreated ones. Thus, as these treatments improve the physico-chemical properties of Ti without affecting its biocompatibility, they could be combined with modifications that favor bone formation in order to develop new implant surfaces.

La hidroxiapatita sintética en polvo ha sido utilizada durante años para aplicaciones ortopédicas, en forma de recubrimientos biocerámicos. En este estudio, fue utilizada una hidroxiapatita, de origen natural, obtenida mediante una reacción hidrotermal, a partir de corales marinos porites. La hidroxiapatita fue proyectada por plasma térmico atmosférico sobre titanio grado II, para explorar el efecto de la temperatura del sustrato y el modo de proyección en la cristalinidad, humectabilidad y biocompatibilidad del recubrimiento. La composición de fase y cristalinidad del recubrimiento fueron determinadas por difracción de rayos x; la humectabilidad fue medida por el método de la gota de contacto y la proliferación celular fue evaluada por MTT [(bromuro de 3-(4,5-dimetiltiazol-2-il)-2,5) difenil tetrazolio]. Los resultados sugieren que los recubrimientos obtenidos con precalentamiento del sustrato, aseguran mayor cristalinidad; las superficies obtenidas con el sustrato rotando, presentaron mejor humectabilidad y el recubrimiento obtenido con el sustrato con precalentamiento y rotando, mostró mayor proliferación celular.

Synthetic hydroxyapatite powder has been used for years for orthopedic applications as bioceramic coatings. In this study was used a natural hydroxyapatite obtained by hydrothermal reaction, from marine coral porites. The hydroxyapatite was sprayed by atmospheric thermal plasma on grade--II titanium to explore the effect of substrate temperature and the projection mode in crystallinity, wettability and biocompatibility of the coating. Phase composition and crystallinity of the coating were determined by X-ray diffraction, wettability was measured by the drop contact method and cell proliferation was assessed by MTT(3-(4,5-Dimethylthiazol-2-il)-2,5)diphenyltetrazolium bromide). The results suggest that the coatings obtained preheating the substrate ensure higher crystallinity. The surfaces obtained rotating the substrate had better wettability and the coating obtained by rotating and with preheating substrate showed increased cell proliferation.

Thin films of titanium were deposited onto Al2O3 substrate by hollow cathode discharge method for the formation of a ceramic-ceramic joint using indirect brazing method. An advantage of using this technique is that a relatively small amount of titanium is required for the metallization of the ceramic surface when compared with other conventional methods. Rapidly solidified brazing filler of Cu49Ag45Ce6 in the form of ribbons was used. The thickness of deposited titanium layer and the brazing temperature/time were varied. The quality of the brazed joint was evaluated through the three point bending flexural tests. The brazed joints presented high flexural resistance values up to 176 MPa showing the efficiency of the technique.