Investigation of silver diffusion in TiO2/Ag/TiO2 coatings

Low emissivity (low-E) coatings consisting of dielectric/silver/dielectric multi-layer stacks are applied to large-area architectural glazing to reduce heat losses from buildings. In this work TiO2/Ag/TiO2 stacks were deposited onto soda-lime glass by pulsed DC reactive magnetron sputtering. The coatings were annealed in the range 100-600 C to study silver diffusion through neighbouring layers. Depth-profiling analysis was performed on these samples using time-of-flight secondary ion mass spectrometry and selected samples were also analysed by X-ray photoelectron spectroscopy and Rutherford backscattering spectrometry. Fick's second diffusion law was used to find diffusion coefficient values and to investigate the temperature dependence of silver diffusion. To investigate film morphology and composition, scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) were performed. The purpose of this study is the requirement for the understanding of the issue of silver diffusion during annealing treatments used in glass fabrication and the results obtained show that silver diffuses through the adjacent layers in a stack during heat treatment. However, in the temperature range investigated, the diffusion rates did not follow an Arrhenius dependence. At higher temperatures and longer annealing times sodium also diffuses from the glass into the coating, replacing the silver between the titania layers. © 2013 Published by Elsevier Ltd. on behalf of Acta Materialia Inc. All rights reserved

A comparative in vivo study of strontium-functionalized and SLActive™ implant surfaces in early bone healing

Vincent Offermanns,1 Ole Z Andersen,2 Michael Sillassen,2 Klaus P Almtoft,3 Inge H Andersen,3 Frank Kloss,4 Morten Foss2,5 1Department of Cranio-Maxillofacial and Oral Surgery, Medical University of Innsbruck, Innsbruck, Austria; 2Interdisciplinary Nanoscience Center (iNANO), Faculty of Science and Technology, Aarhus University, Aarhus, Denmark; 3Tribology Center, Danish Technological Institute, Aarhus, Denmark; 4Private Practice, Lienz, Austria; 5Department of Physics and Astronomy, Faculty of Science and Technology, Aarhus University, Aarhus, Denmark Purpose: Studies have shown that strontium-doped medical applications benefit bone metabolism leading to improved bone healing and osseointegration. Based on this knowledge, the aim of the study was to evaluate the performance of an implant surface, functionalized by a physical vapor deposition (PVD) coating (Ti-Sr-O), designed to yield predictable release of strontium. The Ti-Sr-O functionalized surface is compared to a routinely used, commercially available surface (SLActive™) with respect to bone-to-implant contact (BIC%) and new bone formation (BF%) in two defined regions of interest (ROI-I and ROI-II, respectively).Materials and methods: Ti-Sr-O functionalized, SLActive, and Grade 4 titanium implants were inserted in the femoral condyle of adult male New Zealand White rabbits. The PVD magnetron-sputtered Ti-Sr-O surface coating was characterized using scanning electron microscopy (SEM) for morphology and coating thickness. Strontium release and mechanical stability of the coating, under simulated insertion conditions, were evaluated. Furthermore, histomorphometrical BIC and BF were carried out 2 weeks after insertion.Results: Histomorphometry revealed increased bone formation of Ti-Sr-O with significant differences compared to SLActive and Grade 4 titanium in both regions of interest, ROI-I and ROI-II, at 0–250 µm and 250–500 µm distance from the implant surfaces. Analogous results of bone-to-implant contact were observed for the two modified surfaces. Conclusion: The results show that a nanopatterned Ti-Sr-O functionalized titanium surface, with sustained release of strontium, increases peri-implant bone volume and could potentially contribute to enhancement of bone anchorage of osseointegrated implants. Keywords: biofunctionalization, wettability, physical vapor deposition, bioactive, surface modification, bone&nbsp

Bone regenerating effect of surface-functionalized titanium implants with sustained-release characteristics of strontium in ovariectomized rats

Vincent Offermanns,1 Ole Zoffmann Andersen,2 Gregor Riede,1 Inge Hald Andersen,3 Klaus Pagh Almtoft,3 Søren Sørensen,3 Michael Sillassen,2 Christian Sloth Jeppesen,3 Michael Rasse,1 Morten Foss,2 Frank Kloss1 1Department of Cranio-, Maxillofacial and Oral Surgery, Medical University Innsbruck, Innsbruck, Austria; 2Interdisciplinary Nanoscience Center (iNANO), Faculty of Science and Technology, Aarhus University, Aarhus, Denmark; 3Tribology Centre, Danish Technological Institute, Aarhus, Denmark Abstract: Since strontium (Sr) is known for its anabolic and anticatabolic effect on bone, research has been focused on its potential impact on osseointegration. The objective of this study was to investigate the performance of nanotopographic implants with a Sr-functionalized titanium (Ti) coating (Ti–Sr–O) with respect to osseointegration in osteoporotic bone. The trial was designed to examine the effect of sustained-release characteristics of Sr in poor-quality bone. Three Ti–Sr–O groups, which differed from each other in coating thickness, Sr contents, and Sr release, were examined. These were prepared by a magnetron sputtering process and compared to uncoated grade 4 Ti. Composition, morphology, and mechanical stability of the coatings were analyzed, and Sr release data were gained from in vitro washout experiments. In vivo investigation was carried out in an osteoporotic rat model and analyzed histologically, 6 weeks and 12 weeks after implantation. Median values of bone-to-implant contact and new bone formation after 6 weeks were found to be 84.7% and 54.9% (best performing Sr group) as compared to 65.2% and 23.8% (grade 4 Ti reference), respectively. The 12-week observation period revealed 84.3% and 56.5% (best performing Sr group) and 81.3% and 39.4% (grade 4 Ti reference), respectively, for the same measurements. The increase in new bone formation was found to correlate with the amount of Sr released in vitro. The results indicate that sputtered nanostructured Ti–Sr–O coatings showed sustained release of Sr and accelerate osseointegration even in poor-quality bone, and thus, may have impact on practical applications for medical implants. Keywords: nanotopography, osteoinduction, osseointegration, osteoporosis, roden