de Wild, Michael
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- PublikationLattice Microarchitecture for Bone Tissue Engineering from Calcium Phosphate Compared to Titanium(Mary Ann Liebert, 10/2018) Chen, Tse-Hsiang; Ghayor, Chafik; Siegenthaler, Barbara; Schuler, Felix; Rüegg, Jasmine; de Wild, Michael; Weber, Franz E. [in: Tissue Engineering. Part A]Additive manufacturing of bone tissue engineering scaffolds will become a key element for personalized bone tissue engineering in the near future. Several additive manufacturing processes are based on extrusion where the deposition of the filament will result in a three-dimensional lattice structure. Recently, we studied diverse lattice structures for bone tissue engineering realized by laser sintering of titanium. In this work, we used lithography-based ceramic manufacturing of lattice structures to produce scaffolds from tricalcium phosphates (TCP) and compared them in vivo to congruent titanium scaffolds manufactured with the identical computer-aided design data to look for material-based differences in bony healing. The results show that, during a 4-week period in a noncritical-size defect in a rabbit calvarium, both scaffolds with the identical microarchitecture performed equally well in terms of bony regeneration and bony bridging of the defect. A significant increase in both parameters could only be achieved when the TCP-based scaffolds were doped with bone morphogenetic protein-2. In a critical-size defect in the calvarial bone of rabbits, however, the titanium scaffold performed significantly better than the TCP-based scaffold, most likely due to its higher mechanical stability. We conclude that titanium and TCP-based scaffolds of the same microarchitecture perform equally well in terms of bone regeneration, provided the microarchitecture meets the mechanical demand at the site of implantation.01A - Beitrag in wissenschaftlicher Zeitschrift
- PublikationOsteoconductive Lattice Microarchitecture for Optimized Bone Regeneration(Mary Ann Liebert, 06/2018) de Wild, Michael; Ghayor, Chafik; Zimmermann, Simon; Rüegg, Jasmine; Nicholls, Flora; Schuler, Felix; Chen, Tse-Hsiang; Weber, Franz E. [in: 3D Printing and Additive Manufacturing]Selective laser melting (SLM) is one methodology to realize additive manufacturing and is mainly used to join metal powder in a layer-by-layer manner to produce a solid three-dimensional (3D) object. For bone tissue engineering purposes, scaffolds can readily be designed as 3D data model and realized with titanium known for its excellent osseointegration behavior. The microarchitecture, that is, design with submillimeter features, of additively manufactured scaffolds is in many cases a lattice structure. This study aimed to apply SLM that allows a high degree of microarchitectural freedom to generate lattice structures and to determine the optimal distance between rods and the optimal diameter of rods for osteoconduction (bone ingrowth into scaffolds) and bone regeneration. For the biological readout, diverse SLM-fabricated titanium implants were placed in the calvarium of rabbits and new bone formation and defect bridging were determined after 4 weeks of healing. The results from the middle section of the defects show that with a lattice microarchitecture, the optimal distance between titanium rods is around 0.8 mm and the optimal rod dimension is between 0.3 and 0.4 mm to optimize defect bridging and bone regeneration.01A - Beitrag in wissenschaftlicher Zeitschrift
- PublikationMechanical anisotropy of titanium scaffolds(De Gruyter, 2017) Weber, Franz E.; de Wild, Michael; Rüegg, Jasmine; Schumacher, Ralf [in: Current Directions in Biomedical Engineering]The clinical performance of an implant, e.g. for the treatment of large bone defects, depends on the implant material, anchorage, surface topography and chemistry, but also on the mechanical properties, like the stiffness. The latter can be adapted by the porosity. Whereas foams show isotropic mechanical properties, digitally modelled scaffolds can be designed with anisotropic behaviour. In this study, we designed and produced 3D scaffolds based on an orthogonal architecture and studied its angle-dependent stiffness. The aim was to produce scaffolds with different orientations of the microarchitecture by selective laser melting and compare the angle-specific mechanical behaviour with an in-silico simulation. The anisotropic characteristics of open-porous implants and technical limitations of the production process were studied.01A - Beitrag in wissenschaftlicher Zeitschrift
- PublikationInfluence of microarchitecture on osteoconduction and mechanics of porous titanium scaffolds generated by selective laser melting(Mary Ann Liebert, 2016) de Wild, Michael; Zimmermann, Simon; Rüegg, Jasmine; Schumacher, Ralf; Fleischmann, Thea; Ghayor, Chafik; Weber, Franz E. [in: 3D Printing and Additive Manufacturing]Bone regeneration is naturally based on bone forming cells, osteoinduction by diverse growth factors, and osteoconduction. The latter one used as term in this study is the ingrowth of bone in 3D structures, which leads to an optimal case in creeping substitution of the scaffold by newly formed bone. Autologous bone is still the gold standard for bone substitutes. In most cases, newly developed bone substitutes consist of calcium phosphate, since hydroxyapatite is the main component of bone and mimics cancellous bone in microstructure. In this study, we wanted to elucidate the optimal microarchitecture for osteoconduction and determine compression strength and Young’s Modulus of the selected architectures. Selective laser melting of titanium was used as tool to generate diverse architectures in a repetitive and precise way. To link 3D scaffold architecture to biological readouts, bone ingrowth, bone to implant contact, and defect bridging of noncritical-sized defects in the calvarial bone of rabbits were determined. In this series, 5 different microarchitectures were tested with pore sizes ranging from 700 to 1300 lm and constrictions between 290 and 700 lm. To our surprise, all microstructures showed the same biological response of excellent osteoconduction. However, the mechanical yield strength of these structures differed by the factor of three and reached up to three times the strength of cancellous bone at a porosity of 72.3–88.4%. These results suggest that the microarchitecture of bone substitutes can be optimized toward mechanical strength in a wide range of constrictions and pore sizes without having a negative influence on osteoconduction.01A - Beitrag in wissenschaftlicher Zeitschrift
- PublikationStiffness - anisotropy of porous implant geometries(2015) de Wild, Michael; Schumacher, Ralf; Rüegg, Jasmine; Zimmermann, Simon; Weber, Franz E. [in: eCM Congress XVI]04B - Beitrag Konferenzschrift