2018, Matter, Nathalie, Schuler, Felix, Schumacher, Ralf, de Wild, Michael

2016-05, Rüegg, Jasmine, Böhringer, Stephan, Kessler, Anja, Schumacher, Ralf, Schkommodau, Erik, de Wild, Michael

2015-08, Braissant, Olivier, Chavanne, Philippe, de Wild, Michael, Pieles, Uwe, Stevanovic, Sabrina, Schumacher, Ralf, Straumann, Lukas, Wirz, Dieter, Gruner, Philipp, Bachmann, Alexander, Bonkat, Gernot

Biomaterials with antimicrobial properties are now commonly used in different clinical specialties including orthopedics, endodontic, and traumatology. As a result, assessing the antimicrobial effect of coatings applied on implants is of critical importance. In this study, we demonstrate that isothermal microcalorimetry (IMC) can be used for monitoring bacterial growth and biofilm formation at the surface of such coatings and for determining their antimicrobial effects. The antibacterial effects of silver doped hydroxyapatite (HA) and calcium hydroxide coatings on Staphylococcus epidermidis were determined with a minimal workload. Using the Gompertz growth model we determined biofilm growth rates close to those values reported in the literature. Furthermore, we were able to estimate the reduction in the bacterial inocula originally applied at the surface of the coatings. Therefore, in addition to monitoring the antimicrobial effect of silver doped HA and calcium hydroxide coatings, we also demonstrate that IMC might be a valuable tool for assessing such antimicrobial properties of implant coatings at a minimal workload.

2015, de Wild, Michael, Schumacher, Ralf, Rüegg, Jasmine, Zimmermann, Simon, Weber, Franz E.

2018, Zimmermann, Simon, Schumacher, Ralf, Bill, Oliver, Dalcanale, Federico, de Wild, Michael

2016, de Wild, Michael, Zimmermann, Simon, Rüegg, Jasmine, Schumacher, Ralf, Fleischmann, Thea, Ghayor, Chafik, Weber, Franz E.

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.

2015, Schumacher, Ralf, Rohner, A.M., Melzner, Alexander, de Wild, Michael

2017, Weber, Franz E., de Wild, Michael, Rüegg, Jasmine, Schumacher, Ralf

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.

2016, Saxer, Sina, Rüegg, Jasmine, Dietschy, Alain, Schumacher, Ralf, de Wild, Michael, Wiese, Björn, Wohlfender, Fabian

2015, de Wild, Michael, Hoffmann, Waldemar, Schlottig, Falko, Schumacher, Ralf, Bormann, Therese, Martin, Ivan, Müller, Bert, Mürrle, Ulrich