Schumacher, Ralf

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Schumacher
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Ralf
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Ralf Schumacher

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2012 - 20152
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    Publikation
    Novel microcalorimetric assay for antibacterial activity of implant coatings. The cases of silver‐doped hydroxyapatite and calcium hydroxide
    (Wiley, 08/2015) Braissant, Olivier; Chavanne, Philippe; de Wild, Michael; Pieles, Uwe; Stevanovic, Sabrina; Schumacher, Ralf; Straumann, Lukas; Wirz, Dieter; Gruner, Philipp; Bachmann, Alexander; Bonkat, Gernot [in: Journal of Biomedical Materials Research Part B: Applied Biomaterials]
    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.
    01A - Beitrag in wissenschaftlicher Zeitschrift
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    Publikation
    Tailoring selective laser melting process parameters for NiTi implants
    (Springer, 12/2012) Bormann, Therese; Schumacher, Ralf; Müller, Bert; Mertmann, Matthias; de Wild, Michael [in: Journal of Materials Engineering and Performance]
    Complex-shaped NiTi constructions become more and more essential for biomedical applications especially for dental or cranio-maxillofacial implants. The additive manufacturing method of selective laser melting allows realizing complex-shaped elements with predefined porosity and three-dimensional micro-architecture directly out of the design data. We demonstrate that the intentional modification of the applied energy during the SLM-process allows tailoring the transformation temperatures of NiTi entities within the entire construction. Differential scanning calorimetry, x-ray diffraction, and metallographic analysis were employed for the thermal and structural characterizations. In particular, the phase transformation temperatures, the related crystallographic phases, and the formed microstructures of SLM constructions were determined for a series of SLM-processing parameters. The SLM-NiTi exhibits pseudoelastic behavior. In this manner, the properties of NiTi implants can be tailored to build smart implants with pre-defined microarchitecture and advanced performance.
    01A - Beitrag in wissenschaftlicher Zeitschrift