Session IV – Rapid Fire Presentations (V22–V31)

Abstract

EinleitungFür den Knochenersatz im Schädelbereich werden alloplastische Materialien wie Metalle, Polymere und Keramiken erfolgreich eingesetzt. Alle zur Verfügung stehenden Materialien haben allerdings Nachteile, so dass weiterhin nach alternativen Implantatmaterialien gesucht wird. Zur Bewertung ihrer Funktion und Biokompatibilität sind adäquate Tiermodelle unverzichtbar. The combination of biodegradable metals and ceramics states a promising approach towards completely biodegradable composite materials for load-bearing applications, e.g. as implants or bone replacements. A fast degrading and osteoinductive ceramic, like beta-tricalcium phosphate (TCP), enables the ingrowth of bone whereas a slower degrading metal, such as iron or ironbased alloys, provides structural strength over a longer period of time until complete replacement by bone. Therefore in the present study we designed a composite material where the ceramic phase is accessible completely to allow its complete degradation while also the metal phase is continuous to maintain mechanical strength. This situation was achieved by realizing an interpenetrating phase composite (IPC) structure. Material/MethodeAs implant devices are often rather complexly shaped, it is also desirable to combine such a structure with a complex geometry. Therefore powder injection molding (PIM) was used for processing, offering the opportunity to easily adjust metal and ceramic shares by suitably mixing the respective material powders.Using the approach described, we produced IPCs with iron based alloys and TCP in different compositions. As metallic phases, plain iron and iron-phosphorus (Fe-0.6P) were evaluated. The results of compressive tests showed that the properties could be influenced in wide ranges depending on the composition, processing method and sintering conditions. Also, the controlled introduction of pores via temporary placeholders was employed successfully in order to adjust the mechanical behavior even further. Additionally the in vitro degradation was investigated by using physiological sodium chloride and phosphate buffered saline solutions. The specimens were placed in the fluids for up to two months at 37 °C. Each medium was changed every two weeks, the pH as well as the ion concentrations of Fe 2+ and Ca 2+ were measured and the weight change analyzed. The mechanical properties after partial degradation were determined by compression tests, and significant degradation of mechanical properties was found after two months in medium. Initial biocompatibility was verified by employing extract tests with the supernatants to determine the cytotoxicity as well as by cell growth experiments. Due to their excellent biocompatibility, calcium phosphates are frequently used in bone substitutes. The hydraulic phase alpha-TCP Ca 3 (PO 4 ) 2 , which reacts to calcium-deficient hydroxyapatite (CDHA), is a common component of bone cements. Exact knowledge of the hydration process is essential for successful clinical application. Partial amorphization of alpha-TCP, which...