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Titanium and stainless steel are commonly known as osteosynthesis materials with high strength and good biocompatibility. However, they have the big disadvantage that a second operation for hardware removal is necessary. Although resorbable systems made of polymers or magnesium are increasingly used, they show some severe adverse foreign body reactions or unsatisfying degradation behavior. Therefore, we started to investigate molybdenum as a potential new biodegradable material for osteosynthesis in craniomaxillofacial surgery. To characterize molybdenum as a biocompatible material, we performed in vitro assays in accordance with ISO Norm 10993-5. In four different experimental setups, we showed that pure molybdenum and molybdenum rhenium alloys do not lead to cytotoxicity in human and mouse fibroblasts. We also examined the degradation behavior of molybdenum by carrying out long-term immersion tests (up to 6 months) with molybdenum sheet metal. We showed that molybdenum has sufficient mechanical stability over at least 6 months for implants on the one hand and is subject to very uniform degradation on the other. The results of our experiments are very promising for the development of new resorbable osteosynthesis materials for craniomaxillofacial surgery based on molybdenum.
Bei der Vorrichtung zum Verdampfen einer Flüssigkeit ist eine offenporöse Struktur (1) in einem Gehäuse (8) angeordnet, die zumindest bereichsweise als eine Heizvorrichtung ausgebildet oder mittels einer externen Heizvorrichtung oder Bereiche der offenporösen Struktur (1) auf eine Temperatur, die mindestens der Siedetemperatur der jeweiligen Flüssigkeit entspricht, erwärmbar ist. Die Flüssigkeit ist in einem außerhalb des Gehäuses (8) angeordneten Reservoir (4), mit einer Menge aufgenommen, die während des Betriebs eine kontinuierliche Verdampfung von Flüssigkeit ermöglicht. Das Reservoir ist über mindestens eine Leitung (3) für Flüssigkeit mit dem Gehäuse (8) verbunden und in der mindestens einen Leitung (3) ist/sind ein Ventil und/oder eine Pumpe oder ein Verdichter (5) angeordnet. Die Leitung (3) mündet in mindestens eine Öffnung mindestens einer Düse (2) oder mindestens eine Austrittsöffnung und die Düse (2), deren Öffnung(en) und/oder die mindestens eine Austrittsöffnung der Leitung (3) ist/sind so angeordnet, dass Flüssigkeit auf Oberflächenbereiche der offenporösen Struktur (1) auftrifft und/oder in Poren der offenporösen Struktur (1) eintritt, wenn Flüssigkeit durch die eine Leitung (3) strömt.
Biodegradable metals have entered the implant market in recent years, but still do not show fully satisfactory degradation behaviour and mechanical properties. In contrast, it has been shown that pure molybdenum has an excellent combination of the required properties in this respect. We report on PM based screen printing of thin-walled molybdenum tubes as a processing step for medical stent manufacture. We also present data on the in vivo degradation and biocompatibility of molybdenum. The degradation of molybdenum wires implanted in the aorta of rats was evaluated by SEM and EDX. Biocompatibility was assessed by histological investigation of organs and analysis of molybdenum levels in tissue extracts and body fluids. Degradation rates of up to 13.5 μm/y were observed after 12 months. No histological changes or elevated molybdenum levels in organ tissues were observed. In summary, the results further underline that molybdenum is a highly promising biodegradable metallic material.
Fused Filament Fabrication (FFF) is a widespread additive manufacturing technology, mostly in the field of printable polymers. The use of filaments filled with metal particles for the manufacture of metallic parts by FFF presents specific challenges regarding debinding and sintering. For aluminium and its alloys, the sintering temperature range overlaps with the temperature range of thermal decomposition of many commonly used “backbone” polymers, which provide stability to the green parts. Moreover, the high oxygen affinity of aluminium necessitates the use of special sintering regimes and alloying strategies. Therefore, it is challenging to achieve both low porosity and low levels of oxygen and carbon impurities at the same time. Feedstocks compatible with the special requirements of aluminium alloys were developed. We present results on the investigation of debinding/sintering regimes by Fourier Transform Infrared spectroscopy (FTIR) based In-Situ Process Gas Analysis and discuss optimized thermal treatment strategies for Al-based FFF.