In vivodegradation effects of alloy MgNd2 in contact with mucous tissue

Abstract

Magnesium alloys are currently being investigated for use as resorbable biomaterials. Various applications for magnesium based implant materials have already been presented. Currently, stents and structures that sustain diseased or narrowed vessels seem to be the most promising areas. This study focuses on the use of a magnesium fluoride (MgF2 ) coated magnesium neodymium based alloy (MgNd2 ) and its use as a postsurgery stent material to avoid proliferation in the sinus region. Simple cylindrical shaped specimens were sown to the sinus' mucosa of pigs and left in place for different periods of time to investigate the long-term corrosion resistance of the alloy and its coating during direct contact with physiological tissue. Investigations made within this study explicitly focused on the corrosive behavior of the alloy in the region of a physiological sinus. Thus, losses in mass and volume, and element analyses were considered to obtain information about the specimens' corrosion performance over time. Furthermore, micrographs support the alloy specific corrosion type analyses which focus on grain boundary effects. This study demonstrates the general in vivo applicability of fluoride coated MgNd2 . The progress of corrosion was determined to be adequate and homogeneous over a total period of 180 days.

Biodegradable nasal stents (MgF2‐coated Mg–2 wt %Nd alloy)—A long‐termin vivostudy

“…While common alloying elements like Zn and Al form phases with significantly nobler corrosion potentials (Mg 2 Al 3 : −1.01 V SCE ; MgZn 2 : −1.03 V SCE), Mg 3 Nd's corrosion potential is close to the Mg matrix's potential of −1.65 V SCE minimizing the adverse effect of microgalvanic coupling between matrix and precipitate. As shown by Seitz et al the majority of MgNd precipitates seem to distribute along grain boundaries which could result in a slower corrosion due to a barrier effect as described by Song et al Micrographs of alloy Mg‐2Nd have shown no preferential corrosion of grain boundaries or grains within a period of 180 days postsurgery into the sinus region of pigs . Within the same study, the in vivo corrosion rate of Mg‐2Nd was determined to be below 0.02 mg(cm 2 h −1 ) −1 …”

“…Regarding its biocompatibility, alloy MgNd2 was successfully tested in contact with nasal mucosa in an animal study . Moreover, it showed suitable corrosion pattern in contact with nasal mucosa …”

“…Neodymium additions significantly reduce elongation properties and increase yield strength properties in as cast condition with increasing Nd amounts due to the formation of brittle eutectics . The extrusion of Mg‐2Nd alloy however results in an alloy with low yield properties and highly elastic properties making it an ideal candidate for biomedical applications that have to undergo cold deformation during implantation.…”

“…As shown by Seitz et al the majority of MgNd precipitates seem to distribute along grain boundaries which could result in a slower corrosion due to a barrier effect as described by Song et al Micrographs of alloy Mg‐2Nd have shown no preferential corrosion of grain boundaries or grains within a period of 180 days postsurgery into the sinus region of pigs . Within the same study, the in vivo corrosion rate of Mg‐2Nd was determined to be below 0.02 mg(cm 2 h −1 ) −1 …”

Stents und Platzhalter in der endoskopischen endonasalen Nasennebenhöhlenchirurgie

“…Allerdings zeigten sich histologisch an der Kontaktfläche zur Schleimhaut sowohl der Stirnhöhle als auch des Recessus frontalis reaktive Gewebe-Hyperplasien und Fibrosen, die als unerwünscht einzuordnen waren. Die schrittweise Degradation des Stents war auch nach 180 Tagen noch nicht abgeschlossen [56][57][58][59]. Fragen zur lokalen und systemischen Toxizität scheinen bisher nicht ausreichend beantwortet zu sein.…”