Abstract
In this study, a specific Mg–Zn–RE alloy membrane with 6 wt.% zinc and 2.7 wt.% rare earth elements (Y, Gd, La and Ce) was prepared to investigate implant degradation, transport mechanism and guide bone regeneration in vivo. The Mg-membrane microstructure and precipitates were characterized by the scanning electron microscopy (SEM) and the transmission electron microscopy (TEM). The Mg-membrane degradation process and effect on osteogenesis were investigated in a critical-sized rat calvarial defect model via micro-CT examination and hard tissue slicing after 2-, 5- and 8-week implants. Then, the distribution of elements in organs after 1-, 2- and 4-weeks implantation was examined to explore their transportation routes. Results showed that two types of precipitates had formed in the Mg–membrane after a 10-h heat treatment at 175 °C: γ-phase MgZn precipitation with dissolved La, Ce and Gd, and W-phase Mg3(Y, Gd)2Zn3 precipitation rich in Y and Gd. In the degradation process of the Mg-membrane, the Mg matrix degraded first, and the rare earth-rich precipitation particles were transferred to a more stable phosphate compound. The element release rate was dependent on the precipitate type and composition. Rare earth elements may be transported mainly through the lymph system. The defects were repaired rapidly by the membranes. The Mg-membrane used in the present study showed excellent biocompatibility and enhanced bone formation in the vicinity of the implants.
Highlights
In recent years, magnesium (Mg)-based alloys have become a special focus for medical applications, due to their excellent biomechanical properties and biodegradability [1]
The precipitates distributed at the grain boundaries and inner grains of Mg matrix (Figure 2a) and were identified as RE-rich in the alloy, denoted as ‘dark’ or ‘bright’ particles depending on their appearance resulting from precipitates by energy dispersive spectrometer (EDS) analysis
There is evidence that Mgmay alloybehas effects on growth of regeneration in dental and craniomaxillofacial bone defects. It is well known from animal models adjacent new bone tissues, so magnesium alloy membrane may be an optimum candidate for guided that geometry ofinthe implant, of adjacent tissue, buffering capacity and known blood flow influence bonethe regeneration dental andtype craniomaxillofacial bone defects
Summary
Magnesium (Mg)-based alloys have become a special focus for medical applications, due to their excellent biomechanical properties and biodegradability [1]. Compared with other biomedical metals, the densities of Mg-based alloys are closer to that of human natural bone, and their elastic modulus are more similar to that of natural bone, avoiding “stress shielding” effect caused. Coatings 2020, 10, 496 by mismatch of elastic modulus between implants and human bone tissues [2,3,4]. Mg-based alloys have been shown to have stimulatory effects on the growth of adjacent new bone tissues [8,9]. Various Mg-based alloys have been tailored to optimize degradation behavior and other properties by using appropriate alloying elements, surface modification, coating, thermal treatment, and so on. Several Mg–RE alloy implants have been used successfully in in vivo applications, such as WE43 [17], ZEK100 [18] and LAE442 [19]
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