Biocompatibility Analyses of HF-Passivated Magnesium Screws for Guided Bone Regeneration (GBR)

Abstract

Background: Magnesium (Mg) is one of the most promising materials for human use in surgery due to material characteristics such as its elastic modulus as well as its resorbable and regenerative properties. In this study, HF-coated and uncoated novel bioresorbable magnesium fixation screws for maxillofacial and dental surgical applications were investigated in vitro and in vivo to evaluate the biocompatibility of the HF coating. Methods: Mg alloy screws that had either undergone a surface treatment with hydrofluoric-acid (HF) or left untreated were investigated. In vitro investigation included XTT, BrdU and LDH in accordance with the DIN ISO 10993-5/-12. In vivo, the screws were implanted into the tibia of rabbits. After 3 and 6 weeks, degradation, local tissue reactions and bony integration were analyzed histopathologically and histomorphometrically. Additionally, SEM/EDX analysis and synchrotron phase-contrast microtomography (µCT) measurements were conducted. The in vitro analyses revealed that the Mg screws are cytocompatible, with improved results when the surface had been passivated with HF. In vivo, the HF-treated Mg screws implanted showed a reduction in gas formation, slower biodegradation and a better bony integration in comparison to the untreated Mg screws. Histopathologically, the HF-passivated screws induced a layer of macrophages as part of its biodegradation process, whereas the untreated screws caused a slight fibrous tissue reaction. SEM/EDX analysis showed that both screws formed a similar layer of calcium phosphates on their surfaces and were surrounded by bone. Furthermore, the µCT revealed the presence of a metallic core of the screws, a faster absorbing corrosion front and a slow absorbing region of corroded magnesium. Conclusions: Overall, the HF-passivated Mg fixation screws showed significantly better biocompatibility in vitro and in vivo compared to the untreated screws.

In Vivo Analysis of the Immune Response to Strontium- and Copper-doped Bioglasses

“…This assumption is based on the fact that is well known that an apatite layer is forming at the surface of the BGs that might prevent former pH value shifts [13]. This observation might thus be comparable with findings made after implantation of magnesium-based biomaterials [65]. Recent advances in the understanding of corrosion mechanisms have shown that magnesium's susceptibility to corrosion occurs despite the presence of an oxide layer.…”

In VivoAnalysis of the Immune Response to Strontium- and Copper-doped Bioglass

“…This assumption is based on the fact that is well known that an apatite layer forms at the surface of bioglass that can prevent pH shifts (14). This observation might thus be comparable with findings made after implantation of magnesium-based biomaterials (49). Recent advances in the understanding of corrosion mechanisms have shown that corrosion of magnesium continues despite the presence of an oxide layer.…”

Novel, degradable, and cytoactive bone cements based on magnesium polyphosphate and calcium citrate

“…3D), the peak attributed to the symmetrical stretching vibration of –COO −36 at 1432 cm −1 was weakened, and no peak was detected for the N–H bond. The wide peak at ∼1123 cm −1 was attributed to the overlap of asymmetric stretching vibration peaks of (PO 3 ) 2–22,33 and the C–O bond. 39 The P–O–P bond belonging to polyphosphate was clearly observed.…”

“…20 For example, magnesium, which is widely used, presents good biocompatibility and biodegradability. 21 Schroder et al 20 claimed that magnesium polyphosphate (MPP) can promote the differentiation of bone marrow mesenchymal stem cells in cartilage cell lines and accelerate cartilage regeneration. Mu ¨ller et al 22 prepared a viscous paste-like biological matrix using MPP and hyaluronic acid.…”