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.
Highlights
Insufficient alveolar ridge dimensions represent a common challenge in edentulous jaws, which prevents an immediate placement of dental implants
Mg screws (Figure weeks post implantationem, the analysis showed that the Mg screw shafts were still integrated within newly formed bone tissue and the layer of phosphate and calcium was still detectable at the screw head surfaces (Figure 11)
At 6 weeks post implantationem, the analysis showed that the Mg screw shafts were still integrated within newly formed bone tissue and the layer of phosphate and calcium was still detectable at the screw head surfaces (Figure 11)
Summary
Insufficient alveolar ridge dimensions represent a common challenge in edentulous jaws, which prevents an immediate placement of dental implants. GBR is based on the principle of excluding fast proliferating cells, such as epithelium cells from the augmentation site, while promoting a micromilieu favorable for jawbone regeneration by osteoblasts [6,7]. The use of resorbable membranes, most often collagen based, have been established in dentistry, as their application does not require a second surgical intervention for their removal. The progression from non-resorbable to resorbable membranes shows that degradable materials in surgery and in dental implantology are becoming the materials of choice for most clinicians, and a positive trend toward completely bioresorbable material systems [9,15,16,17,18]. 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. After 3 and 6 weeks, degradation, local tissue reactions and bony integration were analyzed histopathologically and histomorphometrically
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