Biodegradable pure Mg fixation nails for guided bone regeneration membrane: In vitro and in vivo evaluation

Guided Bone Regeneration (GBR) relies on membrane nails to stabilize barrier membranes and promote osseous healing. However, conventional titanium nails need secondary removal surgeries and may impair osteogenesis. Magnesium (Mg), a biodegradable metal, offers a promising alternative due to its degradability, biocompatibility, and osteoconductive properties. However, Mg-based alloys often exhibit rapid and localized corrosion, which may result in premature failure, thus limiting its clinical applicability. Therefore, in this study, two pure Mg with varying purity—commercially pure Mg (CP-Mg, purity: 99.98 wt.%) and ultrahigh-pure Mg (UHP-Mg, purity: 99.99937 wt.%)—were employed to fabricate the membrane nails to enhance their corrosion performance. The mechanical, degradation, and biological properties of the materials were studied by mechanical tests, in vitro corrosion and cell test, and in vivo implant tests. The results demonstrate that the grain sizes of CP-Mg and UHP-Mg are 38 µm and 27 µm, respectively. Both CP-Mg and UHP-Mg membrane nails are capable of shear forces of approximately 55 N, with no significant difference observed between the two materials, fulfilling the practical requirements for clinical applications in membrane fixation. However, in vitro corrosion test reveals that the degradation rate of UHP-Mg membrane nails is significantly lower than that of CP-Mg membrane nails, with improved degradation uniformity, which may mitigate premature mechanical failure resulting from rapid localized degradation. The cellar test shows that UHP-Mg has superior biological properties. Furthermore, in vivo experiments demonstrated that UHP-Mg membrane nails exhibited a slower and more uniform degradation post-implantation, with no positional migration or detachment observed within 4 weeks, and no significant inflammatory response was induced during the experimental period. Additionally, all bone morphology indices in the degraded area were superior to those in CP-Mg membrane nails, demonstrating enhanced osteogenesis. Therefore, UHP-Mg exhibits high potential for clinical application as a barrier membrane fixation nail material. This study provides a theoretical foundation for the future clinical application of degradable Mg implant devices.