Magnesium alloys as a biomaterial for degradable craniofacial screws

Abstract

Recently, magnesium (Mg) alloys have received significant attention as a potential biomaterial for degradable implants, and this study was directed at evaluating the suitability of Mg for craniofacial bone screws. The objective was to implant screws fabricated from commercially available Mg-alloys (pure Mg and AZ31) in-vivo in a rabbit mandible. First, Mg-alloy screws were compared to stainless steel screws in an in-vitro pull-out test and determined to have a similar holding strength (~40N). A finite element model of the screw was created using the pull-out test data, and the model can be used for future Mg-alloy screw design. Then, Mg-alloy screws were implanted for 4, 8, and 12 weeks, with two controls of an osteotomy site (hole) with no implant and a stainless steel screw implanted for 12 weeks. MicroCT (computed tomography) was used to assess bone remodeling and Mg-alloy degradation, both visually and qualitatively through volume fraction measurements for all time points. Histologic analysis was also completed for the Mg-alloys at 12 weeks. The results showed that craniofacial bone remodeling occurred around both Mg-alloy screw types. Pure Mg had a different degradation profile than AZ31, however bone growth occurred around both screw types. The degradation rate of both Mg-alloy screw types in the bone marrow space and the muscle were faster than in the cortical bone space at 12 weeks. Furthermore, it was shown that by alloying Mg, the degradation profile could be changed. These results indicate the promise of using Mg-alloys for craniofacial applications.

In vivo degradation behavior and biological activity of some new Mg–Ca alloys with concentration's gradient of Si for bone grafts

“…In the lot L5, L3 and L4 a significant hypo-phosphatemia was registered (p < 0.05; n = 5) in the second week from the implantation, while in the fourth week the blood phosphate concentration reached values close to control for L5 and L4 groups but not for L3. These variations can be explained by considering the differences between the implants sample: Mg-Ca-Si with Si concentration gradient implant (L3 group) presented in vivo a slower biodegradation process as compared with Mg-Ca-Si implant without Si concentration gradient (L4 group), similar observation being reported by [22,27,28].…”

In vitro and in vivo studies on the degradation of high-purity Mg (99.99wt.%) screw with femoral intracondylar fractured rabbit model

“…In previous study, numerous studies have been focusing on the degradation performance of Mg-based screws inserted to intact host bone, i.e. AZ31 screw in rabbit mandible [29] and sheep hip bone [30], MgCa0.8 alloy screws in rabbit tibiae [31], which performed a in vivo stale and gradual corrosion rate. Furthermore, Gu et.al [12] and Kannan et.al [32] revealed corrosion promotion of Mg-based materials (as cast AZ91D, as extruded As the corrosion proceeds, the degeneration of mechanical integrity was expected.…”

“…Histological examination also showed matured bone tissue ingrowth in HP Mg screw. Much evidence proved good osseointegration and bone ingrowth around Mg alloy screws[29,30,38]. Therefore, it was supposed Mg ion, which evolved during thedegradation of the Mg material, significantly affected the osteogenic differentiation of the surrounding tissue.…”

Surface Roughness Values of Magnesium Alloy AZ31 When Turning by Using Rotary Cutting Tool

“…The feed rate parameter has strong correlation to surface texture. As stated by previous researcher that nose radius and feed rate have a significant correlation to surface texture of new machined surface when machining super alloy materials [10]. Meanwhile, Gusri, et.al [9] found that when machining super alloy material, surface texture of machined surface formed were affected by worm tool.…”