In-situ deposition of apatite layer to protect Mg-based composite fabricated via laser additive manufacturing

Biodegradable magnesium(Mg) and its alloy show huge potential as temporary bone substitute due to the favorable biocompatibility and mechanical compatibility. However, one issue deserves attention is the too fast degradation. In this work, mesoporous bioglass(MBG)with high pore volume(0.59 cc/g) and huge specific surface area(110.78 m^(2)/g) was synthesized using improved sol-gel method, and introduced into Mg-based composite via laser additive manufacturing. Immersion tests showed that the incorporated MBG served as powerful adsorption sites, which promoted the in-situ deposition of apatite by successively adsorbing Ca2+and HPO42-. Such dense apatite film acted as an efficient protection layer and enhanced the corrosion resistance of Mg matrix, which was proved by the electrochemical impedance spectroscopy measurements. Thereby, Mg based composite showed a significantly decreased degradation rate of 0.31 mm/year. Furthermore,MBG also improved the mechanical properties as well as cell behavior. This work highlighted the advantages of MBG in the fabrication of Mg-based implant with enhanced overall performance for orthopedic application.

Microstructure development of Ti scaffold by laser powder bed fusion with chemical polishing and its mechanical properties,biocompatibility

Titanium(Ti)dental scaffolds are widely used in dental prosthetics due to their excellent mechanical properties and biocompatibility.However,conventional Ti scaffolds manufactured through machining often do not fit perfectly with the bone defect site.Laser powder bed fusion(LPBF)technology enables the personalised manufacturing of custom-made Ti scaffolds.A custom-made Ti scaffold was prepared using LPBF and its surface roughness was improved through chemical polishing.To enhance the surface roughness,a nitric acid mixed solution with a specific composition of HF:HNO_(3):C_(3)H_(6)O_(3)=2:2:3 was used.The polishing mechanism was investigated by adjusting the F/Ti ratio to control the formation and dissolution of the oxide film.As a result,the surface of the Ti scaffold after polishing exhibited a smooth and flat appearance compared to the LPBF part,with a reduced surface roughness(Ra)of 1.23±0.19μm.The custom-made Ti scaffold also demonstrated favourable mechanical properties,with a bending strength of 335.18±33.62 MPa and stiffness of 2.13±0.21 GPa.Furthermore,in vitro cell tests confirmed the excellent biocompatibility of the custom-made Ti scaffold.The authors present a feasible strategy for the further clinical application of custom-made Ti scaffolds,offering enhanced surface properties and addressing the limitations of conventional machining methods.