ABSTRACT
Polyetheretherketone (PEEK), a bioinert polymer known for its mechanical properties similar to bone, is capable of averting stress shielding. Due to these attributes, it finds applications in diverse fields like orthopedics, encompassing cervical disc replacement for the neck and spine, along with dentistry and plastic surgery. However, due to insufficient bonding with bone, various methods such as hydroxyapatite (HA) coating on the surface are attempted. Nonetheless, the interface between the polymer and ceramic, two different materials, tended to delaminate after transplantation, posing challenges in preventing implant escape or dislodgement. This research delves into the laser-driven hydroxyapatite penetration-synthesis technique. Differing from conventional coating methods that bond layers of dissimilar materials like HA and PEEK, this technology focuses on synthesizing and infiltrating ionized HA within the PEEK substrate resulting in an interface-free HA-PEEK surface. Conversely, HA-PEEK with this technology applied achieves complete, gap-free direct bone-implant integration. Our research involved the analysis of various aspects. By means of these, we quantitatively assesed the enhanced bone bonding characteristics of HA-PEEK surfaces treated with this approach and offered and explanation for the mechanism responsible for direct bone integration.
ABSTRACT
BACKGROUND: Although several studies on the Mg-Zn-Ca system have focused on alloy compositions that are restricted to solid solutions, the influence of the solid solution component of Ca on Mg-Zn alloys is unknown. Therefore, to broaden its utility in orthopedic applications, studies on the influence of the addition of Ca on the microstructural, mechanical, and corrosion properties of Mg-Zn alloys should be conducted. In this study, an in-depth investigation of the effect of Ca on the mechanical and bio-corrosion characteristics of the Mg-Zn alloy was performed for the optimization of a clinically approved Mg alloy system comprising Ca and Zn. METHODS: The Mg alloy was fabricated by gravitational melting of high purity Mg, Ca, and Zn metal grains under an Ar gas environment. The surface and cross-section were observed using scanning electron microscopy (SEM) and transmission electron microscopy (TEM) to analyze their crystallographic structures. Electrochemical and immersion tests in Hank's balanced salt solution were used to analyze their corrosion resistance. Tensile testing was performed with universal testing equipment to investigate the impact of Ca addition. The examination of cytotoxicity for biometric determination was in line with the ISO10993 standard. RESULTS: In this study, the 0.1% Ca alloy had significantly retarded grain growth due to the formation of the tiny and well-dispersed Ca2Mg6Zn3 phase. In addition, the yield strength and elongation of the 0.1% Ca alloy were more than 50% greater than the 2% Zn alloy. The limited cell viability of the 0.3% Ca alloy could be attributed to its high corrosion rate, whereas the 0.1% Ca alloy demonstrated cell viability of greater than 80% during the entire experimental period. CONCLUSION: The effect of the addition of Ca on the microstructure, mechanical, and corrosion characteristics of Mg-Zn alloys was analyzed in this work. The findings imply that the Mg-Zn alloy system could be optimized by adding a small amount of Ca, improving mechanical properties while maintaining corrosion rate, thus opening the door to a wide range of applications in orthopedic surgery.