| Objective: Polyetheretherketone(PEEK)material is increasingly used in the medical field and is also a hot topic of new implant research.The current research focuses on the material structure design and surface modification.In this study,PEEK material with fully porous structure was manufactured by using 3D printing technique,and the simulated body fluid(SBF)is used for surface coating with hydroxyapatite.And we investigated the feasibility of the manufacturing process and the biomechanical properties of the implant.Methods: The PEEK implant was designed as a cylindrical body with a diameter of 5mm and a height of 8mm,and divided into solid group,porous group and coated group.The pore size of the porous structure was set at 400μm and the porosity was set at 60% and was 3D printed with medical grade pure PEEK wire.After manufacturing,the porosity and the pore size were calculated by the weighing method and Scanning electron microscope,and then the porous PEEK material was coated with hydroxyapatite by SBF soaking.The coating quality was detected by Micro-CT and Energy Dispersive Spectroscopy.The compressive modulus and compressive strength of the three groups of implants were calculated by compression experiments,and the mechanical properties of the porous group and the coated group were compared.Then,three groups of different PEEK materials were implanted into the femoral condyle of New Zealand white rabbits,and the calcein and the tetracycline hydrochloride fluorescent staining were injected at the 2nd and 4th week to label the formation of new bone tissue at different periods.The New Zealand white rabbits were sacrificed at the 8th week,and the femur specimens were collected.The biological activity and bone integration ability of PEEK implants were compared and analyzed under the observation of Micro-CT and histology sections.Results: The pore size of PEEK was 442.2±14.5μm and the porosity of PEEK was 53.9±1.8%,and the results of SEM and EDS showed that there were hydroxyapatite crystals with good homogeneity on the surface of the coated group.The compressive modulus of solid group,porous group and coated group are 1289.43±71.44 MPa,196.36 ± 9.89 MPa and 183.29 ± 7.71 MPa.The compressive strength of solid group,porous group and coated group are 107.24± 5.15 MPa,33.12 ± 3.86 MPa and 29.99 ± 4.16 MPa.Statistical analysis showed that there were no significant differences in compressive modulus and compressive strength between the porous group and coated group(P>0.05).Micro-CT showed that bone volume fraction(BV/TV)in the solid group was(2.09 ± 0.43)%,the porous group was(19.62 ± 3.94)%,and that in the coated group was(30.18 ± 5.93)%.Statistical analysis indicated that the bone volume fraction in the coated group was significantly higher than that in the porous group(P<0.05).The trabecular number,trabecular thickness and the trabecular spacing in the porous and coated groups were(0.58±0.11)/mm and(1.21±0.26)/mm,(0.15±0.02)μm and(0.22±0.02)μm,(1.72±0.61)μm and(0.61±0.16)μm,respectively.The results showed that the promoting ability of bone anabolic function in coated group was higher than that in porous group(P<0.05).Hard tissue section staining and fluorescence staining showed that the coated group was better than the porous group in promoting bone growth in total bone and in different periods.Conclusion: The shape of PEEK implant with full porous structure made by 3D printing is stable and in good agreement with the design and the mechanical properties of its porous structure are close to that of human cancellous bone.The properties of hydroxyapatite coating by SBF soaking method are good as well,and the HA coating is uniform on the surface of PEEK material.Moreover,this method has no significant negative effect on the mechanical properties of PEEK porous structure.The imaging and histological results showed that hydroxyapatite coating on the surface of PEEK porous materials can significantly improve the biological activity and bone integration ability. |
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