| Objective:To study the degradation?osseointegration and biocompatibility of pure magnesium implants treated with ultrasonic micro-arc oxidation-Poly lactic-co-glycolic Acid(PLGA)/nano hydroxyapatite(n HA)composite coating in animals.Methods:The pure magnesium screw and the surface of bone plate were subjected to ultrasonic micro-arc oxidation,and PLGA/n HA composite coating was loaded on the surface by using the porous structure of the surface.it can be divided into two groups,group A is pure magnesium ultrasound group micro-arc oxidation(MAO),group B is pure magnesium implants treated with ultrasonic micro-arc oxidation-PLGA/n HA(MAO-PLGA /n HA group).The implants were implanted into the rabbit mandible,and were killed at 2,4,8 and 12 weeks after implantatin.Sem and elemental analysis were performed on the surface of the magnesium nail before implantation.After the bone block was fixed,the bone block without plate was detected by CT,and the bone block with plate was detected by CBCT,Micro CT and torsion test.The bone blocks without plates were cut into two bone blocks with nails.One bone with nail was embedded in hard tissue for laser confocal focusing,scanning electron microscopy and elemental analysis,another bone block with nail was decalcified and stained with HE.HE staining was performed on the heart,liver,kidney,surrounding soft tissues of the untreated rabbits and the 12-week-old implants.Results:The macroscopic morphology showed that the degradation of magnesium implants in group B> group A,and the surrounding bone tissue of group B was smoother than that of group A.The surface morphology of magnesium nails before implantation was observed by scanning electron microscopy.The surface morphology of magnesium nails in group A showed complex porous morphology,while the surface micropores of magnesium nails in group B were basically disappeared.Element analysis group B added Ca and P elements compared with group A.CT observation of the diameter of magnesium nail in group B>group A.CBCT was used to observe bone mineral density around screws in group B>group A.Micro CT was used to measure the residual volume of magnesium nails and magnesium plates in group B>group A,and the uniform degradation of magnesium nails and magnesium plates in group B lasted from 0 to 12 weeks.According to the regression curve,it was calculated that it would take about 8 months for complete degradation in group A,and about 12 months for complete degradation in group B.Torsion test was used to measure the bone-bonding strength in group B>group A,and the difference was statistically significant(P<0.05).The results of laser confocal detection showed that group B had stronger green fluorescence intensity and larger fluorescence area than group A.The fluorescence in group B was located at the binding interface,while that in group A was located at the bone tissue below the binding interface.Scanning electron microscopy(SEM)showed that during the same period,coating degradation in group B was less than that in group A,and there were more new bones around the implant,and Ca and P elements around the implant were more in group B than in group A.The bone tissue HE staining results showed that osteoblasts and new bone capacity around magnesium nails were in group B > group A.HE staining of the organs and surrounding soft tissues 12 weeks after the surgery showed that the structures of the heart,liver,kidney and surrounding soft tissues were normal in both groups.Conclusion:The ultrasonic micro-arc oxidation surface of pure magnesium loaded with PLGA/n HA composite coating can delay the degradation rate of pure magnesium,accelerate the formation of new bone and promote bone bonding.It has no toxic effect on tissue and has good bone tissue compatibility and biocompatibility. |
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