| In order to solve the problem that the dental implants lack the periodontal tissue structure,the imitation periodontal tissue structure was rapidly constructed on the titanium surface using the bionics.Firstly,the micro-arc oxidation(MAO)technique was used to prepare a porous active coating containing Ca and P on the titanium surface,thusing simulating the imitation cementum structure,and then the microwave treatment was used to form the flexible hydroxyapatite nanowires with a certain orientation on the MAO coating surface,thus releazing the bridging effect of imitation periodontal ligament fiber bundles.A three-layer structure of the imitation periodontal tissue were formed on the titanium surface:titanium/MAO coating/flexible HA nanowire,thus releazing the construction of the interfacial anchoring structure between MAO coating and HA nanowire,and the creataion of the bridging releationship between the imitation cementum coating and alveolarbone through the flexible HA nano wires.Scanning electron microscopy(SEM),X-ray diffraction(XRD),transmission electron microscopy(TEM),Fourier transform infrared absorption spectroscopy(FT-IR),X-ray photoelectron spectroscopy(XPS),inductively coupled plasma mass spectrometry(ICP-OES),pH meter,nanoindentation,mechanics universal testing machines and so on were used to study the effect of the microwave treatment on the formation of HA nanowires,microstructure,mechanical properties and apatite inducing ability,antibacterial ability and cell behavior of TiO2-based MAO coatings.In the in vivo animal experiments,the X-ray imaging(X-ray),Micro-CT,hard tissue section staining analysis,scanning electron microscopy(SEM)and X-ray energy dispersive spectroscopy(EDS)and mechanics universal testing machines were used to evaluate the in vivo osseointegration ability and the interface bonding state of the implants with the different micro/nano composite structure.In order to prepare the bioactive coating of the imitation cementum structure,the electrolyte contaning the EDTA-2Na,Ca(CH3COO)2·H2O,Ca(H2PO4)2·H2O,NaSiO3·9H2O,NaOH and H2O2 was used to successfully prepare the porous MAO coating containing Ca,P,Si and Na elements on the titanium surface,which consisted of a large number of amorphous structures containing Ca,P,Si and Na elements and a small amount of anatase TiO2 phase.With the concentration of Ca(CH3COO)2·H2O in the electrolyte increasing,the concentrations of Ca and P element in the cocating decreased.In addition,after adding the Zn(CH3COO)2 to the electrolyte,the MAO coating was composed of anatase,rutile TiO2 phase and the amorphous structure.Meanwhile,the concentrations of Ca and P elements in the MAO coating decreased.In order to construct the nanowire structure of the imitation periodontal ligament structure,Three different nanostructures were successfully constructed on the MAO coating surface using microwave hydrothermal treatment:hydroxyapatite(HA)nanowires,HA nanorods and Na0.23TiO2 nanoflakes,Na0.23TiO2 nanofalkes.With the increasing of the treatment temperature,treatment time and NaOH concentration,the numbers of the HA nanorods formed on the MAO coating surface increased and then decreased.However,the numbers of the Na0.23TiO2 nanoflake increased with the inceasing of the temperature,NaOH concentration and treatment time due to the strongly reaction between OH-ions and TiO2 phase.Based on the thermodynamic and kinetic caculation for the formation of HA crystals,the concentrations of Ca and P elements in the MAO coating were greatly decreased,resulting in the difficulty of the HA crystal nucleation.Similarly,after the introduction of Zn element,the concentrations of Ca and P elements in the the MAO coating decreased,thus leading to the difficulty of the HA crystasl nucleation during the microwave hydrothermal treatment.After the MAO coating was modified by microwave hydrothermal treatment.The surface roughness,wettability,surface energy,Zeta potential and surface potential of the coating were significantly improved.Meanwhile,the surface elastic modulus and nanohardness of the coating were significantly decreased,due to the formation of a large number HA nanorods or Na0.23TiO2 nanoflakes.In addition,when the NaOH concentration was less or equal to 0.5 mol/L,the interfacial bonding strength between the coating and the substrate is not significantly decreased.At the same time,the HA nanowires formed on the MAO coating have good flexibility characteristic.After the MAO coatings were modified by microwave hydrothermal treatment,the apatite formation ability of the coating was significantly enhanced.On one hand,the HA crystal and apatite have good crystallographic matching,which could provide more nucleation energy for the apatite deposited on the coating surface.On the other hand,the HA crystals on the MAO coating surface were dissolved,the concentrations of Ca2+ and PO43-ions at the interface between the coating and the solution were increased,thusing promoting the formation of apatite.In addition,the cell adhesion,cell proliferation,ALP activity,protein adsorption and gene expression ability of the MAO coating surface treated by microwave hydrothermal treatment were significantly enhanced.The antibacterial ability of the Zn-incorporated MAO coatings was significantly enhanced after the microwave treatment owing to the enrichment of Zn elements on the coating surface.After the MAO titanium implant treated by microwave hydrothermal treatment into the rabbit tibia for 16 weeks,the in vivo compatibility was good,a large amounts of new bone tissue were formed around the implant,the number of soft tissues was small,and the interface bonding force at the interface was very high,showing excellent bone-implant interface bonding status,and a large amount of bone tissue remained on the coating surface after pushing out the implant.Meanwhile,the fracture site occurs both on the side of the bone and the coating,thus showing excellent osseointegration ability.Meanwhile,one end of HA nanowires connected to the original MAO coating,the other end of HA nanowires connected to the bone tissues,which were formed on the MAO implant after microwave hydrothermal treatment with 0.01 mol/L NaOH solution.The bridging effect between the imitation cementum structure coating and bone tissue was constructed by the flexible HA nanowires,thus realizing the purpose of bionic periodontal tissue structure.In summary,a three-layer structure(Titanium/MAO coating/flexible HA nanowires)of the imitation periodontal tissue were succusfully formed on the titanium implant surface by micro arc oxidation and microwave hydrothermal treatment,showing the excellent osseointegration ability. |
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