Research Of Surface Thermal Oxidation Combined With Acid Etching On Titanium Implants To Enhance Osteogenic Activity And In Vivo Osseointegration

Objective: Thermal oxidation combined with oxalic acid etching was used to modify the commercially pure titanium surface to fabricate a thicker titanium dioxide passive layer modified micro/nanostructured titanium surface.The bioactivity and osteogenic acitivity were evaluated in vitro,the bone regeneration and bone-implant contact were investgated in vivo.Material and methods: 1.Taking oxalic etched titanium as substrates,thermal oxidation in ambient atmosphere at 450 oC for different time periods(2,4 and 6 hours)were used to fabricate a titanium dioxide passive layer modified mico/nanostructured titanium surface.2.The surface morphology,crystallinity of the surface layers,chemical compositions and chemical states were evaluated by field-emission scanning electron microscopy(FESEM),X-ray diffractometer(XRD),X-ray photoelectron spectroscopy(XPS).3.Rat bone marrow mesenchymal stem cells(r BMMSCs)were used to evaluate cell bioactivity incuding cell adhesion,attachment and cell viability.The osteogenic activity was investegated by ALP semi-quantification,Alizarin Red S staining and semi-quantification,real-time PCR assay(ALP,BSP,OCN and OPN)and immunofluerence staining assay(OCN).4.Titanium implants were inserted in rabbit femur for in vivo evaluation.Sequential fluorescent labeling and histological staining analysis were used to investgate the new bone formation around implants and bone-implant contact.Results: 1.Micro/nanostructured titanium surfaces were fabricated using thermal oxidation combined with oxalic acid etching.The thickness of oxide passive layers was enhanced and the crystallity was transformed to a mixture of anatase and rutile phase.2.Thermal oxidation treated oxalic etched titanium surfaces remained the biocompatibility and exihited better osteogenic activity,especially in the TO-6 group,compared with the oxalic etched titanium surface.3.After a certain period of thermal oxidation treatment,the micro / nanostructured titanium surface stimulated new bone formation around implants and accelerated bone-implant contact ratio in rabbit femur defect model,especially in TO-6 group compared with the oxalic etched titanium implant.Conclusions: 1.Micro/nanostructured titanium surfaces with a different ratio of anatase and rutile phase were fabricated using thermal oxidation treatment followed with oxalic acid etching.2.Modified with a mixture of anatase and rutile,the micro/nanostructured titanium surfaces exhibited good biocompatilibity and better osteogenic both in vitro and in vivo.3.Serving as a low-cost,effective and relatively simple/facile method,modified with a mixture of anatase and rutile,the micro/nanostructured titanium surfaces thermal oxidation treated titanium implant could potentially be used in clinical applications to improve bone-implant integration.