title: Surface Modification of Porous Titanium Granules for Improving Bioactivity.
abstract: OBJECTIVE
  The highly porous titanium granules are currently being used as bone substitute material and for bone tissue augmentation. However, they suffer from weak bone bonding ability. The aim of this study was to create a nanostructured surface oxide layer on irregularly shaped titanium granules to improve their bioactivity. This could be achieved using optimized electrochemical anodic oxidation (anodizing) and heat treatment processes.
  
  
  METHODS
  The anodizing process was done in an ethylene glycol-based electrolyte at an optimized condition of 60 V for 3 hours. The anodized granules were subsequently annealed at 450°C for 1 hour. Scanning electron microscopy (SEM), energy-dispersive x-ray spectroscopy (EDS), and x-ray diffraction (XRD) were used to characterize the surface structure and morphology of the granules. The in vitro bioactivity of the samples was evaluated by immersion of specimens in simulated body fluid (SBF) for 1, 2, and 3 weeks. The human osteoblastic sarcoma cell line, MG63, was used to evaluate cell viability on the samples using dimethylthiazol-diphenyl tetrazolium bromide (MTT) assay.
  
  
  RESULTS
  The results demonstrated the formation of amorphous nanostructured titanium oxide after anodizing, which transformed to crystalline anatase and rutile phases upon heat treatment. After immersion in SBF, spherical aggregates of amorphous calcium phosphate were formed on the surface of the anodized sample, which turned into crystalline hydroxyapatite on the surface of the anodized annealed sample. No cytotoxicity was detected among the samples.
  
  
  CONCLUSIONS
  It is suggested that anodic oxidation followed by heat treatment could be used as an effective surface treatment procedure to improve bioactivity of titanium granules implemented for bone tissue repair and augmentation.
authors.forename: Zahra Gorgin
authors.initials: ZG
authors.lastname: Karaji
authors.forename: Behzad
authors.initials: B
authors.lastname: Houshmand
authors.forename: Shahab
authors.initials: S
authors.lastname: Faghihi
mesh_terms: D001672:Biocompatible Materials / Q000138:chemical synthesis* / Q000494:pharmacology; D001826:Body Fluids / Q000737:chemistry; D018786:Bone Substitutes / Q000737:chemistry*; D002130:Calcium Phosphates / Q000138:chemical synthesis; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D004566:Electrodes; D006358:Hot Temperature; D006801:Humans; D008422:Materials Testing; D053768:Metal Nanoparticles / Q000737:chemistry*; D008855:Microscopy, Electron, Scanning; D010084:Oxidation-Reduction; D010087:Oxides / Q000737:chemistry; D016062:Porosity; D013499:Surface Properties; D014025:Titanium / Q000737:chemistry* / Q000494:pharmacology; D014961:X-Ray Diffraction
chemical_list: D001672:Biocompatible Materials; D018786:Bone Substitutes; D002130:Calcium Phosphates; D010087:Oxides; C009495:titanium dioxide; C020243:calcium phosphate; D014025:Titanium