title: Functionally gradient bonelike hydroxyapatite coating on a titanium metal substrate created by a discharging method in HBSS without organic molecules.
abstract: OBJECTIVE
  This study evaluated the quality of coatings on titanium surfaces prepared by discharging in Hanks' balanced salt solution without organic molecules (HBSS-).
  
  
  METHODS
  10 x 10 x 1.0-mm titanium plates were used as cathodes of a coating device developed in the laboratory and immersed in HBSS-. A piece of platinum foil was used as a counterelectrode. Discharging was maintained at 1 A and 10 V (416 mA/cm2) for periods of 90, 270, and 540 seconds. Crystal phases of the coatings were identified by x-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). In addition, the surface characterization and Ca/P atomic ratio of the titanium surfaces were determined by x-ray photoelectron spectroscopy (XPS). Furthermore, the surface topography, the thickness of the coatings, and the bonds between coatings and titanium substrates were observed by scanning electron microscopy.
  
  
  RESULTS
  The FTIR and XRD studies demonstrated that the deposits on the titanium after 540 seconds of discharging were crystalline hydroxyapatite. In addition, the thickness of the titanium suboxide layer increased during discharging. The XPS studies indicated that after 540 seconds of processing, the mean Ca/P ratio of the coatings on the titanium was 1.71, which is similar to that of human bone.
  
  
  CONCLUSIONS
  In addition, the replacement of sodium ions with calcium ions seemed important for the promotion of crystallization of the coating. Furthermore, the XPS studies demonstrated that the coatings had a gradient function. Scanning electron microscopy showed that adhesion between coatings and the titanium substrate was close. The coatings were approximately 1 microm thick.
  
  
  CONCLUSIONS
  These findings suggest that a very thin crystalline bonelike hydroxyapatite coating with a gradient function could be prepared on a titanium metal substrate in HBSS- by a discharging method.
authors.affiliation: Department of Oral Biomaterials and Technology, Showa University School of Dentistry, Tokyo, Japan. yookun@dent.showa-u.ac.jp
authors.forename: Yo
authors.initials: Y
authors.lastname: Shibata
authors.forename: Hidetoshi
authors.initials: H
authors.lastname: Takashima
authors.forename: Hiroki
authors.initials: H
authors.lastname: Yamamoto
authors.forename: Takashi
authors.initials: T
authors.lastname: Miyazaki
mesh_terms: D000268:Adhesiveness; D001672:Biocompatible Materials / Q000737:chemistry*; D002118:Calcium / Q000737:chemistry; D020099:Coated Materials, Biocompatible / Q000737:chemistry*; D003460:Crystallization; D003764:Dental Materials / Q000737:chemistry*; D017886:Durapatite / Q000737:chemistry*; D004563:Electrochemistry; D004572:Electrolysis; D004577:Electron Probe Microanalysis; D006801:Humans; D007552:Isotonic Solutions / Q000737:chemistry*; D008855:Microscopy, Electron, Scanning; D010758:Phosphorus / Q000737:chemistry; D017550:Spectroscopy, Fourier Transform Infrared; D013499:Surface Properties; D014025:Titanium / Q000737:chemistry*; D014961:X-Ray Diffraction
chemical_list: D001672:Biocompatible Materials; D020099:Coated Materials, Biocompatible; D003764:Dental Materials; C072670:Hanks Balanced Salt Solution; D007552:Isotonic Solutions; C009495:titanium dioxide; D010758:Phosphorus; D017886:Durapatite; D014025:Titanium; D002118:Calcium