title: Comparison of ultraviolet light-induced photocatalytic bactericidal effect on modified titanium implant surfaces.
abstract: OBJECTIVE
  Titanium dioxide (TiO2), a photocatalyst, is known to decompose various organic compounds under ultraviolet (UV) illumination by generating various radicals, which is useful for killing bacteria. The purpose of the present study was to evaluate the photocatalytic bactericidal effects of variously treated titanium surfaces on Streptococcus sanguinis SL1.
  
  
  METHODS
  Specimens were fabricated from grade 4 commercially pure titanium, 10 mm in diameter and 2 mm in thickness. Three different surfaces were prepared: anodized (AO) at 270 V, heat-treated (HT), and machined (MA). Surface analysis was performed using confocal laser scanning microscope, scanning electron microscopy, and thin-film x-ray diffractometry. The antibacterial activities were assessed by comparing adhesion and survival rates of S sanguinis on various surfaces under UV illumination.
  
  
  RESULTS
  The AO surface was rougher than the HT and MA surfaces. The AO surface showed TiO2 peaks of anatase structure, while the HT surface showed TiO2 peaks of rutile structure in x-ray diffractometry. HT and AO surfaces showed significantly decreased bacterial adhesion under UV illumination (AO and HT > control, AO > MA). In addition, bacterial adhesion decreased more significantly with extended UV illumination time. With respect to survival rates of bacteria, AO and HT showed a significant reduction over time compared to MA. The photocatalytic bactericidal effect was maximal on the AO titanium, followed by HT and MA.
  
  
  CONCLUSIONS
  The photo-induced bactericidal efficacy of TiO2 films is dependent on their surface characteristics.
authors.affiliation: Department of Orthodontics and Dental Research Institute, School of Dentistry, Seoul National University, Seoul, Korea.
authors.forename: Sug-Joon
authors.initials: SJ
authors.lastname: Ahn
authors.forename: Jung-Suk
authors.initials: JS
authors.lastname: Han
authors.forename: Bum-Soon
authors.initials: BS
authors.lastname: Lim
authors.forename: Young-Jun
authors.initials: YJ
authors.lastname: Lim
mesh_terms: D000900:Anti-Bacterial Agents / Q000737:chemistry / Q000494:pharmacology*; D001422:Bacterial Adhesion / Q000187:drug effects; D001431:Bacteriological Techniques; D055664:Electrochemical Techniques; D006358:Hot Temperature; D006801:Humans; D008422:Materials Testing; D050296:Microbial Viability / Q000187:drug effects; D018613:Microscopy, Confocal; D008855:Microscopy, Electron, Scanning; D010083:Oxidants, Photochemical / Q000494:pharmacology; D017319:Photosensitizing Agents / Q000737:chemistry / Q000494:pharmacology*; D013291:Streptococcus / Q000187:drug effects*; D013499:Surface Properties; D013997:Time Factors; D014025:Titanium / Q000737:chemistry / Q000494:pharmacology*; D014466:Ultraviolet Rays; D014961:X-Ray Diffraction
chemical_list: D000900:Anti-Bacterial Agents; D010083:Oxidants, Photochemical; D017319:Photosensitizing Agents; C009495:titanium dioxide; D014025:Titanium