title: Reduction of biofilm formation on titanium surface with ultraviolet-C pre-irradiation.
abstract: OBJECTIVE
  Ultraviolet-C irradiation on titanium implants has been recently introduced as photofunctionalization to enhance osseointegration, which possibly also provide anti-microbial function to titanium surface as with photocatalyst. The purpose of this study was to determine the effect of ultraviolet-C pre-irradiation to various topographical titanium surfaces on the attachment or biofilm formation of wound pathogens in comparison with that of ultraviolet-A pre-irradiation, with consideration for the physicochemical mechanism.
  
  
  METHODS
  The amount of wound pathogens such as Staphylococcus aureus or Streptococcus pyogenes on titanium disks with mirror-polished, turned, acid-etched, or shot-blasted surfaces with or without 500 J/cm2ultraviolet-A or ultraviolet-C pre-irradiation for 8 h incubation in brain heart infusion broth was evaluated by fluorescence microscopic quantification with 5-cyano-2, 3-ditolyl-2 H-tetrazolium chloride staining for viable bacteria. The surface roughness, wettability, and atomic composition of the surface were evaluated before and after ultraviolet-A or ultraviolet-C irradiation.
  
  
  RESULTS
  Regardless of topographies, the amount of bacterial attachment and accumulation was lower on ultraviolet-C pre-irradiated surfaces than on the non-irradiated surface through 8 h incubation. The reducing effect of bacterial accumulation on the roughened surfaces by ultraviolet-A pre-irradiation was inferior to that by ultraviolet-C. Despite no effect on surface topography, ultraviolet-C irradiation changed wettability to superhydrophilicity and reduced carbon contents on any titanium surface with a greater degree than those by ultraviolet-A irradiation.
  
  
  CONCLUSIONS
  Ultraviolet-C irradiation reduced the attachment and biofilm formation of wound pathogens on various topographical titanium surfaces, rivaling or surpassing UVA irradiation in degree. The mechanism might involve superhydrophilicity and carbon elimination on the surface.
authors.affiliation: Department of Removable Prosthodontics & Gerodontology, Tokyo Dental College, Tokyo, Japan.
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Yamada
authors.affiliation: Department of Removable Prosthodontics & Gerodontology, Tokyo Dental College, Tokyo, Japan Oral Health Science Center, Tokyo Dental College, Tokyo, Japan masayamada@tdc.ac.jp.
authors.forename: Masahiro
authors.initials: M
authors.lastname: Yamada
authors.affiliation: Department of Removable Prosthodontics & Gerodontology, Tokyo Dental College, Tokyo, Japan.
authors.forename: Takayuki
authors.initials: T
authors.lastname: Ueda
authors.affiliation: Department of Removable Prosthodontics & Gerodontology, Tokyo Dental College, Tokyo, Japan.
authors.forename: Kaoru
authors.initials: K
authors.lastname: Sakurai
keywords: Hydrocarbon; implant; photo-functionalization; superhydrophilicity; wound pathogen