title: XTT assay of ex vivo saliva biofilms to test antimicrobial influences.
abstract: OBJECTIVE
  Many dental diseases are attributable to biofilms. The screening of antimicrobial substances, in particular, requires a high sample throughput and a realistic model, the evaluation must be as quick and as simple as possible. For this purpose, a colorimetric assay of the tetrazolium salt XTT (sodium 3'-[1-[(phenylamino)-carbony]-3,4-tetrazolium]-bis(4-methoxy-6-nitro)benzene-sulfonic acid hydrate) converted by saliva biofilms is recommended. Cleavage of XTT by dehydrogenase enzymes of metabolically active cells in biofilms yields a highly colored formazan product which is measured photometrically.
  
  
  METHODS
  The suitability of the XTT assay for detecting the vitality of ex vivo saliva biofilms was tested to determine the efficacy of chlorhexidine and ozone versus saliva biofilms grown on titanium discs.
  
  
  RESULTS
  The XTT method lends itself to testing the vitality of microorganisms in saliva biofilms. The sensitivity of the arrays requires a specific minimum number of pathogens, this number being different for planktonic bacteria and those occurring in biofilms. The antibacterial effect after treatment with chlorhexidine or ozone was measured by XTT conversion that was significantly reduced. The antimicrobial efficacy of 60 s 0.5% and 0.1% chlorhexidine treatment was equal and comparable with 60 s ozone treatment.
  
  
  CONCLUSIONS
  The XTT assay is a suitable method to determine the vitality in saliva biofilms, permitting assessment of the efficacy of antimicrobial substances. Its quick and easy applicability renders it especially suitable for screening.
authors.affiliation: Unit of Periodontology, Dental School, University of Greifswald, Greifswald, Germany.
authors.forename: Ina
authors.initials: I
authors.lastname: Koban
authors.forename: Rutger
authors.initials: R
authors.lastname: Matthes
authors.forename: Nils-Olaf
authors.initials: NO
authors.lastname: Hübner
authors.forename: Alexander
authors.initials: A
authors.lastname: Welk
authors.forename: Rabea
authors.initials: R
authors.lastname: Sietmann
authors.forename: Jürgen
authors.initials: J
authors.lastname: Lademann
authors.forename: Axel
authors.initials: A
authors.lastname: Kramer
authors.forename: Thomas
authors.initials: T
authors.lastname: Kocher