title: Red fluorescent biofilm: the thick, the old, and the cariogenic.
abstract: BACKGROUND
  Some dental plaque fluoresces red. The factors involved in this fluorescence are yet unknown.
  
  
  OBJECTIVE
  The aim of this study was to assess systematically the effect of age, thickness, and cariogenicity on the extent of red fluorescence produced by in vitro microcosm biofilms.
  
  
  METHODS
  The effects of biofilm age and thickness on red fluorescence were tested in a constant depth film fermentor (CDFF) by growing biofilms of variable thicknesses that received a constant supply of defined mucin medium (DMM) and eight pulses of sucrose/day. The influence of cariogenicity on red fluorescence was tested by growing biofilm on dentin disks receiving DMM, supplemented with three or eight pulses of sucrose/day. The biofilms were analyzed at different time points after inoculation, up to 24 days. Emission spectra were measured using a fluorescence spectrophotometer (λexc405 nm) and the biofilms were photographed with a fluorescence camera. The composition of the biofilms was assessed using 454-pyrosequecing of the 16S rDNA gene.
  
  
  RESULTS
  From day 7 onward, the biofilms emitted increasing intensities of red fluorescence as evidenced by the combined red fluorescence peaks. The red fluorescence intensity correlated with biofilm thickness but not in a linear way. Biofilm fluorescence also correlated with the imposed cariogenicity, evidenced by the induced dentin mineral loss. Increasing the biofilm age or increasing the sucrose pulsing frequency led to a shift in the microbial composition. These shifts in composition were accompanied by an increase in red fluorescence.
  
  
  CONCLUSIONS
  The current study shows that a thicker, older, or more cariogenic biofilm results in a higher intensity of red fluorescence.
authors.affiliation: Department of Preventive Dentistry, Academic Centre for Dentistry Amsterdam (ACTA), University of Amsterdam and VU University, Amsterdam, The Netherlands; c.volgenant@acta.nl.
authors.forename: Catherine M C
authors.initials: CM
authors.lastname: Volgenant
authors.affiliation: Department of Preventive Dentistry, Academic Centre for Dentistry Amsterdam (ACTA), University of Amsterdam and VU University, Amsterdam, The Netherlands.
authors.forename: Michel A
authors.initials: MA
authors.lastname: Hoogenkamp
authors.affiliation: Department of Preventive Dentistry, Academic Centre for Dentistry Amsterdam (ACTA), University of Amsterdam and VU University, Amsterdam, The Netherlands.
authors.forename: Mark J
authors.initials: MJ
authors.lastname: Buijs
authors.affiliation: Department of Preventive Dentistry, Academic Centre for Dentistry Amsterdam (ACTA), University of Amsterdam and VU University, Amsterdam, The Netherlands.
authors.forename: Egija
authors.initials: E
authors.lastname: Zaura
authors.affiliation: Department of Preventive Dentistry, Academic Centre for Dentistry Amsterdam (ACTA), University of Amsterdam and VU University, Amsterdam, The Netherlands.
authors.forename: Jacob M
authors.initials: JM
authors.lastname: Ten Cate
authors.affiliation: Department of Preventive Dentistry, Academic Centre for Dentistry Amsterdam (ACTA), University of Amsterdam and VU University, Amsterdam, The Netherlands.
authors.forename: Monique H
authors.initials: MH
authors.lastname: van der Veen
keywords: biofilms; dental plaque; fluorescence; microbiology; microbiota; microcosm