title: Difference in initial dental biofilm accumulation between night and day.
abstract: OBJECTIVE
  The study of initial microbial colonization on dental surfaces is a field of intensive research because of the aetiological role of biofilms in oral diseases. Most previous studies of de novo accumulation and composition of dental biofilms in vivo do not differentiate between biofilms formed during day and night. This study hypothesized that there is a diurnal variation in the rate of accumulation of bacteria on solid surfaces in the oral cavity.
  
  
  METHODS
  In situ biofilm from healthy individuals was collected for 12 h during day and night, respectively, subjected to fluorescent in situ hybridization and visualized using confocal laser scanning microscopy.
  
  
  RESULTS
  Analysis of the biofilms using stereological methods and digital image analysis revealed a consistent statistically significant difference between both the total number of bacteria and the biovolume in the two 12-h groups (p = 0.012), with the highest accumulation of bacteria during daytime (a factor of 8.8 and 6.1 higher, respectively). Hybridization with probes specific for streptococci and Actinomyces naeslundii indicated a higher proportion of streptococci in biofilms grown during daytime as compared to night-time. No differences could be observed for A. naeslundii. The degree of microbial coverage and the bacterial composition varied considerably between different individuals.
  
  
  CONCLUSIONS
  The data provide firm evidence that initial biofilm formation decreases during the night, which may reflect differences in the availability of salivary nutrients. This finding is of significant importance when studying population dynamics during experimental dental biofilm formation.
authors: Department of Dental Pathology, Operative Dentistry and Endodontics, School of Dentistry, Aarhus Faculty of Health Sciences, Aarhus University, Denmark. idige@odont.au.dk
authors: Irene
authors: I
authors: Dige
authors: Sebastian
authors: S
authors: Schlafer
authors: Bente
authors: B
authors: Nyvad
mesh_terms: D001419:Bacteria / Q000145:classification / Q000254:growth & development* / Q000302:isolation & purification; D001483:Base Sequence; D018441:Biofilms; D002940:Circadian Rhythm; D015169:Colony Count, Microbial; D015342:DNA Probes; D006801:Humans; D017404:In Situ Hybridization, Fluorescence; D018613:Microscopy, Confocal; D012016:Reference Values; D014070:Tooth / Q000382:microbiology*
chemical_list: D015342:DNA Probes