title: Use of a dissolved oxygen microsensor for assessing the viability and thickness of microbial biofilm on root surfaces.
abstract: OBJECTIVE
  To evaluate the use of a dissolved oxygen microsensor (DOMS) for assessing the viability and thickness of microbial biofilms on the apical external surface of contaminated human tooth roots.
  
  
  METHODS
  Apical biofilm formation was evaluated in 15 roots contaminated in vitro with a polymicrobial mixture of Staphylococcus aureus, Enterococcus faecalis, Pseudomonas aeruginosa and Candida albicans for 7, 21 and 60 days and in three freshly extracted roots with associated radiographically visible periapical lesions. In each root, the thickness and viability (measured by the amount of dissolved oxygen) of biofilm formed on the apical 2 mm were examined with the DOMS. Scanning electron microscopy (SEM) was used as an auxiliary analysis to confirm the existence of the biofilms detected by the DOMS.
  
  
  RESULTS
  The DOMS detected dissolved oxygen on the biofilms formed on the three residual roots up to thickness of 375 μm, 480 μm and 1650 μm. In the 15 roots contaminated in vitro, the DOMS detected dissolved oxygen in six specimens up to thicknesses from 75 to 250 μm, and the intensity of the metabolic activity (biofilm thickness) was directly proportional to the contamination time. SEM confirmed the presence of biofilm in all roots.
  
  
  CONCLUSIONS
  The dissolved oxygen microsensor allowed the measurement of the amount of dissolved oxygen in the biofilm, which is indicative of the intensity of the microbial metabolic activity (viability), correlating the results with biofilm thickness. The DOMS was effective in freshly extracted roots, but had limitations in roots contaminated in vitro after short periods (7 and 21 days) of contamination.
authors.affiliation: School of Dentistry, University of Ribeirão Preto, Ribeirão Preto, SP, Brazil.
authors.forename: F S F
authors.initials: FS
authors.lastname: Tomazinho
authors.forename: M D
authors.initials: MD
authors.lastname: Sousa-Neto
authors.forename: J D
authors.initials: JD
authors.lastname: Pécora
authors.forename: A W
authors.initials: AW
authors.lastname: Lamon
authors.forename: B C
authors.initials: BC
authors.lastname: Gonzalez
authors.forename: Y T C
authors.initials: YT
authors.lastname: Silva-Sousa
mesh_terms: D018441:Biofilms; D002176:Candida albicans; D013293:Enterococcus faecalis; D006801:Humans; D066298:In Vitro Techniques; D050296:Microbial Viability; D008855:Microscopy, Electron, Scanning; D010100:Oxygen / Q000378:metabolism*; D011550:Pseudomonas aeruginosa; D013211:Staphylococcus aureus; D014092:Tooth Root / Q000382:microbiology*
chemical_list: D010100:Oxygen
keywords: biofilm; dissolved oxygen; endodontics; probe; scanning electron microscopy