title: Relationships between the antibacterial activity of sodium hypochlorite and treatment time and biofilm age in early Enterococcus faecalis biofilms.
abstract: OBJECTIVE
  To determine the relationships between the antibacterial activity of NaOCl and treatment time and biofilm age in early Enterococcus faecalis biofilms using a linear fitting procedure.
  
  
  METHODS
  Enterococcus faecalis biofilms were formed on hydroxyapatite discs. To investigate the relationship between the antibacterial activity of NaOCl and biofilm age, 22-, 46-, 70- and 94-h-old biofilms were exposed to NaOCl (0-3%) for 5 min. To investigate the relationship between the antibacterial activity of NaOCl and treatment time, 70-h-old biofilms were exposed to NaOCl (0-3%) for 1, 3, 5 and 7 min. After treatment, colony-forming units (CFUs) were counted. To determine the relationships between these variables, linear fitting was performed.
  
  
  RESULTS
  The change in the minimum biofilm eradication concentration (MBEC) of NaOCl followed a linear pattern of biofilm age (R = 0.941, R(2)  = 0.886) or treatment time dependence (R = -0.948, R(2)  = 0.898). Below the MBEC, the fitting lines for bacterial CFU count versus NaOCl concentration (R ≤ -0.973, R(2)  ≥ 0.948) in the 22-, 46-, 70- and 94-h-old biofilms implied that the antibacterial activity of NaOCl decreased as the biofilm age increased. The fitting lines for bacterial CFU count versus NaOCl concentration (R ≤ -0.970, R(2)  ≥ 0.942) in the 1-, 3-, 5- and 7-min treatments implied that the antibacterial activity of NaOCl increased with treatment time.
  
  
  CONCLUSIONS
  These results suggest that the antibacterial activity of NaOCl against early E. faecalis biofilms in root canals may follow a linear pattern depending on biofilm age or treatment time.
authors.affiliation: Department of Preventive Dentistry and Institute of Oral Bioscience, BK21 Plus Program, School of Dentistry, Chonbuk National University, Jeonju, Korea.
authors.forename: N P T
authors.initials: NP
authors.lastname: Chau
authors.affiliation: Department of Preventive Dentistry and Institute of Oral Bioscience, BK21 Plus Program, School of Dentistry, Chonbuk National University, Jeonju, Korea.
authors.forename: N H
authors.initials: NH
authors.lastname: Chung
authors.affiliation: Department of Preventive Dentistry and Institute of Oral Bioscience, BK21 Plus Program, School of Dentistry, Chonbuk National University, Jeonju, Korea.
authors.forename: J G
authors.initials: JG
authors.lastname: Jeon
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D018441:Biofilms / Q000187:drug effects* / Q000254:growth & development; D015169:Colony Count, Microbial; D013293:Enterococcus faecalis / Q000187:drug effects* / Q000254:growth & development; D012973:Sodium Hypochlorite / Q000494:pharmacology*; D013997:Time Factors
chemical_list: D000900:Anti-Bacterial Agents; D012973:Sodium Hypochlorite
keywords: Enterococcus faecalis biofilms; antibacterial activity; biofilm age; sodium hypochlorite; treatment time