title: Efficacy of low concentrations of sodium hypochlorite and low-powered Er,Cr:YSGG laser activated irrigation against an Enterococcus faecalis biofilm.
abstract: OBJECTIVE
  To establish the antibacterial efficacy of low concentrations of sodium hypochlorite with and without Er,Cr:YSGG laser activation on Enterococcus faecalis biofilms in extracted teeth.
  
  
  METHODS
  The root canals of 96 decoronated single-rooted extracted human teeth were prepared to a size 40, 0.06 taper 1 mm beyond the apex. They were mounted within a flow cell, which was sterilized before pumping a nutrient media through the root canals. The flow cell was inoculated with E. faecalis (ATCC 700802) and cultivated for 4 weeks. The root-ends were sealed, and the roots were then subjected to one of six treatment groups: group 1: syringe irrigation (SI) with saline (control) using a 27 -gauge Monoject needle 1 mm from the apex for 2 min; group 2: as for group 1 but with 1% NaOCl; group 3: as for group 1 but with 4% NaOCl; group 4: 0.5% NaOCl irrigation for 15 s followed by laser-activated irrigation (LAI) with four 15-s cycles replenishing the irrigant between cycles; group 5: as for group 4 but with 1% NaOCl as the irrigant; group 6: as for group 4 but with 4% NaOCl as the irrigant. Following treatment, teeth were crushed and viable bacteria were quantitated by serial dilution and plating. The colony-forming unit values were compared between groups using one-way anova and Tukey-adjusted post hoc tests. A two-tailed P value of <0.05 was considered statistically significant.
  
  
  RESULTS
  The mean number of cells recovered from the 1% NaOCl SI group was significantly higher than that from the 4% NaOCl LAI group (P = 0.02).
  
  
  CONCLUSIONS
  Within the limitations of this laboratory study, low-powered (0.5 W) Er,Cr:YSGG laser activation did not improve the antibacterial effect of low concentrations of sodium hypochlorite.
authors.affiliation: Discipline of Endodontics, The University of Adelaide, Adelaide, SA, Australia.
authors.forename: J E
authors.initials: JE
authors.lastname: Christo
authors.affiliation: Oral Microbiology Laboratory, School of Dentistry, The University of Adelaide, Adelaide, SA, Australia.
authors.forename: P S
authors.identifier: http://orcid.org/0000-0001-7554-9717
authors.initials: PS
authors.lastname: Zilm
authors.affiliation: Discipline of Public Health, The University of Adelaide, Adelaide, SA, Australia.
authors.forename: T
authors.initials: T
authors.lastname: Sullivan
authors.affiliation: Discipline of Endodontics, The University of Adelaide, Adelaide, SA, Australia.
authors.forename: P R
authors.initials: PR
authors.lastname: Cathro
mesh_terms: D018441:Biofilms; D015169:Colony Count, Microbial; D003786:Dental Pulp Cavity / Q000382:microbiology*; D004203:Disinfection; D013293:Enterococcus faecalis / Q000187:drug effects*; D006801:Humans; D066298:In Vitro Techniques; D053844:Lasers, Solid-State; D012388:Root Canal Irrigants / Q000494:pharmacology*; D012973:Sodium Hypochlorite / Q000494:pharmacology*
chemical_list: D012388:Root Canal Irrigants; D012973:Sodium Hypochlorite
keywords: Sodium hypochlorite; biofilm; endodontics; laser-activated irrigation; root canal disinfection