title: The bactericidal effect of Ho:YAG laser irradiation within contaminated root dentinal samples.
abstract: OBJECTIVE
  This in vitro study investigates the bactericidal effect of pulsed Ho:YAG laser irradiation in the depth of contaminated dentin specimens.
  
  
  BACKGROUND
  Previous studies have shown the effectiveness of laser irradiation in bacterial reduction of infected root canal.
  
  
  METHODS
  Root dentin of bovine teeth were sliced longitudinally in 180 samples of 100 microm, 300 microm, and 500 microm thickness, sterilized, dried, and inoculated on one side, with 1 microL of Enterococcus faecalis suspension. The opposite side's were irradiated four times for 5 seconds each with Ho:YAG laser irradiation, a wavelength of 2.10 microm, using four different energy settings: 1 W/5 Hz; 1 W/10 Hz; 1.5 W/5 Hz, and 2.0 W/5 Hz through a 320-microm quartz fiber at an angle of approximately 5 degrees. In addition, two control groups were investigated, the first was inoculated and not submitted to any treatment, the second was inoculated and treated with NaOCl and H2O2. The remaining bacteria from each dentin sample in a transport media were removed by vibration, serially diluted, and plated out on culture dishes selective for Enterococcus faecalis.
  
  
  RESULTS
  When compared with the untreated control group or even with the group treated with NaOCl plus H2O2, counting of colonies forming units (CFU) from the laser-treated samples revealed a high significant bacterial elimination with a maximum of 98.46% and a minimum of 83.65%.
  
  
  CONCLUSIONS
  Our findings demonstrate a significant decrease of the bacterial population in depth, suggesting that the Ho:YAG laser irradiation could be effective to eliminate the microorganisms harbored within dentin or contaminated canals.
authors.affiliation: Department of Restorative Dentistry, School of Dentistry, Universidade de São Paulo, São Paulo, Brazil.
authors.forename: S
authors.initials: S
authors.lastname: Gouw-Soares
authors.forename: N
authors.initials: N
authors.lastname: Gutknecht
authors.forename: G
authors.initials: G
authors.lastname: Conrads
authors.forename: F
authors.initials: F
authors.lastname: Lampert
authors.forename: E
authors.initials: E
authors.lastname: Matson
authors.forename: C P
authors.initials: CP
authors.lastname: Eduardo
mesh_terms: D000818:Animals; D002417:Cattle; D015169:Colony Count, Microbial; D003804:Dentin / Q000382:microbiology* / Q000528:radiation effects*; D013293:Enterococcus faecalis / Q000528:radiation effects*; D066298:In Vitro Techniques; D028022:Low-Level Light Therapy