title: The Bactericidal Effect of 2780 and 940 nm Laser Irradiation on Enterococcus faecalis in Bovine Root Dentin Slices of Different Thicknesses.
abstract: OBJECTIVE
  The aim of this in vitro study was to investigate the antibacterial effect of the dual wavelength (2780 nm Er,Cr:YSGG and 940 nm diode) laser in elimination of Enterococcus faecalis in comparison with a 2780 nm Er,Cr:YSGG laser alone.
  
  
  BACKGROUND
  Various laser wavelengths have been introduced as an adjunct in root canal treatment because of laser's bactericidal effect.
  
  
  METHODS
  Seventy- five slices of dentin with thicknesses of 300, 500, and 1000 μm (n = 25 each) obtained from caries-free bovine teeth were inoculated with 1 μL of E. faecalis suspension [1.67 × 10(7) colony-forming units (CFU)] and divided randomly into three groups: (A) samples indirectly irradiated with power settings of 1.06 W, 50 Hz, and 50 μs for Er,Cr:YSGG laser; (B) samples indirectly irradiated with Er,Cr:YSGG laser with the same power settings as group A and simultaneously with a 940 nm diode laser of 0.51 W in pulsed mode; and five samples from each thickness that were chosen as an unirradiated control group (Co). After irradiation, the CFU of E. faecalis were counted and the bacterial reduction was analyzed using Kruskal-Wallis nonparametric and post-hoc Dunnett tests.
  
  
  RESULTS
  There were statistical differences between groups A and B compared with the control group over all the three dentin slice thicknesses (p < 0.001). However, there was no statistical difference between groups A and B in killing of E. faecalis on 500 μm dentin slices. There were significantly more viable bacteria in group A than in group B in 300 and 1000 μm dentin slices (p < 0.01).
  
  
  CONCLUSIONS
  The results of this in vitro study showed that the dual wavelength laser system obtained a significantly higher bactericidal effect on E. faecalis than Er,Cr:YSGG laser, reaching a depth of 1000 μm of dentin.
authors.affiliation: 1 Department of Conservative Dentistry, Periodontology and Preventive Dentistry, RWTH University Hospital Aachen , Aachen, Germany .
authors.forename: Norbert
authors.initials: N
authors.lastname: Gutknecht
authors.affiliation: 1 Department of Conservative Dentistry, Periodontology and Preventive Dentistry, RWTH University Hospital Aachen , Aachen, Germany .|2 Department of Biomedical Applications, Institute of Laser for Postgraduate Studies, University of Baghdad , Baghdad, Iraq .
authors.forename: Tamara Sardar
authors.initials: TS
authors.lastname: Al-Karadaghi
authors.affiliation: 2 Department of Biomedical Applications, Institute of Laser for Postgraduate Studies, University of Baghdad , Baghdad, Iraq .
authors.forename: Mohammed Abbood
authors.initials: MA
authors.lastname: Al-Maliky
authors.affiliation: 3 Division of Oral Microbiology and Immunology, Department of Conservative Dentistry, Periodontology and Preventive Dentistry, RWTH University Hospital Aachen , Aachen, Germany .
authors.forename: Georg
authors.initials: G
authors.lastname: Conrads
authors.affiliation: 1 Department of Conservative Dentistry, Periodontology and Preventive Dentistry, RWTH University Hospital Aachen , Aachen, Germany .
authors.forename: Rene
authors.initials: R
authors.lastname: Franzen
mesh_terms: D000818:Animals; D002417:Cattle; D015169:Colony Count, Microbial; D003804:Dentin / Q000382:microbiology* / Q000528:radiation effects*; D013293:Enterococcus faecalis / Q000254:growth & development* / Q000528:radiation effects*; D054023:Lasers, Semiconductor; D053844:Lasers, Solid-State; D046509:Tissue Culture Techniques