title: Microhardness of radicular dentin treated with 980-nm diode laser and different irrigant solutions.
abstract: OBJECTIVE
  The aim of this study was to evaluate the microhardness of radicular dentin after treatment with 980-nm diode laser and different irrigant solutions.
  
  
  BACKGROUND
  There are few reports of the consequences of diode laser irradiation emitted at 980 nm on the mechanical properties of dentin.
  
  
  METHODS
  Seventy-two single canal, human canines with complete root formation were randomly distributed among three groups (n=24), according to the irrigant solution used in the biomechanical preparation: distilled water; 1% NaOCl; and, 1% NaOCl + 17% EDTA. These groups subsequently were divided into three subgroups (n=8), according to the diode laser parameter: no irradiation (control); 1.5 W/100 Hz; and 3.0 W/100 Hz. Laser was applied with helicoidal movements for 20 sec. Roots were sectioned in slices and the fragment corresponding to the middle third was submitted to the microhardness test (KHN) at depths of 30, 90, 150, and 300 μm.
  
  
  RESULTS
  ANOVA and Tukey tests showed that the microhardness of the groups irradiated with 1.5 W/100 Hz (49.7±11.2) and 3.0 W/100 Hz (50.6±11.9) were statistically similar to each other (p>0.05) and different (p<0.05) from the non-irradiated group (45.0±9.7). Higher microhardness values were obtained at 150 μm (49.2±11.0) and 300 μm (52.3±11.3) which were similar among themselves and different (p<0.05) only at the depth of 30 μm (44.4±10.5). No differences were found among the irrigant solutions (p>0.05).
  
  
  CONCLUSIONS
  The microhardness of the radicular dentin increased after irradiation with 980-nm diode laser.
authors.affiliation: School of Dentistry, University of Ribeirão Preto, Ribeirão Preto, SP, Brazil.
authors.forename: Raqueli
authors.initials: R
authors.lastname: Viapiana
authors.forename: Manoel D
authors.initials: MD
authors.lastname: Sousa-Neto
authors.forename: Aline Evangelista
authors.initials: AE
authors.lastname: Souza-Gabriel
authors.forename: Edson
authors.initials: E
authors.lastname: Alfredo
authors.forename: Yara Teresinha Correa
authors.initials: YT
authors.lastname: Silva-Sousa
mesh_terms: D003481:Cuspid / Q000528:radiation effects; D003804:Dentin / Q000528:radiation effects*; D006245:Hardness Tests; D006801:Humans; D054023:Lasers, Semiconductor; D008422:Materials Testing; D012388:Root Canal Irrigants
chemical_list: D012388:Root Canal Irrigants