title: Comparison of Shear Bond Strength of Orthodontic Brackets Bonded to Enamel Prepared By Er:YAG Laser and Conventional Acid-Etching.
abstract: BACKGROUND
  The purpose of this study was to compare shear bond strength (SBS) of orthodontic brackets bonded to enamel prepared by Er:YAG laser with two different powers and conventional acid-etching.
  
  
  METHODS
  Forty-five human premolars extracted for orthodontic purposes were randomly assigned to three groups based on conditioning method: Group 1- conventional etching with 37% phosphoric acid; Group 2- irradiation with Er:YAG laser at 1 W; and Group 3- irradiation with Er:YAG laser at 1.5 W. Metal brackets were bonded on prepared enamel using a light-cured composite. All groups were subjected to thermocycling process. Then, the specimens mounted in auto-cure acryle and shear bond strength were measured using a universal testing machine with a crosshead speed of 0.5 mm per second. After debonding, the amount of resin remaining on the teeth was determined using the adhesive remnant index (ARI) scored 1 to 5. One-way analysis of variance was used to compare shear bond strengths and the Kruskal-Wallis test was performed to evaluate differences in the ARI for different etching types.
  
  
  RESULTS
  The mean and standard deviation of conventional acid-etch group, 1W laser group and 1.5W laser group was 3.82 ± 1.16, 6.97 ± 3.64 and 6.93 ± 4.87, respectively.
  
  
  CONCLUSIONS
  The mean SBS obtained with an Er:YAG laser operated at 1W or 1.5W is approximately similar to that of conventional etching. However, the high variability of values in bond strength of irradiated enamel should be considered to find the appropriate parameters for applying Er:YAG laser as a favorable alternative for surface conditioning.
authors.affiliation: Assisstant Professor, Department of Orthodontic, School of Dentistry, Tehran University of Medical Science, Tehran, Iran.
authors.forename: M H
authors.initials: MH
authors.lastname: Hosseini
authors.forename: F
authors.initials: F
authors.lastname: Namvar
authors.forename: J
authors.initials: J
authors.lastname: Chalipa
authors.forename: K
authors.initials: K
authors.lastname: Saber
authors.forename: N
authors.initials: N
authors.lastname: Chiniforush
authors.forename: S
authors.initials: S
authors.lastname: Sarmadi
authors.forename: A H
authors.initials: AH
authors.lastname: Mirhashemi