title: Effects of two erbium-doped yttrium aluminum garnet lasers and conventional treatments as composite surface abrasives on the shear bond strength of metal brackets bonded to composite resins.
abstract: BACKGROUND
  Bonding brackets to dental surfaces restored with composites are increasing. No studies to date have assessed the efficacy of laser irradiation in roughening of composite and the resulted shear bond strength (SBS) of the bonded bracket. We assessed, for the 1(st) time, the efficacy of two laser beams compared with conventional methods.
  
  
  METHODS
  Sixty-five discs of light-cured composite resin were stored in deionized distilled water for 7 days. They were divided into five groups of 12 plus a group of five for scanning electron microscopy (SEM): Bur-abrasion followed by phosphoric acid etching (bur-PA), hydrofluoric acid conditioning (HF), sandblasting, 3 W and 2 W erbium-doped yttrium aluminum garnet laser irradiation for 12 s. After bracket bonding, specimens were water-stored (24 h) and thermocycled (500 cycles), respectively. SBS was tested at 0.5 mm/min crosshead speed. The adhesive remnant index (ARI) was scored under ×10 magnification. SEM was carried out as well. Data were analyzed using analysis of variance (ANOVA), Kruskal-Wallis, Tukey, Dunn, one-sample t-test/Wilcoxon tests, and Weibull analysis (α =0.05).
  
  
  RESULTS
  The SBS values (megapascal) were bur-PA (11.07 ± 1.95), HF (19.70 ± 1.91), sandblasting (7.75 ± 1.10), laser 2 W (15.38 ± 1.38), and laser 3 W (20.74 ± 1.73) (compared to SBS = 6, all P = 0.000). These differed significantly (ANOVA P = 0.000) except HF versus 3 W laser (Tukey P > 0.05). ARI scores differed significantly (Kruskal-Wallis P = 0.000), with sandblasting and 2 W lasers having scores inclined to the higher end (safest debonding). Weibull analysis implied successful clinical outcome for all groups, except for sandblasting with borderline results.
  
  
  CONCLUSIONS
  Considering its high efficacy and the lack of adverse effects bound with other methods, the 3 W laser irradiation is recommended for clinical usage.
authors.affiliation: Department of Orthodontics, Dental Faculty, Mazandaran University of Medical Sciences, Sari, Iran.
authors.forename: Farhad
authors.initials: F
authors.lastname: Sobouti
authors.affiliation: Department of Orthodontics, Dental Research Center, School of Dentistry, Mashhad University of Medical Sciences, Mashhad, Iran.
authors.forename: Sepideh
authors.initials: S
authors.lastname: Dadgar
authors.affiliation: Dental Faculty, Student Research Committee, Mazandaran University of Medical Sciences, Sari, Iran.
authors.forename: Zahra
authors.initials: Z
authors.lastname: Sanikhaatam
authors.affiliation: Dentist in Private Practice, Tehran, Iran.
authors.forename: Nazanin
authors.initials: N
authors.lastname: Nateghian
authors.affiliation: Department of Restorative Dentistry, Dental Faculty, Mazandaran University of Medical Sciences, Sari, Iran.
authors.forename: Mahdi Gholamrezaei
authors.initials: MG
authors.lastname: Saravi
keywords: Bracket bonding; composite surface treatments; dental materials; direct composite veneer; erbium: Doped yttrium aluminum garnet laser; shear bond strength