title: Comparison of the shear bond strength of orthodontic brackets in bonding and rebonding: preparation with laser versus conventional acid etch technique.
abstract: OBJECTIVE
  The purpose of this study was to compare the bond strength of orthodontic brackets using laser versus acid etching.
  
  
  BACKGROUND
  Debonding of brackets is a common problem in orthodontic treatments.
  
  
  METHODS
  Eighty extracted premolar teeth were divided into two groups. The enamel of the teeth in group A and B were etched using CO2 laser and phosphoric acid, respectively. The brackets were bonded to the teeth using Transbond XT and then debonded from the teeth by Instron machine. The remaining composite on the tooth surface was removed by a tungsten carbide polishing bur. Both groups were divided into two subgroups (A1, A2 and B1, B2). The teeth were prepared again with laser in A1, B1 subgroups and with acid in A2, B2 subgroups. At each stage, the shear bond strength and residual adhesive index were measured. One way ANOVA and χ(2) tests were used to analyze data.
  
  
  RESULTS
  The mean shear bond strength was significantly lower in group A and higher in group B compared with all other groups (p < 0.05). Most of the bond failures were degree 0 and 1 in groups A, A1, and B1, and degree 2 and 3 in groups B, A2, and B2.
  
  
  CONCLUSIONS
  Primary preparation with acid has a higher bond strength value than does CO2 laser. Less adhesive residue remained on enamel after tooth preparation with laser following debonding. Secondary preparation of the enamel using laser has higher bond strength value than does primary preparation with laser, which can rationalize use of laser in rebonding of brackets.
authors.affiliation: Department of Orthodontics, Faculty of Dentistry, Shiraz University of Medical Sciences, Shiraz, Iran. morteza_oshagh@yahoo.com
authors.forename: Morteza
authors.initials: M
authors.lastname: Oshagh
authors.forename: Hamid Reza
authors.initials: HR
authors.lastname: Pakshir
authors.forename: H Zarif
authors.initials: HZ
authors.lastname: Najafi
authors.forename: Mohammad Mehdi
authors.initials: MM
authors.lastname: Naseri
authors.forename: N Iraji
authors.initials: NI
authors.lastname: Nasrabadi
authors.forename: Sepideh
authors.initials: S
authors.lastname: Torkan
mesh_terms: D000134:Acid Etching, Dental; D001840:Dental Bonding / Q000379:methods*; D045662:Dental Etching; D006801:Humans; D054020:Lasers, Gas; D016910:Orthodontic Brackets; D019279:Resin Cements / Q000627:therapeutic use; D033081:Shear Strength
chemical_list: D019279:Resin Cements; C477790:Transbond XT