title: In vitro effects  of several surface preparation methods on shear bond strength of orthodontic brackets to caries-like lesions of enamel.
abstract: OBJECTIVE
  The aim of this study was to evaluate the efficiency of several surface preparation methods for improving shear bond strength of brackets to demineralised enamel.
  
  
  METHODS
  
  
  
  METHODS
  in vitro study. Eighty premolars were selected and divided into 5 groups. Group 1 served as the control, while the remaining 4 groups were immersed in a demineralising solution (pH 4.8) for 12 weeks. In groups 1 (control) and 2 (demineralised/control) conventional acid etching was used. In group 3, a solution of 5% sodium hypochlorite (NaOCl) was applied on enamel surface for one minute after acid etching. The brackets in group 4 were bonded with Transbond Plus self-etching primer, and group 5 underwent treatment with a 2% sodium fluoride (NaF) gel, which was applied on the enamel surface for 4 minutes before etching. Shear bond strength (SBS) and adhesive remnant index (ARI) were determined in all groups, and surface morphology was examined under scanning electron microscope (SEM).
  
  
  RESULTS
  The mean SBS of acid-etched demineralised enamel was significantly lower than that of acid-etched sound enamel (p<0.05). Treatment of caries-like lesions with 5% NaOCl or self-etching primer failed to improve the bond strength. After NaF treatment and acid etching of demineralised enamel, both type 1 and type 2 etching patterns were observed and the resulting SBS was comparable to that of sound enamel (p>0.05).
  
  
  CONCLUSIONS
  The application of 2% NaF on enamel caries before bracket bonding is an effective way for enhancing the bond strength.
authors.affiliation: School of Dentistry, Mashhad University of Medical Sciences, Mashhad, Iran.
authors.forename: M
authors.initials: M
authors.lastname: Shahabi
authors.forename: H
authors.initials: H
authors.lastname: Moosavi
authors.forename: A
authors.initials: A
authors.lastname: Gholami
authors.forename: F
authors.initials: F
authors.lastname: Ahrari
mesh_terms: D000704:Analysis of Variance; D001641:Bicuspid; D002327:Cariostatic Agents / Q000627:therapeutic use; D016009:Chi-Square Distribution; D001840:Dental Bonding; D003743:Dental Enamel; D045662:Dental Etching / Q000379:methods*; D003799:Dental Stress Analysis; D006801:Humans; D016910:Orthodontic Brackets; D033081:Shear Strength; D012969:Sodium Fluoride / Q000627:therapeutic use; D018709:Statistics, Nonparametric; D013499:Surface Properties; D017001:Tooth Demineralization / Q000473:pathology*; D019246:Tooth Preparation / Q000379:methods
chemical_list: D002327:Cariostatic Agents; D012969:Sodium Fluoride