title: The Effect of Four Surface Treatment Methods on the Shear Bond Strength of Metallic Brackets to the Fluorosed Enamel.
abstract: BACKGROUND
  Some studies have reported the bond strength to be significantly lower in fluorotic enamels than the non-fluorosed.
  
  
  OBJECTIVE
  The purpose of this study was to evaluate the shear bond streongth of metallic brackets to non-fluorosed and fluorosed teeth after different enamel conditioning.
  
  
  METHODS
  A total of 176 freshly extracted human premolars (88 non-fluorosed and 88 fluorosed teeth) were used in this study for bonding the metallic brackets. Teeth with moderate fluorosis were used according to Thylstrup and Fejereskov index (TFI). Eighty non-fluorosed and 80 fluorosed teeth (TFI=4-6) were randomly divided into 8 equal groups of 20 teeth each. The remaining 16 teeth were used for scanning electron microscopy observation. The enamel surface was conditioned by 4 methods: acid etching  for 30 sec, acid etching for 120 sec, air abrasion followed by acid etching, and Er: YAG laser etching followed by acid etching. The morphology of etching patterns in different groups was studied under scanning electron microscope.
  
  
  RESULTS
  The shear bond strength of fluorosed teeth to the brackets was significantly lower than non-fluorosed ones (p= 0.003). The shear bond strength of laser-acid groups in both non-fluorosed and fluorosed teeth was significantly lower than other groups (p< 0.001). Weibull analysis indicated that the chance of failure under the applied force was different between fluorosed and non-fluorosed group. The scanning electron microscope observations revealed that the fluorosed teeth treated with phosphoric acid had fewer irregularities compared to non-fluorosed teeth. The most irregularities were detected in the teeth conditioned with phosphoric acid for 120 seconds.
  
  
  CONCLUSIONS
  Fluorotic enamel adversely affects the bond strength of orthodontic brackets. None of the conditioning methods tested in this study could significantly improve shear bond strength of metallic brackets. Er: YAG laser conditioning followed by acid further reduced the bond strength in non-fluorosed and fluorosed teeth.
authors.affiliation: Orthodontic Research Center, Dept. of Orthodontics, School of Dentistry, Shiraz University of Medical Sciences, Shiraz, Iran.
authors.forename: Hooman
authors.initials: H
authors.lastname: Zarif Najafi
authors.affiliation: Orthodontic Research Center, Dept. of Orthodontics, School of Dentistry, Shiraz University of Medical Sciences, Shiraz, Iran.
authors.forename: Vahid
authors.initials: V
authors.lastname: Moshkelgosha
authors.affiliation: Student Research Committee, School of Dentistry, Shiraz University of Medical Sciences, Shiraz, Iran.
authors.forename: Atefeh
authors.initials: A
authors.lastname: Khanchemehr
authors.affiliation: Student Research Committee, School of Dentistry, Shiraz University of Medical Sciences, Shiraz, Iran.
authors.forename: Akram
authors.initials: A
authors.lastname: Alizade
authors.affiliation: School of Dentistry, Tehran Islamic Azad University of Medical Sciences, Tehran, Iran.
authors.forename: Ali
authors.initials: A
authors.lastname: Mokhtar
keywords: Air abrasion; Bond strength; Fluorosis; Laser