title: Comparison of Bond Strength of Metal and Ceramic Brackets Bonded with Conventional and High-Power LED Light Curing Units.
abstract: OBJECTIVE
  The aim of this study was to evaluate the effect of conventional and high-power light emitting diode (LED) light curing units on shear bond strength (SBS) of metal and ceramic brackets to tooth surface.
  
  
  METHODS
  Forty sound bovine maxillary central incisors were used for the study. The teeth were divided into four groups (n=10). Teeth surfaces were etched with 37% phosphoric acid for 20 seconds. After applying a uniform layer of adhesive primer on the etched enamel, composite was placed on the base of brackets. The samples were light cured according to the manufacturer's instructions and thermocycled. The SBS was measured. The failure mode was scored using the adhesive remnant index (ARI).
  
  
  RESULTS
  The mean SBS of samples in groups A (high-power LED, metal bracket), B (high-power LED, ceramic bracket), C (conventional LED, metal bracket) and D (conventional LED, ceramic bracket) was 23.1±3.69, 10.7±2.06, 24.92±6.37 and 10.74±3.18MPa, respectively. The interaction effect of type of LED unit (high-power/conventional) and bracket type on SBS was not statistically significant (P=0.483). In general, type of LED unit did not affect SBS. Type of bracket significantly affected SBS (P<0.001). The ARI score was not significantly influenced by the interaction between the type of LED unit and bracket.
  
  
  CONCLUSIONS
  The obtained SBS is the same for both bracket types by use of high-power and conventional LED light curing units. Regardless of the type of LED unit, SBS of ceramic brackets was significantly lower than that of metal brackets.
authors.affiliation: Assistant Professor, Dental Research Center, Dentistry Research Institute, Tehran University of Medical Sciences, Tehran, Iran; Department of Orthodontics, School of Dentistry, Tehran University of Medical Sciences, Tehran, Iran.
authors.forename: Javad
authors.initials: J
authors.lastname: Chalipa
authors.affiliation: Assistant Professor, Department of Orthodontics, School of Dentistry, Ilam University of Medical Sciences, Ilam, Iran.
authors.forename: Yasamin Farajzadeh
authors.initials: YF
authors.lastname: Jalali
authors.affiliation: Assistant Professor, Department of Orthodontics, School of Dentistry, Yasuj University of Medical Sciences, Yasuj, Iran.
authors.forename: Fatemeh
authors.initials: F
authors.lastname: Gorjizadeh
authors.affiliation: Private Practice, Tehran, Iran.
authors.forename: Pedram
authors.initials: P
authors.lastname: Baghaeian
authors.affiliation: Assistant Professor, Dental Research Center, Dentistry Research Institute, Tehran University of Medical Sciences, Tehran, Iran; Department of Orthodontics, School of Dentistry, Tehran University of Medical Sciences, Tehran, Iran.
authors.forename: Mohammad Hashem
authors.initials: MH
authors.lastname: Hoseini
authors.affiliation: Assistant Professor, Department of Orthodontics, Qazvin University of Medical Sciences, Qazvin, Iran.
authors.forename: Omid
authors.initials: O
authors.lastname: Mortezai
keywords: Light-Curing of Dental Adhesives; Orthodontic Brackets; Shear Strength