title: Evaluation of shear bond strength of orthodontic brackets bonded with nano-filled composites.
abstract: OBJECTIVE
  The purpose of this study was to evaluate the shear bond strength (SBS) of orthodontic brackets bonded with two types of nano-composites in comparison to a conventional orthodontic composite.
  
  
  METHODS
  Sixty extracted human first premolars were randomly divided into 3 groups each containing 20 teeth. In group I, a conventional orthodontic composite (Transbond XT) was used to bond the brackets, while two nano-composites (Filtek TM Supreme XT and AELITE Aesthetic Enamel) were used in groups II and III respectively. The teeth were stored in distilled water at 37°C for 24 hours, thermocycled in distilled water and debonded with a universal testing machine at a crosshead speed of 1 mm/min. The adhesive remnant index (ARI) was also evaluated using a stereomicroscope.
  
  
  RESULTS
  AELITE Aesthetic Enamel nano-composite revealed a SBS value of 8.44±2.09 MPa, which was higher than Transbond XT (6.91±2.13) and Filtek TM Supreme XT (6.04±2.01). Statistical analysis revealed a significant difference between groups II and III (P < 0.05). No significant difference was found between groups I and III, and between groups I and II (P > 0.05). Evaluation of ARI showed that Transbond XT left fewer adhesive remains on teeth after debonding.
  
  
  CONCLUSIONS
  Results of this study indicate that the aforementioned nano-composites can be successfully used for bonding orthodontic brackets.
authors.affiliation: Assistant Professor, Department of Orthodontics, Tehran University of Medical Sciences, Tehran, Iran.
authors.forename: Javad
authors.initials: J
authors.lastname: Chalipa
authors.affiliation: Professor, Dental Research Center, Dentistry Research Institute, Department of Orthodontics, Tehran University of Medical Sciences, Tehran, Iran.
authors.forename: Mohammad Sadegh Ahmad
authors.initials: MS
authors.lastname: Akhondi
authors.affiliation: Assistant Professor, Department of Orthodontics, Qazvin University of Medical Sciences, Qazvin, Iran.
authors.forename: Sepideh
authors.initials: S
authors.lastname: Arab
authors.affiliation: Post Graduated Student of Epidemiology, Dental Research Center, Tehran University of Medical Sciences, Tehran, Iran.
authors.forename: Mohammad Javad
authors.initials: MJ
authors.lastname: Kharrazifard
authors.affiliation: General Dental Practitioner, Tehran, Iran.
authors.forename: Maryam
authors.initials: M
authors.lastname: Ahmadyar
keywords: Bond Strength; Composite; Nano; Shear