title: Effects of fluoride release from orthodontic bonding materials on nanomechanical properties of the enamel around orthodontic brackets.
abstract: BACKGROUND
  The aim of the present study is to evaluate the effects of a fluoride-releasing composite resin bonding material on reducing enamel demineralization underneath and around orthodontic brackets and compare that with a conventional adhesive system.
  
  
  METHODS
  Buccal surfaces of 10 intact extracted premolar teeth were divided into two parts with nail varnish and stainless steel brackets were randomly bonded by two resin composite systems: (Transbond XT) and (Transbond XT plus Color Change) (3M, Unitek, Monrovia, CA, USA) on two sides of the teeth and then samples were placed in a demineralization solution. It is claimed that the second system has the ability of fluoride release. Elastic modulus and hardness of enamel were measured with nanoindentation test in 6 depths in 1-36 μm from the enamel surface and in 7 regions: Control (intact enamel surface), underneath the brackets and also 50 and 100 μm from the brackets edge. These nanomechanical features were evaluated in different regions and depths using analysis of variance and paired t-test (P < 0.05).
  
  
  RESULTS
  Considerable difference can be seen in different depths and regions in terms of hardness and elastic modulus. The region under the bracket with fluoridated adhesive shows similar results with intact enamel, whereas these parameters in fluoride less side show a significant reduction (P < 0.05).
  
  
  CONCLUSIONS
  Results show that use of resin composite bonding system with the ability of fluoride release for bracket bonding, may reduce demineralization of enamel around brackets during orthodontic treatment.
authors.affiliation: Torabinejad Dental Research Center and Department of Orthodontics and Dentofacial Orthopedics, School of Dentistry, Isfahan University of Medical Sciences, Isfahan, Iran.
authors.forename: Seyed Hamid
authors.initials: SH
authors.lastname: Raji
authors.affiliation: Department of Orthodontics, School of Dentistry, Arak University of Medical Sciences, Arak, Iran.
authors.forename: Hamed
authors.initials: H
authors.lastname: Banimostafaee
authors.affiliation: Department of Orthodontics, School of Dentistry, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran.
authors.forename: Fatemeh
authors.initials: F
authors.lastname: Hajizadeh
keywords: Elastic modulus; enamel demineralization; fluoride releasing adhesive; hardness nanoindentation