title: Comparative assessment of different recycling methods of orthodontic brackets for clinical use.
abstract: BACKGROUND
  This study aimed to assess bond strength of the resin/bracket interface, under in-vitro shear stress, of metal brackets recycled by different clinical protocols.
  
  
  METHODS
  Sixty stainless steel orthodontic brackets were bonded on acrylic resin. The Transbond XT™ resin was applied at the base of the bracket aided by a matrix, obtaining 1 mm of thickness, and photoactivated with a LED device (40 s; 500 mW/cm2). Samples were randomly divided into four groups (N.=15) according to the reconditioning/recycling protocol: aluminum oxide (AO) 90 µm; hydrofluoric acid 60 s (HA60); hydrofluoric acid 120 s (HA120); hydrofluoric acid 60 s + silane (HA60S). After recycling, the resin was applied at the base of the bracket for shear testing in a universal testing machine (0.5 mm/min). After reconditioning/recycling, the surfaces were analyzed by Scanning Electron Microscopy. Data obtained after the shear test were subjected to ANOVA and Tukey's test (P<0.05).
  
  
  RESULTS
  The AO group presented higher values of shear bond strength compared to the other reconditioning/recycling protocols (P<0.05). The HA120 and HA60S groups presented statistically similar results, but HA120 presented strength below the recommended limit.
  
  
  CONCLUSIONS
  The recycling technique by aluminum oxide sandblasting was more effective for reconditioning orthodontic brackets when compared to the other protocols. The reconditioning technique with 10% hydrofluoric acid followed by the application of silane bonding agent may be used as an alternative protocol.
authors.affiliation: Postgraduate Program in Restorative Dentistry, Institute of Science and Technology, São Paulo State University, São José dos Campos, Brazil.
authors.forename: Ayla M
authors.initials: AM
authors.lastname: de Oliveira Correia
authors.affiliation: Postgraduate Program in Restorative Dentistry, Institute of Science and Technology, São Paulo State University, São José dos Campos, Brazil.
authors.forename: Felipe
authors.initials: F
authors.lastname: de Souza Matos
authors.affiliation: Department of Dental Materials and Prosthodontics, Institute of Science and Technology, São Paulo State University, São José dos Campos, Brazil.
authors.forename: Renata
authors.initials: R
authors.lastname: Pilli Jóias
authors.affiliation: Department of Dental Materials and Prosthodontics, Institute of Science and Technology, São Paulo State University, São José dos Campos, Brazil.
authors.forename: Sigmar
authors.initials: S
authors.lastname: de Mello Rode
authors.affiliation: Department of Biomaterials and Oral Biology, University of São Paulo, São Paulo, Brazil.
authors.forename: Paulo F
authors.initials: PF
authors.lastname: Cesar
authors.affiliation: Department of Dentistry, Federal University of Sergipe, Lagarto, Brazil - paranhos@ortodontista.com.br.
authors.forename: Luiz R
authors.initials: LR
authors.lastname: Paranhos
mesh_terms: D000537:Aluminum Oxide; D017438:Bisphenol A-Glycidyl Methacrylate; D001840:Dental Bonding; D003799:Dental Stress Analysis; D020878:Device Removal; D004868:Equipment Failure; D006801:Humans; D006858:Hydrofluoric Acid; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D016910:Orthodontic Brackets; D011897:Random Allocation; D059027:Recycling / Q000379:methods*; D033081:Shear Strength; D012821:Silanes
chemical_list: D012821:Silanes; C065742:Transbond; D017438:Bisphenol A-Glycidyl Methacrylate; D000537:Aluminum Oxide; D006858:Hydrofluoric Acid