title: In vitro cyclic shear fatigue of the bracket-adhesive complex: a pilot study.
abstract: OBJECTIVE
  The aim of this study was to describe the effect of fatigue on the shear strength of the bracket-adhesive complex.
  
  
  METHODS
  Brackets with laser-structured (Discovery®, Dentaurum) and foil mesh bases (Ultra-Minitrim®, Dentaurum) were bonded onto silanized stainless steel flat plates with two chemically curing adhesives (No-Mix Bonding System, Dentaurum; Concise™, 3M Unitek) and aged in distilled water at 37°C for 3 days. One group of specimens was used to determine shear-bond strength. The second group underwent shear-fatigue testing with a testing machine (Zwick 1445) according to the staircase method for 1,000 cycles, and the surviving specimens were subjected to shear-strength testing. The shear strength of the fatigued and non-fatigued specimens were then compared.
  
  
  RESULTS
  Fatigued specimens demonstrated an 8% gain in shear strength in material group A (Discovery®/No-Mix) and a 10% loss of shear strength in material group D (Ultra-Minitrim®/Concise™) compared to the non-fatigued group. We observed no statistically significant differences in material groups B (Ultra-Minitrim®/No-Mix) and C (Discovery®/Concise™). The fatigue ratio varied between 60% and 67%. Among the non-fatigued specimens, the bracket Discovery® with laser-structured base showed circa 59% greater shear strength than the foil-mesh bracket Ultra-Minitrim®, and the adhesive Concise™ about 66% more shear strength than the No-Mix.
  
  
  CONCLUSIONS
  Shear fatigue of the bracket-adhesive complex for 1,000 cycles revealed a variable, material-dependent influence on the shear strength of the bracket-adhesive complex. However, the effect of fatigue on shear strength was less significant than the effect of other factors such as bracket and adhesive type.
authors.affiliation: Department of Orthodontics, University of Bonn, Welschnonnenstr. 17, 53111, Bonn, Germany. nikolaos.daratsianos@uni-bonn.de
authors.forename: N
authors.initials: N
authors.lastname: Daratsianos
authors.forename: A
authors.initials: A
authors.lastname: Jäger
authors.forename: T
authors.initials: T
authors.lastname: Eliades
authors.forename: C
authors.initials: C
authors.lastname: Bourauel
mesh_terms: D017438:Bisphenol A-Glycidyl Methacrylate; D001840:Dental Bonding / Q000379:methods*; D003738:Dental Cements; D003799:Dental Stress Analysis / Q000379:methods*; D019544:Equipment Failure Analysis; D006801:Humans; D066298:In Vitro Techniques; D016382:Orthodontic Appliance Design; D016910:Orthodontic Brackets; D010865:Pilot Projects; D019279:Resin Cements; D033081:Shear Strength; D013314:Stress, Mechanical
chemical_list: D003738:Dental Cements; D019279:Resin Cements; D017438:Bisphenol A-Glycidyl Methacrylate