title: Influence of filler level on the bond strength of orthodontic adhesives.
abstract: OBJECTIVE
  To evaluate the effect of different filler contents of orthodontic adhesives on shear bond strength and Adhesive Remnant Index (ARI).
  
  
  METHODS
  Four experimental adhesive groups were created: group 1 was an unfilled urethane-dimethacrylate (UDMA) adhesive, group 2 consisted of UDMA and a filler content of 30 vol%, group 3 consisted of UDMA and a filler content of 50 vol%, and group 4 was manufactured with a filler level of 70 vol% in a UDMA matrix. The embedded filler was silicon dioxide. After etching and priming, stainless steel brackets were bonded to extracted human third molars (n = 60) with the experimental adhesives (15 teeth per group). After storage in distilled water for 72 hours, shear bond strength and ARI scores were evaluated. Kruskal-Wallis and post hoc test were performed for statistical analysis.
  
  
  RESULTS
  Shear bond strength of UDMA-based adhesives depends on filler content. Higher adhesive filler levels reveal greater bond strength between enamel and stainless steel brackets. ARI scores showed no significant difference among the groups. However, higher filled adhesives (filler content 70 vol%) seem to present higher ARI scores.
  
  
  CONCLUSIONS
  Highly filled UDMA adhesives offer greater bond strength than do lower filled or unfilled resins.
authors.affiliation: Department of Orthodontics, University Clinics, University of Regensburg, Regensburg, Germany. Andreas.Faltermeier@klinik.uni-regensburg.de
authors.forename: Andreas
authors.initials: A
authors.lastname: Faltermeier
authors.forename: Martin
authors.initials: M
authors.lastname: Rosentritt
authors.forename: Rupert
authors.initials: R
authors.lastname: Faltermeier
authors.forename: Claudia
authors.initials: C
authors.lastname: Reicheneder
authors.forename: Dieter
authors.initials: D
authors.lastname: Müssig
mesh_terms: D000269:Adhesives / Q000737:chemistry*; D006801:Humans; D008422:Materials Testing; D008689:Methacrylates / Q000737:chemistry*; D016910:Orthodontic Brackets; D011140:Polyurethanes / Q000737:chemistry*; D033081:Shear Strength; D012822:Silicon Dioxide / Q000737:chemistry*; D018709:Statistics, Nonparametric
chemical_list: D000269:Adhesives; D008689:Methacrylates; D011140:Polyurethanes; C091839:urethanetrimethacrylate; D012822:Silicon Dioxide