title: Comparison of shear bond strength of orthodontic brackets using various zirconia primers.
abstract: OBJECTIVE
  The aim of this study was to compare the shear bond strength (SBS) of orthodontic brackets bonded to zirconia surfaces using three different zirconia primers and one silane primer, and subjected to thermocycling.
  
  
  METHODS
  We designed 10 experimental groups following the surface treatment and thermocycling. The surface was treated with one of the following method: no-primer (NP), Porcelain Conditioner (PC), Z-PRIME Plus (ZP), Monobond Plus (MP) and Zirconia Liner Premium (ZL) (n=20). Then each group was subdivided to non-thermocycled and thermocycled groups (NPT, PC, ZPT, MPT, ZLT) (n=10). Orthodontic brackets were bonded to the specimens using Transbond™ XT Paste and light cured for 15 s at 1,100 mW/cm(2). The SBS was measured at a 1 mm/min crosshead speed. The failure mode was assessed by examination with a stereomicroscope and the amount of bonding resin remaining on the zirconia surface was scored using the modified adhesive remnant index (ARI).
  
  
  RESULTS
  The SBS of all experimental groups decreased after thermocycling. Before thermocycling, the SBS was ZL, ZP ≥ MP ≥ PC > NP but after thermocycling, the SBS was ZLT ≥ MPT ≥ ZPT > PCT = NPT (p > 0.05). For the ARI score, both of the groups lacking primer (NP and NPT) displayed adhesive failure modes, but the groups with zirconia primers (ZP, ZPT, MP, MPT, ZL, and ZLT) were associated with mixed failure modes.
  
  
  CONCLUSIONS
  Surface treatment with a zirconia primer increases the SBS relative to no-primer or silane primer application between orthodontic brackets and zirconia prostheses.
authors.affiliation: Department of Orthodontics, National Health Insurance Corporation Ilsan Hospital, Goyang, Korea.
authors.forename: Ji-Yeon
authors.initials: JY
authors.lastname: Lee
authors.affiliation: Department of Orthodontics, National Health Insurance Corporation Ilsan Hospital, Goyang, Korea.
authors.forename: Jin-Seok
authors.initials: JS
authors.lastname: Kim
authors.affiliation: Department of Orthodontics, The Institute of Craniofacial Deformity, College of Dentistry, Yonsei University, Seoul, Korea.
authors.forename: Chung-Ju
authors.initials: CJ
authors.lastname: Hwang
keywords: Orthodontic brackets; Shear bond strength; Zirconia; Zirconia primer