title: Influence of cement thickness on resin-zirconia microtensile bond strength.
abstract: OBJECTIVE
  The aim of this study was to evaluate the influence of resin cement thickness on the microtensile bond strength between zirconium-oxide ceramic and resin cement.
  
  
  METHODS
  Thirty-two freshly extracted molars were transversely sectioned at the deep dentin level and bonded to air-abraded zirconium oxide ceramic disks. The specimens were divided into 8 groups based on the experimental conditions (cement type: Rely X UniCem or Panavia F 2.0, cement thickness: 40 or 160 µm, storage: thermocycled or not). They were cut into microbeams and stored in 37℃ distilled water for 24 h. Microbeams of non-thermocycled specimens were submitted to a microtensile test, whereas those of thermocycled groups were thermally cycled for 18,000 times immediately before the microtensile test. Three-way ANOVA and Sheffe's post hoc tests were used for statistical analysis (α=95%).
  
  
  RESULTS
  All failures occurred at the resin-zirconia interface. Thermocycled groups showed lower microtensile bond strength than non-thermocycled groups (P<.001). Differences in cement thickness did not influence the resin-zirconia microtensile bond strength given the same resin cement or storage conditions (P>.05). The number of adhesive failures increased after thermocycling in all experimental conditions. No cohesive failure was observed in any experimental group.
  
  
  CONCLUSIONS
  When resin cements of adhesive monomers are applied over air-abraded zirconia restorations, the degree of fit does not influence the resin-zirconia microtensile bond strength.
authors: Department of Prothodontics, Gangnam Severance Dental Hospital, College of Dentistry, Yonsei University, Seoul, Korea.
authors: Tae-Hoon
authors: TH
authors: Lee
authors: Jin-Soo
authors: JS
authors: Ahn
authors: June-Sung
authors: JS
authors: Shim
authors: Chong-Hyun
authors: CH
authors: Han
authors: Sun-Jai
authors: SJ
authors: Kim