title: The effect of preparation order on the crystal structure of yttria-stabilized tetragonal zirconia polycrystal and the shear bond strength of dental resin cements.
abstract: OBJECTIVE
  The purpose of this study was to evaluate the effect of preparation order on the crystal structure of yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) and the shear bond strength of dental resin cements.
  
  
  METHODS
  One-hundred fifty pre-sintered Y-TZP cylinders (Ø 9mm×13.5mm) were prepared and divided into three groups (control group, SBS group and SAS group). Specimens in control group were not treated. Specimens in SBS group were sandblasted and then densely sintered, and specimens in SAS group were sintered in advance, and then sandblasted. The specimens were analyzed by X-ray diffractometry, confocal laser scanning microscopy and Energy dispersive X-ray spectroscopy before and after sandblasting. All specimens were embedded in polytetrafluoroethylene (PTFE) molds using PMMA and each group was divided into five subgroups. The mixed resin cements (Clearfil SA luting cement, Zirconite, Superbond C&B, Rely-X Unicem, and Multilink) were placed onto the Y-TZP surfaces using PTFE molds with Ø 3mm×3mm, followed by storage in distilled water at 37°C for 24h, and thermocycling (5000 cycles at 5°C and 55°C with a 30s dwelling time). All specimens were tested for the shear bond strengths with a universal testing machine, and fractured surfaces were evaluated by SEM. Statistical analysis was performed using one-way ANOVA and Scheffé comparison with α=.05.
  
  
  RESULTS
  Sandblasting of the zirconia significantly increased shear bond strength of resin cements, but the preparation order had no significant influence on the shear bond strength in both test groups. In SEM observation, the natures of the surface faceting of the zirconia grains were totally different between SBS and SAS groups. SBS group exhibited less monoclinic structures than SAS group.
  
  
  CONCLUSIONS
  Sandblasting of pre-sintered Y-TZP and then sintering may induce favorable proportion of tetragonal structures. This might have positive effect on the clinical performance of zirconia restorations.
authors.affiliation: Department of Prosthodontics and Dental Research Institute, School of Dentistry, Seoul National University, 275-1, Yeongeon-dong, Jongno-gu, Seoul, Republic of Korea.
authors.forename: Ji-Eun
authors.initials: JE
authors.lastname: Moon
authors.forename: Sung-Hun
authors.initials: SH
authors.lastname: Kim
authors.forename: Jai-Bong
authors.initials: JB
authors.lastname: Lee
authors.forename: Seung-Ryong
authors.initials: SR
authors.lastname: Ha
authors.forename: Yu-Sung
authors.initials: YS
authors.lastname: Choi
mesh_terms: D020906:Air Abrasion, Dental; D000704:Analysis of Variance; D003460:Crystallization; D018360:Crystallography, X-Ray; D001840:Dental Bonding; D003776:Dental Porcelain / Q000138:chemical synthesis* / Q000737:chemistry*; D003799:Dental Stress Analysis; D006358:Hot Temperature; D008422:Materials Testing; D018613:Microscopy, Confocal; D008855:Microscopy, Electron, Scanning; D019279:Resin Cements; D033081:Shear Strength; D013052:Spectrometry, X-Ray Emission; D018709:Statistics, Nonparametric; D013499:Surface Properties; D015019:Yttrium / Q000737:chemistry*; D015040:Zirconium / Q000737:chemistry*
chemical_list: D019279:Resin Cements; C499362:yttria stabilized tetragonal zirconia; D003776:Dental Porcelain; D015019:Yttrium; D015040:Zirconium