title: Shear bond strength of veneering porcelain to zirconia and metal cores.
abstract: BACKGROUND
  Zirconia-based restorations have the common technical complication of delamination, or porcelain chipping, from the zirconia core. Thus the shear bond strength between the zirconia core and the veneering porcelain requires investigation in order to facilitate the material's clinical use.
  
  
  OBJECTIVE
  The purpose of this study was to evaluate the bonding strength of the porcelain veneer to the zirconia core and to other various metal alloys (high noble metal alloy and base metal alloy).
  
  
  METHODS
  15 rectangular (4×4×9mm) specimens each of zirconia (Cercon), base metal alloy (Tillite), high noble metal alloy (Degudent H) were fabricated for the shear bond strength test. The veneering porcelain recommended by the manufacturer for each type of material was fired to the core in thickness of 3mm. After firing, the specimens were embedded in the PTFE mold, placed on a mounting jig, and subjected to shear force in a universal testing machine. Load was applied at a crosshead speed of 0.5mm/min until fracture. The average shear strength (MPa) was analyzed with the one-way ANOVA and the Tukey's test (α= .05). The fractured specimens were examined using SEM and EDX to determine the failure pattern.
  
  
  RESULTS
  The mean shear strength (± SD) in MPa was 25.43 (± 3.12) in the zirconia group, 35.87 (± 4.23) in the base metal group, 38.00 (± 5.23) in the high noble metal group. The ANOVA showed a significant difference among groups, and the Tukey's test presented a significant difference between the zirconia group and the metal group. Microscopic examination showed that the failure primarily occurred near the interface with the residual veneering porcelain remaining on the core.
  
  
  CONCLUSIONS
  There was a significant difference between the metal ceramic and zirconia ceramic group in shear bond strength. There was no significant difference between the base metal alloy and the high noble metal alloy.
authors.affiliation: Graduate Student, Department of Prosthodontics, Graduate School, Seoul National University, Seoul, Korea.
authors.forename: Bu-Kyung
authors.initials: BK
authors.lastname: Choi
authors.forename: Jung-Suk
authors.initials: JS
authors.lastname: Han
authors.forename: Jae-Ho
authors.initials: JH
authors.lastname: Yang
authors.forename: Jai-Bong
authors.initials: JB
authors.lastname: Lee
authors.forename: Sung-Hun
authors.initials: SH
authors.lastname: Kim