title: Effect of framework design on fracture resistance of zirconium oxide posterior fixed partial dentures.
abstract: BACKGROUND
  The effect of framework design modifications in all-ceramic systems is not fully understood. The aim of this investigation was to evaluate the effect of different framework designs on fracture resistance of zirconium oxide posterior fixed partial dentures (FPD).
  
  
  METHODS
  Thirty two posterior zirconia FPD cores were manufactured to replace a second premolar. The specimens were divided into four groups; I: 3 × 3 connector and standard design, II: 3 × 3 connector and modified design, III: 4 × 4 connector dimension, and standard design and IV: 4 × 4 connector dimension and modified design. After storing for one week in artificial saliva and thermocycling (2000 cycles, 5-55°C), the specimens were loaded in a universal testing machine at a constant cross-head speed of 0.5 mm/min until failure occurred. The Weibull, Kruskal-Wallis, and Mann-Whitney tests were used for statistical analysis (α = 0.05).
  
  
  RESULTS
  The mean fracture resistance of groups with 4 × 4 mm connector was significantly higher than groups with 3 × 3 mm connector (P < 0.001). Although, the fracture resistance of the modified frameworks was increased in the present study (1.1 times), they were not significantly different from anatomic specimens (P = 0.327).
  
  
  CONCLUSIONS
  The fracture resistance of the zirconia posterior-fixed partial dentures was significantly affected by the connector size; it was not affected by the framework modification.
authors.affiliation: Dental Materials Research Center and Department of Prosthodontics, School of Dentistry, Isfahan University of Medical Sciences, Isfahan, Iran.
authors.forename: Hadi
authors.initials: H
authors.lastname: Salimi
authors.forename: Ramin
authors.initials: R
authors.lastname: Mosharraf
authors.forename: Omid
authors.initials: O
authors.lastname: Savabi
keywords: Ceramic; dental materials; dental porcelains; dental prosthesis design; fixed bridges; zirconia
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