title: Effect of different veneering techniques on the fracture strength of metal and zirconia frameworks.
abstract: OBJECTIVE
  To determine whether the fracture strengths and failure types differed between metal and zirconia frameworks veneered with pressable or layering ceramics.
  
  
  METHODS
  A phantom molar tooth was prepared and duplicated in 40 cobalt-chromium abutments. Twenty metal (IPS d.SIGN 15, Ivoclar, Vivadent, Schaan, Liechtenstein) and 20 zirconia (IPS e.max ZirCAD, Ivoclar) frameworks were fabricated on the abutments. Each framework group was randomly divided into 2 subgroups according to the veneering material: pressable and layering ceramics (n=10). Forty molar crowns were fabricated, cemented onto the corresponding abutments and then thermocycled (5-55℃, 10,000 cycles). A load was applied in a universal testing machine until a fracture occurred on the crowns. In addition, failure types were examined using a stereomicroscope. Fracture load data were analyzed using one-way ANOVA and Tukey HSD post-hoc tests at a significance level of 0.05.
  
  
  RESULTS
  The highest strength value was seen in metal-pressable (MP) group, whereas zirconia-pressable (ZP) group exhibited the lowest one. Moreover, group MP showed significantly higher fracture loads than group ZP (P=.015) and zirconia-layering (ZL) (P=.038) group. No significant difference in fracture strength was detected between groups MP and ML, and groups ZP and ZL (P>.05). Predominant fracture types were cohesive for metal groups and adhesive for zirconia groups.
  
  
  CONCLUSIONS
  Fracture strength of a restoration with a metal or a zirconia framework was independent of the veneering techniques. However, the pressing technique over metal frameworks resisted significantly higher fracture loads than zirconia frameworks.
authors.affiliation: Department of Prosthodontics, Faculty of Dentistry, University of Ege, Izmir, Turkey.
authors.forename: Ayse Gozde
authors.initials: AG
authors.lastname: Turk
authors.affiliation: Department of Prosthodontics, Faculty of Dentistry, University of Ege, Izmir, Turkey.
authors.forename: Mubin
authors.initials: M
authors.lastname: Ulusoy
authors.affiliation: Private practice, Izmir, Turkey.
authors.forename: Mert
authors.initials: M
authors.lastname: Yuce
authors.affiliation: Department of Prosthodontics, Faculty of Dentistry, Cumhuriyet University, Sivas, Turkey.
authors.forename: Hakan
authors.identifier: 0000-0002-4770-4297
authors.initials: H
authors.lastname: Akin
keywords: Compressive strength; Crowns; Dental porcelain; Zirconia
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