title: Zirconia versus metal: a preliminary comparative analysis of ceramic veneer behavior.
abstract: OBJECTIVE
  Clinical studies have revealed a high rate of fracture for porcelain-veneered zirconia-based restorations that varies between 6% and 15% over a 3- to 5-year period. These are high values compared to the 4% fracture rate shown by conventional metal-ceramic restorations over 10 years. To date, little in vitro research has been carried out on the fracture resistance of the new generation of ceramic crowns. The aims of this study were to develop preliminary research on the mechanical failure behavior of three types of porcelain-veneered crowns with zirconia cores when subjected to static compressive loading and to analyze fracture characteristics using scanning electron microscopy (SEM).
  
  
  METHODS
  Eighty individual full-coverage crowns were studied: 60 crowns with a zirconia core and 20 with a metal core (control).
  
  
  RESULTS
  Values obtained in compressive testing were as follows: ZirPress: 1,818.01 N, ZirCAD: 1,773.92 N, Lava: 2,210.95 N, and metal-ceramic (control): 2,310.49 N. SEM analysis revealed that 71.66% of zirconia-based restoration mechanical failures were cohesive, while 100% of mechanical failures for metal-ceramic restorations were adhesive.
  
  
  CONCLUSIONS
  The mechanical behavior of the porcelain veneering on a zirconia core is more fragile than that on metal-ceramic crowns, and when load forces exerted on these restorations lead to mechanical failure, this will occur in the interior of the porcelain veneering.
authors.affiliation: Department of Stomatology, University of Valencia, Valencia, Spain. rubenagustinpanadero@gmail.com
authors.forename: Ruben
authors.initials: R
authors.lastname: Augstin-Panadero
authors.forename: Antonio
authors.initials: A
authors.lastname: Fons-Font
authors.forename: Juan Luis
authors.initials: JL
authors.lastname: Roman-Rodriguez
authors.forename: Maria
authors.initials: M
authors.lastname: Granell-Ruiz
authors.forename: Jamie
authors.initials: J
authors.lastname: del Rio-Highsmith
authors.forename: Maria Fernanda
authors.initials: MF
authors.lastname: Sola-Ruiz
mesh_terms: D002858:Chromium Alloys; D019245:Compressive Strength; D003442:Crowns; D003776:Dental Porcelain; D017267:Dental Prosthesis Design; D019232:Dental Restoration Failure; D003799:Dental Stress Analysis; D003801:Dental Veneers; D019544:Equipment Failure Analysis; D006801:Humans; D008422:Materials Testing; D016876:Metal Ceramic Alloys; D008855:Microscopy, Electron, Scanning; D009532:Nickel; D018709:Statistics, Nonparametric; D015040:Zirconium
chemical_list: D002858:Chromium Alloys; D016876:Metal Ceramic Alloys; D003776:Dental Porcelain; D009532:Nickel; D015040:Zirconium; C028541:zirconium oxide