title: Post-fatigue fracture resistance of metal core crowns: press-on metal ceramic versus a conventional veneering system.
abstract: BACKGROUND
  The aim of this in vitro study was to compare the mechanical failure behavior and to analyze fracture characteristics of metal ceramic crowns with two veneering systems - press-on metal (PoM) ceramic versus a conventional veneering system - subjected to static compressive loading.
  
  
  METHODS
  Forty-six crowns were constructed and divided into two groups according to porcelain veneer manufacture. Group A: 23 metal copings with porcelain IPS-InLine veneering (conventional metal ceramic). Group B: 23 metal copings with IPS-InLine PoM veneering porcelain. After 120,000 fatigue cycles, the crowns were axially loaded to the moment of fracture with a universal testing machine. The fractured specimens were examined under optical stereomicroscopy and scanning electron microscope.
  
  
  RESULTS
  Fracture resistance values showed statistically significant differences (Student's t-test) regarding the type of ceramic veneering technique (p=0.001): Group A (conventional metal ceramics) obtained a mean fracture resistance of 1933.17 N, and Group B 1325.74N (Press-on metal ceramics). The most common type of fracture was adhesive failure (with metal exposure) (p=0.000). Veneer porcelain fractured on the occlusal surface following a radial pattern.
  
  
  CONCLUSIONS
  Metal ceramic crowns made of IPS InLine or IPS InLine PoM ceramics with different laboratory techniques all achieved above-average values for clinical survival in the oral environment according to ISO 6872. Crowns made with IPS InLine by conventional technique resisted fracture an average of 45% more than IPS InLine PoM fabricated with the press-on technique. Key words:Mechanical failure, conventional feldspathic, pressable ceramic, chewing simulator, thermocycling, compressive testing, fracture types, scanning electron microscope.
authors.affiliation: DDS, PhD, MD, Adjunct Lecturer, Department of Buccofacial Prosthetics. Faculty of Medicine and Dentistry, University of Valencia, Spain.
authors.forename: M Fernanda
authors.initials: MF
authors.lastname: Solá-Ruiz
authors.affiliation: DDS, PhD, Associate Lecturer, Department of Buccofacial Prosthetics. Faculty of Medicine and Dentistry, University of Valencia, Spain.
authors.forename: Rubén
authors.initials: R
authors.lastname: Agustín-Panadero
authors.affiliation: DDS, Collaborator Lecturer, Department of Buccofacial Prosthetics. Faculty of Medicine and Dentistry, University of Valencia, Spain.
authors.forename: Carlos
authors.initials: C
authors.lastname: Campos-Estellés
authors.affiliation: DDS, PhD, MD, Senior Lecturer, Department of Buccofacial Prosthetics. Faculty of Medicine and Dentistry, University of Valencia, Spain.
authors.forename: Carlos
authors.initials: C
authors.lastname: Labaig-Rueda