title: Fracture resistance and failure mode of posterior fixed dental prostheses fabricated with two zirconia CAD/CAM systems.
abstract: BACKGROUND
  In recent years there has been an improvement of zirconia ceramic materials to replace posterior missing teeth. To date little in vitro studies has been carried out on the fracture resistance of zirconia veneered posterior fixed dental prostheses. This study investigated the fracture resistance and the failure mode of 3-unit zirconia-based posterior fixed dental prostheses fabricated with two CAD/CAM systems.
  
  
  METHODS
  Twenty posterior fixed dental prostheses were studied. Samples were randomly divided into two groups (n=10 each) according to the zirconia ceramic analyzed: Lava and Procera. Specimens were loaded until fracture under static load. Data were analyzed using Wilcoxon´s rank sum test and Wilcoxon´s signed-rank test (P<0.05).
  
  
  RESULTS
  Partial fracture of the veneering porcelain occurred in 100% of the samples. Within each group, significant differences were shown between the veneering and the framework fracture resistance (P=0.002). The failure occurred in the connector cervical area in 80% of the cases.
  
  
  CONCLUSIONS
  All fracture load values of the zirconia frameworks could be considered clinically acceptable. The connector area is the weak point of the restorations. Key words:Fixed dental prostheses, zirconium-dioxide, zirconia, fracture resistance, failure mode.
authors.affiliation: DDS, Researcher, Department of Buccofacial Prostheses, Faculty of Odontology, University Complutense of Madrid, Spain.
authors.forename: Carlos
authors.initials: C
authors.lastname: López-Suárez
authors.affiliation: DDS, PhD, Associate Professor, Department of Buccofacial Prostheses, Faculty of Odontology, University Complutense of Madrid, Spain.
authors.forename: Esther
authors.initials: E
authors.lastname: Gonzalo
authors.affiliation: DDS, PhD, Associate Professor, Department of Buccofacial Prostheses, Faculty of Odontology, University Complutense of Madrid, Spain.
authors.forename: Jesús
authors.initials: J
authors.lastname: Peláez
authors.affiliation: DDS, Researcher, Department of Buccofacial Prostheses, Faculty of Odontology, University Complutense of Madrid, Spain.
authors.forename: Verónica
authors.initials: V
authors.lastname: Rodríguez
authors.affiliation: MD, DDS, PhD, Professor, Department of Buccofacial Prostheses, Faculty of Odontology, University Complutense of Madrid, Spain.
authors.forename: María-Jesús
authors.initials: MJ
authors.lastname: Suárez