title: Fracture resistance of the veneering on inlay-retained zirconia ceramic fixed partial dentures.
abstract: OBJECTIVE
  The aim of this in vitro study was to evaluate the fracture load of zircon frames veneered with a polymer glass holding box inlay-retained fixed partial dentures (FPDs). The influence of the position of the frame and the span length was tested. Additionally, the fracture load values of zircon frames veneered with a press ceramic were evaluated.
  
  
  METHODS
  Box inlay cavities were prepared on mandibular molars and premolars. Forty-eight FPDs were manufactured using industrially prefabricated zircon frames veneered with the polymer glass Artglass. Sixteen FPDs received individually manufactured CAD/CAM zircon frames veneered with a press ceramic. All FPDs underwent thermal cycling and mechanical loading (ML). The load to fracture was measured and fracture sites were evaluated.
  
  
  RESULTS
  Four polymer veneered FPDs showed fractures in the veneering material after ML. The mean fracture resistance ranged from 531 N to 727 N. No significant influence of frame localization could be observed. Significantly greater fracture resistance values were found in the ceramic veneered FPDs (1276 N to 1413 N). There was no significant effect of span length in the polymer veneered group or in the all-ceramic group, with the exception of a significant peak in fracture load value for intermediate span lengths in the polymer group with a localized occlusal zircon frame.
  
  
  CONCLUSIONS
  Polymer veneered FPDs with Y-TZP frames showed acceptable fracture resistance values, but they cannot yet be unreservedly recommended for clinical use. Fracture values for CAD/CAM manufactured Y-TZP frames combined with a press ceramic deserve further clinical investigation.
authors.affiliation: Department of Prosthodontics, University of Heidelberg, Germany. Brigitte_Ohlmann@med.uni-heidelberg.de
authors.forename: Brigitte
authors.initials: B
authors.lastname: Ohlmann
authors.forename: Olaf
authors.initials: O
authors.lastname: Gabbert
authors.forename: Marc
authors.initials: M
authors.lastname: Schmitter
authors.forename: Herbert
authors.initials: H
authors.lastname: Gilde
authors.forename: Peter
authors.initials: P
authors.lastname: Rammelsberg
mesh_terms: D003188:Composite Resins / Q000737:chemistry; D003801:Dental Veneers; D003830:Denture, Partial, Fixed; D008422:Materials Testing / Q000379:methods*; D016474:Weight-Bearing; D015019:Yttrium / Q000737:chemistry*; D015040:Zirconium / Q000737:chemistry*
chemical_list: C498018:Artglass (dental composite); D003188:Composite Resins; C499362:yttria stabilized tetragonal zirconia; D015019:Yttrium; D015040:Zirconium; C028541:zirconium oxide