title: In vitro performance of full-contour zirconia single crowns.
abstract: OBJECTIVE
  Zirconia based restorations exhibited high failure rates due to veneering-porcelain fractures. Milling to full-contour might be an alternative approach for zirconia restorations. The aim of this study was to evaluate full-contour zirconia crowns in terms of light-transmission, contact wear (restoration and antagonist) and load-bearing capacity. Powder build-up veneered zirconia substructures and CAD/CAM-veneered zirconia substructures served as controls.
  
  
  METHODS
  Four different kinds of crowns were fabricated on 12 metal dies: zirconia substructure with powder build-up porcelain (veneering technique), zirconia substructure with CAD/CAM generated veneering (sintering technique), full-contour zirconia glazed (glazed full-contour) and full-contour zirconia polished (polished full-contour). All crowns had the same dimensions. After light-transmission was measured the crowns were cemented on the corresponding metal dies. The specimens were loaded according to a special wear method in the chewing simulator (120,000 mechanical cycles, 5 kg load, 0.7 mm sliding movement, 320 thermocycles). Wear of the restoration and the antagonist were measured. All specimens were loaded until failure. One-way ANOVA and a LSD post-hoc test were used to compare data at a level of 5%.
  
  
  RESULTS
  Polished full-contour showed significantly higher light transmission than the other groups (p=0.003; ANOVA). Polished full-contour exhibited significantly less contact wear at the restoration (p=0.01; ANOVA) and higher contact wear at the antagonist (p=0.016; ANOVA) compared to the other groups. Glazed full-contour zirconia showed similar contact wear at the antagonist compared to veneering technique (p=0.513, post-hoc LSD). Crowns with conventional veneering showed significantly lower load-bearing capacity (p<0.001; ANOVA).
  
  
  CONCLUSIONS
  Milling zirconia to full-contour with glazed surface might be an alternative to traditionally veneered restorations.
authors.affiliation: Department of Prosthodontics, Munich Dental School, Munich, Germany. florian.beuer@med.uni-muenchen.de
authors.forename: Florian
authors.initials: F
authors.lastname: Beuer
authors.forename: Michael
authors.initials: M
authors.lastname: Stimmelmayr
authors.forename: Jan-Frederik
authors.initials: JF
authors.lastname: Gueth
authors.forename: Daniel
authors.initials: D
authors.lastname: Edelhoff
authors.forename: Michael
authors.initials: M
authors.lastname: Naumann
mesh_terms: D017076:Computer-Aided Design; D003442:Crowns; D003776:Dental Porcelain; D017267:Dental Prosthesis Design; D019554:Dental Restoration Wear; D003799:Dental Stress Analysis; D003801:Dental Veneers; D006801:Humans; D008963:Molar; D055620:Optical Phenomena; D019231:Tooth Preparation, Prosthodontic; D015040:Zirconium
chemical_list: D003776:Dental Porcelain; D015040:Zirconium; C028541:zirconium oxide