title: Veneered Zirconia-Based Restorations Fracture Resistance Analysis.
abstract: OBJECTIVE
  To examine the effects of the veneering technique on the fracture resistance of zirconia-based crowns.
  
  
  METHODS
  An artificial tooth was prepared with a 1.2 mm heavy chamfer finish line and 8° taper. The prepared tooth was scanned using CAD/CAM technology to fabricate 45 cobalt chromium (CoCr) testing dies. One CoCr die was scanned, and 45 zirconia copings were milled and divided according to the veneering technique into three groups of 15 specimens each: layering veneering (LV) using Vita Vm9, overpressing veneering (OV) using Vita Pm9, and digital veneering (DV) using Vita Triluxe forte. The crowns were cemented onto the testing dies using glass ionomer cement. The specimens were thermocycled (3000 cycles, 5° to 55°) then statically loaded (3.7 mm ball, 0.5 mm/min crosshead speed) until failure. Failed crowns were inspected using a magnifier, and failure patterns were identified. One-way ANOVA and multiple comparison Bonferroni tests were applied for statistical analysis of the results.
  
  
  RESULTS
  Means and standard deviations of failure loads were 1200 ± 306 N for the LV group, 857 ± 188 N for the OV group, and 638 ± 194 N for the DV group. The differences in failure loads were statistically significant between all groups (p < 0.05). Failure mode was predominantly cohesive for LV and OV groups, whereas it was predominantly adhesive for the DV group.
  
  
  CONCLUSIONS
  The LV group was superior to other groups in terms of fracture resistance, while the DV group was inferior to the other groups in the same aspect.
authors.affiliation: Professor of Fixed Prosthodontics, Aesthetic Dentistry and Dental Implants, Faculty of Dentistry-Jordan University of Science and Technology, Irbid, Jordan.
authors.forename: Ahed
authors.initials: A
authors.lastname: Al-Wahadni
authors.affiliation: Private practice in prosthodontics, Amman, Jordan.
authors.forename: Ahmad
authors.initials: A
authors.lastname: Shahin
authors.affiliation: Clinical Professor of Prosthodontics, Director-Division of Maxillofacial Prosthetics, Stony Brook University School of Dental Medicine, Stony Brook, NY.
authors.forename: Kenneth S
authors.initials: KS
authors.lastname: Kurtz
mesh_terms: D002858:Chromium Alloys / Q000737:chemistry; D017076:Computer-Aided Design; D003442:Crowns; D017267:Dental Prosthesis Design; D019232:Dental Restoration Failure; D003799:Dental Stress Analysis; D003801:Dental Veneers; D015040:Zirconium / Q000737:chemistry*
chemical_list: D002858:Chromium Alloys; D015040:Zirconium; C028541:zirconium oxide
keywords: Zirconia; crowns; digital layering; fracture; pressing; resistance; strength; veneering