title: Reliability and failure modes of implant-supported zirconium-oxide fixed dental prostheses related to veneering techniques.
abstract: OBJECTIVE
  To compare fatigue failure modes and reliability of hand-veneered and over-pressed implant-supported three-unit zirconium-oxide fixed-dental-prostheses(FDPs).
  
  
  METHODS
  Sixty-four custom-made zirconium-oxide abutments (n=32/group) and thirty-two zirconium-oxide FDP-frameworks were CAD/CAM manufactured. Frameworks were veneered with hand-built up or over-pressed porcelain (n=16/group). Step-stress-accelerated-life-testing (SSALT) was performed in water applying a distributed contact load at the buccal cusp-pontic-area. Post failure examinations were carried out using optical (polarized-reflected-light) and scanning electron microscopy (SEM) to visualize crack propagation and failure modes. Reliability was compared using cumulative-damage step-stress analysis (Alta-7-Pro, Reliasoft).
  
  
  RESULTS
  Crack propagation was observed in the veneering porcelain during fatigue. The majority of zirconium-oxide FDPs demonstrated porcelain chipping as the dominant failure mode. Nevertheless, fracture of the zirconium-oxide frameworks was also observed. Over-pressed FDPs failed earlier at a mean failure load of 696 ± 149N relative to hand-veneered at 882 ± 61N (profile I). Weibull-stress-number of cycles-unreliability-curves were generated. The reliability (2-sided at 90% confidence bounds) for a 400N load at 100K cycles indicated values of 0.84 (0.98-0.24) for the hand-veneered FDPs and 0.50 (0.82-0.09) for their over-pressed counterparts.
  
  
  CONCLUSIONS
  Both zirconium-oxide FDP systems were resistant under accelerated-life-time-testing. Over-pressed specimens were more susceptible to fatigue loading with earlier veneer chipping.
authors.affiliation: Department of Periodontology and Implant Dentistry, Department of Biomaterials and Biomimetics, New York University College of Dentistry, New York 10010, USA.
authors.forename: Marta
authors.initials: M
authors.lastname: Baldassarri
authors.forename: Yu
authors.initials: Y
authors.lastname: Zhang
authors.forename: Van P
authors.initials: VP
authors.lastname: Thompson
authors.forename: Elizabeth D
authors.initials: ED
authors.lastname: Rekow
authors.forename: Christian F J
authors.initials: CF
authors.lastname: Stappert
mesh_terms: D017076:Computer-Aided Design; D000044:Dental Abutments; D003776:Dental Porcelain; D017267:Dental Prosthesis Design; D019094:Dental Prosthesis, Implant-Supported; D019232:Dental Restoration Failure; D003799:Dental Stress Analysis; D003801:Dental Veneers; D003830:Denture, Partial, Fixed; D006244:Hardness; D006801:Humans; D008334:Mandible; D003765:Models, Dental; D016019:Survival Analysis; D015019:Yttrium; D015040:Zirconium
chemical_list: C499362:yttria stabilized tetragonal zirconia; D003776:Dental Porcelain; D015019:Yttrium; D015040:Zirconium