title: Lifetime prediction of zirconia and metal ceramic crowns loaded on marginal ridges.
abstract: To evaluate the fatigue life of zirconia-veneered and metal-ceramic crowns comprised by an even thickness or a modified framework design when loaded on marginal ridges.
  
  
  
  Eighty marginal ridges were present after fabrication of forty molar crowns cemented onto composite-resin replicas and divided (n=20/each), in the following groups: metal-ceramic with even thickness (MCev) or with a modified framework design (MCm, lingual collar with proximal struts); porcelain-fused to zirconia with even thickness (PFZev) or with the modified framework design (PFZm). Each marginal ridge (mesial and distal) was subjected to cyclic loading separately with a lithium disilicate indenter for 106cycles or until fracture. Kruskal-Wallis and Wilcoxon matched pair test (p<0.05) evaluated both marginal ridges. Every 125,000 cycles, the test was interrupted for damage inspection. Weibull distribution (90% confidence bounds) determined the probability of survival (reliability).
  
  
  
  Weibull 2-parameter contour-plot showed significantly higher fatigue life for PFZev compared to MC, and comparable with PFZm. A significant decrease in reliability was observed between groups from 625,000 until 106cycles. Metal-ceramic groups presented significantly lower probability of survival at 106cycles (MCev=0.66% and MCm=4.73%) compared to PFZm (23.41%) and PFZev (36.68%). Fractographic marks showed a consistent fracture origin and direction of crack propagation. Reliability was higher for porcelain-fused to zirconia than for metal ceramic crowns, regardless of framework design.
  
  
  
  Zirconia-veneered crowns presented decreased fracture rates compared to metal ceramics, even when loaded at marginal ridges, regardless of framework design.
authors.affiliation: Department of Prosthodontics, University of São Paulo-Bauru College of Dentistry, Bauru, SP, Brazil. Electronic address: viniciuspfardin@gmail.com.
authors.forename: Vinicius P
authors.initials: VP
authors.lastname: Fardin
authors.affiliation: Department of Prosthodontics, University of São Paulo-Bauru College of Dentistry, Bauru, SP, Brazil.
authors.forename: Vitor Guarconi
authors.initials: VG
authors.lastname: de Paula
authors.affiliation: Department of Prosthodontics, University of São Paulo-Bauru College of Dentistry, Bauru, SP, Brazil.
authors.forename: Estevam A
authors.initials: EA
authors.lastname: Bonfante
authors.affiliation: Department of Biomaterials and Biomimetics, New York University, New York, NY, USA; Department of Periodontology and Implant Dentistry, New York University College of Dentistry, New York, NY, USA; Division of Engineering, New York University Abu Dhabi, Abu Dhabi, United Arab Emirates.
authors.forename: Paulo G
authors.initials: PG
authors.lastname: Coelho
authors.affiliation: Department of Prosthodontics, University of São Paulo-Bauru College of Dentistry, Bauru, SP, Brazil.
authors.forename: Gerson
authors.initials: G
authors.lastname: Bonfante
mesh_terms: D002516:Ceramics; D003442:Crowns; D003776:Dental Porcelain; D017267:Dental Prosthesis Design; D019232:Dental Restoration Failure; D003799:Dental Stress Analysis; D003801:Dental Veneers; D008422:Materials Testing; D015203:Reproducibility of Results; D015040:Zirconium
chemical_list: D003776:Dental Porcelain; D015040:Zirconium; C028541:zirconium oxide
keywords: Crowns; Fatigue; Metal ceramic; Weibull; Zirconia