title: In vitro fatigue resistance of CAD/CAM composite resin and ceramic posterior occlusal veneers.
abstract: BACKGROUND
  Thin, bonded, posterior occlusal veneers constitute a conservative alternative to traditional complete coverage crowns. Information regarding selection of the appropriate material and its influence on fatigue resistance, which may affect the longevity of the restoration, is missing.
  
  
  OBJECTIVE
  The purpose of this study was to assess and compare the fatigue resistance of composite resin and ceramic posterior occlusal veneers.
  
  
  METHODS
  Thirty extracted molars received a standardized nonretentive tooth preparation (simulating advanced occlusal erosion), including removal of occlusal enamel, exposure of dentin, and immediate dentin sealing (Optibond FL). All teeth were restored with a 1.2-mm-thick occlusal veneer (Cerec 3 chairside CAD/CAM system). The restorations (n=10) were milled from leucite-reinforced and lithium disilicate ceramics (IPS Empress CAD and IPS e.max CAD, respectively) and a composite resin (Paradigm MZ100). The intaglio surfaces of the ceramic restorations were conditioned by hydrofluoric acid etching and silane. Airborne-particle abrasion and silane were used to condition the composite resin restorations. Preparations were airborne-particle abraded and etched. All restorations were bonded with preheated luting material and submitted to cyclic isometric loading at 5 Hz, starting with a load of 200 N (x5000 cycles), followed by stepwise loading of 400, 600, 800, 1000, 1200, and 1400 N at a maximum of 30,000 cycles each. The number of cycles at initial failure (first cracks) was recorded. Specimens were loaded for a maximum of 185,000 cycles. Groups were compared using the life table survival analysis (alpha=.016, Bonferroni method).
  
  
  RESULTS
  IPS Empress CAD failed at an average load of 900 N, with no specimen withstanding all 185,000 load cycles (survival 0%), while IPS e.max CAD and Paradigm MZ100 demonstrated survival rates of 30% and 100%, respectively. None of the specimens exhibited catastrophic failure, but only cracks limited to the restorative material.
  
  
  CONCLUSIONS
  Posterior occlusal veneers made of composite resin (Paradigm MZ100) had significantly higher fatigue resistance (P<.002) compared to IPS Empress CAD and IPS e.max CAD.
authors.affiliation: University of Southern California, Herman Ostrow School of Dentistry of USC, Los Angeles, Calif, USA. magne@usc.edu
authors.forename: Pascal
authors.initials: P
authors.lastname: Magne
authors.forename: Luís Henrique
authors.initials: LH
authors.lastname: Schlichting
authors.forename: Hamilton Pires
authors.initials: HP
authors.lastname: Maia
authors.forename: Luiz Narciso
authors.initials: LN
authors.lastname: Baratieri
mesh_terms: D000538:Aluminum Silicates; D003188:Composite Resins; D017076:Computer-Aided Design; D001840:Dental Bonding; D045662:Dental Etching / Q000379:methods; D003776:Dental Porcelain; D017267:Dental Prosthesis Design; D019232:Dental Restoration Failure; D003799:Dental Stress Analysis; D003801:Dental Veneers; D017220:Dentin-Bonding Agents; D006801:Humans; D015993:Life Tables; D018020:Lithium Compounds; D008963:Molar; D015040:Zirconium
chemical_list: D000538:Aluminum Silicates; D003188:Composite Resins; D017220:Dentin-Bonding Agents; D018020:Lithium Compounds; C452079:paradigm MZ100; D003776:Dental Porcelain; C078519:leucite; D015040:Zirconium