title: Monolithic and bi-layer CAD/CAM lithium-disilicate versus metal-ceramic fixed dental prostheses: comparison of fracture loads and failure modes after fatigue.
abstract: OBJECTIVE
  The authors analyzed the effect of fatigue on the survival rate and fracture load of monolithic and bi-layer CAD/CAM lithium-disilicate posterior three-unit fixed dental prostheses (FDPs) in comparison to the metal-ceramic gold standard.
  
  
  METHODS
  The authors divided 96 human premolars and molars into three equal groups. Lithium-disilicate ceramic (IPS-e.max-CAD) was milled with the CEREC-3-system in full-anatomic FDP dimensions (monolithic: M-LiCAD) or as framework (Bi-layer: BL-LiCAD) with subsequent hand-layer veneering. Metal-ceramic FDPs (MC) served as control. Single-load-to-failure tests were performed before and after mouth-motion fatigue.
  
  
  RESULTS
  No fracture failures occurred during fatigue. Median fracture loads in [N], before and after fatigue were, respectively, as follows: M-LiCAD, 1,298/1,900; BL-LiCAD, 817/699; MC, 1,966/1,818. M-LiCAD and MC FPDs revealed comparable fracture loads and were both significantly higher than BL-LiCAD. M-LiCAD and BL-LiCAD both failed from core/veneer bulk fracture within the connector area. MC failures were limited to ceramic veneer fractures exposing the metal core. Fatigue had no significant effect on any group.
  
  
  CONCLUSIONS
  Posterior monolithic CAD/CAM fabricated lithium-disilicate FPDs were shown to be fracture resistant with failure load results comparable to the metal-ceramic gold standard. Clinical investigations are needed to confirm these promising laboratory results.
  
  
  CONCLUSIONS
  Monolithic CAD/CAM fabricated lithium-disilicate FDPs appeared to be a reliable treatment alternative for the posterior load-bearing area, whereas FDPs in bi-layer configuration were susceptible to low load fracture failure.
authors.affiliation: Department of Prosthodontics, School of Dentistry, Albert-Ludwigs-University Freiburg, Hugstetter Strasse 55, Freiburg, Germany.
authors.forename: Stefan
authors.initials: S
authors.lastname: Schultheis
authors.forename: Joerg R
authors.initials: JR
authors.lastname: Strub
authors.forename: Thomas A
authors.initials: TA
authors.lastname: Gerds
authors.forename: Petra C
authors.initials: PC
authors.lastname: Guess
mesh_terms: D000538:Aluminum Silicates; D017076:Computer-Aided Design; D001840:Dental Bonding; D003738:Dental Cements; D003776:Dental Porcelain; D019232:Dental Restoration Failure; D003799:Dental Stress Analysis; D003801:Dental Veneers; D003779:Denture Design; D003830:Denture, Partial, Fixed; D006801:Humans; D008422:Materials Testing; D016876:Metal Ceramic Alloys; D018709:Statistics, Nonparametric
chemical_list: D000538:Aluminum Silicates; D003738:Dental Cements; C075815:IPS-Empress ceramic; D016876:Metal Ceramic Alloys; C076808:Monobond S; C493120:lithia disilicate; D003776:Dental Porcelain