title: Fracture resistance of three all-ceramic restorative systems for posterior applications.
abstract: BACKGROUND
  The failure loads of all-ceramic crowns are influenced not only by the fracture resistance of the component materials but also by prosthesis geometry and size and location of flaws, thus there is a need for a study that compares the fracture resistance of all-ceramic systems using a simple and reproducible specimen geometry that includes flaws occurring at material interfaces.
  
  
  OBJECTIVE
  The research aim was to compare the in vitro fracture resistance and origin of failure of simulated first molar crowns fabricated using 3 all-ceramic systems, IPS Empress 2, Procera AllCeram, and In-Ceram Zirconia.
  
  
  METHODS
  Twenty axisymmetric crowns of each system were fabricated to fit a preparation with 1.5- to 2.0-mm occlusal reduction. The center of the occlusal surface on each of 15 specimens per ceramic system was axially loaded to fracture in a universal testing machine, and the maximum load (N) was recorded. Fractured surfaces were examined using optical and electron microscopy to determine the most prevalent origin of failure in each ceramic system. Five crowns per system were sectioned, and thickness of the luting agent, core material, and veneer porcelain layers were measured. The 95% confidence intervals of the Weibull modulus and characteristic failure load were compared between the 3 systems. Two-way multivariate analysis of variance was used to analyze the thickness of the luting agent, ceramic core, and veneer porcelain layers (alpha=.05).
  
  
  RESULTS
  The 95% confidence intervals for Weibull modulus were 1.8 to 2.3 (IPS Empress 2), 2.8 to 3.6 (Procera AllCeram), and 3.9 to 4.9 (In-Ceram Zirconia). The 95% confidence intervals for characteristic failure load were 771 to 1115 N (IPS Empress 2), 859 to 1086 N (Procera AllCeram), and 998 to 1183 (In-Ceram Zirconia). The origin of failure was most commonly found at the interface between the ceramic core and veneer porcelain for IPS Empress 2 and between the ceramic core and luting agent layer for the other systems.
  
  
  CONCLUSIONS
  There was no significant difference in fracture resistance; however, there was a significant difference in failure origin between the all-ceramic systems studied.
authors.affiliation: Department of Restorative Sciences, Graduate Prosthodontics, Baylor College of Dentistry, Dallas, Tex, USA.
authors.forename: Konstantinos
authors.initials: K
authors.lastname: Pallis
authors.forename: Jason A
authors.initials: JA
authors.lastname: Griggs
authors.forename: Ronald D
authors.initials: RD
authors.lastname: Woody
authors.forename: Guillermo E
authors.initials: GE
authors.lastname: Guillen
authors.forename: Amp W
authors.initials: AW
authors.lastname: Miller
mesh_terms: D000537:Aluminum Oxide / Q000737:chemistry; D002516:Ceramics / Q000737:chemistry*; D016001:Confidence Intervals; D003442:Crowns; D003738:Dental Cements / Q000737:chemistry; D003776:Dental Porcelain / Q000737:chemistry*; D017267:Dental Prosthesis Design; D019232:Dental Restoration Failure; D003801:Dental Veneers; D006801:Humans; D018020:Lithium Compounds / Q000737:chemistry; D008422:Materials Testing; D008854:Microscopy, Electron; D008963:Molar; D015999:Multivariate Analysis; D013314:Stress, Mechanical; D013499:Surface Properties
chemical_list: C105314:AllCeram; D003738:Dental Cements; C118557:Empress 2; C485633:In-Ceram Zirconia; D018020:Lithium Compounds; D003776:Dental Porcelain; D000537:Aluminum Oxide