title: Static and fatigue mechanical behavior of three dental CAD/CAM ceramics.
abstract: The aim of this study was to measure the mechanical properties and fatigue behavior of three contemporary used dental ceramics, zirconia Cercon(®) (ZC), lithium disilicate e.max(®) CAD (LD), and polymer-infiltrated ceramic Enamic(®) (PIC).
  
  
  
  Flexural strength of each CAD/CAM ceramic was measured by three point bending (n=15) followed by Weibull analysis. Elastic modulus was calculated from the load-displacement curve. For cyclic fatigue loading, sinusoidal loading with a frequency of 8Hz with minimum load 3N were applied to these ceramics (n=24) using three point bending from 10(3) to 10(6) cycles. Fatigue limits of these ceramics were predicted with S-N fatigue diagram. Fracture toughness and Vickers hardness of the ceramics were measured respectively by single edge V-notch beam (SEVNB) and microindentation (Hv 0.2) methods. Chemical compositions of the materials׳ surfaces were analyzed by EDS, and microstructural analysis was conducted on the fracture surfaces by SEM. One-way ANOVA was performed and the level of significance was set at 0.05 to analyze the numerical results.
  
  
  
  The mean flexural strength of ZC, LD, and PIC was respectively 886.9, 356.7, and 135.8MPa. However, the highest Weibull modulus belonged to PIC with 19.7 and the lowest was found in LD with 7.0. The fatigue limit of maximum load for one million cycles of ZC, LD, and PIC was estimated to be 500.1, 168.4, and 73.8GPa. The mean fracture toughness of ZC, LD, and PIC was found to be respectively 6.6, 2.8, and 1.4MPam(1/2), while the mean Vickers hardness was 1641.7, 676.7, and 261.7Hv. Fracture surfaces followed fatigue loading appeared to be smoother than that after monotonic loading.
  
  
  
  Mechanical properties of ZC were substantially superior to the two other tested ceramics, but the scattering of data was the least in PIC. The fatigue limit was found to be approximately half of the mean flexural strength for all tested ceramics.
authors.affiliation: Department of Mechanical Engineering, Ferdowsi University of Mashhad, Mashhad, Iran; Dental Materials Science, Faculty of Dentistry, The University of Hong Kong, Hong Kong SAR. Electronic address: ehsan.homaei@gmail.com.
authors.forename: Ehsan
authors.initials: E
authors.lastname: Homaei
authors.affiliation: Department of Mechanical Engineering, Ferdowsi University of Mashhad, Mashhad, Iran. Electronic address: farhang@um.ac.ir.
authors.forename: Khalil
authors.initials: K
authors.lastname: Farhangdoost
authors.affiliation: Dental Materials Science, Faculty of Dentistry, The University of Hong Kong, Hong Kong SAR. Electronic address: jkhtsoi@hku.hk.
authors.forename: James Kit Hon
authors.initials: JKH
authors.lastname: Tsoi
authors.affiliation: Dental Materials Science, Faculty of Dentistry, The University of Hong Kong, Hong Kong SAR. Electronic address: jpmat@hku.hk.
authors.forename: Jukka Pekka
authors.initials: JP
authors.lastname: Matinlinna
authors.affiliation: Oral Rehabilitation, Faculty of Dentistry, The University of Hong Kong, Hong Kong SAR. Electronic address: ehnpow@hku.hk.
authors.forename: Edmond Ho Nang
authors.initials: EHN
authors.lastname: Pow
mesh_terms: D002516:Ceramics; D017076:Computer-Aided Design; D003776:Dental Porcelain; D003799:Dental Stress Analysis; D055119:Elastic Modulus; D006244:Hardness; D008422:Materials Testing; D015040:Zirconium
chemical_list: D003776:Dental Porcelain; D015040:Zirconium; C028541:zirconium oxide
keywords: Dental CAD/CAM ceramics; Fatigue; Flexural strength; Lithium disilicate; Polymer infiltrated ceramics; Weibull analysis; Zirconia