title: Subcritical crack growth behavior and life data analysis of two types of dental Y-TZP ceramics.
abstract: OBJECTIVE
  The aim of this study was to evaluate the mechanical properties and the subcritical crack growth behavior of a presintered dental Y-TZP (Kavo Everest ZS) and a hot isostatic pressed Y-TZP (Kavo Everest ZH) and to perform life data analysis.
  
  
  METHODS
  For each material 150 bending bars were produced. The initial fracture strength was determined in a four-point bending test. The subcritical crack growth parameters n and A were determined in a dynamic fatigue method at four decreasing loading rates from 110MPa/s to 0.11MPa/s in distilled water at 38°C. For each loading rate Weibull statistics were performed and the Weibull moduli m and characteristic strengths σ(0) were calculated. Using these data, strength-fracture probability-life time (SPT) predictions were derived for 1 day, 1 year, 5 years and 10 years, based on a static crack growth mechanism.
  
  
  RESULTS
  The "hipped" Y-TZP ceramic exhibited a higher initial strength (σ(c)=1618.18), characteristic strength (σ(0)=837.15) and fracture toughness (K(IC)=4.52MPa/m(1/2)) than the pre-sintered ceramic (σ(c)=1431, σ(0)=745.46 and K(IC)=3.17MPa/m(1/2), respectively). Fatigue parameters, n and A, were 28.5 and 7.97×10(-24) for Everest ZH and 30.15 and 5.47×10(-20) for Everest ZS. The predicted fracture stress at 5% failure probability for a lifetime of 10 years was 259.34MPa for Everest ZH and 263.2MPa for Everest ZS.
  
  
  CONCLUSIONS
  Although the "hipped" Y-TZP showed favorable initial mechanical properties, no significant difference could be found in the susceptibility of both ceramics to subcritical crack growth and their long-term strength.
authors.affiliation: Clinic for Prosthetic Dentistry and Dental Material Science, University of Saarland, 66424 Homburg Saar, Germany. zmgimi@uniklinik-saarland.de
authors.forename: Gergo
authors.initials: G
authors.lastname: Mitov
authors.forename: Janina
authors.initials: J
authors.lastname: Gessner
authors.forename: Ulrich
authors.initials: U
authors.lastname: Lohbauer
authors.forename: Karsten
authors.initials: K
authors.lastname: Woll
authors.forename: Frank
authors.initials: F
authors.lastname: Muecklich
authors.forename: Peter
authors.initials: P
authors.lastname: Pospiech
mesh_terms: D003442:Crowns; D003776:Dental Porcelain / Q000737:chemistry*; D019232:Dental Restoration Failure; D003799:Dental Stress Analysis; D003830:Denture, Partial, Fixed; D004548:Elasticity; D019544:Equipment Failure Analysis; D006358:Hot Temperature; D008422:Materials Testing; D011312:Pressure; D013499:Surface Properties; D016019:Survival Analysis; D015019:Yttrium / Q000737:chemistry*; D015040:Zirconium / Q000737:chemistry*
chemical_list: C499362:yttria stabilized tetragonal zirconia; D003776:Dental Porcelain; D015019:Yttrium; D015040:Zirconium