title: Effect of the microstructure on the lifetime of dental ceramics.
abstract: OBJECTIVE
  To evaluate the effect of the microstructure on the Weibull and slow crack growth (SCG) parameters and on the lifetime of three ceramics used as framework materials for fixed partial dentures (FPDs) (YZ - Vita In-Ceram YZ; IZ - Vita In-Ceram Zirconia; AL - Vita In-Ceram AL) and of two veneering porcelains (VM7 and VM9).
  
  
  METHODS
  Bar-shaped specimens were fabricated according to the manufacturer's instructions. Specimens were tested in three-point flexure in 37°C artificial saliva. Weibull analysis (n=30) and a constant stress-rate test (n=10) were used to determine the Weibull modulus (m) and SCG coefficient (n), respectively. Microstructural and fractographic analyzes were performed using SEM. ANOVA and Tukey's test (α=0.05) were used to statistically analyze data obtained with both microstructural and fractographic analyzes.
  
  
  RESULTS
  YZ and AL presented high crystalline content and low porosity (0.1-0.2%). YZ had the highest characteristic strength (σ(0)) value (911MPa) followed by AL (488MPa) and IZ (423MPa). Lower σ(0) values were observed for the porcelains (68-75MPa). Except for IZ and VM7, m values were similar among the ceramic materials. Higher n values were found for YZ (76) and AL (72), followed by IZ (54) and the veneering materials (36-44). Lifetime predictions showed that YZ was the material with the best mechanical performance. The size of the critical flaw was similar among the framework materials (34-48μm) and among the porcelains (75-86μm).
  
  
  CONCLUSIONS
  The microstructure influenced the mechanical and SCG behavior of the studied materials and, consequently, the lifetime predictions.
authors.affiliation: Department of Restorative Dentistry, University of Passo Fundo, Passo Fundo, RS, Brazil.
authors.forename: Márcia
authors.initials: M
authors.lastname: Borba
authors.forename: Maico D
authors.initials: MD
authors.lastname: de Araújo
authors.forename: Karen A
authors.initials: KA
authors.lastname: Fukushima
authors.forename: Humberto N
authors.initials: HN
authors.lastname: Yoshimura
authors.forename: Paulo F
authors.initials: PF
authors.lastname: Cesar
authors.forename: Jason A
authors.initials: JA
authors.lastname: Griggs
authors.forename: Alvaro
authors.initials: A
authors.lastname: Della Bona
mesh_terms: D000537:Aluminum Oxide; D000538:Aluminum Silicates; D003460:Crystallization; D003776:Dental Porcelain / Q000737:chemistry*; D019232:Dental Restoration Failure; D003799:Dental Stress Analysis; D003801:Dental Veneers; D003830:Denture, Partial, Fixed; D004548:Elasticity; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D016062:Porosity; D017680:Potassium Compounds; D013052:Spectrometry, X-Ray Emission; D013499:Surface Properties; D016019:Survival Analysis; D013718:Tensile Strength; D015019:Yttrium; D015040:Zirconium
chemical_list: D000538:Aluminum Silicates; D017680:Potassium Compounds; C499362:yttria stabilized tetragonal zirconia; D003776:Dental Porcelain; C016447:feldspar; D015019:Yttrium; D015040:Zirconium; D000537:Aluminum Oxide