title: Weibull analysis and flexural strength of hot-pressed core and veneered ceramic structures.
abstract: OBJECTIVE
  To test the hypothesis that the Weibull moduli of single- and multilayer ceramics are controlled primarily by the structural reliability of the core ceramic.Methods. Seven groups of 20 bar specimens (25 x 4 x 1.2 mm) were made from the following materials: (1) IPS Empress--a hot-pressed (HP) leucite-based core ceramic; (2) IPS Empress2--a HP lithia-based core ceramic; (3 and 7) Evision--a HP lithia-based core ceramic (ES); (4) IPS Empress2 body--a glass veneer; (5) ES (1.1 mm thick) plus a glaze layer (0.1 mm); and (6) ES (0.8 mm thick) plus veneer (0.3 mm) and glaze (0.1 mm). Each specimen was subjected to four-point flexure loading at a cross-head speed of 0.5 mm/min while immersed in distilled water at 37 degrees C, except for Group 7 that was tested in a dry environment. Failure loads were recorded and the fracture surfaces were examined using SEM. ANOVA and Duncan's multiple range test were used for statistical analysis.
  
  
  RESULTS
  No significant differences were found between the mean flexural strength values of Groups 2, 3, 5, and 6 or between Groups 1 and 4 (p>0.05). However, significant differences were found for dry (Group 7) and wet (Groups 1-6) conditions. Glazing had no significant effect on the flexural strength or Weibull modulus. The strength and Weibull modulus of the ES ceramic were similar to those of Groups 5 and 6.
  
  
  CONCLUSIONS
  The structural reliability of veneered core ceramic is controlled primarily by that of the core ceramic.
authors.affiliation: School of Dentistry, The University of Passo Fundo, P.O. Box 611/613, Passo Fundo, RS 99001-970, Brazil. dbona@upf.br
authors.forename: Alvaro Della
authors.initials: AD
authors.lastname: Bona
authors.forename: Kenneth J
authors.initials: KJ
authors.lastname: Anusavice
authors.forename: Paul H
authors.initials: PH
authors.lastname: DeHoff
mesh_terms: D000538:Aluminum Silicates; D000704:Analysis of Variance; D003442:Crowns; D003776:Dental Porcelain; D003799:Dental Stress Analysis; D003801:Dental Veneers; D004548:Elasticity; D018020:Lithium Compounds; D008422:Materials Testing; D018583:Pliability; D012044:Regression Analysis; D018709:Statistics, Nonparametric; D013499:Surface Properties; D016019:Survival Analysis; D017155:Wettability
chemical_list: D000538:Aluminum Silicates; C118557:Empress 2; C480139:Evision Ceramic; C075815:IPS-Empress ceramic; D018020:Lithium Compounds; D003776:Dental Porcelain; C078519:leucite