Weibull analysis and flexural strength of hot-pressed core and veneered ceramic structures.
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.
Bona
Alvaro Della
AD
School of Dentistry, The University of Passo Fundo, P.O. Box 611/613, Passo Fundo, RS 99001-970, Brazil. dbona@upf.br
Anusavice
Kenneth J
KJ
DeHoff
Paul H
PH
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
D000538:Aluminum Silicates; C118557:Empress 2; C480139:Evision Ceramic; C075815:IPS-Empress ceramic; D018020:Lithium Compounds; D003776:Dental Porcelain; C078519:leucite