Influence of lamination on the flexural strength of a dental castable glass ceramic

This study evaluated the effect of veneering Dicor castable ceramic with Vitadur N and Dicor Plus feldspathic porcelains. A biaxial flexure test was conducted on five groups of specimens (Dicor castable ceramic, Vitadur N dentinal porcelain, Dicor Plus dentinal porcelain, Dicor core veneered with Vitadur N and Dicor core veneered with Dicor Plus castable ceramic). Each group consisted of 10 disks of nearly identical dimensions with a 1.98 +/- 0.04 mm thickness and 15.7 +/- 0.35 mm in diameter. Statistical analysis indicated that there was neither significant difference (p > 0.05) between mean flexural strength of Dicor Plus and Vitadur N ceramic or Vitadur N and Dicor/Vitadur N ceramic specimens. The mean flexural strength of Dicor/Vitadur N specimens was significantly lower than the mean flexural strength of Dicor ceramic specimens. Conversely, there was no significant difference between mean flexural strength of Dicor ceramic and Dicor/Dicor Plus ceramic specimens. Scanning electron microscope (SEM) examinations of Dicor/Dicor Plus ceramic specimens suggested better wetting of Dicor core by Dicor Plus ceramic with lower incidence of porosity at the interface. However, Dicor/Vitadur N ceramic specimens exhibited a higher incidence of porosity at the interface. This indicated that lamination of Dicor castable ceramic material with feldspathic porcelain for esthetics could be attained without sacrificing strength of the original material, provided that appropriate veneering material was selected.