A comparison of fracture strength of yttrium-oxide- partially-stabilized zirconia ceramic crowns with varying core thickness, shapes and veneer ceramics.

The fracture strengths of stylized all-ceramic crowns manufactured using an yttrium-oxide-partially-stabilized (Y-TZP) zirconia ceramic core (Denzir) veneered with lithium disilicate glass-ceramics (IPS Empress 2 or IPS Eris) were evaluated. The Denzir cores were manufactured in two ways: either with different thickness in different parts of the restoration, called an 'adapted Denzir core'; or with a uniform core thickness of 0.5 mm. IPS Empress 2 all-ceramic crowns served as reference. There was no significant difference between the crowns with an 'adapted Denzir core' veneered with the two brands of glass-ceramics. No significant difference was seen between the crowns with a 0.5 mm Denzir core veneered with the two brands of glass-ceramics. The crowns with an 'adapted Denzir core' exhibited significantly higher values than those with a 0.5 mm Denzir core and than the IPS Empress 2 crowns used as reference. No significant differences were seen among the IPS Empress 2 crowns used as reference and the crowns with a 0.5 mm Denzir core. The mode of failure varied among the Empress 2 crowns and the crowns with a core of a Y-TZP zirconia ceramic. Long-term studies are necessary to assess the clinical performance of this restorative system.