Method: Sixty full anatomical crowns were constructed using a CAD/CAM system (Cerec, Sirona) and divided into 3 groups (n=20); Monolithic Lithium disilicate (IPS e.max CAD), hand-layer-veneered Y-TZP based crowns (IPS e.maxZirCAD/Ceram) and digitally-veneered Y-TZP based crowns (IPS e.max,ZirCAD/e.max CAD On). Crowns were cemented to aged resin-based composite dies with self-cure resin cement. All specimens were subjected to cyclic loading then to compressive load until failure. Failure mode was designated as bulk fracture through the crown or chipping of the veneer ceramic; Scanning electron microscopy was performed for fractographic analysis. Data were analyzed statistically by one-way ANOVA and Tukey's post-hoc test (α=0.05).
Result: Monolithic e.max CAD and ZirCAD/CAD On groups exhibited superior failure resistance with mainly bulk fracture as failure mode leading to the exposure of the core dentin/zirconia; while ZirCAD/Ceram hand-layer exhibited significantly lower fracture resistance and a delamination/chipping of the veneer ceramic.
Conclusion: IPS.e.max CAD and ZirCAD/CAD On crowns exhibit a high failure resistance and similar failure mode; and can be considered as a promising option for clinical use.