Abstract
Purpose: The purpose of this study was to evaluate the fracture resistance of occlusal veneers constructed from Lithium Disilicate (IPS e-max CAD), Zirconia reinforced Lithium Silicate (Celtra Duo) and Resin Matrix ceramics (Shofu) materials with two restoration thicknesses. Materials and Methods: 42 Human 2 nd mandibular molars were selected and fixed into epoxy resin transparent blocks. Teeth were divided into 2 groups (n=21) according to the occlusal thickness: conventional 1.5mm and thin 1mm. Occlusal veneers preparation was done with planner occlusal reduction and 0.7mm chamfer finish line. Samples were divided into three subgroups (n=7) according to the ceramic material: subgroup(A); Lithium Disilicate (IPS e-max CAD), subgroup (B); zirconia lithium silicate (Celtra Duo) and subgroup (C); Hybrid ceramics (Shofu HC). All prepared teeth were Scanned with Omnicam scanner. Designing was done by cerec 3D software version 4.5. CEREC MCXL 4-Axis machine was used for milling of occlusal veneers. All restorations were bonded to prepared teeth with dual cured resin cement then, thermally aged for 100000 cycles. All specimens were subjected to a compressive load to fracture of 5000N using a computerized universal testing machine. Results: Results of the one-Way ANOVA test showed that the highest mean fracture values were for IPS e-max CAD. Comparison between the two tested thicknesses showed non-significant difference as P>0.05. Comparison between the different materials showed significant difference as P<0.05.
Conclusion: Both conventional and thin occlusal veneer thickness presented fracture resistance mean values that exceed the range of clinical acceptability.