الفهرس 
AcknowledgementOnly 14 pages are availabe for public view
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Abstract
Statement of problem: Veneered Zirconia restorations exhibit very high modulus of elasticity and high incidence of veneering layer chipping. Therefore, the continuous search for high strength esthetic restorations is never ending.
Purpose: To evaluate the fracture resistance and mode of failure of of CAD/CAM milled PEEK core veneered by milled High impact polymer composite compared to CAD-On Zirconia core veneered by lithium disilicate.
Material and Methods: Fourteen freshly extracted molars were mounted in epoxy blocks and uniformly prepared with a circular deep chamfer finish line of 1.0 mm width. They were divided in to two groups according to the type of crown material (n=7): group A: Teeth restored by ZirCAD core veneered by e.max-CAD and group B: Teeth restored by PEEK BioHPP core veneered by HIPC. All crowns were adhesively cemented. The crowns were then subjected to thermo-mechanical aging using a chewing simulator then static compressive loading till failure using a universal testing machine and failure types were determined.
Results: It was found that PEEK group recorded statistically non-significant (p>0.05) higher mean value (2851.1±241.02 N) than Zirconia group (2786±240 N) as indicated by unpaired t-test. The mode of fracture in the Zirconia group was manifested as veneer chipping in almost all of the specimens. All the PEEK specimens showed cohesive failure in both core and veneer layers upon failure.
Conclusions: Within the limitations of this study, it can be concluded that PEEK veneered by HIPC can be considered a potential permanent crown and bridge material with comparable results to veneered zirconia restorations.