الفهرس 
AcknowledgementOnly 14 pages are availabe for public view
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Abstract
The principle aim of this investigation was to evaluate the influence of heat treatment on the fracture toughness and microstructure of yttria-stabilized tetragonal zirconia polycrystals (Y-TZP) substrate. Forty ceramic discs (10-mm x 4-mm) were prepared from YZ blocks using CAD/CAM technology, and divided into four groups according to frequency of the heat treatments, ten samples for each Group. Group I, no heat treatment (control group). Group II, are heat treated once corresponding to the first step of the veneering process. Group III, are heat treated five times to mimic the full veneering process. Group IV, Are heat treated seven times to represent the full veneering process plus two times entries for any correction reason.