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Abstract

All-ceramics have been increasingly used in prosthetic dentistry to fabricate a wide variety of restorations]1[ The most recently core materials are the yttrium oxide partially stabilized zirconia (Y-TZP), were found as a new material for all dental ceramic restorations Partially stabilized yttria tetragonal zirconia polycrystalline (Y-TZP) ceramics are a relatively new class of dental ceramics introduced to the market. that are made into blanks and milled to the favorite dimensions using the CAD/CAM (Computer Aided Design/Computer Aided Manufacturing) technology. Objective: To evaluate the effect of different thicknesses on the hardness of disks fabricated by the yttrium oxide partially stabilized zirconia (Y-TZP). Method: This quantitative study was conducted to assess and evaluate the surface hardness of disks in terms of fabrication thirty disc-shaped of wax pattern were prepared in three core thicknesses materials (0.5 mm, 1mm and 1.5 mm), and each all-ceramic system with a 10 mm diameter were prepared according to ISO specification 6872 Vickers diamond indenter was utilized in accordance with micro-hardness tester. Result: The hardness of tetragonal yttrium partial stabilized zirconia with different thicknesses (0.5,1 and 1.5) mm, were as follows: The mean value of 1mm thickness (2557.2967) is greater than mean value of 0.5 mm (2240.4433) in a high significant amount (H.S), and also greater than mean value of 1.5mm (2520.3600) in a significant amount. So, the partially stabilized zirconia specimens with 1mm thickness has better hardness than 1.5mm and 0.5 mm thicknesses. Conclusion: The results concluded that the tetragonal partially stabilized zirconia displays a higher surface hardness for thickness with 1mm than the specimens with 0.5 mm and 1.5mm thickness with the same materials

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