الفهرس 
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Abstract
Sintering process is an important step in the fabrication of dental zirconia, which has been recently introduced as a high strength ceramic core material for fixed dental prosthesis. Microwave sintering of dental zirconia is an alternative method, and has many advantages over the conventional sintering techniques.
The objective of this study was to evaluate the effect of microwave assist sintering of yttrium partially stabilized Zirconia blocks, compared to conventional sintering technique as regard: microstructure, crystal structure, dimensional changes after sintering, and bi-axial flexural strength.
Forty discs (17.5 mm in diameter × 1.5 mm in thickness) were prepared from )Cercon® smart(blocks, then discs were randomly allocated into two equal groups, each consisted of twenty discs.
Twenty discs were sintered at 1250°C using Microwave Assist Technology furnace (MRF 16/22 furnace), by raising its temperature to the coupling temperature of Zirconia (800 °C), and then microwave was switched on using 100 % MW power. The furnace was held at 1250°C for 60 min., with total sintering time of 4 hours and half. The other twenty discs were conventionally sintered at 1350 °C using conventional furnace for Zirconia (Cercon® heat); according to manufacturer recommendation, with total sintering time of six hours.
Subsequently, each group was further divided in to four equal sub groups; each consisted of five disc. The first sub group was to evaluate the microstructure using scanning electron microscope, the second sub group was for investigating the crystal structure using X-ray diffraction method, the third sub group was for estimating the linear shrinkage by measuring dimensional changes after sintering, and the forth sub group were loaded until fracture using universal testing machine to determine their bi-axial flexural strength, finally statistical analysis was carried out.