الفهرس 
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Abstract
This study was carried out to evaluate and compare the vertical marginal gap distance, fracture resistance, cyclic loading and hardness of all-ceramic crowns IPs e.max press and IPs Impress1(heat-pessable technique). Specially designed stainless steel dies were constructed and a total number of 30 samples were constructed representing two equal groups (15 samples), according to material , The samples of each group were tested to determine the vertical marginal gap distance, then were subjected to cyclic loading test.
As regard the vertical marginal gap test, the results showed that IPs impress1 crowns recorded a higher vertical marginal gap mean value (55 ± 6 µm) than obtained with e.max Press crowns (48 ± 8 µm). The cyclic loading test data revealed that IPs e.max crowns recorded a higher fracture resistance mean value (1929.3± 49.4 N) than IPs IMPRESS1 crowns what recorded (1709.3 ±41.4N), The other part of this study aimed to evaluate the shear bond strength of heat pressed ceramics after different surface treatments.A total of 80 discs (10-mm x 2-mm) were prepared from IPs e max press and IPs impress1 ingots and divided into four groups according to the surface treatments, ten samples for each Group , Surface Scanning was employed to examine the surface topography of the ceramic disc surfaces before and after surface treatments with 3 different types of microscopy scanning (scanning electron microscopy, atomic force microscopy, and confocal microscopy)
Regarding the effect of surface treatment on bond strength, the acid etched group recorded the highest shear bond strength mean value for impress1 and e-max irrespectively While control group recorded a lower shear bond strength mean value . microscopic scanning suggested that the laser energy promoted the following surface changes: little material removal related to formation of pores, melting of the most superficial ceramic layer and its re-solidification related to the formation of elevation over the surface. While for the acid etched groupthere were small micro retentive grooves. What is more preffered for mechanical bond.