الفهرس 
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Abstract
This study was conducted to evaluate the effect of two different bleaching agents on the micro- hardness and surface roughness of two resin based restoratives (micro-hybrid composite resin and resin modified glass ionomer). A total of
120 specimens of the resin based restoratives were prepared in the form of cylindrical discs obtained with standard splitted mold 6 mm in diameter and 2 mm in depth. Sixty specimens of each resin based material were randomly divided into two
major groups before bleaching into: a1- storage in distilled water in a glass container at 370 C in an incubator for three months, a2- storage in distilled water in a glass container at370C in an incubator for one week. Samples in each major group were further sub grouped into b1- control samples, b2-
samples bleached using (30 %carbamide peroxide agent once daily for thirty minutes for 3 days, b3- samples bleached using (6% carbamide peroxide once daily for twenty minutes for 14 days). The specimens then subjected to micro-hardness and
surface roughness testing.
Results showed that the aging of samples for three
months showed statistically significantly lower mean microhardness value and higher mean surface roughness value than one week. Bleaching with two different types of the bleaching
agents significantly lowered the mean micro- hardness value and increased mean surface roughness value of both resin restoratives.