الفهرس 
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Abstract
This study was carried out to evaluate the tensile bond strength of the repair joint between an aged composite material when repaired by the same material and when repaired by a different one using different surface treatment repair protocols.
Ten whole hourglass from each composite material serving as this study’s control, and 80 half-slabs from an Ormocer composite material were made in an especially designed split copper mold all stored in tab water for six months. After six months the 80 half-slabs were divided in to 2 groups according to the repair material used (40 by Ormocer composite, 40 by nanohybrid composite), then each group was further sub-divided into 4 sub-groups according to the adhesive category received (silane-containing,2-step SE, 2-step ER, 1-step SE). Tensile bond strength of the repair joint was evaluated using a universal testing machine at crosshead speed 0.5mm/min. Data was collected and analysed using SPSS version 17.0. Fractured surfaces were examined using digital microscope at 55x magnification.
The results showed that the adhesive category had no statistically significant effect on the tensile bond strength of the repair joint, while as for the repair material, and its interaction with the adhesive, both had a statistically significant effect on the tensile bond strength of the repair joint.
Under the limitations of this study, several conclusions can be drawn about the Ormocer material used in this study:
1- The cohesive strength of the material decrease upon aging, consequently the freshly repaired joints are stronger than the repaired material itself.
2- The repair material has the main effect in the success of the repair process.
3- Bis-GMA based composite is preferred than Ormocer as a repair material.
4- Silane doesn’t affect the repair bond strength of the Ormocer material.
5- The adhesive protocol weather it is self-etch or etch and rinse doesn’t affect the repair bond strengt