الفهرس 
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Abstract
The aim of this study was to compare the effect of different acidic environmental conditions on the push out bond strength of mineral trioxide aggregate (MTA) and Endosequence Root Repair Material (ESRRM) to the dentinal wall of the tooth.
Forty two extracted human maxillary incisors were used in this study. The teeth underwent root canal treatment and obturation. A three mm root end resection was made on each tooth, and a class I cavity preparation was done in the apical part using Ultrasonics. The teeth were then divided into two equal groups according to the root end filling material used: Group I mineral trioxide aggregate and Group II Endsoequence root end repair filling material. The two groups were further divided into three subgroups according to the media used: Saline, Butyric acid, Blood.
Immediately after filling the root end of each specimen was wrapped in a piece of gauze soaked in the solution and was left for four days in an incubator at 37 C.
The last two mm of each root were then sectioned horizontally. Each root section was subjected to a compressive load via a universal testing machine, to evaluate the push out bond strength of MTA and ESRRM to the dentinal walls. The samples were placed into a custom made copper mold with a central hole to allow free motion of the plunger. Load was applied on the root end filling by a special plunger of one mm diameter size and at a crosshead speed of one mm/min until failure occurred.
After extrusion of the filling material the root slices were then examined under stereomicroscope at X 40 magnification to determine the mode of failure: adhesive, cohesive and mixed failure.
There was no significant difference in the mean push out bond strength of MTA and ESRRM in the presence of saline. While both showed statistically significant difference in the presence of butyric acid and blood. MTA had a higher value in the acidic group, while the ESRRM had a higher value in the blood group.