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Abstract
Eighty single rooted teeth were used in this study. Teeth were sectioned leaving a root length of 13 mm. Sixty roots were used for fracture resistance test, and were divided into four groups (n=15); group I: (negative control) received no instrumentation nor obturation; groupII: (positive control) instrumented but not obturated; group III:obturated with AH Plus /Gutta -Percha points ; group IV obturated with Endorez / Endorez points. For scanning electron microscopic evaluation (SEM), the remaining twenty roots were divided into two groups (n=10) group A: obturated with AH Plus /Gutta - Percha points; group B: obturated with Endorez / Endorez points. All the instrumented teeth were prepared using Revo-S Ni-Ti rotary system and irrigated using 5 % NaOCl during instrumentation, then received a final flush of 17 %EDTA, followed by a final rinse of distilled water. Obturation was carried using single cone technique. For fracture resistance test, roots were mounted in acrylic blocks then, the blocks were mounted on the lower fixed compartment of Lloyd testing machine. The upper plate of the machine including a metal rod was then mounted directly over the canal opening of each root, which was subjected to a slowly increasing vertical load until the fracture occurred