الفهرس 
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Abstract
The aim of the study was to evaluate the effect of three irrigation regimens namely
• 2.5 % NaOCl followed by MTAD
• 2 % CHX followed by MTAD
• 2.5 % NaOCl followed by 17 % EDTA
On:
Ι-The change in mineral content of root canal dentin.
ΙΙ-The cleanliness of root canal dentin.
A total of thirty six human permanent single rooted teeth with mature apices were used in this study .The Crowns of teeth were decoronated at the cementoenamel junction and stored in distilled water till used .
Samples were divided into two main groups according to the evaluation method , either for change in mineral content (group Ι: containing twelve roots) or cleanliness of root canal dentin (group ΙΙ: containing twenty four roots). In group Ι teeth were split longitudinally forming a total of twenty four specimens .Two indentations was made at junction of root thirds. The mineral content of the specimen is measured at the center of the two indentations before being subjecting it to irrigating solution using energy dispersion X-ray analysis (EDX) .
Then the dentin specimens were divided into 3 subgroups and subjected to irrigation protocol . Subgroup Ι a : eight dentin specimens were subjected to 10 ml of 2.5 % NaOCl for 10 min (each 5 ml for 5 minutes) followed by 5 ml of MTAD for 5 min, while Subgroup Ι b : Eight dentin specimens were subjected to 10 ml of 2% chlorohexidine for 10 min followed by 5ml of MTAD for 5 min. finally subgroup Ι c: 8 dentin specimens were subjected to 10 ml of 2.5 % NaOCl for 10 min followed by 5 ml of EDTA for 5 min.
After being subjected to the irrigation regimen, the specimens were washed with distilled water then the mineral content was assessed again using energy dispersion X-ray analysis.
For the second part of this study : twenty four root canals were divided into three subgroups being instrumented to a master apical file size 50 and coronal flaring was done with gated glidden sizes 2,3 and 4.
In Subgroup ΙΙ a : 8 roots were irrigated with 1 ml of 2.5% NaOCl between each 2 successive and the final flush was done with 5 ml MTAD for 5 minutes ,while for the subgroup ΙΙ b roots were irrigated with 1 ml of chlorohexidine between each 2 successive instruments followed by final flush with 5 ml MTAD for 5 minutes ,and finally roots of subgroup ΙΙ c were irrigated with 1 ml of 2.5 % NaOCl between each 2 successive instruments then final flush with 5 ml of 17 % EDTA for 5 minutes.
The root thirds was examined under stereo microscope and the percentage of debris was calculated by dividing the pixels of debris by the total pixels representing the entire area of the canal.
Results showed that there was increase in percent change of calcium and phosphorus for subgroup Ι a(NaOCl +MTAD) while subgroups Ι b(CHX+MTAD) and Ι c (NaOCl + EDTA) showed decrease in mineral content levels.
As regards to results of cleanliness of root canal dentin showed that subgroup ΙΙ c (NaOCl + EDTA) followed by subgroup ΙΙ a (NaOCl +MTAD) while the least cleanliness was observed in subgroup ΙΙ b (CHX+MTAD) .
While concerning the cleanliness in regard to thirds ,the apical third had the highest debris percent followed by middle thrd while the coronal third had the lowest debris percent.
The smear layer was covering the entire root canal in subgroup ΙΙ b (CHX+MTAD) ,while in subgroup ΙΙ a (NaOCl +MTAD)the smear layer was heavy in apical third,finally subgroup ΙΙ c (NaOCl + EDTA) showed clean root canal walls in all thirds.