الفهرس 
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Abstract
The aim of this in vitro study was to assess and compare different irrigating solutions namely; Qmix, 5.2% NaOcl, and 2% CHX regarding the cytotoxicity of these irriganting solutions on human bone marrow MSCs, this was done by using MTT tetrazolium assay.
MSCs were obtained from bone marrow sample supplied by VACSERA Company. Cells were grown in Dulbecco`s modified Eagle’s medium (DMEM) supplies with 10% fetal calf serum (FCS) and 1% penicillin/streptomycin antibiotics, and incubated at 37 ºC and 5% CO2 in the air. After 80% confluence, cells were detached from the flask by trypsinization, counted under inverted microscope using haemocytometer, and identified by its morphology and ability to form adherent colonies.
The cells were seeded in 96-well microliter plates at a concentration of 3x 103 cells/ well in a 150 µm fresh medium. They were incubated for 24 hours at 37 ºC to allow attachment of cells to the plates. Cells were treated with the three solutions to examine the cytotoxicity of the irrigants after incubation periods of 2, 4, and 24 hours. For this purpose, three 96-well microliter plates were used; one for each time interval. Each plate was divided into 3 groups, each of 24 wells, based on the type of irrigant applied.
After incubation periods, 10 μl of the MTT reagent was applied and left for another 2 hours, then the photometric determination of absorbance was achieved at 570 nm using micro- plate ELISA reader. The experiment was repeated 2 times for each group at each interval.
The collected data was statistically analyzed using SPSS® Statistics Version 20 statistical software. One-way ANOVA followed by tukey post hoc test was used to evaluate the statistical differences between the groups. Statistically, a significant difference was set at P ≤ 0.05. The collected data also was tabulated and illustrated graphically.
The results of this investigation showed that:
• On comparing the cytotoxic effect of each irrigating solution on MSCs at different time intervals, it was found that the least effect was obtained at 2 hours interval followed by 4 hours and 24 hours interval that showed the highest cytotoxic effect.
• On comparing the cytotoxicity of the three irrigants either at each time interval or regardless of the time factor, it was found that Qmix exerted the least effect on MSCs, followed by 2% CHX, then 5.2% NaOcl that showed the highest morbidity rate.