Method: Sixty extracted central incisor teeth were prepared to simulate divergent open apex of immature teeth and divided into 4 groups of 14 teeth. All Groups 1 & 2 received 2 or 4 mm apical plugs, respectively; both groups had cotton pellet soaked in normal saline placed in contact with MTA for 2 days. Groups 3&4 received 2 or 4 mm apical plug; respectively; both were immersed in PBS for 40 days. Two teeth served as negative and two as positive controls. All samples were immersed in methylene blue for 48 hours and tested by Dye- extraction method .Sample absorbance was measured by spectrophotometer. Data were analyzed statistically (two way ANOVA). The precipitate resulting from interaction of MTA with PBS was evaluated by SEM and FTIR
Result: : There was no statistically difference in dye penetration between groups (P>0.05).FTIR revealed the precipitate from the interaction between MTA and PBS was B-type carbonated apatite. SEM showed a white line at the interface of MTA and dentin
Conclusion:
Based on the results,we concluded that:1)HA crystals that were synthesized in microscopic gaps between MTA and dentin were not able to prevent leakage.2)The evaluation of the sealing ability of MTA in the presence of methylene blue coud be influened by the PH of methyleneblue.3)Thickness of MTA fillings seems does not effect on microleakage, therefore it is necessary that the remaining space of the canal be obturated with appropriate material. Keyword:MTA hydrations conditions,MTAplug,Dye extraction