Introduction:
Successful endodontic therapy depends on a well-adapted filling in conjunction with sealer after canal preparation. A properly placed coronal restoration should complete the task of the therapy.
Frequently, the proper restoration requires the placement of a post and core. Therefore, the possible effect of a post space preparation on the quality of the apical seal becomes important.
The purpose of this study was to compare the effect of immediate and delayed post space preparation on apical seal using two currently used sealers (AH₂₆ or Roth sealers) with different properties.
Materials and Methods:
Seventy six freshly extracted single root teeth were used in this study. Teeth were randomly divided into four groups.  In addition to 15 experimental teeth in each group, there were 2 positive controls and 2 negative controls.
All root canals were instrumented and filled with lateral condensation of gutta-percha and AH₂₆ sealer in group 1 and 2 and Roth sealer in group 3 and 4. In groups 1 and 3, post space was immediately prepared with peeso-reamers, leaving 5mm of remaining filling.
Teeth of group 2 and 4 were placed in 100% humidity and 37^oc for 1 and 2 weeks respectively. Then the post space was prepared in the same manner as former groups.
After that, the teeth were immersed passively in India ink for 3 days. Finally the teeth were washed and cleared with use of %5 nitric acid and methyl salicylate.
The extent of dye penetration was determined with use of stereomicroscope and by two independent observers. The data were obtained and then analyzed statistically.
Results:
The lowest and highest rates of dye penetration were detected for group 1 and group 4 respectively.
There was a significant difference between the immediate and delayed post space preparation, but such a difference, was not perceived between two sealers.
Conclusion:
The immediate preparation of post space after obturation and before setting of the sealer, is recommended. In this manner, the voids and the gaps created with post space preparation would be filled by flow of unset sealer.