Effect of dowel space preparation on the apical seal of root canal fillings.

The effect of post preparation on the apical seal was studied using simulated root canals. The maximum level of removal was tested with residual fillings 1, 2, 3, and 4 mm long. All of the artificial canals were filled with gutta-percha, Grossman's sealer, and lateral condensation. The removal was immediate and carried out with warm pluggers and the dowel space was completed with a Peeso drill. Stainless steel posts were cemented with zinc phosphate cement in the free space of the root canals. The coronal access of the canals was sealed with temporary fillings. After setting the materials, the specimens were immersed in a 2% methylene blue dye solution for 72 h and were observed with a measuring microscope. The final length of the apical fillings was found to be different from the intended length in every group. As far as leakage was concerned, 1, 2, and 3 mm-long fillings did not show a significant difference when compared with the negative control group (that is to say, filled canals where no dowel space was created). In the 4 mm fillings the leakage value was zero. These findings may be of clinical importance when restoring short roots.