Effect of calcium hydroxide dressing on seal of permanent root filling

Low apical leakage along root fillings following an application of calcium hydroxide was reported in a few methylene blue dye penetration studies. It has been found recently that methylene blue is decolored by calcium hydroxide, indicating that the short penetration of methylene blue may not be due to a tight seal only. Of the 80 roots of human maxillary central incisors used in this study, 40 roots (group 1) received calcium hydroxide root canal dressing whereas another 40 roots (group 2) did not. All the roots were then obturated with gutta-percha and Tubli-Seal sealer. Leakage along 20 filled roots in each group was measured using a modified fluid transport model at 48 h, 2, 4, 8 and 16 weeks after obturation; whereas leakage of another 20 filled roots in each group was measured using dye penetration with 1% methylene blue. Using the fluid transport model, no significant difference was found between the two groups at any time interval (P = 0.4847, 0.3875, 0.9490, 0.4786, 0.9148 respectively after 48 h, 2, 4, 8 and 16 weeks); using the methylene blue penetration method, leakage in group 1 (with root canal dressing) was significantly less than that in group 2 (without root canal dressing) (P = 0.0374). The contradiction in results from the different models indicated that problems existed with the models.