The Effect of Calcium Hydroxide Removal and the Influence on the Sealing Ability of Root Canals

The aims of this study are to evaluate the effectiveness of calcium hydroxide removal by using different irrigation regimens and the effect of the canal seals influenced by debris in root canal. 200 human premolar teeth were prepared, and divided randomly into two groups. Group A was filled with chemical calcium hydroxide and group B was filled with finished product calcium hydroxide. Each group was divided into 6 subsets and the calcium hydroxide in the root canal was removed in different ways: Group A1 and B1 by injection syringe and distilled water; group A2 and B2 by injection syringe and 2.5% sodium hypochlorite; group A3 and B3 by injection syringe, 2.5% sodium hypochlorite and 17% EDTA; group A4 and B4 by ultrasonic and distilled water; group A5 and B5 by ultrasonic and 2.5% sodium hypochlorite; group A6 and B6 by ultrasonic, 2.5% sodium hypochlorite and 17% EDTA. Then, 8 teeth were randomly selected from each subset group and observed by scanning electron microscope. The other specimens were obturated by lateral condensation of cold gutta-percha, stained by Indian ink and then made into transparent teeth models. The results showed that in the same irrigation regimen, there was no significant difference between group A and group B; the result of groups associated with ultrasonic was better than that with injection syringe, which was of significant difference. The rinse solution of EDTA was the best, while distilled water was the worse. The length of dye staining had no significant difference among all groups. The conclusions are that ultrasonic is better than injection syringe; association of sodium hypochlorite and EDTA is the best rinse solution to remove the calcium hydroxide. However, none of these methods or rinse solutions can remove all the calcium hydroxide. The calcium hydroxide remains exert no remarkable influence on the root canal sealer.