Effect of calcium hydroxide on the dissolution of soft tissue on the root canal wall.

Calcium hydroxide [Ca(OH)2] paste can aid in the cleaning of a root canal because of its soft tissue-dissolving potential. In this study, we examined with a scanning electron microscope the dissolution by Ca(OH)2 paste of pulpal tissue attached to uninstrumented bovine root canal walls. Extracted bovine anterior teeth were divided into small specimens at the middle portion of the roots. The experimental groups were treated with sodium hypochlorite (NaOCl), Ca(OH)2, or a combination of Ca(OH)2 + NaOCl. The control group was given no treatment. The root canal walls were observed with a scanning electron microscope, and the amount of remaining pulp tissue was compared. The amount of debris was reduced remarkably in the groups treated with NaOCl for > 30 s, or Ca(OH)2 for 7 days. The combination of Ca(OH)2 + NaOCl was more effective than the separate treatments. The results suggest that Ca(OH)2 as a root canal medicine serves as an effective agent in removing tissue debris remaining on the root canal walls.