Abstract
Extracted maxillary and mandibular molars with the curved fine root canals untreated were employed. Enlarging and preparation of the root canals were made with ultrasonic files during the root canals were poured water. Two cleansers, NaOCl (1.25%, 2.5%, 5%) and EDTA (1.875%, 3.75%, 7.5%), were used in combination for ultrasonic cleansing and the inner walls of the root canals were observed by SEM. The results were as follows : 1. When the canals were cleansed with water only, smeared layer was observed in mid-canal and root apex ; the root canal could not be cleansed sufficiently. 2. When the canals were cleansed with 1.25% NaOCl-1.875% EDTA and 2.5% NaOCl-3.75% EDTA, cleansing effects were sufficient at mid-canal but insufficient at root apex. No difference was found between the two. 3. When the canals were cleansed with 5.0% NaOCl-7.5% EDTA, cleansing effect was sufficient at mid-canal and root apex.
