A silicone model method to compare three methods of preparing the root canal.

To compare the ability of three methods of preparing root canals to provide a properly shaped canal, silicone models were used. The canals of extracted teeth were prepared and filled with a silicone impression material. The teeth were dissolved, and the remaining models were studied and photographed. The hand instrument group and the SET angle were equal. The subsonic instrument did not shape a canal as well as the other two.