Ultrasound in endodontics: a quantitative and histological assessment using human teeth.

Hand instrumentation of the root canal was compared with ultrasonic instrumentation in 20 maxillary premolars with 2 root canals. The buccal and lingual canals were alternately instrumented by the 2 techniques until they had reached clinically ideal conditions for filling. After mechanical preparation, an attempt was made to evaluate root shape and the enlarging ability of the 2 techniques. For this purpose, a crosswise cut slice approximately 100 microns thick was cut off at the middle level of the root, which permitted comparative quantification of the instrumented area of the buccal and lingual canals. Crosscut serial sections of the remaining parts of the root were obtained for a systematic study of the entire extension of the root canal. It was concluded that the presence of debris inside the root canal depended more on the anatomical variation of the canal than on the technique used. No statistically significant differences in root canal area were evident at the middle third level of the root.