A COMPARISON OF 4 INSTRUMENTATION TECHNIQUES ON APICAL CANAL TRANSPORTATION

The ability of four instrumentation techniques to enlarge and maintain the central axis of 51 curved canals was evaluated radiographically. Curved canals in extracted human teeth were instrumented using a step- back preparation with K-files, crown-down preparation with K-files, so nic instrumentation with Shaper-Sonic files, and the NiTiMatic prepara tion system, Following coronal preflaring, each canal was instrumented to a #35 file 1 mm from the anatomic foramen. Radiographs were taken with mercury filling the canal system using a specially designed model that allowed for the pre- and postinstrumentation canal to be viewed on the same radiograph. Canal enlargement and apical transportation re sulting from the various instrumentation techniques were evaluated usi ng computer analysis. No statistically significant differences were fo und for canal transportation. Sonic instrumentation significantly incr eased coronal flaring. The crown-down and sonic techniques produced mo re ledges. Elbow formation was associated with all instrumentation tec hniques. The model system developed for this study provided an accurat e method of assessing the preparation techniques and the instrument ef fects on the canal walls.