COMPARISION OF APICAL TRANSPORTATION USING HERO 642 ROTARY NI-TI INSTRUMENTS AND STAINLESS STEEL HAND K-FILE DURING ROOT CANAL PREPARATION

Materials & Methods:  Total of 45 freshly extracted first and second mandibular permanent human molars with  curvature  ranging between 20° and 40°(according to Schneider's method) were randomly divided into two groups of 20 each and 5 as negative control group. In the first group, canals were instrumented with conventional stainless steel hand K-files using step back technique. In the second group, canals were instrumented with rotary HERO 642 files using crown down technique according to Manufacturer's recommendation. In each canal, a preinstrumentation radiograph with initial file size #15 was taken with Radio Visio Graph (RVG) system using standard radiographic condition. Post instrumentation radiograph with master apical file size #30 was also taken. Photoshop C.S 8.0 used to determine the angle of transportation via comparing the initial and final radiographs, at the apical, middle and coronal thirds of the root.

Results: The mean degree of transportation in apical, mid root and coronal thirds were 3.7, 3.47, and 3.8, in hand group, while  in rotary group were 2.5, 3.45, and 4.5 degree. Student t-test and one way (ANOVA) showed no statistical significant differences between two techniques.

Conclusion: Results  indicated that the mean degree of apical transportation during instrumentation of curved root canals has no significant difference between K-files and HERO  rotary files..However, HERO has less transportation. In addition, preflaring with Gates glidden drills has significant effect in reducing the  amount of transportation in K-file group.