Shaping of curved root canals instrumented with stainless steel and nickel titanium files

The cleaning efficiency and the quality of the surgical preparation is mainly conditioned by root canal anatomy, the instruments and the technique employed. The purpose of the present study was to evaluate the extent of straightening of curved root canals and the changes in endodontic anatomy caused by the use of Flex-R, Onyx-R and Nitiflex files with the balanced forces technique. Sixty mandibular molars were selected for evaluation of angulation and transportation. Pre and post instrumentation radiographs were taken of the mesiodistal and buccolingual aspects of each tooth. The radiographs were projected on a transparent sheet, the contours of each tooth and file were outlined and the canal curvature was measured. Pre and post instrumentation tracings were overlaid and the extent of transportation was measured with a micrometric caliper. Statistical analysis of the data was performed employing Student's "t" test, Analysis of Variance and Bonferroni's test. The results showed that all the instruments reduced canal curvature significantly. Transportation in the mesiodistal direction did not reach statistical significance whereas transportation in the buccolingual direction was statistically significant.