Comparing apical preparations of root canals shaped by nickel-titanium rotary instruments and nickel-titanium hand instruments

This study measured displacement of canal centers in extracted human teeth after preparation by Lightspeed and nickel-titanium K-files, The specimens were divided into two groups (n = 11), after radiographing the roots from t he buccolingual and mesiodistal planes with pathfinding files in situ, More strongly and less strongly curved canals were, respectively, assigned to t he Lightspeed and nickel-titanium K-file groups. Using a reassembly techniq ue, cross-sections at 1.25 mm, 3.25 mm, and 5.25 mm from the apices were ma de of the experimental roots embedded in clear plastic. Stereomicroscopic 3 5-mm slides were taken of the uninstrumented sectioned canals. The sections were reassembled and then prepared to size 50 Master Apical Rotary and siz e 40 Master Apical Files, for the Lightspeed and K-file groups, respectivel y. Similar 35-mm slides of the instrumented canals were taken and electroni cally superimposed over their uninstrumented counterparts. Displacements of root canal centers after preparation and increases in cross-sectional area s of the prepared root canals were evaluated at specific levels. No signifi cant differences in displacement of canal centers or between the mean cross -sectional areas of the instrumented root canals were recorded between the Lightspeed and K-file groups. Both types of instruments produced similar di splacement of canal centers after preparation.