Instrumentation of curved molar root canals with the roane technique

Fifty root canals in extracted human molar teeth were assigned to two curvature groups, unidirectional and S curve. Teeth were mounted in special acrylic blocks and canals were instrumented with straight (noncurved) Unitek K files to a file size #45 using the technique of Roane. The position in the root canal of a series of instruments from file #20 to #45 was compared with the original position in the canal of a #10 or #15 file by means of a method utilizing drawings and projected radiographic images of the files. Results indicated that at file size #45 the original canal position was maintained in approximately 40% of instances; however, at file size #40 the original canal position was maintained in 80% of instances. This study suggests that effective instrumentation of curved root canals may be accomplished with straight instruments of fairly large size without significant deviation from the original canal position.