Efficacy of three techniques in cleaning the apical portion of curved root canals

Various techniques for root canal instrumentation may have different effects in cleaning curved root canals, especially their apical portions. One hundred thirty-five mesiobuccal canals with an average curvature of 25 degrees from human mandibular molars were treated with step-back, crown-down pressureless, or balanced-force techniques with 2% sodium hypochlorite used as an irrigant. The cleaning efficacy of these techniques was evaluated by counting the remaining surface debris under a stereomicroscope with a calibrated eyepiece micrometer. The results indicated that the apical portion of the canal was less clean than the middle and coronal portions regardless of the technique performed and that the balanced-force technique produced a cleaner apical portion of the canal than did the other techniques studied.