Effects of four instrumentation techniques on curved canals: a comparison study

Standardized canals (42 degrees curvature) in clear resin blocks were instrumented from size #15 to #35 by four different instrumentation techniques [SW (Senia-Wildey) instrumentation technique, "balanced force" technique, "step back" technique, and a technique combining a reaming motion and the "balanced force" technique] using Flexoreamer Batt-tip, Flex-R file, or K-Flexofile Batt-tip. Changes in canal shape were investigated under standardized conditions using a computer driven testing device. Changes in shape differed significantly (p < 0.05) between the three instruments and between the four techniques (p < 0.0001) in all of the 14 measuring points. Best results were obtained when the curved canals were first enlarged with Flexoreamer Batt-tip or Flex-R file #15 and #20 using a reaming motion followed by #25 to #35 instruments using the "balanced force" technique. Overall, under the conditions of this study, this combined technique provided satisfactory canal preparation with no ledging or canal transportation.