A comparison using macroradiography of canal shapes in teeth instrumented ultrasonically and by hand

Forty teeth with severely curved canals were divided into two groups and the root canals were prepared either ultrasonically or with hand instruments. Canal shapes were compared qualitatively and quantitatively using subtraction macroradiography; this allowed the pre- and postinstrumented canal shapes to be viewed on the same print. The times to carry out instrumentation and the incidence of elbows were recorded. In addition, the following measurements were taken from the radiographs using a digitizer: apical and coronal areas, distance of elbow from canal curvature, change in width at elbow and 0.5 mm apical to it, and apical transport width. Subjective evaluation revealed that no difference was apparent between the methods as to the places where the dentin was removed; both instruments exhibited unequal dentin removal along the canal length with more removal occurring coronally. The quantitative results indicated an absence of differences in the following: the time of instrumentation, the incidence of elbows, the distance of elbow from the point of curvature, the change in width at the region of the elbow, and the apical transport width. These findings indicated that ultrasonic files behaved similarly to hand instruments when used in a filing action.