Histological evaluation of ultrasonic and sonic instrumentation of curved root canals.

Fifty extracted human mandibular first and second molars with mesial canal curvatures of 18 to 35 degrees were randomly divided into five groups. After routine endodontic access and canal length determination, one of the mesial root canals was instrumented using tap water and one of the following instrumentation methods: (a) hand instrumentation; (b) ultrasonic instrumentation with the Cavi-Endo unit; (c) ultrasonic instrumentation with the Enac unit; (d) sonic instrumentation with the Medidenta unit; and (e) sonic instrumentation with the Endostar 5 unit. The other mesial canal was used as a control. The mesial roots were decalcified, serially sectioned, stained with hematoxylin and eosin, and blindly evaluated using the light microscope. The mean canal wall planing and soft tissue debridement scores were compared by analysis of variance. There was no statistically significant difference among the groups for wall planing or soft tissue debridement.