Histological evaluation of ultrasonic debridement comparing sodium hypochlorite and water

Twenty extracted human mandibular first and second molars with mesial canal curvatures of 18 to 35 degrees were randomly divided into two groups. Following routine endodontic access and canal length determination one of the mesial root canals was ultrasonically instrumented, using tap water in the first group or 2.6% sodium hypochlorite irrigation in the other. In both groups the other mesial canal was used as a control. The mesial roots were decalcified, serially sectioned, and stained with hematoxylin and eosin. Wall planing and soft tissue debridement were blindly evaluated using the light microscope. Mean canal wall planing and soft tissue debridement scores were compared by multiple t tests. Sodium hypochlorite, in conjunction with ultrasonic instrumentation, was more effective than tap water in wall planing when the entire root length was considered. Sodium hypochlorite, in conjunction with ultrasonic instrumentation, was more effective than tap water in soft tissue debridement in the middle third of the canal. Both irrigants were ineffective in conjunction with ultrasonic instrumentation in removing soft tissue from the main canal, the isthmus between canals, the canal fins, and the multiple branches or deltas often encountered in the apical one-third of the canal.