Remaining dentin/cementum thickness after hand or ultrasonic instrumentation

A quantitative study was undertaken to measure remaining dentin/cementum thickness after using step-down, step-back hand instrumentation or ultrasonically energized instrumentation techniques. A model system was used which enabled the same canal system of extracted human mandibular molars to be accurately evaluated and measured before and after instrumentation. Although no statistical difference was demonstrated in the encroachment upon the furcal aspect of mesial roots of mandibular molars, both techniques came dangerously close to creating stripping and perforations in a high percentage of cases.