Authors: Reynolds MA, Madison S, Walton RE, Krell KV, Rittman BR.
Title: An in vitro histological comparison of the step-back, sonic, and ultrasonic instrumentation techniques in small, curved root canals.
Journal: J Endod
Date: Jul 1987
Citation: 13(7):307-14
Category: Access and Canal Instrumentation
Evidence-based Ranking: 5
Purpose/Objectives: To compare, by histological examination, the effectiveness of four different methods of root canal instrumentation in small, curved canals. Materials & Methods: Eighty five extracted teeth with moderately curved canals (15-30 degrees) were used in the study. The teeth were divided into four groups of 20 teeth each plus 5 teeth that were uninstrumented served as controls. The four instrumentation methods compared were the step-back hand instrumentation technique, sonic instrumentation with the Endostar 5, and ultrasonic instrumentation with the Cavi-Endo and PZ-KTec prototype systems. Following canal preparation, the teeth were decalcified in sodium formate formic acid and were cross-sectioned for histological evaluation of the coronal, middle and apical thirds. The specimens were evaluated for areas of remaining debris and predentin, the percentage of planed canal walls and the percentage of increase in canal area.

Results: The results showed significant differences among the four canal preparation methods in all evaluation categories. Overall, the step-back technique increased canal area and planed more walls during preparation than the sonic and ultrasonic techniques. The PZ-KTec system was significantly less effective than the other instrumentation techniques in debris removal and increasing the canal area. AuthorÂ’s Conclusion: There are significant differences among the four groups tested. The step-back hand instrumentation method was more effective than the sonic and ultrasonic systems for 1) increasing canal area; 2) removing predentin and debris; and 3) planing canal walls. The differences noted were primarily in the coronal and middle regions; the apical areas showed less contrast between techniques.

Validity of Conclusion: Conclusions are valid. ReviewerÂ’s Comments: This paper is a good comparison of the four instrumentation techniques and suggests that sonic and ultrasonic instrumentation is dampened in small, curved, confined canals and is less effective than in large straight canals as reported by earlier studies.