Root canal preparation with a novel nickel-titanium instrument evaluated with micro-computed tomography: Canal surface preparation over time

Introduction: The aim of this part of an ongoing study was to describe the dentin removal ability of a novel nickel-titanium instrument, the self-adjusting file (SAF), by using micro-computed tomography. Methods: Twenty maxillary incisors were scanned preoperatively at 20-μm resolution and postoperatively after up to 6 minutes of preparation with an SAF with 1.5-mm or 2-mm diameter. SAFs were operated with continuous irrigation in a handpiece that provided an oscillating, in-and-out movement. Changes in canal volume compared with preoperative values as well as unprepared canal surface area were determined. Data were normally distributed and compared by analysis of variance and regression analyses. Results: Preoperatively canal volumes were statistically similar in both groups (9.86 ± 3.97 mm and 9.80 ± 2.67 mm). Volumes increased during preparation to 13.58 ± 3.85 mm (after 6 minutes with SAF 1.5 mm) and 16.43 ± 3.64 mm (after 5 minutes with SAF 2.0 mm), and overall canal shapes were adequate. Unprepared canal surface area decreased from 63.0% ± 15.1% (2 minutes with SAF 1.5 mm) to 8.6% ± 4.1% (5 minutes with SAF 2.0 mm). Conclusions: Preparation of straight root canals in maxillary anterior teeth left little canal surface uninstrumented after shaping with the SAF. The timeframe of clinical application will depend on the amount of desired dentin removal and done with an SAF selected on the basis of apical gauging