Abstract
Purpose: Nickel-titanium (NiTi) rotary files are becoming more popular and an important part of the equipment for root canal treatment. The superelasticity and shape memory of the instruments have improved the shaping procedures in root canal preparation, making it easier and faster. In this study, we assessed the educational effectiveness of J- and S-shaped root canal preparation with FKG Race in dental students’ hands-on practical classes.
Methods: Fifty-six third-year students in the School of Dentistry, Osaka University performed J- and S-shaped root canal preparation in transparent epoxy resin blocks with FKG Race twice each. After penetration with a #15 K-file, root canal length was measured. Cervical preflaring and glide path preparation were performed with PreRace and #15 K-file, respectively. Then, the working length was determined by subtracting 1 mm from the root canal length. Root canal preparation was performed with Race (#30/6%, #30/4%, #25/4%, and #20/4%) in order and the final preparation was carried out with #30/6%. In order to evaluate the quality of root canal preparation, we photographed the epoxy resin blocks before and after the instrumentation by micro-computed tomography and measured the root canal width perpendicular to the long axis of the root canal at 1, 2, 3, 4, 5, and 6 mm from the root apex. The increase in root canal width and the time for preparation were compared between the students and specialists certified by the Japanese Society of Conservative Dentistry.
Results: In the J-shaped root canal preparation by the students for the first time, 62.5% of the students had apical perforation and 5.4% had ledge formation. In the second-time preparation of the J-shaped root canal, 30.4% of the students had apical perforation, 3.6% had separated files, and 3.6% had ledge formation. In the S-shaped root canal preparation by the students for the first time, 23.2% of the students had apical perforation and 7.1% had separated file. In the second-time preparation of the S-shaped root canal, separated file occurred in 7.1%. In terms of speed of root canal preparation, the second try at S-shaped preparation by the students was significantly faster than the first try. The distances between pre- and post-instrumentation at the different levels showed no significant differences among the first and second trials by the students and specialists.
Conclusion: In the practice of curved-root canal preparation using NiTi files, students can quickly and accurately achieve successful preparation even for difficult S-shaped root canals, especially by paying attention when preparing a root apex.
