Root Canal Preparation of a Curved Root Canal Model with Ni-Ti Files: A Comparison of the Single Length Technique and Crown Down Technique

<p> Purpose: The purpose of this study was to evaluate the total preparation time, the pushing and pulling forces, and the amount of canal transportation after preparing curved root canal resin models using the full length technique (single length technique: NF) or crown down technique (NC) with nickel titanium (Ni-Ti) rotary instrumentation (NEX NiTi FILE Ms: NEX).</p><p> Methods: Transparent resin models which had curved root canals of 30 degrees were used for root canal preparation with NF, NC and stainless-steel K-files (SSK) (n=9 per group). The total preparation time and the pushing and pulling forces during preparation were measured. Photographs taken before and after preparation of the root canal were superimposed. The amount of root canal transportation was measured at 1-mm intervals from the apical foramen to the 8-mm level. The data were subjected to one-way analysis of variance followed by Bonferroni or Games-Howell multiple comparison tests (p<0.05).</p><p> Results: The average total preparation time was significantly shorter in NF and NC than in SSK, but there was no significant difference between NF and NC. The average pushing and pulling forces were significantly lower in both NF and NC than in SSK, but there was no significant difference between NF and NC. There were significant differences in the amount of canal transportation between NF and SSK at positions 0, 1, 2, 4, 5, 7 and 8 mm; between NC and SSK at 0, 1, 2, 7 and 8 mm; but no significant differences between NF and NC at any position.</p><p> Conclusion: Both the single length technique using NEX and the crown down technique of root canal preparation were able to properly enlarge and form the curved root canal better than SSK. The results also showed that the single length technique using NEX was effective in introducing a new root canal formation method using Ni-Ti files from the existing method using SSK.</p>