Nickel-titanium versus stainless-steel finger spreaders in curved canals

Placement of endodontic spreaders to within 1 to 2 mm of the root canal working length has been advocated for optimum gutta-percha obturation. Due to their stiffness, stainless-steel (SS) spreaders will often fail to achieve this position in curved canals. Newly marketed nickel-titanium (NiTi) spreaders may offer an advantage in this regard due to the increased flexibility of these instruments. Seventy mesial and distal mandibular molar canals were instrumented to a #35 master apical file size. Measurements of the canal curvature were made from preoperative radiographs. Canal curvature angles ranged from 0 to 51 degrees. The teeth were placed in a radiographic mount to ensure a constant focal length, and postoperative radiographs were exposed with comparably sized SS and NiTi spreaders inserted into each prepared canal. Measurements of spreader tip to apex distance were made with a micrometer to the nearest 0.02 mm on the radiographs. Using a t test for paired samples, it was shown that NiTi spreaders penetrated to a significantly greater depth than SS spreaders in curved canals (p < 0.001).