NiTiflex-file is suited to be used both in straight canals as well as in curved canals. The NiTiflex-file prepares dentin both in filing motion (up and down) and when rotated. In curved canals the recommended techniques are continuous rotation when the resistance is small and balanced force against greater resistance. Use of balanced force instead of continuous rotation is easier because of the K-file design, which causes a screwing effect in continuous rotation. The use of filing motion in curved canals can cause transportation and ledging, and is not recommended.