Studies on Ni-Ti Spreader

Abstract

On 6 types of Ni-Ti spreader (Roeko NiTi # 15; Roeko NiTi # 25; Roeko NiTi # 35; Roeko NiTi D11T; Brasseler Naviflex NT D11T; Brasseler Naviflex NT 4SP), dimensions were measured under digital microscope, and a load application test was performed in the axial direction of the spreader. The results were as follows: 1. In Roeko NiTi # 15, D₃ was 0.38 mm, D₁₆ was 0.61 mm, taper was 0.018, and tip angle was 28.9°. Similarly, the above values were 0.32 mm, 0.68 mm, 0.027, and 28.0° respectively in Roeko NiTi # 25. The values were 0.50 mm, 0.70 mm, 0.016, and 32.5° respectively in Roeko NiTi # 35, and the values were 0.37 mm, 0.88 mm, 0.039, and 10.6° respectively in Roeko NiTi D11T. The values were 0.27 mm, 0.77 mm, 0.038, and 29.9° respectively in Brasseler Naviflex NT D11T, and 0.30 mm, 1.06 mm, 0.059, and 35.9° respectively in Brasseler Naviflex NT 4SP. 2. When a load was applied in the axial direction of the spreader, the load was 0.56 kgf in case the portion of 16 mm in length from the tip in Roeko NiTi # 15 was bent at a stroke. When the portion of 5 mm in length from the tip was fixed and the portion of 11 mm in length from the tip was bent at a stroke, the load was 4.32 kgf. The above values were 1.13 kgf and 7.52 kgf respectively in Roeko NiTi # 25, 1.24 kgf and 8.58 kgf in Roeko NiTi # 35, 0.82 kgf and 10.28 kgf in Roeko NiTi D11T, 0.63 kgf and 7.27 kgf in Brasseler Naviflex NT D11t, and 1.02 kgf and 17.61 kgf in Brasseler Naviflex NT 4SP. 3. The Ni-Ti spreader has super-elasticity and is flexible. Thus, it is difficult to apply pressure on it in the axial direction, during lateral condensation. However, this study revealed that sudden bending may be avoided if at least the tip portion of 5 mm in length from the tip is inserted into the root canal.