Insertion torque

The insertion torque curve was divided into four regions. The first was the region where the torque rose suddenly immediately after insertion, which was seen in all implant bodies (shown as ① in the figure, and hereinafter called the initial area). The second was the region where the torque rose linearly with a moderate gradient, which was seen in all implant bodies except for Brånemark MKIV (MK4) (shown as ② in the figure, and hereinafter called the parallel area). The third was the region where torque rose suddenly, which was seen in Bone Level RC (BL), Tapered Effect RN (TE), and MK (shown as ③ in the figure, and hereinafter called the tapered area). The fourth was the region where the torque reached a critical point, rose suddenly, and then rose gently, which was seen in Brånemark MKIII (MK3) and MK4 (shown as ④ in the figure, and hereinafter called the tapered area).

Regarding the Standard RN (ST), the axial surface and lateral surface were parallel, while for ST6, 8, and 10, only the length was different. The insertion torque curve of the ST3 class shown in Fig. 2a resembled closely, and moderate gradient lines were presented after the initial area in which the torque rose immediately after implantation (parallel area). The length and insertion torque values of the parallel area varied as the length of the implant varied among 6, 8, and 10 mm.

The torque curve for BL3 in Fig. 3a presented a sudden rise in torque on a quadratic function in the initial area immediately after insertion and a subsequent parallel area (tapered area). As the length of the implant varied among 8, 10, and 12 mm, only the length of the parallel area changed, and the initial area and tapered area had almost the same form. The lateral surface for BL was entirely parallel, while the axial surface had a taper only in the cervical region and the thread of the area was decreased in height. The torque curve for the BL3 class in Fig. 3a showed a rapid rise in torque in the form of a tapered area in the initial area immediately after implantation and in a subsequent parallel area. When the length of the implant varied among 8, 10, and 12 mm, only the length of the parallel area changed, and the initial area and tapered area had almost the same form.