The distribution of the maximum principal stress in the cortical bone concentrated on the neck of the implant body. In the TL implants, tensile stress was concentrated on the buccal side and compressive stress on the lingual side. In the BL implants, tensile stress concentration was observed on the lingual side. The distributions were similar between the cpTi and TiZr implants (Figs. 4 and 5). The maximum stress value of the TL implants was smaller than that of the BL implants, and TiZr revealed a smaller value than cpTi in the same length. Regardless of the implant body design and material, the stress concentration increased as the implant length decreased (Fig. 6). The TL implants revealed a comparable maximum stress value to 2.0 mm longer BL implants.

The distribution of von Mises stress in the implant component was concentrated on the connection part of the implant, which was above the bone in the TL design and under the bone in the BL design. In the implant body, stress concentration was observed on the lingual side, and stress propagated along the interface with the superstructure (Fig. 7). The maximum von Mises stress value of the TL implants was smaller than that of the BL implants, and TiZr revealed a smaller value than cpTi in the same length. Regardless of the design or material used, the stress concentration increased with decreasing implant length (Fig. 8). The 4.0 mm TL implant revealed the same amount of stress as the 8.0 mm BL implant, suggesting considerably lower stress in the TL versus BL design.