## 4 Discussion
In addition, in teeth regions where high stress is generated, high stress will also be generated on the alveolar bone in these regions due to the different occlusion conditions and the different dental implant systems involved (ICP and RMOL occlusions will generate high stress on the alveolar bone, which is consistent with the results of previous studies [24]. However, RGF occlusion has a smaller impact on the stress on the alveolar bone). Moreover, when examining the stress on the alveolar bone in areas of a single tooth, it can be seen that areas in connection with the cortical bone have higher stress. The production of this high stress can be explained by [PERSON]'s law (stress = Young's Modulus \(\times\) strain). When the dental implant system receives an external force, it will have a slight downward displacement, compressing the alveolar bone and generating the same displacement at the junction of the cortical bone and trabecular bone (creating the same strain here). At the same time, the stress is proportional to the Young's Modulus. In this study, the Young's Modulus of the cortical bone is 13,800 MPa, and that of the trabecular bone is 345 MPa. Thus, the cortical bone above the alveolar bone has a higher stress. Therefore, in the design of some implants, the number of threads is increased at the neck of the implant, increasing its contact area with the surface of the alveolar bone, preventing the dental implant system from loosening up when external forces are exerted, thereby enhancing the success rate of implantation. The distribution of von Mises stress on the dental implant system shows that the high stresses on the dental implants under the impact of external forces mainly arise near the neck of the dental implant, where the dental implant contacts with the abutment. Therefore, when the tooth receives an external force, it will directly deform the neck of the dental implant. According to [PERSON]'s law, high stress will be generated in this area. In addition, it was found that the alveolar bone of the implants adjacent to the implants that were affected by external forces will also experience high stress due to deformation. Moreover, when examining the stress on the abutment and abutment screw, it can be seen that the high stress on abutment arises at its junction with the dental implant. The high stress on the abutment screw arises in the area where the screw head is connected to the abutment, also corresponding to the area where the geometric shape of the screw head and screw bends. Therefore, the design of the abutments and abutment screws should avoid the generation of high stress by the geometric shape. Otherwise, since the patient will chew with the dental implant system for a long time, the dental implant system may be damaged due to fatigue. This study has some limitations. In the FEA, all the material properties were assumed to be homogeneous, isotropic, and linearly elastic. These assumptions were in accordance with previous studies [34; 35], and the purpose was to simplify the simulation in this study and allow easier comparisons of the results. Although the results of the research will be slightly different from the actual situation, the main trends of the results will still hold true. In addition, the computer simulation model used in this study was simplified. We only constructed models of dental implants and did not include the crowns. The main reason for this is that the structures and shapes of the teeth can be different. Our study aimed to examine how dental implants at different positions are impacted by the occlusal forces. To reduce the confounding effect from the shapes and structures of the crowns of the different teeth, we only applied external forces to the abutments to facilitate the evaluation of the impact at different positions. Furthermore, our model used seven dental implants (normally, the model with 14 dental implants should be established in this study).